JP2011077476A - Susceptor for epitaxial growth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a susceptor for epitaxial growth capable of manufacturing an epitaxial wafer having small variance in resistance resulting from automatic doping of an epitaxial layer during vapor-phase growth. <P>SOLUTION: A plurality of spot facings of the susceptor are each a two-staged spot facing having a first spot facing 13 having a diameter large enough to mount and store a semiconductor wafer 21 at a bottom surface part, and a second spot facing 14 having a larger diameter than the first spot facing 13, being concentric with the first spot facing 13, and having a bottom surface part 14a formed at a position above the bottom surface part 13a of the first spot facing 13, proximity parts of adjacent spot facings being formed of only a side face part 13b of the first spot facing and the bottom surface part 14a of the second spot facing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a susceptor for holding a wafer horizontally when an epitaxial layer is vapor-phase grown on the surface of a semiconductor wafer using a vapor phase growth apparatus. More particularly, the present invention relates to an epitaxial growth susceptor that can produce an epitaxial wafer with less resistance variation due to auto-doping of an epitaxial layer during vapor phase growth.

  Epitaxial wafers are used for manufacturing integrated circuits such as bipolar transistors and MOSLSIs. In manufacturing an epitaxial wafer, it is important that the epitaxial layer is uniformly grown to a predetermined thickness and the resistivity is uniform. There are vertical (batch type), barrel type, single wafer type reaction apparatuses, etc., as apparatuses used for manufacturing epitaxial wafers. For example, in a vertical type (batch type) apparatus, a semiconductor wafer is placed on a susceptor, this is held horizontally and heated, and a source gas is supplied to deposit an epitaxial layer on the upper main surface of the semiconductor wafer. It is formed by.

  As shown in FIG. 6, the susceptor 51 is provided with a plurality of counterbore 52 on which the semiconductor wafer 21 is placed. When the semiconductor wafer 21 placed on the counterbore 52 is transported from the reaction apparatus, it is necessary to avoid contact between the hand transporting the wafer 21 and the epitaxial layer 21a. Therefore, the counterbore 52 is composed of a bottom surface portion 53a and a side surface portion 53b on which the semiconductor wafer 21 is placed during the epitaxial growth, and the first counterbore 53 corresponding to the outer diameter of the semiconductor wafer 21 is shown in FIG. And a stepped portion having a second counterbore 54 composed of a bottom surface portion 54a and a side surface portion 54b having a diameter larger than that of the first counterbore 53 (see Patent Document 1).

JP-T-2005-505134 (paragraph [0056], paragraph [0057], FIG. 7 and FIG. 8)

  However, in the susceptor 11 formed in such a step, the second counterbore 54 has a wall portion formed by the upper surface of the susceptor 11 main body and the side surface portion 54b of the second counterbore 54 at a location where adjacent counterbore are adjacent to each other. There is a pocket between the counterbore 54 and the semiconductor wafer 21 where the source gas tends to stay. For this reason, a large amount of dopant diffuses in the edge portion of the epitaxial layer 12b in the semiconductor wafer 21 due to the influence of the source gas in which the dopant released from the side surface of the semiconductor wafer 21 stays in this pocket. By such auto-doping at the edge portion of the epitaxial layer 12b, the grown epitaxial layer 12b can be formed such that the resistivity of the edge portion becomes smaller than the resistivity of the epitaxial layer other than the edge portion, and the resistivity becomes uniform. The problem that it is not possible arises.

  An object of the present invention is to provide an epitaxial growth susceptor capable of producing an epitaxial wafer with less resistance variation due to auto-doping at the edge of the epitaxial layer during vapor phase growth.

  According to a first aspect of the present invention, a plurality of counterbore having the same diameter is formed on the upper surface of a disc-shaped susceptor body, and each center of the plurality of counterbore has a predetermined radius from the center of the susceptor body. A first counterbore having a diameter that can be accommodated by placing a semiconductor wafer on the bottom surface, the first counterbore being formed so that adjacent counterbore are adjacent to each other on the same circumference. A susceptor for epitaxial growth which is a two-stage counterbore having a second counterbore having a diameter larger than the counterbore and concentric with the first counterbore and having a bottom face formed at a position higher than the bottom face of the first counterbore, The adjacent portion between adjacent counterbore is formed by only the side surface portion of the first counterbore and the bottom surface portion of the second counterbore.

  The second aspect of the present invention is an invention based on the first aspect, and further, the upper main surface of the semiconductor wafer placed and accommodated on the bottom surface portion of the first counterbore is lower than the upper surface of the susceptor body without the counterbore. A counterbore is formed so as to be in a position.

  A third aspect of the present invention is an invention based on the first or second aspect, and is characterized in that the width of the second counterbore bottom surface portion in the proximity direction in the proximity portion is 1 to 4 mm.

  A fourth aspect of the present invention is an invention based on the first to third aspects, and is further located at a height between the upper main surface of the semiconductor wafer accommodated by the upper surface of the first counterbore and the wafer thickness center. It is characterized by doing.

  A fifth aspect of the present invention is an invention based on the first to fourth aspects, wherein b / a is 0, where a is the radius of the susceptor and b is the distance to the center of the adjacent portion in the susceptor radial direction. .45 to 0.7.

  In the susceptor for epitaxial growth according to the first aspect of the present invention, a plurality of counterbore having the same diameter is formed on the upper surface of a disc-shaped susceptor body, and the centers of the plurality of counterbore have a predetermined length from the center of the susceptor body. The epitaxial growth susceptor is formed on the same circumference of the circle and is formed so that adjacent counterbores are close to each other. Each of the plurality of counterbores has a first counterbore having a diameter capable of accommodating the semiconductor wafer placed on the bottom surface portion, a diameter larger than the first counterbore, and concentric with the first counterbore. It is a two-stage counterbore having a second counterbore having a bottom face formed at a position higher than the bottom face of the counterbore. Adjacent portions of adjacent counterbore are formed only by the side surface portion of the first counterbore and the bottom surface portion of the second counterbore. In this way, the adjacent portion between the adjacent counterbore is configured by only the side surface portion of the first counterbore and the bottom surface portion of the second counterbore. It is difficult for the raw material gas to stay between the semiconductor wafer and the semiconductor wafer. Thereby, the dispersion | variation in the resistance of an epitaxial layer by the auto dope from the side surface of a semiconductor wafer can be suppressed.

It is a top view showing the susceptor of this invention. It is the sectional view on the AA line of FIG. It is explanatory drawing which shows the distance to the X-axis direction and Y-axis direction from a wafer center. It is the figure showing resistance value distribution in the X-axis direction in the epitaxial layer of the epitaxial wafer formed using the susceptor of this invention. It is the figure showing resistance value distribution in the Y-axis direction in the epitaxial layer of the epitaxial wafer formed using the susceptor of this invention. It is a top view showing the conventional susceptor. It is the BB sectional view taken on the line of FIG. It is the figure showing resistance value distribution in the X-axis direction in the epitaxial layer of the epitaxial wafer formed using the conventional susceptor. It is the figure showing resistance value distribution in the Y-axis direction in the epitaxial layer of the epitaxial wafer formed using the conventional susceptor.

  Next, an embodiment for carrying out the present invention will be described based on the drawings. A vapor phase growth apparatus used for manufacturing an epitaxial wafer is a vertical type vapor phase growth apparatus called a mini batch furnace capable of epitaxially growing a plurality of semiconductor wafers simultaneously. This vertical vapor phase growth apparatus includes a box-shaped chamber, a susceptor capable of mounting a plurality of wafers substantially horizontally, source gas supply means for supplying source gas into the chamber, and carrier gas in the chamber. A carrier gas supply means for supplying to the chamber and a heating means for heating the inside of the chamber.

  In the susceptor of the present invention installed in this apparatus, a plurality of counterbore 12 having the same diameter is formed on the upper surface of the disc-shaped susceptor 11 main body as shown in FIG. 1 or FIG. The number of counterbore is preferably 5 to 10 per susceptor 11 main body, more preferably 9 pieces.

  The plurality of counterbore 12 is formed such that each center of the plurality of counterbore 12 is on the same circumference of a circle having a predetermined length as a radius from the center of the susceptor 11 main body, and adjacent counterbore 12 are close to each other. . Specifically, each of the second counterbore 14 of adjacent counterbore 12 described later is in contact with each other so as to overlap each other, and each first counterbore is formed so as to be close to each other. Each of the plurality of counterbore 12 is a two-stage counterbore composed of a first counterbore 13 and a second counterbore 14. The first counterbore 13 has a diameter that can be accommodated by placing the semiconductor wafer 21 on the bottom surface, and includes a bottom surface portion 13a and a side surface portion 13b. The second counterbore 14 has a larger diameter than the first counterbore 13 and is concentric with the first counterbore 13. Moreover, it has the bottom face part 14a in the position higher than the bottom face part 13a of the 1 counterbore 13, and is comprised from the bottom face part 14a and the side part 14b. And the characteristic structure of this invention exists in the adjacent part of these counterbore 12 formed only in the side part 13b of the 1st counterbore, and the bottom face part 14a of the 2nd counterbore. More specifically, the “proximity portion” defined in the present invention is the same as shown in FIG. 2 while the outer peripheral portion of the second counterbore 14 disappears at the portion of the adjacent counterbore 12 as shown in FIG. In addition, the side face 14b of the second counterbore 14 does not exist, and the bottom face parts 14a of the adjacent second counterbore 14 are configured to overlap each other, and the side face 13b of the first counterbore 13 and the second The part formed only by the bottom face part 14a of the counterbore 14 is meant.

  In the conventional susceptor 51 shown in FIG. 6 or FIG. 7, as described above, the wall portion formed by the upper surface of the susceptor 51 main body and the side surface portion 54 b of the second counterbore 54 exists between the adjacent counterbore 52, thereby There is a space where the source gas tends to stay between the second counterbore 54 and the semiconductor wafer 21 with respect to the gas flow. On the other hand, in the susceptor 11 of the present invention shown in FIG. 1 or FIG. 2, the adjacent portion where the adjacent counterbore 12 overlaps each other is configured as described above, and therefore there is no space portion in which the source gas tends to stay. Thereby, during the epitaxial growth, the source gas flows smoothly, autodoping from the side surface of the semiconductor wafer 21 can be suppressed, and variations in the resistivity of the epitaxial layer can be suppressed.

  In the susceptor 11 of the present invention, the counterbore 12 is formed so that the upper main surface of the accommodated semiconductor wafer 21 is positioned lower than the upper surface of the susceptor 11 main body without the counterbore. By forming in this way, it can suppress that source gas mainly contacts a wafer outer peripheral part, and can achieve the uniform thickness of the epitaxial layer in a wafer surface. Moreover, it is preferable that the width | variety of the 2nd counterbore 14 bottom face part of the proximity | contact direction in a proximity | contact part, ie, the width of the side wall which divides two adjacent 1 counterbore 13 in FIG. If the thickness is less than 1 mm, the strength of the side wall becomes too weak, and the side wall may be lost when the wafer transfer jig contacts the side wall. On the other hand, if the width of the side wall is too wide, the interval between the counterbore 12 becomes wide, and the number of counterbore that can be arranged in the susceptor decreases.

  The top surface of the first counterbore 13, that is, the bottom surface of the second counterbore, is located between the upper main surface of the accommodated semiconductor wafer 21 and the center of the wafer thickness so that the semiconductor wafer 21 placed does not jump out of the counterbore 12 during the epitaxial growth process. It is preferable to be configured to be located at a height of. Further, in order to heat the semiconductor wafer 21 uniformly, the counterbore 12 is preferably arranged closer to the center of the susceptor. The radius of the susceptor 11 is a, and the distance to the center of the adjacent portion in the radial direction of the susceptor 11 is b. The counterbore 12 is preferably arranged so that b / a is 0.45 to 0.7. When b / a is less than the lower limit value, the number of counterbore that can be arranged in the susceptor is reduced, and the mass productivity of the epitaxial wafer is deteriorated. On the other hand, if b / a exceeds the upper limit value, the counterbore 12 is arranged from the outer periphery of the susceptor, so that the wafer 21 cannot be heated uniformly during epitaxial growth, and the film thickness distribution of the formed epitaxial layer Variations and slipping are likely to occur.

Next, an epitaxial wafer manufacturing method using a vapor phase growth apparatus equipped with the susceptor of the present invention will be described. A source gas is supplied into the chamber from the source gas supply means provided in the vapor phase growth apparatus, and a carrier gas is supplied into the chamber from the carrier gas supply means. 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.

  In the epitaxial wafer manufacturing method using this apparatus, first, a plurality of semiconductor wafers 21 are respectively placed on the susceptor 11. Examples of the semiconductor wafer 21 include a silicon wafer, a GaSb wafer, a GaAs wafer, an InP wafer, a ZnS wafer, and a ZnSe wafer. Here, a plurality of wafers 21 are placed on the susceptor 11 such that the flat edge of the orientation flat of the wafer 21 is directed radially from the center of the susceptor 11. Next, the inside of the chamber is heated to a temperature range of 1000 to 1200 ° C. suitable for epitaxial growth. Next, the susceptor 11 on which the wafer 21 is placed is rotated in a horizontal state clockwise at a speed of 4 to 20 rpm. The supply ratio of the source gas and the carrier gas is preferably 10:90 to 30:70.

  In this state, the source gas and the carrier gas are supplied at a constant rate so as to flow in the horizontal direction in the chamber, and an epitaxial layer is formed on the surface of the wafer 21 until a predetermined film thickness is obtained. As a result, as shown in FIG. 2, the wafer 21 becomes a wafer 21 on which a substrate 21b, an oxide film 21c formed in advance on the back surface of the substrate 21b, and an epitaxial layer 21a formed by epitaxial growth are formed.

  Here, FIG. 1 shows the flow of the source gas during the epitaxial growth seen from the upper surface of the susceptor 11 when the susceptor 11 of the present invention is used. Moreover, the gas flow seen from the AA line cross section in FIG. 1 is shown in FIG.

  On the other hand, FIG. 6 shows the flow of the raw material gas seen from the upper surface of the susceptor when the conventional susceptor is used, and FIG. 7 shows the gas flow seen from the cross section taken along the line BB in FIG. As shown in FIG. 7, when the conventional susceptor 51 is used, the retention of the source gas occurs between the second counterbore 54 and the semiconductor wafer 21, and this retention causes the side surface of the semiconductor wafer 21. Due to autodoping, the resistance in the vicinity of the edge of the epitaxial layer is lowered, resulting in variation in resistance. On the other hand, as shown in FIG. 2, when the susceptor 11 of the present invention is used, the adjacent portion of the adjacent counterbore 12 is composed only of the side surface portion 13b of the first counterbore and the bottom surface portion 14a of the second counterbore. In the vicinity of the matching counterbore 12, the source gas hardly accumulates between the second counterbore 14 and the semiconductor wafer 21, and the source gas flows smoothly. For this reason, variation in resistance of the epitaxial layer due to auto-doping from the side surface of the semiconductor wafer 21 can be suppressed.

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

<Example 1>
An epitaxial layer was formed on a silicon wafer having an oxide film on the back surface by using a vertical type vapor phase growth apparatus equipped with the susceptor of the present invention to obtain an epitaxial wafer. As shown in FIG. 1 or 2, the susceptor includes nine counterbore 12 in which the adjacent portions of the adjacent counterbore 12 are formed only by the side surface portion 13 b of the first counterbore and the bottom surface portion 14 a of the second counterbore. The width of the second counterbore bottom surface portion 14a in the proximity direction in the proximity portion is 2 mm, the radius a of the susceptor 11 is 317.5 mm, and the distance b from the center of the susceptor 11 to the center of the proximity portion in the radial direction of the susceptor 11 is 212 mm It was used. That is, a material having a b / a of about 0.67 was used.

  Specifically, first, a plurality of wafers were respectively placed on the susceptor so that the flat edge of the orientation flat of the wafer was directed radially from the susceptor center. Next, the inside of the chamber was heated to a temperature range of 1100 ° C. Next, the material gas is supplied from the source gas supply means into the source gas chamber, the carrier gas is supplied from the carrier gas supply means, and the susceptor on which the wafer is placed in the chamber is placed clockwise at a speed of 8 rpm. Rotated horizontally. At this time, the supply ratio of the source gas and the carrier gas was 20:80.

  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. Obtained.

<Comparative Example 1>
An epitaxial layer is formed on a silicon wafer having the same quality and the same dimensions as those of the silicon wafer of the first embodiment having an oxide film on the back surface in the same manner as in the first embodiment except that a vertical type vapor phase growth apparatus having a conventional susceptor is used. An epitaxial wafer was obtained. As the susceptor, the conventional susceptor shown in FIG. 2 having eight counterbore 52, the radius of the susceptor 51 is 317 mm, and the distance from the center of the susceptor 51 to the center of the counterbore 52 is 205 mm.

<Comparison test and evaluation>
For the epitaxial wafer obtained in Example 1, the resistance value distribution in the plane of the epitaxial layer was measured. Specifically, the surface of the epitaxial layer was taken in the X-axis direction and the Y-axis direction as shown in FIG. 3, and the resistance value distribution at this time was measured. These results are shown in FIGS. 4 and 5, respectively.

  Moreover, the resistance value distribution in the plane of the epitaxial layer was measured for the epitaxial wafer obtained in Comparative Example 1. Specifically, the surface of the epitaxial layer was taken in the X-axis direction and the Y-axis direction as shown in FIG. 3, and the resistance value distribution at this time was measured. These results are shown in FIGS. 8 and 9, respectively.

  4, 5, 8, and 9, the resistance value distribution on the surface of the epitaxial layer of the epitaxial wafer of Example 1 is particularly in the X-axis direction compared to the resistance value distribution of Comparative Example 1. It was confirmed that the variation in resistance value was greatly improved.

11 Susceptor 12 Counterbore 13 First Counterbore 13a Bottom Face 13b Side Face 14 Second Counterbore 14a Bottom Face 14b Side Face 21 Semiconductor Wafer

Claims (5)

A plurality of counterbore having the same diameter is formed on the upper surface of the disc-shaped susceptor body, and the centers of the plurality of counterbore are on the same circumference of a circle having a predetermined length from the center of the susceptor body, Adjacent counterbores are formed so as to be close to each other, and each of the plurality of counterbore has a first counterbore having a diameter that can be accommodated by placing a semiconductor wafer on a bottom surface portion, and a larger diameter than the first counterbore. A susceptor for epitaxial growth, which is a two-stage counterbore having a second counterbore having a diameter and concentric with the first counterbore and having a bottom face formed at a position higher than the bottom face of the first counterbore,
An epitaxial growth susceptor, wherein adjacent portions of adjacent counterbore are formed only by a side surface portion of a first counterbore and a bottom surface portion of a second counterbore.   2. The susceptor for epitaxial growth according to claim 1, wherein a counterbore is formed such that an upper main surface of a semiconductor wafer placed and accommodated on a bottom surface portion of the first counterbore is positioned lower than an upper surface of the susceptor body having no counterbore.   The susceptor for epitaxial growth according to claim 1 or 2, wherein a width of the second counterbore bottom portion in the proximity direction in the proximity portion is 1 to 4 mm.   4. The susceptor for epitaxial growth according to claim 1, wherein the upper surface of the first counterbore is located at a height between the upper main surface of the semiconductor wafer accommodated and the thickness center of the wafer.   The susceptor for epitaxial growth according to any one of claims 1 to 4, wherein b / a is 0.45 to 0.7, where a is the radius of the susceptor and b is the distance to the center of the adjacent portion in the radial direction of the susceptor. .

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