JPS6221283A - Superconductive integrated circuit - Google Patents

Abstract

PURPOSE:To omit a resistor protecting insulating film, to simplify processes and to improve integration density, by providing a contact layer comprising the same material as that of a resistor at a contact part of first and second superconductors. CONSTITUTION:For a resistor 4, a metal with a thickness of 100nm or less, whose etching selection ratio with respect to a second superconductor 3 is 5 or more, e.g., Au, Pd, Al, or Al alloy, is used. The etching speed of the metal is very slow in reactive ion etching. Even if etching is continued after the etching of the superconductor 3 is finished, the reduction in film thickness is small. Therefore a protecting film is not required. The length of the resistor 4 is specified by the end part of the superconductor 3. A registration space is not required, and integration density is improved. The same material as that of the resistor 4 is used for a contact layer 7, which connects the first and second superconductors 2 and 3. Therefore, the resistor 4 and the layer 7 can be simultaneously formed by the same process. Since the thickness of these parts are thin, the electric resistance between the superconductors 2 and 3 is very small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a superconducting integrated circuit fully utilizing Josephson elements.

[Conventional technology]

The prior art will be explained using FIG. 2. / is the substrate, λ is the first superconductor, 3 is the second superconductor, ≠ is the resistor, an insulating layer that insulates the first and second superconductors except for the shield contact part, 6 is the This is an insulating layer that protects the resistor.

[Problem that the invention seeks to solve]

Conventionally, molybdenum is used as the resistor, niobium is used as the second superconductor, and the second superconductor is OF, , O
It was formed by reactive ion etching using gases such as B and F. If the protective insulating film B does not exist, if etching progresses excessively during the processing of the second superconductor, the resistor ≠.

Although it is directly etched, molybdenum is etched to the same extent as niobium, so the etching of the second superconducting layer must be precisely controlled so that the surface of the resistor is etched right up to the surface, so it is necessary to finish each etching just in case. There is. By the way, etching generally progresses non-uniformly within the wafer, and it is difficult to accurately detect the end point. Therefore, in the past, it was necessary to cover the resistor μ with the protective film insulating layer 2. In order to keep this in mind, the maximum resistance is determined not by the edge of the second superconductor 3, but by the edge of the opening in the insulating film (excess length ≠ storage space). I feel it's necessary. 9. The second superconductor 3 needs to be in contact with the first superconductor λ and the resistor at the same time, and both are sputter-cleaned with argon immediately before the niobium evaporation. . At this time, the power required to remove contamination or oxide film on the niobium surface must be the same as the power necessary and sufficient to clean the resistor surface. It has not been possible to use a resistive material whose film thickness is easily reduced by argon sputter cleaning.

As mentioned above, in the past, an extra process was required due to the need for a protective insulating layer, and the registration space required, which was disadvantageous for integration. There were restrictions on the selection of resistive materials due to constraints on cleaning conditions.

SUMMARY OF THE INVENTION An object of the present invention is to provide a superconducting circuit with simple steps and high integration density.

[Means for solving problems]

The present invention differs from the prior art in that the resistor protection insulation a is not used and a contact layer made of the same material as the resistor is provided in the contact portion.

[For production]

By doing this, it is possible to eliminate the need for insulation replacement to protect the resistor, which is conventionally required, simplify the process, improve integration density, and make the contact between the resistor and other superconductors the same. Since the cleaning can be carried out under the following cleaning conditions, the selection of resistor materials can be expanded.

〔Example〕

Hereinafter, the present invention will be explained in more detail using the drawings.

FIG. 1 is a detailed diagram of the present invention, where / is a substrate, C is a first superconductor, niobium, 3 is a second superconductor, niobium, G is a resistor, 7 is an insulating film for insulating the second superconductor, and 7 is a contact layer for connecting the first and second superconductors. As a resistor,
Gold, palladium, aluminum, and an aluminum alloy containing aluminum with a thickness of 1100 nm or less are used. Compared to niobium, the etching speed of gold, palladium, platinum, aluminum, and aluminum alloys during reactive ion etching using OF, 0BrF, and gas is much slower, and the etching rate continues even after etching of a 2g2 superconductor is completed. Even with extra etching, the film thickness decreases only slightly, so a protective film is not necessary. Therefore, the length of the resistor ≠ is determined by the second
This is the end of the superconductor 3, and unlike conventional registration spaces, it is not necessary and the integration density can be improved.

The contact layer 7 uses the same material as the 5 resistors≠.

Therefore, the resistor ≠ and the contact layer 7 can be formed simultaneously in the same process. The thickness of the contact layer and resistor is /
00 nm or less, the electrical resistance between the first and second superconductors and 3 is negligibly small, or they are coupled in a superconducting state due to the proximity effect. . When depositing this layer 7, it is necessary to sputter clean the surface of the second superconductor, niobium, to ensure good electrical contact.

The second superconductor! ? i. It is necessary to connect the contact layer 7 and the resistor ≠, but in the present invention, since both are made of the same material, the resistor ≠ is connected to the contact layer 7 during sputter cleaning, as in the case where there is no protective film in the prior art. The film thickness of c
b, or the electrical connection to the first superconductor will not become insufficient. Therefore, it is possible to use a material such as gold or palladium, which has a slow etch rate during reactive etching of niobium but a faster sputter etch rate during sputter cleaning with argon gas than niobium.

〔Effect of the invention〕

As explained above, since no protective film is used, the process is simplified, and since the resistor and superconductor can be connected without a resistor storage base, there is an advantage that the integration density can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 1 is a sectional view of a conventional superconducting circuit. /...substrate, co...first superconductor, 3...second
Superconductor, ≠...resistance,! ...Insulation tribe, B...
- Insulating film for resistance protection, 7... contact layer.

Claims (1)

[Claims] 1. A first and a second superconductor, a contact portion that electrically connects the first and second superconductors to each other, and a contact portion that electrically connects the second superconductor and the second superconductor. a resistor connected to the superconducting integrated circuit, a contact layer interposed between the first and second superconductors and in contact with the first and second superconductors; and are metal layers made of the same metal material, each having a thickness of 100 nm or less and having an etching selectivity of 5 or more with respect to the second superconductor. 2. Claim 1, wherein the second superconductor is niobium, and the metal layer forming the contact layer and the resistance layer is an alloy containing palladium, gold, platinum, aluminum, or aluminum. Superconducting integrated circuit as described in section.