JPH07201747A - Formation of compound semiconductor layer - Google Patents

Abstract

PURPOSE:To provide a method of forming such a compound semiconductor layer as a silicon layer is not exposed on the outer edge part of the surface of a substrate using an epitaxial growth device of a face-down structure that the compound semiconductor layer supports the outer edge part of the substrate surface. CONSTITUTION:A method of forming a compound semiconductor layer has a stage of growing a first compound semiconductor layer 12 by an epitaxial growth device of a structure that a compound semiconductor layer is placed on a substrate 2 with a face to grow the compound semiconductor turned upward, and a stage of growing a second compound semiconductor layer 13 in such a way as to place the layer 12 with the face of the layer 12 turned downward on a susceptor of the epitaxial growth device of the structure, that the compound semiconductor layer is placed on the substrate with a face to grow the compound semiconductor facing turned downward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a compound semiconductor layer on a substrate, and more particularly, to an apparatus for placing a silicon substrate surface downward and growing a compound semiconductor on the silicon substrate surface facing downward. The present invention relates to a method for forming a compound semiconductor layer used.

[0002]

2. Description of the Related Art Compound semiconductors are in great demand because of the excellent performance of elements formed thereon, their ability to operate at high speeds and high frequencies, and their use in light emitting devices. . However, the substrate of compound semiconductor alone is 6
Compared with silicon substrates, which have achieved large diameters of ~ 8 inches and even 12 inches, their size is still 3
It is as small as about 4 inches and lacks mass productivity of devices formed thereon.

Therefore, what is attracting attention is a compound semiconductor substrate in which a compound semiconductor layer is grown on a silicon substrate by an epitaxial growth method. By epitaxially growing the compound semiconductor on the silicon substrate in this manner, the diameter can be increased.

In this apparatus for forming a compound semiconductor layer on a silicon substrate, when divided by the method of mounting the silicon substrate, the silicon substrate surface is mounted with the surface on which the compound semiconductor layer is formed facing up, and the compound semiconductor layer is mounted. There are an apparatus for epitaxial growth and an apparatus for placing the surface of the silicon substrate downward and performing epitaxial growth. In the former device,
The back surface of a silicon substrate is placed on a vacuum chuck or a susceptor that electrostatically attracts, and a CVD apparatus is a common one. On the other hand, the apparatus for placing the surface of the silicon substrate downward is one in which the outer edge portion of the silicon substrate is held by a susceptor such that most of the surface of the silicon substrate can be placed in an open state and is epitaxially grown. Among the CVD apparatuses, such a downwardly mounted type is seen in MOCVD used for epitaxially growing a compound semiconductor, and also molecular beam epitaxy (M
In the BE) device or the like, this downward mounting is performed.

FIGS. 1 and 2 are drawings for explaining a susceptor 1 and a silicon substrate 2 which support and hold a silicon substrate in an apparatus for such downward mounting. In such a downwardly mounted apparatus, the surface of the silicon substrate 2 on which the epitaxial growth is performed is faced downward, and only the outer edge portion of the silicon substrate is held in a state where most of the surface is released. Then, a compound semiconductor or the like is epitaxially grown on the open surface of the silicon substrate 2. Particularly in MBE, since the Nukudosen cell for molecularizing the raw material can be attached only upward, such downward mounting is performed because it is provided below the surface of the silicon substrate 2.

The formation of the compound semiconductor layer by such a downward mounting has no influence on the growth layer due to the fall of the dust adhering to the inner wall of the reaction system chamber, and in particular, the annealing in the reaction system chamber is performed at a high temperature. In this case, since dust is likely to be generated, the effect of placing the device downward is great. Further, it is used for improving the quality of the growth layer because the amount of undecomposed material in the source gas is small. further,
The MBE is excellent in the controllability of the thickness of the growth layer and can be controlled in the order of nanometers, so that it has been indispensable in the recent ultrafine processing technology.

[0007]

However, when the compound semiconductor layer is grown on the surface (downward) of the silicon substrate by placing the compound semiconductor layer downward, as shown in FIGS. Since it is hidden by the susceptor 2, the compound semiconductor does not grow in the outer edge portion L, and silicon is exposed in the outer edge portion L after the growth is completed.

Therefore, when a process for forming an element is performed on the compound semiconductor layer grown on this silicon substrate,
In particular, silicon exposed in the compound semiconductor may be mixed in as an impurity during a heat treatment, etching, cleaning, or the like. For example, in the case of a compound semiconductor made of a III-V group element, since silicon acts as a donor source,
There is a problem that the characteristics of the formed element are changed by the silicon mixed in the compound semiconductor layer.

Therefore, the present invention provides a method of forming a compound semiconductor layer using an epitaxial growth apparatus by downward mounting, in which a substrate material such as silicon is not exposed at the outer edge portion of the substrate. is there.

[0010]

According to the present invention for solving the above-mentioned problems, a step of epitaxially growing a first compound semiconductor layer by an epitaxial growth apparatus in which a surface of a substrate on which a compound semiconductor is to be grown is placed upward, First
The first compound semiconductor layer is placed face down on an epitaxial growth apparatus in which the surface on which the compound semiconductor is grown is placed face down, and the second compound semiconductor layer is epitaxially grown. And a step of forming a compound semiconductor layer.

[0011]

According to the present invention configured as described above, the first compound semiconductor layer is epitaxially grown on the surface of the substrate by the epitaxial growth apparatus mounted upward, so that the surface of the substrate is covered with the first compound semiconductor layer. After that, the second compound semiconductor layer is epitaxially grown on the first compound semiconductor layer by an epitaxial growth apparatus in which the surface on which the compound semiconductor is grown is placed downward.
As a result, even if the second compound semiconductor layer is placed face down and epitaxially grown, the surface of the substrate is entirely covered with the first compound semiconductor. The material is not mixed as an impurity in the compound semiconductor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the accompanying drawings.

In this embodiment, a silicon substrate 2 is used as a substrate for forming a compound semiconductor layer. First, as the silicon substrate 2, a substrate turned off by 3 ° in the [011] direction of the (100) plane is used. On this silicon substrate 2,
As shown in FIG. 3, the GaAs layer 12 is epitaxially grown as a first compound semiconductor layer. The GaAs layer 12 is epitaxially grown by using the MOCVD apparatus in which the surface of the silicon substrate 2 is placed upward and is grown by the usual two-step growth method and thermal annealing method. Specifically, polycrystalline GaAs is grown by introducing the raw materials trimethylgallium and arsine onto the silicon substrate 2 at 400 ° C., and a GaAs single crystal is grown at an actual growth temperature of 650 ° C. (two-step growth). ). Then, the supply of the raw materials is stopped, annealing is performed at an annealing temperature of 850 ° C. or higher for 5 minutes, and the temperature is lowered to 400 ° C. This operation is repeated 4 times (thermal cycle annealing).

The thickness of the GaAs layer 12 is preferably about 1 to 3 μm. When the thickness is less than the lower limit of 1 μm, the surface of the silicon substrate 2 can be completely covered by the growth method.
If a compound semiconductor layer having good crystallinity can be obtained, 1
Although it may be thinner than μm, about 1 μm is preferable in order to obtain the GaAs layer under this condition in the MOCVD apparatus which is mounted upward by the current technology. On the other hand, the upper limit is that the thickness of the epitaxially grown film that can be formed on silicon is up to about 4 μm in the current technology, and the crystallinity becomes worse in the epitaxially grown layer thicker than that. In consideration of stacking a compound semiconductor layer on top of this, 3
The limit is about μm. In this embodiment, 1 μm
And

Next, a GaAs layer 13 is epitaxially grown as a second compound semiconductor on the GaAs layer 12 by an MBE device. FIG. 4 is a schematic diagram for explaining the MBE device. In the epitaxial growth of GaAs by this apparatus, first, the silicon substrate 2 on which the GaAs 12 is formed is placed on the susceptor 2 provided at the tip of the manipulator 46 with the epitaxial growth surface (the GaAs layer 12) facing down. And the reaction system chamber 4
The inside of 0 was decompressed to a high vacuum of about 10 ¹⁰ torr, and the Nukudosen cell 43 provided directly under the substrate was heated to obtain Ga as a raw material.
As is emitted as a molecular beam of Ga and As into the chamber 40 through the orifice 42, and GaAs is emitted to the substrate.
Grow layer 13. The MBE is provided with an air lock 45, a liquid nitrogen shroud 47, an ion gauge 48, a film thickness meter 49, etc., as shown in FIG. In addition to the above, some MBEs are provided with an evaluation device such as reflected light energy electron diffraction and electron spectroscopy.

During the growth of the GaAs layer 13 by this MBE, the substrate is supported by the outer edge portion of the substrate as shown in FIGS. 1 and 2, and its portion L is the susceptor 1.
GaAs does not grow because it is hidden by
Silicon is not exposed by forming the aAs layer 12.

When epitaxial growth is carried out with the epitaxial growth surface of such a substrate facing downward, as shown in FIG. 5, the surface of the silicon substrate is GaAs.
Is covered by. Therefore, this GaAs layer 13
Even if the process for element formation is performed, since the silicon surface is not exposed, there is no possibility that silicon will be mixed into the GaAs layer 13.

The susceptor 1 to be mounted with the epitaxial growth surface facing downward in the above embodiment is ring-shaped as shown in FIGS. 1 and 2 for explaining the present invention. In addition to such a ring-shaped device, for example, there is a device with three-point support as shown in FIG. 6, but regardless of the shape of the susceptor, when the support part is placed downward, Since no compound semiconductor is formed, it is possible to completely cover silicon by using the present invention.

In the above embodiment, GaAs is used.
Was formed as the first and second compound semiconductor layers,
Besides aAs, it can be preferably used for a compound semiconductor layer such as AlGaAs, InP, GaP, etc., and the first compound semiconductor layer and the second compound semiconductor layer may have different compositions. In addition to the MBE as in the above embodiment, MOCV may be used as the downwardly mounted epitaxial growth apparatus.
The present invention can be applied to a D device or the like.

[0020]

As described above, according to the present invention,
When performing the epitaxial growth of the compound semiconductor layer with the epitaxial growth surface facing downward, first, the epitaxial layer is formed on the substrate surface by using the device by the upward mounting, and then the epitaxial growth by the downward mounting is performed. During the device formation process, a compound semiconductor layer of good film quality can be formed by utilizing the merit of forming an epitaxial growth device by placing the compound semiconductor layer downward, and the substrate material is not exposed during device formation. In addition, the substrate material is prevented from being mixed in as an impurity, and the deterioration of the characteristics of the element can be prevented.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a susceptor for explaining a downward mounting of a substrate surface.

FIG. 2 is an enlarged sectional view of a portion A in FIG.

FIG. 3 is a cross-sectional view of a substrate after epitaxial growth by upward mounting according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of an MBE device.

FIG. 5 is a sectional view of a substrate after epitaxial growth by downward mounting according to an embodiment of the present invention.

FIG. 6 is a partially cutaway perspective view of the susceptor for explaining the downward mounting of the substrate surface.

[Explanation of symbols]

1 ... Susceptor, 2 ... Silicon substrate, 12 ... GaAs (first compound semiconductor layer), 13 ... GaAs (second compound semiconductor layer).

 ─────────────────────────────────────────────────── ─── 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 step of epitaxially growing a first compound semiconductor layer by an epitaxial growth apparatus in which a surface of a substrate on which a compound semiconductor is grown is placed upward, and a step of growing the first compound semiconductor layer on the substrate. A step of mounting the first compound semiconductor layer downward and epitaxially growing the second compound semiconductor layer on an epitaxial growth apparatus in which a surface on which a semiconductor is grown is mounted downward. Forming method.