JPS6029235B2 - Manufacturing method of superconducting circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a first step of forming a superconductor layer made of niobium (Nb) on a substrate, and a non-conductor layer on the substrate extending above the superconductor. and a second step of forming a superconductor layer.

In the manufacturing method of such a superconducting circuit device, a superconductor layer made of niobium is formed on a substrate as a superconductor wiring layer, a superconductor layer for grounding, a superconductor electrode layer of a Josephson junction element, etc. , and also has a configuration in which a non-superconductor layer extending over the superconductor layer is formed on the substrate as an insulating layer, a protective layer, an interlayer insulating layer, a tunnel barrier layer of a Josephson junction element, etc. , is widely applied when manufacturing various superconducting circuit devices.

By the way, in the method for manufacturing the above-mentioned superconducting circuit device, conventionally, the second step of forming a non-superconducting layer on the substrate is performed using a vacuum evaporation method, a sputtering method, or a chemical vapor deposition method (CVD method). It was normal for the process to use one of these methods.

However, when the second step is a step using a vacuum hollywood deposition method, it is difficult to form a non-superconductor layer with few pinholes.

Moreover, in order to avoid this, the non-superconductor layer had to be formed thickly. For this reason, the second
The process is a process using a vacuum evaporation method,
This conventional method for manufacturing a superconducting circuit device has the drawback that it is not possible to easily manufacture a superconducting circuit device with desired good characteristics.

Further, when the second step is a step using a sputtering method or a CVD method, it is necessary to heat the substrate together with the superconductor layer to a high temperature.

In addition, the ions of the non-superconductor that will become the non-superconductor layer collide with the superconductor layer made of niobium at a relatively high collision velocity, and the superconductor layer is heated as described above. Due to these factors, the superconductor layer has a disadvantage of having a low superconducting transition temperature and a long magnetic penetration distance, resulting in a deteriorated superconductor layer. Note that when the superconductor layer has a large magnetic penetration distance, the superconductor layer has a large self-inductance. Furthermore, in order to avoid the above-mentioned disadvantages, it was necessary to form a thick superconductor layer in the first step. Therefore, in the case of a conventional manufacturing method for a superconducting circuit device in which the second step is a step using a sputtering method or a CVD method, the superconducting circuit device is manufactured as having a Josephson junction element, When the superconductor layer of the Josephson junction element is the superconductor layer formed in the first step described above, the Josephson junction element has a low gap voltage and therefore a slow operation speed. In addition, when manufacturing a superconducting circuit device in which the superconductor layer formed in the first step described above is used as a wiring layer, the wiring layer is formed with a large self-inductance. Furthermore, by forming the non-superconductor layer with steps, it is easy to make the superconducting circuit device have the desired characteristics.
It had the disadvantage that it could not be manufactured at a low cost.

Therefore, the present invention proposes a novel method for manufacturing a superconducting circuit device that does not have the above-mentioned drawbacks, and this will become clear from the description of embodiments of the present invention below.

1A to 1C show an example of a method for manufacturing a superconducting circuit device according to the present invention.

In an example of the method for manufacturing a superconducting circuit device according to the present invention,
A required substrate 1 is prepared in advance (FIG. 1A).

Then, a superconductor layer 2 made of niobium (Nb) was formed on the substrate 1 by various methods known per se.
Form into a desired pattern (FIG. 1B).

Next, a non-superconductor layer 3 is formed on the substrate 1, extending over the superconductor layer 2 (FIG. 1C).

In this case, the non-superconductor layer 3 is formed as described below with reference to FIG. That is, the plasma apparatus 10 shown in FIG. 2 is prepared.

This plasma device 10 includes a plasma generation section 13 having a microwave inlet 11 and a gas inlet 12, and a substrate placement section 15 communicating with the plasma generation section 13 and having another gas introduction row 4 and a gas outlet 19. It has a container 16 having a.

Further, the plasma apparatus 1 also has a magnetic field applying means 17 made of a permanent magnet or a DC electromagnet.

This magnetic field applying means 17 extends inside the container 16 in a direction connecting the plasma generation section 13 and the substrate placement section 15 as shown by the dotted line, and the inside of the substrate placement section 15 is compared to the inside of the plasma generation section 13. They are arranged around the plasma generating part 13 of the container 16 so as to provide a magnetic field 18 having a sparse density distribution. Therefore, as shown in FIG.
The substrate 1 on which the superconductor layer 2, obtained in the step described above with reference to FIG. 1B is formed, is placed in the substrate placement section 15.
Next, the inside of the container 16 is exhausted through the gas outlet 19.

Next, while evacuating the inside of the container 16 through the gas exhaust port 19, the first gas GI is introduced into the plasma generation section 13 from the gas introduction port 12, and the microwave M is introduced from the microwave introduction port 11. At the same time, into the container 14,
The above-described magnetic field 18 is applied from the magnetic field applying means 17 to generate plasma ions of the first gas GI within the plasma generating section 13 .

Plasma ions generated within the plasma generating section 13 are then introduced into the substrate placement section 15 by the magnetic field 18 described above.

Further, within the substrate placement section 15, plasma ions of the first gas GI are introduced into a second gas inlet GI in advance from the gas inlet 14.
gas G2 and the reaction product is deposited as a non-superconductor on the substrate 1 to form a non-superconductor layer 3 extending over the superconductor layer 2 on the substrate 1. Let it form.

In the manner described above, the non-superconductor layer 3 is formed as shown in FIG. 1C.

Hereinafter, the non-superconductor layer 3 formed as described above is subjected to a patterning process which is known per se,
Other superconductor layers extending over the patterned or unpatterned non-superconductor layer 3 may be formed on the substrate 1 by various methods known per se. Then, the desired superconducting circuit device is manufactured.

The above is an example of a method for manufacturing a superconducting circuit device according to the present invention.

The method for manufacturing a superconducting circuit device according to the present invention includes a first step (FIG. 1B) of forming a superconductor layer 2 on a substrate 1.
) and a second step (FIG. 1C) of forming a non-superconductor layer 3 on the substrate 1 extending over the superconductor layer 2.

The second step is the plasma apparatus 10 described above.
In the plasma generating section 13 of the container 16, the first
The plasma ions of the gas GI are generated, the plasma ions are introduced into the substrate placement section 15, and the plasma ions are introduced into the substrate placement section 1.
5 reacting the plasma ions with a second gas G2;
The reaction product is deposited as a non-superconductor on the substrate 1 to form a non-superconductor layer 3 on the substrate 1 extending over the superconductor layer 2. .

Therefore, in the second step, the non-superconductor layer 3 extending above the superconductor layer can be easily formed on the substrate 1 with fewer pinholes without increasing its thickness. can be formed. Further, there is no need to heat the substrate 1 together with the superconductor layer 2 to a high temperature of 10,000° C. or higher.

Furthermore, plasma ions do not collide with the superconductor layer 2 at a high collision speed. Furthermore, as mentioned above, since the superconductor layer 2 is not heated to a high temperature, the superconductor layer 2 becomes deteriorated with a low superconducting transition temperature and a large magnetic penetration distance. I don't have it. Furthermore, in order to avoid such inconveniences, it is not necessary to form the superconductor layer 2 thickly in the first step. Therefore, according to the method for manufacturing a superconducting circuit device according to the present invention, the superconducting circuit device is manufactured as having a Josephson junction element, and the superconductor layer of the Josephson junction element is replaced with the above-mentioned first layer. In the case of the superconductor layer 2 formed in the step of When manufacturing the superconductor layer 2 formed in the process as a wiring layer, the wiring layer may be formed with a large self-inductance, or the non-superconductor layer 3 may be formed with a step. It has the characteristics that it can be manufactured easily and at low cost as it has the desired excellent properties without being affected. In addition, such a feature is particularly due to the fact that in the second step, the first gas GI is oxygen gas or nitrogen gas, and the second gas G2 is a silicon compound such as Si3. (Si02) or silicon nitride (
This was noticeable when Si3N4) was deposited on the substrate 1 as a reaction product as a non-superconductor.

Incidentally, in the second step, the first gas GI is oxygen gas, and the second gas G2 is Si gas, so that silicon oxide Si02 has a reactivity as a non-superconductor. As a component, when deposited on the substrate 1 at room temperature, the superconducting transition temperature Tc of the superconductor layer 2 described above with respect to the rate (in nm) at which the non-superconductor is deposited on the substrate 1. The relationship shown in the solid line in FIG. 3 was obtained. On the other hand, the second step may be performed by the sputtering method using a secondary magnetron and the sputtering method using a parallel plate described at the beginning.
In both cases, the relationship between the superconducting transition temperature Tc of the superconductor layer 2 and the rate at which the non-superconductor is deposited on the substrate 1 is shown in Figure 3. The results were obtained as shown by the dotted and chain lines. From this, according to the present invention, the superconducting transition temperature Tc of the superconductor layer 2 with respect to the rate at which the non-superconductor is deposited on the substrate 1 is
It will be clear that a wide range of rates at which the non-superconductor is deposited on the substrate 1 preserves high values compared to the conventional case. Also, the rate at which the non-superconductor is deposited on the substrate 1 (n
According to the present invention, the relationship between the magnetic penetration distance (nm) and the magnetic penetration distance (nm) in the superconductor layer 2 was obtained as shown by the solid line in FIG. 4 (m/min).

On the other hand, regardless of the present invention, the second step uses the conventional sputtering method using a magnetron and the sputtering method using a parallel plate (both of which have a substrate temperature of 2500°) as described at the beginning. In the case of the process in which the non-superconductor was deposited on the substrate 1, the relationship between the periodic penetration distance in the superconductor 2 and the rate at which the non-superconductor was deposited on the substrate 1 was obtained as shown by the dotted line and the chain line in FIG. Note that the second step is
In the case of the process using the above-described secondary sputtering method, as the rate at which the non-superconductor is deposited on the substrate 1 increases, as shown by the dotted line and the chain line in FIG.
The reason why the magnetic penetration depth in the superconductor layer 2 increases is that the kinetic energy of the Si02 particles incident on the superconductor layer 2 increases as the rate at which the non-superconductor is deposited on the substrate 1 increases. It is presumed that this is because the superconductor layer 2 is damaged accordingly. From what is shown in FIG. 4, according to the present invention, the magnetic penetration distance in the superconductor layer 2 is dependent on the rate at which the non-superconductor is deposited on the substrate 1.
It will be clear that the value remains small over a wider range of speeds at which the non-superconductor is deposited on the substrate 1 than in the conventional case. For this reason, the superconductor layer 2 has a low self-inductance, and therefore, when the method for manufacturing a superconducting circuit device according to the present invention is applied to manufacturing a Josephson junction element, the Josephson junction element has a characteristic It can be manufactured as a good product. Note that the above description merely shows an example of the method for manufacturing a superconducting circuit device according to the present invention, and various modifications and changes may be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

FIGS. 1A to 1C are schematic cross-sectional views showing sequential steps of an example of a method for manufacturing a superconducting circuit device according to the present invention. FIG. 2 is an example of a plasma device used in the second step in the method for manufacturing a superconducting circuit device according to the present invention, and a schematic cross-sectional view for explaining the second step. FIG. 3 shows the rate (nm
/min) of the superconductor layer versus the superconducting transition temperature Tc (K
) is a diagram showing the relationship between FIG. 4 shows the magnetic penetration distance (nm) of the superconductor layer versus the rate (nm/min) of depositing the non-superconductor layer on the substrate in a specific example of the method for manufacturing a superconductor circuit device according to the present invention. FIG. 1
...Substrate, 2...Superconductor layer, 3...
...Non-superconductor layer, 10...Plasma device, 11.
...Microwave inlet, 12...First gas inlet, 13...Plasma generation part, 14.
...Second gas introduction port, 15...Substrate arrangement section, I
C... Container, 17... Magnetic field applying means, 18
...Magnetic field, 19...Gas exhaust port, GI
...First gas, 2...Second gas,
M...Microwave. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A first step of forming a superconductor layer made of niobium on a substrate, and forming a non-superconductor layer extending on the superconductor layer on the substrate. a second step of
In the method for manufacturing a superconducting circuit device, in the second step, a plasma generating section having a microwave inlet and a first gas inlet, and a second plasma generating section communicating with the plasma generating section and
a container having a substrate placement portion having a gas inlet; and a container having a substrate placement portion extending in a direction connecting the plasma generation portion and the substrate placement portion within the container, the inside of the substrate placement portion being sparsely spaced compared to the plasma generation portion. The plasma is generated using a plasma apparatus having a magnetic field applying means for applying a magnetic field having a density distribution, and with the substrate on which the superconductor layer is formed being placed in the substrate placement part of the container, the plasma is generated. A first gas is introduced into the unit from the first gas introduction port, and a microwave is introduced from the microwave introduction port,
Applying the magnetic field from the magnetic field applying means into the container to generate plasma ions of the first gas in the plasma generating section; , the plasma ions of the first gas are introduced into the substrate placement section, and the plasma ions of the first gas are reacted with the second gas introduced in advance from the second gas introduction port, and the reaction product is produced. A method for manufacturing a superconducting circuit device, characterized in that a non-superconductor layer is formed on the substrate by depositing on the substrate as a non-superconductor. 2. In the method for manufacturing a superconducting circuit device according to claim 1, the first gas is oxygen gas or nitrogen gas, and the second gas is silicon compound gas, and therefore, the silicon oxide A superconducting circuit device, characterized in that a substance or silicon nitride is deposited on the substrate as the reaction product as the non-superconductor.