JP2713304B2 - Semiconductor device with superconducting wiring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a semiconductor device, particularly a semiconductor device provided with a wiring made of a superconductor (superconducting wiring), and is equivalent to a wiring made of a normal conductor (normal conducting wiring) while securing an integration density. The object of the present invention is to provide a semiconductor device having a wiring made of a superconductor through which a current can flow. In a semiconductor device provided with a wiring made of a superconductor, the current of the wiring is at least between electrical connection portions. Is configured so that the profile of the cross section perpendicular to the direction has at least one protrusion.

[Industrial applications]

The present invention relates to a semiconductor device, and more particularly to a semiconductor device including a wiring made of a superconductor (superconducting wiring).

[Conventional technology]

It is an essential requirement of the semiconductor device to increase the integration density especially as an integrated circuit. As the integration density increases, it is always one of the major technical issues to minimize the signal delay time in the wiring in the integrated circuit.

Since the superconductor loses its electrical resistance at a temperature lower than the critical temperature, the signal delay time can be remarkably reduced if it is used for wiring. In particular, recently discovered high-temperature ceramic superconductors such as Y ₁ Ba ₂ Cu ₃ O ₇ have a much higher critical temperature than previously known metal superconductors. There is an increasing expectation that they can be used as wiring materials without requiring a great economic and technical burden.

[Problems to be solved by the invention]

However, when a superconductor is used for the wiring, there is a problem that a current of the same size as that of a wiring using a normal conductor (normal conductor) as in the related art cannot flow, that is, the allowable current is small.

The first cause is that there is a critical current unique to a superconductor. When a current exceeding the critical current flows through the superconductor, the superconducting state is destroyed by the magnetic field generated by the current and shifts to a normal conducting state, and a finite electric resistance appears. When measured on a rectangular parallelepiped block, the critical current is generally quite small (for example, about 3000 A / cm ² for Y ₁ Ba ₂ Cu ₃ O ₇ )
Therefore, the current (10 ^-5 A / cm
² ) can not flow. The critical current is a unique value determined by the composition and structure of the superconductor, and the allowable current is determined by the selection of the superconductor. Therefore, in order to increase the allowable current as the wiring, the current flow path must be increased.

The second cause is directly related to this current flow path. That is, since no magnetic field can exist inside the superconductor, only the surface serves as a current flow path. In the normal conductor, the entire cross section perpendicular to the direction of the current is the flow path of the current, so when increasing the current in the normal conductor wiring, if the area of the cross section is increased by increasing the thickness and width of the wiring Good. However, in order to increase the allowable current in superconducting wiring where current flows only on the surface,
Since the surface area must be increased instead of the cross-sectional area, the allowable current cannot be effectively increased in the same manner as the normal conductive wiring. That is, an increase in the thickness of the wiring has a small effect, and an increase in the width of the wiring is limited from the viewpoint of the integration density, and both are insufficient.

As described above, in order to effectively apply superconducting wiring to a semiconductor device, particularly to an integrated circuit, there is a specific problem which cannot be solved by the conventional normal conducting wiring technology.

Therefore, an object of the present invention is to provide a semiconductor device provided with a superconducting wiring capable of flowing a current equivalent to that of a normal conducting wiring while securing an integration density.

[Means for solving the problem]

According to the present invention, according to the present invention, in a semiconductor device having a wiring made of a superconductor, at least one projecting portion of a cross section perpendicular to a current direction of the wiring is formed at least between electrical connection portions. And a semiconductor device having a portion.

In the present invention, it is advantageous that the superconducting wiring is made of a ceramic superconductor.

In the present invention, it is advantageous to dispose a large number of protrusions and make the above-mentioned cross section into a comb tooth shape.

It is particularly advantageous to set the height of the protruding portion to be equal to or greater than the wiring width and to set the number of arrangement to two or more.

The present invention can increase the surface area of the wiring, that is, the flow path of the superconducting current, with the same wiring width by providing the protruding portion in the profile of the cross section perpendicular to the current direction of the superconducting wiring. While increasing the allowable current. The dimensions and the number of protrusions can be appropriately determined according to the required allowable current.

The electrical connection portion may have an appropriate shape as required for connection as long as the surface area is not reduced as compared with other portions.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

〔Example〕

Examples of the cross section of the superconducting wiring according to the present invention are shown in FIGS.

FIG. 1A shows an example in which one protruding portion p having a height h is provided on a cross section having a wiring width w. FIG. 2 is a perspective view showing an example of a superconducting wiring having such a cross section. Protrusion p
Are formed along the direction of the current (arrow C). 2 × with the same wiring width w as compared to a flat case where there is no protrusion
The surface area of the superconducting wiring increases by an amount corresponding to h, and the flow path of the superconducting current, that is, the allowable current of the wiring increases accordingly.

In general, the thickness of the wiring is considerably smaller than the width of the wiring, so if the height h of the protrusion is equal to the wiring width w, for example, the surface area of the wiring is almost doubled.

If the number of projecting portions to be provided is increased as shown in FIGS. 1B to 1D with the same wiring width w, the allowable current can be easily increased by a correspondingly large number. First
FIG. 1 (b) shows an example in which a large number of protrusions are arranged in a comb-like shape on one side of a wiring film, and FIG. 1 (c) shows an example in which a large number of projections are arranged on both sides. FIG. 1 (d) is an example in which a recessed portion which enters from the opposite side of the wiring film exists inside the protrusion arranged as shown in FIG. 1 (b), and the number of protrusions is two. The effect of increasing the allowable current, which is almost the same as the doubling, can be obtained.

The superconducting wiring of the example of FIG.
It was formed by the following steps shown in (7). However, the number of protrusions was set to 10.

The Si substrate 1 was oxidized in steam at 1100 ° C. to form an SiO ₂ film 2 on the surface to a thickness of 1 μm (FIG. 3 (1)). This Si
Sputtering is performed on the O ₂ film 2 using Y ₂ O ₃ , BaCO ₃ , and CuO as a source to form a Y ₁ Ba ₂ Cu ₃ O ₇ film 3 having a thickness of 3000 ° (FIG. 3 (2)). After that, the Y ₁ Ba ₂ Cu ₃ O ₇ film 3 was patterned according to a predetermined wiring pattern (FIG. 3 (3)). A PSG film 4 was formed thereon to a thickness of 1 μm (FIG. 3 (4)). After a groove-like pattern was formed on the PSG by photoetching along the wiring pattern (FIG. 3 (5)), the Y ₁ Ba ₂ Cu ₃ O ₇ film 3 ′ was again formed in the same manner as above.
Was formed (FIG. 3 (6)). Further, after patterning the Y ₁ Ba ₂ Cu ₃ O ₇ film 3 ′ (FIG. 3 (7)), 900 ° C.
For about 3 hours to perform sintering of Y ₁ Ba ₂ Cu ₃ O ₇ .

The superconducting wiring of the example of FIG.
It was formed by the process shown in (8).

As in the case of FIG. 1B, an SiO ₂ film 12 was formed on the Si substrate 11 (FIG. 4A). On this SiO ₂ film 12, PSG film 14
Was formed to a thickness of 1 μm (FIG. 4 (2)). After forming a groove pattern on the PSG (FIG. 4 (3)), Y ₁ Ba ₂ Cu ₃
An O ₇ film 13 was formed in the same manner as above (FIG. 4 (4)), and a PSG film 14 ′ was formed thereon again in the same manner as above (FIG. 4 (5)). After patterning the PSG film 14 'as shown in FIG. 4 (6), the Y ₁ Ba ₂ Cu ₃ O ₇
3 'was formed (FIG. 4 (7)). Y ₁ Ba ₂ Cu ₃ O ₇
It was removed by plasma etching up to the height of the SG film 14 '(FIG. 4 (8)).

The superconducting wiring of the example of FIG.
0).

FIG. 5 (1) shows the same process steps as FIG. 4 (4).
101 is a Si substrate, 102 is a SiO ₂ film, 103 is a Y ₁ Ba ₂ Cu ₃ O ₇ film, 104 is
PSG. The following steps are as follows. In FIG. 5, (2) the Y ₁ Ba ₂ Cu ₃ O ₇ film 103 is removed to the height of the PSG 104 by plasma etching, (3) the PSG film 104 ′ is formed again, and (4) the PSG film 104 ′ is patterned. (5) Again Y ₁ Ba
₂ Cu ₃ O ₇ film 103 ′ is formed, (6) Y ₁ Ba ₂ Cu ₃ O ₇ film 103 ′ is removed to the height of PSG 104 ′ by plasma etching, (7) PS
G film 104 ″ is formed, (8) PSG film 104 ″ is patterned,
(9) Y ₁ Ba ₂ Cu ₃ O ₇ film 103 ″ is formed, (10) Y ₁ Ba ₂ Cu ₃ O ₇ film 1
03 ″ was removed to the level of PSG104 ″ by plasma etching.

〔The invention's effect〕

The present invention increases the flow path of the superconducting current flowing only on the surface of the superconducting wiring, so that the same current as that of the normal conducting wiring can flow while securing the integration density.
It greatly contributes to realizing a remarkable reduction in signal delay time when used for wiring of a superconductor and a semiconductor device.

[Brief description of the drawings]

1 (a) to 1 (d) are cross-sectional views showing examples of superconducting wiring included in a semiconductor device according to the present invention, and FIG. 2 is a cross-sectional view having a cross section shown in FIG. 1 (a). FIGS. 3 (1) to 3 (7) are perspective views showing examples of the conductive wiring, FIGS. 3 (1) to 7 (7) are cross-sectional views showing steps of forming a superconducting wiring having the cross section of FIG. 1 (b), FIGS. (8) is a cross-sectional view showing a step of forming a superconducting wiring having the cross section of FIG. 1 (c), and FIGS. 5 (1) to (10) are cross-sectional views of FIG. 1 (d). FIG. 5 is a cross-sectional view showing a step of forming a superconducting wiring having the same. p: Projection, 1, 11, 101: Si substrate, ₂ , 12, 102: SiO ₂
Film, 3,3 ′, 13,13 ′, 103,103 ′, 103 ″ ... Y ₁ Ba ₂ Cu ₃ O
₇ films, 4,14,14 ', 104,104', 104 "... PSG film.

Claims (1)

(57) [Claims] 1. A semiconductor device having a wiring made of a superconductor, characterized in that at least one projecting portion has a cross-sectional profile perpendicular to a current direction of the wiring between at least electrical connection portions. Semiconductor device.