CN103676473B - Method for preparing metal pattern on curved surface by combining nano-imprinting with wet etching - Google Patents

Abstract

The invention discloses a method for preparing a metal pattern on a curved surface by combining nanoimprint lithography with wet etching. The method comprises the steps of firstly evaporating a layer of metal on a curved surface, then impressing patterns on the metal through a transfer method, etching away a residual layer through a reactive ion etching method, etching the metal to a substrate by taking an impressing glue as a mask, and then removing the impressing glue on the upper layer of the metal pattern through the reactive ion etching to obtain the metal pattern. The method is simple and easy to implement, can replace the lift-off process to prepare the metal pattern on a plane, is less prone to damage the integrity of the pattern and reduces the occurrence of defects compared with the common lift-off process; and metal patterns can be prepared on the curved surface, which cannot be realized by the lift-off process. The invention has wide application prospect in the fields of manufacturing fiber Bragg gratings, refraction/diffraction mixed optical elements, nano-electromechanical systems and the like.

Description

Method for preparing metal patterns on curved surfaces by combining nanoimprinting with wet etching

technical field

The invention relates to a method for preparing a metal pattern on a curved surface by using nanoimprint technology combined with wet etching.

Background technique

Recently, the preparation of nanostructures on curved and complex surfaces has attracted more and more attention, especially in the fields of artificial compound eyes, hemispherical electronic eye cameras, photovoltaic devices, image sensor arrays, micro actuators and fiber optic sensors. widely. In 1995, since Steven Y. Chou and others invented nanoimprint technology, nanoimprint technology has attracted the attention of many researchers and engineers in the field of microstructure production due to its advantages of high efficiency, high resolution and low cost. . Although many micro-nanofabrication techniques can fabricate patterned nanostructures on planar substrate surfaces, most of these techniques are not suitable for fabricating nanopatterns on non-planar substrate surfaces. Therefore, it is urgent to develop a low-cost and reliable method for preparing curved surface nanopatterns. At present, various nano-patterns can be imprinted on curved surfaces through elastomeric soft templates, but so far, no matter what kind of lithography or imprinting technology is used, metal patterns cannot be transferred to curved surfaces.

The commonly used metal pattern preparation process is realized by lift-off process. The process is to use thermoplastic polymer as the lift-off layer, spin-coat the thermoplastic polymer solution on the substrate, and then directly heat emboss, or spin-coat silicon-containing thermosetting embossing glue on it, through reactive ion etching After removing the residual layer by etching and evaporating the metal, the metal on the remaining polymer is removed by using the solubility of the thermoplastic polymer in an organic solvent, so as to obtain a metal pattern on the substrate. The lift-off process needs to obtain a uniform lift-off layer, and it is impossible to use the spin-coating process to obtain a uniform film on the curved surface; while using a soft template for curved surface imprinting, only UV-curable imprinting glue can be used for embossing, and After the imprinting glue is cured under ultraviolet light, a cross-linked network is formed, so that it can no longer be dissolved in organic solvents and cannot be lifted off.

Contents of the invention

Aiming at the deficiencies in the prior art, the object of the present invention is to propose a method for preparing a metal structure on a curved surface.

The method for preparing a metal structure on a curved surface proposed by the present invention is based on an ultraviolet nanoimprint combined with a wet etching method. It is characterized in that first a layer of metal film is vapor-deposited on the curved surface, and then the structure is imprinted on the metal film by a double transfer method using a soft imprint template and cured by ultraviolet light. The residual layer is removed by etching, and after the metal is exposed, the remaining The polymer is used as an etching mask, the metal is wet etched, and the final metal structure is obtained after removing the polymer mask by reactive ion etching.

Concrete technical scheme of the present invention is as follows:

The method for preparing a metal pattern on a curved surface by combining nanoimprinting with wet etching, the specific steps are as follows:

1) First, clean the surface of the curved surface material with deionized water, and after drying, evaporate a layer of metal film on the curved surface material by electron beam evaporation or magnetron sputtering. The metal can be gold, silver, copper, aluminum or Chromium, with a thickness of 1 to 100 nanometers;

2) Spin-coat a layer of UV-curable imprinting glue on the surface of the clean silicon wafer. The UV-curing nano-imprinting glue is a prepolymer containing (meth)acrylate groups, The solution of the body or the mixture of the former two in the high boiling point solvent of the ultraviolet photoinitiator;

3) Cover the flexible nano-imprint template on the spin-coated imprint glue, and cover it on the metal-coated curved surface prepared in step 1) after 1-5 minutes, and UV-cure;

4) After the embossing glue is cured, remove the embossed soft template on the surface to obtain a polymer imprinted structure on the curved surface, and there is a uniform metal film under the imprinted structure;

5) Use oxygen plasma for reactive ion etching to remove the imprinting glue;

6) Wet etching is carried out in the etching solution with the cured polymer as a mask;

7) Reactive ion etching is performed with oxygen plasma to remove the solidified polymer, thereby obtaining a metal pattern on the curved surface.

When the evaporated metal is gold or silver, the composition of the wet etching solution is an aqueous solution of ferric nitrate nonahydrate and thiourea, and its pH value is adjusted to 1-5 with dilute hydrochloric acid; when the evaporated metal is copper, wet The composition of the wet etching solution is an aqueous solution of ferric chloride; when the evaporated metal is chromium, the composition of the wet etching solution is a glacial acetic acid solution of ammonium cerium nitrate.

The invention is simple and easy, and can replace the lift-off process to prepare metal patterns on a plane, which is less likely to damage the integrity of the graphics and reduce the occurrence of defects than the commonly used lift-off process; it can also prepare and prepare metal patterns on curved surfaces, and Patterning on curved surfaces is not possible with lift-off processes. The method of the present invention not only utilizes the ultraviolet curability of the existing embossing glue, but also can obtain high-resolution nano-patterns on the curved surface without lifting off the process, thereby laying a solid foundation for the preparation of various new micro-nano device components. It has broad application prospects in the manufacture of fiber Bragg gratings (fiberBragggrating), hybrid optical elements (HybridOptics) and nanoelectromechanical systems (NEMS). So far, there have not been any reports of this method.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

detailed description

The method will be further described below in conjunction with the accompanying drawings.

The present invention proposes a novel metal pattern preparation method, which uses metal vapor deposition to evenly coat a layer of metal film on the curved surface, and then prepares a polymer on the metal film by double transfer embossing method on the curved surface. Afterwards, the residual layer is removed by reactive ion etching to expose the substrate, and the remaining polymer is used as a mask for wet etching to etch the underlying metal film to form the desired pattern. The specific operation steps are as follows:

(1) Evaporation of metal on the curved surface

First, a layer of metal is plated on the curved surface, and the metal can be gold, silver, copper, aluminum, or chrome. The method of electron beam evaporation can be adopted, and the method of magnetron sputtering can also be adopted, and the thickness of the evaporated metal is 1-100 nanometers.

(2) Double transfer method imprints patterns on curved surfaces

First, spin-coat a layer of UV-curable embossing glue on the silicon wafer. The embossing glue can use various conventional silicon-free liquid UV-curable monomers or prepolymers, including but not limited to CN975, CN996, etc. Then cover it with a soft template made of polydimethylsiloxane, uncover it after 1 to 5 minutes, and cover it on a metal-coated curved surface, and put it under the condition of nitrogen protection under a high-pressure mercury lamp Curing under irradiation. After the imprint glue is cured, the template is peeled off to obtain the polymer structure.

(3) Wet etching prepares metal structures on curved surfaces

Oxygen plasma etching is used to remove the residual layer of the polymer structure, and after exposing the underlying metal, the metal is placed in the etching solution, etched until the substrate is exposed, and then the polymer is removed by oxygen plasma etching to obtain Metal pattern on the surface.

In this embodiment, a gold grating structure is prepared on a curved surface by combining nanoimprinting with wet etching.

The substrate with a curved surface can be silicon, silicon dioxide, silicon nitride, and plastics such as polyethylene, polypropylene, polymethyl methacrylate, and polyimide. Firstly, 30 nanometer gold is deposited on the curved surface by electron beam evaporation, and it is set aside.

In addition, 80 nanometers of CN975 (Sartomer Company) containing 3% photoinitiator were spin-coated on the silicon wafer, and the polydimethylsiloxane soft template was covered on it. The structure was a grating structure with a period of 550 nanometers. The groove depth is 110 nm. After 3 minutes, the soft template was removed, and then the soft template was covered on the gold-plated curved surface. After 15 minutes of UV curing under the protection of nitrogen, a 100-watt high-pressure mercury lamp was used, and the soft template was removed to obtain the imprinting adhesive. structure.

The above curved surface imprinted with the structure was dry-etched in oxygen plasma for 15 seconds, the residual layer of the imprinted structure was removed, and wet-etched in the etching solution for 5 minutes. The etching solution was Fe( Aqueous solution of NO ₃ ) ₃ .9H ₂ O and 30mmol/L thiourea.

Claims (5)

1. The method for preparing a metal pattern on a curved surface by combining nanoimprinting with wet etching, is characterized in that the specific steps are as follows: 1) First, clean the surface of the curved surface material with deionized water, and after drying, form a layer of metal film on the curved surface material by electron beam evaporation or magnetron sputtering; 2) Spin-coat a layer of UV-curable embossing glue on the surface of the clean silicon wafer; 3) Cover the flexible nano-imprint template on the spin-coated imprint glue, peel it from the surface of the silicon wafer after 1-5 minutes, and cover it on the curved surface with metal prepared in step 1), and uv curing; 4) After the embossing glue is cured, remove the embossing soft template on the surface, and then obtain the embossing glue with structure on the curved surface, and there is a uniform metal film under the embossing glue; 5) Reactive ion etching is carried out using oxygen plasma to remove the residual layer of imprinting glue and expose the underlying metal; 6) Wet etching with embossing glue as a mask in the etching solution; 7) Reactive ion etching is carried out with oxygen plasma to remove the embossing glue, so as to obtain a metal pattern on the curved surface. 2. The nano-imprinting method according to claim 1 in combination with wet etching to prepare a metal pattern on a curved surface, wherein step 2) the UV-cured nano-imprinting glue of spin coating is a pre-polymer containing acrylate group A solution of a polymer, an acrylate group-containing monomer, or a mixture of the two in a high-boiling solvent dissolved in an ultraviolet photoinitiator. 3. The method for preparing a metal pattern on a curved surface by combining nanoimprinting with wet etching according to claim 1, wherein the material of the metal thin film in step 1) is gold, silver, copper, aluminum or chromium. 4 . The method for preparing a metal pattern on a curved surface by combining nanoimprinting with wet etching according to claim 3 , wherein the metal thin film has a thickness of 1-100 nanometers. 5. according to claim 3 or 4 described nano-imprints in conjunction with the method for preparing metal pattern on curved surface by wet etching, it is characterized in that, when the material of metal thin film is gold or silver, the composition of wet etching solution It is an aqueous solution of ferric nitrate nonahydrate and thiourea, and its pH value is adjusted to 1-5 with dilute hydrochloric acid; when the evaporated metal is copper, the composition of the wet etching solution is an aqueous solution of ferric chloride; When the material is chromium, the composition of the wet etching solution is glacial acetic acid solution of ammonium cerium nitrate.