JPH06267867A - Compound semiconductor crystal growth method and ohmic contact formation method using the same - Google Patents

Abstract

(57) [Summary] [Object] To provide a crystal growth method of a compound semiconductor and an ohmic contact formation method for an n-type semiconductor using the same. A method for forming a non-alloy ohmic contact composed of indium gallium arsenide (InGaAs) having the same conductivity type as that of the first semiconductor layer and an electrode metal for a first semiconductor layer having an n-type conductivity The InGaAs layer is composed of a composition gradient layer 3 in which the In composition is gradually increased from 0 and a composition uniform layer 4 having a uniform In composition, and the InGaAs layer is formed of triethylgallium (TEG) and trimethylindium. It is formed by a method of epitaxial growth using (TMI) and arsine (AsH ₃ ) as raw materials.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a compound semiconductor crystal in a method for manufacturing a semiconductor device and an n method using the same.
Related to the method of forming ohmic contacts to semiconductors.

[0002]

2. Description of the Related Art In order to realize high performance of electronic devices and optical devices, formation of low resistance ohmic contacts is essential. Instead of the AuGe / Ni alloy type contact, which is normally used as an ohmic contact for n-type GaAs, as shown in FIG.
A non-alloy type contact having an n-ln _X Ga _{1 -x} As layer 2 composed of a composition gradient layer 3 and a composition uniform layer 4 is provided between the electrode and the electrode metal (metal) 5 so that the Schottky barrier becomes 0. Proposed and demonstrated its usefulness.

Then, the above-mentioned ln _X G is formed by the MOCVD method.
When forming the a _{1 -x} As layer 2, GaAs and InGaA are used.
Since the lattice does not match with s, it is necessary to grow at a low temperature of about 450 ° C. to form InGaAs having a good surface morphology on GaAs. Conventionally, trimethylgallium (TMG) has been used as a gallium raw material in the growth of InGaAs.

[0004]

However, in this temperature range, as shown in FIG. 3, GaAs using TMG is used.
The growth rate of TMG is equivalent to the reaction-controlled region, and the growth rate is TMG.
Not proportional to supply. Therefore, when TMG, TMI and AsH ₃ are used as raw materials, it is difficult to form the InGaAs composition gradient layer 3 as designed. For example, by linearly changing the supply amount of the raw material organic metal, I
When the nGaAs composition gradient layer 3 is formed, the In composition distribution in the InGaAs layer 2 is as shown in FIG.
The effective film thickness of. In this case, the conduction band is shown in FIG.
As shown in (B), an energy barrier 6 for electrons is generated, so that a sufficiently low contact resistivity cannot be obtained.
Thus, it was difficult to form the non-alloy type ohmic contact as shown in FIG. 2 as designed by using TMG and TMI.

The present invention solves the disadvantage that it is difficult to form an InGaAs composition gradient layer in a non-alloy type ohmic contact using InGaAs, and provides a method for easily forming a non-alloy type contact having a sufficiently low contact resistivity. The purpose is to provide.

[0006]

A crystal growth method for a compound semiconductor according to the present invention which achieves the object is to use indium gallium arsenide (trioxide gallium (TEG), trimethyl indium (TMI) and arsine (AsH ₃ ) as raw materials. InGaAs) crystal is epitaxially grown.

On the other hand, a first ohmic contact forming method according to the present invention is characterized in that a non-alloy type ohmic contact including an InGaAs layer is formed by the crystal growth method.

In the second ohmic contact forming method according to the present invention, in the first forming method, when the compositionally graded layer is formed, the supply amount of trimethylindium is increased according to a linear function, and trimethylindium is added. It is characterized in that it is formed by decreasing the supply amount of the above according to the hyperbolic function shown in the equation (1) of the following "Equation 2".

[Equation 2]

[0009]

In the present invention, by using TEG, TMI and AsH ₃ as raw materials, the composition gradient layer in the non-alloy type contact layer using InGaAs can be easily formed even at a low temperature of about 450 ° C. Ga using TEG and AsH ₃
The growth rate of As growth is proportional to the TEG supply amount up to a low temperature of about 350 ° C. Therefore, for example, TEG and TMI
By linearly changing the supply amount of, the composition gradient layer as shown in FIG. 2 can be formed as designed. By this method, it is possible to form a non-alloy type ohmic contact having a sufficiently low contact resistivity.

Further, according to the present invention, in the formation of the non-alloy type contact layer using the InGaAs layer, the supply amount of TMG at the time of forming the compositionally graded layer of the InGaAs layer is changed according to the hyperbolic function shown in the above "Formula 2". .

Further, G using TMG at around 450 ° C.
The growth of aAs is in the reaction rate-determining region, and the dependence of the growth rate on the amount of the raw material organometallic supply is as shown in FIG. Langmuir-Hinshelwood says that undecomposed raw materials of group III and group V are adsorbed on independent sites in the reaction-controlled region.
It is often described as a type, and the dependence of the growth rate on the raw material supply is approximated by a hyperbolic function.

Therefore, the growth rate can be linearly changed by changing the raw material supply amount according to the hyperbolic function with respect to time as shown in the equation (1). That is, by changing the TMG supply amount according to the equation (1), G
The change with time of the aAs growth rate becomes linear, so that the change in In composition as shown in FIG. 2 can be obtained in the compositionally graded layer.

[0013]

EXAMPLE An n-type G doped with Si using the present invention
An example of forming an ohmic contact with aAs is shown in FIG.

(Embodiment 1) As shown in FIG. 1, MOCV
The semi-insulating GaAs substrate 1 is loaded in the D device, and MOCV
The Si-doped GaAs layer 2 is grown by the D method. Then, the Si-doped InGaAs composition gradient layer 3 is grown to 500 Å.

The composition gradient layer 3 is formed as follows. The amount of TEG supplied is from the amount supplied during GaAs growth to the amount supplied during InGaAs composition uniform layer growth, and T
The amount of MI supplied is linearly changed from 0 to the amount supplied during growth of the InGaAs composition uniform layer.

During this period, the supply amount of the doping material for Si doping is constant. Furthermore, Si-doped InGa
The As composition uniform layer 4 is grown by 500Å. The wafer thus obtained is taken out from the MOCVD apparatus and loaded into a metal film forming apparatus, for example, a vacuum vapor deposition apparatus, to form a metal film, which is used as the electrode 5.

If this embodiment is applied to, for example, the step of forming an emitter electrode of a heterojunction bipolar transistor (HBT), it is possible to form an emitter electrode having a sufficiently low emitter parasitic resistance, so that the high frequency characteristics of the HBT can be expected to be improved.

Regarding the composition of the InGaAs composition uniform layer, if the In composition is 0.5 or more, a sufficiently low contact resistivity can be obtained, which is effective. InGaAs
The layer thickness was set to 500 Å for both the composition-graded layer and the composition-uniform layer, but within the range that does not affect the device yield, the composition-graded layer is 500 Å or more, and the composition-uniform layer is 400
There is no problem if it is Å or more.

In this embodiment, Si is used as the n-type impurity, but other n-type impurities such as Sn may be used. Further, the supply amount of the Si doping raw material in the composition gradient layer is constant, but the supply amount may be changed according to the change of the composition.

(Embodiment 2) A semi-insulating GaAs substrate 1 is loaded in a MOCVD apparatus, and a Si-doped GaAs layer 2 is grown by MOCVD. Then, the composition gradient layer 3 is formed into 5
00Å grow up. Further, a Si-doped InGaAs composition uniform layer 4 having an In composition of 0.6 is grown by 500Å. The wafer thus obtained is taken out from the MOCVD apparatus and loaded into a metal film forming apparatus, for example, a vacuum vapor deposition apparatus, to form a metal film, which is used as the electrode 5.

If this embodiment is applied to, for example, the step of forming an emitter electrode of a heterojunction bipolar transistor (HBT), it is possible to reduce the emitter parasitic resistance.
Therefore, improvement of the high frequency characteristics of the HBT can be expected.

In the above-mentioned embodiment, the composition of the InGaAs composition uniform layer 4 is set to 0.6, but if it is 0.5 or more, a sufficiently low contact resistivity can be obtained and the same effect can be obtained. . Further, the film thickness of the composition gradient layer 3 is set to 500 Å, but it may be 200 Å or more. Similar effects can be obtained if the film thickness of the uniform composition layer is 50 Å or more.

In this embodiment, Si is used as the n-type impurity, but other n-type impurities such as Sn may be used.

[0024]

As described above, according to the present invention, triethylgallium (TEG) and trimethylindium (T) are used.
By performing epitaxial growth using MI) and arsine (AsH ₃ ) as raw materials, it becomes possible to easily form the compositionally graded layer as designed in the non-alloy type ohmic contact to the n-type semiconductor using InGaAs. In addition, according to the present invention, n using InGaAs is used.
In the non-alloy ohmic contact with the type semiconductor, the In composition in the compositionally graded layer can be changed linearly.

[Brief description of drawings]

FIG. 1 is for explaining an embodiment of the present invention.

FIG. 2 is a view for explaining a non-alloy type ohmic contact to an n-type semiconductor using InGaAs in the present invention.

FIG. 3 TMG + AsH at a growth temperature of around 450 ° C.
₃ , and GaAs and InA by TMI + AsH ₃
It shows the organometallic partial pressure dependence of the growth rate of s.

FIG. 4 shows InG in a non-alloy type ohmic contact to an n-type semiconductor formed by using TMG and TMI.
The distribution of the In composition in the aAs layer in the depth direction and the forbidden band structure. In the figure, the solid line represents the distribution of the In composition in the actually formed InGaAs layer in the depth direction and the forbidden band structure. Is a distribution of In composition in the depth direction and a forbidden band structure in the InGaAs layer to be formed.

[Explanation of symbols]

 1 semi-insulating GaAs substrate 2 Si-doped GaAs layer 3 composition gradient layer 4 Si-doped InGaAs composition uniform layer 5 electrode

Claims (3)

[Claims] 1. A crystal growth method for a compound semiconductor, which comprises epitaxially growing an indium gallium arsenide (InGaAs) crystal using triethylgallium (TEG), trimethylindium (TMI) and arsine (AsH ₃ ) as raw materials. 2. A non-alloy ohmic contact composed of indium gallium arsenide (InGaAs) having the same conductivity type as that of the first semiconductor layer and an electrode metal is provided for a first semiconductor layer having an n-type conductivity type. In the forming method, the InGaAs layer is composed of a composition gradient layer in which the In composition is gradually increased from 0 and a composition uniform layer having a uniform In composition, and the InGaAs layer is formed by the triethylgallium according to claim 1. (TEG), trimethylindium (TMI), and arsine (AsH ₃ ) are used as raw materials to form an ohmic contact by a method of epitaxial growth. 3. The method according to claim 2, wherein the amount of trimethylindium supplied is increased according to a linear function when the compositionally graded layer is formed, and the amount of trimethylindium supplied is changed to the following formula (1). A method for forming an ohmic contact, which is characterized in that the ohmic contact is formed by decreasing according to the hyperbolic function shown. [Equation 1]