JP3376849B2 - Manufacturing method of semiconductor thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a p-type gallium nitride compound semiconductor thin film used in optical devices such as blue and green light emitting diodes.

[0002]

2. Description of the Related Art Recently, blue and green light emitting devices using gallium nitride compound semiconductors have been receiving attention. In order to manufacture such a light emitting device, a method of stacking an n-type semiconductor thin film doped with an n-type impurity and a p-type semiconductor thin film doped with a p-type impurity to form a pn junction is generally used. There is. A metal organic chemical vapor deposition method is well known as a method for growing a gallium nitride-based compound semiconductor thin film. According to this method, an organometallic compound gas (trimethylgallium (hereinafter abbreviated as "TMG")) and trimethylaluminum (hereinafter abbreviated as "TMA") are used as source gases in a reaction tube provided with a sapphire substrate.
Etc.) and ammonia, and the substrate temperature is set to about 900.
C. to 1100.degree. C., a gallium nitride-based compound semiconductor thin film is grown on a substrate, and an n-type or p-type semiconductor thin film is grown while simultaneously supplying other impurity gas as needed. is there. Silicon (Si) is well known as an n-type impurity. Well-known p-type impurities include zinc (Zn) and magnesium (Mg). Organometallic compounds are introduced into a cylinder containing these organometallic compounds with a small amount of hydrogen as a sub-carrier gas, and vaporized or sublimated into the sub-carrier gas by bubbling or the like (hereinafter, for convenience, "bubbled The organometallic compound is gasified and further transported by a main carrier gas such as hydrogen or nitrogen in order to efficiently supply it to the reaction tube. Conventionally, in a crystal growth apparatus for growing a gallium nitride-based compound semiconductor, a thin film growth surface of a substrate is held upward, as disclosed in JP-A-4-297023 and JP-A-2-229476. The method of doing is generally used. In addition, Mg as a p-type impurity
When growing gallium nitride (GaN) doped with Al2O3, there are disclosed in Japanese Patent Publication No. 2540791 and JP-A-6-151962.
As disclosed in the publication, hydrogen is generally used as a carrier gas.

By the way, the present inventor has filed Japanese Patent Application No. 08-0727.
In No. 21, there is shown a metal-organic vapor phase epitaxy apparatus capable of uniformly growing a thin film of a gallium nitride-based compound semiconductor or the like on a substrate in which the thin film growth surface is held downward. According to the present metal-organic vapor phase epitaxy apparatus, the excellent effect that the raw material is efficiently supplied to the substrate surface can be obtained even when growing a GaN-based compound semiconductor that requires a high temperature of 1000 ° C. or higher.

[0004]

However, the present inventor has found that hydrogen is used as a carrier gas on a substrate in which a thin film growth surface is held downward by a metal organic chemical vapor deposition method.
While doping Mg as a type impurity, a gallium nitride-based compound semiconductor thin film or aluminum gallium nitride (AlGa
N) When growing a gallium nitride-based compound semiconductor thin film such as a thin film, it was discovered that there is a problem that if the p-type impurity is doped at a high concentration, cracks are likely to occur in the film. When a light emitting device is manufactured by using the gallium nitride-based compound semiconductor thin film or the Al gallium nitride-based compound semiconductor thin film doped with p-type impurities thus grown,
Since cracks occur in the laminated structure grown on the substrate,
There is a problem that the yield is poor because some of them do not emit light even when energized, some of them emit light only when they emit light, and some of them deteriorate instantly.

In order to realize a light emitting device having low electric resistance, that is, low operating voltage and low heat generation, a p-type layer heavily doped with p-type impurities is indispensable, and in order to improve the reliability of the device. It is necessary to realize a crack-free thin film.

The present invention solves the above problems, and gallium nitride-based compound semiconductors are provided on a substrate having a thin film growth surface facing downward in order to obtain good crystallinity and uniformity at high temperatures of 1000 ° C. or higher. In a metal-organic vapor phase epitaxy apparatus for growing a thin film, when growing a gallium nitride-based compound semiconductor thin film doped with Mg as a p-type impurity, it is possible to efficiently dope Mg with a high concentration without causing cracks. It is intended to provide a way.

[0007]

In order to solve the above problems, a p-type gallium nitride-based compound semiconductor thin film manufacturing method of the present invention is a method of doping a substrate with p-type impurities by metal organic chemical vapor deposition. In the method of growing a gallium nitride-based compound semiconductor thin film, a carrier for transporting a source gas to a reaction tube while holding the surface of the substrate on which the p-type impurity-doped gallium nitride-based compound semiconductor thin film is grown facing downward. As a gas, a carrier gas based on nitrogen mixed with hydrogen of 20% or less and hydrogen of 2% or more and 20% or less is used.

With this configuration, in the metal-organic vapor phase epitaxy apparatus for growing the gallium nitride compound semiconductor thin film on the substrate holding the thin film growth surface downward, the hydrogen concentration in the nitrogen-based carrier gas is set to 20% or less. It is possible to provide a method for improving the crystallinity of a gallium nitride-based compound semiconductor thin film doped with Mg as a p-type impurity and producing a Mg-doped gallium nitride-based compound semiconductor thin film with a good yield without causing cracks. Becomes Furthermore, the hydrogen concentration in the nitrogen-based carrier gas is set to 2
% Or more and 20% or less, the occurrence of cracks is suppressed and the Mg doping efficiency is not deteriorated.
It is possible to provide a method for producing a gallium nitride-based compound semiconductor thin film doped with.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the invention described in claim 1 of the present invention, a source gas is transported to a reaction tube using a nitrogen-based carrier gas mixed with hydrogen at a concentration of 20% or less, A method of manufacturing a semiconductor thin film, which comprises growing a p-type impurity-doped gallium nitride-based compound semiconductor thin film on a substrate mounted in a reaction tube, and improving the crystallinity of the p-type gallium nitride-based compound semiconductor thin film. However, it has the effect that it can be grown without causing cracks.

The invention according to claim 2 of the present invention is
A method of manufacturing a semiconductor thin film as described above, characterized in that a substrate is mounted with a thin film growth surface facing downward, and an effect of improving crystallinity of a p-type gallium nitride compound semiconductor thin film and allowing growth without causing cracks. Is further improved.

The invention according to claim 3 of the present invention is a method for producing a semiconductor thin film, characterized in that the growing method is a metal organic chemical vapor deposition method. It has an effect of improving crystallinity and being able to easily form a film without generating a crack.

The invention according to a fourth aspect of the present invention is characterized in that a nitrogen-based carrier gas mixed with hydrogen at a concentration of 2% or more and 20% or less is used as the carrier gas. A method of manufacturing a semiconductor thin film,
The crystallinity of the p-type gallium nitride-based compound semiconductor thin film is improved, and the semiconductor thin film can be efficiently doped with p-type impurities at a high concentration without causing cracks.

Specific examples of embodiments of the present invention will be described below with reference to the drawings. First, the crystal structure of the surface of the gallium nitride-based compound semiconductor thin film was observed when the concentration of hydrogen gas in all carrier gases was changed.

(Embodiment 1) FIG. 1 is a schematic cross-sectional view showing the main part of the metal-organic vapor phase epitaxy apparatus used in the first embodiment of the present invention, showing the structure of the reaction part and its reaction part. A gas system that communicates is shown. In FIG. 1, a reaction tube 1
A substrate holder 3 for holding the thin film growth surface of the substrate 2 downward is disposed inside the substrate holder 3.
Is heated by the heating element 4. The organometallic compound gas which is the raw material gas is a sub-carrier gas consisting of hydrogen gas whose flow rate is controlled by the flow rate controllers 5c, 5d and 5e, and TMG, TMA, biscyclopentadienyl magnesium (hereinafter, referred to as “Cp ₂ "Mg" is abbreviated.)
It is vaporized and taken out by introducing and bubbling it into the cylinder containing the. These organometallic compound gases efficiently react with ammonia whose flow rate is controlled by the flow rate controller 5f, and a main carrier gas which is a mixed gas of nitrogen gas and hydrogen gas whose flow rate is controlled by the flow rate controllers 5a and 5b. The gallium nitride-based compound semiconductor thin film is formed on the heated substrate 2 after the ammonia, which is the source gas, reacts with the organometallic compound gas supplied to the tube. The rest of the raw material gas is discharged as exhaust gas 6.

The p-type gallium nitride-based compound semiconductor thin film is
It is grown by the following steps. First, a well-cleaned sapphire substrate is placed in a substrate holder inside a reaction tube. The substrate is heated at 1100 ° C. for 10 minutes while flowing hydrogen gas to clean the surface. After that, the temperature is 600 ℃
After cooling to 600 ° C., hydrogen gas as a main carrier gas, a sub-carrier gas for TMA, and ammonia are made to flow at 600 ° C., and an AlN layer as a buffer layer is made 500 times.
It is grown to a film thickness of angstrom. Next, after stopping only the TMA sub-carrier gas and raising the temperature to 1050 ° C., a mixed gas of nitrogen gas and hydrogen gas as the main carrier gas, a new TMG sub-carrier gas, and Cp
_{(2) An} Mg sub-carrier gas is flowed for 60 minutes to grow a gallium nitride-based compound semiconductor thin film doped with Mg to a thickness of 2 μm. By doping with Mg, the gallium nitride-based compound semiconductor thin film can be made p-type. After the growth, the raw material gases TMG gas, Cp ₂ Mg gas, and ammonia are stopped, the nitrogen gas and the hydrogen gas are allowed to flow at the same flow rates to cool to room temperature, and then the wafer is taken out from the reaction tube.

(Second Embodiment) A device similar to that of the first embodiment is used.
In the second embodiment, the n-type nitriding is performed on the substrate.
Gallium compound semiconductor thin film and p-type gallium nitride compound
Object semiconductor thin films are sequentially stacked. That is, first, wash well
Place the sapphire substrate on the substrate holder inside the reaction tube.
It Substrate at 1100 ° C for 10 minutes while flowing hydrogen gas
Heat for a while to clean the surface. After that, increase the temperature to 6
Main carrier gas at 600 ℃ after cooling to 00 ℃
As hydrogen gas, TMA auxiliary carrier gas,
While flowing the near and, 5 AlN layer as a buffer layer
It is grown to a film thickness of 00 angstrom. Next, Al
Nitrogen gas is used as the main carrier gas on the N-layer buffer layer.
Gas, hydrogen gas, TMG gas, Si as raw material gas
Source 10ppm SiH _FourFlow (monosilane) gas
While growing for 60 minutes, Si-doped n-type nitride
Growth of gallium nitride-based compound semiconductor thin film with a thickness of 2 μm
Let Continuously, SiH_FourTurn off the gas and add a new main carrier
Nitrogen gas, hydrogen gas, Cp as a gas₂Mg sub-cap
Grow for 15 minutes while flowing rear gas to remove Mg.
0.5μ of the p-type gallium nitride compound semiconductor thin film
It was grown to a film thickness of m. After growth, the source gas is TMG
Gas and Cp₂Stop the Mg gas and ammonia, nitrogen gas
And hydrogen gas at the same flow rate while cooling to room temperature
After that, the wafer was taken out from the reaction tube.

[0017]

EXAMPLE Next, a specific example of the first embodiment of the present invention will be described.

(Example 1) In Example 1, the carrier gas is composed of an auxiliary carrier gas used for bubbling an organometallic compound and a main carrier gas for efficiently supplying a raw material gas to a reaction tube. When growing a gallium nitride-based compound semiconductor thin film doped with Mg, the concentration of hydrogen gas in all carrier gases was set to 0.5%. That is, 9.95 liters / minute of nitrogen gas, 0.45 liters / minute of hydrogen gas as a main carrier gas for efficiently supplying the raw materials, and an auxiliary carrier gas composed of hydrogen gas used for bubbling TMG and Cp ₂ Mg. 4cc each
/ Min and 50 cc / min.

FIG. 2 is a micrograph showing the crystal structure of the surface of a gallium nitride-based compound semiconductor thin film formed by doping Mg when the concentration of hydrogen gas in all carrier gases is 0.5%.

(Embodiment 2) Embodiment 2 has the same configuration as that of Embodiment 1 except that the concentration of hydrogen gas is 15%. FIG. 3 shows that the concentration of hydrogen gas in all carrier gases is 15
FIG. 5 is a microscopic diagram showing a crystal structure of a surface of a gallium nitride-based compound semiconductor thin film formed by doping Mg when it is defined as%.

Comparative Example 1 In Comparative Example 1, the concentration of hydrogen gas was set to 30%. Hydrogen gas concentration in carrier gas is about 3
When a Mg-doped gallium nitride-based compound semiconductor thin film is grown under the condition of 0% or more, it is difficult to grow a gallium nitride-based compound semiconductor thin film evenly on a buffer layer composed of an AlN layer formed on a substrate. Therefore, after the undoped GaN having a thickness of about 0.4 μm is formed flat on the AlN buffer layer in advance under the condition that the hydrogen gas concentration in the carrier gas is 20% or less, specifically 15%, the desired Mg-doped The gallium nitride-based compound semiconductor thin film was continuously grown.

FIG. 4 is a micrograph showing the crystal structure of the surface of a gallium nitride-based compound semiconductor thin film formed by doping Mg when the concentration of hydrogen gas in all carrier gases is 30%.

(Comparative Example 2) Comparative Example 2 had the same form as Comparative Example 1 in all cases except that the concentration of hydrogen gas was 100% (only hydrogen).

FIG. 5 is a micrograph showing the crystal structure of the surface of a gallium nitride-based compound semiconductor thin film formed by doping with Mg when the concentration of hydrogen gas in all carrier gas is 100%.

Example 1, Example 2, Comparative Example 1, Comparative Example 2
As can be seen from the above, when the carrier gas having a hydrogen concentration of 100% in Comparative Example 2 is used, fine cracks are densely generated on the surface of the entire surface of the wafer as shown in FIG. As the hydrogen concentration decreases, the density of cracks on the surface tends to decrease. When the hydrogen concentration of Comparative Example 1 is 30%, the density of cracks is small as shown in FIG. 4, but the density of cracks is relatively high at the peripheral portion of the wafer. When the hydrogen concentration in each of Examples 1 and 2 is 15% or less, no cracks occur at all as shown in FIGS. 3 and 2, and a flat surface with good crystallinity is obtained. Further, when the hydrogen concentration is 20%, cracks are generated only in a part of the wafer peripheral portion, but cracks are not generated in most of the wafer surface, and a flat surface with good crystallinity similar to FIG. 3 is obtained. can get. That is, in order to suppress the generation of cracks, it is effective to set the hydrogen concentration to 20% or less in all nitrogen-based carrier gases including the hydrogen carrier gas used for bubbling of the organometallic compound.

Next, the relationship between the hydrogen concentration of the carrier gas and the element concentration of Mg as a p-type impurity incorporated in the gallium nitride-based compound semiconductor thin film was investigated.

Example 3 In Example 3, the concentration of hydrogen gas in all carrier gases is 5%. The manufacturing process of the p-type gallium nitride-based compound semiconductor thin film is the same as that of the first embodiment.

Hydrogen gas as a main carrier gas, 10 cc / min of a TMA sub-carrier gas, and 5 liter / min of ammonia are flown while an AlN layer as a buffer layer is grown to a film thickness of 500 angstrom. . Next, stop the TMA sub carrier gas only and
After the temperature was raised to 50 ° C., nitrogen gas was introduced at 9.5 liters / minute and hydrogen gas was introduced at 0.45 liters / minute as a main carrier gas, and 4 cc / minute of CMP was newly added as an auxiliary carrier gas of TMG. ₂ Mg Mg sub carrier gas 50cc /
The film is grown for 60 minutes while flowing for a minute to grow a Mg-doped gallium nitride-based compound semiconductor thin film to a film thickness of 2 μm. After growth, TMG gas and Cp ₂ M, which are raw material gases,
The g gas and the ammonia are stopped, the nitrogen gas and the hydrogen gas are allowed to flow at the same flow rates, the temperature is cooled to room temperature, and then the wafer is taken out from the reaction tube. Mg thus obtained
When the doped gallium nitride-based compound semiconductor thin film was observed with a microscope, it was a flat surface without cracks as in FIGS. 2 and 3.

The element concentration of Mg in the thin film is 3.3 × 10 ¹⁹
/ Cm ³ . (Example 4) In Example 4, the concentration of hydrogen gas in all carrier gases was 10%. 1050 of Example 3 above
In the step of growing a gallium nitride-based compound semiconductor thin film doped with Mg at ℃, the main carrier gas is 9 liter / min of nitrogen gas and 0.95 liter / min of hydrogen gas.
A gallium nitride-based compound semiconductor thin film doped with Mg is grown in the same manner as in Example 3 except that the flow is performed in minutes. At this time, the concentration of hydrogen gas in all carrier gases is 5%. After the growth, when observing the surface of the Mg-doped gallium nitride compound semiconductor thin film with a microscope, it was a flat surface without cracks as in FIG. The elemental concentration of Mg in the thin film was 2.3 × 10 ¹⁹ / cm ³ .

(Embodiment 5) In Embodiment 5, the concentration of hydrogen gas in all carrier gases is 20%. In the step of growing the gallium nitride-based compound semiconductor thin film doped with Mg at 1050 ° C. in Example 3 above, nitrogen gas was 8 liter / min and hydrogen gas was 1.9 as the main carrier gas.
In the same manner as in Example 3 except that the flow rate was 5 liters / minute, M
A gallium nitride-based compound semiconductor thin film doped with g is grown. After the growth, when observing the surface of the Mg-doped gallium nitride compound semiconductor thin film with a microscope, it was found that cracks were generated in a part of the peripheral edge of the wafer, but most of them were flat surfaces without cracks as in FIG. Met. The elemental concentration of Mg in the thin film was 5.4 × 10 ¹⁹ / cm ³ .

Comparative Example 3 In Comparative Example 3, the concentration of hydrogen gas in all carrier gases is 0.5%. In the step of growing the Mg-doped gallium nitride-based compound semiconductor thin film at 1050 ° C. in Example 3 described above, the same procedure as in Example 3 was carried out except that nitrogen gas was flowed as the main carrier gas at 9.95 l / min. A gallium nitride-based compound semiconductor thin film doped with is grown. However, as described above, before the growth of the Mg-doped gallium nitride-based compound semiconductor thin film, the hydrogen gas concentration was set to 10% under the condition of the carrier gas.
Undoped GaN about 0.4 μm thick on the 1N buffer layer
After that, a Mg-doped gallium nitride-based compound semiconductor thin film was continuously grown with a carrier gas having a hydrogen gas concentration of 0.5%. After the growth, when observing the surface of the Mg-doped gallium nitride compound semiconductor thin film with a microscope, it was a flat surface without cracks as in FIG. Mg in thin film
Had an elemental concentration of 1.9 × 10 ¹⁸ / cm ³ .

(Comparative Example 4) In Comparative Example 4, the concentration of hydrogen gas in all carrier gases was 100%. In the step of growing the gallium nitride-based compound semiconductor thin film doped with Mg at 1050 ° C. in the above-mentioned Example 3, Mg was carried out in the same manner as in Example 3 except that hydrogen gas was flowed as a main carrier gas at 9.95 l / min. A gallium nitride-based compound semiconductor thin film doped with is grown. However, as described above, before the growth of the Mg-doped gallium nitride-based compound semiconductor thin film, the hydrogen gas concentration was set to 10% under the condition of the carrier gas.
Undoped GaN about 0.4 μm thick on the 1N buffer layer
After that, a Mg-doped gallium nitride-based compound semiconductor thin film was continuously grown with a carrier gas having a hydrogen gas concentration of 100%. After the growth, when observing the surface of the Mg-doped gallium nitride compound semiconductor thin film with a microscope, fine cracks as shown in FIG. 5 were generated at high density over the entire wafer. The element concentration of Mg in the Mg-doped gallium nitride-based compound semiconductor thin film is 2.0 × 10 ²⁰ / cm ^3.
Met.

FIG. 6 shows the relationship between the hydrogen concentration in all carrier gases and the element concentration of Mg taken in the gallium nitride-based compound semiconductor thin film. Here, Cp ₂ M as the Mg source
As for g gas, bubbling gas was fixed at 50 cc / min and the supply amount was constant. As shown in FIG. 6, as the hydrogen concentration increases, the elemental concentration of Mg taken into the gallium nitride-based compound semiconductor thin film dramatically increases. Even if the hydrogen concentration of the carrier gas is only 2%, the elemental concentration of Mg increases about 5 times as compared with the case where the hydrogen concentration is 0.5%. When the hydrogen concentration is 5%, the elemental concentration of Mg increases about 10 times as much as when the hydrogen concentration is 0.5%.
The efficiency with which is taken into the membrane is significantly improved. When the hydrogen concentration is further increased, the elemental concentration of Mg taken into the gallium nitride-based compound semiconductor thin film gradually increases. Such dependency of the Mg element concentration on the hydrogen concentration in the nitrogen-based carrier gas is because the Cp ₂ Mg gas is more likely to diffuse in the gas phase as the hydrogen concentration in the carrier gas increases, and the amount reaching the substrate surface increases. It is speculated that it may be.

Therefore, in the Mg-doped gallium nitride-based compound semiconductor thin film growth, the preferable hydrogen concentration including the auxiliary carrier gas consisting of hydrogen used for bubbling of the organometallic compound in the entire nitrogen-based carrier gas is in the film. It is 2% or more from the request of promoting the incorporation of Mg element into the film, and 20% or less from the request of suppressing the generation of cracks in the film, and more preferably 5% or more and 15% or less.

Next, a specific example of the second embodiment of the present invention will be described. (Example 6) Next, p consisting of a p-type gallium nitride compound semiconductor thin film and an n-type gallium nitride compound semiconductor thin film
An n-junction was formed to manufacture a light emitting diode. The concentration of hydrogen gas in all carrier gases is 10%.

After growing an AlN layer buffer layer on a sapphire substrate in the same manner as in Example 1 above,
Nitrogen gas as a main carrier gas is 9 liters / minute, hydrogen gas is 1 liters / minute, while TMG gas is newly added at 4 cc / minute and SiH ₄ (monosilane) gas of 10 ppm as a Si source is added at 100 cc / minute. While growing for 60 minutes, an n-type gallium nitride-based compound semiconductor thin film doped with Si was grown to a film thickness of 2 μm. Continuing,
Stop the SiH ₄ gas and use 9 l / min of nitrogen gas and 0.95 l / min of hydrogen gas as the new main carrier gas.
Cp ₂ Mg sub-carrier gas was flowed at 50 cc / min for 15 minutes to grow a Mg-doped p-type gallium nitride compound semiconductor thin film with a thickness of 0.5 μm. After growth, TMG gas and Cp ₂ M, which are raw material gases,
After the g gas and the ammonia were stopped and the nitrogen gas and the hydrogen gas were allowed to flow at the same flow rates to cool to room temperature, the wafer was taken out from the reaction tube.

When the surface of the wafer was observed with a microscope,
The surface was a flat surface without cracks throughout the surface.

A part of the p-type GaN layer of the pn junction composed of the n-type gallium nitride-based compound semiconductor thin film and the p-type gallium nitride-based compound semiconductor thin film thus formed is partially etched to form a part of the n-type GaN layer. Was exposed, and ohmic electrodes were formed on the respective layers of p-type GaN and n-type GaN. Then, the back surface of the sapphire substrate is polished to 100 μm.
It was thinned to about m and separated into chips by scribing. After bonding this chip to the stem with the pn junction forming surface facing upward, the n-type and p-type electrodes of the chip were respectively connected to the electrodes on the stem with wires, and then resin-molded to produce a light emitting diode. 20 LEDs
When driven with a forward current of mA, the forward voltage is 4
V, the emission output was 30 μW, and blue-violet emission was exhibited at a wavelength of about 430 nm. In this laminated structure, indium gallium nitride (InGaN) is provided between the n-type gallium nitride compound semiconductor thin film and the p-type gallium nitride compound semiconductor thin film.
N) By forming a thin film and using this as a light emitting layer to form a double hetero structure, it is possible to manufacture a light emitting diode having higher light emitting efficiency.

Comparative Example 5 On the other hand, in Example 6, M
Using only hydrogen gas as a main carrier gas when growing a g-doped p-type gallium nitride compound semiconductor thin film,
A GaN pn junction film was formed under the same conditions as in Example 6 except for the above. That is, the concentration of hydrogen gas in all carrier gases is 100%. In the produced pn junction film, fine cracks were generated over the entire surface of the wafer. When a light emitting diode was manufactured in the same manner as in Example 6, many of them did not emit light even when an electric current was applied, and even if they emitted light, they deteriorate instantly and stopped emitting light, and the characteristics could not be measured. There wasn't.

By the way, in considering the cause of cracking in the gallium nitride-based compound semiconductor thin film when the hydrogen concentration in the carrier gas is higher than 20%, it is necessary to consider the following two factors. Be done.

That is, firstly, the higher the hydrogen concentration, the more Mg element is contained in the gallium nitride compound semiconductor thin film, so that the residual stress in the thin film becomes large. Secondly, hydrogen is compared to nitrogen. Due to its high thermal conductivity, the higher the hydrogen concentration, the more cooling during the thin film growth (the same hydrogen concentration as during growth).
In (2), the cooling rate is high, and the stress change due to the difference in the coefficient of thermal expansion between the substrate and the thin film becomes severe. Therefore, the present inventors conducted the following two experiments in order to investigate the influence of these two factors.

First, as a first experiment, the elemental concentration of Mg in the film was about 5 when the hydrogen concentration in all carrier gases was 100% (only hydrogen) and when the hydrogen concentration was 15%.
× 1019 / cm ³ in the Mg source so that the same degree Cp ₂
When the Mg-doped gallium nitride-based compound semiconductor thin film is grown by adjusting the supply amount of Mg gas, the hydrogen concentration becomes 100%.
When hydrogen (only hydrogen) was used, cracks were generated over the entire wafer surface, whereas when hydrogen concentration was 15%, no cracks were generated and a flat surface with good crystallinity was obtained. .

Next, as a second experiment, after the Mg-doped gallium nitride-based compound semiconductor thin film was grown with the hydrogen concentration of the carrier gas being 100% (only hydrogen), the hydrogen gas was switched to nitrogen gas, and the temperature was changed to room temperature in nitrogen gas. When cooled to below, cracks were generated over the entire surface of the wafer as in the case of cooling in hydrogen gas.

From the above two experimental results, it is highly likely that the presence or absence of cracks is essentially determined by the hydrogen gas concentration itself in the carrier gas during the growth of the Mg-doped gallium nitride compound semiconductor thin film.

[0045]

As described above, according to the present invention, when a gallium nitride-based compound semiconductor thin film doped with Mg as a p-type impurity is grown, the occurrence of cracks is suppressed and the concentration of Mg in the thin film is high. It has an excellent effect that it can be taken into. Further, even when a light emitting device such as a light emitting diode or a laser diode is manufactured using this p-type gallium nitride compound semiconductor thin film doped with p-type impurities, the operating resistance is reduced without causing cracks in the grown laminated structure. Therefore, an excellent effect that a light emitting device having excellent performance and reliability can be manufactured with high yield is obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a main part of a metal-organic vapor phase epitaxy apparatus used in a first embodiment of the present invention.

[FIG. 2] Concentration of hydrogen gas in all carrier gases is 0.5%
View showing the crystal structure of the surface of the gallium nitride-based compound semiconductor thin film formed by doping with Mg

FIG. 3 is a micrograph showing the crystal structure of the surface of a gallium nitride-based compound semiconductor thin film formed by doping Mg when the concentration of hydrogen gas in all carrier gases is 15%.

FIG. 4 is a micrograph showing the crystal structure of the surface of a gallium nitride-based compound semiconductor thin film formed by doping Mg when the concentration of hydrogen gas in all carrier gases is 30%.

FIG. 5: Concentration of hydrogen gas in all carrier gases is 100%
View showing the crystal structure of the surface of the gallium nitride-based compound semiconductor thin film formed by doping with Mg

FIG. 6 is a diagram showing the relationship between the hydrogen concentration in all carrier gases and the element concentration of Mg taken in the gallium nitride-based compound semiconductor thin film.

[Explanation of symbols]

1 reaction tube 2 substrates 3 substrate holder 4 heating element 5a, 5b, 5c, 5d, 5e, 5f Flow rate controller 6 exhaust gas

Continuation of the front page (56) Reference JP-A-9-36426 (JP, A) JP-A-8-264455 (JP, A) JP-A-8-148718 (JP, A) JP-A-8-97149 (JP , A) JP 63-178516 (JP, A) JP 4-155918 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 H01L 33/00

Claims (4)

(57) [Claims] 1. A carrier gas containing nitrogen as a base and hydrogen in a concentration of 20% or less is used to transport a source gas to a reaction tube, and a substrate mounted in the reaction tube is doped with p-type impurities. A method of manufacturing a semiconductor thin film, which comprises growing a gallium nitride-based compound semiconductor thin film. 2. The method for producing a semiconductor thin film according to claim 1, wherein the substrate is mounted with a semiconductor thin film growth surface facing downward. 3. The method for producing a semiconductor thin film according to claim 1, wherein the growing method is a metal organic chemical vapor deposition method. 4. The carrier gas based on nitrogen containing hydrogen mixed in a concentration of 2% or more and 20% or less is used as the carrier gas. Manufacturing method of semiconductor thin film.