Wafer process position correction system and method

Abstract

The present invention discloses a wafer process position correction system and method, wherein the system comprises a first pair of opposing beam sensors, a second pair of opposing beam sensors and a third pair of opposing beam sensors arranged at the entrance of a cassette transmission cavity, each pair of opposing beam sensors comprises an upper opposing beam sensor located at the top of the cassette transmission cavity and a lower opposing beam sensor located at the bottom of the cassette transmission cavity, the upper opposing beam sensor and the lower opposing beam sensor are symmetrically arranged, and a robotic arm extends back from between the upper opposing beam sensor and the lower opposing beam sensor when taking out a wafer in the cassette transmission cavity. The second pair of opposing beam sensors are located between the first pair of opposing beam sensors and the third pair of opposing beam sensors, and the distance between the first pair of opposing beam sensors and the third pair of opposing beam sensors is greater than the length of the flat edge of the wafer, and a strip hole is provided on the robotic arm. The present invention obtains multiple position data information of the wafer, identifies the deflection direction of the flat edge of the wafer, and thereby avoids the error caused by the flat edge of the wafer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a wafer process position correction system and method. Background Art

[0002] In semiconductor PECVD equipment, calibrating the position of the wafer is an important step to ensure that the equipment correctly aligns the wafer and places it in the correct position. This ensures the accuracy and consistency of thin film deposition and other processes.

[0003] The general steps for wafer position correction in semiconductor PECVD equipment are: Prepare alignment marks: Process or etch alignment marks on the edge or specific position of the wafer. Alignment marks are usually some special patterns or structures, such as crosses, T-shaped, or other easily recognizable shapes. Place the wafer: Place the wafer to be corrected on the table of the PECVD equipment and ensure that the alignment mark is located within the recognition area of ​​the equipment. Manual alignment: In some equipment, the operator may need to manually adjust the position of the wafer so that the alignment mark is within the field of view of the equipment recognition system. Automatic alignment: Most modern PECVD equipment is equipped with an automatic alignment function that automatically detects the alignment marks on the surface of the wafer and accurately aligns the wafer to the reference position of the equipment by using an optical or laser system. Correction completed: Once the automatic alignment is completed, the equipment will record the position offset of the wafer and use it to correct the position of the wafer. Repeated calibration: Multiple alignment marks are usually calibrated to improve the accuracy and stability of the measurement. The equipment automatically calculates the average position of the wafer and uses this correction value to align the wafer in subsequent processes. Check and adjust: The operator may need to check the correction results and make fine adjustments to ensure that the wafer is aligned to the required accuracy.

[0004] The working principle of some common automatic alignment systems: Optical alignment systems use optical cameras or microscopes to observe alignment marks on the surface of the wafer. These alignment marks are usually special patterns or structures, such as crosses, T-shaped or other easily recognizable shapes. The camera or microscope captures the image of the alignment mark and transmits it to the computer system for image processing. The computer system performs image processing and analysis on the captured alignment mark image. This includes algorithms such as edge detection, shape recognition and image matching. Through these processing steps, the system is able to accurately identify the position and shape of the alignment mark. Once the position of the alignment mark is accurately calculated, the automatic alignment system will calculate the offset of the wafer, that is, the offset of the current position of the wafer relative to the reference position of the equipment. The automatic alignment system transmits the calculated offset to the equipment control system, which adjusts the position of the wafer accordingly so that it is accurately aligned to the reference position of the equipment. This adjustment process can be completed in a very short time, usually within a few seconds. In the process, alignment may need to be performed in multiple steps, so the automatic alignment system repeats the same process in each step to ensure that the wafer is always in the correct position. The optical alignment system can achieve high-speed and high-precision alignment, providing a reliable automation solution for the semiconductor manufacturing process. Through automatic alignment, the accuracy and consistency of the process can be greatly improved, resulting in high-quality semiconductor devices.

[0005] The above wafer position correction method is relatively cumbersome and costly. For some methods that use a small number of sensors for detection and correction, although the structure is simple, it is only applicable to round wafers or wafers with small gaps. For 4-inch and 6-inch wafers with large flat edges, the different deflection directions of the flat edges will inevitably affect the data measured by the detection mechanism, thereby affecting the accuracy of wafer correction. Summary of the invention

[0006] The object of the present invention is to provide a wafer process position correction system and method, which obtains multiple position data information of the wafer, identifies the deflection direction of the flat edge of the wafer, and thus avoids the error caused by the flat edge of the wafer.

[0007] In the first aspect, the present application proposes a wafer process position correction system, including a first pair of opposing shooting sensors, a second pair of opposing shooting sensors and a third pair of opposing shooting sensors arranged at the entrance of the cassette transmission chamber, each pair of opposing shooting sensors includes an upper opposing shooting sensor located at the top of the cassette transmission chamber and a lower opposing shooting sensor located at the bottom of the cassette transmission chamber, the upper opposing shooting sensor and the lower opposing shooting sensor are symmetrically arranged, and the robotic arm extends back from between the upper opposing shooting sensor and the lower opposing shooting sensor when taking out the wafer in the cassette transmission chamber.

[0008] In a preferred embodiment, the second pair of through-beam sensors are located between the first pair of through-beam sensors and the third pair of through-beam sensors, and the distance between the first pair of through-beam sensors and the third pair of through-beam sensors is greater than the length of the flat side of the wafer.

[0009] In a preferred embodiment, the robot arm is provided with strip-shaped holes.

[0010] In a preferred embodiment, the first pair of through-beam sensors, the second pair of through-beam sensors and the third pair of through-beam sensors are located on the same horizontal line.

[0011] In a preferred embodiment, the first pair of through-beam sensors and the third pair of through-beam sensors are arranged symmetrically about the center line of the wafer.

[0012] In a second aspect, the present application proposes a wafer process position correction method, comprising:

[0013] First, the reference wafer in the cassette transfer chamber is accurately placed on the robotic arm. The robotic arm carries the reference wafer and extends it back from between the first pair of opposing sensors, the second pair of opposing sensors, and the third pair of opposing sensors. When the second pair of opposing sensors detects the bar-shaped hole on the robotic arm, the reference point P7 is obtained. When the three pairs of opposing sensors detect the edge of the reference wafer, the front left reference point P1, the front middle reference point P3, and the front right reference point P5 are obtained respectively. The robotic arm continues to extend back. When the reference wafer leaves the sensor detection position, the rear left reference point P 2. The difference between the rear middle reference point P4, the rear right reference point P6, the rear left reference point P2 and the front left reference point P1 is the distance swept by the first pair of through-beam sensors on the reference wafer, i.e., the left reference chord length; the difference between the rear right reference point P6 and the front right reference point P5 is the distance swept by the third pair of through-beam sensors on the reference wafer, i.e., the right reference chord length; the vertical distance from the center of the reference wafer to the left reference chord length is the left reference transverse distance; the vertical distance from the center of the reference wafer to the right reference chord length is the right reference transverse distance; the distance between the rear middle reference point P4 and the reference point P7 is the reference longitudinal distance;

[0014] During operation, after the robot arm grabs the wafer to be corrected from the cassette transfer chamber and extends back each time, it will obtain the front left working point P1, the rear left working point P2, the front middle working point P3, the rear middle working point P4, the front right working point P5, the rear right working point P6, and the working point P7. The difference between the rear left working point P2 and the front left working point P1 is the distance scanned by the first pair of through-beam sensors on the wafer to be corrected, that is, the left working chord length. The difference between the rear right working point P6 and the front right working point P5 is the distance scanned by the third pair of through-beam sensors on the wafer to be corrected, that is, the right working chord length. The vertical distance from the center of the wafer to be corrected to the left working chord length is the left working lateral distance, and the vertical distance from the center of the wafer to be corrected to the right working chord length is the right working lateral distance. The distance between the rear middle working point P4 and the working point P7 is the working longitudinal distance.

[0015] Obtain the left lateral deviation and the right lateral deviation, wherein the left lateral deviation is the difference △X1 between the left working lateral distance and the left reference lateral distance, and the right lateral deviation is the difference △X2 between the right working lateral distance and the right reference lateral distance. If the difference △X1 and the difference △X2 are both within the allowable working error range, then any difference can be taken for lateral position compensation. If the difference △X1 and the difference △X2 are zero, then no lateral position compensation is required.

[0016] In a preferred manner, it also includes: if at least one of the difference △X1 and the difference △X2 exceeds the allowable working error range, then the rear difference between the rear right working point P6 and the rear left working point P2 is obtained, and the front difference between the front right working point P5 and the front left working point P1 of the current wafer to be corrected is obtained according to the rear difference; based on the front difference, the position information of P1 and P5 is checked to obtain the deflection direction of the flat edge of the wafer to be corrected.

[0017] In a preferred manner, if the deflection direction of the flat edge of the wafer to be corrected affects the detection of the front left working point P1, the lateral position compensation is performed through the right lateral deviation; if the deflection direction of the flat edge of the wafer to be corrected affects the detection of the front right working point P5, the lateral position compensation is performed through the left lateral deviation.

[0018] In a preferred manner, it also includes: obtaining a longitudinal deviation, where the longitudinal deviation is a difference △Y between the working longitudinal distance and the reference longitudinal distance, and performing longitudinal position compensation according to the difference △Y; if the difference △Y is within the error range, no correction is required.

[0019] In a preferred manner, the deflection angle of the flat edge of the wafer to be corrected is determined by the difference between the rear middle working point P4 and the front middle working point P3, that is, the larger the difference, the larger the deflection angle.

[0020] Compared with the prior art, the above technical solution adopted by the present invention has the following advantages: the present invention adopts 3 pairs of opposing beam sensors arranged at a certain distance on the left, middle and right, and the detection mechanism has a simple structure and low cost. The detection error caused by the flat edge is avoided by calculating and judging the deflection direction of the flat edge of the wafer, and the correction method is efficient and reliable. The opposing beam sensor detects multiple position information of the wafer and captures the position data in real time, which reduces the error and avoids the introduction of external errors. It is not only suitable for 4-inch and 6-inch wafers with flat edges, but also for 8-inch and 12-inch round wafers with notches. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of a wafer process position correction system;

[0022] Figure 2 This is a schematic diagram of the reference points when calibrating the wafer process position.

[0023] Explanation of the serial numbers in the figure: 1. Cassette transmission cavity; 2. Wafer to be corrected; 3. First pair of through-beam sensors; 4. Second pair of through-beam sensors; 5. Third pair of through-beam sensors; 6. Strip holes; 7. Robotic arm. Specific implementation methods

[0024] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application, that is, the embodiments described are only part of the embodiments of the present application, not all of the embodiments.

[0025] The present embodiment provides a wafer process position correction system, comprising a first pair of opposing beam sensors, a second pair of opposing beam sensors and a third pair of opposing beam sensors which are arranged at the entrance of a cassette transmission chamber and are located on the same horizontal line, the second pair of opposing beam sensors are located between the first pair of opposing beam sensors and the third pair of opposing beam sensors, the first pair of opposing beam sensors and the third pair of opposing beam sensors are symmetrically arranged about the center line of the wafer, and the distance between the two is greater than the length of the flat edge of the wafer; each pair of opposing beam sensors comprises an upper opposing beam sensor located at the top of the cassette transmission chamber and a lower opposing beam sensor located at the bottom of the cassette transmission chamber, the upper opposing beam sensor and the lower opposing beam sensor are symmetrically arranged, and the robotic arm extends back from between the upper opposing beam sensor and the lower opposing beam sensor when taking out the wafer in the cassette transmission chamber; the robotic arm is provided with a strip hole.

[0026] This embodiment also provides a wafer process position correction method, including: a reference position acquisition step, a lateral deviation acquisition step and a longitudinal deviation acquisition step;

[0027] The reference position acquisition step is as follows: firstly, the reference wafer in the cassette transfer cavity is accurately placed on the robot arm, and the robot arm carries the reference wafer and extends it back from between the first pair of opposing sensors, the second pair of opposing sensors and the third pair of opposing sensors. When the second pair of opposing sensors detects the bar-shaped hole on the robot arm, the reference point P7 is acquired. When the three pairs of opposing sensors detect the edge of the reference wafer, the front left reference point P1, the front middle reference point P3 and the front right reference point P5 are acquired respectively. The robot arm continues to extend back, and when the reference wafer leaves the sensor detection position, the reference points P7, P8 and P9 are acquired respectively. The rear left reference point P2, the rear middle reference point P4, and the rear right reference point P6, the difference between the rear left reference point P2 and the front left reference point P1 is the distance swept by the first pair of through-beam sensors on the reference wafer, i.e., the left reference chord length; the difference between the rear right reference point P6 and the front right reference point P5 is the distance swept by the third pair of through-beam sensors on the reference wafer, i.e., the right reference chord length; the vertical distance from the center of the reference wafer to the left reference chord length is the left reference lateral distance; the vertical distance from the center of the reference wafer to the right reference chord length is the right reference lateral distance; the distance between the rear middle reference point P4 and the reference point P7 is the reference longitudinal distance;

[0028] The lateral deviation acquisition step is: when working, the robot arm grabs the wafer to be corrected from the cassette transmission cavity and then extends it back each time, it will obtain the front left working point P1, the rear left working point P2, the front middle working point P3, the rear middle working point P4, the front right working point P5, the rear right working point P6, and the working point P7. The difference between the rear left working point P2 and the front left working point P1 is the distance scanned by the first pair of through-beam sensors on the wafer to be corrected, that is, the left working chord length. The difference between the rear right working point P6 and the front right working point P5 is the distance scanned by the third pair of through-beam sensors on the wafer to be corrected, that is, the right working chord length. The distance from the center of the wafer to be corrected to the left working chord length is The vertical distance is the left working lateral distance, and the vertical distance from the center of the wafer to be corrected to the right working chord length is the right working lateral distance; the distance between the rear middle working point P4 and the working point P7 is the working longitudinal distance; the left lateral deviation and the right lateral deviation are obtained, the left lateral deviation is the difference △X1 between the left working lateral distance and the left reference lateral distance, and the right lateral deviation is the difference △X2 between the right working lateral distance and the right reference lateral distance. If the difference △X1 and the difference △X2 are both within the allowable working error range, then any difference can be taken for lateral position compensation. If the difference △X1 and the difference △X2 are zero, no lateral position compensation is required. Since the flat edge of the wafer is on the side of the head, it only causes errors in the position information of P1, P3, and P5. If at least one of the difference △X1 and the difference △X2 exceeds the allowable error range of the work, the rear difference between the rear right working point P6 and the rear left working point P2 is obtained, and the front difference between the front right working point P5 and the front left working point P1 of the current wafer to be corrected is obtained according to the rear difference; the position information of P1 and P5 is checked according to the front difference, and the deflection direction of the flat edge of the wafer to be corrected is obtained. If the deflection direction of the flat edge of the wafer to be corrected affects the detection of the front left working point P1, the lateral position compensation is performed through the right lateral deviation; if the deflection direction of the flat edge of the wafer to be corrected affects the detection of the front right working point P5, the lateral position compensation is performed through the left lateral deviation.

[0029] The longitudinal deviation acquisition step is: acquiring the longitudinal deviation, the longitudinal deviation being the difference △Y between the working longitudinal distance and the reference longitudinal distance, and performing longitudinal position compensation according to the difference △Y; if the difference △Y is within the error range, no correction is required.

[0030] According to the left lateral deviation or right lateral deviation and the longitudinal deviation value △Y, the purpose of correcting the deviation is achieved by controlling the rotation and extension of the robot arm.

[0031] The present invention obtains multiple position data information of the wafer through multiple sensors, and then identifies the deflection direction of the flat edge of the wafer, thereby avoiding the error caused by the flat edge of the wafer. It is applicable to a wider range of wafer types, has a simple structure and low cost.

[0032] In this application, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article, or apparatus.

[0033] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A wafer process position correction method, characterized in that: The process includes first accurately placing the reference wafer in the cassette transfer cavity on the robotic arm, and the robotic arm carrying the reference wafer extends back from between the first pair of opposing sensors, the second pair of opposing sensors, and the third pair of opposing sensors. When the second pair of opposing sensors detects the bar-shaped hole on the robotic arm, the reference point P7 is obtained. When the three pairs of opposing sensors detect the edge of the reference wafer, the front left reference point P1, the front middle reference point P3, and the front right reference point P5 are respectively obtained. The robotic arm continues to extend back, and when the reference wafer leaves the sensor detection position, the rear left reference point P6 is respectively obtained. P2, rear middle reference point P4, rear right reference point P6, the difference between the rear left reference point P2 and the front left reference point P1 is the distance swept by the first pair of through-beam sensors on the reference wafer, i.e., the left reference chord length, the difference between the rear right reference point P6 and the front right reference point P5 is the distance swept by the third pair of through-beam sensors on the reference wafer, i.e., the right reference chord length, the vertical distance from the center of the reference wafer to the left reference chord length is the left reference lateral distance, the vertical distance from the center of the reference wafer to the right reference chord length is the right reference lateral distance; the distance between the rear middle reference point P4 and the reference point P7 is the reference longitudinal distance; During operation, after the robot arm grabs the wafer to be corrected from the cassette transfer chamber and extends back each time, it will obtain the front left working point P1, the rear left working point P2, the front middle working point P3, the rear middle working point P4, the front right working point P5, the rear right working point P6, and the working point P7. The difference between the rear left working point P2 and the front left working point P1 is the distance scanned by the first pair of through-beam sensors on the wafer to be corrected, that is, the left working chord length. The difference between the rear right working point P6 and the front right working point P5 is the distance scanned by the third pair of through-beam sensors on the wafer to be corrected, that is, the right working chord length. The vertical distance from the center of the wafer to be corrected to the left working chord length is the left working lateral distance, and the vertical distance from the center of the wafer to be corrected to the right working chord length is the right working lateral distance. The distance between the rear middle working point P4 and the working point P7 is the working longitudinal distance. Obtain a left lateral deviation and a right lateral deviation, wherein the left lateral deviation is the difference △X1 between the left working lateral distance and the left reference lateral distance, and the right lateral deviation is the difference △X2 between the right working lateral distance and the right reference lateral distance. If the difference △X1 and the difference △X2 are both within the allowable working error range, then any difference can be taken for lateral position compensation. If the difference △X1 and the difference △X2 are zero, then no lateral position compensation is required. The above method is implemented in a wafer process position correction system, which includes a first pair of opposing shooting sensors, a second pair of opposing shooting sensors and a third pair of opposing shooting sensors arranged at the entrance of a cassette transmission chamber, each pair of opposing shooting sensors includes an upper opposing shooting sensor located at the top of the cassette transmission chamber and a lower opposing shooting sensor located at the bottom of the cassette transmission chamber, the upper opposing shooting sensor and the lower opposing shooting sensor are symmetrically arranged, and the robotic arm extends back from between the upper opposing shooting sensor and the lower opposing shooting sensor when taking out the wafer in the cassette transmission chamber.

2. A wafer process position correction method according to claim 1, characterized in that: The second pair of through-beam sensors is located between the first pair of through-beam sensors and the third pair of through-beam sensors, and the distance between the first pair of through-beam sensors and the third pair of through-beam sensors is greater than the length of the flat side of the wafer.

3. The wafer process position correction method according to claim 1, characterized in that: The mechanical arm is provided with strip-shaped holes.

4. The wafer process position correction method according to claim 1, characterized in that: The first pair of through-beam sensors, the second pair of through-beam sensors and the third pair of through-beam sensors are located on the same horizontal line.

5. A wafer process position correction method according to claim 1 or 4, characterized in that: The first pair of through-beam sensors and the third pair of through-beam sensors are arranged symmetrically along the wafer center line.

6. The wafer process position correction method according to claim 1, characterized in that: Also includes: If at least one of the difference △X1 and the difference △X2 exceeds the allowable working error range, the rear difference between the rear right working point P6 and the rear left working point P2 is obtained, and the front difference between the front right working point P5 and the front left working point P1 of the current wafer to be corrected is obtained based on the rear difference; the position information of P1 and P5 is checked based on the front difference to obtain the deflection direction of the flat edge of the wafer to be corrected.

7. A wafer process position correction method according to claim 6, characterized in that: If the deflection direction of the flat edge of the wafer to be corrected affects the detection of the front left working point P1, the lateral position compensation is performed through the right lateral deviation; if the deflection direction of the flat edge of the wafer to be corrected affects the detection of the front right working point P5, the lateral position compensation is performed through the left lateral deviation.

8. The wafer process position correction method according to claim 1, characterized in that: Also includes: Acquire a longitudinal deviation, where the longitudinal deviation is a difference △Y between a working longitudinal distance and a reference longitudinal distance, and perform longitudinal position compensation according to the difference △Y; If the difference △Y is within the error range, no correction is required.

9. A wafer process position correction method according to claim 8, characterized in that: The deflection angle of the flat edge of the wafer to be corrected is determined by the difference between the rear middle working point P4 and the front middle working point P3, that is, the larger the difference, the larger the deflection angle.

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