JP2556211B2 - Apparatus for growing semiconductor crystal layer and method for growing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for growing a semiconductor crystal layer, and more particularly to a method for observing the state of the semiconductor crystal layer from the outside and irradiating light from the outside to grow the semiconductor crystal layer. .

[0002]

2. Description of the Related Art Metalorganic vapor phase epitaxy (hereinafter MOCVD
Method) or the molecular beam epitaxy method is used to grow a semiconductor crystal on the substrate installed in the reaction vessel, the problem is how to provide a “peep window” that does not become dirty in the reaction vessel. Has become. It is during the growth of semiconductor crystals by these methods,
The purpose is to change the growth state by observing the growing state of the crystal from the outside, or by irradiating the crystal layer with light through a "peep window" and applying light energy to the growing crystal layer. Because there is.

Conventionally, several structures have been proposed and used as the "viewing window" of a reaction container. FIG. 4 shows, as an example, a conventional device having a "viewing window". In this apparatus, the reaction vessel 1 has a double tube structure using a quartz pipe, and an induction coil 12 for heating the substrate 8 is wound further outside the outer tube. The inner tube has a “peep window 13” opened above the substrate 8. A reaction gas is supplied to the inside of the inner tube to grow a semiconductor crystal layer on the surface of the substrate. For example, hydrogen is flown in the outer tube,
The reaction gas is prevented from flowing into the outer tube.

[0004]

However, the apparatus of this structure has a drawback that the inner surfaces of the inner tube and the outer tube are contaminated by the reaction gas and cannot be used continuously many times. Since the reaction gas constantly flows on the inner surface of the inner pipe, decomposition products of the reaction gas immediately adhere to the inner tube and become blackened.
Similarly, in the outer tube as well, the hydrogen gas flowing through the outer tube becomes turbulent in the vicinity of the "viewing window", and the reaction gas flows into the outer tube and contacts the inner surface of the outer tube just above the "viewing window". As a result, the portion is gradually contaminated and the substrate becomes invisible.

Therefore, the entire reaction vessel must be replaced after several uses. When replacing the reaction vessel, moisture in the air is adsorbed inside the reaction vessel, so complicated steps such as vacuum baking and gas baking need to be repeated many times over several days to remove the moisture. It is extremely time-consuming.

By the way, there is a method of growing a semiconductor crystal layer while irradiating light. This method has a feature that the growth temperature can be remarkably lowered by irradiating light, and in order to irradiate light, a light source is arranged outside the reaction vessel. The light source illuminates the epitaxial crystal layer with light that passes through the "peep window." In this method, it is extremely important to keep the "viewing window" clean. The dirty "peep window" absorbs light and reduces the light irradiation intensity on the epitaxial crystal layer.

The present invention was developed in order to solve these drawbacks, and the object of the present invention is "a viewing window".
Another object of the present invention is to provide a semiconductor crystal layer growth apparatus capable of observing the state of crystal growth while preventing contamination for a long time. Another important object of the present invention is to utilize a semiconductor crystal layer growth apparatus having a "peep window" which does not become dirty,
Another object of the present invention is to provide a method for growing a semiconductor crystal layer by efficiently irradiating light from the “peep window”.

[0008]

The crystal growth apparatus and the growth method of the present invention have the following configurations in order to achieve the above-mentioned object. First, the semiconductor crystal layer growth apparatus is
It comprises a reaction vessel 1, a susceptor 2 arranged to mount a substrate 8, a heater 3 for heating the susceptor, and a reaction gas supply pipe 4 for supplying a reaction gas toward the substrate.

Further, this apparatus is equipped with a transparent tube 5 for allowing gas to flow into the reaction vessel 1. The transparent tube 5 has a tubular shape in which the rear end is thinner than the front end, at least a part of which is exposed to the outside of the reaction vessel 1, and the front end of the transparent tube 5 is opened inside the reaction vessel. The rear end of the transparent tube 5 is connected to a gas supply source, and by flowing the gas through the transparent tube 5, it is possible to prevent the transparent tube 5 from being contaminated by the reaction gas and to grow on the substrate 8 through the transparent tube 5. The semiconductor crystal state can be observed, and the substrate 8 can be irradiated with light through the transparent tube 5.

Further, in the method for growing a semiconductor crystal layer of the present invention, the substrate 8 is placed on the susceptor 2 arranged inside the reaction container 1 having the above-mentioned structure, and the susceptor 2 is heated,
The reaction gas is supplied toward the substrate 8 and the light emitted from the light source 9 disposed outside the transparent tube 5 is further passed through the transparent tube 5 while flowing the gas from the rear end of the transparent tube 5. 8
The semiconductor crystal layer is grown by irradiating the substrate.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. However, the following embodiments are merely examples embodying the technical idea of the present invention, and the present invention is not limited to the following. This invention can be modified in various ways within the scope of the claims. Further, in this specification, for easy understanding of the claims, the numbers corresponding to the members shown in the examples are
It is added to the members shown in the column of "Means for solving the problem". However, the members shown in the claims are not limited to the members of the embodiment.

FIG. 1 shows an example of a semiconductor crystal layer growth apparatus having the structure of the present invention. This device is, for example, GaN,
The AlN, InN semiconductor crystal or a mixed crystal of these is MO
This is an apparatus for epitaxial growth by the CVD method. This apparatus includes a reaction container 1, a susceptor 2, a heater 3, a reaction gas supply pipe 4, and a transparent pipe 5.

The reaction vessel 1 is made of stainless steel and has a structure capable of being shielded from the outside air. Although not shown, the reaction container 1 is provided with an entrance / exit through which the substrate 8 can be put in and taken out,
A lid that can keep the inside of the reaction vessel airtight is provided at the entrance and exit. Further, the reaction container 1 is provided with an exhaust port for exhausting the gas inside. The exhaust port is connected to the vacuum pump 6, and the vacuum pump 6 can forcibly exhaust air.

The susceptor 2 is heated by the heater 3. Therefore, the susceptor 2 has heat resistance and is made of a substance that does not react with the gas in the reaction vessel 1 in a heated state. For example, the surface of the susceptor made of carbon is further coated with silicon carbide. .

The heater 3 is disposed below the susceptor 2 so as to approach but not contact, and has a structure for heating the susceptor 2 from below. The heater 3 is turned on / off or the energization current is controlled to heat the susceptor 2 to a set temperature. The heater 3 is controlled by a temperature sensor (not shown) built in the susceptor 2.

The heater 3 can be arranged at any position where the susceptor 2 can be heated. Although not shown,
It is also possible to provide the heater inside the susceptor so as to be integrated with the susceptor.

The reaction gas supply pipe 4 supplies the reaction gas to the upper surface of the substrate 8 provided on the susceptor 2. Therefore, the reaction gas supply pipe 4 is fixed horizontally or slightly inclined so as to penetrate the reaction container 1 in an airtight manner. The reaction gas supply pipe 4 has its tip extended to the vicinity of the substrate 8.

For example, an epitaxial layer of GaN is formed on the substrate 8
In the case of forming on the above, hydrogen is supplied from the reaction gas supply pipe 4,
A mixed gas of ammonia gas and trimethylgallium (TMG) gas is supplied toward the surface of the substrate 8.

The transparent tube 5 is made of quartz glass, for example.
It is made of a transparent material that can withstand the temperature of the susceptor heated to 1000 ° C or higher. Transparent tube 5
Penetrates the upper surface of the reaction vessel 1 in an airtight manner, and the upper end thereof is projected to the outside of the reaction vessel 1. The transparent tube 5 has a cylindrical shape with its rear end narrower than its front end, and has a conical shape whose opening area increases downward. Transparent tube 5
The rear end is connected to a source of gas, hydrogen, nitrogen,
A gas that does not contaminate the transparent tube, such as argon or helium, may be flowed toward the substrate 8 either alone or as a mixture. Further, the transparent tube 5 is designed such that the cross-sectional area of the tip opening (lower end opening) is substantially equal to the area of the substrate 8 so that those gases can be uniformly sprayed onto the upper surface of the substrate 8. ing. Further, the lower end of the transparent tube 5 approaches the upper surface of the substrate 8 and opens. The distance between the lower end of the transparent tube 5 and the substrate 8 is adjusted to 5 mm to 50 cm, preferably 10 mm to 30 cm.

The transparent tube 5 is most preferably a conical shape, but it does not necessarily have to be a conical shape, and may be an elliptic cone shape or a polygonal pyramid shape whose cross-sectional area increases toward the opening end. Good. In the case of a transparent tube having a polygonal pyramid shape, it is preferable that the corner angle of the polygonal cross section is curved with a predetermined curvature.

Conventionally, a vertical pyramid-shaped quartz tube has a conical shape or a polygonal pyramidal quartz tube whose corners are curved with a predetermined curvature.
It is used as a reaction vessel for the equipment. With this shape, the gas flowing inside becomes a uniform laminar flow, which allows the gas to flow uniformly.

Further, in the apparatus shown in FIG. 2, a light source 9 is provided above the transparent tube 5. The light source 9 can irradiate the semiconductor crystal layer with light to grow the semiconductor crystal layer at a low temperature. The light source 9 is arranged above the transparent tube 5, and the light emitted from the light source 9 is focused by the lens 10 and the reflecting mirror 11 to uniformly irradiate the surface of the semiconductor crystal layer laminated on the substrate. When the light is focused and irradiated as described above, there is a feature that the semiconductor crystal layer can be irradiated with stronger light. An ultraviolet lamp such as a mercury lamp or a xenon lamp is used as the light source. The lamp used for the light source may have a power of 200 W to several kW.

Further, FIG. 3 shows an apparatus for supplying a reaction gas from one of the cylindrical reaction vessels 1 to grow a semiconductor crystal layer on the substrate 8. This device is, for example, GaAs, G
This is a device often used when growing crystals of aAlAs or the like, and the reaction vessel 1 has a horizontally extended cylindrical shape. A susceptor 2 is provided inside the reaction vessel 1,
The induction coil 12 heats the susceptor 2. A transparent tube 5 is provided above the substrate 8 so as to extend vertically. The transparent tube 5 may have the same structure as the device shown in FIGS. 1 and 2. The upper end of the transparent tube 5 is connected to a gas source such as hydrogen or nitrogen. The gas supplied to the transparent tube 5 uniformly flows down in the transparent tube 5 in a laminar flow state so that the reaction gas does not enter the inside of the transparent tube 5.

Although not shown further, the device shown in FIG.
As in the device shown in FIG. 2, a light source may be provided above the transparent tube 5 to irradiate the substrate with light.

Using the semiconductor crystal layer growth apparatus shown in FIG. 1, a GaN semiconductor crystal layer was grown under the following conditions. [Example 1] A sapphire substrate that was cleaned and cleaned was replaced with a susceptor 2.
Then, the susceptor 2 is transferred into the reaction container 1. After the reaction container 1 is evacuated by the vacuum pump 9, H ₂ is flown from the reaction gas supply pipe to replace the inside with H ₂ . Then, the susceptor 2 is raised to 1050 ° C. while supplying H ₂ gas. This state is maintained for 10 minutes to remove the oxide film on the sapphire surface. While flowing hydrogen, raise the temperature of the susceptor 2 to 993 ° C.
Lower to and keep still until stable. Next, ammonia gas as a nitrogen source is supplied from the reaction gas supply pipe 4 at a flow rate of 5.0 l / min, and hydrogen is supplied as a carrier gas at a flow rate of 1.0 l / min. Flow at a flow rate of / minute and keep this state until the temperature stabilizes. Subsequently, in addition to ammonia gas and hydrogen, TMG gas as a Ga source was allowed to flow at 2.7 × 10 ⁻⁵ mol / min for 60 minutes from the reaction gas supply pipe to grow a GaN epitaxial layer. During this time, the susceptor 2 is slowly rotated.

Infrared rays radiated from the epitaxial layer in the step (1) are detected by a monochromatic narrow wavelength band radiation thermometer 14 which measures an infrared ray intensity of 0.96 μm. The infrared intensity detected by the radiation thermometer 14, that is, the temperature is shown in FIG.
Is shown in. As the epitaxial layer grows as shown in FIG. 5, the infrared intensity oscillates, and by measuring this, the film thickness of the epitaxial layer can be known. It is also possible to irradiate a laser beam of a specific wavelength and measure the film thickness from the change in this intensity.

Although GaN was grown 100 times continuously by this method, the transparent tube 5 was not contaminated at all. For this reason,
The growth state of the semiconductor crystal layer could be observed through the transparent tube 5, and the growth state of the semiconductor crystal layer could always be known accurately using a radiation thermometer.

[Embodiment 2] Using the apparatus shown in FIG.
A GaAs crystal layer was grown while irradiating ultraviolet rays from the light source 9. A GaAs crystal is used for the substrate 8 placed on the susceptor 2. From the reaction gas supply pipe 4, arsine (AsH ₃ ) is supplied as an As source, TMG gas is supplied as a Ga source, and hydrogen is supplied as a carrier gas.

As the light source 9, a 500 W mercury lamp is used. Ultraviolet rays radiated from the mercury lamp are condensed by a lens and the substrate 8 is irradiated.

In this state, the substrate temperature is set to about 4 by the heater 3.
Light irradiation MOCV of GaAs by heating to 00-500 ° C
Growth is performed by the D method. Hydrogen gas is constantly flowed through the transparent tube 5 at a flow rate of 10.0 l / min from the start of the reaction to the end of the reaction.

In this state, the GaAs epitaxial layer was grown for 60 minutes, but the transparent tube 5 was not contaminated at all, and ultraviolet rays could be uniformly irradiated during the reaction. In addition,
Using the apparatus shown in FIG. 2, a GaAs crystal layer was grown 100 times in succession by the light irradiation MOCVD method, but the transparent tube 5 was not contaminated at all. Therefore, it was possible to efficiently irradiate the GaAs substrate with ultraviolet rays through the transparent tube 5.

[0032]

The semiconductor layer crystal growth apparatus of the present invention is
The reaction vessel is equipped with a transparent tube as a “viewing window”. The transparent tube has a tubular shape with a rear end narrower than the front end, at least a part of which is exposed to the outside of the reaction vessel, and the front end of the transparent tube is opened inside the reaction vessel. Further, gas is supplied from the rear end of the transparent tube. In the device with this structure, the tip of the transparent tube is opened in the reaction vessel, and the gas does not become a turbulent flow inside the transparent tube but becomes a laminar flow, so the reaction gas enters the inside of the transparent tube. , Does not stain the transparent tube.

Therefore, in the device of the present invention, the transparent tube is not contaminated with the reaction gas for an extremely long time, and the "viewing window"
And has the advantage that the growth state of the semiconductor crystal layer can be accurately observed. By the way, the device prototyped by the present inventor has achieved the excellent effect of almost completely eliminating the contamination of the transparent tube even after being used for several hundred hours.

Furthermore, according to the method of the present invention, the semiconductor crystal layer is irradiated with light by using a transparent tube which is a "viewing window" which does not become dirty even when used for an extremely long time. Therefore, the light emitted from the light source has a characteristic that the epitaxial crystal layer can be efficiently irradiated without being attenuated and the semiconductor crystal layer can be grown by effectively utilizing the light energy.

Further, in the apparatus of the present invention, since the transparent tube is not contaminated, it is not necessary to replace it, and the cleaning means utilizing vacuum baking, gas baking or the like is extremely reduced, and the semiconductor crystal layer can be efficiently produced. There are features.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a semiconductor crystal layer growth apparatus showing an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a semiconductor crystal layer growth apparatus showing another embodiment of the present invention.

FIG. 3 is a schematic sectional view of a semiconductor crystal layer growth apparatus showing another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a conventional semiconductor crystal layer growth apparatus.

FIG. 5 is a graph showing temperature characteristics measured from infrared intensity emitted from an epitaxial crystal layer in Example 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reaction container 2 ... Susceptor 3 ... Heater 4 ... Reaction gas supply pipe 5 ... Transparent pipe 6 ... Vacuum pump 7 ... Gas supply source 8 ... Substrate 9 ... Light source 10 ... Lens 11 ... Reflector 12 ...
Induction coil 13 Peep window 14 Radiation thermometer

Claims (2)

(57) [Claims] 1. A reaction container, a susceptor disposed inside the reaction container for mounting a substrate, a means for heating the susceptor, and a reaction gas supply pipe for supplying a reaction gas toward the substrate. In a semiconductor crystal layer growth apparatus, a reaction vessel is provided with a transparent tube through which gas flows, and the transparent tube has a tubular shape with a rear end narrower than a front end, and at least a part of the transparent tube is exposed to the outside of the reaction vessel. The front end of the transparent tube is opened in the reaction vessel, and the rear end of the transparent tube is connected to the gas supply source so that the state of the semiconductor crystal layer of the substrate can be observed through the transparent tube. An apparatus for growing a semiconductor crystal layer, which is configured. 2. The gas is caused to flow from the rear end of the transparent tube of the growth apparatus according to claim 1 into the reaction vessel, and further,
A method for growing a semiconductor crystal layer, comprising irradiating a substrate with light emitted from a light source through a transparent tube from a light source arranged outside the transparent tube.