JP2010034330A - Epitaxial wafer and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epitaxial wafer and a method of manufacturing the same capable of easily manufacturing an epitaxial wafer with a gettering layer contacting an epitaxial film, and providing a high gettering effect. <P>SOLUTION: Since the gettering layer 12 contacting the epitaxial film 11 and formed of a carbon diffusion layer is formed, a heavy metal pollution substance in the epitaxial film 11 can be effectively gettered to the gettering layer 12 in, for instance, heat treatment in a device formation process. Since the gettering layer 12 formed of the carbon diffusion layer is formed on a surface of a silicon wafer W, formation of the gettering layer 12 in contact with the epitaxial film 11 which is difficult by a conventional carbon ion implantation method is facilitated. Thereby, a high gettering effect is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an epitaxial wafer and a manufacturing method thereof, and more particularly to an epitaxial wafer and a manufacturing method thereof capable of obtaining a high gettering effect even in a large-diameter epitaxial wafer.

The diameter of silicon wafers has been increasing year by year, and at present, wafers with a diameter of 300 mm have become mainstream. In the future, production of larger diameter wafers is also expected.
A silicon wafer is manufactured by first pulling up a single crystal ingot by the CZ method, and subjecting the ingot to steps such as slicing, chamfering, lapping, etching, mirror polishing, and cleaning. However, as the diameter of the wafer increases, the single crystal ingot pulled by the CZ method and the silicon wafer produced from now on have technical problems in the ingot pulling, the yield, technical problems in wafer processing, etc. As a result, crystal defects increased.
Therefore, in the future, in order to eliminate defects on the wafer surface on which devices are formed, for example, a vapor phase epitaxial method as disclosed in Patent Document 1 is used, and the surface (mirror surface) of a large-diameter wafer exceeding 300 mm in diameter. A method of growing an epitaxial film can be considered. This epitaxial film is used for device formation.

  However, in the case of an epitaxial wafer, there has been a problem that intrinsic gettering (IG) ability is lower than that of a mirror-polished wafer. This is because the growth temperature of the epitaxial film is as high as 1050 to 1150 ° C. and the heating rate is no longer present, so that the oxygen precipitation nuclei in the wafer are reduced or eliminated during the growth of the epitaxial film. This is because oxygen precipitates that become gettering sites are hardly formed inside.

  Thus, as a conventional technique for solving this problem, for example, one disclosed in Patent Document 2 is known. This is a semiconductor substrate manufacturing process in which carbon ions are implanted into the surface of a silicon wafer to form a gettering layer with carbon as a gettering site on the surface of the wafer, and then an epitaxial film is epitaxially grown on the surface of the silicon wafer. Is the method. If the gettering site is carbon, the site will not decrease or disappear due to heat during epitaxial growth as in the case of the oxygen precipitation nuclei described above.

JP 2006-278791 A JP-A-5-152304

  However, in Patent Document 2, since an ion implantation method is used as a method for forming a gettering layer using carbon as a gettering site, it is difficult to control the formation of the gettering layer reaching a predetermined depth from the surface of the silicon wafer. Met. Therefore, the gettering layer is formed, for example, at a position several μm away from the surface of the silicon wafer, and it is difficult to form the gettering layer in contact with the epitaxial film. Therefore, the gettering capability of the gettering layer is reduced by the distance from the epitaxial film to the gettering layer.

  Accordingly, the present invention provides an epitaxial wafer in which a gettering layer is in contact with an epitaxial film, and an epitaxial wafer capable of obtaining a high gettering effect even in a large-diameter epitaxial wafer, and a method for manufacturing the same. The purpose is to do.

  The invention according to claim 1 is an epitaxial wafer in which an epitaxial film is formed on the surface of a silicon wafer, and a carbon diffusion layer is formed on the surface of the silicon wafer on which the epitaxial film is formed.

  According to the first aspect of the present invention, the gettering layer (intrinsic gettering layer; hereinafter referred to as “IG layer”) made of a carbon diffusion layer is formed in contact with the epitaxial film. During the heat treatment, heavy metal contaminants such as nickel and copper in the epitaxial film can be effectively gettered (captured) into the IG layer. Moreover, heavy metal contaminants in the silicon wafer can also be gettered to the IG layer.

As the silicon wafer, a single crystal silicon wafer or a polycrystalline silicon wafer can be employed. For example, boron can be added to the silicon wafer as a dopant. The amount of boron added can be adjusted so that the specific resistance of the silicon wafer is 0.001 Ω · cm to 10 Ω · cm. However, from the viewpoint of improving the gettering ability by adding boron, it is preferable to increase the amount of boron.
The diameter of the silicon wafer is arbitrary. For example, it may be 150 mm, 200 mm, or 300 mm or more.

The material of the epitaxial film may be the same silicon as the wafer or may be different from the wafer, such as gallium arsenide.
The thickness of the epitaxial film is set in the range of several μm to several hundred μm depending on the type of device. For example, it is several μm to several tens of μm for bipolar devices, and several μm or less for MOS devices.
The thickness of the carbon diffusion layer is arbitrary and is, for example, 100 nm to 1 μm. If the thickness is within this range, heavy metal contaminants in the epitaxial film can be effectively gettered.

  The invention according to claim 2 is the epitaxial wafer according to claim 1, wherein the carbon diffusion layer is also formed on the back surface of the silicon wafer on which the epitaxial film is not formed.

  According to the second aspect of the present invention, a gettering layer (extrinsic gettering layer; hereinafter referred to as “EG layer”) made of a carbon diffusion layer is formed not only on the front surface but also on the back surface of the silicon wafer. Therefore, during the heat treatment in the device formation process, heavy metal contaminants in the epitaxial film are gettered to the IG layer, while heavy metal contaminants existing in the heat treatment atmosphere outside the silicon wafer are gettered to the EG layer. . In addition, heavy metal contaminants in the silicon wafer can also be captured by the IG layer during the heat treatment. As a result, regardless of the diameter of the wafer, a high gettering effect can be obtained in the epitaxial wafer.

  According to a third aspect of the present invention, there is provided a carbon-containing film forming step of immersing a silicon wafer in a carbon-containing solution to form a carbon-containing film on the surface of the silicon wafer, and a silicon wafer on which the carbon-containing film is formed. A carbon diffusion layer forming step of forming a carbon diffusion layer by thermally diffusing the carbon in the carbon-containing film to a surface layer portion of the silicon wafer; and an epitaxial film on the surface of the silicon wafer on which the carbon diffusion layer is formed And an epitaxial growth step for forming an epitaxial wafer.

  According to the invention described in claim 3, since the IG layer composed of the carbon diffusion layer in contact with the epitaxial film is formed on the epitaxial wafer, for example, during the heat treatment in the device forming process, nickel and copper in the epitaxial film are formed. Such heavy metal contaminants can be effectively gettered (captured) into the IG layer. Moreover, heavy metal contaminants in the silicon wafer can also be gettered to the IG layer.

As the solution containing carbon, an organic solution such as chlorinated hydrocarbons, alcohols, acetates, or ethers can be employed. Among these, it is preferable to use an N-methyl-2-pyrrolidone solution because it is easily adsorbed on the surface of the wafer. Further, the carbon concentration in the carbon-containing film is preferably 1 × 10 ^{12 to} 5 × 10 ¹² atoms / cm ² .
When the carbon concentration is less than 1 × 10 ¹² atoms / cm ² , the intrinsic gettering capability sufficient for the gettering layer formed of the carbon diffusion layer formed by thermally diffusing the carbon in the carbon-containing film on the surface layer portion of the silicon wafer. Cannot be granted. If the carbon concentration exceeds 5 × 10 ¹² atoms / cm ² , when the carbon in the carbon-containing film is thermally diffused to the surface layer portion of the silicon wafer, the carbon concentration is excessive, so that some carbon reacts with silicon. Thus, silicon carbide (SiC) is formed. The carbon concentration in the carbon-containing solution, the temperature, the time for immersing the silicon wafer in the carbon-containing solution, and the like may be appropriately changed so that the carbon concentration in the carbon-containing film falls within the above range.

  The invention according to claim 4 is the method for producing an epitaxial wafer according to claim 3, wherein the carbon diffusion layer is also formed on the back surface of the silicon wafer on which the epitaxial film is not formed.

  According to invention of Claim 4, the EG layer which consists of a carbon diffusion layer is formed also in the back surface of the silicon wafer. Therefore, during the heat treatment in the device formation process, heavy metal contaminants in the epitaxial film are gettered to the IG layer, while heavy metal contaminants existing in the heat treatment atmosphere outside the silicon wafer are gettered to the EG layer. . In addition, heavy metal contaminants in the silicon wafer can also be captured by the IG layer during the heat treatment. As a result, a high gettering effect can be obtained in the epitaxial wafer regardless of the diameter of the wafer.

  The invention according to claim 5 is the epitaxial wafer manufacturing method according to claim 3 or 4, wherein the carbon-containing film is a natural oxide film containing carbon.

The natural oxide film preferably contains carbon having a concentration of 1 × 10 ^{12 to} 5 × 10 ¹² atoms / cm ² .
In addition to the method of immersing a silicon wafer in a solution containing carbon, the method of forming a natural oxide film containing carbon includes a method of cleaning a silicon wafer in an atmosphere containing carbon, and a silicon wafer after cleaning. A method of drying in an atmosphere containing carbon can be employed. In short, the method is not limited to these methods as long as a natural oxide film containing carbon having a concentration of 1 × 10 ^{12 to} 5 × 10 ¹² atoms / cm ² can be formed.

  The invention according to claim 6 is a carbon diffusion layer forming step of forming a carbon diffusion layer by heat-treating a silicon wafer in a gas atmosphere containing carbon and thermally diffusing the carbon in the gas to a surface layer portion of the silicon wafer. And an epitaxial growth step of forming an epitaxial film on the surface of the silicon wafer on which the carbon diffusion layer is formed.

According to the invention described in claim 6, the silicon wafer is heat-treated in a gas atmosphere containing carbon. As a result, carbon in the gas is thermally diffused from the surface layer portion of the silicon wafer into the wafer, and a carbon diffusion layer is formed in the wafer surface layer portion. Thereafter, an epitaxial film is epitaxially grown on the surface of the wafer on which the carbon diffusion layer is formed, and an epitaxial wafer is manufactured.
Thus, since the formation method of the gettering layer by the heat treatment of the silicon wafer in the gas atmosphere containing carbon is adopted, the carbon diffusion layer is in contact with the epitaxial film, which is difficult with the conventional carbon ion implantation method. It becomes easy to form the IG layer. Thereby, for example, during the heat treatment in the device formation process, heavy metal contaminants in the epitaxial film can be effectively gettered to the IG layer. In addition, heavy metal contaminants in the silicon wafer can be gettered to the IG layer during the heat treatment. As a result, regardless of the diameter of the wafer, a high gettering effect can be obtained in the epitaxial wafer.

The gas containing carbon may be a gas containing a substance containing carbon such as methane or ethylene, or may be a gas mixed with a carrier gas. As the carrier gas, an inert gas such as argon gas, hydrogen gas, nitrogen gas, or the like can be used.
The thickness of the carbon diffusion layer is arbitrary and is, for example, 100 nm to 1 μm. When the thickness is in this range, it takes no long time to form the carbon diffusion layer, and the heavy metal contaminants in the epitaxial film can be effectively gettered.
The heat treatment temperature is 500 to 750 ° C. Below 500 ° C., it takes a long time to form the carbon diffusion layer. Conversely, if it exceeds 750 ° C., SiC (silicon carbide) is formed.
The heat treatment time is arbitrary as long as the heat treatment is performed at a temperature of 500 to 750 ° C. and the carbon diffusion layer has a thickness of, for example, 100 nm to 1 μm.

  The invention according to claim 7 is the method for producing an epitaxial wafer according to claim 6, wherein the carbon diffusion layer is also formed on the back surface of the silicon wafer on which the epitaxial film is not formed.

  According to the seventh aspect of the present invention, the EG layer made of the carbon diffusion layer is also formed on the back surface of the silicon wafer. Therefore, during the heat treatment during device formation, heavy metal contaminants in the epitaxial film are gettered to the IG layer, while heavy metal contaminants present in the heat treatment atmosphere outside the silicon wafer are gettered to the EG layer. . In addition, heavy metal contaminants in the silicon wafer can also be captured by the IG layer during the heat treatment. As a result, regardless of the diameter of the wafer, a high gettering effect can be obtained in the epitaxial wafer.

According to the first, third, and sixth aspects of the invention, a gettering layer (IG layer) made of a carbon diffusion layer is formed on the surface of the silicon wafer in contact with the epitaxial film. Therefore, for example, during heat treatment in the device formation process, heavy metal contaminants such as nickel and copper in the epitaxial film can be effectively gettered to the IG layer.
Further, it becomes easy to form the IG layer in contact with the epitaxial film, which is difficult with the conventional carbon ion implantation method. Thereby, for example, during the heat treatment in the device formation process, heavy metal contaminants in the epitaxial film can be effectively gettered to the IG layer. Moreover, heavy metal contaminants in the silicon wafer can also be gettered to the IG layer. Thus, a high gettering effect can be obtained in an epitaxial wafer regardless of the diameter of the wafer.

  In particular, according to the invention described in claim 2, claim 4 and claim 7, the gettering layer (EG layer) made of the carbon diffusion layer is also formed on the back surface of the silicon wafer on which no epitaxial film is formed. Therefore, the heavy metal contaminant in the epitaxial film is gettered to the IG layer formed of the carbon diffusion layer on the wafer surface. In addition, heavy metal contaminants present in the heat treatment atmosphere are gettered to the EG layer formed of the carbon diffusion layer on the back surface of the wafer. In addition, heavy metal contaminants in the silicon wafer can also be captured by the IG layer during the heat treatment. Thereby, a higher gettering effect can be obtained as compared with the case where the EG layer is not formed on the back surface of the silicon wafer.

  Examples of the present invention will be specifically described below. First, with reference to FIGS. 1-4, the epitaxial wafer which concerns on Example 1, and its manufacturing method are demonstrated.

In FIG. 1, reference numeral 10 denotes an epitaxial wafer according to Embodiment 1 of the present invention. The epitaxial wafer 10 is obtained by forming a gettering layer (IG layer) 12 made of a carbon diffusion layer on the surface of a silicon wafer W on which an epitaxial film 11 is formed.
Hereinafter, the manufacturing method of this epitaxial wafer 10 will be described with reference to the flow sheet of FIG.
First, a silicon wafer W sliced from a single crystal silicon ingot pulled up by the CZ method is prepared. Boron is added to the silicon wafer W as a dopant until the specific resistance of the silicon wafer W becomes 0.01 Ω · cm.

Next, the sliced silicon wafer W is chamfered into a predetermined shape using a chamfering grindstone in a chamfering process. As a result, the peripheral portion of the silicon wafer W has a predetermined rounded cross section.
In the subsequent lapping process, lapping of the chamfered wafer is performed by a lapping machine.
In the next etching step, the lapped wafer is immersed in a predetermined etching solution (mixed acid or alkali + mixed acid) to remove distortion in the lapping process, distortion in the chamfering process, and the like. In this case, etching is usually performed on one side by 20 μm and on both sides by about 40 μm.
Thereafter, the silicon wafer W is fixed to a polishing board, and the surface of the silicon wafer W is subjected to one-side mirror polishing.

Then, the surface of the silicon wafer W subjected to mirror polishing is immersed in an N-methyl-2-pyrrolidone solution, and a carbon-containing film containing 2 × 10 ¹² atoms / cm ² of carbon on the surface of the silicon wafer W. 13 is formed (FIG. 3).
Next, the silicon wafer W having the carbon-containing film 13 formed on the surface is inserted into an annealing furnace and annealed at 1000 ° C. for 2 hours in an atmosphere of argon gas. As a result, the carbon in the carbon-containing film 13 formed on the surface of the silicon wafer W is thermally diffused to the surface layer portion of the silicon wafer W, and the gettering layer 12 made of the carbon diffusion layer is formed on the wafer surface layer portion (FIG. 4).

  Thereafter, the silicon wafer W is placed in a reaction chamber of a single wafer epitaxial growth apparatus held in a hydrogen gas atmosphere at about 850 ° C. Then, after the temperature in the reaction chamber is raised to approximately 1150 ° C. at a temperature raising rate of about 5 ° C./second, hydrogen baking is performed for 60 seconds. Thereby, the natural oxide film and particles on the surface of the silicon wafer W are removed, and the surface of the silicon wafer W is cleaned.

The epitaxial film 11 is grown on the surface of the silicon wafer W continuously with the hydrogen baking. That is, a mixed gas obtained by diluting SiHCl ₃ as a silicon source gas with hydrogen gas is introduced into the reaction chamber. Silicon produced by thermal decomposition or reduction of a raw material gas on a silicon wafer W heated to a high temperature of 1000 ° C. to 1150 ° C. with a pressure of 100 ± 20 KPa is reacted at a reaction rate of 3.5 to 4.5 μm / min. Precipitate. Thereby, an epitaxial film 11 having a thickness of 3 to 10 μm is grown on the surface of the silicon wafer W on which the gettering layer 12 is formed (FIG. 1). At this time, the epitaxial film 11 and the gettering layer 12 made of a carbon diffusion layer are in contact with each other.
The epitaxial wafer 10 is manufactured through the above steps.

  Thus, since the formation method of the gettering layer 12 which consists of a carbon diffusion layer to the silicon wafer W by annealing was employ | adopted, the gettering layer in contact with the epitaxial film 11 which was difficult with the conventional carbon ion implantation method was used. 12 can be easily formed. Thereby, the problem that the intrinsic gettering capability of the epitaxial wafer 10 is lower than that of the mirror-polished wafer is solved. That is, for example, during the heat treatment in the device forming process at the shipping destination, heavy metal contaminants such as nickel and copper in the epitaxial film 11 can be effectively gettered to the gettering layer 12 (IG layer). In addition, heavy metal contaminants in the silicon wafer W can also be gettered to the gettering layer 12 at this time. Such a gettering effect can be obtained regardless of the diameter of the silicon wafer W. As a result, high gettering capability can be given to the epitaxial wafer 10 having a large diameter exceeding 300 mm in diameter.

Next, with reference to FIGS. 5-7, the manufacturing method of the epitaxial wafer which concerns on Example 2 of this invention is demonstrated.
The epitaxial wafer 20 of Example 2 is obtained by forming the epitaxial film 11 on the surface of the silicon wafer W. The surface of the silicon wafer W on which the epitaxial film 11 is formed and the back surface of the silicon wafer W on which the epitaxial film 11 is not formed. Further, gettering layers 12 made of a carbon diffusion layer are respectively formed.

Hereinafter, with reference to the flow sheet of FIG. 6, the manufacturing method of the epitaxial wafer 20 of Example 2 is demonstrated.
The etched silicon wafer W obtained through the same steps as in the first embodiment is fixed to a polishing board, and single-side mirror polishing is performed on the surface of the wafer.
Thereafter, the silicon wafer W was placed on a donut-shaped susceptor, the furnace temperature was maintained at about 850 ° C., and the single wafer held in a hydrogen gas atmosphere containing 60% hydrocarbon compound (methane (CH ₄ ) gas) It is installed in the reaction chamber of the epitaxial growth system. Then, after the temperature in the reaction chamber is raised to about 1150 ° C. at a rate of temperature increase of about 5 ° C./second, hydrogen baking is performed for 60 seconds. As a result, the natural oxide film and particles on the front and back surfaces of the silicon wafer W are removed, and the front and back surfaces of the silicon wafer W are cleaned. At the same time, carbon in the gas is thermally diffused into the silicon wafer W from the wafer front surface and the back surface of the wafer, and gettering layers 12 made of a carbon diffusion layer having a thickness of 0.8 μm are formed on the front and back surfaces of the silicon wafer W, respectively. (FIG. 7).

After hydrogen baking, a mixed gas obtained by diluting SiHCl ₃ with hydrogen gas is introduced into the reaction chamber, and the epitaxial film 11 is grown on the surface of the silicon wafer W under the above-described epitaxial growth conditions. Thereby, the epitaxial film 11 grows on the surface of the silicon wafer W (FIG. 5). As a result, an epitaxial wafer 20 is obtained in which the gettering layer 12 on the front side of the silicon wafer W is an IG layer and the gettering layer 12 on the back side of the silicon wafer W is an EG layer.

Thus, since the formation method of the gettering layer 12 by the heat treatment of the silicon wafer W in the gas atmosphere containing carbon is adopted, it is easy to form the gettering layer 12 in contact with the epitaxial film 11. Thereby, for example, during the heat treatment in the device forming process, heavy metal contaminants in the epitaxial film 11 can be effectively gettered to the IG layer 12. In addition, heavy metal contaminants present in the heat treatment atmosphere outside the silicon wafer can be gettered to the EG layer 12. Further, at this time, heavy metal contaminants in the silicon wafer W can also be gettered to the IG layer 12. As a result, the gettering effect in the epitaxial wafer 20 can be enhanced.
Other configurations, operations, and effects are substantially the same as those of the first embodiment, and thus description thereof is omitted.

It is sectional drawing of the epitaxial wafer which concerns on Example 1 of this invention. It is a flow sheet of the manufacturing method of the epitaxial wafer concerning Example 1 of this invention. It is sectional drawing which shows the carbon containing film formation process in the manufacturing method of the epitaxial wafer which concerns on Example 1 of this invention. It is sectional drawing which shows the annealing process in the manufacturing method of the epitaxial wafer which concerns on Example 1 of this invention. It is sectional drawing of the epitaxial wafer which concerns on Example 2 of this invention. It is a flow sheet of the manufacturing method of the epitaxial wafer concerning Example 2 of this invention. It is sectional drawing which shows the hydrogen baking process in the gas atmosphere containing carbon in the manufacturing method of the epitaxial wafer which concerns on Example 2 of this invention.

Explanation of symbols

10,20 epitaxial wafer,
11 Epitaxial film,
12 Gettering layer (carbon diffusion layer),
13 carbon-containing film,
W Silicon wafer.

Claims (7)

In an epitaxial wafer in which an epitaxial film is formed on the surface of a silicon wafer,
An epitaxial wafer in which a carbon diffusion layer is formed on the surface of the silicon wafer on which the epitaxial film is formed.   The epitaxial wafer according to claim 1, wherein the carbon diffusion layer is also formed on a back surface of the silicon wafer on which the epitaxial film is not formed. A carbon-containing film forming step of immersing a silicon wafer in a solution containing carbon and forming a carbon-containing film on the surface of the silicon wafer;
A carbon diffusion layer forming step of heat-treating the silicon wafer on which the carbon-containing film is formed and thermally diffusing the carbon in the carbon-containing film to a surface layer portion of the silicon wafer;
An epitaxial wafer manufacturing method comprising: an epitaxial growth step of forming an epitaxial film on a surface of the silicon wafer on which the carbon diffusion layer is formed.   4. The method of manufacturing an epitaxial wafer according to claim 3, wherein the carbon diffusion layer is also formed on the back surface of the silicon wafer on which the epitaxial film is not formed.   The method for producing an epitaxial wafer according to claim 3 or 4, wherein the carbon-containing film is a natural oxide film containing carbon. A carbon diffusion layer forming step of heat-treating a silicon wafer in a gas atmosphere containing carbon, and thermally diffusing carbon in the gas to a surface layer portion of the silicon wafer to form a carbon diffusion layer;
An epitaxial wafer manufacturing method comprising: an epitaxial growth step of forming an epitaxial film on a surface of the silicon wafer on which the carbon diffusion layer is formed.   The method for producing an epitaxial wafer according to claim 6, wherein the carbon diffusion layer is also formed on a back surface of the silicon wafer on which the epitaxial film is not formed.

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