JP2736417B2 - Semiconductor element manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor device having a GaAs semiconductor film formed on an alumina single crystal substrate.

[Prior art and its problems]

In recent years, the technology of applying a GaAs semiconductor film to a light emitting element or a light receiving element has been remarkably advanced. For example, a technique of epitaxially growing a GaAs semiconductor film on an alumina single crystal substrate has been disclosed in JP-A-62-202894 and JP-A-62-202894. 62−2321
According to this proposal, trimethylgallium (Ga (CH ₃ ) ₃ ) and arsine (AsH ₃ ) are used as reaction gases, and a metal-organic thermal decomposition vapor deposition (Metal-Organ) method is used.
A GaAs film is epitaxially grown on an alumina single crystal substrate by IC Chemical Vapor Deposition (abbreviated as MOCVD method). Then, the semiconductor element thus obtained is a light emitting element that can emit light from the substrate side.

However, the present inventors have found that the Ga
As semiconductor film has not yet obtained sufficient crystallinity,
It was found that further improvement was required.

Accordingly, it is an object of the present invention to provide a method for manufacturing a semiconductor device capable of obtaining the above GaAs semiconductor film.

[Means for solving the problem]

According to the present invention, in a method of manufacturing a semiconductor device in which a GaAs semiconductor film is formed on a C-plane alumina single crystal substrate installed in a reaction chamber by a MOCVD method, the vapor phase growth method includes the following steps (A) to (A). A method for manufacturing a semiconductor device, comprising the step of: C) is provided.

(A): The substrate is set within a temperature range of 350 to 550 ° C. and a mixed gas composed of an Al element-containing gas and an As element-containing gas, or an Al element-containing gas, a Ga element-containing gas, and an As element-containing gas. Is introduced into the reaction chamber, and an Al _x Ga _1-x As film (0 <x ≦ 1) having a thickness of 300 ° or less is generated by a vapor deposition method (B). Set the temperature in the temperature range of 550 to 950 ° C. and introduce the As element-containing gas into the reaction chamber. (C): Set the substrate in the temperature range of 550 to 700 ° C. Introducing an element-containing gas into a reaction chamber to form a GaAs semiconductor film by a vapor phase epitaxy method Hereinafter, the present invention will be described in detail.

The semiconductor device formed by the manufacturing method of the present invention is as shown in FIG. 1. In the figure, reference numeral 1 denotes an alumina single crystal substrate, and the epitaxial growth surface of the substrate is a C-plane. AlGaAs film 2 is formed on
As semiconductor film 3 is formed.

The present inventors have found that when a film in which part or all of GaAs is replaced with AlAs is formed between the GaAs semiconductor film 3 and the substrate 1,
It has been found that while the thickness of the film 2 is relatively small, it significantly affects the improvement of crystallinity.

When this element ratio is represented by the composition formula Al _x Ga _1-x As,
It is preferable to set the X value within the range of 0 <x ≦ 1, preferably 0.3 <x <0.8. If the x value is zero, that is, Ga
The crystallinity of the As semiconductor layer is somewhat inferior.

The thickness of the AlGaAs film 2 is 300 mm or less, preferably 10 to 3 mm.
The thickness is preferably set to 00 °, optimally in the range of 50 to 100 °, and if the thickness exceeds 300 °, the crystallinity is degraded.

The semiconductor element is formed by, for example, a manufacturing method described below.

This production method comprises the following steps (A) to (C):
D method.

(A): The substrate is set within a temperature range of 350 to 550 ° C. and a mixed gas composed of an Al element-containing gas and an As element-containing gas, or an Al element-containing gas, a Ga element-containing gas, and an As element-containing gas. Is introduced into the reaction chamber, and a 300-mm-thick Al _{x is} deposited on a C-plane substrate by vapor phase epitaxy.
A Ga _1-x As film is generated. In this step, the substrate temperature is set lower than the substrate temperature in the following steps (B) and (C), and nuclei required for crystal growth are generated by the CVD method.

The substrate temperature may be set in the range of 350 to 550 ° C, preferably 390 to 500 ° C.
When the temperature exceeds 50 ° C., homogeneous nuclei do not grow and defects occur at the interface.

The next step (B) is the Al produced by the step (A).
The GaAs film is thermally annealed to improve the crystallinity of the film, and the substrate temperature required for the thermal annealing is 550 to 950.
° C, preferably in the range of 650-850 ° C. Note that increasing the substrate temperature increases the As vapor pressure of the AlGaAs film,
As element-containing gas is introduced into the reaction chamber.

Step (C) is a step of performing epitaxial growth of GaAs, introducing a Ga element-containing gas and an As element-containing gas into the reaction chamber, and setting the substrate temperature to 550 to 700 ° C., preferably
When the temperature is set in the range of 570 to 650 ° C., these gases are thermally decomposed, and a GaAs film grows epitaxially on the AlGaAs film.

The Ga element-containing gas includes Ga (CH ₃ ) ₃ and Ga (C ₂ H ₅ ) ₃ , and the As element-containing gas includes AsH ₃ and AsCl ₃ .
In addition, Al element-containing gas includes Al (CH ₃ ) ₃ , Al (C ₂ H ₅ ) ₃ , Al
(Iso-C ₄ H ₉ ) ₃ and the like. Then, H ₂ or an inert gas (Ar, He, N ₂ , Ne, etc.) is used as a carrier gas for these gases.

Thus, according to the production method of the present invention, the alumina single crystal C
In epitaxial growth on a plane substrate, the off angle of the C plane is preferably set to 5 ° or less (excluding 0 °), preferably in the range of 0.5 to 3 °. The surface has remarkable smoothness.

Further, according to the manufacturing method of the present invention, it is preferable to set the following conditions in each step in order to improve the crystallinity of the GaAs semiconductor film.

In the step (A), the molar volume [A] of the As element-containing gas with respect to the total amount of the molar volume [Ga] of the Ga element-containing gas and the molar volume [Al] of the Al element-containing gas introduced into the reaction chamber [A
The ratio of [s], that is, ([As] / [Ga] + [Al]) is set to 10 or more, preferably 50 to 200, and all the gas inside the reaction chamber is set to 50 to 760 Torr.

In the step (B), the amount of the As element-containing gas introduced into the reaction chamber is 0.1 to 5 mol% by volume, preferably
What is necessary is just to set to 0.5 to 2 mol% by volume.

In the step (C), [As] / ([Ga] + [Al]) and the total gas pressure may be set to the same conditions as in the step (A).

Next, a high frequency induction heating type MOCVD apparatus will be described with reference to FIG.

In the figure, reference numeral 4 denotes a reaction chamber in which a susceptor 5 is installed, and an alumina single crystal substrate 6 is installed on the susceptor 5. A high frequency coil 7 is wound around the reaction chamber 4, and a high frequency power supply (not shown) is connected to the high frequency coil 7.
When high frequency power is applied to the high frequency coil 7, the susceptor 5 is induction heated. An ultra-high vacuum exhaust device 8 and an exhaust gas processing device 9 are connected to the reaction chamber 4, and the inside of the reaction chamber is evacuated by the ultra-high vacuum exhaust device 8 before film formation to remove residual gas inside the reaction chamber. Then, the As compound in the exhaust gas is removed by the exhaust gas processing device 9.

AsH ₃ gas in the first tank 10 and Si ₂ H in the second tank 11
_{The six} gases are sealed, and the flow rates discharged from these tanks are adjusted by mass flow controllers 12 and 13 and supplied to the first main pipe 14.

The third tank 15 is sealed with H ₂ gas, and this gas is highly purified through a purifier 16.
Is supplied to the mass flow controller 1
Adjusted by 7,18.

19 is a first bubbler containing a liquid of Ga (CH ₃ ) ₃ , 20 is a second bubbler containing a liquid of Al (CH ₃ ) ₃ , and 21 and 22 are respective bubblers 19 and 20. Is a thermostat for setting the temperature to a required temperature. The high-purity H ₂ gas supplied from the third tank 15 is introduced into the first bubbler 19 and the second bubbler 20, whereby the liquid in the bubbler is gasified and the second main pipe
Introduced to 23. The gas introduced into the second main pipe 23 is adjusted by the mass flow controllers 24 and 25, and
The high-purity H ₂ gas supplied from the tank 15 is introduced into the second main pipe 23 while being adjusted by the mass flow controller 18, and the H ₂ gas is a carrier gas of Ga (CH ₃ ) ₃ gas or Al (CH ₃ ) ₃ gas. become.

Thus, AsH ₃ gas and Si ₂ H ₆ gas are carried by the first main pipe 14, and Ga (CH ₃ ) ₃ gas and Al (CH ₃ ) ₃ gas are carried by the second main pipe 23, and are introduced into the reaction chamber 4. 26, 27, 28, 29,
30,31,32,33,34,35,36,37,38,39 indicate valves.

In the MOCVD apparatus having the above configuration, the substrate 6 that has been subjected to a predetermined cleaning process is placed on the susceptor 5. Then, in the step (A), the valves 34 to 39 are fully opened, and high-purity H ₂ gas is introduced into the reaction chamber 4 from the third tank 15,
Further, the valve 27 is fully opened, the AsH ₃ gas is released from the first tank 10, the amount of the released AsH ₃ gas is adjusted by the mass flow controller 12, and the gas is introduced into the first main pipe 14. Then, the valve 30 is closed, the valves 28 and 29 are fully opened, and H ₂ gas is introduced into the bubbler 19 to obtain Ga (CH ₃ ) ₃ gas. Further, the valve 33 is closed, the valves 31 and 32 are fully opened, and H ₂ gas is introduced into the bubbler 20 to obtain Al (CH ₃ ) ₃ gas. The supply amounts of these gases are set by the temperatures of the thermostats 21 and 22 and the mass flow controllers 24 and 25, and are introduced into the second main pipe 23.

In the next step (B), the valves 29 and 30 are closed and Ga (CH ₃ )
₃ gases and valves 32 and 33 are closed to prevent the introduction of Al (CH ₃ ) ₃ gas, and the temperature is set to be higher than the substrate temperature set in step (A) by induction heating. I do.

In the step (C), the valves 26 and 27 are opened and a Ga (CH ₃ ) ₃ gas is introduced into the reaction chamber to grow a GaAs film epitaxially.

In the case where the GaAs film is epitaxially grown, the valve 26 is opened, and when the Si ₂ H ₆ gas is introduced into the reaction chamber while adjusting the flow rate by the mass flow controller 24, the Si element is doped into the GaAs film, and the film is n-type. Can be controlled by semiconductor.

〔Example〕

 Next, examples of the present invention will be described.

In the MOCVD apparatus of FIG. 2 described above, a C-plane 2 ゜ off alumina single crystal substrate 6 is set on the susceptor 5 and
H ₂ gas from the tank 15 and AsH ₃ gas (H ₂ gas) from the first tank 10
10% diluted by gas) at a flow rate of 300 sccm
Further, Ga (CH ₃ ) ₃ gas is introduced into the reaction chamber 4 from the first bubbler 19 at a flow rate of 20 sccm, and Al (CH ₃ ) ₃ gas is introduced from the second bubbler 20 to the reaction chamber 4 at a flow rate of 10 sccm. Set the substrate temperature to 400 ° C and the reaction pressure to 50 Torr,
Then, the time of the vapor phase growth was changed, thereby forming AlGaAs films of various thicknesses. In addition, when the element ratio of each AlGaAs film was determined from the angle of the X-ray peak using a two-crystal X-ray diffractometer, all were Al _0.5 Ga _0.5 As.

For each AlGaAs film, the following (B) step and (C)
The process was performed.

According to the step (B), the substrate temperature is set to 700 ° C., and Ga
The introduction of (CH ₃ ) ₃ gas and Al (CH ₃ ) ₃ gas was stopped, and the other conditions were set to the same conditions as above, and thermal annealing was performed for 20 minutes.

According to the step (C), the substrate temperature is set to 600 ° C.
(CH ₃ ) ₃ gas was introduced into the reaction chamber at a flow rate of 20 sccm and AsH ₃ gas was introduced into the reaction chamber at a flow rate of 300 sccm, and the other conditions were set exactly the same as in the step (B). 3μ thickness
The m m GaAs film was epitaxially grown.

For the various semiconductor devices thus obtained, various Ga
When the crystallinity of the As epitaxial film at room temperature was measured using a two-crystal X-ray diffractometer, the results shown in FIG. 2 were obtained. This measurement was performed using the X-ray source CuKα ₁ ,
The test was performed under the conditions of a crystal InP (400) and an output of 30 KV.

In this example, instead of forming the AlGaAs film, the emission of the Al (CH ₃ ) ₃ gas was stopped to form a GaAs film, and various semiconductor devices obtained thereby were used as comparative examples.

In FIG. 2, the horizontal axis is the thickness of the AlGaAs film or the GaAs film of the comparative example, the vertical axis is the half-width indicating the crystallinity of the GaAs semiconductor film, and the mark ○ is the measurement plot of the present example. The symbol ● indicates a measurement plot of the comparative example, and a and b indicate respective characteristic curves.

As is clear from FIG. 2, the semiconductor device of this example has a smaller half width at 300 mm or less in thickness of the AlGaAs film than that of the comparative example. I understand.

〔The invention's effect〕

As described above, according to the semiconductor device of the present invention, the epitaxial growth surface of the GaAs semiconductor has smoothness, and thus, when used as a light emitting device, its luminous efficiency is significantly increased.

Further, according to the semiconductor element of the present invention, there is an advantage that fine processing can be performed on a semiconductor surface, and therefore, various thin film devices can be manufactured.

Although the present embodiment describes the epitaxial growth of a GaAs semiconductor film, the same effect can be obtained by using the manufacturing method of the present invention for GaAlAs, GaAsP, and GaInAs in which part of GaAs is replaced by Al, P, In, or the like. I think that is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a layer structure of a semiconductor device formed by the manufacturing method of the present invention, and FIG. 2 is a CVD device used in the embodiment.
FIG. 3 is an explanatory view of the device, and FIG. 3 is a diagram showing the half width of a GaAs film. 1 ... Alumina single crystal substrate 2 ... AlGaAs film 3 ... GaAs semiconductor film

Claims (1)

(57) [Claims] 1. An alumina single crystal C installed inside a reaction chamber.
In a method of manufacturing a semiconductor device in which a GaAs semiconductor film is formed on a surface substrate by metal organic chemical vapor deposition vapor deposition, the vapor phase growth comprises the following steps (A) to (C) in sequence. Element manufacturing method. (A): The substrate is set within a temperature range of 350 to 550 ° C. and a mixed gas comprising an Al element-containing gas and an As element-containing gas, or an Al element-containing gas, a Ga element-containing gas, and an As element-containing gas. Is introduced into the reaction chamber, and an Al _x Ga _1-x As film (0 <x ≦ 1) having a thickness of 300 ° or less is generated by a vapor deposition method (B). The temperature is set within a temperature range of 550 to 950 ° C., and an As element-containing gas is introduced into the reaction chamber. (C): setting the substrate in a temperature range of 550 to 700 ° C., introducing a Ga element-containing gas and an As element-containing gas into the reaction chamber, and forming a GaAs semiconductor film by a vapor deposition method.