A coating apparatus and method for improving photoresist residue on the side edges of a photomask substrate

Abstract

The application discloses a coating device and method for improving photoresist residue on the side edge of a photo mask substrate, and relates to the technical field of photoresist coating. The application comprises a top cover, an enclosure cover body and a rotary table. The rotary table is rotatably arranged inside the enclosure cover body, and the top of the rotary table is used for placing a substrate. The top of the enclosure cover body is provided with an opening, which is used for placing and taking out the substrate. The top cover is used for closing the opening of the enclosure cover body. The top cover is provided with an air inlet, which is used for outputting air flow to the rotary table. The enclosure cover body is provided with a plurality of exhaust outlets arranged in the circumferential direction, which are used for exhausting the gas inside the enclosure cover body. The height of the exhaust outlet is higher than the height of the top of the rotary table. In the application, the exhaust outlet is arranged on the side, so that the flow path of the gas is in the shape of L. The downward flow trend of the gas is avoided, the downward force of the gas on the photoresist is avoided, and the photoresist is prevented from flowing to the side of the substrate.

Description

Technical Field

[0001] This invention relates to the field of photoresist coating technology, and specifically provides a coating apparatus and method for improving the coating of residual photoresist on the side of a photomask substrate. Background Technology

[0002] Applying photoresist to a substrate is a step in photomask fabrication. Spin coating is a commonly used method for photoresist application. It utilizes the centrifugal force generated by the substrate's rotation to evenly coat the photoresist onto its surface. When using spin coating, the substrate is fixed to a rotating turntable, and the photoresist is dropped onto the center of the rotating substrate. Under centrifugal force, the photoresist flows towards the edges of the substrate, while excess photoresist detaches from the edges. The photoresist remaining on the substrate surface forms a relatively uniform photoresist layer.

[0003] Patent CN120306209A discloses a photoresist coating apparatus and method. This patent utilizes an air jet device at the top of a housing, which jets air downwards during turntable rotation. The airflow contacts the photoresist from the top, but after contact, it cannot flow downwards and instead flows along the surfaces of the substrate and turntable to both sides. Finally, the airflow reaches the edge of the turntable and flows downwards to the outlet. The airflow path is zigzag-shaped from entry to exit. However, in implementing this method, it was found that when the photoresist reaches the substrate edge, some is thrown out by centrifugal force, while some flows from the substrate edge to the side of the substrate due to the airflow. This latter portion of photoresist, flowing to the side of the substrate, requires a separate process to remove the photoresist from the substrate side after coating. Therefore, although the above solution can make the photoresist coating thickness more uniform through airflow, the airflow also causes photoresist to adhere to the sides of the substrate, requiring a separate photoresist removal process for the sides, which leads to more complex processes and increased costs. Summary of the Invention

[0004] This invention provides a coating apparatus for improving the coating of photoresist residue on the side of a photomask substrate. By improving the uniformity of photoresist coating through airflow, it solves the problem of photoresist adhesion on the side of the substrate.

[0005] The technical solution of the present invention is as follows:

[0006] A coating apparatus for improving the residual photoresist on the side of a photomask substrate includes a top cover, a sealing cover, and a turntable. The turntable is rotatably disposed inside the sealing cover. The top of the turntable is used to place the substrate. The top of the sealing cover has an opening for inserting and removing the substrate. The top cover is used to close the opening of the sealing cover. The top cover has an air inlet for outputting airflow to the turntable. The sealing cover has several circumferentially arranged exhaust ports for discharging gas from inside the sealing cover. The height of the exhaust ports is higher than the height of the top of the turntable. In this design, the exhaust ports on the sealing cover allow the gas blown out from the air inlet to flow downwards to the substrate and then flow along the surface of the substrate towards the exhaust ports, forming an L-shaped flow path. Because the bottom of the cover does not vent, after air enters through the air inlet, the amount and pressure of gas at the bottom of the cover will remain stable after a brief change. The gas will not tend to flow downwards during the flow process, which can prevent the airflow from exerting a downward force on the photoresist, thereby preventing the photoresist from flowing downwards to the side of the substrate.

[0007] If the area of ​​the turntable is larger than the area of ​​the substrate, the top surface of the turntable and the top surface of the substrate form a step. When airflow moves from the substrate to the turntable, it tends to flow downwards, potentially causing photoresist to flow down to the sides of the substrate. Therefore, the top surface area of ​​the turntable is smaller than the area of ​​the substrate. In this design, the area of ​​the turntable is smaller than the area of ​​the substrate, allowing the substrate to completely cover the turntable from above. Therefore, after reaching the edge of the substrate, the airflow flows directly towards the exhaust port, preventing a downward flow and thus avoiding the photoresist flowing down the sides of the substrate.

[0008] To address the problem of photoresist falling onto the inner wall of the sealing housing after being ejected from the substrate, flowing downwards along the inner wall of the side barriers, and becoming dispersed and difficult to handle, a collection platform is installed inside the sealing housing. This collection platform is positioned circumferentially on the turntable, and its height is lower than the turntable. The collection platform is used to collect the photoresist ejected from the substrate. In this solution, the ejected photoresist falls onto the collection platform, concentrating its position and preventing it from flowing randomly. This concentrated photoresist facilitates unified processing and reduces the difficulty of handling the photoresist.

[0009] As photoresist continuously accumulates on the collection stage, it can obstruct the exhaust port. Therefore, it is necessary to treat the photoresist on the collection stage. However, periodic treatment of the photoresist would halt the photoresist coating process, reducing coating efficiency and impacting normal production. To address this, the enclosure is equipped with a photoresist suction hole, which is connected to the interior of the enclosure and flush with the top surface of the collection stage. This suction hole is used to draw photoresist from the collection stage. In this solution, the photoresist continuously adsorbs from the collection stage through the suction hole; photoresist falling onto the collection stage does not accumulate but is directly sucked away, thus solving the problem of photoresist accumulation on the collection stage.

[0010] Preferably, the cover is provided with multiple adhesive suction holes, which are evenly distributed along the circumference. In this solution, multiple adhesive suction holes are provided to evenly absorb photoresist from the circumference, ensuring that photoresist at all points on the collection stage can be absorbed, and preventing photoresist accumulation in any particular area of ​​the collection stage.

[0011] To address the high maintenance costs of the collection station, the collection station comprises several unit blocks, which are combined to form the collection station. In this solution, when a malfunction occurs and maintenance is required, a single unit block can be disassembled or replaced, without replacing the entire collection station, thus reducing maintenance costs.

[0012] To address the issue of photoresist ejected from the substrate falling directly to the bottom of the sealing cover instead of onto the collection stage, the inner edge of the collection stage extends to the underside of the substrate. In this design, because the inner edge of the collection stage extends to the underside of the substrate, the photoresist ejected from the substrate inevitably moves outwards, ensuring it lands on the collection stage and preventing it from falling to the bottom of the sealing cover.

[0013] To address the issue of the collection platform interfering with the rotation of the substrate, the top surface of the collection platform is lower than the top surface of the turntable, creating a gap between the collection platform and the substrate. In this design, the gap between the collection platform and the substrate prevents interference with the substrate's rotation, ensuring normal substrate rotation.

[0014] Preferably, the top of the turntable is equipped with an adsorption device, which is used to fix the substrate. In this solution, fixing the substrate by adsorption allows for rapid fixation of the substrate even when the substrate area is larger than the turntable.

[0015] The present invention also provides a method for improving the coating of residual photoresist on the side of a photomask substrate, comprising the following steps:

[0016] S1. Place the substrate on the turntable and fix it in place;

[0017] S2. Cover the cover plate to seal the enclosure;

[0018] S3. After rotating the turntable, drop photoresist into the center of the substrate;

[0019] S4. A vertically downward airflow is introduced into the upper side of the substrate, and an exhaust port is provided on the side above the substrate for exhaust, so that the airflow inside the cover flows in an L-shape.

[0020] In the above method, by placing the exhaust port above the substrate, the airflow flows horizontally along the substrate surface after contacting the substrate, preventing the airflow from flowing downwards and causing the photolithography to flow from the edge of the substrate to the bottom.

[0021] The beneficial effects of this invention are:

[0022] This invention places the exhaust port on the side, making the gas flow path L-shaped, thus avoiding the downward flow of gas and preventing the photoresist from being subjected to downward force from the gas, thereby preventing the photoresist from flowing to the side of the substrate. Attached Figure Description

[0023] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the airflow direction inside the enclosure in the prior art;

[0025] Figure 2 This is a schematic diagram of the airflow direction and photoresist flow position at the edge of a substrate in the prior art.

[0026] Figure 3 This is a schematic diagram of the airflow direction in this invention;

[0027] Figure 4 This is a partial cross-sectional view of the collection platform after the adhesive suction holes are integrated in this invention;

[0028] Figure 5 This is a top view of the collection platform in this invention with a flow guide channel installed;

[0029] Figure 6 This is a cross-sectional view of the present invention, showing an air inlet at the bottom of the cover.

[0030] In the above figures, the corresponding reference numerals are as follows:

[0031] 1. Enclosure; 2. Top cover; 3. Air inlet; 4. Photoresist droplet inlet; 5. Exhaust outlet; 6. Turntable; 7. Substrate; 8. Photoresist; 9. Photoresist droplet; 10. Collection stage; 11. Adhesive suction hole; 12. Adhesive suction branch; 13. Adhesive suction main channel; 14. Boss; 15. Unit block. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described in conjunction with the accompanying drawings and through specific embodiments.

[0033] Example 1:

[0034] like Figure 3 As shown, this embodiment provides a coating apparatus for improving the residual photoresist on the side of a photomask substrate, including a turntable 6, a cover 1, and a top cover 2. The turntable 6 is rotatably disposed within the cover 1, and the cover 1 surrounds the turntable 6 from the side and bottom. An opening is formed at the top of the cover 1, and the top cover 2 is detachably connected to the cover 1 to close the opening. The opening at the top of the cover 1 is used for inserting and removing the substrate 7. An air inlet 3 is provided at the bottom of the top cover 2, and an exhaust port 5 is provided on the side of the cover 1. The height of the exhaust port 5 is higher than the height of the top surface of the substrate 7 placed on the turntable 6. The top surface of the turntable 6 is used to place the substrate 7, and the area of ​​the turntable 6 is smaller than the area of ​​the substrate 7 to be placed. After the substrate 7 is placed on the top surface of the turntable 6, the substrate 7 completely covers the turntable 6 from above. After the substrate 7 is placed, the height of the exhaust port 5 is not lower than the height of the substrate 7. The airflow blown in by the air inlet 3, after contacting the substrate 7, will flow along the top surface of the substrate 7 to the side, and finally be discharged from the exhaust port 5 of the cover 1. The airflow path is L-shaped. The top cover 2 has a photoresist drop inlet 4 at its center for dropping photoresist. After the top cover 2 closes the cover 1, the photoresist 8 drops from the photoresist drop inlet 4 and falls on the rotation center of the substrate. Therefore, the photoresist drop inlet 4 is located directly above the turntable 6, and the photoresist drop inlet 4 coincides with the rotation axis of the turntable 6.

[0035] Therefore, during operation, photoresist 8 is dropped into the center of substrate 7. Under the combined action of centrifugal force and airflow, photoresist 8 flows towards the edge of substrate 7. After some photoresist 8 flows to the edge of substrate 7, centrifugal force and airflow will only exert a horizontal outward force on the excess photoresist 8. The excess photoresist 8 will be flung out horizontally instead of flowing downward to the side of substrate 7, reducing the need for photoresist 8 removal from the side of substrate 7.

[0036] Multiple exhaust ports 5 are provided in the circumferential direction of the cover body 1. Each exhaust port 5 is evenly arranged in the circumferential direction, so that a stable outward airflow is formed on the top of the substrate 7.

[0037] The air inlet can be a jet nozzle located on the inner side of the top cover 2, the photoresist droplet inlet can be a nozzle located on the inner side of the top cover 2, and the exhaust port can be a hole opened on the side of the cover 1.

[0038] A collection platform 10 is also provided inside the cover 1. The collection platform 10 has a ring structure, and its outer side is connected to the inner side of the cover 1. The inner side of the collection platform 10 extends to the lower side of the substrate 7. There is a gap between the top surface of the collection platform 10 and the top surface of the turntable 6, so that the top surface of the collection platform 10 does not contact the bottom surface of the substrate 7. The photoresist droplets 9 that are basically ejected will fall onto the collection platform 10 under the action of gravity.

[0039] As an optional technical solution, the collection platform 10 can be a ring structure formed by combining multiple unit blocks 15. The unit block 15 can be a plastic block.

[0040] The cover 1 is also provided with adhesive suction holes 11 around its perimeter. The height of the adhesive suction holes 11 is lower than that of the exhaust port 5, and the adhesive suction holes 11 are flush with the top surface of the collection platform 10. The adhesive suction holes 11 use negative pressure adsorption to draw up the photoresist 8 on the collection platform 10, thereby achieving the function of real-time removal of the photoresist 8 on the collection platform 10.

[0041] With the suction hole 11 provided, the internal air pressure of the cover 1 will decrease more rapidly. In order to maintain a positive pressure inside the cover 1, the efficiency of the air inlet 3 in blowing in the suction hole 11 is improved.

[0042] There are multiple suction holes 11, each arranged circumferentially, used to collect adhesive from various locations on the collection platform 10. The end of the suction hole 11 located outside the cover 1 is connected to a suction pipe. The photoresist 8 on the collection platform 10 enters the suction pipe through the suction hole 11 and is then discharged along the suction pipe.

[0043] Several guide channels can be provided on the top of the collection stage 10. One end of the guide channel is aligned with the suction hole 11, and the other end of the guide channel extends to various parts of the top of the collection stage 10. The guide channels are distributed in a fan shape to facilitate the flow of photoresist 8 from various locations to the position of the suction hole 11.

[0044] The top of the turntable 6 is provided with an adsorption structure. When the substrate 7 is placed on the top of the turntable 6, the turntable 6 uses the adsorption structure to adsorb and fix the substrate 7, preventing the substrate 7 from falling off the turntable 6 during rotation.

[0045] Example 2:

[0046] This second embodiment provides a coating apparatus for improving the residual photoresist on the side of the photomask substrate. Unlike the first embodiment, the adhesive suction hole 11 in this second embodiment is integrated into the collection stage 10.

[0047] The collection stage 10 is provided with a boss 14, and a suction hole 11 is provided on the side of the boss 14. The suction hole 11 is basically horizontal, and the bottom of the suction hole 11 is lower than the top surface of the collection stage 10, so as to facilitate the flow of photoresist 8 into the suction hole 11. The cover 1 is provided with a through hole for the suction pipe to pass through. One end of the suction pipe passes into the cover 1 and communicates with one end of the suction hole 11. The other end of the suction hole 11 is used to attract the photoresist 8 on the collection stage 10.

[0048] The suction hole 11 can be either circular or rectangular. A rectangular hole has a flat bottom side, which makes the bottom side of the suction hole 11 wider, making it easier for the photoresist 8 to enter the suction hole 11.

[0049] like Figure 5 As shown, as an optional technical solution, the top surface of the collection stage 10 is provided with multiple guide channels, which are arranged in a fan shape, with one end of each guide channel facing the suction hole 11. The guide channels are used to guide the photoresist 8 from various parts of the collection stage 10 to the suction hole 11. The guide channels serve to guide the flow direction of the photoresist 8 and prevent the photoresist 8 from flowing randomly.

[0050] like Figure 4 As shown, as an optional technical solution, the collection platform 10 is equipped with a main suction channel 13 and multiple suction branches 12. The main suction channel 13 is connected to several branches, and each suction branch 12 is connected to a suction hole 11. The suction pipe is connected to the main suction channel 13. This installation method only requires one negative pressure pipe connected to the main suction channel 13, which can significantly reduce the number of suction pipes and facilitate pipe layout. When a negative pressure device is connected to the outside of the suction pipe, the negative pressure device generates negative pressure when it is working. The negative pressure is transmitted to the suction hole 11 through the suction pipe, the main suction channel 13, and the suction branches 12, so that the suction hole 11 can adsorb the photoresist 8 on the collection platform 10. After the photoresist 8 is sucked into the suction hole 11, it enters the suction pipe through the suction hole 11, the suction branches 12, and the main suction channel 13. At this time, a collection container can be set in the middle of the suction pipe to collect the photoresist 8. The main suction channel 13 can be equipped with a branch that runs through the side of the unit block to facilitate the connection between the suction pipe and the main suction channel.

[0051] Example 3:

[0052] This embodiment three provides a coating device for improving the residual photoresist on the side of the photomask substrate. Unlike embodiment one, this embodiment three also has an air inlet 3 at the bottom of the cover.

[0053] like Figure 6As shown, the bottom of the cover 1 is provided with several air inlets 3, such as two, three, four or more. The air inlets 33 are arranged in a circular array to ensure that the airflow entering from the bottom of the cover 1 can flow evenly upwards and around.

[0054] When the air inlets 3 at the bottom of the cover are arranged in a circular array, the diameter of the circular array is smaller than the inner diameter of the collection stage 10. The airflow entering through the air inlets 3 can directly flow vertically upward from the bottom of the cover to the bottom of the turntable 6 or the substrate 7, then through the gap between the substrate 7 and the collection stage 10, and finally flow to the exhaust port or the suction hole 11. When the gas flows from the gap between the substrate 7 and the collection stage 10 toward the suction hole 11, it exerts a force on the photoresist 8 on the collection stage 10, causing the photoresist 8 to flow toward the suction hole 11, improving the efficiency of photoresist 8 being sucked away and reducing the amount of photoresist 8 remaining on the collection stage 10.

[0055] When the solution of this embodiment three is combined with the solution of embodiment two, the airflow and the guide groove work together to further promote the photoresist 8 to flow to the suction hole 11, reduce the amount of photoresist 8 flowing toward the edge of the collection stage 10 and remaining, and improve the recovery rate of photoresist 8.

[0056] The air inlet 3 at the bottom of the cover 1 is oriented upwards to blow gas upwards. The gas passes through the gap between the collection stage 10 and the substrate 7 and enters the adhesive suction hole 11 or the exhaust port 5. In other words, there is also airflow towards the exhaust port on the lower side of the substrate 7. The airflow on the lower side is balanced with the airflow on the upper side, ensuring that the airflow on the upper side does not shift downwards. This also further prevents the photoresist 8 at the edge of the substrate 7 from flowing downwards along the sidewall of the substrate 7.

[0057] As a preferred embodiment, the total air intake volume of the air inlet 3 at the bottom of the cover 1 is greater than the total air intake volume of the air inlet 3 on the top cover 2. In this case, the airflow on the lower side of the substrate 7 is greater than the airflow on the upper side of the substrate 7, and the airflow on the lower side of the substrate 7 will have a certain upward flow. This can cause the photoresist 8 at the edge of the substrate 7 to be subjected to some upward airflow force, thus providing a reverse force to prevent the photoresist 8 from flowing downward along the sidewall of the substrate 7. The total air intake volume at the bottom can be 1.5-3 times the total air intake volume at the top, and a ratio of 2 can be selected.

[0058] Example 4:

[0059] This fourth embodiment provides a method for improving the coating of residual photoresist on the side of a photomask substrate, implemented based on the apparatus described in Embodiment 1, Embodiment 2, or Embodiment 3.

[0060] A method for improving the coating of residual photoresist on the side of a photomask substrate includes the following steps:

[0061] S1. Place the substrate 7 on the turntable 6, and fix the substrate 7 by adsorption on the turntable 6.

[0062] S2. By sealing the space where the substrate 7 is located by the cover plate, the photoresist 8 is coated in a relatively enclosed space, reducing the possibility of the photoresist 8 being contaminated.

[0063] S3. Rotate the turntable 6 and drop photoresist 8 into the center of the substrate 7. The photoresist 8 is then subjected to centrifugal force and flows towards the edge of the substrate 7, spreading the photoresist 8 on the surface of the substrate 7, thereby forming a photoresist 8 layer on the surface of the substrate 7.

[0064] S4. Gas is blown downwards from the top side of the substrate, causing the gas to flow vertically downwards. After contacting the substrate 7, the gas flows laterally along the surface of the substrate 7. This gas flow exerts a force on the photoresist 8, causing it to flow towards the edge of the substrate 7. An exhaust port 5 is provided on the side of the substrate 7, allowing the airflow to exit through the exhaust port 5. The height of the exhaust port 5 is set to be the same as or slightly higher than the substrate 7, making the gas flow path within the enclosure L-shaped. This prevents the photoresist 8 from being subjected to downward airflow, thus preventing it from flowing to the sidewalls. When blowing gas from the top side of the substrate, gas can also be blown in from the bottom side of the substrate simultaneously, so that both the top and bottom sides of the substrate are subjected to gas simultaneously. This ensures that when the photoresist flows to the edge of the substrate, the forces exerted on both the top and bottom sides of the photoresist are balanced by the gas, or that the photoresist is subjected to an upward force, preventing it from encountering resistance when flowing downwards, thus achieving the effect of preventing the photoresist from flowing to the sidewalls of the substrate.

[0065] S5. While the air inlet 3 blows air, the suction hole 11 starts to suck air. The suction hole 11 faces the collection stage 10. The suction force generated by the air sucks the photoresist 8 towards the suction hole 11, so that the photoresist 8 can flow to the suction hole 11 and is eventually sucked away by the suction hole 11.

[0066] The small diameter of the suction hole 11 will attract the flow of photoresist 8 within a small area, preventing a large amount of gas from flowing towards the suction hole 11, thereby preventing a large amount of airflow from flowing towards the suction hole 11 on the lower side, reducing the impact of the airflow flowing on the lower side on the flow of photoresist 8.

Claims

1. A coating apparatus for improving residual photoresist on the side of a photomask substrate, characterized in that, The device includes a top cover, a cover body, and a turntable. The turntable is rotatably disposed inside the cover body. The top of the turntable is used to place a substrate. The top of the cover body has an opening for inserting and removing the substrate. The top cover is used to close the opening of the cover body. The top cover has an air inlet for outputting airflow to the turntable. The cover body has several exhaust ports arranged in a circumferential direction for discharging gas from inside the cover body. The height of the exhaust ports is higher than the height of the top of the turntable.

2. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 1, characterized in that, The top surface area of ​​the turntable is smaller than the area of ​​the substrate.

3. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 1, characterized in that, The inside of the cover is equipped with a collection platform, which is located in the circumferential direction of the turntable. The height of the collection platform is lower than that of the turntable. The collection platform is used to collect the photoresist that falls off the substrate.

4. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 3, characterized in that, The cover is equipped with a suction hole, which is connected to the interior of the cover and is flush with the top surface of the collection stage. The suction hole is used to draw photoresist from the collection stage.

5. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 4, characterized in that, The cover body is equipped with multiple adhesive suction holes, which are evenly distributed along the circumference.

6. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 3, characterized in that, The collection platform comprises several unit blocks, which are combined to form the collection platform.

7. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 3, characterized in that, The inner edge of the collection platform extends to the underside of the substrate.

8. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 3, characterized in that, The top surface of the collection platform is lower than the top surface of the turntable, creating a gap between the collection platform and the substrate.

9. The coating apparatus for improving residual photoresist on the side of a photomask substrate according to claim 1, characterized in that, An adsorption device is provided on the top of the turntable, and the turntable fixes the substrate through the adsorption device.

10. A coating method for improving the application of residual photoresist on the side of a photomask substrate, characterized in that, The apparatus applicable to any one of claims 1-9 comprises the following steps: S1. Place the substrate on the turntable and fix it in place; S2. Cover the cover plate to seal the enclosure; S3. After rotating the turntable, drop photoresist into the center of the substrate; S4. A vertically downward airflow is introduced into the upper side of the substrate, and an exhaust port is provided on the side above the substrate for exhaust, so that the airflow inside the cover flows in an L-shape.

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