JP3241155B2 - Semiconductor substrate manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor substrate, and more particularly, to a method of manufacturing a semiconductor substrate suitable for an electronic device or an integrated circuit. About.

[0002]

2. Description of the Related Art In order to respond to demands for higher speed, higher performance, and higher functionality of devices, various research and development on semiconductors have been conducted with a focus on miniaturization. Among them, in particular, in recent years, in order to eliminate any impurity contamination and obtain a target performance, there has been a discussion on cleanliness in all aspects such as equipment, cleaning, and film formation from a clean room environment (T. Ohmi). , Proc.
EMI Technology Symposium,
PP. A1-1 'to A1-21, Dec. , 198
6).

[0003] Among them, the surface treatment of a substrate before the formation of a deposited film by epitaxial growth is one of the techniques that have been regarded as important, because it very sensitively affects the crystal structure, physical properties and the like of the obtained deposited film. This cleansing technology is C
In the VD method, the substrate temperature is generally raised to about 1000 ° C. and a chlorine-based gas is used. Other M
A high-temperature treatment after forming a protective oxide film, a method of removing the oxide film with a Si beam, a method of using H plasma, a method of using Ar ion sputtering having an energy of 100 eV or more (WR), which are often used in the BE method. Burger
et al, IEEE Electron Device
e Lett. EDL-8, 168 (1987)) and a method by low energy Ar ion irradiation reported by the authors (T. Ohmi, T. Ichikawa et a).
1, Appl. Phys. Lett. 53, 45 (19
88)).

On the other hand, regarding the importance of surface cleaning,
This is particularly important not only in the case of a single crystal Si wafer but also in the field of a porous layer, which has recently been studied in the field of light emission. Porous is
A method of realizing an SOI structure (FIPOS (Full I
resolution by Porous Oxidiz
ed Silicon)), applications in recent years are expected as Si light emitting devices. It is important to clean the surface of the porous layer, but other than that, heat treatment is performed to remove moisture and other impurities (including gas) remaining inside the pores of the porous layer before epitaxial growth. , A method of irradiating a Si beam during heat treatment (TLL)
in et al, Appl. Phys. Lett. 4
8, 1793 (1986)) and ion sputter cleaning of Ne (MIJ BEAL et a).
1, J .; Vac. Sci. Technol. B3
(2), pp732 (1985)).

[0005]

However, in the method of cleaning in which the above-mentioned high-temperature process is performed in a film forming chamber where epitaxial growth is performed, a large amount of gas is degassed from a substrate including a porous layer, and this gas contaminates the film forming chamber. As a result, there is a problem that impurities are taken into the deposited film.
That is, when a high-temperature heat treatment is performed on the substrate to remove impurities on the surface and inside of the porous layer, an extremely large amount of gas is released from the inside of the porous layer. For this reason, when this is performed in the film formation chamber, contamination by gas in the film formation chamber and incorporation of impurities into the deposited film become large. Also, once the gas is released into the film formation chamber, it takes a considerable time to reach a desired degree of vacuum in film formation in a high vacuum region such as MBE or sputtering. The working efficiency becomes very poor as compared with the substrate without. Further, the porous layer may be deteriorated by the high temperature process.

On the other hand, the most problematic method for performing surface cleaning by ion irradiation is ion damage to a substrate. In most cases, to remove the damage,
Further heat treatment is usually performed. In addition, the present inventors have reported a method for cleaning the surface without damage to the substrate due to low energy ion irradiation in the report shown above, and it is possible to remove the adsorbed impurity layer on the substrate surface without damage. There are problems in that the substrate must be left in a high vacuum until some degassing is performed in the film chamber, and it is difficult to remove adsorbed impurities inside the porous material having a depth of several μm. .

An object of the present invention is to provide a method of manufacturing a semiconductor substrate which meets the above-mentioned problems and the above-mentioned requirements.

[0008]

In order to achieve the above object, the present invention provides: (1) a step of heating a substrate having a porous layer in a first container, and placing the substrate in a second container. A method for manufacturing a semiconductor substrate, comprising a step of transporting and forming an epitaxial growth film on the substrate. (2) The method of manufacturing a semiconductor substrate according to (1), wherein the transfer of the substrate from the first container to the second container is performed in a vacuum. (3) The method for manufacturing a semiconductor substrate according to (1) or (2), wherein the heating in the first container is performed in a vacuum state. (4) The method of manufacturing a semiconductor substrate according to any one of (1) to (3), wherein the heating of the base is lamp heating. (5) The method of manufacturing a semiconductor substrate according to any one of (1) to (4), wherein the main component of the base is Si. (6) The method for manufacturing a semiconductor substrate according to (4), wherein the lamp used for heating the lamp is a Xe lamp. (7) The formation of the epitaxially grown film in the second container is performed when the partial pressure of molecules other than the source gas is 10 ^-8 Torr.
The method of manufacturing a semiconductor substrate according to any one of the above (1) to (3), which is performed in the following ultra-high vacuum. (8) The method of manufacturing a semiconductor substrate according to any one of (1) to (3), wherein the epitaxial growth film is formed by any one of a sputtering method, a CVD method, and an MBE method. (9) The method for manufacturing a semiconductor substrate according to the above (1), wherein the heating is a resistance heating method. (10) The method of manufacturing a semiconductor substrate according to any one of (1) to (3), wherein the heating is performed at about 500 ° C. (11) The wavelength of the lamp used for heating the lamp is 1
The method for manufacturing a semiconductor substrate according to the above (4), wherein the thickness is not more than μm. (12) The material of the base is GaAs, Ge, SiC,
Alternatively, the method of manufacturing a semiconductor substrate according to any one of the above (1) to (3), which is SiGe. (13) The method of manufacturing a semiconductor substrate according to any one of (1) to (3), wherein a passive oxide film is formed on an inner surface of the second container. Is included.

[0009]

According to the above-described structure, problems such as contamination in the deposition container, incorporation of impurities into the film, deterioration of the porous layer, problems when returning to the high vacuum region, and damage to the substrate due to ion irradiation are solved. It is possible to degas a substrate such as a Si wafer or a substrate including a porous layer without causing any gas. Further, a cleaning effect can be added, and thereafter, a desired film can be easily formed.

[0010] The substrate having a porous layer is not particularly limited, such as a partially single-pored Si single crystal substrate or a completely porous Si substrate.

[0011] As a material of the substrate, GaAs is typically used for Si.
It is not limited, including s, Ge, SiC, SiGe, and the like, and a mixture thereof.

It is more preferable that the transfer from the container to be heated to the deposition container is performed in a vacuum, from the viewpoint that no new contaminants are adsorbed during the transfer.

[0013] The heating method of the substrate is most preferably a lamp heating method, in which the temperature can be rapidly raised and lowered in order to suppress the deterioration of the porous layer, and degassing can be performed in a short time. In particular, when porous Si is formed on the surface, a lamp having a main wavelength of 1 μm or less is effective.

When a lamp is used, the cleaning effect in the short wavelength region is strong, and the absorption coefficient of porous Si is small as shown in FIG. And effective.

The Xe lamp has the wavelength spectrum shown in FIG. 5, and can selectively heat not only the surface of the substrate but also the surface of the porous pores inside the substrate in relation to the absorption wavelength. Can be said to be a lamp that can realize efficient degassing. When heating by a method other than the ramp method, for example, it is also possible to use a resistance heating method, but it also heats other than the substrate, preventing effective degassing,
In some cases, it takes time to cool after stopping the heating.

Further, the method of separating the heating vessel from the deposition vessel is such that when the deposition in the vessel in which the deposition is performed is performed in an ultra-high vacuum apparatus in which the partial pressure of molecules other than the deposit is 10 ^-8 Torr or less. This method is particularly effective because the deposition vessel is in a vacuum region where recovery from contamination is not easy.

Hereinafter, the present invention will be described in detail with reference to embodiments.

FIG. 1 shows an example of an apparatus used in carrying out the present invention, but it is not particularly limited to this apparatus. The apparatus is an RF-DC coupled bias sputtering apparatus and has a two-chamber configuration.

In FIG. 1, reference numeral 91 denotes a deposition container (chamber) for forming a deposited film on a substrate by epitaxial growth, and the inside thereof can be evacuated.

Reference numeral 92 denotes a target, 93 denotes a permanent magnet, 94
Is a substrate, 95 is a substrate support, 96 is a high-frequency power supply, 97 is a matching circuit, 98 is a DC power supply for determining the DC potential of the target, 99 is a DC power supply for determining the DC potential of the base, and 100 and 101. Is the target,
And a low-pass filter of a substrate.

The deposition container 91 is made of SUS316, and the inner surface of the container is subjected to electrolytic polishing and electrolytic composite polishing as surface treatment.
Rmax (surface roughness) <0.1 μm as surface smoothness
A passive oxide film of high-purity oxygen is formed on the mirror-finished surface. The gas exhaust system, including the mass flow controller and the filter, is made of SUS316, and is subjected to electrolytic polishing and passivation oxidation so as to minimize the amount of impurities carried into the container when the gas is introduced. The exhaust system is configured as follows. The main pump is a magnetically levitated random type turbo molecular pump. A dry pump is used as an auxiliary pump. The exhaust system is an oil-free system, and the system is configured so as to reduce impurity contamination. The second-stage turbo-molecular pump is a large-flow-rate pump, and the evacuation speed is maintained even with the degree of vacuum on the order of mTorr during plasma generation. As a result, the amount of impurities in Ar introduced into the deposition container 91 is several p
pb or less, and 2 × 10 ⁻¹¹ Torr can be achieved as the background vacuum degree when the substrate temperature is not increased. In addition, since a variable high-frequency power supply 96 whose frequency can be changed to several hundred MHz is connected to the target 92, high-density plasma can be generated. A DC power supply for applying a DC potential is connected via the low-pass filters 100 and 101, and these can control the potential of the target 92 and the base 94a.

The substrate 94 is introduced into the vacuum deposition container 91 via a load lock chamber 201 which is a different container provided in contact with the container. by this,
The contamination of the container 91 with impurities is prevented. The load lock chamber 201 is provided with an Xe lamp 203, which heats the base 94 and cleans the base.

Next, a case where a semiconductor substrate is manufactured using the sputtering apparatus having the above configuration will be described.

First, the production of a porous Si substrate will be described. Here, an example of porous Si formed by anodization will be described. A Si single crystal substrate is prepared, and the entire surface or a part thereof is made porous. The Si substrate is made porous by an anodizing method using an HF solution. This porous Si
The layer can be changed to a density of 1.1 to 0.6 g / cm ³ by changing the HF solution concentration to 50 to 20% (the density of single crystal Si is 2.33 g).
/ Cm ³ ).

[0025] Porous Si is manufactured by Uhlir et al.
It was discovered during the research process of electropolishing of semiconductors in 56 (A. Uhril, Bell Syst. Tech.
J. , Vol 35, p. 333 (1956)).

According to observation with a transmission electron microscope, pores having an average diameter of about 600 angstroms are formed in the porous Si layer. The density is less than half that of single crystal Si. However, since single crystallinity is maintained, it is also possible to epitaxially grow a single crystal Si layer on top of the porous layer, and there are several reports (Unagami J. Electrocheche).
m. Soc. : Solid-state science
e and technology pp. 133
9). However, the crystallinity of the grown single crystal film is not perfect, and defects often remain. When high temperature processing or high temperature film formation is performed to improve crystallinity, porous Si
May be altered, and the characteristics of the porous Si itself, such as accelerated oxidation, may change. Especially at 1000 ° C. or higher, rearrangement of internal pores may occur.

Since the porous layer has a large amount of voids formed therein, the surface area increases drastically. As a result, a large amount of gas, mainly water, is released when the liquid is directly loaded into the deposition container of the sputtering apparatus. In order to prevent this, a load lock, which is a vacuum container adjacent to the deposition container, is formed before film formation. The substrate is degassed by heating the substrate in a vacuum state in a chamber to clean the substrate.

For example, if light is irradiated by a Xe lamp, the substrate temperature can be raised to about 500 ° C. in several tens of seconds. The porosity is about 40%, and the porous layer having a thickness of 2 μm is made of Si.
In the case of a substrate formed on a (100) substrate, degassing can be performed almost completely by lamp irradiation for about 20 minutes.

FIG. 2 shows the change in the degree of vacuum during this irradiation.
Here, different degassing conditions are used for other porous conditions, so that different conditions are used for the temperature and time.

FIG. 2 also shows an example of a single crystal Si substrate for reference. In the case of porous Si, a larger amount of gas is released by two digits or more than that of single crystal Si. Next, the substrate is introduced into the deposition vessel. At this time, the difference in the degree of vacuum change in the deposition vessel depending on the presence or absence of Xe lamp irradiation in the load lock chamber is shown in FIG.
Shown in By performing Xe lamp irradiation, it is possible to greatly reduce the standby time. Further, since degassing is performed in the load lock chamber, contamination in the deposition container can be prevented, and incorporation of impurities into the film can be suppressed.

Then, epitaxial growth is performed on the surface of the porous substrate by sputtering in the above-mentioned deposition vessel to form a silicon single crystal layer. By setting conditions such as substrate surface cleaning conditions, substrate bias, target bias, and pressure, a low-defect single-crystal Si film or a porous Si that inherits the porous layer on the porous substrate can be used to form the underlying porous layer. It can be formed in a short time without deteriorating.

[0032]

The present invention will be described below with reference to specific examples.

Example 1 A P-type (100) single crystal Si substrate having a thickness of 525 microns was anodized in an HF solution.

The anodizing conditions were as follows.

Current density: 5 (mA · cm ⁻² ) Anodizing solution: HF: H ₂ O: C ₂ H ₅ OH = 1:
1: 1 Time: 2 (min) Thickness of porous Si: 2 (μm) Porosity: 40 (%) The P-type (100) porous Si substrate was introduced into a load lock chamber of a sputtering apparatus. The degree of vacuum after introduction is 7 × 10 ^-8 T
orr. Next, irradiation was performed with a Xe lamp (1 kW) for 20 minutes to degas. 5 × 10 ^-6 Torr after irradiation
r, the degree of vacuum gradually increased, and then increased to 3 × 10 ⁻⁸ Torr after 20 minutes. When the irradiation with the Xe lamp was stopped, the degree of vacuum became 5 × 10 ⁻⁹ Torr. After that, it is introduced into a sputtering chamber composed of a deposition container,
After one hour, 0.2 micron Si on a porous Si substrate
An epitaxial layer was grown at a low temperature. The degree of vacuum before introducing Ar was 3 × 10 ⁻⁹ Torr. The deposition conditions were as follows. Surface cleaning conditions Temperature: 451 ° C. Atmosphere: Ar pressure: 15 mTorr Substrate potential: 5 V Target potential: −5 V High frequency power: 5 W RF frequency: 100 MHz Deposition conditions RF frequency: 100 MHz High frequency power: 100 W Temperature: 451 ° C. Ar gas pressure: 15 mTorr Growth Time: 20 min Film thickness: 0.2 μm Target current potential: −150 V Substrate DC potential: +20 V A low-defect Si single crystal film was grown on the porous material. The term “low defect” means such a low defect that no defect is confirmed by cross-sectional TEM observation using a transmission electron microscope or observation using Secco etching. At this substrate temperature, no alteration of the porous layer was observed. This whole process is 165
Minutes. Further, the amount of carbon existing at the interface was 10 ¹³ atm / cm ² when the lamp was not irradiated, and decreased to 10 ¹² atm / cm ² when the irradiation was performed.

Example 2 A P-type (100) single crystal Si substrate having a thickness of 525 microns was anodized in an HF solution.

The anodizing conditions were as follows.

Current density: 5 (mA · cm ⁻² ) Anodizing solution: HF: H ₂ O: C ₂ H ₅ OH = 1:
1: 1 time: 10 (min) Thickness of porous Si: 10 (μm) Porosity: 40 (%) The P-type (100) porous Si substrate was introduced into a load lock chamber of a sputtering apparatus. The degree of vacuum after introduction is 10 ^-7 Torr
r. Then, irradiation was performed with a Xe lamp at 500 ° C. for 50 minutes to degas. After the irradiation, the degree of vacuum deteriorates up to 5 × 10 ⁻⁵ Torr, and then the degree of vacuum gradually increases.
After 0 minute, the pressure became 3 × 10 ⁻⁸ Torr. When the irradiation with the Xe lamp was stopped, the degree of vacuum became 6 × 10 ⁻⁹ Torr. Thereafter, the substrate was once taken out to the atmosphere, and then carried into a deposition container. Thereafter, an epitaxial Si single crystal film of 3 μm was deposited on the P-type (100) porous Si substrate by a normal CVD method. The deposition conditions are as follows.

Source gas: SiH ₂ Cl ₂ ··· 500 sccm Carrier gas: H ₂ ··· 180 l / min Substrate temperature: 950 ° C. Pressure: 80 Torr Growth time: 9 min Low-defect with pores closed on the porous material Was grown. This step was 65 minutes throughout.

Example 3 A P-type (100) single crystal Si substrate having a thickness of 525 microns was anodized in an HF solution.

The anodizing conditions were as follows.

Current density: 5 (mA · cm ⁻² ) Anodizing solution: HF: H ₂ O: C ₂ H ₅ OH = 1:
1: 1 Time: 2 (min) Thickness of porous Si: 2 (μm) Porosity: 40 (%) The P-type (100) porous Si substrate was introduced into a load lock chamber. The degree of vacuum after the introduction was 7 × 10 ⁻⁸ Torr. Then, irradiation was performed with a halogen lamp for 20 minutes to degas. After irradiation, the degree of vacuum deteriorates up to 8 × 10 ⁻⁶ Torr, and then gradually increases, and after 50 minutes, 7 × 10 ⁻⁶ Torr
It became 10 ^-8 Torr. When the irradiation of the halogen lamp was stopped, the degree of vacuum became 9 × 10 ⁻⁹ Torr. Then MBE
(Molecular Beam Epitaxy: molecular Beam
(Epitaxis) method, the single-crystal Si layer was
m. The deposition conditions are as follows.

Temperature: 800 ° C. Pressure: 10 ⁻⁹ Torr Growth time: 35 minutes Defects of this crystal were confirmed by cross-sectional TEM observation with a transmission electron microscope and observation by secco etching, but no defect was found. This process could be performed in 150 minutes throughout.

Example 4 A P-type (100) single crystal Si substrate having a thickness of 525 μm was anodized in an HF solution.

The anodizing conditions were as follows.

Current density: 5 (mA · cm ⁻² ) Anodizing solution: HF: H ₂ O: C ₂ H ₅ OH = 1:
1: 1 Time: 2 (min) Thickness of porous Si: 2 (μm) Porosity: 40 (%) The P-type (100) porous Si substrate was introduced into a load lock chamber of a sputtering apparatus. The degree of vacuum after introduction is 7 × 10 ^-8 T
orr. Then, degassing was performed by a resistance heating method. During the resistance heating, the deposition vessel is also heated, and the degree of vacuum is reduced to a maximum of 10 ^-5 Torr.
Minutes later, it was 7 × 10 ⁻⁸ Torr. When the resistance heating was stopped, the degree of vacuum became 2 × 10 ⁻⁸ Torr after 60 minutes.
Then, one hour after introduction into the sputtering chamber, an epitaxial layer was grown at a low temperature of 0.2 μm on the porous Si substrate. The degree of vacuum before introducing Ar was 3 × 10 ⁻⁹ Torr. The deposition conditions are as follows. Surface cleaning conditions Temperature: 385 ° C. Atmosphere: Ar pressure: 15 mTorr Base potential: 5 V Target potential: −5 V High frequency power: 5 W RF frequency: 100 MHz Deposition conditions RF frequency: 100 MHz High frequency power: 100 W Temperature: 385 ° C. Ar gas pressure: 15 mTorr Growth Time: 20 min Film thickness: 0.2 μm Target current potential: -150 V Substrate DC potential: +30 V A single-crystal film inheriting the porosity was grown on the porosity. Further, at this substrate temperature, no alteration of the porous layer was confirmed. This entire process lasted 250 minutes.

[0047]

As described in detail above, according to the present invention,
It is possible to propose a method of manufacturing a semiconductor substrate that can meet the above-mentioned problems and the above-mentioned requirements.

According to the invention, the substrate is heated in a vacuum,
After that, by performing deposition on the substrate in a room different from the heated room, contamination in the film formation chamber, incorporation of impurities into the film, deterioration of the porous layer, return to a high vacuum region, and ion The substrate including the porous layer can be degassed without causing a problem of damage to the substrate due to irradiation, and then a film can be formed. This has a great effect on greatly shortening time and improving impurity contamination. In addition, it is particularly effective if the transfer from the room to be heated to the room to be deposited is performed in a vacuum, and this method is also advantageous in that the partial pressure of molecules other than the deposit is 10 ⁻⁸ when the deposition in the container in which the deposition is performed is performed. This is effective when performed in an ultra-high vacuum apparatus of Torr or less.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a bias sputtering apparatus used for carrying out the present invention.

FIG. 2 is a graph showing a change in the degree of vacuum in a load lock chamber when a porous Si substrate and a non-porous Si substrate are irradiated with an Xe lamp.

FIG. 3 is a graph showing a change in the degree of vacuum when a porous Si substrate is introduced into a sputtering chamber depending on the presence or absence of Xe lamp irradiation.

FIG. 4 is a graph showing a light absorption coefficient of a substrate.

FIG. 5 is a spectrum showing a wavelength distribution of a Xe lamp.

[Explanation of symbols]

 91 Deposition container 92 Target 93 Permanent magnet 94 Base 95 Base support 96 High frequency power supply 97 Matching circuit 98,99 DC power supply 100,101 Low pass filter 201 Load lock chamber

Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 21/203 H01L 21/203 MS 21/205 21/205 (58) Investigated field (Int.Cl. ⁷ , DB name) C23C 16 / 00-16/56 C23C 14/00-14/58 C30B 1/00-35/00 H01L 21/203-21/205

Claims (13)

(57) [Claims] 1. A method comprising: heating a substrate having a porous layer in a first container; and transporting the substrate into a second container to form an epitaxially grown film on the substrate. Manufacturing method of a semiconductor substrate. 2. The method according to claim 1, wherein the transfer of the substrate from the first container to the second container is performed in a vacuum. 3. The method according to claim 1, wherein the heating in the first container is performed in a vacuum state. 4. The method according to claim 1, wherein the heating of the base is lamp heating. 5. The method for manufacturing a semiconductor substrate according to claim 1, wherein a main component of said base is Si. 6. The lamp used for heating the lamp is X
The method for manufacturing a semiconductor substrate according to claim 4, wherein the method is an e-lamp. 7. The formation of the epitaxially grown film in the second container is performed when the partial pressure of molecules other than the source gas is 10 ⁻⁸ T.
4. The method of manufacturing a semiconductor substrate according to claim 1, wherein the method is performed in an ultra-high vacuum of orr or less. 5. 8. The method of manufacturing a semiconductor substrate according to claim 1, wherein said epitaxial growth film is formed by any one of a sputtering method, a CVD method, and an MBE method. 9. The method according to claim 1, wherein the heating is a resistance heating method. 10. The method according to claim 1, wherein the heating is performed at about 500 ° C. 11. The method according to claim 4, wherein a wavelength of the lamp used for heating the lamp is 1 μm or less. 12. The material of the substrate is GaAs, Ge, S
The method for manufacturing a semiconductor substrate according to claim 1, wherein the method is one of iC and SiGe. 13. The method according to claim 1, wherein a passivation oxide film is formed on an inner surface of the second container.