JPH08236453A - Method for growing crystal of compound semiconductor - Google Patents

Abstract

PURPOSE: To form a compound semiconductor layer having a small dislocation density on the surface of a silicon substrate. CONSTITUTION: After a p-type impurity-doped layer 6 is formed on the surface of a silicon substrate 5, a compound semiconductor layer 7 is formed on the layer 6 by growing the crystal of a compound semiconductor. Therefore, the compound semiconductor layer 7 can be grown two-dimensionally on the substrate 5, because the charge mismatching which occurs at the boundary between the substrate 5 and layer 7 is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor crystal growth method for forming a compound semiconductor crystal on a silicon substrate.

[0002]

2. Description of the Related Art Gallium arsenide (GaAs) on a silicon substrate
Semiconductor wafers made by epitaxial growth of compound semiconductors such as silicon are compound semiconductors such as GaAs that can be applied to silicon to which VLSI technology can be applied and high speed and low power consumption electronic devices or optical devices (LEDs or semiconductor lasers). And are attracting attention as a technology for integrating them.

However, gallium arsenide has a lattice constant which is 4% larger than that of silicon, and a thermal expansion coefficient of about 3%.
It is 2.5 times the value. This difference in lattice constant causes misfit dislocations due to lattice mismatch, and the difference in thermal expansion coefficient is
In the cooling step after the growth of the compound semiconductor, there is a problem that the wafer warps and dislocations are generated due to the warp relaxation, and it has been impossible to form a good quality gallium arsenide layer on the silicon substrate. In order to solve these problems, gallium arsenide crystal is grown on a silicon substrate through an amorphous low-temperature gallium arsenide buffer layer. 2
A step growth method or a method of introducing a superlattice structure into the intermediate layer has been proposed. However, even when these methods are used, the dislocation density of the gallium arsenide layer is, for example, a value that is two to three orders of magnitude higher than the dislocation density of about 10 ³ cm ^-2 that is allowable in semiconductor lasers. , Further improvement was needed.

[0004]

As described above, when a compound semiconductor is crystal-grown on a silicon substrate, there is a problem that a high-quality compound semiconductor layer having a low dislocation density cannot be formed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a compound semiconductor crystal growth method capable of growing a compound semiconductor layer having a low dislocation density on a silicon substrate. To provide.

[0006]

In order to achieve the above object, the method for growing a compound semiconductor crystal according to claim 1 is a method for growing a compound semiconductor crystal, which comprises growing a compound semiconductor on the surface of a silicon substrate. The method further comprises the steps of forming a p-type impurity doping layer doped with p-type impurities on the surface of the silicon substrate, and crystallizing the compound semiconductor on the p-type impurity doping layer. is there.

A method of growing a compound semiconductor crystal according to a second aspect is the method of growing a compound semiconductor crystal according to the first aspect.
The p-type impurity doping layer is formed by a method of diffusing the p-type impurity into the silicon substrate or a method of ion-implanting the p-type impurity into the silicon substrate.

A crystal growth method for a compound semiconductor according to a third aspect is the crystal growth method for a compound semiconductor according to the first aspect,
It is characterized in that the p-type impurity doping layer is formed by crystal growth of silicon into which the p-type impurity is introduced.

The compound semiconductor crystal growth method according to claim 4 is the compound semiconductor crystal growth method according to any one of claims 1 to 3, wherein the p-type impurity doping layer is locally formed on the surface of the silicon substrate. It is characterized by comprising a step of forming and a step of selectively growing a crystal of the compound semiconductor on the p-type impurity doping layer.

[0010]

[Function] When a compound semiconductor such as gallium arsenide is crystal-grown on a silicon substrate, defects such as misfit dislocations which occur at the interface between silicon and gallium arsenide are formed in the island shape of gallium arsenide at the initial stage of gallium arsenide crystal growth. It is known to grow and occur when islands combine. Therefore, it is possible to significantly reduce defects such as misfit dislocations by suppressing island-shaped (three-dimensional) growth and growing it in a plane (two-dimensional) at the initial stage of crystal growth. Become.

Here, it is considered that the origin of the three-dimensional growth is due to the mismatch of charges generated at the interface between the nonpolar semiconductor silicon substrate and the polar semiconductor gallium arsenide layer. In particular, formed on the surface of the silicon substrate,
There is a large charge mismatch between As (group V atom) in the first layer and silicon, and this is alleviated, so that gallium arsenide crystal grows in an energy-stable island shape. Therefore, by neutralizing this charge, island growth can be suppressed and planar growth can be promoted.

Crystal growth of gallium arsenide on the surface of the silicon substrate will be described with reference to the sectional view of FIG. When crystal-growing gallium arsenide on the surface of the silicon substrate 1, first, arsenic atoms 2 grow as the first layer and then gallium atoms 3 grow on the surface of the silicon substrate 1. In the crystal growth method, the surface of the silicon substrate 1 is doped with the p-type impurity 4 so that the charge generated between the first layer of arsenic atoms 2 formed on the surface of the silicon substrate 1 and the silicon substrate 1 is increased. It is possible to eliminate the incompatibility due to the charges of the doped atoms, and it is possible to grow a high-quality compound semiconductor such as gallium arsenide with a low dislocation.

[0013]

EXAMPLE An example of the method for growing a compound semiconductor crystal according to the present invention will be described with reference to the sectional view of FIG. First,
Each structure will be described. 5 is a silicon substrate, 6 is a p-type impurity doping layer formed on the surface of the silicon substrate 5, and 7 is a compound formed on the p-type impurity doping layer 6 and made of gallium arsenide or the like. It is a semiconductor layer.

Next, the manufacturing method will be described. First,
A p-type impurity is doped from the surface of the silicon substrate 5 by diffusion to form a p-type impurity doping layer 6. Boron (B 2) is used as the p-type impurity, and heat treatment is performed in a boron atmosphere to diffuse the boron to the surface of the silicon substrate 5. As the diffusion conditions, for example, introduced into the inside of the diffusion furnace by a carrier gas using BCl ₃ , for example, 1000
C., heating for 1 hour. Thereby, the silicon substrate 5
The concentration of boron on the surface of is about 5 × 10 ²⁰ cm ^-3 .

Next, metal organic chemical vapor deposition (MOVPE)
Or a molecular beam epitaxy (MBE) method, etc., a compound semiconductor such as gallium arsenide is crystal-grown on the p-type impurity doping layer 6. In the case of crystal growth, a two-step growth method (a method of growing gallium arsenide crystal on a silicon substrate 5 via an amorphous low-temperature gallium arsenide buffer layer) or a method of providing an intermediate layer into which a superlattice structure is introduced You may form using. However, the boron diffusion method is not limited to the embodiment. Further, the p-type impurity is not limited to boron, and it does not matter as long as it becomes a p-type impurity in silicon, such as gallium (Ga) and aluminum (Al).

In the embodiment shown in FIG. 1, the p-type impurity is introduced into the silicon substrate by the diffusion method, but it may be introduced by the ion implantation method. In this case, after introducing boron into the silicon substrate by boron ion implantation,
A heat treatment is performed to activate p-type and crystallize. Even when the ion implantation method is used, the p-type impurity is not limited to boron as in the diffusion method.

A different embodiment of the method of growing a compound semiconductor crystal according to the present invention will be described with reference to the sectional view of FIG.
In the embodiment shown in FIG. 2, p-type impurity-introduced silicon is crystal-grown on the surface of a silicon substrate 8 to form a p-type epitaxial layer 9, and gallium arsenide or the like is formed on the p-type epitaxial layer 9. The obtained compound semiconductor layer 10 is crystal-grown. As a method for crystallizing the p-type epitaxial layer 9, a silicon MBE method may be used in addition to the general vapor phase growth method. Boron, for example, is used as the p-type impurity.

A further different embodiment of the compound semiconductor crystal growth method of the present invention will be described with reference to the sectional view of FIG. In the embodiment shown in FIG. 3, p is formed on the surface of a silicon substrate.
A p-type impurity doping layer is locally formed and a compound semiconductor is selectively grown on the p-type impurity doping layer.

When a compound semiconductor such as gallium arsenide is crystal-grown on a silicon substrate, strain or dislocation occurs in the compound semiconductor due to a difference in lattice constant and a difference in thermal expansion coefficient. The method of reducing the region where the compound semiconductor is formed is an effective method. As a method of reducing the region where the compound semiconductor is formed, there is a method of selectively growing the compound semiconductor on a silicon substrate.
The example shown in (1) uses this method.

In order to form the substrate shown in FIG. 3, first, a p-type impurity doping layer 12 is formed by selectively performing p-type impurity doping on the surface of the silicon substrate 11, and then the surface of the silicon substrate 11 is formed. After an insulating film (for example, a silicon nitride film 13) is formed on the p-type impurity-doped layer 12, the silicon nitride film 13 at a portion on the p-type impurity doping layer 12 where the compound semiconductor is selectively grown is removed to form an opening 14. Next, when the compound semiconductor is crystal-grown, the compound semiconductor does not grow on the silicon nitride film 13 and the compound semiconductor layer 15 is formed on the silicon exposed in the opening 14. The MOVPE method is used for crystal growth of compound semiconductors.

[0021]

As described above, according to the compound semiconductor crystal growth method of the first to fourth aspects, charge mismatch generated at the interface between the silicon substrate and the compound semiconductor crystal growth layer is suppressed, A compound semiconductor crystal can be two-dimensionally grown on a silicon substrate, and a low-dislocation, high-quality compound semiconductor such as gallium arsenide can be crystal-grown.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a compound semiconductor crystal growth method of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the compound semiconductor crystal growth method of the present invention.

FIG. 3 is a sectional view showing still another embodiment of the compound semiconductor crystal growth method of the present invention.

FIG. 4 is a cross-sectional view showing an example of a silicon substrate on the surface of which a compound semiconductor layer made of gallium arsenide is formed by using the compound semiconductor crystal growth method of the present invention.

[Explanation of symbols]

1, 5, 8, 11 Silicon substrate 6,12 p-type impurity doping layer 9 p-type epitaxial layer (p-type impurity doping layer)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01S 3/18 H01S 3/18

Claims (4)

[Claims] 1. A method for crystal growth of a compound semiconductor, which comprises growing a compound semiconductor on the surface of a silicon substrate by crystal growth.
A compound comprising: a step of forming a p-type impurity doping layer doped with a p-type impurity on a surface of the silicon substrate; and a step of crystal-growing the compound semiconductor on the p-type impurity doping layer. Semiconductor crystal growth method. 2. The p-type impurity doping layer is formed by a method of diffusing the p-type impurity into the silicon substrate or a method of ion-implanting the p-type impurity into the silicon substrate. The crystal growth method for a compound semiconductor according to claim 1. 3. The p-type impurity doping layer is formed into the p-type impurity doping layer.
2. The crystal growth method for a compound semiconductor according to claim 1, wherein the crystal growth is performed by crystal growth of silicon doped with a type impurity. 4. A step of locally forming the p-type impurity doping layer on the surface of the silicon substrate, and a step of selectively crystal-growing the compound semiconductor on the p-type impurity doping layer. 4. The method for growing a compound semiconductor crystal according to claim 1, wherein: