Method for manufacturing a lens by gray-scale lithography combined with a baking process to correct the curvature of the lens

Abstract

This invention discloses a method for fabricating lenses using grayscale photolithography combined with a baking process to correct lens curvature. The method includes the following steps: S1, substrate surface pretreatment; S2, grayscale photoresist fabrication; S3, grayscale photolithography; S4, post-exposure baking; S5, development; S6, lens morphology measurement; S7, preliminary layer-by-layer progressive thermal baking correction; and S8, grayscale photolithography exposure dose distribution adjustment. This method uses grayscale photolithography to fabricate optical lenses, offering higher controllability and the ability to fabricate high-precision, complex 3D micro / nano structures. It also has advantages over traditional processes for processing aspherical and even freeform lenses, and is easier to process some special structures. Furthermore, the lens morphology, curvature, and height can be corrected through subsequent baking processes to produce lenses with optimal precision optical effects. This method also results in more consistent lens templates, better morphology, and shorter fabrication time.

Description

Technical Field

[0001] This invention relates to the field of optical lens manufacturing technology, and in particular to a method for manufacturing lenses using grayscale photolithography that combines a baking process to correct the lens curvature. Background Technology

[0002] Currently, traditional methods for manufacturing lenses include machining (sculpting) and photolithography. Lenses made using traditional methods have a certain upper limit to their precision due to limitations in processing equipment and processes, and it is even impossible to create certain special structures. Moreover, once a lens is formed, it is almost impossible to modify or adjust it based on the original design. If adjustments are needed, the design parameters must be readjusted, a new substrate must be prepared, and the lens must be remade. This process usually requires multiple rounds of adjustments, which is time-consuming and costly. Summary of the Invention

[0003] To solve the above-mentioned technical problems, this invention designs a method for fabricating lenses using grayscale photolithography that combines a baking process to correct the lens curvature.

[0004] The present invention adopts the following technical solution:

[0005] A method for fabricating lenses using grayscale photolithography combined with a baking process to correct lens curvature, characterized in that the method comprises the following steps:

[0006] S1. Substrate surface pretreatment: Polish the upper and lower surfaces of the substrate to maintain good flatness, and clean the substrate to keep the surface clean.

[0007] S2. Fabrication of grayscale photoresist substrate: A photoresist layer is added to the substrate by spin coating or spray coating. After spin coating, thermal curing or soft baking is performed to obtain the photoresist substrate.

[0008] S3, Grayscale Lithography: Import the design requirements into the grayscale lithography equipment, place the photoresist plate on the equipment platform, adjust to the appropriate exposure dose and exposure time, and start grayscale lithography on the photoresist plate in the corresponding exposure area;

[0009] S4. Post-exposure baking: Place the photoresist plate after grayscale photolithography on a hot plate for baking;

[0010] S5. Development: The developing solution is used to wet the surface of the baked photoresist plate. After the photoresist and the developing solution have reacted, deionized water is used for spin coating and rinsing. The surface is then dried by air drying or spin coating using an ion air gun. A lens structure appears on the photoresist plate.

[0011] S6. Lens morphology measurement: The morphology curvature and height parameters of the lenses on the photoresist plate are measured to obtain the test results of the morphology curvature and height parameters of the lenses on the grayscale photoresist plate.

[0012] S7. Preliminary Layer-by-Layer Progressive Thermal Baking Correction: Based on the test results, preliminary layer-by-layer progressive baking parameters are set. The photoresist plate with the lens is placed cyclically on the hot plate and the cold plate. After each round of thermal baking correction, the lens morphology needs to be measured. Based on the measurement results, the set layer-by-layer progressive baking parameters are fine-tuned until the thermal baking correction is completed, and the morphology curvature and height parameters of the lens meet the preliminary correction requirements.

[0013] S8. Grayscale lithography exposure dose distribution adjustment: Based on the results of the preliminary lens fabrication, the difference between different positions and the design value is obtained. Based on this difference, the distribution of grayscale lithography exposure dose is compensated accordingly. Then, the above steps S1-S6 are repeated to obtain a photoresist plate with a precisely corrected lens morphology. Then, the photoresist plate is subjected to progressive thermal baking correction layer by layer to finally obtain an optical lens whose morphology curvature and height parameters meet the final requirements.

[0014] Preferably, in step S1, the flatness of the substrate is required to be less than 5 μm.

[0015] Preferably, in steps S3 and S4, the exposure dose, exposure time, and baking temperature and time need to be adjusted according to the photoresist type and thickness.

[0016] Preferably, in step S7, the error between the curvature of the optical lens required for preliminary correction and the design value is less than ±2µm, and the height error is less than ±2µm.

[0017] Preferably, in step S8, the error between the curvature of the final optical lens and the design curvature is less than ±1 μm, and the height error is less than ±1 μm.

[0018] The beneficial effects of the present invention are: (1) The method of the present invention uses grayscale lithography to fabricate optical lenses, which has higher controllability and the ability to fabricate high-precision, complex 3D micro-nano structures. It also has more advantages over traditional processes for processing aspherical and even free-form surface lenses, and it is easier to process some special structures. Most importantly, the lens fabricated using grayscale lithography can have its shape, radius of curvature, and lens height corrected by subsequent baking processes. This process is relatively simple and controllable, and multiple rounds of adjustments can be made in a short time to produce a lens with the best precision optical effect; (2) The lens templates fabricated by this method have higher consistency and better shape than those fabricated by traditional processes, and the fabrication time is shorter. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below through specific embodiments: Example

[0020] A method for fabricating lenses using grayscale photolithography that combines baking processes to correct lens curvature, for producing lenses with a curvature of ±1µm and a height parameter of 36±1µm, comprising the following steps:

[0021] S1. Substrate surface pretreatment: Polish the upper and lower surfaces of the substrate respectively. After polishing, the surface flatness of the substrate is 5um (TTV). The substrate is then cleaned to keep the surface of the substrate clean.

[0022] S2. Fabrication of grayscale photoresist substrate: A photoresist layer is added to the substrate by spin coating or spray coating. After spin coating, thermal curing or soft baking is performed to obtain the photoresist substrate. The baking is carried out by hot plate baking at a temperature of 85±10℃ for 40±5 mins, followed by cooling for 30 mins.

[0023] S3. Grayscale Lithography: Import the design pattern into the grayscale lithography equipment, place the photoresist plate on the equipment platform, and adjust to a suitable exposure dose. The maximum output energy of the exposure dose is 1500 mJ / cm². 2 (Different grayscale values ​​use different energies), begin grayscale photolithography on the photoresist plate in the corresponding exposure area, the total photolithography time for a 6-inch area is approximately 40 hours;

[0024] S4. Post-exposure baking: Place the photoresist plate after grayscale photolithography on a hot plate for baking; the baking temperature is 100℃ and the time is 1min;

[0025] S5. Development: The developing solution is used to wet the surface of the baked photoresist plate. After the photoresist and the developing solution have reacted, deionized water is used for spin coating and rinsing. The surface is then dried by air drying or spin coating using an ion air gun. A lens structure appears on the photoresist plate.

[0026] S6. Lens morphology measurement: The curvature and height parameters of the lens on the photoresist plate were measured, and the curvature of the lens on the grayscale photoresist plate was 3.7122um and the height parameter was 39.5um.

[0027] S7. Preliminary Layer-by-Layer Progressive Thermal Baking Correction: Based on the test results, preliminary layer-by-layer progressive baking parameters are set. The photoresist plate with the lens is cyclically placed on the hot plate and the cold plate. After each round of thermal baking correction, the morphology of the lens needs to be measured. Based on the measurement results, the set layer-by-layer progressive baking parameters are fine-tuned until the thermal baking correction is completed. The first round is baked at a temperature of 90℃ for 2 minutes. After baking and cooling, the curvature becomes 2.2402um and the height becomes 38.1um. The second round is baked at a temperature of 100℃ for 2 minutes. After baking and cooling, the curvature becomes 1.1458um and the height becomes 36.9um. The third round is baked at a temperature of 110℃ for 2 minutes. After baking and cooling, the curvature becomes 0.7931um and the height becomes 36.3um.

[0028] S8. Grayscale lithography exposure dose distribution adjustment: Based on the results of the preliminary lens fabrication, the difference between different positions and the design value is obtained. Based on this difference, the distribution of grayscale lithography exposure dose is compensated accordingly. Then, the above steps S1-S6 are repeated to obtain a photoresist plate with a precisely corrected lens morphology. Then, the photoresist plate is subjected to progressive thermal baking correction layer by layer. Finally, the curvature of the lens morphology becomes 0.2611um and the height becomes 35.9um.

[0029] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A method for fabricating lenses using grayscale photolithography combined with a baking process to correct lens curvature, characterized in that, The method steps are as follows: S1. Substrate surface pretreatment: Polish the upper and lower surfaces of the substrate to maintain good flatness, and clean the substrate to keep the surface clean. S2. Fabrication of grayscale photoresist substrate: A photoresist layer is added to the substrate by spin coating or spray coating. After spin coating, thermal curing or soft baking is performed to obtain the photoresist substrate. S3, Grayscale Lithography: Import the design requirements into the grayscale lithography equipment, place the photoresist plate on the equipment platform, adjust to the appropriate exposure dose and exposure time, and start grayscale lithography on the photoresist plate in the corresponding exposure area; S4. Post-exposure baking: Place the photoresist plate after grayscale photolithography on a hot plate for baking; S5. Development: The developing solution is used to wet the surface of the baked photoresist plate. After the photoresist and the developing solution have reacted, deionized water is used for spin coating and rinsing. The surface is then dried by air drying or spin coating using an ion air gun. A lens structure appears on the photoresist plate. S6. Lens morphology measurement: The morphology curvature and height parameters of the lenses on the photoresist plate are measured to obtain the test results of the morphology curvature and height parameters of the lenses on the grayscale photoresist plate. S7. Preliminary Layer-by-Layer Progressive Thermal Baking Correction: Based on the test results, preliminary layer-by-layer progressive baking parameters are set. The photoresist plate with the lens is placed cyclically on the hot plate and the cold plate. After each round of thermal baking correction, the lens morphology needs to be measured. Based on the measurement results, the set layer-by-layer progressive baking parameters are fine-tuned until the thermal baking correction is completed, and the morphology curvature and height parameters of the lens meet the preliminary correction requirements. S8. Grayscale lithography exposure dose distribution adjustment: Based on the results of the preliminary lens fabrication, the difference between different positions and the design value is obtained. Based on this difference, the distribution of grayscale lithography exposure dose is compensated accordingly. Then, the above steps S1-S6 are repeated to obtain a photoresist plate with a precisely corrected lens morphology. Then, the photoresist plate is subjected to progressive thermal baking correction layer by layer to finally obtain an optical lens whose morphology curvature and height parameters meet the final requirements.

2. The method for fabricating lenses using grayscale photolithography with a baking process to correct lens curvature according to claim 1, characterized in that, In step S1, the flatness of the substrate is required to be less than 5 μm.

3. The method for fabricating lenses using grayscale photolithography to correct lens curvature in conjunction with a baking process according to claim 1, characterized in that, In steps S3 and S4, the exposure dose, exposure time, and baking temperature and time need to be adjusted according to the photoresist type and thickness.

4. The method for fabricating lenses using grayscale photolithography in conjunction with a baking process to correct lens curvature according to claim 1, characterized in that, In step S7, the error between the curvature of the optical lens required for preliminary correction and the design value is less than ±2µm, and the height error is less than ±2µm.

5. The method for fabricating lenses using grayscale photolithography to correct lens curvature in conjunction with a baking process according to claim 1, characterized in that, In step S8, the final obtained optical lens has a curvature error of less than ±1µm and a height error of less than ±1µm compared with the design value.