JPS62296510A - Formation of compound semiconductor thin film and apparatus therefor - Google Patents

Abstract

PURPOSE:To form a compound semiconductor film with good reproducibility by providing a pair of vapor phase reaction chambers to be independently closed, and a semiconductor substrate replacing chamber or passage having a pair of gate valves for opening or closing between the pair of vapor phase reaction chambers. CONSTITUTION:Vapor growth chambers 22, 23 are independently provided for purifying the surface of an Si substrate 24 and for growing an Si film on the substrate. Further, a semiconductor substrate replacing chamber 21 or passage having a pair of gate valves 32, 33 for opening or closing therebetween is interposed between the chamber 22 and the chamber 23 to move a susceptor 25 for placing the substrate between the chambers 22 and 23 without contacting it with an atmospheric air. Thus, a compound semiconductor film having excellent crystallinity can be formed with good reproducibility.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Technical Field to which the Invention Pertains) The present invention provides a silicon thin film and GaAs film on a silicon substrate.
The present invention relates to a method and apparatus for forming a compound semiconductor thin film made of an m-v group compound such as GaP, or a ■-■ group compound such as CdS.

(Prior Art) In recent years, a technique for forming a thin film of a compound semiconductor such as GaAs or GaP on a silicon semiconductor substrate has attracted much attention. The goal of this technology is to create new functional devices that have not existed before by complementary fusion of the features of silicon semiconductors and the respective features of compound semiconductors. For example, the realization of multifunctional opto-electronic integrated circuits by forming a GaAs film on a silicon (St) substrate, compound semiconductor solar cells and St.
These include the realization of highly efficient and low-cost solar cells by increasing the number of junctions in solar cells.

Incidentally, conventionally, metal organic pyrolysis vapor deposition (MOCVD) has been mainly used to form a compound semiconductor thin film such as GaAs on an 81 substrate. This is MOC
This is because the VD method has excellent film thickness, controllability of film composition, and mass production. However, until now APB (antiphase boundary) has been deposited on a Si substrate with a mirror surface.
The reproducibility in forming a compound semiconductor thin film that does not contain y) is extremely poor, and the situation has never been comparable to established techniques. The main reason for this is that no MOCVD apparatus suitable for epitaxial growth of compound semiconductors on Si substrates has been developed. In other words, conventionally, such epitaxial growth on a different type of substrate has been performed using a normal apparatus for epitaxial growth on a similar type of substrate. As a result, there were important problems as described below.

FIG. 3 is a configuration diagram of a conventional vertical reaction tube type MOCVD apparatus, in which 1 is an 81-substrate exchange chamber, 2 is a growth chamber, 3 is a carburetor segment, 4 is an St substrate, and 5 is a reaction product deposit. It is. By having a two-chamber configuration of the SI substrate exchange chamber 1 and the growth chamber 2 in this way, the introduction of oxygen and moisture into the growth chamber 2 due to SI substrate exchange is reduced, and a high-quality epitaxially grown film can be obtained. . An important point in forming a compound semiconductor thin film on a Si substrate is to achieve a clean 81 substrate surface free from oxides and the like. To clean the surface of the 81 substrate, a method is usually used in which the St substrate is heated to a high temperature of about 1.000°0 in hydrogen gas. The formation of a compound semiconductor thin film including the St substrate surface cleaning treatment using the apparatus shown in FIG. 3 was performed in the following order. The first is the 9-year firing treatment of the susceptor 3. This is to remove the compound semiconductor that has adhered to the surface of the susceptor 3 due to the previous growth.The susceptor 3 is placed at a predetermined position in the growth chamber 2, and while hydrogen gas is introduced into the growth chamber 2, the temperature is raised to 1,000°C or higher. Heat. Through this treatment, the compound semiconductor adhering to the surface of the susceptor 3 is decomposed and removed. Next is loading of the Si substrate 4 and surface cleaning treatment. Place the Si substrate 4 on the susceptor 3 in the 81 substrate exchange chamber 1 through the St substrate exchange port, evacuate the Sl substrate exchange chamber 1, then evacuate the growth chamber 2, and then move the susceptor 3 into the growth chamber 2. place it in the specified position.

Next, while introducing hydrogen gas into the growth chamber 2, the susceptor 3
is heated to raise the temperature of the 81 substrate 4 to 1,000° C. (substrate heat treatment).

(Problems with Prior Art) However, the above-described conventional compound semiconductor thin film forming method and apparatus have the following problems.

That is, on the inner wall of the growth chamber 2, there is a reaction product deposit 5 generated in the previous growth reaction, and this is partially decomposed and removed during the 9-baking treatment of the susceptor 3, but the heating temperature is low. Therefore, most of the particles remain even during the cleaning process of the Si substrate 4. The components of this remaining reaction product deposit 5 include, in addition to the synthesized compound semiconductor, the organic metal itself, and intermediate reaction products between the organic metal and the hydride of group (I) elements. Some of these are also decomposed by the radiant heat from the susceptor 3 during the cleaning process of the Fist substrate 4, and the growth chamber 2
Specifically, oxides adhere to and contaminate the surface of the active Si substrate 4 which has been removed and cleaned by heating.

These contaminants are chemically bonded to St and cannot be removed at temperatures of about 1,000°C. The next step is the growth of a compound semiconductor on the Si substrate 4, but if the compound semiconductor is grown on the 81 substrate 4 with such surface contaminants, these contaminants may be the cause of nucleation. Therefore, a specular film cannot be obtained, and the grown film has an APR (
antl-phase boundary). The amount of reaction product deposits 5 in the growth chamber 2 and the way they are layered vary depending on the number of film growths and the flow of gas during growth. , the amount of signposts also differs. Finally, the degree of surface contamination of the St substrate 4 differs with each growth, and when there is no surface contamination, a mirror-like film without APR may be obtained, but the reproducibility is extremely low. Ta.

In addition, when producing a compound semiconductor element on an S1 element, conventionally, an 81 film was first formed on an 81 substrate to produce an St element, and then the Sl substrate was exposed to the atmosphere and then another It is also possible to fabricate a compound semiconductor device by forming a compound semiconductor film on the 81 layer using a device, but in this case, as described above, the 81 substrate is heated by 1, It is necessary to clean it by heating it to over 000°0. However, such high-temperature treatment causes the problem of deterioration of the Si element, and even if the S1 element can withstand such high-temperature treatment, conventional MOCVD equipment still suffers from the above-mentioned surface contamination problem. Therefore, in any case, it was impossible to form a compound semiconductor film that does not contain AP13'i with good reproducibility.

(Means for solving the problems) The present invention has been made in view of the above circumstances, and includes 81
The present invention aims to solve the problem of surface contamination of a substrate and provide a method and apparatus for forming an 81 thin film and a compound semiconductor thin film on an St substrate with high quality and good reproducibility.

The present invention provides a first method for solving the above problems.
By providing an independent vapor phase growth furnace for cleaning the surface of the 81 substrate and growing the 61 film on the 81 substrate, the problem of surface contamination such as oxides on the St substrate when forming compound semiconductor thin films can be solved. This is an attempt to solve the problem. Second, by interposing a semiconductor substrate exchange chamber or passageway between the 81 vapor phase growth chamber and the compound semiconductor vapor phase growth chamber, which has a pair of f-) valves for opening and closing between them. The susceptor placed between these growth chambers is made to be able to move without being exposed to the outside air, thereby solving problems such as deterioration of St crystals due to high temperature treatment and generation of APR.

Hereinafter, the present invention will be explained with reference to an illustrated embodiment.

(Example) FIG. 1 shows an example of the apparatus used in the method of forming a compound semiconductor thin film of the present invention, and FIG.
FIG. 2 is a schematic diagram of the device shown in the figure, viewed from above. In these figures, 21 is a semiconductor substrate exchange chamber, 22 is an S1 pitaxial growth reaction chamber (hereinafter referred to as the first reaction chamber), and 23 is an organometallic pyrolysis furnace for compound semiconductor thin film growth (hereinafter referred to as the second 24 is an Sl substrate, 25 is a susceptor, 26 and 27 are susceptor moving jigs, 28 is a vacuum pump, 29, 30.31 is a gas introduction pipe, 32 and s
sB is dirt pulp, 34 and 35 are high frequency heating coils, and 36 is a gas exhaust pump.

Next, an example will be described in which this apparatus is used to grow a St thin film on the Si substrate 24, and further to grow a GaAs thin film thereon.

91 Example 1 First, the susceptor 25 was sufficiently air-baked in the reaction chamber 22 of the ship 1, and then the susceptor 25 was transferred to the semiconductor substrate exchange chamber 21. Next, the degreased Si substrate 24 was set in the susceptor 25 in the semiconductor substrate exchange chamber 21, and the exchange chamber was evacuated using the pump 28 to create a vacuum, and the first reaction chamber 22 was also evacuated. . Then,
After opening the dart pulp 32 and moving the susceptor 25 to the first reaction chamber 22 using the moving jig 26, the dart pulp 32 was closed again, and then the mixture was diluted with hydrogen gas, for example, to 50% through the gas introduction pipe 29. Susceptor 25 and S! while flowing HCt gas! The substrate 24 was heated at 1100''O for 10 minutes using the high frequency heating coil 34.

By this operation, the oxide on the surface of the S1 substrate 24 was completely removed, and the surface of the Si substrate 24 was etched, for example, by about 0.3 μm, so that a very clean surface 81 could be formed. After completing this etching process, the Si substrate 24 is
Heat to 0°0, and in that state, introduce H7 through the gas introduction pipe 29 at a flow rate of 10t/min and 5Ict4 to 20#IlZ for 20 minutes.
An 81 film with a Ω mouth was grown (this grown St film showed no dislocations or stacking faults at all as a result of inspection, which suggests that the 81 film was grown on the extremely clean surface of the 81 substrate 24). ). During this 81 film growth process, H2 gas is flowed into the semiconductor substrate exchange chamber 21 at a flow rate of 217 minutes, and after the second reaction chamber 23 is evacuated, H2 gas is passed through the gas introduction pipe 30 at a flow rate of 217 minutes. The exchange chamber 21 and the second reaction chamber 23 were kept in a H2 gas atmosphere.

After the above-mentioned 81 film growth is completed, the temperature of the Sl substrate 24 is lowered to 200° C. or less, and then the dirt pulp 32 is opened and the susceptor 25 is
was transferred to the exchange chamber 21, and then the dart pulp 32 was closed. Next, open the dart pulp 33, move the susceptor 25 to the second reaction chamber 23 using the moving jig 27, and then f-)
Valve 33 was closed. During such movement of the susceptor 25, the 81 substrate 24 is transported in a very high purity H2 gas atmosphere, so there is no risk that the surface of the grown St film will be contaminated or oxidized.

Next, H2 gas was flowed into the second reaction chamber 23 from the gas introduction pipe 30 for 317 minutes, and A s H5 was flowed at a flow rate of 10 ml and 11 minutes, and at the same time, the exhaust pump 16 was used to pump the second reaction chamber 23 to zero.
．． The susceptor 25 was heated to 450°0 using the high frequency heating coil 35 while maintaining the pressure at 1 atm. 20° in this state
50 m/! of H2 gas bubbled through triethyl gallium kept at 0. A GaAs film of approximately 150× was grown on the grown St model film (low temperature grown film).

Next, the temperature of the susceptor 25 is raised to 700°0, and in addition to the bubbled H2 gas, SiH with a concentration of 100 ppm is added.
4 was simultaneously flowed for 1 hour at a rate of 3rnl/min (high temperature growth film). Thereafter, the heating was stopped, and when the temperature reached 400°C or lower, the supply of A m H3 and H2 gas was stopped. The reason why GaAs epitaxial growth is performed in two stages, low temperature and high temperature, is to obtain a mirror-like film, and this is not an essential operation for growing a GaA film on a clean 81 surface, which is the gist of the present invention. do not have. The thickness of the nine GaAa films thus obtained was 2.5 μm, and as a result of an etch test using molten KOH, one APR was not generated over the entire surface of the 81 substrate with a diameter of 2 inches. It was confirmed that there was no such thing. Furthermore, the carrier concentration of the GaAs film with is I
X 10”cm-3, mobility is 7,000cIr at room temperature
L2/V, S, and G grown on a GaAs substrate
aj) It was confirmed that there was no inferiority compared to that of the V membrane.

Note that after the growth of the GaA1 film, polycrystalline GaAs will adhere to the part of the susceptor 25 that is not covered by the 81 substrate 24, but the susceptor 25 should be thoroughly baked in the first reaction chamber 22 as described above. As a result, this adhered GaAs polycrystal could be completely removed.

The growth of the GaAs film on the St mock film was performed by the same operation as above.
After 0 attempts, the variation in GaAs film thickness and mobility was within 5 inches, and a mirror-like GaA film with extremely good reproducibility and no APR was obtained.

Example 2 An example of manufacturing a so-called monolithic cascade type solar cell in which a St solar cell and a GaAs solar cell are laminated on one 81 substrate will be described using the apparatus shown in FIG.

The edge of the n-type S1 substrate after degreasing and cleaning was placed in the first reaction chamber 22 according to the same procedure as in Example 1, and Si was heated using HCt gas.
The surface of the substrate was etched. After that, H2 was flowed at a flow rate of 101/min, 5tcz4 at 201114/min, and 180 ppm phosphine at a flow rate of 11/min for 20 minutes, then the supply of only phosphine was stopped, and 1100 p/min was supplied instead.
p of diborane was introduced for 5 minutes at a flow rate of 10 doors l/min.

As a result, an n-type S1 with a thickness of 6 μm is placed on the n-type 81 substrate 24.
film (carrier concentration 1017σ-3), followed by a thickness of 1,
A p-type S1 film (1918m-') of 5 fim was formed, and then the susceptor 25 was moved to the second reaction chamber 23 in the same manner as in Example 1. First, while heating to 450℃, add triethyl gallium C (50ml for 11 minutes) and silane (30ml).
R1/min) was flowed for 2 minutes, and then the temperature of the susceptor 25 was raised to 700° C. while maintaining both flow rates, and the flow was continued for about 1 hour. At this point, only the supply of silane was stopped, and 1000 pp.
ml of dimethyl zinc was flowed for 10 minutes at a flow rate of 200 ml/Z. This results in a 2.5 μm thick n-type GaAs film (
10cIIt), on which a 0.4 pm thick p-type GaA
s film (5x 10"cTL-3) is formed.Furthermore, the temperature of the susceptor 25 is raised to 800°0, and trimethylaluminum (-15°0 heat retention, H2 flow 'M'1
2ml/Z) was flowed for 10 minutes, and finally the supply of trimethylaluminum was stopped and only triethylgallium and dimethylzinc were flowed for 2 minutes.

As a result, a thickness of 0 is formed on the GaA@ film including the pn junction.
, 5 μm p-type At, ), B G&o, z Aa and a 0.174 m thick GaAs film were laminated. The former was used as a window layer for irradiating sunlight, and the latter was used as a cap layer for electrodes.

The solar cell produced in this way has a wavelength of 0.3 to 1.1 μm.
It was confirmed that the two solar ponds were working organically since the solar cell exhibited spectral sensitivity characteristics that reacted to light of 2.0 V, and an open-circuit voltage of 2 V was obtained.

(Effects of the Invention) As described in detail above, when forming a composite semiconductor thin film, the present invention first grows a St film on a St substrate in a vapor phase, and then grows a GaA film while maintaining it in a high purity H2 gas atmosphere. By transporting the film to the growth chamber, the problem of contaminants on the 81 surface was completely solved, and it became possible to produce a compound semiconductor thin film with excellent crystallinity with good reproducibility.

In the above example, an example was explained in which an S1 film not containing a dopant was formed on an St substrate. By forming a junction and laminating a GaAs film or an AtGaA@ film having a pn junction on the S1 film, it is possible to fabricate a monolithically laminated element such as an S1 element and a compound semiconductor element, such as a multijunction solar cell. can.

Furthermore, as mentioned above, the susceptor does not come into contact with the outside air,
Since it is possible to freely move back and forth between the two growth furnaces (first and second reaction chambers), it is also possible to fabricate an element with a multilayer structure in which an S1 film is further vapor-phase grown on a compound semiconductor film.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a semiconductor thin film manufacturing apparatus according to an embodiment of the present invention, FIG. 2 is a schematic diagram of the apparatus shown in FIG. 1 viewed from above, and FIG. 3 is a conventional semiconductor thin film manufacturing apparatus. FIG. DESCRIPTION OF SYMBOLS 1...81 substrate exchange chamber, 2... Growth chamber, 3... Carbon susceptor, 4...81 substrate, 5... Reaction deposit, 2I... Semiconductor substrate exchange chamber, 22...・First reaction chamber, 23... Second reaction chamber, 24... Sl substrate,
25...Susceptor, 26.27...Susceptor moving jig, 28...Vacuum pump, 29,30.31...Gas introduction pipe, 32,33...ff-) Pulp% 34.3
5... High frequency heating coil, 36... Exhaust pump. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (4)

[Claims] (1) A cleaning process to remove foreign matter from the surface of the silicon substrate; introducing a raw material gas containing silicon hydride or chloride as a main component onto the substrate, and causing a thermal decomposition reaction to cause silicon to form on the substrate. A step of epitaxially growing a film; then, the substrate is introduced into a compound semiconductor growth chamber via a path maintained in a hydrogen atmosphere, and a Group II or III element of the periodic table is introduced into the growth chamber. A method for forming a compound semiconductor thin film, comprising the step of epitaxially growing a compound semiconductor thin film on the epitaxially grown silicon film by thermal decomposition of an organic metal and a Group VI or Group V element hydride. (2) Claim 1, in which the epitaxial growth of a compound semiconductor thin film is performed in two stages: low temperature and high temperature.
A method for forming a compound semiconductor thin film as described in . (3) The method for forming a compound semiconductor thin film according to claim 1, wherein the epitaxial growth step of the silicon film is performed in an atmosphere containing a dopant gas. (4) a pair of gas-phase reaction chambers each having an exhaust port, a susceptor introduction means for holding a semiconductor device substrate, a heating mechanism, and a raw material gas introduction port, and which can be closed independently; the pair of gas-phase reaction chambers; A semiconductor substrate exchange chamber or a passageway is provided between the chambers and has a pair of gate valves for opening and closing between the chambers, and the gas phase reaction chambers are connected through the semiconductor substrate exchange chamber or passageway. A compound semiconductor thin film forming apparatus characterized in that a susceptor can be moved without coming into contact with outside air.