Laser scribing height measurement method

Abstract

The application provides a laser scribing height measuring method, comprising the following steps: controlling a horizontal motion platform to move in a horizontal plane, wherein the movement of the horizontal motion platform in the horizontal plane at least comprises an acceleration stage and a deceleration stage; when the horizontal motion platform starts to move, controlling a height measuring instrument to start to sample at a predetermined period, so that the height measuring instrument obtains height data of a measuring target at multiple positions at least in one of the acceleration stage and the deceleration stage; performing function approximation processing on the height data obtained by the height measuring instrument, to obtain a function formed by the height data and motion coordinates; and determining the height of the measuring target on the function according to processing coordinates of laser scribing. The laser scribing height measuring method provided by the application can measure in the whole movement process of the horizontal motion platform, and is beneficial to improving the efficiency and precision of laser scribing.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser processing technology, and in particular to a laser scribing and height measuring method. BACKGROUND

[0002] The height measuring process is completed on the basis that the moving platform reaches the set speed and keeps the speed for uniform speed height measuring. Based on the premise, if the moving speed of the platform is simply increased, the relative speed of the sampling points will be reduced in proportion to the increase ratio, so that a relatively small amount of data points cannot compensate for the coordinate information of the actual processing position required in the follow-up cutting process, and thus the entire scribing task fails. Meanwhile, in the prior art, when the moving speed of the platform reaches the uniform speed, the processing method is triggered according to the position, and the same processing speed is required for measurement and point taking, so that corresponding acceleration and deceleration sections are required on both sides of the uniform speed section, increasing the system running time. When the set speed is increased, the platform needs to increase longer acceleration and deceleration distances to link the uniform speed process, and thus the position of the height measuring instrument and the follow-up head is coupled by the moving distance of the platform, which reduces the running accuracy to a certain extent. In addition, the higher the set speed, the greater the acceleration and deceleration distances of the platform, and the longer the running time required, resulting in a longer time consumed by the entire height measuring process, and thus the processing efficiency of the equipment is reduced. SUMMARY

[0003] The laser scribing and height measuring method provided by the present application can measure during the entire movement of the horizontal moving platform, which is beneficial to improving the efficiency and accuracy of laser scribing.

[0004] The present application provides a laser scribing and height measuring method, comprising:

[0005] controlling the horizontal moving platform to move in the horizontal plane, wherein the movement of the horizontal moving platform in the horizontal plane at least includes an acceleration stage and a deceleration stage;

[0006] controlling the height measuring instrument to start sampling at a predetermined period when the horizontal moving platform starts moving, so that the height measuring instrument obtains height data of the measurement target at multiple positions at least in one of the acceleration stage and the deceleration stage;

[0007] performing function approximation processing on the height data obtained by the height measuring instrument to obtain a function formed by the height data and the movement coordinates;

[0008] determining the height of the measurement target on the function according to the processing coordinates of the laser scribing.

[0009] Optionally, before the function approximation processing on the height data obtained by the height measuring instrument, the method further comprises:

[0010] comparing the intervals of the motion coordinates corresponding to the obtained height data;

[0011] when the intervals of the motion coordinates corresponding to the continuous height data are in an increasing relationship, determining that the continuous height data are height data obtained in an acceleration phase;

[0012] when the intervals of the motion coordinates corresponding to the continuous height data are in a decreasing relationship, determining that the continuous height data are height data obtained in a deceleration phase.

[0013] Optionally, in the acceleration motion process, a sampling starting point position of the height measuring instrument is at an edge of the measurement target.

[0014] Optionally, in the deceleration motion process, a sampling ending point position of the height measuring instrument is at an edge of the measurement target.

[0015] Optionally, the processing of the height data obtained by the height measuring instrument comprises:

[0016] performing polynomial fitting on the height data of the acceleration phase and the deceleration phase respectively and the corresponding motion coordinates in a least square method to form fitting functions corresponding to the acceleration phase and the deceleration phase respectively.

[0017] Optionally, the motion process of the horizontal motion platform in the horizontal plane further comprises a uniform speed phase, and the uniform speed phase is between the acceleration phase and the deceleration phase.

[0018] Optionally, before the function approximation processing of the height data obtained by the height measuring instrument, the method further comprises:

[0019] comparing the intervals of the motion coordinates corresponding to the obtained height data;

[0020] when a difference value of the intervals of the motion coordinates corresponding to adjacent height data in the continuous height data does not exceed a predetermined threshold, determining that the continuous height data are height data obtained in a uniform speed phase.

[0021] Optionally, the method further comprises: processing the height data obtained in the uniform speed phase according to a cubic spline interpolation algorithm to obtain a spline function corresponding to the uniform speed phase.

[0022] Optionally, in the uniform speed motion phase, an interval between the motion coordinates corresponding to adjacent height data is greater than an interval between adjacent machining coordinates.

[0023] Optionally, in the uniform speed motion phase, a relative motion speed between the measurement target and the height measuring instrument is 2000 mm / s to 5000 mm / s.

[0024] In the technical scheme provided by the present application, the height detector starts to sample at a predetermined period as soon as the horizontal movement platform starts to move, without reserving an extra area for acceleration and deceleration of the movement platform, so that the movement distance of the movement platform during the height measurement can be reduced, and the processing precision of the laser scribing can be improved. Meanwhile, since the movement distance of the platform is reduced, the movement time of the platform during the height measurement can be effectively reduced, and the efficiency of the laser scribing can be effectively improved. In addition, the height data obtained by the height detector is subjected to function approximation processing to form a function curve of the height data with respect to the movement coordinates, so that the height data at any coordinate can be obtained, and the height data at any processing coordinate can be obtained during the following movement, and there is no case that the height data cannot correspond to the processing coordinates. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A flow chart of a laser scribing height measurement method according to an embodiment of the present application;

[0026] Figure 2 A flow chart of a judgment movement stage of a laser scribing height measurement method according to another embodiment of the present application;

[0027] Figure 3 A flow chart of a judgment movement stage of a laser scribing height measurement method according to another embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the objects, technical schemes and advantages of the embodiments of the present application clearer, the technical schemes in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0029] An embodiment of the present application provides a laser scribing height measurement method, as shown in Figure 1 The method comprises the following steps.

[0030] In step 100, a horizontal movement platform is controlled to move in a horizontal plane, wherein the movement of the horizontal movement platform in the horizontal plane comprises at least an acceleration stage and a deceleration stage.

[0031] In some embodiments, the horizontal movement platform carries a measurement target, for example, a wafer to be sliced. In order to reduce the time of the height measurement process as much as possible, the movement speed of the horizontal movement platform needs to be accelerated after the horizontal movement platform starts, and then decelerated when the horizontal movement platform approaches the end position. As a preferred embodiment, the movement process of the horizontal movement platform can only include an acceleration phase and a deceleration phase, which can reduce the movement time of the horizontal movement platform as much as possible and improve the efficiency. As another preferred embodiment, if the maximum speed of the horizontal movement platform is limited by the accuracy or the driving structure, the horizontal movement platform can be accelerated, kept uniform for a period of time, and then decelerated.

[0032] Step 200, when the horizontal movement platform starts to move, the height gauge is controlled to start sampling at a predetermined period, so that the height gauge obtains the height data of the measurement target at multiple positions at least in one of the acceleration phase and the deceleration phase.

[0033] In some embodiments, the height gauge starts sampling when the horizontal movement platform starts to move. In this way, the whole movement process of the horizontal movement platform is accompanied by the height sampling of the height gauge, and the movement acceleration and movement deceleration adjustment of the horizontal movement platform is not needed, which can effectively reduce the movement distance and movement time of the horizontal movement platform and improve the processing accuracy and processing efficiency. In some preferred embodiments, taking the height measurement process of a wafer as an example, for the height measurement track close to the center of the wafer, the length is relatively long, and the horizontal movement platform can have an acceleration phase, a deceleration phase, or even a uniform speed phase; for the height measurement track far from the center of the wafer, the length is usually relatively short, and the farther the height measurement track is from the wafer, the shorter the length is. For the height measurement track close to the edge of the wafer, the length is usually extremely short, and in the height measurement process, limited by the control and response of the equipment, there can be a possibility that the acceleration phase and the deceleration phase cannot be converted in time. In this case, the measurement position of the height gauge can be beyond the range of the wafer when the horizontal movement platform is in the acceleration phase, and the measurement position of the height gauge will be on the extension line of the current height measurement track at this time. In the subsequent deceleration process, the height gauge cannot obtain the height data of the wafer, and therefore, in the current height measurement track, the height gauge only obtains the height data in the acceleration phase. Under the foregoing premise, when the next height measurement track is measured, the measurement position of the height gauge will be on the extension line of the next height measurement track at the beginning of the measurement. In the measurement process of the next height measurement track, the measurement position of the height gauge is outside the range of the wafer in the initial acceleration phase of the horizontal movement platform, and the measurement position of the height gauge can be within the range of the wafer when the horizontal movement platform enters the deceleration phase. At this time, the height gauge only obtains the height data in the deceleration phase.

[0034] Step 300, function approximation processing is performed on the height data obtained by the altimeter to obtain a function of the height data and the motion coordinates;

[0035] In some embodiments, since the height data obtained by the altimeter is obtained in the whole process of the motion of the horizontal motion platform, in which the acceleration and deceleration motion of the horizontal motion platform is accompanied, or the high-speed uniform motion of the horizontal motion platform is further included, in this case, the collection coordinates of the collected original data points cannot well adapt to the processing coordinates in the subsequent follow-up process. Therefore, in this step, the function approximation processing is performed on the height data obtained by the altimeter to form a function between the height data and the motion coordinates, and the function is a continuous curve, and only the motion coordinates need to be obtained to determine the height data corresponding to the motion coordinates.

[0036] Step 400, according to the processing coordinates of the laser scribing, the height of the measurement target is determined on the function.

[0037] In some embodiments, in the processing process of the laser scribing, it is necessary to determine the height at the processing coordinates, since the function obtained first is the function of the height data about the motion coordinates, therefore, only the processing coordinates need to be substituted into the function to determine the corresponding height data.

[0038] In the technical scheme provided in the embodiments of the present application, the altimeter starts to sample at a predetermined period when the horizontal motion platform starts to move, without reserving an additional area for the acceleration and deceleration process of the motion platform, which can reduce the moving distance of the motion platform in the height measurement process, and is beneficial to improve the processing precision of the laser scribing. At the same time, since the motion distance of the platform is reduced, the moving time of the platform in the height measurement process can be effectively reduced, and the efficiency of the laser scribing can be effectively improved. In addition, by performing the function approximation processing on the height data obtained by the altimeter to form a function curve of the height data about the motion coordinates, the height data under any coordinate can be obtained, and in the follow-up process, the height data under any processing coordinate can be obtained, and there is no case that the height data cannot correspond to the processing coordinates.

[0039] As an optional implementation, as shown in Figure 2 Before the function approximation processing is performed on the height data obtained by the altimeter in step 300, it further includes:

[0040] Step 310, the motion coordinate intervals corresponding to the obtained height data are compared;

[0041] In some embodiments, the altimeter has a corresponding motion coordinate for each sampling, and because the horizontal motion platform has different speeds in the acceleration stage, the deceleration stage and the uniform speed stage, but the sampling period of the altimeter is the same, by comparing the corresponding motion coordinates of each height data, the motion stage in which the height data is sampled can be determined.

[0042] In step 320, when the interval of the corresponding motion coordinates of the continuous height data is in an increasing relationship, it is determined that the continuous height data is height data obtained in the acceleration stage.

[0043] In some embodiments, when in the acceleration stage, because the speed of the horizontal motion platform is getting faster and faster, the interval of the corresponding motion coordinates of the height data obtained by using the same sampling period will be getting larger and larger, therefore, when the interval of the corresponding motion coordinates of the continuous height data is in an increasing relationship, it can be determined that the continuous height data is height data obtained in the acceleration stage.

[0044] In step 330, when the interval of the corresponding motion coordinates of the continuous height data is in a decreasing relationship, it is determined that the continuous height data is height data obtained in the deceleration stage.

[0045] In some embodiments, when in the deceleration stage, because the speed of the horizontal motion platform is getting slower and slower, the interval of the corresponding motion coordinates of the height data obtained by using the same sampling period will be getting smaller and smaller, therefore, when the interval of the corresponding motion coordinates of the continuous height data is in a decreasing relationship, it can be determined that the continuous height data is height data obtained in the deceleration stage.

[0046] In the embodiment, by comparing the interval of the corresponding motion coordinates of the height data, the motion stage corresponding to each data can be quickly determined. For different motion stages, different ways of data processing can be used to form a function that is more consistent with the data.

[0047] As an optional embodiment, in the acceleration motion process, the sampling starting point position of the altimeter is at the edge of the measurement target. In some embodiments, because the altimeter starts sampling at the beginning of the acceleration motion, setting the sampling starting point position of the altimeter at the edge of the measurement target can reduce the number of invalid data points, and effectively reduce the moving distance of the motion platform.

[0048] As an optional embodiment, during the deceleration movement, the sampling end position of the altimeter is at the edge of the measurement target. In some embodiments, since the deceleration movement is to make the movement platform stop moving and then start the height measurement of the next track, if the sampling end position of the altimeter exceeds the edge of the measurement target, not only invalid data points will be introduced, but also the moving distance of the horizontal movement platform will be increased; if the sampling end position of the altimeter does not reach the edge of the measurement target, the complete height measurement of the current track cannot be completed. Therefore, in the present embodiment, the sampling end position is set at the edge position of the measurement target.

[0049] As an optional embodiment, the height data obtained by the altimeter is processed, including:

[0050] The height data of the acceleration phase and the deceleration phase are respectively fitted with the corresponding movement coordinates by using the least square method to form the fitting functions corresponding to the acceleration phase and the deceleration phase respectively.

[0051] In some embodiments, when the platform is in the non-uniform speed phase, the speed changes with time at time, and the sampling period of the altimeter always remains constant, therefore, the data points recorded by the altimeter present uneven distribution in the X direction (i.e. the movement direction of the horizontal movement platform). In order to meet the position triggering requirement in the later laser processing process, the coordinate information of the required processing position can be obtained by performing curve fitting operation in the two-dimensional plane on these data points and taking points on the fitting curve. Although the curve after fitting does not strictly pass through each known data point, it achieves a "best" approximation effect as a whole, and ensures that the absolute value of the error between the known points and the predicted points is less than 1.5um, meeting the requirement of high-precision processing. The least square method is a commonly used method for solving curve fitting, which realizes the fitting process by making the sum of squares of errors between the obtained data and the actual data minimum. Polynomial fitting is to solve the square sum of deviations between the fitting function value and the sample points based on the least square principle. For given data points (x i ,y i )(i=1,2,3,...,n), the polynomial fitting function

[0052] F(x)=a0+a1x+a2x ^2 +...+a m x ^m , (m<n-1, a m is the coefficient to be solved), according to the least square principle, the formula for calculating the square sum of errors of each equation is as follows:

[0053]

[0054] According to the foregoing consensus, a set of a m (m = 0, 1, 2,..., m) to minimize the error sum of squares R, that is, to obtain the least square fitting polynomial of the given data. Based on this method, the fitting function expressions F1(x) and F2(x) generated by the acceleration height measurement and the deceleration height measurement can be calculated respectively, and the corresponding height data can be obtained according to the horizontal coordinates (i.e., motion coordinates) of the required processing position points. Wherein, y i y represents the i-th height data, and F(x) represents the fitting value at the motion coordinate corresponding to y i y represents the i-th height data, and F(x) represents the fitting value at the motion coordinate corresponding to y

[0055] As an optional implementation, the movement process of the horizontal movement platform in the horizontal plane further includes a uniform speed stage, and the uniform speed stage is between the acceleration stage and the deceleration stage. In some embodiments, when the maximum movement speed of the horizontal movement platform is limited by the accuracy or the driving mechanism, the horizontal movement platform can be selected to maintain a uniform speed movement at the maximum movement speed that can be reached.

[0056] As an optional implementation, before the function approximation processing of the height data obtained by the height gauge, the method further includes:

[0057] In step 340, the motion coordinate intervals corresponding to the obtained height data are compared.

[0058] In some embodiments, in the movement process with the uniform speed stage, the motion coordinate intervals corresponding to each height data in the uniform speed stage will be substantially consistent, and therefore, the height data in the uniform speed stage can be found through the comparison of the motion coordinate intervals.

[0059] In step 350, when the interval difference of the motion coordinates between adjacent height data in the continuous multiple height data does not exceed a predetermined threshold, the continuous multiple height data are determined as the height data obtained in the uniform speed stage.

[0060] In some embodiments, the predetermined threshold refers to the allowable range of the interval difference of the motion coordinates between adjacent height data in the uniform speed stage, and when the interval difference between the motion coordinates of the continuous multiple height data is within the allowable range, the continuous multiple height data are determined as the height data obtained in the uniform speed stage. In some preferred embodiments, the predetermined threshold can be set according to the measurement error.

[0061] As an optional implementation, the method further includes: processing the height data obtained in the uniform speed stage according to a cubic spline interpolation algorithm to obtain a spline function corresponding to the uniform speed stage.

[0062] In some embodiments, when the platform maintains a constant speed, although the height measuring instrument can achieve uniform height measurement points at equal intervals, the positions of the sampling points do not meet the requirement of one-to-one correspondence with the processing coordinates. Therefore, by selecting a data interpolation method and pre-setting the range of abscissa values ​​of the points to be interpolated and the corresponding interpolation interval, the final coordinates of the actual processing position can be obtained.

[0063] There are many two-dimensional interpolation methods for planes. Considering the limitations of the controller in terms of program complexity and comparing the advantages and disadvantages of different interpolation methods, the cubic spline interpolation algorithm was ultimately selected to perform the corresponding interpolation processing on the uniform velocity segment height measurement data. A spline, originally a commonly used drawing tool in engineering design, connects known points into a smooth curve, ensuring continuous curvature at the connection points.

[0064] In mathematics, a piecewise polynomial that exhibits a certain degree of smoothness is called a spline function. Specifically, given a partition Δ of the interval [a, b], where Δ: a = x0 <x1<…<x n-1 <x n =b

[0065] When the function Ψ(x) satisfies:

[0066] (1) In each subinterval [x i ,x i-1 The expression (i = 0, 1, ..., n-1) contains a polynomial of degree k.

[0067] (2) It has a continuous derivative of order k-1 on [a,b].

[0068] Then Ψ(x) is called a k-th order spline function with respect to the partition interval Δ.

[0069] x0, x1, ..., x n These are called spline nodes, x1, x2, ..., x3. n-1 These are called internal nodes, x0 and x... n These are called boundary points. The set of all such spline functions is denoted as Sp(Δ,k), and is called the space of k-th degree spline functions.

[0070] In practical applications, k is generally chosen to be 2 or 3. The interpolation algorithm used in this implementation is the cubic spline interpolation method when k=3. The general form of the cubic spline function is:

[0071]

[0072] in,

[0073] Based on this function expression, the corresponding function value S3(x) can be obtained by inputting the x-coordinate of the position to be inserted.

[0074] As an optional embodiment, in the uniform motion stage, the interval between the motion coordinates corresponding to the adjacent height data is greater than the interval between the adjacent machining coordinates. In some embodiments, the greater the interval between the motion coordinates corresponding to the adjacent height data is set, the faster the speed of the uniform motion is. In this embodiment, the motion speed of the horizontal motion platform in the uniform motion stage is greater than the motion speed of the horizontal motion platform in the laser scribing process.

[0075] As an optional embodiment, in the uniform motion stage, the relative motion speed between the measurement target and the altimeter is 2000mm / s-5000mm / s. In this embodiment, the relative motion speed between the altimeter and the measurement target is set to a high speed, and the requirement of the accuracy can still be met. For the relative motion speed, 2000mm / s, 3000mm / s, 4000mm / s, or 5000mm / s can be selected.

[0076] Those skilled in the art can understand that all or part of the processes in the above method embodiments can be completed by a computer program instructing related hardware. The program can be stored in a computer readable storage medium, and when the program is executed, the processes of the above embodiments can be included. The storage medium can be a read-only memory (ROM) or a random access memory (RAM).

[0077] The above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for measuring height using laser scribing, characterized in that, include: Controlling a horizontal motion platform to move within a horizontal plane, wherein the motion process of the horizontal motion platform within the horizontal plane includes at least an acceleration phase and a deceleration phase; When the horizontal motion platform begins to move, the control altimeter begins to sample at a predetermined period so that the altimeter obtains height data of the target at multiple locations at least during one of the acceleration and deceleration phases. The height data obtained by the altimeter is subjected to function approximation processing to obtain a function composed of the height data and the motion coordinates; The height of the target to be measured is determined on the function based on the processing coordinates of the laser scribing. Before performing function approximation processing on the height data obtained by the altimeter, the method further includes: Compare the motion coordinate intervals corresponding to the obtained height data; When the interval between motion coordinates corresponding to multiple consecutive height data is in an increasing relationship, the multiple consecutive height data are determined to be height data obtained during the acceleration phase. When the intervals of motion coordinates corresponding to multiple consecutive height data are in a decreasing relationship, the multiple consecutive height data are determined to be height data obtained during the deceleration phase.

2. The method according to claim 1, characterized in that, During the acceleration phase, the sampling starting point of the altimeter is located at the edge of the target being measured.

3. The method according to claim 1, characterized in that, During the deceleration phase, the sampling endpoint of the altimeter is located at the edge of the target being measured.

4. The method according to claim 1, characterized in that, Processing the height data obtained by the altimeter includes: The height data of the acceleration and deceleration phases are respectively fitted to the corresponding motion coordinates using the least squares method to form the fitting functions corresponding to the acceleration and deceleration phases, respectively.

5. The method according to claim 1, characterized in that, The motion process of the horizontal motion platform in the horizontal plane also includes a constant speed phase, which is between the acceleration phase and the deceleration phase.

6. The method according to claim 5, characterized in that, Before performing function approximation processing on the height data obtained by the altimeter, the method further includes: Compare the motion coordinate intervals corresponding to the obtained height data; When the difference between adjacent motion coordinates in multiple consecutive height data does not exceed a predetermined threshold, the multiple consecutive height data are determined to be height data obtained during the uniform speed phase.

7. The method according to claim 5, characterized in that, The method further includes: processing the height data obtained in the uniform speed phase using a cubic spline interpolation algorithm to obtain the spline function corresponding to the uniform speed phase.

8. The method according to claim 5, characterized in that, During the constant speed phase, the interval between motion coordinates corresponding to adjacent height data is greater than the interval between adjacent processing coordinates.

9. The method according to claim 8, characterized in that, During the uniform velocity phase, the relative speed between the target and the altimeter is 2000 mm / s to 5000 mm / s.

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