JPS63239190A - Method for selectively growing crystal - Google Patents

Abstract

PURPOSE:To form crystal having good heat release properties and easy application to a device by selectively forming an inorganic nonoxidative compd. good in insulating properties and heat conductivity on a nucleus nonformation face. CONSTITUTION:A nucleus nonformation face 1 which consists of an inorganic nonoxidative compd. (e.g. BN) having heat conductivity and insulating properties and is small in nucleus formation density is prepared. A nucleus formation face 3 having small area sufficient to grow crystal of only single nucleus and having nucleus formation density larger than the nucleus formation density of the face 1 is formed thereon. Then single crystal 4 consisting of the single nucleus is grown by performing crystal formation treatment to the faces 1, 3.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for selectively growing crystals, particularly a single crystal or a single crystal with a grain size that is created by utilizing the difference in the nucleation density of the deposited material depending on the type of the deposition surface material. This invention relates to a controlled selective growth method for polycrystals.

[Prior Art] Conventionally, single-crystal thin films used in semiconductor electronic devices, optical devices, and the like have been formed by epitaxial growth on single-crystal substrates. For example, it is known that Si, Ge, GaAs, etc. are epitaxially grown on a St single crystal substrate (silicon wafer) from the liquid phase, gas phase, or solid phase, and on a GaAs single crystal substrate, GaAs, GaAJ, etc.
It is known that single crystals such as 2s and the like can be epitaxially grown. Using the semiconductor thin film thus formed, semiconductor devices, integrated circuits, semiconductor lasers and LE
A light emitting element such as D is manufactured.

In addition, recently there has been much research and development into ultrahigh-speed transistors using two-dimensional electron gas and superlattice devices using quantum wells. (Molecular beam epitaxy) and MOC
High-precision epitaxial technology such as VD (organometallic chemical vapor deposition).

In such epitaxial growth on a single crystal substrate, it is necessary to match the lattice constant and thermal expansion coefficient between the single crystal material of the substrate and the epitaxially grown layer. If this alignment is insufficient, lattice defects will develop in the epitaxial layer. Additionally, elements constituting the substrate may diffuse into the epitaxial layer.

Thus, it can be seen that the conventional method of forming a single crystal thin film by epitaxial growth largely depends on the substrate material. Mathews et al. investigate combinations of substrate materials and epitaxially grown layers (EPITAXIAL G
ROWTH, Academtc Press, New
York.

1975 ed, by J.W.Mathew
s).

Furthermore, the size of the substrate is currently about 6 inches for Si wafers, and the increase in the size of GaAs and sapphire substrates is even slower. In addition, single crystal substrates are expensive to manufacture, resulting in a high cost per chip.

As described above, in order to form a single-crystal layer from which a high-quality device can be manufactured by the conventional method, there is a problem in that the types of substrate materials are limited to an extremely narrow range.

On the other hand, research and development of three-dimensional integrated circuits, in which semiconductor elements are stacked in the normal direction of a substrate to achieve high integration and multi-functionality, has been actively conducted in recent years, and there has also been active research and development in three-dimensional integrated circuits, in which semiconductor elements are stacked in the normal direction of a substrate. Research and development of large-area semiconductor devices, such as solar cells arranged in a pattern or switching transistors for liquid crystal pixels, is becoming more common year by year.

What these two methods have in common is that they require a technique for forming a semiconductor thin film on an amorphous insulator and forming electronic elements such as transistors thereon. Among these, a technique for forming a high quality single crystal semiconductor on an amorphous insulator is particularly desired.

Generally, when a thin film is deposited on an amorphous insulator substrate such as 5in2, the crystal structure of the deposited film becomes amorphous or polycrystalline due to the lack of long-range order in the substrate material. Here, an amorphous film is one in which short-range order at the level of the nearest neighbor atoms is preserved, but no longer-range order, and a polycrystalline film is one that has a specific crystal orientation. It is a collection of single crystal grains separated by grain boundaries.

For example, when forming Si on 5in2 by CVD method, if the deposition temperature is below about 600℃, it will become amorphous silicon, and if the temperature is higher than that, the grain size will be distributed between several hundred to several thousand. It becomes polycrystalline silicon. However, the grain size and distribution of polycrystalline silicon vary greatly depending on the formation method.

Furthermore, by melting and solidifying the amorphous or polycrystalline film using an energy beam such as a laser or a rod-shaped heater,
Polycrystalline thin films with large grain sizes on the order of microns or millimeters have been obtained (Single-Crystal
5ilicon on non-single-c
rystalinsulators, Journal
of crystal growth vol.

63, No. 3.0ctober, 1983 ed.
ited by G, W.

Cullen).

When a transistor is formed in the thin film of each crystal structure formed in this way and the electron mobility is measured from its characteristics,
For amorphous silicon, ~0.1c+n2/V・sec,
1 to 10ca for polycrystalline silicon with a grain size of several hundred
+2/V-see, large-grain polycrystalline silicon obtained by melting and solidification has a mobility comparable to that of single-crystal silicon.

This result shows that there is a large difference in electrical characteristics between an element formed in a single crystal region within a crystal grain and an element formed along a grain boundary. In other words, the deposited film on an amorphous layer obtained by the conventional method has an amorphous or polycrystalline structure with a grain size distribution, and the devices fabricated there have a higher level of performance than those fabricated on a single crystal layer. As a result, its performance will be greatly degraded. Therefore, its applications are limited to simple switching elements, solar cells, photoelectric conversion elements, etc.

In addition, the method of forming a polycrystalline thin film with a large grain size by melting and solidifying requires a large amount of time to achieve a large grain size ratio because the amorphous or single crystal thin film is scanned with an energy beam on each wafer. It has the problem that it has poor performance and is not suitable for large-area applications.

[Problem to be Solved by the Invention 1] As mentioned above, with conventional crystal growth methods and the crystals formed thereby, it is not easy to achieve three-dimensional integration or increase the area, and practical application to devices is difficult. is difficult,
Crystals such as single crystals and polycrystals required for producing devices with excellent properties have not been able to be easily formed at low cost.

Therefore, the present invention solves the above-mentioned conventional problems, and provides a method for forming single crystals and polycrystals that are easy to three-dimensionally integrate and have a large area, are easy to practically apply to devices, and have excellent properties. The purpose is to provide

[Means for Solving the Problems] In order to achieve these objectives, the method of selectively growing crystals of the present invention consists of an inorganic non-oxide having thermal conductivity and insulating properties, and a crystal with a low nucleation density. Small non-nucleating surface (SMD)
It has a sufficiently small area for crystal growth of only a single nucleus, and the nucleation density (N
It is characterized in that a crystal formation process is performed on a nucleation surface (SNDL) having a larger nucleation density (NDL) than DS) to grow a single crystal from a single nucleus.

[Function] The present invention utilizes the fact that the nucleation density (ND) of a crystal to be grown differs depending on the material from which the crystal is grown. For example, when depositing S1 crystal, Sin,
has a small nucleation density (NDS) and SiN has a large nucleation density (N[lL). And Sin2 side and Si
When the N-plane is on the substrate, due to this difference in nucleation density (ΔND), the St crystal grows deposited on SiN but does not grow on 5in2. The surface with such a large nucleation density (NDL) on which crystals accumulate and grow is called the nucleation surface (SNDL).
A surface that has a small nucleation density (NDS) and on which no crystal grows is called a non-nucleation surface (SNDS). At this time, a single crystal grows on the nucleation surface (SNOL).

Furthermore, according to the present invention, by selecting an inorganic non-oxide with good insulation properties and good thermal conductivity for the non-nucleation surface, it is possible to create a crystal with good heat dissipation properties and easy practical application to devices. can be formed.

[Example] Examples of inorganic non-oxides with good thermal conductivity and good insulation used in the present invention include TiB2. ZrB2.

HfB2. TaBz, MoB2. (:rB2.NbB2
．． MoB, NbB, WB, Mo2B.

Various borides such as ThB2, BN, Al1N, Hf
N.TaN.

Various nitrides such as ZrN, TjN, ThN, NbN, VN, CrN and Si3N4, 82C, Tic, 2r
C, HfC, ThC, VC, NbC, WC, W2C.

Examples include various carbides such as Cr2C3, SiC and TaC. The thermal conductivity of such an inorganic non-oxide is preferably 0°01cal 7cm-5ec·°C or higher in order to achieve heat dissipation.

Among inorganic non-oxides, BN has excellent insulation, heat resistance, and wear resistance. Furthermore, 8N has an insulating property similar to that of silicon oxide, a thermal conductivity several times that of copper, and an ultra-low
The use of SI as an insulating material is being considered. Therefore, in the embodiment of the present invention, a BN will be taken as an example and explained with reference to the drawings.

Figure 1 is a formation process diagram showing a first embodiment of the selective growth method of the present invention. In the figure, 1 is a BN substrate, 2 is a resist material or a mask, and 3 is a Si3N4 layer forming a nucleation region. Further, 4 is a grown crystal.

First, a resist material 2 is applied to the surface of the BN substrate 1, and a resist pattern is formed by photolithography [FIG. 2(A)]. At this time, in order to cause single crystal growth, the size of the resist pattern must be sufficiently small, for example, several microns.
It is necessary to make it about m. Next, a Si3N4 layer 3 of about 0.15 μm is deposited by plasma CVD method [FIG. 1(B)]. After that, resist material 2 is removed and 5iJ4
A three-layer pattern is formed. Next, the entire substrate is heated and H
After cleaning the substrate by flowing CJ2 gas over the substrate, it was washed under reduced pressure using St(:lL4) diluted with 112
~200 Torr) A Si layer 4 is deposited on the substrate at a substrate temperature of 850° C. [FIG. 1(C)]. At this time, if the size of the Si3N4 layer 3 is made sufficiently small, the Si layer 4 will grow as a single crystal. At that time, generation and growth of SL crystal nuclei were not observed in the area where BN was exposed on the surface. S
The size of the i-layer 4 was approximately 90 μm when Si3N was used and the layer size was 3 μm.

Example 2 FIG. 2 is a formation process diagram showing a second embodiment of the selective growth method of the present invention. In the figure, 5 is a quartz substrate, and 6 is a BN film.

First, a BN film 6 with a low nucleation density is placed on a quartz substrate 5.
It is deposited by the Vp method [Figure 2 (A)]. Here IVI
The I method is a method in which nitrogen ion irradiation and vacuum deposition of metallic boron are performed simultaneously. In this example, nitrogen ions (N2”
) is supplied from the PIG ion source to 5 with an extraction voltage of V, and B
was supplied by EB evaporation. The obtained ON layer 6 has B/N
The ratio was 1.6 and the film thickness was 0.2 μm. Also, this B
NI] Mo6 is polycrystalline, -Tokyo cubic BN (C-
BN) phase was included.

Thereafter, when a Si layer was deposited in the same manner as in Example 1, single crystals or twin crystals grew around the nucleation region 3, and nucleation and growth from areas other than the nucleation region 3 were suppressed.

Example 3 The same procedure as Example 2 was carried out except that BNni having a low nucleation density as shown in FIG. 2(A) was deposited by plasma CVD. In this example, 8, H, and C2HB and 1
12 was used to obtain BNli. The obtained 88 layers are B-C
The amorphous ON thin film made of -H had a thickness of 0.15 μm and was transparent.

Otherwise, when a Si layer is deposited in the same manner as in Example 1, single crystals or twin crystals grow around the nucleation region 3, and the region 3
Nuclei generation and growth from other sources were suppressed.

[Effects of the Invention] As explained above, according to the present invention, by selecting an inorganic non-oxide with good insulation properties and good thermal conductivity for the non-nucleation surface, heat dissipation is good and the device is This has the effect of forming crystals that are easy to use in practical applications.

[Brief explanation of the drawing]

FIG. 1 is a formation process diagram showing a first embodiment of the selective crystal growth method of the present invention, and FIG. 2 shows a second embodiment of another crystal selective growth method of the present invention. It is a formation process diagram. DESCRIPTION OF SYMBOLS 1... BN substrate, 2... Resist material or mask, 3... Nucleation region, 4... Crystal, 5... Quartz substrate, 6... BN film.

Claims (1)

[Claims] It is made of an inorganic non-oxide having thermal conductivity and insulation, and has a non-nucleation surface (S_N_D_S) with a low nucleation density and a sufficiently small area for crystal growth of only a single nucleus,
and the nucleation density (N
A method for selectively growing a crystal, characterized in that a crystal formation treatment is performed on a nucleation surface (S_N_D_L) having a nucleation density (ND_L) greater than D_S) to grow a single crystal from the single nucleus.