Automatic alignment of overhead transport vehicles to semiconductor manufacturing tool load ports

Abstract

Described herein are methods and systems for automatically aligning an overhead hoist transport (OHT) vehicle to a load port of a wafer fabrication tool during equipment operation and installation phases in a semiconductor manufacturing facility. In one aspect, an alignment frame including a digital image capture device is attached to a wafer-in-process (WIP) transport pod. Images captured by the image capture device are analyzed to determine a positioning error of the OHT vehicle relative to the alignment frame based on the position of the OHT vehicle in the images. In another aspect, an inertial measurement device is coupled to a gripper assembly of the OHT vehicle. Inertial measurement signals are collected when the gripper assembly docks with the WIP transport pod. The inertial measurement signals are analyzed to determine an initial positioning error of the gripper assembly relative to the WIP transport pod.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority to U.S. patent application Ser. No. 18 / 369,484, filed Sep. 18, 2023, and entitled "Automatic Alignment Of Overhead Transport Vehicles To Load Ports Of Semiconductor Fabrication Tools." This U.S. patent application claims priority under 35 U.S.C. § 119 to U.S. provisional patent application Ser. No. 63 / 407,473, filed Sep. 16, 2022, and entitled "Method and System for Automatic Alignment of Overhead Hoist Transport Vehicles to Load Ports in Semiconductor Fabrication Plants." The subject matter of both applications is incorporated herein by reference in its entirety.

[0002] The described embodiments relate to systems and methods for wafer transport in semiconductor manufacturing facilities. [Background technology]

[0003] Semiconductor devices are fabricated by a series of processing steps applied to a wafer. The various features and structural levels of the semiconductor device are formed by these processing steps. For example, lithography, among other processes, is a semiconductor manufacturing process that involves creating patterns on a semiconductor wafer. Further examples of semiconductor manufacturing processes include, but are not limited to, chemical-mechanical polishing, etching, deposition, and ion implantation. Multiple semiconductor devices are fabricated on a single semiconductor wafer, which is then separated into individual semiconductor devices.

[0004] A series of processing steps is performed by multiple different wafer processing tools, e.g., lithography tools, etch tools, etc. Therefore, wafers must be transported from one tool to another to progress through the series of wafer processing steps. Typically, in facilities that manufacture large volumes of wafers, wafers are transported from one tool to another in groups, rather than individually. Each set of manufactured wafers is stored in a work-in-process (WIP) transport pod. An example of a WIP transport pod is the standardized front-opening integrated pod (FOUP) commonly used in semiconductor manufacturing facilities. The WIP transport pod provides a controlled and protected environment for the wafers as they move from one tool to another. Typically, the WIP transport pod is docked to a load port of the semiconductor manufacturing tool. A load port subsystem individually removes wafers from the WIP transport pod, prepares each wafer for processing, and returns the processed wafers to the WIP transport pod. The WIP transport pod is then uncoupled from the semiconductor manufacturing tool's load port and transported to the next process destination, eg, the next wafer processing tool in the sequence, a storage rack, etc.

[0005] Modern semiconductor manufacturing facilities typically use overhead hoist transport (OHT) systems to dock, detach, and transport WIP transport pods between various process destinations. OHT systems typically include multiple OHT vehicles that travel along tracks suspended from the ceiling of the semiconductor manufacturing facility. The trucks and OHT vehicles are typically positioned above the load ports of wafer processing machines. The OHT vehicles travel along the tracks and stop directly above the load ports of the wafer processing tools. Each OHT vehicle typically uses a cable drive system to raise and lower a gripper assembly, which is selectively attached to and detached from the WIP transport pod. When collecting a WIP transport pod from the load port, the gripper assembly is lowered from the OHT vehicle onto the WIP transport pod. The gripper assembly grasps a handle mechanism attached to the top of the WIP pod. The OHT vehicle then lifts the gripper assembly and the attached WIP transport pod into the OHT vehicle's payload bay. Once the WIP transport pod is secured in the payload bay of the OHT vehicle, the OHT vehicle moves along the track system to its next process destination. When placing the WIP transport pod on the load port of a wafer processing tool, the gripper assembly and attached WIP transport pod are lowered from the OHT vehicle to the load port. The gripper assembly releases a handle mechanism attached to the top of the WIP pod, effectively removing the WIP transport pod from the gripper assembly. The OHT vehicle then lifts the removed gripper assembly into the payload bay of the OHT vehicle. The OHT vehicle then moves along the track system to its next destination.

[0006] FIG. 1 is a simplified diagram illustrating an OHT system 100 positioned above a load port 120 of a wafer fabrication tool in one embodiment. As shown in FIG. 1, the OHT system 100 includes a track 101 and an OHT vehicle 102. An actuator 103 is used to move the OHT vehicle 102 along the track 101. Cables 104A and 104B suspend a gripper assembly 105 from the OHT vehicle 102. A cable drive system (not shown) of the OHT vehicle 102 is used to raise and lower the gripper assembly 105. The gripper assembly 105 includes gripper elements 106A and 106B. An actuator (not shown) of the gripper assembly 105 moves the gripper elements 106A and 106B laterally, as indicated by the arrows in FIG. 1 . The gripper assembly 105 also includes an alignment mechanism 107 to facilitate alignment with a WIP transport pod 110.

[0007] FIG. 1 also shows a WIP transport pod 110 positioned on the load port 120. As shown in FIG. 1, the WIP transport pod 110 includes a transport mechanism 109 coupled to the WIP transport pod 110. The transport mechanism 109 includes an alignment mechanism 108 that engages with the alignment mechanism 107 when the gripper assembly 105 is aligned with and in contact with the transport mechanism 109. In one example, as shown in FIG. 1, the gripper assembly 105 is decoupled from the payload bay of the OHT vehicle and is in transit between the payload bay of the OHT vehicle and the WIP transport pod 110. This configuration is typical when the gripper assembly is being moved into a position to lock onto the transport mechanism 109 of the WIP transport pod 110 or when it is being moved into the payload bay of the OHT vehicle after being unlocked from the WIP transport pod 110.

[0008] 2 is a simplified diagram illustrating the gripper assembly 105 aligned and locked to the transport mechanism 109 of the WIP transport pod 110. As shown in FIG. 2, alignment mechanisms 107, 108 contact and determine the position of the gripper assembly 105 relative to the transport mechanism 109. Additionally, gripper elements 106A, 106B move to a clamping position, i.e., the gripper elements 106A, 106B move toward the transport mechanism 109, effectively locking the gripper assembly 105 to the transport mechanism 109. This configuration is typical when the WIP transport pod 110 is positioned at the load port 120 and the gripper assembly 105 and WIP transport pod 110 are about to move toward a payload bay of an OHT vehicle, or when the gripper elements 106A, 106B move to an unclamping position, i.e., away from the transport mechanism 109, effectively unlocking the gripper assembly 105 from the transport mechanism 109.

[0009] 3 is a simplified diagram showing the gripper assembly 105 and WIP transport pod 110 secured to the payload bay of an OHT vehicle. This configuration is typical when the OHT vehicle 102 is moving the WIP transport pod 110 to another process destination, or when the gripper assembly 105 is moving the WIP transport pod 110 toward a load port 120.

[0010] A common problem with OHT systems is misalignment between the OHT vehicle and the WIP transport pod placed on the load port. When alignment mechanisms 107 and 108 make contact, they mechanically align the gripper assembly 105 with the WIP transport pod's transport mechanism. However, this alignment is satisfactory when the misalignment is small. If the misalignment exceeds a relatively small tolerance, the gripper assembly cannot reliably lock onto the WIP transport pod. At the very least, this results in a failure requiring operator intervention. However, in some cases, failure to properly secure the payload can cause the OHT vehicle to drop the WIP transport pod, damaging it and the wafers contained within, resulting in operational delays. The cost of such an incident can easily total hundreds of thousands of dollars. To reduce the likelihood of such an incident, alignment between the OHT system and the WIP transport pod placed on the wafer processing tool's load port is performed during the setup of a new semiconductor fabrication facility. In addition, the alignment procedure is repeated periodically to ensure that any misalignment that may occur over time, e.g., due to physical movement of the device's position, accumulation of position measurement errors, etc., is well within the mechanical tolerances of the alignment mechanism.

[0011] Currently, the alignment of each OHT vehicle with the WIP transport pods located at the load port is performed manually, a labor-intensive, time-consuming, and costly process. When a new semiconductor manufacturing facility is commissioned, it can take weeks to complete the alignment of hundreds of OHT vehicles. Furthermore, periodic realignment is performed manually, requiring production to be interrupted during each realignment session.

[0012] In summary, it would be desirable to improve the OHT system to allow for rapid and accurate initial alignment with the load port of a wafer fabrication tool. Additionally, it would be desirable to improve the OHT system to allow for periodic realignment with the load port of a wafer fabrication tool without interrupting the fabrication process. Summary of the Invention

[0013] SUMMARY OF THE INVENTION A method and system for automatically aligning an overhead hoist transport (OHT) vehicle with a wafer fabrication tool's load port during the operation and installation phase of equipment in a semiconductor fabrication facility is described herein.

[0014] In one aspect, an automated wafer transport pod alignment system automatically aligns an overhead hoist transport (OHT) vehicle with a wafer fabrication tool's load port during equipment installation at a semiconductor fabrication facility. During installation, alignment of the OHT vehicle with the wafer fabrication tool's load port is achieved in a fraction of the time required to perform the alignment manually. This provides significant cost savings for semiconductor fabrication facilities with hundreds of wafer fabrication tools.

[0015] The alignment frame includes one or more geometric features that position the alignment frame in two or more degrees of freedom relative to a wafer-in-process (WIP) transport pod when the alignment frame contacts the WIP transport pod. A digital image capture device is coupled to the alignment frame. The field of view of the digital image capture device faces away from the WIP transport pod. An image of an overhead hoist transport (OHT) vehicle is captured by the digital image capture device when the OHT vehicle is within the field of view of the digital image capture device. The image is analyzed to determine a position of the OHT vehicle in the image. A positioning error of the OHT vehicle relative to the alignment frame is determined based on the position of the OHT vehicle in the image. The positioning error is communicated to the OHT vehicle. In some embodiments, a positioning setpoint of the OHT vehicle is adjusted to reduce the positioning error of the OHT vehicle relative to the alignment frame.

[0016] In another aspect, an automated wafer transport pod alignment system continuously and automatically aligns an overhead hoist transport (OHT) vehicle with a wafer fabrication tool load port during operation of equipment in a semiconductor manufacturing facility. In this way, misalignment between the overhead hoist transport (OHT) vehicle and the wafer fabrication tool load port remains well within limits requiring offline realignment to be performed.

[0017] An inertial measurement device is coupled to a gripper assembly of an overhead hoist transport (OHT) vehicle. The gripper assembly includes one or more geometric features that position the gripper assembly at a predetermined position relative to a wafer-in-process (WIP) transport pod when the gripper assembly docks with the WIP transport pod. The inertial measurement device generates measurement signals indicative of acceleration, velocity, or both, of the gripper assembly when the gripper assembly docks with the WIP transport pod. The measurement signals are analyzed to determine an initial positioning error of the gripper assembly relative to the WIP transport pod. The initial positioning error is communicated to the OHT vehicle. In some embodiments, a positioning setpoint of the OHT vehicle is adjusted to reduce the initial positioning error of the OHT vehicle relative to the alignment frame.

[0018] The foregoing is a summary and, as such, necessarily contains simplifications, generalizations, and omissions of detail. Accordingly, those skilled in the art will appreciate that this summary is illustrative only and is not intended to be limiting in any way. Other aspects, inventive features, and advantages of the devices and / or processes described herein will become apparent from the non-limiting detailed description set forth herein. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a simplified diagram illustrating an overhead hoist transport (OHT) system positioned above a load port of a wafer fabrication tool in one embodiment.

[0020] [Figure 2]FIG. 1 is a simplified schematic diagram showing the gripper assembly aligned and locked to the transport mechanism of a wafer-in-process (WIP) transport pod.

[0021] [Figure 3] FIG. 1 is a simplified schematic showing the gripper assembly and WIP transport pod secured to the payload bay of an OHT vehicle.

[0022] [Figure 4] 1 is a simplified diagram illustrating an automated wafer transport pod alignment system in one embodiment.

[0023] [Figure 5] 5 is a simplified diagram showing in more detail the automatic wafer transport pod alignment system shown in FIG. 4.

[0024] [Figure 6] 1 is a simplified diagram illustrating an image captured by a digital image capture device of an automated wafer transport pod alignment system in one example.

[0025] [Figure 7] 1 is a flowchart of a method suitable for aligning an OHT system with a load port of a wafer fabrication tool as described herein.

[0026] [Figure 8] 1 is a simplified diagram illustrating the initial contact stage of the gripper assembly contacting the transport handle of the WIP transport pod.

[0027] [Figure 9] FIG. 10 is a simplified diagram illustrating contacting the gripper assembly with the transport handle of the WIP transport pod at a stage after initial contact.

[0028] [Figure 10] 10 is a simplified schematic diagram illustrating the contact of the gripper assembly with the transport handle of the WIP transport pod at a stage subsequent to that shown in FIG. 9.

[0029] [Figure 11] FIG. 10 illustrates an automated wafer transport pod alignment system in another embodiment.

[0030] [Figure 12] 10 is a flowchart of another method suitable for aligning an OHT system with a load port of a wafer fabrication tool as described herein. DETAILED DESCRIPTION OF THE INVENTION

[0031] Reference will now be made in detail to background examples and certain embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0032] Described herein are methods and systems for automatically aligning an overhead hoist transport (OHT) vehicle with a wafer fabrication tool's load port during equipment operation and installation phases in a semiconductor fabrication facility. During installation, alignment of the OHT vehicle with the wafer fabrication tool's load port is achieved in a fraction of the time required to perform the alignment manually. This provides significant cost savings for semiconductor fabrication facilities with hundreds of wafer fabrication tools.

[0033] In one aspect, an automated wafer transport pod alignment system automatically aligns an overhead hoist transport (OHT) vehicle to a wafer fabrication tool load port during the equipment installation phase in a semiconductor fabrication facility.

[0034] 4 is a simplified diagram illustrating an automated wafer transport pod alignment system 130 in one embodiment. As shown in FIG. 4, the automated wafer transport pod alignment system 130 includes an alignment frame 131 that includes one or more geometric features 132 that position the alignment frame 131 in a predetermined position relative to the transport mechanism 109 of the wafer in process (WIP) transport pod 110. When the alignment features 132 contact complementary alignment features on the transport handle 109, the alignment features 132 align the alignment frame 131 relative to the WIP transport pod 110. As shown in FIG. 4, the alignment coordinate frame {X A , Y A , Z A} is fixed to the WIP transport pod 110 (axis Y A (Points into the drawing page.) In some embodiments, the alignment mechanism 132 includes a kinematic mount that can move the alignment frame 131 to a predetermined position relative to the transport mechanism 109 in six degrees of freedom, e.g., X A Axis, Y A axis and Z A The predetermined position of the alignment frame 131 along the X axis, A Axis, Y A axis and Z A However, in general, the alignment mechanism 132 will position the alignment frame 131 at least X A In many embodiments, the alignment mechanism 132 positions the alignment frame 131 in a predetermined position relative to the transport mechanism 109 in the X direction. A A predetermined position for the transport mechanism 109 in the X direction and A axis and Y A In some embodiments, the alignment mechanism 132 is similar to the alignment mechanism used as part of the gripper assembly 105.

[0035] Automated wafer transfer pod alignment system 130 also includes a digital image capture device 137 coupled to alignment frame 131. In the embodiment shown in FIG. 4, digital image capture device 137 is mounted to electronics mounting board 134, which is mounted to alignment frame 131. In some other embodiments, digital image capture device 137 is mounted directly to alignment frame 131. In the embodiment shown in FIG. 4, digital image capture device 137 includes image detector 133 and optical lens element 135. Typically, image detector 133 is a photosensitive detector, such as a charge-coupled device (CCD) detector, a complementary metal-oxide semiconductor (CMOS) detector, or the like. Optical lens element 135 includes one or more optical elements used to form the field of view of digital image capture device 137.

[0036] 4, the field of view 138 of the digital image capture device 137 faces toward the side of the OHT vehicle 102 opposite the WIP transport pod 110. In the embodiment shown in FIG. 4, the size of the field of view 138 expands from the digital image capture device 137 toward the OHT vehicle 102 and includes the entire OHT vehicle 102.

[0037] In some embodiments, the digital image capture device 137 is a built-in stereo camera system, however, in general, any suitable image capture device can be used.

[0038] The automated wafer transfer pod alignment system 130 also includes one or more computing systems coupled to the alignment frame. In the embodiment shown in FIG. 4 , the computing system 140 is mounted to the electronics mounting board 134, which is mounted to the alignment frame 131. In some other embodiments, the computing system 140 is mounted directly to the alignment frame 131. In some other embodiments, the computing system 140 is integrated with the digital image capture device 137, and the integrated unit is mounted to the alignment frame 131. As shown in FIG. 5 , the computing system 140 includes a sensor interface 146, at least one processor 141, memory 142, a bus 143, and a wireless communication transceiver 147. The sensor interface 146, the processor 141, the memory 142, and the wireless communication transceiver 147 are configured to communicate via the bus 143. In some embodiments, the computing system 140 is a single-board computer system, such as a single-board computer manufactured by Raspberry Pi.

[0039] Sensor interface 146 includes a digital input / output interface configured to communicate with digital image capture device 137 and receive digital image data 149 captured by digital image capture device 137. In this example, digital image capture device 137 includes on-board electronics and generates digital signals 149 indicative of the captured image.

[0040] Memory 142 includes memory 144 that stores image data communicated from digital image capture device 137. Image data 149 stored in memory 144 is used to estimate alignment errors in the position of OHT vehicle 102 relative to WIP transport pod 110. Memory 142 also includes memory 145 that stores program code that, when executed by processor 141, causes processor 141 to perform the automatic alignment functionality described herein.

[0041] In some examples, processor 141 is configured to store digital image data 149 received by sensor interface 146 in memory 144. Additionally, processor 141 is configured to read digital image data 149 stored in memory 144 and estimate a registration error based on the digital image data 149. Additionally, processor 141 is configured to transmit a signal indicative of the estimated registration error to wireless communication transceiver 147. In some embodiments, wireless communication transceiver 147 is configured to wirelessly communicate a radio frequency signal 160 indicative of the estimated registration error from computing system 140 to computing system 150 via a wireless communication link. As shown in FIG. 5 , wireless communication transceiver 147 transmits radio frequency signal 160 via antenna 148. Radio frequency signal 160 includes digital information indicative of the estimated registration error and is communicated from computing system 140 to computing system 150.

[0042] Generally, the computing system 150 is integrated with the OHT system 100. In some embodiments, the computing system 150 is integrated with the OHT vehicle subsystem 102. In some other embodiments, the computing system 150 is located remotely from the OHT vehicle subsystem 102.

[0043] 5, computing system 150 includes control device interface 156, at least one processor 151, memory 152, bus 153, and wireless communication transceiver 157. Control device interface 156, processor 151, memory 152, and wireless communication transceiver 157 are configured to communicate via bus 153.

[0044] Processor 151 is configured to receive a signal indicative of the estimated alignment error from wireless communication transceiver 157. In some embodiments, wireless communication transceiver 157 is configured to receive a radio frequency signal 160 indicative of the estimated alignment error wirelessly from computing system 140 over a wireless communication link. As shown in Figure 5, wireless communication transceiver 157 receives radio frequency signal 160 via antenna 158. Radio frequency signal 160 includes digital information indicative of the estimated alignment error.

[0045] The memory 152 includes a memory 154 that stores the alignment position error signal transmitted from the computing system 140. In some examples, the processor 151 is configured to store the alignment position error signal received from the computing system 140 in the memory 154. Additionally, the processor 151 is configured to read the alignment position error signal stored in the memory 144 and generate an updated positioning setpoint based on the alignment positioning error. In some embodiments, the processor 151 generates the updated positioning setpoint when the alignment positioning error exceeds a predetermined threshold stored in a memory, such as the memory 154. If the alignment positioning error is less than the predetermined threshold, the positioning setpoint of the OHT vehicle 102 is not updated. The predetermined threshold is set to a value for the alignment position error that ensures there is essentially no risk of misalignment between the gripper assembly 105 and the WIP transport pod 110 during production.

[0046] In some embodiments, the control device interface 156 includes a digital input / output interface configured to communicate digital control command signals 159 to the actuators 161 of the OHT vehicle 102 that cause the OHT vehicle 102 to move to an updated positioning setpoint, thereby positioning the OHT vehicle 102 above the WIP transport pod 110 with a small alignment error. In some other embodiments, the control device interface 156 includes suitable digital-to-analog conversion (DAC) electronics configured to communicate analog control command signals 159 to the actuators 161 of the OHT vehicle 102 that cause the OHT vehicle 102 to move to an updated positioning setpoint.

[0047] In some other embodiments, the control command signal 159 of the control device interface is a signal indicating an updated positioning setpoint that is communicated to a motion controller, which communicates a control signal to an actuator 161 of the OHT vehicle 102 to move the OHT vehicle 102 to the updated position setpoint.

[0048] The memory 142 also includes a memory 145 that stores program code that, when executed by the processor 141, causes the processor 141 to perform the auto-alignment functionality described herein.

[0049] In some embodiments, the automated wafer transport pod alignment system 130 also includes a rechargeable battery coupled to the alignment frame. The rechargeable battery is electrically coupled to and provides power to one or more computing systems, digital image capture devices, or both. In a preferred embodiment, the rechargeable battery powers both the one or more computing systems and the digital image capture devices, such that the automated wafer transport pod alignment system 130 can be used to perform alignment operations at a wafer fabrication tool and can be moved to another wafer fabrication tool without having to provide electrical connections to the automated wafer transport pod alignment system 130. In some embodiments, the rechargeable battery stores enough energy to power the automated wafer transport pod alignment system for at least four hours before needing to be recharged.

[0050] 4, the rechargeable battery 136 is mounted to the electronics mounting board 134 and is electrically coupled to the computing system 140 and the digital image capture device 137. In some other embodiments, the rechargeable battery 136 is mounted directly to the alignment frame 131 and is electrically coupled to the computing system 140 and the digital image capture device 137.

[0051] 4, the digital image capture device 137 captures an image of the OHT vehicle 102 when the OHT vehicle 102 is within the field of view 138 of the digital image capture device 137. FIG. 6 is a simplified diagram illustrating an image 165 captured by the digital image capture device 137. The image 165 includes various features of the OHT system 100, including the OHT track 101, the OHT vehicle 102, the gripper assembly 105, the gripper elements 106A, 106B, and the alignment mechanism 107.

[0052] The computing system 140 analyzes the detected image and determines a position of the overhead transport vehicle within the detected image. In some examples, the computing system 140 extracts one or more geometric features of the OHT vehicle from the image and determines a pixel location associated with the one or more features within the image. The position of the OHT vehicle within the detected image is determined based on the pixel locations of the identified features. In some examples, the one or more extracted features include geometric features that position the gripper assembly relative to the WIP transport pod when the gripper assembly contacts the WIP transport pod. In the example shown in FIG. 6 , features indicative of the geometry of the alignment mechanism 107 are extracted by the computing system 140, and a pixel location 166 associated with the center of the alignment mechanism 107 is determined by the computing system 140.

[0053] Additionally, computing system 140 determines a positioning error of OHT vehicle 102 relative to the alignment frame based on the position of the overhead transport vehicle in the detected image. The position of digital image capture device 137 is fixed relative to alignment frame 131, which is located at a predetermined position relative to transport mechanism 109 of WIP transport pod 110. Thus, the field of view of digital image capture device 137 captured by image 165 is fixed in position relative to WIP transport pod 110. As a result, pixel locations in image 165 correspond to different positions in a coordinate frame attached to WIP transport pod 110.

[0054] In one example, pixel coordinates (X A , Y A 1. Furthermore, pixel location 166 associated with the center of alignment feature 107 has pixel coordinates (X G , Y G ) When the OHT vehicle 102 is perfectly aligned with the WIP transport pod 110, pixel location 166 associated with the center of alignment feature 107 will be the same as pixel location 167 in image 165.

[0055] However, due to misalignment, there is an error E in the location of the center of alignment feature 107 in the X direction relative to the center of alignment feature 108. The magnitude of this alignment error can be measured as the number of pixels separating pixel locations 166, 167. Furthermore, the corresponding physical distance associated with the alignment error is determined based on the known pixel pitch of detector 133 and the known geometric characteristics of the optical projection of the image of OHT vehicle 102 onto detector 133. In other words, the spacing between pixels in image 165 is known based on the pixel pitch of detector 133, the known distance in the Z direction between detector 133 and OHT vehicle 102, and the magnification characteristics of optics 135. Therefore, a simple conversion factor is used to convert the alignment error expressed in image space to an alignment position error expressed in physical space.

[0056] The alignment position error, expressed in physical space, is then communicated from computing system 140 to computing system 150. Computing system 150 then calculates an updated setpoint position for the OHT vehicle 102 that will close the gap between the current position of the OHT vehicle 102 and the position of the OHT vehicle 102 where the OHT vehicle 102 should be aligned with the WIP transport pod 110. In some examples, the updated setpoint is determined by adding the alignment position error to the current setpoint. Computing system 150 then communicates control commands to actuators of the OHT vehicle 102 to move the OHT vehicle 102 to the updated setpoint position.

[0057] In some examples, the steps of collecting images, estimating an alignment position error and an updated position setpoint, and moving the OHT vehicle 102 to the updated position setpoint are repeated in sequence until the alignment position error is less than a predetermined threshold, at which point the alignment relative to the position setpoint is deemed sufficiently close and no further adjustment of the position setpoint is required.

[0058] After the OHT vehicle is aligned with the load port, the automatic wafer transport pod alignment system 130 is removed by the user from the WIP transport pod 110 and placed on a WIP transport pod located on another load port for alignment.

[0059] Figure 7 is a flowchart of a method 200 suitable for aligning an OHT system with a load port of a wafer fabrication tool as described herein. In some embodiments, the automated wafer transport pod alignment system 130 described with reference to Figures 4 and 5 can operate according to the method 200 shown in Figure 7. However, in general, implementation of method 200 is not limited to the embodiment of the automated wafer transport pod alignment system described with reference to Figures 4 and 5. These figures and corresponding descriptions are provided as examples, as many other embodiments and operational examples are considered to be within the scope of this patent specification.

[0060] At block 201, an alignment frame is placed on a work-in-process (WIP) transport pod at a predetermined position relative to the work-in-process (WIP) transport pod.

[0061] A digital image is captured that includes an overhead hoist transport (OHT) vehicle positioned above the WIP transport pod at block 202. The digital image is captured by a digital image capture device coupled to the alignment frame.

[0062] In block 203, the location of the OHT vehicle within the captured image is determined by the computing system.

[0063] At block 204, a positioning error of the OHT vehicle relative to the alignment frame is determined based on the position of the OHT vehicle in the image.

[0064] At block 205, the positioning error is communicated to the OHT vehicle.

[0065] 8 is a simplified diagram showing the initial contact of the gripper assembly 105 with the transport handle 109 of the WIP transport pod 110. Elements with the same reference numerals shown in FIGS. 1 to 3 are the same as those shown in FIG. 8. As shown in FIG. 8, a coordinate frame {X G , Y G , Z G}X G There is a misalignment in the direction that coincides with the axis. This initial positioning error prevents the gripper assembly from smoothly docking with the transport handle 109.

[0066] 9 is a simplified diagram showing contact of the gripper assembly 105 with the transport handle 109 of the WIP transport pod 110 at a stage after initial contact. Elements with the same reference numerals shown in FIGS. 1 to 3 are the same as those shown in FIG. 9. As shown in FIG. 9, contact between the alignment mechanism 107 of the gripper assembly 105 and the alignment mechanism 108 of the transport handle 109 causes the gripper assembly to rotate in a negative X direction. G Move in the Y direction G Rotate around the axis.

[0067] FIG. 10 is a simplified diagram illustrating contact of the gripper assembly 105 with the transport handle 109 of the WIP transport pod 110 at a stage subsequent to that shown in FIG. 9. Elements with the same reference numerals shown in FIGS. 1-3 are similar to those shown in FIG. 10. As shown in FIG. 10, the alignment mechanism 107 of the gripper assembly 105 and the alignment mechanism 108 of the transport handle 109 are in full contact and aligned. However, the full contact situation causes the gripper assembly 105 to move in a negative X-axis direction relative to the setpoint position of the OHT vehicle 102. G Move in the direction.

[0068] 8-10, the alignment mechanisms 107, 108 realign the gripper assembly 105 with respect to the WIP transport pod 110 to overcome small misalignments between the OHT vehicle 102 and the WIP transport pod 110. This does not pose an operational issue as long as the setpoint misalignment remains relatively small.

[0069] In another aspect, an automatic wafer transport pod alignment system continuously and automatically aligns an overhead hoist transport (OHT) vehicle with a wafer fabrication tool load port during operation of equipment in a semiconductor manufacturing facility. In this way, misalignment between the overhead hoist transport (OHT) vehicle and the wafer fabrication tool load port remains well within limits requiring offline realignment to be performed.

[0070] 11 illustrates another embodiment of an automated wafer transport pod alignment system 170. As shown in FIGS. 8-11, the automated wafer transport pod alignment system 170 includes an inertial measurement device 171 coupled to a gripper assembly of an overhead hoist transport (OHT) vehicle. The inertial measurement device 171 is configured to generate a measurement signal 189 indicative of the acceleration, velocity, or both, of the gripper assembly when the gripper assembly docks with the WIP transport pod.

[0071] 11, automated wafer transport pod alignment system 170 also includes one or more computing systems 180. As shown in FIG. 11, computing system 180 includes a sensor interface 186, at least one processor 181, memory 182, a bus 183, and a wireless communication transceiver 187. Sensor interface 186, processor 181, memory 182, and wireless communication transceiver 187 are configured to communicate via bus 183. In some embodiments, computing system 180 is a single-board computer system, such as a single-board computer manufactured by Raspberry Pi.

[0072] Sensor interface 186 includes a digital input / output interface configured to communicate with inertial measurement device 171 and receive digital signals 189 measured by inertial measurement device 171. In this example, inertial measurement device 171 includes on-board electronics and generates digital signals 189 indicative of measured acceleration, velocity, or both.

[0073] Memory 182 includes memory 184 that stores inertial measurement data communicated from inertial measurement device 171. Inertial measurement data 189 stored in memory 184 is used to estimate alignment errors of the position of OHT vehicle 102 relative to WIP transport pod 110. Memory 182 also includes memory 185 that stores program code that, when executed by processor 181, causes processor 181 to perform the auto-alignment functionality described herein.

[0074] In some examples, processor 181 is configured to store inertial measurement data 189 received by sensor interface 186 in memory 184. Additionally, processor 181 is configured to read inertial measurement data 189 stored in memory 184 and estimate a registration error based on the inertial measurement data 189. Additionally, processor 181 is configured to transmit a signal indicative of the estimated registration error to wireless communication transceiver 187. In some embodiments, wireless communication transceiver 187 is configured to wirelessly communicate a radio frequency signal 190 indicative of the estimated registration error from computing system 180 to computing system 150 via a wireless communication link. As shown in FIG. 11 , wireless communication transceiver 187 transmits radio frequency signal 190 via antenna 188. Radio frequency signal 190 includes digital information indicative of the estimated registration error and is communicated from computing system 180 to computing system 150.

[0075] 11, computing system 180 and inertial measurement device 171 are packaged in a housing (not shown) that is attached to an electronics mounting board (not shown) and attached to gripper assembly 105. In some other embodiments, computing system 180 and inertial measurement device 171 are combined into a single packaged device that is attached to gripper assembly 105.

[0076] The computing system 180 analyzes the detected inertial measurement signals and determines an initial positioning error of the gripper assembly relative to the WIP transport pod based on signals indicating the acceleration, velocity, or both of the gripper assembly when the gripper assembly docks with the WIP transport pod.

[0077] In some examples, the computing system 180 integrates signals indicative of the acceleration, velocity, or both, of the gripper assembly 105 as it docks with the WIP transport pod 110 to determine the X G The initial positioning error is the displacement in the X direction of the gripper assembly relative to the WIP transport pod. G It is estimated as a directional displacement.

[0078] In some examples, integration begins when the acceleration signal exceeds a predetermined threshold level. The predetermined threshold level is set to indicate when initial contact between the gripper assembly 108 and the transport handle 109 occurs. If the misalignment is significant, initial contact between the gripper assembly 108 and the transport handle 109 causes a sudden increase in acceleration. In some embodiments, the time window over which integration is performed is set to a predetermined period corresponding to the expected time between initial contact and docking of the gripper assembly 105 with the WIP transport pod 110. In some other embodiments, the time window over which integration is performed is determined based on an average acceleration or an average velocity. In these embodiments, integration ends when the average acceleration or average velocity falls below a predetermined threshold. The predetermined thresholds for average acceleration and average velocity are set to low values ​​that indicate that the gripper assembly 105 has docked and is no longer moving significantly.

[0079] Additionally, computing system 180 is configured to communicate the determined initial positioning error of the gripper assembly relative to the WIP transport pod to the OHT vehicle. In response, computing system 150 calculates an updated setpoint position for the OHT vehicle 102 that will close the gap between the current position of the OHT vehicle 102 and the position of the OHT vehicle 102 where the OHT vehicle 102 should be aligned with the WIP transport pod 110. In some examples, the updated setpoint is determined by adding the initial positioning error to the current setpoint. Thereafter, computing system 150 communicates control commands 191 to actuators 161 of the OHT vehicle 102 to move the OHT vehicle 102 to the updated setpoint position the next time the OHT vehicle 102 needs to dock with the WIP transport pod 110.

[0080] In some examples, the steps of collecting inertial measurement data, estimating initial positioning errors, and updating the position setpoint are repeated each time an OHT vehicle docks with a WIP transport pod. Continuous fine-tuning of each OHT vehicle's position setpoint relative to each load port ensures that each OHT vehicle remains aligned with all load port destinations at the semiconductor manufacturing facility.

[0081] Figure 12 is a flowchart of a method 210 suitable for aligning an OHT system with a load port of a wafer fabrication tool as described herein. In some embodiments, the automated wafer transport pod alignment system 170 described with reference to Figures 8-11 can operate according to the method 210 shown in Figure 12. However, in general, implementation of method 210 is not limited to the embodiment of the automated wafer transport pod alignment system described with reference to Figures 8-11. These figures and corresponding descriptions are provided as examples, as many other embodiments and operational examples are considered to be within the scope of this patent specification.

[0082] At block 211, measurement signals are generated that indicate the acceleration, velocity, or both, of a gripper assembly of an overhead hoist transport (OHT) vehicle when the gripper assembly docks with a wafer in process (WIP) transport pod. The gripper assembly includes one or more geometric features that position the gripper assembly in a predetermined position with two or more degrees of freedom relative to the wafer in process (WIP) transport pod when the gripper assembly docks with the WIP transport pod.

[0083] At block 212, an initial positioning error of the gripper assembly relative to the WIP transport pod is determined based on signals indicative of the acceleration, velocity, or both, of the gripper assembly when the gripper assembly docks with the WIP transport pod.

[0084] At block 213, the initial positioning error is communicated to the OHT vehicle.

[0085] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Storage media may be any available medium that can be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to transmit or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Additionally, any connection is properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, microwave, etc., the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, microwave, etc. are included within the definition of medium. As used herein, disk and disc include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs. Disks typically reproduce data magnetically, while discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0086] Although certain specific embodiments have been described above for purposes of illustration, the teachings of this patent specification have general applicability and are not limited to the specific embodiments described above. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments may be made without departing from the scope of the invention as set forth in the claims.

Claims

1. an alignment frame including one or more geometric features that, when the alignment frame contacts a wafer-in-process (WIP) transport pod, position the alignment frame in a predetermined position relative to the WIP transport pod in two or more degrees of freedom; a digital image capture device coupled to the alignment frame, the digital image capture device having a field of view facing away from the WIP transport pod when the alignment frame contacts the WIP transport pod; one or more computing systems coupled to the alignment frame; receiving an image captured by the digital image capture device, wherein an overhead hoist transport (OHT) vehicle is within the field of view of the digital image capture device; determining a position of the OHT vehicle within the image; determining a positioning error of the OHT vehicle relative to the alignment frame based on a position of the OHT vehicle within the image; transmitting the positioning error to the OHT vehicle; a computing system configured to:

1. An automatic wafer transport pod alignment system comprising:

2. 10. The automatic wafer transport pod alignment system of claim 1, further comprising a rechargeable battery coupled to the alignment frame and electrically coupled to the one or more computing systems, the digital image capture device, or both.

3. 2. The automatic wafer transport pod alignment system of claim 1, wherein the one or more computing systems include a wireless communication device, the wireless communication device is communicatively connected to the overhead transport vehicle, and the positioning error is transmitted from the wireless communication device to the OHT vehicle.

4. The automatic wafer transport pod alignment system of claim 1 , wherein the digital image capture device is a stereo camera.

5. 2. The automatic wafer transport pod alignment system of claim 1, wherein determining the position of the OHT vehicle involves extracting one or more geometric features of the OHT vehicle from the image and determining pixel locations associated with the one or more features in the image.

6. 6. The automatic wafer transport pod alignment system of claim 5, wherein the one or more geometric features of the OHT vehicle include one or more geometric features that position the gripper assembly of the OHT vehicle in a predetermined position relative to the wafer-in-process (WIP) transport pod with two or more degrees of freedom when the gripper assembly of the OHT vehicle contacts the WIP transport pod.

7. placing an alignment frame on a work-in-process (WIP) transfer pod at a predetermined position relative to the WIP transfer pod; capturing a digital image including an overhead hoist transport (OHT) vehicle positioned above the WIP transport pod, the digital image being captured by a digital image capture device coupled to the alignment frame; determining a position of the OHT vehicle within the captured image; determining a positioning error of the OHT vehicle relative to the alignment frame based on a position of the OHT vehicle within the image; transmitting the positioning error to the OHT vehicle; A method comprising:

8. The method of claim 7 , further comprising adjusting a positioning setpoint of the OHT vehicle based on the positioning error if the positioning error exceeds a predetermined threshold.

9. The method of claim 7 , further comprising powering the digital image capture device from a rechargeable battery coupled to the alignment frame.

10. The method of claim 7 , wherein communicating the positioning error to the OHT vehicle involves a wireless communication device coupled to the alignment frame and communicatively connected to the OHT vehicle.

11. The method of claim 7 , wherein the digital image capture device is a stereo camera.

12. 8. The method of claim 7, wherein determining the position of the OHT vehicle involves extracting one or more geometric features of the OHT vehicle from the image and determining pixel locations associated with the one or more features in the image.

13. 13. The method of claim 12, wherein the one or more geometric features of the OHT vehicle include one or more geometric features that position the gripper assembly of the OHT vehicle in a predetermined position relative to the wafer-in-process (WIP) transport pod with two or more degrees of freedom when the gripper assembly contacts the WIP transport pod.

14. an inertial measurement device coupled to a gripper assembly of an overhead hoist transport (OHT) vehicle, the gripper assembly including one or more geometric features that position the gripper assembly in two or more degrees of freedom relative to a wafer in process (WIP) transport pod when the gripper assembly is docked to the WIP transport pod, the inertial measurement device configured to generate measurement signals indicative of acceleration, velocity, or both, of the gripper assembly when the gripper assembly is docked to the WIP transport pod; One or more computing systems, receiving the signal indicative of the acceleration, velocity, or both of the gripper assembly when the gripper assembly docks with the WIP transport pod; determining an initial positioning error of the gripper assembly relative to the WIP transport pod based on the signal indicative of acceleration, velocity, or both of the gripper assembly when the gripper assembly docks with the WIP transport pod; transmitting the initial positioning error to the OHT vehicle; a computing system configured to:

1. An automatic wafer transport pod alignment system comprising:

15. 15. The automated wafer transport pod alignment system of claim 14, wherein the one or more computing systems are coupled to the gripper assembly.

16. 15. The automatic wafer transport pod alignment system of claim 14, wherein the one or more computing systems include a wireless communication device, the wireless communication device is communicatively connected to the OHT vehicle, and the initial positioning error is communicated from the wireless communication device to the OHT vehicle.

17. 15. The automated wafer transport pod alignment system of claim 14, wherein determining the initial positioning error of the gripper assembly relative to the WIP transport pod involves integrating the signal indicative of acceleration, velocity, or both.

18. generating measurement signals indicative of acceleration, velocity, or both, of a gripper assembly of an overhead hoist transport (OHT) vehicle when the gripper assembly docks with a work-in-process (WIP) transport pod, the gripper assembly including one or more geometric features that position the gripper assembly in a predetermined position with two or more degrees of freedom relative to the WIP transport pod when the gripper assembly docks with the WIP transport pod; determining an initial positioning error of the gripper assembly relative to the WIP transport pod based on the signal indicative of the acceleration, velocity, or both, of the gripper assembly when the gripper assembly docks with the WIP transport pod; transmitting the initial positioning error to the OHT vehicle; A method comprising:

19. The method of claim 18 , wherein the initial positioning error is communicated to the OHT vehicle via a wireless communications link.

20. 20. The method of claim 18, wherein determining the initial positioning error of the gripper assembly relative to the WIP transport pod involves integrating the signal indicative of acceleration, velocity, or both.

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