JP2012094615A - Deposition method for silicon oxide film and manufacturing method for silicon epitaxial wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deposition method for a silicon oxide film by a chemical vapor deposition (CVD) method, which can form a silicon oxide containing fewer OH groups without performing extra modification process such as thermal treatment or chlorine processing after the deposition of the silicon oxide film.SOLUTION: According to a method for depositing a silicon oxide film on a silicon wafer for epitaxial growth by a CVD method, the silicon oxide film is formed by the CVD method under a reaction gas atmosphere containing chlorine gas in addition to silicon source gas on a silicon wafer prior to the growth of an epitaxial layer on its surface.

Description

  The present invention relates to a method for forming a silicon oxide film, and more particularly to a method for forming a silicon oxide film using a CVD method.

  A silicon epitaxial wafer can be manufactured by vapor-phase-growing an epitaxial layer in a reaction gas atmosphere on the surface of a silicon wafer (substrate) for epitaxial growth (epitaxial growth step). A silicon wafer for epitaxial growth is usually prepared according to the following process. First, a silicon single crystal ingot grown by FZ (floating zone) method, CZ (Czochralski) method or the like is sliced using a slicer or the like (slicing step). The edge of the wafer after slicing is chamfered (chamfering process), both surfaces are lapped (lapping process), and further subjected to chemical etching (etching process). Further, the wafer after the etching process is mirror-polished by mechanochemical polishing (mirror polishing process) and subjected to final cleaning.

  In the epitaxial growth step, impurities (dopant) added in advance to the silicon wafer (substrate) are once released mainly from the back surface into the atmosphere of the epitaxial growth step, and the impurities are taken into the epitaxial layer during vapor phase growth. An auto doping phenomenon occurs. Conventionally, the epitaxial layer is contaminated with impurities due to this auto-doping phenomenon. In order to reduce the occurrence of the auto-doping phenomenon, a method is known in which an oxide film is formed on the back surface of the epitaxial growth silicon wafer (substrate) by chemical vapor deposition (CVD) or the like before the epitaxial growth step. (Patent Document 1).

Usually, in order to form a silicon oxide film on the back surface of the silicon wafer (substrate) by the CVD method, an inert gas such as nitrogen is used as a carrier gas, and 0.05 volume% to 0.15 volume as a silicon source gas. % Silicon silane (SiH ₄ ) and 0.5% by volume to 1.5% by volume of oxygen, and in a reaction gas atmosphere in which these are mixed, the silicon wafer (substrate) is in a temperature range of 350 ° C. to 450 ° C. Heat with. The silicon oxide film thus formed usually contains 3% by mass or more of OH groups.

However, when the epitaxial growth process is performed by the conventional method on the surface of the silicon wafer for epitaxial growth having the silicon oxide film containing 3% by mass or more of OH groups on the back surface in this way, the OH groups contained in the silicon oxide film As a result, it is a problem that a minute oxide film is formed on the surface of the silicon wafer (substrate) or the growing epitaxial layer, thereby deteriorating the surface state of the silicon epitaxial wafer. In addition, HCl gas and silicon source gas used in the epitaxial growth process are very corrosive when moisture is present in the reaction furnace, and for epitaxial growth having a silicon oxide film containing 3% by mass or more of OH groups on the back surface. When the epitaxial growth process is performed on the surface of the silicon wafer, metal contamination and crystal defects are caused in the manufactured silicon epitaxial wafer. Among these, metal contamination is caused by corrosion of metal members in the reactor, gas supply pipe or exhaust pipe of the vapor phase thin film growth apparatus by HCl gas or silicon source gas in the presence of moisture, and the metal from them enters the wafer. It is generated by being taken in. In addition, for example, crystal defects are generated when silicon raw material such as trichlorosilane reacts with moisture in a reaction furnace of a vapor phase thin film growth apparatus to generate SiO ₂ particles, which are grown on the silicon wafer (substrate) or the growth. Caused by falling on the epitaxial layer inside.

  Therefore, after forming a silicon oxide film by the CVD method, heat treatment is performed to modify the silicon oxide film (Patent Documents 2 and 3) and chlorine treatment is performed to modify the silicon oxide film. (Patent Document 3). However, in both cases, the modification methods described in Patent Document 2 and Patent Document 3 require that a separate process be prepared after the silicon oxide film is formed, resulting in problems of throughput reduction and cost increase. there were. In particular, in the case of heat treatment, since a high temperature process is added, there is a concern about a change in wafer characteristics. Therefore, a film forming method capable of forming a silicon oxide film by a CVD method in which the content of OH groups is suppressed without performing a modification process such as heat treatment or chlorination has been desired.

Japanese Patent Publication No. 6-80634 Japanese Patent No. 4470231 JP 2002-164286 A

  The present invention has been made in view of the above-described problems, and is a method of forming a silicon oxide film by a CVD method without performing another modification step such as heat treatment or chlorine treatment after the silicon oxide film is formed. It is an object of the present invention to provide a silicon oxide film forming method capable of forming a silicon oxide film in which the OH group content is suppressed. Another object of the present invention is to provide a method for manufacturing a silicon epitaxial wafer using the silicon wafer on which the silicon oxide film is formed as a substrate.

In order to achieve the above object, in the present invention,
A method of forming a silicon oxide film using a CVD method on a silicon wafer for epitaxial growth,
At least the silicon oxide film by the CVD method in a reactive gas atmosphere containing chlorine gas in addition to the silicon source gas with respect to the back surface of the silicon wafer before the epitaxial layer is grown on the surface of the silicon wafer for epitaxial growth A method for forming a silicon oxide film is provided.

  As described above, at least the back surface of the silicon wafer before the epitaxial layer is grown on the surface of the silicon wafer for epitaxial growth is subjected to the CVD method in a reactive gas atmosphere containing chlorine gas in addition to the silicon source gas. With the silicon oxide film forming method for forming a silicon oxide film, a silicon oxide film with a reduced OH group content can be formed. Therefore, even if a modification process such as heat treatment or chlorination is not performed in another process after that, in the subsequent epitaxial growth process, an autodoping phenomenon is prevented and the silicon epitaxial wafer derived from moisture desorbed from the silicon oxide film is removed. A silicon oxide film that can suppress adverse effects such as deterioration of the surface state, metal contamination, and crystal defects can be formed. Furthermore, since the silicon oxide film formed according to the present invention can suppress the adverse effect without performing a modification process such as a heat treatment or a chlorination process in a separate process thereafter, the silicon oxide film is high in the entire silicon epitaxial wafer manufacturing process. Throughput and cost reduction can be realized.

  Moreover, it is preferable that the chlorine gas is contained in the reaction gas atmosphere in an amount of 0.05% by volume to 1% by volume.

As described above, the chlorine gas is contained in the reaction gas atmosphere in an amount of 0.05% by volume or more and 1% by volume or less, so that the removal of the OH group of the silicon oxide film is sufficiently advanced, and the silicon oxide film contains the OH group The rate is further suppressed, and the reaction of the silicon source gas, for example, the reaction of monosilane (SiH ₄ ) with oxygen, or the corrosion of the CVD oxide film growth apparatus can be suppressed.

  Further, it is preferable that a silicon epitaxial wafer is manufactured by performing epitaxial growth on the surface of a silicon wafer having a silicon oxide film formed on at least the back surface of the silicon wafer by the silicon oxide film forming method.

  Thus, by the silicon oxide film forming method, epitaxial growth is performed on the surface of the silicon wafer having the silicon oxide film formed on at least the back surface of the silicon wafer, that is, the OH group content. By using a silicon wafer having a suppressed silicon oxide film as an auto-doping phenomenon prevention film as a substrate, epitaxial growth is performed, thereby deteriorating the surface state of the silicon epitaxial wafer derived from moisture desorbed from the silicon oxide film, metal contamination, A silicon epitaxial wafer having an epitaxial layer in which adverse effects such as crystal defects are suppressed can be manufactured. Furthermore, according to the method for manufacturing a silicon epitaxial wafer according to the present invention, after the formation of the silicon oxide film, it is not necessary to perform a modification step such as a heat treatment or a chlorine treatment during the epitaxial growth step. Overall, high throughput and cost reduction can be realized.

  As described above, according to the present invention, it is possible to form a silicon oxide film for preventing the auto-doping phenomenon and having a reduced OH group content. In addition, since the silicon oxide film has a reduced OH group content, there is no need to subsequently perform a modification process such as heat treatment or chlorination for the purpose of removing the OH groups. Therefore, the silicon oxide film forming method can realize high throughput and cost reduction in the entire silicon epitaxial wafer manufacturing process. In addition, according to the present invention, in the subsequent epitaxial growth process, the silicon oxide film that can suppress adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, metal contamination, and crystal defects derived from moisture desorbed from the silicon oxide film Can be formed. Furthermore, according to the method for manufacturing a silicon epitaxial wafer according to the present invention, by performing epitaxial growth, adverse effects such as deterioration of the surface state of the silicon epitaxial wafer derived from the OH group of the silicon oxide film, metal contamination, and crystal defects are suppressed. A silicon epitaxial wafer having an epitaxial layer formed can be manufactured at low cost and high productivity.

It is the figure which showed the example of the general CVD oxide film growth apparatus. It is the figure which showed the example of the general single wafer type vapor phase thin film growth apparatus. It is the figure which showed the infrared absorption spectrum of the silicon oxide film in Examples 1-3 and the comparative example 1. FIG.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
As described above, there has been a demand for a film forming method capable of forming a silicon oxide film by a CVD method in which the content of OH groups is suppressed without separately performing a modification process such as heat treatment or chlorination. .

  Conventionally, in a silicon epitaxial wafer manufacturing process, a silicon wafer for epitaxial growth is manufactured from a silicon single crystal ingot grown by FZ method or CZ method through a slicing process, chamfering process, lapping process, etching process, and mirror polishing process. Then, an oxide film for preventing auto-doping phenomenon is formed on the back surface (oxide film forming process), and further an oxide film modifying process such as heat treatment or chlorination is performed, and then the surface of the silicon wafer for epitaxial growth is formed. The epitaxial growth process of the epitaxial layer was given to the side. If the oxide film modification step is not performed, adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, metal contamination, and crystal defects occur in the subsequent epitaxial growth step. However, as described above, performing the oxide film reforming process such as heat treatment or chlorination has caused a problem of causing a reduction in throughput and an increase in cost of the entire manufacturing process of the silicon epitaxial wafer. Further, in the case of heat treatment, there has been a concern about changes in wafer characteristics due to passing through an additional high-temperature process.

  Therefore, the present inventor has conducted intensive studies, paying attention to the oxide film forming process, and forming a silicon oxide film by a CVD method in a reactive gas atmosphere containing chlorine gas in addition to the silicon source gas. It was found that the content of OH groups contained in the formed silicon oxide film can be suppressed, and the silicon oxide film thus formed is a silicon epitaxial film derived from moisture desorbed from the silicon oxide film in the subsequent epitaxial growth process. The inventors have found that adverse effects such as deterioration of the surface condition of the wafer, metal contamination, and crystal defects can be sufficiently suppressed, and the present invention has been completed. This will be described in detail below.

The present invention is a method of forming a silicon oxide film on a silicon wafer for epitaxial growth using a CVD method,
At least the silicon oxide film by the CVD method in a reactive gas atmosphere containing chlorine gas in addition to the silicon source gas with respect to the back surface of the silicon wafer before the epitaxial layer is grown on the surface of the silicon wafer for epitaxial growth A method for forming a silicon oxide film is provided.

[CVD oxide growth equipment used for CVD]
Hereinafter, a CVD oxide film growth apparatus for performing the CVD method and a CVD method using the apparatus will be described by way of example, but the CVD method of the present invention is not limited thereto. FIG. 1 shows an example of a CVD oxide film growth apparatus 10 for performing the CVD method. The CVD oxide film growth apparatus 10 includes an oxide film growth unit 11 for growing a CVD oxide film, a cassette 13, and a belt conveyor 14 that conveys a silicon wafer from upstream to downstream of the oxide film growth unit 11. The oxide film growth section 11 is constituted by a heating means 12 (for example, a halogen lamp) for setting the silicon wafer in the oxide film growth section 11 to a growth temperature (for example, 350 ° C. to 450 ° C.) of the silicon oxide film. Provided). First, the silicon wafers 15 for epitaxial growth before growing the epitaxial layer are extracted one by one from the cassette 13 and transferred onto the belt conveyor 14 sequentially so that the back surface on which the silicon oxide film is formed is on the upper side. Included. At this time, in the oxide film growth unit 11, a reactive gas is supplied toward the silicon wafer 15 on the belt conveyor 14. Further, the CVD oxide film growth portion 11 is set to a growth temperature of 350 ° C. to 450 ° C. by the heating means 12. Accordingly, the content of OH groups is gradually suppressed on the back surface of the silicon wafer 15 while the silicon wafer 15 for epitaxial growth is slowly conveyed on the belt conveyor 14 in the direction of arrow F. The silicon oxide film thus formed is formed, and the silicon wafer 16 for epitaxial growth having the silicon oxide film formed on the back surface by the CVD method is formed (oxide film forming step).

[Silicon wafer before growing epitaxial layer]
In the method for forming a silicon oxide film according to the present invention, a silicon oxide film is formed on the back surface of a silicon wafer for epitaxial growth before an epitaxial layer is grown on the surface. The silicon wafer is not particularly limited as long as it is produced by a method for producing a silicon wafer for normal epitaxial growth. From a silicon single crystal ingot grown by the FZ method or the CZ method, a slicing process and a chamfering process are performed. It is manufactured through a lapping process, an etching process, a mirror polishing process, and the like.

[Chlorine gas]
In the method for forming a silicon oxide film according to the present invention, a silicon oxide film is formed by the CVD method in a reaction gas atmosphere containing chlorine gas in addition to a silicon source gas such as SiH ₄ . The chlorine gas is a chlorine gas represented by Cl _2. Thus, when the reaction gas contains chlorine gas in addition to the silicon source gas, the OH groups contained in the silicon oxide film to be formed are reduced. Furthermore, it is possible to form a silicon oxide film that can suppress adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, metal contamination, and crystal defects caused by moisture desorbed from the silicon oxide film in the subsequent epitaxial growth process. .

The chlorine gas is preferably included in the reaction gas atmosphere in an amount of 0.05% by volume or more and 1% by volume or less. If the chlorine gas content is 0.05% by volume or more, it is preferable because the removal of OH groups from the silicon oxide film easily proceeds. Further, if the chlorine gas content is 1% by volume or less, the reaction of the silicon raw material gas, for example, the reaction of monosilane (SiH ₄ ) and oxygen may be hindered, or the CVD oxide film growth apparatus may be corroded. Less preferred. Further, if the chlorine gas is contained in the reaction gas atmosphere in an amount of 0.05% by volume or more and 1% by volume or less, the content of OH groups in the silicon oxide film to be formed is 0.5% by mass or less. You can also. In this way, if the epitaxial growth process is performed using a silicon wafer having a silicon oxide film having an OH group content of 0.5% by mass or less as a substrate, adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, metal contamination, and crystal defects are caused. Is preferable because the silicon epitaxial wafer is suppressed more effectively. Further, the concentration of the chlorine gas is preferably 1: 1 with the concentration of the silicon raw material contained in the silicon raw material gas, for example, monosilane. If the chlorine gas has such a concentration, the OH group is more efficiently reduced. Can be made.

[Reactive gas]
In the silicon oxide film forming method according to the invention, the silicon oxide film is formed by the CVD method in a reactive gas atmosphere containing chlorine gas in addition to the silicon source gas. The reaction gas includes chlorine gas in addition to the silicon source gas, and also includes a gas necessary for the reaction for forming the carrier gas and the silicon oxide film. Monosilane (SiH ₄ ) is preferable as the silicon source gas, nitrogen as an inert gas is preferable as the carrier gas, and oxygen is preferable as a gas necessary for the reaction for forming the silicon oxide film. The conditions are not limited to this.

[Formation of silicon oxide film by CVD method]
In the silicon oxide film forming method according to the present invention, the silicon oxide film is formed using the CVD method. As the CVD method, either an atmospheric pressure CVD method or a low pressure CVD method can be used. The CVD method is performed on at least the back surface of the silicon wafer before the epitaxial layer is grown, but can also be performed on the back surface and the side surface. Furthermore, it may grow on the outer peripheral portion of a part of the surface. The CVD method can be performed using the above-described CVD oxide film growth apparatus 10. The thickness of the silicon oxide film is not particularly limited as long as it can suppress the auto-doping phenomenon, but is preferably 3000 to 8000 mm. If it is 3000 mm or more, it is preferable because it is difficult to be removed in the hydrogen treatment step in the epitaxial growth process, and if it is 8000 mm or less, it is preferable because the silicon oxide film forming process does not take a long time.

  As described above, by forming a silicon oxide film according to the method for forming a silicon oxide film according to the present invention, a silicon oxide film in which the OH group content is suppressed can be formed. As described above, since the content of OH groups in the silicon oxide film is reduced, the moisture desorbed from the silicon oxide film during the subsequent epitaxial growth process without performing a separate modification process such as heat treatment or chlorine treatment. Thus, the silicon oxide film can suppress adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, metal contamination, and crystal defects.

[Method for measuring OH group content in silicon oxide film]
The presence or absence of OH groups contained in the silicon oxide film formed by the silicon oxide film forming method according to the present invention can be examined by infrared absorption characteristics. The infrared absorption characteristic regarding the O—H bond appears as absorption near the wave number 3200-3600 cm ⁻¹ , and the infrared absorption intensity reflects the content of OH groups. Therefore, the OH group content in the silicon oxide film can be calculated from the infrared absorption intensity of the OH bond near the wave number 3200-3600 cm ⁻¹ . Specifically, the infrared absorption intensity around a wave number of 3200-3600 cm ⁻¹ of a silicon wafer having a known OH group content is measured, and the silicon wafer has an OH group content by relative evaluation with the value of the silicon wafer. Calculate the rate.

  According to another aspect of the present invention, there is provided a method for producing a silicon epitaxial wafer, wherein epitaxial growth is performed on a surface of a silicon wafer having a silicon oxide film formed on at least the back surface of the silicon wafer by the silicon oxide film forming method. I will provide a.

[Vapor phase thin film growth equipment used for epitaxial growth process]
Hereinafter, the vapor phase thin film growth apparatus for performing the epitaxial growth and the epitaxial growth process using the apparatus will be described by way of example, but the epitaxial growth process of the present invention is not limited thereto. FIG. 2 shows an example of a single wafer vapor phase thin film growth apparatus for performing the epitaxial growth. The single-wafer vapor phase thin film growth apparatus 20 vapor-deposits a thin film while radiatively heating silicon wafers placed one by one in a reaction vessel 21 made of transparent quartz from above and below using infrared lamps 29a and 29b. It is what makes you do. This silicon wafer is a silicon wafer 16 having a silicon oxide film formed on its back surface by the CVD method. The infrared lamps 29a and 29b are arranged in a double concentric circle, and the infrared lamp 29a constitutes one set on the outside, and the infrared lamp 29b constitutes one set on the inside. The inside of the reaction vessel 21 is divided into an upper space 21a and a lower space 21b by a susceptor 25 on which the silicon wafer 16 is placed. In this upper space 21a, the silicon material gas for epitaxial growth introduced together with the carrier gas such as H ₂ gas from the upper gas supply port 22 flows in the direction of arrow A in the figure while forming a substantially laminar flow on the surface of the silicon wafer 16. , And is discharged from the exhaust port 24 on the opposite side. A purge gas such as H ₂ gas is supplied to the lower space 21b from the lower gas supply port 23 at a higher pressure than the silicon raw material gas for epitaxial growth. The reason why the purge gas is set to a high pressure is to prevent the silicon raw material gas for epitaxial growth from entering the lower space 21b from the gap between the reaction vessel 21 and the susceptor 25.

  The lower space 21b incorporates support means made of quartz for supporting the susceptor 25 from its back surface and lift pins 28 for attaching and detaching the silicon wafer 16 on the susceptor 25. The support means can be moved up and down as indicated by an arrow B in the figure, and includes a rotating shaft 26 and a plurality of spokes 27 branched radially from the rotating shaft 26. A vertical pin 27 b is provided at the end of the spoke 27, and the tip of the vertical pin 27 b is supported by being fitted into recesses 25 c and 25 d provided on the back surface of the susceptor 25. . The rotating shaft 26 can be rotated in the direction of arrow C in the figure by driving means (not shown).

  The lift pin 28 has a head whose diameter is enlarged, and this head is suspended from a tapered side wall portion of a through hole 25b provided on the bottom surface of a counterbore portion 25a of the susceptor 25 on which the silicon wafer 16 is placed. Yes. The shaft portion of the lift pin 28 is inserted into a through hole 27a formed in the middle portion of the spoke 27, so that the lift pin 28 is stably suspended.

  The silicon wafer 16 is attached to and detached from the susceptor 25 by raising and lowering the support means. For example, when removing the silicon wafer 16 from the susceptor 25, the support means is lowered and the lower end portion of the lift pin 28 is brought into contact with the inner wall of the lower space 21 b of the reaction vessel 21. The lift pin 28 biased by this abuts the back surface of the silicon wafer 16 at the head thereof, and the silicon wafer 16 floats above the counterbore portion 25a. Thereafter, a hand (not shown) is inserted into the space between the susceptor 25 and the silicon wafer 16, and the silicon wafer 16 is transferred and conveyed.

[Epitaxial growth process]
The epitaxial growth process according to the present invention is not particularly limited as long as it is a method of growing an epitaxial layer on a silicon wafer having a silicon oxide film formed on the back surface by the CVD method using a silicon source gas for epitaxial growth. A method using the single-wafer vapor phase thin film growth apparatus 20 as shown will be exemplified below.
First, the silicon wafer 16 having a silicon oxide film formed thereon by the CVD method is put into a reaction vessel 21 set to a charging temperature (for example, about 650 ° C.) (a charging process).
Next, the inside of the reaction vessel 21 is heated (heated up) to a hydrogen heat treatment temperature (for example, about 1100 ° C. to 1180 ° C.) (temperature raising step), and the oxide film on the surface of the silicon wafer introduced by performing the hydrogen heat treatment is converted into hydrogen. Etching to remove (hydrogen treatment step). During this hydrogen treatment process, the silicon oxide film for preventing the autodoping phenomenon is left without being completely removed.
Next, the inside of the reaction vessel 21 is set to a growth temperature (for example, about 1060 ° C. to 1150 ° C.), and a silicon raw material gas for epitaxial growth (for example, trichlorosilane or the like) is supplied onto the surface of the charged silicon wafer 16. Thus, a silicon epitaxial wafer is manufactured by vapor-phase growth of an epitaxial layer on the surface of the introduced silicon wafer 16 (epitaxial growth step). Specifically, the hydrogen heat treatment is performed until just before the start of vapor phase growth.
Next, the inside of the reaction vessel 21 is cooled (cooled down) to a take-out temperature (for example, about 650 ° C. as in the above-described charging temperature) (temperature drop step), and the silicon epitaxial wafer is taken out from the reaction vessel 21 (take-out step).

  As described above, the silicon wafer on which the silicon oxide film in which the OH group content is suppressed is used as a substrate, and moisture is desorbed from the silicon oxide film during the epitaxial growth process by performing epitaxial growth on the surface. The amount is suppressed, and as a result, adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, metal contamination, and crystal defects can be suppressed.

  According to the above embodiment, the present invention provides a method for forming a silicon oxide film in which the OH group content is suppressed, and the surface state of the wafer derived from moisture desorbed from the silicon oxide film in the subsequent epitaxial growth step. This is a silicon oxide film forming method capable of suppressing adverse effects such as deterioration, metal contamination, and crystal defects. Further, the present invention performs epitaxial growth on the surface of a silicon wafer having a silicon oxide film in which the OH group content is suppressed, so that the amount of moisture desorbed from the silicon oxide film during the epitaxial growth process is as follows. As a result, the silicon epitaxial wafer manufacturing method can suppress adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, metal contamination, and crystal defects.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to the following Example.

  The silicon wafer before growing the epitaxial layer used in Examples 1 to 3 and Comparative Example 1 is a slicing process, a chamfering process, a lapping process, an etching process, and a mirror polishing process for a silicon single crystal ingot grown by the CZ method. It produced by giving.

[Example 1]
As Example 1 of the silicon oxide film forming method according to the present invention, 0.05 volume% monosilane (SiH ₄ ) as a silicon source gas and a silicon oxide film are formed on the back surface of the silicon wafer. The CVD oxidation shown in FIG. 1 at 450 ° C. in a reaction gas atmosphere containing 0.6% by volume of oxygen as a necessary gas, nitrogen gas as a carrier gas, and 0.5% by volume of chlorine gas (Cl ₂ ). A 5000 nm silicon oxide film was formed by CVD using a film growth apparatus.

[Example 2]
As Example 2 of the silicon oxide film forming method according to the present invention, 0.05 volume% monosilane (SiH ₄ ) as a silicon source gas and a silicon oxide film are formed on the back surface of the silicon wafer. The CVD oxidation shown in FIG. 1 at 450 ° C. in a reaction gas atmosphere containing 0.6 vol% oxygen as a necessary gas, nitrogen gas as a carrier gas, and 0.05 vol% chlorine gas (Cl ₂ ). A 5000 nm silicon oxide film was formed by CVD using a film growth apparatus.

[Example 3]
As Example 3 of the silicon oxide film forming method according to the present invention, 0.05 volume% monosilane (SiH ₄ ) as a silicon source gas and a silicon oxide film are formed on the back surface of the silicon wafer. The CVD oxidation shown in FIG. 1 at 450 ° C. in a reactive gas atmosphere containing 0.6 vol% oxygen as a necessary gas, nitrogen gas as a carrier gas, and 1.0 vol% chlorine gas (Cl ₂ ). A 5000 nm silicon oxide film was formed by CVD using a film growth apparatus.

[Comparative Example 1]
As Comparative Example 1, 0.05 volume% monosilane (SiH ₄ ) as a silicon source gas and 0.6 volume% as a gas necessary for a reaction for forming a silicon oxide film with respect to the back surface of the silicon wafer. A CVD method was performed using a CVD oxide film growth apparatus shown in FIG. 1 at 450 ° C. in a reaction gas atmosphere containing oxygen and nitrogen gas as a carrier gas to form a 5000-inch silicon oxide film.

The results of the OH group content (% by volume) of the silicon oxide films of the silicon substrates formed in Examples 1 to 3 and Comparative Example 1 are shown in Table 1 below. When the infrared absorption spectrum was examined for Examples 1 to 3, for example, as shown in FIG. 3, the absorption intensity in the vicinity of wave number 3200-3600 cm ⁻¹ derived from the O—H bond is greatly different, and a comparative example calculated from this absorption intensity. The OH group content of Example 1 was 0.45% by mass, whereas the OH group content of Example 2 was 0.48% by mass, whereas the OH group content of Example 1 was 4.0% by mass. It was confirmed that the OH group content in Example 3 was significantly reduced to 0.22% by mass. Further, when the chlorine gas is 0.05 vol% or more and 1.0 vol% or less, 0.05 vol% or more and 1 vol% as a reactive gas with respect to at least the back surface of the silicon wafer before growing the epitaxial layer. It was shown that a silicon oxide film in which the content of OH groups is suppressed can be formed by forming a silicon oxide film by the CVD method using the following atmospheric gas mixed with chlorine gas.

[Example 4-6]
Next, as Example 4-6 of the method for manufacturing a silicon epitaxial wafer according to the present invention, the surface of the silicon wafer having the silicon oxide film formed in Example 1-3 is mirror-polished, and then epitaxial growth is performed on the surface. Example 4-6 was performed. In the epitaxial growth, a single-wafer vapor phase thin film growth apparatus 20 shown in FIG. 2 is used at a growth temperature of about 1100 ° C. in a mixed gas atmosphere using TCS (trichlorosilane) as a silicon source gas for epitaxial growth and H ₂ as a carrier gas. The epitaxial layer was grown to about 5 μm.

[Comparative Example 2]
As Comparative Example 2, the surface of the silicon wafer having the silicon oxide film formed in Comparative Example 1 was mirror-polished, and then epitaxial growth was performed on the surface. Epitaxial growth is performed using a single-wafer vapor phase thin film growth apparatus 20 shown in FIG. 2 in a mixed gas atmosphere using TCS (trichlorosilane) as a silicon source gas for epitaxial growth and H ₂ as a carrier gas. The layer was grown about 5 μm.

  The haze levels of the surfaces (epitaxial surfaces) of the silicon epitaxial wafers of Example 4-6 and Comparative Example 2 were relatively compared by visual inspection under a condenser lamp. The metal contamination was evaluated by measuring the lifetime value of a silicon epitaxial wafer produced after 1000 silicon epitaxial wafers of each example were produced. Furthermore, the crystal defects were evaluated based on the average number of defects of 10 silicon epitaxial wafers produced after producing 1000 silicon epitaxial wafers of each example.

The results are shown in Table 2 below. Assuming that the wafer having a silicon oxide film formed by the silicon oxide film forming method according to the present invention is used as a substrate and the haze level of the epitaxially grown silicon epitaxial wafer (Example 4) is 1, the comparative example 2 is level 2. It was confirmed that the haze level of the epitaxial silicon was improved by the method of the present invention. Here, the haze level is a relative evaluation of the haze in the visual inspection, and the larger the numerical value of the level, the worse the haze is. Further, since the wafer lifetime value of Example 4-6 is clearly longer than that of Comparative Example 2, even if the silicon epitaxial wafer production process is repeated a plurality of times, the metal contamination of the produced silicon epitaxial wafer is low. It was shown to be kept at. Furthermore, since the value of the crystal defect of Example 4-6 is clearly lower than that of Comparative Example 2, even if the silicon epitaxial wafer manufacturing process is repeated a plurality of times, generation of crystal defects in the manufactured silicon epitaxial wafer is not caused. It was shown to be kept low. These results indicate that the silicon oxide film formed by the silicon oxide film forming method according to the present invention has a reduced moisture content, so that even if the silicon epitaxial wafer manufacturing process is repeated a plurality of times. It shows that the corrosion of metal members in the reaction path, gas supply pipe or exhaust pipe of the phase thin film growth apparatus can be suppressed, and that the silicon raw material can be prevented from reacting with moisture in the reaction furnace, so that the generation of SiO ₂ particles can be suppressed. ing. In addition, such differences in metal contamination become more prominent each time the number of productions is repeated, and from a long-term viewpoint, maintenance costs for vapor phase thin film growth apparatuses and the like can be reduced, and a more efficient production process Thus, a silicon oxide film forming method and a silicon epitaxial wafer manufacturing method can be achieved.

  As a result, by using a silicon wafer having a silicon oxide film in which the OH group content is suppressed as a substrate and performing epitaxial growth on the surface, the amount of moisture desorbed from the silicon oxide film during the epitaxial growth process is reduced. As a result, it has been shown that the silicon epitaxial wafer manufacturing method can suppress adverse effects such as deterioration of the surface state of the silicon epitaxial wafer, deterioration of the wafer lifetime due to metal contamination, and increase of crystal defects.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

DESCRIPTION OF SYMBOLS 10 ... CVD oxide film growth apparatus, 11 ... Oxide film growth part, 12 ... Heating means, 13 ... Cassette, 14 ... Belt conveyor, 15 ... Silicon wafer before growing epitaxial layer, 16 ... Silicon oxide film by CVD method Deposited silicon wafer, 20 ... Single wafer vapor phase growth apparatus, 21 ... Reaction vessel, 21a ... Upper space, 21b ... Lower space, 22 ... Upper gas supply port, 23 ... Lower gas supply port, 24 ... Exhaust 25, susceptor, 25a, counterbore part, 25b, through hole, 25c, recess (on the back of the susceptor), 25d, recess on the back of the susceptor, 26 ... rotating shaft, 27 ... spoke, 27a ... through hole, 27b ... Vertical pin, 28 ... Lift pin, 29a ... Infrared lamp (outside), 29b ... Infrared lamp (inside), A ... Upper gas flow Movement direction, B: Operation direction of the support means, C: Rotation direction of the rotating shaft 6, F: Conveyance direction of the silicon wafer on the belt conveyor.

Claims (3)

A method of forming a silicon oxide film using a CVD method on a silicon wafer for epitaxial growth,
At least the silicon oxide film by the CVD method in a reactive gas atmosphere containing chlorine gas in addition to the silicon source gas with respect to the back surface of the silicon wafer before the epitaxial layer is grown on the surface of the silicon wafer for epitaxial growth A method for forming a silicon oxide film, comprising:   2. The method for forming a silicon oxide film according to claim 1, wherein the chlorine gas is contained in the reaction gas atmosphere in an amount of 0.05% by volume to 1% by volume. A silicon oxide film according to claim 1 or 2, wherein the silicon wafer is epitaxially grown on the surface of the silicon wafer having a silicon oxide film formed on at least the back surface of the silicon wafer. Epitaxial wafer manufacturing method.

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