CN110187599B

CN110187599B - Micro-lens mask and preparation method thereof

Info

Publication number: CN110187599B
Application number: CN201910590015.0A
Authority: CN
Inventors: 王军; 崔官豪; 刘贤超; 姬春晖; 苟君
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2019-07-02
Filing date: 2019-07-02
Publication date: 2020-04-07
Anticipated expiration: 2039-07-02
Also published as: CN110187599A

Abstract

The invention discloses a microlens mask and a preparation method thereof, belonging to the technical field of nano-photonic devices, and the method comprises the following steps: assembling a single-layer polystyrene microsphere on a substrate to form a first sample wafer; coating a first colloid on the first sample wafer, and etching the first colloid to expose part of the polystyrene microspheres to form a second sample wafer; removing the polystyrene microspheres on the second sample wafer to obtain a spherical cavity mold; filling a second photoresist in the spherical cavity mold, and shaping and exposing to solidify the second photoresist; and separating the second photoresist and the spherical cavity mold to obtain the reusable microlens mask. The microlens mask prepared by the invention can be repeatedly used in large-area auxiliary photoetching of micro-nano patterns, and has the advantages of low cost, short period, high efficiency and the like.

Description

Micro-lens mask and preparation method thereof

Technical Field

The invention relates to the technical field of nano photonic devices, in particular to a micro lens mask and a preparation method thereof.

Background

Under the development and application requirements of high-integration chips, plasma-based physical functional devices and the like, the large-area rapid preparation of micro-nano characteristic dimension structural patterns and arrays becomes a hot focus. Various micro-nano processes developed in recent years, such as electron and ion beam lithography, double/multi-beam interference lithography, near-field probe scanning lithography, nano-imprinting method and the like, bring huge economic benefits to the society and make great contribution to the promotion of technological development.

The traditional ultraviolet laser double/multi-beam interference lithography method has the advantages of low cost and high efficiency in the aspect of preparing micro-nano pattern arrays, but has the defect that the prepared patterns are single in appearance, such as conventional one-dimensional gratings and two-dimensional circular hole/column arrays. The micro-nano structure prepared by electron and ion beam photoetching method is various and flexible, but the price is high, so the micro-nano structure is more limited to be used in the scientific research field. The efficiency of the near-field probe scanning photoetching method is low, the problem that micro-nano patterns can not be rapidly and repeatedly prepared is solved by the nano-imprinting technology, but the preparation of a template is mostly finished by high-precision electron and ion beam photoetching, and the process is complex. In contrast, the microsphere array assisted lithography combines the traditional ultraviolet lithography and the participation of the microsphere structure as the unique point of the mask, so that the method has the characteristics of low cost and high efficiency, has more flexibility, and can prepare the micro-nano pattern arrays with more morphologies and three-dimensional structures, but the microspheres serving as the mask in the microsphere assisted lithography method need to be removed after each exposure, and then the microsphere mask needs to be repeatedly assembled again when a sample is manufactured every time, namely the microsphere array mask can not be reused, thereby limiting the wide application of the microsphere array mask to a certain extent.

The invention provides a preparation method of a micro-lens mask plate by using microspheres as an auxiliary mask and the fluidity and plasticity of a colloid material.

Disclosure of Invention

The invention aims to overcome the defect that a microsphere array mask in the prior art cannot be recycled, and provides a microlens mask and a preparation method thereof.

The purpose of the invention is realized by the following technical scheme: a preparation method of a micro-lens mask comprises the following steps:

s01: assembling a single-layer polystyrene microsphere on a substrate to form a first sample wafer;

s02: coating a first colloid on the first sample wafer, and etching the first colloid to expose part of the polystyrene microspheres to form a second sample wafer;

s03: removing the polystyrene microspheres on the second sample wafer to obtain a spherical cavity mold;

s04: filling a second photoresist in the spherical cavity mold, and curing the second photoresist;

s05: and separating the second photoresist and the spherical cavity mold to obtain the reusable microlens mask.

Specifically, assembling the monolayer polystyrene microspheres on the substrate further comprises:

s011: forming polystyrene microspheres which are closely arranged on a substrate;

s012: and etching the polystyrene microspheres in close arrangement to obtain the polystyrene microspheres in non-close arrangement.

Specifically, the gas-liquid surface assembly method or the spin coating method is adopted for forming the polystyrene microspheres which are closely arranged on the substrate.

Specifically, the etching of the polystyrene microspheres in close arrangement is performed by RIE etching to reduce the diameter of the polystyrene microspheres. Wherein, the power range of RIE etching is 30-150w, the gas pressure range is 1-12pa, and the flow rate of the passing gas is 20-150 sccm.

Specifically, the first colloid is a mixed solution colloid of PMMA and chloroform, and the thickness range is 800-4000 nm.

Specifically, curing the second photoresist includes covering the second photoresist with a clean glass sheet 6 to shape the second photoresist and UV exposing through the glass sheet 6 to cure the glue, and the UV exposure 7 dose may be in the range of 70-200mJ/cm 2.

Specifically, the second photoresist is a high-transparency high-molecular polymer with a thickness ranging from 1 um to 5um, and the filling manner of the second photoresist includes but is not limited to spin coating with a rotation speed ranging from 800 and 4000 rad/s.

Specifically, the etching of the first colloid is IBE etching employed. Wherein the IBE etching power range is 50-250w, the gas pressure range is 0.5-7pa, and the gas flow rate is 20-100 sccm.

Specifically, the step of removing the polystyrene microspheres on the second sample further comprises:

s031: and placing the second sample wafer on a heating table for heating, and recovering the flatness of the surface of the first colloid.

Specifically, the polystyrene microspheres on the second sample are removed by using cyclohexane and ultrasonic waves.

The micro-lens mask comprises a substrate and a plurality of first micro-lenses with spherical surfaces, the first micro-lenses and the substrate are integrally formed, and the first micro-lenses and the substrate are both made of high-transparency high-molecular polymers.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention utilizes the fluidity of high-transparent high molecular polymer (such as PMMA photoresist) to fill the microlens mask prepared by the spherical cavity mold, and the size of the microlens can reach sub-wavelength and below. When the light source irradiates, the great number of microlenses with high uniformity on the mask plate enable the incident light energy to be concentrated to the convergence center of each lens by the optical characteristics of the microlenses, so that when the microlens mask plate is used for exposure, each light beam convergence position has higher energy and smaller light spot size, and therefore, the photoetching effect with high resolution and good uniformity is obtained, and meanwhile, if the mask plate is controlled to move according to a certain track during exposure, an array pattern consistent with the moving track can be generated at one time, and the photoetching efficiency can be greatly improved.

(2) According to the invention, by controlling the thickness of the spin-coated photoresist, the etching time, the power and other parameters of RIE and IBE, the spherical radian of the micro-lens mask can be changed, the period and the unit size of the micro-lens mask can be tuned, and the size selection range of the prepared micro-lens mask is wide.

(3) According to the invention, the polystyrene microspheres which are closely arranged are formed on the substrate by a gas-liquid surface assembly method or a spin coating method, and then the polystyrene microspheres are etched by RIE to form a polystyrene microsphere array which is not closely arranged, so that the traditional mask plate does not need to be specially prepared for exposure.

(4) The microlens mask manufactured by the invention has simple preparation process, can be repeatedly used in large-area auxiliary photoetching of micro-nano patterns, and has low cost, short period and high efficiency.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention.

FIG. 1 is a schematic flow chart of the steps of the method of the present invention;

FIG. 2 is a top view of assembled compact microspheres on a silicon substrate;

FIG. 3 is a top view after reactive ion etching of dense microspheres;

FIG. 4 is a schematic illustration of spin coating a PMMA-chloroform mixture on a microsphere layer and sputter etching the treated surface with an ion beam;

FIG. 5 is a schematic cross-sectional view of a sample wafer after etching the surface of the sample wafer and heating the sample wafer to flatten the surface of the PMMA mixture film;

FIG. 6 is a schematic diagram of a spherical cavity mold obtained by removing the microspheres from the sample wafer;

FIG. 7 is a schematic view showing that PMMA photoresist is spin-coated on the sample wafer obtained after the above steps, and is covered with a cleaning glass slide for setting and the PMMA colloid is cured by UV exposure;

FIG. 8 is a schematic diagram of the mold and the solidified PMMA colloid being separated to obtain the prepared microlens mask;

FIG. 9 is a schematic view of a microlens reticle.

In the figure: 1-substrate, 2-polystyrene microsphere, 3-first colloid, 4-IBE etching method, 5-second photoresist, 6-glass sheet, 7-UV exposure, 8-microlens mask, 81-first microlens, 82-substrate

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that directions or positional relationships indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like are directions or positional relationships described based on the drawings, and are only for convenience of description and simplification of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

As shown in fig. 1, in embodiment 1, a method for manufacturing a microlens mask includes the following steps:

s01: assembling a single-layer polystyrene microsphere 2 array on a substrate 1 to form a first sample wafer; specifically, as shown in fig. 2, a clean and dry silicon substrate 1 is prepared, 25ml of polystyrene microspheres with 5% w/v diameter of 600nm are used, 0.4ml of absolute ethyl alcohol is added, the polystyrene microsphere 2 array which is closely arranged is assembled on the silicon substrate 1 by a gas-liquid surface assembly method, the size of the polystyrene microsphere 2 can be changed according to the size of a microlens mask 8 to be prepared, and the effect of assembling the single-layer polystyrene microsphere 2 array on the silicon substrate 1 is shown in fig. 2. Further, the RIE etching method is used to etch the polystyrene microsphere 2 array, so as to reduce the diameter of the polystyrene microsphere 2, and the polystyrene microsphere 2 array in the close arrangement is changed into the polystyrene microsphere 2 array in the non-close ordered arrangement, as shown in fig. 3. Furthermore, the power range of RIE etching is 30-150W, the gas pressure range is 1-12pa, the etching rate can be adjusted by changing the RIE etching power and the gas introduction rate and the like through the gas flow rate of 20-150sccm, the diameter change rate of the polystyrene microsphere 2 can be controlled, for example, the oxygen introduction rate is 100sccm under the gas pressure of 70W and 70mTorr, 4300s of polystyrene microsphere 2 is etched by RIE in the oxygen ion environment, and the diameter of the polystyrene microsphere 2 is changed from 600nm to about 500 nm.

S02: coating a first colloid 3 on the first sample wafer, and etching the first colloid 3 to expose part of the polystyrene microspheres 2 to form a second sample wafer; specifically, the method of coating the first colloid 3 includes, but is not limited to, spin coating, and the rotation speed range of the spin coating of the first colloid is 800-4000rad/s, preferably, the rotation speed of the spin coating of the first colloid is 4000rad/s, the thickness range of the first colloid 3 is 0.8-4 μm, and preferably, the thickness of the first colloid 3 is 800 nm; further, as shown in fig. 4, the IBE etching method 4 is adopted to etch the first colloid 3, the IBE etching method 4 has the characteristics of good directionality and good etching rate controllability, the etching depth is adjusted by controlling the IBE etching time and rate, and the polystyrene microspheres 2 with different depths are exposed in the air, so that the spherical radian of the microlens mask is changed. Wherein the IBE etching power range is 50-250w, the gas pressure range is 0.5-7pa, and the gas flow rate is 20-100 sccm. Further, the first colloid 3 is specifically PMMA powder and chloroform 10: 1, preparing mixed solution colloid.

S03: removing the polystyrene microspheres 2 on the second sample wafer to obtain a spherical cavity mold; specifically, cyclohexane at 35 ℃ is adopted to cooperate with ultrasonic waves to remove the polystyrene microspheres 2, and the polystyrene microspheres are washed by deionized water and then dried to obtain the orderly-arranged hemispherical cavity mold, as shown in fig. 6.

S04: filling a second photoresist 5 in the hemispherical cavity mold, and curing the second photoresist 5; specifically, the filling manner of the second photoresist 5 includes, but is not limited to, spin coating, the rotation speed range of the spin coating of the second photoresist is 800-4000rad/s, preferably, the rotation speed of the spin coating of the second photoresist is 4000rad/s, and the thickness of the second photoresist 5 is 1-5 μm; wherein curing the second photoresist comprises covering the second photoresist with a clean glass plate 6 to shape the second photoresist and curing the second photoresist by UV exposure through the glass plate 6, the dose of UV exposure 7 may be in the range of 70-200mJ/cm2, as shown in fig. 7. Further, the second photoresist 5 is a high-transparent high molecular polymer, such as a high-transparent high molecular polymer PMMA photoresist.

S05: and separating the second photoresist 5 and the hemispherical cavity mold to obtain the reusable microlens mask 8. Wherein, the size of the micro lens array on the micro lens mask 8 can reach sub-wavelength and below. The microlens mask prepared by the invention does not need to be repeatedly assembled with microlenses every time the exposure process is carried out, so the microlens mask can be repeatedly used in large-area auxiliary photoetching micro-nano patterns, and has low cost, short period and high efficiency.

Example 2

The embodiment has the same inventive concept as embodiment 1, and in embodiment 2, a method for manufacturing a microlens mask specifically includes the following steps:

s11: assembling a single-layer polystyrene microsphere 2 array on a substrate 1 to form a first sample wafer; specifically, a clean and dry silicon substrate 1 is prepared, 25ml of polystyrene microspheres with a diameter of 600nm of 5% w/v are used, 0.4ml of absolute ethanol is added, and the closely arranged array of polystyrene microspheres 2 is assembled on the silicon substrate 1 by an air-liquid surface assembly method, and it is understood that the method for assembling the monolayer array of polystyrene microspheres 2 on the substrate 1 herein includes, but is not limited to, the air-liquid surface assembly method, and other assembly methods such as a spin coating method, and the size of the polystyrene microspheres 2 can be changed according to the size of the microlens mask 8 to be prepared. Further, the RIE etching method is adopted to etch the polystyrene microsphere 2 array, the diameter of the polystyrene microsphere 2 is reduced, and the polystyrene microsphere 2 array which is arranged closely is changed into the polystyrene microsphere 2 array which is arranged non-closely and orderly. Furthermore, the power range of RIE etching is 30-150W, the gas pressure range is 1-12pa, the IBE etching rate can be adjusted by changing the RIE etching power and the gas introduction rate and the like through the gas flow rate of 20-150sccm, the diameter change rate of the polystyrene microsphere 2 is controlled, for example, the oxygen introduction rate is 100sccm under the pressure of 70W and 70mTorr, 4300s of polystyrene microsphere 2 is etched by RIE in the oxygen ion environment, and the diameter of the polystyrene microsphere 2 is changed from 600nm to about 500 nm.

S12: coating a first colloid 3 on the first sample wafer, and etching the first colloid 3 to expose part of the polystyrene microspheres 2 to form a second sample wafer; specifically, the method of coating the first colloid 3 includes, but is not limited to, spin coating, and the rotation speed range of the spin coating of the first colloid is 800-4000rad/s, preferably, the rotation speed of the spin coating of the first colloid is 4000rad/s, the thickness range of the first colloid 3 is 0.8-4 μm, and preferably, the thickness of the first colloid 3 is 800 nm; further, the IBE etching method 4 is adopted to etch the first colloid 3, the etching depth is adjusted by controlling the etching time and the etching speed, and the polystyrene microspheres 2 with different depths are exposed in the air, so that the spherical radian of the micro-lens mask is changed. Wherein the IBE etching power range is 50-250w, the gas pressure range is 0.5-7pa, and the gas flow rate is 20-100 sccm. Further, the first colloid 3 is specifically PMMA powder and chloroform 10: 1, preparing mixed solution colloid. As an option, the first colloid 3 is specifically PDMS.

S13: the second sample wafer is placed on the heating table for heating, and the flatness of the surface of the first colloid 3 is recovered. Wherein the heating temperature is 60-120 ℃, the heating time is 15-60 minutes, the heated second sample is kept still for 1 hour to solidify and attach the first colloid 3 on the silicon substrate 1, and the cross-sectional schematic diagram is shown in fig. 5.

S14: removing the polystyrene microspheres 2 on the second sample wafer to obtain a spherical cavity mold; specifically, cyclohexane at 35 ℃ is adopted to match with ultrasonic waves to remove the polystyrene microspheres 2, and the polystyrene microspheres are washed by deionized water and then dried to obtain the orderly-arranged spherical cavity mold. Further, the spherical cavity mold includes but is not limited to a hemispherical cavity mold, and spherical cavity molds with different central angles can be obtained by controlling the IBE etching time and rate to adjust the etching depth.

S15: filling a second photoresist 5 in the spherical cavity mold, and curing the second photoresist 5; specifically, the size of the microlens mask unit can be changed by controlling the thickness of the second photoresist, the size selection range of the prepared microlens mask is wide, the manner of filling the second photoresist 5 in the embodiment includes but is not limited to spin coating, the rotation speed range of the spin coating of the second photoresist is 800 and 4000rad/s, as a preference, the rotation speed of the spin coating of the second photoresist is 4000rad/s, and the thickness of the second photoresist 5 is 1-5 μm; wherein curing the second photoresist comprises covering the second photoresist with a clean glass plate 6 to shape the second photoresist and curing the second photoresist by UV exposure through the glass plate 6, the UV exposure 7 dose being in the range of 70-200mJ/cm 2. Further, the second photoresist 5 is a high-transparent high molecular polymer, such as a high-transparent high molecular polymer PMMA photoresist. As an option, an inorganic transparent material may be used instead of the second photoresist in this scheme, such as silicon dioxide. When the central angle of the spherical cavity in the spherical cavity mold is greater than or equal to 180 degrees, silicon dioxide is deposited into the spherical cavity mold to form the microlens mask.

S16: and separating the second photoresist 5 and the spherical cavity mold to obtain the reusable microlens mask 8. The micro-lens mask 8 can be obtained by preparing the micro-lens mask array in a top-down preparation mode and separating the second photoresist from the spherical cavity mold, and the size of the micro-lens array on the micro-lens mask 8 can reach sub-wavelength and below. The microlens mask prepared by the invention does not need to be repeatedly assembled with microlenses every time the exposure process is carried out, so the microlens mask can be repeatedly used in large-area auxiliary photoetching micro-nano patterns, and has low cost, short period and high efficiency.

Example 3

The embodiment provides a microlens mask, specifically, as shown in fig. 2, the microlens mask 8 includes a substrate 82 and a plurality of first microlenses 81 whose surfaces are spherical surfaces, and the first microlenses 81 and the substrate 82 are integrally formed.

Further, the first microlens 81 and the substrate 82 of the microlens mask 8 are made of a high-transparency high-molecular polymer, such as a high-transparency high-molecular polymer PMMA photoresist, and an inorganic transparent material, such as silicon dioxide. Because the micro-lens mask 8 is prepared by the fluidity of the high-transparency high-molecular polymer, the first micro-lens on the micro-lens mask 8 can concentrate the incident light converging center, so that when the micro-lens mask 8 is used for exposure, each light beam converging part has higher energy and smaller light spot size, and the photoetching effect with high resolution and good uniformity is obtained.

Furthermore, the invention utilizes the fluidity of the high-transparent high molecular polymer (such as PMMA photoresist) to fill the microlens mask 8 prepared by the spherical cavity mold, and the size of the first microlens array formed by the first microlenses 81 can reach sub-wavelength and below. Because the first micro lens 81 is not required to be repeatedly assembled when the micro lens mask prepared by the invention is subjected to the exposure process every time, the micro lens mask 8 can be repeatedly used in large-area auxiliary photoetching micro-nano patterns, and has low cost, short period and high efficiency. Furthermore, the micro-lens mask 8 is controlled to move according to a certain track during exposure, so that an array pattern consistent with the moving track can be generated at one time, and the photoetching efficiency can be greatly improved.

The above detailed description is for the purpose of describing the invention in detail, and it should not be construed that the detailed description is limited to the description, and it will be apparent to those skilled in the art that various modifications and substitutions can be made without departing from the spirit of the invention.

Claims

1. A method for preparing a micro-lens mask is characterized by comprising the following steps: the method comprises the following steps:

assembling a single-layer polystyrene microsphere (2) on a substrate (1) to form a first sample wafer;

coating a first colloid (3) on the first sample wafer, and etching the first colloid (3) to expose part of the polystyrene microspheres (2) to form a second sample wafer;

removing the polystyrene microspheres (2) on the second sample wafer to obtain a spherical cavity mold;

filling a second photoresist (5) in the spherical cavity mould, and curing the second photoresist (5);

and separating the second photoresist (5) and the spherical cavity mold to obtain the reusable micro-lens mask (8).

2. The method for preparing a microlens mask according to claim 1, wherein: the assembling of the monolayer polystyrene microspheres (2) on the substrate (1) further comprises:

forming polystyrene microspheres (2) which are closely arranged on a substrate (1);

and etching the polystyrene microspheres (2) which are arranged closely to obtain the polystyrene microspheres (2) which are not arranged closely.

3. The method for preparing a microlens mask according to claim 2, wherein: the polystyrene microspheres (2) which are tightly arranged on the substrate (1) adopt a gas-liquid surface assembly method or a spin coating method.

4. The method for preparing a microlens mask according to claim 2, wherein: the RIE etching method is adopted for etching the polystyrene microspheres (2) which are closely arranged so as to reduce the diameter of the polystyrene microspheres (2).

5. The method for preparing a microlens mask according to claim 1, wherein: the first colloid (3) is specifically a mixed solution colloid of PMMA and chloroform.

6. The method for preparing a microlens mask according to claim 1, wherein: the second photoresist (5) is a high-transparency high-molecular polymer.

7. The method for preparing a microlens mask according to claim 1, wherein: the etching of the first colloid (3) is an IBE etching (4).

8. The method for preparing a microlens mask according to claim 1, wherein: the step of removing the polystyrene microspheres on the second sample sheet (2) further comprises the following steps: and (3) placing the second sample wafer on a heating table for heating, and recovering the flatness of the surface of the first colloid (3).

9. The method for preparing a microlens mask according to claim 1, wherein: and the step of removing the polystyrene microspheres (2) on the second sample sheet is to remove the polystyrene microspheres (2) by adopting cyclohexane and ultrasonic waves.

10. The microlens mask prepared by the method for preparing a microlens mask according to any one of claims 1 to 9, characterized in that: the micro-lens mask (8) comprises a substrate (82) and a plurality of first micro-lenses (81) with spherical surfaces, the first micro-lenses (81) and the substrate (82) are integrally formed, and the first micro-lenses (81) and the substrate (82) are made of high-transparency high-molecular polymers.