JPH0395979A - Method of diagnosing whether superconductive integrated circuit is good or bad - Google Patents

Abstract

PURPOSE:To diagnose a circuit all over en bloc at the defective conductivity and insulation places of a superconductive integrated circuit by applying anode oxidation to the side of a semiconductor substrate, and judging the conditions of oxide film formation at the surface of an electrode, and discriminating whether it lies in the electrode to be connected electrically with a superconductive grand plane or the electrode to be insulated. CONSTITUTION:A superfine probe 42 soaked in a jelly-form electrolyte 41 is connected to the negative pole of a DC power source 25. A wafer 31 is connected to the positive pole of the DC electrode 25 so as to form an anode. For this reason, the electrode, which is conductive with the wafer 31 by the application of the DC power source 25 acts as an anode and forms an oxide film, and the electrode, which is insulated from the wafer 31 by an insulator, never oxidizes. The oxide film about several hundred nm in thickness used in a superconductive integrated circuit 11 transmits some of the light from the outside and reflect the other at the surface. The transmitted light is reflected at the boundary face between the oxide film and a metallic electrode, and it interferes with the light reflected from the surface of the oxide film and exhibits the color in accord with the thickness of the oxide film. Accordingly, by the existence of color, the discrimination between the place where an oxide film is present or the place where it is not present can be carried out.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a method for diagnosing the quality of a superconducting integrated circuit, which tests the quality of the electrical connection of electrodes by anodizing the superconducting integrated circuit. It is.

[Conventional technology]

FIG. 5 is a perspective view showing an example of a conventional method for diagnosing the quality of a superconducting integrated circuit, in which 1 is a superconducting integrated circuit, 2 is a first electrode, 3 is a second electrode, and 4 is an insulating layer or a resistor. 5 is a DC power supply, 6 is a current terminal, 7 is a voltmeter, and 8 is a voltage terminal. In this way, in the conventional diagnostic method, a constant current is passed between the first and second electrodes 2 and 3 where a conduction point or an insulation point is to be detected, and the voltage between each electrode 2.3 is measured.
was performing detection.

[Problem to be solved by the invention]

However, as circuits become finer in the conventional diagnostic method described above, the current terminal 6 and the voltage terminal 8 are connected to each electrode 2 and 3.
It has become difficult to connect to.

(2) In one measurement, only the continuity or insulation between a pair of electrodes 2.3 can be determined. Therefore, it takes a lot of time and effort to detect continuity and insulation between all the electrodes of the superconducting integrated circuit 1.

There was a problem.

This invention was made in order to solve the above problems, and by partially anodizing the electrodes of a superconducting integrated circuit, it is possible to easily diagnose continuity and insulation in the superconducting integrated circuit. The purpose is to obtain a method for diagnosing the quality of integrated circuits.

[Means to solve the problem]

The method for diagnosing the quality of superconducting integrated circuits according to the present invention involves performing anodic oxidation using the semiconductor substrate side as the anode, determining the state of formation of an oxide film on the surface of the target electrode, and electrically connecting it to the superconducting ground plane. This is to identify whether the electrode should be connected or insulated.

(Function) In this invention, since the electrode that is electrically connected to the substrate acts as an anode, its surface is oxidized to form an oxide film, and the insulated electrode does not act as an anode.
Since no oxide film is formed, the degree of conduction and insulation can be diagnosed based on the degree of oxidation.

[Example] First, a superconducting integrated circuit and an anodizing method will be explained.

(1) About superconducting integrated circuits FIG. 2 is a sectional view showing a superconducting integrated circuit.

In this figure, a superconducting integrated circuit 11 is connected to a semiconductor substrate 12.
A superconducting ground plane 13, an insulating layer 14 on top. The first one consists of superconductivity (or normal conduction). Second electrode 15.1
It consists of 6.

The superconducting ground plane 13 is necessary for magnetic field confinement and as an earth i-pole, and circuit components using other electrodes, such as Josephson elements, resistors, and wiring, use the insulating layer 14 on the superconducting ground plane 13. (not shown). Furthermore, there is a first electrode 15 that needs to be electrically connected to the superconducting ground plane 13, and a second electrode 16 that needs to be insulated. It is necessary for the circuit to operate properly that the insulation is configured as designed.

(2) About the anodic oxidation method Figure 3 is a schematic diagram showing the equipment for the anodic oxidation method.
is an electrolytic tank, 22 is an electrolytic solution, and 23.24 is the electrolytic solution 22.
25 is a DC power supply, 26 is an ammeter, 27 is a metal plate that is insoluble in
is a voltmeter.

In this way, two metal plates 23 and 24 are placed in the electrolyte 22.
and connect one metal plate 23 to the anode of the DC power supply 25 and the other metal plate 24 to the cathode of the DC power supply 25. The hydroxide ions in the electrolytic solution 22 are attracted by electrical attraction to the metal plate 23 connected to the anode, and emit electrons on the surface of the metal plate 23 to generate oxygen. The generated oxygen oxidizes the surface of the metal plate 23.

In this way, when the semiconductor substrate 12 shown in FIG. 2 formed in the superconducting integrated circuit 11 is used as the metal plate 23, the superconducting ground plane 13 is in electrical contact with the semiconductor substrate 12, so the superconducting ground plane 13 is in electrical contact with the semiconductor substrate 12. The first electrode 15 electrically connected to the plane 13 acts as the metal plate 23 in FIG. 3, and an oxide film is formed on the surface. Conversely, the second electrode 16 insulated from the superconducting ground plane 13 does not act as the metal plate 23 and its surface is not oxidized. Therefore, the degree of conduction and insulation between each electrode 15, 16 and the superconducting ground plane 13 can be diagnosed depending on the degree of oxidation.

However, in the anodic oxidation method in which the entire semiconductor substrate 12 is immersed in the electrolytic solution 22 as shown in FIG. The board 12 cannot be used. As shown in FIG. 4, on a wafer 31 serving as one substrate, there are usually several dozen chips 32 having the same circuit by means of first and second electrodes 15, 16 shown in FIG. Manufactured. chip 32
It is known that the variation in characteristics (including the location of defective parts) between the two is extremely small. Therefore, if a sampling inspection is performed using only one arbitrary chip 32A as a test pattern, only that chip 32A will be destroyed, and the subsequent steps can be continued for the other chips 32.

Fig. 1 is a structural diagram showing an embodiment of the present invention, Fig. 3,
The same reference numerals as in FIG. 4 indicate the same parts, 41 is a jelly-like electrolytic solution, 42 is an ultrafine probe immersed in the electrolytic solution 41, and is connected to the negative electrode of the DC power source 25. wafer 31
is connected to the positive electrode of the DC power supply 25 to form an anode. Therefore, the electrode (corresponding to the first electrode 15 in FIG. 2) that is electrically connected to the wafer 31 when the DC power supply 25 is energized acts as an anode to form an oxide film, and the wafer 31 and the insulator (
The electrode 8i (corresponding to the second electrode f!16 in FIG. 2) which is insulated by the insulating layer 14 (corresponding to the insulating layer 14 in FIG. 2) is not oxidized, so that no oxide film is formed.

In this way, the jelly-like electrolyte 41 is applied only to the chip 32A.
By dropping the liquid and using the cathode of the ultrafine probe 42, sampling inspection becomes possible.

As each t-pole 15, 16 of the superconducting integrated circuit 11, Nb
was used. As the electrolyte 41, ammonium borate 1
58g. Ethylene glycol 1124ml. water 760m
A mixed solution of 1 was used. A voltage of about 20V was applied. The electrode material is limited to metals that are easily oxidized.

As the electrolytic solution 41, the ion concentration of the aqueous solution is improved,
It can be widely used as long as it has good wettability with the wafer 31 (substrate). As for the voltage, choose a value that will moderately oxidize the surface.

Note that in the case of Nb, if it is completely electrically connected to the superconducting ground plane 13, an oxide film of about 400 layers is formed at 20V.

Next, the determination of the anodic oxide film will be described.

Typically, an oxide film with a thickness of about several hundred nm used in the superconducting integrated circuit 11 transmits some light from the outside and reflects some light on its surface. The transmitted light is reflected at the interface between the oxide film and the metal electrode, interferes with the light reflected on the surface of the oxide film, and exhibits a color depending on the thickness of the oxide film. Therefore, it is possible to distinguish between areas with and without an oxide film based on the presence or absence of color.

(Effects of the Invention) As explained above, the present invention performs anodic oxidation using the semiconductor substrate side as the anode, determines the state of oxide film formation on the surface of the target electrode, and electrically connects it to a superconducting ground plane. Since it identifies whether an electrode should be isolated or insulated, it is possible to diagnose conduction defects and insulation defects in a superconducting integrated circuit at once across the entire circuit, making inspection easy and economical. has advantages.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a sectional view showing an example of a superconducting integrated circuit, Fig. 3 is an explanatory diagram of an anodizing method, and Fig. 4 is a shape of a wafer and a chip. FIG. 5 is a perspective view showing a conventional method for diagnosing a superconducting integrated circuit. In the figure, 11 is a superconducting integrated circuit, 12 is a semiconductor substrate, and 13 is a superconducting integrated circuit.
is a superconducting ground plane, 14 is an insulating layer, and 15 is a first
, 16 is a second electrode, 21 is an electrolytic tank, 22 is an electrolytic solution, 23.24 is a metal plate, 25 is a DC power supply, 31 is a wafer, 32 is a chip, 32A is an arbitrary chip, 41 is an electrolytic solution , 42 are ultrafine probes. Figure 1 Figure 5 Bow

Claims (1)

[Claims] A superconducting integrated circuit in which a superconducting ground plane that is electrically connected to the semiconductor substrate is formed on a semiconductor substrate, and an electrode that is to be electrically connected to the superconducting ground plane and an electrode that is to be electrically insulated are formed. In the method for diagnosing the quality of a circuit, anodic oxidation is performed using the semiconductor substrate side as an anode, the formation state of an oxide film on the surface of the target electrode is determined, and the electrode to be electrically connected to the superconducting ground plane is determined. Or, a method for diagnosing the quality of a superconducting integrated circuit, the method comprising identifying whether the electrode is an electrode that should be insulated or not.