CN115188878A - Preparation method of Josephson junction - Google Patents

Abstract

The invention discloses a preparation method of the Josephson junction. First, a semiconductor substrate is provided, and a first conductive pattern layer is formed on the surface of the semiconductor substrate; part of the first conductive pattern layer is etched and removed to obtain a first-direction wire; the obtained first-direction wire is subjected to surface pretreatment and Oxidation; on the surface pretreatment and the oxidized first-direction wires, a second conductive pattern layer is formed, and the second conductive pattern layer covers the surface of the semiconductor substrate and the first-direction wires; then the obtained second conductive pattern Part of the pattern layer is etched and removed to obtain a second-direction lead; the second-direction lead intersects with the first-direction lead to prepare a Josephson junction. By preparing the Josephson junction in the present invention, sputtering at a turning angle can be avoided, thereby facilitating mass production; in addition, the uniformity is greatly improved compared with the prior art.

Description

A kind of preparation method of Josephson junction

1. Technical field:

The invention belongs to the technical field of semiconductor production technology, in particular to a method for preparing a Josephson junction on a semiconductor substrate.

2. Background technology:

In recent years, superconducting electronics technology has a wide range of needs and applications in the fields of quantum computing, high-performance digital integrated circuits, highly sensitive magnetic field detection, precision physical quantity calibration, and microwave radiation detection. The superconducting Josephson junction is the most basic device in superconducting electronics technology. Therefore, the preparation of high-quality Josephson junctions has become one of the urgent problems to be solved by those skilled in the art.

During the fabrication of some special semiconductor devices, a structure in which two aluminum lines directly intersect will appear. For example: in the preparation process of the Josephson junction, it is necessary to make the first aluminum wire, the thickness of the first aluminum wire is about 40nm, and then prepare a second aluminum wire that intersects with the first one. The line thickness is about 60nm.

In the prior art, the preparation and similar cross-wire structures usually adopt the following methods:

In the first step, a layer of methyl methacrylate MMA is spin-coated on the substrate, and then a layer of polymethyl methacrylate PMMA is spin-coated.

The second step is to expose the two layers of glue together by means of electron beam exposure. Using the different photosensitive rates of PMMA and MMA, the size of the patterns formed in the two layers of glue after exposure and lithography is different, and a trapezoid with a narrow top and a wide bottom is obtained. Then, the aluminum lines in different directions are prepared twice by sputtering at different angles. The specific process is: firstly sputtering aluminum in the Y direction, then oxidize the surface layer, and then perform aluminum sputtering in the X direction by turning the angle. , and finally strip off the photoresist.

The technical problems existing in the existing preparation methods are: the electron beam exposure efficiency is extremely low, and large-scale mass production cannot be realized;

3. Contents of the Invention:

The technical problem to be solved by the present invention is: according to the technical problems existing in the above-mentioned prior art, the present invention provides a method for preparing crossed wires on a semiconductor substrate, that is, the present invention provides a method for preparing a Josephson junction. The preparation of the Josephson junction by the method of the present invention can avoid sputtering at a turning angle, thereby facilitating mass production; in addition, the uniformity is greatly improved compared with the prior art.

In order to solve the above problems, the technical scheme adopted by the present invention is:

The present invention provides a kind of preparation method of Josephson junction, described preparation method comprises the following steps:

a. Provide a semiconductor substrate, and form a first conductive pattern layer on the surface of the semiconductor substrate;

b. Partially etched and removed the first conductive pattern layer to obtain a first-direction wire strip;

c, carrying out surface pretreatment and oxidation on the obtained first-direction wire strip;

d. A second conductive pattern layer is formed on the first direction wire bar after surface pretreatment and oxidation, and the second conductive pattern layer covers the surface of the semiconductor substrate and the first direction wire bar;

e. Partially etched and removed the obtained second conductive pattern layer to obtain a second-direction lead; the second-direction lead intersects with the first-direction lead to prepare a Josephson junction.

According to the above-mentioned preparation method of the Josephson junction, the semiconductor substrate is a high-resistance silicon substrate or a sapphire substrate.

According to the above-mentioned preparation method of the Josephson junction, the first conductive pattern layer and the second conductive pattern layer are both formed by a sputtering process or an evaporation process; the metal material used in the sputtering process is titanium, tungsten or aluminum.

According to the above-mentioned preparation method of the Josephson junction, the specific operation process of the partial etching and removal in step b is: combining photolithography and etching process, firstly coating photoresist on the first conductive pattern layer, then exposing and developing , transfer the preset first wire pattern on the photoresist, and the rest are etching windows; finally, the first conductive pattern layer is etched to form the first direction wire.

According to the above-mentioned preparation method of the Josephson junction, the light source used for the exposure is ultraviolet light.

According to the above-mentioned preparation method of the Josephson junction, the specific process of surface pretreatment and oxidation in step c is as follows: using Ar plasma to bombard the surface of the wire strip in the direction of the first layer to remove the natural oxide layer on the surface, and place the Josephson junction on the surface. The resistance of the Senjun junction is affected; oxygen is used in the oxidation process to oxidize the surface of the wire strip in the direction of the first layer at normal temperature to form a Josephson junction structure.

According to the above-mentioned preparation method of the Josephson junction, the specific process of the partial etching in step e is as follows: first, the second conductive pattern layer is coated with photoresist, exposed to light, and developed; then dry etching and wet etching are used in turn. etching to form second-direction wire strips.

According to the preparation method of the above Josephson junction, when the dry etching is removed, the depth of the dry etching is 50 nm; when the wet etching is removed, 10% tetramethylammonium hydroxide TMAH is used, and the corrosion The temperature was 23°C.

According to the above-mentioned preparation method of the Josephson junction, the widths of the first-direction conductor lines and the second-direction conductor lines are both 100-350 nm.

According to the above-mentioned preparation method of the Josephson junction, the cross wire in the step e adopts the Josephson junction.

Positive beneficial effects of the present invention:

1. The technical solution of the present invention adopts a completely different idea from the prior art, first sputtering a conductive layer in a large area, and then etching to form a wire strip with a preset pattern, thereby avoiding sputtering at different angles at different positions, In this way, the uniformity of the conductor lines is improved. Thereby, a cross-conductor structure with good and stable electrical properties is obtained; meanwhile, the technical problem of low electron beam exposure efficiency is avoided, and it can be applied to the needs of mass production.

2. In the technical solution of the present invention, when the second conductive pattern layer is etched, the first dry etching, and then wet etching scheme is adopted, which not only ensures the accuracy of the size of the wire, but also avoids The first conductive pattern layer causes damage. The advantage of dry etching is that small-sized patterns can be engraved, but the selectivity of the underlying aluminum is not good; the advantage of wet etching is that it can stop on the aluminum oxide, but there will be lateral undercutting during the etching process, resulting in the failure of the lines. Accurate control of width. Combining the advantages of these two etching schemes, since the dry etching is only etched to half, it will not cause damage to the underlying pattern; the wet etching corrosion time is short, and there will be no obvious lateral undercutting phenomenon.

3. In the preparation method of the present invention, all the steps of sputtering the wires are full-surface sputtering, and there is no need to rotate the substrate or the angle of the sputtering equipment, and the obtained cross-wire structures are uniformly distributed and have good performance.

4. Although the preparation process of the existing technology is simple, the obtained cross wires have poor uniformity everywhere and low product yield. To this end, the present invention changes the idea, instead of forming grooves for sputtering wires in advance, but sputtering wires in a large area, and then patterning to obtain wire strips with predetermined images. Therefore, using the method of the present invention to prepare the Josephson junction structure can solve the technical problems existing in the prior art.

4. Description of the attached drawings:

Fig. 1 is a structural schematic diagram of the Josephson junction prepared by the present invention.

In FIG. 1 , the metal materials used for sputtering the first conductive pattern layer and the second conductive pattern layer are both aluminum.

Fig. 2 is a schematic diagram comparing the flow chart of the Josephson junction preparation method of the present invention and the existing process flow chart.

FIG. 3 is a physical diagram of a Josephson junction sample prepared by the present invention.

Five, the specific implementation:

The present invention is further described below in conjunction with the examples, but does not limit the protection scope of the technical solutions of the present invention.

Example 1:

The preparation method of the Josephson junction of the present invention, the detailed steps of this preparation method are as follows:

a. Provide a high-resistance silicon substrate, and use a sputtering process to form a first conductive pattern layer on the surface of the high-resistance silicon substrate. The metal material used in the sputtering process is aluminum (metal aluminum is used because it has good electrical conductivity. and stability); the formation of the first conductive pattern layer is to cover the surface of the high-resistance silicon substrate in a large area;

b. Partially etch and remove the first conductive pattern layer to obtain a first-direction wire strip, and the obtained first-direction wire strip has a width of 100 nm to 200 nm;

The specific operation process of the partial etching removal is as follows: combining photolithography and etching processes, firstly coating photoresist on the first conductive pattern layer, then exposing and developing, and transferring the preset first wire pattern on the first conductive pattern layer. On the photoresist, the rest are etching windows; finally, the first conductive pattern layer is etched to form the first direction wire strip; wherein, the light source used for exposure is ultraviolet light (the exposure does not use electron beams, in order to facilitate large-scale quantities. Produce);

c, carrying out surface pretreatment and oxidation on the obtained first-direction wire strips (surface pretreatment and oxidation are for isolation from the second-direction wire strips formed in subsequent processes);

The specific process of the surface pretreatment and oxidation is as follows: using Ar plasma to bombard the surface of the wire strip in the direction of the first layer to remove the natural oxide layer on the surface, and the placement will affect the resistance of the Josephson junction; the oxidation process uses Oxygen, at room temperature, oxidizes the surface of the wire in the first layer direction to form a Josephson junction structure;

d. On the first-direction wire bar after surface pretreatment and oxidation, a second conductive pattern layer is formed by a sputtering process, and the second conductive pattern layer covers the surface of the high-resistance silicon substrate and the first-direction wire bar;

The metal material used in the sputtering process is aluminum, and it is sputtered in a large area; at this time, the surface of the wire strip in the first direction will form a second conductive pattern layer simultaneously with the exposed surface of the substrate; and the surface of the wire strip in the first direction will form a second conductive pattern layer will have a conformal feature with the second conductive layer of the exposed substrate surface, that is, have substantially the same thickness;

e. Part of the obtained second conductive pattern layer is then removed by etching to obtain a second-direction lead (the width of the obtained second-direction lead is 100 nm to 200 nm); the second-direction leads and the first-direction lead The lines are crossed to prepare a Josephson junction;

The specific process of the partial etching is as follows: firstly, coating photoresist on the second conductive pattern layer, exposing it, and developing it; When removing by etching, the depth of dry etching is 50 nm; when removing by wet etching, 10% tetramethylammonium hydroxide TMAH is used, and the etching temperature is 23°C.

Claims (10)

1. A method of preparing a josephson junction, comprising the steps of:

a. providing a semiconductor substrate, and forming a first conductive pattern layer on the surface of the semiconductor substrate;

b. partially etching and removing the first conductive pattern layer to obtain a first direction conducting wire strip;

c. carrying out surface pretreatment and oxidation on the obtained first-direction conducting wire;

d. forming a second conductive pattern layer on the first direction conducting wire strip after surface pretreatment and oxidation, wherein the second conductive pattern layer covers the surfaces of the semiconductor substrate and the first direction conducting wire strip;

e. then, partially etching and removing the obtained second conductive pattern layer to obtain a second direction conducting wire strip; and the second direction lead bars are crossed with the first direction lead bars to prepare the Josephson junction.

2. A method of making a josephson junction according to claim 1, wherein: the semiconductor substrate is a high-resistance silicon substrate or a sapphire substrate.

3. A method of preparing a josephson junction according to claim 1, wherein: the first conductive pattern layer and the second conductive pattern layer are both formed by adopting a sputtering process or an evaporation process; the metal material adopted in the sputtering process is titanium, tungsten or aluminum.

4. A method of preparing a josephson junction according to claim 1, wherein: the specific operation process of the partial etching removal in the step b is as follows: combining photoetching and etching processes, firstly coating photoresist on the first conductive pattern layer, then exposing and developing, transferring a preset first lead bar pattern on the photoresist, and taking the rest as an etching window; and finally, etching the first conductive pattern layer to form a first direction conducting wire strip.

5. A method of making a Josephson junction according to claim 4, wherein: the light source used for the exposure is ultraviolet light.

6. A method of preparing a josephson junction according to claim 1, wherein: the specific processes of surface pretreatment and oxidation in the step c are as follows: bombarding the surface of the first layer of direction wire strips by using Ar plasma to remove a natural oxide layer on the surface, and placing the surface to influence the Josephson junction resistance; and oxidizing the surface of the first layer direction conducting wire strip by using oxygen at normal temperature in the oxidation process to form a Josephson junction structure.

7. The method of claim 1, wherein the step e of partially etching comprises the steps of: firstly, coating photoresist on the second conductive pattern layer, exposing and developing; and then sequentially adopting dry etching and wet etching to form the second direction conducting wire strip.

8. A method of preparing a josephson junction according to claim 7, wherein: when the dry etching is removed, the depth of the dry etching is 50nm; when the wet etching is used for removing, 10% of tetramethyl ammonium hydroxide TMAH is adopted, and the corrosion temperature is 23 ℃.

9. A method of preparing a josephson junction according to claim 1, wherein: the width of each of the first direction conducting wire strips and the second direction conducting wire strips is 100-350 nm.

10. A method of preparing a josephson junction according to claim 1, wherein: step e, the crossed wires adopt Josephson junctions.

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