Method for replicating microstructure patterns

Abstract

The method includes the steps of preparing a first multilayer structure including a substrate, a thin film, and a first photoresist layer, preparing a second multilayer structure including a mold having a microstructure pattern and a second photoresist layer, combining the first multilayer structure and the second multilayer structure such that the first photoresist layer contacts the second photoresist layer, and applying pressure and temperature. Articles including the microstructure patterns are also disclosed.

Description

Technical Field

[0001] [Related Applications] This application claims priority to U.S. Patent Application No. 17 / 338,144, filed on June 3, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure generally relates to a method comprising the steps of providing a first multilayer structure including a substrate, a thin film, and a first photoresist layer; providing a second multilayer structure including a mold having a microstructural pattern and a second photoresist layer; combining the first multilayer structure and the second multilayer structure such that the first photoresist layer contacts the second photoresist layer; and applying pressure and temperature. Also disclosed are articles including a microstructural pattern.

Background Art

[0003] The polymer-on-glass replication process or stamping process can be used to create diffuser structures. When an etching process follows, it is desirable to have a zero-base portion or a negligible thickness (e.g., on the order of hundreds of nanometers) of the polymer layer. In an etching process following the replication of a microstructure, the etching process window needs to be centered on the depressions / protrusions of the microstructure within the polymer layer. Controlling the base portion of the polymer layer after replication is difficult, and subsequent control of an etching process for a thin film such as a high refractive index material becomes difficult.

Brief Description of the Drawings

[0004] The features of the present disclosure are exemplarily shown in the following figures and are not limited thereto. In these figures, the same numerals indicate the same elements, that is, [Figure 1A] a first multilayer structure and a second multilayer structure according to one aspect of the present invention. [Figure 1B]1A-1C illustrate steps of combining a first multi-layer structure and a second multi-layer structure according to one embodiment of the present invention. [Figure 1C] FIG. 13 illustrates removing the mold from the combined first and second multi-layer structures. [Figure 1D] FIG. 13 illustrates the steps of irradiating the combined photoresist stack with a flood exposure from a collimated light source and developing the photoresist stack to expose a surface portion of the thin film. [Figure 1E] FIG. 2 illustrates an etching step. [Figure 2A] FIG. [Figure 2B] FIG. 2B illustrates a step of applying a third photoresist layer onto the mold of FIG. 2A. [Figure 2C] FIG. 13 illustrates the step of applying a fourth photoresist layer. [Figure 2D] FIG. 1B shows the first multilayer structure of FIG. 1A. [Figure 3A] 1A-1C illustrate steps for disposing a thin film on a substrate. [Figure 3B] FIG. 1B illustrates the step of applying a photoresist layer onto the thin film to form the second multi-layer structure of FIG. 1A. Summary of the Invention

[0005] In one aspect, a method for replicating a microstructure pattern is disclosed, the method comprising the steps of preparing a multi-layer structure including a substrate, a thin film, and a positive tone photoresist, preparing a thermally conductive mold having a microstructure pattern, and applying the thermally conductive mold to the multi-layer structure under pressure and temperature, wherein the microstructure pattern of the thermally conductive mold is replicated on the positive tone photoresist of the multi-layer structure.

[0006] In another aspect, an article is disclosed that includes a substrate and a thin film having a microstructured pattern.

[0007] Additional features and advantages of the various embodiments will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the various embodiments. The objectives and other advantages of the various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the specification.

Best Mode for Carrying Out the Invention

[0008] For purposes of simplification and illustration, the present disclosure will mainly be described with reference to its examples. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be readily apparent that the present disclosure may be practiced without these specific details. In other instances, some methods and structures are not described in detail so as not to unnecessarily obscure the present disclosure.

[0009] Furthermore, the elements depicted in the accompanying figures may include additional components, and some of the components described in these figures may be removed and / or modified without departing from the scope of the present disclosure. Additionally, the elements depicted in the figures may not be drawn to scale, and thus, the elements may have different sizes and / or configurations than those shown in the figures.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the various embodiments of the present teachings. In its broad and diverse embodiments, what is disclosed herein are articles, as well as methods of manufacturing and using the articles.

[0011] The present disclosure describes a method comprising the steps of preparing a first multilayer structure 16 including a substrate 14, a thin film 12, and a first photoresist layer 10a; preparing a second multilayer structure 17 including a mold (molding die) 18 having a microstructural pattern 20a and a second photoresist layer 10b; combining the first multilayer structure 16 and the second multilayer structure 17 such that the first photoresist layer 10a contacts the second photoresist layer 10b; and applying pressure and temperature.

[0012] The second microstructure layer 17 may include a mold 18 having a microstructural pattern 20a and a second photoresist layer 10b. The mold 18 can be made of a material capable of receiving and holding the microstructural pattern 20a. Non-limiting examples of materials include metals, semiconductors, nickel, silicon, dielectrics such as fused silica, glass, quartz, and combinations thereof. In one aspect, the mold 18 can be made of a conductive material. In another aspect, the mold 18 can be made of a thermally conductive material.

[0013] The microstructural pattern 20a can be a random or periodic pattern. In one aspect, the microstructural pattern 20a can be a binary (two-valued) pattern. In another aspect, the microstructural pattern 20a can be a grayscale non-binary pattern. The microstructural pattern 20a can include various shapes, forms, images, depressions, protrusions, and combinations thereof of various sizes. The microstructural pattern 20a can include a uniform portion and an irregular portion. For example, as shown in FIG. 1A, the microstructural pattern 20a includes three separate portions of triangular depressions uniformly separated from each other by flat portions.

[0014] In one aspect, the mold 18 can include a release agent (not shown) applied as a coating over the microstructural pattern 20a. The release agent can be a hydrophobic self-assembled monolayer such as a low surface energy fluoropolymer or a hydrophobic silane. The release agent can be applied to the mold by any deposition process capable of depositing the release agent in the depressions / projections of the microstructural pattern 20a. Non-limiting examples of suitable deposition processes include spin coating, dip coating, chemical vapor deposition, physical vapor deposition such as sputtering or thermal evaporation, and physical application such as buffing the surface of the microstructural pattern 20a with the release agent.

[0015] The second photoresist layer 10b of the second multilayer structure 17 can have a replicated microstructural pattern 20b, and the base portion 22 of the second photoresist layer 10b does not have the replicated microstructural pattern 20b. The replicated microstructural pattern 20b can be the inverse pattern of the microstructural pattern 20a of the mold 18. For example, while the microstructural pattern 20a includes three separate portions of triangular-shaped depressions, the microstructural pattern 20b includes three separate portions of triangular-shaped protrusions. In one aspect, the second photoresist layer 10b can be adjacent to (sharing a common boundary with), on, and / or nested with the mold 18.

[0016] The first photoresist layer 10a and the second photoresist layer 10b can be made of the same material or different materials. In one aspect, the first photoresist layer 10a and the second photoresist layer 10b can be made of the same material but can have different viscosities before being applied as layers.

[0017] The first multilayer structure 16 can include a substrate 14, a thin film 12, and a first photoresist layer 10a. The thin film 12 can be any thin film, including a single layer of material and / or a multilayer stack. In one embodiment, the thin film 12 can be a high refractive index material thin film, i.e., a thin film made from a material having a refractive index of about 2 to about 4. In one embodiment, the thin film 12 can have a gradient or continuous change in refractive index, or a periodic refractive index profile in the material. The thin film 12 can be present at a thickness ranging from about 1 micron to about 20 microns, for example, from about 1 micron to about 15 microns, and as a further example, from about 3 microns to about 10 microns. The thin film can be present on the surface of the substrate 14 and / or on the surface of the first photoresist layer 10a.

[0018] In another embodiment, the thin film 12 can be a multi-layer stack that can include one or more layers of reflector material, magnetic material, dielectric material, and absorbing material.

[0019] Substrate 14 can be any material capable of receiving multiple layers. In one embodiment, substrate 14 can be a transparent material. Non-limiting examples of suitable substrate materials include glasses and polymers such as polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene, amorphous copolyester, polyvinyl chloride, liquid silicone rubber, cyclic olefin copolymers, ionomer resins, transparent polypropylene, fluorinated ethylene propylene, styrene methyl methacrylate, styrene acrylonitrile resin, polystyrene, and methyl methacrylate-acrylonitrile-butadiene styrene. Substrate 14 can be present at a thickness ranging from about 50 microns to about 2000 microns, for example, from about 100 microns to about 1500 microns, and as a further example, from about 150 microns to about 1000 microns.

[0020] As shown in FIGS. 1A and 1B, the first multilayer structure 16 and the second multilayer structure 17 can be combined such that the first multilayer structure 16 contacts the second multilayer structure 17. In one aspect, the outer surface of the second photoresist layer 10b of the second multilayer structure 17 can be adjacent to and / or present on the outer surface of the first photoresist layer 10a of the first multilayer structure 16.

[0021] The method can include applying pressure and temperature to the first multilayer structure 16 while in contact with the second multilayer structure 17. The pressure can range from about 1 PSI to about 20 PSI, such as from about 1 PSI to about 15 PSI, and as a further example, from about 3 PSI to about 10 PSI. The temperature can range from about 60°C to about 90°C, such as from about 65°C to about 85°C. The contact time can range from about 1 minute to about 60 minutes, such as from about 2 minutes to about 55 minutes, and as a further example, from about 5 minutes to about 50 minutes.

[0022] As shown in FIG. 1C, the method can include removing the mold 18. The first photoresist layer 10a and the second photoresist layer 10b can bond to form a photoresist stack 10c that, for example, does not contain air pockets or bubbles between the first multilayer structure 16 and the second multilayer structure 17. The photoresist stack 10c can include a replicated fine structure pattern 20b and a base portion 22 of the (former) second photoresist layer 10b that does not have the replicated fine structure pattern 20b.

[0023] As shown in FIG. 1D, the method may include subjecting the combined photoresist stack 10c to a flood exposure using a collimated light source 24, which exposes the replicated microstructure pattern 20b and the base portion 22 of the photoresist stack 10c that does not have the replicated microstructure pattern 20b. The collimated light source 24 may be a light source that emits collimated light, such as a photomask aligner lamp, a dedicated i-line UV exposure tool, or a UV-LED / laser setup. In another embodiment, the collimated light source may be a light source that emits collimated light, such as a lens or mirror that receives diffuse light and emits collimated light. The application of the flood exposure may be followed by a subsequent development step to develop the base portion 22 of the photoresist stack 10c to completion or near completion, such that the surface portion 26 of the thin film 12 may be fully exposed or may be located directly below the replicated microstructure pattern 20b by hundreds of nanometers to a few microns. In one embodiment, after irradiation with collimated light and subsequent development steps, the structure includes the substrate 14, the thin film 12, and a replicated microstructure pattern 20b adjacent to or on the surface of the thin film 12. In one embodiment, the base portion 22 of the photoresist stack 10c is not present. As shown in FIG. 1E, the method also includes etching the photoresist stack 10c and the thin film 12 to form an etching microstructure pattern 20b from the photoresist stack 10c into the thin film 12. After etching, the thin film 12 includes portions having the replicated microstructure pattern 20c and / or portions having the original thickness of the thin film 12. There may be portions that do not include the thin film 12, i.e., portions where the thin film 12 is not present. The etching step can be performed using any technique that simultaneously etches the photoresist material and the underlying thin film 12. Non-limiting examples of suitable etching techniques include reactive ion etching (RIE), inductively coupled plasma-reactive ion etching (ICP-RIE), and ion milling.

[0024] The etched fine structure pattern 20c in the thin film 12 may have a reverse pattern to the fine structure pattern 20a of the mold 18, and may or may not have the same aspect ratio. The replicated fine structure pattern 20b in the photoresist stack 10c may have a reverse pattern to the fine structure pattern 20a of the mold 18, or may be substantially identical. The etched fine structure pattern 20c in the thin film 12 may have the same characteristics as the replicated fine structure pattern 20b of the photoresist stack 10c, and may or may not have the same aspect ratio.

[0025] The method also includes the step of creating a second multilayer structure 17. As discussed herein, the mold 18 can include a release agent that is applied as a release coating (not shown) to the surface of the mold, such as the surface of the mold 18 including the fine structure pattern 20a as shown in FIG. 2A. Release agents are disclosed herein. The applied release coating can be treated, such as by ultraviolet ozone treatment or mild oxygen plasma, to make the surface of the release coating hydrophilic. This can be done to facilitate the application of the photoresist layer 10d onto the mold.

[0026] As shown in FIG. 2B, the method can include the step of applying a third photoresist layer 10d onto the release coating. The third photoresist layer 10d can be applied to cover the surface of the mold 18 and / or the release coating with a coverage rate of about 50% to about 100% and with a thickness sufficient to cover. The third photoresist layer 10d can be applied with a thickness in the range of about 1 micron to about 20 microns, for example, about 1 micron to about 15 microns, and as a further example, about 2 microns to about 10 microns. The third photoresist layer 10d can be applied by a vapor deposition process. Non-limiting examples of the film-forming process include a spin-coating process, a spray-coating process, and a dip-coating process.

[0027] In particular, the third photoresist layer 10d can be applied such that all depressions / protrusions of the microstructure pattern 20a are imitated in the third photoresist layer 10d. The third photoresist layer 10d can include a surface that conforms to the microstructure pattern 20a of the mold, and can also include a conformable or planar side surface that can receive the fourth photoresist layer 10e.

[0028] After application, the third photoresist layer 10d can be heated / baked at a temperature ranging from about 50°C to about 90°C for a time ranging from about 1 second to about 30 minutes. Heating / baking can be performed on a hot plate or in an oven. In one embodiment, the third photoresist layer 10d can be spin-coated and baked on a hot plate at 75°C for about 2 minutes.

[0029] After the third photoresist layer 10d is heated / baked, a fourth photoresist layer 10e can be applied on the surface of the third photoresist layer 10d, as shown in FIG. 2C. The third photoresist layer 10d and the fourth photoresist layer 10e can comprise the same or different materials. The fourth photoresist layer 10e can be applied to provide a flat outer surface. The fourth photoresist layer 10e can be applied to a thickness ranging from about 1 micron to about 20 microns, for example, from about 1 micron to about 15 microns, and further example, from about 2 microns to about 10 microns. The fourth photoresist layer 10e can be applied by a vapor deposition process. Non-limiting examples of vapor deposition processes include spin coating, spray coating, and dip coating. The fourth photoresist layer 10e can be successively spin coated and baked on a hotplate at 75°C for about 2 minutes to form the photoresist stack 10b. Any combination of heating / baking time and temperature ranging from 30 seconds to 5 minutes and 60° C. to 95° C., respectively, can be used to bake the photoresist interlayers (10d and 10e).

[0030] After application of the fourth photoresist layer 10e, the structure (including the mold 18 with optional release coating, the third photoresist layer 10d, and the fourth photoresist layer 10e) can be heated / baked at a temperature ranging from about 50°C to about 90°C for a time ranging from about 1 second to about 30 minutes. Heating / baking can be performed on a hot plate or in an oven. In this manner, the second multilayer structure 17 can be formed.

[0031] The method may also include forming a first multi-layer structure 16. As shown in FIG. 3A, a thin film 12 may be disposed on a surface of a substrate 14. The thin film 12 and the substrate 14 may be as described herein. As shown in FIG. 3B, a first photoresist layer 10a may be applied to a surface of the thin film 12 to form a first multi-layer structure 16. The first photoresist layer 10a may be as described herein. In one embodiment, each layer of the first multi-layer structure 16 is planar and / or smooth.

[0032] The article can include a substrate and a thin film that includes a replicated microstructured pattern.

[0033] From the above description, those skilled in the art can appreciate that the present teachings can be implemented in a variety of forms. Thus, although these teachings have been described with reference to specific embodiments and examples thereof, the true scope of the present teachings should not be so limited. Various changes and modifications can be made without departing from the scope of the teachings herein.

[0034] The present disclosure is intended to be broadly interpreted. The present disclosure is intended to disclose equivalents, means, systems, and methods for achieving the coatings, devices, activities, and mechanical actions disclosed herein. For each coating, device, layer, article, method, means, mechanical element, or mechanism disclosed, the present disclosure is intended to encompass and teach equivalents, means, systems, and methods for implementing the many aspects, mechanisms, and devices disclosed herein. Furthermore, the present disclosure relates to methods and articles formed by the methods and their many aspects, features, and elements. The present disclosure is intended to encompass equivalents, means, systems, and methods of using articles, such as optical devices, and their many aspects, consistent with the description and spirit of the operations and functions disclosed herein. The claims of this application are similarly intended to be broadly interpreted. The description of the invention in its many embodiments herein is merely exemplary in nature, and thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not considered to depart from the spirit and scope of the invention.

Claims

1. 1. A method comprising the steps of: providing a first multi-layer structure including a substrate, a thin film, and a first photoresist layer; providing a second multi-layer structure including a mold having a microstructured pattern and a second photoresist layer having a surface that matches the microstructured pattern of the mold to form a replicated microstructured pattern; combining the first multi-layer structure and the second multi-layer structure such that the first photoresist layer contacts the second photoresist layer; applying pressure and temperature; A method comprising:

2. 2. The method of claim 1, wherein the second photoresist layer has a base portion that does not have the replicated microstructure pattern.

3. 10. The method of claim 1, wherein the thin film is a thin film of a high refractive index material.

4. The method of claim 1 , wherein the mold having the microstructured pattern is coated with a release agent.

5. The method of claim 1 further comprising removing the mold.

6. 3. The method of claim 2, wherein the first photoresist layer and the second photoresist layer combine to form a photoresist stack that is free of air pockets.

7. 7. The method of claim 6, wherein the photoresist stack comprises the replicated microstructure pattern and the base portion without the replicated microstructure pattern.

8. 7. The method of claim 6, further comprising the steps of: irradiating the photoresist stack with a flood exposure using a collimated light source; and developing the photoresist stack; The method, wherein collimated light illuminates the replicated microstructure pattern and the base portion of the photoresist stack that does not contain the replicated microstructure pattern.

9. 9. The method of claim 8, further comprising etching the photoresist stack and the thin film to form the microstructure pattern etched from the photoresist stack into the thin film.

10. In the method according to claim 9, the etched fine structure pattern of the thin film has an inverse pattern, which may or may not have the same aspect ratio as the fine structure pattern of the mold. The replicated fine structure pattern of the photoresist stack has an inverse pattern while being substantially the same as the fine structure pattern of the mold. Also, The etched fine structure pattern in the thin film has the same pattern, which may or may not have the same aspect ratio as the replicated fine structure pattern in the photoresist stack. A method.

11. In the method according to claim 1, the second multilayer structure is formed by applying a release coating to the mold and subjecting the surface of the applied release coating to a treatment for making it hydrophilic. A method.

12. A method according to claim 11, further comprising the step of applying a third photoresist layer on the release coating.

13. A method according to claim 12, further comprising the step of heating at a temperature in the range of about 50°C to about 90°C for a time in the range of about 1 second to about 30 minutes after applying the third photoresist layer.

14. A method according to claim 13, further comprising the step of applying a fourth photoresist layer on the third photoresist layer after heating the third photoresist layer, wherein both the third photoresist layer and the fourth photoresist layer together form the second photoresist layer. A method.

15. A method according to claim 14, further comprising the step of heating at a temperature in the range of about 50°C to about 90°C for a time in the range of about 1 second to about 30 minutes after applying the fourth photoresist layer.

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