JPH04364720A - Method and apparatus for metal organic chemical vapor deposition - Google Patents

Abstract

PURPOSE:To reduce the mixture of carbon into crystals in chemical vapor deposition of GaAs using solid arsenic and TMG. CONSTITUTION:A substrate 1 is mounted on a holder 3 in a reaction tube 2 and heated to 600-800 deg.C. TMG 6 is supplied in the form of hydrogen bubbles from the left side of the reaction tube. Arsenic is heated by a heater 12 and supplied in vapor form. Hydrogen is used as a carrier gas. The source gas and carrier gas are supplied to the surface of the wafer through a hot platinum net. The carrier gas, hydrogen, is activated by the catalytic reaction of the platinum net. As a result, the separation of the methyl group in the TMG is promoted, and thus the mixture with carbon is minimized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organometallic chemical vapor deposition method and apparatus for growing a compound semiconductor on a substrate.

0002

2. Description of the Related Art MOVPE (metal-organic vapor phase epitaxy) is widely used as a method for epitaxial growth of compound semiconductors, typically GaAs.

By the way, when growing GaAs by MOVPE, arsine gas is generally used as a raw material for arsenic, but this arsine gas is extremely toxic, and there is a strong demand for the development of an arsenic raw material that can replace arsine.

[0004] In recent years, organic arsenic compounds that are liquid at room temperature, such as tert-butylarsine, dimethylarsine, and triethylarsine, have been reported, but their toxicity is still at the same level as arsine gas.

On the other hand, metal (solid) arsenic is easy to handle and store, and is also safe.
of Electronic Materials),
Vol. 14, No. 4, 1985, pp. 433
449, there is a report on the use of this metal arsenic as a substitute material for arsine.

[0006]

[Problems to be Solved by the Invention] Using metallic arsenic as a substitute material certainly improves safety, but on the other hand, trimethylgallium ((C
There is a problem in that a large amount of carbon C contained in H3)3 Ga, simply referred to as TMG) and triethyl gallium ((C2 H5) 3 Ga, simply referred to as TEG) is mixed into the produced film.

[0007] This is a conventional arsine gas (AS H3
), arsine not only serves as a raw material for arsenic, but also plays an important role in the dissociation process of organic matter in TMG and TEG. As-H
It is designed to be supplied from bonds, and As2 and As4
This is because metallic arsenic, which uses carbon as a growth species, has a problem in that it cannot easily supply the hydrogen necessary for this carbon removal.

[0008] In view of these problems, the present invention proposes that when producing a compound semiconductor, even if a solid raw material is used instead of a highly toxic raw material gas as typified by the above-mentioned GaAs production, there will be no damage in the produced film. It is an object of the present invention to provide an organometallic compound vapor phase growth method and apparatus capable of suppressing carbon contamination.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an organic metal containing one element constituting the compound semiconductor crystal when performing organic metal chemical vapor deposition of a compound semiconductor crystal on a semiconductor substrate. A material is supplied onto the substrate, a solid raw material containing other elements constituting the compound semiconductor crystal is vaporized and supplied onto the substrate, hydrogen gas is supplied as a carrier gas, and the hydrogen gas is activated by a catalytic reaction. The compound semiconductor crystal is grown by supplying the compound semiconductor crystal onto the substrate, and the apparatus includes an organometallic material source containing one element constituting the compound semiconductor crystal, and another material constituting the compound semiconductor crystal. A gasification device that gasifies a solid raw material containing an element, a hydrogen gas supply device that supplies hydrogen as a carrier gas, and a catalyst device that activates the hydrogen gas by a catalytic reaction and supplies it to the substrate. .

0010

[Operations and Effects] As described above, in the present invention, hydrogen in the carrier gas is activated using a catalyst in the dissociation of organic matter from an organometallic material containing one element constituting a compound semiconductor crystal. The dissociation of organic substances can be easily promoted without using hazardous gas and without increasing the size of the device, and solid raw materials containing other elements constituting compound semiconductor crystals can be used.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on embodiments shown in the drawings. FIG. 1 shows a schematic configuration of a growth apparatus for growing GaAs as an embodiment of the present invention.

In this apparatus, a T-shaped quartz tube (diameter 26 mm, length 400 mm) is used as the reaction tube 2,
A crucible 10 is formed using the T-shaped trunk portion as an arsenic reservoir.

A substrate 1 on which a GaAs film is to be grown is attached to a substrate holder 3 and placed at a T-shaped branch position within the reaction tube 2. Then, the substrate temperature is raised to 600~
The heating is externally controlled to about 800°C, for example 650°C.

In this embodiment, the substrate 1 is made of semi-insulating GaA doped with Cr and O and having a plane orientation of (100).
s substrate is used, which has been degreased and surface treated with sulfuric acid and hydrogen peroxide before being attached to the substrate holder 3.

The constituent elements of the compound semiconductor crystal, ie, GaAs, to be grown by chemical vapor deposition in this embodiment are each independently supplied to the substrate 1. That is, as a raw material for gallium, TMG 6 is introduced into the reaction tube 2 from the organometallic material inlet 5 by bubbling hydrogen gas to the substrate 1 in the figure.
It is introduced from the left. Here, the bubbling flow rate FTMG of the TMG 6 is controlled by the mass flow controller 7 as described later (in this example, it is 5×10−6
Furthermore, the flow rate FH of hydrogen gas introduced from the carrier gas supply port 8 as a carrier gas for the TMG 6 is controlled by the mass flow controller 9 as described later (in this example, the flow rate FH is 5×10 −4 m
3/min).

On the other hand, metal (solid) arsenic 11 is used as a raw material for arsenic, and is supplied as vapor from a crucible 10 below the substrate 1 in the figure. Note that the vapor pressure of arsenic is controlled by adjusting the temperature of the crucible 10 with a heater 12.
In this example, the arsenic vapor pressure was raised to 9.
It is approximately 2×103 Pa.

[0017] Here, the substrate holder 3 is the crucible 10.
The inner wall of the crucible 10 is heated to prevent reactants from adhering to it. The raw material gases of gallium and arsenic introduced into the reaction tube 2 in this way and the carrier gas are supplied to the surface of the substrate 1 through the platinum mesh 13 attached to the substrate holder 3 so as to cover the substrate 1, and the substrate 1 is caused to undergo a chemical reaction. A GaAs film is grown on top. And the reaction gas is supplied by rotary pump 1
5 and is discharged from the exhaust port 14. At the same time, the interior of the reaction tube 2 is pumped with a 1.3×104
The pressure is controlled to be reduced to approximately Pa.

Next, the bubbling flow rate FTMG of TMG6 and the flow rate FH of carrier gas (hydrogen) set in this embodiment will be explained. First, substrate 1 (semi-insulating G
In order to grow GaAs with crystallinity equivalent to that of aAs substrate), the molar ratio of group V elements to group III elements (V/III
ratio) is set. Crystallinity of grown film and V/III
The relationship with the ratio is shown in Figure 2. In Fig. 2, the crystallinity of the film is evaluated by the half width of the X-ray double crystal rocking curve using (400) reflection, and the V/III ratio is determined by the carrier gas flow rate FH and the bubbling flow rate FTMG of TMG.
It is derived from the following equation based on the flow rate ratio of .

[0019]

[Equation 1] V/III = (PAS/PTMG) x (FH /F
TMG) Here, PAS and PTMG are each 535℃
The vapor pressure of arsenic (9.2×103 Pa) at 3℃
The vapor pressure of TMG (1.0×103 Pa) at

As is clear from FIG. 2, when the V/III ratio is increased to 45, the half width decreases to 0.015 degrees, which is the same as that of the bulk (substrate 1). That is, V/I
II. Each flow rate FH, F so that the ratio is 45 or more.
By setting TMG, it is possible to grow a GaAs growth film on the substrate with crystallinity comparable to that of the substrate.

Furthermore, in this embodiment, each flow rate FH
, carrier concentration mixed into the grown film for FTMG (
Optimum FH and FTMG flow conditions are set based on the dependence on the background carrier concentration (hereinafter referred to as background carrier concentration).

FIG. 3 shows the relationship between the background carrier concentration and the carrier gas flow rate FH in the case without the platinum mesh 13. In addition, TMG's bubbling flow rate FTMG
The conditions are 10×10 −6 m 3 /min, and the grown film is of P type. Further, the carrier concentration is determined by the Pauw method. As can be seen from Figure 3, FH is 5×10
-4m3/min, the carrier concentration is the minimum value 8×
1016 cm-3, and it can be understood that carrier contamination is reduced.

In addition, FIG. 4 shows FH under this flow rate condition (5
The relationship between the background carrier concentration and the TMG bubbling flow rate FTMG is shown when the platinum mesh 13 is not used (×10 −4 m 3 /min). As can be seen from Figure 4, FTMG is 5×10-6 m3/mi
At n, the background carrier concentration is the minimum value 2×101
6 cm −3 , and it can be understood that carrier contamination is reduced.

[0024] This FH has the least amount of carrier contamination.
, in order to grow a GaAs film under FTMG flow conditions and further reduce carriers mixed into the GaAs film,
In this embodiment, the substrate 1 is covered with a platinum mesh 13.

The function of the platinum wire mesh 13 will be explained below. In MOVPE using TMG, TM is generally produced in the gas phase.
G decomposes to produce monomethyl gallium (CH3 Ga) (reaction 1).

[0026]

[Chemical formula 1] (CH3)3 Ga→CH3 Ga+2CH3
Here, if arsine is present, monomethyl gallium reacts with AsH or As to eliminate methyl radicals in a gaseous state and generate GaAs on the substrate (reaction 2
, 3).

[0027]

[Chemical formula 2] GaCH3 +AsH→GaAs+CH4 ↑

[0028]

[Chemical formula 3] GaCH3 +As→GaAs+CH3 ↑However, in the case of this example using metallic arsenic as the raw material,
Since AsHx of arsine is not present, it is thought that the methyl radical is eliminated by hydrogen such as a carrier gas. That is, monomethyl gallium reacts with hydrogen molecules or hydrogen atoms on the substrate surface to generate GaAs (reaction 4).

[0029]

[Chemical formula 4] GaCH3 +H+As→GaAs+CH4
↑Therefore, in this (reaction 4), in order to promote the desorption reaction of methyl radicals and reduce carbon contamination, the substrate 1 is covered with a platinum mesh 13, and the raw material gas and carrier gas are passed through the platinum mesh 13. The liquid is supplied to the surface of the substrate 1.

That is, the platinum mesh 13 acts as a catalyst for activating hydrogen that reacts with monomethyl gallium in order to promote (reaction 4). In this embodiment, the platinum wire mesh 13
For example, an 80 mesh mesh is used, and a double structure is used to increase the surface area of the catalyst. In addition, the platinum mesh 13 is heated to 600 to
It is heated to 800°C, for example 650°C.

FIG. 5 shows the results of mass spectrometry of the gas phase products discharged from the exhaust port 14 using a quadrupole mass spectrometer (QMS), and the relative intensities of CH3 + and CH4 + and the substrate temperature, that is, the platinum mesh It is shown in relation to the temperature of No. 13.

From FIG. 5, it can be seen that the intensities of CH3 + and CH4 + become stronger as the substrate temperature increases. In addition, when a platinum catalyst is used, CH3 + and CH4 +
The strength is approximately 1.5 times that of the case without platinum catalyst,
It can be seen that (reaction 4) is promoted by the presence of platinum mesh 13.

Table 1 shows the carrier concentration, the half width of the X-ray rocking curve, and the etch pit density of the GaAs grown film when the platinum mesh 13 was used and when it was not used.

[0034]

[Table 1] From Table 1, it can be seen that when platinum mesh 13 is used, the background carrier concentration and etch pit density due to carbon contamination are reduced, and platinum is effective for high-quality GaAs growth using metallic arsenic. .

As described above, according to this embodiment, TM
When G is supplied by bubbling hydrogen gas and solid arsenic is heated and supplied as vapor to grow a GaAs film on a semi-insulating substrate in chemical vapor phase, the hydrogen gas of the carrier gas is activated by the catalytic reaction of platinum. Since the TMG is supplied to the substrate in the form of oxidized arsenic, it is possible to promote the elimination reaction of the methyl group of TMG on the substrate, and as a result, GaAs with less carbon contamination can be grown using TMG and solid arsenic as raw materials. Can be done. The carrier concentration of the sample grown using platinum mesh as a catalyst was 6 x 1015 cm-3, and the carrier concentration of the sample grown without using a catalyst was 2 x 1016 cm.
-3.

[0036] In the above embodiment, Ga
Although it was used to grow As, other solid materials such as P, S, and Se, as well as TEG, TEIn, TEAl, DEZn, etc.
If organic metals such as InAs, InP, G
aP, AlAs, AlP and its mixed crystals, ZnS,
ZnSe and its mixed crystals can be grown.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a GaAs film growth apparatus according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the half width of the X-ray double crystal rocking curve of a grown film and the V/III ratio.

FIG. 3 is a characteristic diagram showing the relationship between background carrier concentration and carrier gas flow rate FH.

FIG. 4 is a characteristic diagram showing the relationship between background carrier concentration and TMG bubbling flow rate FTMG.

FIG. 5 is a characteristic diagram showing the relationship between the relative intensities of CH3 + and CH4 + and substrate temperature.

[Explanation of symbols]

1 Substrate (semi-insulating GaAs substrate) 2 Reaction tube 3　Substrate holder 4 Infrared lamp 6 TMG 7 Mass flow controller 9 Mass flow controller 10 Crucible 11 Metal arsenic 12 Heater 13　Platinum wire mesh

Claims (2)

[Claims] 1. When performing organometallic chemical vapor deposition of a compound semiconductor crystal on a semiconductor substrate, an organometallic material containing one element constituting the compound semiconductor crystal is supplied onto the substrate to form the compound semiconductor crystal. A solid raw material containing other elements is vaporized and supplied onto the substrate, hydrogen gas is supplied as a carrier gas, and the hydrogen gas is activated by a catalytic reaction and supplied onto the substrate to grow the compound semiconductor crystal. An organometallic chemical vapor deposition method characterized by: 2. An apparatus for organic chemical vapor deposition of a compound semiconductor crystal on a semiconductor substrate, comprising: an organometallic material source containing one element constituting the compound semiconductor crystal; and another element constituting the compound semiconductor crystal. The present invention is characterized by comprising: a gasification device that gasifies the solid raw material contained therein; a hydrogen gas supply device that supplies hydrogen as a carrier gas; and a catalyst device that activates the hydrogen gas through a catalytic reaction and supplies it to the substrate. Organometallic chemical vapor deposition equipment.