JPH01270593A - Method for forming compound semiconductor layer - Google Patents

Abstract

PURPOSE:To form a compound semiconductor layer having flat surface and prescribed thickness exclusively in a prescribed region by forming a silicon single crystal substrate covered with an insulation layer having an opening at a prescribed position and carrying out selective epitaxial growth of a compound semiconductor layer on the substrate surface exposed in the above opening using an ALE process. CONSTITUTION:A silicon single crystal substrate 1 has a surface covered with an insulation layer 2 (e.g., SiO2 layer) having an opening 8 at a prescribed position. The substrate is placed in a vapor growth apparatus and heated at a prescribed temperature. Raw material gases containing individual elements for constructing the desired compound semiconductor layer are introduced into the vapor growth apparatus staggering the introduction time. The above compound semiconductor layer 6 can be selectively deposited by epitaxial growth on the surface of the silicon single crystal substrate 1 exposed in the opening 8. A single crystal layer having a thickness of about 3mum which is required to form a semiconductor device can be produced by selectively depositing a single crystal layer 7 on the above semiconductor layer 6 by a vapor growth process which gives a high-purity single crystal at high rate of growth.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for forming a compound semiconductor layer on a silicon single crystal substrate.

The purpose of this method is to selectively form a compound semiconductor layer that is flat and has the thickness necessary to form a semiconductor device only in a predetermined region on a silicon single crystal substrate.

A silicon single crystal substrate having one surface on which an insulating layer with openings provided at predetermined positions is formed is placed in a vapor phase growth apparatus, and a source gas containing individual elements constituting a desired compound semiconductor layer is supplied. The compound semiconductor layer is selectively grown on the surface of the silicon single crystal substrate exposed in the opening by introducing the compound semiconductor layer into the vapor phase growth apparatus at different times.

[Industrial application field]

The present invention relates to a method for epitaxially growing a compound semiconductor layer, and particularly to a method for forming a single crystal layer of a compound semiconductor such as gallium arsenide on a silicon single crystal substrate.

[Conventional technology]

Gallium arsenide (GaAs) and indium phosphide (InP)
Or attempts to form single crystal layers of these compound semiconductors on silicon substrates in order to meet the demands for higher performance, higher integration, and improved mass productivity of semiconductor devices using single crystal mixed compound semiconductors. is being carried out. This is a composite substrate consisting of a silicon substrate and a compound semiconductor single crystal layer.

(a) Silicon substrates can be obtained in relatively large-diameter wafers, which can improve the mass productivity of semiconductor devices conventionally manufactured using compound semiconductor substrates (bl Silicon substrates have poor thermal conductivity compared to compound semiconductor layers. (C) Formation of semiconductor devices suitable for each of the silicon substrate and the compound semiconductor single crystal layer. By doing.

It has the advantage that it is possible to form a composite monolithic integrated circuit 5 in which different types of semiconductor devices are combined, such as an OBIC (photoelectric integrated circuit) in which a silicon transistor and a light emitting diode are mounted on one semiconductor substrate.

Generally, the thermal expansion coefficient of a compound semiconductor single crystal layer is larger than that of a silicon substrate, so when a silicon substrate with a compound semiconductor single crystal layer formed on its entire surface is cooled to room temperature,
Warpage may occur in the substrate with the compound semiconductor single crystal layer on the inside, and in severe cases.

Cracks appear in the compound semiconductor single crystal layer. As a method for preventing this, it is effective to form a compound semiconductor single crystal layer in an island shape. A silicon substrate has a compound semiconductor single crystal layer formed into an island shape.

It is also advantageous in complex monolithic integrated circuits such as those described above.

That is, a desired semiconductor device is formed on a silicon substrate in advance, a compound semiconductor single crystal layer is selectively grown in an island shape in a predetermined region on the silicon substrate, and a desired semiconductor device is formed in this compound semiconductor single crystal layer. do.

[Problem to be solved by the invention]

A method for growing a single crystal layer of a compound semiconductor such as GaAs on a silicon substrate is bimolecular beam electron beam extraction (MBE).
Conventionally, a metal organic chemical vapor deposition (MOCVD) method has been used (Takashi Ueda et al., 1985 Spring Proceedings of the Japan Society of Applied Physics P, 689, etc.).

For example, as shown in FIG.
An iO□ (silicon dioxide) layer 2 is formed, and a 5i0
Two layers 2 are selectively removed to form an opening (window), and a GaAs layer 3 is epitaxially grown on the silicon substrate 1 exposed within the window. At the same time, a polycrystalline GaAs layer 4 is formed on the SiO□ layer 2.

The GaAs layer 3 grown as described above contains SiO
A raised portion 5 is generated near the layer 2, and this portion remains even after the polycrystalline GaAs layer 4 is removed by lift-off or the like. Therefore, the surface of the island-shaped GaAs layer 3 is not flat.

When attempting to form a semiconductor device on the uneven island-shaped GaAs layer 3 as described above, it is difficult to focus the optical pattern projected onto the GaAs layer 3 during the exposure process, or the thickness of the GaAs layer 3 is not uniform. There have been problems such as No. 5 that cause variations in the characteristics of semiconductor devices formed.

An object of the present invention is to enable selective formation of a metal compound semiconductor layer having a flat surface and a predetermined thickness only in a predetermined region on a silicon substrate.

[Means to solve the problem]

The above purpose is to install a silicon single crystal substrate having one surface on which an insulating layer with openings provided at predetermined positions is formed in a vapor phase growth apparatus, and to individually contain elements constituting a desired compound semiconductor layer. selectively growing the compound semiconductor layer on the silicon single crystal substrate surface exposed in the opening by introducing raw material gases at different times into the vapor phase growth apparatus; A raw material gas containing each of the semiconductor layer constituent elements and at least one of which is a chloride or hydride of the constituent element is simultaneously introduced into the vapor phase growth apparatus, and on the compound semiconductor layer grown in the opening, This is achieved by the compound semiconductor layer forming method according to the present invention, which is characterized in that a compound semiconductor single crystal layer having a larger thickness is additionally grown.

[For production]

Atomic layer epitaxy (atomic layer epitaxy) in which the surface of a silicon single crystal substrate where a compound semiconductor single crystal layer is not formed is covered with an insulating layer such as SiO2, and source gases containing individual elements constituting the compound semiconductor single crystal layer are introduced at different times. ALE
) method to epitaxially grow a compound semiconductor single crystal layer.

A compound semiconductor single crystal layer can be selectively grown only on the surface of the silicon substrate 1 that is not covered with an insulating layer, and no compound semiconductor layer can be formed on the insulating layer. Then,
A vapor phase growth method using a raw material gas consisting of at least one chloride or hydride of the elements constituting the compound semiconductor layer and simultaneously introducing these raw material gases allows the compound semiconductor layer selectively grown by the above ALE method to have a higher A thicker compound semiconductor single crystal layer can be selectively grown at a faster growth rate.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In the following drawing G, the same parts as in the previous drawings are given the same reference numerals.

FIG. 1 is a cross-sectional view of a main part for explaining the present invention in detail. On a silicon substrate 1, a Sin2 layer 2 with openings provided at predetermined positions is provided.

On the silicon substrate 1 exposed in the opening.

A GaAs layer 6 with a thickness of about 0.1 μm is formed by selective epitaxial growth using the ALE method.

Furthermore, a GaAs layer 6" is formed by epitaxially growing a GaAs layer 6 with a thickness of about 3 μM using ASCI:1 (arsenic trichloride) as a raw material gas by a normal vapor phase growth method.
are selectively formed.

For details of the ALE method, see the report by Ozeki et al.
of the 19th Conference
n 5solid 5tate Devices and
Materials.

Tokyo, 1987. PP, 475). here.

To give only an overview: 1. The same raw material gas and similar growth equipment as in the normal MOCVD method are used. In the MOCVD method, for example, when growing GaAs, raw material gases containing the constituent elements Ga and As are supplied simultaneously, whereas in the ALE method.

This differs from the MOCVD method in that Ga and true raw material gases are alternately supplied at different times. GaAs can be epitaxially grown directly on a silicon substrate by both the MOCVD method and the ALE method.

However, according to the MOCVD method, GaAs is also generated on the SiO□ surface as described above, whereas A
The inventors have discovered that according to the LE method, GaAs is not generated on the SiO□ surface, and furthermore, no raised portions are formed around the GaAs layer selectively grown within the openings of the SiO□ mask layer. . The basic structure of the present invention is to apply this phenomenon.

Therefore, according to the method of the present invention, it is possible to selectively grow the GaAs layer 6 with excellent flatness within the opening of the Sin layer 2. However, the average growth rate of a single crystal layer by the ALE method is as low as about 0.1 μm/hour, and it takes a long time to grow a single crystal layer with a thickness of about 3 μm, which is necessary for forming a semiconductor device. It takes. Additionally, there is currently a slight problem with the purity of the grown single crystal layer. For this reason.

The present invention provides a single crystal layer having a desired layer thickness on an epitaxial layer selectively grown by the ΔLE method, using a vapor phase growth method that allows a high growth rate and a high purity single crystal layer to be obtained. As a component, it includes selectively growing.

One of the vapor phase epitaxy methods that can grow a high-purity single crystal layer with a high growth rate as described in Section 2 is a vapor phase epitaxy method that uses chloride-based raw gas ( J.
Komeno et al., J. Electro
chem.

Soc, 124 (1977) pp, 1440).

According to the chloride-based vapor phase growth method, it is possible to grow a high-purity compound semiconductor single crystal layer having a thickness of about 3 μm, which is necessary for forming semiconductor devices such as those described in Section 2, in a short time of one hour or less. I can do it. however.

It is not possible to grow a single crystal layer such as GaAs directly on a silicon substrate. This is thought to be due to the following reasons.

In other words, the oxygen contained in the 5 basic gases, or.

The quartz material of the vapor phase growth apparatus reacts with IICI (hydrogen chloride), and the oxygen generated oxidizes the silicon substrate surface, covering the surface with an oxide film. For the above HCI, Asl13 (
It is produced when a chloride-based raw material gas such as arsenic trichloride (arsenic trichloride) and hydrogen, which is a carrier gas, react at high temperatures.

The HCI etches the formed GaAs, but at a higher rate than the rate of formation of the GaAs layer relative to the 5i02 layer. Therefore, according to the chloride-based vapor phase growth method.

Neither single crystal nor polycrystalline layers of GaAs are grown on the silicon substrate.

The present invention includes, as a component, the application of this property to a method for selectively growing a thick compound semiconductor single crystal layer on a compound semiconductor epitaxial growth layer selectively formed by the ALE method.

That is, if a GaAs layer is formed by the ALE method described above on the surface of the silicon substrate exposed in the opening of the SiO□ layer, a GaAs layer is epitaxially grown on this GaAs layer by a chloride-based vapor phase epitaxy method. of SiO□
The fact that no GaAs layer is formed on the layer is utilized.

FIG. 3 is a cross-sectional view of a main part for explaining one embodiment of the present invention, showing the process of selective epitaxial growth of a GaAs layer on a silicon substrate.

Prior to the growth of the GaAs layer, as shown in Figure 3 (al).

A SiO□ layer 2 serving as a mask is formed on a silicon substrate 1-1- in the following manner.

■ The silicon substrate 1 is degreased and cleaned, and then the natural oxide film on the surface is removed by immersing it in a 10% hydrofluoric acid solution. Forming a SiO□ layer 2 with a thickness of about 0.2 μm ■ Using normal photo-I lithography technology, an opening (window) 8 is provided at a predetermined position in the 5iO7 layer 2, and the surface of the silicon substrate 1 is exposed within the window 8. For example, if a MOSFET (Si-M
OSFET), and MESFET in the GaAs layer.
(GaAs-MESFET).

When forming a composite integrated circuit by forming each of them, a 51-MOSFET is formed in advance on the silicon substrate 1 between the above steps (a) and (111).

However, the metal electrode or contact hole is formed using GaA.
This is done after the s-layer is generated.

After the SiO□ layer 2 serving as a mask is formed on the silicon substrate 1 in the above manner, the silicon substrate 1 is immediately placed in a vapor phase growth apparatus, and is grown using the ALE method.
A GaAs layer 6 is selectively epitaxially grown on the surface of the silicon substrate 1 exposed within the window 8.

When growing a gallium arsenide (GaAs) single crystal layer by the AI or E method, for example, trimethyl gallium (T) IG) is used as the Ga source gas, and hydrogen is diluted to 10% as the As source gas. Arsine (Asl13)
Use. The silicon substrate 1 on which the mask SiO□ layer 2 is formed is placed in a vapor phase growth apparatus capable of performing the ALE method, and the following processing is performed under reduced pressure of about 20 Torr.

Arsine is introduced into the growth apparatus, and the silicon substrate 1 is heated at 900 to 1000°C for 10 to 10 minutes using a high frequency induction heating method.
Haze for 30 minutes. In this process.

The natural oxide film on the surface of silicon substrate 1 is removed.

The temperature is then lowered to 300-500°C. After the temperature stabilizes, supply of the raw material gas is repeated in one cycle of hydrogen-TMG-hydrogen-arsine. Through the above steps, as shown in FIG. 3 (bl), when a GaAs layer 6 with a thickness of about 0.1 μm is grown on the surface of the silicon substrate 1 exposed in the window 8, the supply of the raw material gas is stopped.

The silicon substrate 1 is taken out from the vapor phase growth apparatus in which the above ALE growth was performed, and immediately placed in an apparatus for chloride-based vapor phase growth, and then chloride-based vapor phase growth is performed as follows. .

That is, a bubbler filled with ASC13 is heated to a predetermined temperature, and hydrogen gas is introduced into it.

ASC13 is introduced into the vapor phase growth apparatus. ASC13 and hydrogen react in the high temperature part of the vapor phase growth apparatus to form IAs4.
and HCI. Gallium (Ga) saturated with As4 is installed in the second flow section of the vapor phase growth apparatus. GaCl generated when this Ga reacts with HCl
5 (gallium trichloride) and As4 are transported by the carrier gas and react near the Si substrate 1. the result.

A single crystal GaAs layer 7 is grown using the GaAs layer 6 as a seed. Note that, as described above, no GaAs layer is formed on the SiO□ layer 2.

As shown in FIG. 3 TCI, when the GaAs layer 7 reaches a predetermined thickness (for example, 3 μm), the supply of source gas is stopped, the silicon substrate 1 is cooled, and the silicon substrate 1 is taken out from the vapor phase growth apparatus. The 5iOz layer 2 on the silicon substrate 1 on which the GaAs layer 7 is formed is removed by a normal etching method using a solution to obtain the structure shown in FIG. A desired semiconductor device such as a MESFET is formed according to normal processes such as ion implantation and formation of metal electrodes or wiring.

Note that, if necessary, at the same time as the introduction of AsC1 described in -1-, an impurity raw material gas containing an impurity element to be doped into the GaAs layer 7 can be introduced to give a predetermined carrier concentration to the GaAs layer 7. .

Figure 4 shows the cross-sectional shape of the structure shown in Figure 1 after selectively removing the Sin and layer 2 using a stylus-type surface step measuring device.
This is a graph obtained by observation using the Terly Step. The vertical axis shows the height from the surface of the silicon substrate 1, and the horizontal axis shows the distance in the surface direction. As shown in the figure, the height of the surface of the GaAs layer 7 from the surface of the silicon substrate 1 is about 3 μm, and the width in the horizontal axis direction is about 40 μm. As shown, GaAs
The surface of the layer 7 has a raised portion 5 of the conventional GaAs layer 3.
(See Figure 2)

In Example 1, a chloride such as AsCIa was used as one of the raw material scraps for growing the GaAs layer 7. The reason why a GaAs layer is not formed on the SiO□ layer 2 is because of this.

In the 8102 layer-1-, IIcI due to the GaAs deposition rate.
This is because the etching speed is higher due to This 1 (
CI is.

As mentioned above, this is generated by the reaction between ASCI3 and hydrogen as a carrier gas. therefore,
IIC in one reaction system using an organometallic compound as a raw material gas
Even if l gas is introduced, the GaAs layer 7 can be selectively grown in the same way.

Even if A s If 3, which is a hydride of arsenic, is used instead of Δs C+ , , in the above example, GaA
GaAs layer 7 can be selectively grown only on s-layer 6.

Further, in the above embodiment, after selectively growing the GaAs layer 6 on the silicon substrate 1 by the ALIE method, the Sin2 layer 2 is grown.
In some cases, a single crystal layer of better quality can be obtained by growing the GaAs layer 7 after removing the . This is a mask S
This is because contamination from the iO□ layer 2 is eliminated.

The removal of the Sin2 layer 2 is 10% as in the above example.
This is carried out by immersing the silicon substrate 1 in an IIF solution. After removing the Sin2 layer 2, 1hsO4 (sulfuric acid) and H
After etching the surface of the GaAs layer 6 by about 50 nm using a mixed aqueous solution of 2O2 (hydrogen peroxide), the silicon substrate 1 was placed in a chloride-based vapor phase growth apparatus, and GaAs was grown in the same manner as in the above embodiment. The G-detailed S layer 7 is selectively grown on the layer 61.

The exposed silicon substrate 1 after the removal of the Sin2 layer 2 as described above has a structure as shown in FIG. 5(a).

A natural oxide film 9 with a thickness of about 1.0 nm is formed.

In chloride-based vapor phase growth, even with such a thin natural oxide film 9, GaAs is not generated in this layer 6-, and GaAs is generated only in the GaAs layer 6-, )u.
Layer 7 is selectively grown.

The present invention relates to compound semiconductors other than GaAs such as indium phosphide (InP), indium galliu J,R (InGa
P).

It goes without saying that selective growth of single crystal layers such as aluminum gallium arsenide (AIGaAs), Galium J, phosphorus (GaP), etc. is also possible.

〔Effect of the invention〕

According to the present invention, a compound semiconductor single crystal layer having good flatness and a thickness necessary for forming a semiconductor device can be selectively grown in a predetermined region of a silicon substrate surface, and Ga This has a great effect in promoting the practical application of semiconductor devices using composite substrates with /Is on Si structure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part for explaining the present invention in detail. FIG. 2 is a cross-sectional view of a main part of a composite substrate with a GaAs on Si structure made by a conventional method. FIG. 3 is a sectional view of a main part in a process of an embodiment of the present invention. FIG. 4 shows GaAson formed by the method of the present invention.
A graph showing a cross-sectional shape of a composite substrate having a Si structure. FIG. 5 is a sectional view of a main part for explaining the process of another embodiment of the present invention. In fig. 1 is a silicon substrate. 2 is a SiO□ layer. 3, 6 and 7 are GaAs layers. 4 is a polycrystalline GaAs layer. 5 is the raised part. 8 is a window. 9 is a natural oxide film. Love＼＼7 Boat

Claims (3)

[Claims] (1) A silicon single crystal substrate having one surface on which an insulating layer with openings provided at predetermined positions is formed is placed in a vapor phase growth apparatus and heated to a predetermined temperature to form a desired compound semiconductor layer. The compound semiconductor layer is selectively epitaxially grown on the surface of the silicon single crystal substrate exposed in the opening by introducing source gases containing individual constituent elements into the vapor phase growth apparatus at different times. Characteristic compound semiconductor layer formation method. (2) A step of placing a silicon single crystal substrate having one surface on which an insulating layer with openings provided at predetermined positions is formed in a vapor phase growth apparatus and heating it to a predetermined temperature, and forming a desired compound semiconductor layer. A step of introducing raw material gases containing individual constituent elements into the vapor phase growth apparatus at different times; and a raw material gas containing individual constituent elements of the compound semiconductor layer into the vapor phase growth apparatus, 1. A method for forming a compound semiconductor layer, comprising sequentially performing steps of simultaneously introducing source gases, at least one of which is a non-organic compound. (3) The method includes the steps of selectively removing the insulating layer immediately before introducing the inorganic compound raw material gas, and exposing the silicon single crystal substrate from which the insulating layer has been removed to an oxidizing atmosphere. 3. The method for forming a compound semiconductor layer according to claim 2.