CN115890012A - Wafer cutting path generation and laser cutting method - Google Patents
Wafer cutting path generation and laser cutting method Download PDFInfo
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Abstract
The invention discloses a wafer cutting path generation method and a laser cutting method, which comprise the following steps: obtaining cutting area information; scanning the cutting area to obtain the shape of the cutting area and generate fitting surface information of the scanning area; acquiring the current photographing height according to the fitting surface information, and performing image acquisition by using a fine positioning camera according to the current photographing height; evaluating a current cutting image according to a set threshold, and if the current cutting image reaches the threshold, analyzing and generating current first three-dimensional cutting point information of a cutting path according to the current image position and the current photographing position; if the threshold value is not reached, adjusting the photographing height to obtain a plurality of cut images under a plurality of heights, evaluating the cut images, selecting the best first image position and the corresponding adjusted photographing position, and analyzing to generate the current first three-dimensional cutting point information; and generating a plurality of pieces of three-dimensional cutting point information, fitting to generate a cutting path and executing a cutting method. According to the cutting path generation method and the cutting method, the wafer cutting precision is obviously improved.
Description
Technical Field
The invention belongs to the technical field of semiconductor processing, particularly relates to a wafer cutting path generation and laser cutting method, and more particularly relates to a wafer cutting path generation and laser invisible cutting method in wafer invisible cutting.
Background
Most of the existing laser invisible cutting equipment adopts a visual guidance technology to process, namely, a wafer image is firstly collected, and then a cutting path is generated according to image processing to carry out laser cutting. The quality of the collected image influences the cutting path planning to a certain extent so as to determine the quality of invisible cutting, and because in a high-precision vision positioning occasion, the visual field of a camera is very small, the focal length is also very small, the chip cannot be clearly identified in one height.
In the prior art, the surface topography of a wafer is usually measured by a non-contact method, but the topography acquisition quality in a common measurement method has respective limitations, for example, laser triangulation is influenced by the surface inclination and roughness of a measured object, the white light confocal angle range is limited, structured light measurement is not beneficial to measuring an object with a complex surface structure, a laser interferometry is not suitable for detecting a large-size object and is not suitable for measuring a complex curved surface with large concave-convex change, other problems such as complex structure and low precision exist in stereoscopic vision, a nuclear magnetic resonance instrument cannot measure a magnetic metal object, an ultrasonic measurement technology is sensitive to temperature, and the like.
The quality of the obtained shape by the non-contact measurement method is limited by a measurement device per se and cannot obtain a high-precision measurement result, the reliability of the measured shape is poor on the second aspect because the wafer material comprises silicon, germanium, silicon carbide, gallium arsenide, zinc oxide, diamond, aluminum nitride, silicon dioxide, sapphire and the like, the refraction and the reflectivity of different materials are different, and the third aspect is influenced by the whole cutting system (the cutting of the wafer comprises multiple processes such as bearing, high-speed movement measurement and adjustment and the like), high-speed movement in the cutting process or the vibration of the whole equipment in the image acquisition process can cause the separation of a focusing plane in the wafer image acquisition or the influence of an image caused by the fact that the micro change of the movement cannot be obtained in real time, and the generation and the planning of a cutting path are influenced by the image generation of a smear.
Disclosure of Invention
The invention provides a method for generating a wafer cutting path and a laser cutting method, which are used for obtaining a wafer contour image and accurately positioning the cutting path, further positioning the cutting path based on the scanned surface topography of a wafer and a fine positioning mode, cutting according to the cutting path and remarkably improving the wafer cutting precision.
The invention discloses a wafer cutting path generation method, which comprises the following steps:
acquiring the information of a wafer contour image by using a contour camera to obtain information of a cutting area;
obtaining surface topography information of a cutting area and generating fitting surface information of a scanning area;
acquiring a current photographing height at a cutting image acquisition position according to fitting surface information, and executing current cutting image acquisition by using a fine positioning camera according to the current photographing height;
evaluating the current cutting image according to a set threshold value,
if the current three-dimensional cutting point information reaches the threshold value, analyzing and generating the current three-dimensional cutting point information of the cutting path according to the current image position and the current photographing position;
if the threshold value is not reached, adjusting the photographing height to obtain a plurality of cutting images under a plurality of heights, evaluating the plurality of cutting images, selecting the optimal image position and the corresponding adjusted photographing position, and analyzing to generate the current three-dimensional cutting point information;
and updating the acquisition position of the cutting image, repeating the steps to correspondingly generate a plurality of pieces of three-dimensional cutting point information, and fitting to generate a cutting path.
In one embodiment, when positioning is realized by using a chip image, in the three-dimensional coordinates of the three-dimensional cutting point information, the X coordinate and the Y coordinate are obtained from the X coordinate and the Y coordinate of the chip position in the cutting image multiplied by a calibration transformation matrix of the fine positioning camera and the cutting carrier, and a correction parameter D is added, wherein the Z coordinate is obtained from a photographing height parameter at the optimal image position.
Further, the method for evaluating the current cutting image according to the set threshold value comprises the following steps:
and positioning the cutting image based on gray matching, acquiring a normalized cross-correlation value between the current cutting image and the template image, and comparing the correlation value with the set threshold value.
Further, obtaining the surface topography information of the cutting region and generating the fitting surface information of the scanning region further comprises: and positioning the wafer, and obtaining the information of the positioned conversion fitting surface.
Furthermore, the method for positioning the wafer and obtaining the positioned information of the transformation fitting surface comprises the following steps: the fine positioning camera collects at least one chip image at different positions, a fitting curve is generated according to the positions of the chips, a fine alignment angle is obtained by comparing the fitting curve with a template, angle adjustment is carried out to complete positioning, and information of a positioned transformation fitting surface is obtained.
Further, the adjustment of the photographing height by the set step distance at least comprises a plurality of times of height adjustment of the current height direction upwards and downwards.
Furthermore, the wafer is arranged on the cutting platform deck, and the method also comprises a calibration step before a contour camera is adopted to collect the contour image information of the wafer and obtain the information of a cutting area; obtaining the position relations of the contour camera, the surface appearance detection device, the fine positioning camera and the cutting carrying platform through the calibration step;
or unifying the coordinate systems of the contour camera, the surface topography detection device, the fine positioning camera and the cutting carrying platform.
Furthermore, the cutting image acquisition position is a chip position, and the three-dimensional cutting point information is obtained according to the required distance between the cutting line and the chip and the adjustment photographing height.
The invention also provides a method for executing laser cutting according to the generated wafer cutting path, which comprises the following steps of executing laser cutting according to the generated cutting path after the cutting path is generated by fitting;
and repeating the cutting path generating step and the laser cutting step until all cutting tasks are completed.
The invention also provides a method for performing laser cutting according to the generated wafer cutting path,
after the cutting path is generated by fitting, executing laser cutting according to the generated cutting path;
repeating the cutting path generating step and the laser cutting step until the cutting task in the first direction is completed;
controlling the cutting carrying platform to rotate to enable the wafer to rotate 90 degrees, and obtaining the transformed fitting surface information;
and finishing the cutting task in a second direction, wherein the first direction is vertical to the second direction.
The invention also discloses computer equipment which comprises a memory and a processor, wherein the memory stores computer programs, and the computer equipment is characterized in that the steps of the method are realized when the processor executes the computer programs.
The invention also discloses a computer-readable storage medium on which a computer program is stored, which is characterized in that the computer program realizes the steps of the above method when being executed by a processor. .
According to the method for generating the wafer cutting path and the laser cutting method, the following beneficial effects can be obtained:
(1) According to the invention, the white light confocal measuring is adopted to measure the surface appearance of the wafer, when the fine positioning camera is used for positioning and shooting, the shooting height is changed according to the fitted appearance change, and after the fitting analysis is finished, the shooting is adjusted and the shot image is analyzed in real time. If the matching score of the pattern in the image is found to be low by analyzing the image, the photographing height is continuously adjusted at the corresponding position to trigger photographing, the picture with the highest pattern matching degree and the corresponding position information are used for analyzing the cutting channels of the invisible cutting, and each cutting channel is positioned by selecting a clear picture for analysis, so that the positioning precision can be improved.
(2) The invention considers that the wafer is placed on the polyester film adhesive tape when being cut, and the wafer can expand and move in the cutting process due to the stress of the polyester film adhesive tape.
(3) By adopting the method, the distance between the final cutting line and the X and Y directions of the chip and the distance between the final cutting line and the surface of the cutting path (the recessive cutting depth) are controlled within 1 mu m.
Drawings
Fig. 1 is a schematic flow chart of wafer dicing path generation implemented according to the present invention.
Fig. 2 is a schematic overall flow chart of one embodiment of a wafer laser cutting method implemented according to the present invention.
Fig. 3 is a schematic diagram of a wafer dicing stage involved in a wafer laser dicing method implemented according to the present invention.
Fig. 4 is a flowchart illustrating the step S10 of confirming the dicing area in the method for generating the dicing path and laser dicing according to the present invention.
Fig. 5 is a flowchart corresponding to S20 in the method for generating a wafer dicing path and laser dicing according to the present invention.
Fig. 6 is a flow chart of single scribe lane positioning cutting in the wafer dicing path generation and laser cutting method according to the present invention.
Fig. 7-8 are schematic diagrams illustrating the dicing direction and scribe line direction of the wafer dicing path generating and laser dicing method according to the present invention.
Fig. 9 is a schematic diagram of obtaining a rotation center of a cutting stage in a wafer cutting path generation and laser cutting method implemented according to the present invention.
Fig. 10 is a schematic diagram of the calibration of the fine positioning camera and the confocal probe in the method of generating the wafer dicing path and performing laser dicing according to the present invention.
Fig. 11 is a schematic diagram of the calibration of the fine positioning camera and the cutting stage in the wafer cutting path generation and laser cutting method according to the present invention.
Fig. 12 is a schematic diagram illustrating the calibration of the profile camera and the cutting stage in the wafer cutting path generation and laser cutting method according to the present invention.
11. Marble platform, 12.X axis linear module, 13.Y axis linear module, 14 rotating table, 21 confocal probe, 22. Fine positioning camera, 23, calibration plate, 231, mark on calibration plate, 51, contour camera, 52, fine positioning camera, 53, calibration plate.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a cutting path generation method and a cutting method, which are used for obtaining a wafer contour image and accurately positioning a cutting path, further positioning the cutting path based on the scanned wafer surface morphology and a fine positioning mode, and cutting according to the cutting path, so that the wafer cutting precision can be obviously improved. The method provided by the invention is particularly suitable for laser invisible cutting of a minified chip. The following embodiments are described by taking laser stealth dicing of a thinned chip of a wafer as an example, but the present invention is not limited thereto, and the present invention is applicable to dicing similar objects to be diced arranged in an array.
According to the technical characteristics corresponding to the embodiment of the invention, the wafer is generally 4 inches, 6 inches, 8 inches, 12 inches and the like, the miniLed chip is an LED chip with the size of 50-200 microns, laser invisible cutting is adopted on the wafer according to a cutting path to obtain a plurality of miniLed chips, and the surface morphology acquisition device is a confocal probe in one implementation mode and can also be other non-contact surface morphology detection devices for distance measurement and height measurement to realize the morphology acquisition of a cutting area. The contour camera is a camera with a larger view field, and the fine positioning camera is a camera with a smaller view field and higher precision.
A cutting area, which is an area position of a chip to be cut arranged on a wafer, that is, an area of the wafer requiring invisible processing, generally, the chips to be cut are arranged in an array, and the cutting area between rows or columns may also be referred to as a cutting street in the following embodiments, wherein one form is a cutting street having a groove; the cutting path is data information for performing specific invisible cutting operation after processing.
Fig. 3 is a schematic diagram of a wafer cutting table related to a cutting path generation method and a cutting method according to the present invention, which includes a cutting stage for supporting a wafer to be cut and driving the wafer to move in a horizontal direction, and includes a marble platform 11 capable of moving in a planar three-dimensional direction through a driving mechanism, specifically, the driving mechanism includes an X-axis linear module 12, a Y-axis linear module 13, and a dd motor 14 for respectively moving in an X direction, a Y direction, and a θ direction, and includes a fine positioning camera 22 disposed above the cutting stage for collecting images, and a confocal probe 21 also disposed above the cutting stage for collecting morphology. Referring to fig. 12, there is shown a schematic diagram of a wafer positioning stage and a wafer cutting stage involved in the cutting path generating method and the cutting method according to the present invention, the wafer positioning stage is used for carrying a wafer to be cut and positioning the contour, and a contour camera 51 is disposed thereon for capturing the contour image of the wafer, and then the wafer is moved to the cutting stage.
As shown in fig. 1, which is a schematic flow diagram of a cutting path generation implemented according to the present invention, the present invention implements a method for generating a wafer cutting path and a laser cutting method, and mainly includes:
s10, acquiring a wafer contour image by using a contour camera to obtain cutting area information;
s20, scanning the cutting area by using a surface topography detection device to obtain the topography of the cutting area and generate fitting surface information of the scanning area;
s30, acquiring a current photographing height at a first cutting image acquisition position according to the fitting surface information, and executing first cutting image acquisition by adopting a fine positioning camera according to the current photographing height;
evaluating the current cutting image according to a set threshold value,
if the current three-dimensional cutting point information reaches the threshold value, generating current three-dimensional cutting point information of the cutting path according to the current cutting image position and the current photographing position;
if the threshold value is not reached, adjusting the photographing height to obtain a plurality of cutting images under a plurality of heights, evaluating the plurality of cutting images, and selecting the best first cutting image position and the corresponding image to generate current three-dimensional cutting point information;
and repeating the operation of the step at other cutting image acquisition positions to generate a plurality of cutting point information, and fitting to generate a cutting path.
And S40, executing laser cutting according to the generated cutting path. And generating a part of cutting paths and executing cutting, and repeating the steps until the cutting is finished, or executing laser cutting according to the cutting paths after all the cutting paths are generated.
As shown in fig. 2, according to an embodiment of the present invention, the method for generating the wafer dicing path and the dicing method include the following steps:
s10: acquiring a wafer contour image by using a contour camera to obtain cutting area information;
s20, scanning the scanning area by using a confocal probe to obtain the shape of the cutting area and generate fitting surface information of the scanning area;
s20, carrying out precise alignment on the wafer, and obtaining the information of the transformation fitting surface after the precise alignment;
s30, acquiring the current photographing height at the first cutting image acquisition position according to the fitting surface information, and executing first cutting image acquisition by adopting a fine positioning camera according to the current photographing height;
evaluating the current cutting image according to a set threshold value,
if the current three-dimensional cutting point information reaches the threshold value, generating current three-dimensional cutting point information of the cutting path according to the current cutting image position and the current photographing height;
if the threshold value is not reached, adjusting the photographing height to obtain a plurality of cutting images under a plurality of heights, evaluating the plurality of cutting images, and selecting the best first cutting image position and the corresponding image to generate the current three-dimensional cutting point information;
and repeating the operation of the step at other cutting image acquisition positions to generate a plurality of cutting point information, and fitting to generate a cutting path.
Specifically, in the present embodiment, as shown in the cutting path generation method and the cutting method shown in fig. 2, in combination with S40: executing a laser cutting process according to the generated cutting path, wherein the laser cutting process comprises the steps of sequentially generating the cutting path in the first direction and executing cutting; and then, controlling the cutting carrier to rotate to enable the wafer to rotate by 90 degrees, obtaining the information of the co-fitting surface after the secondary transformation, sequentially generating a cutting path in a second direction perpendicular to the first direction, and performing cutting. In a specific embodiment, the first direction is represented by the Y-direction and the second direction is represented by the X-direction.
It should be noted that, in the above two-direction cutting scheme, multiple times of cutting path generation in one direction may be also completed, and then the cutting step is performed, or after all the cutting paths in the first direction are generated, the cutting task is performed afterwards.
Further, the method for generating a wafer dicing path and the dicing method of the present invention further include, before S10: s00 preparing materials; specifically, a wafer is placed in a wafer box; after S40, further comprising S50: receiving materials; specifically, the wafer is moved back to the wafer box.
In order to realize that the cutting path generation method and the cutting method equipment can automatically operate, the laser cutting is implemented, and the calibration is required to be completed firstly. The calibration is a process of unifying coordinate systems of a cutting carrier, a fine positioning camera, a confocal probe, a profile camera and a laser processing module, which can be understood by a person skilled in the art; or, the position relation of the wafer under the cutting carrying platform, the fine positioning camera, the confocal probe, the contour camera and the laser processing module is obtained. As a non-limiting example, in the present invention, the dicing stage can be moved in three dimensions, and the wafer to be diced is placed on the dicing stage. In the implementation of the present invention, the calibration work to be performed is: obtaining a rotation center of a cutting carrier, calibrating a fine positioning camera and a confocal probe, calibrating the fine positioning camera and the cutting carrier, and calibrating a contour camera and the cutting carrier; the present invention is not limited thereto as long as the relevant calibration can be accomplished. The specific method of calibration can be selected from one of a plurality of calibration methods in the field. The calibration is executed according to the specific situation of the equipment, wherein the step S10 and the steps S20 to S30 can be executed at two stations, or can be executed at one station.
The wafer dicing path generating method and the dicing method will be described in more detail below.
In S10, a profile camera is used to acquire a wafer profile image to obtain cutting region information, and confocal probe scanning region information is obtained according to the cutting region information, as shown in fig. 4, the specific steps are as follows:
s11: acquiring a wafer contour image by using a contour camera;
s12: obtaining a wafer contour area and a target cutting area, and determining a mass center of the target cutting area and a circumscribed rectangular area parallel to the image coordinate;
specifically, a wafer contour region is obtained through binarization, a region maximum region of the wafer contour region is selected as a target cutting region, a centroid of the region is represented by (roicntr, roicnterc), and a circumscribed rectangular region of the region parallel to image coordinates is represented by Rectangle1;
s13: obtaining a cutting region centroid (rointerx, rointery) of the cutting stage according to a positional relationship (such as a transformation matrix B in the following embodiments) obtained by calibrating the profile camera and the cutting stage and a target cutting region centroid (rointerr, rointerc), obtaining a scanning region stagerectrange 1 of the confocal probe according to the transformation matrix B of the positional relationship obtained by calibrating the profile camera and the cutting stage and a circumscribed Rectangle1 parallel to image coordinates, and the positional relationship (offsfsx, offsetY, fsetotz) between the fine positioning camera and the confocal probe obtained by calibration; wherein:
s20, scanning the scanning area by using a confocal probe to obtain the surface topography of the cutting area and generate fitting surface information; carrying out precise alignment on the wafer, and obtaining transformation fitting surface information after the precise alignment; as shown in fig. 5, the specific steps are as follows:
s21, scanning the morphology of the cutting area by a confocal probe, processing the measured point cloud data, and fitting by adopting a least square method to obtain a Plane (X, Y, Z) of a fitting surface.
Specifically, in the step, a confocal probe scanning grid Line (Line) is obtained according to a confocal probe scanning area StageRectane 1 and a confocal probe scanning Line Distance set by a formula 1 ，Line 2 ，Lime 3 …Line k ) Wherein k is the number of the corresponding grid line, each grid line must be parallel to the X-axis or Y-axis of the cutting platform, and when being parallel to the X-axis of the cutting platform, the kth grid line has the following mathematical expression:
Y k ＝Y min +(k-1)*Distance，X k ∈[X intersect1 ，X intersect2 ]
Y min the scanning area of the confocal probe is the minimum value of the StageRectangle1 corresponding to the Y-axis direction of the cutting platform, X intersect1 And X intersect2 Is a line Y k The value of the cutting platform in the X-axis direction at two intersections with the region stagerectrangle 1.
Using a confocal probe according to the grid Line (Line) 1 ，Line 2 ，Lime 3 …Line k ) And scanning and collecting the surface topography of the cutting area.
Processing the measured point cloud data, and fitting by a least square method to obtain a Plane (X, Y, Z);
in this step, the recipe is template information of the wafer to be processed, including the diameter of the wafer, the thickness of the wafer, the transverse width of the cutting street, the longitudinal width of the cutting street, the length and width of the chip, the position of the template, etc.;
in this embodiment, the scanning of the confocal probe can be performed at fixed intervals, or at uniform intervals in the middle region, and the scanning intervals in the edge region can be reduced.
S22, controlling the cutting carrying platform to move to a first position, enabling the first chip to be located under the visual field of the fine positioning camera, photographing the first chip area by the fine positioning camera according to fitting surface information, and positioning the first chip according to gray scale matching;
in this embodiment, the first chip is a chip at the center of the wafer, which is convenient for searching and positioning.
Specifically, the cutting platform moves to the first position for the ith time
(ROIStageR+i*ChipX/3，ROIStageC，Z＝Plane(ROIStageR+i*ChipX/2，ROIStageC))
At the initial position (planning and searching the first chip), the fine positioning camera photographs the chip at the corresponding position of the wafer, and positions the first chip according to gray scale matching, wherein ChipX is the width of a single chip; wherein i is greater than or equal to 1.
S23, evaluating the first chip image according to a set threshold, judging whether the threshold is reached, and entering the next step S24; if not, the process returns to the previous step S22.
Specifically, whether a threshold is reached is determined according to the matching score, so that whether the first chip is located is determined.
S24: the angle of the first chip calculated by positioning and the template angle recorded in the formula are used for obtaining the angle theta between the first chip and the template 1 (ii) a Obtaining the position (ModelX) of the first chip according to the coordinates of the template image and the position relation (transformation matrix A) between the template image coordinates and the precise positioning camera and the cutting carrier platform which are obtained by calibrating 1 ，ModelY 1 )；
S25 position of first chip (ModelX) 1 ，ModelY 1 ) Controlling the cutting stage to move as reference to obtain the positions (ModelX) of the second chip and the third chip in the same direction 2 ，ModelY 2 )、(ModelX 3 ，ModelY 3 ). Then, fitting a straight line by adopting a least square method according to the positions of the first chip, the second chip and the third chip to obtain an angle theta between the straight line and the positive direction 2 。
In this step, the second chip and the third chip are chips disposed next to the first chip in the Y direction, so as to be conveniently searched and located. Specifically, the operation is performed at each time of (ModelX) 1 ，ModelY 1 ) As reference, along theta 1 And theta 1 Moving the wafer by the distance of the high GapY of one cutting channel and the high ChipY of one chip through the cutting carrier in the direction of +180 degrees, photographing by using a fine positioning camera, positioning a second chip (one chip above the first chip) and a third chip (one chip below the first chip) according to template matching, and obtaining (ModelX) by the same method 2 ，ModelY 2 )、(ModelX 3 ，ModelY 3 )；
According to (ModelX) 1 ，ModelY 1 )、(ModelX 2 ，ModelY 2 ) And (ModelX) 3 ，ModelY 3 ) Fitting the straight line by using a least square method to obtain an angle theta 2 。
S26: by moving the cutting tableMoving the wafer around the center of rotation (X) of the cutting table center ，Y center ) Angle of rotation theta 2 And obtaining the information of the transformation fitting surface.
Specifically, the wafer is moved around the center (X) of the cutting platform by the movement of the cutting platform center ，Y center ) Angle of rotation theta 2 At this time, the process of the present invention,
position of first chip (ModelX) 1 ，ModelY 1 )
Coordinate change to (ModelAfterRotatedX) 1 ，ModelAfterRotatedY 1 ) Plane (X, Y, Z) becomes Plane2 (X, Y, Z). Wherein, (ModelAfterRotatedX) 1 ，ModelAfterRotatedY 1 ) The position of the cutting platform corresponding to the first chip in the center of the cutting area is understood.
In the embodiment of the invention, after the precise positioning camera acquires the images of the chip to obtain clear images, the chip area can be selected as the matching template when the chip has no obvious angle in the images. The actual positioning of the scribe line needs to be achieved by positioning a single chip multiple times, and the single chip is positioned by using a matching algorithm based on gray values.
The specific steps of S30 and S40 are as follows: referring to fig. 6, which is a flowchart illustrating a step S30 of a scribe line positioning process in the wafer dicing method according to an embodiment of the present invention, in steps S30 and S40, scribe lines in the Y direction of the wafer are determined one by one and stealth dicing is performed according to fitting surface data or fitting surface data conversion. Since each scribe line in the vertical direction is implemented in a similar manner, in this embodiment, the implementation method starts from the middle chip and searches the last chip in one direction (shown in fig. 7 and 8).
And the matching positioning based on the gray scale is judged, and a score of 0.5 is set as a judgment basis, so that a more accurate positioning result can be obtained. After the positioning fails once, the data are continuously collected for 4 times at the positions below and above the corresponding photographing height, the photographing range is expanded to 0.004mm, the situation that data of a part of points using the Plane2 which is fit to the photographing Plane cannot be clearly gathered can be avoided, data points which are fitted by cutting channels are increased, and the hidden cutting depth is more stable.
S31, controlling the cutting carrier to move to a first position, enabling the first chip to be located under the visual field of the fine positioning camera, and setting the height of the cutting carrier according to the information of the transformation fitting surface; photographing the first chip by using a fine positioning camera, and positioning the position of the first chip in the image based on gray scale matching;
specifically, the cutting carrier is controlled to move to enable the first chip to be positioned under the visual field of the fine positioning camera, the height of the cutting carrier is set according to the transformation fitting surface,
(ModelAfterRotatedX 1 ，ModelAfterRotatedY 1 +i*j*(ChipY+GnpY))，Z＝Plane2(ModelAfterRotatedX 1 ，ModelAfterRotatedY 1 +i*j*(ChipY+GapY))
at the moment, the first chip is positioned under the visual field of the fine positioning camera, the fine positioning camera is used for shooting the first chip, and the position of the first chip in the image is positioned based on gray scale matching (ImageCutLineR) k ，ImageCutLinC k )；
S32: judging whether the matching is successful, specifically, if the score is greater than 0.5, judging that the matching is successful;
if the matching is successful, the next step S33 is carried out;
if the matching is unsuccessful, controlling the cutting carrier to move up and down for a certain distance, specifically, moving to the positions of Z-2 × StepZ, Z-StepZ, Z + StepZ and Z +2 × StepZ, adopting a fine positioning camera to collect the first chip image again, and positioning the position of the chip in the image based on gray level matching (ImageCutLineR) k ，ImageCutLineC k ) Judging whether the matching is successful again, if the score is larger than 0.5, judging that the matching is successful; if the matching is successful, the next step S33 is carried out;
s33, when the image acquisition of the first chip for multiple times meets the judgment condition, acquiring the Z corresponding to the image with the maximum score as the optimal image height Zbest k The corresponding position is the position of the first chip in the image (ImageCutLineR) k ，ImageCutLineC k )。
According to the position of the first chip in the image, the position relation (matrix A) between the fine positioning camera and the cutting carrier is obtained, and the distance D required by the cutting line and the chip is added to obtain the plane positionSelecting the best height Zbest k For height position, a point (StageCutLineX) on the cutting path is obtained k ，StageCutLineY k ，Zbest k )；
Specifically, the calibrated position relationship between the fine positioning camera and the cutting stage is used to obtain the x and y movement required from the target point to the center of the camera, and the actual position to which the cutting stage needs to be moved is the current photographing position plus the movement required.
S34: controlling the cutting carrier to move to other positions, enabling other chips to be located under the visual field of the fine positioning camera, and setting the height of the cutting carrier according to the information of the transformation fitting surface; photographing other chips by using a fine positioning camera, positioning the positions of the other chips in the image based on gray scale matching, and repeating the steps from S31 to S33 to obtain a plurality of points (StageCutLineX) on the cutting path k ，StagecutLineY k ，Zbest k ) Until all the chips in the Y direction corresponding to the first chip are executed;
s35: points on multiple cutting paths (StageCutLineX) k ，StagecutLineY k ，Zbest k ) And offset (deltaX, deltaY, drataZ) between the fine positioning camera and the laser processing module, fitting a three-dimensional straight line, namely a cutting line; specifically, in this embodiment, a least-square is used to fit a three-dimensional straight line.
S36: the laser processing module processes according to the path of the cutting line and executes laser cutting; specifically, in this embodiment, the cutting stage moves along the cutting line path, so that the laser processing module can be guaranteed to process along the cutting line path.
S37: and positioning and cutting the rest Y-direction cutting lines according to the methods from S41 to S46.
S38, the wafer is rotated around the rotation center (X) of the cutting carrier by the cutting carrier center ，Y center ) And rotating the wafer clockwise by 90 degrees, obtaining second transformation fitting surface information, and referring to steps S31 to S37, finishing the positioning and cutting of the X-direction cutting path.
Specifically, the wafer is rotated around the rotation center (X) of the cutting stage by the cutting stage center ，Y center ) After a 90 ° rotation clockwise, the center of the cutting area (modelafter rotad x) 1 ，ModelAfterRotatedY 1 ) Becomes (ModelAfterRotatedX) 2 ，ModelAfterRotatedY 2 ) The fitted Plane of the cut region, plane2 (X, Y, Z), becomes Plane3 (X, Y, Z).
Specifically, when the scribe line in the X direction is positioned, the movement interval used for searching the chip is represented by a mathematical expression (ChipX + CapX) in which the size of the scribe line in the X direction is added to the size of the chip in the X direction.
In the above embodiment, in S30, the first position and the other positions may use the known sizes of the chips and the scribe lines of the wafer; preferably, known dimensions are used initially, followed by the actual spacing; more preferably, the actual spacing is adjusted.
In the above embodiment S30, when determining the cutting path and cutting according to the cutting path, the present invention preferably performs the cutting according to the cutting path by positioning a cutting path, because the wafer is usually fixed on the mylar tape, and the wafer expands and moves during the cutting process due to the stress of the mylar tape, so that the influence of the expansion and the movement is reduced. Of course, after all cutting paths in one direction are determined, unified cutting can be performed; then determining a cutting path in the other direction, and then performing unified cutting; it is also possible to determine all cutting paths in both directions and then perform a uniform cut.
In the invention, S20, in the precise alignment of the wafer and the evaluation of S30, a gray-scale matching based positioning chip is adopted to obtain the normalized cross-correlation value between the current precise positioning camera image and the template image, and the correlation value is compared with the set threshold value. In the present application, the threshold value is preferably set to 0.5, but may be set to another set value. Specifically, based on a ncc matching algorithm of gray scale matching, after a single chip is clearly imaged by a fine positioning camera, when the chip is ensured to have no obvious angle in an image, a chip area can be selected as a matching template. In the actual S20, the precise alignment of the wafer and the evaluation in S30 need to be realized by positioning a single chip, and the single chip is positioned by using a matching algorithm based on gray scale values. A gray value based match may eventually return an instance of the highest score that exceeds the set score.
The score is essentially the value of the normalized cross-correlation of template t (r, c) and image i (r, c) ncc (r, c):
wherein n is the number of template points, R is the template area, u is the row coordinate of the template, v is the column coordinate of the template, R is the row coordinate of the image, c is the column coordinate of the image, m t Mean gray value for template region:
m i (r, c) is a region of the template size drawn from the point of the image (r, c), the mean gray value of the region:
in the present invention, the calibration comprises:
1. obtaining the center of rotation of a cutting stage
As shown in fig. 9, the calibration plate is placed on the wafer dicing stage. After the cutting carrying platform is reset, the DD motor is rotated to theta degrees, a mark on the calibration plate is observed by using a fine positioning camera, and when the mark is clear and the center position of the mark is concentric with the center of the cross auxiliary line of the camera, the coordinate X of the cutting carrying platform at the moment is recorded A /Y A/ Z A (ii) a Then, the DD motor is rotated to (theta + 180) DEG or (theta-180) °, the same mark is observed by using a fine positioning camera, and when the mark state is clear and the center position of the mark is concentric with the center of the cross auxiliary line of the camera, the coordinate X of the cutting carrier at the moment is recorded B /Y B /Z B (ii) a Then, the rotation center, (Xcenter, ycenter) =0.5 = ((X) is obtained A +X B ),(Y A +Y B ))。
2. Calibration of fine positioning camera and confocal probe
Fig. 3, 9 and 10 show the confocal probe 21, the fine positioning camera 22, the circular calibration plate 23 and the cross mark231 on the calibration plate.
Placing the calibration plate on the cutting platform deck, opening the fine positioning camera, controlling the X-axis/Y-axis/Z-axis movement of the cutting platform deck to make the center of the calibration plate mark concentric with the cross auxiliary line of the camera, and recording the coordinate X of the cutting platform deck at the moment 1 /Y 1 /Z 1 (ii) a Controlling the X-axis/Y-axis/Z-axis movement of the cutting carrier to make the light spot of the confocal probe align to the center of the mark pattern, ensuring the reading of the confocal probe in the middle area of the measuring range, and recording the coordinate X of the cutting carrier at the moment 2 /Y 2 /Z 2 And obtaining the position relation between the fine positioning camera and the confocal probe:
(offsetX，offsetY，offsetZ)＝(X 1 -X 2 ，Y 1 -Y 2 ，Z 1 -Z 2 ) That is, when the center of the fine positioning camera is aligned with a specific position of the cutting stage, the X-axis, the Y-axis and the Z-axis of the cutting stage are relatively moved by the offset X,The offset Y and the offset Z can ensure that the confocal probe is exactly aligned with the specific position.
Here, the fine positioning camera and the confocal probe calibration are taken as an example, and in actual execution, the confocal probe and the cutting carrier calibration can also be adopted, so that the fine positioning camera and the confocal probe establish a relationship.
3. Calibration of fine positioning camera and cutting platform deck
As shown in fig. 11, the calibration plate is placed on the cutting stage, the X-axis/Y-axis/Z-axis movement of the cutting stage is controlled, the fine positioning camera is turned on, the center of the mark is concentric with the cross auxiliary line of the fine positioning camera, the coordinates (Xencoder 1, yencoder 1) of the cutting stage at this time are recorded, and simultaneously, the center position (Row 1, column 1) of the mark at this time is obtained using the Harris corner point extraction algorithm; then, the X-axis/Y-axis/Z-axis movement of the cutting stage is controlled multiple times (at least 6 times) to make the mark point appear in each quadrant of the field of view of the fine positioning camera, and the coordinates (Xencoder 2, yencoder 2), (Xencoder 3, yencoder 3), (Xencoder 4, yencoder 4) … of the corresponding cutting stage and the image coordinates (Row 2, column 2), (Row 3, column 3), (Row 4, column 4) … of the center of the corresponding mark are recorded, assuming that n coincident points are collected, the relationship between the fine positioning camera and the cutting stage of any k-th point is:
wherein a, b, c and d are constant parameters, xencoder k And Yencoder k The kth point corresponding to the coordinates of the cutting platform, xencoder 1 And Yencoder 1 Corresponds to the coordinates of the cutting platform for the first point, row k And Column K For the image coordinates corresponding to the k-th point, row 1 And Column 1 Substituting the data of the n points into the formula for the image coordinate corresponding to the first point, and calculating the optimal transformation matrix A between the fine positioning camera and the cutting stage by using least-squares, namely moving any point (Rowr, columnr) in the field of view of the fine positioning camera to the center of the field of view of the fine positioning camera, wherein the corresponding X axis/Y axis needs to be in phaseMoves (a: (Rowr-Row 1) + b: (Column-Column 1), (c: (Rowr-Row 1) + d: (Column-Column 1)).
4. And calibrating the contour camera and the cutting carrier.
Shown in fig. 12, with a contour camera 51, a fine positioning camera 22, a circular calibration plate 53. The wafer is initially positioned at a feeding station, and is photographed by using a profile camera and then transferred to a cutting carrying platform. After the field of view of the profile camera is calibrated, pixel coordinates (PixelRow, pixelColumn) of 7 or more marks uniformly distributed on the circumference of a calibration plate are confirmed, then the cutting stage is controlled to move, so that the corresponding mark is positioned at the center of the field of view of the fine positioning camera, and the coordinate of the corresponding X-axis/Y-axis/Z-axis is (encoerx, encoery, encoerz), so that a transformation matrix B between the profile camera and the cutting stage is established, and the transformation matrix B has the following formula:
wherein aa, bb, cc, dd are constant parameters, t x 、t y Respectively, along the X-axis and Y-axis translation of the cutting stage.
As can be understood by those skilled in the art, the above calibration is a process of unifying coordinate systems of the cutting stage, the fine positioning camera, the confocal probe, the profile camera, and the laser processing module; the present invention is not limited to this, and those skilled in the art can calibrate the laser beam by using the methods in the prior art as needed, for example, calibrating the fine positioning camera, the confocal probe, the profile camera, and the laser processing module with the cutting stage to obtain a unified coordinate system.
The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (11)
1. A method for generating a wafer cutting path is characterized by comprising the following steps:
acquiring the wafer contour image information by using a contour camera to obtain cutting area information;
obtaining surface appearance information of a cutting area and generating fitting surface information of a scanning area;
acquiring a current photographing height at a cutting image acquisition position according to the fitting surface information, and executing current cutting image acquisition by using a fine positioning camera according to the current photographing height;
evaluating the current cutting image according to a set threshold value,
if the current three-dimensional cutting point information reaches the threshold value, analyzing and generating the current three-dimensional cutting point information of the cutting path according to the current image position and the current photographing position;
if the threshold value is not reached, adjusting the photographing height to obtain a plurality of cutting images under a plurality of heights, evaluating the plurality of cutting images, selecting the optimal image position and the corresponding adjusted photographing position, and analyzing to generate the current three-dimensional cutting point information;
and updating the acquisition position of the cutting image, repeating the steps to correspondingly generate a plurality of pieces of three-dimensional cutting point information, and fitting to generate a cutting path.
2. The method for generating a dicing path according to claim 1, wherein the method for evaluating the current dicing image based on the set threshold value comprises:
and positioning the cutting image based on gray matching, acquiring a normalized cross-correlation value between the current cutting image and the template image, and comparing the correlation value with the set threshold value.
3. The wafer dicing path generating method according to claim 1 or 2, wherein obtaining the information of the surface topography of the dicing area and generating the information of the fitting surface of the scanning area further comprises:
and positioning the wafer, and obtaining the information of the positioned conversion fitting surface.
4. The wafer dicing path generating method according to claim 1 or 2, wherein the method of positioning the wafer and obtaining the positioned conversion fitting surface information is: the fine positioning camera collects at least one chip image at different positions, a fitting curve is generated according to the positions of the chips, a fine alignment angle is obtained by comparing the fitting curve with a template, angle adjustment is carried out to complete positioning, and information of a positioned transformation fitting surface is obtained.
5. The method as claimed in claim 1 or 2, wherein the adjusting the photographing height is adjusted by a predetermined step distance, which at least includes a plurality of height adjustments of the current height direction up and down.
6. The wafer cutting path generation method as claimed in claim 1 or 2, wherein the wafer is arranged on the cutting stage, and further comprising a calibration step before acquiring the wafer contour image information by using a contour camera and obtaining the cutting area information; obtaining the position relations of the contour camera, the surface appearance detection device, the fine positioning camera and the cutting carrying platform through the calibration step;
or unifying the coordinate systems of the contour camera, the surface topography detection device, the fine positioning camera and the cutting carrying platform.
7. The wafer cutting path generation method according to claim 1 or 2, wherein the cutting image acquisition position is a chip position, and the three-dimensional cutting point information is obtained according to a required distance between the cutting line and the chip and the adjustment of the photographing height.
8. The method of performing laser dicing according to the wafer dicing path generating method of any one of claims 1 to 7, wherein after fitting the generated dicing path, further comprising performing laser dicing according to the generated dicing path;
and repeating the cutting path generating step and the laser cutting step until all cutting tasks are completed.
9. The method of performing laser dicing according to the wafer dicing path generating method of any one of claims 1 to 7, characterized in that:
performing laser cutting according to the generated cutting path after fitting the generated cutting path;
repeating the cutting path generating step and the laser cutting step until the cutting task in the first direction is completed;
controlling the cutting carrying platform to rotate to enable the wafer to rotate 90 degrees, and obtaining the transformed fitting surface information;
and finishing the cutting task in a second direction, wherein the first direction is vertical to the second direction.
10. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor implements the steps of the method of any one of claims 1 to 9 when executing the computer program.
11. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 9.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116168027A (en) * | 2023-04-24 | 2023-05-26 | 山东交通学院 | Intelligent woodworking machine cutting method based on visual positioning |
| CN116995030A (en) * | 2023-09-27 | 2023-11-03 | 武汉华工激光工程有限责任公司 | Full-automatic wafer fragment cutting method and device |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116168027A (en) * | 2023-04-24 | 2023-05-26 | 山东交通学院 | Intelligent woodworking machine cutting method based on visual positioning |
| CN116995030A (en) * | 2023-09-27 | 2023-11-03 | 武汉华工激光工程有限责任公司 | Full-automatic wafer fragment cutting method and device |
| CN116995030B (en) * | 2023-09-27 | 2023-12-29 | 武汉华工激光工程有限责任公司 | Full-automatic wafer fragment cutting method and device |
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