JP2013049592A - Method for manufacturing crystal substrate, and substrate holding tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means capable of manufacturing a crystal substrate inexpensively.SOLUTION: In this method, a crystal film (30) is grown on a crystal growing surface (21) of a base substrate (20) held by a substrate holding tool (10) of a vapor phase growth apparatus and having an orientation flat (23), and a crystal substrate (35) is manufactured from the crystal film (30). The substrate holding tool (10) includes an opening part (12) for exposing a part of the crystal growing surface (21) of the base substrate (20), and the opening part (12) includes an arc-shaped portion (13) and a chord-shaped portion (14) on its contour, and the inner wall of the chord-shaped portion (14) has a wall surface (15) approximately parallel to a surface determined by rotating the orientation flat (23) integer-fold of 30° or 90° around the center axis of the base substrate (20) as a rotation axis.

Description

  The present invention relates to a method for manufacturing a crystal substrate and a substrate holder for a vapor phase growth apparatus.

  Conventionally, crystal substrates used for manufacturing semiconductor devices have orientation flats (hereinafter sometimes abbreviated as “orientation flats”), notches, index flats, etc., as marks for identifying the crystal plane orientation and front and back. A notch is formed.

  For example, Patent Document 1 discloses a method for manufacturing a nitride semiconductor substrate, which includes a step of forming a protective film having a portion hollowed out in a desired shape on a base substrate, and a nitride formed on the hollowed-out portion. The method includes a step of growing a semiconductor layer and a step of peeling off the nitride semiconductor layer, wherein the desired shape includes an orientation flat and / or an index flat in the nitride semiconductor substrate.

JP 2010-285325 A

  However, in the method for manufacturing a nitride semiconductor substrate described in Patent Document 1, it is necessary to form a protective film for each base substrate, which increases man-hours and increases manufacturing costs. In addition, the miscellaneous crystals deposited on the protective film may decrease the crystallinity of the peripheral portion of the nitride semiconductor layer or cause cracks or cracks. To avoid this, a thick protective film is formed. Manufacturing cost is further increased.

  Then, this invention is made | formed in view of this situation, and it aims at providing the means which can manufacture a crystal substrate at low cost.

  In order to solve the above problem, the present invention grows a crystal film on a crystal growth surface of a base substrate having an orientation flat held by a substrate holder of a vapor phase growth apparatus, and manufactures the crystal substrate from the crystal film. In the method, the substrate holder includes an opening that exposes a part of a crystal growth surface of the base substrate, and the opening includes an arc-shaped portion and a string-shaped portion in its outline, and the string The inner wall of the shape portion has a wall surface substantially parallel to a surface obtained by rotating the orientation flat by an integral multiple of 30 ° or 90 ° with the central axis of the base substrate as a rotation axis.

  Further, the present invention is a substrate holder for a vapor phase growth apparatus for holding a base substrate having an orientation flat and a crystal growth surface, wherein the opening exposes a part of the crystal growth surface of the base substrate. And a reference surface facing substantially parallel to the orientation flat of the base substrate, the opening includes an arcuate portion and a chordal portion in its contour, and an inner wall of the chordal portion is the reference A wall surface substantially parallel to a surface obtained by rotating the surface by an integral multiple of 30 ° or 90 ° with the central axis of the opening as a rotation axis is provided.

  According to the present invention, notches such as orientation flats can be formed at low cost on a crystal substrate.

It is the schematic top view (a) of the substrate holder which concerns on the manufacturing method of the crystal substrate of one embodiment of this invention, and the schematic sectional drawing (b) in the XX cross section. It is a schematic top view which shows an example of the crystal substrate manufactured by the manufacturing method of the crystal substrate of one embodiment of this invention. It is a schematic top view of the substrate holder which concerns on the manufacturing method of the crystal substrate of one embodiment of this invention.

  Hereinafter, embodiments of the invention will be described with reference to the drawings as appropriate. However, the crystal substrate manufacturing method and substrate holder described below are for embodying the technical idea of the present invention, and the present invention is not limited to the following unless otherwise specified. . In addition, the size, positional relationship, and the like of members illustrated in each drawing may be exaggerated for clarity of explanation.

<Embodiment 1>
FIG. 1A is a schematic top view of a substrate holder according to the method for manufacturing a crystal substrate of Embodiment 1, and FIG. 1B is a schematic cross-sectional view taken along the line XX. FIG. 2 is a schematic top view showing an example of a crystal substrate manufactured by the method for manufacturing a crystal substrate of the first embodiment. As shown in FIGS. 1 and 2, in the method for manufacturing a crystal substrate according to the first embodiment, a crystal film 30 is grown on a crystal growth surface 21 of a base substrate 20 held by a substrate holder 10 of a vapor phase growth apparatus. The crystal substrate 35 is manufactured from the crystal film 30. That is, the crystal substrate 35 is obtained by separating the crystal film 30 grown on the base substrate 20 from the base substrate 20. Thereafter, the crystal film 30 separated from the base substrate 20 is finished as a crystal substrate 35 by appropriately performing chamfering processing of the edge and polishing of the main surface.

  As shown in FIG. 2, the crystal substrate 35 has a notch 36 in which a part of a substantially circular edge is notched. In the present embodiment, the notch 36 forms a flat surface that is an orientation flat on the end surface of the crystal substrate 35 and is substantially parallel to the crystal surface of the substrate. The notch 36 is formed during the growth process of the crystal film 30.

  As shown in FIG. 1, the substrate holder 10 includes an opening 12 that exposes a part of the crystal growth surface 21 of the base substrate 20, and the crystal growth surface of the base substrate 20 is defined by the outline of the opening 12. The crystal growth region in 21 can be controlled. Further, the crystal plane orientation of the crystal film 30 grown on the base substrate 20 tends to depend on the crystal plane orientation of the base substrate 20 and can be predicted thereby. Furthermore, if the crystal film 30 is grown on the base substrate 20 on a trial basis and the crystal plane orientation is measured, the relationship between the crystal plane orientation of the base substrate 20 and the crystal plane orientation of the crystal film 30 can be known more accurately. it can. As an example, when the base substrate 20 is sapphire and the crystal film 30 is a nitride semiconductor and is grown in the c-axis direction [0001], the M plane ({1-100} plane) of the crystal film 30 is the base It has been found that there is a tendency to be substantially parallel to the A surface ({11-20} surface) of the substrate 20. Therefore, a part of the outline of the opening 12 of the substrate holder 10 is notched or protruded inward so that the crystal plane orientation can be identified in accordance with the crystal plane orientation of the crystal film 30. Thus, the notch 36 can be formed in the growth process of the crystal film 30.

  In particular, as in the present embodiment, when the notch 36 is an orientation flat, the opening 12 of the substrate holder 10 has an arcuate portion 13 and a chord-like portion (first chord-like portion) 14 in its outline. including. Further, the inner wall of the string-like portion 14 has a wall surface 15 substantially parallel to the crystal plane of the crystal film 30. The crystal plane of the crystal film 30 is defined as a crystal plane substantially parallel to a plane obtained by rotating the orientation flat 23 of the base substrate 20 by an integral multiple of 30 ° or 90 ° with the central axis of the base substrate 20 as the rotation axis. . The central axis of the base substrate 20 is a perpendicular line at the center of the crystal growth surface 21 (not considering the off angle). As a result, the growth of the crystal film 30 is restricted by the inner wall of the chord 14 and a notch 36 is formed. The crystal film 30 grows in contact with the wall surface 15, whereby a flat surface substantially parallel to the crystal plane of the crystal film 30 can be formed in the notch 36. The arc-shaped portion 13 has a function of making the crystal film 30 easy to grow into a circular shape (considering notches) and suppressing the occurrence of cracks, chipping, cracks, and the like of the crystal substrate 35.

  In addition, the notch 36 of the crystal substrate 35 may be a notch. In that case, the opening part 12 of the board | substrate holder 10 contains the protrusion part which protrudes inside in the V shape at the outline. Then, the central axis of the protrusion passing through the tip of the protrusion may be substantially parallel to the crystal plane of the crystal film 30.

  The allowable accuracy of the crystal plane orientation indicated by the notch 36 such as the orientation flat or notch of the crystal substrate 35 varies depending on the use of the crystal substrate 35, but is, for example, within ± 3.0 °, preferably within ± 1.0 °. More preferably, it is within ± 0.5 °, and most preferably within ± 0.1 °.

  As described above, in the present invention, after the crystal film 30 is separated from the base substrate 20, the step of forming the notch 36 by processing such as grinding can be omitted, and the crystal substrate 35 can be manufactured at low cost. it can. In addition, generation of cracks, chipping, cracks, and the like due to such processing can be suppressed, and the yield can be increased.

  Moreover, the substrate holder 10 can be used repeatedly. Further, unlike the prior art, no special processing such as formation of a protective film is required for each base substrate. Further, by adjusting the thickness of the opening 12 of the substrate holder 10 in accordance with the growth film thickness of the crystal film 30, the influence from miscellaneous crystals that may be deposited on the substrate holder 10 can be reduced. Can do. Therefore, it is easy to manufacture the crystal substrate 35 with good crystallinity at low cost.

  The crystal film 30 has a plurality of crystal planes that can be handled equivalently due to the symmetry of the crystal structure. For this reason, in the crystal substrate 35, the notch 36 has a plurality of positions where the notch 36 can be formed only for the purpose of identifying the crystal plane orientation. However, the crystal film 30 tends to inherit characteristics such as the off-angle and dislocation distribution of the base substrate 20, and the notch 36 is formed at a position where such other characteristics in addition to the crystal plane orientation can be identified. More preferably. In the present invention, since the notch 36 is formed during the growth process of the crystal film 30, in addition to the crystal plane orientation of the crystal film 30, the off-angle of the crystal film 30 and the dislocation distribution are relatively determined depending on the position of the notch 36. It can be easily identified. After separating the crystal film 30 from the base substrate 20, even the work of knowing the crystal plane orientation becomes complicated, so this means is very simple and useful.

  Hereinafter, the preferable aspect of the structure of this invention is explained in full detail.

  As shown in FIG. 1, the substrate holder 10 is opened up and down, and includes a cylindrical cylindrical portion 101 and a support portion 102 that protrudes inward from one end thereof. The substrate holder 10 supports the peripheral portion of the base substrate 20 inserted into the cylindrical portion 101 with the support portion 102. Then, a part of the crystal growth surface 21 of the base substrate 20, specifically, the central part is exposed to the opening 12 of the support part 102. After that, the soaking plate 40 is inserted into the cylindrical portion 101, whereby the base substrate 20 is pressed against the support portion 102.

  The substrate holder 10 may be composed of one part, or may be composed of a plurality of parts such as a holder body 100 and a ring 110 as shown in the figure. The ring 110 is interposed between the base substrate 20 and the holder main body 100 and constitutes a part of the support portion 102. At this time, the arc-shaped portion 13 and the string-shaped portion 14 are provided in the outline of the opening of the ring 110. As described above, if the portion of the substrate holder 10 that is in contact with the crystal film 30 and the portion that is separated from the crystal film 30 are formed of separate parts, it is easy to select a suitable configuration for each portion.

  As described above, the substrate holder 10 holding the base substrate 20 is installed in the reaction furnace of the vapor phase growth apparatus. Then, a raw material is supplied on the crystal growth surface 21 of the base substrate 20, and the crystal film 30 is grown. At this time, in many cases, the substrate holder 10 is rotated. The substrate holder 10 may be installed in a reaction furnace of the vapor phase growth apparatus with the crystal growth surface 21 of the base substrate 20 facing upward in the vertical direction (face-up type). 20 crystal growth surfaces 21 may be installed in a state in which they face downward in the vertical direction (face-down type).

  The base substrate 20 preferably has an orientation flat 23 on its end face. The substrate holder 10 preferably includes a reference surface 17. The reference surface 17 is provided so as to face substantially parallel to the orientation flat 23 of the base substrate 20 when the substrate holder 10 holds the base substrate 20. As a result, the orientation of the base substrate 20 can be regulated by the reference surface 17 and installed on the substrate holder 10. Then, the position and direction of the chord 14, and thus the position and direction of the wall surface 15 are set with reference to this reference surface 17. Then, the installation accuracy of the wall surface 15 with respect to the crystal plane orientation of the base substrate 20 can be increased, and the notch 36 can be easily formed in the crystal substrate 35 with high accuracy. The reference surface 17 may be a virtual plane such as a plane (tangential plane) in contact with two pins provided on the substrate holder 10 in addition to being provided as a part of the constituent surface of the substrate holder 10.

  The cutout 36 serving as the orientation flat of the crystal substrate 35 may be a surface that is oblique with respect to its main surface (upper surface: front), but in many cases is formed by a substantially vertical surface. Therefore, the wall surface 15 of the string-like portion 14 of the substrate holder 10 is preferably provided substantially perpendicular to the crystal growth surface 21 of the base substrate 20. That is, it is preferable that the surface in contact with the crystal growth surface 21 of the base substrate of the support portion 102 of the substrate holder 10 and the wall surface 15 are substantially perpendicular. Further, as described above, in order to reduce the influence from miscellaneous crystals, the thickness (height) of the inner wall of the opening 12 of the substrate holder 10, that is, the thickness of the ring 110 in the example shown in FIG. It is preferable that the thickness be equal to or greater than the film 30.

  The length of the notch 36 serving as the orientation flat of the crystal substrate 35 is about 20% to 40% of the diameter of the substrate 35 from the viewpoint of the function as the orientation flat and the effective area of the main surface of the crystal substrate 35. For example, in the case of the crystal substrate 35 having a diameter of 3 inches or 75 mm, it is preferably 15 mm or more and 30 mm or less. Note that, as indicated by a broken line in FIG. 2, the crystal film 30 separated from the base substrate 20 is usually subjected to a grinding process (rounding process) for shaping it into a circular shape. At that time, depending on the position of the processing center, the notch 36 may be cut and become smaller. For this reason, it is preferable that the length of the chordal portion 14 is longer than the preferable length of the notch 36 so that the notch 36 can secure a length sufficient to function as an orientation flat. And about 25% to 45% of the diameter of the desired crystal substrate.

  When the crystal film 30 is a crystal belonging to the hexagonal system, the C plane ({0001} plane) and the M plane, and the C plane and the A plane are perpendicular to each other. In addition, the A plane and the M plane have a relationship of being rotated by 30 ° with the c axis as the rotation axis. For example, the notch 36 of the crystal substrate 35 whose main surface is substantially parallel to the C plane can be formed substantially parallel to the M plane or the A plane. For example, the notch 36 of the crystal substrate 35 whose main surface is substantially parallel to the M plane can be formed substantially parallel to the C plane or the A plane.

  Further, when the crystal film 30 is a crystal belonging to a cubic system, one of the {100} planes is in a perpendicular relationship with four consecutive planes. Further, the {011} plane is perpendicular to two of the {100} planes, and is in a relationship rotated by 45 ° with the remaining four of the {100} planes. For example, the notch 36 of the crystal substrate 35 whose main surface is substantially parallel to the (100) plane can be formed, for example, substantially parallel to the (01-1) plane or the (011) plane. The (01-1) plane and the (011) plane are perpendicular to each other.

  Here, assuming that the crystal plane orientation of the crystal film 30 is substantially coincident with the crystal plane orientation of the base substrate 20, the crystal film 30 is a crystal plane indicated by the orientation flat 23 of the base substrate 20, that is, a crystal plane substantially parallel to the orientation flat 23. In many cases, the substrate has a crystal plane substantially parallel to a plane rotated by an integral multiple of 30 ° or a plane rotated by an integral multiple of 90 ° with the central axis of the base substrate 20 as a rotation axis. Therefore, the wall surface 15 of the string-like portion of the substrate holder 10 is 30 ° with the orientation flat 23 of the base substrate 20 as the rotation axis or the reference surface 17 as the rotation axis as the rotation axis. Alternatively, it is preferable to be substantially parallel to a plane rotated by an integral multiple of 90 °, because a notch 36 serving as an orientation flat can be easily formed on the crystal substrate 35 with high accuracy corresponding to many crystal systems.

  As the crystal film 30 grows on the base substrate 20, a relatively stable crystal plane tends to appear as a facet plane. In particular, when the crystal film 30 is a hexagonal crystal, for example, a nitride semiconductor, relatively stable crystal planes include C plane, M plane, R plane ({1-102} plane), {1- 101} plane, {11-22} plane, {11-21} plane, A plane, and the like. Therefore, as shown in FIG. 2, the crystal film 30 before being rounded may have a facet surface 37 on the end face thereof. Also, the crystal growth in the a-axis direction <11-20> in such a crystal film 30 tends to be faster than the crystal growth in the m-axis direction <1-100>. Therefore, the {11-22} plane, the {11-21} plane, the A plane, etc. appear at the initial growth stage of the crystal film 30, and as the crystal growth proceeds, the more stable C plane, M plane, R plane, {1 The −101} plane tends to gradually expand.

  Therefore, when the crystal film 30 is a crystal belonging to the hexagonal system, the wall surface 15 of the string-like portion of the substrate holder 10 is preferably substantially parallel to the A plane of the crystal film 30. As a result, the crystal film 30 is likely to grow in contact with the wall surface 15, and the notch 36 serving as an orientation flat is easily formed on the crystal substrate 35 with high accuracy.

  As shown in FIG. 2, the crystal substrate 35 has a predetermined diameter Φ. In the present embodiment, the crystal substrate 35 may be manufactured without rounding the crystal film 30. In this case, the diameter Φ is substantially equal to the diameter of the as-grown (state before machining) of the crystal film 30 separated from the base substrate 20. That is, this diameter Φ is obtained during the growth process of the crystal film 30. However, a slight reduction in diameter due to chamfering of the edge is considered.

  As described above, in the present invention, since the crystal growth region in the crystal growth surface 21 of the base substrate 20 can be controlled by the contour of the opening 12 of the substrate holder 10, the arc-shaped portion 13 has a predetermined diameter. By having the diameter d substantially equal to Φ, the crystal film 30 having a diameter substantially equal to the predetermined diameter Φ can be grown. Therefore, the step of rounding the crystal film 30 after separating the crystal film 30 from the base substrate 20 can be omitted, and the crystal substrate 35 can be manufactured at low cost. In addition, generation of cracks, chipping, cracks, and the like due to the rounding process can be suppressed, and the yield can be increased.

  The diameter d of the arcuate portion 13 of the opening 12 of the substrate holder 10 is appropriately adjusted according to the desired diameter of the crystal substrate 35. However, general standards for the diameter of the crystal substrate 35 include 2 inches, 2.5 inches, 3 inches, 4 inches, 5 inches, 6 inches, 50 mm, 75 mm, 100 mm, 125 mm, and 150 mm. Therefore, the predetermined diameter Φ is preferably approximately equal to any one of these values. Thereby, it is possible to obtain a crystal substrate 35 that is compatible with many manufacturing apparatuses and jigs and is easy to use. Note that a tolerance of ± 0.5 mm is considered.

  The growth of the crystal film 30 in the lateral direction is restricted by the inner wall of the opening 12 of the substrate holder 10. Therefore, the inner wall surface of the arc-shaped portion 13 is preferably provided substantially perpendicular to the crystal growth surface 21 of the base substrate 20 in order to accurately control the diameter of the crystal film 30. That is, it is preferable that the surface in contact with the crystal growth surface 21 of the base substrate of the support portion 102 of the substrate holder 10 and the wall surface of the inner wall of the arc-shaped portion 13 are substantially perpendicular. The diameter d of the arc-shaped portion 13 is defined by the diameter at the end of the inner wall of the arc-shaped portion 13 in contact with the crystal growth surface 21 of the base substrate 20 regardless of the angle of the wall surface of the inner wall of the arc-shaped portion 13. Shall. Further, in order to accurately control the diameter of the crystal film 30 by the substrate holder 10, the thickness (height) of the inner wall of the opening 12 of the substrate holder 10, that is, the thickness of the ring 110 in the example shown in FIG. The thickness is preferably equal to or greater than the thickness of the crystal film 30.

  As described above, the crystal film 30 separated from the base substrate 20 may have a facet surface at the periphery thereof. If the crystal film 30 is not rounded, the crystal substrate 35 may have an as-grown facet surface 37 on its end face, as shown in FIG. Even if the edge of the crystal film 30 is chamfered, in many cases, part of the facet surface 37 will remain. For example, the crystal substrate 35 having a principal surface substantially parallel to the C plane manufactured by the manufacturing method of the present invention has an M plane, an R plane, a {1-101} plane, a {11-22} plane, It has at least one facet surface 37 of {11-21} plane and A plane. Among them, the facet surface 37 that is particularly often seen is the R surface, and then the {11-22} surface is often seen. Note that such an as-grown facet surface 37 can also function as an orientation flat.

  Further, as described above, the crystal film 30 can be grown in a shape depending on the outline of the opening 12 of the substrate holder 10, but the end face is formed by the facet surface 37 appearing on the peripheral edge thereof. It may have a part which grows away from the inner wall of ten openings 12. Further, the peripheral edge portion of the crystal film 30 is behind the inner wall of the opening 12 of the substrate holder 10 and the growth film thickness tends to be relatively small. Thus, the crystal film 30 tends to taper as it grows on the base substrate 20. In view of this, the diameter d of the arc-shaped portion 13 of the substrate holder 10 may be made a predetermined amount larger than the diameter of the crystal substrate 35 to be obtained. More specifically, the arc-shaped portion 13 of the substrate holder 10 may have a diameter larger than the predetermined diameter Φ within a range of 2% or less of the predetermined diameter Φ. Thereby, it is easy to match the diameter of the crystal substrate 35 with the predetermined diameter Φ to be obtained.

<Embodiment 2>
FIG. 3 is a schematic top view of a substrate holder according to the method for manufacturing a crystal substrate of the second embodiment. The substrate holder 11 in the example shown in FIG. 3 includes a plurality of openings 12 and can hold a plurality of base substrates 20. Thereby, the crystal film 30 can be simultaneously grown on the plurality of base substrates 20, and the crystal substrate 35 can be efficiently manufactured. In addition, it is preferable that the plurality of openings 12 are provided so that the centers thereof are substantially located on concentric circles. This makes it easy to improve the uniformity of the crystal film 30 on each base substrate 20 and the in-plane distribution of crystallinity. Further, the substrate holder 11 includes a reference surface 17 that faces the opening 12 and faces the orientation flat 23 of the base substrate 20 to be held substantially in parallel. Thereby, as described above, the installation accuracy of the string-like portion 14 (wall surface 15) with respect to the crystal plane orientation of the base substrate 20 can be increased, and the notch 36 such as an orientation flat (main orientation flat) is accurately formed on the crystal substrate 35. Easy to form.

  The opening 12 of the substrate holder 11 includes, in its outline, a second chord 19 that is not parallel to the chord 14 and has a different size from the chord 14. Thereby, in the growth process of the crystal film 30, notches for identifying the front and back of the crystal substrate 35 such as an index flat can be easily formed in the crystal film 30. The second string portion 19 may be relatively small as long as it can be visually recognized, and is preferably smaller than the string portion 14, for example. Further, the inner wall of the second chord portion 19 may also have a wall surface substantially parallel to the crystal plane of the crystal film 30. Thereby, the notch formed in the crystal substrate 35 by this 2nd string-like part 19 can be functioned also as a sub orientation flat.

  In addition, the shape of the notch for identifying the front and back of the crystal substrate 35 is not limited to a string shape (straight shape). In that case, instead of the second chord 19, the opening 12 of the substrate holder 10 has a protruding portion that protrudes inward in an arbitrary shape such as a V shape, a U shape, or a semicircular shape. including. And this protrusion part is not located on the center line (vertical bisector) of the 1st chord-like part 14, or the base substrate 20 side in the inner wall of the opening part 12 or its opposite side (preferably It is biased toward the base substrate 20 side). Thereby, the position of the notch of the crystal substrate 35 formed by the projecting portion differs between the front side and the back side of the substrate, so that the front and back sides of the crystal substrate 35 can be identified.

  In addition, it is preferable that the positions, directions, and sizes of the first chord portion 14 and the second chord portion 19 and the diameter d of the arcuate portion 13 in each opening portion 12 are the same, but the opening portion 12. It may be changed every time. Further, the second string-like portion 19 can also be applied to the substrate holder 10 of the first embodiment. Furthermore, also in the substrate holder 11 of the present embodiment, the circular portion of the crystal film 30 can be omitted by applying the arc-shaped portion 13 described in the first embodiment.

  Hereinafter, each component of the present invention will be described.

(Substrate holder)
The substrate holders 10 and 11 may be any ones that can withstand a high temperature atmosphere during the growth of the crystal film 30 and have sufficient mechanical strength to hold the base substrate 20. Further, in order to suppress displacement and distortion of the base substrate 20 during the growth of the crystal film 30, the substrate holders 10 and 11 preferably have a thermal expansion coefficient higher than that of the base substrate 20. Examples of the material for the substrate holders 10 and 11 include carbon (carbonaceous, graphite), SiC, and BN. Carbon is particularly preferable.

(Base substrate)
The base substrate 20 may be any substrate on which the crystal film 30 can be grown, preferably epitaxially grown. Examples of the material of the base substrate 20 include sapphire (Al ₂ O ₃ ), spinel (MgAl ₂ O ₄ ), GaN, AlGaN, AlN, Si, SiC, GaAs, GaP, InP, ZnS, ZnO, ZnSe, diamond, and the like. It is done. In addition, a composite substrate in which a layer of a material different from that, preferably a material similar to the crystal film 30 is formed on a self-supporting substrate made of a material different from the crystal film 30 may be used. In particular, when the crystal film 30 is a nitride semiconductor, a sapphire whose crystal growth surface 21 is substantially parallel to the C plane (0001) or a composite substrate in which a nitride semiconductor layer is formed thereon is preferable. Note that the crystal growth surface 21 of the base substrate 20 may be inclined (off) by a predetermined angle from a specific crystal plane. The size of the base substrate 20 is, for example, 1 inch or more and 8 inches or less, preferably 2 inches or more and 6 inches or less, more preferably 2 inches or more and 4 inches or less. The thickness of the base substrate 20 is, for example, 30 μm to 3 mm, preferably 0.1 mm to 2 mm, more preferably 0.5 mm to 2 mm. If the base substrate 20 has such a size and thickness, cracks and cracks in the crystal film 30 can be easily suppressed. The shape of the base substrate 20 (considering notches such as orientation flats) is preferably circular, but may be rectangular, triangular, semicircular, fan-shaped, or the like.

(Crystal film)
The crystal film 30 only needs to be capable of crystal growth on the base substrate 20 by vapor phase growth. The crystal film 30 may be a single layer film or a multilayer film, and may be a self-standing substrate or a semiconductor element structure. The material of the crystal film 30 is mainly represented by the general formula Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1) such as GaN, AlGaN, InGaN, and the like. A nitride semiconductor. A part of the group III element may be substituted with B, and a part of N may be substituted with P, As, or the like. Nitride semiconductors are relatively difficult to obtain bulk crystals, and their crystal substrates are still more expensive than other materials, and the present invention is particularly effective. In addition, the material of the crystal film 30 is a GaAs compound (mainly expressed by the general formula Al _v In _w Ga _1-vw As (0 ≦ v ≦ 1, 0 ≦ w ≦ 1, v + w ≦ 1)). , GaP-based compound (mainly represented by the general formula _{Al s in t Ga 1-s} -t P (0 ≦ s ≦ 1,0 ≦ t ≦ 1, s + t ≦ 1)), ZnS, ZnSe, ZnO, Si, SiC, diamond, etc. may be used. The crystal film 30 may be appropriately doped with impurities in order to control the conductivity type. In particular, when the crystal film 30 is a nitride semiconductor, the n-type impurity can be Si, O, S, or the like, and the p-type impurity can be Mg, Zn, C, or the like. Among these, the n-type impurity is preferably Si, and the p-type impurity is preferably Mg. The concentration of these impurities may be, for example, 1 × 10 ¹⁷ / cm ³ or more and 1 × 10 ²¹ / cm ³ or less.

  Further, as a method of separating the crystal film 30 from the base substrate 20, a method of removing the base substrate 20 by polishing, a chemical treatment or laser irradiation is performed near the interface between the crystal film 30 and the base substrate 20 to form the crystal film 30. Examples thereof include a method of peeling from the base substrate 20 and a method of naturally peeling the crystal film 30 from the base substrate 20 due to thermal stress after the crystal film 30 is grown. In particular, by utilizing natural peeling, the crystal film 30 can be easily separated from the base substrate 20 at a low cost.

(Vapor phase growth equipment)
Vapor phase epitaxy (VPE: Vapor Phase Epitaxy), chemical vapor deposition (CVD: Chemical Vapor Deposition), molecular beam epitaxy (MBE: Molecular Beam Epitaxy), etc. Apparatus). In particular, the VPE method and the CVD method are preferable, and more specifically, a hydride vapor phase epitaxy (HVPE) capable of relatively high-speed crystal growth, and an organic in which growth rate and film thickness can be easily controlled. A metal organic chemical vapor deposition (MOCVD) method is suitable. You may use combining these methods. In particular, when the crystal film 30 is a nitride semiconductor, the HVPE method uses ammonia (NH ₃ ) and a group III element halide (eg, GaCl) as main raw materials. In the MOCVD method, NH ₃ and trimethyl gallium (TMG) are used as main raw materials. In addition, when doping impurities as described above, a dopant such as silane (SiH ₄ ) or cyclopentadienyl magnesium (Cp ₂ Mg) is used together with these main raw materials. Further, by doping such impurities, the growth mode of the crystal film 30 can be controlled (for example, lateral growth can be promoted).

  Examples according to the present invention will be described in detail below. Needless to say, the present invention is not limited to the following examples.

<Example 1>
First, with a MOCVD apparatus, a buffer layer and a GaN foundation layer are grown on a sapphire substrate by 25 μm, and this is used as a foundation substrate. At this time, the buffer layer and the base layer are grown under conditions that promote natural peeling of the crystal film grown thereon. This sapphire substrate has a diameter of 89 mm and a thickness of 0.5 mm, and has an orientation flat with an A surface of 15 mm in length at its end face. The crystal growth surface of the sapphire substrate has an off angle of 0.35 ° or less from the C plane (0001) so that the right side is higher when the orientation flat is facing forward.

  Next, the base substrate thus manufactured is fixed to a substrate holder. This substrate holder is composed of two parts, a holder body and a ring. Both parts are made of carbon. The inner wall of the cylindrical portion of the holder body has a contour in which a part of a circle having a diameter of 89.2 mm is cut out by a chord having a length of 15 mm corresponding to the contour of the base substrate. The wall surface of the part is the reference plane. In addition, the outline of the opening part of the support part of a holder main body is a circle with a diameter of 83 mm. The outer shell of the ring substantially coincides with the contour of the inner wall of the cylindrical portion of the holder body (considering the fitting tolerance). Thereby, a ring is substantially fixed to a holder main body. The opening portion of the ring has a contour in which a part of a circle having a diameter of 80 mm is cut out by a chord (string portion) having a length of 26 mm. The chord-like portion is provided in a direction rotated 90 ° counterclockwise from the portion of the outer chord. The thickness of the ring is 1 mm. And a base substrate is inserted in the cylindrical part of a holder main body, the orientation flat is made to face substantially parallel to a reference plane, and it is installed on a ring. Thereby, the base substrate is also substantially fixed to the holder body. Finally, a soaking plate is placed on the back surface of the base substrate.

  As described above, the substrate holder holding the base substrate is installed in the reaction furnace of the HVPE apparatus, and GaN is grown on the base substrate by about 1 mm at 1020 ° C. At this time, it is preferable to adjust conditions so that the growth film thickness of a peripheral part becomes a little larger than that of a center part. Thereafter, when the substrate holder is taken out of the HVPE apparatus, a GaN crystal film that is naturally separated from the sapphire substrate when the temperature is lowered can be obtained. This crystal film has a contour in which a part of a circle having a diameter of 80 mm is cut out by a chord having a length of 26 mm, which substantially matches the contour of the opening of the ring. Then, the end face of the cutout of the crystal film can be confirmed to be a plane where the amount of deviation from the A-plane of GaN is about 0.83 ° when evaluated by the X-ray diffraction method. If the crystal film is rounded so as to leave a range of 3 inches in diameter from the center, a notch with a length of 15 mm that can function as an orientation flat can be left.

<Example 2>
In the second embodiment, the configuration and process excluding the ring of the substrate holder are the same as those in the first embodiment. The opening of the ring in Example 2 has a contour in which a part of a circle having a diameter of 76.7 mm is cut out by a chord (string portion) having a length of 16 mm. Using such a substrate holder, in the same manner as in Example 1, a GaN crystal having a contour in which a part of a circle having a diameter of 76.24 to 76.51 mm is cut out by a string having a length of about 16 mm. A membrane can be obtained. After that, this crystal film was not rounded, but was subjected to double-sided polishing and edge chamfering, and a part of a circle with a diameter of about 3 inches was cut out by a string with a length of about 16 mm. A GaN crystal substrate is finished. In addition to the surface formed by chamfering the edge, the as-grown R-plane, {11-22} plane, and the like are observed on the end face of the GaN crystal substrate.

  The method for manufacturing a crystal substrate according to the present invention can be used for manufacturing a wafer of a semiconductor element such as a light emitting device such as an LED or LD, an electronic device such as a transistor, or a substrate for crystal growth of such a wafer.

DESCRIPTION OF SYMBOLS 10,11 ... Board | substrate holder, 100 ... Holder main body, 101 ... Cylindrical part, 102 ... Support part, 110 ... Ring, 12 ... Opening part, 13 ... Arc-shaped part, 14 ... String-like part (1st string 15) wall surface, 17 ... reference plane, 19 ... second string-like portion 20 ... base substrate, 21 ... crystal growth surface, 23 ... orientation flat 30 ... crystal film, 35 ... crystal substrate, 36 ... notch , 37 ... Faceted surface 40 ... Soaking plate

Claims (7)

A method of producing a crystal substrate from the crystal film by growing a crystal film on a crystal growth surface of a base substrate having an orientation flat held by a substrate holder of a vapor phase growth apparatus,
The substrate holder includes an opening that exposes a part of a crystal growth surface of the base substrate,
The opening includes an arcuate portion and a chordal portion in its outline,
The method for producing a crystal substrate, wherein the inner wall of the string-like portion has a wall surface substantially parallel to a surface obtained by rotating the orientation flat by an integral multiple of 30 ° or 90 ° with the central axis of the base substrate as a rotation axis.   2. The method for manufacturing a crystal substrate according to claim 1, wherein the opening includes a second chord-shaped portion that is not parallel to the chord-shaped portion and has a size different from that of the chord-shaped portion.   The method for manufacturing a crystal substrate according to claim 1, wherein the crystal film is a nitride semiconductor. A crystal substrate having a diameter Φ approximately equal to any one of 2 inch, 2.5 inch, 3 inch, 4 inch, 5 inch, 6 inch, 50 mm, 75 mm, 100 mm, 125 mm, and 150 mm from the crystal film. A method of manufacturing
4. The manufacturing of the crystal substrate according to claim 1, wherein the arc-shaped portion has a diameter substantially equal to the diameter Φ or a diameter larger than the diameter Φ in a range of 2% or less of the diameter Φ. Method. A substrate holder for a vapor phase growth apparatus for holding a base substrate having an orientation flat and a crystal growth surface,
An opening for exposing a part of the crystal growth surface of the base substrate, and a reference surface facing substantially parallel to the orientation flat of the base substrate,
The opening includes an arcuate portion and a chordal portion in its outline,
The inner wall of the string-like portion is a substrate holder having a wall surface substantially parallel to a surface obtained by rotating the reference surface by an integral multiple of 30 ° or 90 ° about the central axis of the opening.   6. The substrate holder according to claim 5, wherein the opening includes a second string-shaped portion that is not parallel to the string-shaped portion and has a size different from that of the string-shaped portion in an outline thereof.   The arcuate portion is approximately equal to a diameter Φ approximately equal to any one of 2 inches, 2.5 inches, 3 inches, 4 inches, 5 inches, 6 inches, 50 mm, 75 mm, 100 mm, 125 mm, and 150 mm. The substrate holder according to claim 5 or 6, wherein the substrate holder has a diameter or a diameter larger than the diameter Φ in a range of 2% or less of the diameter Φ.

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