TWI726344B - Method for manufacturing epitaxial silicon wafer and epitaxial silicon wafer - Google Patents

Abstract

The invention provides a method and an epitaxial silicon wafer capable of manufacturing an epitaxial silicon wafer with high gettering ability while suppressing the formation of epitaxial defects. The method for manufacturing an epitaxial silicon wafer of the present invention is characterized in that it includes: a first step of performing a silicon wafer having a surface, a back surface, and an edge area in a carbon-containing gas environment at a temperature of 800°C or higher and 980°C or lower Heat treatment to form a carbon diffusion layer on the surface portion of at least the surface side of the silicon wafer; and the second step is to form a carbon diffusion layer on the surface portion of the silicon wafer on the surface side at a temperature of 900°C or higher and 1000°C or lower The temperature forms a silicon epitaxial layer.

Description

Method for manufacturing epitaxial silicon wafer and epitaxial silicon wafer

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

In the past, silicon wafers have been widely used as substrates for semiconductor devices. However, mixing heavy metals into silicon wafers can cause poor pause time, poor retention, poor bonding leakage, and oxide film defects. Dielectric breakdown, etc., has a significant adverse effect on component characteristics. Therefore, by forming a gettering layer for trapping heavy metals inside the wafer, the diffusion of heavy metals into the device formation area is suppressed. Here, it is important to form a gettering layer directly under the element formation region so as to be able to trap heavy metals such as titanium or molybdenum with a slow diffusion rate.

In addition, in recent years, it is required that there be no crystal defects in the element formation area, so that an epitaxial silicon wafer having a silicon epitaxial layer formed on a silicon wafer is used as a substrate. The epitaxial silicon wafer is formed, for example, by forming a gettering layer on the surface of the silicon wafer, and then forming a silicon epitaxial layer on the gettering layer by a chemical vapor deposition (CVD) method or the like.

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

In order to form a gettering layer directly under the silicon epitaxial layer by ion implantation, it is necessary to implant ions to a position shallower from the surface of the silicon wafer. However, if ions are implanted to a shallow position from the surface of the wafer, implantation defects are formed on the surface of the wafer, and a large number of epitaxial defects are formed in the epitaxial layer formed thereon.

In addition, as another method of forming the gettering layer, the following method is proposed: heat treatment is performed on the silicon wafer in a carbon-containing gas environment to diffuse carbon into the inside of the silicon wafer, and the formed carbon diffusion layer is used as the gettering layer. In addition to the layer. For example, in Patent Document 2, a method for manufacturing an epitaxial wafer is described in which a gas containing carbon is supplied to a silicon wafer at a temperature of 1000°C or higher and 1200°C or lower to form a silicon wafer including thermally decomposed wafers. A layer of carbon gas, and an epitaxial layer is formed thereon, thereby manufacturing an epitaxial wafer with a gettering layer directly under the epitaxial layer.

Furthermore, Patent Document 3 describes a method for manufacturing an epitaxial wafer as follows: 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 temperature is 500°C to 750°C The silicon wafer is heat-treated at a temperature of 10°C, so that the carbon in the carbon-containing film is thermally diffused to the surface of the silicon wafer, and then an epitaxial layer is formed on the formed carbon diffusion layer.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3384506

[Patent Document 2] Japanese Patent Laid-Open No. 2013-51348

[Patent Document 3] Japanese Patent Laid-Open No. 2010-34330

However, it is known that a large number of epitaxial defects are also formed in the epitaxial wafer manufactured by the method described in Patent Document 2. In addition, regarding the epitaxial wafer manufactured by the method described in Patent Document 3, it is known that the gettering ability is insufficient.

Therefore, the object of the present invention is to provide a method and an epitaxial silicon wafer capable of manufacturing an epitaxial silicon wafer with high gettering ability while suppressing the formation of epitaxial defects.

The present invention for solving the above-mentioned problems is as follows.

[1] A method of manufacturing an epitaxial silicon wafer, which is characterized by comprising: a first step, for a silicon wafer with a surface, a back surface, and edge regions, in a carbon-containing gas environment at a temperature of 800°C or more and 980°C or less Heat treatment is performed at temperature to form a carbon diffusion layer on at least the surface layer portion of the silicon wafer on the surface side; and the second step is to form a carbon diffusion layer on the surface layer portion on the surface side of the silicon wafer , The silicon epitaxial layer is formed at a temperature above 900°C and below 1000°C.

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

[3] The method for manufacturing an epitaxial silicon wafer as described in [2], further comprising: a third step, before the first step, forming a protective film on the back surface of the silicon wafer ; And the fourth step, before or after the second step, the The protective film is removed.

[4] The method for manufacturing an epitaxial silicon wafer according to [2], wherein, in the first step, the first step is performed on both the front side and the back side of the silicon wafer The carbon diffusion layer is formed on the surface portion, and the method of manufacturing the epitaxial silicon wafer further has: a fifth step. Before or after the second step, the carbon diffusion layer formed on the surface portion on the back surface is removed. The diffusion layer is removed.

[5] The method for manufacturing an epitaxial silicon wafer according to [2], wherein, in the first step, for the two silicon wafers whose back surfaces overlap each other, the two silicon wafers The carbon diffusion layer is formed on at least the surface side of each circle. The method of manufacturing the epitaxial silicon wafer further has: a sixth step, after the first step, the two silicon wafers are peeled off .

[6] The method for manufacturing an epitaxial silicon wafer according to any one of [1] to [5], further comprising: a seventh step, after the first step and before the second step , Removing the carbon diffusion layer formed on the surface layer portion of the edge region of the silicon wafer.

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

[8] The method for manufacturing an epitaxial silicon wafer according to any one of [1] to [6], wherein the first step is to introduce the silicon wafer to the point where the silicon wafer can be introduced Carbon gas heat treatment equipment, the second step is to heat all the heat The silicon wafer is introduced into the epitaxial growth furnace.

[9] The method for manufacturing an epitaxial silicon wafer according to any one of [1] to [8], wherein in the first step, the peak concentration of carbon in the carbon diffusion layer The heat treatment is performed so as to become 1×10 ¹⁷ atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ³ or less. In the second step, the peak hydrogen concentration in the carbon diffusion layer becomes 1× The epitaxial growth process is performed at ^{10 18} atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ^{3 or less.}

[10] An epitaxial silicon wafer characterized by having: a carbon diffusion layer formed on at least a surface layer portion of the silicon wafer having a surface, a back surface, and an edge region; and a silicon epitaxial layer formed on On the carbon diffusion layer of the surface layer portion on the surface side, the peak carbon concentration of the carbon diffusion layer is 1×10 ¹⁷ atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ³ or less. The hydrogen of the carbon diffusion layer is 1×10 17 atoms/cm 3 or more and 1×10 20 atoms/cm 3 or less. The peak concentration 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], wherein the thickness of the carbon diffusion layer is 200 nm or less.

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

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

According to the present invention, it is possible to manufacture an epitaxial silicon wafer with high gettering ability while suppressing the formation of epitaxial defects.

1: epitaxial silicon wafer

11: Silicon wafer

11a: surface

11b: back

11c: marginal area

12: Carbon diffusion layer

13: Silicon epitaxial layer

14: Protective film

20: Pedestal

21: recess

21a: side wall

21b: bottom surface

(A) to (c) in FIG. 1 are diagrams showing the flow of the method for manufacturing an epitaxial silicon wafer of the present invention.

FIG. 2 is a diagram showing an epitaxial silicon wafer having a carbon diffusion layer on both the front surface and the back surface.

3 is a diagram showing an example of a susceptor for preventing a carbon diffusion layer from being formed on the back surface of the silicon wafer.

4 is a diagram showing a silicon wafer with a protective film for preventing a carbon diffusion layer from being formed on the back surface.

Fig. 5 is a diagram showing two silicon wafers whose back surfaces overlap each other.

6 is a graph showing the concentration distribution of carbon and hydrogen in the epitaxial silicon wafer of Example 2 of the invention.

(Method of manufacturing epitaxial silicon wafer)

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (A) to (c) in FIG. 1 show the flow of the method for manufacturing an epitaxial silicon wafer of the present invention. The manufacturing method of the epitaxial silicon wafer of the present invention is characterized in that it includes: a first step ((b) in FIG. 1), for a silicon wafer 11 having a surface 11a, a back surface 11b, and an edge region 11c (FIG. 1 (a)), heat treatment is performed at a temperature of 800°C or more and 980°C or less in a carbon-containing gas environment to form a carbon diffusion layer 12 on at least the surface layer portion of the silicon wafer 11 on the surface 11a side; and the second step ((C) in FIG. 1), on the carbon diffusion layer 12 formed on the surface layer portion on the surface 11a side of the silicon wafer 11, the silicon epitaxial layer 13 is formed at a temperature of 900°C or more and 1000°C or less.

As described above, Patent Document 2 and Patent Document 3 propose a technique of diffusing carbon into the inside of a silicon wafer and using the formed carbon diffusion layer as a gettering layer. However, a large number of epitaxial defects are formed in the epitaxial wafer manufactured by the method of Patent Document 2, and the epitaxial wafer manufactured by the method of Patent Document 3 has insufficient suction ability.

The inventors conducted a detailed investigation of the cause of the problem. As a result, it was found that the reason for the insufficient gettering ability of the epitaxial wafer obtained by the method of Patent Document 3 is that the heat treatment temperature is as low as 500°C to 750°C, so that the carbon in the carbon-containing film is not sufficiently diffused to Inside the wafer.

On the other hand, it is known that the reason why a large number of epitaxial defects are formed in the epitaxial wafer obtained by the method of Patent Document 2 is that although the carbon diffusion layer is formed on the surface of the silicon wafer by heat treatment, Since the heat treatment temperature is as high as 1000°C to 1200°C, the silicon constituting the carbon diffusion layer is sublimated, and the remaining carbon is bonded to each other to precipitate, and the crystalline structure of the wafer surface layer is disordered.

Based on the above research, it is expected that by performing heat treatment at a temperature between the temperature described in Patent Document 3 and the temperature described in Patent Document 2, the formation of epitaxial defects can be suppressed while producing epitaxial crystals with high gettering ability. Wafer.

However, when the inventor performs heat treatment within the temperature range to manufacture epitaxial silicon wafers, it is known that a large number of epitaxial defects will still be formed. Therefore, the inventors investigated the cause. As a result, it can be seen that the reason is that the general formation temperature of the silicon epitaxial layer formed on the carbon diffusion layer is about 1150°C. However, since the formation temperature is high, the silicon in the carbon diffusion layer sublimates as described above and carbon precipitates.

Based on the above research, the inventors have reached the following conclusion: In order to produce epitaxial silicon wafers with high gettering ability while suppressing the formation of epitaxial defects, it is necessary to fully diffuse carbon to silicon in a carbon-containing gas environment. The inside of the wafer and the formed carbon diffusion layer silicon will not be sublimated and carbon will not be deposited at a temperature, and regarding the formation of the silicon epitaxial layer, it is also necessary that the silicon in the formed carbon diffusion layer will not sublime , Carry out at low temperature where carbon will not precipitate.

In addition, the inventors conducted diligent research on specific temperature conditions, and found that by performing heat treatment of silicon wafers in a carbon-containing gas atmosphere at a temperature of 800°C or higher and 980°C or lower, the temperature is 900°C or higher and 1000°C or higher. The formation of the silicon epitaxial layer is carried out below °C, and the epitaxial silicon wafer with high gettering ability can be obtained while suppressing the formation of epitaxial defects, thereby completing the present invention. Hereinafter, each step will be described.

<First Step>

First, a silicon wafer 11 ((a) in FIG. 1) having a surface 11a, a back surface 11b, and an edge region 11c is heat-treated at a temperature of 800°C or higher and 980°C or lower in a carbon-containing gas environment. The surface layer portion of the circle 11 on at least the surface 11a side forms the carbon diffusion layer 12 ((b) in FIG. 1).

As the silicon wafer 11, it is possible to use the Tchaikovsky method (Czochralski, CZ method) or floating zone method (Floating Zone, FZ method) and bred single crystal silicon ingots obtained by wafer processing. In order to obtain higher absorption capacity, carbon and/or nitrogen can also be added to the silicon wafer 11. In addition, arbitrary appropriate impurities may be added to make it n-type or p-type. The diameter of the silicon wafer 11 can be set to 200 mm, 300 mm, or 450 mm, for example. Regarding the resistivity, it can also be appropriately set according to the design.

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

In addition, 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. Thereby, while suppressing the generation of slip, it is possible to suppress the formation of epitaxial defects due to oxygen precipitation.

As described above, in the present invention, it is important to set the heat treatment temperature in a carbon-containing gas environment 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 environment, such as methane gas, cannot be decomposed, and carbon cannot be diffused from the surface of the silicon wafer 11 to the inside of the wafer.

On the other hand, when the heat treatment temperature exceeds 980° C., since the heat energy is high, the silicon in the formed carbon diffusion layer 12 sublimates. As a result, carbon remaining in the carbon diffusion layer 12 is bonded to each other and precipitated, and the crystal structure of silicon is disordered, and a large number of 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. The heat treatment temperature is more preferably set to 800°C or more and 950°C or less.

By performing the heat treatment at the temperature in the above-mentioned range, it is possible to diffuse carbon into the inside of the wafer without disturbing the crystal structure of the surface layer portion of the silicon wafer 11 to form the carbon diffusion layer 12. Furthermore, the concentration of carbon contained in the carbon diffusion layer 12 is 1×10 ¹⁷ atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ³ or less, so that the carbon diffusion layer 12 can be contained in the carbon diffusion layer 12 sufficiently for the absorption of heavy metals. Concentration of carbon. Furthermore, the carbon concentration is the maximum concentration inside the silicon wafer 11, and the carbon concentration is the maximum (peak) at the interface between the silicon wafer 11 and the silicon epitaxial layer 13.

In addition, the heat treatment time is preferably set to 1 minute or more and 40 minutes or less. By setting the heat treatment time to 1 minute or more, carbon in a carbon-containing gas atmosphere can be sufficiently diffused from the surface of the silicon wafer 11, thereby forming a carbon diffusion layer 12 containing high-concentration carbon on the surface of the silicon wafer 11. . By setting the heat treatment time to 1 minute or more, the thickness of the carbon diffusion layer 12 becomes 20 nm or more. In addition, even if the heat treatment is performed for more than 40 minutes, the diffusion of carbon into the wafer is saturated. Therefore, the upper limit of the heat treatment time is preferably set to 40 minutes or less. The upper limit of the thickness of the formed carbon diffusion layer 12 is approximately 200 nm.

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

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

Regarding the formation of the surface layer portion of the carbon diffusion layer 12 only on the surface 11a side of the silicon wafer 11, for example, a susceptor as shown in FIG. 3 may be used instead of the type of supporting the edge region 11c of the silicon wafer 11 by line contact. Pedestal to carry on. That is, the susceptor 20 shown in FIG. 3 has a recess 21 partitioned by a side wall 21 a and a bottom surface 21 b, and the bottom surface 21 b has a larger diameter than the silicon wafer 11. By disposing the silicon wafer 11 on the bottom surface 21b of the susceptor 20 and performing heat treatment in a state where the back surface 11b is in contact with the bottom surface 21b, the carbon diffusion layer 12 can be formed only on the surface layer portion on the surface 11a side.

In addition, as shown in FIG. 4, by forming a protective film 14 on the back surface 11b of the silicon wafer 11 (the third step), and performing the heat treatment with the protective film 14 formed thereon, it is possible to use only the silicon wafer The surface layer portion on the surface 11a side of 11 forms the carbon diffusion layer 12. The formed protective film 14 can be removed by, for example, grinding before or after the second step described later (fourth step). In addition, as the protective film 14, any film that can prevent the diffusion of carbon may be used, and an oxide film, a nitride film, or the like can be applied.

Furthermore, after temporarily forming the carbon diffusion layer 12 on both the surface 11a side and the back surface 11b side of the silicon wafer 11, the carbon diffusion layer 12 formed on the surface layer portion on the back surface 11b side can be removed. The carbon diffusion layer 12 is formed on the surface layer portion on the surface 11a side. Regarding the removal of the carbon diffusion layer 12 formed on the surface layer portion on the side of the back surface 11b, the carbon diffusion layer 12 can be removed by, for example, polishing before or after the second step described later (fifth step).

In addition, in order to form the carbon diffusion layer 12 only on the surface portion on the surface 11a side of the silicon wafer 11, as shown in FIG. 5, it is also possible to prepare two silicon wafers 11 in which the back surfaces 11b overlap each other, and in the first step In, the carbon diffusion layer 12 is formed on two silicon wafers 11 each of the surface layer portions on the surface 11a side. In this case, after the first step, the two silicon wafers are separated from each other (the sixth step), and in the second step, a silicon epitaxial layer 13 is formed on the carbon diffusion layer 12 formed on the surface layer portion on the surface 11a side. .

Furthermore, in the case where the carbon diffusion layer 12 is formed only on the surface layer portion on the surface 11a side of the silicon wafer 11 in the above manner, the surface layer of the edge region 11c where the outer peripheral portion of the wafer 11 is chamfered The carbon diffusion layer 12 is also formed in the part. The carbon of the carbon diffusion layer 12 formed in the edge region 11c is diffused out of the wafer due to the heat treatment performed in the subsequent device processing, and the carbon is absorbed into the silicon epitaxial layer (device formation region) 13 Worry. Therefore, it is preferable to remove the carbon diffusion layer 12 formed on the surface layer portion of the edge region 11c before the second step described later (seventh step). The carbon diffusion layer 12 formed on 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 where the second step described later is performed. Specifically, first, the silicon wafer 11 is introduced into an epitaxial growth furnace, hydrogen is introduced into the furnace, and the temperature is raised to 1100°C to 1150°C to perform hydrogen baking to remove the natural oxide film on the surface of the silicon wafer 11. Then, the temperature in the furnace is lowered to a temperature of 800° C. to 980° C., and carbon-containing gases such as hydrogen (carrier gas) and methane gas are introduced into the furnace, and the furnace is maintained for 1 minute, for example. Thereby, carbon is diffused from the surface of the silicon wafer 11 to the inside of the wafer, and the carbon diffusion layer 12 can be formed on at least the surface 11a. Next, the formation of the silicon epitaxial layer 13 in the second step can be performed.

In addition, the first step can be performed by introducing the silicon wafer 11 as a substrate into a dedicated heat treatment device capable of introducing carbon-containing gas, and then A carbon-containing gas is introduced into the furnace to make the furnace a carbon-containing gas environment, and then the temperature is raised to a predetermined heat treatment temperature. The heat treatment device is not particularly limited, and a vertical or horizontal device can be used. In addition, a device that processes a wafer such as a rapid thermal anneal (RTA) device can also be used, but it is preferable to use a batch type heat treatment device that can simultaneously heat treat multiple wafers. In this case, the heat-treated silicon wafer 11 can be introduced into the epitaxial growth furnace to perform the second step.

<Second step>

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

Specifically, the silicon wafer 11 with the carbon diffusion layer 12 formed in the first step is introduced into an epitaxial growth furnace, hydrogen is introduced into the furnace, and the temperature is raised to about 1100°C to 1150°C for hydrogen baking. The natural oxide film on the surface of the silicon wafer 11 is removed. Then, for example, using hydrogen as a carrier gas, silane gas (SiH ₄ ), dichlorosilane gas (SiH ₂ Cl ₂ ), etc., which can be decomposed at 900°C or more and 1000°C or less, is introduced into the furnace as source gas . Thereby, 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 silane gas (SiH ₄ ) having many hydrogen bonds.

The thickness of the epitaxial silicon layer 13 can be appropriately set according to the design, for example, can be set in the range of 1 μm to 15 μm. In addition, the resistivity of the silicon epitaxial layer 13 can also be appropriately set according to the design.

In the case where the formation temperature of the silicon epitaxial layer 13 is less than 900°C, it is not good. The decomposition of the silane-based gas as the source gas is performed well. In addition, when the formation temperature of the silicon epitaxial layer 13 exceeds 1000° C., the silicon in the carbon diffusion layer 12 formed in the first step is sublimated, and carbon is bonded to each other to be precipitated. As a result, the crystal structure of silicon is disordered, and a large number of 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 set to 900° C. or more and 1000° C. or less.

In this way, the epitaxial silicon wafer 1 of the present invention can be manufactured. In the formed carbon diffusion layer 12, hydrogen contained in the source gas or hydrogen as a carrier gas is trapped. The hydrogen trapped in the carbon diffusion layer 12 has the following effect: it diffuses into the silicon epitaxial layer 13 during the heat treatment of the element formation step, and passivate the 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 higher and 1000° C. or lower. Therefore, compared with the case where the silicon epitaxial layer 13 is formed at a high temperature of about 1150° C., the carbon diffusion layer 12 can trap a high concentration of hydrogen, and the passivation effect of defects can be improved.

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

(Epitaxial silicon wafer)

Next, the epitaxial silicon wafer of the present invention will be described. The epitaxial silicon wafer 1 of the present invention has: a carbon diffusion layer 12 formed on the surface portion of at least the surface 11a side of the silicon wafer 11 having a surface 11a, a back 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 surface 11a side. Here, the epitaxial silicon wafer 1 of the present invention is characterized in that the peak carbon concentration of the carbon diffusion layer 12 is 1×10 ¹⁷ atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ³ or less. The peak hydrogen concentration is 1×10 ¹⁸ atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ³ or less.

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

In addition, not only the heat treatment at the relatively low temperature, but also the formation of the silicon epitaxial layer 13 is also performed at a relatively low temperature. As a result, the formation of epitaxial defects is suppressed, and the number of epitaxial defects is four or less in terms of a size of 90 nm or more. In this way, the epitaxial silicon wafer 1 of the present invention not only has fewer epitaxial defects, but also has a high gettering ability.

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.} Diffusion, the function of passivating defects.

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

[Example]

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

(Invention example 1)

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

(Invention example 2)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 1. However, the heat treatment temperature in the first step was set to 950° C., and the epitaxial silicon wafer of Inventive Example 2 was obtained. The other conditions are exactly the same as Inventive Example 1.

(Invention example 3)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 1. However, the heat treatment temperature in the first step was set to 980° C., and the epitaxial silicon wafer of Inventive Example 3 was obtained. The other conditions are exactly the same as Inventive Example 1.

(Comparative example 1)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 1. However, the heat treatment temperature of the first step was set to 750° C., and the epitaxial silicon wafer of Comparative Example 1 was obtained. The other conditions are exactly the same as Inventive Example 1.

(Comparative example 2)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 1. However, the heat treatment temperature in the first step was set to 1000° C., and the epitaxial silicon wafer of Comparative Example 2 was obtained. The other conditions are exactly the same as Inventive Example 1.

(Comparative example 3)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 1. However, the heat treatment temperature in the first step was set to 1100° C., and the epitaxial silicon wafer of Comparative Example 3 was obtained.

(Invention example 4)

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

(Invention Example 5)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 2. However, the formation temperature of the silicon epitaxial layer in the second step was set to 1000° C., and the epitaxial silicon wafer of Inventive Example 5 was obtained. The other conditions are exactly the same as in Inventive Example 2.

(Comparative Example 4)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 2. However, the formation temperature of the epitaxial layer in the second step was set to 850°C. As a result, the silicon epitaxial layer cannot be grown.

(Comparative Example 5)

The epitaxial silicon wafer was produced in the same manner as in Invention Example 2. However, the formation temperature of the epitaxial layer in the second step was set to 1180° C., and the epitaxial silicon wafer of Comparative Example 5 was obtained. The other conditions are exactly the same as in Inventive Example 2.

<Evaluation of epitaxial defects>

Regarding each of the epitaxial silicon wafers of Inventive Example 1 to Inventive Example 5, Comparative Example 1 to Comparative Example 3, and Comparative Example 5, the number of epitaxial defects formed in the epitaxial silicon layer was evaluated. Specifically, using a surface defect inspection device (manufactured by KLA-Tencor: Surfscan SP-2), the surface of the epitaxial wafer of each sample was observed and evaluated, and the size of 90nm or more was investigated. The occurrence of the light point defect (LPD). At this time, the observation mode is set to the oblique mode (oblique incident mode), and the estimation of surface pits is performed based on the detection size ratio of the wide/narrow (Wide Narrow) channel. Then, a scanning electron microscope (Scanning Electron Microscope, SEM) was used to observe and evaluate the location where the LPD was generated, and to evaluate whether the LPD was a stacking fault (SF). The number of detected epitaxial defects (pieces/wafer) is shown in Table 1.

As is clear from Table 1, regarding Inventive Example 1 to Inventive Example 5 and Comparative Example 1, the formation of epitaxial defects per wafer is less than five. On the other hand, in Comparative Example 2 and Comparative Example 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 exceeded 1000° C., a large number of epitaxial defects were formed. It is considered that the reason is that the silicon of the formed carbon diffusion layer sublimates and carbon precipitates.

<Evaluation of Absorption Ability>

With respect to each of the epitaxial silicon wafers of Inventive Example 1 to Inventive Example 5, Comparative Example 1 to Comparative Example 3, and Comparative Example 5, the gettering ability was evaluated. Specifically, a nickel (Ni) contamination solution (1.0×10 ¹³ /cm ² ) was used to deliberately contaminate the surface of the epitaxial layer of each epitaxial wafer using the spin-coating contamination method, and then the surface of the epitaxial layer of each epitaxial wafer was deliberately contaminated, and then subjected to 1000℃, 3 Minutes of diffusion heat treatment. After that, photolithography was performed for 3 minutes, and the pits that can be observed on the surface of the epitaxial layer were observed using an optical microscope, and the gettering ability was evaluated by the presence or absence of the pits. The evaluation results are shown in Table 1.

As clear from Table 1, about invention example 1 to invention example 5, comparison In Example 2, Comparative Example 3, and Comparative Example 5, pits were not observed, but in Comparative Example 1, where the heat treatment temperature was as low as 750°C, pits were observed, and the absorption ability was insufficient. It is considered that this is because in Comparative Example 1, the heat treatment temperature is low, and therefore carbon cannot be sufficiently diffused into the inside of the wafer.

<Evaluation of Carbon Concentration and Hydrogen Concentration>

Regarding Invention Example 1 to Invention Example 5, Comparative Example 1 to Comparative Example 3, and Comparative Example 5, the obtained epitaxial silicon wafer was subjected to Secondary Ion Mass Spectrometry (SIMS) measurement to measure the carbon concentration and Hydrogen concentration. Table 1 shows the obtained carbon concentration and hydrogen concentration. In addition, the concentration distribution of carbon and hydrogen in the epitaxial silicon wafer of Inventive Example 2 is shown in FIG. 6.

As shown in Table 1, regarding Inventive Examples 1 to 5 and Comparative Example 2, Comparative Example 3, and Comparative Example 5 where the heat treatment temperature is high, the carbon concentration is 5×10 ¹⁸ atoms/cm ³ or more, and the carbon concentration is high. In contrast, with respect to 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, regarding the hydrogen concentration, in Invention Example 1 to Invention Example 5 with high absorption capacity, Invention Example 1 where the heat treatment temperature is relatively low is 10 ¹⁸ atoms/cm ³ grade, but Invention Example 2 to Invention Example 5 are 10 ¹⁹ atoms. /cm ³ level, the carbon diffusion layer contains a high concentration of hydrogen. In addition, regarding Comparative Example 2 and Comparative Example 3 in which the formation temperature of the silicon epitaxial layer is within the range specified by the present invention, the hydrogen concentration is also on the order of 10 ¹⁹ atoms/cm ³ .

[Industrial availability]

According to the present invention, it is possible to manufacture epitaxial silicon wafers with high gettering ability while suppressing the formation of epitaxial defects, so it can be effectively used in semiconductor wafer manufacturing in.

1: epitaxial silicon wafer

11: Silicon wafer

11a: surface

11b: back

11c: marginal area

12: Carbon diffusion layer

13: Silicon epitaxial layer

Claims (13)

A method for manufacturing an epitaxial silicon wafer, which is characterized in that it comprises: a first step of performing heat treatment on a silicon wafer with a surface, a back surface and an edge region in a carbon-containing gas environment at a temperature above 800°C and below 980°C , Forming a carbon diffusion layer on at least the surface layer portion of the silicon wafer on the surface side; and the second step is to form a carbon diffusion layer on the surface layer portion of the silicon wafer on the surface side with 900 The silicon epitaxial layer is formed at a temperature above ℃ and below 1000℃. The method of manufacturing an epitaxial silicon wafer according to claim 1, wherein, in the first step, the carbon diffusion layer is formed only on the surface layer portion on the surface side of the silicon wafer . The method for manufacturing an epitaxial silicon wafer as described in item 2 of the scope of patent application further has: a third step, before the first step, forming a protective film on the back surface of the silicon wafer; and In the fourth step, the protective film is removed before or after the second step. The method of manufacturing an epitaxial silicon wafer according to claim 2, wherein, in the first step, the surface layer portion of both the surface side and the back side of the silicon wafer The carbon diffusion layer is formed, and the method for manufacturing the epitaxial silicon wafer further has: a fifth step, before or after the second step, forming the carbon diffusion layer on the surface portion of the back side Remove. The method for manufacturing an epitaxial silicon wafer according to the second patent application, wherein, in the first step, the two silicon wafers whose back surfaces overlap each other are Round, the carbon diffusion layer is formed on the surface portion of at least the surface side of each of the two silicon wafers. The method of manufacturing the epitaxial silicon wafer further has: a sixth step, after the first step, The two silicon wafers are peeled off. For example, the method for manufacturing an epitaxial silicon wafer described in any one of the first to fifth items of the scope of the patent application further has: a seventh step, after the first step and before the second step, The carbon diffusion layer formed on the surface layer portion of the edge region of the silicon wafer is removed. According to the method for manufacturing an epitaxial silicon wafer according to any one of items 1 to 5 of the scope of the patent application, the first step is performed in an epitaxial growth furnace where the second step is performed. According to the method for manufacturing an epitaxial silicon wafer according to any one of the scope of the patent application item 1 to item 5, wherein the first step is to introduce the silicon wafer to the point where the carbon-containing gas can be introduced The second step is to introduce the heat-treated silicon wafer into an epitaxial growth furnace. The method for manufacturing an epitaxial silicon wafer according to any one of claims 1 to 5, wherein, in the first step, the peak carbon concentration in the carbon diffusion layer becomes 1 ×10 ¹⁷ atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ³ or less. In the second step, the peak hydrogen concentration in the carbon diffusion layer becomes 1×10 ¹⁸ atoms/cm ^The epitaxial growth process is performed at 3 or more and 1×10 ²⁰ atoms/cm ^{3 or less.} An epitaxial silicon wafer, characterized by having: a carbon diffusion layer formed on at least the surface side of a silicon wafer having a surface, a back surface, and edge regions; and a silicon epitaxial layer formed on the surface On the carbon diffusion layer of the surface layer portion on the side, the peak carbon concentration of the carbon diffusion layer is 1×10 ¹⁷ atoms/cm ³ or more and 1×10 ²⁰ atoms/cm ³ or less, and 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. In the epitaxial silicon wafer described in item 10 of the scope of patent application, the thickness of the carbon diffusion layer is 200 nm or less. The epitaxial silicon wafer according to the 10th or 11th patent application, wherein the carbon diffusion layer is formed only on the surface layer portion on the surface side. In the epitaxial silicon wafer described in item 10 or item 11 of the scope of the patent application, the carbon diffusion layer is not formed on the surface portion of the edge region.

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