Position calibration device for exposure lens and calibration method thereof

Abstract

A position calibration device for exposure lens is used to determine the position coordinates of the exposure lens of a direct writing lithography device, which comprises a four-quadrant photoelectric detector installed on a moving platform of the lithography device and a mask located above the four-quadrant photoelectric detector, wherein the mask is provided with periodically distributed light-transmitting parts and light-blocking parts corresponding to at least one quadrant of the four-quadrant photoelectric detector. The position of the exposure lens is determined by generating a corresponding light spot through the exposure lens and moving the four-quadrant photoelectric detector. By setting the periodically distributed light-transmitting parts and light-blocking parts, the four-quadrant photoelectric detector can move the same distance under the light spot, and the light energy transmitted to the detector is proportionally increased, thereby improving the detection sensitivity.

Description

Technical Field

[0001] This invention relates to the field of photolithography technology, specifically to a position calibration device and calibration method for an exposure lens. Background Technology

[0002] Photolithography is used to print characteristic patterns on the surface of a substrate, which can be used to manufacture semiconductor devices, integrated chips, displays, circuit boards, etc. Photolithography is generally divided into mask lithography and direct-write lithography. Mask lithography requires the fabrication of different masks for different exposure patterns, and the high precision and long production cycle of the masks make it difficult to meet the increasing demands of applications. Direct-write lithography, based on digital micromirror devices (DMMs), can flexibly transfer different patterns. The process is relatively simple and low-cost, and it is widely used in the circuit fabrication of PCBs and semiconductor devices. Direct-write lithography modulates a light beam using a DMM, which is then projected onto the substrate, which moves with the platform, through an exposure lens to form pattern strips. Multiple lenses create different pattern strips on the substrate, which are then stitched together to form a complete pattern. The accuracy of the exposure lens's position calibration directly affects the accuracy of the pattern strip stitching during direct-write lithography; therefore, exposure lens position calibration is an indispensable step in the exposure process of direct-write lithography equipment. Existing direct-write lithography equipment mainly uses the following two methods for exposure lens position calibration: Firstly, as disclosed in CN111221224A, a series of marker points are exposed on a sensitive ruler by an exposure lens, and then the coordinates of each exposed point are obtained by a camera to obtain the position coordinates of the corresponding lens. However, this method is prone to large errors when the camera captures the exposed marker points because the edges of the exposed marker points on the sensitive ruler become blurred over time, which cannot meet the requirements of ultra-high precision photolithography.

[0003] Secondly, by placing the energy detector under the exposure lens, the lens generates a light spot. Moving the energy detector balances the detected values. When positional accuracy requirements are not high, the sensitivity of a conventional energy detector is generally sufficient. However, for high-precision lithography scenarios, the sensitivity requirements for the energy detector are very high. For example, for an energy detector with an overall effective photosensitive size of 300µm and a peak energy detection of 10mW, to achieve a detection accuracy of 0.3µm, the energy detector needs extremely high sensitivity, capable of detecting light energy changes of approximately 0.01mW. This places very stringent requirements on the design and fabrication of the energy detector, resulting in extremely high costs. Summary of the Invention

[0004] The purpose of this invention is to provide a position calibration device and calibration method for an exposure lens to gradually reduce or overcome the problems and defects in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An exposure lens position calibration device is used to determine the position coordinates of the exposure lens of a direct-write lithography apparatus. It includes a four-quadrant photodetector mounted on the motion platform of the lithography apparatus and a photomask located above the four-quadrant photodetector. The photomask has periodically distributed transparent and opaque portions corresponding to at least one quadrant of the four-quadrant photodetector, and the transparent and opaque portions are striped.

[0006] Preferably, the photomask is divided into four equal quadrants, which are separated by a dividing line. The intersection of the dividing line is the center of the photomask. Each quadrant includes periodically distributed transparent and opaque parts.

[0007] Preferably, the photomask is mounted above the four-quadrant photodetector, such that the dividing line coincides with the blind zone of the four-quadrant photodetector in the direction perpendicular to the photomask surface.

[0008] Preferably, the light-transmitting and opaque portions in each quadrant of the photomask are arranged in alternating parallel stripes, and there is at least one quadrant with stripes parallel to the X direction and one quadrant with stripes parallel to the Y direction.

[0009] Preferably, the dimensions of the light-transmitting and opaque portions are determined based on the photosensitive size and required sensitivity of the four-quadrant photodetector.

[0010] According to another aspect of the present invention, a method for determining the center position of an exposure lens is provided based on the above-described exposure lens position calibration device, wherein the exposure lens projects a pattern of alternating bright and dark light spots corresponding to the photomask; the center position of the exposure lens is determined by detecting a reading in a quadrant, wherein the quadrant is an overlapping quadrant, and the center position of the exposure lens is obtained based on the position where the reading is the largest in the quadrant; Alternatively, the center position of the exposure lens can be determined by detecting the readings in two quadrants, one of which is the overlapping quadrant and the other is the misaligned quadrant. The center position of the exposure lens can be obtained from the position where the difference between the readings in the overlapping quadrant and the misaligned quadrant is the largest.

[0011] According to another aspect of the present invention, an exposure lens position calibration method is provided based on the above-described exposure lens position calibration device, comprising: 1) controlling the motion platform to move to the alignment system, obtaining the initial position coordinates (X', Y') of the photomask center through the alignment system, and controlling the system to determine the initial coordinates of the motion platform at this time as (X0, Y0); 2) the exposure lens generates a pattern of alternating bright and dark spots; 3) the motion platform moves to the exposure lens, such that the four-quadrant photodetector is approximately located under any of the exposure lenses to be calibrated; 4) keeping the Y-axis coordinate of the motion platform stationary, moving the motion platform along the X direction, during the movement, the control system selects any overlapping quadrant as the first detection quadrant and any misaligned quadrant as the second detection quadrant within the four-quadrant photodetector, obtaining the difference between the readings of the first detection quadrant and the second detection quadrant in real time, and determining the X-axis coordinate X1 of the motion platform when the difference is the largest; 5) keeping the X-axis coordinate of the motion platform stationary, The motion platform moves along the Y direction. During the movement, the control system selects any overlapping quadrant as the third detection quadrant and any misaligned quadrant as the fourth detection quadrant within the four-quadrant photodetector. The difference between the readings of the third and fourth detection quadrants is obtained in real time, and the Y-axis coordinate Y1 of the motion platform when the difference is the largest is determined. 6) The position coordinates of the exposure lens are determined based on the initial coordinates (X', Y') of the photomask center, the initial coordinates (X0, Y0) of the motion platform, and the coordinates (X1, Y1) when the reading difference is the largest.

[0012] Preferably, the interior of the alternating light and dark patterned spot is divided into four quadrants, and the distribution of light and dark in each quadrant is determined according to the distribution of the light-transmitting and opaque parts in the corresponding quadrant on the photomask.

[0013] Preferably, the overlapping quadrant refers to the quadrant in which the distribution of light and dark on the light spot corresponds one-to-one with the transparent and opaque parts on the photomask, and the misaligned quadrant refers to the quadrant in which the distribution of light and dark on the light spot corresponds to the transparent and opaque parts on the photomask in a misaligned manner.

[0014] Preferably, in step 4, at least one of the overlapping quadrants and the misaligned quadrants is a quadrant in which the stripes are distributed parallel to the Y direction, and in step 5, at least one of the overlapping quadrants and the misaligned quadrants is a quadrant in which the stripes are distributed parallel to the X direction.

[0015] Compared with the prior art, the present invention has the following technical effects: by setting a photomask above the four-quadrant photodetector, and using the periodically distributed transparent and opaque parts on the photomask and the exposure lens to generate alternating bright and dark patterned light spots corresponding to the transparent and opaque parts on the photomask, the light transmitted to the four-quadrant photodetector can be doubled, making it easier to measure the amount of change and reducing the design requirements of the detector hardware; in addition, by changing the size of the transparent and opaque parts on the photomask, the required sensitivity can be flexibly changed, which can meet the application needs of different scenarios. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an exemplary photolithography device of the present invention.

[0017] Figure 2 This is a schematic diagram of an exemplary four-quadrant photodetector.

[0018] Figure 3 This is a schematic diagram of an exemplary striped photomask and light spot.

[0019] Figure 4 This is an exemplary schematic diagram of a single-quadrant photomask and light spot. Implementation

[0020] To make the technical solution of the present invention clearer, embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the specific description of the embodiments is only for teaching those skilled in the art how to implement the present invention, and is not intended to exhaustively describe all feasible methods of the present invention, nor is it intended to limit the specific scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "center," "upper," "lower," "front," "rear," "left," "right," "horizontal," "inner," "outer," "vertical," "horizontal," "lateral," "longitudinal," and "vertical" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing or simplifying the invention and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed, installed, or operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] Figure 1 A simplified diagram of a common direct-write lithography apparatus is shown. This apparatus includes at least an exposure system 1, an alignment system 2, a motion platform 3, and a control system (not shown). The exposure system includes at least multiple exposure lenses. The control system controls the motion platform to move along the X, Y, and Z directions and obtains the real-time position coordinates of the motion platform. The substrate to be processed is placed on the motion platform. The motion platform is moved to the alignment system to align the substrate and confirm its position information. Then, the motion platform moves to the exposure lenses for lithography. The control system performs pattern processing according to the pre-determined position of the exposure lenses. The exposure lenses project a pattern beam onto the motion platform, and the control system controls the motion platform to move under the exposure lenses to complete the scanning and stitching of the pattern on the substrate.

[0023] To calibrate the position of the exposure lens, the photolithography equipment further includes an energy detector. Preferably, the energy detector is a four-quadrant photodetector. A four-quadrant photodetector operates using the semiconductor photovoltaic effect, where each quadrant can be considered an independent photodiode. Figure 2 As shown, the four-quadrant photodetector is divided into four quadrants, each of which serves as an independent photosensitive surface 4, namely, quadrant A, quadrant B, quadrant C, and quadrant D. Each photosensitive surface is identical and isolated by a blind zone 5. The specific principle for determining its position is as follows: When the light spot 6 illuminates the photosensitive surface 4, each quadrant generates a photocurrent of corresponding magnitude based on the received light energy within its region. Assuming the light energy of the light spot in the four quadrants is Ia, Ib, Ic, and Id respectively, the readings in each quadrant reflect the photocurrent within that quadrant, namely ia, ib, ic, and id. When ia minus ib equals id minus ic, it proves that the light spot is bisected by the blind zone in the Y direction; when ib minus ic equals ia minus id, it proves that the light spot is bisected by the blind zone in the X direction; when both ia minus ib equals id minus ic and ib minus ic equals ia minus id, the center a of the light spot coincides with the center O of the four-quadrant photodetector. The location of the light spot center can be determined by moving the light spot or the four-quadrant photodetector so that the center of the light spot coincides with the center of the detector.

[0024] To reduce the sensitivity requirements of the four-quadrant photodetector during position calibration, this invention further includes a photomask designed for use with the four-quadrant photodetector. The photomask is divided into four quadrants of equal area, separated by a dividing line 7. The intersection of the dividing lines is the center of the photomask. Each quadrant includes periodically distributed transparent portions 8 and opaque portions 9. The transparent portions 8 allow light to pass through, while the opaque portions 9 block light transmission. Furthermore, the photomask is mounted above the four-quadrant photodetector such that, in the direction perpendicular to the photomask surface, the dividing line 7 of the photomask coincides with the blind zone 5 of the four-quadrant photodetector. The four-quadrant photodetector is then fixed to a motion platform. The photomask can be directly fixed to the four-quadrant photodetector via a connector, or it can be mounted on a motion platform and suspended above the four-quadrant photodetector via a connector.

[0025] When position calibration is required, each exposure lens produces the same pattern spot. The outer contour of the pattern spot is the same as the contour of the photomask, and the interior is also divided into four quadrants. The bright and dark areas are distributed alternately in each quadrant. The bright part 8' is the part with light beam projection, and the dark part 9' is the part without light beam projection. Furthermore, the distribution of light and dark in each quadrant of the light spot is determined by the distribution of the transparent part 8 and the opaque part 9 in each quadrant of the photomask. As long as at least one quadrant has a one-to-one correspondence between the light and dark distribution and the transparent and opaque parts in the corresponding quadrant of the photomask, and one quadrant has a misaligned correspondence between the light and dark distribution and the transparent and opaque parts in the corresponding quadrant of the photomask, the quadrant in which the light and dark distribution corresponds one-to-one with the transparent and opaque parts is called the overlapping quadrant, and the quadrant in which the light and dark distribution corresponds misaligned with the transparent and opaque parts is called the misaligned quadrant. One-to-one correspondence means that the bright part with light beam projection corresponds to the transparent part, and the dark part without light beam projection corresponds to the opaque part. Misaligned correspondence means that the bright part with light beam projection corresponds to the opaque part, and the dark part without light beam projection corresponds to the transparent part. It is easy to understand that the photomask and the patterned light spot can have two overlapping quadrants and two misaligned quadrants, or one overlapping quadrant and three misaligned quadrants, or three overlapping quadrants and one misaligned quadrant.

[0026] The specific calibration method for the exposure lens proposed in this invention is as follows: First, the motion platform is moved to the alignment system, and the initial position coordinates of the photomask center are obtained through the alignment system. The control system then determines the initial position coordinates of the motion platform at this time. Then, the exposure lens generates a corresponding patterned light spot. Further, the motion platform is first moved to the exposure lens so that the four-quadrant photodetector is approximately located under any of the exposure lenses to be calibrated. Next, while keeping the Y-axis coordinate of the motion platform stationary, the motion platform is moved along the X-direction. During the movement, the control system selects any overlapping quadrant within the four-quadrant photodetector. As the first detection quadrant, any misaligned quadrant is selected as the second detection quadrant. The difference between the readings of the first and second detection quadrants is obtained in real time. The X-axis coordinate X1 of the motion platform when the difference is maximum is determined. Then, the X-axis coordinate of the motion platform is kept constant, and the motion platform moves along the Y direction. During the movement, the control system selects any coincident quadrant as the third detection quadrant and any misaligned quadrant as the fourth detection quadrant within the four-quadrant photodetector. The difference between the readings of the third and fourth detection quadrants is obtained in real time, and the Y-axis coordinate Y1 of the motion platform when the difference is maximum is determined. By selecting coincident and misaligned quadrants, when the center of the photomask and the center of the light spot are completely coincident, the beam of light in the coincident quadrant is illuminated, while no beam of light is illuminated in the misaligned quadrant, and the difference between the readings of the two quadrants is maximized. In other words, when moving along the X direction, at the position with the maximum difference, the patterned light spot is bisected horizontally by the Y-direction dividing line; when moving along the Y direction, at the position with the maximum difference, the patterned light spot is bisected vertically by the X-direction dividing line. Finally, the position coordinates of the exposure lens can be determined based on the initial coordinates of the center of the photomask, the initial coordinates of the motion platform, and the coordinates when the reading difference is the largest.

[0027] In one embodiment, the light-transmitting and opaque portions in each quadrant of the photomask are alternately distributed in a parallel stripe pattern, and at least one quadrant with stripes arranged parallel to the Y direction and one quadrant with stripes arranged parallel to the X direction are on the four quadrants of the photomask. For example Figure 3 The striped photomask shown in -a has stripes arranged parallel to the Y direction in the first and second quadrants, and parallel to the X direction in the third and fourth quadrants. In the diagram, white stripes represent the light-transmitting portion 8, and gray stripes represent the opaque portion 9. Correspondingly, the patterned light spot produced by each exposure lens is also divided into four quadrants, each containing alternating bright and dark stripes. In the diagram, white stripes represent the bright portion 8', indicating the area where a light beam is projected, and gray stripes represent the dark portion 9', indicating the area where no light beam is projected. Specifically, the stripe arrangement direction in the patterned light spot is the same as the stripe arrangement direction in the corresponding quadrant on the photomask to ensure overlapping and misaligned quadrants. For example... Figure 3The light spot shown in -b has two overlapping quadrants and two misaligned quadrants with the photomask. Specifically, the second and third quadrants are overlapping, while the first and fourth quadrants are misaligned. That is, the bright and dark fringes in the second and third quadrants of the light spot correspond one-to-one with the transparent and opaque fringes in the second and third quadrants of the photomask, while the bright and dark fringes in the first and fourth quadrants of the light spot correspond one-to-one with the transparent and opaque fringes in the first and third quadrants of the photomask. When calibrating the lens's X-coordinate, at least one quadrant with fringes parallel to the Y-direction must be selected. For example, the second quadrant of a four-quadrant photodetector can be selected. Since the second quadrant is overlapping, it can be used as the first detection quadrant. Then, the first quadrant of the four-quadrant photodetector can be selected as the second detection quadrant. When calibrating the lens's Y-coordinate, at least one quadrant with fringes parallel to the X-direction must be selected. For example, the third quadrant of a four-quadrant photodetector can be selected as the third detection quadrant, and the fourth quadrant as the fourth detection quadrant. It should be understood that... Figure 3 The photomask and light spot are merely examples; in practical applications, the stripe distribution of the photomask and light spot can be flexibly adjusted.

[0028] The position calibration method described above selects two quadrants as detection quadrants. As an alternative implementation, this invention also proposes determining the center position of the exposure lens using a single quadrant. In this case, the single quadrant to be selected is a coincident quadrant, such as... Figure 4 The illustrated mask and spot configuration allows the center position of the exposure lens to be determined based on the position where the reading is highest within the quadrant. Specifically, the motion platform is first kept stationary along its Y-axis and moved along the X-axis to determine its X-coordinate at the point of maximum reading within the quadrant. Then, the motion platform is moved again while maintaining its X-axis stationary, and its Y-coordinate at the same point of maximum reading within the quadrant is determined. Therefore, the position coordinates of the exposure lens can be determined based on the initial coordinates of the mask center, the initial coordinates of the motion platform, and the coordinates at the point of maximum reading.

[0029] Furthermore, the number and size (number and side length of squares, number and short side length of stripes) of the transparent and opaque portions on the photomask need to be determined based on the effective photosensitive size of the selected four-quadrant photodetector and the required sensitivity. When the effective photosensitive size of the four-quadrant photodetector is D micrometers and the calibration accuracy is 10... -3 When the required sensitivity is D micrometers, and an M-fold increase in sensitivity compared to the case without a photomask is desired, then the short side lengths of the transparent and opaque portions are chosen to be D / M micrometers. For example, if the effective photosensitive size of a four-quadrant photodetector is 300µm, then to increase the sensitivity by 10 times, the stripe width is selected to be 30µm.

[0030] This invention involves placing a photomask with periodically distributed transparent and opaque portions above a four-quadrant photodetector. Simultaneously, an exposure lens generates alternating bright and dark patterned light spots corresponding to the transparent and opaque portions on the photomask. This allows the four-quadrant photodetector to move the same distance under the light spots, resulting in a proportional change in the transmitted light energy. This facilitates measurement of the change and reduces the design requirements for the detector hardware. Furthermore, by changing the dimensions of the transparent and opaque portions on the photomask, the required sensitivity can be flexibly adjusted to meet the application needs of different precision levels.

[0031] Finally, it should be noted that due to the limitations of written expression, the above description is merely exemplary and not exhaustive. The present invention is not limited to the disclosed embodiments. Without departing from the scope and spirit of the above examples, those skilled in the art can make several improvements and modifications, which should also be considered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A position calibration device for an exposure lens, used to determine the position coordinates of an exposure lens in a direct-write lithography apparatus, characterized in that: The device includes a four-quadrant photodetector mounted on the motion platform of the photolithography equipment and a photomask located above the four-quadrant photodetector. The photomask has periodically distributed transparent and opaque portions corresponding to at least one quadrant of the four-quadrant photodetector. The transparent and opaque portions are striped. The exposure lens can produce alternating bright and dark spots. The distribution pattern of the bright and dark spots is determined according to the distribution pattern of the transparent and opaque portions on the photomask.

2. The position calibration device according to claim 1, characterized in that: The photomask is divided into four equal quadrants, which are separated by dividing lines. The intersection of the dividing lines is the center of the photomask. Each quadrant includes periodically distributed transparent and opaque parts.

3. The position calibration device according to claim 2, characterized in that: The photomask is mounted above the four-quadrant photodetector, such that the dividing line coincides with the blind zone of the four-quadrant photodetector in the direction perpendicular to the photomask surface.

4. The position calibration device according to claim 2, characterized in that: The light-transmitting and opaque parts in each quadrant of the photomask are arranged in parallel stripe patterns, and there is at least one quadrant with stripes parallel to the X direction and one quadrant with stripes parallel to the Y direction.

5. The position calibration device according to claim 1, characterized in that: The dimensions of the light-transmitting and opaque portions are determined based on the photosensitive size and required sensitivity of the four-quadrant photodetector.

6. A method for determining the center position of an exposure lens using the position calibration device as described in any one of claims 1-5, characterized in that: The exposure lens projects alternating bright and dark patterned light spots corresponding to the photomask; The center position of the exposure lens is determined by detecting the reading in one quadrant, which is an overlapping quadrant. The center position of the exposure lens is obtained based on the position where the reading is the largest in that quadrant. Alternatively, the center position of the exposure lens can be determined by detecting the readings in two quadrants, one of which is the overlapping quadrant and the other is the misaligned quadrant. The center position of the exposure lens can be obtained from the position where the difference between the readings in the overlapping quadrant and the misaligned quadrant is the largest.

7. A method for calibrating the position of an exposure lens using the position calibration device as described in any one of claims 1-5, characterized in that: 1) Control the motion platform to move to the alignment system, obtain the initial position coordinates (X', Y') of the photomask center through the alignment system, and the control system determines the initial coordinates of the motion platform at this time as (X0, Y0). 2) The exposure lens produces a pattern of alternating bright and dark light spots; 3) Move the motion platform to the exposure lens so that the four-quadrant photodetector is approximately located under any of the exposure lenses to be calibrated; 4) Keep the Y-axis coordinate of the motion platform stationary and move the motion platform along the X direction. During the movement, the control system selects any overlapping quadrant as the first detection quadrant and any misaligned quadrant as the second detection quadrant within the four-quadrant photodetector. The difference between the readings of the first detection quadrant and the second detection quadrant is obtained in real time, and the X-axis coordinate X1 of the motion platform when the difference is the largest is determined. 5) Keep the X-axis coordinate of the motion platform stationary, move the motion platform along the Y direction. During the movement, the control system selects any overlapping quadrant as the third detection quadrant and any misaligned quadrant as the fourth detection quadrant within the four-quadrant photodetector. The difference between the readings of the third detection quadrant and the fourth detection quadrant is obtained in real time, and the Y-axis coordinate Y1 of the motion platform when the difference is the largest is determined. 6) Determine the position coordinates of the exposure lens based on the initial coordinates (X', Y') of the center of the photomask, the initial coordinates (X0, Y0) of the motion platform, and the coordinates (X1, Y1) when the reading difference is the largest.

8. The method for calibrating the position of an exposure lens according to claim 7, characterized in that: The alternating light and dark patterned spot is divided into four quadrants. The distribution of light and dark in each quadrant is determined by the distribution of the light-transmitting and opaque parts in the corresponding quadrant on the photomask.

9. The method for calibrating the position of an exposure lens according to claim 8, characterized in that: The overlapping quadrant refers to the quadrant in which the distribution of light and dark on the light spot corresponds one-to-one with the transparent and opaque parts on the photomask, and the misaligned quadrant refers to the quadrant in which the distribution of light and dark on the light spot corresponds to the transparent and opaque parts on the photomask in a misaligned manner.

10. The method for calibrating the position of an exposure lens according to claim 9, characterized in that: In step 4, at least one of the overlapping quadrants and the misaligned quadrants is a quadrant in which the stripes are distributed parallel to the Y direction, and in step 5, at least one of the overlapping quadrants and the misaligned quadrants is a quadrant in which the stripes are distributed parallel to the X direction.

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