JPH08241863A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE: To form a film which has few defects and is high in quality on a porous semiconductor layer by a method wherein a protective layer is formed on the porous semiconductor layer provided onto semiconductor substrate, the protective layer is removed off in a film forming device, and a film is formed on the porous semiconductor layer in the film forming device. CONSTITUTION: A P-type silicon wafer 1 is subjected to anodizing, whereby a porous silicon layer 2 is formed thereon. After the silicon wafer 1 is cleaned, a silicon oxide film 4 is formed on the surface of the porous silicon layer 2. The P-type silicon wafer 1 is introduced into an epitaxial growth device, and then the silicon oxide film 4 is removed from the P-type silicon wafer 1. A single crystal silicon layer 3 is formed on the porous silicon layer 2 through an epitaxial growth method in the epitaxial growth device. By this setup, the single crystal silicon layer which has few crystal defects caused by particles or the like and is high in quality is formed on the porous silicon layer 2.

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 semiconductor substrate, and more particularly to a method for manufacturing a semiconductor substrate having a porous semiconductor layer.

[0002]

2. Description of the Related Art When a silicon wafer is put in a hydrofluoric acid solution and an electric current is applied thereto, porous silicon having a large number of elongated pores of about 1 to 10 nm is formed on the silicon wafer. This process is called anodization (A. Uhril: B
ell Syst. Tech. J. 35 (1956).
333). Porous silicon obtained by anodization has many unique properties, and various researches and developments are being carried out by utilizing these properties. For example, porous silicon has a property of emitting light when a voltage is applied, and its application as a light emitting element is expected.

Further, although porous silicon has a structure having a large number of pores, it maintains the single crystallinity of silicon, so that it is possible to perform homoepitaxial growth or heteroepitaxial growth on porous silicon. Is. For example, the MBE method (S. Konaka et a
l. Appl. Phys. Lett. 41 (198
2). 86) or plasma CVD method (H. Takai).
et al. J. Electron. Mater. 1
2 (1983). 973), low pressure CVD method (LV
escan et al. Mater. Lett. 7
(1988). 94) and the like to form a single crystal silicon layer on the porous silicon. Further, porous silicon has a property of being more reactive than silicon. For example, when porous silicon is oxidized, its oxidation rate is about 100 times faster than that of silicon. When etching is performed with hydrofluoric acid / hydrogen peroxide (HF / H ₂ O ₂ ), the etching rate is 10 ⁴ times that of silicon. Utilizing these properties, a step of forming a thick insulator in a silicon integrated circuit to perform element isolation, and formation of a single crystal silicon layer on the insulator, which is useful as a material for realizing a high-speed IC or a three-dimensional IC Is expected to be applied to the fabrication of a manufactured SOI substrate. For example, FIPOS (Full Isolation by Po), which is a technology for completely separating an integrated circuit using a porous silicon oxide film.
rous Oxidized Silicon, K.M. I
mai, Solid-State Electron
cs, 24 (1981) 159) or a silicon direct bonding technique (T.P.T.) for attaching a single crystal silicon layer grown on a porous silicon substrate onto an amorphous substrate or a single crystal silicon substrate via an oxide film. Yonehara, et. Al.
Appl. Phys. Lett. 64 (16) (199
4) It is applied to 2108).

As described above, it is possible to form a single crystal silicon layer by performing epitaxial growth on the porous silicon layer, and this technique uses SOI as described above.
Although it can be applied to a substrate or the like, conventionally, this technique has been performed by the following method. FIG. 5 (a)
8A to 8C are process diagrams showing formation of a single crystal silicon layer on a porous silicon layer according to a conventional example. Here, 1 is a silicon wafer, 2 is a porous silicon layer, and 3 is a single crystal silicon layer. The steps in FIG. 5 are as follows.
(A) The silicon wafer 1 is anodized, and (b) the porous silicon layer 2 is formed on the silicon wafer 1. (C)
After cleaning the surface of the porous silicon layer 2 to remove organic substances, particles, metal ions, a natural oxide film, etc., epitaxial growth is performed on the porous silicon layer 2 to form the single crystal silicon layer 3. As a result, a single crystal silicon layer can be formed on the porous silicon layer, and a semiconductor substrate having the single crystal silicon layer formed on the porous silicon layer is obtained.

Here, after forming the porous silicon layer,
Although a single crystal silicon layer is formed through cleaning, porous silicon undergoes so-called pore rearrangement in which silicon atoms aggregate and the diameter of pores increases when heat-treated at a high temperature of 850 ° C or higher. Be seen. Such a structural change of porous silicon causes problems such as a decrease in etching rate when etching is performed with hydrofluoric acid / hydrogen peroxide (HF / H ₂ O ₂ ). Therefore, when performing epitaxial growth at high temperature. , The porous silicon layer is oxidized at a low temperature of about 300 ° C. to 450 ° C. (R. Herino et al. Ma.
ter. Lett. 2 (1984). 519) and then
In some cases, a single crystal silicon layer is formed after cleaning to remove an oxide film formed on the surface together with organic substances, particles, metal ions, and the like. In any case, it is necessary to clean the surface of the porous silicon layer before the formation of the single crystal silicon layer, and therefore the cleaning of the porous silicon layer is performed. Wet cleaning and dry cleaning are used as cleaning methods. For example, in the case of wet cleaning, the following RCA cleaning is basically used (W. Kern. Et al. RCA rev. Ju.
ne (1970) 187. ). (1) Removal of organic substances and metal ions with sulfuric acid / hydrogen peroxide mixture (H ₂ SO ₄ / H ₂ O ₂ ) at 120 ° C., (2) Pure water rinse, (3) Dilute hydrofluoric acid (HF / H
Natural oxide film removal by ₂ O), (4) pure water rinse,
(5) 80 ° C. Ammonia hydrogen peroxide (NH ₄ OH / H ₂ O ₂ /
H ₂ O) by organics and particle removal, (6)
Rinsing with pure water, (7) Removal of natural oxide film and metal ions with dilute hydrofluoric acid, (8) Rinsing with pure water, (9) Removal of metal ions with hydrochloric acid / hydrogen peroxide mixture (HCl / H ₂ O ₂ / H ₂ O) at 80 ° C And surface stabilization, (10) pure water rinse, (11) natural oxide film and metal ion removal with dilute hydrofluoric acid, (12) pure water rinse, (13) drying. However, the present situation is that various modifications are made according to the purpose, such as the omission of a part of dilute hydrofluoric acid.

[0006]

However, in the above-mentioned conventional example, there is a problem that the surface of the porous silicon layer cleaned by cleaning is exposed for a long time before the epitaxial growth. That is, when particles are attached to the surface of the porous silicon layer that is exposed during transport from the cleaning tank into the epitaxial growth device or when set on the susceptor, pits are formed in the single crystal silicon layer using these as nuclei during epitaxial growth. , Various crystal defects such as stacking faults occur. These crystal defects reduce the quality such as crystallinity of the single crystal silicon layer,
When an element is formed on the single crystal silicon layer, it adversely affects the carrier lifetime, the element breakdown voltage, etc., which may cause a decrease in reliability and a decrease in yield.

Usually, a surface cleaning step such as hydrogen baking or pre-etching with hydrogen chloride is carried out before the epitaxial growth, but none of them has a great effect of removing particles. Therefore, it is necessary to protect the surface of the porous silicon layer from contaminants, especially particles, after cleaning until the epitaxial growth.

[0008]

A method of manufacturing a semiconductor substrate according to the present invention comprises a step of forming a protective layer for protecting a porous semiconductor layer provided on the semiconductor substrate and removing the protective layer in a film forming apparatus. And a step of forming a film on the porous semiconductor layer in the film forming apparatus.

The method of manufacturing a semiconductor substrate of the present invention further comprises a step of forming a protective layer for protecting the porous semiconductor layer provided on the semiconductor substrate, a step of removing the protective layer in an epitaxial growth apparatus, and a step of performing the epitaxial growth. Forming a single crystal semiconductor layer on the porous semiconductor layer in the device.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings. [First Embodiment] FIG. 1 is a process diagram showing a first embodiment of a method for manufacturing a semiconductor substrate according to the present invention. Here, 1 is a P-type silicon wafer, 2 is a porous silicon layer, 4 is a silicon oxide film, and 3 is a single crystal silicon layer.

The steps in FIG. 1 are as follows.
(A) P-type silicon wafer 1 is anodized, and (b) P
A porous silicon layer 2 is formed on a mold silicon wafer 1. (C) After cleaning, a silicon oxide film 4 (hereinafter referred to as an oxide film) is formed on the surface of the porous silicon layer 2.
(D) After transporting the P-type silicon wafer 1 into the epitaxial growth apparatus, the oxide film 4 is removed. (E) The single crystal silicon layer 3 is formed by performing epitaxial growth on the porous silicon layer 2. As a result, a semiconductor substrate in which a single crystal silicon layer is formed on the porous silicon layer is obtained.

An example in which the above-mentioned semiconductor substrate is specifically manufactured by using this embodiment is shown below. Anodization is performed on a P-type silicon wafer having a thickness of 625 μm, a diameter of 125 mm, and a specific resistance of 0.02 Ωcm. Here, the chemical conversion liquid is HF: C.
_{Using 2} H ₅ OH: H ₂ O = 1: 1: 1, 1.0 A /
When a direct current of cm ² is applied for 7 minutes, a porous silicon layer having a thickness of 8 μm is formed on the P-type silicon wafer. Subsequently, the porous silicon layer is washed in the order shown below.
(1) Ammonia hydrogen peroxide at 75 ° C (NH ₄ OH: H
₂ O ₂ : H ₂ O = 1: 1: 6) is washed for 10 minutes to remove organic substances and particles. (2) Rinse with pure water for 10 minutes. (3) The native oxide film is removed by performing a treatment in 2.0% dilute hydrofluoric acid for 20 seconds. (4) Rinse with pure water for 10 minutes. (5) 80 ° C Hydrochloric acid / hydrogen peroxide (HCl: H
₂ O ₂ : H ₂ O = 1: 1: 8) is performed for 20 minutes to remove metal ions, and an oxide film of about 1 nm is formed on the surface of the porous silicon layer to protect the surface.
(6) Rinse with pure water for 10 minutes. (7) Dry with a spin dryer. After cleaning, the P-type silicon wafer is transferred into the epitaxial growth apparatus. After that, Ne ⁺ ions were added at a temperature of 60 ° C., an acceleration voltage of 7 kV, and an ion current of 10 ⁻³ A for 3 times.
The surface is cleaned by performing sputter etching for minutes to remove the oxide film. Then, after heat-treating at 750 ° C. for 15 minutes, epitaxial growth is performed on the porous silicon layer using SiH ₂ 31 amu (atomic mass unit) at a temperature of 300 ° C. and a pressure of 7 × 10 ⁻¹⁰ Torr to obtain a thickness. 1
A μm single crystal silicon layer is formed. As a result, a semiconductor substrate having a 1 μm-thick single crystal silicon layer formed on a 8 μm-thick porous silicon layer is obtained.

By using the process shown in the first embodiment,
A high-quality single crystal silicon layer with few crystal defects due to the influence of particles or the like can be formed over the porous silicon layer.

The details of this embodiment can be performed under various conditions as shown below. In this embodiment, the porous silicon layer is formed on the P-type silicon wafer, but it is also possible to use an n-type silicon wafer. When a P-type silicon wafer is used, the specific resistance is 0.
It is possible to use a wafer of 01 to 0.02 Ωcm, and when an n-type silicon wafer is used, the specific resistance is 0.01.
Wafers of ~ 1 Ωcm can be used. Also,
Various types of wafer diameters and thicknesses can be selected according to the purpose and are not particularly limited. Regarding the composition of the chemical conversion liquid, HF: C ₂ H ₅
It is possible to use in the range of OH: H ₂ O = 1: 0: 1 to 1: 3: 1. 30% porosity of porous silicon layer
Since it is possible to perform epitaxial growth if the surface is a mirror surface below, it is possible to freely select any combination satisfying this condition with the combination of the specific resistance, the composition of the chemical conversion liquid and the applied current. is there. The method of cleaning the porous silicon layer is not limited to this example, and various methods can be used. Ammonia The peroxide solution _{NH 4 OH: H 2 O 2} : H 2 O =
1: 1: 5 to 1: 2: 7, temperature 70 to 85 ° C., time 10
It is possible to use in the range of up to 20 minutes, and for hydrochloric acid hydrogen peroxide, HCl: H ₂ O ₂ : H ₂ O = 1: 1: 6
It can be used in the range of 1: 2: 8, temperature 70 to 85 ° C., and time 10 to 20 minutes. Dilute hydrofluoric acid can be used within a range of 5% or less. In addition to hydrofluoric acid, buffered hydrofluoric acid (NH ₄ F / HF / H ₂ O)
It is also possible to use hydrofluoric acid / hydrogen peroxide (HF / H ₂ O ₂ / H ₂ O). Furthermore, it is also possible to add a small amount of IPA (isopropyl alcohol C ₃ H ₇ OH) or HCl to dilute hydrofluoric acid for use. In addition, it is possible to remove organic substances with pure water containing ozone, and it is also possible to add a chelating agent into ammonia-peroxide water to suppress the adhesion of metal ions. The cleaning sequence can be freely selected in addition to the present embodiment as long as a natural oxide film can be formed on the surface of the porous silicon layer at the final stage without seriously damaging the porous silicon layer. It is possible. For example, cleaning and treatment using hydrochloric acid / hydrogen peroxide mixture or ammonia / hydrogen peroxide mixture may be performed without performing treatment with diluted hydrofluoric acid or buffered hydrofluoric acid in the final stage of washing. Since the epitaxial growth is performed at a low temperature at which the structure of the porous silicon layer does not change, in addition to the molecular beam epitaxy method (MBE method) shown in this embodiment, a liquid phase growth method (LPE method), a vapor deposition method, a bias method, etc. Sputtering method, low pressure vapor deposition method (low pressure CVD method), plasma CVD
It is possible to use the method etc. In this case, the epitaxial growth is performed at 750 ° C. or lower, preferably 600 ° C. or lower.

In addition, the method of the cleaning tank, the method of drying, the method of transferring the wafer, etc. are not limited to this embodiment, and various forms can be used. For example, as a system of the cleaning tank, a stationary system, a circulation system, an overflow system, a quick dump system, a cascade overflow system, or the like can be used. As the drying method, other than this embodiment, IPA
It is possible to use steam drying, acetone and IPA drying, nitrogen gas blowing and the like.

As the protective layer used in this embodiment, in addition to the oxide film, NSG (Non Silicate Glass) and BSG (Boro Sil) are used.
icate Glass), PSG (Phospho Silicate Glass),
It is also possible to use BPSG (Boro Phospho Silicate Glass) or the like (the same applies to each embodiment described below.) [Second Embodiment] Second Embodiment of the method for manufacturing a semiconductor substrate according to the present invention An example will be described below. FIG. 1 is used as a process diagram showing this embodiment.

The steps in FIG. 1 are as follows.
(A) P-type silicon wafer 1 is anodized, and (b) P
A porous silicon layer 2 is formed on a mold silicon wafer 1. (C) After cleaning, the porous silicon layer 2 is oxidized at a low temperature to form an oxide film 4 on the surface. (D) After transporting the P-type silicon wafer 1 into the epitaxial growth apparatus, the oxide film 4 is removed. (E) The single crystal silicon layer 3 is formed by performing epitaxial growth on the porous silicon layer 2. As a result, a semiconductor substrate in which a single crystal silicon layer is formed on the porous silicon layer is obtained.

An example in which the above-mentioned semiconductor substrate is specifically manufactured by using this embodiment is shown below. Anodization is performed on a P-type silicon wafer having a thickness of 625 μm, a diameter of 125 mm, and a specific resistance of 0.01 Ωcm. Here, the chemical conversion liquid is HF: C.
_{Using 2} H ₅ OH: H ₂ O = 1: 1: 1, 1.0 A /
When a direct current of cm ² is applied for 14 minutes, a 15 μm thick porous silicon layer is formed on the P-type silicon wafer.
Subsequently, the porous silicon layer is washed in the order shown below.
(1) The organic substances are removed by washing with pure water containing 25 ° C. and 2.5 ppm of ozone for 10 minutes. (2) Rinse with pure water for 10 minutes. (3) Ammonia-hydrogen peroxide mixture at 75 ° C. (NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 5)
Cleaning is performed for a minute to remove organic substances, particles and metal ions. (4) Rinse with pure water for 10 minutes.
(5) Treatment in 2.5% dilute hydrofluoric acid for 20 seconds to remove the natural oxide film and metal ions. (6) 1 rinse with pure water
Do it for 0 minutes. (7) Dry with a spin dryer. After washing, the porous silicon layer is oxidized at 400 ° C. for 60 minutes to form a thermal oxide film on the surface of the porous silicon layer to protect the surface of the porous silicon layer. Then, the P-type silicon wafer is transferred into the epitaxial growth apparatus and set on the susceptor. Before the epitaxial growth, the temperature of 1040
230 liters / min of hydrogen at ℃ and pressure of 760 Torr
For 15 minutes to remove the thermal oxide film formed on the surface. After exposing the surface of the porous silicon layer by this,
Temperature 1040 ° C, pressure 760 Torr, dichlorosilane 0.2 l / min, hydrogen 230 l / min
For 10 minutes to perform epitaxial growth, a single crystal silicon layer having a thickness of 2 μm is formed on the porous silicon layer. As a result, a semiconductor substrate in which a 2 μm thick single crystal silicon layer is formed on a 15 μm thick porous silicon layer is obtained.

By using the process shown in the second embodiment,
A high-quality single crystal silicon layer with few crystal defects due to the influence of particles or the like can be formed over the porous silicon layer. Further, in this embodiment, since the porous silicon layer is oxidized at a low temperature, the structure of the porous silicon layer does not change even if the heat treatment is performed at a high temperature. That is, as described above, when porous silicon is subjected to heat treatment at a high temperature of 850 ° C. or higher, silicon atoms aggregate to increase the diameter of pores, so-called pore rearrangement occurs. The structural change of the porous silicon layer can be suppressed by oxidizing the porous silicon layer at a low temperature to form an oxide film on the inner surface of the porous silicon layer as in this embodiment. After forming an oxide film on the porous silicon layer and exposing the surface,
A state of epitaxially growing a single crystal silicon layer is schematically shown in FIGS.

Therefore, in the epitaxial growth method, the atmospheric pressure CVD method can be used in addition to the MBE method, the LPE method and the like shown in the first embodiment. For example, when dichlorosilane (SiH ₂ Cl ₂ ) is used, 890 to 1150 ° C.
It is possible to carry out epitaxial growth within the range.
In addition to this, trichlorosilane (SiHCl ₃ ) is 100
0 to 1150 ° C., 800 to 11 for silane (SiH ₄ ).
00 ° C, 115 for tetrachlorosilane (SiCl ₄ )
It is possible to perform epitaxial growth in the range of 0 to 1200 ° C. Further, hydrogen baking before epitaxial growth has the functions of cleaning the surface of the porous silicon layer and flattening the surface in addition to the removal of the thermal oxide film described above.
In the case of D, it can be performed in the range of 900 to 1150 ° C. In addition to this, when the low pressure CVD method, the plasma CVD method, the thermal CVD method, the photo CVD method, the vapor deposition method, the bias sputtering method, or the like is used, the epitaxial growth can be performed at a higher temperature. The porous silicon layer can be oxidized at a temperature of 200 to 480 ° C. for 30 minutes to 2 hours.

For the other details, the same method as shown in the first embodiment can be applied. [Third Embodiment] A third embodiment of the method for manufacturing a semiconductor substrate according to the present invention will be described below. FIG. 1 is used as a process diagram showing this embodiment.

The steps in FIG. 1 are as follows.
(A) P-type silicon wafer 1 is anodized, and (b) P
A porous silicon layer 2 is formed on a mold silicon wafer 1. (C) After treating the porous silicon layer at a low temperature, washing is performed to form the oxide film 4 on the porous silicon layer 2.
(D) After transporting the P-type silicon wafer 1 into the epitaxial growth apparatus, the oxide film 4 is removed. (E) The single crystal silicon layer 3 is formed by performing epitaxial growth on the porous silicon layer 2. As a result, a semiconductor substrate in which a single crystal silicon layer is formed on the porous silicon layer is obtained.

An example in which the above-mentioned semiconductor substrate is specifically manufactured by using this embodiment is shown below. Anodization is performed on a P-type silicon wafer having a thickness of 625 μm, a diameter of 125 mm, and a specific resistance of 0.02 Ωcm. Here, the chemical conversion liquid is HF: C.
_{Using 2} H ₅ OH: H ₂ O = 1: 1: 1, 1.0 A /
When a direct current of cm ² is applied for 5 minutes, a 5 μm thick porous silicon layer is formed on the P-type silicon wafer. Then, the porous silicon layer is washed by the same method as in Example 2, and then an oxidation treatment is performed at 350 ° C. for 50 minutes to form a thermal oxide film on the surface of the porous silicon layer. After that, the porous silicon layer is washed in the following order. (1) 2.
The organic matter is removed by washing with pure water containing 5 ppm of ozone for 10 minutes. (2) 80 ° C Ammonia hydrogen peroxide (N
Particles, organic substances and metal ions are removed by washing with H ₄ OH: H ₂ O ₂ : H ₂ O = 1: 2: 6) for 10 minutes. (3) Rinse with pure water for 10 minutes. (4)
It is treated in 2.5% dilute hydrofluoric acid for 20 seconds to remove the oxide film in the portion where the single crystal silicon layer is formed. (5) Rinse with pure water for 10 minutes. (6) 70 ° C. Hydrochloric acid / hydrogen peroxide (HCl: H
₂ O ₂ : H ₂ O = 1: 2: 7) for 10 minutes to remove metal ions and form a natural oxide film of about 1 nm on the surface. (7) Rinse with pure water for 10 minutes.
(8) Dry with a spin dryer. This cleans the surface of the porous silicon layer and forms a natural oxide film on the surface as a protective layer. After that, the P-type silicon wafer is transferred into the epitaxial growth apparatus for epitaxial growth. The conditions shown in the second embodiment were used as the conditions for removing the natural oxide film and forming the single crystal silicon layer. As a result, the thickness of 2 μm is formed on the porous silicon layer having a thickness of 5 μm.
A semiconductor substrate having a single crystal silicon layer of m is obtained.

By using the process shown in the third embodiment,
A high-quality single crystal silicon layer with few crystal defects due to the influence of particles or the like can be formed over the porous silicon layer. Further, in this embodiment, since the porous silicon layer is oxidized at a low temperature, the structure of the porous silicon layer does not change even if the heat treatment is performed at a high temperature. In this embodiment, as compared with the second embodiment, the thermal oxide film is not used as a protective film,
Since the natural oxide film is formed as a protective film after removing the thermal oxide film in the portion where the single crystal silicon layer is formed, and this natural oxide film is removed in the film forming apparatus, it is possible to remove the porous silicon at a high temperature. It has the effect of suppressing structural changes.

Regarding the method for cleaning the porous silicon layer before the epitaxial growth and the method for forming the natural oxide film, the natural oxide film can be formed on the surface of the porous silicon layer at the final stage without causing a large damage to the porous silicon layer. Any item can be freely selected without being limited to the above specific example.

Regarding other details of this embodiment,
It is possible to apply the same method shown in the second embodiment. [Fourth Embodiment] FIG. 2 is a process diagram showing a fourth embodiment of the method for manufacturing a semiconductor substrate according to the present invention. Where 1 is P
A type silicon wafer, 2 is a porous silicon layer, 3 is a single crystal silicon layer, 4 is an oxide film, and 5 is an amorphous silicon layer.

The steps in FIG. 2 are as follows.
(A) P-type silicon wafer 1 is anodized, and (b) P
A porous silicon layer 2 is formed on a mold silicon wafer 1. (C) An oxide film 4 is formed on the surface of the porous silicon layer 2. (D) An amorphous silicon layer 5 is laminated on the oxide film 4. (E) After transporting the P-type silicon wafer 1 into the epitaxial growth apparatus, the oxide film 4 and the amorphous silicon layer 5 are removed. (F) The single crystal silicon layer 3 is formed by performing epitaxial growth on the porous silicon layer 2.
As a result, a semiconductor substrate in which a single crystal silicon layer is formed on the porous silicon layer is obtained.

An example in which the above semiconductor substrate is specifically manufactured by using this embodiment is shown below. A P-type silicon substrate having a diameter of 125 mm, a thickness of 625 μm and a specific resistance of 0.01 Ωcm is anodized under the conditions shown in the first embodiment. As a result, a porous silicon layer having a thickness of 8 μm is formed on the P-type silicon wafer. Then, the porous silicon layer is washed and oxidized by the method shown in the second embodiment to form an oxide film having a thickness of 1 nm on the porous silicon layer. After that, the temperature is 250 ° C. and the pressure is 1 × 10 ⁻⁷ Torr on the oxide film.
After depositing amorphous silicon at a temperature of 780 ° C and pressure of 1
When heat treatment is performed at × 10 ^-7 Torr for 30 minutes, SiO ₂
By the reaction of + Si (amorphous silicon) → 2SiO ↑, the oxide film is reduced and removed, and the clean porous silicon layer surface is exposed. After that, epitaxial growth is performed using the method shown in the first embodiment to obtain a semiconductor substrate in which a 1 μm-thick single crystal silicon layer is formed on a 8 μm-thick porous silicon layer.

By using the process shown in the fourth embodiment, it is possible to form a high-quality single crystal silicon layer with few crystal defects due to the influence of particles etc. on the porous silicon layer.

Further, compared with the methods shown in the first to third embodiments, the reducing power is high and there is an advantage that the oxide film can be surely removed. In this embodiment, amorphous silicon is laminated on the oxide film by the vapor deposition method, but in addition to this, glow discharge method, arc discharge method, reactive sputtering method, thermal CVD method,
It is also possible to use a photo CVD method or a plasma CVD method. Since the thickness of the amorphous silicon layer is optimized by the oxide film thickness on the surface of the porous silicon layer, the amorphous silicon layer having a required thickness may be formed according to the oxide film thickness. Further, although the amorphous silicon layer is laminated in this embodiment, the oxide film may be reduced and removed after the polycrystalline silicon layer is laminated. In addition, the oxide film can be removed by irradiating a beam of silicon or gallium at a temperature of about 800 ° C. and a high vacuum of 10 ⁻³ Torr or less.

Regarding other details of the present embodiment, the second,
It is possible to apply the same method as shown in the third embodiment. [Fifth Embodiment] FIG. 3 is a process diagram showing a fifth embodiment of the method for manufacturing a semiconductor substrate according to the present invention. Where 1 is P
Type silicon wafer, 2 a porous silicon layer, 4 a first oxide film, 3 a single crystal silicon layer, 6 a second oxide film, 7
Is a silicon wafer.

The steps in FIG. 3 are as follows.
(A) P-type silicon wafer 1 is anodized, and (b) P
A porous silicon layer 2 is formed on a mold silicon wafer 1. (C) First as a protective film on the surface of the porous silicon layer 2
Oxide film 4 is formed. (D) After transporting the P-type silicon wafer 1 into the epitaxial growth apparatus, the first oxide film 4 is removed. (E) The single crystal silicon layer 3 is formed by performing epitaxial growth on the porous silicon layer 2.
(F) The surface of the single crystal silicon layer 3 is oxidized to form the second oxide film 6. (G) The second oxide film 6 and the silicon wafer 7 are bonded together. After further bonding, heat treatment is performed to completely bond the both. (H) The P-type silicon wafer 1 and the porous silicon layer 2 are removed, and the S in which the single crystal silicon layer 3 is formed on the second oxide film 6 which is an insulating layer.
A semiconductor substrate having an OI structure is obtained.

An example in which an SOI substrate is specifically manufactured using this embodiment is shown below. Thickness 625 μm, diameter 12
Anodization is performed on a P-type silicon wafer having a specific resistance of 5 Ω and a resistance of 0.01 Ωcm. Here, the chemical conversion liquid is HF: C ₂ H ₅
OH: H ₂ O = 1: 1: 1, 1.0 A / cm ²
When a direct current of 10 μm is applied for 8 minutes, a 10 μm thick porous silicon layer is formed on the P-type silicon wafer. Then 2.0% dilute hydrofluoric acid and HCl: H ₂ O ₂ : H ₂ O =
After washing with hydrochloric acid / hydrogen peroxide mixture of 1: 2: 8 for 10 minutes each, oxidation is performed at 350 ° C. for 70 minutes to form an oxide film as a protective film on the surface of the porous silicon layer. Then, the P-type silicon wafer is transferred into the epitaxial growth apparatus and set on the susceptor. Before performing the epitaxial growth, 230 liter / min of hydrogen is flown for 8 minutes at a temperature of 1120 ° C. and a pressure of 760 Torr to remove the thermal oxide film formed on the surface. After exposing the surface of the porous silicon layer by this, a temperature of 1040 ° C., a pressure of 760 Torr, 0.2 l / min of dichlorosilane, and 230 l / min of hydrogen were flown for 9 minutes to perform epitaxial growth. A 1.8 μm-thick single crystal silicon layer is formed.

After this, an oxygen / hydrogen mixed atmosphere (O ₂ : H
₂ = 4: 6) and oxidation is performed at 1000 ° C. for 185 minutes to form an oxide film having a thickness of 800 nm on the single crystal silicon layer. Then, this oxide film, thickness 625 μm, diameter 125 m
m and a silicon wafer having a specific resistance of 1.0 Ωcm in a nitrogen atmosphere, and then heat-treated at 1150 ° C. for 5 minutes to completely bond the two. Further, after removing the P-type silicon wafer by grinding, hydrofluoric acid / hydrogen peroxide mixture (HF: H ₂
The porous silicon layer is removed by etching with O ₂ = 1: 5). As a result, an SOI substrate in which a 1 μm thick single crystal silicon layer is formed on an 800 nm thick oxide film is obtained.

By using the process shown in the fifth embodiment,
A semiconductor substrate having an SOI structure can be manufactured using a semiconductor substrate in which a high-quality single crystal silicon layer with few crystal defects due to the influence of particles or the like is formed over a porous silicon layer.

The SOI substrate is a semiconductor substrate which has many advantages over the conventional bulk substrate, such as high-speed operation and high integration. However, by taking the steps shown in this embodiment, a high-quality SOI substrate is obtained. An SOI substrate can be obtained. This makes it possible not only to improve the manufacturing yield of the SOI substrate, but also to manufacture high-quality semiconductor devices with high yield using this substrate. For example, when a TFT liquid crystal image display device is manufactured, high speed operation can be performed by using an SOI substrate and a high-definition image display element can be formed. By using the steps shown in this embodiment, Since defects in the image display element can be reduced, high-quality image display can be realized, and the manufacturing yield of the entire semiconductor device can be improved. In addition, the SOI substrate manufactured according to this example has an advantage that the degree of freedom in element design is increased because the entire surface of the substrate has an SOI structure and that the entire surface of the substrate can be utilized, so that productivity can be improved. Have

The details of the present embodiment are not limited to the above specific examples, and various conditions can be used. For the steps up to the formation of the single crystal silicon layer, the same methods shown in the first to fourth embodiments can be applied. Regarding the bonding step, the oxide film formed on the single crystal silicon layer and the silicon wafer are bonded in this embodiment, but the single crystal silicon layer or the oxide film formed on the single crystal silicon layer and the silicon wafer are bonded together. It is also possible to bond the oxide film formed above. In this case, the oxide film thickness, the diameter of the silicon wafer, the thickness, the specific resistance, etc. can be freely selected according to the purpose. Further, the single crystal silicon layer or the oxide film formed over the single crystal silicon layer and the insulator can be attached to each other. For example, synthetic quartz glass, fused quartz glass, crystallized glass, high melting point glass, soda glass, borosilicate glass, quartz glass and the like can be used. The size of the insulator can be freely selected according to its application. In addition to the above oxide film, it is also possible to use a silicon nitride film. The substrate bonding atmosphere can be performed in the air, a nitrogen atmosphere, pure water, or the like. The heat treatment after bonding the substrates is 800 to 1 when a silicon wafer is used in an oxygen atmosphere, a nitrogen atmosphere, an oxygen / nitrogen mixed atmosphere, or the like.
150 ° C, quartz glass at 200 to 400 ° C for 1 minute to 2
It can be done in a range of time. In addition to the removal of the P-type silicon wafer shown in this embodiment, a hydrofluoric / nitric acid-based etching solution (eg, HF: HNO ₃ : CH ₃ COOH = 1: 1) is used.
2:17) and the like. [Sixth Embodiment] FIG. 4 is a process drawing showing a sixth embodiment of the method for manufacturing a semiconductor substrate according to the present invention. Where 1 is P
A type silicon wafer, 2 is a porous silicon layer, 4 is an oxide film, 3 is a single crystal silicon layer, 8 is a trench, and 9 is an oxidized porous silicon layer.

The steps in FIG. 4 are as follows.
(A) P-type silicon wafer 1 is anodized, and (b) P
A porous silicon layer 2 is formed on a mold silicon wafer 1. (C) An oxide film 4 is formed on the surface of the porous silicon layer 2. (D) After transporting the P-type silicon wafer 1 into the epitaxial growth apparatus, the oxide film 4 is removed. (E) The single crystal silicon layer 3 is formed by performing epitaxial growth on the porous silicon layer 2. (F) Single crystal silicon layer 3
A trench 8 is formed on the top to expose the porous silicon layer 2. (G) The porous silicon layer 2 is selectively oxidized to obtain a semiconductor substrate having an SOI structure in which the single crystal silicon layer 3 is formed on the oxidized porous silicon layer 9 which is an insulating layer.

An example of concretely manufacturing an SOI substrate using this embodiment is shown below. Thickness 625 μm, diameter 12
Anodization is performed on a P-type silicon wafer having 5 mm and a specific resistance of 0.02 Ωcm. As the chemical conversion conditions, the conditions shown in the fifth embodiment were used to form a porous silicon layer having a thickness of 10 μm on the P-type silicon wafer. Then, after cleaning the porous silicon layer by the method shown in the second embodiment, it is oxidized at 450 ° C. for 45 minutes to form an oxide film as a protective film on the surface of the porous silicon layer. Then, the P-type silicon wafer is transferred into the epitaxial growth apparatus and set on the susceptor. Before performing epitaxial growth, the temperature of 1120
At a temperature of 80 ° C. and a pressure of 80 Torr, 230 liter / min of hydrogen is flowed for 10 minutes to remove the thermal oxide film formed on the surface.
After exposing the surface of the porous silicon layer by this, a temperature of 900 ° C., a pressure of 80 Torr, dichlorosilane of 0.2 liter / min, and hydrogen of 230 liter / min are flown for 12 minutes to perform epitaxial growth. A 1.3 μm single crystal silicon layer is formed. After that, after performing mask patterning with a nitride film, R
A trench reaching the porous silicon layer is formed on the single crystal silicon layer by IE (reactive ion etching). In this state, 500 P-type silicon wafers
When the oxidation treatment is performed at 80 ° C. for 80 minutes, a thin oxide film is formed on the side wall of the trench portion of the single crystal silicon layer and the porous silicon layer is oxidized to become an insulating layer. Finally, the nitride film is removed to obtain an SOI substrate having a 1.3 μm thick single crystal silicon layer on a 10 μm thick oxidized porous silicon layer.

By using the process shown in the sixth embodiment,
A semiconductor substrate having an SOI structure can be manufactured using a semiconductor substrate in which a high-quality single crystal silicon layer with few crystal defects due to the influence of particles or the like is formed over a porous silicon layer.

The SOI substrate shown in this embodiment has a lower degree of freedom in device design than the SOI substrate shown in the fifth embodiment because the entire surface of the substrate cannot have an SOI structure.
Since the manufacturing method is relatively simple and the SOI substrate can be manufactured with one silicon wafer, the manufacturing cost can be reduced, and element isolation can be performed more easily depending on the patterning method. Have the advantages of.

The details of the present embodiment are not limited to the above specific examples, and various conditions can be used. For the steps up to the formation of the single crystal silicon layer, the same methods as those shown in the first to fourth embodiments can be applied. As for the method of forming the trench, in addition to the method shown in the present embodiment, wet etching such as an aqueous solution of potassium hydroxide, a mixed solution of ethylenediamine, catechol and pyrazine, an aqueous solution of hydrazine, tetramethylammonium hydride (TMAH), or plasma etching. Can be done by. The oxidation of the porous silicon layer can be performed within the range of 250 to 750 ° C. Although the inside of the trench is hollow in this embodiment, it is also possible to oxidize the porous silicon layer and then stack an oxide film or polycrystalline silicon inside the trench to flatten the substrate.

[0043]

As described above, according to the present invention,
After forming a protective layer for protecting the porous semiconductor layer provided on the semiconductor substrate, removing the protective layer in a film forming apparatus and forming a film on the porous semiconductor layer in the film forming apparatus. Thus, it is possible to form a high-quality film with few defects on the porous semiconductor layer with less particles and the like attached to the porous semiconductor.

In the present invention, for example, when a single crystal silicon layer is formed on a porous silicon layer, it becomes possible to form a single crystal silicon layer having few crystal defects on the porous silicon layer. There is an effect that the quality of the single crystal silicon layer can be improved. This also has the effect of improving the quality of the element formed on the single crystal silicon layer and the semiconductor device manufactured using this element. For example, since there is little decrease in the withstand voltage of the element, the desired performance can be obtained, and the reliability of the element and the device can be improved. Further, from this, there is an effect that not only the semiconductor substrate but also the yield of the semiconductor element and the semiconductor device can be improved.

[Brief description of drawings]

1 to 3 of a method for manufacturing a semiconductor substrate according to the present invention.
FIG. 6 is a process drawing showing an example of FIG.

FIG. 2 is a process drawing showing a fourth embodiment of the method of manufacturing a semiconductor substrate according to the present invention.

FIG. 3 is a process drawing showing a fifth embodiment of the method for manufacturing a semiconductor substrate according to the present invention.

FIG. 4 is a process drawing showing a sixth embodiment of the method for manufacturing a semiconductor substrate according to the present invention.

FIG. 5 is a process diagram showing formation of a single crystal silicon layer on a porous silicon layer according to a conventional example.

FIG. 6 is a diagram schematically illustrating a process of forming an oxide film on a porous silicon layer, exposing the surface, and then epitaxially growing a single crystal silicon layer.

[Explanation of symbols]

 1 (P-type) Silicon Wafer 2 Porous Silicon Layer 3 Single Crystal Silicon Layer 4 (Silicon) Oxide Film (First Oxide Film) 5 Amorphous Silicon Layer 6 Second Oxide Film 7 Silicon Wafer 8 Trench 9 Oxidized Porous Quality silicon layer

Claims (5)

[Claims] 1. A step of forming a protective layer for protecting a porous semiconductor layer provided on a semiconductor substrate, a step of removing the protective layer in a film forming apparatus, and the porous semiconductor in the film forming apparatus. A method of manufacturing a semiconductor substrate, comprising: forming a film on a layer. 2. A step of forming a protective layer for protecting a porous semiconductor layer provided on a semiconductor substrate, a step of removing the protective layer in an epitaxial growth apparatus, and a step of removing the protective layer on the porous semiconductor layer in the epitaxial growth apparatus. And a step of forming a single crystal semiconductor layer on the substrate. 3. The method of manufacturing a semiconductor substrate according to claim 1, wherein the protective layer is an oxide layer. 4. A step of forming an insulating layer on the single crystal semiconductor layer of the semiconductor substrate according to claim 2, bonding the insulating layer to another substrate, and removing the semiconductor substrate including the porous semiconductor layer. A method of manufacturing a semiconductor substrate, comprising: 5. A method comprising: patterning the single crystal semiconductor layer of the semiconductor substrate according to claim 2 to provide an opening; and oxidizing the porous semiconductor layer through the opening. Of manufacturing a semiconductor substrate.