Patent Publication Number: US-6707545-B1

Title: Optical signal routing method and apparatus providing multiple inspection collection points on semiconductor manufacturing systems

Description:
This application is a continuation-in-part of U.S. application Ser. No. 09/391,341 filed on Sep. 7, 1999, entitled “Particle Detection and Embedded Vision System to Enhance Substrate Yield and Throughput.” 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to inspection methods and apparatus. More particularly, the invention relates to a method and apparatus for inspection of substrates to identify process and handling related defects and conditions. 
     2. Background of the Related Art 
     A chip manufacturing facility is composed of a broad spectrum of technologies. Cassettes containing semiconductor substrates are routed to various stations in the facility where they are either processed or inspected. 
     Semiconductor processing generally involves the deposition of material onto and removal (“etching”) of material from substrates. Typical processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, chemical mechanical planorization (CMP) etching and others. During the processing and handling of substrates, the substrates undergo various structural and chemical changes. Illustrative changes include the thickness of layers disposed on the substrate, the material of layers formed on the substrate, surface morphology, changes in the device patterns, etc. These changes must be controlled in order to produce the desired electrical characteristics of the devices formed on the substrate. In the case of etching, for example, end-point detection methods are used to determine when the requisite amount of material has been removed from the substrate. More generally, successful processing requires ensuring the correct process recipe, controlling process excursions (e.g., gas flow, temperature, pressure, electromagnetic energy, duration, etc) and the like. 
     In addition, the processing environment must be sufficiently stable and free from contamination. Sources of contamination include wear from mechanical motion, degradation of seals, contaminated gases, other contaminated substrates, flaking of deposits from processing chambers, nucleation of reactive gases, condensation during chamber pumpdown, arcing in plasma chambers and so forth. Such sources of contamination produce particles that contact the substrates and can result in defective devices. As the geometries of device features shrink, the impact of contamination increases. Thus, current semiconductor manufacturing routinely includes inspection of substrates for particles to identify “dirty” processes or equipment. 
     Additionally, substrate centerfinding and orientation necessary steps during processing to generate positional information regarding substrates. In conventional systems such procedures are performed at designated locations in the processing system. Thus, a substrate must be shuttled to the designated locations in order to undergo each procedure, thereby decreasing system throughput. 
     Another situation which can cause increased processing costs is improper substrate routing in the chip manufacturing facility. Occasionally, a substrate may be improperly routed to a process chamber where the processing conditions cause a volatile reaction, thereby damaging the substrate and/or the processing chamber. For example, consider the case of a substrate with a photoresist layer that has been inadvertently routed to a PVD chamber. Processing this substrate in the PVD chamber is known to cause severe damage to the chamber, resulting in substantial repair and/or replacement costs. Because current processing systems are not equipped to prevent misrouting, the cost of ownership is increased. 
     Currently, comprehensive testing and analysis of substrates for process integrity and contamination requires the periodic or often constant removal of one or more substrates from the processing environment into a testing environment. Thus, production flow is effectively disrupted during transfer and inspection of the substrates. Consequently, conventional metrology inspection methods can drastically increase overhead time associated with chip manufacturing. Further, because such an inspection method is conducive only to periodic sampling due to the negative impact on throughput, many contaminated substrates can be processed without inspection resulting in fabrication of defective devices. Problems are compounded in cases where the substrates are re-distributed from a given batch making it difficult to trace back to the contaminating source. 
     Thus, what is needed is an integrated metrology and process inspection system, a “gate-keeper” apparatus and method, capable of examining a substrate for selected characteristics which include particles, processing flaws, orientation, centerfinding, reflectivity, substrate type, discontinuity, etc. as an integral part of the processing system. Preferably, such an inspection can be performed prior to, during, and after substrate processing, thereby determining real time pre- and post-processing conditions of the substrate. 
     Other functions routinely performed in conventional processing systems and inspection systems include calibration of robots and the inspection equipment. Current methods of calibration negatively impact throughput because the production must be halted in order to perform the calibration. Degradation usually goes undetected until a catastrophic failure occurs. A preferred processing system would include an integrated, or embedded, device capable of continuously monitoring the status of the robot and inspection system and facilitate automatic corrective action. Thus, the processing system could be further integrated and throughput can be increased. In addition, it would be preferable for such an integrated device to be capable of monitoring robot behavior. Robot behavior of interest includes acceleration, speed, repeatability, stability, etc. Additionally, it would be preferable for such an integrated device to determine the presence of contamination on the robot blade which supports substrates during transfer. The presence of such contamination indicates that the backsides of substrates are being scratched during a substrate handling step or the accumulation of processing byproduct. Heretofore, however, no such integral devices or methods have been known to exist in processing systems. 
     Another disadvantage with conventional inspection systems is the prohibitive cost of the systems. Current systems are typically expensive stand-alone platforms that occupy clean-room space. As a result of the large area, or “footprint,” required by the stand-alone inspection platforms, the cost of owning and operating such a system is high. With regard to particle detection, the cost is further increased because of the electro-optics equipment utilized. This equipment is configured to produce high-resolution detection of small-scale particles and requires high-fidelity mechanisms, which are expensive to operate. Additionally, considerations of reduced throughput described above further increase the cost of conventional inspection systems. 
     Therefore, there is a need for an integrated system capable of rapidly inspecting semiconductor substrates and determining one or more conditions of the substrate in order to detect anomalies and facilitate a subsequent substrate handling decision. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides a substrate inspection system for use in substrate processing systems. In one aspect of the invention, at least one optical inspection system is used to inspect the surface topography of processed substrates. The optical inspection system transmits signals representing surface topographical characteristics of the substrate, at a particular process, to a process monitoring controller configured to operate one or more optical inspection systems. 
     In one embodiment, the process monitoring controller determines the state of the particular substrate surface with respect to a reference substrate value. If the substrate characteristics exceed a predetermined value, the substrate may be sent to a secondary metrology inspection step for a more refined and in-depth analysis. Moreover, the process monitoring controller may also utilize the information to optimize or alter the processing system substrate manufacturing processes. 
     In another embodiment, a plurality of optical inspection systems are used to monitor the substrate surface topography at various inspection locations positioned along a plurality of substrate transfer paths in conjunction with a process monitoring controller. Such a process monitoring system can optimize the throughput of the substrate processing through continued monitoring and analysis. The integrated inspection allows the optimization of process recipes through near real-time monitoring of process recipe changes and subsequent effects upon the process. 
     One embodiment of the invention involves a system for software control of the process inspection and system throughput enhancement. The system comprises a data-processing system comprising a controller containing a program for process monitoring. The program when executed on the data-processing system is configured to perform the steps comprising configuring a optical inspection system in response to a system configuration event; providing adjustment settings for the optical inspection system; receiving, from the optical inspection system, topographical information of the substrate surface, determining if the substrate topographical condition has exceeded predetermined values; and if the substrate surface has exceeded the predetermined values, determining if the substrate requires additional more in-depth analysis. 
     One embodiment of the invention includes a program product containing a program for optical character recognition and particle and defect detection, the program when executed by a controller comprises configuring a system in response to a system configuration event, providing adjustment settings for the system, providing a signal from a signal source to a receiver wherein the signal illuminates a substrate and the signal receiver receives reflections and/or scattered signal from the substrate surface to detect surface topographical defects. 
     Preferably, the program product is adapted to provide substrate positional information, substrate reflectivity information, specular information, spectral information, three-dimensional images, substrate defect information, substrate damage information, particle contamination information for the substrate support member and a substrate disposed thereon, alphanumeric character information, robot behavior information, calibration information for a robot, a transmitter unit and/or a receiver unit, and any combination thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1A is a plan view of a typical processing system for semiconductor processing wherein the present invention may be used to advantage. 
     FIG. 1B is a high-level system view of a processing inspection system. 
     FIG. 1C illustrates a process inspection system comprising one embodiment of the invention having a plurality of optical inspection systems coupled to an optical signal multiplexer that is in communication with receiver for use with the present invention. 
     FIG. 2 is a perspective view of a Factory Interface used with the present invention comprising one embodiment of the present invention comprising two transmitter units and a receiver unit for use with the present invention. 
     FIGS. 3A-C are top views of the processing system of FIG. 2 showing various positions of a substrate disposed on a blade during linear movement of the pod blades. 
     FIG. 4 is a perspective view of a Factory Interface used with the present invention comprising one embodiment of the present invention comprising one transmitter unit and a receiver unit. 
     FIGS. 5A-C are top views of the processing system of FIG. 4 showing various positions of a substrate disposed on a blade during extension movement of the pod blade. 
     FIG. 6 is a partial perspective view of a transfer chamber used with the present invention comprising one embodiment of the present invention comprising one transmitter unit and a receiver unit. 
     FIGS. 7A-C are top views of the processing system of FIG. 6 showing various positions of a substrate disposed on a blade during rotation of the blade. 
     FIGS. 8A-C are top views of the processing system of FIG. 6 showing various positions of a substrate disposed on a blade during linear movement of the blade. 
     FIG. 9 is a cross sectional view of a chamber and a lid assembly illustrating one embodiment of an optical inspection system. 
     FIG. 10 is a cross sectional view of a chamber and a lid assembly illustrating one embodiment of an optical inspection system. 
     FIG. 11 is a perspective sectional view of a chamber and a lid assembly illustrating one embodiment of an optical inspection system. 
     FIGS. 12A-C is a cross sectional view of a chamber and a lid assembly from FIG. 11 showing various positions of a substrate disposed on a blade during linear movement of the blade. 
     FIGS. 13A-C is a cross sectional view of a chamber and a lid assembly illustrating one embodiment of an optical inspection system showing various positions of a substrate disposed on a blade during a substrate surface scanning sequence. 
     FIG. 14 is one embodiment of a moving view of a substrate detection system for use with the present invention. 
     FIG. 15 is a graphical representation of specular intensity distribution of reflections from a patterned substrate illuminated by a light source. 
     FIG. 16 is a comparative graphical representation of specular intensity distribution on patterned substrates. 
     FIG. 17 is a plot showing specular signature differences with respect to a 40 second over etch time. 
     FIG. 18 is a etch endpoint plot based on changes in process plasma intensity. 
     FIG. 19 is a plot illustrating changes in mean intensity values for various over etch times. 
     FIG. 20 is a plot illustrating delta-mean intensity values for a succession of inspected substrates. 
     FIG. 21 is a plot showing changes in etch photo resist strip time specular signatures. 
     FIG. 22 is a plot illustrating intensity plots for strip times with respect to a reference substrate. 
     FIG. 23 is a plot illustrating intensity scans for strip times after photo resist has been removed. 
     FIG. 24 is a graph of repeatability difference plots to determine system noise. 
     FIG. 25 is a top down substrate surface view for spectral analysis. 
     FIG. 26 is a high-level architecture of one embodiment for a system configured to perform particle detection and other process monitoring methods. 
     FIG. 27 is a flow diagram for a method for program control of process monitoring and particle detection using the system. 
     FIG. 28 is a flow diagram for process monitoring and process report generation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     I. Processing System 
     Embodiments of the invention have particular advantages in a multi-chamber processing system (e.g., a cluster tool). One exemplary multi-chamber processing system commonly used in the semiconductor industry, well suited for supporting the detection apparatus described herein, is known as a cluster tool. A cluster tool is a modular system comprising multiple chambers which perform various functions including substrate center-finding and orientation, degassing, annealing, deposition and/or etching. The multiple chambers are mounted to a central transfer chamber which houses a robot adapted to shuttle substrates between the chambers. The transfer chamber is typically maintained at a vacuum condition and provides an intermediate stage for shuttling substrates from one chamber to another and/or to a load lock chamber positioned at a front end of the cluster tool. 
     FIG. 1A is a plan view of a typical processing system  100  for semiconductor processing wherein the present invention may be used to advantage. Two such platforms are the Centura® and the Endura® both available from Applied Materials, Inc., of Santa Clara, Calif. The details of one such staged-vacuum substrate processing system is disclosed in U.S. Pat. No. 5,186,718, entitled “Staged-Vacuum Wafer Processing System and Method,” Tepman et al., issued on Feb. 16, 1993, which is incorporated herein by reference. The exact arrangement and combination of chambers may be altered for purposes of performing specific steps of a fabrication process. 
     In accordance with the present invention, the processing system  100  generally comprises a plurality of chambers and robots and is preferably equipped with a processing system controller  102  programmed to carry out the various processing methods performed in the processing system  100 . A front-end environment  104  (also referred to herein as a Factory Interface or FI) is shown positioned in selective communication with a pair of load lock chambers  106 . Pod loaders  108 A-B disposed in the front-end environment  104  are capable of linear, rotational, and vertical movement to shuttle substrates between the load locks  106  and a plurality of pods  105  which are mounted on the front-end environment  104 . The load locks  106  provide a first vacuum interface between the front-end environment  104  and a transfer chamber  110 . Two load locks  106  are provided to increase throughput by alternatively communicating with the transfer chamber  110  and the front-end environment  104 . Thus, while one load lock  106  communicates with the transfer chamber  110 , a second load lock  106  communicates with the front-end environment  104 . A robot  113  is centrally disposed in the transfer chamber  110  to transfer substrates from the load locks  106  to one of the various processing chambers  114  and service chambers  116 . The processing chambers  114  may perform any number of processes such as physical vapor deposition, chemical vapor deposition, and etching while the service chambers  116  are adapted for degassing, orientation, cool down and the like. A number of view ports  120  provide visual access into the transfer chamber  110 . 
     Embodiments of the invention include Optical Inspection Sub-Systems (OIS)  150  configured for gathering optical data. As will be described below, an OIS  150  generally comprises a transmitter unit adapted to provide a signal and a receiver unit adapted to receive reflected (bright field illumination) and/or scattered portions of the signal (dark field illumination) from the substrate surface. 
     A plurality of OISs  150  may be located anywhere on and/or coupled to the processing system  100  for process monitoring, for example within the factory interface  104 , the transfer chamber  110 , processing chamber  114 , service chambers  116 , and the like. The information received from each OIS  150  can then be processed to determine various conditions of substrates moving within the processing system  100 . 
     Embodiments of the OIS  150  include various receivers and transmitters. In one embodiment, the receiver is a charge coupled device (CCD) camera used to detect light in the visible spectrum. Another receiver can be a spectrometer used to receive incoming light and to output data indicating the various light wavelengths and their intensity. For example, a red light would have greater light component intensities grouped within the lower wavelengths of the visible spectrum. The spectrometer typically includes an optical prism (or grating) interface to optically split the incoming signal into its components, which in turn is projected onto a linear CCD detector array. One embodiment of a spectrometer may comprise a CCD detector array comprising thousands of individual detector elements to receive the resultant spectrum from the prism (or grating). The relative intensity of the light spectrum components represents the overall color of, for example, a substrate surface, substrate surface pattern, or plasma process. 
     In another embodiment, the receiver is an optical character recognition receiver (OCR). OCR receivers are used to detect and discriminate between optical characters and substrate patterns. Substrates often include identifying information inscribed on a surface of the substrate. Typically, the identifying information is a series of alphanumeric characters. In one embodiment, an OCR receiver is used to advantage to detect the characters and determine whether a substrate having a specific OCR marking, is being handled properly (e.g., routed to the proper chamber for processing). In another embodiment, the OCR is used to associate related metrology information. 
     Each of the receivers may comprise optical devices to focus and collect the reflected/and or scattered signals from the substrate. For example, the spectrometer may utilize a fiber optic collector to receive and direct the light spectrum, or may use a “lens perspective system” such as a “fish-eye” to collect a large amount of light, or special lenses that can modify the field of view for a specific substrate inspection. Lens arrangements may be used to increase or concentrate light. Collecting more light over a greater field of view averages out local substrate surface variations. 
     The transmitters of the OIS  150  may be of various configurations adapted for a particular purpose during process inspection. For example, a line-light source may be used to only illuminate a portion of the substrate, or a flash device may be used to strobe the substrate during the process to gather spectral information. Each of the transmitters may incorporate a beam-focusing optical system to concentrate and project energy on to the substrate. 
     The various receiver and transmitter embodiments may be used individually or in combination to collect process data throughout the processing system  100 . Data collected from the various embodiments is used to monitor the substrate processing status at various stages of the manufacturing process. The operation of the OISs  150  is controlled by an Process Monitoring Controller (PMC)  86 . As shown in FIG. 1A, the PMC  86  is electrically coupled to each OIS  150  by an IO (input-output) cable  90  adapted to provide command signals to the respective OIS  150 . Further, the PMC  86  receives output signals from the respective OISs  150  by the IO cable  90 . Although the processing system controller  102  for the processing system  100  is preferably separate from the PMC  86 , in one embodiment the PMC  86  may serve as the control unit for the processing system  100 , thereby eliminating the need for an additional control unit. 
     Upon initiation by a user, the PMC  86  continues to monitor substrates which enter the field of view of the OIS  150 . If the PMC  86  detects a condition being monitored (e.g., a contaminated substrate), the user may be alerted by a warning message displayed on a display unit (not shown). Additionally or alternatively, the processing system controller  102  can be instructed by the PMC  86  to transfer the substrate to a particular location for eventual disposition, cleaning or further inspection. For example, in one embodiment, the processing system  100  includes an inspection platform  135  for particle detection but the inspection platform  135  function could be expanded to include OISs  150  on the FI  104 , and elsewhere on the processing system  100 . 
     The inspection platform  135  could be adapted to perform various metrology tasks such as surface anomaly detection, pattern recognition, spectral/spectrum analysis, and the like in conjunction with particle detection. Illustratively, the inspection platform  135  is an integrated particle monitoring (IPM) system which is configured for embodiments of the present invention. In general, an IPM is a particle inspection platform commonly used on cluster tools. One IPM which can be used to advantage is known as Excite™ available from Applied Materials, Inc, of Santa Clara, Calif. When implemented according to the present invention, the IPM operates as a process monitoring device capable any of the present inventive processes, including any equivalents. Accordingly, the inspection platform  135  is capable or more than mere particle detection. 
     In one embodiment, the particular location for an OIS  150  is determined by the routing of substrates within the processing system  100  (in order to use the robots to advantage) as well as accessibility of the location. For example, the view ports  120  provide suitable locations for an OIS  150  because the view ports  120  provide a field of view of the robot blade  48  entering or exiting a chamber (e.g., the load lock  106 , cooldown chamber  116  or processing chamber  114 ) or moving between locations within the transfer chamber  110 . Illustratively, arrows  122 ,  124  indicate points where optical inspection of a substrate may be performed using the ports  120 . Arrows  122  represent points where the robot blade  48  is rotated and arrows  124  represent points where the robot blade  48  is extended or retracted. One embodiment wherein an OIS  150  is located on the transfer chamber  110  is described below with reference to FIG.  6 . 
     In some embodiments, the OIS  150  has application at any position in the processing system  100  where substrates are in motion. In one embodiment, the factory interface  104  provides additional inspection sites. Illustrative inspection sites are represented by arrows  132 ,  134 , and  138 . Arrows  132 ,  134 ,  136 , and  138  additionally illustrate the substrate transfer paths. Arrows  136  indicates the movement of substrates between the factory interface  104  and the pods  105 . Arrows  132  and  138  indicate the movement of substrates between the factory interface  104  and the load locks  106 . Arrows  134  indicate the movement of substrates within the factory interface  104  and, in particular, between the pod loaders  108 A and  108 B. OISs  150  may be located along each of the transfer paths  132 ,  134 , and  138 , to monitor the manufacturing process. However, as will be described below, embodiments are also contemplated in which the substrate being inspected is not moving. 
     FIG. 1B illustrates a high level view of a substrate inspection system. In one embodiment, the inspection system comprises a PMC  86 , coupled to a processing system controller  102 , a factory interface controller  159 , a plurality of OISs  150  and a inspection system  135 . The PMC  86  is used to control the process monitoring of the OISs  150 . The auxiliary user interface  152  allows for stand alone operation allowing an operator to control PMC  86 . In one embodiment, interface  152  may be a Graphical User Interface (GUI). The process monitoring information obtained may be directed to substrate manufacturing data servers  162  via cable  90 . 
     For example, in one embodiment, the OIS  150  may include a cluster of light sources and one receiver. FIG. 1C illustrates a plurality of light sources  56  and fiber optic cables  143 A-H coupled to an optical signal multiplexer  141  that is in communication with receiver  58 . The optical cables are positioned to collect reflected and/or scattered light through windows  120  and then send optical signals to multiplexer  141 . Mutliplexer  141  sends optical data to the spectrum analyzer  58  in multiplexed form allowing a single receiver to effectively monitor a multitude of inspection sites. In one embodiment, the receiver  58  is a spectrometer. 
     II. Factory Interface: 
     FIGS. 1,  2 ,  4  illustrate embodiments wherein the transmitter unit and the receiver unit of the OIS  150  are disposed on or in the F 1   104  along the various paths of substrate movement as illustrated by arrows  132 ,  134 ,  136 ,  138 , other embodiments may be used to advantage. FIG. 2 shows is an illustrative view of the FI  104  comprising the pod loaders  108 A and  108 B, OIS  150 A, mounting member  160 , a transfer support member  166  including a substrate alignment detector  168 , and a substrate holder  162 . The FI further comprises a frame  218 . The mounting member  160  is fastened to the frame  218  by conventional means such as bolts, clamps or other fasteners as are known in the art. 
     FIG. 2 illustrates one embodiment of the OIS  150  used for substrate scanning along process arrow  134 . An OIS  150 A comprising a pair of light sources  56 A and  56 B (i.e., transmitters), and a receiver  58 A are disposed upon mounting member  160 . The light sources  56 A and  56 B are angled to provide two angles of illumination. Illustratively, light source  56 A provides front substrate illumination and light source  56 B provides rear substrate illumination. In one embodiment, the angle between the light sources  56 A and  56 B is at about orthogonal to provide the least amount of illumination overlap (i.e. illumination cross-talk). Although not shown, the light sources  56 A and  56 B may include beam-shaping optics (e.g., lenses and the like) to allow for refinement and adjustment of the optical beams provided by the respective light sources. The light receiver  58  is positioned to receive reflected and/or scattered portion of the light from the surface of the substrate  37 . The light receiver  58  is selected according to the data to be collected. In illustrative embodiments, the light receiver  58  comprises a CCD device, a time delay integration (TDI) camera, a photo-multiplier tube (PMT) a spectrometer, an OCR camera and the like. The light receiver  58  may further include optics devices adapted to assist in the collection of information. For example, in one embodiment, the light receiver  58 A includes a fiber optics bundle to capture and route the received light from an inspection point to the receiver  58 . 
     In operation, the substrate  37  is moved between locations in the F 1  by the pod loaders  108 A and  108 B. The OIS  150 A then scans the substrate  37  such that the reflected and/or scattered light is received by the light receiver  58  for processing as described below. 
     Illustratively, the substrate  37  is positioned by either pod loader  108 A or  108 B under the OIS  150 A for scanning as the substrate  37  is being shuttled between the load locks  106  and substrate holder  162 . Preferably, the substrate  37  is scanned during a normal substrate handling. For example, during a normal substrate exchange step between pod loaders  108 A and  108 B, the substrate  37  may be scanned by OIS  150 A while in transit. 
     For example, consider the case where the substrate  37  is being moved from pod loader  108 A to the pod loader  108 B. Initially, the substrate  37  is carried by pod loader  108 A and placed in substrate holder  162 . Substrate holder  162  facilitates the passthrough/exchange between the pod loaders  108 A-B. During this movement, the substrate  37  can be scanned by the front illumination light  56 A. In one embodiment, the substrate is moved beyond midpoint for a full substrate scan.  3 A-C illustrates the movement of the substrate  37  as it is scanned with the front illumination light  56 A. FIG. 3A shows the pod blade  48  immediately after initiating the movement of the substrate  37  toward the substrate holder  162  so that the leading edge of the substrate  37  is positioned in the path of the signal  54 . Thus, a portion of the light projection  53  formed by light source  56 A, represented by the shaded area, is shown intersecting the leading edge of the substrate  37 . During the continued movement of the pod blade  48  as shown in FIGS. 3B-C, the light projection  53  scans the upper surface of the substrate  37 . Reflected and/or scattered light is received by receiver  58  for processing as described below. Pod loader  108 B may use the identical process as described above to scan the substrate  37 . 
     In another embodiment, it is contemplated that a single pod loader  108  may be used for movement utilized by the two light sources  56 A and  56 B. For example, OIS  150 A scans the substrate using the front illumination light source  56 A and receiver  58  as the substrate is loaded into substrate holder  162  by pod loader  108 A. When the substrate is withdrawn from the substrate holder  162  by pod loader  108 A, light source  56 B is activated to provide rear illumination for scanning the substrate as the substrate is withdrawn from the substrate holder  162 . Receiver  58 A receives the reflected and/or scattered light from the substrate as it is being placed upon substrate holder  162  and withdrawn by pod loader  108 A. 
     FIG. 4 illustrates another embodiment of an OIS  150 B used when the substrate follows the transfer path as illustrated by arrows  132 ,  138 . OIS  150 B comprises a single light source  56 A which may include beam-shaping optics, and a light receiver  58 . OIS  150 C is disposed upon mounting member  160 . The light source  56 A provides substrate illumination and may include beam-shaping optics. In one embodiment, as the substrate  37  is moved from the factory interface  104  into the load locks  106 , the reflected and/or scattered light is received by receiver  58  which sends signals to the PMC  86  for processing as described below. 
     FIGS. 5A-C illustrate the sequence of the scan using OIS  150 B. FIG. 5A shows the pod blade  48  immediately after initiating the movement of the pod  108 A toward the load lock  106  so that the leading edge of the substrate is positioned in the path of the signal  54 . Thus, a portion of the light projection  53 , represented by the shaded area is shown intersecting the leading edge of the substrate  37 . During the continued movement of the pod blade  48  as shown in FIGS. 5B-C, the light projection  53  scans the upper surface of the substrate  37 . Reflected and/or scattered light is received by receiver  58  for processing as described below. 
     As noted above, the receiver in each embodiment of the OIS  150  may be selected from any of a CCD device, a time delay integration (TDI) camera, a photo-multiplier tube (PMT), a spectrometer, an OCR camera and the like. In general, CCDs, TDIs and PMTs are configured to collect image intensity variations across the substrate for specular signature analysis and variances associated flake/particle contamination. The spectrometer is configured to gather the light signal reflected/scattered from surface of the substrate  37  and generate an output representing the color spectrum components of the signal. The OCR gathers the light signal reflected/scattered from surface of the substrate  37  and generates an output representing the optical characters disposed on the upper surface of the substrate  37 . In any case, optics devices may be utilized to advantage. For example, in the case of the spectrometer, the received light signals may be propagated from a collection point to the spectrometer via a fiber optics bundle. Additionally, a diffuser lens may be coupled to the fiber-optic bundle to be used to effectively increase the field of view and send the spectrometer an averaged light spectrum of the image. 
     Alternatively, the receiver of the OIS  150  may include a combination of detector devices. For example, one embodiment of the receiver comprises a spectrometer and a CCD camera. In such a case, the spectrometer may be positioned adjacent to the CCD camera in a manner to allow both devices to share the same field of view of the substrate  37 . Such embodiments allow for multiple methods of process monitoring without significant increases to the data acquisition time. Illustrative process monitoring methods are described in more detail below. 
     It should be understood that the relationship of the transmitters (i.e., the light sources) and the receivers are merely illustrative. In each embodiment described above, the positions of the receivers and the transmitters may be reversed. For example, with regard to FIG. 2, the OIS  150 A may comprise a pair of receivers mounted where the light sources  56 A-B are shown. A light source can then be mounted where the receiver  58 A is shown. In such an embodiment, the receivers are about obliquely angled with respect to the upper surface of a substrate positioned directly below the light source. In operation, the receivers are positioned to receive reflected and/or scattered portion of the light from the surface of the substrate  37 . As the substrate  37  is moved between pod loaders  108 A and  108 B, the OIS  150 A scans the substrate  37 , the reflected and/or scattered light is then received by the receivers for processing as described below. The movement of the substrate  37  between pod loaders is identical to that shown in FIGS. 3A-C. 
     III. Transfer Chamber: 
     FIG. 6 is a perspective cutaway of a processing system  100  of the present invention comprising a transfer chamber  42  and a vacuum chamber  44  mounted thereon (see FIG.  3 A-C). The transfer chamber  42  and the vacuum chamber  44  are selectively communicable through an aperture  46  which can be sealed by a conventional apparatus such as a slit valve door window located above the slit valve door (not shown). The aperture  46  is sized to accommodate the transfer of substrates there through. A robot  50  is centrally disposed in the transfer chamber  42  and comprises a blade  48  configured to hold the substrate  37  coupled to the robot hub  51  by frog-leg type linkage  39 . The robot  50  enables rotational and radial movement of the blade  48  along a transfer plane, thereby shuttling substrates between various positions within the system. The transfer chamber  42  and the vacuum chamber  44  are preferably components of a processing system  100  such as the one shown in FIG.  1 A. Thus, the vacuum chamber  44  may be a load lock chamber  106  providing an interfacing chamber between a front-end environment and the transfer chamber  42 , while the transfer chamber  42  provides a vacuum environment communicable with various peripheral chambers. Alternatively, the vacuum chamber  44  may be a process chamber, such as a cooldown chamber or orientation chamber as shown in the embodiment described below in reference to FIGS. 12A-C. 
     As shown in FIG. 6 a transmitter unit  56  and a receiver unit  58  are externally mounted to a lid  52  of the transfer chamber  42 . In one embodiment, the transmitter unit  56  includes a light source  60  and beam-shaping optics  62  and is positioned to emit a signal  54  into the cavity  41  of the transfer chamber  42  via a view port  64 . The view port  64  comprises an opening formed in the lid  52  and is hermetically sealed with plate  66  made of a material transparent to the signal  54  of the light source  60 . In one embodiment, the plate  66  may comprise Quartz Glass™, for example, or any energy transparent medium such as glass, transparent polymers, GaAr, and the like, adapted to allow the transmission of the light. 
     In operation, the signal  54  propagates parallel to the x-axis shown in FIG.  2  and is directed onto an upper surface of a substrate  37  rotating (or otherwise moving relative to the signal  54 ) through the cavity  41  of the transfer chamber  42 . The signal defines a light projection  53  upon falling on the substrate  37 . As described in detail below, the spot size of the light projection  53  may be varied according to the substrate size by adjusting the beam shaping optics  62  and the position of the light source  60 . 
     In one embodiment the light source  60  can be, for example, a coherent light source such as a laser, a non-coherent broad-spectrum light source, or other non-coherent narrow spectrum source such as infrared. In other embodiments, the light source  60  may include illumination signals such as radio frequencies, microwaves, and the like. In general, the light source  60  is selected according to scattering intensity, brightness and cost. Where a laser source is used, the laser source is preferably operable at about 808 nm. However, other laser sources, such as 650 nm or 680 nm wavelength laser sources, may also be used. 
     In general, the spot size of the light projection  53  is substantially determined by the beam-shaping optics  62  and the position of the transmitter unit  56  relative to the substrate surface plane. The beam-shaping optics  62  is selected to provide a spot size according to the dimensions of the substrate. In one embodiment, the spot is concentrated into a tight light-line. The width of the line allows for accommodating the blade movement (e.g., vertical movement) across the light-line. For a 260 mm substrate, for example, the spot size of the light projection  53  is preferably at about 1 mm (width) and at about the width of the substrate 260 mm (length, y-axis) on the upper surface of a substrate. Thus, in operation, the entire breadth of a 260 mm substrate is exposed to the signal  54  after a single scan. However, in other embodiments, only a portion of the substrate is exposed to the signal  54 . With regard to particle detection, for example, typical sources of catastrophic process chamber contamination, such as flaking (also known as chamber excursions), provide hundreds of particles that may settle on the processing surface of a substrate. Although it is preferable to inspect the full substrate, successful process inspection often requires that only a portion of the contamination be to confirm the presence of a contaminated substrate. Process monitoring for other substrate characteristics (e.g., film thickness, end point confirmation, etc.) may also be accomplished with a limited surface inspection. 
     The receiver unit  58  is shown mounted in a view port  70  formed in the lid  52  and defines a signal path  61  toward the substrate  37  moving through the cavity  41 . The receiver unit  58  is secured above an energy transparent plate  72  made of a material selected according to the operating wavelength of the signal  54  and preferably is made of the same material as the plate  66  disposed in view port  64 . For example, where the signal source  60  is a laser source operating at about 808 nm, the material for the plates  66 ,  72  is selected to accommodate an 808 nm signal. The receiver unit  58  is positioned to receive a scattered portion  74  of the signal  54  from the substrate  37  during operation. The scattered and/or reflected portion  74  is represented by a multiplicity of arrows oriented at various angles relative to the upper surface of the substrate  37  and indicates the presence of an obstruction, such as particulate contamination or a device pattern disposed on the upper surface of the substrate  37 . A reflected portion  69  of the signal  54  propagates at angles relative to the substrate  37  substantially equal to the angle of incidence α. The reflected portion  69  represents the portion of the signal  54  substantially unobstructed upon intercepting the upper surface of the substrate  37 . 
     The receiver unit  58  includes an optics assembly  80  comprising one or more lens and a detector  82 . The detector  82  of the receiver unit  58  preferably comprises a charge-coupled device (CCD) line camera. A CCD line camera is a preferred detector because the angular relationship between the source and the receiver can be maintained across the full substrate thus producing a consistent illuminated receiving environment. By using a CCD line camera to successively scan a substrate in motion in the receiving environment, an image is formed. However, while CCD detectors are preferred, other detectors, including time delay integration (TDI) cameras, or photo-multiplier tubes (PMT&#39;s) may be used to advantage in embodiments of the invention. In other embodiments, the receiver unit  58  is selected from one or more of a spectrometer and an OCR receiver. 
     The foregoing description for positioning the transmitter unit  56  and receiver unit  58  is merely illustrative and other embodiments are possible. For instance, while FIG. 6 shows the transmitter unit  56  and the receiver unit  58  disposed outside the cavity  41  of the transfer chamber  42 , in another embodiment the transmitter unit  56  and the receiver unit  58  are positioned inside the cavity  41 , and thus, under vacuum conditions. In another embodiment, mirror surfaces can be located in the cavity  41  to allow more critical angles to be achieved. 
     The operation of embodiment shown in FIG. 6 is illustrated by FIGS. 7A-C which are top views of the processing system  100  showing the blade  48  and substrate  37  in various positions during rotation through the transfer chamber  42 . FIG. 3A shows the blade  48  immediately after initiating counter-clockwise rotation so that the leading edge  92  of the substrate  37  is positioned in the path of the signal  54 . Thus, a portion of the light projection  53 , represented by the shaded area, is shown intercepting the leading edge  92  of the substrate  37 . During the continued rotation of the blade  48 , shown by FIGS. 3B-C, the light projection  53  scans the upper surface of the substrate  37 . The light projection  53  illuminates obstruction  75  on the substrate  37  which causes scattering and/or reflection of the signal  54 . Although the obstruction  75  may be in the micrometer range it is shown greatly exaggerated for clarity. Obstruction  75  may be a process chamber flake, a surface defect (erosion, dishing, etc.), or an intended device feature. The scattered and/or reflected portion  74  of the signal  54  is then collected by the receiver unit  58 . Where the detector  82  is a CCD, the scattered and/or reflected portion  74  is focused by the receiver optics  80 , imaged onto the elements of the CCD, converted into an electrical signal and transmitted to the PMC  86  for processing. 
     It is understood that the foregoing sequence may be performed before and/or after the substrate  37  undergoes a processing cycle in a processing chamber. For example, FIGS. 3A-C may represent a substrate being transferred from a load lock chamber to a processing chamber along process inspection routes  122  and  124 . Alternatively, FIGS. 7A-C may represent a processed substrate being transferred to a cooldown chamber or being returned to a load lock  106  after it has been processed. 
     In another embodiment, process inspection is performed during retraction or extension of the robot  50  into or out of a processing chamber or service chamber, or load locks along inspection route  124 . FIGS. 8A-C illustrate the operation of such a process inspection embodiment. FIGS. 8A-C are top views of the processing system  100  showing the blade  48  and substrate  37  in various positions during linear movement through the transfer chamber  42  out of chamber  44 . 
     FIGS. 8A-C is a top view of the processing system  100  showing the blade  48  and substrate  37  disposed thereon during the extension of the blade  48  into the chamber  44  from the transfer chamber  42  via the aperture  46 . The chamber  44  may be any type chamber such as, for example, a process chamber, a cooldown chamber, a metrology chamber, or a substrate orientation chamber. In FIG. 8A the blade  48  is shown immediately after initiating linear movement from the vacuum chamber  44  to the transfer chamber  42  so that the leading edge  92  of the substrate  37  is positioned in the path of the signal  54 . Thus, a portion of the light projection  53 , represented by the shaded area, is shown intercepting the leading edge  92  of the substrate  37 . 
     In order to maximize the exposed surface area of the substrate  37 , the signal  54  preferably intercepts the substrate  37  as the substrate  37  exits the chamber  42  at the aperture  46 . Such a positioning ensures exposure of substantially the entire upper surface of the substrate  37  after full retraction of the blade  48 , thereby maximizing the surface area of the substrate  37  which is scanned by the signal  54 . During the continued linear movement of the blade  48 , shown by FIGS. 8B-C, the light projection  53  scans the upper surface of the substrate  37 . 
     The embodiments shown in FIGS. 4,  7 A-C, and  8 A-C are merely illustrative. In an alternative embodiment, a pair of transmitter units  56  and receiver units  58  may be used in combination to monitor a substrate during linear motion and rotational motion, respectively. Such an arrangement can improve the accuracy of detection. A person skilled in the art will recognize other embodiments. Further, while a single surface scan of the substrate provides a high degree of accuracy relative to perform the processing monitoring methods of the invention, additional methods may be employed to enhance process monitoring. For example, the robot blade  48  may be dithered, oscillated, or repositioned so that a given obstruction can be moved into the field of view of another CCD detector element in the array of elements or perhaps an auxiliary high resolution camera. Additionally, a multi-mode camera may be used where the focus, field of view, and the like may be changed automatically to enhance the view of the obstruction. Interpolating across multiple detector elements using the robot provides additional resolution for performing various monitoring methods. 
     In another embodiment, the OIS  150  is configured to receive primarily reflected light (as opposed to scattered) in a gray-field configuration from the transfer chamber  110 . Embodiments are shown in FIGS. 9 and 10. FIGS. 9 and 10 show a partial cross sectional view of the processing system  100  and, in particular, of a process chamber  114  and the transfer chamber  110 . The robot  113  is shown carrying a substrate  37  and positioned adjacent to the entry of the process chamber  114 . The receiver unit  58 C in FIG.  9  and the transmitter unit  56  are mounted to member  176  and disposed in a view port  120  with a field of view of the substrate  37 . In another embodiment, the receiver unit  58 D in FIG.  10  and the transmitter unit  56  are mounted to member  176  and disposed in a view port  120  with a field of view of the substrate  37 . The receiver units  58 C or  58 D are preferably any device adapted to receive spectral data. 
     When the substrate  37  is positioned below the OIS  150 C as shown, light emitted from the transmitter unit  56  is reflected and/or scattered from the upper surface of the substrate  37 . When the substrate  37  is positioned below the OIS  150 D as shown in FIG. 10, light emitted from the transmitter unit  56  is reflected and/or scattered from the upper surface of the substrate  37 . In some embodiments, the substrate  37  is scanned with an illumination source  56  in the manner described above. In other cases, all or substantially all of the substrate is illuminated with a broadband flash device or similar apparatus. In any case, the reflected portion is collected by the receiver unit  58 C in FIG. 9, or  58 D in FIG. 10, and transmitted to the PMC  86  for processing. In particular, the collected information is processed to identify spectral characteristics of the substrate  37 . Details of spectral analysis are described below. 
     In one embodiment, as illustrated by FIG. 9, the receiver unit may be a spectrometer  58 C designed to receive incoming energy/signal and output the distribution of spectral components and their intensities to determine the constituents of the energy. The spectrometer  58 C is coupled to the view coupled to the view port  66  via an optics assembly  170  comprising a fiber-optic cable and/or Fish-Eye, and/or diffuser lens and other optics to focus, shape, and control the signal to allow the spectrometer  58 C to view the substrate  37  as a whole and/or portions thereof. 
     In another embodiment, as shown in FIG. 10, the receiver unit  58  shown in FIG. 10 comprises an OCR camera  58 D. The OCR camera  58 D is configured to capture an image of characters located on the upper surface of the substrate  37  for identification purposes. It is contemplated that the characters may include bar codes and other symbolic identification markings. Such a device was described above and a detailed discussion is not needed. 
     While FIGS. 6,  7 A-C,  8 A-C,  9 , and  10  illustrate embodiments wherein the transmitter unit  56  and receiver unit  58  are disposed on or in the transfer chamber, other embodiments may be used to advantage. In general, the transmitter unit  56  and receiver unit  58  may be positioned at any point on the processing system  100  where the signal  54  may be directed onto the upper surface of a moving, or non-moving, substrate and scattered and/or reflected signals  74  may be detected by the receiver unit  58 . Multiple transmitters/receivers can be located throughout the system. 
     IV. Lid Assembly 
     FIGS.  11  and  12 A-C show a lid assembly  1100  illustrating one embodiment of an OIS  150 . The lid  1100  is adapted to be disposed on a (or otherwise be part of) a process chamber or service chamber. The lid assembly  1100  includes various devices and features which operate as parts of an OIS. The lid assembly  1100  generally includes a body defining three ports  1110 ,  1112 ,  1114  therein. In one embodiment, a first port  1110  provides line of sight for a receiver unit, or camera  1116 , such as a charge coupled device (CCD) for receiving optical inputs from within the chamber. A second and third port  1112  and  1114  are formed within the lid  1100  to enable one or more transmitter units, or light sources  1118 ,  1120 , to be coupled through each of the ports into the chamber and also to provide light traps (i.e., exits for reflected and/or scattered light from the substrate surface) for the light sources  1118  and  1120 . In one embodiment, the light sources  1118  and  1120  are a combination fiber optic bundle and light source configured to form a horizontal light-line. The camera  1116  and the light sources  1118 ,  1120  are each secured to the chamber by mounting brackets  1152 ,  1153 ,  1154 . In one embodiment, the light sources  1118  and  1120  can be halogen light sources or other light sources capable of operating in the 400 nm to 750 nm range. Each of the ports  1110 ,  1112 , and  1114  has an energy transparent window  1122 ,  1124 , and  1126  disposed therein to provide vacuum isolation within the chamber on which the lid assembly is disposed. In the particular embodiment shown, the lid assembly  1100  also includes optics assemblies  1121  and  1123  disposed between the windows  1124  and  1126  and the light sources  1118  and  1120 , respectively. The optics assemblies  1121 ,  1123  can include any combination of filters, diffusers, lenses and the like. 
     The lid assembly  1100  mounting the windows  1122 ,  1124 , and  1126  and the CCD or camera  1116  and light sources  1118 ,  1120  can be made of aluminum or other machineable materials that meets outgassing and porosity requirements of the vacuum environment. Each of the surfaces within the lid assembly  1100  are preferably machined or polished to provide a desired surface reflectivity. One embodiment allows the lid assembly  1100  to made of a metallic material comprising a surface  1130  having the appropriate roughness or polish. In each of the ports for the light sources  1118  and  1120  and the CCD  1116 , the surfaces are polished. For example, the surfaces in the CCD port  1110  can be finished to  32 RA, the surfaces in the first light source port  1114  can be finished to  16 RA and the surfaces in the second light source port  1112  can be finished to  8 RA. The surfaces are finished to a surface smoothness which minimizes scattering of secondary light back into the optical environment of the chamber. 
     The highly reflective surfaces are positioned so that reflected light is effectively directed out of the chamber through windows  1126  and/or  1124 . 
     FIGS. 12A-C show a cross-sectional view the lid assembly  1100  located at an upper end of a processing chamber  1101 , such as a cooldown chamber. The chamber  1101  generally includes a chamber body having sidewalls  1102  and a bottom  1104 . A support member  1106  may be disposed through the bottom of the chamber to receive and support a substrate  37  introduced into the chamber  1101 . The support member  1106  may include a cooling system, such as fluid channels and cooling fluid source, to provide substrate cooling for example. The lid assembly  1100  having an OIS  150 E mounted thereon is disposed at the upper surface of the chamber walls and forms a seal therewith. 
     The port  1110  for the CCD  1116  is disposed at a first angle θ 1  relative to a horizontal line in which the substrate  37  would be introduced into the chamber  1101  (i.e., a substrate transfer path). This angle enables the camera  1116  to have a line of sight view to the substrate  37  as the substrate  37  enters the chamber  1101  on a robot blade  48 . Each of the ports  1110 ,  1112 , and  1114  for the light sources  1118 ,  1120  are disposed at an angle such that a first light source  1118  provides front illumination of the substrate and a second light source  1120  provides rear illumination of a substrate  37  that is introduced into the chamber  1101  with respect to the CCD  1116 . Front and rear illumination may occur on introduction or retraction from the chamber  1101  simultaneously or separately, e.g., one on introduction, the other on retraction. The port  1112  provided for the first light source  1118  is disposed at a second angle θ 2  off set from the angle θ 1  of the port  1110  and camera  1116 . The port  1114  for the second light source  1120  (i.e., the rear illumination light source  1120 ) is disposed at yet a third angle θ 3  relative to the transfer plane of the substrate and offset from both the first and the second angles θ 1 , θ 2 . A signal reflecting surface  1128  is disposed on one wall of the port  1114  to enable the second light source  1120  to be disposed at a steeper angle of incidence with respect of the substrate  37  while still providing a required incident of light upon the substrate  37 . As shown in FIG. 12A, the angle of incidence of the optical beam emitted by the light source  1120  relative to the substrate  37  is θ 4 . 
     In some embodiments, the orientation of the camera  1116  and the light sources  1118 ,  1120  may be automatically adjusted (as opposed to manually). For example, although not shown, servos or similar actuators coupled to a control system may be used to move the various components adjust aperture size and focus from a remote location. In one embodiment, two cameras  1116  may be mounted side by side to enhance the view of the substrate and increase the resolution of the image if used in tandem. 
     Each of the ports  1112  and  1114  for the first and second light sources  1118 ,  1120  are positioned to act as a light trap for the other light source. That is, the port  1114  for the second light  1120  source acts as a light trap for the light from the first light source  1118  reflected and/or scattered off the substrate surface. Similarly, the port  1112  for the first light source  1118  acts as a light trap for light reflected from the second light source  1120 . The polished surface of the lid  1130  adjacent to the light source port  1126  may also act effectively as a light trap by minimizing back scatter, of the light, within the CCD  1116  line of sight. The interior surface of the lid  1130  adjacent to the light source port  1126  may be polishing so as to minimize scatter of light back to the camera on its principal axis. 
     Each of the ports  1112 ,  1114 , and  1110  for the CCD  1116  and the light sources  1118  and  1120  may also include optical filters such as polarizers, color spectrum filters, and other bandwidth selective mediums. The filters can be positioned on the atmospheric side of the windows  1126 ,  1122  and  1124  disposed in each of the openings in the ports  1112 ,  1114 , and  1110 . The filters may also be disposed within or integral to the windows  1122 ,  1124 , and  1126 . 
     Filters can be used to increase the contrast between a patterned background on the substrate  37  and obstructions on the substrate and minimize degradation of the image by rejecting longer wavelength improperly focused light, or by reducing the specular content of the light and increasing the scattering component. For example, in one embodiment, color spectrum filters can be used to enhance, or select, the images collected energy (i.e., signal energy) associated with obstructions. If material on the substrate, such as photoresist, is blue and obstructions are red, a red spectrum filter could be used on the source and on the camera to minimize the intensity of wavelengths associated with the photoresist and enhance the wavelengths associated with of the obstructions. 
     Linear polarizing filters can be used to discriminate between the specular and scattering components of the received light. For example, a patterned viewed through two linear polarization filters arranged so that they are 90° with respect to each other provide filtering of principally the scattering component of the light. Changes in the scattering component represent changes in substrate structuring pattern and/or contamination. Filters can be used to enhance optical recognition (i.e., OCR) for multiple purposes. For example, one filter may be used to enhance particle detection while another filter could be used to enhance character recognition, such as substrate identification characters. In one embodiment, light sources  1118 ,  1120  and the receiver CCD  1116  may comprise a plurality of different filters to provide a different image for multiple substrate scans to enhance process inspection. In another embodiment filters (not shown) are mounted between the CCD  1116  and port  1124  to allow the various filters to be installed independent of the CCD  1116  operation. 
     As can be seen in FIGS. 12A-C, the first light source  1118  for front illumination is directed at an angle away from the line of sight of the CCD  11   16 . The angle of incidence of the light source  1118  on the substrate  37  is determined so that the reflections from the light source  1118  are into the light trap source formed by the port  1114  for the second light source  1120 . Consequently, the CCD  1116  only collects the light, which is reflected and/or scattered back by obstructions on the surface of the substrate  37  from the illumination. The remaining reflected light will be absorbed or routed through the light traps  1112  and  1114  or reflected off surface  1130 . 
     The second light source  1120  is disposed to project the light at an angle toward the CCD  1116 . By illuminating the substrate  1108  at this angle, rear illumination is provided. As shown in FIGS. 12A-C, the second light source  1120  is disposed at an angle opposite to the direction in which the light source  1120  must be projected. The first light source  1118  impinges upon the inner surface  1128  of the signal port  1114  and is reflected down onto the substrate  37  at a desired angle. Reflective light along the normal projection of the second light source  1120  is reflected into the light trap formed by the first light source port  1112 . Light reflected by irregularities on the surface of the substrate  37  maybe reflected along the line of sight of the CCD  1116 . 
     FIGS. 12A-C illustrates both a first and a second light source  1118  and  1120 . However, a single light source, i.e., the first light source  1120  or the second light source  1118 , may be used to advantage depending upon needs of the specific process and substrate characteristics. For example, a detection of a smooth substrate may require illumination from a single light source. In contrast, a patterned substrate may best be inspected by using two light sources and polarizers. It is believed that embodiments having two light sources may be utilized to advantage by providing a contrast between images generated using both front and rear illumination. Information requiring receipt and interpretation by the detection system will be reflected along the line of sight of the camera or CCD to provide sufficient information to make the determination sufficient to the particular process. Moreover, a scan may be done on the insertion of the substrate  37  into the chamber using one of the light sources  1118  and  1120  and a different scan may be made as the substrate  37  is removed from the chamber  1101 , offering two different views of the same substrate  37  for process monitoring purposes. 
     Taken together, the three positions of the blade  48  extending into the chamber  1101  shown in FIGS. 12A-C illustrate a scanning process whereby the upper surface of the substrate  1108  is scanned. In operation, the optical information collected by the receiver unit  1116  (e.g., OCR camera) is used to analyze characteristics of the substrate  37 , such as particles, defects, surface damage, patterns, identifier information (e.g., alphanumeric characters). Methods for processing such information are discussed below. 
     In another embodiment, the lid assembly  1100  also includes a spectrometer  1150 . Thus, FIGS. 12A-C show a spectrometer  1150  mounted adjacent the light source  1120  on mounting member  1152 . The spectrometer  1150  is coupled to window  1126  via a fiber optic cable  1155 . The fiber optic cable center is disposed off-center, but proximate to the major axis of the reflected light from either light source  1120  and/or  1118 . In this configuration, the fiber optic cable  1155  captures large amounts of the broadband light source used to provide for other substrate inspections. In is contemplated that the spectrometer may be located and coupled to any window  1122 ,  1124 ,  1126  via a fiber optic cable. 
     V. Scanner 
     FIGS. 13A-C are cross-sectional views of a lid assembly  1300  illustrating one embodiment of an OIS  150 , for a process chamber  114 , such as a cooldown chamber. The chamber  114  generally includes a chamber body having sidewalls  1302  and a bottom  1304 . A support member  1306  may be disposed through the bottom of the chamber to receive and support a substrate  37  introduced into the chamber  114 . The support member  1306  may include a cooling system, such as fluid channels and cooling fluid source, to provide substrate cooling for example. 
     The OIS  150 F, comprising receiver  58 , transmitter  56 , and connecting member  1308  is provided at the upper surface of the chamber walls and sealably seats thereon. The lid assembly generally includes a body defining a port  1310  therein to provide a line of sight for receiver  58  and transmitter  56 . In one embodiment, the port  1310  is sealed with an energy transparent medium  1312  to allow the transmission of signals  54  from transmitter  56 . 
     Receiver  58  and transmitter  56  are coupled to each other through connecting member  1308  forming a scan assembly  1325 . Preferably, the transmitter  56  and receiver  58  are angled such that the reflected and/or scattered light  1307  enters receiver  58  to accentuate dark field illumination of light filed illumination. Scan assembly  1325  comprises a motor (not shown) and is adapted to traverse along the length and width of the lid assembly  1300  upon rod assembly  1318 . Preferably, the rod assembly  1308  allows the support member  1308  to fully traverse the substrate  37 . 
     FIGS. 13A-C illustrate the operation of a process inspection embodiment. FIGS. 13A-C are side views of the chamber  114  showing the scan assembly  1325  in various positions during movement along the processing chamber  114 . 
     FIG. 13A is a side view of the assembly  1300  showing the support member  1308  and substrate  37  disposed thereon in the processing chamber  114 . FIG. 13A shows the scan assembly  1325  immediately after initiating linear movement so that the leading edge  92  of the substrate  37  is within the path of the signal  54 . 
     The processing chamber  114  may be any type chamber such as, for example, a cooldown chamber or a substrate orientation chamber. Further, the OIS  15 OF may be located in any location upon tool  100  or in a dedicated inspection/metrology chamber to provide process monitoring. 
     The scan assembly  1325  continues to move from one side of the chamber  114  to an opposite side. To enhance resolution a series of scan can be performed with the OIS  15 OF stepping incrementally to a new region of the substrate. Thus, the signal  54  is moved across substrate  37 , thereby exposing the upper surface of the substrate  37  to the signal  54 . Substrate obstructions (particles, patterns, dishing, and the like) disposed on the upper surface of the substrate  37  cause the signal  54  to scatter and/or be reflected, shown by arrow  74 . The scattered portion  74  of the signal  54  is collected by the receiver unit  58 , converted into an electrical signal and transmitted to the PMC  86  for processing. FIGS. 13B-C illustrate the continued linear motion of the scan assembly  1325 , illuminated by signal  54  on the upper surface of the substrate  37 . 
     While embodiments shown in FIGS. 11 and 13 are described with reference to a process chamber  114 , embodiments may also be used in other areas of the tool such as the transfer chamber  110 , load lock interfaces and/or factory interface  104 . These locations will enable substrates to be inspected both before and after processing without impact to system throughput. 
     VI. Substrate Alignment and Detection 
     Determination of the location of a defect on the substrate can be made by identifying particular features on the substrate or blade. For example, in one embodiment the PMC  86  may be programmed to detect the leading edge, i.e., the substrate curvature which first enters the field-of-view of the receiver unit, and lagging edge, i.e., the last curvature to be detected by the receiver unit, during linear or rotational movement of the substrate. The substrate edges provide reference points which may then be used to generate one of two coordinates, i.e., X and Y because the acquisition rate and field of view of the CCD detector elements is known. The acquisition rate refers to the line acquisition frequency of the camera in generating the image during the movement of the substrate in the field-of-view of the CCD detector. Preferably, consecutive images are generated so that no overlapping or missing portion of the substrate results. Thus, the processed output of the CCD detector is a “photograph” of the complete substrate surface. The position of the defect/obstruction may be determined using the detector array of the CCD detector. 
     FIG. 14 illustrates a substrate detection system  1400  comprising two or more sensors that detect the substrate. In one embodiment, the detection system comprises a first sensor  1410 A and a second sensor  1410 B. The sensors detect the edge of the blade  48  and the substrate as it moves across the sensors  14010 A-B. 
     Operation of the detector is illustrated by FIG.  14 . FIG. 14 shows the substrate  37  supported by a blade  48  and in motion toward sensors  1410 A-B. As the substrate is moved into the optical path of the signals of the sensors  1410 A-B, the waveform output changes. The resultant change in output may be used to determine the presence, position, and velocity of the substrate. In particular, the detector output is an electrical signal denoting a logic high as a positive detection criteria. 
     In position A the output signal is low going high at T=t 1 , to show that substrate has just been detected. The output signal of  1410 A is high illustrates a high at T=t 1  as the blade is detected by sensor  1410 A. Position B illustrates the edge of the blade  48  crossing in front of sensor  1410 A, the waveform at T=t 2  shows a high. The output for sensor  1410 B is low indicating that the blade  48  has not yet been detected by detector  1410 B. Position C and E illustrate the edges of the blade  48  moving toward and crossing in front of sensor  1410 B. The waveform illustrates that at T=t 3  the signal goes high indicating the blade edge has been detected by the sensor  1410 B. 
     At T=t 2  and T=t 4  the blade has fully crossed the detector and the substrate is being sensed. As the substrate has an uneven reflective surface false triggers may be seen by areas  1430 A and  1430 B. As t 1 ,t 2 ,t 3 , and t 4  the areas  1430 A-B are do not care regions. Discrimination of these potentially false signals is accomplished by verification and comparison to timing intervals unique to the blade edge velocity, width, sensor spacing and angles. 
     The direction of motion of the substrate may be obtained by processing which sensor  1410 A or  1410 B detected the substrate first. Speed is determined but knowing the distance between the two sensors and dividing by total time. 
     VII. Conclusion of Apparatus Discussion 
     The foregoing embodiments provide a detection apparatus and method capable of monitoring substrates on-the-fly and in situ to the processing system. In situ, on-the-fly inspection minimizes the need for conventional stand-alone inspection platforms comprising dedicated actuating mechanisms such as are routinely used in the art. In other embodiments, the inspection is performed while the substrate is stationary, such as in the cooldown chamber. Further, embodiments of the present invention also use to advantage components typically included in any conventional processing system, such as the robot  113  (shown in FIG.  1 A), to enable a stageless inspection system. In any case, process monitoring can be performed at various positions in a processing system during normal and necessary operation sequences without transferring the substrates to a separate stand-alone inspection platform, thereby minimizing the impact on throughput. Consequently, each substrate moving through the process system can be inspected, thereby achieving an improvement over prior art systems and processes wherein only periodic sampling was possible due to the negative effect on throughput. 
     In production, embodiments of the invention provide viable means for determining whether production should be halted and a particular substrate should be examined more carefully for contamination, process related defects or routing errors. Thus, only selected substrates need undergo additional inspection. Substrates may not need further alignment or other positional adjustment if they are verified by the system. Further, the use of conventional features such as transfer chambers and view ports provided therein, process chambers such as cooldown or orientation chambers and transfer robots facilitates retrofitting existing systems with embodiments of the invention without the need for expensive time consuming retrofitting, cleaning and revalidation. 
     It should be noted that, although the embodiments of the invention facilitate on-the-fly inspection, other embodiments may be used to advantage in dedicated metrology platforms such as the inspection platform  135  (shown in FIG. 1A) described above. In particular, process monitoring methods described below, such as specular and/or scattering and spectral analysis, are not dependent on a specific mechanism and need not be performed on-the-fly. 
     VIII. Embedded Process Monitoring: 
     The inventors have discovered that the inspection devices described herein can be adapted to perform numerous inventive uses needed in processing systems, e.g., the determination of selected substrate characteristics including contamination, reflectivity, (specular or scattering) substrate type, discontinuity, orientation and centerfinding, as well as performing calibration of robots and the inspection equipment and monitoring robot behavior. The following discussion provides various embodiments for the present invention but is not intended to be exclusive, as those skilled in the art will readily recognize other possible embodiments. 
     The present invention also allows for process monitoring and subsequent further evaluation by the inspection system  135 . As a substrate is processed each OIS  150  produces spectral signatures, colors, and the like representing the substrate condition/status. In one embodiment, at each process step the PMC  86  monitors the condition using the data obtained from each OIS  150 . If a defect is detected in the condition the PMC  86  may make a determination as to whether the substrate should be sent to the inspection platform  135  for further analysis, or request operator intervention to remove the offending substrates within the system or continue on to its next scheduled processing step. In one embodiment, the inspection platform  135  is adapted to perform the identical tests as the OIS  150  but with much higher resolution. It can either inspect the full substrate or focus on specific regions(s). Unless there is a catastrophic process event that causes the process to stop, the metrology unit may examine the suspect substrate while the process continues, thereby avoiding a significant effect on throughput. 
     The inspection platform  135  is merely representative of one site for further inspection. In general, a system may include any number of inspection sites in addition to the OISs  150 . Thus, secondary and even tertiary inspection platforms may be provided in some embodiments. 
     Accordingly, the invention provides an apparatus and method for generating realtime information about selected characteristics of a substrate. Substrate inspection is preferably performed before and after processing. A preferred operation of the invention may be understood with reference to FIG.  1 A. Optical inspection of substrates may be initially accomplished by the OISs  150  located in the Factory Interface  104 . Thus, substrates can be analyzed prior to entry into the processing system vacuum environment where process chambers, service chambers are located  110 . Upon transfer of a substrate from the transfer chamber  110  into a process chamber  114  or service chamber  116  by the robot  113 , embodiments of the invention preferably operate to scan the substrate or otherwise capture an image of a portion, or all, of the substrate. Following processing, the substrates may again be scanned during the retraction of the substrate from the processing or service chamber. Additionally, a determination may be made regarding the process results. For example, the collected substrate image scan may be used to generate information on process uniformity and confirm process endpoint in was achieved. 
     Accordingly, the substrate can be continually monitored at various stations in the processing system  100 . In each instance, the resultant image produces information regarding process uniformity, smoothness, substrate type, orientation, centerfinding, discontinuity/edge defects (structural defects of the substrate due to thermal migration, for example, which may lead to portions of the substrate breaking off), specular and/or scattering signature, presence of particles and other process conditions. In one embodiment, the OIS  150  and PMC  86  operate to generate a map (e.g., two-dimensional or three-dimensional) of the substrate topology. The map can then be analyzed for texture characteristics such as planarity, uniformity and thickness. In addition, any substrate damage or defect, such as chips or fractures may be detected and mapped. Analysis can be enhanced by use of a color CCD detector and/or spectrometer. 
     Another substrate characteristic which may be determined, is the optical surface characteristics of the substrate. Information regarding optical surface characteristics can be used to determine whether certain process conditions have been successfully achieved, such as the endpoint of an etch process. Because the endpoint information is available in near real-time, i.e., substantially contemporaneously with the end of the process, and proximate the processing chamber, an under-processed substrate may be immediately returned for additional processing. Conventionally, substrates are taken to a remote location for endpoint examination. A subsequent determination that a substrate is under-processed typically results in the substrate being discarded because the time involved in returning the substrate for additional processing and possible growth of a native oxide is cost prohibitive. Furthermore, processing time is often extended to avoid potentially under processing substrates thereby reducing potential system throughput 
     Thus, the invention provides near real-time pre- and post-processing information regarding characteristics of a substrate during a process. Because the information is near real-time an immediate cost efficient decision can be made about how to handle the defective substrates. Further, because each substrate is inspected nearly immediately after processing in the system, as opposed to selected substrates from a batch, the information can be used to quickly rectify identified problems with our further compromising additional substrates and the processing environment. Thus, the process monitoring is nearly real time allowing the process recipe to be optimized and kept very close to the process tolerances thereby increasing the throughput. 
     Accordingly, the apparatus acts as a processing system “gate-keeper” which make continual first level assignments for substrate and system characteristics. In the event that acceptance criteria are not met, additional analysis can be performed by the inspection platform  135  or similar inspection platform. Such a system increases the opportunities for identifying a broad spectrum of process and handling routing defects in situ without any adverse effect on throughput. 
     A. Specular Analysis 
     In one embodiment, specular and/or scattering information is utilized to analyze characteristics of substrates. Such embodiments have particular applicability with patterned substrates which include topography variances that can cause scattering of incident light. Where patterned substrates are to be examined, the invention utilizes the unique intensity distribution of the signature produced by illuminating the substrate. The unique signature is the result of the patterns/structures formed on the substrate. Because the topography due to patterns on substrates that undergo a particular process is substantially repetitive, the signature will be at about consistent for each of the substrates processed yet different from other substrates processed. Thus, the unique signature may be stored in memory and used to compare surface conditions of substrates during production. Additionally, an average signature of the last “n” processed substrates, where n is an integer greater than 1, may be used as a dynamic reference (or calibration) substrate. 
     FIG. 15 represents a substrate image scan of 3 million data points showing a specular and/or scattering signature  150  for a calibration substrate scanned according to the techniques described above. The number of occurrences (y-axis), or readings by the detection equipment, at a particular intensity (x-axis) level are plotted. Subsequently, two different test substrates were scanned in a similar manner resulting in two separate and distinct specular signatures. To determine the relative conditions of the surfaces of the substrates, the signatures for the two test substrates were compared to the signature  150  for the calibration substrate signatures  150 . The graphs  152 ,  154  shown in FIG. 16 are the result of subtracting the number of occurrences at a given intensity or the calibration substrate from the number of occurrences at the same given intensity for the two test substrates. Thus, a first graph  152  represents the difference in the recorded intensity output of the detection equipment between the first test substrate and the calibration substrate and shows little variation. A second graph  154  represents the difference in the recorded output of the detection equipment between the second test substrate and the calibration substrate and shows a significant variation, indicating a difference in the surface conditions of the compared substrates. 
     Specular and/or scattering information can be collected, for example, using the above-described embodiments equipped with a line camera (e.g. the CCD  1116  shown in FIGS.  11  and  12 A-C). In such embodiments, the line camera positioned so that it collects light scattered from the substrate. In the case of a CCD camera, the camera&#39;s CCD detector consists of, for example, 4096 pixel elements oriented in a linear array. These elements serve to provide light intensity values in the x-axis. Values for the y-axis are generated by collecting a succession of data sets (x values), while the robot moves the substrate into (or out of) the cooldown chamber. Each pixel value in the data set ranges from 0 to 255 units and represents the intensity level of the collected light for a specific portion of the substrate. In this case this scanning process results in a data array that exceeds 16.5 million intensity values for each substrate. Among other things, data array can be used for particle detection and process conformance verification using specular and/or scattering signature analysis. 
     In one embodiment, the number of occurrences of the 0 to 255 intensity values can be expressed in an intensity distribution histogram. These intensity distribution histograms are directly associated with the structures on the substrate&#39;s surface, so they can be thought of as a unique specular and/or scattering signature of a substrate type that has been processed in a specific way. Given the amount of data involved, even subtle changes on the substrate&#39;s surface can cause substantial changes to the specular and/or scattering signature. These changes can be plotted to show the differences between specular and/or scattering signatures with respect to same reference. The reference signature which is subtracted from the other signatures should represent the ideal/desired processing target. In the event that a certain failure mode is known to exist for a specific process that signature can be used as a reference. The resulting difference plots represents changes in the structure on the substrates surface. FIG. 17 contains a series of over etch specular and/or scattering signature differences with respect to a nominal over etch time of 40 seconds. 
     For clarity, the first 100 out of the 255 intensity bins/ranges are shown. As indicated in FIG. 17, the changes in the specular and/or scattering signatures are substantial and due to different processing conditions. For example, at intensity bins below 18, etch times under the nominal 40 seconds exhibit about 260,000 more occurrences than the etch times above 40 seconds. While at intensity bins above 18, etch times under the nominal 40 seconds exhibit hundreds of thousands of occurrences less than the etch times above 40 seconds. These signature changes are the result of features/structures changing on the substrate as a result of processing in other words. Below 40 seconds, the structures have not fully emerged and above 40 seconds the etch process is attacking the photoresist and the aluminum lines. For clarity, FIG. 18 represents a conventional endpoint plot with the over etch intervals marked. 
     The specular and/or scattering signature approach can be expressed as mean brightness values (FIG. 19) to simplify the display provided to the user. The system operator would observe a succession of mean values as the system processes the substrates. Warning and alarm regions would be marked providing the user with quick feedback on process integrity. 
     FIG. 20 illustrates the mean intensity values of substrates calculated as a delta-mean for a reference specular and/or scattering signature. The delta-mean value represents the average weighted mean brightness value associated with the intensity distribution of a substrate with respect to a reference mean brightness values. FIG. 20 represents a succession of delta-mean values for substrates with respect to a reference substrate mean value. As mentioned above, warning and alarm control limits would be marked providing the user with quick feedback on process integrity. 
     Although this discussion has focused on specular and/or scattering signatures from etch processing, which already has a runtime endpoint system, embodiments of the invention are equally applicable to monitoring other process steps involving changes to structures on the substrate. For example, FIG. 21 reflects changes in specular and/or scattering signatures as strip time is increased. 
     EXAMPLE 
     Substrates were processed on a Centura system equipped with a DPS Metal Etch Chamber and an ASP strip/passivation chamber, both available from Applied Materials, Inc., located in Santa Clara, Calif. After etch and strip processing, this hot substrate is cooled to near room temperature in a cooldown chamber which includes an apparatus system according to an embodiment of the invention. 
     Processed substrates consisted of EPIC-generated substrates, utilizing Applied Materials equipment for all steps except for lithography. The photoresist/metal stack on the substrates was: 8000 A DUV photoresist/250 A TiN ARC/5500 A Al—Cu0.5%/250 A TiN/200 A Ti/3000 A thermal oxide. A dense pattern covered about 50% of the substrate, consisting of 0.25 μm lines/spaces. 
     All substrates were etched using a typical recipe. This etched the metal stack entirely, leaving approximately 5200 A of photoresist on most patterned features (3700 A at the shoulder of patterned lines). 
     As chip geometries shrink, a greater diversity is observed between the thin Metal 1 stack and the (especially on logic) highest level of metal. Communication chips are the most extreme, with 4000 A aluminum Metal 1 and a sometimes 4 um thick aluminum top metal. The capability of ASP chambers thus must match all metal stacks, while yield becomes more sensitive to corrosion and photoresist remaining on substrates. 
     An ASP recipe was employed for the purposes of this experiment. This recipe consisted of only one process step flowing only H 2 O at lower pressures than typically used in the ASP chamber. The new recipe: One step of 250 C temperature, 0.5 Torr pressure, 750 sccm H2O flow, 1400 W microwave power, variable time as specified in matrix. 
     Etched substrates were run measured with an embodiment of the invention various ASP processing times: 0, 10, 20, 26, 40, 50 seconds and longer up to 200 seconds. FIG. 22 shows that the intensity scans change for the various times up to 50 seconds of ASP processing. Since strip times longer than 40 seconds look the same as 40-50 seconds on the FIG. 22 scale, these are re-plotted to another graph, FIG.  23 . This indicates complete photoresist removal at 40 seconds. 
     No obvious trends are evident in these curves, so these are suspected of being noise. To verify the noise level, a single stripped substrate is inspected six times in succession to determine repeatability. This information is shown in FIG.  24 . Given the repeatability scans look similar to the FIG. 23 scans, thus it can be concluded that the substrates were completely stripped at 40 seconds, and that the noise level is confined to an envelope which is about 15,000 counts at the zero intensity and decaying for brighter intensity values. This envelope can be multiplied by 3 to provide a 3-sigma envelope. Anything beyond this envelope represents statistically valid data. In a production facility, sigma would be measured for each product type, and include a systematic study of sources of variation. 
     In any case, it can be seen that the 26 second strip time shows a peak at intensity bin 10 of 70,000 which is more than double the projected 3-sigma envelope. This is a reference measurement of the remaining photoresist. The photoresist should be detectable on a 35-second stripped substrate, since this signal would be&gt;3 sigma. Thus, 700 A of photoresist can be detected on a substrate. 
     In another embodiment, a moving average (i.e., box car average) of the mean values may be used. An average of successive mean values obtained during the production process may be obtained by summing a quantity of previous mean values and then dividing by the number of successive mean values summed. Once the average mean value has been obtained, the average mean value may be used as a moving reference to compare against a new substrate mean values. If the new substrate mean value is within tolerance values about the average mean value, a new reference average mean value is calculated by replacing one of the previous mean values with a current mean value from a current substrate and calculating as above. Warning an alarm control limits would be maintained to ensure the average mean value does not “creep” up or down possibly exceeding the process tolerances. 
     By using an optimally processed substrate as a reference signature, it is possible to quickly conduct a series of recipe experiments and observe the results without having to remove the substrate for independent verification. The scan may be done until the signature differences are relatively close. 
     In addition, images of patterned substrates which contain useful information obtained according to embodiments of the invention can be used for measuring other process-related parameters on substrates. For example, photoresist remaining on patterned substrates following metal etch and strip/passivation processing can be detected. 
     In metal etch processes, substrates are etched and stripped in-situ. In-situ stripping and passivation is required in order to prevent corrosion of the etched aluminum structures on the processed substrates. All photoresist must be removed from substrates because the photoresist, contains chlorine, that will cause corrosion of the aluminum following venting of the substrates to the manufacturing atmosphere containing some humidity. In a typical manufacturing situation, substrates will be exposed to air from one (1) hour to one (1) day before subsequent processing, where corrosion would be halted. 
     In a production environment, an OIS  150  of the invention could be used as a photoresist detector to prevent any substrates having residual photoresist thereon from being vented to atmosphere, where corrosion could occur. Embodiments of the invention could be used to measure a large number of substrate condition, such as large particles, residual photoresist, oxide thickness in the corners of substrates, etc. Other detection processes could be achieved using embodiments of the invention, limited only by the extent to which there are structure changes on the substrate surface. 
     In one embodiment, a number of processing systems  100  having inspection devices associated therewith could be networked together and could track individual substrates&#39; data to detect process integration issues. For example, oxide thickness could be tracked using spectral scans of the corners of substrates from oxide deposition, through oxide etch/strip to metal etch/strip. Metal stack changes in thickness and uniformity could similarly be tracked. Large particles could be tracked through various process steps so that the particle-generating hardware could be accurately and quickly identified. A networked inspection web could form the capability for process integration monitoring of substrates through the production line from start to finish of the manufacturing process. 
     At least one embodiment of the invention uses a two-tier particle detection method. The first tier uses various blob analysis techniques to determine approximate size and position of particles as represented by pixel occurrences. This information can also be used to determine the proximity of these pixel occurrences. The second tier uses the number of pixel occurrences above an intensity threshold to determine warning and alarm conditions. This approach allows approximate size and position of particles to be determined and individual pixel intensity thresholds to initiate an alarm. 
     In one embodiment, maximizing the contrast of the obstructions may be accomplished by selecting a polarized light source and linear polarization filters configured to select light that has been rotated at about 90 degrees from the polarization direction of the polarized light source. This “cross polarization” filtering method results in scattered light being the principal component entering the receiver. Signal scattering represents signals that have been rotated in a random fashion. Rotation occurs when the signal illuminates features/structures on the surface of the substrate. Using cross polarization allows for the selective removal of specular components of the reflected light pattern from substrates having and accentuating the scattered light to increase the contrast of obstructions. This approach serves to emphasize light contribution from structures of a patterned substrate thereby increasing sensitivity to intensity variations caused by process problems, substrate layer or thickness problems and/or routing errors. 
     In another embodiment, detecting changes in the intensity of the reflected signal is used to accentuate the reflected light caused, in some cases, by micro-mirrors formed by a “dished” substrate surface. The dished surface directs signal away from and towards the receiver. 
     B. Spectral Analysis 
     In other embodiments, spectral data acquired from a substrate is image is used to advantage. Spectral data may be collected using a spectrometer, color CCD camera or other devices known in the art. Illustrative embodiments using color acquisition devices were described above. For example, FIG.  9  and FIGS. 12A-C shows an OIS  150  using a spectrometer. 
     In one embodiment, the spectral data collected from a given substrate is used to generate a spectral signature, in much the same manner a specular signature (discussed earlier) is generated. The spectral signature represents the color constituents and intensity of the substrate. As described with regard to specular signatures, this color signature may then be compared to a reference color signature to determine characteristics such as the substrate type and residual materials in processing. 
     FIG. 25 illustrates the various regions of a substrate  37  were spectral data may be used to discern process issues. For example, substrate region  2505  is defined by a hashed area indicating various electronic devices etched and processed into the substrate during processing. Substrate region  2510  is a magnified view of a processed area of the substrate. Substrate region  2520  is an open area of the substrate  37  processed but without any etched circuitry. Substrate area  2530  is the overall view of the substrate  37  from a micro view, capturing all of the substrate in one view. Substrate region  2540  illustrates an area of substrate  37  that may be viewed by a receiving device of an OIS  150  as described above. 
     All of these regions provide spectral information when illuminated by a signal such as a light source. Differing color/spectral signatures may be used to determine regional and global process anomalies. For example, consider the case where the substrate region  2520  is normally a green color when viewed by a spectrometer. During the process inspection by the OIS  150  the spectrometer captures a view of the substrate region  2520  for a new substrate and discovers that the coloration has a blue component. As it is known that as substrate thickness varies, so does the color, the change from green to blue-green may indicate that there is a process issue, or perhaps, that the substrate layer thickness was incorrect. 
     Each area viewed  2510 ,  2520 ,  2530 , and  2540 , represent different process monitoring points and potential issues. For example, the coloration of the substrate region  2520  may indicate a change in the plasma density during processing. Over etching may also produce a different spectral signature. 
     In one embodiment, a succession of color scans of the same substrate are overlaid to provide a color contour map of the substrate. The color contour map enhances the process inspection by effectively illustrating color changes across the substrate. For example, a substrate having a uniform smooth surface normally would have little change in color variation. A substrate color contour map illustrating variations in color may relate to changes in substrate thickness and/or uniformity of the plasma process step. 
     In another embodiment, the amount of energy received is a function of the size of the fiber optic cable. For example, as shown in FIG. 9, a fiber optic cable  170  is used to direct the reflected light from light source  56 . The fiber optic cable is made from a plurality of strands of fiber optic filaments. Increasing the number of strands increases the amount of collected signal energy that is transmitted to the spectrometer  58 C. 
     In one embodiment, the angle of the detector or fiber optic cable is moved relative to the major axis of reflected light to enhance a particular color spectrum. Different spectrums relate to topographical and/or material differences in substrates such as substrate thickness, obstructions, type of substrate material, and the like. 
     C. Substrate Type Identification and Routing 
     In one embodiment, the invention determines the substrate type. As noted above, the pattern of substrates provides a unique specular and spectral signature. Accordingly, the invention may be used to recognize substrates based on their signature by scanning the substrate in the manner described above and transmitting the received signal to the PMC  86  for processing. As mentioned above with reference to FIG. 9 the receiver  58  receives the reflected and scattered portion of the light and determines the color of the substrate surface. The scanned pattern is then compared to stored color and/or specular signatures to determine the substrate type. Such an application provides the ability to detect a substrate that may have been misrouted through the system. For example, the OIS  150  could detect and reject a substrate with photoresist which has been mistakenly routed to a physical vapor deposition (PVD) chamber, thereby preventing potential damage to a process chamber and the substrate. In addition, recognition of the substrate pattern can be used to automatically change the process recipe according to the substrate type. Furthermore, substrate recognition allows the apparatus to automatically select the appropriate test/monitoring criteria for warning and alarm conditions. 
     D. 3D Imaging 
     The invention also enables monitoring of obstructions in three dimensions (3D). In one embodiment, referring again to FIG. 2, the substrate is scanned in two or more directions with light source  56 A and then scanned in two or more directions with light source  56 B. Receiver  58  captures the reflected and/or scattered signals from sources  56 A-B comprising two or more different images. As the sources  56 A-B are angled at about orthogonal from each other the light illumination impinges on the substrate surface obstructions from two differing angles (i.e. perspectives). Therefore, the image from light source  56 A therefore obtains information pertaining to one side of obstructions while the image from light source  56 B offers information pertaining to the opposite side of the obstruction. 
     It is contemplated that using light source  56 A and  56 B scanning may be done in any plane and substrate movement in any direction. For example, a substrate may be moved in one direction to be scanned by light source  56 A, and then moved in the same, or different direction, to be scanned by light source  56 B. In another embodiment, a plurality of light sources may be used at differing angles to scan the substrate. 
     Using data summation and image processing techniques, an approximate three-dimensional representation of the surface of the substrate may be obtained. This image enables the process monitoring system to ascertain the magnitude, height, and/or depth of a particular, obstruction, or patterned feature. Thus, three-dimensional imaging enables mapping of the surface topology of the substrate for comparison to other substrate topologies and determination of the relative uniformity of the surface. 
     E. Optical Character Recognition 
     In another embodiment, the invention provides for Optical Character Recognition (OCR). OCR refers to the detection and processing of alphanumeric characters through video imaging. Substrates are often identified by characters which are typically inscribed on the substrate surface. As illustrated in FIG. 10, the transmitter unit (shown hidden) and the receiver unit  58  of the present invention provide an apparatus capable of illuminating and detecting the characters and then directing a signal to the PMC  86  for processing. The receiver unit  58  is positioned to receive reflected and/or scattered light. In operation, a substrate is scanned in the manner described above. During the scan the signal  54  will strike the characters on the substrate and be reflected/scattered according to the geometry of the characters. As described above, the reflection/scattering is unique to the particular arrangement and configuration of the characters. OCR technology generally utilizes pattern recognition algorithms adapted to recognize and read images (e.g., characters, symbols, bar codes, and the like). 
     F. Orientation and Center-Finding 
     In another embodiment, the invention is used to determine a substrate&#39;s orientation and center. Orientation and center-finding are necessary to ensure proper positioning of the substrate in a chamber for processing. For example, etching often involves the use of a mask, guard-ring or clamp to cover certain portions of the substrate surface. In order to position the mask, guard-ring or clamp on the appropriate portions of the substrate the center of the substrate must be place accurately in the process chamber. Accordingly, the curvature of the substrate edge can be used to center/orient the substrate. Further, the flat or notch (typically provided on substrates) can be used to verify the orientation. 
     Substrate center-finding currently employs the use of one or more sensors to determine the center of a substrate. Use of the present invention enables substrate center-finding capability, thereby minimizing the need for additional sensors. In particular, the substrate can be scanned in the FI  104  for process monitoring and particle detection. Accordingly, the information received during the scan can be processed to determine the center and/or orientation. 
     In one embodiment, the center and/or orientation is found while the substrate is moving. As described above, a substrate can be illuminated and scanned by the OIS  150  (i.e., the transmitter unit  56  and the receiver unit  58 ) during the retraction, extension, and/or rotation of the blade. Thus, in one embodiment, the diameter and, therefore, the center, of the substrate can be determined by the PMC  86 . For example, as the substrate is moved into the path of the signal, the leading edge of a substrate is detected due to reflected light. Once the substrate passes through and beyond the signal, the receiver unit  58  ceases to detect a signal. The time between initial detection of a signal and ceasing detection is recorded. For a known robot speed, the recorded time may be used to calculate the diameter of the substrate. If the substrate is determined not to be centered relative to a calibrated value, an adjustment is made to the destination coordinate of the robot to correct the offset. It is understood that the particular method of calculating the substrate center is not limiting of the invention and people skilled in the art will recognize other possibilities. For example, in another embodiment, detection of the leading and lagging edges of the substrate may be associated with the encoder value of the robot at the time of detection. The encoder values can then be compared to calibrated values for substrates of the same diameter to determine any offset that must be accommodated. 
     In another embodiment, a substrate&#39;s orientation and center can be found while the substrate is positioned in a chamber (i.e., while the substrate is stationary), such as a cool down chamber, a degas chamber, or any other chamber of a processing system such as the one shown in FIG.  1 A. Center-finding and orientation can be simultaneously done by positioning the substrate in the field of view of the receiver unit  58 . FIGS. 13A-C shows one embodiment of an OIS  150  adapted for orientation and center-finding in cases where the substrate is not moving. The surface of the substrate is illuminated by the movement of the OIS components, rather than the movement of the substrate. Alternatively, with reference to FIGS. 9 and 10 the transmitter unit may be configured to illuminate a sufficient portion of the substrate without any movement of either the OIS components or the substrate (such as where the transmitter unit comprises a flash device and any respective optics). In this manner, the chamber acts both as an area for analysis of the substrate as well as performing a processing function such as cooling or degassing. As a result, analysis can proceed without affecting the throughput of the processing system. 
     G. Device Calibration 
     In addition to inspecting a substrate, the invention is also adapted for calibration. In one embodiment, the invention may be used to calibrate the detection devices. Because the illumination and detection optics of the invention may not be uniform, the operation must be normalized. In one embodiment, normalization is accomplished in the following way. When the OIS  150  (the transmitter unit and the receiver unit) is first installed, a substrate will be placed upside down on a robot blade to provide a scattering surface. The robot blade will then move the substrate under the OIS  150 . During the rotation or linear movement of the blade, both peak-to-peak and root-mean-square (RMS) measurements are made across the surface of the substrate taken by the OIS  150  and transmitted to the PMC  86 . A comparison is then made between the average reading of each OIS  150  measurement to determine the correction factors necessary to normalize the system. Subsequently, the substrate is removed and the solid portion of the robot blade (i.e., excluding holes and edges) is then scanned in a similar fashion. The peak-to-peak and average intensity values on the blade is then compared to the normalized correction factors to determine appropriate blade correction factors across its stroke. With the blade normalization factors in place, the blade can act as a resident calibration reference. Thus, the OIS  150  in conjunction with the PMC  86  can monitor the empty blade during normal operation to determine if the receiver and transmitter are functioning properly. If the receiver and transmitter are contaminated, or degraded, it will be detected by the foregoing background test. Also, the planarity and consistency of the blade are monitored and confirmed. 
     H. Blade Contamination 
     Additionally, contamination disposed on the surface of the blade is also detected by the test described in the foregoing embodiment. Contamination on the blade indicates that the backsides of substrates are being scratched at some point during the handling of the substrate and/or residual process byproducts have collected on the substrate. Thus, if contamination is detected on the blade, the system can be halted for inspection, thereby preventing further contamination to the processing environment. 
     I. Robot Calibration 
     In another embodiment, the OIS  150  facilitates robot calibration. The processing system robots, such as the transfer chamber robot  113 , periodically require calibration in order to ensure proper orientation and alignment. Because the OIS  150  is mounted at a fixed location on a processing system, the OIS  150  can provide a point of reference for the transfer chamber robot calibration to the PMC  86 . Once the blade normalization factors have been determined, as described above, the blade features can be detected to verify the robot position. Velocity and vibration can be monitored to monitor/adjust proportional, integral and differential (PID) values of the motion control system. Sufficient variance between the detected position values and the calibrated position values stored by the PMC  86  indicates misalignment of the blade. The misalignment can therefore be corrected automatically. 
     J. Robot Behavior 
     The invention also enables monitoring of robot behavior. For example, as the robot blade is rotated through the optical path  61  (shown in FIG. 6) of the receiver unit  58 , the blade edge nearest to the center of rotation will enter into the optical path first. This edge will then enter the field-of-views (FOVs) of each detector element successively at a rate which is determined by the blade velocity. This allows the OIS  150  to independently monitor the behavior of a robot including characteristics such as settling time, accelerations and stability can be measured/monitored. The collected data can be used to manually or automatically set the PID parameters of the robot  113 . 
     Various other possible applications are not discussed here in detail. For example, the invention may be used to detect the presence of a substrate on a robot blade as well as determining whether the substrate is in a blade clamp used to secure the substrate during the movement of the blade. Those skilled in the art will recognize other applications contemplated by the present invention. 
     Thus, the invention facilitates the integration of numerous functions currently achieved by different components in a typical processing tool. One or more OIS units  150  advantageously positioned, such as in a transfer chamber, can perform multiple process monitoring functions. Accordingly, the invention provides a multi-purpose apparatus capable of achieving a relatively higher level of system integration and reducing the system operating costs. 
     K. First Wafer Effect 
     One common condition in semiconductor processing is known as “first wafer effect.” First wafer (i.e. substrate) effect is the impact of clean chamber conditions on substrate processing. Chambers must be cleaned periodically to remove residue build-up which accumulates over time on the internal the chamber surfaces. However, it was discovered that the pre-cleaning substrate processing results differed from the post-cleaning processing results. In particular, the first N number of substrates after a cleaning cycle exhibited different characteristics from subsequently processed substrates. Accordingly, a cleaned chamber is typically subjected to a seasoning process whereby the chamber is allowed to reach an equilibrium under which substrates are substantially uniformly processed. The seasoning involves operating the chamber under processing conditions (or modified processing conditions in order to accelerate the desired result) to allow the chamber surfaces to be coated with material. However, one problem with a seasoning process is determining when the chamber is sufficiently seasoned. 
     One embodiment of the invention allows for an end-point detection of a seasoning process. Specifically, substrates are processed in a cleaned chamber during the seasoning of the chamber. Each substrate is then inspected by one or more OIS  150 . Once a processed substrate exhibits predetermined characteristics, the chamber is known to be sufficiently seasoned. 
     L. Throughput Monitoring 
     In another embodiment, throughput is monitored. Throughput can be monitored by determining when a given substrate enters the processing system and when the substrate exits the processing system (or completes a particular processing phase within the system). In addition, the time the substrate is resident in the cooldown chamber can also be observed and recorded. The data collected according to this method for multiple substrates can then be used to determine peak throughput, average throughput, frequency of arrival, variability of frequency and other related information. 
     M. Process Monitoring Normalization 
     In one embodiment, process monitoring differences are normalized. The process system  100  may contain a plurality of OIS  150  each monitoring a different area of the process. Each of the OISs  150  contributes a baseline process reading that fluctuates as substrates are processed. Overtime, the fluctuations maybe different enough between each OIS  150  to cause a false process degradation reading and alarm. To ensure minimal false alarms, a normalization substrate is sent through the process system and measured by each OIS  150 . Any variation between OISs  150  are normalized to the normalization substrate. 
     In one embodiment, the reference wafer may be used to calibrate other processing systems  100 . For example, if processing system  100  has known values based on a reference substrate, the same, or similar values, are expected at another identical processing system. 
     IX. Data Processing Systems 
     A program product readable by the PMC  86  determines which tasks are performable on a substrate. Preferably, the program product is software readable by the PMC  86  and includes code to generate at least substrate positional information, substrate reflectivity information, specular and/or scattering information, substrate defect information, substrate damage information, particle contamination information for smooth and patterned substrates, particle contamination information for the robot blade, alphanumeric character information, robot behavior information, calibration information for the robot and the detection devices and any combination thereof. 
     In one embodiment, the invention may be implemented as a computer program-product for use with the control PMC  86 . The program(s) defining the functions of the embodiments described herein can be provided to a computer via a variety of signal-bearing media, which include but are not limited to, (i) information permanently stored on non-writable storage media (e.g. read-only memory devices within a computer such as read only CD-ROM disks readable by a CD-ROM or DVD drive; (ii) alterable information stored on a writable storage media (e.g. floppy disks within diskette drive or hard-disk drive); or (iii) information conveyed to a computer by communications medium, such as through a computer or telephone network, including wireless communication. Such signal-bearing media, when carrying computer-readable instructions that direct the functions of the present invention, represent alternative embodiments of the present invention. It may also be noted that portions of the product program may be developed and implemented independently, but when combined together are embodiments of the present invention. 
     FIG. 26 is a high-level architecture of one embodiment for a system  2600  configured to perform particle detection and other process monitoring methods. Although described separately from the PMC  86 , the system  2600  may be an embodiment of the PMC  86  or may be integrated with the PMC  86 . 
     The system  2600  generally includes an application layer  2602 , a driver layer  2604 , a hardware interface layer  2606 , an internal hardware layer  2608 , an external hardware layer  2610  and a factory interface layer  2612 . Each layer of the system  2600  may include any combination of hardware and software adapted to support particular functionality. In general, the application layer  2602 , driver layer  2604 , hardware interface layer  2606  and internal hardware layer  2608  are components of the Optical Inspection Systems (OIS)  150  described above. The external hardware layer  2610  represents any system in which an OIS  150  has been implemented. For example, the external hardware layer  2610  may be the cluster tool described above with reference to FIG.  2 . The factory interface layer  2612  represents the access point between peripheral devices and the OIS  150  and the external hardware layer  2610 . In one embodiment, the factory interface layer  2612  includes a host and a data collection server. 
     The application layer  2602  comprises a GUI (graphical user interface)  2620 , a server process  2622 , a particle detection process  2624 , a process monitoring process  2626  and a database  2628 . The GUI  2620  is a task configured to interface a user and the server process  2622 . In some embodiments, the GUI  2622  comprises dialog boxes (displayable on a monitor) which convey or request information from the user. In particular, the GUI  2622  operates to generate local requests in response to user issued commands. The commands may be input to any input device such as a keyboard, keypad, light-pen, touch-screen, track-ball, or speech recognition unit, audio/video player, and the like. 
     The local requests generated by the GUI  2620  are sent to the server process  2622  for processing. In addition to receiving requests from local clients such as the GUI  2622 , the server process  2622  may also receive requests from remote clients. In FIG. 26, the remote clients are represented by the external hardware layer  2610  and the external interface layer  2612 . 
     In response to the various client requests, the server process  2622  takes steps to generate a reply or otherwise handle the request. For example, the user-issued command from the GUI  2620  may cause the server process  2622  to call the particle detection process  2624  or the process monitoring process  2626 , both of which are described in more detail below. Additionally, the server process  2622  is responsible for communicating with the other layers of the system  2600 . The server process  2622  is further adapted to perform the initialization of the system  2600 . Initialization may include reading a configuration file containing information for the configuration of system  2600 . The configuration file may be stored in the database  2628 . Thus, the server process  2622  operates as a central information managing entity for the application layer  2602 . 
     In general, the particle detection process  2624  supports the inspection of substrate images for particles and the generation of reports. To this end, the particle detection process  2624  implements one or more particle detection algorithms. Examples of algorithms include “Blob” analysis algorithms and “pixel” analysis algorithms. The substrates inspected by the process  2624  may be smooth (unpatterned) or patterned. 
     The process monitoring process  2626  implements one or more process monitoring algorithms such as mean intensity analysis. In general, the process monitoring process  2626  supports the inspection of histograms and the generation of comparison plots. Embodiments of the particle detection process  2624  and the process monitoring process  2626  are described below with reference to FIG. 27-28. 
     The application layer  2602  communicates with the other layers of the system  2600  through one of various interfaces. Illustratively, the application layer  2602  includes a Semiconductor Equipment Communications Standard (SECS) interface  2630 , a reporter interface  2632 , a camera interface  2634 , and a light source interface  2636 . 
     The SECS interface  2630  reformats and communicates information between the server process  2622  and remote clients. The remote clients are represented by the external hardware layer  2610  and the external interface layer  2612 . 
     The reporter interface  2632  is an interface task responsible for generating reports each time a substrate is inspected and then storing the reports to a local or remote disk storage facility. In one embodiment, the disk storage facility is a part of the factory interface layer  2612 . 
     The camera interface  2634  is an interface task configured to support the operation of the receiver units (and other detecting devices, such as the substrate sensors) described above and represented by the internal hardware layer  2608 . In general, the camera interface  2634  assists in the acquisition of substrate images, performing process monitoring and particle detection and setting up the receiver units. Setting up the receiver units may include downloading the receiver settings, focusing the receiver and adjusting the position (orientation) of the receiver. In addition, the camera interface  2634  initiates a request for report generation (handled by the reporter interface  2632 ). In operation, the camera interface  2634  receives instructions for the operation of the receiver units from the server process  2622 . The instructions are then sent to the internal hardware layer  2608  via the driver layer  2604  and hardware interface layer  2606 . Command responses are subsequently received by the camera interface  2634  (from the driver layer  2604 ) and transmitted to the server process  2622 . In one embodiment, the driver layer  2604  comprises a National Instruments Image driver (NI IMAQ) driver and the hardware interface layer  2606  comprises a Frame Grabber Card with RS232 and TTL ports, each adapted to support the messages routed between the camera interface  2634  any internal hardware layer  2608 . 
     The light source interface  2634  is an interface task configured to support the operation of the transmitter units described above and represented by the internal hardware layer  2608 . In general, the functions of the light source interface  2634  include determining the current light intensity and adjusting the light intensity. In operation, information received from the server process  2622  is transmitted via the light source interface  2634  to a driver in the driver layer  2604  and then to a card in the hardware interface layer  2606 . In one embodiment, the driver is an Omega ADLIB driver and the card is a DI/DO card. Responses from the internal hardware layer  2608  are routed to the light source interface  2634  in reverse order. 
     Although shown as a single system, the components of application layer  2602  may be distributed in a networked environment. For example, the GUI  2620  may be located on a workstation networked to a remotely located server computer on which the server process  2622 , particle detector application and process monitoring application reside. 
     FIG. 27 is a flow diagram for a method  2700  for program control of process monitoring and particle detection using the system  2600 . For brevity, the process monitoring is limited to specular analysis. However, persons skilled in the art will recognize application to other process monitoring embodiments of the invention, including spectral analysis. 
     Method  2700  is entered into at step  2705  when the system  2600  is activated. At step  2710 , the system  2600  is initialized and is ready to receive program input events. At step  2712  method  2700  receives an event. 
     At step  2715 , the method determines whether a system configuration has occurred. System configuration events include configuring data storage directories, establishing defect maps, setting alarms, defect count thresholds, and other program settings. If a system configuration event has not occurred, method  2700  proceeds to step  2725  described below. If a system configuration event has occurred, method  2700  proceeds to step  2720  to obtain and set the system configurations. At step  2720 , the behavior of the program can be tuned, runtime counters set to track the operation of the program, and other system configurations set via system parameters contained within one or more data structures. In one embodiment, the data structures containing the system configurations may be stored within the database  2628  (shown in FIG.  26 ). 
     At step  2725 , method  2700  determines whether a system set up event has occurred. If not, method  2700  proceeds to step  2735 . System set-up events include receiver calibration (e.g., alignment and focus), setting receiver sampling rates, setting receiver parameters, and other system adjustments. If a system set up event has occurred, method  2700  proceeds to step  2730  to setup the system. Illustratively, step  2730  includes allowing the user to view and adjust specular images and respective statistical information of the signal pattern, thereby providing the user with meaningful feedback for adjusting the receiver  616  alignment characteristics.In addition, at step  2730 , the receiver sampling rate is set. In one embodiment, step  2730  includes allowing the user to align and adjust the transmitter units independently to achieve a desired illumination of the substrate. 
     At step  2735 , method  2700  determines whether the event is for particle detection or process monitoring. If not, method  2700  proceeds to step  2745 . If the event is for particle detection, method  2700  proceeds to step  2740  to detect contamination on the substrate. One embodiment of a method for particle detection/process monitoring is described below with reference to FIG.  28 . 
     At step  2745 , the method  2700  queries whether the event is a termination event, such as when a user closes the active application. If so, the method  2700  is exited at step  2755 . Otherwise, the method  2700  handles the event at step  2750  and then returns to step  2712  to get the next event. 
     FIG. 28 is a flow diagram illustrating a method  2800  for particle detection and process monitoring. Method  2800  is entered into at step  2805  from step  2740 . At step  2810 , the PMC  86  operates to detect the incoming substrate. One method for detecting a substrate is described above with reference to FIG.  14 . At step  2815 , the substrate is scanned or otherwise illuminated and the resultant signal patterns are stored. Illustrative methods of scanning/illuminating the substrate are described above. 
     At step  2820 , method  2800  generates a histogram (also referred to herein as the current histogram) of pixel intensity based on information collected at step  2815 . In addition, a mean intensity value for the substrate is calculated. 
     The method  2800  then proceeds along two logic paths according to the desired processing. In the case of particle detection, the method  2800  proceeds via logic path  2822  to step  2825 . In the case of process monitoring, the method  2800  proceeds via logic path  2824  to step  2850 . 
     If method  2800  proceed via path  2822 , the information is binarized at step  2825 . Binarization is the binary representation of a gray-scale substrate image which is represented as an array of pixel values, illustratively between 0 and 255, where 0 is black and 255 is white. A gray-scale image is binarized by selecting a threshold intensity such that each value below the threshold is black and each value above the threshold is white. The value of the threshold can be determined empirically according to a particular application. 
     Further, at step  2825 , morphological operations are performed to manipulate and enhance the captured image by filtering noise and other extraneous signal information. Noise may be due to substrate deformations and vibration (e.g. the substrate is not perfectly flat or motionless at all times) which inadvertently causes variations (e.g., power modulation) in the scattering/reflection of the signal. Moreover, changes and contamination within the chamber such as particles floating in the chamber, optical degradation of window, heat flow within the chamber, and the like, are also time-variant and thus impart noise. Additionally, electrical noise (e.g., electronic noise, white noise, pink noise and the like) is also imparted by both the transmitter unit  56  and the receiver  58 . 
     Methodologies to filter the signal noise are well known but depend upon the type of noise being filtered. Some methodologies include filtering the received signal using digital signal processing (DSP), electronic filters (e.g., low pass, high pass, band pass, and the like), signal sampling, averaging, and the like. 
     Image enhancement is accomplished using known spectral selection algorithms that can enhance image contrast and color, or by spectral filters to block unwanted spectrums. Moreover, image enhancement may be accomplished through DSP and other digital enhancement techniques well known in the art. 
     At step  2830 , method  2800  searches the substrate image for particles based on illumination intensity and size. Blob analysis utilizes pixel intensity and proximity as a means to identify the size and location of particles in an area on the substrate. Taken together steps  2825  and  2830  constitute “blob” analysis. 
     The results determined by the “blob” analysis are then analyzed at step  2835 . In addition, a status of the substrate is rendered at step  2835 . In one embodiment, the substrate status includes a passing status, a warning status, and failing status. The user may then be notified of the status, for example, by an audible or visual signal. Upon analyzing the histogram data and particle data, method  2800  proceeds to step  2840  to generate reports including an output substrate image, a histogram data report, and defect summary to the end user. The method then exits at step  2845  and returns to method  2700 . 
     Returning to step  2820 , if selection is made to proceed via logic path  2824 , the method  2800  proceeds to step  2850 . At step  2850 , the current histogram data generated at step  2820  is plotted. At step  2852 , the histogram plot is compared to a reference histogram and the result is plotted to represent the difference between the current histogram and the reference histogram. At step  2854 , method  2800  plots a trend of the mean intensity of the current histogram against the reference histogram. An example of a graph illustrating this trend is described above with reference to FIG.  20 . The results of steps  2852  and  2854  are analyzed to determine a status of the substrate at step  2856 . In one embodiment, the substrate status includes a passing status, a warning status, and failing status. The method  2800  then proceeds to step  2840  to generate reports which can be viewed by an end user. The reports may include an output substrate image, a histogram data report, and defect summary. 
     In one embodiment, an alarm is issued to the user upon the occurrence of predetermined events indicative of a defective substrate. A user is allowed to define alarm criteria based on number of occurrences that take place above a user-defined intensity threshold. Accordingly, the alarm detection thresholds can be moved closer to the noise floor established by a patterned substrate. Occurrences of intensities, which exceed the threshold are totaled and compared to a user-defined count value threshold. If the totaled occurrences exceed the count value an alarm is issued. For example, the intensity threshold level may be set so that 3,500 counts (+/−50 counts) are accumulated across the image. Upon encountering a contaminated wafer and obtaining 3,555 counts, the 5 counts above the 3,550 would cause an alarm condition to occur. As the count number increases above the count threshold the confidence in alarming increases accordingly. This represents a secondary decision quality score and can be used to establish confidence intervals. 
     In another embodiment, an automated mode is implemented for defining the alarm and warning thresholds. The automated mode utilized statistical values such as the mean and standard deviation of intensity across one or multiple reference substrates. The alarm thresholds are then based on some multiple of the standard deviation that could be selected by the user or predetermined based on empirical data. The standard deviation for smooth wafers would be much smaller than patterned wafers so the detection threshold would be much nearer to the mean. Such an automated approach avoids any undesirable effect resulting from subjective input from a user setting the alarm and warning thresholds. 
     While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.