JP5559669B2 - Group III nitride single crystal manufacturing method and seed crystal substrate used therefor - Google Patents

Description

  The present invention relates to a method for growing a group III nitride single crystal and a seed crystal substrate used therefor.

  Gallium nitride (GaN) crystal has attracted attention as an excellent blue light emitting element material, and has been put into practical use as a blue-violet semiconductor laser element for light emitting diodes and optical pickups. In recent years, development as semiconductor films, green laser substrates, high-brightness and high-efficiency LED substrates and power device substrates constituting electronic devices such as high-speed IC chips used in mobile phones and the like has become active.

GaN
A method has been reported in which a template substrate is obtained by depositing a seed crystal film of AlN or AlN on a single crystal substrate such as sapphire and a GaN single crystal is grown on the template substrate.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-182551), a large number of polygonal seed crystal films are formed on a template substrate, and a GaN single crystal is laterally overgrown thereon.

  On the other hand, when a gallium nitride (GaN) seed crystal film is vapor-phase grown on a substrate such as sapphire by the MOCVD method and a gallium nitride single crystal is grown on the gallium nitride single crystal by the flux method, it is grown due to the difference in thermal expansion. Cracks occur in the single crystal thick film. For this reason, attention has been paid to a technique for reducing the stress applied to the single crystal and preventing the crack by naturally separating the grown single crystal from the substrate as a crack prevention measure.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2005-12171), a void is formed on the surface of the seed crystal substrate, and crystal growth is performed from this portion, thereby reducing the contact area with the grown crystal and utilizing the difference in thermal expansion during cooling. The crystal after growth is peeled off.

  Similarly, the seed crystal film is patterned by etching to form voids, the contact area between the single crystal and the substrate is reduced, and the single crystal is peeled off using the stress during cooling after growing the single crystal as a trigger (Patent document 3; PCT / JP2010 / 060257: unpublished at the time of this application) (patent document 4; PCT / JP2010 / 061740: unpublished at the time of this application) (patent document 5: JP 2009-18975) (patent document 6: WO2009 / 011407 A1) (Patent Document 7: JP-A-2004-247711) (Patent Document 8: JP-A-2009-120465) (Patent Document 9: Patent-4396816) (Patent Document 10: JP-A-2008-239365).

JP2004-182551 JP2005-12171 PCT / JP2010 / 060257 PCT / JP2010 / 061740 JP2009-18975 WO2009 / 011407 A1 JP2004-247711 JP2009-120465 Patent-4396816 JP2008-239365

  As described above, various methods have been proposed so far. However, it is required to further reduce the generation of cracks by improving the quality of a single crystal grown by a flux method and promoting the peeling of the single crystal. However, referring to the above method, using a template substrate with groove processing as a seed crystal substrate and trying to grow crystals by the sodium flux method and self-supporting by peeling, there are cases where peeling is possible without causing cracks. However, there were many cases where cracking did not occur even when peeling, and it was difficult to obtain crystals without cracks with good reproducibility.

An object of the present invention is to use a template substrate subjected to surface processing as a seed crystal substrate, and perform crystal growth by a flux method to produce a free-standing nitride single crystal peeled off from the substrate without cracks with good reproducibility. It is to provide a method for obtaining a high yield.

In the present invention, a seed crystal film made of a group III metal nitride single crystal is formed on a substrate, and a non-growth surface is formed on the substrate at this time; and a III crystal is formed on the seed crystal film by a flux method. A growth process for growing a group III metal nitride single crystal;
A method comprising:
The substrate includes an outer edge provided over the entire circumference along the outer edge of the substrate, and a central portion provided inside the outer edge, and a plurality of band-shaped portions made of a seed crystal film are arranged in the central portion. are, are a plurality of separation portions array of seed crystal film over the entire circumference of the outer edge, the seed crystal area ratio of the outer edges rather smaller than the seed crystal area ratio of the central portion, between the seed crystal film The present invention relates to a method for producing a group III metal nitride single crystal, wherein a non-growth surface is formed on the substrate and the group III metal nitride single crystal grown by a flux method is peeled off from the substrate .

The present invention also includes a substrate, a seed crystal film made of a group III metal nitride single crystal formed on the substrate, and a non-growing surface, and the group III metal is formed on the seed crystal film by a flux method. A seed crystal substrate for growing a nitride single crystal and peeling a group III metal nitride single crystal grown by a flux method from the substrate,
The substrate includes an outer edge provided over the entire circumference along the outer edge of the substrate, and a central portion provided inside the outer edge, and a plurality of band-shaped portions made of a seed crystal film are arranged in the central portion. are, are a plurality of separation portions array of seed crystal film over the entire circumference of the outer edge, the seed crystal area ratio of the outer edges rather smaller than the seed crystal area ratio of the central portion, of the seed crystal film The non-growing surface is formed between them.

  The present inventor considered that the reason why the reproducibility of the nitride single crystal grown by the flux method is poor is that the separation does not occur in the same manner every time. In addition, the cause of the high occurrence frequency of cracks in the single crystal was considered that the timing at which peeling occurred was late. Therefore, the present invention has been reached as a result of studying a method of causing peeling in the same manner at an earlier timing.

  That is, the nitride single crystal grown on the template substrate gradually increases in stress due to the difference in thermal expansion coefficient between the substrate material and the nitride single crystal during the cooling process, and the shape of the substrate is distorted (warped). As a result, the stress required for peeling is relaxed. As a result, it was considered that the timing of peeling was not aligned and cracks were caused.

  Here, by reducing the contact area (seed crystal area) between the seed crystal at the outer edge portion and the substrate surface, the stress necessary for peeling is reduced at the outer edge portion. As a result, the nitride single crystal at the outer edge begins to peel off at a lower stress concentration before the central portion peels off. At the same time as the peeling starts, the warping of the shape of the substrate is eased at the peeled portion. Therefore, a greater stress concentration occurs in a region that has not yet been peeled off at the outer edge portion, and peeling progresses symmetrically from the outer peripheral portion toward the central portion.

  At the same time, a band-shaped seed crystal film is formed at the center, and the separation progresses in an orderly manner in the longitudinal direction of the band-shaped portion. As a result, it was found that the reproducibility of single crystal peeling was good and the crack generation rate was reduced.

(A) is a top view which shows typically the seed crystal substrate 9 which concerns on a reference form, (b) is a front view of (a). It is a top view which shows typically the seed crystal substrate 11 which concerns on the example of this invention. (A)-(e) is an example which shows the shape of the isolation | separation part formed in the outer edge part, respectively. It is a top view which shows typically 11 A of seed crystal substrates which concern on the example of this invention. (A) is sectional drawing which shows typically the state which formed the seed crystal film 2 on the surface 1a of the board | substrate 1, (b) is typical which shows the state in which the seed crystal film 3 spaced apart from each other was formed. FIG. (A) is sectional drawing which shows typically the state which grew the group III metal nitride single crystal 4 on the seed crystal film 3 of FIG. 5 by the flux method, (b) is the single crystal 4 from the board | substrate 1. FIG. It is sectional drawing which shows typically the state which made it peel. (A) is sectional drawing which shows typically the state which formed the seed crystal film 2 in the surface 1a of the board | substrate 1, (b) is the state which formed the recessed part 5 and the seed crystal film 3 mutually spaced apart. It is sectional drawing shown typically. (A) is sectional drawing which shows typically the state which grew the group III metal nitride single crystal 4 on the seed crystal film 3 of FIG. 7 by the flux method, (b) is the single crystal 4 from the board | substrate 1. FIG. It is sectional drawing which shows typically the state which made it peel. It is a top view which shows typically the pattern of the seed crystal substrate produced by the comparative example.

  In the reference example shown in FIG. 1, a large number of band-shaped seed crystal films 10 made of a group III metal nitride single crystal are formed on the surface 1 c of the substrate 1. Each strip-like portion extends one-dimensionally, for example, in the direction of arrow A (B). A non-growing surface 1b is provided between the adjacent strips 3. Each non-growing surface 1b also extends in the direction of arrow A (B).

  Here, the various band-like crystal films 10 extend one-dimensionally in a certain direction, and a nitride single crystal is grown thereon. Therefore, the single crystal is considered to peel along the direction of the seed crystal film when the temperature is lowered after the growth. However, in reality, according to the study by the present inventor, it was found that the single crystal does not peel in a certain direction, but when viewed microscopically, it peels in various directions at different timings. It was. That is, even if a large number of strip-shaped single crystal films 10 are formed in a certain direction, it is difficult to control the direction of peeling of the single crystal film formed thereon by the flux method.

FIG. 2 is a plan view schematically showing the seed crystal substrate 11 according to the embodiment of the present invention.
The surface 1c of the substrate 1 is divided into an outer edge portion 13 set over the entire circumference along the outer edge 1d of the substrate 1 and a central portion 12 set inside thereof. In the central portion 12, a large number of band-like portions 19 made of a single crystal are formed and arranged. Adjacent belt-like portions 19 are separated by a belt-like non-growing surface 1b. Each strip 19 extends in the direction of arrow A (B). In addition, the outer edge portion 13 is formed with a predetermined-shaped separation portion made of a seed crystal and arranged. Each separation part is separated from each other by a non-growing surface.

  FIGS. 3A to 3E are examples showing the shape of the separation portion provided on the outer edge portion. In (a), the separation part 20 has a strip shape. In (b), the separation part 21 is circular. In (c), the separation part 22 has a triangular shape. In (d), the separation part 23 has a quadrilateral shape. In (e), the separation part 24 has a hexagonal shape.

  In the seed crystal substrate 11 </ b> A shown in FIG. 4, the surface 1 c of the substrate 1 is divided into an outer edge portion 13 set over the entire circumference along the outer edge of the substrate 1 and a central portion 12 set inside the outer edge portion 13. ing. In the central portion 12, a large number of band-like portions 19 made of a single crystal are formed and arranged. Adjacent belt-like portions 19 are separated by a belt-like non-growing surface 1b. Each strip 19 extends in the direction of arrow A (B). On the outer edge portion 13, a band-like portion 25 made of a seed crystal is formed and arranged. The separation portions 25 are separated from each other by the non-growing surface 1e. Moreover, in this example, each strip | belt-shaped part 25 is extended toward arrow A (B) direction.

  The non-growth surface is a surface on which the nitride single crystal does not grow directly by the flux method. Specifically, the non-growing surface is an exposed surface of the substrate or the surface of another film (for example, an oxide thin film layer) formed on the substrate. Alternatively, if the group III metal nitride single crystal film on the substrate is thin or a group III metal nitride single crystal film is formed on the bottom surface of the recess, nitriding is performed on the group III metal nitride single crystal. Since the material single crystal may not grow by the flux method, it becomes a non-growth surface.

  In addition, the seed crystal strips provided at the outer edge portion and the central portion mean an elongated seed crystal film having a substantially constant width W. Needless to say, the width only needs to be constant in design, and inevitable manufacturing errors are allowed.

  In the present invention, the seed crystal area ratio at the outer edge is smaller than the seed crystal area ratio at the center. Here, the seed crystal area ratio is (area of seed crystal film) / (area of seed crystal film + area of non-growth surface). The seed crystal area ratio of the outer edge portion is (the area of the seed crystal film) / (the area of the seed crystal film + the area of the non-growth surface) in the outer edge portion, and (the area of the seed crystal film + the area of the non-growth surface) Area) is equal to the total area of the outer edge. The ratio of the seed crystal area in the central portion is (the area of the seed crystal film) / (the area of the seed crystal film + the area of the non-growing surface) in the central portion, and (the area of the seed crystal film + the area of the non-growing surface). Area) is equal to the total area of the central part.

  That is, a plurality of strip-like portions are arranged at the central portion, and a plurality of separation portions are arranged at the outer edge portion. And the area ratio of a seed crystal differs between a center part and an outer edge part.

  The outer shape of the substrate is not limited, but a circle and a regular polygon (for example, a regular triangle, a square, a regular hexagon, a regular octagon, etc.) are practical.

  The outer contour of the outer edge has a shape that matches the shape of the edge of the substrate. The inner contour of the outer edge is preferably similar to the outer edge of the substrate or circular. When the width WO (see FIG. 2) of the outer edge portion is constant, the inner contour of the outer edge portion is similar to the outer edge of the substrate. When the inner contour of the outer edge is circular, the outer contour of the central portion is circular.

  The ratio WO / WI of the width WO of the outer edge portion to the diameter WI of the central portion is preferably 0.1 or more, and more preferably 0.2 or more, from the viewpoint of promoting peeling from the outer edge portion. WO / WI is preferably 1 or less, and more preferably 0.5 or less, from the viewpoint of forming a high-quality film over a wide area. However, the width WO of the outer edge is an average value of the width of the outer edge over the entire circumference. The central portion diameter WI is an average value over the entire circumference of the distance from the center O of the substrate to the outer contour of the central portion.

  The ratio CO / CI with respect to the seed crystal area ratio CI at the center of the seed crystal area ratio CO at the outer edge is preferably 0.91 or less, more preferably 0.5 or less, from the viewpoint of promoting peeling from the outer edge. preferable. Further, from the viewpoint of promoting the growth of the nitride single crystal at the outer edge, the CO / CI is preferably 0.01 or more, and more preferably 0.1 or more.

  The seed crystal ratio CO of the outer edge portion is preferably 10% or less, and more preferably 5% or less, in order to promote peeling from the outer edge portion. Further, from the viewpoint of promoting the growth of the nitride single crystal at the outer edge, CO is preferably 0.1% or more, and more preferably 1% or more.

  The seed crystal ratio CI at the center is preferably 20% or less, more preferably 15% or less, in order to promote peeling from the outer edge. Further, from the viewpoint of improving the quality of the nitride single crystal in the central portion, CI is preferably 5% or more, and more preferably 10% or more.

  In a preferred embodiment, the separation portions are regularly arranged over the entire circumference of the outer edge portion. This is because the separation parts may be arranged one-dimensionally in a constant manner in the circumferential direction of the outer edge part, and may be arranged in a constant period in the circumferential direction and the radial direction of the outer edge part. Good.

  In a preferred embodiment, the belt-like parts are regularly arranged in the central part. As shown in FIGS. 2 and 4, the band-shaped portions may be arranged at a constant cycle in one direction, or may be arranged at a constant cycle in both the vertical and horizontal directions.

  In the outer edge portion and the central portion, the aspect ratio of the strip portion is not limited, but the average value is preferably 0.00005 or more, and more preferably 0.0005 or more. Moreover, it is preferable that the longitudinal direction of various crystal films is the same.

  From the viewpoint of growing a high-quality nitride single crystal on the seed crystal film, the width W of the belt-shaped portion made of the seed crystal is preferably 0.005 to 0.2 mm, and 0.01 to 0.00 mm. More preferably, it is 1 mm.

  The area of each separation part in the outer edge part is preferably smaller than the area of each band-like part in the central part, which makes it easy to reduce the seed crystal density in the outer edge part. From this viewpoint, it is preferable that the ratio of the area of each separation portion in the outer edge portion to the area of each band-like portion in the central portion is 0.2 or less as an average value of the entire outer edge portion. From the viewpoint of promoting the growth of a single crystal in the outer edge portion, the ratio of the area of each separation portion in the outer edge portion to the area of each strip portion in the central portion is 0.01 or more as an average value of the entire outer edge portion. It is preferable that

Next, the form of the seed crystal film and the non-growing surface will be illustrated.
As shown in FIG. 5A, the surface 1a of the substrate 1 is processed smoothly, and a well-oriented seed crystal film 2 is formed on the surface 1a.
Next, the seed crystal film 2 is processed to form a plurality of seed crystal films 3 separated from each other, as shown in FIG. A non-growing surface 1b is formed between adjacent seed crystal films 3.

Next, as shown in FIG. 6A, a group III metal nitride single crystal 4 is formed on the seed crystal film 3 by a flux method. In this step, the single crystals 4 formed on the adjacent seed crystal films 3 are connected to cover the substrate 1.
Next, in the temperature lowering process after the growth of the single crystal 4, as shown in FIG. 6B, the single crystal 4 is peeled off from the substrate 1 naturally or with little effort, as shown in FIG. Extremely high.

  7 and 8 show another embodiment. As shown in FIG. 7A, the surface 1a of the substrate 1 is processed smoothly, and the seed crystal film 2 is formed on the surface 1a. Next, the surface 1a of the substrate 1 is processed to form a plurality of seed crystal films 3 separated from each other as shown in FIG. 7B. However, in this example, the recess 5 is formed by further processing from the substrate surface 1a toward the inside. Therefore, the seed crystal film 3 remains on the protrusions 8 between the recesses 5. On the protrusion 8, the film formation surface 1a remains and a side wall surface 8a is formed. The side wall surface 8a and the recess bottom surface 1b are processed surfaces formed by processing.

Next, as shown in FIG. 8A, a group III metal nitride single crystal 4 is formed on the seed crystal film 3 by a flux method. In this step, the single crystals 4 formed on the adjacent seed crystal films 3 are connected to cover the substrate 1.
Next, in the temperature lowering process after the growth of the single crystal 4, as shown in FIG. 8B, the single crystal 4 is peeled from the template substrate naturally or with little effort, as shown in FIG. Extremely high.

  The thickness T (see FIGS. 5 and 7) of the substrate 1 is particularly preferably 0.8 mm or more and 1.2 mm or less, which can promote natural peeling from the single crystal substrate. From this viewpoint, the thickness T of the substrate is more preferably 0.9 mm or more, and further preferably 1.1 mm or less.

  Preferably, the angle θ formed by the longitudinal direction of the side wall surface 8a of the protrusion 8 and the a-axis of the substrate is 25 ° or less, more preferably 20 ° or less, and even more preferably 10 ° or less. Most preferably, the longitudinal direction of the side wall surface of the protrusion is parallel to the a-axis of the substrate body.

Here, the a-axis is <1 1 of hexagonal single crystal.
-2 0>. Since both sapphire and gallium nitride are hexagonal, a1, a2, and a3 are equivalent, [2 -1 -1 0], [1 1 -2 0], [-1 2 -1 0], [-2 [1 1 0], [-1 -1 2 0], [1 -2 1 0] are equivalent. Of these six, the a-axis often uses [1 1 -2 0] by convention, and the a-axis in this application means all of these equivalent axes and is expressed as [1 1 -2 0] Even when doing so, all of the equivalent axes are included.

The material of the substrate is not particularly limited, but a perovskite type composite such as sapphire, silicon single crystal, SiC single crystal, MgO single crystal, spinel (MgAl ₂ O ₄ ), LiAlO ₂ , LiGaO ₂ , LaAlO ₃ , LaGaO ₃ , NdGaO _3, etc. An oxide can be illustrated. The composition formula _{[A 1-y (Sr 1-} x Ba x) y ] _{[(Al 1-z Ga z)} 1-u · D u ] _O 3 (A is a rare earth element; D is niobium and One or more elements selected from the group consisting of tantalum; y = 0.3-0.98; x = 0-1; z = 0-1; u = 0.15-0.49; x + z = 0 .1 to 2) cubic perovskite structure composite oxides can also be used. SCAM (ScAlMgO ₄ ) can also be used.

  The formation method of the non-growing surface 1b is not limited. In particular, by grooving by sandblasting, it is possible to produce a deep groove (depth of 10 microns or more) that is difficult to produce by lithography at a low cost. Further, it is sufficient that the processed surface is smooth, the processing strain remains, and is not epi-ready (that is, a surface state where the GaN thin film does not grow), for example, laser processing, plasma etching, dicing (diamond blade) may be used. .

The depth d of the recess 5 in FIGS. 7B and 8B is 100 from the viewpoint of promoting the peeling of the grown single crystal and preventing the substrate 1 from cracking from the recess.
μm or less is preferable, 1 μm or less is more preferable, and 0.1 μm or less is most preferable. In sandblasting, when the 600-800th alumina abrasive grains are used, the processing speed of the sapphire substrate is several tens times slower than that of the GaN thin film, which is suitable for adjusting the depth of the recess.

The group III metal nitride single crystal constituting the seed crystal film is a nitride of one or more metals selected from Ga, Al, and In, such as GaN, AlN, GaAlN, and GaAlInN. Of these, GaN, AlN, and GaAlN are preferable.
The formation method of the seed crystal film is preferably the MOCVD method from the viewpoint of controllability of impurity concentration and film thickness uniformity.

  The thickness of the seed crystal film is not particularly limited. From the viewpoint of suppressing the meltback of the seed crystal film, the thickness is preferably 1 μm or more, and more preferably 5 μm or more. In addition, when the base film is thick, it takes time to form the base film, so that the film thickness is preferably as thin as possible so as not to melt back. From this viewpoint, the thickness of the seed crystal film can be 30 μm or less.

Next, a group III metal nitride single crystal is grown on the seed crystal film by a flux method.
The type of flux is not particularly limited as long as a group III metal nitride single crystal can be produced. In a preferred embodiment, a flux containing at least one of sodium metal and calcium metal is used, and a flux containing sodium metal is particularly preferred.

  In the flux, the raw material of the target group III metal nitride single crystal is mixed and used. This group III metal nitride single crystal is a nitride of one or more metals selected from Ga, Al, In, and B, such as GaN, AlN, GaAlN, GaAlInN, and BN. GaN and GaAlN are preferable.

The raw material constituting the flux is selected according to the target group III metal nitride single crystal.
As the gallium source material, a gallium simple metal, a gallium alloy, and a gallium compound can be applied, but a gallium simple metal is also preferable in terms of handling.

As the aluminum raw material, an aluminum simple metal, an aluminum alloy, and an aluminum compound can be applied, but an aluminum simple metal is also preferable in terms of handling.
As the indium raw material, indium simple metal, indium alloy, and indium compound can be applied, but indium simple metal is preferable from the viewpoint of handling.

III
The growth temperature of the group metal nitride single crystal and the holding time during the growth are not particularly limited, and are appropriately changed according to the type of the desired group III metal nitride single crystal and the composition of the flux. In one example, when a gallium nitride single crystal is grown using sodium or lithium-containing flux, the growth temperature can be set to 800 to 1000 ° C.

  In a preferred embodiment, the group III metal nitride single crystal is grown in an atmosphere composed of a mixed gas containing nitrogen gas. The total pressure of the atmosphere is not particularly limited, but is preferably 10 atm or more, and more preferably 30 atm or more from the viewpoint of preventing evaporation of the flux. However, since the apparatus becomes large when the pressure is high, the total pressure of the atmosphere is preferably 200 atm or less, and more preferably 100 atm or less.

Also, the nitrogen partial pressure in the atmosphere is not particularly limited, but when growing a gallium nitride single crystal, 10 to 200 atmospheres is preferable, and 30 to 100 atmospheres is more preferable. When growing an aluminum nitride single crystal, 0.1 to 50 atm is preferable, and 1 to 10 atm is more preferable.
A gas other than nitrogen in the atmosphere is not limited, but an inert gas is preferable, and argon, helium, and neon are particularly preferable. The partial pressure of a gas other than nitrogen is a value obtained by subtracting the nitrogen gas partial pressure from the total pressure.

  The actual training method in the present invention is not particularly limited. For example, the template substrate can be immersed in a flux in a crucible, the crucible can be accommodated in a pressure resistant container, and heated while supplying a nitrogen-containing atmosphere in the pressure resistant container. In addition, the flux can be brought into contact with the surface of the seed crystal film by fixing the template substrate at a predetermined position and raising the crucible containing the flux upward.

Example 1
A seed crystal substrate 11A having the shape shown in FIG. 4 was produced, and a single crystal was grown thereon by a flux method.

Specifically, a φ3 inch sapphire substrate was prepared. On the surface, a circular region of φ2 inches from the center O was a central portion 12, and a ring-shaped region having a width of 0.5 inches outside thereof was an outer edge portion 13. In the central part 12, the width of the belt-like part 19 was 50 μm, the width of the non-growing part 1b was 450 μm, the period was 500 μm, and the length was 4000-50800 μm (average 39900 μm). The belt-like portion 19 is formed over the entire central portion 12. The seed crystal ratio CI in the central portion 12 is 10.00%. Moreover, in the outer edge part 13, the width | variety of the strip | belt-shaped part 20 was 5 micrometers, the width | variety of the non-growth part 1b was 450 micrometers, the period was 455 micrometers, and length was 4000-56700 micrometers (average 20000 micrometers). The belt-like portion 25 is formed over the entire circumference of the outer edge portion 13. The seed crystal ratio CO in the outer edge portion 13 is 1.10%). The thickness of the seed crystal film is 5 μm.

  Next, 30 g of metal gallium (Ga) as a raw material, 40 g of metal sodium (Na) as a flux, and the template substrate were weighed and accommodated in a growth container. The growth conditions were such that the nitrogen pressure was 4.0 MPa and the temperature was 870 degrees to grow a gallium nitride single crystal. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 10 out of 10, and the number of samples where cracks occurred was 0 out of 10.

(Example 2)
A gallium nitride single crystal was grown in the same manner as in Example 1. However, in the outer edge portion, the width of the belt-like portion 25 was 5 μm, the length was 4000 to 56700 μm (average 20000 μm), and the width of the non-growth portion between the adjacent belt-like portions was 100 μm. The seed crystal ratio CO at the outer edge is 4.76%. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 10 out of 10, and the number of samples where cracks occurred was 0 out of 10.

(Example 3)
A gallium nitride single crystal was grown in the same manner as in Example 1. However, in the outer edge portion, the width of the band-shaped portion 25 was 5 μm, the length was 4000 to 56700 μm (average 20000 μm), and the width of the non-growth portion between the adjacent band-shaped portions was 500 μm. The seed crystal ratio CO at the outer edge is 0.99%. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 10 out of 10, and the number of samples where cracks occurred was 2 out of 10. Although the releasability is very good, the area of the seed crystal is narrow, so that grain boundaries and foreign substances are mixed inside the GaN crystal grown on the outer periphery, and stress is concentrated non-uniformly to cause cracks.

(Example 4)
A gallium nitride single crystal was grown in the same manner as in Example 1. However, in the outer edge portion, the width of the band-shaped portion 25 was 1 μm, the length was 4000 to 56700 μm (average 20000 μm), and the width of the non-growth portion between adjacent band-shaped portions was 1000 μm. The seed crystal ratio CO at the outer edge is 0.10%. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 10 out of 10, and the number of samples in which cracks occurred was 3 out of 10. Although the peelability was good, the narrow area of the seed crystal could cause grain boundaries and foreign matter to enter the inside of the GaN crystal grown on the outer periphery, resulting in uneven stress concentration and cracking. It was.

(Example 5)
A gallium nitride single crystal was grown in the same manner as in Example 1. However, in the outer edge portion, the width of the belt-like portion 25 was 6 μm, the length was 4000 to 56700 μm (average 20000 μm), and the width of the non-growing portion between the adjacent belt-like portions was 100 μm. The seed crystal ratio CO at the outer edge is 5.66%. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 8 out of 10, and the number of samples where cracks occurred was 2 out of 10.

(Example 6)
A gallium nitride single crystal was grown in the same manner as in Example 1. However, in the outer edge portion, the width of the band-shaped portion 25 was 20 μm, the length was 4000 to 56700 μm (average 20000 μm), and the width of the non-growing portion between the adjacent band-shaped portions was 200 μm. The seed crystal ratio CO at the outer edge is 9.09%. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 7 out of 10, and the number of samples where cracks occurred was 3 out of 10.

(Comparative Example 1)
A seed crystal substrate 9A having the shape shown in FIG. 1 was produced, and a single crystal was grown thereon by a flux method.

Specifically, a φ3 inch sapphire substrate was prepared. A band 10 of a seed crystal was formed on the entire surface of a sapphire substrate having a diameter of 3 inches. The width of the belt-shaped portion 10 was 50 μm, the length was 4000 to 76200 μm (average 59800 μm), and the width of the non-growing portion b was 450 μm. The seed crystal ratio is 10.00% over the entire substrate surface. The thickness of the seed crystal film is 5 μm.
Next, a gallium nitride single crystal was grown by the flux method in the same manner as in Example 1. Then, the grown GaN substrate and template substrate were taken out of the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 7 out of 10, and the number of samples where cracks occurred was 10 out of 10. Since there was no place to be the starting point of peeling, peeling did not proceed evenly from the outer periphery, and uneven stress concentration occurred and cracks occurred.

(Comparative Example 2)
A single crystal was grown in the same manner as in Example 1. However, in the center part 12, the width | variety of the strip | belt-shaped part 19 was 5 micrometers, the width | variety of the non-growth part 1b was 200 micrometers, and length was 4000-50800 micrometers (39900 micrometers on average). The belt-like portion 19 is formed over the entire central portion 12. The seed crystal ratio CI in the central portion 12 is 2.44%. Moreover, in the outer edge part 13, the width | variety of the strip | belt-shaped part 25 was 5 micrometers, the width | variety of the non-growing part 1e was 100 micrometers, and length was 4000-56700 micrometers (average 20000 micrometers). The belt-like portion 25 is formed over the entire circumference of the outer edge portion 13. The seed crystal ratio CO at the outer edge is 4.76%). The thickness of the seed crystal film is 5 μm.

Next, a gallium nitride single crystal was grown by a flux method in the same manner as in Example 1. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.
A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 7 out of 10, and the number of samples where cracks occurred was 10 out of 10.

  The single crystal peels off because the seed crystal area ratio is low in both the outer peripheral part and the central part. However, since the seed crystal area ratio is lower in the central region, the peeling does not proceed evenly from the outer periphery, resulting in uneven stress concentration. Occurred and cracks occurred.

(Comparative Example 3)
A pattern as shown in Patent Document 2 (FIG. 2B of JP-A-2005-12171) was formed on the surface of the sapphire substrate. Other than that, a gallium nitride single crystal was grown in the same manner as in Example 1.

  A planar pattern of the seed crystal substrate 30 and the seed crystal film is schematically shown in FIG. Specifically, a 51 × 51 mm square region was set in the center of the φ3 inch sapphire substrate 1, and a large number of band-like portions 29 made of gallium nitride single crystal were formed. However, the width | variety of each strip | belt-shaped part 29 is 5 micrometers, and the width | variety of the non-growing part 1b is 45 micrometers. In the circular region 13 2 inches from the center of the substrate 1, a large number of strips 29 are regularly arranged over the whole, and the seed crystal area ratio is 10.00%. In the region 13 having a width of 1 inch on the outer edge side of the substrate, the band-like portions 29 exist at four corners, but most of them do not have the seed crystal film. The seed crystal area ratio in the outer edge portion 13 is 0.55%. The thickness of the seed crystal film is 5 μm.

  Next, a gallium nitride single crystal was grown by a flux method in the same manner as in Example 1. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 10 out of 10, and the number of samples where cracks occurred was 10 out of 10. The average seed crystal area ratio in the outer peripheral part is lower than that in the central part, but since the seed crystal parts in the outer peripheral part are concentrated in four places in the cross direction, there are no seed crystals between the seed crystal concentration regions. It is an area that does not. Therefore, peeling did not start reproducibly at the boundary between the outer peripheral portion and the central portion of the portion, and uneven stress concentration occurred and cracks occurred.

(Comparative Example 4)
A gallium nitride single crystal was grown in the same manner as in Example 1. However, in this example, a large number of circular single crystal films with a radius of 25 μm were formed over the entire sapphire substrate with a diameter of 3 inches. The interval between adjacent single crystal films is 90 μm. The seed crystal area ratio is 10.02%. The thickness of the seed crystal film is 5 μm.

  Next, a gallium nitride single crystal was grown by a flux method in the same manner as in Example 1. After completion of the growth, the grown GaN substrate and template substrate were taken out from the flux.

  A total of 10 times of cultivation were performed in the same manner. The number of samples from which the grown φ3 inch GaN substrate was peeled off from the template substrate was 7 out of 10, and the number of samples where cracks occurred was 10 out of 10.

Claims (10)

Forming a seed crystal film made of a group III metal nitride single crystal on the substrate, and forming a non-growth surface on the substrate at this time; and a group III metal by a flux method on the seed crystal film; A growth process for growing a nitride single crystal;
A method comprising:
The substrate includes an outer edge portion provided over the entire periphery along the outer edge of the substrate, and a central portion provided on the inner side of the outer edge portion, and a plurality of seed crystal films formed in the central portion. A band-shaped portion is arranged, a plurality of separation portions made of the seed crystal film are arranged over the entire circumference of the outer edge portion, and the seed crystal area ratio of the outer edge portion is larger than the seed crystal area ratio of the central portion rather small, the seed crystal film the and non-growing surface is formed between, characterized in that for peeling the group III metal nitride single crystal grown by the flux method from the substrate, the group III metal nitride A method for producing a single crystal.   The method according to claim 1, wherein the separation portions are arranged at a constant period in the outer edge portion.   The method according to claim 1 or 2, wherein the strips are arranged at a constant period in the central part.   The method according to any one of claims 1 to 3, wherein a dimension of the separation part provided at the outer edge part is different from a dimension of the belt-like part provided at the center part. .   The method according to claim 4, wherein a shape of the separation portion provided at the outer edge portion is a band shape, a circular shape, or a regular polygon shape. A substrate, a seed crystal film made of a group III metal nitride single crystal formed on the substrate, and a non-growth surface; and a group III metal nitride single crystal formed on the seed crystal film by a flux method. A seed crystal substrate for peeling off the group III metal nitride single crystal grown by a flux method from the substrate,
The substrate includes an outer edge portion provided over the entire periphery along the outer edge of the substrate, and a central portion provided on the inner side of the outer edge portion, and a plurality of seed crystal films formed in the central portion. A band-shaped portion is arranged, a plurality of separation portions made of the seed crystal film are arranged over the entire circumference of the outer edge portion, and the seed crystal area ratio of the outer edge portion is larger than the seed crystal area ratio of the central portion rather small, and wherein the non-growing surface between the seed crystal film is formed, the seed crystal substrate.   The seed crystal substrate according to claim 6, wherein the separation parts are arranged at a constant period in the outer edge part.   The seed crystal substrate according to claim 6 or 7, wherein in the central portion, the band-like portions are arranged at a constant period.   The seed crystal according to any one of claims 6 to 8, wherein a size of the separation portion provided at the outer edge portion is different from a size of a belt-like portion provided at the central portion. substrate. The seed crystal substrate according to claim 9, wherein a shape of the separation portion provided at the outer edge portion is a band shape, a circular shape, or a regular polygonal shape.

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