JPH09252026A - Superconductor device - Google Patents

Abstract

PURPOSE: To provide a superconductor device using a low-durable temp. Josephson element by mounting its junction by hot compression bonding and reduce the man-hours and enhance the adhesion of the entire chip by a multi- contact connection at once. CONSTITUTION: A chip substrate 2 having bumps is hot compression bonded to a glass-epoxy mounting board 6 having a plated Sn superconductor film 8 on a Cu interconnection base pattern 7 at a bonding temp. of 100 deg. for a bonding time of 2 min, using a flip chip bonder. Though the bonding temp. is set to 100 deg., the durable temp. of an Nb-Al tunnel barrier type Josephson element is 150 deg. and bonding temp. is 150 deg. max. The critical contact of the bonded part is 15mA or more, showing a sufficient superconductor property. The bond strength is 0.2N per bond, and the entire board has a strength of 3.4N with 17 bonded units.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device mounted with a superconducting circuit chip to which a Josephson element is applied,
Particularly, the present invention relates to a superconducting device using a Josephson element having a low heat resistance temperature.

[0002]

2. Description of the Related Art Conventionally, superconducting connection between a superconducting circuit chip and a mounting substrate is performed by superconducting wire bonding using a superconducting wire or flip chip by fusion bonding, as disclosed in, for example, JP-A-3-12941. Bonding is used. FIG. 3 is a diagram showing a superconducting device according to a conventional example, and shows a superconducting device using a superconducting connection by superconducting wire bonding. 12 is a superconducting circuit chip, 16 is a mounting substrate, 13 is a pad, 15 is a buffer layer, 17 is a superconducting substrate electrode, 11 is a superconducting wire, and the superconducting circuit chip 12 forms a superconducting circuit on the mounting substrate 16. A buffer layer 15 is formed on the pad 13 to increase the bonding strength while maintaining the superconductivity, and the superconducting substrate electrode 17 and the pad 1 are bonded to each other.
3 was connected by wire bonding of the superconducting wire 11.

In superconducting flip-chip bonding, bumps made of a superconducting material formed by a ball bonding method are used to heat the joint to a temperature of 200 ° C. and perform superconducting connection by melt-bonding.

[0004]

In the conventional superconducting device using the above-mentioned superconducting wire bonding, it is necessary to bond as many wires as the number of bonding terminals, so that the number of steps is large, and the bonding wire forms an inductance to form a circuit. There is a problem that the characteristics are affected and the bonding wire and the surface of the chip are exposed, resulting in damage or electrical short circuit. In the conventional superconducting device using flip chip bonding, the temperature of the joint must be heated to about 200 ° C., so that the heat resistance temperature of the niobium (Nb) -aluminum (Al) system is about 150 ° C. In the superconducting device using the tunnel barrier type Josephson element, there was a problem that the element characteristics were deteriorated and could not be actually implemented.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to bond a chip having a Josephson junction and a superconducting circuit having a buffer layer at the junction for connecting substrates to each other. The bonding portion was mounted by thermocompression bonding at a temperature of 150 ° C. or less on a substrate having a wiring pattern made of a superconducting material, via a bump made of a superconducting material arranged in the portion.

[0006]

With the superconducting device as described above, a superconducting device using a Josephson element having a low heat resistant temperature can be realized, and since multiple points are connected at one time, the number of steps is reduced and the bonding strength of the entire chip is increased. It is possible to reduce the inductance of the joint and protect the chip surface because the chip is mounted face down.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are a partial sectional view and a plan view of a superconducting device showing an embodiment of the present invention. FIG. 1 is a diagram showing a superconducting junction. 1 is a superconducting bump. The material of the superconducting bump 1 is lead tin (Pb-Sn)
A superconducting material such as an alloy or a lead-indium-gold (Pb-In-Au) alloy is used, and a ball formed by arc discharge is used as a wire rod of the same material, and is formed by a ball bonding method. Reference numeral 2 is a chip substrate, 3 is a superconducting circuit pattern, 4 is an insulating layer, and 5 is a buffer layer, and a pad portion for connecting to an external circuit of the superconducting circuit pattern 3 which constitutes the wiring of the superconducting circuit 9 shown in FIG. 10 is formed with a buffer layer 5 for increasing the bonding strength while maintaining superconductivity.

The superconducting circuit 9 is, for example, a DC drive type quantum interference device (DC SQUID), an AC drive type quantum interference device (RF SQUID), a Josephson logic circuit device, a Josephson array, and a pole such as silicon (Si). It is formed by a thin film process on the chip substrate 2 using a material exhibiting an insulating property at a low temperature. Examples of the material of the superconducting circuit pattern 3 include niobium (Nb) and lead-indium alloy (P
b-In), Pb-In-Au, or other thin film of a superconducting material is used, and the material of the insulating layer 4 is silicon dioxide (Si).
O2), silicon oxide (SiO), Si, or other material exhibiting an insulating property at an extremely low temperature is used, and the buffer layer 5 is made of gold (Au), platinum (Pt) palladium (Pd), silver (Ag), Lead (Pb), another alloy containing Pb as a main element, or the like is used.

When the thickness of the buffer layer 5 is, for example, 5 nm to 200 nm when Au is used as the material, the bonding strength can be increased while maintaining the superconductivity of the bonding. 6 is a mounting substrate, 7 is a wiring base pattern, and 8 is a superconducting film. The wiring base pattern 7 is formed on the mounting substrate 6, and the superconducting film 8 is further formed on the wiring base pattern 7 by plating. The wiring base pattern 7 and the superconducting film 8 form the same pattern to form a superconducting wiring pattern. As the material of the mounting board 6, an insulating material such as plastic, FRP, or ceramic is used.
The wiring base pattern 7 functions as a buffer layer for plating the superconducting film 8, and its material is copper (C
A resistance material such as u) or palladium (Pd) is used, but another high resistance material can also be used. Superconducting film 8
For example, a Pb-Sn plated film is used as the material of, but another superconductive material that can be plated can also be used.

Further, the wiring base pattern 7 is eliminated and the Nb sputtered film wiring, Pb-In-A, is directly formed on the mounting substrate 6.
It is also possible to form a superconducting film such as a u-deposited film wiring to form a superconducting wiring pattern. However, when Nb is used as the material of the superconducting wiring pattern, it is necessary to dispose a thin film having the same material and function as the buffer layer 5 at the junction.

In the plan view of the superconducting circuit chip shown in FIG. 2, 9 is a superconducting circuit and 10 is a bonding pad.
400μm × 400μ on the chip substrate 2 of mm × 5mm
Seventeen m bonding pads 10 are arranged, including reinforcing pads not involved in electrical connection. Nb
-Al-based tunnel barrier type Josephson device D
The C SQUID pad 10 is composed of a superconducting circuit pattern 3 made of a Nb sputtered film and a buffer layer 5 made of an Au sputtered film having a thickness of 30 nm. A ball having a diameter of 90 μm formed by arc discharge was placed as a superconducting bump 1 having a diameter of 110 μm on each pad under the bonding conditions of an output of 0.6 W, an oscillation time of 20 ms, and a weight of 0.32 N by a ball bonding method.

Next, the bumped chip substrate 2 is placed on the Cu wiring base pattern 7 using a flip chip bonder under the conditions of a bonding temperature of 100 ° C., a bonding time of 2 min, and a weight of 0.7 N per bump. Plated Pb-S
It was thermocompression bonded to the glass epoxy mounting substrate 6 having the n superconducting film 8. Although the junction temperature is set to 100 degrees in the above-mentioned embodiment, the heat resistance temperature of the Nb-Al-based tunnel barrier type Josephson element is 150 degrees, and the junction temperature is the upper limit of 150 degrees.

When the above-mentioned superconducting device is constructed, the critical current of the junction is 15 mA or more, which shows sufficient superconductivity.
The bond strength was 0.2 N per bond, and the strength of 3.4 N for 17 bonds was obtained for the entire substrate. In addition, the characteristics of the DC SQIUD after mounting did not deteriorate. The superconducting device as described above enables a superconducting device using a Josephson element with a low heat resistance temperature, and since multiple points are connected at one time, it is possible to reduce the number of steps and increase the bonding strength of the entire chip. Since the inductance of the joint is reduced and the chip is mounted face down, the chip surface can be protected.

In the above embodiment, the superconducting bumps 1 are arranged one by one on each pad, but a plurality of superconducting bumps 1 are arranged on one pad and the bonding weight per bump must be changed. The bonding strength of the entire substrate can be increased. Even if multiple superconducting bumps 1 are placed on one pad,
The action and effect are the same as those in the above-mentioned embodiment.

[0015]

As described above, according to the present invention, it is possible to realize a superconducting device using a Josephson element having a low heat resistant temperature, and to connect multiple points at one time. Strength can be increased,
Since the inductance of the joint is reduced and the chip is mounted face down, the chip surface can be protected. Therefore, it is possible to provide a highly reliable superconducting device with excellent mass productivity.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a superconducting device showing an embodiment of the present invention.

FIG. 2 is a plan view of a superconducting circuit chip that constitutes a superconducting device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a conventional superconducting device.

[Explanation of symbols]

 1 superconducting bump 2 chip substrate 3 superconducting circuit pattern 4 insulating layer 5 buffer layer 6 mounting substrate 7 wiring base pattern 8 superconducting film 9 superconducting circuit 10 pad 11 superconducting wire 12 superconducting circuit chip 13 pad 15 buffer layer 16 Mounting board 17 Superconducting board electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Kaya 6-31-1 Kameido, Koto-ku, Tokyo Seiko Denshi Kogyo Co., Ltd. (72) Toshinori Kogashi 8-5-1 Shimonrenjaku, Mitaka-shi, Tokyo Tanaka Denshi Kogyo Co., Ltd. (72) Inventor Hideyuki Akimoto 8-5-1, Shimorenjaku, Mitaka-shi, Tokyo Tanaka Electronics Industry Co., Ltd. (72) Inventor Hiroyuki 8-5-1, Shimorenjaku, Mitaka-shi, Tokyo Tanaka Electronic Industry Co., Ltd.

Claims (2)

[Claims] 1. A chip having a Josephson junction and having a superconducting circuit having a buffer layer at a joint for connecting to a substrate is formed by a superconductor via a bump made of a superconducting material arranged at the joint. A superconducting device mounted on a substrate having a wiring pattern made of a conductive material, wherein the joint is mounted by thermocompression bonding. 2. The superconducting device according to claim 1, wherein the joint portion is thermocompression bonded at a temperature of 150 ° C. or lower.