A method for low-cost and rapid preparation of sub-micron large-area nanoimprint template

Abstract

The application provides a method for rapidly and low-cost preparing a sub-micron large-array nano-imprint template, and the steps comprise: (1) building a Mach-Zehnder holographic exposure light path; (2) spin-coating photoresist on a silicon wafer surface, fixing the silicon wafer on an exposure platform, performing holographic exposure, and recording interference fringe patterns on the photoresist layer; (3) developing the exposed silicon wafer, removing the photoresist in the exposed area, and transferring the patterns to the silicon wafer through ICP etching to prepare a silicon hard template; (4) spin-coating anti-sticking liquid on the silicon hard template to perform anti-sticking treatment; (5) mixing polydimethylsiloxane A glue and B glue at a mass ratio of 1:1, and pouring the mixture on the surface of the silicon hard template subjected to the anti-sticking treatment to obtain a PDMS soft template; and (6) performing nano-imprinting by using the polydimethylsiloxane soft template. The application solves the problems of high cost, long cycle and complex process of the existing electron beam exposure technology.

Description

Technical Field

[0001] This invention relates to the field of micro-nano manufacturing technology, and more specifically, to a low-cost, rapid method for preparing submicron-scale large-area nanoimprint templates. Background Technology

[0002] Nanoimprint lithography, with its advantages of high precision, high throughput, and relatively low cost, has become a key technology for micro- and nano-pattern transfer in fields such as semiconductors, optics, and biosensing. However, the quality and manufacturing cost of nanoimprint templates are the core bottlenecks restricting the large-scale industrialization of this technology.

[0003] Currently, electron beam lithography is the mainstream method for preparing submicron-scale, and especially large-area (centimeter-scale) nanoimprint templates. However, this technique has the following inherent drawbacks: High cost: Electron beam exposure equipment is extremely expensive, with high maintenance costs, long processing time per cycle, and high consumable costs, resulting in high template preparation costs.

[0004] The process is lengthy: For large-area templates at the centimeter level, the electron beam must be scanned and written point by point and step by step. A complete preparation cycle often takes several days, exceeding 72 hours, which cannot meet the needs of rapid iteration and mass production.

[0005] Poor process compatibility: Electron beam exposure is extremely sensitive to environmental factors such as vibration and electromagnetic interference, as well as the surface condition of the substrate, which can easily lead to pattern defects. This makes yield control difficult and further increases the overall cost.

[0006] Therefore, the industry urgently needs a new method to replace traditional electron beam exposure and achieve low-cost, high-efficiency preparation of high-quality submicron-scale large-area nanoimprint templates. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-cost and rapid method for preparing submicron-scale large-area nanoimprint templates, so as to solve the problems of high cost, long cycle and complex process of existing electron beam lithography technology.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a low-cost and rapid method for preparing submicron-scale large-area nanoimprint templates, comprising the following steps: (1) Construct a Mach-Zehnder holographic exposure optical path, which includes a laser, shutter, half-wave plate, polarizing beam splitter, power monitor, mirror, collimating mirror, pinhole filter and substrate, and adjust the angle between the object light and the reference light to 15°-25°, and the light intensity ratio to 1:1 to 1:3. (2) Spin-coat photoresist on the surface of the silicon wafer, fix the silicon wafer on the exposure platform, perform holographic exposure, and record the interference fringe pattern on the photoresist layer; (3) The exposed silicon wafer is developed to remove the photoresist in the exposed area, and then the pattern is transferred to the silicon wafer by inductively coupled plasma etching to prepare a silicon hard template. (4) The silicon hard template is spin-coated with anti-adhesion liquid for anti-adhesion treatment, and then dried for later use; (5) Mix polydimethylsiloxane A glue and B glue at a mass ratio of 1:1, pour the mixture onto the surface of the silicone hard template treated with anti-adhesion, and peel it off after curing on a hot plate to obtain PDMS soft template. (6) Nanoimprinting is performed using the polydimethylsiloxane soft template.

[0009] Preferably, in step (2), the photoresist is a positive photoresist, the spin coating speed is 3000-5000 r / min, the spin coating time is 30-60 s, and the photoresist film thickness is 200-300 nm; the holographic exposure dose is 50-100 mJ / cm², and the exposure time is 300-600 s.

[0010] Preferably, in step (3), the developing solution used is a 2.38wt% tetramethylammonium hydroxide aqueous solution, the developing temperature is 23-25℃, and the developing time is 60-90s; the gas used for ICP etching is a mixture of SF6 and O2 with a volume ratio of 5:1 to 10:1, an etching power of 300-500W, an etching time of 1-5min, and an etching depth of 100-300nm.

[0011] Preferably, in step (4), the anti-adhesion liquid used in the anti-adhesion treatment is a 0.5-1.0wt% fluorinated silane anhydrous ethanol solution, the spin coating speed is 2000-4000 r / min, the spin coating time is 30-60s, the drying temperature is 80-100℃, and the drying time is 10-20min.

[0012] Preferably, in step (5), the stirring speed when mixing the polydimethylsiloxane A glue and B glue is 500-800 r / min, the stirring time is 10-15 min, the hot plate curing temperature is 80-120℃, and the curing time is 30-60 min.

[0013] Preferably, in step (1), the period of the interference fringes is controlled to be 180-1000nm by adjusting the angle between the object light and the reference light to be in the range of 15°-25°; and the duty cycle of the interference fringes is controlled to be 0.3-0.7 by adjusting the light intensity ratio to be in the range of 1:1 to 1:3.

[0014] Preferably, in step (3), after the inductively coupled plasma etching is completed, the residual photoresist mask is removed by oxygen plasma ashing.

[0015] Preferably, in step (1), in the Mach-Zehnder holographic exposure optical path, the TE light emitted by the laser passes through the shutter and half-wave plate, and is split into two beams by a polarizing beam splitter. One beam passes through a mirror, a pinhole filter, and a collimating lens to reach the substrate as the object light, and the other beam passes through a polarizing beam splitter, a half-wave plate, a mirror, a pinhole filter, and a collimating lens to reach the substrate as the reference light. The two beams interfere on the substrate surface to form interference fringes.

[0016] The nanoimprint template prepared by the above method is a polydimethylsiloxane soft template with a micro-nano structure feature size of 180-1000 nm, an array size of centimeters, and a feature size accuracy of ±25 nm.

[0017] Preferably, the area of ​​the template is 2.5cm × 2.5cm, and the feature size accuracy is ±15nm to ±20nm.

[0018] Compared with the prior art, the present invention has the following significant advantages: 1. Extremely low cost: By using Mach-Zehnder holographic exposure technology instead of expensive electron beam exposure, equipment costs are reduced by more than 60%. At the same time, the process is simple and the consumables are inexpensive, making the overall template preparation cost only 1 / 50 to 1 / 100 of that of traditional electron beam exposure methods.

[0019] 2. Short preparation cycle: From optical path setup to obtaining PDMS soft template, the entire process can be controlled within 3-5 hours. Compared with electron beam exposure method, the preparation cycle is shortened by more than 80%, realizing the rapid preparation of submicron-scale large-area templates.

[0020] 3. High precision and large array size: By precisely controlling the optical path parameters, feature size accuracy better than ±25 nm can be achieved, with actual measurements reaching ±15-20 nm for template fabrication. Simultaneously, holographic exposure can complete centimeter-level large-area pattern recording in a single operation, avoiding alignment errors and pattern defects caused by step-by-step stitching, and ensuring the consistency and integrity of the pattern within the array.

[0021] 4. Strong process compatibility: This method has relatively relaxed requirements for the operating environment and substrate. The prepared PDMS soft template has good flexibility and good compatibility with various nanoimprinting equipment and a variety of substrates to be imprinted, making it easy to achieve industrialization and application. In addition, after anti-sticking treatment, the silicon hard template can be reused more than 50 times, further reducing long-term usage costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the Mach-Zehnder holographic exposure optical path of the present invention.

[0023] Figure 2 This is a flowchart of the nanoimprint template preparation process of the present invention.

[0024] Figure 3 Atomic force microscopy (AFM) morphology of the micro / nano structure on the surface of the silicon hard template prepared in this invention.

[0025] Figure 4 Atomic force microscopy (AFM) morphology of the micro / nano structure on the surface of the PDMS soft template prepared in this invention.

[0026] Figure 5 This is a schematic diagram illustrating the principle of using the PDMS soft template prepared in this invention for nanoimprinting. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it.

[0028] Example 1: Fabrication of a PDMS soft template with a period of approximately 475 nm and a 2 cm × 2 cm area. 1. Optical path setup: Refer to Figure 1 Construct the Mach-Zehnder holographic exposure optical path. Select a semiconductor laser with a wavelength of 325 nm. Adjust the beam splitter to make the intensity ratio of the object beam and the reference beam 1:1. Adjust the angle of the reflector so that the angle between the two beams on the substrate surface is 20°, thereby forming interference fringes with a period of approximately 475 nm.

[0029] 2. Photoresist coating: A 2-inch single-crystal silicon wafer was selected as the substrate. Positive photoresist (model AZ 5214) was spin-coated at a speed of 4000 r / min for 45 seconds to obtain a photoresist film with a thickness of about 250 nm.

[0030] 3. Holographic Exposure: The coated silicon wafer is fixed on the exposure stage and holographic exposure is performed with an exposure dose of 80mJ / cm² for 200 seconds.

[0031] 4. Development and Etching: The exposed silicon wafer is immersed in a 2.38% TMAH developer at 23-25℃ for 75 seconds. ICP etching is then performed with an SF6:O2 volume ratio of 8:1, a power of 400W, an etching time of 2 minutes, and an etching depth of approximately 150nm. Finally, residual photoresist is removed by oxygen plasma ashing to obtain the silicon hard template.

[0032] 5. Anti-sticking treatment: Prepare a 0.8wt% fluorinated silane anhydrous ethanol solution, spin-coat it onto the surface of the silicone hard template at a speed of 2400r / min for 30 seconds, and then dry it at 90℃ for 15 minutes.

[0033] 6. Preparation of PDMS Flexible Template: PDMS A adhesive (prepolymer) and B adhesive (curing agent) are mixed at a mass ratio of 1:1 and stirred at 600 r / min for 12 minutes. The mixture is poured onto the treated silicone rigid template and cured on a hot plate at 100℃ for 45 minutes. After cooling, it is peeled off to obtain a PDMS flexible template with a 2cm × 2cm area array and a period of approximately 475nm.

[0034] Testing showed that the feature size accuracy of the PDMS soft template prepared in this embodiment was ±15nm, and the pattern consistency deviation within the array was ≤3%. The total cycle from start to finish of preparation to obtaining the soft template was approximately 2 hours, and the cost was approximately 1 / 100 of that of the electron beam lithography method.

[0035] Example 2: Fabrication of a PDMS soft template with a period of approximately 728 nm and a 2.5 cm × 2.5 cm area. 1. Optical path setup: A semiconductor laser with a wavelength of 450nm is selected. The beam splitter is adjusted to make the intensity ratio of the object beam to the reference beam 1:2. The angle of the reflector is adjusted so that the angle between the two beams on the substrate surface is 18°, forming interference fringes with a period of approximately 728nm.

[0036] 2. Photoresist Coating: A 6-inch single-crystal silicon wafer was selected. Positive photoresist (model AZ6130) was spin-coated at a speed of 3500 rpm for 50 seconds to obtain a photoresist film with a thickness of approximately 280 nm.

[0037] 3. Holographic exposure: Holographic exposure is performed with an exposure dose of 70mJ / cm² for 250 seconds.

[0038] 4. Development and Etching: The exposed silicon wafer is developed in a 2.38% TMAH developer at 23-25℃ for 85 seconds. ICP etching is then performed with an SF6:O2 volume ratio of 7:1, a power of 450W, an etching time of 3 minutes, and an etching depth of approximately 180nm. Finally, residual photoresist is removed by oxygen plasma ashing to obtain the silicon hard template.

[0039] 5. Anti-sticking treatment: Prepare a 0.6wt% fluorinated silane anhydrous ethanol solution, spin-coat it onto the surface of the silicone hard template at a speed of 2800r / min for 30 seconds, and then dry it at 85℃ for 18 minutes.

[0040] 6. Preparation of PDMS soft template: Mix PDMS A and B adhesives at a mass ratio of 1:1 and stir at 700 r / min for 14 minutes. Pour the mixture onto the treated silicone hard template and cure on a hot plate at 110℃ for 50 minutes. After cooling, peel off to obtain a PDMS soft template with a 2.5cm × 2.5cm area array and a period of approximately 728nm.

[0041] Testing showed that the feature size accuracy of the PDMS soft template prepared in this embodiment was ±20nm, and the pattern consistency deviation within the array was ≤2.5%. The total cycle from the start of preparation to obtaining the soft template was approximately 1.5 hours, and the cost was approximately 1 / 60 of that of the electron beam exposure method.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for low-cost and rapid preparation of a sub-micron large-area nanoimprint template, characterized in that, Includes the following steps: (1) Construct a Mach-Zehnder holographic exposure optical path, which includes a laser, shutter, half-wave plate, polarizing beam splitter, power monitor, mirror, collimating mirror, pinhole filter and substrate, and adjust the angle between the object light and the reference light to 15°-25°, and the light intensity ratio to 1:1 to 1:

3. (2) Spin-coat photoresist on the surface of the silicon wafer, fix the silicon wafer on the exposure platform, perform holographic exposure, and record the interference fringe pattern on the photoresist layer; (3) The exposed silicon wafer is developed to remove the photoresist in the exposed area, and then the pattern is transferred to the silicon wafer by inductively coupled plasma etching to prepare a silicon hard template. (4) The silicon hard template is spin-coated with anti-adhesion liquid for anti-adhesion treatment, and then dried for later use; (5) Mix polydimethylsiloxane A glue and B glue at a mass ratio of 1:1, pour the mixture onto the surface of the silicone hard template treated with anti-adhesion, and peel it off after curing on a hot plate to obtain PDMS soft template. (6) Nanoimprinting is performed using the polydimethylsiloxane soft template.

2. The method for low-cost and rapid preparation of sub-micron large array nanoimprint template according to claim 1, characterized in that, In step (2), the photoresist is a positive photoresist, the spin coating speed is 3000-5000 r / min, the spin coating time is 30-60 s, and the photoresist film thickness is 200-300 nm; the exposure dose of the holographic exposure is 50-100 mJ / cm², and the exposure time is 150 s-600 s.

3. The method for low-cost and rapid preparation of sub-micron large-area nanoimprint template according to claim 1, characterized in that, In step (3), the developing solution used is a 2.38wt% tetramethylammonium hydroxide aqueous solution, the developing temperature is 23-25℃, and the developing time is 60-90s; the gas used for ICP etching is a mixture of SF6 and O2 with a volume ratio of 5:1 to 10:1, the etching power is 300-500W, the etching time is 1-5min, and the etching depth is 100-300nm.

4. The method for low-cost and rapid preparation of sub-micron large array nanoimprint template according to claim 1, characterized in that, In step (4), the anti-adhesion liquid used in the anti-adhesion treatment is a 0.5-1.0wt% fluorinated silane anhydrous ethanol solution, the spin coating speed is 2000-4000 r / min, the spin coating time is 30-60s, the drying temperature is 80-100℃, and the drying time is 10-20min.

5. The method of claim 1, wherein the method is characterized by, In step (5), the stirring speed when mixing polydimethylsiloxane A glue and B glue is 500-800 r / min, and the stirring time is 10-15 min; the hot plate curing temperature is 80-120℃, and the curing time is 30-60 min.

6. The method of claim 1, wherein the method is characterized by, In step (1), the period of the interference fringes is controlled to be 180-1000nm by adjusting the angle between the object light and the reference light to be within the range of 15°-25°; the duty cycle of the interference fringes is controlled to be 0.3-0.7 by adjusting the light intensity ratio to be within the range of 1:1 to 1:

3.

7. The method of claim 1, wherein the method is characterized by, In step (3), after the inductively coupled plasma etching is completed, the residual photoresist mask is removed by oxygen plasma ashing.

8. The method of claim 1, wherein the method is characterized by, In step (1), in the Mach-Zehnder holographic exposure optical path, the TE light emitted by the laser passes through the shutter and half-wave plate, and is then split into two beams by a polarization beam splitter. One beam passes through a mirror, a pinhole filter, and a collimating lens before reaching the substrate as the object light, and the other beam passes through a polarization beam splitter, a half-wave plate, a mirror, a pinhole filter, and a collimating lens before reaching the substrate as the reference light. The two beams interfere on the substrate surface to form interference fringes.

9. A nanoimprint template prepared according to the method of any one of claims 1 to 8, characterized in that, The template is a polydimethylsiloxane soft template with a micro-nano structure featuring a size of 180-1000 nm, an array size of centimeters, and a feature size accuracy of ±25 nm.

10. The nanoimprint template according to claim 9, wherein The template has an array size of 2.5cm × 2.5cm and a feature size accuracy of ±15nm to ±20nm.

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