JPS58125881A - Constitution of vertical type resistance circuit - Google Patents

Abstract

PURPOSE:To increase the degree of integration of the resistor for the titled resistance circuit by a method wherein a thin film resistor, consisting of AuIn2, CuSb, Sb, Te, Si, Ge and the like, is interposed between two superconductive electrodes, and the resistance part and its contact part are arranged in three- dimension form. CONSTITUTION:A photoresist layer 10, having a prescribed aperture provided on a silicon or glass substrate 9 and a Pb-In-Au alloy film 11, which will be used as the lower electrode for Josephson element, is vapor-deposited on the whole surface. Then, the layer 10 is removed together with the film 11 located above the layer 10, a lower electrode 3 consisting of the film 11 is left on the substrate 9 alone, a resistance part 6 consisting of AuIn2, AuCr and the like is formed on a part of the surface of the lower electrode 3 through a resistance part 7, and the above is surrounded by an interlayer insulating film 8. Subsequently, an upper electrode 5 consisting of an integrally formed PbAu alloy is coated in such a manner that it will be positioned on the resistance part 6 and the tunnel barrier layer 4 of the lower electrode 3 adjoining the resistance part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for configuring a vertical resistance circuit realized by sandwiching a resistance thin film between two superconducting electrodes.

Conventionally, resistors have been used as important circuit elements in Josephson element integrated circuits. Figure 1 shows the most basic circuit diagram, in which a diode Sefson element and a resistor are connected in parallel.

Most of the complicated circuits are constructed by combining the circuits shown in FIG. In the Josephson integrated circuit constructed using the circuit shown in Figure 1, a tunnel-type Jiso-Sefson junction element is used, in which an oxide film is interposed between two superconducting thin films, and each electrode is connected to a resistive thin film. The circuit shown in Figure 1 is realized. An example is shown in FIG. As shown in FIG. 2, the resistive circuit portion consists of a portion that connects the resistive portion and each superconducting electrode. In the figure, current flows in the direction indicated by the arrow. Letting the length of the resistance in the direction of the arrow be l, if we examine the change in the resistance value H with respect to l, as shown in Figure 3, even in the limit of l = 0, R
is a non-zero value FL. It has (>0). This is the contact resistance generated at the connection between each superconductor thin film and the resistor. Generally, it is desirable that this value R0 is sufficiently smaller than H, and for this purpose it is necessary to provide a large connection area. In practice, for this reason, the area of the connection portion and the area of the actual resistance portion may be approximately the same.

This is a major obstacle in terms of integration. Conventionally, as a method to solve this problem, a method has been proposed in which a dicarbonate Sefson element, which is a resistor, is placed directly below the joint portion, as shown in FIG. When this type of structure is used, it is the most representative and practical. Pb alloy film electrode and Au1n
In a circuit using a resistor, there is a big practical problem in that the tunnel barrier layer, which exists only by the thickness of the resistor and the lower electrode, changes over time due to the diffusion phenomenon of In.

The present invention makes it possible to eliminate obstacles to integration that occur in order to reduce the contact resistance at the connection portion between a resistor and a superconductor in an integrated circuit without adversely affecting the integrated circuit elements. The purpose of this invention is to provide a method for configuring a thin film resistor circuit.

In the present invention, by sandwiching the resistor between two superconducting thin films, the actual resistance part and the two connection parts are arranged three-dimensionally in the film thickness direction, and no extra area is required for connection. The basic idea is to construct a resistor circuit for an integrated circuit.

An embodiment of the present invention will be described below with reference to FIG. Fifth
In Figure (A), for example, an AZ1350J positive resist film 10 manufactured by Sibley Co., Ltd. is coated as a phytoresist for using a lift-off method on a silicon or glass substrate 9 to a thickness of about 1 [μm] (hereinafter referred to as phytoresist). (The same type of phytoresist is used in the step of 1) After that, the phytoresist film IO is patterned by applying a normal lithography technique, and openings in the resist film are formed in some parts. Next, in the step shown in FIG. 5(B), an alloy of Pb, In, Au, etc., which constitutes the lower electrode of the di-Sephson element, is vapor-deposited. Next, in the step of FIG. 5(C), the substrate 9 is immersed in, for example, acetone to remove the phytoresist film IO and the vapor deposited film deposited on the resist film, thereby forming the lower electrode 3. In the conventional circuit including a resistor circuit, as shown in FIGS. 2 and 4, it is necessary to form the resistor before forming the lower electrode, but the present invention According to 1, it is also possible to form the lower electrode first as shown in this embodiment. Next, in the step shown in FIG. 5(D), for example, Au I n! .

A resistor is formed on the lower electrode by vapor deposition of AuCr, Curb, CuA/ or a composite thereof, or a semimetal/semiconductor such as Bi, Sb, Te, G, or a compound thereof. Immediately before vapor deposition of the resistive film, the contact resistance can be reduced by etching the surface of the lower electrode that will be connected to the resistor using a plasma etching method using etching gas such as argon or oxygen. can be reduced and kept constant. Subsequently, in the step shown in FIG. 5(E),
Using a lift-off method similar to that shown in FIGS. 5A to 5C, an interlayer insulating film layer 8 with openings formed on the surface of the lower electrode 3 and the upper part of the resistor 6 is formed by vapor deposition of, for example, SiO. Next, in the step of FIG. 5(F), after forming a resist film for the upper electrode of the diagonal Sefson element in the same manner as the step of FIG. 5(A), for example, argon gas is applied.

The surface of the lower electrode and the upper part of the resistor exposed in the opening of the SiO interlayer insulating layer 8 are cleaned by plasma etching using an etching gas such as oxygen, and then the exposed portion of the lower electrode 3 is cleaned using a thermal oxidation method or a plasma oxidation method. A tunnel barrier layer is formed by oxidizing the material by, for example, Next, Figure 5 (G
), for example, Pb, Au alloy or Pb, Bi
By forming the upper electrode 5 of the alloy film, a circuit is completed in which the tunnel type diode and Sefson element and the resistor are connected in parallel.

According to this embodiment, by sandwiching the resistor between the two electrodes of the Jiso-Sefson element, the actual resistance portion and the connection portion are arranged three-dimensionally, and the resistor is integrated. Furthermore, by separating the resistor from the junction part of the Josephson element by an appropriate distance, it is possible to prevent the resistor from changing the tunnel barrier layer over time due to diffusion phenomena. By sandwiching the resistor between body layers, the actual resistor part and the contact parts at both ends can be arranged three-dimensionally, which makes it possible to integrate the resistor without requiring extra area for the contact part. It has a big effect. Also, this configuration method is
The requirement is to sandwich the resistor between two superconductor layers, and any two superconductor layers can be selected.

Therefore, it has the effect of increasing the degree of freedom in circuit configuration.

[Brief explanation of drawings]

Figure 1 is a circuit diagram including a Josephson element and a resistor;
The figure is a perspective view of a circuit including a Josephson element and a resistor, the third figure is a graph showing the relationship between resistance length and resistance value, the fourth figure is a sectional view of the main part of a circuit including a Josephson element and a resistor, and the third figure is a graph showing the relationship between resistance length and resistance value. 5
Figures (A) to (G) are sectional views of main parts showing the manufacturing process of a vertical resistance circuit according to an embodiment of the present invention. 1... Di-Sefson element, 2... Resistor, 3... Lower electrode of the D-Sefson element, 4...
...Tunnel barrier layer, 5...Top electrode, 6...Resistance part, 7...Contact resistance part, 8...Interlayer Insulating layer, 9... substrate, 10... resist film, 11... vapor deposited film.

Claims (1)

[Claims] 1. A thin film resistor is sandwiched between both electrodes of a Girocefson element, or one or both of the electrode films is replaced with another superconductor layer, and the resistor is sandwiched between two superconductors. A method for configuring a vertical resistance circuit, characterized in that the resistor and the connection portions at both ends thereof are arranged three-dimensionally so that the current path flowing through the resistor is in the direction of its film thickness. 26 AuIn2.2 as the material of the thin film resistor. Au
Cr. The I vertical resistor according to claim 1, characterized in that Curb, CuA/or a composite thereof, or a semimetal/semiconductor such as Bi, Sb, Te, Si, Go, or a compound thereof is used. How to configure a circuit.