JPH03126697A - Manufacturing method of diamond single crystal substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing a diamond single crystal substrate useful for manufacturing diamond semiconductor devices and diamond single crystal heat sinks.

[Conventional technology]

It is important that the semiconductor material used to form the semiconductor device be a good single crystal or single crystal layer. In particular, single crystals with few crystal defects are essential for improving the characteristics of semiconductor devices. Conventionally, silicon, gallium arsenide, etc. have been mainly used as such semiconductor materials. Diamond also has favorable properties as a semiconductor, and its application to applications such as semiconductor elements with excellent heat resistance and environmental resistance, and high-output power transistors is being considered. However, diamond materials cannot be obtained easily and cheaply. At present, the industrial production of single-crystal diamond is limited to a few cubic squares obtained through ultra-high-pressure synthesis. Not only are they small, but they are also expensive, which is a serious problem in producing large quantities of inexpensive semiconductor devices. On the other hand, recently, a vapor phase synthesis method (CVD) has been established in which a mixture of carbon-containing gas and hydrogen is excited using microwaves or heat to cause a gas phase reaction and form a diamond thin film on a substrate. . Single crystal diamond, metal, silicon, etc. have been tried as substrates. When a diamond single crystal is used as a substrate, the formation of a single crystal diamond film epitaxially grown on the diamond substrate has been confirmed. FuJImorl et al, Vacuum vol.
, 311i, 99"102,198B but this CVD
Even if this method is used, only a polycrystalline diamond layer can be grown on a foreign substrate such as silicon. A single-crystal diamond layer can only be formed on an expensive single-crystal diamond substrate produced by the high-pressure synthesis method described above. For this reason, it is currently not possible to provide an inexpensive thin-film single-crystal diamond substrate. Here, the term "thin film single crystal diamond substrate" means that a diamond single crystal thin film is grown on some kind of substrate and used as the substrate. Many attempts have been made to epitaxially grow diamond single crystals on various substrates. For example, JP-A-Sho E
No. i4-3098 states that when diamond is vapor phase grown on a magnesia spinel single crystal substrate, it becomes a single crystal. However, such proposals have poor reproducibility and are problematic in practice. Diamond is also increasingly being applied to mechanical parts such as cutting tools and heat sinks. For this purpose, the only single-crystal diamond material to be used is one produced by high-pressure synthesis, as in the case of semiconductors. At present, even in this field, inexpensive diamond single crystal substrates have not been provided.

[Problem to be solved by the invention]

As mentioned above, diamond single-crystal substrates required for semiconductor device formation and heat sink applications have conventionally only been synthesized under high pressure, or formed on high-pressure synthesized substrates by CVD. Ta. Since the diamond single crystal itself synthesized under high pressure is expensive, it has been a problem in producing inexpensive diamond semiconductor elements or diamond heat sinks in large quantities. It is an object of the present invention to solve these problems and provide inexpensively large quantities of diamond single crystal substrates necessary for semiconductor element formation, cutting tool applications, and the like.

[Means to solve the problem]

The method for manufacturing a diamond single crystal substrate of the present invention includes the steps of epitaxially growing a metal single crystal thin film made of at least one of Cu or N1 on a diamond single crystal substrate, and epitaxially growing a diamond single crystal film on the metal single crystal thin film. a step of adhering the diamond single crystal film to a base or molding the diamond single crystal film with a resin; and selectively etching the metal single crystal thin film to peel off the diamond single crystal film from the diamond substrate. It is characterized by having a process. This will be explained using drawings. FIG. 1 shows a state in which a metal single crystal thin film 2 made of at least one of Nl or Cu is epitaxially grown on a diamond single crystal substrate 1. As shown in FIG. 5- The diamond single-crystal substrate 1 used here is a substrate cut from synthetic diamond or natural diamond produced by high-pressure synthesis or the like, or a diamond single-crystal layer is epitaxially grown on the substrate by a known CVD method. A thin film substrate may be used. The metal single crystal thin film 2 made of at least one of Cu and N1 can be formed by a known molecular beam evaporation method (MBE method). Here, the metal single crystal thin film 2 may be a single metal layer of Cu or N1, or may be a multilayer film in which Cu and N1 are alternately laminated. The thickness of the metal single crystal thin film is desirably 100λ or more, since if it is too thin, the etching solution will not permeate the film during subsequent etching, making it difficult to peel off. The reason why the metal thin film must be a single crystal is that a diamond single crystal must be epitaxially grown thereon. The diamond single crystal thin film 3 on top of the diamond single crystal thin film 3 is deposited using the known CVD method (
For example, it can be formed by a microwave plasma CVD method). There are two methods for the next step, and you can choose one of them. One method is to braze a base 5 onto the diamond single crystal thin film 3 using a solder 4, as shown in FIG. This is because when the diamond single crystal thin film is peeled off later, since the diamond single crystal thin film is too thin to maintain its shape independently, the base 5 gives it a shape and supports it. The base 5 and the solder 4 may be made of materials that are difficult to dissolve in the selective etching solution. For example, the base 5 may be made of stainless steel or the like. Another method, as shown in FIG. 5, is to directly mold the diamond single crystal thin film 3 with resin 6, which is difficult to dissolve in a selective etching solution, instead of the wax or base. This is because the resin 6 gives the diamond single crystal thin film its shape and holds it. Next, the metal single crystal thin film is selectively etched. The etching solution etches Nl and Cu, but it is necessary that it does not etch diamond. For example, an etching solution such as nitric acid or ferric chloride aqueous solution can be used. After the metal single crystal thin film is selectively etched, as shown in FIG. 4, the film supported on the wax base becomes as shown in FIG. 6. A diamond single crystal film 3 is deposited on a wax 4 on a base 5.
The structure is adhesively supported. Since the diamond single-crystal film 3 is exposed on the surface, it can be used as a diamond single-crystal substrate, a substrate for a semiconductor element, or a substrate for a mechanical component. A diamond single crystal film molded with resin as shown in FIG. 5 is as shown in FIG. 7. There is a diamond single crystal film 3 on the resin 6, which improves flatness and
Mechanical strength etc. are provided by resin. This diamond single crystal film 3 can also be used as a semiconductor element substrate or a mechanical component substrate. The diamond single crystal substrate 1 used initially returns to its original isolated state and can be used again. In the same way, many diamond single crystal substrates can be obtained.

[For works]

The crystal structure of N1 and Cu is fcc (face-centered cubic). Diamond has what is called a unique diamond structure. FCC and diamond structure are of course important. However, the diamond structure has two fcc (1/4.1/4.
It is a structure that looks like they are combined with a difference of 1/4). Therefore, the atomic arrangement in each plane orientation is the same in Cu, Nl, and diamond. They have the advantage of having similar atomic arrangements. Second, the lattice constants are similar. The lattice constant of diamond is 3,5[;7λ. Cu
The lattice constant of 1N1 is 3. B147λ, 3.52
It is 38 pieces. Lattice parameter misfit ratio (as ao)/a. are small at 1.3% and 1.2% for Cu and Ni, respectively. For these two reasons, it is possible to epitaxially grow diamond on Cu and Nl, or epitaxially grow Nl and Cu on diamond. 9- In fact, the present inventor has: (1) epitaxially grown a metal film made of at least one of Cu1N+ on a diamond single-crystal substrate, and (2) epitaxially grown a diamond single-crystal film on the metal single-crystal film. Successful. Furthermore, diamond is hardly etched by ferric chloride aqueous solution, nitric acid, etc., which are common etching solutions for Cu and N1. For this reason, these etching solutions
The diamond single crystal film can be easily peeled off from the diamond single crystal substrate by removing only the metal film. This peeled diamond single crystal film can be used as a substrate for forming semiconductor elements, a substrate for cutting tools, and the like. Therefore, using the diamond single crystal substrate as a base substrate, it is possible to repeatedly manufacture a diamond single crystal film as a substrate for forming a semiconductor element or a substrate for a cutting tool. Since the diamond substrate can be used over and over again and individual original substrates are not required, inexpensive diamond single crystal substrates can be manufactured and supplied in large quantities.

[Example work]

A Cu film having a thickness of 200λ was formed by MBE at a substrate temperature of 300'C using a diamond single crystal of size 8 mm x 8 m11 thickness 1 mm 1 plane orientation (111) as a substrate prepared by high-pressure synthesis. When the crystal state of this film was observed by reflection electron beam diffraction, spot-shaped diffraction points on the single crystal (111) plane were observed. In other words, on the (111) plane diamond, there is a (1
11) Single crystal Cu was epitaxially grown so that the planes were parallel. Furthermore, a diamond film was formed on the Cu single crystal film by microwave CVD. The conditions are raw material gas
H2 substrate temperature containing 0.5% CH4 90
0"C Vacuum degree 20 Torr Diamond film thickness 1 μm The crystalline state of this diamond film was also investigated by reflection electron beam diffraction. As a result, spot-shaped diffraction points of the single crystal (111) plane were obtained. In other words, the diamond was It is a crystal, and the crystal orientation matches that of the underlying Cu layer.Next, gold is used to coat this single crystal diamond film to a thickness of 1 m.
m stainless steel was brazed. Thereafter, the Cu single crystal film was etched with a ferric chloride aqueous solution, and the diamond single crystal film was separated from the diamond single crystal substrate. The crystallinity of the obtained single crystal diamond film on stainless steel was again evaluated by reflection electron beam diffraction. It was confirmed from the spot-like diffraction points that it was a (111) plane of a single crystal.

[Example ■]

Using the high-pressure synthetic diamond single crystal substrate used in Example I again, a film thickness of 3 was formed by MBE at a substrate temperature of 100°C.
A Nl film of 00λ was formed. The crystalline state of this N1 film was examined by reflection electron beam diffraction. Similarly, spot-like diffraction points on the (111) plane of the single crystal were observed. This means that the N1 film is a single crystal, and its crystal orientation matches that of diamond. A diamond film was formed on this N1 film by microwave plasma CVD. The conditions are raw material gas 0.
H2 containing 5% CH4 Substrate temperature: 900°C, degree of vacuum: 20 Torr, diamond film thickness: 2000λ. This diamond film was also evaluated by reflected electron beam diffraction. As a result, spot-like diffraction points on the single crystal (111) plane were obtained, and it was confirmed that the diamond film was single crystal. Next, in the same manner as in Example 2, the diamond film was brazed with gold using stainless steel as a base. Thereafter, the old single crystal layer was etched with a 10% nitric acid aqueous solution, and the diamond single crystal film was separated from the diamond single crystal substrate. The crystallinity of the separated diamond film on the stainless steel base was evaluated again by reflection electron beam diffraction. As a result, this diamond film becomes (111)
It was confirmed that it was a single crystal.

[Example ■]

A diamond film was continuously produced on stainless steel 12 times by repeatedly using the high-pressure synthetic diamond single crystal substrate used in Examples I and II. When the diamond film produced in this manner is examined by reflected electron beam diffraction, spot-like diffraction points are obtained that all correspond to the single crystal (111) plane. All of the obtained diamond films are single crystal films. In this way, the diamond single-crystal substrate can be used over and over again, and the properties of the diamond film formed thereon will not deteriorate even after repeated use.

【Effect of the invention】

According to the present invention, a metal single crystal film and a diamond single crystal film are grown on a diamond single crystal substrate, and the metal single crystal film is removed by etching, so the original diamond single crystal substrate can be used over and over again. . As a result, diamond single-crystal substrates necessary for forming semiconductor elements, cutting tools 14, etc. can be supplied in large quantities and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a structure in which a single crystal metal film is epitaxially grown on a diamond single crystal substrate. FIG. 2 is a cross-sectional view of a structure in which a diamond single crystal film is epitaxially grown on the single crystal metal film. FIG. 3 is a cross-sectional view during selective etching of a metal single crystal film. FIG. 4 is a cross-sectional view of the state in which selective etching of the metal single crystal film is being performed after brazing the base onto the diamond single crystal film. FIG. 5 is a cross-sectional view showing a state in which a metal single crystal film is being selectively etched after resin is molded onto a diamond single crystal film. FIG. 6 is a cross-sectional view of the structure shown in FIG. 4, with the diamond film exposed on the surface after the metal film has been etched away. FIG. 7 is a cross-sectional view of the structure shown in FIG. 5 with the diamond film exposed on the surface after the metal film has been etched away.・Diamond single-crystal substrate ・Metal single-crystal film ・Diamond single-crystal film ・ Wax ・ Base ・ Resin Yui Kawamoto Tsune Tsukasa Nobu Fujita Yoshihiko

Claims (1)

[Claims] A step of epitaxially growing a metal single crystal thin film made of at least one of Cu or Ni on a diamond single crystal substrate, a step of epitaxially growing a diamond single crystal film on the metal single crystal thin film, and a step of epitaxially growing a diamond single crystal film on the metal single crystal thin film, and using the diamond single crystal film as a base. A diamond single crystal substrate comprising the steps of adhering or molding a diamond single crystal film with a resin, and selectively etching the metal single crystal thin film and peeling off the diamond single crystal film from the diamond substrate. manufacturing method.