JP2011060979A - Method of manufacturing epitaxial wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epitaxial wafer improved in uniformity of a thickness distribution of an epitaxial layer formed on a surface of a wafer by suppressing the same growth unevenness for each half rotation generated during use of a conventional sheet type epitaxial device adopting only rotation. <P>SOLUTION: A method of manufacturing an epitaxial wafer that uses the sheet type epitaxial device forming an epitaxial layer on a surface of a mounted wafer by horizontally placing the single semiconductor wafer on a susceptor provided in a chamber and rotating in a horizontal state, and supplying a material gas into the chamber while rotating the susceptor so that the material gas flow in the horizontal direction is characterized in that the susceptor revolves while rotating in the horizontal direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an epitaxial wafer using a single-wafer epitaxial apparatus, which can improve the thickness distribution uniformity of an epitaxial layer to be formed.

  In the exposure process of a device, if the distance between the wafer surface and the light source varies depending on the location, the focus at the time of exposure does not match, and a part where the pattern is not formed as designed is formed. Such a symptom is called poor defocus. For this reason, the wafer is required to have flatness that satisfies the design rules of each product type.

  2. Description of the Related Art Conventionally, when manufacturing an epitaxial wafer, a single-wafer type epitaxial apparatus has been used which has a box-shaped chamber in which a source gas flows in a horizontal direction and epitaxially grows a single wafer. In such a single wafer type epitaxial apparatus, a single wafer is placed on a susceptor installed in a chamber, the inside of the chamber is heated, and a source gas is supplied so as to flow horizontally in the chamber. Thus, the epitaxial growth is performed on the wafer placed on the susceptor. Normally, in a single wafer epitaxial apparatus, in order to make the thickness of an epitaxial layer formed on a wafer as uniform as possible, epitaxial growth is performed while rotating the wafer by rotating the susceptor in a horizontal state.

  Then, when an epitaxial wafer on which an epitaxial layer having a desired thickness is formed using this single wafer type epitaxial apparatus is observed, for example, there are many cases in which the thickness distribution is as shown in FIG. The thin line drawn in the wafer of FIG. 5 is a contour line, and shows a change in the thickness of the entire wafer surface.

  In this thickness distribution, there are a region where the change in thickness is gentle and a region where the change in thickness is abrupt. In particular, it can be confirmed that the region located at the center of the wafer becomes thicker than the desired thickness, becomes thinner with a gentle change toward the outside, and becomes thinner than the desired thickness in the vicinity of the outer periphery.

  In this way, the thickness varies depending on the region in the wafer surface, because each point on the wafer always rotates around the same radius of rotation, so in the epitaxial apparatus maintaining a constant gas flow and a constant temperature distribution, At the point near the wafer center, the movement speed due to rotation is small and the contact time with the source gas is longer, so the epitaxial growth rate is large. Since the contact time is shortened, the epitaxial growth rate is reduced, so that uneven growth occurs in the wafer surface, and it is presumed that the same thickness distribution tends to be obtained at the same rotation radius.

  In particular, in a single-wafer epitaxial apparatus with a small turning radius, the thickness of the epitaxial layer tends to change sharply in a narrow site, and the site flatness is large, which is a problem.

  On the other hand, in order to ensure a good film thickness distribution, the distribution path of the source gas flowing on the substrate is controlled so that the source gas flows relatively straight on the susceptor, thereby providing a uniform distribution path on the substrate. And a method for manufacturing an epitaxial wafer using the same are disclosed (for example, refer to Patent Document 1 and Patent Document 2).

Japanese Patent Laying-Open No. 2005-183511 (Claim 1, paragraphs [0007] and [0042], FIG. 7) JP 2003-203866 A (Claim 1, paragraphs [0007], [0010], [0044], FIG. 13)

  However, even in the conventional apparatuses and methods described in Patent Documents 1 and 2 described above, the growth unevenness of the same thickness distribution occurs at the same rotation radius within the wafer surface, and the required flatness is still sufficient. There was a risk that it could not be met.

  An object of the present invention is to provide an epitaxial wafer manufacturing method using a single wafer type epitaxial apparatus that can improve the thickness distribution uniformity of an epitaxial layer formed on the wafer surface.

  According to a first aspect of the present invention, a single semiconductor wafer is placed horizontally on a susceptor that rotates in a horizontal state provided in a chamber, and flows horizontally in the chamber while rotating the susceptor. In a method for manufacturing an epitaxial wafer using a single-wafer epitaxial apparatus that supplies a raw material gas to form an epitaxial layer on the surface of a mounted wafer, the susceptor revolves while rotating in a horizontal state.

  A second aspect of the present invention is an invention based on the first aspect, wherein the revolution radius is 10 to 50% of the wafer diameter.

  A third aspect of the present invention is an invention based on the first aspect, further characterized in that the rotation speed is 10 to 40 rpm and the revolution speed is 5 to 40 rpm.

  A fourth aspect of the present invention is an invention based on the first aspect, wherein the revolution is a circular orbit.

  In the present invention, since the susceptor on which the wafer is placed during epitaxial growth is configured to revolve while rotating in a horizontal state, the position of each point on the wafer moves while shifting due to rotation combined with rotation and revolution. Therefore, the contact time with the source gas in the vicinity of the wafer center and near the outer periphery is made uniform compared to the rotation only of rotation like the conventional single wafer epitaxial apparatus, and the thickness distribution is the same for each rotation radius. Since uneven growth is suppressed, it is possible to obtain an epitaxial wafer in which the thickness distribution uniformity of the epitaxial layer formed on the wafer surface is improved.

It is the schematic which has the structure which the wafer mounted in the susceptor in the manufacturing method of this invention rotates and revolves. It is a figure which shows a locus | trajectory when the wafer mounted in the susceptor in the manufacturing method of this invention rotates and revolves. FIG. 3 is a diagram showing the thickness distribution of the epitaxial layer from the wafer center to the outer periphery in Example 1. The figure which shows the thickness distribution of the epitaxial layer from the wafer center in Comparative Example 1 to an outer periphery. The figure which shows the thickness distribution of the epitaxial layer of the wafer epitaxially grown using the single wafer type epitaxial device which rotates only the conventional autorotation.

  Next, an embodiment for carrying out the present invention will be described based on the drawings.

  The present invention is an epitaxial wafer manufacturing method using a single-wafer epitaxial apparatus in which an epitaxial layer is formed on the surface of a single silicon wafer by epitaxial growth.

  Here, the silicon wafer serving as the base material for forming the epitaxial layer preferably has a diameter of 5 to 12 inches (125 to 300 mm) in consideration of practical aspects such as the size of the epitaxial growth apparatus. A silicon wafer having an orientation flat or a notch is used.

The epitaxial apparatus used in the manufacturing method of the present invention is a single wafer epitaxial apparatus capable of epitaxially growing a single wafer. This single wafer type epitaxial apparatus includes a box-shaped chamber, a susceptor on which a single wafer is placed, a source gas supply means for supplying source gas into the chamber, a carrier gas supply means for supplying carrier gas into the chamber, and A heating means for heating the inside of the chamber is provided. The shape of the susceptor is a disk shape, and is installed in the chamber so as to rotate and revolve in a horizontal state. Specifically, the susceptor rotates in a horizontal state around a first axis that is coaxial with the susceptor center, and revolves around a second axis that is biased toward the first axis. For example, as shown in FIG. 1, the center 11 a of the susceptor 11 and the first shaft 12 are positioned coaxially, and a first motor 13 that rotates the first shaft 12 is connected below the first shaft 12. The first motor 13 is installed on the revolution radius R of the second shaft 14 biased to the first shaft 12, and the second motor 15 that rotates the second shaft 14 is connected to the second shaft 14. Rotation of the susceptor of the present invention may be achieved. The deviation of the second axis depends on the size of the wafer to be processed, but considering practical aspects such as the size of the epitaxial growth apparatus, it is preferable that the deviation is 12 to 150 mm from the first axis. The revolution radius is 10 to 50% of the wafer diameter due to the deviation within the above range. In addition, the revolution takes a circular orbit. In addition, the susceptor is provided with a recess at a position where the wafer is placed so that the single wafer is positioned concentrically with the center of the susceptor. Further, the source gas is supplied from the source gas supply means into the chamber, and the carrier gas is supplied from the carrier gas supply means into the chamber. Examples of the source gas include SiH ₂ Cl ₂ , SiHCl ₃ , SiH _{4, and} SiCl ₄ , and examples of the carrier gas include H ₂ . Further, the orientations of the supply ports of the source gas supply means and the carrier gas supply means are fixed so that the supplied source gas and carrier gas flow horizontally in the chamber. Furthermore, the heating means has a configuration capable of heating the inside of the chamber to 1000 to 1200 ° C.

  The manufacturing method of the present invention will be described using a single wafer epitaxial apparatus having the above-described configuration.

  First, a wafer with a single orientation flat is placed horizontally on a recess provided in the susceptor on a susceptor provided in the chamber. Next, the inside of the chamber is heated to a temperature range of 1000 to 1200 ° C. suitable for epitaxial growth.

  Next, the susceptor on which the wafer is placed is rotated in a horizontal state. Specifically, the first shaft is rotated clockwise at a speed of 10 to 40 rpm to rotate the susceptor around the first axis, and the second axis is rotated clockwise at a speed of 5 to 40 rpm. Is revolved around the second axis. Due to this combined rotation and revolution, the wafer takes a locus as shown in FIGS. 2 (a) and 2 (b) and moves while shifting the position of each point on the wafer. Compared to rotation only by rotation, the contact time with the source gas near the wafer center and near the outer periphery is made uniform, and growth unevenness with the same thickness distribution for each rotation radius generated by the conventional method is suppressed. be able to. In this state, the source gas and the carrier gas are supplied at a constant ratio so as to flow in the horizontal direction in the chamber, and an epitaxial layer is formed on the surface of the wafer until a predetermined film thickness is obtained. The supply ratio of the source gas and the carrier gas is preferably 12:88 to 30:70.

  As described above, the manufacturing method according to the present invention suppresses the growth unevenness having the same thickness distribution for each rotation radius, which was generated when the conventional single-wafer epitaxial apparatus adopting only the rotation is used. An epitaxial wafer can be obtained in which the thickness distribution uniformity of the epitaxial layer formed on the wafer surface is improved.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
First, a silicon wafer having a diameter of 6 inches (about 150 mm) and an orientation flat having a crystal orientation of (100) was prepared.

  In addition, a single wafer epitaxial apparatus capable of epitaxially growing a single wafer was prepared. This single wafer type epitaxial apparatus includes a chamber, a susceptor on which a single wafer is placed, a source gas supply means for supplying a source gas into the chamber, a carrier gas supply means for supplying a carrier gas into the chamber, and heating the inside of the chamber. Heating means is provided. The susceptor has a disk shape and is installed in the chamber so as to rotate about the first axis in a horizontal state and to revolve about a second axis that is offset by 50 mm from the first axis. In addition, a 6-inch wafer has a size that allows one wafer to be placed, and a recess is provided at a position where the wafer is placed so that the wafer is located concentrically from the center of the susceptor. Further, the orientations of the supply ports of the source gas supply means and the carrier gas supply means are fixed so that the supplied source gas and carrier gas flow horizontally in the chamber.

  Next, the prepared 6-inch wafer was placed on a susceptor. Then, the inside of the chamber is heated to 1000 to 1200 ° C., the first axis of the susceptor on which the wafer is placed is rotated clockwise at a speed of 15 rpm, and the second axis offset 50 mm from the first axis is rotated at a speed of 8 rpm. The raw material gases trichlorosilane and hydrogen are supplied at a rate of 10 slm and 50 slm so as to flow horizontally in the chamber in that state, and the thickness of the wafer becomes 20 μm. Thus, an epitaxial layer was formed to obtain an epitaxial wafer.

<Comparative Example 1>
Using a conventional single wafer epitaxial apparatus provided with a susceptor that rotates about the first axis in a horizontal state, the first axis of the susceptor on which the wafer is placed is rotated in a horizontal state clockwise at a speed of 15 rpm. Except for the above, an epitaxial layer was formed in the same manner as in Example 1 to obtain an epitaxial wafer. That is, the used single-wafer epitaxial apparatus does not include the second axis biased to the first axis.

<Comparison test 1>
For the epitaxial wafers obtained in Example 1 and Comparative Example 1, the thickness of the epitaxial layer was measured by FTIR (Fourier transform infrared spectroscopy). The results are shown in FIGS. 3 and 4, respectively. The vertical axis in FIGS. 3 and 4 is expressed as a ratio when the desired epitaxial layer thickness of 20 μm is 1.000.

  As is clear from FIG. 4, in the epitaxial wafer of Comparative Example 1, the film thickness is within the range of 1.005 to 1.015 and greater than the desired thickness at a distance of 15 mm from the wafer center, and the thickness is inclined. The difference was getting bigger. At a distance of 15 mm to 55 mm, the film thickness was in the range of 0.995 to 1.005 and almost desired, but when the film thickness exceeded 55 to 60 mm, 0.990 to 0.995. And within a range of less than the desired thickness, and the thickness decreased rapidly. The distribution from the wafer center to one outer periphery and the distribution from the wafer center to the other outer periphery show similar curves, and thus it was confirmed that uneven growth occurred at each rotation radius.

  On the other hand, as is clear from FIG. 3, in the epitaxial wafer of Example 1, the film thickness from the wafer center to the outer periphery is in the range of 0.995 to 1.005, and the thickness is extremely large from the wafer center to the outer periphery. There was no change in thickness, and the change in thickness was gentle.

  From the above, it was confirmed that the manufacturing method of the present invention is effective in improving the thickness distribution uniformity of the epitaxial wafer.

Claims (4)

A single semiconductor wafer is horizontally placed on a susceptor that rotates in a horizontal state provided in a chamber, and a source gas is supplied so as to flow in the horizontal direction while rotating the susceptor, In the method of manufacturing an epitaxial wafer using a single wafer type epitaxial apparatus for forming an epitaxial layer on the surface of the wafer placed as described above,
An epitaxial wafer manufacturing method, wherein the susceptor revolves while rotating in a horizontal state.   The method for producing an epitaxial wafer according to claim 1, wherein the revolution radius is 10 to 50% of the wafer diameter.   The method for producing an epitaxial wafer according to claim 1, wherein the rotation speed is 10 to 40 rpm and the revolution speed is 5 to 40 rpm.   The method for manufacturing an epitaxial wafer according to claim 1, wherein the revolution is a circular orbit.