JPH07321058A - Manufacture of iii-v mixed crystal compound semiconductor film - Google Patents

Abstract

PURPOSE:To make small the recesses and projections of the surface of an InGaAs film and to reduce the clouding of the surface due to the recesses and projections to improve significantly a fine processability in a process of manufacturing a device. CONSTITUTION:In the case where an InxGa1-xAs film 2 or an In0.5Ga0.5As film 3 is grown on a GaAs substrate 1, a trimethylindium and a triethylgallium are used as a group III raw material, the ratio V/III of the feed rate of a group V raw material to the feed rate of the group III raw material is made such small as 1 to 20 or smaller and the growth temperature of the InGaAs film is dropped lower than a substrate temperature setting the substrate temperature as 400 to 500 deg.C. When the ratio V/III is made small and the growth temperature of the InGaAs film is dropped, the motion of In is inhibited so that the In is made hard to perform a three-dimensional growth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a III-V mixed crystal compound semiconductor film, and more particularly to a method for manufacturing an InGaAs film.

[0002]

2. Description of the Related Art Conventionally, as HEMTs and HBTs, Ga
A growth of GaAs and AlGaAs on an As substrate is often used. In order to improve the performance of this HEMT or HBT, GaAs and AlGa on the GaAs substrate are used.
The use of InGaAs as the contact layer instead of As growth has been studied, and early commercialization is expected.

By the way, as a method for growing n-type InGaAs on a substrate, TMIn and TMG are used as group III raw materials.
a, AsH ₃ is used as a V group raw material, and disilane (Si ₂ H ₆ ) is used as an n-type dopant. The ratio V / III of the supply amount of the V group raw material and the III group raw material is 30 to 60, and the raw material is 550 750
The n-type In is supplied to the substrate heated to ℃.
A method of growing a GaAs film has been proposed.

[0004]

[Problems to be Solved by the Invention] However, InGaAs
Has a lattice constant different from that of GaAs or AlGaAs, so InG is grown on GaAs or AlGaAs at a normal GaAs or AlGaAs growth temperature of 550 to 750 ° C.
When aAs is grown, there is a defect that the surface becomes uneven and becomes cloudy in white. The unevenness of the surface of InGaAs becomes a problem in fine processing in the device manufacturing process and deteriorates the characteristics of the element.

Therefore, in HEMT and HBT,
GaAs instead of InGaAs for those contact layers
Is used. Therefore, it is necessary to form the metal electrode and the ohmic contact layer by heat treatment, resulting in a complicated manufacturing process and high cost. The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to reduce the unevenness of the surface of the InGaAs film, and to reduce the cloudiness of the surface due to the unevenness. To provide. In addition, the purpose of the present invention is to provide a novel II that can significantly improve the microfabrication in the device manufacturing process
An object of the present invention is to provide a method for manufacturing a group IV mixed crystal compound semiconductor film. Another object of the present invention is to provide a novel method for producing a group III-V mixed crystal compound semiconductor film, which can omit the heat treatment step, simplify the production step, and reduce the cost.

[0006]

The method for producing a III-V mixed crystal compound semiconductor film according to the present invention comprises:
In a vapor phase growth method of supplying a raw material containing a group I and a group V element to grow a III-V mixed crystal compound semiconductor film, TMIn and TMGa are used as a group III raw material and
When the ratio V / III of the supply amount of the group raw material is 20 or less, 400
The InGaAs film is grown by supplying it to a substrate heated to ˜500 ° C. To grow an n-type InGaAs film, an n-type dopant is further doped.

In this case, in order to prevent the growth rate from decreasing, it is preferable to use TEGa in place of TMGa. In order to prevent a decrease in electron mobility, it is preferable to use Se as the n-type dopant instead of Si. For inexpensive and stable production, the group V raw material is preferably AsH ₃ .

Further, in order to prevent unevenness from being formed on the surface of the InGaAs film, Si or Ga is used as the substrate.
It is preferable to use a substrate in which a compound semiconductor film is crystallized on As, InP or their substrate.

Further, the above-mentioned InGaAs film is required to be as flat as possible in consideration of the device manufacturing process, and is an epitaxial wafer for HBT or HE.
It is preferably applied to the contact layer of the MT epitaxial wafer.

[0010]

Function: The surface of the InGaAs growth film becomes uneven because the decomposed In easily moves on the substrate, and thus In gathers.
This is because it is easy for the dimension to grow. If the growth temperature is lowered, In
Is suppressed and it becomes difficult to grow three-dimensionally, so that the crystal surface becomes flat. The growth temperature is preferably 500 ° C. or lower. 40
If the temperature is lower than 0 ° C, the crystal will not grow, so
500 ° C. is the optimum growth temperature, which leads to InGa
The As surface is less likely to be uneven, and the flatness is greatly improved.

By the way, the growth rate of TMGa used as a Group III Ga raw material is lowered at a growth temperature of 400 to 500 ° C., and the decomposition efficiency is lowered. On the other hand, TEGa has a constant decomposition rate even at 400 to 500 ° C. because of its low decomposition temperature, and is superior to TMGa in terms of decomposition efficiency.

When V / III is 20 or less in crystal growth, the haze level is significantly improved. However, if V / III is reduced to reduce the surface haze level, n-type In
In the case of growing a GaAs film, when the n-type dopant is Si, the smaller V / III is, the lower the electron mobility becomes. In this respect, the electron mobility does not decrease when Se is used.

TMIn and triethylindium (TEIn) can be considered as the In raw material, but since TEI reacts with AsH ₃ of the As raw material at room temperature, InGaAs is used.
Can not be used to grow.

Although AsH ₃ and trimethyl arsenic (TMAs) are used as As raw materials, it is preferable to use AsH ₃ which is the lowest in cost and most used.

[0015]

EXAMPLES Examples of the method for producing a III-V mixed crystal compound semiconductor film of the present invention will be described below. As shown in FIG.
A wafer on which a GaAs film is grown is shown. On the GaAs substrate 1, a graded In _X Ga _1-X As film 2 in which the InAs mixed crystal ratio x changes from 0 to 0.5, and In _0.5 Ga _0.5.
The As film 3 is sequentially formed.

The crystal having the structure shown in FIG. 1 was grown, and the relationship between the haze level on the crystal surface and the growth temperature was investigated. The result is shown in FIG. V / III is 15. As is clear from FIG. 2, at the conventional growth temperature of 550 to 750 ° C., the haze level is high and many irregularities occur on the crystal surface. At a growth temperature of 400 to 500 ° C, the haze level is low, and InG
It was found that the irregularities on the surface of the aAs film became smaller.

By the way, although TMGa is generally used as a Ga raw material, when TMGa is used, as shown in FIG.
In the low temperature growth of 0 ° C. or lower, the growth rate is reduced and the decomposition efficiency of the raw material is reduced. Therefore, if the growth temperature is set to 500 ° C. or lower using TMGa, the surface haze level cannot be reduced without lowering the decomposition efficiency of the raw material.
However, as shown in the figure, TEGa does not deteriorate the decomposition efficiency of the raw material even at low temperature growth. Therefore, in order to reduce the haze level by keeping the growth temperature at 500 ° C. or lower without lowering the decomposition efficiency of the raw material, it is preferable to use TEGa.

Further, in crystal growth, the ratio V / III of the supply amounts of the group V raw material and the group III raw material is an important growth condition. Therefore, a crystal having the structure shown in FIG. 1 was grown, and the V / III dependence of the surface haze level was investigated. The result is shown in FIG.
The growth temperature is 450 ° C. As is clear from FIG. 4, when the conventional V / III is 30 to 60, the haze level is high and many irregularities occur on the crystal surface. It was found that when V / III was 20 or less, the haze level was reduced and the unevenness on the surface of the InGaAs film was reduced.

The In _x Ga _1-x As film 2 and the In _0.5 Ga _0.5 As film 3 grown on the GaAs substrate 1 often have n-type conductivity. Si ₂ H ₆ (disilane) is generally used as the n-type dopant material,
In Si ₂ H ₆ doping, as shown in FIG. 5, the electron mobility is higher when V / III is larger, and the electron mobility is lowered when V / III is smaller. Therefore, if V / III is reduced in order to reduce the surface haze level, the electron mobility will decrease. However, when H ₂ Se is used as the dopant material, the electron mobility does not decrease even at low V / III as shown in FIG. Therefore, in order to reduce the haze level by setting V / III to 20 or less without lowering the electron mobility, it is preferable to use H ₂ Se as the dopant raw material.

In order to compare the present example with the conventional example, in this example, the group III raw material is TEGa and TMIn, the group V raw material is AsH ₃ , and the group V and group III raw material feed rates are the same. V / III is 15, the growth substrate temperature is 450 ° C., and in the conventional example, the group III raw material is TEGa and TMIn, the group V raw material is AsH ₃ , and the ratio V / III of the supply amount of the group V and group III raw materials is 50. The temperature of the substrate to be grown was 570 ° C., and the crystals having the structure shown in FIG. 1 were grown. When the haze level showing the degree of haze on the surface was examined, the value of the haze level was smaller and the haze on the surface was less in this example. The details will be described below.

(Embodiment 1) FIG. 7 shows an example of a cross-sectional structure of an HBT, in which an n-type GaAs collector contact layer 12, a GaAs collector layer 13 and a p-type are formed on a semi-insulating GaAs substrate 11.
-Type GaAs base layer 14, n-type Al _0.3 Ga _0.7 As layer and graded n-type Al _x Ga _1-x As layer (x = 0.3
→ 0) and the emitter layer 15 and n-type GaAs
Layer, graded In _X Ga _1-x As layer (x = 0 → 0.
5), an emitter contact layer 16 composed of an n-type In _0.5 Ga _0.5 As layer and an n-type InAs layer is sequentially formed.

In Example 1, the present invention is applied to the production of the n-type In _0.5 Ga _0.5 As layer and the graded n-type In _x Ga _{1 -x} As layer in the emitter contact layer 16, and these layers are formed. Were grown under the following conditions. Growth temperature 450 ℃,
V / III = 15, TEGa = 2.1 cc / min, TMIn =
0.61cc / min, AsH ₃ = 40.7cc / min, H ₂ Se
= 9.3 × 10 ^-3 cc / min. As a result, the surface haze level of HBT showing the maximum frequency was 150 ppm as shown in FIG. 9 (a). As the haze level decreases, the haze on the surface decreases.

Comparative Example 1 n-type I having the same structure as in Example 1
n _0.5 Ga _0.5 As layer and graded n-type In _X Ga
_{The 1-x} As layer was grown under the following conditions. Growth temperature 57
0 ° C, V / III = 50, TMGa = 2.4cc / min, TM
In = 0.61 cc / min, AsH ₃ = 151 cc / min, Si
₂ H ₆ = 2.0 × 10 ^-2 cc / min. As a result, the surface haze level of HBT showing the maximum frequency is shown in FIG. 9 (b).
As shown in FIG.

(Embodiment 2) FIG. 8 shows an example of a cross-sectional structure of a HEMT, in which a GaAs buffer layer 22, an In _0.2 Ga _0.7 As channel layer 23, n are formed on a semi-insulating GaAs substrate 21.
Type Al _0.3 Ga _0.7 As carrier supply layer 24, and n
Type GaAs layer, graded In _X Ga _1-X As layer (x
= 0 → 0.5), n-type In _0.5 Ga _0.5 As layer, n-type I
The contact layer 25 made of an nAs layer is sequentially formed.

In the second embodiment, n in the contact layer 25 is
Type In _0.5 Ga _0.5 As film and graded n-type In _X
Applied to the manufacture of Ga _1-X As films, these layers were used in Example 1
Grew under the same conditions. As a result, the same good surface haze level as in Example 1 was obtained.

Comparative Example 2 The InGaAs film of the contact layer having the HEMT structure shown in FIG. 8 was grown under the same conditions as in Comparative Example 2. As a result, the same bad result as in Comparative Example 1 was obtained.

[0027]

【The invention's effect】

(1) According to the invention as set forth in claim 1 or 2, TMIn and TMGa are used as the group III raw material, the ratio V / III of the supply amount of the group V raw material and the group III raw material is set to 20 or less, and the growth substrate temperature is set. Since the temperature is set to 400 to 500 ° C., the flatness of the surface of the InGaAs film or the n-type InGaAs film can be greatly improved, and as a result, the fine workability in the device manufacturing process can be greatly improved.

(2) According to the invention described in claim 3, III
Since TEGa is used as the group material, the growth rate does not decrease even when the temperature of the substrate to be grown is 500 ° C. or lower, unlike the case of using TMGa.

(3) According to the invention described in claim 4, since Se is used as the n-type dopant, even if the ratio V / III of the supply amount of the group V raw material and the group III raw material is 20 or less, Si The electron mobility does not decrease as in the case of using.

(4) According to the invention described in claim 5, since the group V raw material is AsH ₃ , the InGaAs film can be manufactured more inexpensively and more stably than when an organic compound of arsenic is used.

(5) According to the invention described in claim 6, even when Si, GaAs, InP or a substrate obtained by crystallizing a compound semiconductor film on these substrates is used as the substrate, the surface of InGaAs is uneven. Is not formed and does not fog.

(6) According to the invention described in claim 7, since the above-mentioned InGaAs film is used for the contact layer of the HBT epitaxial wafer or the HEMT epitaxial wafer, the metal electrode and the ohmic contact can be formed without heat treatment. Therefore, the manufacturing process can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a wafer manufactured by the method of the present invention.

FIG. 2 is a characteristic diagram for examining the growth temperature dependence of the haze level when the ratio V / III of the supply amount of the group V raw material and the supply amount of the group III raw material is 15.

FIG. 3 is a characteristic diagram for examining the growth temperature dependence of the growth rate of GaAs using TMGa and TEGa.

[Fig. 4] V / of haze level at a growth temperature of 450 ° C
It is a characteristic diagram which investigated III dependence.

FIG. 5 is a characteristic diagram for examining the relationship between carrier concentration and electron mobility of Si-doped GaAs.

FIG. 6 is a characteristic diagram for examining the relationship between carrier concentration and electron mobility of Se-doped GaAs.

FIG. 7 is a vertical sectional view showing an embodiment of an HBT to which the present invention is applied.

FIG. 8 is a vertical sectional view showing an embodiment of a HEMT to which the present invention is applied.

9 is a graph showing the frequency of haze level on the crystal surface of the structure of FIG. 7, where (a) shows the frequency of the present example and (b) shows the frequency of the conventional example.

[Explanation of symbols]

1 GaAs substrate 2 In _X Ga _1-X As film (x: 0 → 0.5) 3 In _0.5 Ga _0.5 As film

Claims (7)

[Claims] 1. A vapor phase growth method for growing a III-V mixed crystal compound semiconductor film by supplying a raw material containing a group III and group V element onto a heated substrate, and using trimethylindium as a group III raw material. (TMIn) and trimethylgallium (T
MGa) and the ratio V of the supply amount of the group V raw material and the group III raw material
/ III is 20 or less and is supplied to a substrate heated to 400 to 500 ° C. to grow an InGaAs film, and a method for producing a III-V mixed crystal compound semiconductor film. 2. A vapor phase growth method for growing a III-V mixed crystal compound semiconductor film by supplying a raw material containing a group III and group V element onto a heated substrate, and using TMI as a group III raw material.
n and TMGa are used, the ratio V / III of the supply amount of the group V raw material and the group III raw material is set to 20 or less, and Si is used as the n-type dopant.
Is used to grow an n-type InGaAs film by supplying it to a substrate heated to 400 to 500 ° C. III
-Method for producing Group V mixed crystal compound semiconductor film. 3. The method for producing a III-V group mixed crystal compound semiconductor film according to claim 1, wherein triethylgallium (TEGa) is used instead of TMGa. 4. The method for producing a III-V mixed crystal compound semiconductor film according to claim 2, wherein Se is used instead of Si. 5. The method for producing a group III-V mixed crystal compound semiconductor film according to claim 1, wherein the group V source material is arsine (AsH ₃ ). 6. The substrate comprises Si, GaAs, InP
6. A method for producing a III-V mixed crystal compound semiconductor film according to claim 1, wherein a substrate obtained by crystallizing a compound semiconductor film on these substrates is used. 7. The III-V according to claim 1, wherein the InGaAs film is a contact layer of an epitaxial wafer for a heterojunction bipolar transistor (HBT) or an epitaxial wafer for a high electron mobility transistor (HEMT). Method for producing mixed-group compound semiconductor film.