CN111188006B

CN111188006B - Preparation method of micro-nano metal particles in periodic arrangement

Info

Publication number: CN111188006B
Application number: CN202010016684.XA
Authority: CN
Inventors: 周佩珩; 蒋若梅; 王睿; 刘彦宁; 邓龙江
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2020-01-08
Filing date: 2020-01-08
Publication date: 2021-07-06
Anticipated expiration: 2040-01-08
Also published as: CN111188006A

Abstract

The invention relates to the technical field of microstructure processing, in particular to a preparation method of micro-nano metal particles which are periodically arranged. The invention utilizes the phenomenon that an amorphous semiconductor/metal film can be crystallized at a certain temperature, so that fractal polycondensation is generated; the template dewetting method is combined with the fractal polycondensation property of germanium. Firstly, a required periodic structure pattern is obtained on a substrate by utilizing photoetching and plasma etching processes, then a metal film and a Ge film are sputtered, fractal polycondensation is generated by utilizing crystallization of Ge at a certain temperature, and energy is provided to promote migration of metal atoms, so that large-size micro-nano metal particles which are periodically distributed are formed. In contrast, the method disclosed by the invention is based on the template dewetting method and the fractal polycondensation characteristic of the germanium film, realizes relatively accurate control on the distribution of the obtained micro-nano metal particles, and avoids the problems of complex preparation process, high cost and the like in the prior art.

Description

Preparation method of micro-nano metal particles in periodic arrangement

Technical Field

The invention relates to the technical field of microstructure processing, in particular to a preparation method of micro-nano metal particles which are periodically arranged.

Background

Micro-nano metal particles attract a wide range of attention due to their unique optical and electrical properties. Under the irradiation of light, free electrons in the micro-nano metal particles can interact with the micro-nano metal particles, so that a special surface electromagnetic resonance effect, namely local surface plasma resonance, is excited on the metal surface, novel optical effects such as optical enhancement and the like are formed in the nanometer scale of subwavelength, a series of important breakthroughs and progresses are made in the research directions such as optical sensing, photo-thermal, super-resolution imaging, local field enhancement and the like, and the micro-nano metal particle has wide application prospects in the fields such as solar cells, biosensors and the like.

At present, people research preparation methods of various micro-nano metal particles, and the most widely and controllably prepared method of the photon nano structure is based on direct Focused Ion Beam (FIB) milling or multi-stage electron beam and nano imprinting processes, but the preparation methods have the defects of complex preparation process and high cost.

In recent years, the academic community generally holds that a simple and selectable method for forming micro-nano metal particles is based on the dewetting of a metal film on an inert substrate, and the method prepares the metal particles in ordered arrangement by utilizing the characteristic that the surface of the metal film is unstable in a high-temperature environment so as to be dewet, and has the characteristics of simplicity in operation, high transfer rate, good repeatability and the like. But ordered arrangements of metal particles cannot be obtained by mere high temperature de-wetting.

Disclosure of Invention

Aiming at the problems or the defects, the invention provides a preparation method of micro-nano metal particles in periodic arrangement, aiming at solving the problems of complex process, high cost and the like of the existing preparation method of the micro-nano metal particles, and the micro-nano metal particles in ordered arrangement are prepared based on a template dewetting method and the fractal polycondensation characteristic of a germanium film.

A preparation method of micro-nano metal particles in periodic arrangement comprises the following specific steps:

step 1, cleaning the silicon dioxide or silicon substrate.

And 2, preparing a photoresist sacrificial layer on the cleaned silicon dioxide or silicon substrate by a spin coating process, wherein the thickness of the sacrificial layer is 0.8-1.5 microns.

And 3, manufacturing a required periodic structure pattern on the sacrificial layer by using a photoetching process.

And 4, etching the patterned surface of the silicon dioxide or the silicon substrate prepared in the step 3 by using plasma, wherein the etching depth is 400-600nm, and removing the photoresist after the etching is finished.

And 5, sputtering a metal layer with the thickness of 40-60nm and a Ge layer with the thickness of 15-30nm on the patterned surface of the silicon dioxide or silicon substrate obtained in the step 4 by magnetron sputtering in sequence, wherein the metal layer is made of Au or Ag.

And 6, placing the substrate sample obtained in the step 5 in a tubular furnace at the temperature of 600-.

The invention utilizes the crystallization of amorphous semiconductor (Ge)/metal film (Au, Ag) at a certain temperature, thereby generating the phenomenon of fractal polycondensation; a template dewetting method is combined with the fractal polycondensation characteristic of germanium, and a method for preparing orderly-arranged micro-nano metal particles (Au, Ag) is provided. Firstly, a required periodic structure pattern is obtained on a silicon dioxide (or silicon) substrate by utilizing photoetching and plasma etching processes, then a metal film and a Ge film are sputtered, crystallization is carried out at a certain temperature by utilizing Ge to generate fractal polycondensation, and energy is provided to promote migration of metal atoms, so that large-size micro-nano metal particles which are periodically distributed are formed. In contrast, the distribution of the micro-nano metal particles obtained by the traditional de-wetting process is disordered on the substrate, and the distribution of the micro-nano metal particles is accurately controlled based on a template de-wetting method and the fractal polycondensation characteristic of the germanium film.

Drawings

FIG. 1 is a schematic diagram of a photolithographic periodic structure of an embodiment;

FIG. 2 is an SEM image of a cross-section of a silicon dioxide substrate obtained in step 4 of an example;

FIG. 3 is an SEM photograph of the gold-plated surface of the sample obtained in step 4 of the example;

fig. 4 is an SEM image of the micro-nano gold particles with a periodic distribution obtained after annealing in example 6.

Detailed Description

The invention is further explained in detail with reference to the drawings and examples.

Step 1, immersing a silicon dioxide substrate in acetone with the purity of 99.99%, absolute ethyl alcohol with the purity of 99.99% and deionized water in sequence, ultrasonically cleaning for 8min respectively, blowing away residual moisture by using nitrogen, placing the silicon dioxide substrate on a hot plate at the temperature of 120 ℃, and thermally drying for 10min to remove residual water vapor.

And 2, placing the silicon dioxide substrate dried in the step 1 on a desk type spin coater, spin-coating AZ5214 photoresist for 1 mu m, and rotating at the speed of 1000r/m for 10s and then at the speed of 3000r/m for 30 s. The silicon dioxide substrate spin coated with the AZ5214 photoresist was then baked on a hot plate at 100 ℃ for 1 min. And taking out the sample after baking is finished.

And 3, cooling the silicon dioxide substrate sample obtained in the step 2 to room temperature, then placing the silicon dioxide substrate sample on a photoetching table, and photoetching by adopting a reverse photoresist photoetching process to obtain a photoetching pattern as shown in figure 1.

The specific photoetching process comprises the following steps: after exposure for 1.0s, placing the sample on a hot plate at 120 ℃ for baking for 90s, cooling to room temperature, and then placing the sample on a sample table for about 18s of flood exposure; developing with positive photoresist developer, dissolving the deteriorated photoresist, and placing into deionized water after 15-30 s; blowing off residual water with nitrogen, placing on a hot plate at 120 deg.C, and oven drying for 3 min.

FIG. 1 is a schematic diagram of a photo-etching periodic pattern, the periodic structure is black circles which are arranged in a matrix at equal intervals of 2 μm up, down, left and right, the photoresist covers a gray area, the black circle area has no photoresist, the diameter of the black circle is 5 μm, and the period is 7 μm.

And 4, placing the silicon dioxide substrate obtained in the step 3 into a plasma etching machine for etching for 10min, wherein the etching conditions are as follows: CHF₃And O₂The volume ratio of gas is 72: 8, total gas volume 35mt, etching power 150W. And immersing the etched substrate in acetone with the purity of 99.99%, absolute ethyl alcohol with the purity of 99.99% and deionized water in sequence, ultrasonically cleaning for 8min respectively, and blowing away residual water by using nitrogen.

FIG. 2 is a SEM image of the cross section of the etched silicon dioxide substrate obtained in step 4, wherein the etching depth is 400 nm.

And 5, sequentially depositing a layer of Au thin film with the thickness of 50nm and a layer of Ge thin film with the thickness of 20nm on the silicon dioxide substrate obtained in the step 4 through radio frequency magnetron sputtering. The technological parameters are as follows: filling Ar gas during Au plating to ensure that the vacuum degree of the cavity is 0.5Pa and the sputtering power is 150W; and during Ge plating, Ar gas is filled to ensure that the vacuum degree of the cavity is 0.8Pa and the sputtering power is 100W.

And 6, placing the silicon dioxide substrate sample obtained in the step 5 in a tube furnace at 900 ℃, and taking out the silicon dioxide substrate sample for 3 hours to obtain micro-nano Au particles with uniform size and periodic distribution, wherein the large-size Au particles are uniformly distributed in the center of the table top as shown in figure 4.

According to the embodiment, the phenomenon that the fractal polycondensation occurs due to the fact that the amorphous semiconductor/metal film (Au, Ag and the like) can be crystallized at a certain temperature is utilized; combines a template dewetting method with the fractal polycondensation characteristic of germanium, and provides a method for preparing orderly-arranged micro-nano metal particles. Firstly, a required periodic structure pattern, namely a circular pit array with the diameter of 5 mu m and the period of 7 mu m, is obtained on a silicon dioxide (or silicon) substrate by utilizing photoetching and plasma etching processes, then a metal film and a Ge film with certain thickness are sputtered, fractal polycondensation is generated by utilizing crystallization of Ge at certain temperature, energy is provided to promote migration of metal atoms, and accordingly large micro-nano metal particles with periodic distribution are formed. Compared with the traditional de-wetting process, the method has the advantages that the distribution of the micro-nano metal particles obtained by the traditional de-wetting process on the substrate is disordered, and the distribution of the obtained micro-nano metal particles is accurately controlled.

The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims

1. A preparation method of micro-nano metal particles in periodic arrangement comprises the following specific steps:

step 1, cleaning a silicon dioxide or silicon substrate;

step 2, preparing a photoresist sacrificial layer on the cleaned silicon dioxide or silicon substrate through a spin coating process, wherein the thickness of the sacrificial layer is 0.8-1.5 mu m;

step 3, manufacturing a required periodic structure pattern on the sacrificial layer by using a photoetching process;

the periodic structure pattern is a circular matrix array with the diameter of 5 mu m and the period of 7 mu m;

step 4, etching the patterned surface of the silicon dioxide or the silicon substrate prepared in the step 3 by using plasma, wherein the etching depth is 400-600nm, and removing the photoresist after the etching is finished;

step 5, sputtering a metal layer with the thickness of 40-60nm and a Ge layer with the thickness of 15-30nm on the patterned surface of the silicon dioxide or silicon substrate obtained in the step 4 in sequence through magnetron sputtering, wherein the metal layer is made of Au or Ag;

and 6, placing the sample obtained in the step 5 in a tubular furnace at the temperature of 600-.

2. The method for preparing the micro-nano metal particles which are periodically arranged according to claim 1, is characterized in that: the metal layer is an Au layer with the thickness of 50nm, and the amorphous semiconductor layer is a Ge layer with the thickness of 20 nm.

3. The method for preparing the micro-nano metal particles which are periodically arranged according to claim 2, is characterized in that: the annealing temperature in the step 6 is 900 ℃, and the time is 3 hours.