CN107908086B - Method for pre-aligning substrate - Google Patents

Method for pre-aligning substrate Download PDF

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Publication number
CN107908086B
CN107908086B CN201711122043.7A CN201711122043A CN107908086B CN 107908086 B CN107908086 B CN 107908086B CN 201711122043 A CN201711122043 A CN 201711122043A CN 107908086 B CN107908086 B CN 107908086B
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substrate
image
coordinates
edge
workpiece table
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CN107908086A (en
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朱鹏飞
浦东林
朱鸣
邵仁锦
吕帅
张瑾
袁晓峰
陈林森
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Suzhou University
SVG Tech Group Co Ltd
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Suzhou University
SVG Tech Group Co Ltd
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
    • G03F9/7003—Alignment type or strategy, e.g. leveling, global alignment
    • G03F9/7007—Alignment other than original with workpiece
    • G03F9/7011—Pre-exposure scan; original with original holder alignment; Prealignment, i.e. workpiece with workpiece holder
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
    • G03F9/7088—Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)

Abstract

The invention relates to a substrate pre-alignment method, which comprises the steps of projecting a characteristic image and a distance measurement image on a substrate to determine the coordinates of edge points on the edge, calculating the inclination angle of the substrate and the central coordinates of the substrate according to the edge point coordinates, and aligning the central coordinates of the substrate and the imaging central coordinates by moving a workpiece table to realize the quick, efficient and high-precision pre-alignment. Compared with the prior art, the pre-alignment method of the substrate has the advantages of no need of increasing the hardware cost of the existing direct-write equipment, simple steps and high pre-alignment precision.

Description

Method for pre-aligning substrate
Technical Field
The invention relates to a method for pre-aligning a substrate.
Background
The laser maskless direct writing directly images the pattern on the surface of the photoetching substrate through a pattern generator so as to carry out photoetching, although the laser maskless direct writing system does not have the step of alignment among a plurality of sets of mask layers compared with the traditional mask exposure, the direct writing system has a common application scene that the alignment with the existing pattern is realized on the existing substrate through Mark identification marks. Since the field of view of the lens with high magnification is limited in Mark recognition, if the initial placement position and angle of the substrate exceed the field of view range of the lens, subsequent Mark recognition may fail. Therefore, a preliminary pre-alignment operation is required before Mark recognition is performed.
Chinese patent CN102338991A discloses a pre-alignment method controlled by a laser displacement sensor, which adopts a flexible pre-alignment method, places a mask plate on a high-precision platform, automatically finds a boundary by using the laser displacement sensor, calculates the center point of the mask plate, and realizes an accurate pre-alignment function.
The pre-alignment method has the following advantages:
the center of the mask plate is directly calculated by using the controllable high-precision platform movement and the laser displacement sensor, and the center of each layout can be ensured to be superposed with the center of the mask plate in the photoetching process, so that the problem of high cost caused by plate making failure due to the placement deviation of the mask plate is solved.
But still has the following disadvantages:
according to the method, on one hand, a laser displacement sensor needs to be installed, so that the hardware cost is increased, on the other hand, the measuring position of the laser displacement sensor and the CCD imaging position are not coaxial and are in the same position, so that the steps of switching the platform between two coordinates back and forth are complex, and the pre-alignment time is increased.
For the foregoing reasons, there is a need for a simple, efficient and highly accurate method for pre-aligning a substrate.
Disclosure of Invention
The invention aims to provide a substrate pre-alignment method, which can realize the pre-alignment work with high speed, high efficiency and high precision.
In order to achieve the purpose, the invention provides the following technical scheme: a method of pre-aligning a substrate, comprising the steps of:
placing the substrate on a workpiece table, establishing a coordinate system by taking the workpiece table as a reference surface, and setting the x-axis direction and the y-axis direction of the coordinate system to enable the distance between the direct writing lens and the substrate to be within the imaging focal length;
presenting a characteristic image and a ranging image on the substrate to obtain coordinates of at least five edge points, wherein at least two edge points are positioned at different parts on the same edge, and four edge points are respectively taken from four different edges;
determining the inclination angle of the substrate according to the coordinates of two edge points on the same edge;
and rotating the substrate to be right according to the inclination angle to obtain the center coordinate of the rotated substrate.
In order to achieve the purpose, the invention also provides the following technical scheme: a method of pre-aligning a substrate, comprising the steps of:
placing the substrate on a workpiece table, establishing a coordinate system by taking the workpiece table as a reference surface, and setting the x-axis direction and the y-axis direction of the coordinate system to enable the distance between the direct writing lens and the substrate to be within the imaging focal length;
presenting a characteristic image and a ranging image on the substrate to obtain coordinates of two edge points, wherein the two edge points are positioned at different parts on the same edge; determining the inclination angle of the substrate according to the coordinates of two edge points on the same edge;
determining coordinates of the edge points on the other at least three edges of the substrate from the feature image and the ranging image;
and rotating the substrate to be right according to the inclination angle to obtain the center coordinate of the rotated substrate.
Further, the lens projects and forms a projection point in the coordinate system, and acquiring the coordinates of the edge point includes the following steps:
presenting a characteristic image on the surface of the substrate, and identifying the characteristic image through a CCD image acquisition system;
moving the workpiece table to enable the substrate to move relative to one side of the lens, stopping moving the workpiece table when the characteristic image part exceeds the edge, and recording the coordinates of the projection point at the moment;
displaying a ranging image near the edge of the substrate, identifying the ranging image, and obtaining a linear distance D between an edge point on the edge and the projection point;
and obtaining the coordinates of the edge points in the coordinate system according to the projection point coordinates and the straight line distance D.
Further, the step of obtaining the center coordinates of the substrate after the correction comprises the following steps:
and correcting the substrate according to the inclination angle, obtaining new coordinates of four edge points on four different edges in a workpiece table coordinate system after correction, determining the central coordinate of the substrate according to the four new coordinates, and moving the workpiece table to the central position of the substrate.
Furthermore, the workbench is rectangular, the x-axis direction is parallel to two opposite sides of the workpiece table, and the y-axis direction is parallel to the other two opposite sides of the workpiece table.
Further, the feature image and the range image are formed by a spatial light modulator, and the size of the feature image and the range image is smaller than or equal to the size of an effective display area of the spatial light modulator.
Further, the ranging image is a grating stripe image.
Further, the grating stripes in the grating stripe image are perpendicular to the moving direction of the workpiece stage.
Further, the stripe pitch of the grating stripe image in the effective display area is micron order.
Further, the CCD image acquisition system is provided with an image feature detection algorithm, and when at least part of the feature image is missing in the CCD image acquisition system, the image feature detection algorithm gives an evaluation score.
The invention has the beneficial effects that: the pre-alignment method of the substrate determines the coordinates of edge points on the edge by projecting a characteristic image and a ranging image on the substrate, calculates the inclination angle of the substrate and the central coordinates of the substrate according to the edge point coordinates, and finally aligns the central coordinates of the substrate and the imaging central coordinates by moving the workpiece table, thereby realizing the quick, efficient and high-precision pre-alignment work. Compared with the prior art, the pre-alignment method of the substrate has the advantages of no need of increasing the hardware cost of the existing direct-write equipment, simple steps and high pre-alignment precision.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
FIG. 1 is a flow chart of a method of pre-aligning a substrate according to the present invention;
fig. 2 is a diagram of another flow step in a method for pre-aligning a substrate according to the present invention.
FIG. 3 is a schematic diagram of a lithography system according to an embodiment of the present invention;
FIG. 4 is a flowchart illustrating a method for pre-aligning a substrate according to one embodiment of the present invention;
FIG. 5 is a detailed schematic diagram of steps 4 and 5 of the method for pre-aligning a substrate shown in FIG. 4;
FIG. 6 is a schematic diagram of a lithography system according to a second embodiment of the present invention;
FIG. 7 is a flowchart illustrating a method for pre-aligning a substrate according to a second embodiment of the present invention;
fig. 8 is a detailed view illustrating steps 4 'and 5' of the method for pre-aligning the substrate shown in fig. 7.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Referring to fig. 1, the method for pre-aligning a substrate of the present invention includes the following steps:
placing the substrate on a workpiece table, establishing a coordinate system by taking the workpiece table as a reference surface, and setting the x-axis direction and the y-axis direction of the coordinate system to enable the distance between the direct writing lens and the substrate to be within the imaging focal length;
presenting a characteristic image and a ranging image on the substrate to obtain coordinates of at least five edge points, wherein at least two edge points are positioned at different parts on the same edge, and four edge points are respectively taken from four different edges;
determining the inclination angle of the substrate according to the coordinates of two edge points on the same edge;
and rotating the substrate to be right according to the inclination angle to obtain the center coordinate of the rotated substrate.
Alternatively, referring to fig. 2, the method for pre-aligning a substrate of the present invention comprises the following steps:
placing the substrate on a workpiece table, establishing a coordinate system by taking the workpiece table as a reference surface, and setting the x-axis direction and the y-axis direction of the coordinate system to enable the distance between the direct writing lens and the substrate to be within the imaging focal length;
presenting a characteristic image and a ranging image on the substrate to obtain coordinates of two edge points, wherein the two edge points are positioned at different parts on the same edge; determining the inclination angle of the substrate according to the coordinates of two edge points on the same edge;
determining coordinates of the edge points on the other at least three edges of the substrate from the feature image and the ranging image;
and rotating the substrate to be right according to the inclination angle to obtain the center coordinate of the rotated substrate.
Wherein, obtaining the edge point coordinates comprises the following steps:
presenting a characteristic image on the surface of the substrate, and identifying the characteristic image through a CCD image acquisition system;
moving the workpiece table to enable the substrate to move relative to one side of the lens, stopping moving the workpiece table when the characteristic image part exceeds the edge, and recording the coordinates of the projection point at the moment;
displaying a ranging image near the edge of the substrate, identifying the ranging image, and obtaining a linear distance D between an edge point on the edge and the projection point;
and obtaining the coordinates of the edge points in the coordinate system according to the projection point coordinates and the straight line distance D.
Acquiring the center coordinates of the substrate after correction comprises the following steps:
and correcting the substrate according to the inclination angle, obtaining new coordinates of four edge points on four different edges in a workpiece table coordinate system after correction, determining the central coordinate of the substrate according to the four new coordinates, and moving the workpiece table to the central position of the substrate.
The present invention will be described in further detail with reference to specific examples.
Example one
Referring to fig. 3, in the present embodiment, the method for pre-aligning a substrate of the present invention is applied to a photolithography system, and indeed, in other embodiments, the method for pre-aligning a substrate can be applied to other fields. The photoetching system comprises a workpiece table (not shown), a control device (not shown), a light source (not shown), a spatial light modulator (not shown), an imaging system 1 and a CCD image acquisition system 2, wherein a substrate 3 is placed on the workpiece table, and the control device is connected with the workpiece table. The imaging system 1 and the CCD image acquisition system 2 are disposed above the workpiece stage, a lens (not shown) is disposed on the imaging system 1, and the light source projects characteristic light to the imaging system 1 through the spatial light modulator to present a characteristic image 4 on the workpiece stage. The substrate has four edges, and the edges are arranged in pairs in an opposite manner.
Referring to fig. 4 and 5, the substrate 3 is rectangular, and the substrate 3 has two pairs of first edges 31, second edges 32, third edges 33 and fourth edges 34. The method for pre-aligning the substrate in the embodiment specifically comprises the following steps:
step 1, a substrate 3 is placed at the center of a workpiece table, the workpiece table is reset, a plane rectangular coordinate system is established by taking the center of the workpiece table as a coordinate origin, the direction parallel to two opposite sides of the workpiece table is set to be the x-axis direction, and the direction parallel to the other two opposite sides of the workpiece table is set to be the y-axis direction. Moving the workpiece stage to make the initial moment of the lens be located near the center P0, adjusting the focal length of the direct-writing imaging system 1 according to the thickness of the substrate 3, making the distance between the lens and the substrate 3 be within the imaging focal length to make the effective display area of the imaging system be located near the center of the substrate 3, and starting the system focal length locking function;
and 2, turning on a light source, presenting a 512 x 512 pixel square characteristic image 4 on the substrate 3 through the spatial light modulator and the imaging system 1, defining the area where the characteristic image is located as a characteristic area, wherein the center of the characteristic area is superposed with the center of an effective display area, and the size of the characteristic image 4 is smaller than the size of the effective display area. Starting an image feature detection algorithm in the CCD image acquisition system 2 to identify the imaging of the surface of the substrate 3;
and 3, taking the central point of the effective display area as a projection point, and moving the workpiece table at the speed of 10mm/s to enable the substrate 3 to move from the point P0 to the point P6 relative to the lens. And setting an image characteristic detection algorithm in the CCD image acquisition system, wherein the algorithm can give an evaluation score when the shape of the characteristic image is missing or cannot be detected. When the size area of the feature image 4 with 512 x 512 pixels in the CCD image acquisition system is reduced to 75% in step 2, the stage is stopped moving, and a part of the feature image 4 exceeds the first edge 31, and the coordinates of the projection point at that time are recorded and defined as the coordinates (x) of the projection point1，y1)；
And 4, presenting a grating stripe image with 512 multiplied by 512 pixels in the characteristic region through the spatial light modulator and the imaging system 1, wherein the grating stripe in the grating stripe image is vertical to the moving direction of the workpiece table, and the interval between every two grating stripes is 4 pixels, the grating stripe is imaged on the substrate at an interval of 2um, and the total number is 128. Measuring the number L of the grating stripes remained in the CCD image acquisition system at the moment by an image recognition measurement algorithm in the CCD image acquisition system, and calculating the midpoint P of the first edge 31 according to the formula D ═ L-128/2 (x 2)3A straight-line distance D from the projection point1；
Step 5, according to the projection point coordinate (x)1，y1) And straightLine distance D1According to the formula x ═ x1-D1，y＝y1Obtaining a center point P of the first edge 313Coordinates P in the table coordinate system3(x1-D1，y1)；
Step 6, repeating the steps 3 to 5, completing the position detection of the four edges of the substrate 3, and obtaining the coordinate of the center point of each edge, and marking the coordinate as P3、P4、P5And P6；
Step 7, measuring the positions of P1 and P2 on the fourth edge 34 according to the same method, detecting, and obtaining the coordinates of the two points as P1 and P2;
and 8, calculating the inclination angle theta of the substrate 3 according to the positional relationship between P1 and P2 in the step 7 by using a formula theta ═ atan (P2.y-P1.y)/(P2.x-P1.x), and correcting the substrate 3 by the control device according to the inclination angle theta. And calculating new coordinates P3 ', P4', P5 'and P6' of the center point of each edge after correction by a coordinate rotation formula x '═ cos theta + y × sin theta, y' ═ y × cos theta-x sin theta, obtaining the substrate center coordinates of the substrate 3 according to the new coordinates P3 ', P4', P5 'and P6' of the center point of each edge, and moving the workpiece table by the control device according to the substrate center coordinates and the imaging center coordinates to enable the substrate center coordinates to be coincident with the projection point coordinates, thereby completing the pre-alignment of the substrate.
In step 3 of this embodiment, the workpiece stage is controlled to move the substrate 3 at a speed of 10mm/s relative to the lens from point P0 to point P6, and indeed, in other embodiments, the moving direction and speed of the substrate 3 may be selected according to actual conditions.
In this embodiment, the size of the feature image and the ranging image is smaller than or equal to the size of the effective display area of the spatial light modulator. Preferably, when the size area of the feature image in the CCD image acquisition system is reduced to 75%, the moving of the stage is stopped, in order to ensure that part of the feature image has exceeded the edge of the substrate instead of being blocked by dust or defects, and to ensure that a larger part of the subsequently applied grating fringe image can be detected by the CCD image acquisition system, and indeed, in other embodiments, the remaining size area of the feature image can take other values.
In this embodiment, it is preferable that the center point of the effective display area is taken as the projection point, the center of each edge is taken as the edge point, and the center of the workpiece table is taken as the origin of coordinates, so that the substrate center coordinates of the substrate 3 can be simply measured. In addition, in this embodiment, the grating stripe image is input into the feature area for the purpose of simplifying the calculation steps, and indeed, in other embodiments, the grating stripe image may also be input into other positions of the effective display area.
Meanwhile, in the present embodiment, it is preferable to obtain the tilt angle of the substrate 3 more accurately by respectively approaching P1 and P2 at the two ends of the second edge, and indeed, in other embodiments, the tilt angle of the substrate 3 can be calculated by taking any two different points on the edge.
Example two
Referring to fig. 6, in the embodiment, the substrate pre-alignment method of the present invention is applied to a photolithography system, and indeed, in other embodiments, the substrate pre-alignment method can be applied to other fields. The lithography system comprises a workpiece table (not shown), a control device (not shown), a light source (not shown), a spatial light modulator (not shown), an imaging system 1 ' and a CCD image acquisition system 2 ', wherein a substrate 3 ' is placed on the workpiece table, and the control device is connected with the workpiece table. The imaging system 1 ' and the CCD image collecting system 2 ' are disposed above the workpiece stage, a lens (not shown) is disposed on the imaging system 1 ', and the light source projects characteristic light to the imaging system 1 ' through the spatial light modulator to present a characteristic image 4 ' on the workpiece stage. The substrate has four edges, and the edges are arranged in pairs in an opposite manner.
Referring to fig. 7 and 8, the substrate 3 'is rectangular, and the substrate 3' has a first edge 31 'and a second edge 32' opposite to each other, a third edge 33 'opposite to each other, and a fourth edge 34' opposite to each other. The method for pre-aligning the substrate in the embodiment specifically comprises the following steps:
step 1 ', placing a substrate 3' at the center position of a workpiece table, resetting the workpiece table, establishing a plane rectangular coordinate system by taking the center position of the workpiece table as a coordinate origin, setting the direction parallel to two opposite sides of the workpiece table as an x-axis direction, and setting the direction parallel to the other two opposite sides of the workpiece table as a y-axis direction. Moving the workpiece stage to make the lens be located near the center P0 at the initial moment, adjusting the focal length of the direct-writing imaging system 1 'according to the thickness of the substrate 3', making the distance between the lens and the substrate 3 'be within the imaging focal length to make the effective display area of the imaging system be located near the center of the substrate 3', and starting the system focal length locking function;
and 2 ', turning on a light source, and presenting a 512 x 512 pixel square characteristic image 4 ' on the substrate 3 ' through the spatial light modulator and the imaging system 1 ', defining the region where the characteristic image is located as a characteristic region, wherein the center of the characteristic region is coincided with the center of an effective display region, and the size of the characteristic image 4 ' is smaller than the size of the effective display region. Starting an image feature detection algorithm in the CCD image acquisition system 2 'to identify the imaging of the surface of the substrate 3';
and 3 ', taking the central point of the effective display area as a projection point, and moving the workpiece table at the speed of 10mm/s so as to move the substrate 3' relative to the lens from the point P0 to the point P6. And setting an image characteristic detection algorithm in the CCD image acquisition system, wherein the algorithm can give an evaluation score when the shape of the characteristic image is missing or cannot be detected. When the size area of the feature image 4 'with 512 x 512 pixels in the CCD image acquisition system is reduced to 75% in step 2', the stage is stopped, and a part of the feature image 4 'exceeds the first edge 31', and the coordinates of the projection point at that time are recorded and defined as the coordinates (x) of the projection point1’，y1’)；
And 4 ' displaying a grating stripe image with 512 multiplied by 512 pixels in the characteristic region through the spatial light modulator and the imaging system 1 ', wherein the grating stripe in the grating stripe image is vertical to the moving direction of the workpiece table, and the interval of each grating stripe is 4 ' pixels, and the grating stripe is imaged on the substrate at an interval of 2um, and the total number is 128. Measuring the number L of the grating stripes remained in the CCD image acquisition system at the moment by an image recognition measurement algorithm in the CCD image acquisition system, and calculating an edge point P on the first edge 31' according to a formula D ═ L-128/2 (x 2)1' straight-line distance D from the projection point1’；
Step 5', according to the projection point coordinate (x)1’，y1') and a straight-line distance D1', according to the formula x ═ x1’-D1’，y＝y1' deriving the edge point P1' coordinates P in the workpiece Table coordinate System1’(x1’-D1’，y1’)；
Step 6 ', repeating steps 3 ' to 5 ', calculating to obtain another edge point P on the first edge 312According to said P1' and P2The positional relationship of 'the inclination angle θ of the substrate 3' is calculated by the formula θ ═ atan (P2 '. y-P1'. y)/(P2 '. x-P1'. x);
and 7 ', measuring the position detection of the four edges of the substrate 3' according to the same method, and obtaining the coordinate of the central point of each edge, which is marked as P3’、P4’、P5' and P6’；
And 8 ', rotating the substrate 3 ' to be positive through the control equipment according to the inclination angle theta in the step 6 '. And calculating new coordinates P3 ', P4 ', P5 ' and P6 ' of the center point of each edge after correction by a coordinate rotation formula x ' ═ cos theta + y × sin theta, y ' ═ y × cos theta-x sin theta, obtaining the substrate center coordinates of the substrate 3 ' according to the new coordinates P3 ', P4 ', P5 ' and P6 ' of the center point of each edge, and moving the workpiece table by the control device according to the substrate center coordinates and the imaging center coordinates to enable the substrate center coordinates to be coincident with the projected point coordinates, thereby completing the pre-alignment of the substrate.
In step 3 'of this embodiment, the workpiece stage is controlled to move the substrate 3' at a speed of 10mm/s relative to the lens from point P0 to point P6 ', and indeed, in other embodiments, the moving direction and speed of the substrate 3' may be selected according to actual conditions.
In this embodiment, the size of the feature image and the ranging image is smaller than or equal to the size of the effective display area of the spatial light modulator. Preferably, when the size area of the feature image in the CCD image acquisition system is reduced to 75%, the moving of the stage is stopped, in order to ensure that part of the feature image has exceeded the edge of the substrate instead of being blocked by dust or defects, and to ensure that a larger part of the subsequently applied grating fringe image can be detected by the CCD image acquisition system, and indeed, in other embodiments, the remaining size area of the feature image can take other values.
In this embodiment, it is preferable that the center point of the effective display area is taken as the projection point, the center of each edge is taken as the edge point, and the center of the workpiece table is taken as the origin of coordinates, so that the substrate center coordinates of the substrate 3' can be simply measured. In addition, in this embodiment, the grating stripe image is input into the feature area for the purpose of simplifying the calculation steps, and indeed, in other embodiments, the grating stripe image may also be input into other positions of the effective display area.
Also in this embodiment, the inclination angle of the substrate 3 'is preferably determined accurately by the proximity of P1 and P2 on the two ends of the second edge, respectively, and indeed in other embodiments, the inclination angle of the substrate 3' can be calculated at any two different points on the edge.
In summary, the following steps: the pre-alignment method of the substrate comprises the steps of inputting a characteristic image to the substrate through a spatial light modulator, preliminarily determining the edge position of the substrate by detecting the shape change of the characteristic image through a CCD image acquisition system, then accurately measuring the coordinates of edge points on the edge of the substrate by inputting a grating stripe image near the edge, calculating the inclination angle of the substrate and the center coordinate of the substrate according to the edge point coordinates, and finally aligning and coinciding the center coordinate of the substrate and the imaging center coordinate through moving a workpiece table, thereby realizing the quick, efficient and high-precision pre-alignment work. Compared with the prior art, the pre-alignment method of the substrate has the advantages of no need of increasing the hardware cost of the existing direct-write equipment, simple steps and high pre-alignment precision.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A method of pre-aligning a substrate, comprising the steps of:
placing the substrate on a workpiece table, establishing a coordinate system by taking the workpiece table as a reference surface, and setting the x-axis direction and the y-axis direction of the coordinate system to enable the distance between the direct writing lens and the substrate to be within the imaging focal length;
presenting a characteristic image and a ranging image on the substrate, and obtaining coordinates of at least five edge points through a CCD camera, wherein the ranging image is a grating stripe image, at least two edge points are positioned at different parts on the same edge, and four edge points are respectively taken from four different edges;
determining the inclination angle of the substrate according to the coordinates of two edge points on the same edge;
and rotating the substrate to be right according to the inclination angle to obtain the center coordinate of the rotated substrate.
2. A method of pre-aligning a substrate, comprising the steps of:
placing the substrate on a workpiece table, establishing a coordinate system by taking the workpiece table as a reference surface, and setting the x-axis direction and the y-axis direction of the coordinate system to enable the distance between the direct writing lens and the substrate to be within the imaging focal length;
presenting a characteristic image and a ranging image on the substrate, and obtaining coordinates of two edge points through a CCD camera, wherein the ranging image is a grating stripe image, and the two edge points are positioned at different parts on the same edge; determining the inclination angle of the substrate according to the coordinates of two edge points on the same edge;
determining coordinates of the edge points on the other at least three edges of the substrate from the feature image and the ranging image;
and rotating the substrate to be right according to the inclination angle to obtain the center coordinate of the rotated substrate.
3. The method for pre-aligning a substrate according to claim 1 or 2, wherein the lens is projected with a projected point in the coordinate system, and the obtaining of the coordinates of the edge point comprises the steps of:
presenting a characteristic image on the surface of the substrate, and identifying the characteristic image through a CCD image acquisition system;
moving the workpiece table to enable the substrate to move relative to one side of the lens, stopping moving the workpiece table when the characteristic image part exceeds the edge, and recording the coordinates of the projection point at the moment;
displaying a ranging image near the edge of the substrate, identifying the ranging image, and obtaining a linear distance D between an edge point on the edge and the projection point;
and obtaining the coordinates of the edge points in the coordinate system according to the projection point coordinates and the straight line distance D.
4. The method for pre-aligning a substrate according to claim 1 or 2, wherein the step of obtaining the coordinates of the center of the substrate after the alignment comprises the steps of:
and correcting the substrate according to the inclination angle, obtaining new coordinates of four edge points on four different edges in a workpiece table coordinate system after correction, determining the central coordinate of the substrate according to the four new coordinates, and moving the workpiece table to the central position of the substrate.
5. A method of pre-aligning a substrate as claimed in claim 1 or claim 2, wherein the workpiece stage is rectangular, the x-axis direction being parallel to two opposite sides of the workpiece stage and the y-axis direction being parallel to the other two opposite sides of the workpiece stage.
6. The method of prealignment of a substrate according to claim 1 or 2, wherein the feature image and the range image are formed by a spatial light modulator, the size of the feature image and the range image being smaller than or equal to the size of an effective display area of the spatial light modulator.
7. A method of pre-alignment of a substrate as claimed in claim 1 or 2, wherein the range image is a raster stripe image.
8. The method of pre-aligning a substrate of claim 7, wherein the grating stripes in the grating stripe image are perpendicular to the direction of movement of the workpiece stage.
9. The method of pre-aligning a substrate of claim 6, wherein the fringe spacing of the grating fringe image imaged in the active display area is on the order of microns.
10. A method of pre-alignment of a substrate as claimed in claim 1 or 2, wherein the CCD image capture system has an image feature detection algorithm which gives an evaluation score when at least part of the feature image is missing in the CCD image capture system.
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