JPH0573335B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) This invention provides a compound semiconductor layer formed on a heat-treated and cleaned silicon (Si) substrate with a lattice constant different from that of the substrate, particularly a - group compound. The present invention relates to a method of vapor phase epitaxial growth of a semiconductor layer.

(Conventional technology) Conventionally, -
Techniques for producing large, high-quality wafers by growing a group compound semiconductor layer are being developed and put into practical use. As a method for growing these compound semiconductors on a Si substrate by vapor phase epitaxial growth, for example, see the following literature: "Surfase Science", 174 (1986) 19-
30, North-Holland, Amsterdam. This method is
After heat treatment for cleaning the substrate, first, a buffer layer (referred to as a low-temperature buffer layer) is formed at a sufficiently low temperature.
This is a method in which a compound semiconductor layer is grown, the temperature is raised to a normal growth temperature for compound semiconductors, and then a desired compound semiconductor layer is grown at that growth temperature.

First, the metal organic chemical vapor deposition method (MOCVD method) using a two-step growth method disclosed in this document
A brief explanation will be given of the case where a GaAs layer is grown on a Si substrate.

FIG. 2 is an explanatory diagram of growth temperature for explaining this conventional two-step growth method, in which time is plotted on the horizontal axis and temperature (° C.) is plotted on the vertical axis. Further, FIG. 3 is a cross-sectional view of a wafer used to explain the conventional method.

Hydrogen (H ₂ ) is used as a carrier gas for this growth.
Arsine (AsH ₃ ) and trimethylgallium (Ga(CH ₃ ) ₃ ) (abbreviated as TMG) are used as gases and reaction gases.

First, after installing the Si substrate 10 in a reactor, the Si substrate 10 is heated to a temperature of about 900 to 980°C in a mixed gas atmosphere of arsine (AsH ₃ ) and hydrogen (H ₂ ) gas.
Clean the substrate by heat treating with TC for 5 minutes (as shown in Figure 2 I). After that, the temperature is lowered to a temperature TB that is sufficiently lower than the heat treatment temperature, for example, about 400°C, and TMG is introduced into the reactor for 2 minutes to grow the GaAs layer 12 in the first stage (see Figure 2). ) This GaAs layer 12 is a uniform sheet-like layer with a thickness of about 100 Å, and is a low-temperature buffer layer covering the surface of the Si substrate 10. Subsequently, the introduction of TMG is stopped to interrupt the growth, and then the temperature is increased again to 600-650
The temperature is increased to TG in the range of 0.degree. C. to grow a second stage GaAs layer 14 (as shown in FIG. 2). The growth of the GaAs layer 14 in this second stage (as shown in FIG. 2) is performed by introducing TMG into the reactor for, for example, about 15 minutes to obtain a film thickness of about 3 μm.

In this way, in the two-step growth method, the Si substrate is grown at two different temperatures: temperature TB for growing the GaAs low-temperature buffer layer 12 and temperature TG for growing the desired GaAs layer for manufacturing electronic devices. above
This is a technology for growing GaAs layers. According to this method, a polar crystal can be grown on a non-polar crystal, which results in a lattice mismatch between the substrate and the growth layer (4% lattice mismatch between GaAs and Si). ), it is possible to obtain a single-domain GaAs growth layer using vapor phase epitaxial technology. Therefore, the two-step growth method described above is an effective method for growing a crystal having lattice mismatch of a compound semiconductor such as GaAs on a Si substrate.

(Problem to be solved by the invention) However, in the case of this two-step growth method, a step of growing a low-temperature GaAs buffer layer is required, so the number of steps is smaller than that of growing GaAs on a normal GaAs substrate. There was a problem that the amount of time required for growth was longer.

For this reason, it may be possible to omit this step of growing the low-temperature buffer layer and grow a GaAs layer on the Si substrate immediately after cleaning. However, from 600
At a growth temperature of 650°C and a normal growth rate of about 1800 Å/min, due to the migration effect of GaAs reactive species on the Si substrate surface,
The GaAs initial growth layer becomes a three-dimensional island-like growth,
Due to this, the subsequently grown layer of GaAs becomes polycrystalline, resulting in a problem that a single-crystal GaAs layer cannot be obtained.

The present invention has been made in view of the above-mentioned conventional problems.Therefore, an object of the present invention is to shorten the growth process by omitting the growth process of a low-temperature buffer layer, and also to reduce the growth process on the substrate surface. An object of the present invention is to provide a method for growing a compound semiconductor layer, which can suppress polycrystalization caused by migration, easily grow a single crystal compound semiconductor layer, and improve throughput.

(Means for Solving the Problems) In order to achieve this object, the present invention provides a method for vapor phase epitaxial growth of a compound semiconductor layer made of a - group compound semiconductor selected in advance on a silicon (Si) substrate. a step of heat treating the substrate at a temperature at which the surface of the substrate is cleaned; and at a normal growth temperature for the compound semiconductor;
The method is characterized by comprising the step of growing the compound semiconductor on the substrate at a growth rate that does not allow sufficient migration of the constituent atoms of the compound semiconductor.

In a preferred embodiment of the present invention, even after the initial growth stage, growth can be performed at the growth rate at this initial stage.

In another preferred embodiment of the invention,
The growth rate after the initial growth stage can be a different growth rate that is slower than the growth rate during the initial growth stage.

(Function) According to the configuration of the present invention, after cleaning the surface of the Si substrate, at least in the initial stage of growth, the growth rate is faster than the growth rate of a normal compound semiconductor. Since the compound semiconductor layer is grown directly on the substrate surface, the reactive species (constituent atoms) that are the constituent components of the compound semiconductor to be grown cannot migrate sufficiently on the substrate surface.
Before three-dimensional island-like growth occurs, crystal grains of materials with uniform crystal orientation, such as GaAs,
The compound semiconductor layer grows as a single crystal by covering the surface of the Si substrate.

Therefore, the process can be shortened and a single crystal layer of a compound semiconductor layer can be easily grown.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

It should be noted that these figures are merely shown schematically to the extent that the present invention can be understood, and hatchings etc. representing cross sections are omitted. Also,
In these figures, the same components and the like as those shown in FIGS. 2 and 3 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

Furthermore, since the embodiment described below is merely a preferred example, it should be understood that the numerical conditions and other conditions are not limited to the examples given in this embodiment.

Further, in the embodiments described below, a case will be described in which a wafer is obtained by growing a GaAs layer as an example of a - group compound semiconductor on a Si substrate by a metal organic chemical vapor deposition method (MOCVD method).

First Embodiment FIG. 1A is an explanatory diagram of the growth temperature in the first embodiment of the method for growing a compound semiconductor layer of the present invention, with time on the horizontal axis and temperature (°C) on the vertical axis. . FIG. 1B is a partial cross-sectional view of a wafer used to explain the growth method of this embodiment.

First, a Si substrate 10 is placed in a reactor, and _as in _the conventional case, it is heated to
The surface is cleaned by heat treatment at a suitable temperature TC within the range of about 980°C for about 5 minutes (as shown in Figure 1).

Next, in this invention, the temperature in the reactor is set to the normal growth temperature of compound semiconductors, which in this case is
The temperature is lowered to an appropriate temperature TG within the range of about 600 to 650°C, which is the normal growth temperature for GaAs.

In this example, this temperature was 600°C. Then, a reactive gas, that is, a TMG reactor, is used so that the growth rate of GaAs becomes a high growth rate, for example, about 3000 Å/min or faster than the conventional growth rate (about 1800 Å/min). After adjusting the amount of TMG supplied into the reactor, the TMG is introduced into the reactor and growth begins (as shown by A in FIG. 1). Specifically, the flow rate of hydrogen gas, which is the carrier gas, is 5000SCCM, and the flow rates of arsine and TMG (-4.5℃), which are the reaction gases, are respectively
200SCCM, 50SCCM. This adjusts the growth rate to 3000 Å/min. In this example, the growth of GaAs, which is a compound semiconductor, is continued at this growth rate not only at the initial growth stage from the start of growth, but also until the thickness of the GaAs layer 16 reaches the desired thickness (as shown in FIG. 1A). ), a wafer as shown in FIG. 1B is obtained. In Figure 1B, this
GaAs layer 16 is a fast growing layer.

As described above, when the GaAs layer 16 is grown at high speed, the reactive species (constituent atoms) that are the constituent components of the GaAs to be grown cannot migrate sufficiently on the substrate surface, resulting in a three-dimensional island-like structure. Before growth occurs, the surface of the Si substrate is covered with GaAs crystal grains with uniform crystal orientation, so that the GaAs that continues to grow becomes a single crystal, and therefore the Si substrate 1
It is possible to obtain a single crystal layer of GaAs on 0.

Second Embodiment FIG. 4A is an explanatory diagram of the growth temperature in the second embodiment of the method for growing a compound semiconductor layer of the present invention, with time on the horizontal axis and temperature (°C) on the vertical axis. . FIG. 4B is a partial cross-sectional view of a wafer used to explain the growth method of this embodiment.

In the first embodiment described above, GaAs was grown at a normal growth temperature from beginning to end until the designed film thickness was reached, resulting in high-speed growth. Because of the high-speed growth, the growth time for GaAs is short. However, in order to continue high-speed growth, a large amount of reactive gas must be introduced. Therefore, the faster the growth continues, the more frequently the reactant gas cylinder needs to be replaced. Also,
If high-speed growth is performed, reaction products will accumulate on the inner wall of the reaction tube at a faster rate, so the reaction tube must be replaced frequently. Furthermore, reactive gases such as arsine and TMG are expensive, and the cost increases as the growth rate continues. On the other hand, in this second embodiment, the heat treatment of the Si substrate 10 (I
Indicated by ), then first at this normal growth temperature,
At least at the initial growth stage from the start of GaAs growth, the above-mentioned fast high growth rate, for example, about 3000
Growth is performed at a growth rate of about Å/min or faster (as shown in FIG. 4A), and then the growth rate is changed to a conventional growth rate, for example, a growth rate of about 1800 Å/min. The film is grown to a desired design thickness (as shown in FIG. 4A), and a wafer is obtained as shown in FIG. 4B. In the figure, 18 is a high-speed growth layer which functions as a buffer layer, 20 is a growth layer with a normal growth rate,
Both layers 18 and 20 are grown layers 22 of GaAs on the Si substrate 10. In the above-mentioned initial stage of growth, it is preferable to grow a fast-growing layer of GaAs with a thickness sufficient to function as the buffer layer 18 through high-speed growth during that period. Therefore, the high-speed growth time in this initial stage is Any suitable time may be set depending on the design. In the case of this second embodiment as well, by growing the buffer layer 18 at high speed in this way, the reactive species (constituent atoms) that are the constituent components of the buffer layer 18 are reduced to Si.
Since sufficient migration is not possible on the surface of the substrate 10, and therefore, before three-dimensional island-like growth occurs, the Si substrate surface is covered with GaAs crystal grains with uniform crystal orientation. The subsequent growth layer 20 at a normal growth rate can also be grown as a single crystal layer.

The invention is not limited only to the embodiments described above, but can be subjected to many modifications and changes. For example, in the embodiment described above, MOCVD
Although an example of growing a GaA layer on a Si substrate using the method has been described, this invention solves the problem of three-dimensional island-like growth of the semiconductor to be grown in the early stage of growth due to the migration effect of reactive species on the substrate. Therefore, the growth method, growth conditions, type of substrate, and type of compound semiconductor to be grown can be arbitrarily set according to the design. For example, similar effects can be achieved by using InP, GaP, mixed crystals thereof, or other - group compound semiconductor materials on a Si substrate.

(Effects of the Invention) As is clear from the above description, according to the method for growing a compound semiconductor layer of the present invention, the growth rate of the compound semiconductor to be grown at least from the start of growth to the initial growth stage can be adjusted to The reactive species (constituent atoms) that make up compound semiconductors cannot migrate sufficiently on the substrate surface, and therefore, the normal growth of compound semiconductors is accelerated to the extent that the three-dimensional island-like growth can be suppressed. Since the single crystal layer can be grown even at a high growth temperature of Therefore, throughput can be improved.

[Brief explanation of the drawing]

FIG. 1A is an explanatory diagram of growth temperature for explaining the first embodiment of the method for growing a compound semiconductor layer of the present invention, and FIG. 1B is an illustration of the first embodiment of the method for growing a compound semiconductor layer of the present invention. A cross-sectional view of a wafer to be subjected to
FIG. 2 is an explanatory diagram of growth temperature to explain the conventional method, FIG. 3 is a cross-sectional view of a wafer to explain the conventional method, and FIG. 4A shows a second embodiment of the compound semiconductor layer growth method of the present invention. FIG. 4B is a cross-sectional view of a wafer used to explain a second embodiment of the method for growing a compound semiconductor layer according to the present invention. 10...Si substrate, 16...high-speed growth layer, 18...
... Buffer layer (high-speed growth layer), 20 ... Growth layer with normal growth rate, 22 ... Growth layer.

Claims (1)

[Claims] 1. In vapor phase epitaxial growth of a compound semiconductor layer made of a - group compound semiconductor selected in advance on a silicon (Si) substrate, the above method is performed at a temperature at which the surface of the substrate is cleaned. a step of heat treating the substrate, at a normal growth temperature of the compound semiconductor, and
A method for growing a compound semiconductor layer, comprising the step of growing the compound semiconductor layer on the substrate at a growth rate that does not allow sufficient migration of constituent atoms of the compound semiconductor. 2. In vapor phase epitaxial growth of a compound semiconductor layer made of a - group compound semiconductor selected in advance on a silicon (Si) substrate, the step of heat treating the substrate at a temperature at which the surface of the substrate is cleaned; , at a normal growth temperature of the compound semiconductor, and
growing the buffer layer of the compound semiconductor on the substrate at a growth rate that does not allow sufficient migration of constituent atoms of the compound semiconductor, and at a normal growth temperature for the compound semiconductor, and
A method for growing a compound semiconductor layer, comprising the step of growing the compound semiconductor layer on the buffer layer at a normal growth rate for the compound semiconductor.