阅读说明：本技术 一种平面超导纳米桥结的制备方法 (Preparation method of planar superconducting nano bridge junction ) 是由 应利良 张雪 任洁 王镇 于 2020-05-12 设计创作，主要内容包括：本发明涉及一种平面超导纳米桥结的制备方法,在衬底表面进行光刻形成图案,然后沉积金属薄膜；利用离子束刻蚀金属,金属因反溅射现象沿着光刻胶形成侧壁,去胶,即得纳米桥,桥的宽度即为反溅射的金属薄膜厚度,因此可以超越光刻极限；沉积超导薄膜、光刻,刻蚀形成桥两端的电极,即得。本发明具有低成本,易集成,高精度等优势。(The invention relates to a preparation method of a planar superconducting nano bridge junction, which comprises the steps of photoetching the surface of a substrate to form a pattern, and then depositing a metal film; etching metal by using ion beams, forming a side wall along the photoresist by the metal due to a reverse sputtering phenomenon, removing the photoresist to obtain a nano bridge, wherein the width of the bridge is the thickness of the reverse sputtered metal film, so that the width can exceed the photoetching limit; depositing a superconducting film, photoetching and etching to form electrodes at two ends of the bridge. The invention has the advantages of low cost, easy integration, high precision and the like.)

1. A preparation method of a nano bridge junction comprises the following steps:

(1) photoetching the surface of the substrate to form a pattern, and then depositing a metal film;

(2) etching the metal by utilizing an ion beam, forming a side wall of the metal along the photoresist, and removing the photoresist to obtain the nano bridge;

(3) then depositing a superconducting film, photoetching and etching to obtain the nano bridge junction electrode.

2. The method according to claim 1, wherein the substrate in the step (1) is a semiconductor substrate or an insulator substrate.

3. The preparation method according to claim 1, wherein the semiconductor is one or more of Si, Ge and GaN; the insulator is SiO₂、Al₂O₃、HfO₂One or more of them.

4. The method according to claim 1, wherein the metal in step (1) is a superconducting material Nb, NbN, Pb, NbC, Nb₃Sn、Nb₃One or more of Ge, or one of Al, Au, Cu and alloy.

5. The method according to claim 1, wherein the metal film deposited in step (1) is deposited by: electron beam evaporation or magnetron sputtering; the thickness of the deposited metal film is 10nm-500 nm.

6. The preparation method according to claim 1, wherein the ion beam etching in the step (2) is specifically: the IBE etching angle is 10-50 degrees, and the ion beam current is 10-600 mA.

7. The method according to claim 1, wherein the thickness of the sidewall in the step (2) is 2nm to 300 nm.

8. The method according to claim 1, wherein the superconducting material deposited in the superconducting thin film in step (3) is one of Nb, NbN, YBCO; the thickness of the film is 10nm-500 nm.

9. A nanobridge prepared by the method of claim 1, wherein the nanobridge has a width of 2nm to 300nm and a length of 20nm to 1000 nm.

10. An integrated nanobridge prepared based on the method of claim 1.

11. Use of the nanobridge of claim 9.

Technical Field

The invention belongs to the field of preparation of Josephson junctions, and particularly relates to a preparation method of a planar superconducting nano bridge junction.

Background

The superconducting circuit includes a circuit using a superconducting josephson junction, such as a superconducting quantum interference device (SQUID), a single flux quantum device (SFQ), and the like.

In the concept of quantum mechanics, when two metals are separated by a thin insulator, current can flow between the metals, and this "metal-insulator-metal" stack is commonly referred to as a tunnel junction, and the current flowing between them is referred to as a tunnel current. If, in such a stacked sandwich structure, one or both of the metals is a superconductor, it is referred to as a superconducting tunnel junction. According to the Josephson effect, in a superconducting tunnel junction, an insulating layer has some properties of a superconductor, but has weaker superconductivity compared to a conventional superconductor, and is called a "weakly connected superconductor".

The reduction of the size of the Josephson junction can improve the sensitivity of the superconducting quantum interferometer and the integration level of the superconducting digital circuit. Besides the sandwich structure to form the superconducting weak connection, the Josephson junction can also be in the forms of a bridge junction, a step junction and the like. The bridge junction is a superconducting wire, and a narrow channel is formed in the middle of the bridge junction to realize weak connection. The size of the narrow channel is the size of the junction, and how to reduce the size of the channel is the key point of the current bridge junction research.

CN107275472A discloses a method for preparing a high-temperature superconducting thin-film nano-bridge junction, in general, the high-temperature superconducting nano-bridge junction is formed by weak connection at a step, the size of the bridge junction is limited by the photolithography precision, and the size and precision cannot be further improved.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for preparing a planar superconducting nano bridge junction, overcoming the defects that the existing technology for preparing the bridge junction is limited by photoetching precision and cannot be integrated on a large scale.

The invention relates to a preparation method of a nano bridge junction, which comprises the following steps:

(1) photoetching the surface of the substrate to form a pattern, and then depositing a metal film;

(2) etching the metal by using ion beam IBE, forming a side wall of the metal along the photoresist, and removing the photoresist to obtain a nano bridge;

(3) depositing a superconducting film on the substrate, photoetching to form electrode patterns, and etching to form electrodes at two ends of the bridge junction, thus obtaining the nano bridge junction electrode.

The preferred mode of the above preparation method is as follows:

the substrate in the step (1) is a semiconductor substrate or an insulator substrate.

The thickness of the substrate is 100um and above.

The semiconductor is one or more of Si, Ge and GaN; the insulator is SiO₂、Al₂O₃、HfO₂One or more of them.

The metal in the step (1) is a superconducting material Nb, NbN, Pb, NbC, Nb₃Sn、Nb₃One or more of Ge, or one of Al, Au, Cu and alloy.

The deposition mode of depositing the metal film in the step (1) is as follows: electron beam evaporation or magnetron sputtering; the thickness of the deposited metal film is 20nm-500 nm.

The specific process parameters of the IBE etching in the step (2) are as follows: the IBE etching angle is 10-50 degrees, and the ion beam current is 10-600 mA.

The thickness of the side wall in the step (2) is 2nm-300 nm.

The superconducting material in the deposited superconducting thin film in the step (3) is one or more of Nb, NbN and YBCO, the deposition thickness is 20-500nm, and the deposition mode is electron beam evaporation or magnetron sputtering.

Photoetching in the step (3): forming an electrode pattern; etching: RIE, ICP or wet etching is used.

According to the nano bridge junction prepared by the method, the width of the nano bridge junction is 2nm-300nm of the side wall thickness, and the length of the nano bridge junction is the exposure limit of the gap between two electrodes, and is about 20nm-1000 nm.

The invention relates to an integrated nano bridge junction prepared based on the method.

The invention also discloses an application of the nano bridge junction.

Advantageous effects

The invention utilizes the redeposition principle of metal in etching to form an arrayed ultrathin metal side wall and prepare the small-size and large-scale integrated superconducting nano bridge junction.

The preparation process has the advantages of simple flow, no limit of characteristic dimension to the photoetching precision and the like, the existing photoetching precision is usually determined by the precision of an exposure machine, and the formation of the side wall of the invention is similar to the growth of a thin film and is not limited by the photoetching precision.

Drawings

FIGS. 1(a), (b), and (c) are flow charts of the preparation of the nanobridge of the present invention.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.