Abstract:
An apparatus and method of handling substrates is disclosed. A detecting system, capable of determining whether a substrate is tilted in relation to the platen, is positioned proximate to the substrate. In some embodiments, the detecting system is a distance measuring system. In other embodiments, it is an angle sensor. The detecting system is in communication with a controller, which, in turn, is in communication with a substrate handling robot. If, based on information received from the detecting system, the controller determines that the substrate is tilted beyond an acceptable range, it is assumed that the substrate has remained attached to the platen. In such a case, the substrate handling robot does not attempt to remove it from the platen. In this way, the substrate is not damaged.

Description:
[0001]    This application claims priority of U.S. Provisional Patent Application Ser. No. 61/025,142, filed Jan. 31, 2008, the disclosure of which is hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    This disclosure relates to a substrate handling, and more particularly to an apparatus and a method of handling a substrate. 
       BACKGROUND 
       [0003]    An electronic device may result from a substrate that has undergone various processes. One of the processes may include introducing impurities or dopants to alter one or more of electrical, optical, and mechanical properties of the original substrate. For example, charged ions, as impurities or dopants, may be introduced to a substrate, such as a silicon wafer, to alter electrical properties of the substrate. One of the processes that introduces impurities to the substrate may be an ion implantation process. 
         [0004]    Among other tools, an ion implanter is used to perform ion implantation. A block diagram of a conventional ion implanter is shown in  FIG. 1 . The conventional ion implanter may comprise an ion source  102  that may be biased by a power supply  101 . The ion source  102  is typically contained in a vacuum chamber known as a source housing (not shown). The ion implanter system  100  may also comprise a series of beam-line components through which ions  10  pass. The series of beam-line components may include, for example, extraction electrodes  104 , a 90° magnet analyzer  106 , a first deceleration (D 1 ) stage  108 , a 70° magnet collimator  110 , and a second deceleration (D 2 ) stage  112 . Much like a series of optical lenses that manipulate a light beam, the beam-line components can manipulate and focus the ion beam  10  before steering it towards a substrate or wafer  114 , which is disposed on a platen  116 . 
         [0005]    In operation, a substrate handling robot (not shown) disposes the substrate  114  on the platen  116  that can be moved in one or more dimensions (e.g., translate, rotate, and tilt) by an apparatus, sometimes referred to as a “roplat” (not shown). Meanwhile, ions are generated in the ion source  102  and extracted by the extraction electrodes  104 . The extracted ions  10  travel in a beam-like state along the beam-line components and implanted on the substrate  114 . After implanting ions is completed, the substrate handling robot may remove the substrate  114  from the platen  116  and from the ion implanter  100 . 
         [0006]    Referring to  FIGS. 2A and 2B , there is shown a block diagram illustrating the platen  116  supporting the substrate  114  during the ion implantation process. As illustrated in  FIG. 2A , the platen may comprise an edge  202  and a plurality of bumps  204  that are in contact with the substrate  114 . In addition, the platen may also include at least one cooling region  206 . During the implantation process, cooling gas may be provided to the cooling region  206  prevent the substrate  114  from overheating. The platen  116  may further include a plurality of lift pins  208  that may move so as to push the substrate  114  away from the platen  116 .  FIG. 3  is a top view of a platen  116  showing the position of the lift pins  208 . Although this embodiment utilizes three lift pins, the disclosure is not limited to this embodiment. 
         [0007]    Initially, the lift pins  208  are in a lowered position. The substrate handling robot  210  then moves a substrate to a position above the platen  116 . The lift pins  208  may then be actuated to an elevated position (as shown ion  FIG. 2A ) and may receive the substrate  114  from the substrate handling robot  210 . Thereafter, the substrate handling robot moves away from the platen  116  and the lift pins  208  may recede into the platen  116  such that the edge  202  and the bumps  204  of the platen  116  may be in contact with the substrate  114 , as shown in  FIG. 2B . The implantation process may then be performed with the lift pins  208  in this recessed position. After the implantation process, the substrate is unclamped from the platen, having been held in place, such as by electrostatic force. The lift pins  208  may then be extended into the elevated position, thereby elevating the substrate  114  and separating the substrate  114  from the edge  202  and the bumps  204  of the platen  116 , as shown in  FIG. 2A . The substrate handling robot  210  may then be disposed under the substrate  114 , where it can retrieve the implanted substrate  114  at the elevated position. The lift pins  208  may then be lowered, and the robot  210  may then be actuated so as to remove the substrate  114  from the implanter. 
         [0008]    One of the deficiencies of the conventional ion implanter  100  may be found in the process of removing the substrate  114  from the platen  116 . During implantation, a portion of the substrate  114  may be in contact with the edge  202  of the platen  116 . As the substrate  114  is elevated, the contacted portion may remain attached to the edge  202  of the platen  116 , while other portions of the substrate may be elevated. The substrate handling robot  210  attempting to retrieve the substrate  114  may collide with the partially elevated substrate  114 , and the substrate  114  may either break from the collision or fall to another portion of the implanter  100 . 
         [0009]    Since these collisions may decrease the efficiency of the implanter  100 , the cost of processing the substrate  114 , and ultimately the cost of the manufactured semiconductor devices, may increase. As such, a new apparatus and method for removing the implanted substrate  114  from the platen  116  is needed. 
       SUMMARY 
       [0010]    The problems of the prior art are overcome by the apparatus and method of this disclosure. An apparatus having a detecting system and controller and a substrate robot is used to handle processed substrates. The detecting system, capable of determining whether a substrate is tilted, is positioned proximate to the substrate. The detecting system is adapted to measure the tilt of the substrate relative to the platen. The detecting system is in communication with a controller, which, in turn, is in communication with a substrate handling robot. 
         [0011]    In some embodiments, the detecting system is a distance measuring system. In this embodiment, the detecting system measures the distance to the substrate after the robot has placed the substrate on the platen. It then measures the distance to the substrate after the substrate is processed. If the difference between these two distances is too great, the controller determines that the substrate is tilted. 
         [0012]    In other embodiments, the detecting system is an angle sensor. In this embodiment, the detecting system measures the difference in direction between the transmitted wave and the wave reflected off the substrate. If this difference is too great, the controller determines that the substrate is tilted. 
         [0013]    If the controller, based on date received from the detecting system, determines that the substrate is tilted beyond an acceptable range, it is assumed that the substrate has remained attached to the platen. In such a scenario, the substrate handling robot does not attempt to remove it from the platen. By preventing the substrate handling robot from attempting to remove the substrate, the substrate is not damaged. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    In order to facilitate a fuller understanding of the present disclosure, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present disclosure, but are intended to be exemplary only. 
           [0015]      FIG. 1  represents a traditional ion implantation system; 
           [0016]      FIG. 2A  represents a block diagram showing a platen supporting a substrate with the lift pins extended; 
           [0017]      FIG. 2B  represents a block diagram showing a platen supporting a substrate with the lift pins recessed; 
           [0018]      FIG. 3  represents a top of a platen; 
           [0019]      FIG. 4  represents a first embodiment of the apparatus, with the substrate in the correct position; 
           [0020]      FIG. 5  represents a first embodiment of the apparatus, with the substrate in the tilted position; and 
           [0021]      FIG. 6  represents a second embodiment of the apparatus, with the substrate in the tilted position. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    In the present disclosure, several embodiments of an apparatus and a method for handling a processed substrate are introduced. For purpose of clarity and simplicity, the present disclosure will focus on an apparatus and a method for handling a substrate that is processed by a beam-line ion implanter. Those skilled in the art, however, may recognize that the present disclosure is equally applicable to other types of processing systems including, for example, a plasma immersion ion implantation (“PIII”) system, a plasma doping (“PLAD”) system, an etching system, an optical based processing system, and a chemical vapor deposition (CVD) system. As such, the present disclosure is not to be limited in scope by the specific embodiments described herein. 
         [0023]    Referring to  FIG. 3 , there is shown a block diagram of an apparatus for handling a processed substrate, according to one embodiment of the present disclosure. In the present disclosure, the apparatus may be contained in an ion implanter similar to the one shown in  FIG. 1 . The apparatus may comprise at least one substrate orientation detecting system  220  and a controller  230  coupled to the at least one substrate orientation detecting system  220 . Additionally, the controller  230  is coupled to a substrate handling robot  210 . As illustrated in  FIG. 3 , the at least one detecting system  220  may be disposed proximate to the substrate  114 . For example, the detecting system  220  may be disposed in front of the substrate, at a side of the substrate, or behind the substrate. 
         [0024]    In one embodiment, the detecting system  220  is a distance measurement system, capable of determining the distance between the detecting system  220  and the substrate  114  or a specific portion of the substrate  114 . In this embodiment, the detecting system  220  may preferably be an optical light based system, such as a laser based system comprising a light source and one or more light detectors, located proximate to the light source. The light source is used to illuminate the object to be measured. Once illuminated, the object reflects a portion of the light back toward the detecting system. The light detectors determine the angle of incidence of the reflected beam, using various techniques, including but not limited to cameras and focusing lenses. Based on the angle of incidence of the reflected beam, the detecting system can determine the distance to the object. Alternatively, the detecting system may utilize induction or ultrasonic waves to determine the distance to the object. The system may also be an electromagnetic wave based system. 
         [0025]    Time of Flight systems determine the distance to an object based on the time required for light to travel to the object and back to the detecting system. In some embodiments, a periodic waveform, such as a sinusoidal wave is emitted from a laser. The phase difference between the emitted wave and reflected wave is used to determine the distance from the detecting system to the object. Other techniques capable of measuring the distance to an object are also within the scope of the disclosure. 
         [0026]    The detecting system  220  may be configured to observe at least a portion of the substrate. Preferably, the observed portion may be near the center of the substrate  114  or near an outer edge of the substrate  114 . However, it is also within the scope of the present disclosure that the detecting system may be configured to observe other portions of the substrate. Furthermore, the detecting system  220  may also be configured to observe, for example, platen or lift pins. In other embodiments, a plurality of detecting systems  220  is utilized to observe a plurality of locations. For example, detecting systems  220  may be used to measure a plurality of locations along the outer edge of the substrate  114 . In this way, the detecting systems are able to reliably ascertain substrate adhesion issues. 
         [0027]    Hereinafter, operation of the distance based method for determining the orientation of the substrate  114  will be described. Initially, the substrate  114  is received by the lift pins  208 , as shown in  FIG. 4 . The distance between at least a portion of the substrate  114  in the elevated state and the detecting system  220  is measured (the “first distance”). Thereafter, the substrate  114  is lowered and disposed on the platen  116 , and the substrate  114  is processed. After being processed, the substrate  114  is raised to the elevated state by the lift pins  208  to be retrieved by the substrate handling robot  210 . 
         [0028]    Prior to being retrieved, however, the distance between the same portion of the substrate  114  and the detecting system  220  is measured for the second time (the “second distance”). Thereafter, the first and second distances are compared by the controller  230 . If the difference of the first and second distances is unacceptably high (e.g. 1-10 mm), a determination can be made that at least a portion of the substrate  114  is attached to the platen  116  and the substrate  114  is oriented in an excessively tilted state. Thus, the controller  230  compares the difference between the first and second distances to an acceptable range. For example, the controller  230  may be configured such that the difference between the two distances must be in the range between −1 and +1 mm. If such a determination is made, the substrate handling robot  210  may be prevented from retrieving the substrate  114 . Otherwise, the robot  210  may retrieve the substrate  114 . 
         [0029]    Alternatively, the detecting system  210  may be capable of determining the orientation of the object based on angle of the orientation. Preferably, a triangular based detecting system is used in this mode. As described above, the detecting system  220  is preferably an optical light based system. However, those of the art will recognize that the detecting system  220  may also be other types of systems capable of determining the orientation of the substrate. Although the disclosure refers to a light beam being used, those skilled in the art will recognize that any suitable emitted wave (such as ultrasonic, electromagnetic, of light) can be utilized. Processed wafers are generally highly optically reflective, similar to a mirror. This property is conductive to implementing an angle sensor. 
         [0030]    Hereinafter, operation of the angle based method for determining orientation of the substrate  114  will be described. Initially, the substrate  114  is received by the lift pins  208  of the platen  116 , as shown  FIG. 2A . After processing the substrate  114 , the substrate may be raised to the elevated state by the lift pins  208  to be retrieved by the substrate handling robot  210 . 
         [0031]    Prior to being retrieved, an electromagnetic wave, such as an optical beam, from the detecting system  220  may be directed to the substrate. In many cases, the substrate surface  114  may be highly reflective to the optical beam.  FIG. 4  illustrates a scenario in which the substrate  114  has been properly lifted. In this case, the reflected beam travels back toward the detecting system  220 , as the surface of the substrate is roughly orthogonal to the direction of the applied optical beam. However, if a portion of the substrate remains attached to the platen, the substrate  114  may be in the tilted state, as shown in  FIG. 6 . If the degree of tilt is high, the optical beam reflected by the substrate  114  may be sufficiently deflected so that it can no longer be detected by the detecting system  220 . In one embodiment, the detecting system  220  is located about 1 meter from the substrate  114 . In this case, a tilt of 1 degree will deflect the reflected beam by approximately 2 cm. Obviously, a larger tilt angle will deflect the reflected beam even further away from the detecting system  220 , as shown in  FIG. 6 . In this case, the detecting system  220  may not detect, or may detect only a small amount of reflected beam. Thus, the range of acceptable tilt is determined by the width of the light sensor and the distance between the detecting system and the substrate. As the distance between the detecting system  220  and the substrate  114  decreases, the acceptable range of tilt angles increases. Thereafter, the orientation of the substrate  114  may be determined. If the light sensor receives the reflected beam, the tilt angle is within the acceptable range. However, if the light sensor receives an insufficient amount of the reflected beam, the tilt angle is outside the acceptable range. If it is determined that the substrate  114  is in an excessively tilted state, the controller  230  may prevent the substrate handling robot  210  from retrieving the substrate  114 . Otherwise, the robot may retrieve the substrate. 
         [0032]    An advantage of the angle based method may be that the method may compensate the detecting system  220  having difficulty in accurately measuring distance between the substrate  114  and the detecting system  220 . Such a difficulty may arise due to the highly reflective nature of the substrate surface. In the present disclosure, the angle based method may preferably be implemented with a “line” beam rather than a spot beam, as the line beam may accurately determine the tilt state even if angular variation is in one direction. 
         [0033]    In the present disclosure, the detecting system  220  may be oriented such that the line beam has a parallel relationship with any two lift pins. Such an orientation may allow the determination of the substrate&#39;s tilt about a line between the two lift pins.  FIG. 3  illustrated these axes of tilt  209  for a platen having three lifting pins  208 . Also, with this orientation, tilting about the other two axes of tilting (parallel to other two pairs of lift pins) may be detected with about half of the accuracy of tilting about the primary alignment axis. 
         [0034]    In another embodiment, a camera, such as a CCD camera is positioned next to the platen. When the substrate is lifted by the lift pins, the camera is used to capture an image of the substrate configuration. If the image shows that the substrate is flat, and at the proper elevation relative to the platen, the substrate-handling robot is used to remove the substrate. However, if the substrate is tilted, or if the elevation relative to the platen is not within an acceptable range, the robot is prohibited from removing the substrate. 
         [0035]    Thus, the detecting system  220  is adapted to detect a parameter related to the orientation of the substrate. In some embodiments, this parameter is the distance from the detecting system  220  to the substrate  114 . In other embodiments, this parameter is the angle of substrate  114  relative to a fixed surface, such as the platen  116 . Furthermore, as described above, in certain embodiments, multiple detecting systems are utilized to detect these parameters for a plurality of portions of the substrate. 
         [0036]    Although embodiments described herein are directed to a specific apparatus and method for detecting the substrate orientation and for handling the substrate processed by ion implanter, the present disclosure may be applicable to other processing system such as, for example, PIII system, PLAD system, laser processing system. As such, the present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes.