A method and system for concentric positioning and calibration of a wafer robotic arm and a wafer stage.

Abstract

This invention relates to the field of semiconductor equipment technology, and discloses a method and system for concentric positioning and calibration of a wafer robotic arm and a wafer stage. The basic principle is as follows: a camera is mounted on a wafer to form a carrier wafer. The wafer robotic arm picks up the carrier wafer and places it on the wafer stage. During placement, the camera on the carrier wafer captures images of the wafer stage. Based on the captured images, the distance between the center of the carrier wafer and the center of the wafer stage is calculated. Through image acquisition and distance calculation, the carrier wafer is accurately placed on the wafer stage, thereby achieving concentric positioning and calibration of the robotic arm and the wafer stage. This invention simplifies the operation of measuring whether the wafer placed by the wafer robotic arm is centered on the wafer stage, achieving high-precision and high-efficiency placement of the wafer on the wafer stage, and greatly improving the efficiency of equipment maintenance.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, and in particular to a method and system for concentric positioning and calibration of a wafer robotic arm and a wafer stage. Background Technology

[0002] In semiconductor manufacturing, robotic arms are typically used to move wafers. For example, the robotic arm grips the wafer and moves it above a stage according to instructions, then places the wafer onto the stage with the assistance of the stage. Before moving the wafer, the robotic arm must be calibrated to ensure that the wafer and stage are concentric when the robotic arm moves to the target position. Currently, the only way to calibrate the concentricity of the wafer placed by the robotic arm and the wafer stage is to use a graduated glass plate. However, the semiconductor equipment cavity is opaque and sealed. To determine whether the wafer is centered, the cavity cover needs to be opened, which is complex and results in low equipment maintenance efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a simple and efficient method and system for concentric positioning and calibration of a wafer robotic arm and a wafer stage, and to provide at least one beneficial option or create conditions for solving one or more technical problems existing in the prior art.

[0004] To achieve the above objectives, the present invention adopts the following technical solution.

[0005] A method for concentric positioning and calibration of a wafer robotic arm and a wafer stage is proposed. The technical concept is as follows: a camera is mounted on a wafer to form a carrier wafer. The wafer robotic arm picks up the carrier wafer and places it on the wafer stage. During the placement process, the camera on the carrier wafer captures images of the wafer stage. The distance between the center of the carrier wafer and the center of the wafer stage is calculated based on the captured images. By capturing images and calculating distances, the carrier wafer is accurately placed on the wafer stage, thereby achieving concentric positioning and calibration of the robotic arm and the wafer stage.

[0006] More specifically, a camera module is mounted at the center of the carrier wafer, and at least two camera modules are mounted on the periphery of the carrier wafer, with each of the periphery camera modules located on a concentric circle centered on the center of the carrier wafer.

[0007] More specifically, when calculating the distance between the center of the carrier wafer and the center of the wafer stage based on the acquired images, a rectangular coordinate system is established with the center of the carrier wafer or the center of the wafer stage as the origin to obtain the proportional coordinate position of the center of the wafer stage relative to the center of the carrier wafer; then the proportional coordinate position is converted into the actual coordinate position; and the robotic arm is controlled to place the carrier wafer onto the wafer stage according to the actual coordinate position.

[0008] In this invention, a camera module is placed at the center of the carrier wafer; the advantage of placing at least two camera modules around the periphery of the carrier wafer is that, since some wafer stages have a circular pattern at their center, placing a camera module at the center of the carrier wafer is mainly used to collect image data of the circular pattern at the center of the wafer stage; when there is no circular pattern at the center of the wafer stage, edge image data of the wafer stage is collected by at least two (preferably four) camera modules located around the periphery of the carrier wafer, and the positional relationship between the center of the carrier wafer and the wafer stage is obtained by analyzing the edge image data of the circular stage in different orientations, thus meeting the placement requirements of various wafer stages.

[0009] More preferably, the method for determining the proportional coordinate position of the wafer stage center is as follows: 1) When there is a circular pattern at the center of the wafer stage, the central camera module is used to take a picture, and the proportional coordinate position of the wafer stage can be determined by the image taken by the central camera module; 2) When there is no circular pattern at the center of the wafer stage, the camera module located at the periphery of the wafer is used to take a picture; when the camera module captures the edge of the wafer stage, the arc length of the edge in the camera module is identified, and the intersection of the perpendicular bisectors of each arc length is calculated. The position of the intersection of the perpendicular bisectors is the center of the wafer stage, and the proportional coordinate position of the wafer stage is obtained by calculating the position of the intersection.

[0010] More preferably, the method for converting the proportional coordinate position to the actual coordinate position is as follows: measure the actual diameter of the circular pattern at the center of the wafer stage, set the height of the robotic arm, calculate the ratio of the diameter of the circular pattern at the center of the wafer stage in the image data to the actual diameter based on the actual diameter of the circular pattern, the height of the robotic arm, and the image pixels, and calibrate the actual coordinate position of the wafer stage center in the coordinate system at the current height based on this ratio.

[0011] More preferably, the method for converting the proportional coordinate position to the actual coordinate position is as follows: measure the actual outer diameter of the wafer stage, set the height of the robotic arm, calculate the ratio of the outer diameter of the wafer stage to the actual outer diameter in the image data based on the actual outer diameter, the height of the robotic arm, and the image pixels, and calibrate the actual coordinate position of the wafer stage center in the coordinate system at the current height based on this ratio.

[0012] More preferably, the method for converting the proportional coordinate position to the actual coordinate position is as follows: set the height of the robotic arm, keep the robotic arm at a constant height and move in a straight line, calculate the ratio of the actual linear displacement of the robotic arm to the linear displacement of the image data, and calibrate according to the ratio to obtain the actual coordinate position of the wafer stage center in the coordinate system at the current height.

[0013] It should be noted that the above three methods for converting actual coordinate positions can be selected according to different actual needs; in some embodiments, other existing or future known conversion methods can also be used.

[0014] More preferably, a magnetic field sensor is mounted on the carrier wafer, and the direction indicated by the magnetic field sensor is used to determine the X-axis and Y-axis directions in the coordinate system, so as to avoid difficulty in determining the notch direction of the wafer after rotation.

[0015] The carrier wafer can acquire photos taken by the camera module after being rotated, but it cannot determine the relationship between the wafer notch (a notch that all 12-inch wafers have, used to locate the wafer angle) and the angle of the image. Therefore, it is impossible to determine which direction to move to correspond to the position on the X-axis of the image. Experimentation is needed to determine which direction the robotic arm should move to correspond to the position on the image.

[0016] This invention incorporates a magnetic field sensor module and, through calibration and installation, ensures that the N-pole of the magnetic field sensor is parallel to the line connecting the notch to the center of the wafer and points in the direction of the notch, thereby ensuring the accuracy of positioning, calibration, and placement.

[0017] More preferably, when there are two camera modules located on the outer periphery, the two camera modules are asymmetrically distributed, and the centroid of the carrier wafer is located at the center of the carrier wafer through mass balancing.

[0018] When there are three or more camera modules located on the outer periphery, each camera module is evenly distributed on the wafer so that the centroid of the wafer is at the center of the wafer.

[0019] More preferably, the camera module uses wireless communication and wireless charging.

[0020] On the other hand, the present invention also provides a concentric positioning and calibration system for a wafer robotic arm and a wafer stage, which is used to implement the positioning and calibration method described above, comprising: a camera module mounted on a wafer carrier to acquire image data of the wafer stage; a robotic arm for grasping and moving the wafer carrier; a calculation module connected to the camera module for calculating the coordinates of the center of the wafer stage in the wafer carrier coordinate system based on the acquired image data; a control module connected to the robotic arm, the calculation module, and the camera module for controlling the robotic arm to perform calibration and placement actions based on the coordinate information calculated by the calculation module, and controlling the start and stop of the camera module; and a storage module connected to the control module for storing the concentric positioning and calibration data of the robotic arm and the wafer stage.

[0021] More preferably, the camera module includes a main control circuit, a camera sensor, a charging device, a wireless signal transmission circuit, and a storage circuit connected to the main control circuit, and a wireless charging coil, a battery, and a charging port connected to the charging device.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects.

[0023] This invention mounts a central camera module and at least two peripheral camera modules on a wafer carrier. During use, the wafer carrier replaces the actual wafer in production to check the accuracy of wafer placement, thereby achieving position calibration for the wafer robotic arm. This simplifies the operation of measuring whether the wafer is centered on the wafer stage, and the calibration is efficient and accurate, greatly improving the efficiency of maintenance equipment. Furthermore, due to height and distance limitations, a single camera cannot simultaneously capture the center and outer edge of the wafer stage. This invention, by combining the central and peripheral camera modules, can meet various application needs, effectively improving the product's applicability.

[0024] Some other beneficial effects of the present invention will become more apparent in the following description or may be learned through actual production. Attached Figure Description

[0025] Figure 1 The diagram shown is a structural schematic of the camera module.

[0026] Figure 2 The diagram shown illustrates the working principle of the camera module.

[0027] Figure 3 The diagram shown is a system workflow diagram. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] A method for concentric positioning and calibration of a wafer robotic arm and a wafer stage is proposed. The basic concept is as follows: a camera is mounted on a wafer to form a carrier wafer. The wafer robotic arm picks up the carrier wafer and places it on the wafer stage. During the placement process, the camera on the carrier wafer captures images of the wafer stage. The distance between the center of the carrier wafer and the center of the wafer stage is calculated based on the captured images. By capturing images and calculating distances, the carrier wafer is accurately placed on the wafer stage, thereby achieving concentric positioning and calibration of the robotic arm and the wafer stage.

[0030] Specifically, the above-mentioned concentric positioning and calibration method for the wafer robotic arm and wafer stage includes the following steps: 1) Integrating a camera module at the center of the carrier wafer and at least two camera modules on the outer periphery of the carrier wafer, with each camera module on the outer periphery located on a concentric circle centered on the center of the wafer, used to collect image data of the wafer stage; 2) Calculating the distance between the center of the carrier wafer and the center of the wafer stage based on the collected image data, establishing a rectangular coordinate system with the center of the wafer as the origin, and obtaining the proportional coordinate position of the center of the wafer stage; 3) Converting the proportional coordinates into actual coordinate positions; 4) Controlling the robotic arm to place the carrier wafer onto the wafer stage according to the actual coordinate positions, thereby achieving position calibration when the wafer robotic arm places the wafer.

[0031] As a preferred embodiment, the camera module located at the center of the carrier wafer faces directly downwards, while the camera modules located on the outer periphery face diagonally downwards. The design ensures that when the carrier wafer is within 3cm directly above the wafer stage, the camera modules on the outer periphery can capture a section of the outer arc of the wafer stage. This allows the camera modules on the outer periphery to form a certain angle with the plane of the carrier wafer, eliminating the need for them to be perpendicular to the wafer surface downwards.

[0032] It should be noted that the camera module is a known CMOS camera with 2 megapixels, which can meet the requirements for feature recognition of the center and edge of the wafer stage when the distance from the wafer stage is in the range of 15-60mm. The detection accuracy in the horizontal x and y directions can reach 0.1mm.

[0033] When there are two camera modules located on the outer periphery, the two camera modules are asymmetrically distributed to ensure that the center position of the wafer stage can be calculated using two image data sets. When there are three or more camera modules located on the outer periphery, each camera module is evenly distributed on the wafer carrier to ensure that the center of mass of the wafer is at the center of the wafer, thus ensuring rotational balance. In some embodiments, the center of mass of the wafer can also be located at the center of the wafer through mass balancing, and this is not limited to this embodiment.

[0034] Because of the low brightness within the semiconductor device's cavity, as a preferred solution, a light source is also provided around the camera module to ensure the clarity of the captured image. The light source can be a known LED ring light source, surrounding the circumference of the camera module.

[0035] In a preferred embodiment, wireless communication and wireless charging are used to enable wireless operation of the carrier wafer, facilitating data recording and retrieval.

[0036] In a preferred embodiment, the base of the carrier wafer is made of carbon fiber or other lightweight metals. The integration of the camera module, wireless communication module, wireless charging module, etc. on the wafer is a mature existing technology, such as organic adhesive bonding. It is only required that the camera module can be firmly fixed on the carbon fiber wafer base, which will not be described in detail here.

[0037] In a preferred embodiment, a camera module is placed at the center of the wafer carrier; four camera modules are evenly placed at a distance of 3 cm from the outer edge of the wafer. Since some wafer carriers have a circular pattern at their center, a camera module is placed at the center of the wafer to primarily collect image data of the circular pattern at the center of the wafer carrier. When the wafer carrier does not have a circular pattern at its center, edge image data of the wafer carrier is collected by four camera modules located around the perimeter of the wafer carrier. The positional relationship between the wafer center and the wafer carrier is obtained by analyzing the edge image data of the four circular carriers located in different orientations.

[0038] By analyzing the image data collected by the five camera modules in real time, the distance between the center of the carrier wafer and the center of the wafer stage is calculated. A rectangular coordinate system is established with the center of the carrier wafer as the origin to obtain the coordinate position of the center of the wafer stage. Then, the carrier wafer is accurately and quickly placed on the wafer stage, realizing the concentric positioning and calibration of the wafer robotic arm and the wafer stage.

[0039] The method for determining the coordinate position of the center of the wafer stage is as follows: 1) When there is a circular pattern in the center of the wafer stage, the central camera module is used to take a picture. The X-axis and Y-axis coordinates of the wafer stage can be determined by the image taken by the central camera module.

[0040] 2) When there is no circular pattern at the center of the wafer stage, four camera modules located around the wafer are used to take pictures. When the camera module captures the edge of the wafer stage, the arc length of the edge in the camera module can be identified, and the expression of the perpendicular bisector of each arc length in the coordinate system can be calculated. The intersection of the perpendicular bisectors is the center of the wafer stage. The coordinate position of the wafer stage can be obtained by calculating the intersection.

[0041] The two methods above yield proportional coordinates of the wafer stage center in the coordinate system. The actual distance can be obtained through the following three methods:

[0042] Method 1: Measure the diameter of the circular pattern at the center of the wafer stage, set the height of the robotic arm, and input the diameter and the height of the wafer robotic arm into the algorithm software. The algorithm software can calibrate and obtain the actual coordinates of the center of the wafer stage in the camera's Cartesian coordinate system at the current height by calculating the pixel ratio of the central circle of the wafer stage in the image.

[0043] Method 2: Measure the outer diameter of the wafer stage, set the height of the robotic arm, and input the outer diameter and the height of the robotic arm into the algorithm software. The algorithm software can calibrate and obtain the actual coordinates of the center of the wafer stage in the camera's Cartesian coordinate system at the current height by calculating the pixel ratio of the outer diameter of the wafer stage in the image.

[0044] Method 3: When at least two camera modules capture the edge of the wafer stage, save the image. Keep the robotic arm at a constant height and move it in a straight line. Input the displacement of the robotic arm's linear movement into the software. After the robotic arm moves, at least two cameras should still capture the edge of the wafer stage. Click "Calculate," and the software will automatically calculate the displacement of the wafer stage center before and after the movement. Based on the ratio of the calculated displacement to the actual displacement, the actual coordinates of the wafer stage center in the camera's Cartesian coordinate system can be calibrated.

[0045] The following describes a positioning calibration system capable of implementing the above-described positioning calibration method, comprising:

[0046] A camera module, mounted on the wafer carrier, is used to acquire image data from the wafer stage. (See reference...) Figure 1 As shown, the camera module includes a main control circuit, a camera sensor, a charging device, a wireless signal transmission circuit, and a storage circuit connected to the main control circuit. The charging device is equipped with a wireless charging coil, a battery, and a Type-C charging port. It should be noted that the specific implementation of the camera module on the carrier wafer is common technical knowledge known to those skilled in the art and will not be elaborated here. The wireless signal transmission circuit is preferably a Wi-Fi circuit.

[0047] A robotic arm is used to pick up wafers from a carrier and place them onto a wafer carrier platform.

[0048] The calculation module, connected to the camera module, is used to calculate the coordinates of the wafer stage center in the wafer coordinate system of the carrier based on the acquired image data, thereby realizing the positioning, calibration and placement of the wafer on the wafer stage.

[0049] The control module, connected to the robotic arm, the computing module, and the camera module, is used to control the robotic arm to perform the wafer placement action based on the coordinate information calculated by the computing module, and to control the start and stop of the camera module.

[0050] The storage module is connected to the control module and stores the concentric positioning calibration data of the wafer robotic arm and the wafer stage.

[0051] Reference Figure 2The diagram illustrates the working principle of the camera module. Before receiving a transmission wait command, the camera module remains in standby mode. Upon receiving the transmission wait command, the camera module starts, captures images, and uploads them to a computing module, such as a computer (PC). Once started, the camera module can continuously capture images until it receives a command to end the wait, at which point it enters standby mode.

[0052] Reference Figure 3 As shown, the workflow of the above positioning calibration system is as follows: the control module starts up and establishes a WIFI connection with the camera module. When image data needs to be acquired, it sends a waiting transmission command (start command) to the camera module; the calculation module reads the image captured by the camera module and performs image feature recognition and calculation to obtain coordinate information; image reading, recognition and coordinate information calculation can be performed in a loop until the waiting end command is received and the system exits.

[0053] In one embodiment, a magnetic field sensor is also mounted on the carrier wafer to indicate the direction and thus determine the X-axis and Y-axis directions in the coordinate system, avoiding the difficulty in determining the notch direction of the wafer after rotation.

[0054] The carrier wafer can acquire photos taken by the camera module after being rotated, but it cannot determine the relationship between the wafer notch (a notch that all 12-inch wafers have, used to locate the wafer angle) and the angle of the image. Therefore, it is impossible to determine which direction to move to correspond to the position on the X-axis of the image. Experimentation is needed to determine which direction the robotic arm should move to correspond to the position on the image.

[0055] This invention incorporates a magnetic field sensor module and, through calibration and installation, ensures that the N-pole direction of the magnetic field sensor is parallel to the line connecting the notch to the center of the carrier wafer and points in the direction of the notch.

[0056] The notch of the carrier wafer faces the opening of the FOUP (Wafer Loading Unit), and the horizontal center line of the image captured by the camera is defined as the X-axis, and the vertical center line of the image is defined as the Y-axis. The Y-axis direction is the direction of the line connecting the notch to the center of the wafer. When the wafer moves, the angle of the image is rotated according to the angle detected by the magnetic field sensor, thus locating the X and Y axes of the coordinate system. This positioning is convenient and quick. Obviously, those skilled in the art can use other known or future coordinate axis positioning methods according to different actual needs, and are not limited to this embodiment.

[0057] It should also be noted that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Parts not described in the specific embodiments are all prior art or common knowledge.

Claims

1. A method for concentric positioning and calibration of a wafer robotic arm and a wafer stage, characterized in that, A camera is mounted on a wafer to form a carrier wafer. A wafer robotic arm picks up the carrier wafer and places it on a wafer stage. During the placement process, the camera on the carrier wafer captures images of the wafer stage. Based on the captured images, the distance between the center of the carrier wafer and the center of the wafer stage is calculated. Through image acquisition and distance calculation, the carrier wafer is accurately placed on the wafer stage, thereby achieving concentric positioning and calibration between the robotic arm and the wafer stage.

2. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, Includes the following steps: 1) A camera module is mounted at the center of the wafer and at least two camera modules are mounted on the periphery of the wafer to form a carrier wafer. Each of the camera modules on the periphery is located on a concentric circle with the center of the carrier wafer as the center. Image data of the wafer stage is acquired through the camera modules. 2) Calculate the distance between the center of the carrier wafer and the center of the wafer stage based on the acquired image data. Establish a rectangular coordinate system with either the center of the carrier wafer or the center of the wafer stage as the origin to obtain the proportional coordinate position of the center of the wafer stage relative to the center of the carrier wafer. 3) Convert the proportional coordinate position to the actual coordinate position; 4) Control the robotic arm to place the carrier wafer onto the wafer stage according to the actual coordinate position, thereby achieving concentric positioning and calibration between the robotic arm and the wafer stage.

3. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, The method for determining the proportional coordinate position of the wafer stage center is as follows: 1) When there is a circular pattern in the center of the wafer stage, the central camera module is used to take a picture. The scale coordinate position of the wafer stage can be determined by the image taken by the central camera module. 2) When there is no circular pattern in the center of the wafer stage, use a camera module located on the periphery of the wafer stage to take pictures; When the camera module captures the edge of the wafer stage, it identifies the arc length of the edge within the camera module and calculates the intersection of the perpendicular bisectors of each arc length. The intersection of the perpendicular bisectors is the center of the wafer stage. The proportional coordinate position of the wafer stage is obtained by calculating the position of the intersection.

4. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, The method for converting the proportional coordinate position to the actual coordinate position is as follows: Measure the actual diameter of the circular pattern at the center of the wafer stage, set the height of the robotic arm, calculate the ratio of the diameter of the circular pattern at the center of the wafer stage in the image data to the actual diameter based on the actual diameter of the circular pattern, the height of the robotic arm, and the image pixels, and calibrate the actual coordinate position of the wafer stage center in the coordinate system at the current height.

5. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, The method for converting scale coordinates to actual coordinates is as follows: The actual outer diameter of the wafer stage is measured, the height of the robotic arm is set, and the ratio of the outer diameter of the wafer stage to the actual outer diameter in the image data is calculated based on the actual outer diameter, the height of the robotic arm, and the image pixels. Based on this ratio, the actual coordinate position of the wafer stage center in the coordinate system at the current height is calibrated.

6. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, The method for converting scale coordinates to actual coordinates is as follows: The height of the robotic arm is set, and the robotic arm moves in a straight line while maintaining a constant height. The ratio of the actual linear displacement of the robotic arm to the linear displacement of the image data is calculated. Based on this ratio, the actual coordinate position of the wafer stage center in the coordinate system is obtained at the current height.

7. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, A magnetic field sensor is mounted on the carrier wafer, and the X-axis and Y-axis directions in the coordinate system are determined by the direction indicated by the magnetic field sensor.

8. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, When there are two camera modules located on the outer periphery, the two camera modules are asymmetrically distributed, and the centroid of the wafer is placed at the center of the wafer through mass balancing. When there are three or more camera modules located on the outer periphery, each camera module is evenly distributed on the carrier wafer so that the centroid of the carrier wafer is at the center of the wafer.

9. The method for concentric positioning and calibration of a wafer robotic arm and a wafer stage according to claim 1, characterized in that, The camera module uses wireless communication and wireless charging.

10. A concentric positioning and calibration system for a wafer robotic arm and a wafer stage, characterized in that, To implement the positioning calibration method as described in any one of claims 1-9, the method includes: Camera module, which is mounted on the wafer to acquire image data from the wafer stage; Robotic arms are used to grasp and move wafers; The calculation module, connected to the camera module, is used to calculate the coordinates of the wafer stage center in the wafer coordinate system based on the acquired image data; A control module, connected to the robotic arm, the computing module, and the camera module, is used to control the robotic arm to perform wafer placement and to control the start and stop of the camera module. The storage module is connected to the control module and stores the concentric positioning calibration data of the wafer robotic arm and the wafer stage.

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