CN108615699B - Wafer alignment system and method and optical imaging device for wafer alignment - Google Patents
Wafer alignment system and method and optical imaging device for wafer alignment Download PDFInfo
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Abstract
A wafer alignment system and method and an optical imaging device for wafer alignment are provided, wherein, the whole image of the wafer is acquired firstly, the adjusting value of a motion platform is calculated, and the position of the wafer is adjusted according to the adjusting value, so that the edge of the wafer is positioned at a position which can be adjusted finely according to the edge image of the wafer. And acquiring an edge image of the wafer, calculating an adjusting value of the movable platform according to the edge image of the wafer, and finely adjusting the position of the wafer according to the adjusting value so as to finish wafer alignment. Therefore, when the wafer is aligned, the wafer carrying table does not need to be continuously rotated to acquire the wafer edge image, and the wafer carrying table does not need to be replaced after the alignment, so that the wafer alignment efficiency is improved.
Description
Technical Field
The application relates to the technical field of semiconductor detection, in particular to a wafer alignment system and method and an optical imaging device for wafer alignment.
Background
In the prior art, the wafer pre-alignment scheme mainly adopts a method of matching an edge detection sensor (a laser sensor or an image sensor) with rotation of a turntable to obtain edge information of a wafer, and then corrects the pose of the wafer by using a mechanical motion platform to realize the wafer pre-alignment. In the method using the laser sensor, as shown in fig. 1, a servo motor drives a wafer carrying platform to rotate, edge position data can be collected by using an optical sensor system (light source and light sensor), after the wafer rotates for one circle, the data collection is completed, the central coordinate and the deflection angle of the wafer are obtained by using a mathematical algorithm, and then the wafer pose is corrected by using a mechanical motion system of the carrying platform. The wafer carrying table of the optical sensing system used in the pre-alignment method must be smaller than the wafer, so that the wafer carrying table needs to be replaced by a manipulator when entering the subsequent process, and the wafer carrying table must be rotated for one or more circles in the pre-alignment process of the wafer, so that the efficiency is low.
Disclosure of Invention
The application provides a wafer alignment system and method and an optical imaging device for wafer alignment, wherein after an integral image of a wafer is acquired, an adjusting value of a motion platform is calculated, and the position of the wafer is initially adjusted according to the adjusting value, so that the edge of the wafer is positioned at a position which can be finely adjusted according to the edge image of the wafer. And acquiring an edge image of the wafer, calculating an adjusting value of the movable platform according to the edge image of the wafer, and finely adjusting the position of the wafer according to the adjusting value so as to finish the pre-alignment of the wafer. Because the wafer carrying table does not need to be replaced and continuously rotates, the problem of low wafer calibration efficiency in the prior art is solved.
According to a first aspect, there is provided in one embodiment a wafer alignment system comprising:
the motion platform can move in the X axis and the Y axis and rotate around the Z axis;
a wafer carrying platform supported on the motion platform for carrying wafers;
the image acquisition device is arranged above the wafer carrying platform and is used for acquiring an overall image of the wafer and an edge image of the wafer;
the processor is coupled with the image acquisition device and the motion platform and is used for processing the whole image of the wafer, calculating a first adjustment value of the motion platform moving in an X axis and a Y axis and a first angle rotating around a Z axis, and sending the first adjustment value and the first angle to the motion platform so as to control the motion platform to move;
the processor is further used for processing the edge image of the wafer, calculating a second adjusting value of the motion platform moving in the X axis and the Y axis and a second angle rotating around the Z axis, and sending the second adjusting value and the second angle to the motion platform so as to control the motion platform to move.
Further, the image acquisition apparatus includes:
the first sensor is used for acquiring the whole image of the wafer;
the second sensor is used for acquiring an edge image of the wafer;
the first sensor and the second sensor are respectively coupled with the processor for transmitting the integral image of the wafer and the edge image of the wafer to the processor.
Further, the sensor comprises a CCD image sensor and an analog-to-digital converter;
the CCD image sensor is used for acquiring light rays and converting the light rays into analog signals and sending the analog signals to the analog-to-digital converter;
the analog-to-digital converter is used for converting the received analog signals sent by the CCD image sensor into digital signals and sending the digital signals to the processor.
Further, the image acquisition device further comprises an optical imaging device;
the optical imaging device is used for acquiring light rays of a first view field and light rays of a second view field, and projecting the light rays of the first view field onto the first sensor so as to obtain an overall image of the wafer;
and projecting the light rays of the second field of view onto the second sensor to obtain an edge image of the wafer.
Further, the optical imaging device comprises an objective lens group, a spectroscope and a first lens;
the objective lens group focuses the light rays of the first view field, and the focused light rays of the first view field reach the spectroscope;
the spectroscope reflects the focused light rays of the first view field;
the first lens transmits the reflected light rays of the first view field, and the transmitted light rays of the first view field reach the first sensor.
Further, the optical imaging device comprises an objective lens group, a second lens, a galvanometer and a spectroscope;
the objective lens group focuses the second view field, and the focused light of the second view field reaches the second lens;
the second lens transmits the focused light rays of the second field of view;
the galvanometer reflects the light rays of the second field transmitted by the second lens;
the second lens transmits the light of the second view field reflected by the vibrating mirror;
the spectroscope reflects the light of the second view field reflected by the vibrating mirror transmitted by the second lens to reach the second sensor.
Further, the optical imaging device further comprises a biaxial MEMS for enabling the second sensor to acquire the light of the second field of view corresponding to the reflection angle by adjusting the reflection angle of the galvanometer.
According to a second aspect, an embodiment provides an optical imaging apparatus for wafer alignment, including an objective lens set, a third lens, a galvanometer, a fourth lens, and a beam splitter;
the objective lens group transmits the light of the field of view after focusing;
the spectroscope separates a first light ray and a second light ray from the light rays transmitted by the objective lens group;
the first light is the light of the field of view transmitted by the spectroscope after reflecting the focusing of the objective lens group, and the second light is the light of the field of view transmitted by the spectroscope after transmitting the focusing of the objective lens group;
the third lens transmits the first light and is used for receiving the first light by the third sensor;
the fourth lens transmits the second light;
the galvanometer reflects the second light transmitted by the fourth lens;
the fourth lens is further used for transmitting the second light transmitted by the fourth lens through the galvanometer;
the spectroscope is also used for reflecting the second light rays reflected by the vibrating mirror transmitted by the fourth lens and receiving the second light rays by the fourth sensor.
Further, the optical imaging device further comprises a biaxial MEMS for adjusting the reflection angle of the galvanometer.
According to a third aspect, an embodiment provides a wafer alignment method, including:
acquiring an image of the whole wafer;
comparing the whole image of the wafer with a pre-stored whole image of the wafer, and calculating a third adjustment value of the motion platform moving in the X axis and the Y axis and a third angle rotating around the Z axis according to a comparison result;
correcting the position of the wafer according to the third adjusting value and the third angle value;
acquiring an image of the edge of the wafer;
comparing the edge image of the wafer with a pre-stored edge image of the wafer, and calculating a fourth adjustment value of the motion platform moving in the X axis and the Y axis and a fourth angle rotating around the Z axis according to a comparison result;
correcting the position of the wafer according to the fourth adjustment value and the fourth angle.
According to the wafer alignment system and method and the optical imaging device for wafer alignment in the embodiments, the overall image of the wafer is acquired first, the adjustment value of the motion platform is calculated, and the position of the wafer is adjusted according to the adjustment value, so that the edge of the wafer is positioned at a position which can be finely adjusted according to the edge image of the wafer. And acquiring an edge image of the wafer, calculating an adjusting value of the movable platform according to the edge image of the wafer, and finely adjusting the position of the wafer according to the adjusting value so as to finish the pre-alignment of the wafer. So that the wafer pre-alignment is performed without replacing the wafer carrying table and the wafer pre-alignment efficiency is improved.
Drawings
FIG. 1 is a schematic diagram illustrating operation of an edge detection sensor according to the prior art;
FIG. 2 is a schematic diagram of a wafer alignment system according to one embodiment;
FIG. 3 is a schematic diagram of an image capturing device according to an embodiment;
FIG. 4 is a schematic diagram of a coordinate system construction for calculating adjustment values for wafer alignment;
FIG. 5 is a schematic diagram of a coordinate system for calculating a wafer adjustment value by a circle fitting algorithm;
FIG. 6 is a schematic diagram of a coordinate system for detecting a trimming point of a wafer and calculating an angle adjustment value;
FIG. 7 is a schematic diagram of a coordinate system of wafer corner adjustment values;
FIG. 8 is a flow chart of another embodiment of a wafer alignment method.
Detailed Description
The application will be described in further detail below with reference to the drawings by means of specific embodiments. Wherein like elements in different embodiments are numbered alike in association. In the following embodiments, numerous specific details are set forth in order to provide a better understanding of the present application. However, one skilled in the art will readily recognize that some of the features may be omitted, or replaced by other elements, materials, or methods in different situations. In some instances, related operations of the present application have not been shown or described in the specification in order to avoid obscuring the core portions of the present application, and may be unnecessary to persons skilled in the art from a detailed description of the related operations, which may be presented in the description and general knowledge of one skilled in the art.
Furthermore, the described features, operations, or characteristics of the description may be combined in any suitable manner in various embodiments. Also, various steps or acts in the method descriptions may be interchanged or modified in a manner apparent to those of ordinary skill in the art. Thus, the various orders in the description and drawings are for clarity of description of only certain embodiments, and are not meant to be required orders unless otherwise indicated.
The numbering of the components itself, e.g. "first", "second", etc., is used herein merely to distinguish between the described objects and does not have any sequential or technical meaning. The term "coupled" as used herein includes both direct and indirect coupling (coupling), unless otherwise indicated.
Wafer alignment systems and methods are different for patterned and unpatterned wafers. For patterned wafers, this is achieved directly through wafer alignment. The specific process is as follows:
(a) When establishing the Recipe, collecting a repeated high-uniqueness characteristic image along a certain street, recording more than two coordinate positions containing the characteristic image, and performing error elimination on all wafers using the Recipe by taking the coordinate positions as references;
(b) When the Recipe runs, the manipulator places the wafer on the object carrying sucker of the moving platform and stabilizes the wafer, then moves the moving platform to the recorded first coordinate position, then acquires an image, then uses the stored characteristic image to match with the acquired image, and if the matching is successful, the pixel deviation of the characteristic image in the target image is the wafer transmission error of the first coordinate point;
(c) If the matching is unsuccessful, the motion platform needs to be moved spirally by taking the current coordinate position as a center, an image is acquired once when the motion platform is moved once, and the characteristic image is matched with the acquired image until the matching is successful or the limit times are exceeded;
(d) Repeating the steps (b) and (c) from the second coordinate point until all recorded coordinate positions obtain respective transmission errors;
(e) And calculating the transmission error of the whole wafer according to the transmission errors of all the points, wherein the transmission error comprises a translational transmission error and a rotational transmission error.
For a non-patterned wafer, alignment is typically by edge features of the wafer, since no feature images can be extracted inside. The specific process is as follows:
(a) When aligning and calibrating the non-pattern wafer, firstly, carrying out edge feature extraction on the non-pattern wafer, collecting more than 4 edge feature images including two notches (hereinafter referred to as positioning notches) at the edge of the non-pattern wafer, and recording the collecting positions of the edge feature images;
(b) And when the Recipe runs, the manipulator places the wafer on the carrying sucker of the motion platform.
(c) After the motion platform is stabilized, moving the motion platform to a recorded first coordinate position, then acquiring an image, then matching the acquired image with a stored corresponding characteristic image, and acquiring pixel deviation of the characteristic image in a target image after the matching is successful;
(d) If the matching is unsuccessful, the motion platform needs to be moved spirally by taking the current coordinate position as a center, an image is acquired once when the motion platform is moved once, and the characteristic image is matched with the acquired image until the matching is successful or the limit times are exceeded;
(e) Repeating (c) and (d) from the second point until all recorded coordinates result in respective pixel deviations;
(f) And calculating the actual coordinate positions of the edge features according to the pixel deviations of all the points, and fitting a circle according to the coordinate positions. The center of the circle is translational error of the wafer, and the rotation transmission error can be calculated by the midpoint of the connecting line of the center of the circle and the two positioning notch positions.
For a patterned wafer, because the requirement on positioning accuracy is particularly high, the resolution and magnification of the used camera are high, and the corresponding field of view is smaller. When the wafer transmission error is large, the characteristic image is easy to be out of the field of view, if the situation occurs, the target image is required to be searched by taking the coordinate position where the characteristic image is expected to appear as the center in a spiral mode, the moving platform is moved for many times, image matching is carried out for many times, time is very consumed, and when the wafer transmission error is particularly large, the situation that the wafer alignment fails is likely to occur. For the alignment of the unpatterned wafer, the problem of the need for a spiral search for the feature image out of view also arises because the same high resolution small field of view camera is used similarly to the patterned wafer. In addition, since the characteristic images of the non-pattern wafer are distributed on the periphery of the wafer, and the more points used for alignment are distributed more uniformly, the more accurate transmission error data can be acquired, the moving platform needs to be moved frequently when the non-pattern wafer is aligned, and the image matching is performed frequently, so that the time is very long. In addition, the scheme employing an image sensor generally uses a CCD image sensor instead of the optical sensor system in the above scheme. In order to ensure high resolution of the wafer edge image, either an ultra-high resolution camera is used to detect the global image of the wafer, which is very costly, or a wafer carrier is still required to rotate one or more turns, a low resolution camera is used to detect the wafer edge image, but the pre-alignment efficiency is reduced.
MEMS, micro-electromechanical systems, are abbreviations for english Micro Electro Mechanical systems.
In the embodiment of the application, the whole image of the wafer and the edge image of the wafer are acquired, the adjustment value of the movable platform is calculated according to the acquired wafer image and the pre-stored wafer image, and the wafer position is adjusted according to the adjustment value, so that the wafer pre-alignment is completed.
Embodiment one:
referring to fig. 2, a schematic structure diagram of a wafer alignment system according to an embodiment of the application is disclosed, which includes a motion platform 1, a wafer carrier 2, an image acquisition device 3 and a processor 4. The motion stage 1 is movable in the X-axis and the Y-axis and rotates about the Z-axis. The wafer carrier 2 is supported on the motion stage 1 for carrying wafers 5. The image acquisition device 3 is arranged above the wafer carrying platform 2 and is used for acquiring the whole image of the wafer and the edge image of the wafer. The processor 4 is coupled to the image acquiring device 3 and the motion platform 1, and is configured to process the overall image of the wafer, calculate a first adjustment value of the motion platform 1 moving in the X-axis and the Y-axis and a first angle of the motion platform rotating around the Z-axis, and send the first adjustment value and the first angle to the motion platform 1, so as to control the motion platform 1 to move, and further implement adjustment of the position of the wafer 5. The processor 4 is further configured to process a series of edge images of the wafer, calculate a second adjustment value of the movement of the moving platform 1 in the X axis and the Y axis and a second angle of rotation around the Z axis, and send the second adjustment value and the second angle to the moving platform 1 to control the movement of the moving platform 1, so as to further implement adjustment of the position of the wafer 5.
Fig. 3 is a schematic structural diagram of an image capturing device according to an embodiment. The image acquisition device 3 includes an optical imaging device 31, a first sensor 32, and a second sensor 33. A first sensor 32 for acquiring an overall image of the wafer. A second sensor 33, configured to acquire an edge image of the wafer; the first sensor 32 and the second sensor 33 are coupled to the processor 4 for transmitting the acquired global image of the wafer and the edge image of the wafer to the processor 4. The optical imaging device 31 is configured to acquire light of the first field of view 34 and light of the second field of view 35, and project the light of the first field of view 34 onto the first sensor 32 to obtain an overall image of the wafer. The light of the second field of view 35 is projected onto the second sensor 33 to obtain an edge image of the wafer. The optical imaging device 31 includes an objective lens 311, a first lens 313, a galvanometer 315, a second lens 314, and a beam splitter 312. The objective lens group 311 of the optical imaging device 31 is used for focusing the light of the first field of view 34, and the focused light of the first field of view 34 reaches the beam splitter 312. The beam splitter 312 reflects the focused light of the first field of view 34. The first lens 313 transmits the reflected light of the first field of view 34, and the transmitted light of the first field of view 34 reaches the first sensor 32. The objective lens group 311 of the optical imaging device 31 is further configured to focus the light rays of the second field of view 35, and the focused light rays of the second field of view 35 reach the second lens 314. The second lens 314 transmits the light of the focused second field of view 35. The galvanometer 315 reflects light transmitted by the second lens 314 that is of the second field of view 35. The second lens 314 transmits light of the second field of view 35 reflected by the galvanometer 315. The beam splitter 312 reflects the light of the second field of view 35 reflected by the galvanometer 315 transmitted by the second lens 314 onto the second sensor 33.
Further, the optical imaging apparatus of the present embodiment may include two light paths.
Wherein the fields of view comprise a first field of view 34 and a second field of view 35.
The first light path is routed through the objective lens 311, the beam splitter 312, through the first lens 313 to the first sensor 32.
The second light path is routed through the objective lens 311-beam splitter 312-lens 314-galvanometer 315-second lens 314-through mirror 312 to the second sensor.
Specifically, as shown in fig. 3, the objective lens 311 focuses the light of the field of view and transmits the light. The beam splitter 312 splits the light beam transmitted from the objective lens 311 into a first light beam and a second light beam. The first light is the light of the field of view transmitted after focusing by the beam splitter 312 reflecting the objective lens group 311, and the second light is the light of the field of view transmitted after focusing by the beam splitter 312 transmitting the objective lens group 311. The first lens 313 transmits the first light for the first sensor 32 to receive the first light. The second lens 314 transmits the second light. The galvanometer 315 reflects the second light transmitted by the second lens 314. The second lens 314 is further configured to reflect the second light transmitted by the second lens through the oscillating mirror 315. The beam splitter 312 is further configured to reflect the second light reflected by the galvanometer 315 transmitted by the second lens 314, and is configured to receive the second light by the second sensor 33.
The sensor in this embodiment includes a CCD image sensor and an analog-to-digital converter, the analog-to-digital converter receiving light acquired by the CCD image sensor from the optical imaging device and converting the light into an analog signal and transmitting the analog signal to the analog-to-digital converter, and the analog-to-digital converter receiving an analog signal of the CCD image sensor and converting the analog signal into a digital signal and transmitting the digital signal to the processor. Wherein the resolution of the CCD image sensor of the second sensor is higher than the CCD image sensor of the first sensor. By adopting the optical imaging device of the embodiment, the field of view of the second sensor is very small when the edge image of the wafer is acquired, the image acquisition resolution is relatively improved, and the alignment accuracy is further improved. Therefore, the first sensor and the second sensor can both adopt CCD sensors with lower resolution, and the equipment cost is reduced.
Further, the optical imaging device in this embodiment includes a biaxial MEMS for adjusting the reflection angle of the galvanometer 315. The oscillating mirror 315 with the biaxial MEMS can accurately and rapidly adjust the angle, so that the light is reflected back to the second lens 314 again, and is imaged on the CCD image sensor of the second sensor 33 after being reflected by the spectroscope 312, thereby obtaining a high resolution partial image, and completing the scanning and acquisition of the image of the wafer edge within 1 second. The scanning and collecting of the image of the wafer edge, specifically, the reflection angles of the vibrating mirror 315 are controlled by the biaxial MEMS to obtain the edge images of the wafer corresponding to different reflection angles. The wafer rotation motion mode can be not adopted for collection, and the detection resolution and the detection efficiency can be improved.
The working flow of the wafer alignment system in this embodiment is as follows:
(a) The motion stage 1 moves the wafer 5 to a pre-alignment station.
(b) The first sensor 32 of the image acquisition device 3 acquires the light of the first field of view 34 from the optical imaging device 31, and converts the light of the first field of view 34 into an analog signal, and transmits the image information converted into a digital signal by the analog-to-digital converter to the processor 4, even if the processor 4 acquires an overall image of the wafer.
(c) The processor 4 processes the overall image of the wafer 5 and calculates a first adjustment value for the movement of the motion stage 1 in the X-axis and the Y-axis and a first angle for rotation about the Z-axis. Specifically, the coordinates of edge points of the whole image of the wafer are obtained by using an image processing algorithm, and a first adjustment value of X-axis and Y-axis movement and a first angle of Z-axis rotation are obtained by using a least square method.
(d) The processor 4 sends the first adjustment value and the first angle to the motion stage 1 to control the motion stage 1 to move, so as to realize the initial alignment adjustment, and the edge of the wafer 5 is located at a position which can be finely adjusted according to the edge image (i.e. the second field of view 35) of the wafer 5.
(e) The second sensor 33 of the video capturing apparatus 3 captures light of the second field of view 35 from the optical imaging apparatus 31, and converts the light of the second field of view 35 into image information that is converted into an analog signal by an analog-to-digital converter into a digital signal to be sent to the processor 4, even if the processor 4 obtains an edge image of the wafer. The edge images of the wafers corresponding to different reflection angles are obtained by controlling the reflection angles of the vibrating mirror 315 through the biaxial MEMS, and then a series of edge images of the wafers 5 are obtained.
(f) The processor 4 processes a series of edge images of the wafer 5 and calculates a second adjustment of the movement of the motion stage 1 in the X-axis and Y-axis and a second angle of rotation about the Z-axis. Specifically, the edge point coordinates of the wafer edge image are obtained by using an image processing algorithm, and a second adjustment value of X-axis and Y-axis movement and a second angle of Z-axis rotation are obtained by using a least square method.
(g) The processor 4 sends the second adjustment value and the second angle to the motion platform 1 to control the motion platform 1 to move, so as to realize wafer alignment.
The calculation method of the adjustment value of the X-axis and Y-axis movement of the wafer carrying platform and the angle of the Z-axis rotation specifically comprises the following steps: in the process of placing the wafer on the wafer carrying platform, the pose of the wafer relative to the center of the wafer carrying platform can have larger deviation. As shown in fig. 4, the coordinate system is a simplified two-dimensional coordinate system, XOY is a stage coordinate system, and XOY is a machine tool coordinate system. (c) x ,c y ) The coordinates of the center point C of the wafer in the wafer stage coordinate system are regarded as the displacement deviation of the wafer. θ is the deflection angle of the wafer trim and is the angular deflection of the wafer. The displacement offset and the angular offset are calculated using wafer edge point data. To ensure machining accuracy, these deviations should be compensated for. Once the wafer is placed on the carrier, the wafer can no longer move relative to the carrier. The correction process should be divided into two steps. The first step is to correct the angular deviation θ by rotating the wafer carrier, and the second step is to correct the displacement deviation, but it is noted that after correcting the angular deviation θ, the displacement deviation of the wafer is no longer (c) x ,c y ) The recalculation is required.
The wafer center coordinates (c) are calculated by the wafer edge point data acquired by the wafer fitting algorithm x ,c y ). As shown in fig. 5, the vision inspection module is set to collect N discrete points P on the wafer edge i (x i ,y i ) (excluding points on the cut), then construct the function,
wherein r is i ——(x i ,y i ) Point-to-wafer center (c) x ,c y ) Is a distance of (3).
The meaning of E in equation (1) is that all sample points are equal to c x 、c y And R.
The circle with the smallest E can be the best fit circle. However, the formula (1) contains a root formula, which is unfavorable for optimizing the solution.
Respectively using r i 2 And R is 2 Instead of r i And R, although it will be enlargedThe function of a point far from the center of a circle is that the method has an analytic solution, and the circle parameter can be accurately calculated.
The following optimization objective function is used to solve for the circle parameters.
Extremum for E, then E is required to be made to correspond to c respectively x 、c y And R is biased
I.e.
Solving the equation to obtain the position parameter c of the wafer x 、c y And R.
Calculation of angular deviation, assuming Q 1 ，Q 2 ，…，Q m As shown in FIG. 6, rectangular coordinates of the points on the tangential side (x 1 ,y 1 )，(x 2 ,y 2 )，…，(x m ,y m ). And a least square straight line fitting is performed, so that a straight line equation y=kx+b where the trimming is located can be obtained, wherein,
the wafer bias angle may be expressed as,
θ＝-arctank (6)
note that θ has a positive and negative division, a positive value indicates that the trim is biased toward the first quadrant, and a negative value indicates that the trim is biased toward the second quadrant.
After the wafer fitting and trimming (notch) detection, the wafer prealignment system has obtained the position deviation parameter c of the wafer in the wafer carrier coordinate system xoy x 、c y And θ.
The wafer positional deviation is corrected as follows: from the definition of wafer pre-alignment, it is known that the purpose of wafer pre-alignment is to compensate for positional deviations of the wafer in the machine coordinate system after loading of the wafer.
The compensation process of the scheme is carried out in two steps: the first step is to rotate the wafer carrying platform to correct the angle deviation theta; the second step is to correct the displacement deviation; it is noted that after correcting the angular deviation θ, the displacement deviation of the wafer is no longer (c x ,c y ) The recalculation is required. The angular correction is shown in fig. 7. Through the rotation angle of the wafer carrying tableAfter the offset angle compensation is carried out, the trimming edge is perpendicular to the y axis, and the circle center of the wafer moves from the point C to the point C'. From the geometrical relations, the +.>=θ. Therefore, the first step of correction is to rotate the wafer carrying platform by an angle theta to finish angle correction. The displacement correction is performed by setting the coordinates of the C and C' points in the machine coordinate system to be (C x ,C y ) And (C' x ,C' y ) The coordinate of the origin o of the coordinate system of the wafer bearing table in the coordinate system of the machine tool is (o) x ,o y ) Then the plane coordinate conversion relation can be obtained,
due to the coordinates (C) of the point C in the coordinate system of the wafer carrier x ,c y ) Which has been found by a circle fit, there are,
it is thus possible to obtain a solution,
at this time, the wafer center has moved to the C' point, and the required displacement compensation values in the X and Y directions are set to be X c1 And y c1 It is possible to obtain,
thus, in the second step of correction, the X, Y axes are respectively shifted by x c1 And y c1 。
The embodiments described above are applicable not only to patterned wafer alignment, but also to non-patterned wafer alignment. Similar to the existing non-pattern wafer alignment method, the wafer alignment system of the application can obtain the translational adjustment value and the rotational adjustment angle of the wafer. The method comprises the steps of firstly obtaining an integral image of a wafer, calculating an adjusting value of a moving platform, and primarily adjusting the position of the wafer according to the adjusting value, so that the edge of the wafer is positioned at a position which can be finely adjusted according to the edge image of the wafer. And acquiring an edge image of the wafer, calculating an adjusting value of the movable platform according to the edge image of the wafer, and finely adjusting the position of the wafer according to the adjusting value so as to finish the pre-alignment of the wafer. So that the wafer pre-alignment is performed without replacing the wafer carrying table and the wafer pre-alignment efficiency is improved. The wafer alignment system of the present application can completely replace the existing non-pattern wafer alignment system and method. Compared with the existing alignment method of the patterned wafer, the wafer alignment system of the application does not need to frequently move a motion platform, so that frequent image acquisition and frequent pattern recognition are avoided.
Embodiment two:
referring to fig. 8, a flow chart of a wafer alignment method according to another embodiment includes:
step 201, an image of the whole wafer is acquired.
The motion platform 1 moves the wafer 5 to the pre-alignment station, the first sensor 32 of the image acquisition device 3 acquires the light of the first field of view 34 from the optical imaging device 31, converts the light of the first field of view 34 into an analog signal, converts the analog signal into image information of a digital signal through an analog-to-digital converter, and sends the image information to the processor 4, even if the processor 4 acquires an overall image of the wafer.
And 202, processing the whole image of the wafer, and calculating a third adjustment value of the movement of the moving platform in the X axis and the Y axis and a third angle of rotation around the Z axis.
The processor 4 processes the whole image of the wafer 5 and calculates a third adjustment value of the movement of the moving platform 1 in the X-axis and the Y-axis and a third angle of rotation around the Z-axis. Specifically, the coordinates of edge points of the whole image of the wafer are obtained by using an image processing algorithm, and a third adjustment value of X-axis and Y-axis movement and a third angle of Z-axis rotation are obtained by using a least square method.
And 203, adjusting the position of the wafer according to the third adjustment value and the third angle value.
The processor 4 sends the third adjustment value of the X-axis and Y-axis movement and the third angle value of the Z-axis rotation to the moving platform 1, and the moving platform 1 moves according to the third adjustment value of the X-axis and Y-axis movement and the third angle value of the Z-axis rotation to perform initial adjustment of the wafer position.
Step 204, obtaining an image of the edge of the wafer;
the second sensor 33 of the video capturing apparatus 3 captures light of the second field of view 35 from the optical imaging apparatus 31, and converts the light of the second field of view 35 into image information that is converted into an analog signal by an analog-to-digital converter into a digital signal to be sent to the processor 4, even if the processor 4 obtains an edge image of the wafer 5. The edge images of the wafers corresponding to different reflection angles are obtained by controlling the reflection angle of the vibrating mirror 315 through the biaxial MEMS, and then the processor 4 can obtain a series of edge images of the wafers 5.
And 205, processing the edge image of the wafer, and calculating a fourth adjustment value of the movement of the moving platform in the X axis and the Y axis and a fourth angle of rotation around the Z axis.
The processor 4 processes a series of edge images of the wafer 5 and calculates a fourth adjustment value for the movement of the motion stage 1 in the X-axis and the Y-axis and a fourth angle for rotation about the Z-axis. Specifically, the coordinates of the edge points of the wafer edge image are obtained by using an image processing algorithm, and a fourth adjustment value of X-axis and Y-axis movement and a fourth angle of Z-axis rotation are obtained by using a least square method.
And 206, adjusting the position of the wafer according to the fourth adjustment value and the fourth angle.
The processor 4 sends the fourth adjustment value of the X-axis and Y-axis movement and the fourth angle value of the Z-axis rotation to the moving platform 1, and the moving platform 1 moves according to the fourth adjustment value of the X-axis and Y-axis movement and the fourth angle value of the Z-axis rotation to adjust the position of the wafer, so that the alignment of the wafer is finished.
The foregoing description of the application has been presented for purposes of illustration and description, and is not intended to be limiting. Several simple deductions, modifications or substitutions may also be made by a person skilled in the art to which the application pertains, based on the idea of the application.
Claims (2)
1. A wafer alignment system, comprising:
the motion platform can move in the X axis and the Y axis and rotate around the Z axis;
a wafer carrying platform supported on the motion platform for carrying wafers;
the image acquisition device is arranged above the wafer carrying platform and is used for acquiring an overall image of the wafer and an edge image of the wafer;
the processor is coupled with the image acquisition device and the motion platform and is used for processing the whole image of the wafer, calculating a first adjustment value of the motion platform moving in an X axis and a Y axis and a first angle rotating around a Z axis, and sending the first adjustment value and the first angle to the motion platform so as to control the motion platform to move;
the processor is further used for processing the edge image of the wafer, calculating a second adjusting value of the motion platform moving in the X axis and the Y axis and a second angle rotating around the Z axis, and sending the second adjusting value and the second angle to the motion platform so as to control the motion platform to move;
the image acquisition apparatus includes:
the first sensor is used for acquiring the whole image of the wafer;
the second sensor is used for acquiring an edge image of the wafer;
the first sensor and the second sensor are respectively coupled with the processor and are used for sending the whole image of the wafer and the edge image of the wafer to the processor;
the sensor comprises a CCD image sensor and an analog-to-digital converter;
the CCD image sensor is used for acquiring light rays and converting the light rays into analog signals and sending the analog signals to the analog-to-digital converter;
the analog-to-digital converter is used for converting the received analog signals sent by the CCD image sensor into digital signals and sending the digital signals to the processor;
the image acquisition device further comprises an optical imaging device;
the optical imaging device is used for acquiring light rays of a first view field and light rays of a second view field, and projecting the light rays of the first view field onto the first sensor so as to obtain an overall image of the wafer;
projecting the light of the second field of view onto the second sensor to obtain an edge image of the wafer;
the optical imaging device comprises an objective lens group, a spectroscope and a first lens;
the objective lens group focuses the light rays of the first view field, and the focused light rays of the first view field reach the spectroscope;
the spectroscope reflects the focused light rays of the first view field;
the first lens transmits the reflected light rays of the first view field, and the transmitted light rays of the first view field reach the first sensor;
the optical imaging device also comprises a second lens, a galvanometer and a spectroscope;
the objective lens group focuses the second view field, and the focused light of the second view field reaches the second lens;
the second lens transmits the focused light rays of the second field of view;
the galvanometer reflects the light rays of the second field transmitted by the second lens;
the second lens transmits the light of the second view field reflected by the vibrating mirror;
the spectroscope reflects the light of the second view field reflected by the vibrating mirror transmitted by the second lens to reach the second sensor;
the optical imaging device further comprises a biaxial MEMS for enabling the second sensor to acquire light rays of the second field of view corresponding to the reflection angle by adjusting the reflection angle of the vibrating mirror.
2. A wafer alignment method for use in a wafer alignment system as claimed in claim 1 for aligning a wafer on a wafer carrier, the wafer alignment method comprising:
acquiring an image of the whole wafer;
processing the whole image of the wafer, and calculating a third adjustment value of the motion platform moving in the X axis and the Y axis and a third angle rotating around the Z axis;
adjusting the position of the wafer according to the third adjusting value and the third angle value;
acquiring an image of the edge of the wafer;
processing the edge image of the wafer, and calculating a fourth adjustment value of the motion platform moving in the X axis and the Y axis and a fourth angle rotating around the Z axis;
and adjusting the position of the wafer according to the fourth adjusting value and the fourth angle.
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| CN111106054B (en) * | 2019-12-05 | 2022-08-12 | 福建省福联集成电路有限公司 | Method for prejudging wafer calibration value and storage medium |
| US11854853B2 (en) * | 2021-03-12 | 2023-12-26 | Taiwan Semiconductor Manufacturing Co., Ltd. | Wafer positioning method and apparatus |
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| CN116277015B (en) * | 2023-04-07 | 2024-01-23 | 上海感图网络科技有限公司 | Data processing method, device, equipment and storage medium |
| CN116736508B (en) * | 2023-08-16 | 2023-11-28 | 苏州高视半导体技术有限公司 | Wafer focusing method, electronic device and storage medium |
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