阅读说明：本技术 一种高深宽比超导氮化铌纳米线及其制备方法和应用 (High-aspect-ratio superconducting niobium nitride nanowire and preparation method and application thereof ) 是由 张蜡宝 郭书亚 陈奇 潘丹峰 涂学凑 韩航 贾小氢 赵清源 陈健 康琳 吴培亨 于 2020-05-15 设计创作，主要内容包括：本发明公开了一种高深宽比超导氮化铌纳米线及制备方法和应用,采用优化的镀膜技术在衬底表面沉积氮化铌薄膜；在氮化铌薄膜表面旋涂电子束抗刻蚀剂,形成电子束抗刻蚀剂层；采用电子束曝光技术在电子束抗刻蚀剂层上定义氮化铌纳米线图形；采用反应离子刻蚀技术将图形转移到氮化铌薄膜上,得到高深宽比超导氮化铌纳米线。本发明通过将电子束曝光系统和反应离子刻蚀相结合的微纳加工技术,成功制备出了膜厚纳米线,深宽比超过1∶1的超导氮化铌纳米线,可应用与高性能全波段光子探测器和其他相关领域的研究。(The invention discloses a high aspect ratio superconducting niobium nitride nanowire and a preparation method and application thereof, wherein an optimized coating technology is adopted to deposit a niobium nitride film on the surface of a substrate; spin-coating an electron beam anti-etching agent on the surface of the niobium nitride film to form an electron beam anti-etching agent layer; defining a niobium nitride nanowire pattern on the electron beam anti-etching agent layer by adopting an electron beam exposure technology; and transferring the pattern to the niobium nitride film by adopting a reactive ion etching technology to obtain the high-aspect-ratio superconducting niobium nitride nanowire. According to the invention, the superconducting niobium nitride nanowire with the film thickness and the depth-to-width ratio exceeding 1: 1 is successfully prepared by a micro-nano processing technology combining an electron beam exposure system and reactive ion etching, and can be applied to researches of high-performance full-waveband photon detectors and other related fields.)

1. A high aspect ratio superconductive niobium nitride nanowire is characterized in that: the nanowire has a thickness of 20-1000 nm and a width of 10-500 nm.

2. The high aspect ratio superconducting niobium nitride nanowires of claim 1, wherein: the aspect ratio of the niobium nitride nanowire is more than 1: 1, and the duty ratio is more than 1: 3.

3. A preparation method of a high aspect ratio superconducting niobium nitride nanowire is characterized by comprising the following steps: growing a niobium nitride film; forming an electron beam lithography layer on the surface of the niobium nitride film, and defining a niobium nitride nanowire pattern on the electron beam lithography layer by adopting an electron beam exposure technology; and transferring the pattern to the niobium nitride film by adopting reactive ion etching to obtain the high-aspect-ratio superconducting niobium nitride nanowire.

4. The method of claim 3, wherein the method comprises: the electron beam photoetching layer adopts positive photoresist, the etching rate of the photoresist is less than 120 nm/min under the standard etching condition, and the thickness of the photoresist is 40-400 nm.

5. The method of claim 3, wherein the method comprises: the beam current of electron beam exposure is 100 pA-1 nA, and the exposure dose is 200-500 mu C/cm²。

6. The method of claim 3, wherein the method comprises: the etching gas for the reactive ion etching is CF₄The discharge power is 50-100W, the gas flow is 10-50 sccm, the chamber pressure is 1-10 Pa, the etching time is 0.1-4 min, and the etching rate is 0.1-10 nm/s.

7. The method of claim 3, wherein the method comprises: the substrate for growing the niobium nitride film is Si₃N₄/Si/Si₃N₄、MgF₂Or an MgO substrate.

8. The method of claim 3 for preparing high aspect ratio superconducting niobium nitride nanowiresThe method is characterized in that: the duty ratio of the nano-wire is 1: 1, when the line width is 70-90 nm, the line width of the defined nano-wire graph is 110-130 nm, the interval is 30-50 nm, 2-8 times of scanning exposure is adopted, and the exposure dose is 80-100 mu C/cm²。

9. The use of the high aspect ratio superconducting niobium nitride nanowires of claim 1 in high-energy, broad-band photon detectors and superconducting electronics.

Technical Field

The invention relates to a niobium nitride nanowire and a preparation method and application thereof, in particular to a high-aspect-ratio superconducting niobium nitride nanowire and a preparation method and application thereof.

Background

Niobium nitride (NbN) is a low-temperature superconducting material widely studied in recent years, has the characteristics of high superconducting transition temperature (up to 16K), critical current density, superconducting energy gap and the like, has stable physical properties, can grow a high-quality film on a large surface, and is the most commonly used material for preparing superconducting electronic devices such as superconducting nanowire single-photon detectors, terahertz wave detection assisted bolometer mixers, superconducting quantum interference devices and the like. At present, the most representative SNSPD is prepared by mainly growing a high-quality ultrathin NbN film with the thickness of 3-6nm by an epitaxial method, and preparing the film into a meandering nanowire structure by a micro-nano processing means, wherein the width of the NbN nanowire is about 100nm, and the depth-to-width ratio of the NbN nanowire is generally lower than 1: 20.

The SNSPD prepared by the ultrathin NbN film has the advantages of low dark count, wide response spectrum, short recovery time, high time precision and the like, and has been deeply researched and applied in the aspect of detection of visible light/infrared single photons. However, there has been little research on the use of SNSPDs in the direction of high energy photons (ultraviolet light, X-rays, gamma rays, etc.).

Disclosure of Invention

The purpose of the invention is as follows: one of the objectives of the present invention is to provide a high aspect ratio superconducting niobium nitride nanowire, which has a high aspect ratio; the second purpose of the present invention is to provide a method for preparing a high aspect ratio superconducting niobium nitride nanowire, which can prepare the high aspect ratio superconducting niobium nitride nanowire; the invention also aims to provide application of the high-aspect-ratio superconducting niobium nitride nanowire.

The technical scheme is as follows: the invention provides a high-aspect-ratio superconducting niobium nitride nanowire which has a meandering structure, wherein the depth (namely the thickness) of the nanowire is 20-1000 nm, and the width of the nanowire is 10-500 nm;

preferably, the aspect ratio of the niobium nitride nanowire is more than 1: 1, and the duty ratio is more than 1: 3.

Furthermore, the duty ratio of the nanowire is 1: 1, and the side wall of the nanowire is vertical to the surface.

The thickness of the nanowire is 20nm-1000nm, the width of the nanowire is 10nm-500nm, the duty ratio is in the range of 10% -90%, the relative standard deviation of the line width fluctuation is lower than 10%, the standard deviation of the thickness fluctuation is lower than 10%, and the superconductivity loss caused by preparation is lower than 20%.

The invention also provides a preparation method of the high-aspect-ratio superconducting niobium nitride nanowire, which comprises the following steps:

(1) depositing a niobium nitride film on the surface of the substrate by adopting a film coating technology;

(2) spin-coating an electron beam anti-etching agent on the surface of the niobium nitride film to form an electron beam photoetching layer;

(3) defining a niobium nitride nanowire pattern on the electron beam lithography layer by adopting an electron beam exposure technology;

(4) and transferring the nanowire graph to a niobium nitride film by adopting a reactive ion etching technology to obtain the high-aspect-ratio superconducting niobium nitride nanowire.

The preparation method mainly comprises the etching process of optimizing the growth of the film, the exposure of the etching-resistant photoresist and the selection of the high aspect ratio without damaging the material. Wherein the substrate can be Si with double-side polished₃N₄/Si/Si₃N₄Substrate, or MgF₂Substrate, MgO substrate, or other substrate in the prior art; the coating technology can be magnetron sputtering or other coating technologies in the prior art.

The preparation method of the high aspect ratio superconducting niobium nitride nanowire can obtain a meandering NbN nanowire structure with the minimum line width of 20nm, the duty ratio of 1: 1 and the depth of 100nm on a silicon nitride substrate, the sidewall of the nanowire is 90 degrees vertical, the aspect ratio exceeds 1: 1, the superconducting critical current of the nanowire reaches 550 muA under 2.2K, and the hysteresis is 36 muA. The development of the preparation process of the NbN nanowire with the high depth-to-width ratio is beneficial to the research of the superconducting nanowire in the field of high-energy photon detectors.

Preferably, magnetron sputtering coating is adopted in the step (1), and the thickness of the niobium nitride film is 100-200 nm.

Preferably, the electron beam lithography layer adopts positive photoresist, under the standard etching condition (CF4/O2), the etching rate of the photoresist is less than 120 nm/min, and the thickness of the photoresist is 40-400 nm. Optionally, the electron beam resist is an AR-P6200.13 positive electron beam resist; the ultrahigh-resolution non-chemically amplified positive electron beam resist AR-P6200.13 has the highest resolution less than 10nm, has the advantages of higher sensitivity, higher exposure speed and the like, has the dry etching resistance 2 times that of the traditional PMMA glue, and can be used for replacing ZEP 520. The high resolution and etch resistance of AR6200.13 is suitable for high aspect ratio nanowires.

AR-P6200.13 is one of the electron beam exposure resists CSAR 62 (Chemical semi amplified Resist); CSAR 62 consists essentially of a 9% solution of poly (. alpha. -methylstyrene-co-a-chloromethyl acrylate) having a molecular weight of 38000g/mol dissolved in anisole.

Preferably, the beam current of electron beam exposure is 100 pA-1 nA, the scanning step length is 0.1-5 nm, and the exposure dose is 200-500 mu C/cm²。

Preferably, the etching discharge power of the reactive ion etching is 50-100W, and the etching gas is CF₄The gas flow is 10-50 sccm, the chamber pressure is 1-10 Pa, the etching time is 0.1-4 min, and the etching rate is 0.1-10 nm/s.

Optionally, when the duty ratio of the nanowires is 1: 1 and the linewidth is 70-90 nm, the linewidth of the defined nanowire pattern is 110-130 nm, the interval is 30-50 nm, 1-4 scanning exposures are adopted, and the exposure dose is 80-100 μ C/cm². Different doses of meandering nanowires with various line widths and duty ratios of 1: 1 are exposed, and the designed line width has certain deviation from the actual line width due to overexposure caused by the proximity effect, so that when a pattern is designed, the line width/interval (L/S) of a target pattern needs to be adjusted according to the exposure condition, and pattern size compensation of different degrees is performed on different line widths so as to correct the influence caused by the proximity effect.

The line width is 80 +/-5 nm, when the duty ratio is 1: 1, the line width of the defined nano line graph is 120 +/-5 nm, the interval is 40 +/-5 nm, 2-4 times of scanning exposure are adopted, and the exposure dose is 90-95 mu C/cm²。

When the line width is 80nm, the line width of the defined nano line pattern is 120nm, the interval is 40nm, 2-4 times of scanning exposure is adopted, and the exposure dose is 90-95 mu C/cm²。

Wherein, a meandering nanowire pattern is transferred to the NbN film by adopting a Reactive Ion Etching (RIE) technology, and a high aspect ratio structure is obtained; and using a single CF₄The NbN film is etched by gas, and the reaction chemical formula is as follows:

and the discharge power of reactive ion etching and the chamber gas pressure have the largest influence on the etching rate and the lateral etching of the nanowire.

The invention also provides the application of the high-aspect-ratio superconducting niobium nitride nanowire in high-energy broadband photon detectors and superconducting electronic devices.

The absorption rates of the 10nm NbN film to the X-ray photons with 1keV and 6keV are only 3.686% and 0.227% obtained through Geant4 simulation, the SNSPD prepared by the ultrathin NbN film is difficult to effectively detect the high-energy photons, and the absorption rates of the NbN with the film thickness of 100 nanometers to the X-ray photons with 1keV and 6keV are 31.31% and 2.251% obtained through simulation.

The invention principle is as follows: the high aspect ratio superconducting niobium nitride nanowire is prepared by micro-nano processing technologies such as magnetron sputtering, electron beam exposure, reactive ion etching and the like, and a meandering NbN nanowire structure with the aspect ratio exceeding 1: 1 is obtained by optimizing an electron beam exposure process of a positive electron beam resist AR-P6200.13 and adjusting parameters such as chamber air pressure, discharge power, auxiliary gas and the like in the reactive ion etching process.

The method adopts an optimized coating technology to deposit a niobium nitride film on the surface of the substrate; spin-coating an electron beam anti-etching agent on the surface of the niobium nitride film to form an electron beam anti-etching agent layer; defining a niobium nitride nanowire pattern on the electron beam anti-etching agent layer by adopting an electron beam exposure technology; and transferring the pattern to the niobium nitride film by adopting a reactive ion etching technology to obtain the high-aspect-ratio superconducting niobium nitride nanowire. By a micro-nano processing technology combining an electron beam exposure system and reactive ion etching, the superconducting niobium nitride nanowire with the film thickness and the depth-to-width ratio exceeding 1: 1 is successfully prepared, and can be applied to researches of high-performance full-waveband photon detectors and other related fields.

The technical difficulty is as follows: the nanowire is prepared by an ultra-thin (5nm) NbN film in the prior art, so the requirement on the etching resistance of an electron beam etching resist is not high; the preparation of the thick-film NbN nanowire with the high depth-to-width ratio has high requirements on exposure precision and etching resistance, and the structure and the superconducting performance of the material cannot be damaged. In the process for preparing the NbN nanowire by the low-etching-resistance agent, which is researched and developed for the first time, the process is also one of the key factors for successfully preparing the thick-film NbN nanowire; the preparation of the NbN nanowire with the high depth-to-width ratio is successfully realized by combining the preparation process.

The electron beam exposure system has the characteristics of easy control, high precision and high flexibility, has obvious advantages in preparing the nano structure compared with ultraviolet lithography, is an important preparation tool for the current nano structure research, and adopts the electron beam exposure with the highest precision of 8nm to draw the nano line graph in the experiment. In the deep etching field, an Inductively Coupled Plasma (ICP) etching process and a passivation process are mutually exchanged, each etching process is isotropic, ripples can be formed on the side wall, the side wall roughness is large, the current ICP etching process can reduce the side wall roughness to 10nm magnitude, but the current NbN nanowire with the width of hundreds of nanometers is too rough, and the NbN nanowire etching process is difficult to apply. And the Reactive Ion Etching (RIE) process continuously carries out gas conversion, so that the side wall of the prepared nanowire is smooth, the etching depth reaches hundreds of nanometers, and meanwhile, the etching anisotropy can be ensured. However, RIE etching can result in lateral etching, increasing the difficulty of etching NbN thick films. This factor can be adjusted experimentally to optimize the etch parameters. Finally, RIE is selected to prepare the NbN nanowire with high depth-to-width ratio.

Has the advantages that: according to the invention, a complete preparation process is formed for the high aspect ratio superconducting NbN nanowire by researching a micro-nano processing technology combining exposure and reactive ion etching of an electron beam exposure system and adopting a positive electron beam anti-etching agent AR-P6200.13; under the optimized preparation process condition, when the film thickness is 100nm, a meandering NbN nanowire structure with the L/S of 80nm/80nm is obtained, and the depth-to-width ratio of the meandering NbN nanowire structure exceeds 1: 1; the development of the preparation process of the NbN nanowire with the high depth-to-width ratio is beneficial to the preparation of SNSPD for high-energy single photon detection and the research of the superconducting nanowire in the field of high-energy photon detectors. The invention firstly applies the AR6200.13 anti-etching agent to the NbN nanowire preparation process, and combines the preparation process to successfully prepare the thick-film high-depth-to-width-ratio NbN nanowire, thereby providing possibility for further researching the response characteristics of the superconducting NbN nanowire detector in the high-energy photon field.

Drawings

FIG. 1 is a schematic flow diagram of the preparation of high aspect ratio superconducting NbN nanowires; wherein (a) is a schematic diagram after spin-coating an electron beam resist on a substrate, (b) is a schematic diagram after electron beam exposure by using EBL, (c) is a schematic diagram after development, (d) is a schematic diagram after reactive ion etching, and (e) is a schematic diagram after removing the resist;

FIG. 2 is a schematic view of the superconducting transition temperature of a thin film of NbN;

fig. 3 is a plan SEM image of NbN nanowires at different design widths;

FIG. 4 is a plan SEM image of nanowires with an L/S of 100nm/100nm width prepared by different etching recipes;

FIG. 5 is a side SEM image of a test sample after etching;

FIG. 6 is a side SEM image of nanowires with L/S of 80nm/80nm after etching;

FIG. 7 is a TEM image of a cross section of a nanowire with L/S of 80nm/80 nm;

FIG. 8 is a graph of NbN nanowires IV with L/S of 80nm/80 nm.

Detailed Description

The present invention will be described in further detail with reference to examples.

The starting materials and reagents used in the following examples are all commercially available. Wherein the substrate Si₃N₄/Si/Si₃N₄，MgF₂MgO is purchased from mixed fertilizer family crystal; AR-P6200.13 resist, AR600-546 developer, and AR600-71 resist remover were purchased from Beijing Vigorgian science and technology Ltd.

As shown in fig. 1, the preparation process of the high aspect ratio superconducting niobium nitride nanowire of the present invention specifically includes the following steps:

(1) depositing a niobium nitride film on the surface of the substrate by adopting a magnetron sputtering technology, wherein the thickness of the niobium nitride film is 100-200 nm;

(2) adjusting a design definition graph according to a nanowire structure for preparing a target line width/space (L/S);

(3) spin-coating an anti-etching agent on the surface of the niobium nitride film, as shown in fig. 1 (a);

(4) scanning exposure is performed by using an electron beam exposure system EBPG5200 with the highest acceleration voltage of 100kV, as shown in FIG. 1 (b); performing electron beam exposure by using EBPG5200 equipment of Raith company in Germany, wherein the adopted electron beam current is 100 pA-1 nA, and the exposure dose is specifically adjusted according to the size of a graph;

(5) developing, as shown in fig. 1(c), to complete the definition of the designed niobium nitride nanowire pattern on the electron beam resist layer; after exposure, developing for 60s at 20 ℃ by using AR600-546 developer, fixing for 60s by deionized water, and strengthening glue for 60s at 130 ℃ to enhance the etching resistance.

(6) Transferring the nanowire pattern to a niobium nitride film by adopting a reactive ion etching technology after development, as shown in fig. 1 (d); the etching discharge power is 50-100W, the etching gas CF4 is provided, the gas flow is 30sccm, the chamber pressure is 1-2Pa, and the etching time is 1-4 min.

(7) And finally, removing the residual etching resist by using AR600-71 photoresist removing liquid, and obtaining the high-aspect-ratio superconducting niobium nitride nanowire as shown in figure 1 (e).