JPS61135111A - Method of epitaxial growth of compound semiconductor - Google Patents

Abstract

PURPOSE:To reduce the irregularity of concentration of impurity by activating previously the hydrogenated gas at the higher temperature than is received on the substrate region. CONSTITUTION:With the purpose of growth of Ga0.7Al0.3As film, the susceptor 3 and the preheating body 12 are heated at each prescribed temperature by the high-frequency heating. then the AsH3 gas of 10% concentration is sent into the tube 1 together with the H2 gas 5l/min, the carrier gas, from the input port 1a on the top of the reaction tube 1. The TMGaTMAl gas is flowed into the tube 1 together with the H2 gas 600ml/min from the second input port (1g). The growth of film on the substrate is completed by the effect of these gases. The stable film of crystal growth is obtained by the less As molar fraction, and the quantity of deposition of As chemical compound adhering to the susceptor is reduced. The crystal defects caused by the organic metal compound being apt to thermally decompose is also reduced. The organic metal compound thermally decomposes before arriving at the substrate and adheres on the surface of the crystal, and the crystal defects caused thereby decreases.

Description

[Detailed Description of the Invention] (d) Industrial Application Field The present invention relates to a method for vapor phase growth of compound semiconductors.
GaAs and GaA1As are stable and have few crystal defects.
This paper attempts to provide 9 vapor phase growth methods.

(b) Conventional technology One of the vapor phase growth methods for compound semiconductors, such as gallium arsenide (GaAS), involves combining Ga as a gallium (Ga) source with a methi/L' group (-CH8) to form an organic compound. Using volatile trimethylgallium (TMGa) and arsine (AsH8), a hydrogen compound of As, as a source of arsenic (As), hydrogen was used as a carrier gas, and GaAs was deposited on a GaAs substrate by thermal decomposition. Methods of growing crystals are known (for example, Japanese Patent Application Laid-Open No. 58-2
(See Publication No. 13415).

Figure $4 shows an outline of a conventional vapor phase growth apparatus.

The reaction tube 111 is made of high-purity quartz, and has a raw material gas inlet (la), an exhaust gas outlet (lb), and a quadrangular pyramid-shaped susceptor that supports four GaAs substrates (21) on four sides. It is equipped with a through hole (lc) for introducing a rotating shaft (4) for rotating the 13+, and further includes a cooling water inlet (1d) for circulating water as a refrigerant on the outer periphery, a water channel (le), and a drain port. (If). Also, a heater ff1l for induction heating the substrate (2) on the susceptor (3) is provided outside the reaction tube m, and a reaction tube (If) in which the susceptor (3) is disposed is provided. 1) @[(P) at a constant temperature (e.g. 700℃
) Fake it while keeping K. (6) is the susceptor (3)
This is a motor that controls the rotation of the Also, (7) is 10*As
H11 gas supply part, 181191 is TMGa, TM
A/Gas supply section, (10a) to (10d) are carrier gas (H2) supply sections, and (lla-) to (llb) are pulp.

K, who grows GaAs crystal using this equipment, attaches the GaAs substrate (2) to the susceptor (3), heats the susceptor to a predetermined temperature with the heater (5), and then uses the TMQ
a, AsH3 is mixed with carrier gas H2 in a reaction tube (
1) A KGaAs crystal is grown on the substrate by thermal decomposition. At this time, in order to make the crystallinity uniform, the susceptor (3) is rotated, and in order to perform thermal decomposition efficiently, the cooling water in the water channel (i e ) K in the reaction tube T1) is flowed to cool the entire reaction tube. . FIG. 5 shows the correlation between the impurity concentration of the GaAs film and the supply amount of AsH3 when no impurity is added. Here, the GaAs substrate is heated to 700°C, and the concentration of AsH3 is 10@(AsH810*, H290
%), and the TMGaQ supply amount I x 10-4 mo/v/min is assumed to be constant. From this figure, the N-type grown film with little variation in impurity concentration has an AsHB gas flow rate of 400 m1:7.
1200 m//min.

When the flow rate is less than 400 trl'/min, the reproducibility of the impurity concentration deteriorates.

Figure 6 shows the impurity concentration and AsH3 supply of a GaO,s+A10.7As film grown using the above-mentioned apparatus without adding any impurities by newly adding trimethyaminium (TM, +1'). Shows correlation between quantities.

Here, the GaAs substrate is heated to 700°C, and the TM
AJ and TMGa were supplied at a rate of 0.25×10-'mo/v/min and 0.75×10-eyv1 min, respectively.
The concentration of sH1l gas is set to 10g6. Note that H2 was flowed as a carrier gas at 5 liters for 1 minute. From the same figure,
N-type Ga 0.7AJO with little variation in impurity concentration
,llAs grown film has an AsHa gas flow rate of 3000 m//
It can be seen that a large amount of gas is required for more than 1 minute.

(c) Problems to be solved by the invention As mentioned above, to obtain a crystal grown film with good reproducibility of impurity concentration, K is 400 m//min or more for GaAs without addition of impurities, and Ga06'r A z o without addition of impurities. ,a
A large amount of As over 'JK3000m//min'
Requires H3 gas. Furthermore, as the flow rate of AsH1l gas increases, As adducts generated when A11H8 gas is thermally decomposed adhere to the susceptor and cause defects in the crystal growth film. In order to suppress the precipitation of As additives, a method is used to further heat the susceptor, but if this is done, for example, if the temperature exceeds 800°C, there is a problem that re-evaporation of the grown film becomes intense and the crystal growth rate decreases. There is a problem in that the electron mobility of the crystal grown film decreases.

The present invention has been made with this point in mind, and it is an object of the present invention to provide a method for stably growing a compound semiconductor with fewer defects in a crystal grown film.

) Zero means to solve the problem #! 4 activates the hydride gas, which has conventionally been thermally decomposed on the substrate on the susceptor together with the organometallic compound gas, at a temperature higher than the temperature experienced on the substrate before reaching the area on the substrate. The method is characterized in that the region on the substrate is brought into contact with the organic metal compound gas and thermally decomposed together with the organometallic compound gas to grow crystals of the compound semiconductor on the substrate.

(The hydride gas brought to the substrate on which the crystal is to be grown due to thermal decomposition is heated to a higher temperature than that experienced during thermal decomposition and activated in advance, and in that state it is combined with the organometallic compound gas. Since it is thermally decomposed, a compound semiconductor with less variation in impurity concentration can be grown without introducing a large amount of hydride gas.

(f) Example First, the outline of a vapor phase growth apparatus for carrying out the method of the present invention will be explained with reference to the block diagram shown in FIG. In Figure 1, 4! Components having the same functions as those of the conventional device shown in FIG.

The reaction tube (lj) is equipped with an inlet (1f) for the second raw material gas, and AsH3 gas (concentration 10%), which is a hydride gas, and a carrier gas (I (2)) are introduced from the inlet (la),
TMG, which is an organometallic compound, is introduced from the second inlet (1)).
A, TMAJ, and a carrier gas are introduced. A preheating body (I) made of cylindrical carbon whose surface is coated with SIC is placed in the upper region of the part of the reaction tube ill where the susceptor (3) is arranged to constitute a preheating part. The preheating coil/L' installed on the outside of the reaction tube +l is configured to be heated by induction.Sase data (3) is heated to about 700°C, and preheating body 01J is heated to about 850°C. The temperature near the substrate and the preheating body are maintained at the same temperature.Characteristics shown adjacent to reaction tube +11 (Q indicates temperature distribution in region (9) inside the reaction tube).

In order to grow G30.7A and 10.8A$ films using this device, four GaAs sheets were placed on the four sides of the susceptor (31).
After mounting the substrate (2), the susceptor (3) and the preheater 0
4 is heated to a predetermined temperature by high frequency heating.

After that, 1 from the inlet (la) at the top of the reaction tube (1).
0% 4 degree AsHs gas was flowed together with H2 gas, which is f Yaria gas, at 51/min, and H2 gas and c600m//min were also flowed through the second inlet (11). The film is grown on the substrate by flowing as in the example. In order to make this grown film uniform, the susceptor (31) is rotated by a motor (6), and unlike conventional methods, cooling water is circulated through the water channel (1e) of the rounded reaction tube (1) for efficient thermal decomposition. It's the same.

[First embodiment] The susceptor (3) and the preheating body 01J are each made of 7 as described above.
After heating at 00℃, 850″CIC, 4 population (1a)
2 gas 517 minutes and 10% concentration AsH3 gas (As
10% H8, 10% H2) was poured into the second reaction tube (1).
TMG of IXIQ-'mo/L//min from the inlet (IP)
A was flowed together with H2 gas at 600 mJ/min to form a crystal growth film to which no impurities were added on the GaAs substrate (2).

FIG. 2 shows the correlation between the impurity concentration of the crystal grown film and the amount of AsH3 supplied in the first embodiment.

[Second Example] Everything except the state of the raw material gas supplied from the second inlet (1p)! 1% as in the example, TMGa and TMAJ with H2 gas from this second inlet (1) for 600 m//min.
0.75X10 morphs, 0.25X10 respectively
Mo, /I// was used to form a GaAs growth film on Ga 0 , 7A10 and 8 without adding impurities on the GaAs substrate (2). FIG. 3 shows the correlation between the impurity concentration of the crystal grown film and the amount of AsH3 supplied in the second example.

As is clear from FIGS. 2 and 3, a crystal grown film with a stable impurity concentration can be obtained with a relatively small amount of AsH3 gas compared to the results shown in FIGS. 5, kI/I, and 6 using the conventional method described above. It is now possible. In the second example, the composition ratio is G
a 0-7A I! (1-8A s is shown as an example, but the present invention is applicable to all GaχAJLχAs mixed crystal (0xχ<1) systems by adjusting the gas flow rate and the temperature of the susceptor and preheater.

(G) Effects of the Invention In the present invention, the hydride (AsH8) applied to the substrate is activated at a temperature higher than the temperature observed near the substrate before it is brought near the substrate, so the As moiety is lower. Why can you just obtain a stable crystal growth film with AsH?
3. As the As compound adheres to the susceptor due to a decrease in the flow rate,
This has the effect of reducing the amount of precipitation and reducing crystal defects that occur when organometallic compounds that are easily thermally decomposed are thermally decomposed and attached to the crystal surface before reaching the substrate.

[Brief explanation of drawings]

Figure hl/IJ1 is a schematic diagram of a vapor phase growth apparatus for carrying out the method of the present invention, and Figures h42 and 3 are crystal impurities rJI! according to different embodiments of the method of the present invention. FIG. FIG. 4 is a schematic configuration diagram of a conventional vapor phase growth apparatus, and FIGS. 5 and 6 are correlation diagrams of impurity concentrations of two types of crystals and AsH3 supply amount according to the conventional method. (1) Reaction tube, (1'a) (IF) Raw material inlet, (2) Substrate, (3) Susceptor.

Claims (1)

[Claims] (1) In a compound semiconductor vapor phase growth method in which a compound semiconductor crystal is grown by thermally decomposing an organometallic compound gas and a hydride gas on a preheated substrate, the hydride gas is deposited on the substrate and the compound semiconductor crystal is grown. A method for vapor phase growth of a compound semiconductor, characterized in that the temperature is applied at a temperature higher than the processing temperature on the substrate.