JP2010016183A - Vapor-deposition growth device, and method of manufacturing epitaxial wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vapor-deposition growth device capable of preventing the formation of an epitaxial film to the outer circumferential marginal part of the backside of a semiconductor wafer when growing the epitaxial film on the surface of the semiconductor wafer by a vapor-deposition growth device, and to provide a method of manufacturing the epitaxial wafer for forming the epitaxial film to the semiconductor wafer with the use of the vapor-deposition growth device. <P>SOLUTION: A wafer supporting surface 32 formed to a wafer pocket 31 of a susceptor 10 has a surface roughness of 0.1-3.0 μm and a flatness of 10 to 120 μm, and descends in an angle range of 2.86-0.40° to the holizontal plane towards a center of the wafer pocket. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a susceptor that supports a semiconductor wafer in a vapor phase growth apparatus, and a method for manufacturing an epitaxial wafer using the susceptor.

  As a vapor phase growth apparatus for growing a high quality epitaxial film on the surface of a semiconductor wafer, a single wafer type vapor phase growth apparatus is known. A single wafer type vapor phase growth apparatus includes a disk-shaped susceptor in a heat-resistant chamber. While the semiconductor wafer is placed on the susceptor, various source gases are flowed into the chamber while heating the semiconductor wafer. Then, an epitaxial film is grown on the wafer surface by reacting the semiconductor wafer with the source gas.

  The susceptor that supports the semiconductor wafer in the chamber is a substantially disk-shaped or dish-shaped holder that is larger than the semiconductor wafer to be supported. This susceptor is formed with a recess (dent) called a wafer pocket having a depth of about several hundred μm to several mm for receiving a semiconductor wafer. A horizontal substantially ring-shaped wafer support surface that supports the semiconductor wafer is formed in the wafer pocket in contact with the outer peripheral edge of the back surface of the semiconductor wafer.

  By the way, in recent years, with the high integration of semiconductor devices and the ultra-fine line width, the required quality, particularly the in-plane flatness, of the semiconductor wafer as the substrate is becoming more strict. In conventional semiconductor devices, epitaxial wafers that can greatly reduce particles or crystal defects (such as COP) on the substrate surface or surface layer that adversely affect characteristics are often used.

  An epitaxial wafer is formed by epitaxial growth on the surface of a semiconductor wafer manufactured through a slicing process for cutting a wafer from a semiconductor ingot, a grinding process for flattening the wafer surface, a polishing process for mirroring the wafer surface, etc. It is manufactured by doing.

  Quality characteristics required for such an epitaxial wafer include reduction of particles or crystal defects, uniformity of the thickness of the epitaxial film, uniformity of the resistivity of the epitaxial film, and the like. Of these, in particular, in-plane uniformity of the resistivity of the epitaxial film, in order to improve the yield (chip yield) of semiconductor devices, circuits are being formed up to the wafer outer peripheral region. In-plane uniformity of resistivity is required from the periphery, which is the limit of measurable positions in a typical measuring instrument, to about 2 mm.

  In a highly integrated semiconductor device (VSLI), a MOS-based semiconductor device is frequently used. A p / p + (+) epitaxial layer in which an epitaxial film having a lower concentration than that of this substrate is grown on a substrate doped with boron at a high concentration. Wafers are mainstream. In this p / p + (+) epitaxial wafer, the phenomenon in which boron atoms doped in the substrate during the formation of the epitaxial film move to the epitaxial film, so-called auto-doping, is suppressed. This is important in achieving in-plane uniformity.

  In order to suppress this auto-doping, for example, a susceptor for a vapor phase growth apparatus in which a fluid passage is formed in a wafer pocket is known (for example, Patent Document 1).

Further, in the semiconductor device considered the most advanced (design rule 45 nm) and the next-generation device (from 22 nm), the epitaxial wafer represented by flatness is required to be dramatically flattened. In addition to improving the in-plane uniformity of the film thickness of the conventional epitaxial film, this also makes the film thickness uniform from the flatness on the back side of the epitaxial wafer, especially to the outermost peripheral area of the epitaxial wafer, for example, about 2 mm from the periphery. There is a need to do.
International Publication WO2005 / 111266 Publication

  However, conventionally, when an epitaxial film is grown on a semiconductor wafer in a vapor phase growth apparatus, a part of the growth gas for the epitaxial film wraps around the back side of the semiconductor wafer, and the peripheral edge on the back side of the semiconductor wafer. This causes a problem that an epitaxial film grows on the portion (hereinafter referred to as “rear surface deposition”). When backside deposition occurs, the film thickness of the peripheral portion becomes particularly large on the backside of the semiconductor wafer, and the in-plane uniformity of the thickness of the semiconductor wafer is greatly deteriorated. As a result, the yield is reduced when the semiconductor device is formed.

  As a cause of the occurrence of such a backside deposit, in a susceptor that accepts a semiconductor wafer in an epitaxial film growth process, a substantially ring-shaped wafer support surface that is in contact with the outer peripheral edge of the backside of the semiconductor wafer and the backside of the semiconductor wafer. The cause is that the growth gas for the epitaxial film enters from a slight gap. This gap is considered to be generated when the surface roughness of the wafer support surface is large or the flatness of the wafer support surface is low (the variation in the height position is large) as will be described later.

FIG. 11 is a cross-sectional view for explaining the occurrence of rear surface deposition due to warping of a semiconductor wafer.
As shown in FIG. 11 (a), the semiconductor wafer W that has been horizontal before the epitaxial film formation is warped as shown in FIG. 11 (b) due to its own weight and a temperature rise in the epitaxial film formation process. It becomes a state. The inner peripheral edge SE of the wafer support surface S1 at the edge of the wafer pocket WP provided as a recess in the susceptor S contacts the lower surface of the semiconductor wafer W.

  On the other hand, since the semiconductor wafer becomes high temperature in the epitaxial film growth process, the semiconductor wafer supported by the susceptor at the outer peripheral edge is warped, that is, curved so that the height of the central portion is lowered. . For this reason, the inner edge part (edge) of the wafer support surface in a susceptor hits a semiconductor wafer, and there also existed a subject that a ring-shaped contact damage | wound produced in the outer peripheral part of a semiconductor wafer.

  At the same time, as shown in FIG. 11B, the edge SE of the wafer support surface S1 comes into contact with the semiconductor wafer W due to the warp of the semiconductor wafer W during film formation of the epitaxial film, so that the semiconductor wafer W is at the outermost peripheral portion of the wafer. However, it is supported at the edge SE position on the inner side. For this reason, the back surface of the wafer is lifted outside the position of the edge SE, and there is a problem that the deposition gas enters the gap SS as indicated by the arrow G and the back surface deposition occurs.

  The present invention has been made in view of the above circumstances, and when the epitaxial film is grown on the surface of the semiconductor wafer, the epitaxial film can be prevented from being formed on the outer peripheral edge of the back surface of the semiconductor wafer, An object of the present invention is to provide a vapor phase growth apparatus capable of preventing the occurrence of contact scratches on the back surface of a semiconductor wafer and an epitaxial wafer manufacturing method for growing an epitaxial film on a semiconductor wafer using the vapor phase growth apparatus.

The vapor phase growth apparatus of the present invention is a vapor phase growth apparatus for forming a film on the surface of a semiconductor wafer,
A vapor phase growth apparatus susceptor having a wafer pocket for receiving the semiconductor wafer;
The peripheral edge of the wafer pocket is provided with a substantially ring-shaped wafer support surface that supports the semiconductor wafer in contact with the outer peripheral edge of the semiconductor wafer back side and the entire periphery thereof,
The said wafer support surface solved the said subject by inclining so that it may fall in the angle range of 2.86 degrees-0.40 degrees with respect to a horizontal surface toward the center of the said wafer pocket.
The wafer support surface of the present invention may have a surface roughness in the range of Ra 0.1 μm to 3.0 μm.
The wafer support surface of the present invention may have a flatness in the range of 10 to 120 μm.
The wafer support surface of the present invention may be provided as a range of 1 to 11 mm in the radial direction of the wafer pocket.
In the wafer pocket of the present invention, one open end of a fluid passage connected to the outside of the wafer pocket may be formed at a position inside the wafer support surface when the semiconductor wafer is received.
An epitaxial wafer manufacturing method of the present invention is an epitaxial wafer manufacturing method using a susceptor for a vapor phase growth apparatus in which a wafer pocket for receiving a semiconductor wafer is formed in a vapor phase growth apparatus,
The wafer pocket is provided with a substantially ring-shaped wafer support surface that contacts the outer peripheral edge of the back surface of the semiconductor wafer and supports the semiconductor wafer,
The wafer support surface has a surface roughness of 0.1 μm to 3.0 μm, a flatness of 10 μm to 120 μm, and is 2.86 ° to 0.40 ° with respect to a horizontal plane toward the center of the wafer pocket. An epitaxial growth layer can be formed on one surface of a semiconductor wafer by using a susceptor for a vapor phase growth apparatus that is inclined so as to be lowered in the angle range.

  The susceptor for a vapor phase growth apparatus of the present invention is a susceptor for a vapor phase growth apparatus in which a wafer pocket for receiving a semiconductor wafer is formed in the vapor phase growth apparatus, wherein the wafer pocket is an outer peripheral edge of the back surface of the semiconductor wafer. And a substantially ring-shaped wafer support surface for supporting the semiconductor wafer, wherein the wafer support surface has a surface roughness of 0.1 μm to 3.0 μm, a flatness of 10 to 120 μm, and The wafer pocket is inclined so as to fall in an angle range of 2.86 ° to 0.40 ° with respect to a horizontal plane toward the center of the wafer pocket.

According to such a susceptor for a vapor phase growth apparatus, a gap at the contact portion between the wafer support surface and the back surface of the semiconductor wafer can be substantially eliminated. In other words, by setting the surface roughness of the wafer support surface to 0.1 μm to 3.0 μm or less, there is almost no gap at the contact portion between the wafer support surface and the back surface of the wafer when the wafer is placed. To do. Thereby, the reactive gas does not flow into the back side of the wafer, and it is possible to reliably prevent an unnecessary epitaxial growth layer from being formed on the outer peripheral edge of the back side of the wafer.
At the same time, by setting the flatness of the wafer support surface within the above range, when the wafer is placed, the wafer support surface and the back surface of the wafer are in close contact with each other with almost no gap. Thereby, the reactive gas does not flow into the back side of the wafer, and it is possible to reliably prevent an unnecessary epitaxial growth layer from being formed on the outer peripheral edge of the back side of the wafer.

FIG. 10 is a view for explaining the flatness of the wafer support surface, and consists of a sectional view (a) and a plan view (b). In the figure, symbol S indicates a susceptor, and S1 indicates a wafer support surface.
The susceptor S having a circular shape in plan view is provided with a ring-shaped wafer support surface S1 around the recess, and the distance from the center of the susceptor is a predetermined value and the center angle is, for example, 10 ° on the wafer support surface S1. Thus, the measurement point SP is set, the height ST at the measurement point SP is measured, and the difference between the maximum value and the minimum value of the height ST is defined as the flatness of the wafer support surface S1.
In other words, as shown in FIG. 10, the flatness of the wafer support surface S1 is a variation degree (a constant high) of how much the height ST of the wafer support surface S1 around the susceptor S varies over the entire circumference. The low flatness means that the variation value of the height ST is large, and the high flatness means that the variation value of the height ST is small. .

  Further, since the wafer support surface is inclined so as to be lowered toward the center of the wafer pocket in an angle range of 2.86 ° to 0.40 ° with respect to the horizontal plane, the center of the wafer is lowered due to its own weight and thermal deformation. Even if it is curved like this, the edge (edge) of the wafer support surface does not contact the back surface of the wafer. As a result, it is possible to reliably prevent ring-shaped contact flaws caused by contact with the wafer support surface at the outer peripheral edge of the wafer.

  At the same time, as shown in FIG. 11B, when the wafer support surface S1 is horizontal, warpage occurs in the semiconductor wafer W during the formation of the epitaxial film, and the edge SE of the wafer support surface S1 becomes the semiconductor wafer W. Since the semiconductor wafer W is abutted and supported not at the outermost peripheral portion of the wafer but at the edge SE position inside the wafer, the wafer back surface is lifted outside the edge SE position, and the film forming gas is indicated by an arrow G. It is possible to solve the problem that the rear surface deposit occurs by entering the gap SS.

  The wafer support surface of the present invention can be provided in the range of 1 to 11 mm in the radial direction of the wafer pocket, more preferably in the range of 5 to 10 mm, and further from the center of the wafer pocket. Can be set in a range of 144/150 to 155/150 with respect to the radius of the wafer, so that the wafer can be reliably supported.

  In the wafer pocket, it is preferable that one open end of a fluid passage connected to the outside of the wafer pocket is formed at a position inside the wafer support surface when the semiconductor wafer is received. Here, the inside of the wafer support surface means that when the semiconductor wafer is received in the wafer pocket, it opens to a space on the side isolated from the wafer surface side by contact between the wafer peripheral portion and the wafer support surface. To do.

  By forming such a fluid passage and sucking the reaction gas and the carrier gas from the fluid passage and flowing them outside the wafer pocket, the wafer support surface is set as described above, and thus the semiconductor wafer is placed on the outermost edge portion of the wafer. Since it is in a state where it can be supported so as to contact the wafer support surface, even if dopant is released from the back side of the wafer due to heating of the wafer, this dopant does not wrap around the front side of the wafer Therefore, the gas can be smoothly discharged from the lower surface side of the susceptor, thereby preventing the gas flow from the back surface of the wafer to the front surface, thereby preventing the occurrence of autodoping.

  The prevention of auto-doping is extremely effective in the case of a p / p + (+) epitaxial wafer, that is, when the substrate is p + type or p ++ type and the epitaxial film is p type.

Here, in order ¹⁰ 19 atoms / cm ³ impurity concentration than the p ++ type, the resistance value refers to one of the low resistance of about 1~10 (mΩ · cm), the impurity concentration of the p + type ¹⁰ 18 atoms / in cm ^3, the resistance value refers to one 10 to 100 of (mΩ · cm) as low resistance, an impurity concentration of the p type about ¹⁰ 15 atoms / cm ^3, the resistance value> 1 (Ω · cm ) Means high resistance.

The present invention also provides the following method for manufacturing an epitaxial wafer.
That is, the epitaxial wafer manufacturing method of the present invention is an epitaxial wafer manufacturing method using a susceptor for a vapor phase growth apparatus in which a wafer pocket for receiving a semiconductor wafer is formed in a vapor phase growth apparatus, wherein the wafer pocket is And a substantially ring-shaped wafer support surface that contacts the outer peripheral edge of the back surface of the semiconductor wafer and supports the semiconductor wafer. The wafer support surface has a surface roughness of 0.1 μm to 3.0 μm and a flatness of 10 Using a susceptor for a vapor phase growth apparatus that is in a range of ˜120 μm and is inclined so as to be lowered in an angle range of 2.86 ° to 0.40 ° with respect to a horizontal plane toward the center of the wafer pocket An epitaxial growth layer is formed on one surface of the semiconductor wafer.

  According to such an epitaxial wafer manufacturing method, the wafer support surface supporting the wafer is formed in the range of surface roughness of 0.1 μm to 3.0 μm and flatness of 10 to 120 μm during the formation of the epitaxial film. Therefore, it adheres without causing a gap in the contact portion with the back surface of the wafer. Thereby, it is possible to prevent the reaction gas from flowing into the back side of the wafer, to form an unnecessary epitaxial growth layer on the outer peripheral edge of the back side of the wafer, and to prevent the occurrence of autodoping.

  Further, since the wafer support surface is inclined in the angle range of 2.86 ° to 0.40 ° with respect to the horizontal plane so as to be lowered toward the center of the wafer pocket, the center of the wafer is lowered by its own weight and thermal deformation. Even if curved, the edge of the wafer support surface does not contact the back surface of the wafer.

  According to the vapor phase growth apparatus of the present invention, the gap at the contact portion between the wafer support surface and the back surface of the semiconductor wafer can be substantially eliminated. Since the wafer support surface of the susceptor in the conventional vapor phase growth apparatus has low surface roughness and flatness, many gaps are generated at the contact portion between the wafer support surface and the back surface of the wafer when the semiconductor wafer is placed. It was. If there is such a gap, the reactive gas flows from here to the back side of the semiconductor wafer, and an unnecessary epitaxial growth layer is formed on the outer peripheral edge of the back side of the wafer. As a result, the in-plane uniformity of the thickness of the semiconductor wafer is greatly reduced, and the yield is deteriorated when devices are formed.

  However, as in the present invention, by setting the surface roughness of the wafer support surface to 0.1 μm to 3.0 μm and the flatness in the range of 10 to 120 μm, the wafer support surface and the back surface of the wafer are placed when the wafer is placed. Close contact with the contact portion with almost no gap. Thereby, the reactive gas does not flow into the back side of the wafer, and it is possible to reliably prevent an unnecessary epitaxial growth layer from being formed on the outer peripheral edge of the back side of the wafer. As a result, the in-plane uniformity of the wafer thickness can be kept high, and the yield can be improved when devices are formed.

  Further, since the wafer support surface is inclined so as to be lowered toward the center of the wafer pocket in an angle range of 2.86 ° to 0.40 ° with respect to the horizontal plane, the center of the wafer is lowered due to its own weight and thermal deformation. Even if it is curved like this, the edge (edge) of the wafer support surface does not contact the back surface of the wafer. As a result, it is possible to reliably prevent ring-shaped contact flaws caused by contact with the wafer support surface at the outer peripheral edge of the wafer.

  According to the method for producing an epitaxial wafer of the present invention, the wafer support surface supporting the wafer is formed in the range of surface roughness of 0.1 μm to 3.0 μm and flatness of 10 to 120 μm during the formation of the epitaxial film. Therefore, it adheres without causing a gap in the contact portion with the back surface of the wafer. This prevents the reaction gas from flowing into the back side of the wafer and prevents unnecessary epitaxial growth layers from being formed on the outer peripheral edge of the back side of the wafer. Therefore, it is possible to obtain an epitaxial wafer in which the in-plane uniformity of thickness is kept high.

  Further, since the wafer support surface is inclined in the angle range of 2.86 ° to 0.40 ° with respect to the horizontal plane so as to be lowered toward the center of the wafer pocket, the center of the wafer is lowered by its own weight and thermal deformation. Even if curved, the edge of the wafer support surface does not contact the back surface of the wafer. As a result, an epitaxial wafer can be obtained in which the outer peripheral edge of the wafer is free from ring-like contact scratches due to contact with the wafer support surface.

  Hereinafter, the best mode of a vapor phase growth apparatus according to the present invention will be described with reference to the drawings. In addition, this embodiment is specifically described in order to make the gist of the invention better understood, and does not limit the present invention unless otherwise specified.

FIG. 1 is a schematic view showing a single wafer type vapor phase growth apparatus according to an embodiment of the present invention.
The vapor phase growth apparatus 1 includes a frame 5, and an upper dome 3 and a lower dome 4 that respectively cover one open end and the other open end of the frame 5. The frame 5, the upper dome 3, and the lower dome 4 define a sealed epitaxial film forming chamber (chamber) 2. The upper dome 3 and the lower dome 4 may be formed of a transparent material such as quartz glass.

  Outside the upper dome 3 and the lower dome 4, heating devices 6 a and 6 b for heating the wafer W accommodated in the formation chamber 2 through the upper dome 3 and the lower dome 4, respectively. The heating devices 6a and 6b may be anything that irradiates heat rays such as a halogen lamp.

  Near the center of the forming chamber 2, a susceptor 10 for placing the wafer W and a support arm 8 for supporting the susceptor 10 are provided. The support arm 8 is connected to a rotating shaft 7 that passes through the lower dome 4 and extends into the forming chamber 2, and can be rotated by the rotating shaft 7. The configuration of the susceptor 10 will be described in detail later.

  A flange portion (not shown) is provided on the peripheral surface of the frame 5 so as to divide the forming chamber 2 in the upper and lower portions along the entire circumference corresponding to the film forming position of the susceptor 10. The mouths 11 and 12 are formed. Gas discharge ports 13 and 14 are formed at positions facing the gas supply ports 11 and 12, respectively. The first gas supply port 11 includes, for example, a Si-containing gas such as monosilane, disilane, or trichlorosilane that is a film forming gas, a hydrogen gas that dilutes the Si-containing gas, and a dopant gas as necessary. A reaction gas (process gas) GR is supplied into the forming chamber 2. The reactive gas GR flows in the vicinity of the surface s of the wafer W, grows an epitaxial film on the surface s of the wafer W, and is discharged out of the formation chamber 2 from the first gas discharge port 13.

  On the other hand, from the second gas supply port 12, for example, a carrier gas GC such as hydrogen is supplied into the formation chamber 2. The carrier gas GC is introduced to the lower surface side of the susceptor 10 and flows in the vicinity of the rear surface b of the wafer W. Then, unnecessary dopant discharged from the back surface b of the wafer W is removed from the second gas discharge port 14 to the outside of the formation chamber 2 while being removed so as not to stay in the susceptor 10.

  FIG. 2A is an enlarged plan view of a main part when the susceptor in the vapor phase growth apparatus of the present invention is viewed from the upper dome side. FIG. 2B is an enlarged cross-sectional view of a main part when the susceptor in the vapor phase growth apparatus is viewed from the side. The susceptor 10 is a wafer holder on which a wafer W on which an epitaxial film is to be grown is placed, and the entire susceptor 10 is formed, for example, by applying a SiC coating to the surface of a carbon base material or by using SiC.

  The susceptor 10 has a wafer pocket 31 formed of a recess having a diameter larger than the outer diameter of the wafer W. Inside the wafer pocket 31, a substantially ring-shaped wafer support surface 32 for supporting the wafer W in contact with the outer peripheral edge portion on the back surface b side of the wafer W, and a bottom portion 33 more concave than the wafer support surface 32. Is formed.

The wafer support surface 32 is formed to have a surface roughness (Ra) of 0.1 μm to 3.0 μm, preferably 0.2 μm to 2 μm. The flatness is in the range of 10 to 120 μm, preferably 10 to 80 μm. The wafer support surface 32 is lowered toward the center of the wafer pocket 31 in an angle range θ of 2.86 ° to 0.40 °, preferably 1.43 ° to 0.57 ° with respect to the horizontal plane. It is inclined to.
Further, the wafer support surface 32 can be provided as a range of 1 to 11 mm in the radial direction of the wafer pocket 31, more preferably a range of 5 to 10 mm, and further from the center of the wafer pocket 31. Can be set in a range of 144/150 to 155/150 with respect to the radius of the semiconductor wafer W, whereby the semiconductor wafer W can be reliably supported.

  Here, the flatness of the wafer support surface 32 is an imaginary plane composed of a plurality of measurement points on concentric circles on the wafer support surface 32 using a contact-type three-dimensional measuring instrument, as in the example shown in FIG. And the amount of change (maximum value-minimum value) is shown. That is, it represents the amount of change in shape on the wafer support surface 32. The flatness measurement point of the wafer support surface 32 is 147/150 with respect to the wafer radius of the center of the wafer pocket 31, that is, at an intermediate position of the wafer support surface 32 in the radial direction of the wafer pocket 31. The position is set to 36, and there are 36 measurement points.

  By forming the wafer support surface 32 so that the surface roughness and flatness are in the ranges as described above, the gap at the contact portion between the wafer support surface 32 and the back surface b of the wafer W can be substantially eliminated. . For example, as shown in FIG. 3A, the wafer support surface 52 in the conventional susceptor 51 has low surface roughness and flatness, and therefore when the wafer W is placed, the wafer support surface 52 and the wafer W Many gaps U were generated at the contact portion with the back surface b.

  If there is such a gap U, the reactive gas GR flows from here to the back surface b side of the wafer W, and an unnecessary epitaxial growth layer 53 is formed on the outer peripheral edge of the back surface b side of the wafer W. As a result, the in-plane uniformity of the thickness of the wafer W is greatly reduced, and the yield is deteriorated when devices are formed.

  On the other hand, as shown in FIG. 3B, the susceptor 10 of the present invention has the wafer W placed thereon by setting the surface roughness of the wafer support surface 32 to 0.1 μm to 3.0 μm and the flatness of 120 μm or less. At this time, the contact portion between the wafer support surface 32 and the back surface b of the wafer W is in close contact with almost no gap U. Thereby, the reactive gas GR does not flow into the back surface b side of the wafer W, and it is possible to reliably prevent unnecessary epitaxial growth layers from being formed on the outer peripheral edge portion of the back surface b side of the wafer W. As a result, the in-plane uniformity of the thickness of the wafer W can be kept high, and the yield can be improved when devices are formed.

  Further, as shown in FIG. 4, the wafer support surface 32 is inclined so as to be lowered toward the center of the wafer pocket 31 in an angle range θ of 2.86 ° to 0.40 ° with respect to the horizontal plane. Even if the wafer W is bent so that its center is lowered due to its own weight and thermal deformation, the edge 32a of the wafer support surface 32 does not contact the back surface b of the wafer W. As a result, it is possible to reliably prevent ring-shaped contact flaws due to contact with the wafer support surface 32 at the outer peripheral edge of the wafer W.

  In order to form the wafer support surface 32 of the susceptor 10 in a range of surface roughness of 0.1 μm to 3.0 μm and flatness of 10 to 120 μm, mechanical polishing with a diamond tool, co-grinding with an SiC jig, and shot blasting are used. What is necessary is just to form by methods, such as SiC grain spraying.

The susceptor 10 is further preferably provided with an overall warpage amount of 0 to 0.2 mm.
FIG. 12 is an explanatory view showing the measurement of the amount of warpage of the susceptor, and is a sectional view (a) and a plan view (b).
As shown in FIG. 12, the amount of warpage is determined by using a contact-type three-dimensional measuring instrument or the like as a measurement point P as a plurality of concentric circles (8 on the center of the back surface of the susceptor 10 and at a radius R / 2). A virtual plane consisting of a plurality of (8 places) points on the outer edge and a concentric circle on the outer edge is calculated, and the amount of change (maximum value−minimum value) is shown. That is, it represents the amount of swell of the susceptor 10 as a whole.

  Referring to FIG. 2 again, in the wafer pocket 31, when the wafer W is received, one open end 35a of the fluid passage 35 connected to the outside of the wafer pocket 31 is provided at a position on the back surface b side of the wafer W. Is formed. The other open end 35 b of the fluid passage 35 is formed outside the susceptor 10.

  A plurality of fluid passages 35 may be formed in the circumferential direction of the susceptor 10. A carrier gas flows through the fluid passage 35 during vapor phase growth of the wafer W. Thereby, even if the dopant is released from the back surface b of the wafer W due to the heating of the wafer W, the dopant passes from the lower surface of the susceptor 10, that is, through the fluid passage 35 a without being circulated to the front surface s side of the wafer W. Then, it can be discharged from the fluid outlet 35b.

  The fluid passage 35 is not limited to the form shown in FIG. FIG. 5 shows various forms of fluid passages formed in the susceptor 101. FIG. The fluid passage 105 shown in FIG. 5A is configured such that one end 105 a opens into the wafer pocket 103 a and the other end 105 b opens into the side surface 106 of the susceptor 101. According to the fluid passage 105 of this example, it is possible to further prevent the radiant heat from the heating device from being directly applied to the back surface of the wafer W.

  The fluid passage 105 shown in FIG. 5B is configured such that one end 105a opens to the wafer pocket 103a and the other end 105b opens to the back surface 104 of the susceptor 101 and outside the vertical wall surface of the wafer pocket 103a. The shape of the fluid passage 105 is not a straight line but a refracted non-linear shape. Therefore, although the radiant heat from the heating device enters partway through the fluid passage 105, the radiant heat is shielded by the refracted portion of the fluid passage 105 and does not travel further toward the back surface of the wafer W.

  The fluid passage 105 shown in FIG. 5C is configured such that one end 105a opens into the wafer pocket 103a, and the other end 105b opens on the back surface 104 of the susceptor 101 and outside the wafer pocket 103a. Although common with the example shown in FIG. 5B in that it has a refracting portion in the middle of the passage 105, the inner diameter of the fluid passage 105 on the other end 105b side is formed larger than the inner diameter of the fluid passage 105 on the one end 105a side. Has been.

  The fluid passage 105 shown in FIG. 5D has one end 105a that opens into the wafer pocket 103a and the other end 105b that opens on the back surface 104 of the susceptor 101 and outside the wafer pocket 103a. However, the difference is that the fluid passage 105 is formed in a straight line.

  In the example shown in FIG. 5 (e), instead of reducing the inner diameter of the fluid passage 105, the fluid passages 105 are arranged vertically so that the openings of the one end 105a are arranged above and below the vertical wall surface of the wafer pocket 103a. .

  The fluid passage 105 shown in FIG. 5F has one end 105a opened to the wafer pocket 103a and the other end 105b opened to the outside of the wafer pocket 103a on the back surface 104 of the susceptor 101 as shown in FIG. , (C) and in common with the example shown in FIG. 5 (d) in that the fluid passage 105 is formed in a straight line, but the recess 103c is formed on the outer periphery of the floor surface 103b of the wafer pocket 103a. And the floor surface 103b of the wafer pocket 103a is different from the above-described embodiment shown in FIGS. 5 (a) to 5 (e). One end 105a of the fluid passage 105 is opened in the vertical wall surface of the wafer pocket 103a corresponding to the recess 103c.

  The concave portion 103c of the wafer pocket 103a may be formed continuously over the entire outer periphery, or may be formed intermittently. The fluid passage 105 of this example is also shaped so that the radiant heat from the heating device provided below is not directly applied to the back surface of the wafer W via the fluid passage 105. When the floor surface 103b of the wafer pocket 103a is formed shallow in this way, the radiant heat from the back surface of the susceptor 101 is easily transmitted to the inner peripheral portion of the wafer W, and the temperature difference from the outer peripheral portion of the wafer W is reduced. As a result, it is possible to suppress the slip transition of the wafer, which is presumed to be caused by the thermal stress due to the temperature difference.

  The fluid passage 105 shown in FIG. 5 (g) is the same as the example shown in FIG. 5 (f) in that a recess 103c is formed on the outer periphery of the wafer pocket 103a. It is composed only of an inclined surface inclined to the side. One end 105a of the fluid passage 105 opens into a wafer pocket 103a corresponding to the concave portion 103c formed of the inclined surface. The concave portion 103c of the wafer pocket 103a may be formed continuously over the entire outer periphery, or may be formed intermittently. The fluid passage 105 of this example is also shaped so that the radiant heat from the heating device provided below is not directly applied to the back surface of the wafer W via the fluid passage 105.

  The fluid passage 105 shown in FIG. 5 (h) is common to the example shown in FIG. 5 (f) in that a recess 103c is formed on the outer periphery of the wafer pocket 103a. The difference is that in addition to the wall surface, there is an opposing vertical wall surface 103d facing the wall surface. Further, the floor surface 103b of the wafer pocket 103a is formed shallow as in the embodiment of FIGS. 5 (f) and 5 (g).

  One end 105a of the fluid passage 105 opens to the opposite vertical wall surface 103d of the recess 103c, the other end 105b opens to the inner side of the wafer pocket 103a on the back surface 104 of the susceptor 101, and the fluid passage 105 is formed linearly. Has been. The concave portion 103c of the wafer pocket 103a may be formed continuously over the entire outer periphery, or may be formed intermittently. The fluid passage 105 of this example is also shaped so that the radiant heat from the heating device provided below is not directly applied to the back surface of the wafer W via the fluid passage 105.

  Further, in addition to these fluid passages, other fluid passages opened near the center position of the wafer pocket can be provided.

  In the above-described embodiment, the present invention has been described by taking a single-wafer type vapor phase growth apparatus as an example. However, the susceptor of the present invention is not limited to this, and a plurality of conventional susceptors have been implemented. Needless to say, the present invention is also applicable to a batch type vapor phase growth apparatus that processes wafers at a time.

  The epitaxial wafer manufacturing method of the present invention can be realized, for example, by using the above-described susceptor of the vapor phase growth apparatus according to the present invention instead of the susceptor of the conventional single wafer type vapor phase growth apparatus. The wafer W is placed horizontally on the wafer support surface 32 of the susceptor 10 shown in FIG. 2, and the wafer W is flowed while the wafer W is heated to a predetermined temperature by the heating devices 6 a and 6 b while flowing the reaction gas GR. An epitaxial film can be formed on the surface.

  At the time of forming this epitaxial film, the wafer support surface 32 supporting the wafer W is formed with a surface roughness of 0.1 μm to 3.0 μm and a flatness of 120 μm or less. Adheres closely to the contact area without any gaps. Accordingly, the reaction gas GR is prevented from flowing into the back surface b side of the wafer W, and unnecessary epitaxial growth layers are prevented from being formed on the outer peripheral edge portion of the back surface b side of the wafer W. Therefore, it is possible to obtain an epitaxial wafer in which the in-plane uniformity of thickness is kept high.

  Further, since the wafer support surface 32 is inclined with respect to the horizontal plane in an angle range θ of 2.86 ° to 0.40 ° so as to be lowered toward the center of the wafer pocket 31, the wafer W is subjected to its own weight and thermal deformation. The edge 32a of the wafer support surface 32 does not come into contact with the back surface b of the wafer W even if it is curved so that the center is lowered. As a result, an epitaxial wafer can be obtained in which the outer peripheral edge of the wafer W is free from ring-shaped contact scratches due to contact with the wafer support surface 32.

  The susceptor for the vapor phase growth apparatus of the present invention was verified. First, the relationship between the flatness of the wafer support surface and the thickness of the epitaxial film formed on the back side of the wafer was measured. In the measurement, the flatness of the wafer support surface was measured at a position of 148 mm, which is the center of the step width from the center of the susceptor. Further, the thickness of the epitaxial film on the wafer back surface was measured at a position 148 mm outside from the wafer center. The measurement results of the relationship between the flatness of the wafer support surface and the thickness of the epitaxial film on the back side of the wafer when an epitaxial film is formed on the wafer using a susceptor in which the flatness of the wafer support surface is changed stepwise. As shown in FIG.

  According to the results shown in FIG. 6, it was found that when the flatness of the wafer support surface exceeds 120 μm, the thickness of the epitaxial film formed on the wafer back surface side increases rapidly. It was confirmed that the film thickness of the epitaxial film on the back side of the wafer can be kept low by suppressing the flatness of the wafer support surface to 120 μm or less.

  Next, the relationship between the surface roughness (Ra) of the wafer support surface and the thickness of the epitaxial film formed on the back surface side of the wafer was measured. In the measurement, the surface roughness (Ra) of the wafer support surface was a measured value of an area having a width of 1 mm at a position of 148 to 149 mm from the center of the susceptor. Further, the thickness of the epitaxial film on the wafer back surface was measured at a position 148 mm outside from the wafer center. FIG. 7 shows the measurement results of the relationship between the surface roughness (Ra) of the wafer support surface and the thickness of the epitaxial film on the wafer back surface when the flatness of the wafer support surface is 10 μm, 80 μm, and 120 μm.

  According to the results shown in FIG. 7, it was found that when the surface roughness (Ra) of the wafer support surface exceeds 3 μm, the thickness of the epitaxial film formed on the wafer back surface side increases rapidly. Further, it was confirmed that the higher the flatness of the wafer support surface, the lower the thickness of the epitaxial film formed on the wafer back surface side.

  Next, the distribution (variation) on the concentric circles of the thickness of the epitaxial film on the back surface side of the wafer on which the epitaxial film was formed using the susceptor for the vapor phase growth apparatus of the present invention was measured. In the measurement, a susceptor of the present invention was prepared in which the wafer support surface had a flatness of 120 μm, a surface roughness (Ra) of 2.5 μm, and an inclination angle of 1.43 ° with respect to a horizontal plane. For comparison, a conventional susceptor was prepared in which the wafer support surface had a flatness of 300 μm, a surface roughness (Ra) of 2.5 μm, and an inclination angle of 1.43 ° with respect to the horizontal plane.

  An epitaxial film was formed on the wafer using the present invention and a conventional susceptor, respectively. Then, the thickness of the epitaxial film on the back surface was measured in 10 ° increments on a concentric circle 2 mm inside from the edge on the back surface of the wafer on which each epitaxial film was formed (however, the 360 ° (0 °) position was notch Was not measured because it was formed). FIG. 8 shows the measurement results of the thickness of the epitaxial film on the back side of the wafer using the present invention and a conventional susceptor.

  According to the result shown in FIG. 8, the wafer formed with the epitaxial film with the susceptor of the present invention having a high flatness of the wafer support surface (120 μm) has an epitaxial film formed on the back surface of less than 30 μm at the maximum, and The difference between the maximum value and the minimum value of the thickness of the formed epitaxial film is about 10 μm, and it was confirmed that a wafer having excellent thickness uniformity can be obtained even at the outer edge. On the other hand, a wafer having an epitaxial film formed with a conventional susceptor having a low flatness of the wafer support surface (300 μm) has an epitaxial film exceeding 150 μm at the maximum on the back surface, and the maximum film thickness of the formed epitaxial film. There was a problem in the uniformity of the thickness at the outer edge of the wafer, for example, the difference between the value and the minimum value exceeded 50 μm.

  Next, the relationship between the angle of the wafer support surface with respect to the horizontal plane and the scratches and slip lengths formed on the back surface of the wafer was examined. In the measurement, a susceptor was prepared in which the angle of the wafer support surface with respect to the horizontal plane was changed stepwise from 0 ° (horizontal) to 3.7 °. Then, after forming an epitaxial film on the wafer using each susceptor, scratches and slip lengths on the wafer back surface caused by contact between the wafer back surface and the edge of the wafer support surface were evaluated.

  The evaluation of slip is based on the presence or absence of slip and the length of any slip (the length per one and total) while rotating slowly with the back of the wafer facing up under a condenser lamp in a dark room. Length). The scratches were evaluated by visually checking the presence and number of scratches while rotating slowly with the back of the wafer facing up under a condensing lamp in a dark room. FIG. 9 shows the measurement results of the relationship between the angle of the wafer support surface with respect to the horizontal plane, the scratches generated on the back surface of the wafer, and the slip length.

  According to the results shown in FIG. 9, slip occurs when the angle of the wafer support surface with respect to the horizontal plane exceeds 2.86 °, and the length increases as the angle increases. Further, it was confirmed that scratches were generated on the back surface of the wafer when the angle was 0.40 ° or less.

FIG. 1 is a plan view showing an example of a vapor phase growth apparatus of the present invention. FIG. 2 is a view showing a main part of the susceptor of the present invention, and is a plan view (a) and a sectional view (b). FIG. 3 is a schematic diagram showing the operation of the susceptor of the present invention. FIG. 4 is a schematic view showing the operation of the susceptor of the present invention. FIG. 5 is a cross-sectional view showing an example of forming a fluid passage. FIG. 6 is a graph showing the results of an example in which the effect of the present invention was verified. FIG. 7 is a graph showing the results of an example in which the effects of the present invention were verified. FIG. 8 is a graph showing the results of an example in which the effect of the present invention was verified. FIG. 9 is a graph showing the results of an example in which the effect of the present invention was verified. FIG. 10 is a view for explaining the flatness of the wafer support surface, and is a cross-sectional view (a) and a plan view (b). FIG. 11 is a cross-sectional view for explaining the occurrence of rear surface deposition due to warping of a semiconductor wafer. FIG. 12 is an explanatory view showing the measurement of the amount of warpage of the susceptor, and is a cross-sectional view (a) and a plan view (b).

Explanation of symbols

10 susceptors, 31 wafer pockets, 32 wafer support surfaces.

Claims (6)

A vapor phase growth apparatus for forming a film on a semiconductor wafer surface,
A vapor phase growth apparatus susceptor having a wafer pocket for receiving the semiconductor wafer;
The peripheral edge of the wafer pocket is provided with a substantially ring-shaped wafer support surface that supports the semiconductor wafer in contact with the outer peripheral edge of the semiconductor wafer back side and the entire periphery thereof,
The vapor phase growth apparatus characterized in that the wafer support surface is inclined toward the center of the wafer pocket so as to fall in an angle range of 2.86 ° to 0.40 ° with respect to a horizontal plane.   2. The vapor phase growth apparatus according to claim 1, wherein the wafer support surface has a surface roughness in a range of Ra 0.1 μm to 3.0 μm.   3. The vapor phase growth apparatus according to claim 2, wherein the wafer support surface has a flatness in a range of 10 to 120 [mu] m.   4. The vapor phase growth apparatus according to claim 3, wherein the wafer support surface is provided as a range of 1 to 11 mm in a radial direction of the wafer pocket.   The one end of a fluid passage connected to the outside of the wafer pocket is formed in the wafer pocket at a position inside the wafer support surface when the semiconductor wafer is received. 2. The vapor phase growth apparatus according to 1. An epitaxial wafer manufacturing method using a susceptor for a vapor phase growth apparatus in which a wafer pocket for receiving a semiconductor wafer is formed in a vapor phase growth apparatus,
The wafer pocket is provided with a substantially ring-shaped wafer support surface that contacts the outer peripheral edge of the back surface of the semiconductor wafer and supports the semiconductor wafer,
The wafer support surface has a surface roughness of 0.1 μm to 3.0 μm, a flatness of 10 μm to 120 μm, and is 2.86 ° to 0.40 ° with respect to a horizontal plane toward the center of the wafer pocket. An epitaxial wafer manufacturing method, wherein an epitaxial growth layer is formed on one surface of a semiconductor wafer using a susceptor for a vapor phase growth apparatus that is inclined so as to fall within an angle range of.

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