JPH025513A - Manufacture of semiconductor thin film - Google Patents

Abstract

PURPOSE:To selectively produce high quality crystals by a method wherein a material in vapor state is excited by microwave electron cyclotron resonance plasma to be crystal-deposited and the excited material is simultaneously carried to a substrate crystal by divergence magnetic field so that the excited material carried may be selectively crystal-deposited only on the exposed part on the surface of the substrate crystal. CONSTITUTION:A divergence magnetic field is provided with the magnetic field distribution diminishing the intensity of magnetic field from a cavity resonance type plasma 8 producing chamber 7 in the substrate crystal direction. Masking material made of line and space type silicon oxide formed by photolithography are provided on a GaAs substrate 21 and then GaAs single crystals 23 are selectively formed only on the GaAs substrate 21. At this time, as for the microwave electron cyclotron resonance plasma source, arsine diluted with hydrogen (AsH3) is led in so that gallium may be evaporated from a solid material evaporating cell 6 to be crystal-deposited.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for growing a crystal of a semiconductor thin film. The present invention relates to a crystal growth method for selectively obtaining high-quality semiconductor thin films.

[Conventional technology]

Conventionally, methods such as metal organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) have been used to selectively grow semiconductor crystals on a substrate crystal partially covered with a foreign substance (mask material). (For example, regarding the MOVPE method, Y, Takahashi et, a6. J, Cr
ystal Growth, 6B (1984)pp
206--213, On the MBE method, Kaimoto, Ohata: Institute of Electronics, Information and Communication Engineers Technical Research Report IEICE Technical Report Vow. 87.
N00277, P49. ED87-118, 1988).

[Problem to be solved by the invention]

In the conventional MOVPE method, selectivity is obtained by utilizing the property of organometallic materials that the adhesion coefficients between the substrate crystal and the mask material are different. Therefore, the optimum growth temperature can be determined depending on the combination of the semiconductor to be grown and the mask material. There was a problem that various mask materials and semiconductors could not be used at the same time. Furthermore, since the MBE method can obtain selectivity only in a region where the substrate temperature is high, there is a problem in that crystal defects are likely to be generated. Furthermore, a problem common to the above two methods is that no selectivity can be obtained in a region where the substrate temperature is low.

The conventional methods described above have disadvantages when using selective growth, such as not being able to use various mask materials and semiconductors at the same time, and not being able to obtain selectivity at all in a low substrate temperature region.

The present invention has been proposed to improve the above-mentioned drawbacks, and is capable of growing on a substrate crystal partially covered with a foreign material, regardless of the combination of the semiconductor to be grown and the mask material, in a low substrate temperature region. Another object of the present invention is to provide a method for selectively forming a high-quality semiconductor thin film only on uncovered areas.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for growing a semiconductor thin film crystal from a substance in a gas phase onto a substrate crystal whose surface is partially covered with a substance different from that of the semiconductor to be grown. , the substance in the gas phase is excited by a microwave electron cyclotron resonance plasma to grow a crystal, the excited substance is transported onto the substrate crystal by a divergent magnetic field, and the transported excited substance is It is characterized by selectively growing crystals only on the exposed portions of the substrate crystal surface.

[For production]

The present invention uses a combination of a microwave electron cyclotron resonance plasma source and a divergent magnetic field to transport ions of one or more semiconductor constituent elements or reducing or inert elements to a substrate together with electrons, either directly or in a substrate installation chamber. While introducing a gas containing other semiconductor constituent elements, crystal defects can be selectively removed only in the parts not covered with the foreign material even in the low substrate temperature region on the substrate crystal partially covered with the foreign material. The main feature is that it causes less crystal growth.

In other words, according to the present invention, it is possible to control the number of low-energy particles of several tens of electron volts and transport them to the substrate, without causing damage to the grown film, and moreover, more efficiently than in the case of thermal equilibrium crystal growth. A semiconductor crystal growth method is provided, which is characterized by being able to selectively grow crystals with high energy.

In the method according to the present invention as described above, since crystal growth is performed with sufficiently higher energy than thermal equilibrium, the migration of atoms on the substrate surface increases. In this case, migration refers to the movement of atoms that have reached the substrate surface over the surface until they are incorporated into the crystal lattice position. Further, as migration increases, the process of detachment of migrating atoms from the substrate surface by incident low-energy particles is promoted. Therefore, since the crystal lattice positions that exist on the substrate crystal and should be incorporated are not on the mask material, atoms migrating on the mask material are detached, and as a result, crystal growth occurs selectively on the substrate crystal. Furthermore, since the energy is relatively small, high-quality crystals with no damage to the selectively grown crystal layer can be obtained. In other words, when energy is applied to a substance in a gaseous state, when it reaches the substrate crystal surface, migration as explained above increases and promotes the detachment of atoms from the substrate surface. As a result, atoms on the mask material are detached from the surface, and a semiconductor is selectively formed only on the substrate crystal not covered with the mask material. In addition, in the method according to the present invention, crystal growth is performed with sufficiently higher energy than thermal equilibrium, so that the selective growth described above does not occur in a low substrate temperature region where selectivity does not occur in the thermal equilibrium crystal growth method. It is also possible in Furthermore, by selecting the optimum energy value according to the combination of mask material and semiconductor, the above-described selective growth can be realized according to the free combination of mask material and semiconductor. Examples will be described below based on the drawings.

〔Example〕

FIG. 1 schematically shows a manufacturing apparatus used in the present invention.

In FIG. 1a, 1 is a growth chamber in which a substrate crystal 2 is supported. 3 is a connection port to an exhaust pump, 4 is a gas inlet, 5 is a plasma shielding plate, 6 is a solid material evaporation cell, 7
1 is a cavity resonant plasma generation chamber, 8 is a plasma, 9 is a rectangular waveguide, 10 is a magnet, and 11 is a quartz window. 1st
The figure shows the distribution of the divergent magnetic field caused by the magnet 10, and as shown in Figure 1, the cavity resonant plasma generation chamber 7
The strength of the magnetic field is reduced as it moves from the magnetic field to the growth chamber 1.
As a result, plasma diverges and is drawn out.

That is, one of the features of the present invention is that the divergent magnetic field has a magnetic field distribution in which the strength of the magnetic field decreases from the plasma generation chamber toward the substrate crystal direction.

Next, an example of the manufacturing method according to the present invention will be described.

Example 1: As shown in FIG. 2a, a line-and-space silicon oxide mask material 22 formed by photolithography is provided on a GaAs substrate 21, and GaAs is selectively applied only on the GaAs substrate 21. A single crystal 23 was formed. In this example, the microwave electron cyclotron resonance plasma source includes hydrogen diluted arsine (AsH,
) was introduced, and gallium was evaporated from a solid material evaporation cell to grow crystals. The growth conditions are as follows.

Growth conditions of Example 1 - Arsine flow rate: 4 Qsecm - Ga cell temperature: 900°C - Microwave frequency: 2.45 GHz - Micro electrified crab too - Growth rate = 0.8 μm/h - Growth time: 1 hour - Substrate temperature = 450°C ・Thickness of silicon oxide mask material: O, OS μm ・Line and space spacing: 1 μm/1 μm As shown in the figure, crystals grow only where the substrate is exposed when viewed from the top. No growth is occurring on the mask material.

Comparative Example 1: FIG. 2 shows a case where growth was performed on the same substrate as used in Example 1 by conventional molecular beam epitaxial method. The growth conditions are as follows.

Comparative Example 1 Growth conditions - Ga cell temperature = 900°C ・Arsenic pressure 3×10-'Torr ・Growth rate: 0.8 μm/h ・Growth time: 1 hour ・Substrate temperature: 450°C In the figure, 24 is on the mask material A polycrystalline region grown by the MBE method is shown. As can be seen from the figure, crystal growth also occurs on the mask material, resulting in polycrystals with severe quality deterioration.

From the above comparison between Example 1 and Comparative Example 1, it was found that the method according to the present invention promotes the desorption of atoms on the substrate surface and enables selective crystal growth without crystal deposition on the mask material. I know what will happen.

Embodiment 2: FIG. 3a shows a cross-sectional view when a silicon oxide line-and-space mask material 32 is provided on a GaAs substrate 31 and the substrate 31 is etched to a depth of 0.8 μm. Using this FIG. 3a as a substrate, GaAs is selectively grown on the exposed portion of the substrate material using the method according to the present invention in the same manner as in Example 1 (FIG. 3b). At this time, the growth conditions were the same as in Example 1. At that time, the thickness to be grown is set to 0.8 μm, which is up to the position of the original substrate surface,
Thereafter, by removing the silicon oxide line-and-space mask material 32, a growth layer 33 embedded in the GaAs1 plate 31 was realized as shown in FIG. 3C.

In the first and second embodiments described above, GaAs was used as the semiconductor to be selectively grown, but for example, InP may be used.

In the case of compound semiconductor crystal growth such as GaP, AlAs, InAs, and their mixed crystals, the same crystal growth as in the case of GaAs growth can be performed.

Also, although quartz was used as the mask material, SiN, Alz
Ox + AIN, S f C, 7az o3 T
Even if an insulating thin film such as LOZ is used, crystal growth can be performed only on the exposed portion of the substrate in the same way as when quartz is used as a mask material. In addition, although excitation by microwave electron cyclotron resonance was performed on a gas containing a group III element, for example, a gas containing a group III element, or even hydrogen or argon, which hardly remains in the growth layer, can also be used. . In the latter case, the elements constituting the grown film will be supplied by a method similar to the conventional molecular beam epitaxial method.

Further, in the above embodiment, a GaAs crystal made of the same material as the substrate material was grown on the GaAs substrate, but the method of the present invention can also be used when growing a crystal made of a material different from the substrate material, that is, when performing heteroepitaxial growth. Can be applied.

In the present invention, excitation by microwave electron cyclotron resonance plasma is performed on one or more gas phase substances selected from the group consisting of constituent elements of the crystal to be grown and reducing or inert elements. It is a feature.

[Effects of the Invention] As explained above, according to the method of the present invention, the migration of atoms in the lateral direction on the substrate surface is increased, and the atoms are coated with a foreign substance to promote desorption from the surface. Crystal growth can be selectively performed only on uncoated substrate crystals even at relatively low substrate temperatures. Furthermore, the method according to the present invention has the advantage that high-quality crystals with few defects can be obtained because crystal growth is performed by low-energy transport.

[Brief explanation of the drawing]

FIG. 1a is a schematic diagram of the apparatus used in the present invention, FIG. 1 is a distribution of a divergent magnetic field, and FIG. A cross-sectional view when GaAs is grown,
Figure 2 shows a cross section of a GaA3 film grown by molecular beam epitaxial growth on the same substrate as in Figure 2a, and Figure 3a shows a cross section of a GaA film grown using a silicon oxide line and stripe mask formed on the substrate. FIG. 3A is a cross-sectional view of etched GaA film by the method of the present invention.
FIG. 3C shows a cross-sectional view when the silicon oxide line-and-striped mask is removed. l...Growth chamber, 2...Substrate crystal, 3...Connection port,
4... Gas inlet, 5... Plasma shielding plate, 6...
・Solid material evaporation cell, 7... Cavity resonant plasma generation chamber, 8... Plasma, 9... Rectangular waveguide, 10.
...Magnet, 11...Quartz window, 21.31=Ga
As substrate, 22.32-...mask material, 23...G
aAs single crystal, 24... polycrystalline region, 33... growth layer Description of manufacturing method Example 1 of the present invention and conventional manufacturing method Comparative Example 1 Figure 2

Claims (1)

[Scope of Claims] A method for growing a semiconductor thin film crystal from a substance in a gas phase onto a substrate crystal having a structure in which a part of the surface is covered with a substance different from the semiconductor to be grown, comprising: crystal growth by exciting a substance present in the substrate with a microwave electron cyclotron resonance plasma, transporting the excited substance onto the substrate crystal using a divergent magnetic field, and exposing the transported excited substance on the surface of the substrate crystal. 1. A method for manufacturing a semiconductor thin film, characterized in that crystal growth is selectively performed only in a portion of the semiconductor thin film.