JPH0658891B2 - Thin film single crystal diamond substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a substrate having an epitaxially grown layer of single crystal diamond, which is useful for manufacturing a diamond semiconductor device.

[Conventional technology]

It is essential that a semiconductor material for forming a semiconductor element is a good single crystal or a single crystal layer, and particularly in a planar type semiconductor element which is currently the mainstream, it is necessary to form a thin film single crystal layer on a substrate. This is the first step in the forming process.

Silicon and the like have been mainly used as such a semiconductor material, but diamond is also considered to be a heat-resistant semiconductor, a high output power transistor, and the like because of its unique properties as a semiconductor material.

However, at present, the industrial production of single crystal diamond is limited to synthesizing granular ones using ultra-high pressure equipment, and the substrate made from this synthetic diamond grain has an area of several mm square. Is the limit. Therefore, this single crystal diamond substrate cannot be used in the case where a large area is required to form a device for a large current, or in the manufacture of an integrated circuit in which fine processing is performed using a stepper.

Further, since the above synthetic diamond single crystal is expensive in itself, its range of use is limited even when a large amount of inexpensive semiconductor devices are produced.

On the other hand, recently, a gas phase synthesis (CVD) method has been established, in which a mixed gas of methane and hydrogen is excited by using microwave plasma or heat to cause a reaction, and a diamond thin film is projected on a substrate. The formation of a single crystal diamond layer epitaxially grown on a crystalline substrate has been confirmed (Fujimori et al, Vacuum, vol36, 99-102, 1986).

However, even in this CVD method, only the polycrystalline diamond layer can be formed on the silicon substrate, and the single crystal diamond layer can be formed only on the expensive and small area single crystal diamond substrate synthesized by the above high pressure method. The present situation has not yet been to provide an inexpensive and large-area thin film single crystal diamond substrate.

[Problems to be solved by the invention]

In view of the above circumstances, an object of the present invention is to provide an inexpensive and large-area thin film single crystal diamond substrate in which diamond is epitaxially grown on a single crystal silicon substrate.

[Means for solving problems]

The thin film single crystal diamond substrate of the present invention has a single crystal silicon carbide intermediate layer formed on a single crystal silicon substrate, and a single crystal diamond layer epitaxially grown on this single crystal silicon carbide intermediate layer. .

The single crystal silicon substrate used may be a substrate (wafer) cut out from an ingot manufactured by a usual method such as a pulling method. Further, the single crystal silicon carbide intermediate layer and the single crystal diamond layer can be formed by a known CVD method, ion beam deposition method or the like, respectively.

[Action]

The lattice constant of diamond is 3.5667 Å and the lattice constant of silicon is 5.4301 Å, and it is difficult to epitaxially grow diamond directly on a silicon substrate because the crystal structures differ greatly.

Therefore, the inventors of the present invention succeeded in epitaxially growing a single crystal diamond on the silicon substrate by interposing a single crystal silicon carbide having a lattice constant of 4.3596 Å as an intermediate layer on the silicon substrate. It is an ivy.

〔Example〕

Example 1 A (111) plane of a single crystal Si substrate having a diameter of 2 inches was prepared by using 5 in CH _4.
torr 1350 ℃ After carbonizing for 20 minutes, substrate temperature 1300 ℃
And plasma CVD of SiH ₄ and CH ₄ at a vacuum of 2 torr
By the method, a single crystal SiC intermediate layer with a film thickness of 2000 Å was formed.

Then, on the single crystal SiC intermediate layer, a substrate temperature of 900 ° C. and a vacuum degree of 30 torr were applied by a microwave plasma CVD method.
Thickness 3 diamond layer by decomposing of H ₂ containing 0.5% CH ₄
Formed to 000Å.

When the crystal state of the obtained diamond layer was observed by backscattered electron diffraction, spot-like diffraction points were observed,
It was found to be the (111) plane of a single crystal.

Example 2 As in Example 1, a single crystal SiC intermediate layer was formed on a Si substrate. Then, a tungsten filament 2100 was formed on the single crystal SiC intermediate layer at a substrate temperature of 850 ° C. and a vacuum degree of 30 torr.
A diamond layer was formed to a film thickness of 500 Å by a CVD method in which H ₂ containing 0.5% of CH ₄ was excited and decomposed by heating at 0 ° C.

Subsequently, H ₂ containing 0.5% CH ₄ and 0.0002% B ₂ H ₆ was similarly excited and decomposed to form a B-doped diamond layer with a film thickness of 1000 Å.

When the crystal state of the obtained uppermost diamond layer was observed by reflection electron beam diffraction, spot-like diffraction points were observed, and it was found that it was a (111) plane of a single crystal.

The uppermost single crystal diamond layer has a resistivity of 5 × 10 5.
^{It is a} P-type semiconductor measured by Hall effect at ^-1 Ω · cm, and has a carrier density of 4 × 10 ¹⁶ / cm ³ and Hall mobility of 310 cm ^2.
It was confirmed to be / V ・ sec.

Comparative Example A diamond layer was formed on the same single crystal Si substrate as in Example 1 without forming a single crystal SiC intermediate layer by the same microwave plasma CVD method as in Example 1, but crystals were deposited in pieces. A thin film could not be formed by itself.

In addition, when the same substrate was scratched with diamond powder ( ^# 3000) and then a diamond layer was formed in the same manner, a film having triangular crystal planes with irregularities was obtained, and this film was examined by electron diffraction. However, it was confirmed to be polycrystalline.

〔The invention's effect〕

According to the present invention, it is possible to provide an inexpensive and large-area thin film single crystal diamond substrate in which diamond is epitaxially grown on a silicon substrate.

Claims (1)

[Claims] 1. A thin film single crystal diamond substrate having a single crystal silicon carbide intermediate layer formed on a single crystal silicon substrate and a single crystal diamond layer epitaxially grown on this single crystal silicon carbide intermediate layer.