JP3052399B2 - Method for manufacturing compound semiconductor 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 compound semiconductor film widely used in light emitting diodes, semiconductor lasers, photodiodes, solar cells, electronic devices, and the like. The present invention relates to a method for producing a compound semiconductor film having a large crystal grain size.

[0002]

2. Description of the Related Art Compound semiconductor devices are made of GaAs or I.D.
An ingot of nP or the like is sliced to a predetermined thickness, and GaAs, A
It is manufactured by epitaxially growing a compound semiconductor such as lGaAs, InP, InGaAsP and the like, which is lattice-matched to each substrate, and further processing the compound semiconductor. Alternatively, GaAs is introduced by introducing a strained superlattice or a thick buffer layer.
Attempts have also been made to manufacture materials having different lattice constants, such as s / Si and InGaAs / GaAs, by an epitaxial growth method.

[0003]

However, in the above-described conventional growth method, the number of nuclei generated increases with the elapse of the growth time, and the control of nucleation is limited. It is difficult to get.

For example, in the case of a GaAs substrate, a wafer having a diameter of up to 3 inches is only commercially available. Also,
Since compound semiconductor substrates such as GaAs and InP are expensive, the cost of devices manufactured on these substrates is increased.

On the other hand, when inexpensive Si is used as a semiconductor substrate, for example, GaAs and S
Since there is a lattice mismatch of about 4% with the i-substrate, even if a strained superlattice or a buffer layer is introduced, an undesired dislocation remains in the grown film.

Further, since crystal growth is performed at a high temperature,
The difference in the coefficient of thermal expansion between the substrate and the grown film becomes a problem. That is, when there is a large difference between them, there is a problem that stress is generated on the film surface when cooled to room temperature even if lattice matching is performed at the growth temperature.

The present invention has been made to solve the above-mentioned conventional problems, and is directed to a metal organic chemical vapor deposition (MO) method.
It is an object of the present invention to provide a method for forming a semiconductor film having good crystallinity on an amorphous substrate by using VPE (Metal Organic Vapor Phase Epitaxy).

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for forming a compound semiconductor film on the surface of a substrate by supplying a crystal growth raw material onto the amorphous substrate using metal organic chemical vapor deposition. Introduced into the reaction chamber in advance, keeping the substrate temperature in a high temperature state, supplying the Group III element raw material and the Group V element raw material diluted by the carrier gas into the reaction chamber through the introduction pipe while controlling the respective molar flow rates, A first growth step of forming minute crystal nuclei as a reaction product of the two raw materials on the substrate kept in the high temperature state; and elevating the atmosphere in the reaction chamber after the first growth step to reduce the substrate temperature. A second growth step of further raising the temperature and supplying each of the raw materials onto the substrate on which the crystal nuclei are formed to grow the crystal nuclei.

In the present invention, the raw material supplied is selected from the group consisting of III
The group element material can be selected from the group consisting of Al, Ga, In, other group III elemental metals, or organometallic compounds thereof. Examples of the organometallic compound include Al (CH ₃ ) ₃ , Al (C ₂ H ₅ ) ₃ , and G
a (CH ₃ ) ₃ , Ga (C ₂ H ₅ ) ₃ , In (CH ₃ )
₃ and In (C ₂ H ₅ ) ₃ . In addition, P, As, Sb , and other V group materials are used as group V element materials.
It can be selected from the group consisting of element hydrides or their organometallic compounds. Examples of the organometallic compound include P (CH ₃ ) ₃ , P (C ₂ H ₅ ) ₃ ,
As (CH ₃ ) ₃ , As (C ₂ H ₅ ) ₃ , Sb (C
H ₃ ) ₃ and Sb (C ₂ H ₅ ) ₃ .

As a carrier gas for diluting the raw materials, any gas which is inert with both raw materials can be used.
It can be selected from gases such as ₂ , N ₂ and He.

When a crystal made of a compound semiconductor material is grown on a substrate, the size of the crystal is determined by the growth temperature conditions. Therefore, according to the present invention, in the first growth step for forming minute crystal nuclei, the temperature of 800 ° C.
As a second growth step of forming a crystal nucleus so that deposition occurs in an atmosphere having a temperature range of less than 00 ° C. and growing the subsequent crystal nucleus, at a higher temperature than the growth temperature in the first growth step, In addition, it is preferable to supply the raw materials in an atmosphere having a temperature of 1000 ° C. or lower.

That is, by performing the treatment in an atmosphere that satisfies the temperature condition of the following equation (1), 800 ° C. ≦ first growth step <second growth step ≦ 1000 ° C. Deposition does not occur, the size of the crystal nuclei formed by the crystal growth processing in the first growth step can be increased, and a compound semiconductor film having good crystallinity can be formed on the amorphous substrate.

In the present invention, the temperature condition is satisfied, and the pressure in the reaction chamber is 1 Torr or more and 760 Ton.
A following range rr, it is more preferred that the growth pressure in the second growth step by setting the following growth pressure of the first growth step is performed crystal nuclei growth.

That is, it is preferable to perform the treatment in an atmosphere that simultaneously satisfies the temperature conditions and pressure conditions of the following equations (1) and (2). 800 ° C. ≦ first growth step <second growth step ≦ 1000 ° C. (1) 1 Torr ≦ second growth step ≦ first growth step ≦ 760 Torr (2) The treatment is performed in an atmosphere that satisfies the above temperature conditions and pressure conditions simultaneously. By doing so, in the second growth step, the raw material can be absorbed into the crystal nuclei formed on the amorphous substrate in the first growth step and the size thereof can be increased, and the compound semiconductor film having better crystallinity can be formed on the amorphous substrate. Can be formed on.

In the first growth step and the second growth step, the group III element source and the group V element source are diluted into a carrier gas through separate introduction pipes and supplied into the reaction chamber. The ratio V / III is usually introduced in the range of 5 to 200.

Further, the supply time of the raw material into the reaction chamber is not uniquely determined because it depends on the temperature in the reaction chamber (substrate temperature), the supply amount of the adsorbed species per unit time, the volume of the reaction tube, and the like. , Usually in the range of one second to several seconds.

FIG. 3 is a graph showing the growth temperature dependence of the density of GaAs crystal nuclei on an amorphous substrate at atmospheric pressure. The growth of GaAs depends on the GaAs supplied.
Adsorbed species are adsorbed on the surface of the substrate and diffused on the surface with desorption, and with a certain probability, stable nuclei exceeding the critical size (the smallest crystallite size that can be present as a crystal nucleus energetically) Generate FIG. 3 shows that the higher the growth temperature, the lower the nucleus generation density. This is because, at high temperatures, the diffusion length on the surface of the adsorbed species adsorbed on the substrate, that is, the diffusion distance between nuclei becomes longer. If crystal nuclei exist within the diffusion distance of the adsorbed species, the potential energy decreases due to adsorption on the surface. Since the decrease in the potential energy based on the bond between the raw materials is larger than that, the probability that the surface adsorbed species is absorbed by the existing crystal nuclei is increased, and thus the probability of generating new crystal nuclei is reduced.

However, since a certain number of adsorbed atoms always exist on the substrate, the probability of generating a new crystal nucleus is not strictly zero. For this reason, the number of crystal nuclei increases over time, and the nucleus density increases. Further, the supply amount of the raw material per unit time is related to the change in the density of the adsorbed species on the substrate surface, and even when the growth temperature and the total supply amount of the raw material are constant, the supply amount of the raw material per unit time is large. The production density is higher.

When GaAs crystal nuclei are formed on an amorphous substrate under reduced pressure, the value of the density of GaAs crystal nuclei at each growth temperature becomes smaller than when the GaAs crystal nuclei are formed at atmospheric pressure.

FIG. 4 shows GaAs on an amorphous substrate.
5 is a graph showing the growth time dependence of the film thickness. As shown in the figure, the film thickness is proportional to the growth time but does not pass through the origin. The generation of crystal nuclei is qualitatively determined by the amount of decrease in the potential energy due to the formation of the crystal, the amount of increase in the interface energy between the substrate and the crystal, and the amount of increase in the surface energy of the crystal. For this reason, a crystal nucleus is generated only when a number of atoms or more necessary for forming a critical nucleus are bonded. The raw material supplied after the formation of the crystal nuclei has a much lower adhering rate of Ga on the amorphous substrate than on the GaAs film, for example, so that most of the adsorbed species are consumed for crystal growth.

In FIG. 4, the growth delay in the initial stage of the growth corresponds to the time required to form a critical nucleus, and the inclination substantially coincides with the growth rate on the GaAs substrate.

[0022]

According to the present invention, a compound semiconductor film is manufactured through two growth steps on an amorphous substrate using a metalorganic vapor phase epitaxy method. High crystals can be grown.

Further, since the crystal growth is performed by setting the substrate temperature in the second growth step to be higher than the substrate temperature in the first growth step, the diffusion distance of the adsorbed species is lengthened and energy is not increased. By increasing the desorption probability of the stable adsorbed species, the probability of generating new nuclei on the amorphous substrate can be reduced, and the crystal nuclei generated while maintaining the number of crystal nuclei generated in the first growth step can be reduced. Can grow.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming a compound semiconductor film according to the present invention will be described below. First, Si used as the substrate 1
Etching with hydrofluoric acid was performed as a pretreatment of the O ₂ material. Further, in order to prevent abnormal generation of crystal nuclei due to impurities in the substrate 1, the substrate 1 was introduced into a chamber serving as a reaction chamber and exposed to HCl at 1000 ° C. for 15 minutes to clean the surface.

After that, the temperature in the reaction chamber is lowered to 850 ° C. and the pressure is set to the atmospheric pressure (760 Torr).
A second growth was performed. Ga (C
H ₃ ) ₃ (trimethylgallium), AsH ₃ (arsine) as a group V element material, and H ₂ as a carrier gas
Using Ga (CH ₃ ) ₃ and A diluted with H ₂
sH ₃ was introduced into the reaction chamber from separate gas introduction tubes.

Further, the ratio V / III of the molar flow rate of each raw material supplied in this growth step is adjusted to be 40,
The raw material supply amount per unit time is 2 * 10 ^-5 mol / m
The raw material was supplied for 15 seconds, set to in.

[0027] Consequently, FIGS. 1 (a) and a diameter of about 20nm is formed on SiO ₂ substrate 1 as shown in (b) Ga
As crystal nuclei 2 were formed. The growth rate on the substrate 1 under these conditions was about 3 μm / h in the thickness direction. The distance between the formed GaAs crystal nuclei was about 30 μm, and the density was about 10 ⁵ cm ⁻² .

After the first growth, the temperature in the reaction chamber was reduced to 8
The temperature was raised to 80 ° C. and the pressure was reduced to 100 Torr. After the temperature and pressure became constant, the second growth was performed. The second growth uses Ga (CH ₃ ) ₃ as the group III element source, AsH ₃ as the group V element source, and H ₂ as the carrier gas in the same manner as the first growth. The flow rate ratio V / III was adjusted to be 40, and the raw material supply amount per unit time was 2 * 10 ^-5.
By performing the crystal growth for 30 minutes at mol / min, the SiO 2 is grown as shown in FIGS. 2 (a) and 2 (b).
₂ GaAs having a grain size of about 35 μm on the substrate 1
The s film 3 was formed.

In the obtained film, no dislocation due to lattice mismatch occurred, and the rocking curve of the X-ray diffraction peak of the grains was measured.
A full-width half-width comparable to that of the s or GaAs epitaxial film was obtained.

As described above, an amorphous substrate has been
Although the description has been made by taking the iO ₂ substrate as an example, the invention is not limited to the material of the substrate, and can be applied to, for example, a multi-component glass. In addition, by changing the growth conditions,
s growth method as well as InP, AlGaAs,
Various semiconductor materials such as InGaAsP, ZnS, ZnSe, and CdTe can be appropriately selected. Furthermore, the present invention can be applied to a crystal nucleus formed in the first growth step and a crystal formed in the second growth step grown using different raw materials.

[0031]

According to the present invention, a compound semiconductor film is manufactured on an amorphous substrate through two growth steps by using a metal organic chemical vapor deposition method, so that a crystal having a high nucleus density can be grown. it can. In the second growth step, the fine crystals formed in the first growth step act as nuclei, which further grow to have a large grain size and form a compound semiconductor film having good crystallinity on an amorphous substrate. Can be formed. Therefore, a compound semiconductor substrate that is inexpensive and has a large area can be obtained as compared with a conventional substrate. This has the effect of reducing the cost of various compound semiconductor devices including light emitting diodes.

Further, since there is no strong chemical bond between the grown compound semiconductor film and the amorphous substrate,
Stress in the crystal based on the difference in thermal expansion coefficient can be reduced.

Further, by utilizing the feature that a crystalline and large-area substrate can be obtained, application to, for example, a high-efficiency solar cell can be expected.

[0034]

[Brief description of the drawings]

FIG. 1A shows GaAs in a first growth step of the present invention.
Front view of an amorphous substrate on which crystal nuclei are formed, (b)
Is a plan view of FIG.

FIG. 2 (a) shows GaAs after a second growth step of the present invention.
front view of an amorphous substrate on which an s-crystal film is formed,
(B) is a plan view of (a).

FIG. 3 is a graph showing the growth temperature dependence of the density of crystal nuclei in GaAs growth on an amorphous substrate.

FIG. 4 is a graph showing the growth time dependence of the GaAs film thickness on an amorphous substrate.

[Explanation of symbols]

 Reference Signs List 1 amorphous substrate 2 GaAs crystal nucleus 3 GaAs crystal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 H01L 21/365

Claims (3)

(57) [Claims] 1. A method for producing a compound semiconductor film on an amorphous substrate using a metalorganic vapor phase epitaxy method, wherein the compound semiconductor film is introduced into a reaction chamber in advance and placed on a high temperature state together with the atmosphere in the reaction chamber. Supplying a Group III element raw material diluted by a carrier gas and a Group V element raw material diluted by a carrier gas into the reaction chamber while controlling the molar flow rate respectively, through an introduction pipe, and reacting the two raw materials on the substrate. A first growth step of forming fine crystal nuclei as a product, and thereafter, the temperature of the reaction chamber is increased, and the crystal nuclei are supplied to the substrate at the time of forming the crystal nuclei by forming the crystal nuclei. A method for producing a compound semiconductor film, comprising at least a second growth step of further growing. 2. The group III element material is Al, Ga, I
n, another group III elemental metal, or a material selected from the group consisting of organometallic compounds thereof, wherein the group V element material is As, P, Sb , a hydride of another group V element , or a hydride thereof. The method for producing a compound semiconductor film according to claim 1, wherein the method is a material selected from the group consisting of organometallic compounds. 3. A first growth step of forming fine crystal nuclei on the substrate and a second growth step of further growing the crystal nuclei formed on the substrate satisfy the following expression (1). 2. The method of manufacturing a compound semiconductor film according to claim 1, wherein the method is performed in an atmosphere in which the compound semiconductor film is formed. 800 ° C. ≦ first growth step <second growth step ≦ 1000 ° C. (1)