JPH0691022B2 - Compound semiconductor thin film vapor phase growth equipment - Google Patents

Description

The present invention relates to an apparatus for vapor phase epitaxial growth of a III-V group compound semiconductor, and in particular, to an extremely small defect in the grown crystal.

[Conventional technology]

Compound semiconductors such as GaAs and InP are used in optical devices, semiconductor lasers, high electron mobility transistors, etc., and they have excellent characteristics that conventional Si semiconductors do not have. ing.

As a method for obtaining such a compound semiconductor, there are a Czochralski method by pulling from a melt capable of producing a large bulk crystal, a horizontal Bridgman method using a quartz boat, and the like. A thin film layer having a desired conductivity type, carrier density and mixed crystal ratio is formed on the wafer, which is cut out from the bulk crystal into a thin plate and finished through the steps of mechanical polishing, chemical etching, etc. A semiconductor device is manufactured by manufacturing the semiconductor device in multiple layers and further performing steps such as vapor deposition of metal electrodes. One of the methods for forming such a thin film layer is a method for epitaxially growing a target crystal on a substrate in a gas stream of a halogen compound or a hydrogen compound. This vapor phase epitaxial growth method has an advantage that a uniform thin film layer can be easily obtained on a large-area substrate. Among them, an example of a vapor phase growth apparatus for performing vapor phase growth using an organic metal is described below. Shown in the figure. In this device, a quartz susceptor holder (4) is arranged in a horizontal reaction tube (1) provided with a water cooling jacket (2) around the reaction tube (1) having a wedge-shaped cross section on the susceptor holder (4). A susceptor (6) having a forwardly inclined slope is placed toward the gas inlet (5) side of the raw material gas (a) with its sharp end facing the gas inlet (5), and the reaction tube (1) is placed. Water cooling jacket (2)
The compound semiconductor substrate (14) mounted so as to form the same plane as the above-mentioned inclined surface of the susceptor (6) is heated to a predetermined temperature by the high frequency induction coil (3) arranged outside. When growing a GaAs single crystal in such an apparatus, a mixture of a group V hydride gas, arsine (AsH ₃ ) and a group III source gas, trimethylgallium (TMG), as a source gas (a). Using a gas, the carrier gas (H ₂ etc.) (c) is sent from the gas inlet (5) into the reaction tube (1) to cause a thermal decomposition reaction or the like on the heated substrate (14). GaAs on the substrate (14) by
Growing single crystal thin film.

As another growth apparatus, as shown in FIG. 5, a susceptor (6) having a hemispherical upper part and a regular polygonal pyramid lower part in a vertical reaction tube (10) provided with a water cooling jacket (2) around the susceptor (6). Is vertically supported by a support shaft (11) provided on the lower end surface thereof,
The compound semiconductor substrate (14) was attached to each side surface of the susceptor (6) so that the surface thereof was flush with the side surface of the susceptor (6), and was placed outside the water cooling jacket (2) of the reaction tube (10). The high frequency induction coil (3) heats the compound semiconductor substrate (14) mounted on each side surface of the susceptor (6) to a predetermined temperature. In order to grow a GaAs single crystal with such an apparatus, as in the above, AsH ₃ gas and TMG gas are used as the source gas (a) together with the carrier gas (c) and the gas provided at the upper end of the vertical reaction tube (10). It is sent from the introduction pipe (5) into the reaction pipe (10), and a thermal decomposition reaction or the like is caused on the heated substrate (14) to cause the reaction on the substrate (14).
It is a single crystal of GaAs thin film.

In these cases, the homogeneity and completeness of the semiconductor crystal grown on the substrate and the characteristics of the crystal largely depend on the flows of the source gas and the carrier gas, and it is known that the laminar flow is the best state. Has been. Therefore, when using the horizontal reaction tube, as shown in FIG. 4, the compound semiconductor substrate (14) is attached to the upper portion of the slope of the susceptor (6) having a wedge-shaped cross section, and the tip portion of the lower wedge-shaped gas rectifying portion ( 15)
The gas flow is applied to the slope of the rectifying section (15) so that a uniform laminar flow flows over the substrate (14). When a vertical reaction tube is used, as shown in FIG. The upper part of the susceptor (6) is a hemispherical carbon gas rectifier (1
5), and by supplying gas from above the apex of this hemisphere, laminar flow is made to flow down to each surface of the susceptor (3) below.

[Problems to be solved by the invention]

However, the group V hydride gas generally used as a raw material is
Temperature range for crystal growth of III-V group compound semiconductors (6
The thermal decomposition rate is low at 00 to 800 ° C. (particularly at 600 to 700 ° C.), and the decomposition rate is affected by the catalytic action of the polycrystal of the compound attached to the susceptor and the gas rectifying portion. For this reason, the crystals grown immediately after cleaning the gas rectifying section and immediately after removing the deposits on the susceptor surface are the same as the crystals grown with the deposits adhering to the gas rectifying section surface over time. Show different characteristics,
The yield was reduced, and each obtained crystal had instability in quality.

Furthermore, when the same material as the susceptor is used as the material of the gas rectifier, it is heated to the same temperature as the substrate, so the source gas is thermally decomposed where it hits the gas rectifier, and the above-mentioned polycrystalline deposits Will be generated. Therefore, as a method of avoiding this, in order to prevent the gas rectifying section from being heated by induction heating, quartz is usually used as the material of the gas rectifying section. However, even if quartz is used in this way, the above-mentioned deposits do not exist at all, and they are slightly generated. Further, the deposits have poor adhesion to the quartz surface, and the number of operations for crystal growth on the substrate is large. Since the deposits of the above-mentioned polycrystals are separated from the surface of the quartz when it is carried out repeatedly, there is a problem such that when it falls on the substrate surface under the gas flow, it causes a surface defect of the single crystal. .

[Means for solving problems]

As a result of various studies in view of this, the present invention has developed a compound semiconductor thin film vapor phase growth apparatus capable of producing a stable quality epitaxial wafer by eliminating crystal surface defects. Group V hydride gas on a susceptor is developed. In a device for growing a group III-V compound semiconductor thin film on a substrate held on a susceptor, the gas rectifying portion is provided on the upstream side of the susceptor to make a laminar flow of the gas. The gas rectifying portion is formed of a semiconductor crystal containing the above-mentioned group V element as a constituent element.

[Work]

As described above, the use of the semiconductor crystal containing the group V element as a constituent element in the gas rectifying section is accompanied by the III-V group compound crystal which is inevitably generated on the surface of the rectifying section which changes the gas flow into a laminar flow. This is for the purpose of firmly depositing the deposit by growing it on the above-mentioned new semiconductor crystal, which can completely eliminate the exfoliation of the deposit and further promote the decomposition of the group V source gas. Means that a semiconductor crystal that acts as a catalyst has been present from the beginning of single crystal growth on a substrate, and the catalytic action is the same even if a deposit crystal grows on the crystal, and the quality of the wafer is stable. Become.

〔Example〕

 The present invention will be described based on examples.

Example I FIG. 1 shows the case where a horizontal reaction tube is used. In the figure, (1) is a horizontal reaction tube, (2) is a water cooling jacket provided on the outer periphery of the reaction tube, and (3) is a water cooling jacket. A high frequency induction coil provided on the outside is shown, and a quartz susceptor holder (4) is arranged in the horizontal reaction tube (1), and a raw material gas for the horizontal reaction tube (1) having a wedge-shaped cross section is provided on the holder (4) ( a) and the carrier gas (c) are directed to the gas introduction port (5) side, and the susceptor (6) having a slope inclined forward is placed toward the introduction port (5), and the source gas ( a) and a downstream side of the carrier gas (c) flow were made into a carbon crystal growth portion (7), and a GaAs single crystal substrate (8) was attached on the slope so that the upper surface thereof formed the same plane as the slope. .
The tip portion, that is, the source gas (a) and the carrier gas (c)
A gas rectifying section (9) made of quartz was provided on the upstream side of the flow of (1), and a GaAs single crystal substrate (8) was mounted on the slope so that its upper surface was flush with the slope.

After introducing the carrier gas into the reaction tube (1) through the introduction port (5) in the thin film vapor phase growth apparatus as described above, the cooling water (b) is sent to the water cooling jacket (2) to supply the high frequency induction coil (3). The GaAs single crystal substrate (8) is heated by means of the gas, and the raw material gas (a) mixed with the carrier gas is supplied from the gas inlet (5) to the GaAs single crystal substrate (8) of the crystal growth portion (7).
GaAs was grown. The GaAs compound semiconductor thin film thus obtained was an extremely excellent single crystal with very few defects.

In the above case, since the material of the susceptor holder (4) and the gas rectifying portion (9) are both quartz, both can be integrally formed, and the gas rectifying portion (9) is made of carbon and the crystal growth portion (9) is formed. It can be formed integrally with 7), and the number of parts can be reduced.

Example II FIG. 2 shows the case where a vertical reaction tube is used. In the figure, (10) is a vertical reaction tube, (2) is a water cooling jacket provided on the outer periphery of the reaction tube, and (3) is The high frequency induction coil provided outside the water cooling jacket is shown. The vertical reaction tube (10) has a hemispherical gas rectifying section (9) in the upper part and a regular polygonal pyramid-shaped crystal growing section (7) in the lower part. The susceptor (6) is vertically supported by a support shaft (11) provided on the lower end surface thereof. The gas rectifying portion (9) is cut out from a GaAs single crystal ingot, the crystal growth portion (7) is processed from carbon, and the GaAs single crystal substrate (8) is formed on each side surface of the growth portion (7). ) Is mounted so that its surface forms the same plane as the side surface of the crystal growth portion (7).

After introducing the carrier gas (c) into the reaction tube (1) through the introduction port (5) of the reaction tube (10) of such a thin film vapor phase growth apparatus, the cooling water (b) is caused to flow through the water cooling jacket (2). , The GaAs single crystal substrate (8) is heated by the high frequency induction coil (3) and the mixed gas of the raw material gas and the carrier gas is supplied from the gas introduction port (5) to deposit GaAs on the GaAs single crystal substrate (8). I grew it. The GaAs compound semiconductor thin film thus obtained was an extremely excellent single crystal with few defects.

In the above case, the hemispherical gas rectifier is a quartz holder (12) having a polyhedral shape as shown in FIG.
A strip substrate (13) cut out from a GaAs single crystal ingot may be adhered and fixed to each surface of the holder (12) to form a gas rectifying portion, or as shown in FIG. Since the catalytic action of decomposing gas and the production of polycrystalline deposits are only in the part adjacent to the crystal growth part (7) of the gas rectification part, the upper part of the gas rectification part is made into a hemispherical quartz holder (12 '). It is also possible to fix the strip-shaped substrate (13) only on the peripheral surface adjacent to the lower crystal growth portion (7).

〔The invention's effect〕

As described above, according to the present invention, industrially remarkable effects such as the production of a III-V compound semiconductor thin film having extremely few crystal defects and excellent quality stability can be achieved.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention, FIG. 2 is a side sectional view showing another embodiment of the present invention, and FIGS. 3 (a) and (b).
4A and 4B are external views of essential parts showing another embodiment of the present invention.
FIG. 5 and FIG. 5 are side sectional views showing a conventional example. 1 ... Horizontal reaction tube 2 ... Water cooling jacket 3 ... High frequency induction coil 4 ... Susceptor holder 5 ... Gas inlet 6 ... Susceptor 7 ... Crystal growth part 8 ... GaAs single crystal substrate 9 ... Gas rectification Part 10 Vertical reaction tube 11 Support shaft 12, 12 'Quartz holder 13 Strip substrate 14 Compound semiconductor substrate 15 Carbon gas rectifier a Source gas b Cooling Water c ... Carrier gas

Claims (1)

[Claims] 1. A group V hydride gas is caused to flow on the surface of a substrate held on a susceptor, and a gas rectifying section is provided on the upstream side of the susceptor to make the flow of the gas a laminar flow, and the substrate is held on the susceptor. In the apparatus for growing a III-V group compound semiconductor thin film, a gas rectifying part is formed of a semiconductor crystal having the group V element as a constituent element.