JP2006093541A - Wafer holder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer holder by which neither a wafer nor a wafer holder is damaged. <P>SOLUTION: In a wafer holder 10 wherein a wall 4 is formed for regulating the movement of the wafer 2 around a horizontal bottom 3 for placing the wafer 2 including an orientation flat 1 to revolve the wafer 2 around a revolution axis in parallel with a normal of the wafer 2. A portion 5 of the wall 4 facing the orientation flat 1 (counter portion) is expanded like a curve toward the orientation flat 1. Since no corner of the orientation flat 1 is in contact with the counter portion 5, so that neither the wafer 2 nor the wafer holder is damaged. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wafer holder for a wafer having an orientation flat, and to a wafer holder that does not damage either the wafer or the wafer holder.

  As a part of a semiconductor manufacturing apparatus that performs epitaxial growth on a semiconductor substrate by metal organic vapor phase epitaxy, a holder for supporting the semiconductor substrate facing the reaction chamber (hereinafter referred to as a wafer holder) It revolves around a revolution axis parallel to the normal line of the semiconductor substrate. A semiconductor substrate called a wafer has a planar shape obtained by cutting a part of a circle with a straight line. This cut-out portion (string portion) is called an orientation flat (hereinafter referred to as OF). OF is provided to determine the position (orientation) of the wafer.

  A wafer holder for holding a wafer horizontally is provided with a recess or stepped hole (hereinafter referred to as a wafer holding portion) slightly larger than the wafer (hereinafter referred to as a wafer holding portion) on a horizontal surface. A wall for restricting the movement of the wafer is formed around the bottom.

  Hereinafter, the wafer holder will be described in more detail.

  In MOVPE (Metal Organic Vapor Phase Epixy) growth of a semiconductor epitaxial wafer, a specific substrate is used for a desired semiconductor crystal in order to realize epitaxial growth. For example, a GaAs substrate is used as a heteroepitaxial wafer of GaAs / AlGaAs or AlGaInP, and a sapphire substrate is used as an epitaxial wafer of GaN.

  These substrates (wafers) are set in a chamber controlled to a temperature range specific to a desired semiconductor crystal during epitaxial growth. Epitaxial growth is performed by supplying a source gas to the substrate surface.

  At this time, carbon is used for the wafer holder to set the substrate because it has good thermal conductivity, has existing technology that is easy to process and has high accuracy, is inexpensive, is resistant to corrosion, and is light. It is done.

  There are various variations in the overall shape of the carbon wafer holder depending on the structure of the chamber, but variations are limited for the portion where the substrate is set. FIGS. 4 and 5 show typical conventional shapes of a portion for setting a substrate, that is, a wafer holding portion.

  The wafer holder shown in FIGS. 4A and 4B is used in a face-up type chamber. That is, three circular wafer holders 40 are formed on a circular wafer holder 46 as viewed from above. The wafer holder 40 is formed by forming a dent slightly larger than the wafer on the horizontal surface of the wafer holder 46. The whole of the recess is a horizontal bottom for mounting the wafer, and the edge of the recess is formed around the bottom as a wall 44 for restricting the movement of the wafer.

  Both the wafer holder shown in FIGS. 5A and 5B and the wafer holder shown in FIGS. 5C and 5D are used in a face-down type chamber. That is, three circular wafer holders 50 are formed in a circular wafer holder 56 as viewed from above. 5A and 5B, a hole that is slightly larger than the wafer is formed on the horizontal surface of the wafer holder 56, and a step is formed in the middle of the hole. The stepped portion is slightly smaller than the wafer, and this stepped portion forms a horizontal bottom 53 for mounting the wafer. The edge of the hole is a wall 54 for restricting the movement of the wafer. 5C and 5D, the wafer holder 50 ′ has a claw protruding from the edge of the hole formed in the lower surface of the wafer holder 56 ′ by forming a hole slightly larger than the wafer on the horizontal surface of the wafer holder 56 ′. 57 is provided. The claw 57 serves as a member for placing a wafer instead of the bottom.

  A wafer holder in which one or a large number of wafers are set (also referred to as charge) is supplied with a source gas in a temperature-controlled chamber. At that time, an epitaxial growth portion within one wafer surface or between each wafer. In order to average the thickness, carrier concentration, and composition, a mechanism for rotating around a rotation axis parallel to the normal line of the wafer is provided.

  Some types of semiconductor manufacturing apparatuses have a holder that further supports the wafer holder.

  Depending on the method of transmitting power from the power source to the wafer holder and the method of setting the wafer, there are a wafer holder whose rotation axis does not intersect with the wafer and a wafer holder whose rotation axis is at the center of the wafer. The former is called the revolution type and the latter is called the rotation type. The so-called revolution type has both a revolution axis and a revolution axis by devising a power transmission method, and can perform revolution and revolution.

JP 2000-306982 A

  The problem of the background art is that when the growth is performed by giving revolution, the wafer tries to rotate with respect to the wafer holder by the inertial force acting on the wafer. This inertia force leads to problems such as the wafer being displaced from the wafer holder and the surface of the wafer being scratched by a jig for fixing the wafer so as not to be displaced.

  As one method for solving this problem, there is a method in which a single wafer is set on a single-wafer type wafer holder and the growth is performed by giving rotation. However, since only one wafer can be produced at a time, it is not an effective method in the industry. It is more effective for the industry to set a plurality of wafers as one batch in a double-wafer type wafer holder.

  Since many semiconductor epitaxial wafers are provided with the OF described above, the rotation of the wafer can be prevented using this OF. That is, as shown in FIG. 6, a linear portion (opposing portion) 65 facing the OF 1 is formed in the wafer holding portion 60. The facing portion 65 is configured to fill a portion corresponding to a portion of the circular recess or hole where the wafer 2 is cut out. That is, the linear facing portion 65 is formed as a part of the wall 64 for restricting the movement of the wafer 2. In this case, the rotation of the wafer 2 is prevented by the OF 1 interfering with the facing portion 65.

  However, in practice, there is a problem that the weaker one of the corners of the OF and the opposing portion is damaged by the force with which the wafer is rotated by inertia. For example, as shown in FIG. 7A, when a carbon wafer holder 76 is used for a wafer 72 made of a sapphire substrate, the wafer 72 is rotated in the S direction by the inertial force F, and the corner of the OF 71 is opposed to the opposing portion 75. The wafer holder 76 is damaged when it comes into contact (within the broken line circle). On the other hand, as shown in FIG. 7B, when a carbon wafer holder 76 is used for a wafer 72 ′ made of a GaAs substrate, the wafer is caused by inertial force F even if the shape is the same as in FIG. When 72 ′ rotates in the S direction and the corner of OF 71 ′ contacts the opposing portion 75 (within a broken line circle), the wafer 72 ′ is damaged. That is, in the wafer holder in which the linear facing portion 65 is formed as shown in FIG. 6, it is inevitable that either the wafer or the wafer holder is damaged.

  In the design of the wafer holding part, the size of the recess or hole is usually given a margin (clearance) that does not interfere with the removal and insertion of the wafer, including the dimensional tolerance of the processing of the carbon. Also give clearance. However, when the inertial force due to the revolution of the wafer acts on the wafer, the wafer rotates within the clearance. For this reason. As shown in FIG. 7A or 7B, the wafer and the wafer holder come into contact with each other at a sharp point, and the inertial force is concentrated on that point. Further, such contact is repeated on the wafer holder. Such contact damages the weaker material.

  Damage to the wafer leads to a decrease in the yield of the epitaxial wafer. Conversely, damage to the wafer holder leads to generation of carbon powder in the chamber, and such contamination by uncontrollable impurities is undesirable in semiconductor manufacturing.

  Patent Document 1 discloses various members that limit the movement of a wafer in an ion implantation apparatus that irradiates a wafer with an ion beam. However, these members have a portion that covers the top surface of the wafer. In the MOVPE method, if there is a member protruding on the upper surface of the wafer, the member may disturb the gas flow passing through the upper surface of the wafer. The turbulence of the gas flow impairs the uniformity of the growth rate within one wafer surface or between wafers. Therefore, the configuration of Patent Document 1 in which a member is provided on the upper surface of the wafer is not suitable for the MOVPE method.

  Further, Patent Document 1 is intended to securely hold the wafer, and does not solve the problem that occurs when the wafer moves in the clearance.

  Accordingly, an object of the present invention is to provide a wafer holder that solves the above-described problems and does not damage the wafer and the wafer holder.

  In order to achieve the above object, according to the present invention, a wall for restricting movement of the wafer is formed around a horizontal bottom for mounting a wafer having an orientation flat, and is parallel to the normal line of the wafer. In the wafer holder that revolves the wafer around a revolution axis, a portion (opposing portion) of the wall that faces the orientation flat swells in a curved shape toward the orientation flat.

  When the radius of curvature of the facing portion is R1 and the radius of curvature of the wall is R0, 0.3R0 <R1 <5R0 may be satisfied.

  When the distance between the center of curvature of the facing portion and the center of curvature of the wall is L, L <R0 + R1, and the difference (R0 + R1) −L is d, and the length of the orientation flat is D Then, 0 <d <D / 2 may be satisfied.

  The bulging shape of the facing portion may be an elliptical arc.

  The present invention exhibits the following excellent effects.

  (1) Since the corner of the OF does not come into contact with the facing portion, neither the wafer nor the wafer holder is damaged.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, a wafer holder 10 having one or more wafer holders according to the present invention has a horizontal bottom 3 for placing a wafer 2 having an orientation flat (hereinafter referred to as OF) 1. A wall 4 for restricting the movement of the wafer 2 is formed around the wafer holder, and the wall 2 revolves around a revolution axis (not shown) parallel to a normal line (not shown) of the wafer 2. 4, a portion (opposing portion) 5 facing the OF 1 swells in a curved shape toward the OF 1. Since the outline shape of the wafer holder is arbitrary, it is omitted here.

  As described with reference to FIGS. 4 and 5, the wall 4 is formed by a recess or an edge of a hole. The wall 4 is formed in a circular shape having a diameter larger than that of the wafer 2 except for the facing portion. Compared with the background art, in the wafer holder of FIG. 6, the facing portion is a straight line, whereas in the present invention, the facing portion 5 is a curve. In FIG. 1, since the wafer 2 is placed on the bottom 3 so that the center of curvature of the wafer 2 coincides with the center of curvature of the wall 4, the clearance appears evenly on the entire circumference. However, in the facing portion 5, the OF 1 is almost in contact with the maximum bulge portion of the facing portion 5.

  Here, it is assumed that an arc is used as the curve of the facing portion 5. When the radius of curvature of the wall 4 is R0 and the radius of curvature of the facing portion 5 is R1, it is preferable that 0.3R0 <R1 <5R0. The reason why the lower limit of 0.3R0 <R1 is preferable is that the wafer 2 can be prevented from moving more than necessary in the wafer holder 10. On the other hand, the reason why the upper limit R1 <5R0 is preferable is that if R1 is further increased, the facing portion 5 approaches a straight line and the effect becomes small. If R1 <5R0, the swelling of the facing portion 5 is moderate. Become a good curve.

  The lower limit is more preferably 0.5R0 <R1, and the clearance can be made slightly larger than when R1 is brought close to 0.3R0, so that the wafer 2 can be easily taken in and out.

  When the distance between the center of curvature (not shown) of the facing portion 5 and the center of curvature O of the wall 4 is L, a relationship of L <R0 + R1 is required. When the difference (R0 + R1) −L between the sum of the curvature radii R0 and R1 and the distance L between the centers of curvature is defined as d, the difference d may be determined according to the processing dimension of OF1. For example, when the length of OF1 is D, 0 <d <D / 2. The lower limit 0 <d is obvious because L ≠ R0 + R1. The upper limit d <D / 2 takes into account the natural balance of the size of the facing portion 5 compared to the overall size of the wafer 2.

  As a specific example, the curvature radius R1 of the facing portion 5 is set to 30.0 mm with respect to the curvature radius R0 = 25.5 mm of the wall 4. The distance between the centers of curvature L was set to 55.0 mm. At this time, the difference d was 0.5 mm with respect to the length D of OF1 = 16.0 mm.

  According to the wafer holder of the present invention, since the facing portion 5 bulges toward the OF 1, even if the wafer 2 rotates due to inertial force, the OF 1 becomes a tangent to the facing portion 5, and the corner of the OF 1 is the facing portion 5. There is no contact. Thus, since the wafer 2 and the wafer holder (the wall 4 and the facing portion 5) do not contact at a pointed point, the wafer and the wafer holder are not damaged regardless of the strength of each material.

  In addition, although the circular arc is employ | adopted as the bulging shape of the opposing part 5 in the form of FIG. 1, it is clear that the bulging shape should just be a curve which does not reverse bending directions, such as an elliptical arc.

  Next, a wafer holder having a plurality of wafer holding portions will be described.

  As shown in FIGS. 2A and 2B, the wafer holder has a circular upper surface 6, and a plurality (three in this case) of wafer holders 10 are provided on the upper surface 6. Each wafer holding portion 10 is formed with the facing portion 5 swelled in the curved shape described in FIG. The revolution axis of the wafer holder is located at the center of a circle on the upper surface 6, for example, and the respective wafer holders 10 are arranged on the same circumference so that the distance from the revolution axis is uniform. And in each wafer holding part 10, the opposing part 5 is provided in the position far from a revolution axis.

  Next, the wafer holder of FIG. 2 was actually examined for damage to the wafer and the wafer holder. That is, the wafer holder of FIG. 2 was made of carbon and further coated with silicon carbide. For comparison, a wafer holder in which the wafer holding portion 30 having the linear facing portion 35 as shown in FIG. 3 is arranged in the same manner as in FIG. 2 is also made of carbon and further coated with silicon carbide. A MOVPE growth process was repeated in which a wafer made of a sapphire substrate was placed on each wafer holder, and gallium nitride (GaN) was grown on the wafer.

  In the sapphire substrate and the carbon wafer holder, the soft wafer holder is easily damaged. Therefore, the durability of the wafer holder can be examined by repeating the process.

  As a result, the wafer holder in FIG. 2 was not damaged. However, in the wafer holder of FIG. 3, the wafer holder was damaged at the portion where the corner of OF <b> 1 contacts the facing portion 35. When the 2-hour process was performed 10 times, the carbon powder generated from the scratches on the wafer holder contaminated the chamber.

It is a top view of one wafer holding part of a wafer holder showing one embodiment of the present invention. (A) is the top view and side view of a wafer holder which show one Embodiment of this invention, (b) is sectional drawing of the A-A 'line in (a). (A) is the top view and side view of the wafer holder produced for the comparison, (b) is sectional drawing of the B-B 'line in (a). (A) is the top view and side view of the wafer holder of background art, (b) is sectional drawing of the C-C 'line in (a). (A) is a plan view and a side view of a wafer holder according to the background art, (b) is a sectional view taken along line DD ′ in (a), and (c) is a plan view and a plan view of another background art wafer holder. It is a side view, (d) is sectional drawing of the EE 'line in (c). It is a top view of the wafer holding part which prevents rotation of a wafer using OF. (A), (b) is a top view of a wafer holding part when a wafer rotates, respectively.

Explanation of symbols

1 Orientation flat (OF)
2 Wafer 3 Bottom 4 Wall 5 Opposing 6 Wafer Holder

Claims (4)

  A wafer holder for revolving the wafer around a revolution axis parallel to a normal line of the wafer, wherein a wall for restricting movement of the wafer is formed around a horizontal bottom portion for placing a wafer having an orientation flat And a portion of the wall facing the orientation flat (opposite portion) swells in a curved shape toward the orientation flat.   The wafer holder according to claim 1, wherein 0.3R0 <R1 <5R0, where R1 is a curvature radius of the facing portion and R0 is a curvature radius of the wall.   When the distance between the center of curvature of the facing portion and the center of curvature of the wall is L, L <R0 + R1, and the difference (R0 + R1) −L is d, and the length of the orientation flat is D 3. The wafer holder according to claim 2, wherein 0 <d <D / 2. 2. The wafer holder according to claim 1, wherein the bulging shape of the facing portion is an elliptical arc.

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