A wafer pre-alignment method and system based on a turntable

Abstract

The present invention relates to a wafer pre-alignment method and system based on a turntable, which comprises: controlling the turntable to drive the wafer to rotate around a rotation center line, so that the edge of the wafer passes through a position sensor in sequence, and the position sensor detects the distance between different positions on the edge of the wafer and the rotation center line; wherein the position sensor detects N different positions on the edge of the wafer; the rotation angle of the turntable corresponding to the i-th detection position on the edge of the wafer is θ i , and the distance between the i-th detection position and the rotation center line is R i ; According to each θ i and R i , fit the center position of the wafer and the wafer radius r, then segment and filter the wafer notch data, find the lowest point of the wafer notch, then identify the rotation center angle α corresponding to the wafer notch, and then control the rotation of the turntable to adjust the wafer to the specified position. According to the technical solution of the present invention, low-cost, fast and high-precision wafer pre-alignment can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of wafer pre-alignment, and in particular to a wafer pre-alignment method and system based on a turntable. Background Art

[0002] With the development of science and technology, the scale of industrial production is getting larger and larger, so the labor cost will increase, and the efficiency requirements are getting higher and higher. Gradually, a large number of automated or semi-automated tools are introduced into the factory. For example, many processes in IC manufacturing require the accurate positioning and posture of the wafer in advance. When the semiconductor process develops from the micron level to the deep submicron level and nanometer level, the requirements of IC manufacturing equipment for each subsystem have reached a very demanding level. As one of the key components of IC manufacturing equipment, the wafer pre-alignment device, its working performance directly affects the accuracy and efficiency of the entire IC manufacturing process. Wafer notch positioning is one of the main tasks of wafer pre-alignment, and how to achieve pre-alignment of the wafer notch is a technical problem that technicians in this field need to solve. Summary of the invention

[0003] In view of this, the present invention provides a wafer pre-alignment method and system based on a turntable, and the main technical problem to be solved is: how to achieve pre-alignment of wafer notches.

[0004] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0005] An embodiment of the present invention provides a wafer pre-alignment method based on a turntable, wherein the turntable is used to support a wafer and drive the wafer to rotate around a rotation center line of the turntable; wherein the wafer pre-alignment method comprises:

[0006] The control turntable drives the wafer to rotate around the rotation center line, so that the edge of the wafer passes through the position sensor in sequence, and the position sensor detects the distance between different positions on the edge of the wafer and the rotation center line; wherein the position sensor detects N different positions on the edge of the wafer; the rotation angle of the turntable corresponding to the i-th detection position on the edge of the wafer is θ i , and the distance between the i-th detection position and the rotation center line is R i , N is a positive integer greater than or equal to 2, i is a positive integer less than or equal to N;

[0007] According to each of the i and R i , fitting the center position of the wafer and the wafer radius r;

[0008] According to each of the detection positions on the edge of the wafer and the center position of the wafer, segment and filter the wafer gap data;

[0009] According to the wafer notch data, finding the lowest point of the wafer notch;

[0010] According to the lowest point of the wafer notch, the rotation center angle α corresponding to the wafer notch is identified;

[0011] According to the rotation center angle α corresponding to the wafer notch, the turntable is controlled to rotate so as to adjust the wafer to a specified position.

[0012] In some embodiments, an xoy rectangular coordinate system is established in a plane perpendicular to the rotation center line, and the o point of the rectangular coordinate system coincides with the rotation center of the turntable; in the rectangular coordinate system, the coordinates of the center position of the wafer are (x0, y0), and the coordinates of the i-th detection position are (x i ,y i );

[0013]

[0014] In some embodiments, the i and R i , fitting the center position of the wafer and the wafer radius r, specifically:

[0015]

[0016] in,

[0017]

[0018] D=N∑x i y i -∑x i ∑y i ;

[0019]

[0020] F=N∑x i y i -∑x i ∑y i ;

[0021]

[0022] In some embodiments, the wafer gap data is segmented and filtered according to each of the detection positions on the edge of the wafer and the center position of the wafer, wherein:

[0023] The wafer notch data selected by segmentation is Notch.

[0024]

[0025] In some implementations, finding the lowest point of the wafer notch according to the wafer notch data is specifically:

[0026] According to the wafer gap data, a polynomial fitting is performed to smooth the gap data curve,

[0027] The lowest point of the wafer notch is found according to the notch data curve.

[0028] In some implementations, the identification of the rotation center angle α corresponding to the wafer notch according to the lowest point of the wafer notch is specifically:

[0029] The line connecting the lowest point of the wafer notch and the rotation center of the turntable is L1, and the angle between L1 and the x-axis is the rotation center angle α corresponding to the wafer notch.

[0030] In some embodiments, the rotation of the turntable is controlled according to the rotation center angle α corresponding to the wafer notch to adjust the position of the wafer, specifically:

[0031] According to the rotation center angle α corresponding to the wafer notch, the rotation center angle α is compensated for, and the compensation angle is η;

[0032] When the position sensor completes the detection of the distance between different positions on the edge of the wafer and the rotation center line, the turntable rotates by an angle θ along the first direction relative to the initial position; wherein, according to the angle θ, the rotation center angle α and the compensation angle η, the turntable is controlled to rotate by an angle γ along the first direction to adjust the position of the wafer; wherein,

[0033] γ=θ+α-η.

[0034] In some embodiments, a xoy rectangular coordinate system is established in a cross section perpendicular to the rotation center line, and the o point of the rectangular coordinate system coincides with the rotation center line;

[0035]

[0036] Among them, β is the angle between the line O0o connecting the center O0 of the initial position of the wafer and the point o and the x-axis, α is the angle between the line connecting the lowest point of the notch at the initial position of the wafer and the point o and the x-axis; O2 is the center of the wafer at the preset alignment position, N2 is the lowest point of the notch of the wafer at the preset alignment position, OO2 is the length of the line connecting point O2 and point o, and O2N2 is the length of the line connecting point O2 and point N2.

[0037] The present invention also provides a wafer pre-alignment system, which adopts any one of the wafer pre-alignment methods described above.

[0038] By means of the above technical solution, the wafer pre-alignment method and system based on the turntable of the present invention has at least the following beneficial effects:

[0039] The present invention proposes a segmentation model for the center data and the notch data based on the original data. The center of the wafer edge data is accurately identified, the notch position is accurately located based on the curve fitting identification of the notch, and the error compensation model of the eccentric wafer during the wafer loading process is used to compensate for the center position and the notch angle, so as to realize a low-cost, fast and high-precision wafer pre-alignment recognition system.

[0040] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0042] Figure 1 is a flowchart of a wafer pre-alignment method provided by an embodiment of the present invention;

[0043] Figure 2 is a schematic structural diagram of a wafer pre-alignment system provided by an embodiment of the present invention;

[0044] Figure 3 is a top view of a wafer pre-alignment system provided by an embodiment of the present invention;

[0045] Figure 4 It is a schematic diagram reflecting the center position and the notch position of the wafer when it is located at different positions;

[0046] Figure 5 It is another schematic diagram reflecting the center position and the notch position when the wafer is located at different positions.

[0047] Figure numerals: 1. wafer; 2. turntable; 3. position sensor. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0050] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0051] An embodiment of the present invention provides a wafer pre-alignment method based on a turntable 2. Figure 2 As shown, the turntable 2 is used to support the wafer 1 and drive the wafer 1 to rotate around the rotation center line of the turntable 2. Preferably, the turntable 2 is a rotating suction cup, and the turntable 2 fixes the wafer 1 by adsorption to prevent the wafer 1 from loosening from the turntable 2.

[0052] Among them, Figure 1 As shown, the above wafer pre-alignment method includes the following steps:

[0053] Step S1: Control the turntable 2 to drive the wafer 1 to rotate around the rotation center line, so that the edge of the wafer 1 passes through the position sensor 3 in sequence, and the position sensor 3 detects the distance between different positions on the edge of the wafer 1 and the rotation center line. Among them, the position sensor 3 is fixed and the position sensor 3 is preferably an optical sensor to improve the position detection accuracy.

[0054] The position sensor 3 detects N different positions on the edge of the wafer 1. The position on the edge of the wafer 1 detected by the position sensor 3 is called the detection position. The edge of the wafer 1 has N detection positions, namely the first detection position, the second detection position, ..., the Nth detection position. N is a positive integer greater than or equal to 2. Figure 3 As shown, the distance between the i-th detection position on the edge of wafer 1 and the rotation center line is R i , i is a positive integer less than or equal to N. The rotation angle of the turntable 2 corresponding to the i-th detection position on the edge of the wafer 1 is θ i Specifically, the rotation angle of the turntable 2 at the initial position is defined as 0 degrees. i When the angle is , the turntable 2 sends the i-th detection position on the wafer 1 to the position sensor 3, so that the position sensor 3 can measure the distance R between the i-th detection position and the rotation center line. i Conduct testing.

[0055] Step S2: According to each θ i and R i , fit the center position of wafer 1 and the wafer radius r.

[0056] In a specific application example, an xoy rectangular coordinate system is established in a plane perpendicular to the rotation center line, and the o point of the rectangular coordinate system coincides with the rotation center of the turntable 2. In the rectangular coordinate system, the center position coordinates of the wafer 1 are (x0, y0), and the coordinates of the i-th detection position are (x i ,y i ).in,

[0057]

[0058] Among them, linearized least square fitting can be used to process all data collected by the position sensor 2 to improve the center recognition accuracy of the wafer 1.

[0059] like Figure 3 As shown in FIG. 1 , the center of the wafer 1 generally does not coincide with the rotation center o, and there is a deviation between the two. i ,y i ) satisfy the formula:

[0060] (x i -x o ) 2 +(y i -y o ) 2 =r 2 (i=1,2,3,K,N).

[0061] Among them, the deviation of the i-th detection position from the rotation center is δ i , δ i satisfy:

[0062]

[0063] In the above formula: A = -2x o , B=-2y o , Then find the partial derivatives of coefficients A, B, and C respectively.

[0064]

[0065] Then combine like terms to calculate the system of equations.

[0066]

[0067] D=N∑x i y i -∑x i ∑y i ;

[0068]

[0069] F=N∑x i y i -∑x i ∑y i ;

[0070]

[0071] By simplifying the above coefficients, the simplified combined equations are as follows: CA+DB+E=0

[0072] DA+GB+H=0

[0073] Obtain the values ​​of coefficients A, B, and C:

[0074]

[0075] Therefore, by using the least squares method, the initial fitting center (x0, y0) with error and the radius r are calculated from the original data:

[0076]

[0077] Through the above analysis and calculation, in simple terms, according to each θ i and R i , the center position (x0, y0) and radius r of the fitted wafer are:

[0078] in,

[0079]

[0080] D=N∑x i y i -∑x i ∑y i ;

[0081]

[0082] F=N∑x i y i -∑x i ∑y i ;

[0083]

[0084] Step S3: According to each detection position (x i ,y i ) and the center position of wafer 1 (x0, y0), and segment and filter the wafer notch data.

[0085] In a specific application example, the wafer notch data can be segmented and screened in the following manner. The segmented and screened wafer notch data is Notch,

[0086]

[0087] Step S4: Find the lowest point of the wafer notch according to the wafer notch data.

[0088] In a specific application example, the coordinates of each point at the wafer notch are (x, y), and a polynomial fitting can be performed to smooth the notch data curve based on the wafer notch data Notch. The fitted notch data curve is as follows:

[0089]

[0090] Then find the lowest point of the wafer notch based on the notch data curve above.

[0091] Among them, the least squares method can be used to preliminarily calculate the center of the wafer, perform data segmentation, perform minimum linear regression on the edge data of the segmented wafer, calculate the precise center deviation, and perform polynomial fitting on the notch data to find the lowest point of the notch.

[0092] Step S5: According to the lowest point of the wafer notch, identify the rotation center angle α corresponding to the wafer notch.

[0093] In a specific application example, the line connecting the lowest point of the wafer notch and the rotation center of the turntable 2 is L1, and the angle between L1 and the x-axis is the rotation center angle α corresponding to the wafer notch.

[0094] Step S6: According to the rotation center angle α corresponding to the wafer notch, the turntable 2 is controlled to rotate to adjust the position of the wafer 1 to achieve pre-alignment of the wafer 1 .

[0095] In a specific application example, firstly, according to the rotation center angle α corresponding to the wafer notch, the rotation center angle α is compensated, and the compensation angle is η.

[0096] When the position sensor 3 completes the detection of the distance between different positions on the edge of the wafer 1 and the rotation center line, the turntable 2 rotates by an angle θ relative to the initial position in the first direction. Generally, θ is greater than 360 degrees, that is, the turntable 2 rotates at least one circle in the first direction. According to the angle θ, the rotation center angle α and the compensation angle η, the turntable 2 is controlled to rotate by an angle γ in the first direction to adjust the position of the wafer 1. Wherein, γ=θ+α-η.

[0097] like Figure 4 and Figure 5 As shown, the center position of the wafer 1 at the initial position is O0, and the notch position is N0. When the position sensor 3 completes the detection of the distance between different positions on the edge of the wafer 1 and the rotation center line, the turntable 2 rotates by an angle θ in the first direction relative to the initial position. At this time, the center position of the wafer is O1, and the notch position of the wafer is N1. The center position of the wafer at the preset alignment position is O2, and the notch position of the wafer is N2.

[0098] Among them, when wafer 1 is in the initial position, the angle between the line connecting the center of the circle of wafer 1 and the center of rotation and the x-axis is β. Theoretically, the center of the circle of wafer 1 coincides with the center of rotation. At this time, it is only necessary to control the turntable 2 to rotate along the first direction by an angle θ-β, so that the line connecting the center of the circle of wafer and the lowest point of the notch can be parallel to the x-axis, thereby realizing the pre-alignment of wafer 1. However, since the center of the circle of wafer and the center of rotation generally do not coincide, there is a deviation between the two. Therefore, it is necessary to compensate for the angular deviation caused by the deviation of the center position, so an error compensation model is established. To compensate to the O2 position, it is necessary to calculate the angular position η caused by the deviation of the center.

[0099] In a specific application example, η satisfies the following formula.

[0100]

[0101] Among them, β is the angle between the line O0o connecting the center O0 of the initial position of the wafer and the point o and the x-axis, α is the angle between the line connecting the lowest point of the notch at the initial position of the wafer and the point o and the x-axis; O2 is the center of the wafer at the preset alignment position, N2 is the lowest point of the notch of the wafer at the preset alignment position, OO2 is the length of the line connecting point O2 and point o, and O2N2 is the length of the line connecting point O2 and point N2.

[0102] The above steps S1 to S6 can be combined to achieve pre-alignment of the wafer notch. Specifically, the present invention proposes a wafer center and notch positioning algorithm based on data segmentation and an error compensation model under eccentricity. A coordinate association between the feeding system and the target system is established to improve the robustness of the wafer feeding system and the fault tolerance of the wafer feeding, which effectively improves the recognition and processing of the wafer deviation position.

[0103] It should be noted here that the above turntable is rotated by a motor drive, and the calculation of the above formulas is realized by a processor. Specifically, a DSP (Digital Signal Processing) control chip can be used as a processor to realize motor control, high-speed acquisition and algorithm deployment, the motor control is realized through the pulse output module of the DSP control chip, the synchronous high-speed acquisition of the position sensor is realized through the input module of the DSP control chip, and the algorithm deployment is realized through the floating-point computing capability of the DSP control chip.

[0104] Among them, high-speed acquisition requires collecting encoder signals and the corresponding change distance of the wafer edge. According to the rotation center and the sensor position, a coordinate system relative to the pre-alignment system can be established, and then the posture of the wafer in this coordinate system can be determined based on the collected data.

[0105] The present invention uses methods such as linearized least squares circle fitting, polynomial fitting, and minimum linear equation regression to identify the center of a wafer and locate the notch of a wafer based on the collected data. In order to improve the accuracy of wafer center recognition, a data segmentation algorithm model is proposed. A preliminary wafer center location is performed based on a linearized least squares circle fitting method, which can eliminate the influence of the acquisition error on the wafer center location, improve the recognition accuracy, and use polynomial fitting and minimum linear equation regression to preliminarily locate the wafer notch. Then, according to the wafer notch feature data, the wafer notch data is extracted and the wafer edge data is segmented. The center of the circle is fitted to the accurate circle edge data, eliminating the influence of the notch data on the center location.

[0106] Among them, the notch data affects the accuracy of center positioning. Through data segmentation, the actual wafer edge data and notch data can be separated and identified and processed separately, which can improve the center positioning accuracy of wafer pre-alignment and the wafer notch or trimming positioning accuracy in any posture.

[0107] The present invention also provides a wafer pre-alignment system, which adopts any of the wafer pre-alignment methods described above. Since the wafer pre-alignment system adopts the wafer pre-alignment method described above, it can achieve pre-alignment of the wafer notch. Specifically, the present invention proposes a wafer center and notch positioning algorithm based on data segmentation and an error compensation model under an eccentric state. A coordinate association between a feeding system and a target system is established to improve the robustness of the wafer feeding system and the fault tolerance of wafer feeding, thereby effectively improving the recognition and processing of wafer deviation positions.

[0108] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A wafer pre-alignment method based on a turntable, wherein the turntable (2) is used to support a wafer (1) and drive the wafer (1) to rotate around the rotation center line of the turntable (2); characterized in that: The wafer pre-alignment method comprises: The control turntable (2) drives the wafer (1) to rotate around the rotation center line, so that the edge of the wafer (1) passes through the position sensor (3) in sequence, and the position sensor (3) detects the distance between different positions on the edge of the wafer (1) and the rotation center line; wherein the position sensor (3) detects N different positions on the edge of the wafer (1); the rotation angle of the turntable (2) corresponding to the i-th detection position on the edge of the wafer (1) is θ i , and the distance between the i-th detection position and the rotation center line is R i , N is a positive integer greater than or equal to 2, i is a positive integer less than or equal to N; According to each of the i and R i , fitting the center position of the wafer (1) and the wafer radius r; According to each of the detection positions on the edge of the wafer (1) and the center position of the wafer (1), segmenting and filtering the wafer notch data; According to the wafer notch data, finding the lowest point of the wafer notch; According to the lowest point of the wafer notch, the rotation center angle α corresponding to the wafer notch is identified; According to the rotation center angle α corresponding to the wafer notch, the turntable (2) is controlled to rotate so as to adjust the wafer (1) to a specified position; The method of controlling the rotation of the turntable (2) to adjust the position of the wafer (1) is specifically as follows: According to the rotation center angle α corresponding to the wafer notch, the rotation center angle α is compensated for, and the compensation angle is η; When the position sensor (3) completes the detection of the distance between different positions on the edge of the wafer (1) and the rotation center line, the turntable (2) rotates by an angle θ along a first direction relative to the initial position; wherein, according to the angle θ, the rotation center angle α and the compensation angle η, the turntable is controlled to rotate by an angle γ along the first direction to adjust the position of the wafer (1); wherein, γ=θ+α-η.

2. The wafer pre-alignment method according to claim 1, characterized in that: An xoy rectangular coordinate system is established in a plane perpendicular to the rotation center line, and the o point of the rectangular coordinate system coincides with the rotation center of the turntable; in the rectangular coordinate system, the coordinates of the center position of the wafer are (x0, y0), and the coordinates of the i-th detection position are (x i ,y i ); 3. The wafer pre-alignment method according to claim 2, characterized in that: According to each of the θ i and R i , fitting the center position of the wafer and the wafer radius r, specifically: in, D=N∑x i y i -∑x i ∑y i ; F=N∑x i y i -∑x i ∑y i ; 4. The wafer pre-alignment method according to claim 2 or 3, characterized in that: The wafer gap data is segmented and filtered according to each of the detection positions on the edge of the wafer and the center position of the wafer, wherein: The wafer notch data selected by segmentation is Notch.

5. The wafer pre-alignment method according to claim 4, characterized in that: The method of finding the lowest point of the wafer notch according to the wafer notch data is as follows: According to the wafer gap data, a polynomial fitting is performed to smooth the gap data curve; The lowest point of the wafer notch is found according to the notch data curve.

6. The wafer pre-alignment method according to claim 2, 3 or 5, characterized in that: According to the lowest point of the wafer notch, the rotation center angle α corresponding to the wafer notch is identified, specifically: The line connecting the lowest point of the wafer notch and the rotation center of the turntable (2) is L1, and the angle between L1 and the x-axis is the rotation center angle α corresponding to the wafer notch.

7. The wafer pre-alignment method according to claim 1, characterized in that: Establishing an xoy rectangular coordinate system in a cross section perpendicular to the rotation center line, wherein the o point of the rectangular coordinate system coincides with the rotation center line; Among them, β is the angle between the line O0o connecting the center O0 of the initial position of the wafer and the point o and the x-axis, α is the angle between the line connecting the lowest point of the notch at the initial position of the wafer and the point o and the x-axis; O2 is the center of the wafer at the preset alignment position, N2 is the lowest point of the notch of the wafer at the preset alignment position, OO2 is the length of the line connecting point O2 and point o, and O2N2 is the length of the line connecting point O2 and point N2.

8. A wafer pre-alignment system, characterized in that: The wafer pre-alignment method according to any one of claims 1 to 7 is adopted.

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