KR102532382B1 - Epitaxial silicon wafer manufacturing method and epitaxial silicon wafer - Google Patents

Abstract

A method capable of manufacturing an epitaxial silicon wafer having high gettering ability while suppressing formation of epitaxial defects and an epitaxial silicon wafer are provided. A first step of subjecting a silicon wafer having front, back and edge regions to a heat treatment at a temperature of 800 ° C. or more and 980 ° C. or less in a carbon-containing gas atmosphere to form a carbon diffusion layer on at least a surface layer portion on the front side of the silicon wafer; It is characterized by including a second step of forming a silicon epitaxial layer at a temperature of 900 ° C. or higher and 1000 ° C. or lower on the carbon diffusion layer formed on the surface layer portion on the front surface side of the silicon wafer.

Description

Epitaxial silicon wafer manufacturing method and epitaxial silicon wafer

The present invention relates to an epitaxial silicon wafer manufacturing method and an epitaxial silicon wafer.

Conventionally, silicon wafers are widely used as substrates for semiconductor devices. However, when heavy metals are mixed in silicon wafers, device characteristics such as pause time failure, retention failure, junction leakage failure, and oxide film dielectric breakdown are significantly adversely affected. Therefore, diffusion of the heavy metal into the device formation region is suppressed by forming a gettering layer for trapping the heavy metal inside the wafer. Here, it is important to form a gettering layer immediately below the device formation region so that heavy metals having a slow diffusion rate, such as titanium and molybdenum, can be captured.

Also, in recent years, there has been a demand for no crystal defects in the device formation region, and an epitaxial silicon wafer having a silicon epitaxial layer formed thereon is used as a substrate. An epitaxial silicon wafer is formed by forming a gettering layer on the surface layer part of a silicon wafer, and then forming a silicon epitaxial layer on the gettering layer by CVD method etc., for example.

One of the methods of forming the gettering layer is an ion implantation method. For example, in Patent Document 1, a method of implanting carbon ions into the surface of a silicon wafer to form a gettering layer containing high-concentration carbon in the surface layer portion of the wafer, and forming a silicon epitaxial layer on the formed gettering layer This is listed.

In order to form the gettering layer immediately below the silicon epitaxial layer by the ion implantation method, it is necessary to implant ions into shallower positions from the surface of the silicon wafer. However, when ions are implanted at shallow locations from the wafer surface, implantation defects are formed on the wafer surface, and a large number of epitaxial defects are formed in the epitaxial layer formed thereon.

In addition, as another method of forming a gettering layer, a method of performing a heat treatment on a silicon wafer in a carbon-containing gas atmosphere to diffuse carbon into the inside of the silicon wafer and using the formed carbon diffusion layer as a gettering layer has been proposed. . For example, in Patent Document 2, a gas containing carbon is supplied on a silicon wafer at a temperature of 1000 ° C. or more and 1200 ° C. or less to form a gas layer containing pyrolyzed carbon, and an epitaxial layer is formed thereon By doing so, it is described about the manufacturing method of the epitaxial wafer which has a gettering layer immediately below an epitaxial layer.

Further, in Patent Document 3, a silicon wafer is immersed in a solution containing carbon to form a carbon-containing film on the surface of the silicon wafer, and then the silicon wafer is heat-treated at a temperature of 500°C to 750°C to remove carbon in the carbon-containing film from silicon. A method for producing an epitaxial wafer is described in which an epitaxial layer is formed on the formed carbon diffusion layer after thermal diffusion is performed on the surface layer portion of the wafer.

Japanese Patent Publication No. 3384506 Japanese Unexamined Patent Publication No. 2013-51348 Japanese Unexamined Patent Publication No. 2010-34330

However, it has been found that many epitaxial defects are formed also in the epitaxial wafer manufactured by the method described in Patent Literature 2. Moreover, about the epitaxial wafer manufactured by the method of patent document 3, it turned out that gettering ability is inadequate.

Then, the objective of this invention is providing the method and epitaxial silicon wafer which can manufacture the epitaxial silicon wafer which has a high gettering ability, suppressing formation of an epitaxial defect.

This invention which solves the said subject is as follows.

[1] A silicon wafer having front, rear and edge regions is subjected to heat treatment at a temperature of 800 ° C. or higher and 980 ° C. or lower in a carbon-containing gas atmosphere to form a carbon diffusion layer on at least the surface layer portion on the front surface side of the silicon wafer. Step 1;

and a second step of forming a silicon epitaxial layer at a temperature of 900°C or more and 1000°C or less on a carbon diffusion layer formed on a surface layer portion on the front side of the silicon wafer.

[2] The method for manufacturing an epitaxial silicon wafer according to [1] above, wherein, in the first step, the carbon diffusion layer is formed only on a surface layer portion on the front surface side of the silicon wafer.

[3] According to the above [2], further comprising a third process of forming a protective film on the backside of the silicon wafer before the first process, and a fourth process of removing the protective film before or after the second process. A method for manufacturing an epitaxial silicon wafer as described.

[4] In the first step, the carbon diffusion layer is formed on the surface layer portion of both the front side and the back side of the silicon wafer,

The method for manufacturing an epitaxial silicon wafer according to [2] above, further including a fifth step of removing the carbon diffusion layer formed on the surface layer portion on the rear side before or after the second step.

[5] In the first step, the carbon diffusion layer is formed on at least the surface layer portion of each of the two silicon wafers on the front side, with respect to the two silicon wafers on which the back side is overlapped,

The method for manufacturing an epitaxial silicon wafer according to [2] above, further including a sixth step of separating the two silicon wafers after the first step.

[6] Any one of [1] to [5] above, which further includes a seventh step of removing the carbon diffusion layer formed on the surface layer portion of the edge region of the silicon wafer after the first step and before the second step. A method for manufacturing an epitaxial silicon wafer according to the above.

[7] The method of manufacturing an epitaxial silicon wafer according to any one of [1] to [6], wherein the first step is carried out in an epitaxial growth furnace in which the second step is performed. .

[8] The first step is performed by introducing the silicon wafer into a heat treatment apparatus capable of introducing the carbon-containing gas, and the second step is performed by introducing the silicon wafer after heat treatment into an epitaxial growth furnace The method for manufacturing an epitaxial silicon wafer according to any one of [1] to [6].

[9] In the first step, heat treatment is performed so that the carbon peak concentration in the carbon diffusion layer is 1 × 10 ¹⁷ /cm 3 or more and 1 × 10 ²⁰ /cm 3 or less,

Among the above [1] to [8], in the second step, an epitaxial growth treatment is performed so that the hydrogen peak concentration in the carbon diffusion layer is 1 × 10 ¹⁸ atoms/cm 3 or more and 1 × 10 ²⁰ atoms/cm 3 or less The method for manufacturing an epitaxial silicon wafer according to any one of the preceding claims.

[10] a carbon diffusion layer formed on at least a surface layer portion on the front side of a silicon wafer having a front side, a back side and an edge region;

a silicon epitaxial layer formed on the carbon diffusion layer of the surface layer portion on the front surface side;

The carbon peak concentration of the carbon diffusion layer is 1 × 10 ¹⁷ /cm 3 or more and 1 × 10 ²⁰ /cm 3 or less,

An epitaxial silicon wafer, characterized in that the hydrogen peak concentration of the carbon diffusion layer is 1 × 10 ¹⁸ atoms/cm 3 or more and 1 × 10 ²⁰ atoms/cm 3 or less.

[11] The epitaxial silicon wafer according to [10] above, wherein the carbon diffusion layer has a thickness of 200 nm or less.

[12] The epitaxial silicon wafer according to [10] or [11] above, wherein the carbon diffusion layer is formed only on a surface layer portion on the front surface side.

[13] The epitaxial silicon wafer according to any one of [10] to [12] above, wherein the carbon diffusion layer is not formed on the surface layer portion of the edge region.

ADVANTAGE OF THE INVENTION According to this invention, the epitaxial silicon wafer which has a high gettering ability can be manufactured, suppressing formation of an epitaxial defect.

1 is a diagram showing the flow of a method for manufacturing an epitaxial silicon wafer according to the present invention.
Fig. 2 is a diagram showing an epitaxial silicon wafer having carbon diffusion layers on both front and rear surfaces.
3 is a diagram showing an example of a susceptor for not forming a carbon diffusion layer on the back side of a silicon wafer.
4 is a diagram showing a silicon wafer having a protective film for not forming a carbon diffusion layer on the back side.
Fig. 5 is a diagram showing two silicon wafers with their back faces overlapping each other.
6 is a diagram showing the concentration profile of carbon and hydrogen in an epitaxial silicon wafer of Example 2;

(Method of manufacturing epitaxial silicon wafer)

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings. 1 shows the flow of a method for manufacturing an epitaxial silicon wafer according to the present invention. A method for producing an epitaxial silicon wafer according to the present invention is a silicon wafer 11 having a front surface 11a, a rear surface 11b and an edge region 11c (FIG. 1(a)) in a carbon-containing gas atmosphere at 800 A first step (FIG. 1(b)) of forming a carbon diffusion layer 12 on at least the surface layer portion on the front side 11a side of the silicon wafer 11 by performing heat treatment at a temperature of 980°C or higher and a silicon wafer A second step of forming a silicon epitaxial layer 13 at a temperature of 900°C or more and 1000°C or less on the carbon diffusion layer 12 formed on the surface layer portion on the front surface 11a side of (11) (FIG. 1(c)) It is characterized in that it includes.

As described above, Patent Literatures 2 and 3 propose techniques in which carbon is diffused into the inside of a silicon wafer and the formed carbon diffusion layer is used as a gettering layer. However, many epitaxial defects were formed in the epitaxial wafer manufactured by the method of Patent Document 2, and the gettering ability was insufficient about the epitaxial wafer manufactured by the method of Patent Document 3.

The present inventor investigated in detail the cause of the said problem. As a result, it turned out that the cause of the insufficient gettering ability of the epitaxial wafer obtained by the method of Patent Document 3 was that the carbon in the carbon-containing film was not sufficiently diffused into the wafer because the heat treatment temperature was as low as 500 ° C. to 750 ° C. It became.

On the other hand, the cause of the formation of many epitaxial defects in the epitaxial wafer obtained by the method of Patent Document 2 is that although a carbon diffusion layer is formed in the surface layer portion of the silicon wafer by heat treatment, since the heat treatment temperature is as high as 1000 ° C. to 1200 ° C., carbon It was found that this was because the silicon constituting the diffusion layer was sublimated, and the remaining carbons bonded and precipitated, and the crystal structure of the surface layer portion of the wafer was disturbed.

According to the above examination, by performing heat treatment at a temperature between the temperature described in Patent Document 3 and the temperature described in Patent Document 2, an epitaxial wafer having high gettering ability can be manufactured while suppressing formation of epitaxial defects. is expected

However, as a result of manufacturing an epitaxial silicon wafer by performing heat treatment in the above temperature range, it was found that a large number of epitaxial defects were still formed. So, the present inventor investigated the cause. As a result, the general formation temperature of the silicon epitaxial layer formed on the carbon diffusion layer is about 1150 ° C., but since this formation temperature is high, the silicon in the carbon diffusion layer is sublimated as described above, and carbon is precipitated. was found to be

From the above examination, the present inventors, in order to manufacture an epitaxial silicon wafer with high gettering ability while suppressing the formation of epitaxial defects, formed a carbon diffusion layer while carbon was sufficiently diffused into the inside of the silicon wafer in a carbon-containing gas atmosphere It was concluded that it is necessary to carry out at a temperature at which silicon sublimes and carbon does not precipitate, and also for forming a silicon epitaxial layer, it is necessary to carry out at a low temperature at which silicon of the formed carbon diffusion layer sublimes and carbon does not precipitate.

Then, as a result of intensive examination of specific temperature conditions by the present inventors, the heat treatment of the silicon wafer in a carbon-containing gas atmosphere was performed at a temperature of 800 ° C. or more and 980 ° C. or less, and the formation of a silicon epitaxial layer was 900 ° C. or more and 1000 ° C. or less It was found that an epitaxial silicon wafer having a high gettering ability can be obtained while suppressing the formation of epitaxial defects by carrying out in, and completed the present invention. Hereinafter, each process is demonstrated.

<Step 1>

First, a silicon wafer 11 having a front face 11a, a back face 11b, and an edge region 11c (FIG. 1(a)) is subjected to heat treatment at a temperature of 800°C or more and 980°C or less in a carbon-containing gas atmosphere. Thus, the carbon diffusion layer 12 is formed on at least the surface layer portion on the front surface 11a side of the silicon wafer 11 (FIG. 1(b)).

As the silicon wafer 11, one obtained by performing wafer processing on a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method) can be used. In order to obtain higher gettering ability, you may add carbon and/or nitrogen to the silicon wafer 11. Moreover, it is good also as an n-type or p-type by adding arbitrary suitable impurity. The diameter of the silicon wafer 11 can be 200 mm, 300 mm, or 450 mm, for example. Resistivity can also be appropriately set according to design.

In the present invention, "a carbon-containing gas atmosphere" means an atmosphere composed of a gas containing carbon. Examples of the carbon-containing gas include methane gas, ethane gas, and propane gas. Among them, it is preferable to use propane gas or ethane gas from the viewpoint of improving the reaction efficiency of carbon with respect to the silicon wafer 11 .

Further, the oxygen concentration of the silicon wafer 11 is preferably 1×10 ¹⁷ atoms/cm 3 or more and 1×10 ¹⁸ atoms/cm 3 or less. In this way, it is possible to suppress the formation of epitaxial defects resulting from oxygen precipitation while suppressing the occurrence of slip.

As described above, in the present invention, it is important to set the heat treatment temperature in a carbon-containing gas atmosphere to 800°C or more and 980°C or less. When the heat treatment temperature is less than 800°C, the carbon-containing gas constituting the carbon-containing gas atmosphere, such as methane gas, cannot be decomposed, and carbon cannot diffuse from the surface of the silicon wafer 11 into the inside of the wafer.

On the other hand, when the heat treatment temperature exceeds 980°C, since the thermal energy is high, silicon in the formed carbon diffusion layer 12 sublimes. As a result, the carbons remaining in the carbon diffusion layer 12 combine with each other to precipitate, the crystal structure of silicon is disturbed, and many epitaxial defects are formed in the silicon epitaxial layer 13 formed on the carbon diffusion layer 12. . Therefore, the heat treatment temperature is set to 800°C or more and 980°C or less. More preferably, the heat treatment temperature is 800°C or more and 950°C or less.

By performing the heat treatment at a temperature within the above range, the carbon diffusion layer 12 can be formed by diffusing carbon into the inside of the wafer without disturbing the crystal structure of the surface layer portion of the silicon wafer 11. And, the concentration of carbon contained in the carbon diffusion layer 12 is 1×10 ¹⁷ /cm 3 or more and 1×10 ²⁰ /cm 3 or less, so that the carbon diffusion layer 12 can contain carbon at a concentration sufficient for heavy metal gettering. there is. In addition, the said carbon concentration is the maximum concentration in the inside of the silicon wafer 11, and the carbon concentration becomes the maximum (peak) at the interface of the silicon wafer 11 and the silicon epitaxial layer 13.

Moreover, it is preferable to make the heat treatment time into 1 minute or more and 40 minutes or less. By setting the heat treatment time to 1 minute or longer, carbon in the carbon-containing gas atmosphere is sufficiently diffused from the surface of the silicon wafer 11 to form a carbon diffusion layer 12 containing high-concentration carbon in the surface layer portion of the silicon wafer 11. can By setting the heat treatment time to 1 minute or more, the thickness of the carbon diffusion layer 12 becomes 20 nm or more. Further, even if the heat treatment is performed for more than 40 minutes, diffusion of carbon into the inside of the wafer is saturated. Therefore, the upper limit of the heat treatment time is preferably 40 minutes or less. The upper limit of the thickness of the carbon diffusion layer 12 formed is generally 200 nm.

Further, as shown in FIG. 2 , the carbon diffusion layer 12 may be formed not only on the surface layer portion on the front side 11a side of the silicon wafer 11 but also on the surface layer portion on the back side 11b side. Thereby, it can be used as a gettering layer also for the carbon diffusion layer 12 of the surface layer part on the side of the back surface 11b formed, and gettering ability can further be improved.

In addition, the carbon diffusion layer 12 may be formed only on the surface layer portion on the front surface 11a side of the silicon wafer 11 . Thereby, contamination by carbon can be suppressed. Also, the carbon diffusion layer 12 may be formed in the edge region 11c.

The formation of the carbon diffusion layer 12 only on the surface layer portion on the front surface 11a side of the silicon wafer 11 requires, for example, a susceptor of a type that supports the edge region 11c of the silicon wafer 11 in line contact. Instead, it can be implemented using a susceptor as shown in FIG. 3 . That is, the susceptor 20 shown in FIG. 3 has a concave portion 21 partitioned by a side wall 21a and a bottom surface 21b, and the bottom surface 21b has a larger diameter than the silicon wafer 11. Have. By disposing the silicon wafer 11 on the bottom surface 21b of the susceptor 20 and performing heat treatment in a state where the rear surface 11b is in contact with the bottom surface 21b, the front surface 11a side The carbon diffusion layer 12 can be formed only in the surface layer portion.

In addition, as shown in FIG. 4, by forming the protective film 14 on the back surface 11b of the silicon wafer 11 (third process) and performing the above-described heat treatment in the state in which the protective film 14 is formed, The carbon diffusion layer 12 can be formed only on the surface layer portion on the front face 11a side of the silicon wafer 11 . The formed protective film 14 can be removed by polishing, for example, before or after the second step described later (fourth step). Moreover, as the protective film 14, any film capable of preventing diffusion of carbon may be used, and an oxide film, a nitride film, or the like can be applied.

In addition, once the carbon diffusion layer 12 is formed on both the surface layer portions on the front side 11a side and the back side 11b side of the silicon wafer 11, the carbon diffusion layer 12 formed on the surface layer portion on the back side 11b side is By removing it, the carbon diffusion layer 12 can also be formed only in the surface layer part on the front surface 11a side. The removal of the carbon diffusion layer 12 formed in the surface layer portion on the rear surface 11b side can be removed by, for example, polishing before or after the second step described later (fifth step).

Further, in order to form the carbon diffusion layer 12 only on the surface layer portion on the front surface 11a side of the silicon wafer 11, as shown in FIG. It is prepared, and you may form the carbon diffusion layer 12 in the surface layer part of each front surface 11a side of the two silicon wafers 11 in a 1st process. In this case, after the first step, the two silicon wafers are separated from each other (step 6), and in the second step, the silicon epitaxial layer 13 is formed on the carbon diffusion layer 12 formed on the surface layer portion on the front surface 11a side. form

In addition, as described above, in the case where the carbon diffusion layer 12 is formed only on the surface layer portion on the front surface 11a side of the silicon wafer 11, the outer peripheral portion of the wafer 11 is chamfered, and the surface layer portion of the edge region 11c Edo carbon diffusion layer 12 is formed. Carbon in the carbon diffusion layer 12 formed in the edge region 11c is outwardly diffused outside the wafer by undergoing heat treatment performed in the subsequent device process process, forming a silicon epitaxial layer (device formation region) ( 13) There is a risk of carbon inflow. Therefore, it is preferable to remove the carbon diffusion layer 12 formed in the surface layer portion of the edge region 11c before the second step described later (seventh step). The carbon diffusion layer 12 formed in the surface layer portion of the edge region 11c can be removed by polishing.

The first step can be performed in an epitaxial growth furnace in which a second step described later is performed. Specifically, first, a silicon wafer 11 is introduced into an epitaxial growth furnace, hydrogen gas is introduced into the furnace, the temperature is raised to 1100°C to 1150°C, and hydrogen baking is performed to form a natural oxide film on the surface of the silicon wafer 11. Remove Next, the temperature in the furnace is lowered to a temperature of 800 to 980°C, and a carbon-containing gas such as methane gas is introduced into the furnace together with hydrogen gas (carrier gas), and the temperature is maintained for, for example, 1 minute. In this way, carbon can be diffused from the surface of the silicon wafer 11 into the inside of the wafer, and the carbon diffusion layer 12 can be formed on at least the front surface 11a. Subsequently, formation of the silicon epitaxial layer 13 in the second step can be performed.

Further, in the first step, the silicon wafer 11 serving as the substrate is introduced into a dedicated heat treatment apparatus capable of introducing a carbon-containing gas, and then the carbon-containing gas is introduced into the furnace to make the inside of the furnace into a carbon-containing gas atmosphere. , It can be carried out by raising the temperature to a predetermined heat treatment temperature. The heat treatment apparatus is not particularly limited, and a vertical or horizontal type can be used. In addition, although one that processes one wafer may be used like an RTA apparatus, it is preferable to use a batch type heat treatment apparatus capable of heat treating a plurality of wafers simultaneously. In this case, the second step can be performed by introducing the heat-treated silicon wafer 11 into an epitaxial growth furnace.

<Step 2>

Next, in the first step, a silicon epitaxial layer 13 is formed at a temperature of 900°C or more and 1000°C or less on the carbon diffusion layer 12 formed on the surface layer portion on the front surface 11a side (FIG. 1(c) )). This can be performed, for example, by a vapor phase growth method such as a CVD method.

Specifically, in the first step, the silicon wafer 11 on which the carbon diffusion layer 12 is formed is introduced into an epitaxial growth furnace, hydrogen gas is introduced into the furnace, the temperature is raised to about 1100 to 1150 ° C, and hydrogen baking is performed. The natural oxide film on the surface of the silicon wafer 11 is removed. Then, for example, hydrogen gas is used as a carrier gas, and a silane-based gas that decomposes at 900 ° C. or more and 1000 ° C. or less, such as monosilane gas (SiH ₄ ) or dichlorosilane gas (SiH ₂ Cl ₂ ), is used as a source gas. introduced into the furnace. In this way, the silicon epitaxial layer 13 can be formed on the carbon diffusion layer 12 . In addition, from the viewpoint of increasing the hydrogen concentration in the carbon diffusion layer 12, it is preferable to use a monosilane gas (SiH ₄ ) having many hydrogen bonds.

The thickness of the silicon epitaxial layer 13 can be appropriately set according to design, but can be set within the range of 1 to 15 μm, for example. Also, the resistivity of the silicon epitaxial layer 13 can be appropriately set according to design.

When the formation temperature of the silicon epitaxial layer 13 is less than 900°C, the silane-based gas serving as the source gas cannot be decomposed satisfactorily. Moreover, when the formation temperature of the silicon epitaxial layer 13 exceeds 1000 degreeC, the silicon in the carbon diffusion layer 12 formed in the 1st process sublimes, and carbon bonds with each other and precipitates. As a result, the crystal structure of silicon is disturbed, and many epitaxial defects are formed in the silicon epitaxial layer 13 formed on the carbon diffusion layer 12. Therefore, the formation temperature of the silicon epitaxial layer 13 is 900°C or more and 1000°C or less.

In this way, the epitaxial silicon wafer 1 according to the present invention can be manufactured. The formed carbon diffusion layer 12 captures hydrogen contained in the source gas or hydrogen gas serving as a carrier gas. Hydrogen trapped in the carbon diffusion layer 12 diffuses into the silicon epitaxial layer 13 during heat treatment in the device formation process, and has an action of passivating defects in the silicon epitaxial layer 13 . In the present invention, the silicon epitaxial layer 13 is formed at a relatively low temperature of 900°C or more and 1000°C or less. Therefore, compared to the case where the silicon epitaxial layer 13 is formed at a high temperature of about 1150°C, a high concentration of hydrogen can be trapped in the carbon diffusion layer 12, and the passivation effect of defects can be enhanced.

Here, the peak concentration of hydrogen trapped in the carbon diffusion layer 12 is 1×10 ¹⁸ atoms/cm 3 or more and 1×10 ²⁰ atoms/cm 3 or less. In addition, the said hydrogen concentration is the maximum concentration in the inside of the silicon wafer 11, and hydrogen concentration becomes the maximum (peak) in the carbon diffusion layer 12.

(epitaxial silicon wafer)

Next, an epitaxial silicon wafer according to the present invention will be described. An epitaxial silicon wafer 1 according to the present invention includes a carbon diffusion layer 12 formed on at least a surface layer portion on the front surface 11a side of a silicon wafer 11 having a front surface 11a, a rear surface 11b, and an edge region 11c. ) and a silicon epitaxial layer 13 formed on the carbon diffusion layer 12 of the surface layer portion on the front surface 11a side. Here, the carbon peak concentration of the carbon diffusion layer 12 is 1 × 10 ¹⁷ /cm 3 or more and 1 × 10 ²⁰ /cm 3 or less, and the hydrogen peak concentration of the carbon diffusion layer 12 is 1 × 10 ¹⁸ atoms/cm 3 or more and 1 × 10 It is characterized in that it is ²⁰ atoms / cm 3 or less.

As described above, in the method for manufacturing an epitaxial silicon wafer according to the present invention, heat treatment of the silicon wafer 11 in a carbon-containing gas atmosphere is performed at a relatively low temperature of 800°C or more and 980°C or less. As a result, the carbon peak concentration of the carbon diffusion layer 12 is 1 × 10 ¹⁷ /cm 3 or more and 1 × 10 ²⁰ /cm 3 or less, and the carbon diffusion layer 12 has a high gettering ability.

In addition to the above heat treatment at a relatively low temperature, the formation of the silicon epitaxial layer 13 is also performed at a relatively low temperature. As a result, formation of epitaxial defects is suppressed, and the number of epitaxial defects is 4 or less with a size of 90 nm or more. In this way, the epitaxial silicon wafer 1 according to the present invention has few epitaxial defects and high gettering capability.

The thickness of the carbon diffusion layer 12 is 20 nm or more and 200 nm or less. In addition, the carbon diffusion layer 12 contains hydrogen with a high peak concentration of 1×10 ¹⁸ atoms/cm 3 or more and 1×10 ²⁰ atoms/cm 3 or less, and at the time of heat treatment in the device formation process, the silicon epitaxial layer ( 13) It diffuses the inside and has an action of passivating defects.

The carbon diffusion layer 12 may be provided only on the surface layer portion on the front surface 11a side of the silicon wafer 11, or may be provided on both surface layer portions on the front surface 11a side and the rear surface 11b side. Also, it is preferable that the carbon diffusion layer 12 is not formed on the surface layer portion of the edge region 11c.

Example

Examples of the present invention will be described below, but the present invention is not limited to the examples.

(Invention Example 1)

First, as a substrate for an epitaxial silicon wafer, an n-type silicon wafer with a diameter of 200 mm obtained by performing wafer processing on a single crystal silicon ingot grown by the CZ method (resistivity: 50 Ω cm, dopant: phosphorus, phosphorus concentration: 8.6 × 10 ¹³ atoms/cm 3 , oxygen concentration: 9 × 10 ¹⁷ atoms/cm 3) were prepared. This silicon wafer was introduced into a heat treatment furnace and placed on the susceptor shown in FIG. 3 . Subsequently, ethane gas was introduced into the furnace to create an ethane gas atmosphere, and then the temperature in the furnace was raised to 800° C., and the silicon wafer was subjected to heat treatment for 1 minute to form a carbon diffusion layer on the surface layer portion on the front side of the silicon wafer. did Subsequently, after the silicon wafer on which the carbon diffusion layer was formed was taken out of the heat treatment furnace, the silicon wafer on which the carbon diffusion layer was formed was introduced into an epitaxial growth furnace, and hydrogen gas was introduced into the furnace. Then, after the temperature in the furnace was lowered to 980°C, hydrogen gas was introduced into the furnace using a carrier gas, monosilane gas (SiH ₄ ) as a source gas, and phosphine (PH ₄ ) as a dopant gas, and on the carbon diffusion layer An n-type silicon epitaxial layer (dopant: phosphorus, resistivity: 10 Ω·cm, thickness: 4 µm) was formed. In this way, an epitaxial silicon wafer according to Inventive Example 1 was obtained.

(Invention Example 2)

As in Inventive Example 1, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to the invention example 2 was obtained by setting the heat treatment temperature in the first step to 950°C. All other conditions were the same as those of Inventive Example 1.

(Invention Example 3)

As in Inventive Example 1, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to the invention example 3 was obtained by setting the heat treatment temperature in the first step to 980°C. All other conditions were the same as those of Inventive Example 1.

(Comparative Example 1)

As in Inventive Example 1, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to Comparative Example 1 was obtained by setting the heat treatment temperature in the first step to 750°C. All other conditions were the same as those of Inventive Example 1.

(Comparative Example 2)

As in Inventive Example 1, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to Comparative Example 2 was obtained by setting the heat treatment temperature in the first step to 1000°C. All other conditions were the same as those of Inventive Example 1.

(Comparative Example 3)

As in Inventive Example 1, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to Comparative Example 3 was obtained by setting the heat treatment temperature in the first step to 1100°C.

(Invention Example 4)

As in Example 2, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to Inventive Example 4 was obtained by setting the formation temperature of the epitaxial layer in the second step to 900°C. All other conditions are the same as those of Inventive Example 2.

(Invention Example 5)

As in Example 2, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to Inventive Example 5 was obtained by setting the formation temperature of the silicon epitaxial layer in the second step to 1000°C. All other conditions are the same as those of Inventive Example 2.

(Comparative Example 4)

As in Example 2, an epitaxial silicon wafer was produced. However, the formation temperature of the epitaxial layer in the second step was 850°C. As a result, a silicon epitaxial layer could not be grown.

(Comparative Example 5)

As in Example 2, an epitaxial silicon wafer was produced. However, the epitaxial silicon wafer according to Comparative Example 5 was obtained by setting the formation temperature of the epitaxial layer in the second step to 1180°C. All other conditions are the same as those of Inventive Example 2.

<Evaluation of epitaxial defects>

For each of the epitaxial silicon wafers of Inventive Examples 1 to 5 and Comparative Examples 1 to 3 and 5, the number of epitaxial defects formed in the silicon epitaxial layer was evaluated. Specifically, the surface of the epitaxial wafer of each sample was observed and evaluated using a surface defect inspection device (Surfscan SP-2 manufactured by KLA-Tencor), and light point defects (LPD) with a size of 90 nm or more were detected. The occurrence situation was investigated. At that time, the observation mode was set to the oblique mode (oblique incidence mode), and the surface pit was estimated based on the detection size ratio of the wide and narrow channels. Then, using a scanning electron microscope (SEM), the LPD occurrence site was observed and evaluated to evaluate whether or not the LPD was a stacking fault (SF). Table 1 shows the number of detected epitaxial defects (pcs/wafer).

As is clear from Table 1, the number of epitaxial defects per wafer was less than 5 in Inventive Examples 1 to 5 and Comparative Example 1. On the other hand, in Comparative Examples 2 and 3 in which the heat treatment temperature was 1000°C or higher, and Comparative Example 5 in which the formation temperature of the silicon epitaxial layer was higher than 1000°C, a large number of epitaxial defects were formed. This is considered to be because silicon of the formed carbon diffusion layer sublimated and carbon precipitated.

<Evaluation of gettering ability>

The gettering capability was evaluated for each of the epitaxial silicon wafers of Inventive Examples 1 to 5 and Comparative Examples 1 to 3 and 5 above. Specifically, the surface of the epitaxial layer of each epitaxial wafer was deliberately contaminated with a Ni contamination solution (1.0 × 10 ¹³ /cm 2 ) using a spin coat contamination method, followed by diffusion heat treatment at 1000 ° C. for 3 minutes in a nitrogen atmosphere was carried out. Thereafter, light etching was performed for 3 minutes, pits observed on the surface of the epitaxial layer were observed using an optical microscope, and gettering ability was evaluated by the presence or absence of pits. Table 1 shows the evaluation results.

As is clear from Table 1, pits were not observed for Inventive Examples 1 to 5 and Comparative Examples 2, 3 and 5, but pits were observed for Comparative Example 1 having a heat treatment temperature as low as 750°C, and the gettering ability was insufficient. did This is considered to be because, in Comparative Example 1, since the heat treatment temperature was low, carbon could not be sufficiently diffused into the inside of the wafer.

<Evaluation of carbon concentration and hydrogen concentration>

For Inventive Examples 1 to 5 and Comparative Examples 1 to 3 and 5, SIMS (Secondary Ion Mass Spectrometry) measurement was performed on the obtained epitaxial silicon wafer to measure the carbon concentration and hydrogen concentration. Table 1 shows the obtained carbon concentration and hydrogen concentration. Further, the concentration profile of carbon and hydrogen in the epitaxial silicon wafer of Example 2 is shown in FIG. 6 .

As shown in Table 1, the carbon concentration was 5 × 10 ¹⁸ atoms/cm 3 or more and had high gettering ability for Inventive Examples 1 to 5 and Comparative Examples 2, 3, and 5 having high heat treatment temperatures. In contrast, in Comparative Example 1, since the heat treatment temperature was low, carbon could not be sufficiently diffused into the inside of the wafer, and the gettering ability was insufficient.

In addition, the hydrogen concentration was on the order of 10 ¹⁸ atoms/cm 3 for the invention example 1 in which the heat treatment temperature was relatively low among invention examples 1 to 5 having high gettering ability, but was on the order of 10 ¹⁹ atoms/cm 3 for invention examples 2 to 5. , the carbon diffusion layer contained a high concentration of hydrogen. Further, also for Comparative Examples 2 and 3 in which the formation temperature of the silicon epitaxial layer was within the range stipulated in the present invention, the hydrogen concentration was on the order of 10 ¹⁹ atoms/cm 3 .

ADVANTAGE OF THE INVENTION According to this invention, since the epitaxial silicon wafer which has a high gettering ability can be manufactured, suppressing formation of an epitaxial defect, it is useful in semiconductor wafer manufacture.

1: epitaxial silicon wafer
11: silicon wafer
11a: front
11b: back
11c: edge area
12: carbon diffusion layer
13: silicon epitaxial layer
14: protective layer
20: susceptor
21: recess
21a: side wall
21b: bottom surface

Claims (13)

A first step of forming a carbon diffusion layer on at least a surface layer portion on the front surface side of the silicon wafer by subjecting a silicon wafer having front, rear and edge regions to a heat treatment at a temperature of 800 ° C. or higher and 980 ° C. or lower in a carbon-containing gas atmosphere. class,
and a second step of forming a silicon epitaxial layer at a temperature of 900°C or more and 1000°C or less on a carbon diffusion layer formed on a surface layer portion on the front side of the silicon wafer. According to claim 1,
In the first step, the carbon diffusion layer is formed only on a surface layer portion on the front surface side of the silicon wafer. According to claim 2,
The method of manufacturing an epitaxial silicon wafer, further comprising a third step of forming a protective film on the rear surface of the silicon wafer before the first step, and a fourth step of removing the protective film before or after the second step. According to claim 2,
In the first step, the carbon diffusion layer is formed on both surface layer portions of the front side and the back side of the silicon wafer;
The manufacturing method of the epitaxial silicon wafer which further has a 5th process of removing the said carbon diffusion layer formed in the surface layer part of the said rear surface side before or after the said 2nd process. According to claim 2,
In the first step, the carbon diffusion layer is formed on at least the surface layer portion of each of the two silicon wafers on the front surface side of the two silicon wafers on which the back surfaces are overlapped,
The manufacturing method of the epitaxial silicon wafer which further has the 6th process of peeling the said 2 sheets of silicon wafer after the said 1st process. According to any one of claims 1 to 5,
The method of manufacturing an epitaxial silicon wafer further comprising a seventh step of removing the carbon diffusion layer formed on the surface layer portion of the edge region of the silicon wafer after the first step and before the second step. According to any one of claims 1 to 5,
The method of manufacturing an epitaxial silicon wafer, wherein the first step is performed in an epitaxial growth furnace in which the second step is performed. According to any one of claims 1 to 5,
The first step is performed by introducing the silicon wafer into a heat treatment apparatus capable of introducing the carbon-containing gas, and the second step is performed by introducing the silicon wafer after heat treatment into an epitaxial growth furnace. Method for manufacturing a taxial silicon wafer. According to any one of claims 1 to 5,
In the first step, heat treatment is performed so that the carbon peak concentration in the carbon diffusion layer is 1 × 10 ¹⁷ /cm 3 or more and 1 × 10 ²⁰ /cm 3 or less;
In the second step, an epitaxial growth process is performed so that the hydrogen peak concentration in the carbon diffusion layer is 1×10 ¹⁸ atoms/cm 3 or more and 1×10 ²⁰ atoms/cm 3 or less. a carbon diffusion layer formed on at least a surface layer portion on the front side of a silicon wafer having a front side, a back side and an edge region;
a silicon epitaxial layer formed on the carbon diffusion layer of the surface layer portion on the front surface side;
The carbon peak concentration of the carbon diffusion layer is 1 × 10 ¹⁷ /cm 3 or more and 1 × 10 ²⁰ /cm 3 or less,
The hydrogen peak concentration of the carbon diffusion layer is 1 × 10 ¹⁸ atoms/cm 3 or more and 1 × 10 ²⁰ atoms/cm 3 or less,
An epitaxial silicon wafer characterized by having 4 or less epitaxial defects with a size of 90 nm or more. According to claim 10,
The thickness of the carbon diffusion layer is 200 nm or less, epitaxial silicon wafer. According to claim 10 or 11,
The epitaxial silicon wafer, wherein the carbon diffusion layer is formed only on a surface layer portion on the front surface side. According to claim 10 or 11,
The epitaxial silicon wafer, wherein the carbon diffusion layer is not formed on a surface layer portion of the edge region.

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