JPH07201748A - Method for manufacturing semiconductor substrate - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] To provide a method for manufacturing a GaAs / Si semiconductor substrate in which there is no fear of yield reduction due to Si contamination in a device process. [Structure] First, a GaAs film 2 having a first film thickness that is sufficiently smaller than a desired final film thickness is formed on substantially the entire surface of a Si underlayer, and an insulating layer 3 is deposited on the GaAs film 2. Is removed to partially expose the GaAs film 2 and then G is formed on the partially exposed region 2b of GaAs.
aAs is selectively grown to the final film thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor substrate. Specifically, gallium arsenide (GaA)
s) is epitaxially grown on a silicon (Si) base.

[0002]

2. Description of the Related Art Compound semiconductor devices such as GaAs are
Compared with Si devices, it has various advantages such as faster calculation speed, lower power consumption, light emitting and receiving functions, and high radiation resistance, and is used as a high performance and high performance device. Is being done.

However, the compound semiconductor single crystal obtained at present has a problem that the area is smaller than that of the Si single crystal and is generally expensive, which is an obstacle to increasing the size of the device. Was there.

Therefore, a substrate other than GaAs, for example, S
By growing an epitaxial layer of GaAs on the i substrate,
Attempts have been made to obtain an equivalent to a large and inexpensive GaAs substrate.

However, when the GaAs film is directly deposited on the Si substrate by the MOCVD method or the like, the difference between the coefficient of thermal expansion of Si and the coefficient of thermal expansion of GaAs is large and GaA
There is a problem that strain stress occurs in the s film, dislocation occurs in the GaAs film, and warpage occurs in the Si substrate.

Further, as disclosed in, for example, Japanese Unexamined Patent Publication No. 1-266716, an insulating film such as SiO ₂ is partially formed on a Si substrate, and this insulating film is used as a mask for GaA.
Techniques for selectively growing s are known. By selectively growing in this way, the area of the GaAs layer in contact with the Si substrate is reduced, the strain stress remaining in the GaAs layer is reduced, and the dislocations in the GaAs layer are reduced.

[0007]

As described above, SiO existing in a GaAs / Si semiconductor substrate obtained by growing a GaAs layer on a Si substrate using SiO ₂ as a mask.
₂ is used as a mask in a device process such as FET, and then SiO ₂ as a mask is etched.

Therefore, in this etching process, Si
There is a high possibility that the surface of the Si substrate below the O ₂ layer will be exposed. G
Since Si becomes a contamination source in the aAs device process, it was necessary to immediately perform coating with SiO ₂ in the device process when the Si surface was exposed. Moreover, even if the coating with SiO ₂ is immediately performed, the yield is reduced due to the Si contamination of the GaAs device.

Therefore, it is an object of the present invention to provide a novel semiconductor substrate which solves the problems of the prior art as described above. A further object of the present invention is to provide a method for manufacturing a semiconductor substrate that does not have a risk of yield reduction due to Si contamination in a device process.

[0010]

The present invention for solving the above-mentioned problems is a method for manufacturing a semiconductor substrate in which GaAs is laminated on a Si underlayer to a desired final film thickness. A GaAs film having a first film thickness sufficiently smaller than the final film thickness, an insulating layer is deposited on the first film, and the desired region of the insulating layer is removed to partially expose the GaAs film. After that, GaAs is selectively grown to a final film thickness on the partially exposed region of GaAs.

[0011]

In the present invention, the GaAs layer is grown on the Si underlayer using an insulating layer such as SiO ₂ as a mask.
In obtaining a Si semiconductor substrate, GaAs is thinly coated on a Si underlayer before forming an insulating layer.

Therefore, the Ga obtained by the above manufacturing method is
When manufacturing a semiconductor device using an As / Si semiconductor substrate, the Si underlayer is not exposed even if the insulating layer is removed by etching.
The yield reduction due to Si contamination of the device is prevented.

In the manufacturing method of the present invention, Si
Although the GaAs film is first formed on substantially the entire surface of the underlayer, this GaAs film has a small film thickness, and by selectively growing GaAs using an insulating layer mask, the final film thickness can be reduced. The strain stress remaining in the grown GaAs layer is reduced, and dislocations in the GaAs layer are reduced. As in the conventional method, a good quality substrate with few crystal defects can be manufactured.

Hereinafter, the present invention will be described in more detail based on embodiments.

FIG. 1 is a schematic view showing each step of the method for manufacturing a semiconductor substrate of the present invention.

In the present invention, first, as shown in FIG. 1A, the first G layer is formed on the Si substrate 1 over substantially the entire surface.
The aAs layer 2 is formed. The thickness of the first GaAs layer 2 needs to be sufficient to cover the surface of the Si substrate 1 and sufficiently thin. Specifically, for example, 0.1 to
It is desired that the film thickness is about 1.0 μm, more preferably about 0.3 to 0.5 μm. That is, the film thickness is 0.
When the thickness is less than 1 μm, it is difficult to uniformly coat the surface of the Si substrate 1 over substantially the entire surface, and the first Ga
There is a possibility that the effect of preventing Si contamination in the GaAs device process due to the provision of the As layer 2 may not be obtained.
On the other hand, if the film thickness exceeds 1.0 μm, there is a high possibility that dislocations and cracks will occur in the second GaAs layer 4 grown above due to strain stress generated by the difference in thermal expansion coefficient between Si and GaAs. This is because.

The first GaAs layer can be formed by a known method such as metal organic chemical vapor deposition (MOCVD method) or molecular beam epitaxial method (MBE method).

The growth conditions are not particularly limited, but MO
The following is a specific example of growing the first GaAs layer 2 by the CVD method. For example, hydrogen gas is used as the carrier gas, and As source is used as the reaction gas, such as arsine (AsH ₃ ),
As a Ga source, for example, trimethylgallium (Ga
(CH ₃ ) ₃ ) respectively. First, after placing the silicon substrate 1 on the susceptor in the reaction furnace of the MOCVD apparatus, the temperature in the reaction furnace is raised to a temperature of 950 ° C. or higher in a gas atmosphere of H ₂ and AsH ₃ , and at this temperature for a predetermined time, For example, the temperature is maintained for about 5 to 10 minutes, and the high temperature heat treatment removes the natural oxide film on the surface of the Si substrate 1 to clean the substrate surface. Next, the temperature in the reaction furnace is set to 400 to 450 ° C.
By lowering the temperature to about a certain level and introducing Ga (CH ₃ ) ₃ , polycrystalline GaAs is grown on the surface of the cleaned Si substrate 1, and a single crystal of GaAs is grown at an actual growth temperature of 650 to 700 ° C. By growing (two-step growth), the first GaAs layer 2 having a predetermined thickness as described above is formed.

Then, as shown in FIG. 1B, the first Ga
The insulating layer 3 is formed on the As layer 2. The insulating layer 3 can be made of, for example, SiO ₂ , SiN, etc.
It can be formed by a known method such as a chemical vapor deposition method such as D method, low temperature sputtering method and the like. A suitable film thickness of the insulating layer 3 is about 300 to 1000Å.

As shown in FIG. 1C, a predetermined region of the insulating layer 3 formed as described above is removed by a photolithography technique, and the insulating layer 3 is patterned.

Thereafter, the first G
On the region 2b exposed from the insulating layer 3 of the aAs layer 2,
The second GaAs layer 4 is formed by selectively growing GaAs. The thickness of the second GaAs layer 4 is, for example, 1 to 1 which is required for manufacturing a GaAs device.
It is about 3 μm.

For example, similarly to the above, as a concrete example of growing the second GaAs layer 2 by the MOCVD method, first, the silicon substrate 1 after the insulating layer 3 is patterned as described above is reacted by the MOCVD apparatus. After mounting on the susceptor in the furnace, the temperature inside the reaction furnace is raised to a temperature of 650 to 700 ° C. in a gas atmosphere of H ₂ and AsH ₃ , and when the temperature reaches a desired temperature, Ga (CH ₃ ) ₃ is introduced. Then, GaAs is grown on the exposed region 2b to form the second GaAs layer 2 having a predetermined film thickness as described above.

The semiconductor substrate manufacturing method of the present invention is
The present invention is not limited to the embodiment described above, and various changes can be made.

[0024]

EXAMPLES The present invention will be described in more detail below with reference to examples.

The Si substrate 1 having a diameter of 3 inches is placed on the susceptor of the MOCVD apparatus, the temperature inside the reaction furnace is raised to 900 ° C. in a gas atmosphere of H ₂ and AsH ₃ , and this temperature is maintained for about 5 minutes. After the holding, the temperature in the reaction furnace is lowered to about 400 ° C., Ga (CH ₃ ) ₃ is introduced, and polycrystalline GaAs is grown on the surface of the cleaned Si substrate 1, and the actual growth is performed. A GaAs single crystal was grown at a temperature of 650 ° C. to form a first GaAs layer 2 having a film thickness of 1 μm.

Next, this substrate is taken out from the MOCVD apparatus, and is formed on the GaAs layer 2 by plasma CVD.
Form a SiO ₂ insulating layer 3 with a film thickness of 500Å at 00 ° C,
A predetermined region of the insulating layer 3 was removed by photolithography, and the insulating layer 3 was patterned. After that, the substrate is put into the MOCVD apparatus again, the temperature inside the reaction furnace is raised to a temperature of 700 ° C. in a gas atmosphere of H ₂ and AsH ₃ , and when this temperature is reached, Ga (CH ₃ ) ₃ is introduced. , GaAs is grown on the exposed region 2b, and the second G having a film thickness of 2 μm is formed.
The aAs layer 2 was formed to obtain the GaAs / Si substrate of the present invention.

For comparison, the first G on the Si substrate 1
A GaAs / Si substrate of a comparative example was obtained in the same manner as above except that the aAs layer 2 was not formed.

The obtained GaAs of the present invention and comparative GaAs
When the dislocation generation density (etch pit density) in the / Si substrate was examined, the density was in the order of 10 ⁵ / cm ² , and the conventional technique for selectively growing GaAs using the insulating film as a mask (comparative example It was revealed that the generation of dislocations was suppressed also in the method of the present invention, as in (1).

Further, an FET device process was performed using these GaAs / Si substrates. In this process, the SiO ₂ insulating layer 3 is used as a mask,
Etched with HF. When the yield reduction due to Si contamination of the obtained FET devices was compared, the defective element occurrence rate due to Si contamination was 50% when the substrate of the comparative example was used, while the substrate of the example of the present invention was used. If the content is 10%, it is substantially Si by the method of the present invention.
It became clear that the generation of defective products due to contamination was completely suppressed.

[0030]

As described above, according to the present invention, Ga
GaA that does not expose the Si surface during the As device process
It is possible to obtain an s / Si semiconductor substrate, prevent Si contamination, reduce the number of defective elements in the device process, and improve the yield. Further, there is no need to provide a step for preventing contamination when the Si surface is exposed, and the cost of the de-paying process can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing each step in a semiconductor manufacturing method of the present invention.

[Explanation of symbols]

1 ... Si substrate, 2 ... first GaAs layer, 3 ... SiO2 layer,
4 ... Second GaAs layer.

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[Procedure amendment]

[Submission date] February 1, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Moriya 5-10-1 Fuchinobe, Sagamihara-shi, Kanagawa Electronics Research Laboratory, Nippon Steel Corp.

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor substrate comprising GaAs laminated on a Si underlayer, wherein a GaAs film having a first film thickness sufficiently smaller than a desired final film thickness is formed on substantially the entire surface of the Si underlayer. Then, an insulating layer is formed on the upper surface of the insulating layer, and a desired region of the insulating layer is removed to remove the G
The aAs film is partially exposed, and then this partially G
A method of manufacturing a semiconductor substrate, wherein GaAs is selectively grown to a final film thickness on an exposed region of aAs.