JPH04130717A - Formation method of crystal - Google Patents

Abstract

PURPOSE:To generate only a single nucleus on a nucleus formation face and to grow a single crystal even when the nucleus formation density of the nucleus formation face is extremely high as compared with a face where no nucleus is formed by a method wherein a material whose nucleus formation density is high and which is different form a material constituting the nucleus formation face is arranged as a dummy pattern. CONSTITUTION:A material 2 whose nucleus formation density is very high is deposited on a substratum material 1 to form a nucleus formation face. A material 3 whose nucleus formation density is lower than that of the nucleus formation face is deposited in about 200 to 600Angstrom to form a face where no nucleus is formed. Then, a material 4 whose nucleus formation density is high is patterned; a dummy pattern 5 is formed to be adjacent to a part where the nucleus formation face is formed. Then, the face where no nucleus is formed is patterned and etched. A small area which is sufficient to generate only one nucleus to be formed as a single crystal is revealed to form the nucleus formation face. A crystal nucleus 9 is generated, by a CVD method, on a substrate obtained in this manner. At this time, the nucleus is generated on the nucleus formation face 6 and on the dummy pattern 5. When a growth operation progresses, the nucleus 10 generated from the nucleus formation face is grown as the single crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a semiconductor crystal and a semiconductor crystal article obtained by the method, and in particular to a difference in the nucleation density of the deposited material depending on the type of the deposited surface material. The present invention relates to a method for forming a semiconductor single crystal or a semiconductor polycrystal with controlled grain size using the method, and a crystal article obtained thereby.

The present invention relates to the formation of semiconductor crystals such as semiconductor single crystals and semiconductor polycrystals used in electronic devices such as semiconductor integrated circuits, optical integrated circuits, and magnetic circuits, optical devices, magnetic devices, piezoelectric devices, and surface acoustic devices. applied to.

[Conventional technology]

Conventionally, single crystal thin films used in semiconductor electronic devices, optical devices, etc. have been formed by epitaxial growth on single crystal substrates. For example, it is known that Si, Ge, GaAs, etc. can be epitaxially grown on a Si single crystal substrate (Silicon Uni-Hachi) from a liquid phase, gas phase, or solid phase, and GaAs, Ge, GaAs, etc. can be grown on a GaAs single crystal substrate. 'G
It is known that single crystals such as aAlAs 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 MOCVD
(organometallic chemical vapor phase method) and other high-precision epitaxial technologies.

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 epitaxial growth 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.

In this way, it can be seen that the conventional method of forming a single crystal thin film by epitaxial growth is highly dependent on the substrate material.Mathews et al.
GROWTH, Academic Press, Ne
w York1975 ed, by J, W, M
athews).

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 lagging even further behind. In addition, the high manufacturing cost of single crystal substrates increases the 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 higher 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 and switching transistors for liquid crystal pixels, is becoming more active 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.

- When a thin film is deposited on an amorphous insulating substrate such as SiO□ on a boat, 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 Si0g by the CVD method, if the deposition temperature is about 600°C or less, 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 an amorphous or polycrystalline film using an energy beam such as a laser or a rod-shaped heater, a polycrystalline thin film with large grain sizes on the order of microns or millimeters can be obtained (Single-Crystal).
5ilicon on non-single-cry
Stalinsulators, Journal o
f crystal growth vol.

63, No, 3. 0ctober, 1983 e
Dited by G, W.

CuLen).

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,
~O, 1 cm"/sec for amorphous silicon, 1-10 cm"/V for polycrystalline silicon with a grain size of several hundred nanometers
・sec, polycrystalline silicon with a large grain size 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 across 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. However, if the performance is significantly inferior, then what will happen? Therefore, its applications are limited to simple switching elements, solar cells, photoelectric conversion elements, etc.

In addition, the method of forming polycrystalline thin films with large grain sizes by melting and solidifying requires a large amount of time to increase the grain size 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.

On the other hand, compound semiconductors are expected to be a material that can realize new devices such as ultra-high-speed devices and optical devices that cannot be realized with Si.
It could only be grown on i single crystals or compound single crystals, which was a major obstacle in device production.

In order to solve the above-mentioned conventional problems, Yonehara et al. published in Japanese Patent Application Laid-Open No. 63-107016,
-723.64-740, a nucleation surface with a low nucleation density is provided with a nucleation surface that has a sufficiently higher nucleation density than the non-nucleation surface material and is sufficiently fine that only a single nucleus grows. We proposed a method of forming crystals by continuing growth centered on a single nucleus grown on the nucleation surface using a nucleation surface, and demonstrated that single crystals can be formed even on non-single crystal substrates. It was shown that

This formation method involves artificially separating single nuclei to a desired distance, forming them selectively, and avoiding contact and collision of crystal grains until a crystal region of the required size is grown. As a crystal growth method, a chemical transport method (CVD method) is mainly used because of its fast growth rate, excellent mass productivity, and good crystallinity.

Further, the present inventors have proposed a growth method using metal as a non-single crystal nucleation surface by applying the selective nucleation single crystal growth method described above in JP-A-1-132118. This involves growing a semiconductor crystal directly on a metal electrode that is finely patterned with a non-nucleating surface material.

On the other hand, a selective epitaxial growth method using a single crystal substrate as a seed has been proposed as a growth method that takes advantage of the difference in nucleation density. This poses a problem in that the thickness of the film grown on the single crystal portion serving as the seed varies depending on the shape of the non-nucleation surface mask material. Therefore, Miyazaki et al.
In No. 3, it is proposed that a dummy pattern, which is not originally necessary for the device configuration, be created in the vicinity of the main pattern, and that a semiconductor material be selectively grown on both patterns to make the film thickness uniform. In this case, both the dummy pattern and the main pattern use the single crystal substrate as the seed for crystal growth.

[Problem to be solved by the invention j] In the selective nucleation technology that has been proposed in the past, in order to generate only a single nucleus on a nucleation surface of about 1 μm square, it is necessary to The difference in formation density is 102~10”
range was advantageous. Figures 3 and 4 respectively show S
This figure shows the change in nucleation density over time when L and GaAs are nucleated on various materials by the CVD method. In each case, the nucleation density on molybdenum is high, and the difference in nucleation density is 10% compared to silicon oxide and silicon nitride, which have advantageous properties as a non-nucleation surface.
It is about 4. If you try to obtain a single nucleus using a material with an extremely high nucleation density like molybdenum as a nucleation surface, you will need a very fine pattern, and multiple nuclei will occur, resulting in polycrystalline formation. There was also a problem that there was a high probability that the problem would occur.

In addition, to prevent polycrystalization, it is possible to narrow the distance between the nucleation surfaces, but if a metal material is used for the nucleation surface and used as an electrode at the same time, the electrode may form in unnecessary areas. This sometimes creates a problem in that it becomes an obstacle when designing a circuit pattern.

Therefore, the first object of the present invention is to provide a crystal that can grow a single crystal by generating only a single nucleus on the nucleation surface even when the nucleation density on the nucleation surface is extremely high compared to the non-nucleation surface. The object of the present invention is to provide a method for forming the same.

A second object of the present invention is to provide a method for forming a crystal that can grow a single crystal by generating only a single nucleus on nucleation surfaces with appropriate spacing between the nucleation surfaces.

[Means and effects for solving the problem] According to the present invention, a non-nucleation surface with a low nucleation density and a finely patterned nucleation surface having a nucleation density larger than the nucleation density of the non-nucleation surface. in a crystal formation method in which crystal growth is performed by generating nuclei from the nucleation surface by arranging the (And there is provided a method for forming a crystal, characterized in that a dummy pattern is made of a material different from the material constituting the nucleation surface.

The present invention is characterized by the high material placed near the nucleation surface.
By substantially lowering the nucleation density of the nucleation surface,
Crystal growth is performed by generating only a single nucleus.

The nucleation density on the surface of a material having a large area is determined by the growth conditions, as shown in FIGS. 3 and 4. However, in a fine region surrounded by non-nucleation surfaces with a low nucleation density, the nucleation density changes depending on the shape and relative position of the surrounding nucleation surfaces with a high nucleation density.

Under growth conditions that selectively nucleate,
Since the migration distance of the source gas on the substrate surface is long, the nucleation density decreases on small nucleation surfaces adjacent to and separated from large nucleation surfaces. In other words, since more raw materials are decomposed and consumed on large nucleation surfaces, the raw material gas concentration on small nucleation surfaces decreases.

By utilizing this property, by providing a dummy pattern using a material with a high nucleation density around the nucleation surface where the nucleation density is too high, the nucleation surface can be heated to the extent that only a single nucleus is generated. It becomes possible to reduce the nucleation density of.

[Embodiment example J Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(A) to 1(G) schematically show the steps of performing selective nucleation and growing a single crystal by the method of the present invention.

(A) Base material 1 (for example, A1□o,, AIN,
Ceramics such as BH, quartz, high melting point glass, high melting point metal) are coated with materials 2 with a very high nucleation density (for example, T
a1ls, a high melting point material such as Mo) is deposited to form a nucleation surface. Alternatively, a support made of a material with a high nucleation density may be used as the nucleation surface.

(B) Material 3 (SiOP) with lower nucleation density than the nucleation surface
, 5isN4, etc.) about 200 to 600 people,
Material 4 (
Tazor, A12os, Mo, etc.) from 100 to 6
Approximately 00 people will accumulate. At this time, the difference in nucleation density between the nucleation surface material and the dummy pattern material is generally 5 to 50 times,
Preferably it is 5 to 40 times, optimally 10 to 20 times.

(] The material 4 with a high nucleation density is buttered, and a dummy pattern 5 is formed adjacent to the location where the nucleation surface is to be formed.

This dummy pattern is wider than the nucleation surface (preferably 3 μm or more on each side. At this time, the distance between the nucleation surface and the dummy pattern varies depending on the CVD reaction pressure when generating nuclei, but the CVD pressure If it is less than 20 torr,
The distance is generally between 1 and 20 μm, preferably between 1 and 15 μm, optimally between 2 and 8 μm. CVD pressure is 20 torr
In the above case, the distance is generally 1 to 7 LLm, preferably 1
~5 μm, optimally 1-3 μm.

(D) Buttering and etching the non-nucleation surface,
A sufficiently small area (preferably 1, 5 μm square or less) to generate a single nucleus to form a single crystal is exposed and used as a nucleation surface. To form a nucleation surface or dummy pattern, as described above, leave a thin film with a high nucleation density by buttering, or open a hole by etching to expose the material with a high nucleation density. In addition, (H) to (I
), a region 8 with a high nucleation density may be created by implanting ions from above the non-nucleation surface masked with a resist 7.

(E) Crystal nuclei 9 are generated on the thus obtained substrate by CVD. At this time, nucleation occurs on the nucleation surface 6 and the dummy pattern 5. Although the nucleation density on the nucleation surface 6 is very high, only one crystal nucleus is generated because it is finely patterned and surrounded by a dummy pattern with a high nucleation density.

Crystalline materials that can be formed by this CVD method include, for example, S
i, Group II such as Ge, m- such as GaAs, InP, etc.
These include V group compounds, n-v' group compounds such as ZnS and CdSe, and I-III-VI group compounds such as CuGaS2.

In addition, the present invention utilizes metal organic molecular beam deposition (MOMBE), which is known as a selective crystal growth method other than CVD.
It is also applicable to liquid phase epitaxy (fLEP method) and liquid phase epitaxy (fLEP method).

In addition, the materials used for the nucleation surface and dummy pattern are not uniquely determined, but can be used by optimizing the pattern shape as long as the nucleation density satisfies the following relationship under certain growth conditions. Become. (Let the nucleation densities of the nucleation surface, dummy pattern, and non-nucleation surface be X, Y, and Z)
0 grows as a single crystal.

(G) The nuclei 10 grown from the nucleation surface finally collide with the polycrystals grown on the dummy pattern.

[Example] The present invention will be explained below using examples.

<Example 1> FIGS. 2(A) to 2(H) show schematic process diagrams for forming GaAs crystals by the method of the present invention.

(A) 1,500 Mo films 12 were deposited on a quartz substrate 11 by sputtering, and this was used as a nucleation surface material.

A magnetron RF sputtering device was used for sputtering, Ar was introduced at 1 torr, RF power was 1 kW, and the substrate temperature was 250°C.

(B) Next, the SiNx film 13 is deposited with a thickness of 300 nm using the plasma CVD method.
People piled up. The deposition conditions were a substrate temperature of 350°C and a reaction pressure of Q.
, 2t, orr, raw material gas is SiH<101005e
, NH, 200 sccm.

Further, on top of that, an A120m film 14 is applied by vacuum evaporation.
00 people deposited. The deposition conditions were a substrate temperature of 120°C.

The evaporation source was Altoz, Ox gas at 4 x 10-'t.
The heating was carried out by electron beam heating with the introduction up to a temperature of

(C) Buttering with resist using photolithography technology, H-3O4:HzCh:HxO=1
Altos was etched using a 1:2 etchant to form a belt with a width of 3 μm. This is designated as a dummy pattern 15.

(D) After patterning with resist in the same way, dry etching was performed at CF4:O, = 10:1, pressure 10 t.
Etch SiNx under the conditions of orr to 1.0 μm.
Holes were opened on all sides and used as the nucleation surface. The distance from the dummy pattern to the nucleation surface was 3 μm. Figure (H) is
A plan view of this pattern is shown.

(E) Heat treatment at 850°C for 10 minutes in H atmosphere,
Next, GaAs crystal nuclei 17.18 are formed on the nucleation surface 16.1 by the MOCVD method. It is generated on the dummy pattern 15.

Trimethyl gallium (TMG) and tertiary butyl arsenic (TBAs) were used as raw materials, and H2 was used as a diluent gas.

V/m%)L, specific TBAs: TMG is 2o
:1, and the molar ratio of TMG to diluent H2 is 6X
10-', reaction pressure 20 torr.

The substrate temperature was 670°C.

(F) As the growth progressed, the nuclei 18 generated from the nucleation surface 16 grew as single crystals, and the nuclei 17 generated on the dummy pattern became polycrystalline.

(G) The single crystal nucleus 18 that grew from the nucleation surface finally collided with the polycrystal that grew on the dummy pattern.

If a nucleation surface of the same shape in the same substrate has no dummy pattern placed around it, the probability of single crystal growth is 10.
It was less than %. On the other hand, in the case where a dummy pattern was arranged, facets indicating single crystal appeared in 80% or more of the 10 IOXs.

<Example 2> Other embodiments according to the present invention will be described below.

FIGS. 5(A) to 5(H) show schematic process diagrams for forming SL crystals according to the present invention.

(A) Mo was deposited on the alumina substrate 19 by sputtering.
1500 layers of film 20 were deposited and used as the nucleation surface material. For sputtering, a magnetron RF sputtering device was used, Ar was introduced at 0.1 torr, and the RF power was 1 kW.
The test was carried out at a substrate temperature of 250°C.

(B) Next, atmospheric pressure CVD method Te5iox film 21ti-300
People piled up. Growth conditions are substrate temperature 400℃, source gas 1
5% SiH4 (N2 dilution) 500sec, Odo
It was osecm.

(C) Next, using a photolithography technique, the resist 22 was patterned into a belt shape with a width of 3 μm. From above, Si ions 2 are added using an ion implantation device.
3 was implanted at a dose of I x 10"cm-".

(D) The region 24 implanted with Si ions has a higher nucleation density than SiO□, so this was used as a dummy pattern.

(E) After patterning with a resist in the same manner, dry etching was performed to obtain CF<:Oz=10:1. Pressure 1O-
Etching SiNx under 1 torr condition, 1.2
A hole of square μm was made and this was used as the nucleation surface. The distance from the dummy pattern to the nucleation surface was 4 μm.

The planar shape of the pattern is the same as in the previous example, and is shown in FIG.
I).

(F) Heat treatment is performed at 1050° C. for 10 minutes in an H2 atmosphere, and then Si crystal nuclei 26 and 27 are formed on the nucleation surface 25 by the CVD method. The pattern is generated on the dummy pattern 24. The supply gas is 5iHaC1□/HCI/H2=1.2 (1/m1
n)/1.6 (1/mir+)/100(1/m1
n) at a substrate temperature of 990°C and a reaction pressure of 150 torr.
I did a VD.

(G) As the growth progressed, the nucleus 26 generated from the nucleation surface 25 grew as a single crystal, and the nucleus 27 generated on the dummy pattern 24 became polycrystalline.

(H) The single-crystal-like 26 that grew from the nucleation surface finally collided with the polycrystal that grew on the dummy pattern.

If the nucleation surface has the same shape within the same criteria and no dummy pattern is placed around it, the probability of single crystal growth is 4.
It was around 0%. On the other hand, in the case where dummy patterns were arranged, facets indicating single crystal appeared in more than 90% of 10×10 pieces.

[Effects of the Invention] As explained above, according to the present invention, single crystal growth can be achieved with good selectivity even when a material with extremely high nucleation density compared to the non-nucleation surface is used for the nucleation surface. This increases the degree of freedom in material selection.

In conventional methods, when a single crystal is grown on a material with an extremely high nucleation density compared to the nucleation density of a non-nucleation surface, in order to selectively form a single crystal at a desired position with a high yield, It becomes necessary to pattern the nucleation surface more finely, for example, in order to print a pattern of 1 μm or less, the precision of the entire process including the aligner must be increased (
It costs more to maintain. In contrast, according to the present invention, crystal growth by selective nucleation can be performed more easily and inexpensively. At the same time, it is possible to suppress the probability of polycrystals occurring within the nucleation plane to a low level.

When using a metal material on the nucleation surface and simultaneously using it as an electrode,
By narrowing the pattern spacing between the nucleation surfaces, it becomes possible to freely generate single crystals and take out the electrodes at positions as far apart as necessary without lowering the actual nucleation density.

[Brief explanation of the drawing]

Fig. 1 is a process diagram of an embodiment of the present invention, Fig. 2 is a process diagram of GaAs crystal growth showing an embodiment of the present invention, Fig. 3 is a nucleation density of Si on various materials, and Fig. 4 is a process diagram of an embodiment of the present invention. are GaAs nucleation densities on various materials, and FIG. 5 is a process diagram of Si crystal growth showing a second embodiment of the present invention. 1... Base material, 2... Material with high nucleation density, 3... Material with low nucleation density, 4... Material with high nucleation density, 5... Dummy pattern, 6...・Nucleation surface, 7・
...Resist, 8...Ion implantation surface, 9.
...Crystal nucleus, lO...Crystal nucleus, 11...
Quartz substrate, 12... Molybdenum film, 13...
・SiNx film, 14...A1□0 film,
15...Dummy pattern, 16...Nucleation surface, 1
7-GaAs crystal nucleus, 1111-GaAs single crystal, 19... alumina substrate, 20... molybdenum film, 21... SiO□ film, 22...
Resist, 23...Si ion, 24...
・Si implantation region, 25...nucleation surface, 26.
...Si single crystal, 27...Si crystal nucleus.

Claims (3)

[Claims] (1) A non-nucleation surface with a low nucleation density and a finely patterned nucleation surface having a nucleation density higher than the nucleation density of the non-nucleation surface are arranged adjacent to each other, and In a crystal formation method in which crystal growth is performed by generating nuclei, a material having a high nucleation density and different from the material constituting the nucleation surface is used in the vicinity of the nucleation surface so as not to contact the nucleation surface. A method for forming a crystal, characterized by disposing it as a dummy pattern. (2) The method for forming a crystal according to claim 1, wherein the material forming the nucleation surface is a conductive material. (3) The method for forming a crystal according to claim 1, wherein the material forming the dummy pattern is an insulating material.