JPH03225928A - Epitaxial growth method and semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a method for epitaxially growing an InGaAs layer which can be grown at a high temperature, is excellent in surface flatness and is high in carrier concentration by growing a thin film crystal having composition elements different from those of a substrate by means of using compound semiconductor single crystal substrates having surface orientations tilted from a low index surface in a desired direction. CONSTITUTION:Substrates with orientations of the face 100 and those tilted from the face 100 to a orientation [011] and an orientation [011] by 2 deg., 3 deg., 5 deg. are used as GaAs substrates to be used for epitaxial growth, and molecular beam epitaxy(MBE) method is used to grow InxGa1-xAs (x=0.2) having a lattice constant different from that of the substrate by a thickness of 2mum. Substrate temperature at this time is 650 deg.C. As an off-angle increases, an island defect is rapidly reduced until the island defect completely disappears with an off-angle of 5 deg. both in the orientation [011] and in the orientation [011] so that an extremely flat crystal surface without an island defect can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for epitaxially growing a semiconductor crystal that has good surface flatness and can be doped with impurities at a high concentration, and a semiconductor device manufactured using this epitaxial growth method.

[Conventional technology]

Conventionally, electronic devices such as field effect transistors having an InGaAs layer on a GaAs substrate have been described in Journal of Vacuum Science and Technology B6, 620 (1988) (J, Vac,
Sci, Technol, B6 (2) 62
0°1988). According to this description, when an InGaAs layer is grown at a substrate temperature of 560° C. or higher, re-evaporation of In and deterioration of morphology occur.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, since the substrate crystal plane is (100), there is a problem described in the first order.

1, 0aAs When InGaAs is epitaxially grown on the (100) plane, I
Crystal growth at high temperatures was not possible due to the re-evaporation of n.

2. GaAs When InGaAs is formed on the (100) plane, there is a problem that the surface flatness decreases as the In mixed crystal ratio or film thickness increases.

3. InGaAs formed on GaAs (100) plane
When delta doping with Si as an impurity atom was performed, the carrier activation rate could only be increased to about 60%.

Furthermore, when a semiconductor device is manufactured using a conventional epitaxial layer, there is a problem in that it is difficult to form a fine semiconductor element into a desired shape because the epitaxial layer is not flat. In addition, since the carrier concentration is small,
There was a problem that the current gain of the semiconductor element was not improved.

An object of the present invention is to provide a method for epitaxially growing an InGaAs layer that can be grown at high temperatures, has excellent surface flatness, and has a high carrier concentration.

A second object of the present invention is to provide a semiconductor device having a semiconductor element having an InGaAs layer and improved current gain.

[Means to solve the problem]

The above object is (1) epitaxial growth characterized by using a compound semiconductor single crystal substrate having a surface plane tilted in a desired direction from a low index plane and growing a thin film crystal having constituent elements different from that of the substrate; (2) Using a compound semiconductor single crystal substrate whose surface orientation is tilted from a low-index plane, the adhesion coefficient for the atomic step array formed on the substrate surface is compared to the adhesion coefficient for the low-index plane. (3) an epitaxial growth method characterized by growing a compound semiconductor containing at least a large element as a constituent element; an epitaxial growth method characterized by growing a compound semiconductor thin film containing at least In as a constituent element, (4) an epitaxial growth method according to the above 3, wherein the compound semiconductor thin film is (In, Ga) As; (5) an epitaxial growth method according to the above This is achieved by the epitaxial growth method described in 1.2 or 3 above, wherein the surface plane orientation is inclined by 2 degrees or more from the low index plane.

The second object is (6) a semiconductor device comprising a compound semiconductor thin film grown by the epitaxial growth method according to any one of 1 to 5 above;
7) An epitaxial growth layer having a constituent element different from that of the substrate is provided on a compound semiconductor single crystal substrate whose surface orientation is inclined from a low index plane, and at least a portion of a semiconductor element is disposed on the epitaxial growth layer. (8) A semiconductor device characterized in that: (8) an epitaxial growth layer having a lattice constant different from that of the substrate is provided on a compound semiconductor single crystal substrate whose surface orientation is inclined from a low index plane; A semiconductor device characterized in that at least a portion of a semiconductor element is disposed on a layer, (9) an m-v surface plane tilted from a low index plane;
A semiconductor device characterized in that an epitaxially grown layer containing at least In as a constituent element is provided on a group compound semiconductor single crystal substrate, and the epitaxially grown layer has an impurity, (10) the impurity is present in one atomic plane of the epitaxially grown layer. 9. The semiconductor device according to 9 above, wherein the epitaxial growth layer is:
This is achieved by the semiconductor device according to any one of items 7 to 10 above, which is arranged as an active layer of the semiconductor element.

- [Operation] When the crystal substrate surface is tilted from the low index plane, an atomic step array is formed. Since constituent elements or impurity atoms are easily substituted in the step row, the larger the off angle, the easier the substitution, and the probability of two-dimensional nucleation on the terrace surface is reduced. That is, in the step row, the arrangement relationship of dangling bonds of the constituent atoms is different from that on the low index plane, so the adhesion coefficients and substitution positions of the constituent atoms and impurity atoms subjected to epitaxial growth change. Changes in the adhesion coefficient and the substitution position increase as the off-angle increases, so the probability of two-dimensional nucleation on the terrace surface decreases, and impurities are more likely to be substituted at the lattice positions in the step sequence.

This improves the flatness of the crystal surface and the activation rate of impurities.

〔Example〕

Example 1 A first example of the present invention will be described below. As a GaAs substrate for epitaxial growth, the plane orientation is (1
By molecular beam epitaxy (MBE method) using planes tilted 2 degrees, 3 degrees, and 8-5 degrees from the (00) and (100) planes in the (011) direction and (011) direction, respectively,
Inx having a lattice constant different from that of the above substrate
Gal-xAs (x = 0, 2) with a film thickness of 2 μm
grow up. The substrate temperature at this time was 650°C.

In a sample using a substrate with a (100) plane (off angle of 0 degrees), as a result of scanning electron microscopy observation, 105/cI112 island-like defects were generated on the entire wafer surface, but as the off-angle increases, island-like defects decreased rapidly, and at an off-angle of 5 degrees in both the (011) direction and the (011) direction, the island-like defects completely disappeared, and an extremely flat crystal surface free of island-like defects was obtained.

Example 2 A second embodiment of the present invention will be explained with reference to FIG.

When forming InGaAs by the MBE method, the adhesion coefficient of In decreases when the substrate temperature is 580° C. or higher. 1st
The figure shows that when the adhesion coefficient is 1, I nxcx a, -
The In composition of InGaAs produced under growth conditions such that the In composition X of x As is 0.1 is shown. At 600°C, when using a normal (100) GaAs substrate, X is 0.01
5, which is about 15%.

On the other hand, when the substrate surface is inclined from the (100) plane to the (011) direction and the off angle is increased, the In composition tends to increase.

At a substrate temperature of 580° C., the adhesion rate is a little less than 70% on the (100) plane (off angle 0 degrees), but increases to 95% when the off angle is 5 degrees.

Generally, in compound semiconductors, the mobility decreases when the substrate temperature is lowered. In the present invention, even in high-temperature growth of about 580° C., the decrease in In composition can be suppressed, so high-temperature growth is possible, and InGaAs with high mobility can be obtained.

Embodiment 3 Hereinafter, as a third embodiment of the present invention, a method of delta-doping InGaAs with Si as an n-type impurity and epitaxially growing a highly concentrated thin film will be described.

First, a semi-insulating GaAs substrate having a surface inclined from the (100) plane to the (011) direction is subjected to sulfuric acid-based chemical etching. Next, molecular beam epitaxy (MB
E) After installing the substrate in the device, AS at 580-650℃
The substrate surface is heated while being irradiated with four beams. Next, the substrate temperature is lowered to 500° C. and epitaxial growth is started. In epitaxial growth, a shutter of Ga as a raw material is opened, undoped GaAs is deposited to a thickness of 3000 Å or more, and a shutter of In is opened to deposit InGaAs (I).
n composition 0.1) was deposited by 250 people. Next, Ga, In
Close the shutter and open the Si shutter. After irradiating Si until the Si surface density becomes I x 1013 cm-'', the Si shutter is closed, the Ga and In shutters are opened to deposit 250 layers of undoped InGaAs, and then the In shutter is closed and 1000 layers of undoped GaAs are deposited. Ta.

Figure 2 shows delta-doped InGaA prepared by the above method.
FIG. 3 is a diagram showing the off-angle dependence of s.

When the sample is tilted by 5 degrees from the (100) plane to the (011) direction and the (011) direction, the carrier areal density increases by about 20% (11-) compared to the (100) plane sample.

Example 4 Hereinafter, manufacturing of a semiconductor device of the present invention will be explained. FIG. 3 is a cross-sectional view of a field effect transistor. (10
0) Semi-insulating G tilted 5 degrees in the (011) direction from the plane
Undoped G is deposited on the aA s substrate 1 by MBE method.
aAs2 (500nm), undoped Ino, □Ga
o, As layers 3 (10 nm) are sequentially stacked. In the undoped I n, 1 Gao, As layer, I X 1
An SL delta doped layer 3' of 0 cm-2 is inserted.Furthermore, an undoped GaAs layer 4 is formed by MBE method.
(10 nm) and undoped AflGaAs layer 5 (20 nm)
(nm) are stacked. Subsequently, an undoped G a
After partially removing the s-layer 4 and the undoped AflGaAs layer 5, an InGaAs layer 7 is selectively epitaxially grown by MOCVD. Subsequently, 5iO26 is formed on the surface by the CVD method, only the side walls are left by dry etching, Ti/AQ is evaporated, and the saw 12, the drain electrode 8', and the gate electrode 9 are formed by the lift-off method. do.

The field effect transistor manufactured by the above method has a K value of 13 and (100 μm) when the gate length is 0.15 μm.
) A significant performance improvement was achieved compared to the value of 7 when using a substrate with a surface of ).

Furthermore, since the substrate was turned off 5 times at this time, good surface flatness was obtained, and performance with good reproducibility was obtained without a decrease in the In composition.

〔Effect of the invention〕

According to the present invention, since epitaxial growth is performed on a substrate whose surface is inclined from a low index plane, the following effects are achieved.

1. A crystal with excellent surface flatness could be obtained.

2. The adhesion coefficient of atoms constituting the epitaxial crystal could be increased.

3. The activation rate of added impurity atoms could be improved.

Furthermore, using the epitaxial growth method described above, a high-performance semiconductor device having a highly-concentrated impurity layer could be manufactured with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the off-angle dependence of the In composition of Inx Gal-x As for explaining the second embodiment of the epitaxial growth method of the present invention, and FIG. Figure 3 shows off-angle dependence of sheet carrier concentration for explaining the third example of the method.
The figure is a sectional view of a semiconductor device according to an embodiment of the present invention. 1...Semi-insulating GaAs substrate 2...Undoped GaAs 3...Undoped In. , 1Gao, ,As layer 3'・
...Delta doped layer 4...Undoped GaAs layer 5...Undoped AQGaAs layer 6-8in2 7-InGaAs layer 8...
・Source electrode 8'...Drain electrode 9...
gate electrode

Claims (1)

[Claims] 1. A compound semiconductor single crystal substrate having a surface orientation tilted in a desired direction from a low index plane is used to grow a thin film crystal having constituent elements different from that of the substrate. Epitaxial growth method. 2. Using a compound semiconductor single crystal substrate whose surface orientation is tilted from a low-index plane, an element whose adhesion coefficient to the atomic step array formed on the substrate surface is larger than that on the low-index plane An epitaxial growth method characterized by growing a compound semiconductor containing at least as a constituent element. 3. At least I
An epitaxial growth method characterized by growing a compound semiconductor thin film containing n as a constituent element. 4. The epitaxial growth method according to claim 3, wherein the compound semiconductor thin film is (In, Ga) As. 5. The epitaxial growth method according to claim 1, 2 or 3, wherein the surface plane orientation is inclined by 2 degrees or more from the low index plane. 6. A semiconductor device comprising a compound semiconductor thin film grown by the epitaxial growth method according to any one of claims 1 to 5. 7. An epitaxial growth layer having a constituent element different from that of the substrate is provided on a compound semiconductor single crystal substrate whose surface orientation is inclined from a low index plane, and at least a portion of a semiconductor element is disposed on the epitaxial growth layer. A semiconductor device characterized by: 8. An epitaxial growth layer having a lattice constant different from that of the substrate is provided on a compound semiconductor single crystal substrate whose surface orientation is inclined from a low index plane, and at least a portion of a semiconductor element is disposed on the epitaxial growth layer. A semiconductor device characterized by: 9. A semiconductor device characterized in that an epitaxial growth layer containing at least In as a constituent element is provided on a III-V group compound semiconductor single crystal substrate whose surface orientation is tilted from a low index plane, and the epitaxial growth layer has impurities. . 10. The semiconductor device according to claim 9, wherein the impurity is present in one atomic plane of the epitaxial growth layer. 11. The semiconductor device according to claim 7, wherein the epitaxial growth layer is arranged as an active layer of the semiconductor element.