Abstract:
Methods for correcting motion of a robot are provided in the present invention. In one embodiment, a method for correcting motion of a robot includes transferring a first substrate supported on a robot to a processing position using a robotic motion routine, depositing a material on the first substrate in the processing position, determining an offset between a center of the deposited material and a center of the first substrate, adjusting the robotic motion routine to compensate for the offset. In another embodiment, a processing chamber is provided configured to obtain samples from which motion of a robot operated therein may be corrected to improve substrate placement on a substrate support through analysis of material deposited on the substrate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to methods for detecting errors in substrate placement and the correction thereof. More specifically, the present invention generally relates to methods detecting errors in robot motion by analysis of material deposited on a substrate. 
         [0003]    2. Description of the Related Art 
         [0004]    Reliably producing sub-half micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of circuit technology are pushed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on processing capabilities. Reliable placement of a substrate in processing chambers utilized to fabricate VLSI and ULSI devices is critical for enabling increased circuit density and quality of individual substrates and die in next generation devices. 
         [0005]    Conventionally, a robot utilized to place a substrate in a processing chamber relies on sensors to detect the true position of robot or substrate carried thereon, and compares the sensed true position with an expected position based on the angular position of the robot motor(s). The difference between the expected and sensed position of the robot or substrate carried thereon may be utilized to correct the robots motion. Although this methodology generally provides good motion control, little is known about the position of the substrate once the substrate is transferred to a substrate support pedestal from the robot. Since the position of the substrate on the substrate support pedestal is ultimately the important factor for achieving robust processing results, the inventors have realized that it would be beneficial to know not only if the substrate is in an expected position while on the robot, but also if the substrate was actually positioned correctly on the substrate support. Particularly in hot processing chambers and at low vacuum pressures, distortion and thermal expansion of chamber components and robot linkages may significantly change the length and sag of the robot linkages along with the true position of the substrate support, making accurate placement of the substrate a substantial challenge. If the substrates position relative to the substrate support can be determined, then the robot placement routine may be adjusted (e.g., corrected) to ensure that subsequently processed substrates are correctly positioned on the substrate support. 
         [0006]    Therefore, there is a need for an improved method for determining the position of a substrate relative to a substrate support, and to utilize such information to correct a motion routine of a robot so that a substrate may be accurate transferred to the substrate support. 
       SUMMARY OF THE INVENTION 
       [0007]    Methods for correcting motion of a substrate positioning mechanism are provided in the present invention. In one embodiment, a method for correcting motion of a substrate positioning mechanism includes transferring a first substrate supported on a substrate positioning mechanism to a processing position using an automated motion routine, depositing a material on the first substrate in the processing position, determining an offset between a center of the deposited material and a center of the first substrate, and adjusting the automated motion routine to compensate for the offset. 
         [0008]    In another embodiment, a method for correcting motion of a substrate positioning mechanism disposed in a semiconductor processing system, wherein the processing system includes at least one vacuum transfer chamber housing the substrate positioning mechanism, a load lock chamber coupled to the transfer chamber and at least one processing chamber coupled to the transfer chamber is provided that includes transferring a first substrate supported on the substrate positioning mechanism to a processing position using a first motion routine, depositing a material on the first substrate, sensing a metric indicative of a lateral position of the deposited material relative to the substrate while transferring the first substrate from the processing position using a second motion routine, and adjusting first motion in response to the metric. 
         [0009]    In another embodiment, a method for correcting motion of a substrate positioning mechanism includes depositing a material on a substrate at a processing position, sensing a metric indicative of a lateral position of the deposited material relative to the substrate, and adjusting a motion routing in response to the metric. 
         [0010]    In yet another embodiment of the invention, a processing system is provided that includes at least one load lock chamber and at least one processing chamber coupled to a transfer chamber having a substrate positioning mechanism disposed therein. At least one sensor is interfaced with a controller and arranged to obtain a metric indicative of a lateral position of a substrate relative to material deposited thereon. A computer-readable medium is provided having stored thereon a plurality of instructions. The plurality of instructions includes instructions, which, when executed by the controller, cause the processing system to perform the steps of depositing a material on a substrate at a processing position, sensing a metric indicative of a lateral position of the deposited material relative to the substrate, and adjusting a motion routing in response to the metric. 
         [0011]    In still another embodiment of the invention, a method for correcting motion of a substrate positioning mechanism includes processing a material on a substrate at a processing position, wherein the processing produces a processing profile, sensing a metric indicative of a lateral position of the processing profile relative to the substrate, and adjusting motion routine of the substrate positioning mechanism in response to the metric. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
           [0013]      FIG. 1  is one embodiment of an exemplary processing chamber in which the invention may be practiced; 
           [0014]      FIG. 2  is one embodiment of a substrate illustrating the misalignment between the perimeter of the substrate and a deposition pattern present on the backside of the substrate; 
           [0015]      FIGS. 3-4  are partial sectional views of another embodiment of a substrate support and a substrate processed thereon illustrating misalignment between the perimeter of the substrate and a deposition pattern present on the front side of the substrate; 
           [0016]      FIG. 5  is an exemplary processing system which may be utilized to practice the method of the present invention; 
           [0017]      FIGS. 6A-B  are embodiments of a substrate supported on a substrate transfer robot passing through sensing regions of the processing system of  FIG. 5 ; 
           [0018]      FIGS. 7A-B  depict substrates carried by the substrate transfer robot passing through the sensing regions respectfully illustrated in  FIGS. 6A-B ; and 
           [0019]      FIG. 8  is another embodiment of a substrate supported on a substrate transfer robot passing through a sensing region of a processing system. 
       
    
    
       [0020]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
         [0021]    It is to be noted, however, that the appended drawings illustrate only exemplary 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. 
       DETAILED DESCRIPTION 
       [0022]      FIG. 1  depicts one embodiment of a semiconductor processing chamber  100 . Although the processing chamber  100  is illustratively shown as a physical vapor deposition (PVD) chamber, the processing chamber  100  may also be a chemical vapor deposition (CVD) chamber, an atomic layer deposition (ALD) chamber, an electroless deposition chamber, an etching chamber, an electroplating chamber or other processing chamber or module utilized to deposit or etch films on a substrate. The processing chamber  100  includes a chamber body  102  coupled to a power source  104 , a gas source  106  and a controller  108 . The controller  108  is utilized to control the operations of the processing chamber  100  and may be utilized to control and/or correct robotic motion as further described below. 
         [0023]    The controller generally includes a memory  110 , a CPU  112  and support circuits  114 . The CPU  112  may be one of any form of computer processor that can be used in an industrial setting for controlling various chambers and subprocessors. The memory  110  is coupled to the CPU  112 . The memory  110 , or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits  114  are coupled to the CPU  112  for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. 
         [0024]    The chamber body  102  generally includes an exhaust port  116  which is coupled to a pumping system (not shown) and a substrate transfer port  150 . The substrate transfer port  150  is utilized to allow robotic entry and egress of a substrate  122  from the chamber body  102 . 
         [0025]    A substrate support pedestal  118  is disposed in the chamber body  102 . The substrate support pedestal  118  is coupled to a lift mechanism  124  by a rod  126 . The lift mechanism  124  controls the elevation of the substrate support pedestal  118 , typically between a lowered transfer position and an elevated processing position. Bellows  148  are typically coupled between the pedestal  118  and the bottom of the chamber body  102 , and circumscribes the rod  126  to prevent leakage from the processing chamber  100 . 
         [0026]    An edge ring  120  is supported on the perimeter region of the pedestal  118 . A portion of the edge ring  120  generally extends below a perimeter  144  of the substrate  122 . The edge ring  120  has a projection  152  extending upward therefrom, which bounds one side of a gap  140  defined between the projection  152  of the ring  120  and the perimeter  144  of the substrate  122 . 
         [0027]    A target  134  is coupled to the ceiling of the chamber body  102 . The target  132  is coupled to the power source  104 . The target is typically comprised from a material which is sputtered onto the substrate  122  during processing. A magnetron  136  is generally coupled to the top of the chamber body  102  above the target  134  to enhance efficient usage of the target  134  and uniformity of deposition on the substrate  122 . 
         [0028]    In operation, a process gas is provided from the gas source  106  through one or more gas ports  130  formed through the chamber body  102 . Power is applied to the target  134  by the power source  104  and a plasma  132  is formed from the process gas. Ions from the plasma strike the target  134  and sputter off material which then is deposited as deposition material  142  on the front side  138  of the substrate  122 . Some sputtered material enters the gap  140  and deposits on the perimeter  144  and backside  128  of the substrate  122 . 
         [0029]    As depicted in the bottom view of the substrate  122  in  FIG. 2 , the edge  146  of the deposited material  142  present on the backside  128  of the substrate  122  may be non-concentric to the perimeter  144  of the substrate  122 . This is often because the substrate  122  was not positioned correctly with respect to the substrate support pedestal  128  and/or the edge ring  120 . The non-concentricity between the edge  146  and perimeter  144  is illustrated by the offset between the center of the substrate  122  relative to the center of the edge  146  of the deposited material  142 , as shown in  FIG. 2  by center lines  200 ,  210 . 
         [0030]    The inventors have discovered that by determining the offset between centers of the edge  146  of the deposited material  142  and the perimeter  144  of the substrate  122 , the motion of the robot placing the substrate  122  on the substrate support pedestal  118  may be corrected to concentrically align the deposited material on subsequently processed substrates. For example, a plurality of distances between the edge  146  and the perimeter  144  of the substrate, as shown by distance X 1 , X 2 , X 3  and X 4 , may be measured relative to a reference point, such as a notch  220  formed in the substrate  122 , to calculate the offset between the centers  200 ,  210 . The offset information may be utilized to correct the robot motion. In a simple embodiment, the distance X 1 , X 2 , X 3  and X 4  may be measured using hand or other tools outside the processing chamber  100 , and a correction for the robot motion may be provided to the controller  108 . This process may also be automated in a variety of ways. 
         [0031]    The method of using an offset between the centers of the deposited material and the substrate may also be utilized to correct the substrate placement in systems where the edge of the deposited material is present on the front side of the substrate. Such embodiments are representative of processing systems which use a shadow ring to cover the edge of the substrate. 
         [0032]    For example,  FIGS. 3-4  depict a partial sectional view of a substrate support pedestal  300  having a cover ring  302  which underlies a portion of a substrate  322 . A shadow ring  304  is disposed on the cover ring  302  and has a lip  306  which extends over a perimeter  344  of the substrate  322 . During processing, deposited material  324  is deposited on the front side  338  of the substrate  332 . The lip  306  of the shadow ring  304  prevents deposition on the perimeter  344  of the substrate. Thus, the deposited material  342  has an edge  308  generally just inward of the perimeter  344  on the front side  338  of the substrate. 
         [0033]    As illustrated in  FIG. 4 , a center  410  of the deposited material  324  may be offset from a center  400  of the substrate  322 . Measuring the offset between the centers  400 ,  410 , as discussed above, may be utilized to correct the position of the substrate  322  on the pedestal  300  so that the deposited material  342  is concentrically deposited on the substrate  322 . 
         [0034]      FIG. 5  depicts one embodiment of a processing system  500  in which embodiments of the present invention may be practiced. The processing system  500  generally includes a vacuum transfer chamber  502  having a plurality of processing chambers  504  coupled thereto. In one embodiment, at least one of the processing chambers  504  is a deposition chamber, such as the processing chamber  100  depicted in  FIG. 1 . In another embodiment, at least one of the processing chambers  504  is an etch chamber, as utilized in an alternative embodiment of the invention discussed further below. At least one load lock chamber  510  is coupled between the transfer chamber  502  and a factory interface  506  to facilitate transferring substrates from the atmospheric environment of the factory interface  506  and the vacuum environment of the transfer chamber  502 . In the embodiment depicted in  FIG. 5 , two load lock chambers  510  are depicted. 
         [0035]    The factory interface  506  generally includes an atmospheric robot  514  and a plurality of bays adapted to receive a substrate storage cassette  512 . The robot  514  is utilized to transfer substrates between the load lock chambers  510  and substrate storage cassettes  512 . 
         [0036]    A vacuum robot  508  is disposed in the transfer chamber  502  and facilitates transferring substrates between the processing chambers  504  and the load lock chamber  510 . In one embodiment, the vacuum robot  508  is a frog-leg robot having a blade  522  which supports a substrate  122  thereon during substrate transfer. It is contemplated that other types of robots may be utilized. Motion of the robot is generally controlled by the controller  106  coupled to the processing system  500 . 
         [0037]    The processing system  500  includes at least one sensing system  530  suitable for detecting a metric indicative of an offset between centers of the deposited material and the substrate  122 . The indicative metric may be the edge of the substrate and deposited material, an image of the entire substrate and edge of deposited material, an image of a portion of the substrate and edge of the deposited material, electrical properties of the deposited films at the edge (such as Sheet Resistance (Rs), continuity, resistivity and the like), taper of the edge of the deposited material, change material thickness, reflectivity or other metric suitable for determining a positional relation between the deposited material and the substrate that may be utilized to determine a robot correction. The sensing system  530  generally includes a sensor (not shown in  FIG. 5 ) which is suitable for detecting the perimeter  144  ( 344 ) of the substrate  122  ( 344 ) and the edge  146  ( 308 ) of the deposited material  142  ( 342 ). In the embodiment depicted in  FIG. 5 , the sensing system  530  generally includes at least one window  516  which is positioned to enable the sensor to view the substrate. To enhance throughput, the sensor and window  516  may be positioned to view the substrate while carried by one of the robots  508 ,  514 , although the substrate may be viewed at other locations or while the substrate is disposed on objects other than the robot. As shown in the embodiment depicted in  FIG. 5 , the windows  516  may be disposed on the floor and/or ceiling of at least one of the processing chambers  504 , transfer chamber  502 , load lock chamber  510  or factory interface  506 . 
         [0038]    The windows  516  may be fabricated from a material transmissive to the sensor such that the sensor may interface with the substrate. One such window material is quartz or sapphire. It is contemplated that in regions outside of vacuum, such as in the factory interface  506 , the window  516  may be simply an open aperture or an aperture covered by a transmissive glass or plastic material. 
         [0039]      FIG. 6A  depicts one embodiment of the sensing system  530  configured to view the face  338  of the substrate  332  while supported on the blade  522  of the robot  508  (or robot  514 ). The sensing system  530  depicted in  FIG. 6A  includes at least one window  516  positioned such that the substrate  322 , when passed below the window  516  while supported on the robot blade  522 , passes below through the sensing field of the one or more sensors. In the embodiment depicted in  FIG. 6A , sensors  600 A,  600 B are shown. As the substrate moves through the sensing field, the leading and trailing edges of the substrate pass below the sensors  600 A,  600 B. This allows each sensor to obtain multiple samples during one pass of the robot through the sensing field. It is contemplated that one or more sensors may be used to obtain multiple samples by using the robot reposition of the substrate for each sample. It is contemplated that one or more sensors may be used to obtain one or more sample images from which the offset may be resolved. 
         [0040]    In the embodiment depicted in  FIG. 6A , the edge  308  and the perimeter  344  may be detected by the sensor  600 A to measure at distances X 3 , X 4 , as shown by dotted line  602 . The sensor  600 B is positioned to detect the edge  308  and the perimeter  344  of the substrate to resolve distances X 1 , X 2 , as shown by dotted line  604 . As discussed above, distances X 1 -X 4  may be used to determine the offset between the centers of the edge of the deposited material and the edge of the substrate. This information may be utilized to correct the placement of the substrate on the pedestal  118  so that the deposition edge  308  is concentric with the substrate  332 . As the sensors  600 A,  600 B are viewing the front side  338  of the substrate  332 , the windows  516  are typically positioned in the top of at least one of the processing chambers (as shown in phantom as indicated by reference numeral  516  in  FIG. 1 ) the transfer chamber or the load lock chamber. A window may be provided in the factory interface or load lock chamber  510  to correct the positioning of the substrate. 
         [0041]      FIG. 6B  depicts a substrate  122  supported on the blade  522  such that the backside  128  of the substrate  122  is shown. Windows  516  are located in the bottom of the processing system  500  to allow at least one sensor of the system  530  to view the backside  128  of the substrate  122  as the substrate  122  is passed thereover. In the embodiment depicted in  FIG. 6B , two sensors  600 A,  600 B are shown. 
         [0042]    The sensors  600 A,  600 B may generally be any sensors suitable for detecting the edge of the deposited material and the edge of the substrate. In one embodiment, the sensor senses reflectivity. In another embodiment, the sensor may detect changes in color or grayscale that is indicative of the edge of the deposited material and edge of the substrate. In yet another embodiment, the sensor may detect changes in the height or taper at the interface between the deposited material and the substrate. In yet another embodiment, the sensor may be a stylus, mechanical switch, proximity sensor, linear displacement transducer or other sensor suitable for detecting geometric differences between the deposited film and the substrate. In yet another embodiment, the sensor may be a continuity sensor, resistivity sensor or other sensor suitable for detecting electrical properties which may be utilized to detect the interface between the deposited film and the substrate. In yet another embodiment, the sensor may be a camera or other image capturing device. In embodiments wherein the sensor is a camera, machine vision techniques may be utilized to determine the offset in concentricity. The camera may view the entire substrate at once or by viewing portions of the substrate. For example, an image of a portion of the edge (of the substrate or deposited material) may be utilized to determine the radius, and thus the center. By obtaining at least data points indicative of the circumference of the edge  146  of the deposited material  142  and the edge perimeter  144  of the substrate, the centers of the deposited material and the substrate may be determined. The offset between the centers may be utilized to correct the position of subsequent substrates on the pedestal so that the concentricity between the deposition area and the substrate is improved. It is also contemplated that a sensor  800  of the sensing system  530  may be disposed inside the processing system  500 . For example, as depicted in  FIG. 8 , a sensor  800  is disposed inside the transfer chamber  502  and coupled to the controller  108  through a vacuum-tight feedthrough, without need for a window. 
         [0043]    In another embodiment of the invention, the sensing system  530  may be utilized with in an etch system to determine offsets between the substrate placement on a substrate support and a center of processing. For example, a center to edge process profile, such etch rate, microloading, polymerization, etch depth, CD bias and the like, may not be concentric with the substrate. By sensing a metric indicative of the process profile, the center of the process profile may be resolved relative to the center of the substrate. Utilizing this information, the robotic motion utilized to place the next substrate to be processed on the substrate support may be corrected such that the process profile is concentric with the substrate. 
         [0044]    Although the substrate placement correction process is described above for correcting the motion of a substrate transfer robot, the method may be utilized to center a substrate relative a process condition utilizing other motion control devices, such as linear actuator, x/y tables and the like. 
         [0045]    Thus, the present invention provides an improved method for determine the placement of substrates on a substrate support. The method described herein advantageously facilitates obtaining information for utilization for robot calibration and correction in a non-invasive manner that is transparent to throughput considerations. 
         [0046]    While the foregoing is directed to embodiments 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.