JPS61134013A - Compound semiconductor crystal growth method - Google Patents

Abstract

PURPOSE:To bring Ga atoms and Al atoms depositing on a substrate to the state in which both atoms abound in reactivity, and to enable growth at a low temperature by electron-exciting a raw material gas by beams proper to molecular absorption. CONSTITUTION:H2 gas as a carrier gas is fed previously into a reaction pipe 1 at the rate of 10l/min from a third introducing port 2c, a susceptor 3 on which a substrate 4 is placed is heated and held at 470-750 deg.C, a temperature is stabilized and a first light source 8a and a second light source 8b are started, and each laser beam is induced to first and second introducing ports 2a, 2b through mirrors 9a, 9b. AsH3 at the rate of 4.6X10<-3>mol/min is added into H2 gas at the rate of 10l/min beforehand fed from the third introducing port 2c, and induced into the reaction pipe 1. TMG at the rate of 0.7X10<-4>mol/min and H2 gas for carriers at the rate of 0.5l/min are fed from the first introducing port 2a, TMA at the rate of 0.2X10<-4>mol/min and H2 gas for carriers at the rate of 1l/min are supplied from the second introducing port 2b, and a crystal is grown. Accordingly, a Ga0.7Al0.3As crystal obtained has the large mobility of the crystal (maximum 3,220cm<2>/V.S) and holds high mobility up to a substrate temperature of approximately 580 deg.C.

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a compound semiconductor crystal growth method,
More specifically, the present invention relates to a method for vapor phase growth of compound semiconductor crystals using photo-assisted reactions.

(b) Conventional technology One of the vapor phase growth methods for compound semiconductors, such as gallium arsenide (GaAs), involves the use of trimethylgallium (TMG), a type of organic gallium, and arsine (A3), a hydride of arsenic.
11@) Method of crystal growth using thermal decomposition of gas,
So-called Metal Organic Chemical
VaporDepos it 1on (NO-CVD
) method 0Usually, hydrogen (H2) gas is used as the carrier gas.

Such a vapor phase growth method is carried out using a vertical vapor phase growth apparatus shown in FIG. This punch is a quartz reaction tube <1)
A gas introduction pipe (2) for introducing raw material gas consisting of TMG and A3H3 gas together with a carrier gas was provided at the upper end, and a susceptor (3) placed on a pyramid-shaped susceptor (3) was installed inside the reaction tube (1). A crystal substrate (4) is installed, and a susceptor (3) is installed.
) is rotated by a rotating shaft (6) that can be rotated by a motor (5) to prevent uneven thickness of the grown film. Further, a coil (7) is attached to the outer periphery of the reaction tube 1) where the crystal substrate (4) is completely installed, so that high-frequency power can be completely supplied to the filter. During this heating, the crystal substrate (
4) to prevent the raw material gas supplied from the gas introduction tube (2) from being thermally decomposed before reaching the crystal substrate, and to efficiently perform thermal decomposition on the crystal substrate.
The cooling medium (cooling water) is introduced from the cooling medium inlet (la), circulates through the water channel (1b) of this double structure, and is led out from the cooling medium outlet (1c). I try to let them do it. (ld) is a residual gas outlet.

The vertical vapor phase growth apparatus configured in this manner has a simple reaction tube and can easily grow GaAs crystals and the like. The basic type of this conventional device is, for example, disclosed in Japanese Patent Application Laid-open No. 1983-
It is introduced as a conventional example in the publication No. 213415.

(c) Problems to be solved by the invention However, in the above crystal growth method, the substrate temperature is 600°C.
Below this, there is a drawback that high quality crystals cannot be grown. Furthermore, GaI-xAQxA8 (0< x <1
) etc., it is difficult to obtain high quality crystals at temperatures below 700°C.

FIG. 4 is a diagram showing the relationship between the crystal substrate temperature of GaAs grown by the method described above and the mobility at 77K. As is clear from this, the best quality crystal is obtained when the crystal substrate temperature is around 640°C, and a crystal suitable for semiconductor devices cannot be obtained at a temperature below 600°C.

Furthermore, in order to improve the performance of semiconductor devices, microscopic defects in crystals must be reduced. In particular, compound semiconductor crystals include As or P in the VO group of the periodic table of elements.
In order to contain elements with high dissociation pressure such as, it is necessary to lower the temperature of the crystal substrate, prevent the dissociation of the Vb element, and reduce the number of vacancies in the Vb element.

As this low-temperature growth, there is a vapor phase growth method using a light-assisted reaction. (Applied Physics Vol. 52 No. 7 p560-566
Photo-excited CVO, see this method is a substrate heating method that uses optical energy as a heat source, and is effective for pyrolytic crystal growth of TMG+Ash adsorbed on the substrate surface. By employing this method, a high quality GaAs crystal can be grown even if the crystal substrate temperature is lowered to about 450°C.

However, this method uses a single light, @ (wavelength energy), to detect TMG, TMA (trimethylaluminum), A
Since pyrolytic crystal growth such as SH:l is performed, the effect of lowering the temperature is significantly inferior in mixed crystal systems. Figure 5 is Ga←
The solid line (P) in the figure 0, which is the relationship between the crystal substrate temperature and the mobility of the obtained Gao,tAQc+,3As at room temperature when the mixed crystal ratio of x-AlxAs is x-0,3, is photo-assisted. In this case, the optimum substrate temperature is 750 to 800°C. Case 111 (Q) is the case where the substrate was irradiated with a KrF excimer laser having a wavelength of 248 nm, and the optimum substrate temperature was 650 to 730°C, and a temperature reduction of 100°C was attempted. However, no increase in mobility was observed.

(d) Means for solving the problems The present invention uses two types of organometallic compounds (for example, TMG and TM).
A) Optimal light energy for each (wavelength 2 for TMG)
48r+m (7) KrF excimer laser, TMA is irradiated with ArF excimer laser with a wavelength of 193 nm,
By electronically exciting these raw material gases, active atoms (such as G
a and AQ), and these and a hydride (e.g. ASHO)
In this method, atoms (As) are preheated to grow crystals on a crystal substrate. Furthermore, the present invention provides optimal light energy for electronic excitation not only for organometallic compounds but also for hydrides (for example, for ASH3, the wavelength is 193nm).
irradiation with ArF excimer laser (ArF excimer laser).

(E) Effect The present invention provides the optimal light energy (
Since the atoms constituting the crystal are activated by electron excitation and transfer by irradiation with light having a certain wavelength (wavelength), high-quality crystals with high mobility can be produced even if the preheated substrate is at a low temperature.

(F) Embodiment FIG. 1 is a schematic diagram of an embodiment of a vapor phase growth apparatus for applying the method of the present invention. In the figure, functional elements that are the same as those of the conventional device shown in FIG. 3 are given the same reference numerals, and explanations thereof will be omitted.

This device uses two types of organometallic compounds, TMG and TMA.
and a third inlet (2c) that introduces AsH3, which is a hydride, into the reaction tube (1). In addition, first, second, and third light sources (8a) exhibiting optimal light energy for each raw material gas to excite the z111 molecules in each raw material gas introduced into the reaction tube (1).
(8b) (8c), and mirrors (9a) (9b) (9c) for guiding light from each of these light sources to the raw material gas. The first light source (8a) is a K rF excimer laser (energy density 100 w/am", wavelength 248 nm) that irradiates the optimal light energy for TMG introduced into the reaction tube (1) from the first introduction port (2a). Yes, the second and third lights fi (8b) (8c) are the second
, an ArF excimer laser (energy density 80w/cIT+2, wavelength 193nm) that irradiates optimal light energy for TMA and AsH3 introduced into the reaction tube (1) from the third inlet (2b) and (2c), respectively.
> is.

FIG. 2 shows GaatAu manufactured using the above-mentioned apparatus. =A
This shows the relationship between the mobility of the s crystal (room temperature) and the temperature (substrate temperature) of the GaAs crystal substrate (4) placed on the susceptor (3), and the characteristics (R) and (S) are as follows, respectively. This is according to the first and second embodiments.

(First Example) H2 gas, which is a carrier gas, is introduced into the third inlet port (2c
) into the reaction tube (1) at a rate of 10Q7 minutes, and the susceptor (3) on which the substrate (4) was placed was heated at 750°C to 47°C.
The temperature was maintained at 0'C. After the temperature stabilizes, the first light source (
8a) and the second light source (8b) are activated, and the respective laser beams are passed through the mirror (9aH9b) to the first and second inlet ports.
2aH2b). Next, the third inlet (2c)
AsH gas was supplied in advance at 10 g/min from H2 gas.
3 is added at 4.6 x 10-3 mol/min and introduced into the reaction tube (1). Next, 0.0.
7XIO-4°mol/min and H2 gas for carrier 0.5
11/min and also TMA from the second induction port (2b).
0.2X 10 → mol/min and H2 gas 1 for carrier
supply hours per minute. With such a gas supply amount, crystal growth was performed at a substrate temperature of 750° C. to 470° C. As a result, Gact Ak3 A shown by the characteristic (R) in Fig. 2
s crystal could be produced. This is the characteristic shown in Figure 5 (
The crystal mobility (maximum value is 3220an2/Y-S) is significantly higher than the crystal mobility obtained by the conventional method (maximum value is 2800cm"/V・S) as shown in Q), and the substrate temperature is 580cm"/V・S.
It maintains high mobility up to around °C.

(Second Example) In the first example above, no optical energy is applied to the ASH3 supplied from the third inlet (2c), but this example uses the same system as the first example. In addition, light energy is applied to the ASH3 from a third light source (8c). The relationship between the substrate temperature and the mobility obtained by this growth method is further improved than that of the first embodiment, as shown in the characteristic (S) in FIG. Immediately, the temperature was lowered by as much as 50° C., and a good crystal was produced in which the dissociation of As and the thermal distortion of the mixed crystal film were further reduced.

(g) Effects of the Invention As described above, in the method of the present invention, the raw material gases are electronically excited in advance with light suitable for molecular absorption of each raw material gas, so Ga atoms and AQ atoms deposited on the substrate are It is in a highly reactive state, and the density of Ga vacancies and vacancies that occur when reactivity decreases can be reduced, and thermal excitation of vb atoms (AsjK atoms) is not required. This makes low-temperature growth possible. In addition, the present invention relates to Ga1-xAQx
Although the embodiments regarding As have been described in detail, the present invention also applies to Ga.
It goes without saying that good quality crystals can be obtained by selecting an excitation light source even when growing As crystals, InP, or mixed crystals thereof.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a vapor phase growth apparatus for carrying out the method of the present invention, Fig. 2 is a characteristic diagram of substrate temperature versus mobility of a crystal according to the method of the present invention, and Fig. 3 is a schematic diagram of a conventional vapor phase growth apparatus. Diagram,
Figures 4 and 5 show GaAs crystal and GaC obtained by the conventional method.
FIG. 2 is a characteristic diagram of substrate temperature versus mobility of Lt kQa* As crystal. (1)...Reaction tube, (8a) (8b) (8c)-first
, second and third light sources.

Claims (2)

[Claims] (1) A method in which two types of organic metal compounds and a hydride are introduced as starting compounds onto a substrate that has been preheated in a reactor, and a compound semiconductor crystal is grown by a pyrolysis method. A compound semiconductor crystal growth method characterized in that the metal compounds are excited with different light energies suitable for each organometallic compound. (2) The hydride is excited with light energy suitable for the hydride.
1) Compound semiconductor crystal growth method described in section 1).