JPS5931971B2 - Manufacturing method for semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, usually abbreviated as 505, in which a silicon single crystal layer is grown on the surface of sapphire.

Although s0S has various attractive features and is attracting attention as a need for high-speed logic elements, etc., on the other hand, it has various problems and has not become mainstream in the current semiconductor industry.

The problems are as follows. (1) Higher cost than homo-Si epitaxial growth.

The reasons for this are (a) that the sapphire substrate itself is expensive, and (b) that surface treatments such as polishing techniques and chemical surface treatment techniques are difficult for sapphire.

(2) The crystallinity of the Si active layer is poor compared to homosilicon epitaxial growth.

The reason for this is considered to be (a) unstable At atoms mixed into the Si epitaxial active layer as p-type impurities due to the poor crystallinity of the sapphire substrate.

Next, (b) It is thought that the lattice mismatch between the Si layer, which grows on the soil of the sapphire substrate with a thickness of 200 to 300 μm, and the Si layer, which is several microns thick, causes the Si layer to be strained, resulting in poor crystallinity. It will be done. Furthermore, ←→ Distortion caused by the difference in thermal expansion between the sapphire and the Si of the substrate is also considered. In order to eliminate such drawbacks of 505, a 2-5 μm thick Saphire single crystal film is formed on a 200-300 μm thick silicon substrate, and a Si epitaxial active layer is formed on this Saphire single crystal. The present inventors have already proposed a semiconductor device with a new structure. When a thin sapphire layer is formed on such a thick silicon substrate, the crystal structure of the latter is regulated by the former and becomes similar to the latter. Therefore, the soil silicon epitaxial layer of the sapphire layer grows and has good crystallinity in a state similar to that when grown on a silicon substrate. However, it has become clear through research by the present inventor that there is a limit to the improvement of crystallinity of a silicon epitaxial layer using the above-mentioned apparatus, and that the devices and characteristics cannot be sufficiently improved.

Originally, the difference between the lattice constant of silicon (a 5.4301 λ) and the lattice constant of saphire (a - 4.758 λ) is large and reaches 15% with respect to the former. It was found that the lattice mismatch between silicon and sapphire caused by this cannot be completely resolved by growing thin sapphire on a thick silicon substrate. As a result, the topmost silicon epitaxial layer did not exhibit sufficient crystal properties, leaving a serious impact on the characteristics of the semiconductor device. In order to solve the above problems, the present invention has developed α-Ti2O3, which has the same hexagonal crystal type as sapphire (α-BO3) and has a lattice constant closer to that of silicon (lattice constant a=5.37). This paper proposes a method for manufacturing a semiconductor device in which sapphire is doped with . That is, the apparatus according to the present invention is a semiconductor device in which a sapphire insulating layer is epitaxially grown on the surface of a semiconductor silicon substrate, and a semiconductor silicon active layer is epitaxially grown on this insulating layer. 0.1 to 50 (!l) of aluminum atoms are replaced by titanium. The thickness of silicon substrate is usually several hundred micrometers.
It is.

The thickness of the sapphire single crystal is preferably 1 to 30 μm. 1
If the thickness is less than .mu.m, there will be problems of lower breakdown voltage and increased parasitic capacitance between the active layer and the substrate, and if the thickness exceeds 30 .mu.m, the strain due to the difference in coefficient of thermal expansion will increase between silicon and sapphire.

The thickness of the top silicon active layer is not limited and can be used for various purposes. It can be made to any desired thickness. The crystal planes on the silicon substrate surface are (111 plane), (110 plane), (100 plane)
The crystal plane of the surface of the sapphire layer is the (0001) plane and the (1012) plane, and the surface of the silicon active layer has the same crystal plane as the silicon substrate. 0 of the total number of aluminum atoms in sapphire.
1~50% is replaced by titanium, which causes the lattice constant (a) of sapphire to be 4.760λ~5.
, 065λ, approaching the lattice constant of silicon. Titanium is thought to exist in sapphire as a solid solution or precipitate as α(-Ti2O3. Due to the closeness of the lattice constants as described above, the lattice mismatch between the silicon epitaxial layer and the sapphire epitaxial layer will be significantly less.

Therefore, the strain in the silicon active layer grown on the sapphire layer is reduced and the device characteristics are greatly improved. Other effects of titanium contained within the sapphire layer include:
This is due to the fact that titanium does not participate in the conductivity of silicon. That is, At atoms, which are constituent atoms of sapphire, are mixed into the single-crystal silicon epitaxial layer by diffusion, making the silicon epitaxial layer p-type conductive and causing a decrease in crystallinity. However, since titanium atoms are contained in the sapphire layer, the mixing of aluminum is suppressed, and even if a small amount of titanium mixes into silicon, the conductivity type of the silicon does not change. Other effects of Ti contained in sapphire give it malleability,
The purpose is to prevent cracks in the sapphire layer that occur during the manufacturing of semiconductor devices.

Sapphire has a low Young's modulus and poor thermal expansion, so there is a high risk of sagging during the manufacturing process. According to the present invention, it has been confirmed that such a risk is almost eliminated. In the above device, it is well known that the device is completed by doping the silicon active layer with P and N-type impurities, forming an insulating film or electrode wiring on the surface, etc., so the explanation will be omitted. .

A major feature of the present invention is that the titanium-containing sapphire layer is prepared by vapor phase growth.

This preparation method is based on the method proposed by the applicant as a vapor phase growth method for pure sapphire that does not contain titanium, with modifications made thereto. Vapor phase growth method of pure sapphire Liquid or solid aluminum (f!, 99.999%
) and hydrogen chloride gas are used as starting materials.

Aluminum is in solid or liquid form at a temperature convenient for reaction with hydrogen chloride, generally at 550°C.
It is within the range of ~700°C. Hydrogen chloride gas is generally kept at room temperature and contacts the heated aluminum. This contact is thought to cause the following reaction:

By using At metal as one of the starting materials, problems due to the deliquescent nature of the starting materials are avoided. moreover,
Reacts with moisture At present in HCt to form At2O3
to be generated. Therefore, by introducing HCt, Sl
The substrate is not oxidized and the growth of the A4O3 single crystal is not hindered. The gas generated in the above steps, which is considered to be a mixed gas of M°C and H2, is transported to the area of the Si substrate.

The H2 gas used in conventional methods can be used for this conveyance. However, it is preferable to use at least one inert gas selected from the group consisting of Ar and H2, or hydrogen gas containing at least one of such inert gases, as the carrier gas. Since H2 gas is a very light commodity, it lacks the mass and viscosity necessary to move various gas components. However, since the inert gas has a larger mass and viscosity than hydrogen, it rapidly and uniformly moves gas molecules involved in the reaction onto the substrate and drives out components involved in the reaction from the substrate. Therefore, by arranging a plurality of substrates in the flow direction of the reaction gas, batch processing of a large number of substrates becomes possible. The A. The thickness of the /203 single crystal film is uniform regardless of the substrate viewed in the direction of the gas flow. The advantage of using an inert gas alone or in combination is that batch processing becomes possible as described above, and an AbO3 single crystal film with a uniform predetermined thickness can be obtained without increasing the flow rate of the carrier gas. . In addition to this advantage, the advantage of using an inert gas alone or in combination is that it suppresses the reduction reaction of the epitaxially grown single crystal At2O3 with H2. Although there is no particular restriction on the minimum content of inert gas in the H2 gas, significant effects can be observed over a wide range of content as long as the content is several percent or more.

The method of using the carrier gas is to transport only the gas phase generated by contact with M (5HCt), but
When a carrier gas is used for transporting to the ct8At region, the carrier gas for HCI may be the same type of gas as the carrier gas for the gas generated by the contact reaction to transport both. Vapor Phase Growth Method of Sapphire Containing Titanium The key point of this method is to mix the mixed gas produced by the reaction of At and Hct, CO2, and TiC4 together before the Si substrate.

It is thought that CO2 oxidizes Atct3 in the mixed gas according to the following equation. CO2 is TlCI! It is also involved in the oxidation of 4, and this reaction is thought to be according to the following formula.

The gas containing Atcm and the gas containing TlC are not mixed before being oxidized by CO2 gas, and it is necessary that the three gases be mixed together.

CO! It is preferable to perform the mixing in a region as close to the Si substrate as possible. In order to grow sapphire with a predetermined Tl concentration, the Hct flow rate is 100 to 1000 cc.
The flow rate of CO2 is 100 to 5000 ccA.
The flow rate of the pump is preferably 100 to 1000 cc.

The Tict4 source is controlled within a temperature range of -30°C to 100°C. Inside this Tic4 liquid, carry gas H
TiC4 is delivered into the sapphire growth reaction tube by bubbling H2 or a mixed carrier gas of one or more of He, Ar, H2 and H2. Single crystal silicon substrate is approximately 1000℃~1200℃
It is heated and maintained at a temperature of .

By bringing the above three types of mixed gases into contact with this single crystal silicon substrate, a sapphire single crystal containing α-Ti2O3 is epitaxially grown on the substrate. If the temperature of the Sl substrate during growth is made higher than 1200°C, the reactivity of the Si substrate increases and AbO38! ．． This causes a reaction with AbO3 and Ti2O3, making it impossible to obtain a good AbO3 epitaxial layer.

If the substrate temperature is lower than 1000°C, A. //! This method is not practical because the growth rate of the AbO3 single crystal becomes extremely low, and the crystallinity of the resulting AbO3 epitaxial layer also deteriorates. Therefore, the S1 substrate temperature during growth is 1000 to 1200°C, preferably 1050 to 1150°C. According to the method of the present invention, a single crystal of α-A4O containing α-Ti2O3 and having good crystallinity is grown to a thickness of 10 to 30μ by growth for about one hour. Vapor Phase Growth Apparatus Next, a specific example of an apparatus for carrying out the method according to the present invention will be described based on the drawings.

FIG. 1 is a sectional view showing a horizontal vapor phase growth apparatus, in which a hollow body 2 is fixed in a quartz reaction tube 1.

One end of the hollow body 2 is a hydrogen chloride tube 4 that penetrates the quartz reaction tube 1.
The other end is open into the quartz reaction tube 1. The hollow body 2 thus defines a compartment 3 in a part of the space of the quartz reaction tube 1. In the illustrated embodiment, the hollow body 2
An approximately double concentric tube-like structure is formed in the region where the However, it is not necessarily necessary to adopt a double concentric tube structure. A dish 5 is placed inside the hollow body 2 and an aluminum 6 is arranged therein. Known heating means 7 are provided in the region of the hollow body 2 to heat the aluminum 6, and the same heating means extend also to the region following said region, so that the hollow body 2
It also heats the gas delivered from the The flow rate of hydrogen chloride gas is 3 when processing three silicon substrates 8 with a diameter of 33 mm.
00 to 700 cc/min is preferred. A carrier gas inlet 8 is provided at one end of the reaction tube 1 .

The carrier gas flowing from the carrier gas inlet 8 initially enters the hollow body 2.
, and then flows in the direction of the substrate 10 together with the reaction product gas of At and Hct. The flow path of the carrier gas does not necessarily have to be like this, and may be a flow path that directly flows into the outlet end of the hollow body 2. A part of the space of the quartz reaction tube 1 is filled with Si by the base 15.
A substrate support stand 9 made of C-coated carbon, Nb, or the like is fixed.

In the embodiment shown in FIG. 1, the substrate support 9 is arranged so as to face both the outlet end of the hollow body and the gas outlet 11. Three substrates 10 are supported on the substrate support stand 9. Known high-frequency heating means 12 are provided in the area of the substrate. Furthermore, a grinding cap 13 is provided on the outlet side of the reaction tube. A CO2 introduction pipe 14 penetrates the wall surface of the quartz reaction tube 1 and opens between the substrate 10 and the outlet end of the hollow body, approaching the former by d=1/5 to 1/3D with respect to this distance D. .

The tip 16a of the TLC introduction tube 16 is opened at a distance d from the substrate support stand 9. Tict4 introduction tube 1
6 penetrates the quartz reaction tube 1 and connects the Tlct4 gas generator 2
0 (Figure 2). CO2 introduction pipe 14 and Ti
C! ! The four inlet pipes 16 open at approximately the same position when viewed in the gas flow direction, and this opening position is downstream of the At pan 5. Therefore, the formation of undesired products due to mixing of Atct3 and Tlct4 is avoided. FIG. 2 is a sectional view of the TiC gas generator 20.

A quartz container 24 is floating in a constant temperature bath 22 containing an aqueous methanol solution 21. TiC in quartz container 24
t423 is maintained at a constant temperature in the range of -30°C to +100°C. H2 carrier gas is passed through a tube 26 through the quartz container 24 and bubbles within the liquid 23. The vaporized Tict4 is then sent into the furnace through the tube 16. If epitaxial growth of a silicon active layer is performed after forming an A4O3 single crystal layer using the above-mentioned apparatus, an improved SOS can be obtained.
Productivity can be greatly increased in the production of.

When growing silicon, stop feeding Hct and introduce only a carrier gas such as hydrogen gas from the hydrogen chloride pipe 4.
Thereafter, a Si-containing material such as SiH4 or sict4 is introduced from the carrier gas inlet 8. When introducing these gases, it is necessary to shut off the heating means 7 to prevent At from evaporating. Further, the heating means 12 maintains the previous heating so as to perform heating at 1000° C. or higher.

Furthermore, COf! I. CO entry and Tic from Immigration Bureau 14
The introduction of Tict4 from the t4 introduction pipe 16 is blocked. In the above description, a horizontal device has been described in conjunction with the drawings, but exactly the same effects can be achieved in a vertical device.

Further, although the present invention has been described with respect to a method for manufacturing an improved SOS, the present invention is not limited to improved SOS.
It can be applied to all fields in which At2O3 single crystal films are epitaxially grown on substrate soil.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 An At2O3 single crystal was epitaxially grown using the apparatus shown in FIG.

The growth conditions are shown in Table 1.

Claims (1)

[Claims] 1. A gas generated by bringing HCl gas into contact with liquid or solid aluminum is transported toward the semiconductor silicon substrate, and before the generated gas reaches the substrate, the generated gas, CO_2 gas, and TiCl_4 gas are The gas produced by this reaction is mixed with 100
A sapphire film in which some aluminum atoms are replaced by titanium is epitaxially grown on the substrate in contact with the substrate heated to 0 to 1270°C; and silicon is epitaxially grown on the film. A method for manufacturing a semiconductor device.