JPH07176487A - Method for growing semiconductor single crystal and manufacture of laminated boards - Google Patents

Abstract

PURPOSE:To form an epitaxially grown layer in which a defect density is reduced on a porous semiconductor by covering spaces of ramified pores in a surface of the semiconductor with an oxide and then heat-treating the exposed surface of the semiconductor. CONSTITUTION:A surface of a porous semiconductor has many ramified pores 104 like trees. An oxide layer 103a is formed on a surface of the semiconductor by an oxidizing step, and spaces of the pores are covered with an oxide 103b. Then, the oxide of the surface is removed. Thereafter, a substrate is introduced into an epitaxially growing furnace, and a single crystal is grown. In this case, a tree structure of a porous layer is not changed even if it is heat treated in a step of forming a thin oxide film, but migrants of silicon atoms and relocation occur on the surface, thereby becoming an extremely thin single crystal layer. Thus, since a reduced pressure process is not required, generation of particles due to pumping can be completely suppressed. Accordingly, a defect of an SOI substrate due to the particles can be completely excluded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a semiconductor single crystal and a method for manufacturing a bonded substrate, and in particular, growing a single crystal semiconductor on a porous semiconductor and bonding the same to S
The present invention relates to a method for growing a semiconductor single crystal and a method for manufacturing a bonded substrate, which are preferably used when producing an OI (Silicon-On-Insulator) substrate.

[0002]

2. Description of the Related Art A substrate having a thin film single crystal layer on an insulating substrate is called an SOI substrate, and an integrated circuit manufactured using this substrate has a higher speed / speed than a circuit manufactured using a normal bulk semiconductor. It has long been known that operation with low power consumption is possible, and its usefulness has been recognized.

Conventionally, there have been the following three main methods for manufacturing an SOI substrate.

(1) The first method is called a SIMOX method, and a buried oxide film is formed by implanting a high dose amount of oxygen ions to a depth of several thousand angstroms from the surface of a bulk semiconductor substrate. Is the way to do it. Although this method is excellent in the film thickness uniformity of the recrystallized single crystal semiconductor layer, it has drawbacks such as deterioration of crystal quality due to ion implantation and an expensive high-dose ion implantation process, and is widely used in integrated circuits. I haven't arrived.

(2) The second method is a wafer bonding method. In this method, at least one surface is insulated 2
This is a method in which one single crystal is thinned by polishing after bonding a single crystal wafer. Although this method is excellent in single crystal quality, it has not been widely used in integrated circuits because the polishing accuracy is not sufficient and the thickness of the single crystal after thinning is not uniform.

(3) The third method is a recrystallization method. This method is a method in which an amorphous or polycrystalline semiconductor is deposited on an insulating substrate and then melted by a laser or the like to form a single crystal. Although this method has excellent film thickness uniformity,
Due to poor single crystal quality and high manufacturing cost, it has not been widely used in the manufacture of integrated circuits.

A method for manufacturing an SOI substrate which solves these problems has been proposed by Yonehara et al. (Japanese Patent Laid-Open No. 21338/1993).
issue). According to this method, a first substrate on which a single crystal semiconductor is grown on a porous semiconductor layer and a second substrate whose surface is insulated are bonded together, and then the porous semiconductor of the first substrate is selectively removed. By doing so, an SOI substrate is manufactured.
This method is an extremely excellent manufacturing method as a method for obtaining a single crystal semiconductor having a uniform film thickness while maintaining the crystal quality equivalent to that of the wafer bonding method. By this method, an inexpensive and high-quality SOI substrate can be manufactured.

The above SO will be described below with reference to FIGS. 9 to 11.
A method of manufacturing the I substrate will be described. First, the surface of the semiconductor substrate is made porous by the anodization method, and the semiconductor substrate 202
A porous semiconductor layer 201 is formed on the surface (FIG. 9). FIG. 10 is a conceptual diagram of the surface of the porous semiconductor at this time. Note that FIG. 10 is an enlarged view of portion C of FIG. As shown in FIG. 10, the porous semiconductor has a large number of branch-shaped small holes 204 in a tree.

After that, a single crystal layer 205 is formed on the surface of the porous semiconductor layer 201 by epitaxial growth (FIG. 11). Epitaxial growth is 100
When the temperature exceeds 0 ° C, structural changes such as rearrangement of internal holes occur and the characteristics of the enhanced etching are impaired. Therefore, it is desirable that the epitaxial growth be 1000 ° C or less.
Molecular beam epitaxy, plasma CVD, low pressure CVD
Method, optical CVD method, bias sputtering method, or the like is used. After that, after bonding the above wafer with a substrate 212 or a quartz substrate having an insulating film 213 of, for example, several thousand liters on its surface, the semiconductor substrate 202 and the porous semiconductor layer 201 are sequentially removed by etching to form an SOI substrate. To obtain (FIG. 12).

[0010]

However, the conventional method for manufacturing an SOI substrate using the growth of a single crystal semiconductor on a porous semiconductor may cause the following problems.

Among the epitaxial growth methods, the highest quality single crystal can be grown by the CVD method using the thermal decomposition of a silicon compound gas. SiH ₄ , SiHCl ₃ and SiH ₂ Cl ₂ used as the compound gas can be used. , SiCl
₄ is capable of both at a temperature below 1000 ° C. to epitaxially grown only under reduced pressure. For example SiH
_When epitaxially growing with ₂ Cl ₂ at 950 ° C., the gas pressure needs to be 100 Torr or less.
This may cause the following problems.

In the depressurization process, many particles are generated inside the apparatus. This is because in an epitaxial growth apparatus, several tens of batches are usually operated continuously, but in such an apparatus, many particles such as polysilicon are attached to the inner wall, and under reduced pressure, turbulent flow easily occurs in the apparatus. This is because the particles of the device separate from the inner wall and adhere to the wafer.

In general, even if the temperature for single crystal growth is approached, as the critical temperature Tc for single crystal growth is approached,
The defect density in the crystal increases. This is considered to be because it is difficult for the grown atoms to migrate during single crystal growth, and the probability that the lattice position does not reach the lattice position accurately increases. When the same source gas is used for comparison, the higher the growth temperature, the lower the probability of causing defects.

Although defects remain on the surface of the porous semiconductor, the defects are not sufficiently removed at a low temperature and the defects of the single crystal semiconductor grown on the defects cannot be eliminated.

The above items 1 to 3 are schematically shown in FIGS. FIG. 13 shows a cross-sectional view in which a single crystal semiconductor 205 is deposited on the porous semiconductor 201 by epitaxial growth, and FIG. 14 shows a cross-sectional view of a substrate bonded to a base having an insulating film.

As shown in FIG. 13, particles 208 adhered on the porous layer, particles 210 during single crystal growth,
Alternatively, any of the lattice defects and the defects 211 of the single crystal semiconductor generated from the defects on the porous semiconductor are final single crystal defects as shown in FIG. In particular, particle-like defects cause the voids 207 and 209,
After the bonding step, the single crystal layer is missing, and the SOI substrate quality is significantly deteriorated.

One object of the present invention is to provide a method for forming an epitaxial growth layer having a significantly reduced defect density on a porous semiconductor. A further object of the present invention is to significantly improve the quality of the single crystal semiconductor of the SOI substrate.

A further object of the present invention is to provide a method for producing a high quality SOI substrate with high reproducibility and high yield.

[0019]

According to the method for growing a semiconductor single crystal of the present invention, a first step of converting a porous semiconductor surface into an insulating material to form an insulating layer, and removing at least a part of the insulating layer. In the second step of forming the exposed surface of the porous semiconductor, and in the atmosphere containing a reducing gas or a reducing gas as a main component, the porous semiconductor causes a structural change when the insulating layer does not exist. A third step of heat-treating the exposed surface at a first temperature, and a second temperature which is substantially the same as the first temperature or lower than the first temperature in a gas pressure of 1 atm or near atmospheric pressure. And a fourth step of growing a semiconductor single crystal on the porous semiconductor.

In the method for producing a bonded substrate of the present invention, the semiconductor single crystal surface of the porous semiconductor on which the semiconductor single crystal is grown by the above semiconductor single crystal growth method and the insulating surface of the insulating substrate are bonded together. Is characterized by.

[0021]

According to the present invention, the space of the branch-like small holes on the surface of the porous semiconductor is covered with an oxide by forming the insulating layer by converting the surface of the porous semiconductor into an insulating material, and at least a part thereof is removed. First, the surface of the porous semiconductor is exposed, and then, in the reducing gas or in an atmosphere containing a reducing gas as a main component, the porous semiconductor causes a structural change when the insulating layer does not exist.
By heat-treating the exposed surface of the porous semiconductor at the temperature of
The surface is single-crystallized to form a thin single-crystal layer, and then, on the thin single-crystal layer surface, at a gas pressure of 1 atm or in the vicinity thereof, the temperature is almost the same as the first temperature or the first temperature.
The semiconductor single crystal is grown at a second temperature lower than the temperature of.

In the present invention, since the space of the branch-like small holes on the surface of the porous semiconductor is covered with the oxide, 1000
Even if the heat treatment is performed at a temperature higher than 0 ° C, the structure of the porous structure does not change, and therefore, it becomes possible to grow a single crystal under a gas pressure of 1 atm or a pressure in the vicinity thereof. Further, since a semiconductor single crystal is deposited on a thin single crystal layer that has been single-crystallized by heat treatment in a reducing gas or in an atmosphere containing a reducing gas as a main component, it is possible to grow a single crystal with few defects. Become.

As a result, particles and defects in the single crystal semiconductor can be remarkably reduced, and a high quality SOI substrate can be manufactured at low cost and with good reproducibility.

[0024]

Embodiments of the present invention will be described in detail below with reference to the drawings. <Embodiment 1> A first embodiment of the method for manufacturing a bonded substrate according to the present invention will be described with reference to FIGS.

First, the surface of the p-type silicon substrate 102 having a plane orientation of 5 inches (100) is HF (49%) and C ₂ H ₅ O.
Anodization was carried out in a 2: 1 mixture of H at a current density of 0.01 (A / cm ² ). About 15μm by forming for 15 minutes
A porous silicon layer 101 was obtained (FIG. 2). The thickness of the porous silicon layer 101 is determined in consideration of the process margin in the SOI substrate manufacturing process and the wafer warp, and the single crystal growth condition is not affected by the porous silicon layer thickness.

Next, it was oxidized in dry oxygen at 300 to 500 ° C. for 1 hour (FIG. 3). A partial cross-sectional view of the porous surface at this time is shown in FIG. FIG. 4 corresponds to an enlarged view of part A of FIG. As shown in FIG. 4, the porous semiconductor surface has a large number of branch-like small holes 104 of a tree, an oxide layer 103a is formed on the surface of the porous semiconductor by the oxidation step, and the spaces of the small holes are oxide 103b. Covered with. Then dilute HF (0.1-5%)
Etching is performed for 10 to 60 seconds to remove the oxide film on the surface (FIG. 5). A partial cross-sectional view of the porous surface at this time is shown in FIG. FIG. 6 corresponds to an enlarged view of part B of FIG.

Next, the substrate is placed in an epitaxial growth furnace and a single crystal is grown. The growth furnace used was an epitaxial growth furnace manufactured by Nippon Applied Materials. After the substrate is installed on the susceptor, the air in the furnace is
_It was replaced with ₂ gas and then with H ₂ gas. Then the furnace is 1080
The temperature was raised to ° C. Hold at this temperature for 10 minutes. FIG. 1 shows the surface of the substrate after this. Due to the process of forming a thin oxide film, the tree structure of the porous layer does not change even after heat treatment at 1080 ° C, but the migration and rearrangement of silicon atoms occur on the surface, resulting in an extremely thin single crystal layer. It becomes 106. Next, SiH ₂ Cl ₂ gas 50
0 (ml / min) and H ₂ gas 200 (l / min) were introduced, and the silicon single crystal layer 10 was heated at 1040 ° C. and 1 atm.
5 was deposited to 1 μm. A sectional view at this time is FIG. 7.
After that, the temperature of the furnace is lowered, and after being sufficiently replaced with N ₂ , it is taken out of the furnace.

After that, the substrate was bonded to the second silicon substrate 112 having a 4000 Å oxide film 113 formed on the surface by a bonding apparatus, and then heat-treated at 1000 ° C. in N ₂ gas for 1 hour to bond the substrate. Improves the bonding strength.

Next, the conventional method, that is, after grinding the single crystal silicon 102 of the first substrate by a grinder,
Porous silicon layer 1 with a mixed solution of HF: H ₂ O ₂ = 1: 5
01 was removed to obtain an SOI substrate (FIG. 8).

In this embodiment, the heat treatment before the single crystal growth is performed.
The processing temperature was set to 1080 ° C, but 1000 ° C to 1150 ° C
Range, preferably equal to or higher than the growth temperature
The above temperature is good. The time can be about 2 to 30 minutes
It The growth temperature is SiH ₂ Cl₂ When using gas
Can be from 1020 ° C to 1100 ° C. Of growth temperature
The optimization is from the porous silicon layer 101 to the single crystal growth layer.
Of p-type impurities (here, boron atom) into 105
It is better to consider the allowable amount. Mixing amount is p-type
Although it depends on the substance concentration, for example, 0.01 to 0.02 Ω
When using a substrate with a specific resistance of m
Boron is mixed up to 0.5 μm. The mixed boron is
Bond other substrates according to the purpose of using the epitaxial layer
After removing it, remove it by oxidation, etching, mechanical polishing, etc.
It is possible to leave.

It is to be noted that holes are required to produce porous Si, and P-type Si is more easily transformed into porous Si than N-type Si (Nagano, Nakajima, Anno, Ohnaka). , Kajiwara, Technical Report of IEICE, vol.79, SSD79-9549 (19
79), K .; Imai, Solid-State Electoronics, vol.24,
159 (1981)). However, if N-type Si is also injected with holes,
It is known to be transformed into porous Si (RP Holmst
rom and JYChi, Appl.Phys.Lett., vol.42,386 (198
3)).

Further, the growth gas is SiH ₄ (monosilane) gas, SiCl ₄ (tetrachlorosilane) gas, SiHCl ₃
(Trichlorosilane) gas, Si ₂ H ₆ (disilane) gas, Si ₃ H ₈ (trisilane) gas or the like is possible. Although the temperature range in which the single crystal can be grown differs depending on the gas used, the crystallinity of the single crystal is generally better when grown at a high temperature. Further, the gas flow rate during growth is, for example, S
iH ₂ Cl ₂ flow rate 50 to 2000 (ml / min), H
₂ Flow rate of 50-1000 (l / min) is possible,
In the structure of the device used, conditions were selected that would give an appropriate deposition rate and in-plane film thickness distribution. The deposited film thickness can be freely selected according to the purpose of use of the SOI substrate, but in the present embodiment, it was suitable to be about 5000 Å to 3 μm for use as the semiconductor substrate of the transmissive liquid crystal panel. It is possible to set the thickness to 500 to 5000 Å for a high speed integrated circuit, or 3 to 10 μm for a high breakdown voltage circuit.

According to the present embodiment, no depressurization process is required, so that no particles due to pumping are generated. Therefore, the defects of the SOI substrate due to the particles could be completely eliminated. Since the surface of the porous semiconductor was single-crystallized, the crystal quality of the SOI substrate could be significantly improved. Since the crystal was grown at a high temperature, it was possible to remarkably reduce minute defects and dislocations in the crystal.

By carrying out this example, a technique for producing an SOI substrate having excellent single crystal quality and extremely excellent film thickness distribution with good reproducibility and at low cost was established. Example 2 In this example, the single crystallizing step of the surface shown in FIG. 1 was performed in an electric heating furnace. The steps from forming the porous layer to oxidizing the surface and removing the oxide film are exactly the same as in Example 1.

Next, the substrate was placed in an electric furnace and heat-treated for 15 minutes in a mixed gas of N ₂ and H ₂ . The reason why N ₂ and H ₂ are mixed is because safety is taken into consideration, and the effect is the same. The processing time can be 5 to 30 minutes. The temperature was set to 1080 ° C. as in the first embodiment, but the temperature is not limited to this.

After that, in an epitaxial growth furnace, 1040
SiH ₂ Cl ₂ gas was thermally decomposed at 1 ° C. and 1 atm to grow 1 μm single crystal silicon. The subsequent steps are the same as in Example 1.
Is exactly the same as

According to this embodiment, as in the first embodiment,
It was possible to reproducibly manufacture an SOI substrate having extremely excellent crystal quality and a good film thickness distribution. That is, the particle reducing effect could be obtained. The effect of improving the crystallinity of the porous surface could be obtained. The effect of reducing micro defects and dislocation density due to high temperature was obtained. Therefore, the quality yield of the SOI substrate is significantly improved.

Furthermore, by separating the heat treatment apparatus and the growth furnace, it is difficult for impurities in the porous material to enter the growth film. Impurities in the porous structure are unlikely to contaminate the epitaxial growth furnace. The effect such as was obtained.

These effects also contributed to the improvement of the quality and mass productivity of the SOI substrate.

[0040]

As described in detail above, according to the present invention, since the depressurization process is not required, the generation of particles due to pumping can be completely suppressed. Therefore, the defects of the SOI substrate caused by the particles can be completely eliminated. Since the surface of the porous semiconductor is single-crystallized, the crystal quality of the SOI substrate can be significantly improved. Since the crystal can be grown at a high temperature, minute defects and dislocations in the crystal can be remarkably reduced.
It is possible to improve the quality yield of the OI substrate.

Therefore, it is possible to produce an SOI substrate having excellent single crystal quality and extremely excellent film thickness distribution with good reproducibility and at low cost.

[Brief description of drawings]

FIG. 1 is a schematic partially enlarged cross-sectional view for explaining a manufacturing process of a semiconductor single crystal growth method of the present invention.

FIG. 2 is a cross-sectional view for explaining a manufacturing process of an SOI substrate according to the present invention.

FIG. 3 is a cross-sectional view for explaining a manufacturing process of an SOI substrate according to the present invention.

FIG. 4 is a schematic partially enlarged cross-sectional view of part A in FIG.

FIG. 5 is a cross-sectional view for explaining the manufacturing process of the SOI substrate according to the present invention.

6 is a schematic partial enlarged cross-sectional view of a B part in FIG.

FIG. 7 is a cross-sectional view for explaining a manufacturing process of an SOI substrate according to the present invention.

FIG. 8 is a cross-sectional view for explaining the manufacturing process of the SOI substrate according to the present invention.

FIG. 9 is a cross-sectional view for explaining the manufacturing process of the SOI substrate according to the conventional example.

FIG. 10 is a schematic partial enlarged cross-sectional view of a C part in FIG.

FIG. 11 is a cross-sectional view for explaining the manufacturing process of the SOI substrate according to the conventional example.

FIG. 12 is a cross-sectional view for explaining the manufacturing process of the SOI substrate according to the conventional example.

FIG. 13 is a cross-sectional view showing a produced bonded substrate for explaining the problems caused by the conventional manufacturing method.

FIG. 14 is a cross-sectional view showing a manufactured SOI substrate for explaining a problem caused by a conventional manufacturing method.

[Explanation of symbols]

 101 Porous Semiconductor Layer 102 Semiconductor Substrate 103 Porous Semiconductor Oxide Layer 103a, 103b Oxide 104 Branch-like Small Trees 105 Single Crystal Layer 106 Thin Single Crystal Layer

Claims (5)

[Claims] 1. A first step of converting a surface of a porous semiconductor into an insulating material to form an insulating layer, and a second step of forming an exposed surface of the porous semiconductor by removing at least a part of the insulating layer. And a step of heat-treating the exposed surface at a first temperature that causes a structural change in the case where the porous semiconductor does not have the insulating layer in a reducing gas or an atmosphere containing a reducing gas as a main component. And a step of: growing a semiconductor single crystal on the porous semiconductor at a second pressure that is substantially the same as the first temperature or lower than the first temperature in a gas pressure of 1 atm or in the vicinity thereof. A fourth step, and a method for growing a semiconductor single crystal, including: 2. The method for growing a semiconductor single crystal according to claim 1, wherein the insulator is an oxide of the porous semiconductor. 3. The method for growing a semiconductor single crystal according to claim 1, wherein the reducing gas is hydrogen gas. 4. The method for growing a semiconductor single crystal according to claim 1, wherein the porous semiconductor is a p-type semiconductor. 5. A bonding method, characterized in that the semiconductor single crystal surface of a porous semiconductor on which a semiconductor single crystal is grown by the method of growing a semiconductor single crystal according to claim 1 and the insulating surface of an insulating substrate are bonded to each other. Manufacturing method of laminated substrate.