Patent Publication Number: US-11036125-B2

Title: Substrate positioning apparatus and methods

Description:
TECHNICAL FIELD 
     Embodiments of the present disclosure relate generally to processing and aligning workpieces such as substrates and, more specifically, to an apparatus and a method for processing workpieces utilizing a positioning apparatus. 
     BACKGROUND 
     Integrated circuits are manufactured by processes which involve placement of substrates in chambers including holding or “load lock” chambers and a variety of substrate processing chambers, including, but not limited to deposition chambers, thermal processing chambers, etching chambers, plasma chambers, and other chambers to process a substrate. More than one process may be performed in one chamber. For example, plasma processing, thermal processing and etching may be performed in a single chamber or separate chambers. In many semiconductor processing systems, substrates are supplied to chambers by one or more front opening unified pods (FOUPs) including robotic arms or robot arms. Processing of substrates such as producing patterned material on a substrate requires controlled methods for deposition and removal of exposed material. Before deposition and removal, however, accurate placement of the substrate is an important aspect of process control. 
     Due to several reasons, such as variations in substrate placement in a FOUP, substrate placement in processing chambers and consistency and repeatability of wafer transfer from robot arms, substrates are not exactly picked and placed similarly. Therefore, there is a possibility that different substrates are not placed exactly at the same position in a process chamber. This can affect yield performance for processes sensitive to slight variation in flow condition, line of sight, or other process-significant physics or chemistry. 
     Traditionally, detecting a center (or an edge) of a round silicon substrate (also called a wafer) involves using a series of light emitting diodes and sensors, where the wafer blocks the path of light emitted from some of the emitting diodes. This approach is sufficient for round wafers with a sharp edge. However, it has been determined that improved substrate positioning apparatus and methods are required for other generic shapes, such as a polygon, e.g., a rectangular or square substrate, as the traditional methods for detecting the position of round substrates or wafers are inadequate for substrates or wafers that are not round. 
     SUMMARY 
     One or more embodiments of the disclosure are directed to substrate processing apparatus comprising a chamber and a substrate support. The substrate support is configured to support a substrate comprising a top surface and a bottom surface defining a substrate thickness. The substrate support is configured to rotate the substrate 360 degrees through a plurality of rotational angular positions within the chamber. A laser is positioned to direct a radiation beam along the thickness between the top surface and the bottom surface. A sensor is positioned opposite the laser to detect radiation transmitted along the thickness of the substrate between the top surface and the bottom surface. A controller is configured to analyze a signal strength of the radiation detected by the sensor at the plurality of rotational angular positions and to correlate the signal strength at the plurality of rotational angular positions to a position within the chamber. 
     Additional embodiments of the disclosure are directed to extreme ultraviolet (EUV) mask production system. A holding chamber provides access to a substrate handling vacuum chamber including a plurality of ports to provide access to a vacuum chamber including, a physical vapor deposition chamber, a pre-clean chamber, and a multi-cathode PVD chamber. An EUV mask blank loading system is configured to load an EUV mask blank comprising a top surface and a bottom surface defining an EUV mask blank thickness, in at least one of the holding chamber and the vacuum chamber. A substrate support is configured to support and rotate the EUV mask blank 360 degrees through a plurality of rotational angular positions within at least one of the holding chamber the vacuum chamber. A laser is positioned to direct a radiation beam along the thickness between the top surface and the bottom surface. A sensor is positioned opposite the laser to detect radiation transmitted along the thickness of the substrate between the top surface and the bottom surface. A controller is configured to analyze a signal strength of the radiation detected by the sensor at the plurality of rotational angular positions and to correlate the signal strength at the plurality of rotational angular positions to a position within the vacuum chamber. 
     Further embodiments of the disclosure are directed to methods of positioning a substrate in a chamber. A rectangular substrate is placed in a chamber on a substrate support. The substrate comprises a top surface and a bottom surface defining a substrate thickness. The substrate is rotated 360 degrees through a plurality of rotational angular positions within the chamber. A laser directs a radiation beam along the thickness between the top surface and the bottom surface. Radiation from the radiation beam is transmitted along the thickness of the substrate between the top surface and the bottom surface is detected. The signal strength of the radiation detected at the plurality of rotational angular positions is analyzed and the signal strength is correlated at the plurality of rotational angular positions to a position within the chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  is a top plan view of one embodiment of an exemplary processing tool that is used in accordance with one or more embodiment of the disclosure; 
         FIG. 2A  is a schematic top view of a substrate alignment apparatus according on one or more embodiments of the disclosure; 
         FIG. 2B  is a side view of a portion of the substrate alignment apparatus shown in  FIG. 2A ; 
         FIG. 3A  is a top plan view of a rectangular substrate that is aligned in an alignment apparatus in accordance with an embodiment of the disclosure; 
         FIG. 3B  is a top plan view of a substrate alignment apparatus showing a rectangular substrate being aligned in accordance with an embodiment of the disclosure; 
         FIG. 3C  is a top plan view of a substrate alignment apparatus showing a rectangular substrate being aligned in accordance with an embodiment of the disclosure; 
         FIG. 3D  is a top plan view of a substrate alignment apparatus showing a rectangular substrate being aligned in accordance with an embodiment of the disclosure; 
         FIG. 4A  is a graph of beam path length during a measurement process according to an embodiment; 
         FIG. 4B  is a graph of beam signal strength during a measurement process according to an embodiment; and 
         FIG. 5A  is a top plan view of a rectangular substrate that is aligned in a substrate alignment apparatus in accordance with an embodiment of the disclosure; 
         FIG. 5B  is a graph of path length versus angle of rotation of the substrate in  FIG. 5A ; 
         FIG. 6  is a top plan view of a substrate alignment apparatus in accordance with an embodiment of the disclosure; and 
         FIG. 7  is a top view of an exemplary substrate processing system in accordance with certain aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The workpiece aligner apparatus and methods described herein may be embodied in many different forms and are not to be construed as being limited to the embodiments set forth herein. Instead, these embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the system and method to those skilled in the art. 
     For the sake of convenience and clarity, terms such as “top,” “bottom,” “upper,” “lower,” “vertical,” “horizontal,” “lateral,” and “longitudinal” will be used herein to describe the relative placement and orientation of these components and their constituent parts with respect to the geometry and orientation of a component of a device as appearing in the figures. The terminology will include the words specifically mentioned, derivatives thereof, and words of similar meaning and/or significance. 
     As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” is to be understood as including plural elements or operations, until such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended as limiting. Additional embodiments may also incorporate the recited features. 
     A “substrate” as used herein, refers to any substrate or material surface formed on a substrate upon which layer processing is performed during a fabrication process. For example, a substrate surface on which processing is performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, glass-ceramics, low expansion glass, ultra low expansion glass (e.g., ULE® glass available from Corning, Inc.), Zerodur® low expansion lithium aluminosilicate glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, without limitation, wafers such as semiconductor wafers and wafers made from other types of materials such as the materials listed in the previous sentence. Substrates may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal and/or bake the substrate surface. In addition to layer processing directly on the surface of the substrate itself, in the present disclosure, any of the layer processing steps disclosed may also be performed on an under-layer formed on the substrate as disclosed in more detail below, and the term “substrate surface” is intended to include such under-layer as the context indicates. Thus for example, where a layer (a layer may also be referred to a film) or partial layer has been deposited onto a substrate surface, the exposed surface of the newly deposited layer becomes the substrate surface. 
       FIG. 1  shows a top plan view of one embodiment of a processing tool or system  100  that is used for processing substrates, including deposition (e.g., chemical vapor deposition, physical vapor deposition, and atomic layer deposition), etching, heating, thermal processing, baking, and/or curing according to one or more embodiments of the disclosure. In the figure, a pair of FOUPs (front opening unified pods)  102  supply substrates (e.g., specified diameter semiconductor wafers) that may be received by first robot arms  104  and placed into a low-pressure holding chamber or holding area (also called a load lock chamber), which will be referred to herein as a holding chamber  106  before being placed into one of the substrate processing sections  108   a - f  of the process chambers  109   a - c . As used herein, a holding chamber  106  is distinguished from process chambers in that a holding chamber is a chamber in which a substrate to be processed is placed before being moved to a process chamber where one or more processes are conducted. A second robotic arm  110  may be used to transport the substrates from the holding chamber  106  to the processing chambers  109   a - c  and back. 
     The substrate processing sections  108   a - f  of the process chambers  109   a - c  may include one or more system components for depositing (e.g., by chemical vapor deposition, physical vapor deposition, and atomic layer deposition), annealing, heating, thermal processing, curing and/or etching substrates or layers thereon. Thus, the chambers  109   a - c  may be any of a chemical vapor deposition (CVD) chamber, a physical vapor deposition (PVD) chamber, an atomic layer deposition (ALD) chamber, a flowable chemical vapor deposition (FCVD) chamber, a plasma enhanced chemical vapor deposition (PECVD) chamber, an annealing chamber, a thermal processing chamber, a rapid thermal processing (RTP) chamber, a curing chamber, an etching chamber, or a plasma etching chamber. This list of chambers is exemplary only and non-limiting. Exemplary layers may be flowable dielectrics, multilayer reflective stacks, or absorber layers, but many types of layers may be formed or processed with the processing tool. In one configuration, two pairs of the processing sections of the processing chamber (e.g.,  108   c - d  and  108   e - f ) may be used to deposit the material on the substrate, and the third pair of processing sections (e.g.,  108   a - b ) may be used to anneal the deposited material. In another configuration, the two pairs of the processing sections (e.g.,  108   c - d  and  108   e - f ) may be configured to both deposit and anneal a layer on the substrate, while the third pair of processing sections (e.g.,  108   a - b ) may be used for UV or E-beam curing of the deposited layer. In still another configuration, all three pairs of processing sections (e.g.,  108   a - f ) may be configured to deposit and cure a layer on the substrate or etch features into a deposited layer. 
     In yet another configuration, two pairs of processing sections (e.g.,  108   c - d  and  108   e - f ) may be used for both deposition and UV or E-beam curing of the layer, while a third pair of processing sections (e.g.  108   a - b ) may be used for annealing the layer. In addition, one or more of the processing sections  108   a - f  may be configured as a treatment chamber, and may be a wet or dry treatment chamber. These process chambers may include heating the layer in an atmosphere that includes moisture. Thus, embodiments of system  100  may include wet treatment processing sections  108   a - b  and anneal processing sections  108   c - d  to perform both wet and dry anneals on the deposited layer. It will be appreciated that additional configurations of deposition, etching, annealing, and curing chambers for layers are contemplated by system  100 . In some embodiments, the processing sections are arranged or configured as tandem processing regions or chambers. 
     In view of the foregoing, an advantage of one or more embodiments of the present disclosure is that a problem with current substrate position detection and alignment apparatus useful for round substrates but not for non-round substrates is solved by providing a system that is configured to detect the position of a non-round substrate and align the substrate. According to one or more embodiments, as used herein, “non-round” refers to shape that is not a circle and includes a square, a rectangle, a triangle, a hexagon, a polygon, a rhombus, and a parallelogram. In specific embodiments the substrate is square or rectangular. 
     Providing an apparatus that is configured to accurately detect the position of non-round substrates such as polygonal (e.g. rectangular) substrates is very beneficial in the manufacture of elements for extreme ultraviolet lithography (EUV), also known as soft xray projection lithography. EUV has begun to replace deep ultraviolet lithography for the manufacture of 0.13 micron, and smaller, minimum feature size semiconductor devices. EUV systems operate by reflection instead of transmission of light. Through the use of a series of mirrors, or lens elements, and a reflective element, or mask blank, coated with a non-reflective absorber mask pattern, patterned actinic light is reflected onto a resist-coated semiconductor wafer. 
     Conventional EUV blank processes may include, for example, a 152 mm×152 mm blank reticle being placed into a coating tool to apply various coatings. As configured, the square reticle is sandwiched within a carrier assembly (e.g., a 300 mm carrier assembly) to enable the reticle to be transferred through the coating tool like a 300 mm wafer. The carrier assembly may include a carrier base, the reticle blank, and a carrier shield. During manufacture of a reticle, the carrier assembly may be aligned during the manufacturing process. The apparatus and methods disclosed herein are useful in a variety of semiconductor processing chambers, systems and methods. For example, in deposition and etch processes where detection and/or monitoring of an exact position of the wafer inside the chamber is helpful, as position information directly affects process outcome. For example, placement of certain conducting paths, or etching in multiple chambers depend on capability of repeatable and exact placement of a wafer in a chamber. 
     Embodiments of the disclosure provide apparatus and methods used to process a substrate in a chamber, in particular to position a non-round substrate in a holding chamber or a processing chamber. Further described herein are methods and apparatus that detect radiation transmitted along the thickness of the substrate between the top surface and the bottom surface, determine a signal strength as the substrate is rotated and obtaining a signal strength pattern to determine a position of the substrate within the chamber with respect to a center position of the chamber. Embodiments of the disclosure enable the detection of whether a substrate is positioned off center in a chamber, and the degree the substrate is positioned off center. While the methods and apparatus are used for any substrate shape, embodiments of the disclosure are useful for substrates having a rectangular shape. The apparatus and methods disclosed herein are useful in a variety of semiconductor processing chambers, system and methods, for example, in deposition and etch processes, wherein it is critical to detect and monitor an exact position of the wafer inside a chamber, as position information directly affects process outcome. For example, placement of certain conducting paths, or etching in multiple chambers depend on capability of repeatable and exact placement of wafer in a chamber. In addition, according to one or more embodiments, it is also possible to detect and quantify bowing and deformation of the substrate in the chamber. 
     Referring now to  FIGS. 2A-B  and  3 A-D, according to one or more embodiments of the disclosure, a substrate processing apparatus  200  for processing a polygonal substrate, specifically a rectangular substrate  202  is provided. In some embodiments, processing the rectangular substrate  202  involves placing substrate on a chamber surface  204  (e.g., a substrate support  225 ) that supports the substrate  202 . The chamber surface  204  in the plane of the substrate has a center position  203 . The substrate  202  shown in  FIGS. 2A-B  and  3 A-D is rectangular in shape and includes a first corner  202   a , a second corner  202   b , a third corner  202   c  and a fourth corner  202   d . A line extending between the first corner  202   a  and second corner defines a first side  202   e , a line extending between the second corner  202   b  and the third corner  202   c  defines a second side  202   f , a line extending between the third corner  202   c  and the fourth corner  202   d  defines a third side  202   g , and a line extending between the fourth corner  202   d  and the first corner  202   a  defines a fourth side  202   h  of the substrate  202 . The substrate  202  has a top surface  205  and a bottom surface  207 , and a distance between the top surface  205  and the bottom surface define a thickness “t” as shown in  FIG. 2B . In one example, the chamber surface  204  is a surface of chamber for processing an EUV reticle or EUV mask, and the substrate  202  is an EUV reticle blank or EUV mask blank. 
     In some embodiments, the first robot arms  104  and second robot arms  110  shown in  FIG. 1  are configured to place the substrate  202  on the chamber surface  204 . The first robot arms  104  and the second robot arms  110  move in the substrate  202  in the X-Y plane. Thus, the substrate  202  is moved back and forth in the X direction as shown by arrow  220  and back and forth in the Y direction as shown by arrow  222 . Furthermore, the substrate is rotated in the X-Y plane as shown by arrow  224  by either the robot arms or the substrate support  225 , which in some embodiments is a rotating substrate support  225 . Motion is controlled by drive trains comprising one or more of electric motors, transmissions (e.g., a lead screw), belts and pulleys, linear and rotary bearings and mechanical parts. 
     Still referring to  FIGS. 2A-B  and  3 A-D, the apparatus  200  includes a position detection system configured to measure the surface profile of a non-round substrate, for example, a polygonal substrate, and in some embodiments, a rectangular transparent substrate  202  as shown. The apparatus comprises a radiation source  250  that scans the substrate  202  and is communication with a controller  270 . 
     The substrate support  225  is configured to rotate the substrate 360 degrees through a plurality of rotational angular positions within the chamber  204 . The controller controls the rotation of the substrate support  225 . The radiation source  250  in some embodiments is a laser positioned to direct a radiation beam along the thickness “t” between the top surface  205  and the bottom surface  207  as shown by dashed arrow  211 . A sensor  252  is positioned opposite the radiation source  250  to detect radiation transmitted along the thickness of the substrate between the top surface and the bottom surface. The controller  270  is configured to analyze a signal strength of the radiation detected by the sensor  252  at the plurality of rotational angular positions and to correlate the signal strength at the plurality of rotational angular positions to a position within the chamber. 
     The controller  270  is configured to analyze the signal strength of the radiation transmitted along the thickness of a polygonal substrate, such as a rectangular substrate, at the plurality of rotational angular positions. In some embodiments, the controller is configured to analyze the signal strength transmitted along the thickness “t” of a rectangular substrate. In some embodiments, the controller  270  is configured to analyze a signal strength pattern versus a rotational angular position of the substrate as the substrate  202  is rotated through a plurality of rotational angular positions. In some embodiments, the controller  270  controls rotational movement of the substrate support  225 . 
     In some embodiments, the substrate  202  is transparent to the wavelength of radiation  211  emitted by the radiation source  250 . In such embodiments, the radiation sensor  252  is positioned opposite the radiation source  250  to detect radiation transmitted along the thickness “t” of the transparent substrate  202 . In some embodiments, the radiation source  250  comprises a laser source and the radiation sensor comprises a laser sensor that detects laser radiation. According to one or more embodiments, laser sensors are used for detecting presence of a non-round substrate based on position or light intensity. Benefits of a laser sensor include long range, a visible beam spot and precise detection. 
       FIG. 3A  shows a top plan view of a rectangular substrate  202  similar to the substrate  202  shown in  FIGS. 2A-B  having a width “W” and a length “L” greater than the width “W,” although in some embodiments, the L and W are equal, resulting in the rectangular substrate  202  being a square. The rectangular substrate  202  has a longest dimension along the thickness of the diagonal “D.” As seen in  FIG. 3B , the substrate  202  is not aligned in the X-Y plane. The controller  270  sends a signal to the radiation source  250  (e.g., a laser source) to transmit a beam of radiation  211  (e.g., laser radiation along the thickness of the substrate  202 , which is measured by radiation sensor  252  (e.g., laser sensor)). The  FIG. 3B  shows as side view of the apparatus  200  with the radiation source  250  emitting radiation  211  that is sensed by the radiation sensor  252  transmitted along the thickness of the substrate  202 . A first measurement is taken at a first rotational angular position along the thickness of the substrate as indicated by line b 1  in  FIG. 3B . In  FIG. 3C  the controller  270  has sent a signal to rotate the position of the substrate to a second rotational angular position, and the rotational angular position of the substrate  202  has been changed by rotating the substrate support  225  in the direction of arrow  224 . The controller  270  sends another signal to the radiation source  250  and the radiation sensor  252  to obtain a second measurement across the substrate  202  as indicated by line b 2 , which is shorter than b 1 . As shown in  FIG. 3C , the controller sends another signal to the radiation source  250  to transmit a beam of radiation  211  along the thickness of the substrate  202  and the radiation sensor obtains a third measurement along the thickness of the substrate  202  at a distance b 3 , which is shorter than b 2 . 
     The controller  270  controls rotational motion of the substrate  202  as indicated by arrow  224  as the radiation source  250  scans radiation along the thickness of the substrate  202 . It will be understood that the  FIGS. 3B-D  represent only three measurements along the thickness of the substrate  202 , however, in one or more embodiments, the radiation source  250 , the radiation sensor  252  and the controller cooperate to obtain a plurality of measurements along the thickness “t” of the substrate  202 . The radiation source  250  and the radiation sensor  252  are mounted on a carriage (not shown) that is moved by an electric motor, a pneumatic drive or a hydraulic drive (not shown) to increase or decrease the distance between the radiation source  250  and the radiation sensor, depending on the size of the substrate. The controller  270  includes a central processing unit  272 , which is configured to receive radiation intensity measurements from the radiation sensor  252  which are converted to or correlated with signal strength based on the properties of the substrate and the wavelength of the radiation. Depending on the properties of the material (e.g., quartz, glass, etc.), the transmission of the radiation at a particular wavelength is known in advance or is empirically determined for a given path length, as shown in  FIG. 4A . Based on the material properties and the path length, the signal strength is determined for a variety of path lengths as shown in  FIG. 4B . 
     The controller  270 , including the central processing unit (CPU)  272 , further comprises a memory  274  and support circuits  276 , and the controller  270  is coupled to the radiation source  250  and the radiation sensor  252  by communication link (not shown) to facilitate control of loading of a substrate, unloading of a substrate, rotation of the substrate during measurement, and repositioning of a substrate placed in a chamber so that the substrate is placed in the center position  203  of the chamber surface  204 . The memory  274  is any computer-readable medium, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote to the apparatus or CPU  272 . The support circuits  276  are coupled to the CPU  272  for supporting the CPU  272  in a conventional manner. In some embodiments, these circuits include cache, power supplies, clock circuits, input/output circuitry and subsystem, and the like. A software routine or a series of program instructions stored in the memory  274 , when executed by the CPU  272  to cause the apparatus to conduct a measurement at a plurality of rotational angular positions as described with respect to  FIGS. 3A-D . 
     It will be understood that the plurality of measurements along the thickness of the substrate include any suitable number to accurately determine the position of the substrate  202  with respect to a center point  203  of the chamber surface  204 . According to one or more embodiments, the measurements are taken in increments of 90 degrees, 45 degrees, 30 degrees, 20 degrees, 15 degrees, 10 degrees, 9 degrees, 8 degrees, 7 degrees, 6 degrees, 5 degrees, 4 degrees, 3 degrees, 2 degrees, 1 degree, 0.5 degrees, 0.1 degrees or 0.01 degrees. 
     In some embodiments, the controller  270  memory  274  records the signal strength obtained by the radiation sensor  252  at a plurality of rotational angular positions. According to some embodiments, the controller  270  is configured to generate a signal strength pattern at the plurality of rotational angular positions. The signal strength pattern is generated by the CPU  272  processing stored values of signal strength at a plurality of rotational angular positions stored by the memory and generating a plot of signal strength versus rotational angular position as the substrate is rotated 360 degrees. 
       FIG. 5B  shows a representative plot of path length versus rotational angular position as the rectangular substrate shown in  FIG. 5A  is rotated 360 degrees. The shortest path length is at the width W of the rectangle, and the longest path length is at the length L of the rectangle. As discussed above, the signal strength is inversely proportional to the absorption losses and path length of light pathway along the thickness of the substrate, and therefore, the CPU  272  determines a signal strength that correlates to the path length of each measurement at each rotational angular position as the substrate is rotated.  FIG. 5B  represents an ideal profile of path length versus angle for a substrate that is perfectly centered in the chamber at the center position  203 , as represented by a saw tooth or sinusoidal pattern. Deviation from the pattern shown in  FIG. 5B  correlated to signal strength is then correlated to eccentricity of the position of the substrate. 
     Thus, according to some embodiments, placing a rectangular substrate in the chamber and directing a radiation source such as a laser across the chamber and along the thickness of the substrate to a sensor, the eccentricity of the substrate position in the chamber is determined. By rotating the substrate 360 degrees and recording the signal acquired by the radiation sensor, one then determines if the substrate is out of position by comparing the signal strength pattern generated by the CPU versus a known pattern of when the substrate is perfectly centered. For example, if the substrate is in correct position (center point  203 ) then the signal should have a saw-tooth or sinusoidal. i.e., the beam path will be as short at the width of the substrate and as larger at the diagonal of the substrate. 
       FIG. 6  illustrates an example of a square substrate  202  having a Width W=2a and a length L=2a. Assuming the substrate is offset from the center in the y direction by the distance “e”, as the substrate support of the chamber rotates the path length will be different from a saw tooth or sinusoidal pattern. A maximum will occur at an angle larger than 45 degrees, or 
     
       
         
           
             
               
                 
                   
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     For a 360 degree rotation, the graph pattern will not be a saw tooth or a controller pattern, and will not repeat four times. In one or more embodiments, when the processor (controller  270 ) obtains a pattern that does not repeat four times or is not a saw tooth or sinusoidal pattern, or in other words, does not correlate to the signal strength pattern of a pre-determined pattern, the controller  270  will send a signal to adjust the position of the substrate in the chamber because the substrate is not in the center position  203 . Accordingly, the controller  270  sends a signal to a robot arm as in  FIG. 1  to pick the substrate and place it again closer to the center of the chamber, and the apparatus conducts the measurement to confirm that the substrate  202  has been placed in the center position  203 . Thus, in some embodiments, the controller is configured to reposition the substrate  202  in the chamber. The controller sends a signal to a robot arm, for example one of the robot arms described above with respect to  FIG. 1  to pick up the substrate and place the substrate closer to or at the center position  203  of the chamber surface  204 . 
     As discussed above, in some embodiments the apparatus according to some embodiments utilizes laser radiation. In one or more embodiments, laser radiation includes the ultraviolet, visible, and infrared regions of the spectrum. In some embodiments, ultraviolet radiation for lasers consists of wavelengths between 180 and 400 nm. In some embodiments, the visible region consists of radiation with wavelengths between 400 and 700 nm. In some embodiments, the infrared region of the spectrum consists of radiation with wavelengths between 700 nm and 1 mm. 
     As mentioned above, the apparatus and method are beneficial in the manufacture of EUV devices such as EUV masks.  FIG. 7  depicts an EUV mask production system  300 , which includes the apparatus  200  for processing a polygonal substrate, for example, a rectangular transparent substrate comprised of quartz, silica, glass or ultra low expansion glass as described herein according to one or more embodiments. The EUV mask production system  300  may include a mask blank loading and carrier handling system  302  configured to receive one or more mask blanks  304  that are polygonal in shape or polygonal in shape and transparent. A holding chamber  306  provides access to a substrate handling vacuum chamber  308 . In the embodiment shown, the substrate handling vacuum chamber  308  contains two vacuum chambers, e.g., a first vacuum chamber  310  and a second vacuum chamber  312 . Within the first vacuum chamber  310  is a first substrate handling system  314 , and in the second vacuum chamber  312  is a second substrate handling system  316 . 
     The substrate handling vacuum chamber  308  may have a plurality of ports around its periphery for attachment of various other systems or chambers and to provide access to these various other systems or chambers. In this non-limiting embodiment, the first vacuum chamber  310  has a degas chamber  318 , a first physical vapor deposition chamber  320 , a second physical vapor deposition (PVD) chamber  322 , and a pre-clean chamber  324 . Furthermore, the second vacuum chamber  312  may include a first multi: cathode PVD chamber  326 , a flowable chemical vapor deposition (FCVD) chamber  328 , a cure chamber  330 , and a second multi-cathode PVD chamber  332  connected to the second vacuum chamber  312 . 
     The first substrate handling system  314  is capable of moving substrates, such as a substrate  334 , among the holding chamber  306  and the various chambers around the periphery of the first vacuum chamber  310  and through slit valves in a continuous vacuum. The second substrate handling system  316  is capable of moving substrates, such as a substrate  336 , around the second vacuum chamber  312 , while maintaining the substrates in a continuous vacuum. The integrated EUV mask production system  300  may operate with a reticle processing system. The apparatus  200  for processing a polygonal substrate is utilized adjacent or near the carrier handling system  302 . In particular, the three-dimensional (3D) radiation mapping device  260  configured to measure the surface profile of a non-round substrate is used to accurately place the substrates  334  and  336  as described with respect to  FIGS. 2 and 3A -B herein in the various chambers, namely the degas chamber  318 , the first physical vapor deposition chamber  320 , the second physical vapor deposition chamber  322 , the pre-clean chamber  324 , the first multi-cathode PVD chamber  326 , the flowable chemical vapor deposition (FCVD) chamber  328 , the cure chamber  330 , and the second multi-cathode PVD chamber  332 . Accurate placement of the polygonal substrate in one or more of these chambers is critical to meeting production requirements and accurate fabrication of EUV masks and EUV reticles. Existing systems and apparatus are not capable of accurately detecting position and placing non-round substrates, particularly, detecting the position of the substrate relative to a position or point on the robot arm while the substrate is moving, such as when the polygonal substrate is on a robot blade of a robot arm and being moved into a holding chamber or process chamber. 
     Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Although the disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure include modifications and variations that are within the scope of the appended claims and their equivalents.