JPH08316152A - Crystal growing method for compound semiconductor - Google Patents

Abstract

PURPOSE: To achieve the high quality of a compound semiconductor layer formed on a silicon substrate. CONSTITUTION: A Ge layer 2, which is the intermediate layer, is locally formed on a silicon substrate 1. The light, whose wavelength is not absorbed by the silicon substrate 1 but is absorbed only by the Ge layer 2, is irradiated, and only the Ge layer 2 is heated. Thus, a GaAs layer 3, which is the compound semiconductor layer, is formed on the Ge layer 2. Therefore, thermally adverse effects are not applied on the parts other than the GaAs layer 3 on the silicon substrate 1, and the high-quality GaAs layer 3 with less crystal defects can be formed on the silicon substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor crystal growth method, and more particularly to a method for selectively forming a high quality compound semiconductor layer on a silicon substrate crystal.

[0002]

2. Description of the Related Art A device using a compound semiconductor such as GaAs as a substrate has usefulness such as having a light emitting function as compared with a device using silicon as a substrate. A semiconductor wafer obtained by epitaxially growing a compound semiconductor such as gallium arsenide on a semiconductor substrate such as silicon is useful as a material substrate for OEICs (photonic and electronic integrated circuits), solar cells, and light emitting diodes. Further, in the future, when configuring a three-dimensional LSI or the like on the premise of optical interconnection, the part corresponding to the electrode pad of the present element becomes a light emitting element or a light receiving element, so that a monolithic logic element and a light emitting element are used. Intensification is becoming more important.

At present, integrated circuits such as logic elements and memories are formed on a silicon substrate, and light emitting elements are formed on a compound semiconductor. However, in a silicon substrate and a compound semiconductor layer formed thereon, the lattice constant or Since the thermal expansion coefficients are different, there is a problem that many defects occur in the compound semiconductor layer formed by epitaxial growth. Since this defect results in deterioration of the characteristics of the element formed in the compound semiconductor layer, so far, in order to reduce this defect, ion implantation of Ge or the like is locally performed on the silicon substrate to form the intermediate layer, A method of improving the quality of the crystal of the compound semiconductor by forming the compound semiconductor on the intermediate layer has been introduced.

[0004]

However, in the method of forming the intermediate layer by ion implantation of Ge or the like, high temperature annealing is essential for crystal recovery of the silicon substrate, but other than the compound semiconductor layer. When the element is formed on the silicon substrate, the silicon substrate is kept at a high temperature, which causes the rediffusion of the doped impurities, and eventually the characteristics of the element formed on the silicon substrate deteriorates or malfunctions occur. There was a problem of being connected.

The present invention has been made in view of the above problems, and an object thereof is to provide a compound semiconductor layer formed on a silicon substrate without thermally adversely affecting an element formed on the silicon substrate. The object of the present invention is to provide a crystal growth method for a compound semiconductor, which can improve the quality of the compound semiconductor.

[0006]

In order to achieve the above object, a method for growing a compound semiconductor crystal according to the present invention comprises a step of locally forming an intermediate layer on a silicon substrate, and It is characterized in that the compound semiconductor is crystal-grown on the intermediate layer by irradiating with light having a wavelength absorbed by only the intermediate layer to heat only the intermediate layer.

[0007]

According to the present invention, when an intermediate layer is formed in a region where a compound semiconductor layer is formed on a silicon substrate and crystal growth of the compound semiconductor is performed, the intermediate layer absorbs light having a wavelength not absorbed by the silicon substrate. Is irradiated to heat only the portion of the intermediate layer so that the compound semiconductor is crystal-grown only on the intermediate layer. Since only the intermediate layer is selectively heated, a high-quality compound semiconductor layer is selectively formed at a desired position on the silicon substrate without thermally adversely affecting the element formed on the silicon substrate. It becomes possible.

[0008]

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,
A Ge layer, which will be an intermediate layer, is formed on the silicon substrate 1 by electron beam evaporation, and then a Ge layer is formed by photolithography.
As shown in (a), an island of Ge (Ge layer 2) is formed on the silicon substrate 1 by ion milling using He using a resistor having an opening formed at a position where the is removed as a mask.

Next, as shown in (b), the GaAs layer 3 which is a compound semiconductor layer is formed only on the Ge layer 2.
In this case, for example, trimethylgallium ((CH ₃ ) ₃ Ga) and arsine (AsH ₃ ) are used as source gases, and crystal growth is performed by MOCVD (metal organic chemical vapor deposition). When the crystal is grown, the silicon substrate 1 is irradiated with light having a wavelength that absorbs Ge but does not absorb Si. As a result, only the Ge layer 2, which is the intermediate layer, can be selectively heated to a temperature suitable for growing the compound semiconductor.
The layer 3 can be grown.

The wavelength of the light emitted in this case will be described in detail. At room temperature (300K), the longest wavelengths of light absorbed by Ge and Si are about 1.88 μm and about 1.11, respectively.
Although the thickness is μm, even if the Ge layer 2 is selectively heated, the temperature of the silicon substrate 1 adjacent to the Ge layer 2 rises due to heat conduction. As a result, the wavelength of the light absorbed by the silicon substrate 1 (Si) changes, so it is necessary to select the light to be irradiated in consideration of the temperature rise of the silicon substrate 1. For example, when the temperature of the silicon substrate 1 rises to 400 K due to heat conduction, the longest wavelength of the light absorbed by the silicon substrate 1 is about 1.13 μm, so the wavelength of the light to be irradiated is about
It must be 1.2 μm or more and 1.8 μm or less. By heating with the light (infrared ray) in this wavelength range, the MOCVD method with the substrate temperature (the temperature of the Ge layer 2) set to an appropriate value in the range of 600 to 750 ° C. is used, and only on the Ge layer 2 as the intermediate layer. The GaAs layer 3 which is a compound semiconductor layer can be selectively formed.

Although Ge is mentioned as the material for the intermediate layer, it is also possible to use a thin film of GaSb or the like. Further, in the embodiment, the description has been made on the assumption that the Ge layer as the intermediate layer is formed by electron beam vapor deposition, but the invention is not limited to the embodiment, and a sputtering method or the like can be used. Furthermore, it was explained that the Ge islands were formed using the ion milling method.
It is also possible to use the E (reactive ion etching) method or the like. Further, it is also effective to use a mask of metal or the like to limit the vapor deposition portion to form Ge islands without using the photolithography method. Although the MOCVD method is used as the crystal growth method of the compound semiconductor layer, it is also possible to grow it using the MBE (molecular beam epitaxial growth) method or the like while heating the Ge intermediate layer by infrared irradiation.

[0012]

As described above, according to the crystal growth of the compound semiconductor of the present invention, the crystal growth is performed on the silicon substrate without thermally adversely affecting the portion other than the compound semiconductor layer on the silicon substrate. It is possible to form a high quality compound semiconductor layer with few defects.

[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.

[Explanation of symbols]

 1 Silicon substrate 2 Ge layer (intermediate layer) 3 GaAs layer (compound semiconductor layer)

Claims (1)

[Claims] 1. A step of locally forming an intermediate layer on a silicon substrate, and a step of irradiating light having a wavelength not absorbed by the silicon substrate but absorbed by only the intermediate layer to heat only the intermediate layer. A method for growing a crystal of a compound semiconductor, which comprises performing crystal growth of a compound semiconductor on a layer.