US20100145513A1 - Method for monitoring the position of a semiconductor processing robot - Google Patents

Abstract

A robotic positioning system that cooperates with a sensing system to correct robot motion is provided. The sensing system is decoupled from the sensors used conventionally to control the robot's motion, thereby providing repeatable detection of the robot's true position. In one embodiment, the positioning system includes a robot, a controller, a motor sensor and a decoupled sensor. The robot has at least one motor for manipulating a linkage controlling the displacement of a substrate support coupled thereto. The motor sensor is provides the controller with motor actuation information utilized to move the substrate support. The decoupled sensor provides information indicative of the true position the substrate support that may be utilized to correct the robot's motion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation application of the co-pending U.S. application Ser. No. 11/424,377, filed Jun. 15, 2006, which is a divisional application of U.S. patent application Ser. No. 10/697,731, filed Oct. 29, 2003, now U.S. Pat. No. 7,107,125, issued on Sep. 12, 2006, of which both applications are incorporated by reference herein.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• Embodiments of the invention generally relate to robots suitable for use in semiconductor processing systems.
• 2. Background of the Invention
• The modern semiconductor processing system typically includes a central transfer chamber surrounded by a plurality of processing chambers. The central transfer chamber is generally coupled to a factory interface by one or more load lock chambers suitable for transferring the substrate between the vacuum environment of the transfer chamber and the generally atmospheric environment of the factory interface. The factory interface typically contains one or more substrate storage cassettes for staging processed and unprocessed substrates.
• Accurate and repeatable substrate transfer using the robots of the semiconductor processing system is essential to ensure the processing results, to reduce damage to substrates and processing equipment, and to enhance repeatability between substrates.
• FIG. 7 depict one embodiment of a typical single-bladesubstrate transfer robot700 utilized in many semiconductor processing systems. Therobot700 includes ablade710 for supporting asubstrate712 during transfer. Theblade710 is coupled to abody704 by alinkage702. The linkage comprises afirst arm706 and asecond arm708 that are coupled to the body at a first end and coupled to awrist714 at a second end. The wrist is coupled to theblade710. Eacharm706,708 is coupled to a respective motor (not shown) concentrically stacked within thebody704. The positioning of theblade710 is determined by the relative angular positioning of therespective arms706,708 by the concentrically stacked motors. For example, if thelinkages706,708 are rotated by the concentrically stacked motors in the same direction about thecentral axis720 of thebody704, theblade710 is rotated about thecentral axis720 as shown by thearrow716. If the first arm andsecond arm706,708 are rotated in opposite directions, theblade710 is radially extended or retracted, as shown byarrow718.
• However, the ability to accurately position theblade710 may be compromised by a number of factors. For example, thelinkage702 and/or theblade710 may become bent during handling or maintenance procedures. Additionally, thermal expansion of the linkage or loosening of the belts commonly used within the linkage may result in positional drift of the blade. Thus, the blade may not arrive in the position expected based on a calculated movement of the arm. As these aforementioned problems undesirably diminish the ability for efficient and repeatable substrate transfer, it would be desirable to improve the positional accuracy of the robot blade.
• Therefore, there is a need for a method and apparatus for monitoring the position of a substrate transfer robot.
SUMMARY OF THE INVENTION
• A robotic positioning system that cooperates with a sensing system to correct robot motion is provided. The sensing system is decoupled from the sensors used conventionally to control the robot's motion, thereby providing repeatable detection of the robot's true position. In one embodiment, the positioning system includes a robot, a controller, a motor sensor and a decoupled sensor. The robot has at least one motor for manipulating a linkage controlling the displacement of a substrate support coupled thereto. The motor sensor provides the controller with motor actuation information utilized to move the substrate support. The decoupled sensor provides information indicative of the true position of the substrate support that may be utilized to correct the robot's motion.
BRIEF DESCRIPTION OF THE DRAWINGS
• So that the manner in which the above-recited features, advantages and objects of the present invention are obtained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the impended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are, therefore, not be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
• FIG. 1 is a plan view of an exemplary substrate processing system including at least one robot having at least one decoupled robot position sensing system;
• FIG. 2 is a side view of the factory interface illustrating one embodiment of a robotic positioning system that depicts the interface between a substrate transfer robot and a sensing system;
• FIG. 3 depicts a sectional view of one embodiment of the sensing system depicted inFIG. 2;
• FIG. 4 is a side view of another sensing system;
• FIG. 5 is a bottom view of one embodiment of a bracket of the sensing system ofFIG. 4;
• FIG. 6 is a bottom view of another embodiment of a sensing system having sensors mounted to a ceiling of a factory interface; and
• FIG. 7 (prior art) is a plan view of an exemplary substrate transfer robot suitable of a conventional substrate transfer robot suitable for use in a semiconductor processing system.
• To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
DETAILED DESCRIPTION
• FIG. 1 depicts one embodiment of asemiconductor processing system100 having at least onerobotic positioning system150. Theexemplary processing system100 generally includes atransfer chamber102 circumscribed by one ormore processing chambers104, afactory interface110 and one or moreload lock chambers106. Theload lock chambers106 are generally disposed between thetransfer chamber102 and thefactory interface110 to facilitate substrate transfer between a vacuum environment maintained in thetransfer chamber102 and a substantially ambient environment maintained in thefactory interface110.
• Thetransfer chamber102 defines an evacuableinterior volume116 through which substrates are transferred between theprocess chambers104 coupled to the exterior of thetransfer chamber102. Theprocess chambers104 are typically bolted to the exterior of thetransfer chamber102. Examples ofprocess chambers104 that may be utilized include etch chambers, physical vapor deposition chambers, chemical vapor deposition chambers, ion implantation chambers, orientation chambers, lithography chambers and the like.Different process chambers104 may be coupled to thetransfer chamber102 to provide a processing sequence necessary to form a predefined structure or feature upon the substrate surface.
• Theload lock chambers106 are generally coupled between thefactory interface110 and thetransfer chamber102. Theload lock chambers106 are generally used to facilitate transfer of the substrates between the vacuum environment of thetransfer chamber102 and the substantially ambient environment of thefactory interface110 without loss of vacuum within thetransfer chamber102. Eachload lock chamber106 is selectively isolated from thetransfer chamber102 and thefactory interface110, through the use of slit valves (not shown).
• Acontroller170 is coupled to thesystem100 to control processing and substrate transfers. Thecontroller170 includes a central processing unit (CPU)176,support circuits174 andmemory172. TheCPU176 may be one of any form of computer processor that can be used in an industrial setting for controlling various chambers and subprocessors. Thememory172 is coupled to theCPU176. Thememory176, 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. Thesupport circuits174 are coupled to theCPU176 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.
• Afirst transfer robot160 is disposed in thefactory interface110 and is adapted to transfersubstrates112 between at least onesubstrate storage cassette114 coupled to thefactory interface110 and theload lock chambers106. Eachcassette114 is configured to store a plurality of substrates therein. One example of a factory interface that may be adapted to benefit from the invention is described in U.S. patent application Ser. No. 09/161,970 filed Sep. 28, 1998 by Kroeker, which is hereby incorporated by reference in its entirety.
• Asecond robot108 is deposed in thetransfer chamber102 and is adapted to transfersubstrates112 between the processingchambers104 and theload lock chambers106. The secondsubstrate transfer robot108 may include one or more blades utilized to support the substrate during transfer. Thesecond robot108 may have two blades, each coupled to an independently controllable motor (known as a dual blade robot) or have two blades coupled to thesecond robot108 through a common linkage. In one embodiment, the transfersecond robot108 has asingle blade130 coupled to thesecond robot108 by a (frog-leg)linkage132.
• Thefirst transfer robot160 may include one or more blades utilized to support the substrate during transfer. Thefirst transfer robot160 may have two blades, each coupled to an independently controllable motor (known as a dual blade robot) or have two blades coupled to thefirst robot160 through a common linkage. In one embodiment, thefirst robot160 has asingle blade140 coupled to abody142 offirst robot160 by an articulatedlinkage144. A motor (not shown), housed within thebody142 controls the range of motion of theblade140 about acentral axis146 of therobot160.
• To increase the range of motion of thefirst robot160, thebody142 is coupled to aguide138 that is selectively positioned along arail136 by anactuator134. Theactuator134 may be any motion device suitable for positioning thefirst robot160 along therail136, thereby moving thecentral axis146 within thefactory interface110 to facilitate access of theblade140 to substrates within any of thecassettes114 orload lock chambers106. Theactuator134 is generally interfaced with an onboard sensor128, for example a rotary encoder, which provides thecontroller120 with a derived positional information of thebody142 along therail136. The derived position is a position based on an anticipated motion resulting from a predefined actuation. For example, as thebody142 is expected to move a predefined distance per motor revolution, information provided by thesensor128 may be utilized to determine a change in position of thebody142. Referenced from a calibrated position stored in the memory of thecontroller170, the anticipated position of thebody142 may be derived by knowing the motor motion and/or positional information provided by thesensor128. Alternatively, the may be another sensor for providing information indicative of the linear displacement of thebody142, such as a linear displacement transducer and the like.
• At least one of therobots160,108 is interfaced with asensing system120 to comprise arobotic positioning system150. Thesensing system120 provides information to monitor and/or correct the position of the robot. Although therobotic positioning system150 shown to include thefirst transfer robot160 disposed in thefactory interface110 of theexemplary processing system100, therobotic positioning system150 may be configured to include thesecond robot108. It is also contemplated that it is desirable to adapt therobotic positioning system150 for use with other robots utilized in other processing systems or semiconductor FABs, wherever accurate robot positioning and correction is desirable.
• In the embodiment depicted inFIG. 1, thefirst transfer robot160 is interfaced with thesensing system150 such that the positional accuracy of thefirst transfer robot160 may be determined and corrected using one or more sensors decoupled from the sensors on board the robot conventionally used to control the robot's motion. Thesensing system150 includes at least onesensor122 decoupled from therobot160 and configured to provide a metric indicative of a true position of therobot160. The true position is a position based on the actual position of therobot160.
• In the embodiment depicted inFIG. 1, thesensing system150 is configured to provide a metric indicate of the true position of thecentral axis136. Thesensing system150 provides thecontroller120 with the true position which is compared with the derived position. If the true and derived positioned are equivalent, then thebody142 andcentral axis136 of thefirst robot160 is accurately positioned. If the true and derived positioned are not in agreement, thecontroller120 then resolves a motion correction it the motor instructions such that the corrected derived position returns thebody142 to the true position. In this manner, thecentral axis136 of thefirst robot160 may be accurately and repeatably positioned. Moreover, the metric provided by the decoupledsensor122 is transparent to the motion of thefirst robot160 during normal operation, the motion of therobot160 may be monitored and corrected in-situ, without the need to interrupt processing to run calibration procedures.
• FIG. 2 is a side view of thefactory interface110 illustrating one embodiment of an interface between thefirst transfer robot160 and thesensing system120 comprising therobotic positioning system150. Thesensing system120 generally includessensor122 and aflag202. The at least one of thesensor122 orflag202 is coupled to thefactory interface110 and is fixed relative to thecentral axis146 of thefirst robot160. In the embodiment depicted inFIG. 2, thesensor122 is coupled to thefactory interface110 and theflag202 is coupled to theguide138 supporting therobot body142 on therail136.
• Thesensor122 is fixed in a position where theflag202, when passing through or within a predefined sensing field of thesensor122, causes thesensor122 to change states. The position of thecentral axis146 within thefactory interface110 corresponding to where the sensor changes states, known as a calibration position, is indicated by dashedline204. Other reference positions of thecentral axis146 within thefactory interface110 corresponding to where the substrate exchanges (or other process requiring theblade140 to be in a predefined position) are performed, known as a calculated or taught position, are shown by dashedlines208. In the embodiment depicted inFIG. 2, the dashedlines208 indicate the position of the robot'saxis146 where transfers between thefirst robot160 andload lock chambers106 occur. Generally, thefirst robot160 is programmed or taught to move to the taught position by instructing the robot to move a predefined distance (or rotation) as resolved by the on-board sensor128. In other words, movement of thefirst robot160 to the taught position is provided by energizing the actuator134 to move therobot160 by rotating (in the case of a motorized actuator) a number of rotations corresponding to a desired distance needed to reach the taught position as counted to the on-board sensor128.
• Since the on-board sensor128 may accumulate positional error over repeated movements or mechanical backlash and play within the motion components, thefirst robot160 may not arrive in the taught position as indicated by the dashedlines208. To correct motion error or robot drift, thesensor122, which is decoupled from the mechanical linkages of therobot160 and other sources of drift, provides thecontroller170 with a metric indicative of thetrue position robot160 at the calibration position which is compared with the metric provided by the onboard sensor128. Differences between the expected position of thefirst robot160 derived from thesensor128 and the reference metrics at the calibrated position are indicative of drift in robot motion, and provide a metric to correct, e.g., recalibrate the robots movement, to that data provided from the onboard sensor128 accurately positions the first robot in the taught positions.
• The calibration position may be advantageously positioned between taught positions such that normal robot operations during processing passes the flag through the calibration position. Each time the flag passes through the calibration position, the robot motion may be recalibrated in-situ, thereby continually ensuring accurate robot positioning without need for separate recalibration procedures.
• FIG. 3 depicts a sectional view of one embodiment of thesensor122 andflag202 of thesensing system120 depicted inFIG. 2. Thesensor122 is coupled tofactory interface110 and provides thecontroller120 with a metric of robot position at each change in sensor state. Thesensor122 may include a separate emitting and receiving unit or may be self-contained such as “thru-beam” and “reflective” sensors. Thesensor122 may be an optical sensor, a proximity sensor, mechanical limit switch, video imaging device, Hall-effect, reed switch or other type of detection mechanism suitable for detecting the presence of thesecond robot108 when in a predefined position. It is contemplated that a video imaging device may provide metrics indicative of planar position along with elevation, thereby reducing the number of sensors required in a sensing system. It is also contemplated that thesensor122, particularly when embodying an optical sensor or video device, may be located outside thefactory interface110 and positioned to view theflag202, for example, through a window.
• In one embodiment, thesensor122 comprises anoptical emitter302 andreceiver304. One sensor suitable for use is available from Banner Engineering Corporation, located in Minneapolis, Minn. Thesensor122 is positioned such thatflag202, coupled to thesecond robot108, guide138 or other component that moves with the robotcentral axis146, interrupts a signal passing between theemitter302 andreceiver304, such as abeam306 of light. The interruption and/or return to an uninterrupted state of thebeam306 causes a change in state of thesensor122. For example, thesensor116 may have a 4 to 20 ma output, where thesensor122 outputs a 4 ma in the uninterrupted state while the sensor outputs 20 ma in the interrupted state. Sensors with other outputs may be utilized to signal the change in sensor state.
• FIG. 4 depicts anothersensing system400 that may be utilized in place of, or in addition to, thesensing system120 described above. Thesensing system400 includes one ormore sensors402 disposed in a spaced apart relation to thefirst robot160. The one ormore sensors402 may be configured as similar to thesensor122 described above. Thesensors402 are oriented in a position that is fixed relative to thebody142 of thefirst robot160. Thesensors402 are additionally positioned such that theblade140 of thefirst robot160 causes one or more of thesensors402 to change state when moving between the interior of thefactory interface110 and at least one of theload lock chambers106 or cassettes114 (as seen inFIG. 1).
• In one embodiment, abracket404 is coupled to at least one of theguide138 orrobot body142. Thebracket404 provides a mounting surface for thesensors402. It is also contemplated that thebracket404 be coupled to therobot160 in a manner that allows thebracket404 to rotate about thecentral axis146 such that thesensors402 are maintained in radial alignment with theblade140, thereby allowing positional metrics to be obtained with one sensor or group of sensors during the actuation of theblade140.
• Referring additionally to a bottom view of a portion of thebracket404 depicted inFIG. 5, thebracket404 supports a first and at least a second decoupledsensors502,508 of the plurality ofsensors402. The first decoupledsensor502 is configured to provide a metric indicative of the relative distance between theblade140 and the bracket404 (shown by “D” inFIG. 4). The metric provided to thecontroller170 may compared to a metric of blade elevation provided by an onboard sensor504 that provides feedback from the motion of an actuator506 of thefirst robot160 controlling the elevation of theblade140. In one embodiment, the onboard sensor504 is a linear displacement transducer or other sensor suitable to determine the change in elevation of theblade140 as moved by the actuator506. In this manner, drift or differences between the expected position of the blade140 (i.e., the position based on blade actuator motion as monitored by the on board sensor504) may be corrected using the actual position information provided by the decoupledsensor502.
• In the embodiment depicted inFIG. 5, thebracket404 additionally supports at least a second decoupledsensor508 of the plurality ofsensors402 which is configured to provide a metric indicative of the relative distance and/or angular orientation of theblade140 to thecentral axis146 of thefirst robot160. The metric provided to thecontroller170 may compared to a metric of blade position provided by an on-board sensor510 that provides feedback from the motion of a motor(s)512 controlling the rotation and/or extension of theblade140. In the manner, drift or differences between the expected position of the blade140 (i.e., the position based on robot motor motion as monitored by the on board sensor510) may be corrected using the actual position information provided by the decoupledsensor508.
• FIG. 6 is a bottom view of asensing system600 havingsensors602 mounted to aceiling604 of afactory interface110. Thesensors602 are generally configured similar to thesensors402 described above, and are positioned between a firstfactory interface robot604 and a secondfactory interface robot606. Therobots604,606, configured similar to therobot160 described above, may be programmed to pass thererespective blades140 through a calibration position (shown by the center line610) below thesensors602 to obtain true positional metrics that may be utilized to correct the robots motion as described above.
• Thus, a sensing system has been provided that cooperates with a robotic positioning system to correct robot motion. The sensing system is decoupled from the sensors used conventionally to control the robot's motion, thereby providing repeatable detection of the robot's true position. The true position may be compared to an expected position to correct for drift and misalignment. Moreover, the sensing system may be advantageously configured to allow for in-situ data acquisition and motion correction, thereby eliminating the need for separate recalibration procedures.
• While the foregoing is directed to the illustrative 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.

Claims (6)

1. A method for correcting robotic motion, comprising:

sensing an actual position of a robot at a calibration position with a sensor decoupled from the robot;

comparing the actual position of the robot with a calculated position corresponding to the calibration position; and

compensating for differences in the actual position and calculated position.

2. The method ofclaim 1, wherein the sensing further comprises:

moving the robot laterally to a taught position; and

causing the sensor to change state before the robot reaches the taught position.

3. The method ofclaim 2, wherein the sensing further comprises:

moving a blade of the robot to a taught position; and

causing the sensor to change state.

4. A method for correcting robotic motion, comprising:

obtaining a metric indicative of an actual position of a blade of a robot at a first position with a sensor decoupled from the robot;

comparing the actual position of the robot with an expected position derived from a sensor coupled to one or more robot actuators; and

correcting robot motion in response to differences between the actual position and expected position.

5. The method ofclaim 4, wherein the obtaining further comprises:

moving the blade to a taught position; and

causing the sensor to change state.

6. The method ofclaim 4 further comprising:

obtaining a metric indicative of an actual position of a blade of a second robot at the first position with the sensor;

comparing the actual position of the second robot with an expected position derived from a sensor coupled to one or more second robot actuators; and

correcting second robot motion in response to differences between the actual position and expected position.

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