Manufacturing method of infrared material micro-lens array optical element

Abstract

The invention discloses a manufacturing method of an infrared material micro-lens array optical element. The manufacturing method comprises the following steps: firstly, processing a high-precision impressing mold through ultra-precision cutting; secondly, carrying out ultra-precision polishing on the imprint mold and carrying out anti-sticking treatment on the surface of the imprint mold; then, nanometer hot stamping is carried out through the stamping mold; and finally, carrying out etching treatment. The method comprises the following steps: manufacturing a high-precision imprint mold, imprint a curved-surface-shaped micro-lens array made of a photoresist material, and finally performing etching treatment on an infrared material adhered with the micro-lens array made of the photoresist material, thereby finally obtaining the high-precision infrared material micro-lens array optical element. According to the method, the shape-preserving polishing method of the micro-lens array mold is introduced into the manufacturing process of the infrared material micro-lens array optical element, so that the influence of defects such as knife lines and burrs produced after ultra-precision cutting of the mold on the performance of the element is effectively solved, the performance limit of the original technical scheme is broken through, and the optical performance of the infrared material is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical element processing, and particularly to a method for manufacturing an infrared material microlens array optical element. Background Art

[0002] Aerospace detection devices such as star sensors are facing the development needs of lightweight and high performance. Improving the imaging detection ability of their optical systems has an important impact on enhancing the overall performance of the machine. Since the duty ratio of the photosensitive area of the focal plane array of the optical system infrared detector to the entire focal plane area is relatively low, part of the energy cannot be detected. To enhance the light energy utilization rate of the infrared focal plane array, it is urgent to research and develop infrared material microlens array optical elements and their manufacturing technologies.

[0003] With the continuous development and progress of microfabrication technology, the manufacturing technology and application scope of infrared material microlens array optical elements have also been greatly developed. The main manufacturing methods of infrared material microlens array optical elements include moving mask lithography, focused ion beam method, gray-scale mask lithography technology, nanoimprint lithography technology, etc. Combining with subsequent pattern transfer technology further expands the application scope of infrared material microlens array optical elements. To meet the growing demand for infrared material microlens array optical elements, there is an urgent need for a method for manufacturing infrared material microlens array optical elements with high efficiency, high precision, and low cost.

[0004] For the processing of infrared material microlens array optical elements, the currently adopted photolithography processing method. Since it is difficult to achieve the manufacturing accuracy of the gray-scale mask required for photolithography processing, the improvement of the manufacturing accuracy of infrared material microlens array optical elements is limited. Summary of the Invention

[0005] To solve the above problems existing in the prior art, the present invention proposes a method for manufacturing a high-precision infrared material microlens array optical element.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for manufacturing an infrared material microlens array optical element, comprising the following steps:

[0007] A. Design of the microlens array optical element;

[0008] B. Ultra-precision cutting of the imprint mold;

[0009] C. Ultra-precision conformal polishing of the imprint mold;

[0010] D. Detect the surface quality and surface shape accuracy;

[0011] E. Judge whether it meets the index. If it meets, go to step D; otherwise, go to step B;

[0012] F. Perform anti - sticking treatment on the surface of the imprinting mold;

[0013] G. Carry out nano - hot embossing using the imprinting mold;

[0014] H. Detect the hot embossing effect

[0015] I. Judge whether it meets the indicators. If it meets, go to step J; otherwise, go to step G;

[0016] J. Use ICP etching to produce the microlens array structure;

[0017] K. Detect the etching treatment effect;

[0018] L. Judge whether it meets the indicators. If it meets, go to step M; otherwise, go to step J;

[0019] M. Fabricate a high - performance infrared material microlens array optical element.

[0020] Furthermore, the method for ultra - precision cutting and processing the imprinting mold described in step B is the single - point diamond cutting method.

[0021] Furthermore, the method for ultra - precision conformal polishing of the imprinting mold described in step C is the conformal polishing method for micro - array molds or the controlled - shape flexible polishing method for micro - array molds.

[0022] Furthermore, the method for anti - sticking treatment on the surface of the imprinting mold described in step F includes the vapor deposition method and the liquid deposition method.

[0023] Furthermore, the method for nano - imprinting described in step G includes four steps: substrate pretreatment, spin - coating, pre - baking, and hot embossing.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention re - engineers the existing processing flow. First, an ultra - precision imprinting mold with high precision is machined by ultra - precision cutting; second, the imprinting mold is subjected to ultra - precision polishing and anti - sticking treatment on the surface of the imprinting mold; then, nano - hot embossing is carried out using the imprinting mold; finally, etching treatment is performed. By manufacturing a high - precision imprinting mold and embossing a microlens array made of photoresist material with a curved surface shape, and finally etching the infrared material with the microlens array made of photoresist material adhered to it, a high - precision infrared material microlens array optical element is finally obtained. By introducing the conformal polishing method for micro - array molds into the manufacturing process of infrared material microlens array optical elements, the present invention effectively solves the influence of defects such as tool marks and burrs generated after ultra - precision cutting of the mold on the performance of the element, breaks through the performance limit of the original technical solution, and further improves the optical performance of the infrared material. Description of the Drawings

[0026] Figure 1 It is a flow chart of the present invention. Detailed implementation manners

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 Shown is a flow chart of a method for fabricating an infrared material microlens array optical element, and the specific steps are the same as those in the invention content.

[0029] The method for ultra-precision cutting and stamping the mold in step B is as follows: Using the single-point diamond cutting method, on an ultra-precision lathe, using the slow tool servo or fast tool servo processing method, an imprint mold matching the infrared material microlens array optical element to be prepared is processed;

[0030] The material of the imprint mold is a square workpiece with a nickel-phosphorus alloy coating 80 - 200 μm thick on the surface, and the substrate material is copper, aluminum alloy or steel.

[0031] The method for ultra-precision polishing the imprint mold in step C is the conformal polishing method for microarray molds (CN115401534B) or the shape-controlled flexible polishing method for microarray molds (CN 115401530 B) or the shear thickening polishing method.

[0032] The method for vapor deposition in step F is as follows:

[0033] F1. Put the imprint mold into a cleaning agent and perform ultrasonic cleaning for 5 - 10 min, and then dry it with nitrogen;

[0034] F2. Put the imprint mold and the cleaned petri dish on a hot plate at 100 - 130 °C and bake for 5 - 10 min, then take it off and cool to room temperature for later use;

[0035] F3. Place the petri dish on a hot plate at 55 °C, then put the imprint mold into the petri dish, cover the cover, blow in a nitrogen gas stream for 10 min, then remove the nitrogen gas pipe, and change the gas in the petri dish to a nitrogen environment. Absorb a small amount of perfluorooctyltrichlorosilane C8H4C l3 F 13 Si and drop it beside the mold, after heating for 30 min, turn off the power of the hot plate, and open the upper cover after cooling.

[0036] The method for nanoimprinting in step G is as follows:

[0037] G1. Substrate pretreatment

[0038] Select a 2-inch single-polished silicon wafer as the substrate. First, put the substrate into a cleaning agent and perform ultrasonic cleaning for 5 - 10 min, and finally dry it with nitrogen, then heat it on a hot plate and take it off and cool to room temperature for later use.

[0039] G2, Spin Coating

[0040] After the substrate pretreatment, spin coating is carried out. First, a spin coating experiment is conducted to obtain the spin coating curve of the imprinting resist, and a suitable film thickness is selected from it to prepare the spin-coated substrate.

[0041] G3, Pre-baking

[0042] The spin-coated substrate is placed on a hot plate for heating to remove the excess solvent, increase the adhesion between the imprinting resist and the substrate, and prevent the flow of the imprinting resist on the substrate surface, which may cause uneven film thickness.

[0043] G4, Thermal Imprinting

[0044] First, the substrate is placed on the tray of the nanoimprinting machine. Then, the imprinting mold is placed on the surface of the substrate, and a vacuum film is covered. Subsequently, the steps of vacuum pumping, temperature rising, pressure application, filling, temperature dropping, and demolding are carried out in sequence.

[0045] The present invention studies the ultra-precision machining characteristics of the micro-nano machining method for functional micro-structured optical elements, explores the ultra-precision and high-efficiency composite machining technology for non-metallic three-dimensional micro-structured imaging elements, and completes the corresponding three-dimensional micro-structured sample pieces.

[0046] The present invention manufactures a silicon sample piece with a 50×50 microlens array structure by combining thermal imprinting and etching. The process flow mainly includes mold manufacturing process, mold polishing process, mold anti-sticking process, thermal imprinting process, and ICP etching process.

[0047] (1) Mold manufacturing process: The mold material is a nickel-plated steel sheet with a size of 8×8×3 mm. Fast tool servo machining is used, and finally a concave structure opposite to the target microlens array structure is machined on the mold.

[0048] (2) Mold polishing process: The shear thickening polishing method is adopted. The tool marks on the surface of the microlens array structure are removed by non-contact polishing. High-quality surfaces can be obtained while maintaining the original surface shape accuracy. Through detection, the surface shape accuracy and average surface roughness of the mold meet the requirements of subsequent nanoimprinting experiments.

[0049] (3) Mold anti-sticking process: The impurities and water vapor on the mold surface are removed by cleaning and baking. The mold is treated by plasma using a plasma asher to generate nickel oxide on its surface. The plasma-treated mold is immersed in a methyl tert-butyl ether mixed solution with perfluorooctylphosphonic acid as the active ingredient for 4 hours to complete the anti-sticking treatment.

[0050] (4) Hot embossing process: The hot embossing process flow includes substrate pretreatment, spin coating, pre-baking, and embossing. Ultrasonically clean with a cleaning agent for 5 minutes and heat for 2 minutes to remove impurities and water vapor on the silicon wafer surface; then use a spin coater to spin coat the imprinting resin on the silicon wafer surface; heat on a hot plate at 130 °C for 2 minutes; finally, complete hot embossing on an embossing machine.

[0051] (5) ICP etching process: The ICP etching equipment is an Oxford etching machine, the etching gases are C4F8, SF6, and O2, and the etching time is 25 minutes.

[0052] After processing, use a metallurgical microscope, super-depth-of-field microscope, white light interferometer, and atomic force microscope to detect the sample wafers. Extract 6 microlens units from the microlens array of the sample wafers, and judge whether the samples are qualified from four aspects: the number of arrays, the unit size, the unit shape accuracy, and the surface roughness.

[0053] In summary, using the hot embossing and etching processes, a microlens array structure that meets the project technical specifications has been successfully fabricated.

[0054] The present invention is not limited to this embodiment, and any equivalent conceptions or changes within the technical scope disclosed in the present invention are included in the protection scope of the present invention.

Claims

1. A method for manufacturing an infrared material microlens array optical element, characterized in that: The following steps are involved: A. Microlens array optical element design; B. Ultra-precision cutting and stamping molds; C. Ultra-precision conformal polishing of the imprinting mold; D. Check surface quality and surface accuracy; E. Determine whether the indicators are met. If yes, proceed to step D. Otherwise, go to step B; F. Anti-stick treatment is performed on the surface of the stamping mold; G. Nano hot embossing using an imprinting mold; H. Detect the hot embossing effect; I. Determine whether the indicator is met. If yes, go to step J; otherwise, go to step G; J. ICP etches out the microlens array structure; K. Detect the etching treatment effect; L. Determine whether the indicators are met, if yes, go to step M; Otherwise, go to step J; M. Prepare high-performance infrared material microlens array optical elements.

2. The method for manufacturing an infrared material microlens array optical element according to claim 1, characterized in that: The method for ultra-precision cutting the imprinting mold in step B is a single-point diamond cutting method.

3. The method for manufacturing an infrared material microlens array optical element according to claim 1, characterized in that: The method for ultra-precision conformal polishing of the imprinting mold in step C is a microarray mold conformal polishing method or a microarray mold shape-controlled flexible polishing method.

4. The method for manufacturing an infrared material microlens array optical element according to claim 1, characterized in that: The method for performing anti-sticking treatment on the surface of the imprinting mold in step F includes a vapor deposition method and a liquid deposition method.

5. The method for manufacturing an infrared material microlens array optical element according to claim 1, characterized in that: The method for nanoimprinting described in step G includes four steps: substrate pretreatment, coating, pre-baking, and hot embossing.

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