JPH03244119A - Vapor growth method for group iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:To uniformize characteristics with uniform film thickness of a group III-V compound by enlarging the flow ratio of a group III material carrier gas and by displacing a position of mixture of III and V group material carrier gases from the substrate end to the upstream side of gas flow. CONSTITUTION:A group III material carrier gas is introduced from the first supply port 1, and a group V material carrier gas from the second supply port 2. In this case their introduction into the same reaction furnace 10 equalizes pressures on the Bernoulli theorem so that the group V material carrier gas is led into the supply port 1 on the side of group III material carrier gas in the vicinity of outlet of the supply port 2. It follows that a position of mixture of a group III material carrier gas and a group V material carrier gas is displaced from a vapor growth substrate 3 to the side of supply port 1: this provides an effect equal to that of displacement of the vapor growth substrate 3 from region A to B side. This process enables preparation of uniform film thickness of a group III-V compound to uniformize characteristics, thereby realizing a semiconductor device to a purposed design.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for vapor phase growth of ■-V group compound semiconductors, and in particular, for example, GaTnAs, i'
MOCVII (M
etalOrganic Chemical Vapo
r Deposition: Formed by a metal-organic chemical vapor deposition method to form a semiconductor device, e.g.
This is to obtain an ET (field effect transistor).

[Summary of the invention]

■-In the vapor phase growth method for group V compound semiconductors, a group III raw material carrier gas and a group V raw material carrier gas each containing a group III raw material gas and a group V raw material gas are separately controlled in a reactor. First and second gas supply ports are provided in the vicinity of the placement portion of the substrate to be subjected to vapor phase growth, and the flow rate of the Group Ⅲ raw material carrier gas is adjusted to the CIII level.
When the flow rate of the group V raw material carrier gas is CV,
(2) Improve the controllability of the film thickness of the V group compound semiconductor and improve its characteristics.

[Prior Art] In recent years, 111-V group compound semiconductors have been developed, for example, by AZGaln.
P-based semiconductor laser device, selectively doped AI InAs/
It has been widely used in high electron mobility transistors (so-called IIEMTs) using two-dimensional electron gas channels having a Ga InAs structure.

It is extremely difficult to epitaxially grow such compound semiconductors such as ^ZGalnP and Ga1nAs due to thermodynamic limitations, and research and development on epitaxial growth by MOCVD is underway.

The production of the 1-2 group compounds such as AZGaInP is carried out by a methyl-based or ethyl-based MOCVD method. - For boat fishing, the feedstocks for group III metals AI, Ga, and In are organometallic gases such as triethylaluminum, triethylaluminum, and
Using triethylgallium and triethylindium (hereinafter abbreviated as TEAZ, TEGa, and TEIn, respectively), phosphine Pl+3 was used as the feedstock gas for P (phosphorus).
(Arsine As feedstock gas for As (arsenic))
13 is used.

However, in this case, the raw material bases, for example, TEIn and Pl+3, are thermally unstable, whereas TEIn is thermally unstable.
It has been reported that PH is extremely thermally stable, and that when the two are mixed at room temperature, an intermediate parasitic reaction occurs, producing a polymer with a low atmospheric pressure.

Therefore, in order to suppress such intermediate parasitic reactions,
Methods such as reducing the pressure inside the reactor or decomposing and supplying PI in advance have been adopted, but when using reduced pressure growth, the equipment is not only complicated but also has poor controllability.
P) When using the method of pre-decomposing la, the temperature of the supplied gas is increased, so when the decomposed gas and the thermally unstable Tt3+n as described above are mixed together,
There is a problem that undesirable decomposition of TELn and intermediate reactions tend to occur.

Therefore, in Japanese Patent Application Laid-Open No. 61-35514, the applicant proposed (1) to supply Group V raw material gas independently to the reactor, mix both substrates just before reaching the substrate, and form AfGal on the substrate.
We proposed a method for epitaxially growing an nP-based ■-V group compound semiconductor layer.

In the Ga1nAs and AZInAs systems as well, ■.

Good semiconductor compounds have been obtained by the above-mentioned method in which the Group (1) raw material gases are independently introduced into the reactor.

However, it is difficult to make the film thickness of the semiconductor compound produced by this method uniform; for example, the film thickness is large at the center of the wafer and is small at the periphery, which is an inconvenience. Ru.

Thus, for example selectively doped At InAs/Ga In
When a FET with an As structure is fabricated, if the film thickness is d, then
The threshold voltage vth is proportional to the square of the film thickness d2 when the doping is uniform, and proportional to the film thickness d when the doping is performed in a line or only partially in a certain layer. Therefore, as the film thickness becomes non-uniform, the threshold voltage vth also becomes non-uniform, making it difficult to obtain a semiconductor device with desired characteristics.

The object of the present invention is to provide a method for vapor phase growth of a -V group compound semiconductor, which makes it possible to fabricate a compound semiconductor device having a film thickness or characteristics of -1.

[Means for Solving the Problems] FIG. 1 shows a cross-sectional view of the essential parts of an example of a vapor phase growth apparatus used in the method for vapor phase growth of IV group compound semiconductors according to the present invention.

■-In the vapor phase growth method for group V compound semiconductors, a group III raw material carrier gas and a group V raw material carrier gas each containing a group III raw material gas and a group V raw material gas are separately provided in a reactor (10). First and second gas supply ports (1) and (2), which can be separately controlled and fed, are provided near the placement part (4) of the substrate (3) to be subjected to vapor phase growth, and The flow rate of the raw material carrier gas is C11r, and the flow rate of the group V raw material carrier gas is CV.
, v (Function) As described above, in the vapor phase growth method of the ■-V group compound semiconductor according to the present invention, the group ■ and group ■ raw material gases are independently supplied to the reactor. In order to avoid intermediate parasitic reactions, it is therefore desirable that the raw material gases be mixed as much as possible immediately before the substrate (3) to be subjected to vapor phase growth, as shown in FIG.

In addition, the raw material gas mixed just before the substrate (3) moves on the substrate (3) at a certain flow rate, and the process of movement occurs in a region where the growth rate of the compound increases, as shown in Figure 2. It can be roughly divided into three regions: A, region B where the growth rate is approximately constant, and region C where the growth rate decreases.

Therefore, in order to make the film thickness uniform, it is desirable that the substrate (3) to be subjected to vapor phase growth be placed in region B, but as mentioned above, the mixing of the raw material gases should be done just before the substrate (3). Therefore, the base body (1) is substantially shifted toward the area A side.

Such a growth rate distribution is generally determined by the mixture of raw material gases,
It is determined by a combination of elementary processes such as decomposition and diffusion, and the conditions for each elementary process vary depending on the shape of the reactor, growth temperature, etc., but especially in the case of ■-V group compounds, the Since the supply of raw materials is the rate-determining factor for MOCVD, it is expected that the growth rate distribution described above will be greatly influenced by the flow rate and flow rate of the carrier gas for the Group I raw materials relative to the Group V raw materials. Ru.

Therefore, the ratio of the flow rate CIII of the group ■ raw material carrier gas to the flow rate CV of the group V raw material carrier gas, CIII/(C■ +
When CV) was set to 0.77 or more and less than 1.0, a sufficiently uniform film thickness region was obtained.

This seems to be due to the following phenomenon.

In FIG. 1, it is assumed that the Group Ⅰ raw material carrier gas is introduced through the first supply port (1) and the V Group raw material carrier gas is introduced through the second supply port (2). According to Hernoulli's theorem, the gas flow is expressed by the sum of dynamic pressure and static pressure, and within the gas supply ports (1) and (2) on the group Ⅰ side and the group V side. ω1.
ω2 is each flow velocity in each supply port (1) and (2), P,,
P2 is each static pressure, and ρ is the density. Each supply port (1) and (
The shapes of 2) are designed to be the same, and in this case, the supply flow rate and flow rate can be converted by a certain constant.

In this case, since they are introduced into the same reactor (10), the pressures are equal, so the constants on the right side are equal, ω, 〉ω
2, it becomes P+(Pz. Therefore, the group V raw material carrier gas will be drawn into the supply port (1) on the group ■ group raw material carrier gas side near the daylight of the supply port (2), and The position where the group raw material carrier gas and the group (2) raw material carrier gas are mixed is from the vapor phase growth substrate (3) to the supply port (1
) side, and from the area in Figure 2 to B
The same effect will be obtained if the vapor phase growth substrate (3) is shifted to the side.

As a result, the film thickness of the -V group compound can be made uniform, and the characteristics can be made uniform, that is, a semiconductor device according to the intended design can be obtained.

〔Example〕

Hereinafter, a method for vapor phase growth of a ■-V group compound semiconductor according to the present invention will be explained with reference to FIG.

In FIG. 1, (10) is a reactor made of, for example, a quartz tube, and inside the reactor (10) is an arrangement part (10) on which a vapor phase growth substrate (3) made of, for example, a circular InP single crystal is placed. 4
) will be established. This arrangement (4) is set in such a way that the substrate (3) thereon is brought to the required temperature by heating.

This heating means is, for example, a reaction furnace (10), although not shown.
This can be achieved by high-frequency induction heating means using a high-frequency coil provided externally. Further, although not shown in the drawings, the base of the placement part (4) is provided with a rotating means that rotates on its central axis, thereby making it possible to obtain a compound semiconductor having a more uniform film thickness.

Then, at a height between the upper surface of the substrate (3) on this arrangement part (4) and the inner wall surface of the upper part of the reactor (10), and its end surface is above the - side end of the substrate (3). so that it is close to
A first supply port (1) and a second supply port (2) are provided. These first and second supply ports (1) and (2) are
Although not shown, the cross-sectional shape is the same, and the width in the direction perpendicular to the plane of FIG. 1 is, for example, a rectangle that is equal to the diameter of the base body (3).

In such a configuration, for example, a trimethyl compound of group Ⅰ metal, such as trimethyl gallium Ga(CI+3)3
Group Ⅰ raw material carrier gas, in which less than 0.1% of hydrogen H and trimethylindium In(CH3)3 are mixed in the carrier gas at the required mixing ratio, is fed to the first supply port (as shown by arrow g+). 1), and a group V raw material carrier gas in which less than 10% of arsine ASH3 is similarly mixed in carrier gas hydrogen H2 as a V group raw material is fed from the second supply port (2) as shown by arrow g2. Send it in. At this time, the temperature of the substrate (3) is maintained at, for example, 640°C.

In this way, the third and second supply ports (1) and (2)
Each raw material carrier gas introduced from
The compound semiconductor Ga1nAs can be grown on the substrate (3) by moving along the upper surface of the substrate (3) as shown in FIG.

In this case, at each supply port (1) and (2),
Flow rate 10I! , the flow velocity is approximately 1 m/sec in the case of 7 minutes.

By the method described above, a diameter of 2 inches (approximately 50+n
m ) InP one? --For C (3), a group IV compound semiconductor was grown by changing the flow rates of the m and v group raw material carrier gases as shown in Table 1. In addition, after performing vapor phase growth for 1 hour without rotating the placement table (4) on each side, the film thickness of the compound semiconductor layer produced on the substrate (3) was measured using an SEM (scanning electron microscope). It was measured by

Table 1 In Table 1, cm is the flow rate of group II raw material carrier gas, C
V is the flow rate of the group V raw material carrier gas, and each unit of 1 2 is 27 minutes. Note that in the above example, the supply port (1
) and (2) are made equal, so when the flow velocity of each raw material carrier gas is vm and Vv, CIII/
(CIII+CV) is replaced by Vm/(Vm+Vv).

FIG. 3 shows the distribution of the film thickness of the compound semiconductor, in this case GaInAs, with respect to the distance from the open end (5) of the supply port, that is, the end of the vaporized substrate (3) on each side.

In FIG. 3, a to f indicate the distribution of film thickness under the flow conditions of Comparative Examples 1.2 and Examples 1 to 4, respectively, as shown in Table 1.

As shown in FIG. 3, it can be seen that the film thickness is approximately constant from a certain distance, that is, the growth rate is constant.

Flow rate ratio CIII/(CIII+CV), that is, Vm/(
FIG. 4 shows changes in the distance at which the growth rate starts to become constant with respect to Vm→Vv). As shown in Figure 4, CII
It can be seen that by changing the ratio between I and CV, that is, the ratio between Vm and Vv, the distance over which the growth rate becomes constant is approximately proportional. In this case, the case is shown in which the growth is performed without rotating the placement table (4), that is, the wafer (3) on it, but if the wafer (3) is rotated, the non-uniform part of the film thickness in the stopped state is By passing through a position substantially away from the open ends (5) of the supply ports (1) and (2), the portion where the film thickness increases to a certain extent widens. Considering this, even for 2-inch wafers, the flow velocity ratio that can form a uniform film thickness over a distance of 35 mm,
As shown in FIG. 4, if the flow velocity ratio is 0.77 or more, it is possible to obtain a substantially uniform film thickness, that is, substantially uniform characteristics over one-third or more of the area. Furthermore, in order to increase the area with uniform film thickness, it is desirable to set the flow velocity ratio to about 0.83 or more. In this case, if the flow rate ratio of the Group Ⅰ raw material carrier gas is less than 1.0, a uniform Ga film thickness can be obtained.
An InAs film was obtained.

In addition, in Comparative Example 1 and Example 4, the thickness of the compound semiconductor, that is, the growth rate, is lower overall than on the other sides, but this is the case before and after cleaning the device. This is a change that occurred later, and as shown in Figure 4, when looking at the relationship between the flow velocity ratio of each raw material gas and the distance at which the growth rate is constant, it is on a straight line L, indicating a proportional relationship. I understand that.

Further, in the above-mentioned example, a Ga1nAs compound was grown on the InP single crystal substrate (3), but the present invention can also be applied to the production of other ■-V group compound semiconductors.

〔Effect of the invention〕

As described above, according to the group ■-■ gas phase kainacho method according to the present invention, by increasing the flow rate ratio of the group ■ raw material carrier gas, the position where the group ■ and ■ group raw material carrier gases are mixed can be adjusted to It can be substantially shifted upstream in the gas flow from the end of the substrate to be subjected to vapor phase growth.

Therefore, as shown in FIG. 2, it is possible to increase the region B on the substrate where the growth rate is constant with respect to the distance from the supply port, and the flow rate ratio C of the group (III) raw material carrier gas can be increased.
III/(CIII+CV) 0.77 or more 1.0
If it is less than, for example, it is possible to obtain a region with a constant film thickness, that is, with a constant threshold voltage vth, of about one-third or more of the area on a 2-inch wafer substrate, and to make the characteristics uniform, A semiconductor device as designed can be obtained.

Furthermore, the distance from the supply ports (1) and (2) to the substrate (3) is unique to the device, and it is very difficult to make it variable in terms of design. For example, since the pressure difference due to the difference in flow rate of each raw material carrier gas is utilized, there is no need to make any particular changes to the apparatus, and the characteristics can be easily made uniform.

Also, for example, FETs such as AI InAs/Ga1nAs
In the fabrication of steep dissimilar semiconductor interfaces (heterointerfaces)
In order to obtain this, the flow rate, that is, the flow rate, of the group III raw material carrier gas is increased, and the switching time of the raw material gas is shortened, since the group III raw material carrier gas is the rate-limiting supply in the growth of the ■-V group compound by the MOCVD method. Although it is desirable to make the time as short as possible, this is also a preferable method in the method of the present invention because the flow rate of the group (1) raw material carrier gas is made higher than the flow rate of the group (2) raw material carrier gas.

5 6

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the main parts of the vapor phase growth apparatus used in the present invention, Figure 2 is a diagram showing the relationship between the distance from the source gas supply port and the growth rate of compound semiconductors, and Figure 3 is a comparison. Example 1.2
FIG. 4 is a diagram showing the distribution of film thickness with respect to the distance from the supply port in Examples 1 to 4. FIG. It is a figure showing the relationship with the distance which becomes. (1) is the first gas supply port, (2) is the second gas supply port, (3) is the vapor phase growth substrate, (4) is the arrangement portion, (5) is the open end, and (10) is the The reactor (11) is a vapor phase growth apparatus.

Claims (1)

[Claims] In a method for vapor phase growth of III-V compound semiconductors, a group III raw material carrier gas and a group V raw material carrier gas each containing a group III raw material gas and a group V raw material gas are separately controlled in a reactor. First and second gas supply ports are provided in the vicinity of the placement of the substrate to be subjected to vapor phase growth, and the flow rate of the Group III raw material carrier gas is C_III, and the flow rate of the Group V raw material carrier gas is C_III. When the flow rate is C_V, 0.77≦C_III/C_III+C_V<1.0
A method for vapor phase growth of a III-V compound semiconductor, characterized in that: