JP5754191B2 - Method for producing group 13 nitride crystal and method for producing group 13 nitride crystal substrate - Google Patents

Description

  The present invention relates to a method for producing a group 13 nitride crystal, a method for producing a group 13 nitride crystal substrate, a group 13 nitride crystal, and a group 13 nitride crystal substrate.

  At present, most of InGaAlN-based (group 13 nitride) devices used as ultraviolet, purple-blue to green light sources are formed on a sapphire or SiC substrate by MOCVD (metal organic chemical vapor deposition) or MBE. It is manufactured by crystal growth using (molecular beam crystal growth method) or the like. As a problem when sapphire or SiC is used as a substrate, there is an increase in crystal defects caused by a large difference in thermal expansion coefficient and lattice constant from the group 13 nitride. For this reason, it leads to the fault that device characteristics are bad, for example, it is difficult to extend the lifetime of the light emitting device, or the operating power is increased.

  In order to solve these problems, a GaN substrate that is the same as the material for crystal growth on the substrate is most appropriate.

At present, GaN free-standing substrates include ELO (Epitaxial Lateral Overgrowth), advanced-DEEP method, VAS (Void-Assisted Separation) method, etc. on different substrates such as sapphire substrate or GaAs substrate. A growth method that reduces the dislocation density is used to grow GaN thick by HVPE (halogenated vapor phase epitaxy), and then peel off the GaN thick film from a different substrate. The GaN substrate manufactured as described above has a transition density reduced to about 10 ⁶ cm ⁻² and a size of 2 inches has been put into practical use. Recently, a further large-diameter substrate such as 4 inches or 6 inches is desired for reducing the cost of white LEDs and for electronic device applications.

  However, warpage due to the difference in thermal expansion coefficient between different substrate materials and GaN and the generation of cracks are obstacles to the increase in diameter. In addition, since a GaN substrate manufactured by the HVPE method is auto-doped with Si from a quartz reaction tube, it becomes a low-resistance n-type GaN substrate.

On the other hand, as one of the methods for realizing a GaN substrate by liquid phase growth, a flux method for crystal growth of GaN by dissolving nitrogen in a mixed melt of metallic sodium and metallic Ga has been researched and developed. In Non-Patent Document 1, sodium azide (NaN ₃ ) and metal Ga are used as raw materials and sealed in a stainless steel reaction vessel (inner vessel dimensions; inner diameter 7.5 mm, length 100 mm) in a nitrogen atmosphere. It has been reported that a GaN crystal is grown by holding it at a temperature of 600 to 800 ° C. for 24 to 100 hours.

The flux method is capable of crystal growth at a relatively low temperature of 700 to 1000 ° C., and the pressure in the container is relatively low at about 30 to 100 kg / cm ² , and is a crystal growth method that can be industrialized. Further, since Si is not auto-doped from the reaction tube as in the HVPE method, a high-purity crystal can be manufactured, and the carrier concentration and the resistance value can be controlled.

  As a method of manufacturing a GaN substrate using the flux method, Patent Document 1 provides a manufacturing method capable of manufacturing a group 13 nitride substrate having a low dislocation density and a high surface flatness. (1) a step of preparing a group 13 nitride semiconductor layer, (2) a step of forming a patterned mask film on the semiconductor layer, and (3) a plurality of the semiconductor layers exposed from the mask film. As a seed crystal, a method for manufacturing a group 13 nitride substrate including a step of growing a group 13 nitride crystal on the semiconductor layer by a flux method is disclosed.

  However, since the thermal expansion coefficients of the base substrate material and the group 13 nitride crystal are different, warpage and cracks are generated in the process of cooling from the crystal growth temperature to room temperature, and for example, a freestanding group 13 nitride substrate larger than φ3 inches. Has not been put to practical use.

In lateral selective growth (ELO) using selective growth in a vapor phase method, if the interval between selective growth masks is widened, crystal nuclei are generated on the mask and become polycrystalline. I can't take it big. Therefore, the area of the low dislocation density region cannot be increased. Moreover, 2 × 10 ¹⁷ cm ⁻³ or more of Si is doped in the GaN substrate manufactured by the HVPE method which is put into practical use.

  The present invention has been made in view of the above, and has a method for producing a group 13 nitride crystal having a large diameter and little warpage, a method for producing a group 13 nitride crystal substrate, a group 13 nitride crystal, and a group 13 nitride. An object is to provide a crystal substrate.

In order to solve the above-described problems and achieve the object, a method for producing a group 13 nitride crystal according to the present invention includes a group 13 nitride crystal having a lattice point position of a triangular lattice on the main surface of a base substrate. A first step of disposing the growth start regions, a second step of growing the group 13 nitride crystal with the crystal orientation aligned from each of the growth start regions, and the adjacent growth by continuing crystal growth. A third step of connecting a plurality of the group 13 nitride crystals grown from a start region to form a group 13 nitride crystal layer on the main surface of the base substrate; and in the cooling process, see containing and a fourth step of peeling said base substrate and the group 13 nitride crystal layer, in the first step, the triangular lattice is a regular triangle each lattice point interval is equal A regular triangular lattice. And the a-axis of the hexagonal group 13 nitride crystal growing from the growth start region is 30 °. In the second step or the third step, the angle is determined by the flux method. A group 13 nitride crystal is grown .

  In addition, a method for manufacturing a group 13 nitride crystal substrate according to the present invention includes using the group 13 nitride crystal manufactured by the method for manufacturing a group 13 nitride crystal as a substrate, and group 13 nitride on the substrate. And a sixth step of manufacturing a crystal substrate using the group 13 nitride crystal that has been crystal-grown in the fifth step. .

In addition, the group 13 nitride crystal according to the present invention is a hexagonal group 13 nitride crystal, and includes a plurality of hexagonal domains having boundaries with many crystal defects in the c-plane. Among the sides, the interval between parallel sides is 1 mm or more, and the silicon concentration in the crystal is less than 2 × 10 ¹⁷ cm ⁻³ and has an outer diameter greater than 2 inches.

In addition, the group 13 nitride crystal substrate according to the present invention is a hexagonal group 13 nitride crystal substrate, and includes a plurality of hexagonal domains having a boundary with a region having many crystal defects in the c-plane. Among the square sides, the interval between parallel sides is 1 mm or more, the silicon concentration in the crystal is less than 2 × 10 ¹⁷ cm ⁻³ , the radius of curvature is 20 m or more, and the self-supporting surface is c-plane. It is a substrate.

Furthermore, the group 13 nitride crystal substrate according to the present invention is a hexagonal group 13 nitride crystal substrate, and includes a plurality of hexagonal domains having boundaries with many crystal defects in the c-plane. Among the square sides, the interval between parallel sides is 1 mm or more, the silicon concentration in the crystal is 2 × 10 ¹⁷ cm ⁻³ or more, and at least one of calcium, barium, and strontium in the crystal It is a self-supporting substrate having a curvature radius of 20 m or more, an outer diameter larger than 2 inches, and having a c-plane as a main surface.

  According to the present invention, since the growth start region of the group 13 nitride crystal is arranged so as to be the lattice point position of the triangular lattice, the production efficiency of the group 13 nitride crystal having a hexagonal crystal structure can be improved, and the lattice By controlling the arrangement of the points, the distortion of the group 13 nitride layer can be reduced. Thereby, there is an effect that it is possible to provide a method for producing a group 13 nitride crystal, a method for producing a group 13 nitride crystal substrate, a group 13 nitride crystal, and a group 13 nitride crystal substrate with a large diameter and little warpage. .

FIG. 1 is a schematic diagram (plan view) for explaining an arrangement example of the growth start regions formed in the first step. FIG. 2 is a schematic diagram (plan view) for explaining an arrangement example of the growth start regions formed in the first step. FIG. 3A is a schematic diagram (plan view) illustrating a crystal growth process of a group 13 nitride crystal. FIG. 3-2 is a schematic diagram (plan view) illustrating a crystal growth process of the group 13 nitride crystal. FIG. 3-3 is a schematic diagram (plan view) illustrating a crystal growth process of a group 13 nitride crystal. FIG. 3-4 is a schematic diagram (plan view) illustrating a crystal growth process of the group 13 nitride crystal. FIGS. 4-1 is a figure (sectional drawing) explaining an example of a 1st process. FIGS. 4-2 is a figure (sectional drawing) explaining an example of a 2nd process thru | or a 3rd process. FIGS. 4-3 is a figure (sectional drawing) explaining an example of a 4th process thru | or a 6th process. FIG. 4-4 is a perspective view of the group 13 nitride crystal obtained by the sixth step. FIG. 5 is a schematic diagram (cross-sectional view) showing a configuration example of a crystal manufacturing apparatus used in the second to fourth steps. FIG. 6 is a schematic diagram (cross-sectional view) showing a configuration example of a crystal manufacturing apparatus used when the fifth step is performed by a flux method. FIG. 7 is a view (plan view) of the group 13 nitride crystal layer as viewed from the main surface side. FIG. 8 is a view (plan view) of the group 13 nitride crystal substrate as viewed from the main surface side. FIG. 9 is a diagram (plan view) showing an example of a group 13 nitride crystal substrate having different domain sizes. FIG. 10A is a diagram (a cross-sectional view) for explaining an example of the first step in the second embodiment. FIG. 10B is a diagram (cross-sectional view) for explaining an example of the second to third steps. FIG. 10C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps. FIG. 10-4 is a perspective view of the group 13 nitride crystal obtained by the sixth step. FIG. 11A is a diagram (cross-sectional view) for explaining an example of a first step in the third embodiment. FIG. 11B is a diagram (cross-sectional view) for explaining an example of the second to third steps. FIG. 11C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps. FIG. 11-4 is a perspective view of the group 13 nitride crystal obtained by the sixth step. FIGS. 12-1 is a figure (sectional drawing) explaining an example of the 1st process in 4th Embodiment. FIG. 12-2 is a diagram (cross-sectional view) for explaining an example of the second to third steps. FIG. 12C is a diagram (a cross-sectional view) for explaining an example of the fourth to sixth steps. FIG. 12-4 is a perspective view of the group 13 nitride crystal obtained by the sixth step. FIGS. 13-1 is a figure (sectional drawing) explaining an example of the 1st process in 5th Embodiment. FIGS. 13-2 is a figure (sectional drawing) explaining an example of a 2nd process thru | or a 3rd process. FIGS. 13-3 is a figure (sectional drawing) explaining an example of a 4th process thru | or a 6th process. FIG. 13-4 is a perspective view of the group 13 nitride crystal obtained by the sixth step. FIG. 14A is a diagram (cross-sectional view) for explaining an example of the first step in the sixth embodiment. FIGS. 14-2 is a figure (sectional drawing) explaining an example of a 2nd process thru | or a 3rd process. FIG. 14C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps. FIG. 14-4 is a perspective view of the group 13 nitride crystal obtained by the sixth step. FIG. 15A is a diagram (cross-sectional view) for explaining an example of the first step in the seventh embodiment. FIG. 15B is a diagram (cross-sectional view) for explaining an example of the second to third steps. FIG. 15C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps. FIG. 15-4 is a perspective view of the group 13 nitride crystal obtained by the sixth step.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for producing a group 13 nitride crystal, a method for producing a group 13 nitride crystal substrate, a group 13 nitride crystal and a group 13 nitride crystal substrate according to the present invention will be described below with reference to the accompanying drawings. This will be described in detail. In the following description, the drawings merely schematically show the shape, size, and arrangement of the components to the extent that the embodiments can be understood, and the present invention is not particularly limited thereby. . Moreover, the same code | symbol is attached | subjected and shown about the same structure shown by several figures, The duplicate description may be abbreviate | omitted.

<Crystal manufacturing method of group 13 nitride crystal>
The method for producing a group 13 nitride crystal according to the present embodiment includes the following first to fourth steps.
(1) First step of arranging a growth start region of a group 13 nitride crystal so as to be a lattice point position of a triangular lattice on the main surface of the base substrate (2) The crystal orientation is aligned from each growth start region Second Step of Growing Group 13 Nitride Crystal (3) Crystal growth is continued to connect a plurality of group 13 nitride crystals grown from adjacent growth start regions on the main surface of the base substrate. Third Step of Forming Group 13 Nitride Crystal Layer (4) Fourth Step of Peeling Group 13 Nitride Crystal Layer and Substrate in Cooling Process of Group 13 Nitride Crystal Layer

  Next, the first to fourth steps will be described in more detail.

(1) First Step The first step is a step of forming a group 13 nitride crystal growth start region. The first step is a step of disposing a group 13 nitride crystal growth start region on the main surface of the base substrate so as to be located at the lattice points of the triangular lattice.

  The group 13 nitride growth start region is a region where a group 13 nitride crystal starts to grow, and is a region that becomes a so-called seed crystal. In a preferred embodiment, a group 13 nitride formed on the main surface of the base substrate is preferably used as the growth start region. A method for forming a group 13 nitride serving as a growth start region is not particularly limited, but a group 13 nitride crystal can be formed on the base substrate 101 using a method such as MOCVD or HVPE. .

  Next, the arrangement of the group 13 nitride crystal growth start region (seed crystal region) 105 will be described with reference to FIGS. 1 and 2 are schematic views (plan views) for explaining an arrangement example of the growth start regions 105 formed in the first step. FIG. 3 (FIGS. 3-1 to 3-4) is a schematic diagram for explaining the crystal growth process of the group 13 nitride crystal.

  As shown in FIGS. 1 and 2, the group 13 nitride crystal growth start region 105 is arranged in the main surface of the base substrate 101 so as to be the lattice point position of the triangular lattice indicated by the dotted line in the drawing. .

As a preferred embodiment of this triangular lattice, as shown in FIGS. 2 and 3 (FIGS. 3-1 to 3-4), it is preferable that the triangular lattice is an equilateral triangular lattice having the same lattice point interval (lattice interval). Further, as a preferred embodiment of this triangular lattice, as shown in FIG. 3A, the sides constituting each triangle in the triangular lattice are the a-axis of the group 13 nitride crystal formed in the growth start region 105. It is preferable to form an angle of 30 ° with respect to (a ₁ , a ₂ , a ₃ ).

  Further, as a preferred embodiment of this triangular lattice, as shown in FIG. 3A, the interval between adjacent growth start regions 105 is preferably 1 mm or more. In a more preferred embodiment, the interval between adjacent growth start regions 105 is preferably 5 mm or more, more preferably 10 mm or more, and more preferably 25 mm or more. Thus, the larger the distance between adjacent growth start regions 105, the wider the crystal region with few crystal defects and the smaller the group 13 nitride crystal warpage.

  The preferred shape of the group 13 nitride crystal growth start region 105 is preferably one of a circle, a hexagon, and other polygons. In a more preferred embodiment, the group 13 nitride crystal growth start region 105 is preferably circular or hexagonal. In addition, it is preferable that the plurality of growth start regions 105 be separated from each other to have a dot shape.

  Further, the preferred size of the group 13 nitride crystal growth start region 105 is preferably a size that falls within a circle having a diameter of 1 mm or less. That is, in order to separate the base substrate 101 and the group 13 nitride crystal grown on the base substrate 101 by thermal stress, the growth start region 105 is preferably as small as possible.

  The preferred size of the group 13 nitride crystal growth start region 105 is preferably a size that falls within a circle having a diameter of 500 μm or less. As a more preferable size, it is preferable that the size is within a circle having a diameter of 200 μm or less.

As the base substrate 101 used in the first step, it is preferable to use a crystal substrate having a diameter larger than φ2 inches. As the base substrate 101, for example, a single crystal such as sapphire, SiC, MGal ₂ O ₄ , or ZnO can be used.

  Further, as a preferred embodiment of the base substrate 101, it is preferable to use an oxide single crystal substrate such as sapphire. Sapphire single crystal substrates having a size of up to about φ6 inches have been commercialized. Therefore, if a sapphire substrate of this size is used, a group 13 nitride crystal having a size of about φ6 inches can be manufactured.

  FIGS. 4-1 is a figure (sectional drawing) explaining an example of a 1st process. First, as shown in FIG. 2B, a group 13 nitride film 102 is formed on the main surface of the base substrate 101. Then, as shown in (c), a mask 103 is formed on the group 13 nitride film 102. Next, as shown in (d), a resist pattern 104 is formed on the mask 103 by photolithography. Next, an etching process is performed as indicated by an arrow in (d), and a mask 103 having a through hole is formed as illustrated in (e). In this way, the surface of the group 13 nitride film 102 exposed from the through hole can be used as the group 13 nitride crystal growth start region 105.

(2) Second Step The second step is a step of growing a group 13 nitride crystal 106 (see FIG. 3A) with the crystal orientation aligned from each growth start region 105 formed in the first step. It is. In the second step, the group 13 nitride crystal 106 is grown by a flux method.

  FIG. 5 is a schematic diagram (cross-sectional view) showing a configuration example of the crystal manufacturing apparatus 1 used in the second to fourth steps. In the crystal manufacturing apparatus 1, a pedestal 24 is provided in a pressure-resistant container 11 having a closed shape made of stainless steel. The pedestal 24 can be provided with a reaction vessel 12 for introducing a group 13 nitride raw material to grow a group 13 nitride crystal.

The internal space 23 of the pressure vessel 11 is filled with nitrogen (N ₂ ) gas and argon (Ar) gas, and the nitrogen (N ₂ ) pressure and argon (Ar) gas pressure in the pressure vessel 11 are controlled. A gas supply pipe 14 is mounted through the pressure vessel 11 to enable this.

  The gas supply pipe 14 is branched into a nitrogen supply pipe 17 and an argon supply pipe 20 and can be separated by valves 15 and 18 respectively. Further, the pressures of nitrogen and argon can be adjusted by pressure control devices 16 and 19, respectively. The gas supply pipe 14 is provided with a pressure gauge 22 for monitoring the total pressure in the pressure vessel 11.

  Nitrogen gas is a raw material of gallium nitride, and argon, which is an inert gas, is mixed with it to increase the total pressure and suppress the evaporation of sodium, while controlling the pressure of the nitrogen gas independently. It is. Thereby, crystal growth with high controllability becomes possible.

  In a preferred embodiment, the nitrogen gas partial pressure is preferably 1 Pa or more. More preferably, the nitrogen gas partial pressure is preferably 4 MPa.

  The gas supplied from the nitrogen supply pipe 17 is not limited to the nitrogen gas, and other gases may be supplied from the nitrogen supply pipe 17 as long as the gas contains nitrogen.

  The material of the reaction vessel 12 is not particularly limited, and BN sintered bodies, nitrides such as P-BN, oxides such as alumina and YAG, carbides such as SiC, and the like can be used. Further, the reaction vessel 12 can be detached from the pressure vessel 11.

  A heater 13 is installed outside the pressure vessel 11. The heater 13 can be controlled to an arbitrary temperature. Since the set temperature of the heater 13 and the temperature in the reaction vessel 12 are configured so as to be uniform in temperature, the pressure-resistant vessel 11 and the reaction vessel 12 are heated to form in the reaction vessel 12 by raising the temperature of the heater 13. The temperature of the mixed melt 25 can be raised to the crystal growth temperature for growing the group 13 nitride crystal and maintained at that temperature.

  The crystal growth temperature is not particularly limited, but is preferably 700 ° C. to 900 ° C. as a preferred embodiment. In a more preferred embodiment, the crystal growth temperature is preferably 880 ° C.

  Further, the pressure vessel 11 can be detached from the crystal production apparatus 1 at the valve 21 portion, and only the pressure vessel 11 portion can be put into the glove box and operated. That is, the operation of charging the raw material into the reaction vessel 12 is performed by removing the pressure vessel 11 at the valve 21 portion and placing the pressure vessel 11 in the glove box. Thereby, it can suppress that an impurity mixes in the reaction container 12 and the pressure | voltage resistant container 11, and can manufacture a high quality group 13 nitride crystal.

  In the second step, as shown in FIG. 5, the base substrate 101 on which the growth start region 105 has been formed in the first step is placed in the reaction vessel 12.

  The material of the reaction vessel 12 can be selected as appropriate, but alumina, YAG, BN, SiC, TaC or the like can be used.

  Then, in the reaction vessel 12, the pressure vessel filled with the alkali metal as the flux and the group 13 element as the raw material and filled with the raw material gas (gas phase) containing at least nitrogen is heated to the crystal growth temperature. Is done. In the temperature raising process, the alkali metal and the group 13 element in the reaction vessel are dissolved to form a mixed melt 25. Further, nitrogen in the gas phase is dissolved in the mixed melt 25.

  Then, the reaction vessel 12 is maintained at the above-described crystal growth temperature, and the nitrogen pressure in the gas phase is maintained within a predetermined range, and nitrogen is continuously fed into the mixed melt 25 from the gas phase, thereby obtaining a group 13 nitride. Crystal growth conditions for crystals (eg, gallium nitride crystals) can be maintained. In the second step, a group 13 nitride crystal can be grown from nitrogen and a group 13 element dissolved in the mixed melt in this way.

  That is, under the crystal growth conditions, the group 13 nitride crystal 106 starts crystal growth as shown in FIG. 3-2 from the crystal growth region 105 arranged as shown in FIG. 3A in the first step. In this case, the group 13 nitride crystal 106 grown in each crystal growth region 105 grows in a state where the crystal orientation is aligned with the m plane (each side of the hexagon) as the crystal growth plane.

  FIG. 4B is a diagram (sectional view) for explaining an example of the second to third steps performed after the first step described above with reference to FIG. In the second step, the group 13 nitride crystal 106 starts crystal growth in the plurality of growth start regions 105 formed on the group 13 nitride film 102 as shown in FIG. As shown in (f), the group 13 nitride crystal 106 first grows in a hexagonal pyramid shape, and then grows in a hexagonal column shape so as to enlarge the c-plane as shown in (g).

  As the alkali metal used as the flux, sodium (Na) is mainly used, but other alkali metal elements such as lithium (Li) and potassium (K) may be used. Moreover, you may use these in mixture. In a preferred embodiment, sodium is preferably used as the alkali metal used as the flux.

  Further, as the group 13 element as a raw material, at least one of boron (B), aluminum (Al), gallium (Ga), and indium (In) can be used, and one kind of group 13 element is used. Or a mixture of a plurality of Group 13 elements may be used. In a preferred embodiment, gallium is preferably used as the group 13 element.

  Moreover, as nitrogen used as a raw material, nitrogen gas can be generally used, but a gas containing nitrogen such as ammonia can be used. Further, in the gas phase containing nitrogen, an inert gas such as argon (Ar) or other gas may be mixed in addition to the gas containing at least nitrogen.

  The mixed melt may contain a dopant such as germanium (Ge), magnesium (Mg), iron (Fe), manganese (Mn) in addition to the alkali metal, the group 13 element and nitrogen.

  Furthermore, the mixed melt may contain alkaline earth metals that serve as flux, such as calcium (Ca), barium (Ba), strontium (Sr), and carbon (C) that has an effect of reducing miscellaneous crystals. Good.

(3) Third Step In the third step, the group 13 nitride of each domain (region) grown from the adjacent growth start region 105 is further continued by continuing the crystal growth of the group 13 nitride crystal in the second step. The nitride crystals 106 are connected to each other. As a result, a group 13 nitride crystal layer 1100 (see FIG. 3-4) connected in one piece is formed on the main surface of the base substrate 101. In the third step, the group 13 nitride crystal 106 is grown by a flux method.

  That is, in the third step, the temperature of the mixed melt 25 and the nitrogen pressure in the pressure vessel 11 are maintained under the crystal growth conditions described above. Then, the group 13 nitride crystal 106 which has started crystal growth in the second step as shown in FIG. 3-2 is further crystal-grown as shown in FIG. 3-3. Then, as shown in FIG. 3-4, adjacent group 13 nitride crystal domains 106 are connected to each other to obtain one group 13 nitride layer 1100.

  The domain refers to the group 13 nitride crystal 106 in the region grown from each growth start region 105, and is a region with fewer crystal defects than the boundary region 107 between domains. Hereinafter, the domain is referred to as group 13 nitride crystal 106 or simply domain 106.

  Further, in the third step, as shown in FIG. 4-2 (h), the group 13 nitride crystal 106 is further enlarged so that the area of the c-plane is enlarged to cover the surface of the mask 103. Then, as shown in (i), the group 13 nitride crystals 106 grown from the adjacent growth start regions 105 are connected to each other. Further, by further growing a group 13 nitride crystal 106, a group 13 nitride crystal layer 1100 in which a plurality of group 13 nitride crystals 106 are connected as shown in (j) can be obtained. In this case, if the crystal growth of each group 13 nitride crystal 106 is sufficiently performed, the surface of the group 13 nitride crystal layer 1100 can be smoothed as shown in FIG.

  As described above, according to the present embodiment, since the growth start region 105 is arranged at the lattice point position of the triangular lattice, when the hexagonal group 13 nitride crystal 106 grows, the growth starts in a stripe pattern. Compared with a case where a region is arranged or a case where a growth start region is arranged at a lattice point position of a square lattice, a plurality of group 13 nitride crystals 106 grown from adjacent growth start regions 105 are efficiently connected. Can do.

  In addition, when not arranged at lattice points of an equilateral triangular lattice, it is conceivable to grow a crystal so as to fill a gap generated between adjacent group 13 nitride crystals after connecting each domain 106, but depending on the crystal growth conditions, Since it is difficult to grow the crystal in the crystal orientation, it is difficult to smoothly connect the adjacent domains 106 to each other.

  On the other hand, in the present embodiment, since the growth start region 105 is arranged at the lattice points of the equilateral triangular lattice, when the group 13 nitride crystal 106 grows in the a-axis direction, the growth starts from the adjacent growth start regions 105. The direction of the m-plane (each side of the hexagon) of the group 13 nitride crystal 106 can be aligned. Therefore, as shown in FIGS. 3-2 to 3-4, when the group 13 nitride crystal 106 grows with the m-plane as the crystal growth surface, adjacent group 13 nitride crystals as shown in FIG. 106 can be connected without a gap.

  Conventionally, in the vapor phase growth method, if the interval between adjacent growth start regions 105 is increased, crystal nuclei are generated in a place other than the growth start region and become polycrystalline, so the interval between adjacent growth start regions 105 is increased. I couldn't. On the other hand, according to the flux method, there is a crystal growth condition that grows only on the seed crystal. Therefore, by performing crystal growth under an appropriate crystal growth condition, even if the interval between the growth start regions 105 is wide, the crystal Nuclei can be prevented from being generated. Therefore, according to the flux method, the space | interval of the adjacent growth start area | region 105 can be arrange | positioned largely. Accordingly, since a large region can be taken in the lateral direction, that is, the direction in which the c-plane is enlarged, the area of the domain 106 having a low dislocation density can be enlarged.

Generally, when silicon (Si) is added to the mixed melt in the flux method, the crystal growth of the group 13 nitride crystal is significantly inhibited. On the other hand, in the crystal manufacturing method of the present embodiment, the crystal growth process (second process to third process) is performed by the flux method so that Si is not mixed as much as possible. Therefore, in the group 13 nitride crystal layer 1100 Can be reduced to a detection limit (2 × 10 ¹⁷ cm ⁻³ ) or less of SIMS analysis.

  Further, by adding Ca, Ba, Sr or the like into the mixed melt 25, these elements can be dissolved in the group 13 nitride crystal.

  Further, by performing the second to third steps under the crystal growth conditions as described above, the crystal growth is performed so that the c-plane of the group 13 nitride crystal 106 is parallel to the main surface of the base substrate 101. Can do. Thereby, group 13 nitride crystal layer 1100 having a large area can be manufactured along the main surface of base substrate 101.

(4) Fourth Step The fourth step is a step of peeling the group 13 nitride crystal layer and the base substrate in the cooling process of the group 13 nitride crystal layer.

  FIG. 4C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps performed after the third step described with reference to FIG. After the third step, the crystal growth of the group 13 nitride crystal 106 is finished, and the temperature of the reaction vessel 12 is lowered from the crystal growth temperature to room temperature. Since the thermal expansion coefficients of the base substrate 101 and the group 13 nitride crystal layer 1100 are different, in the cooling process in which the temperature of the heater 13 is lowered from the crystal growth temperature to room temperature, as shown in FIG. The crystal layer 1100 is peeled from the base substrate 101. (Fourth process)

  Thus, according to the present embodiment, since the base substrate 101 having a different thermal expansion coefficient from that of the group 13 nitride crystal layer 1100 is used, the group 13 nitride crystal layer 1100 and the base substrate 101 are naturally separated in the cooling process. Can be peeled off.

  In addition, since the stress is uniformly dispersed in the group 13 nitride crystal layer 1100 as compared with the case where the growth start regions are arranged in a striped pattern, even when the group 13 nitride crystal layer 1100 is enlarged, cracks are generated. Can be suppressed.

  Moreover, since each growth start area | region 105 is arrange | positioned at intervals of 1 mm or more, when the adjacent domains 106 contact, the hexagonal outer diameter of each domain 106 will also be 1 mm or more. By adjusting this interval, when the group 13 nitride crystal layer 1100 is peeled from the base substrate 101 in the fourth step, the group 13 nitride crystal layer 1100 can be easily separated. However, the occurrence of cracks and warpage can be suppressed.

<Group 13 nitride crystal>
The group 13 nitride crystal according to this embodiment is the group 13 nitride crystal layer 1100 manufactured in the first to fourth steps described above.

  FIG. 7 is a view (plan view) of group 13 nitride crystal layer 1100 as seen from the c-plane. As shown in FIGS. 7 and 3-4, the group 13 nitride crystal layer 1100 is configured by connecting a plurality of hexagonal domains 106 having the boundary region 107 as a side. Since the dislocation density is high in the boundary region 107, it may be observable with a microscope or the like, or may be observable by etching with an acid or the like. In this case, the position of each domain 106 can be easily determined.

  The group 13 nitride crystal layer 1100 covers the entire main surface area of the base substrate 101 (see FIG. 2). That is, the outer diameter of the group 13 nitride crystal layer 1100 is substantially equal to the outer diameter of the base substrate 101. When the base substrate 101 having an outer diameter of about 2 inches is used as described above, the group 13 nitride crystal layer is used. The outer diameter of 1100 can also be about 2 inches.

  In the group 13 nitride crystal layer 1100, the interval between the parallel sides of the hexagonal domains 106 is equal to the interval between the adjacent growth start regions 105. That is, when the first step is performed with the interval between adjacent growth start regions 105 being 1 mm or more as described above, the distance is 1 mm or more.

<Method for producing group 13 nitride crystal substrate>
The method for producing a group 13 nitride crystal substrate according to this embodiment includes the following steps (5) and (6).
(5) Fifth step (6) for further growing a group 13 nitride crystal on the substrate using the group 13 nitride crystal manufactured in the first to fourth steps as a substrate. A sixth step of manufacturing a crystal substrate using the group 13 nitride crystal grown in the fifth step

  Next, the fifth step and the sixth step will be described in more detail.

(5) Fifth Step In the fifth step, the group 13 nitride crystal layer 1100 peeled in the fourth step is used as a substrate, and a group 13 nitride crystal is further grown on the substrate. is there. Hereinafter, the group 13 nitride crystal layer 1100 may be referred to as a group 13 nitride crystal substrate 1100.

  That is, in the fifth step, as shown in FIG. 4-3 (l), the group 13 nitride crystal layer 1100 peeled off in the fourth step is used as a new substrate and shown in FIG. Thus, a group 13 nitride crystal 1200 is further grown on the main surface of the group 13 nitride crystal layer 1100.

  The group 13 nitride crystal layer 1100 may be used as a substrate as it is, or at least one of the substrates sliced after slicing the group 13 nitride crystal layer 1100 into a plurality of sheets may be used as the substrate.

  As a crystal growth method used in the fifth step, a vapor phase growth method such as MOCVD method, HVPE (halogenated vapor phase epitaxy) method, sublimation method, or a liquid phase growth method such as flux method or ammonothermal method. Can be used.

  As a more preferred embodiment, it is preferable to perform crystal growth by the HVPE method in the fifth step. The HVPE method is a method of growing a group 13 nitride crystal by reaction of a chloride gas of group 13 element and ammonia gas, but has a higher growth rate than other vapor phase growth methods such as MOCVD method and sublimation method. This is a suitable method for growing a thick crystal layer.

  As a more preferred embodiment, it is preferable to perform crystal growth by a flux method in the fifth step.

  FIG. 6 is a schematic diagram (cross-sectional view) showing a configuration example of the crystal manufacturing apparatus 1 used when the fifth step is performed by the flux method. The configuration of the crystal manufacturing apparatus 1 shown in FIG. 6 is the same as the structure of the crystal manufacturing apparatus 1 described above with reference to FIG. As shown in FIG. 6, in the fifth step, a group 13 nitride crystal substrate 1100 is installed in the reaction vessel 12, and a group 13 nitride crystal 1200 is crystallized on the group 13 nitride crystal substrate 1100 by a flux method. Grow. The flux method has been described above with reference to FIG.

  The flux method is a crystal growth method suitable for growing a high-purity and thick crystal layer because the growth rate is higher than that of other liquid-phase growth methods and impurities are less mixed. Further, unlike the HVPE method, there is no possibility that silicon dissolves from the reaction tube, so that an n-type group 13 nitride crystal 1200 having a low Si concentration, that is, a low carrier concentration can be grown.

  In a preferred embodiment, the alkali metal used in the flux method is sodium, and the group 13 element is preferably gallium.

  As described above, according to the fifth step of the present embodiment, since the group 13 nitride crystal substrate 1100 is used as the substrate and the group 13 nitride crystal 1200 is further grown thereon, it grows on the substrate and the substrate. It is possible to improve crystal lattice consistency and thermal expansion coefficient consistency with the crystal. Therefore, the dislocation density of the grown group 13 nitride crystal 1200 can be reduced.

(6) Sixth Step The sixth step is a step of manufacturing a crystal substrate using the group 13 nitride crystal 1200 grown in the fifth step.

  That is, in the sixth step, as shown in FIG. 4-3, the group 13 nitride crystal 1200 manufactured in the fifth step is sliced as shown in FIG. The product crystal substrates 1210a to 1210g (1210) are obtained. The sliced substrate is subjected to various types of processing such as outer diameter processing and surface polishing. The outer diameter processing may be performed on the group 13 nitride crystal 1200 before slicing.

  FIG. 4-4 is a perspective view of the group 13 nitride crystal substrate 1210 obtained by the sixth step. As shown in FIG. 4-4, in group 13 nitride crystal substrate 1210 (1210a to 1210g), a domain 1106 is formed so as to correspond to each domain 106 of group 13 nitride crystal substrate 1100.

<Group 13 nitride crystal>
The group 13 nitride crystal according to the present embodiment is a group 13 nitride crystal 1200 (see FIG. 4-3) manufactured in the fifth step.

When the group 13 nitride crystal 1200 is grown by the HVPE method in the fifth step, Si is dissolved in the reaction tube (auto-doping), so the Si concentration in the group 13 nitride crystal 1200 is 2 ×. More than 10 ¹⁷ cm ⁻³ .

On the other hand, in the case where the group 13 nitride crystal 1200 is grown by the flux method in the fifth step, the crystal growth is performed while reducing Si contamination as much as described above. The Si concentration is below the detection limit (2 × 10 ¹⁷ cm ⁻³ ) of SIMS analysis. As described above, the Si concentration in the crystal can be controlled by selecting the crystal growth method used in the fifth step.

  Further, when Ca, Ba, Sr, or the like is mixed in the mixed melt 25, these elements can be dissolved in the group 13 nitride crystal 1200.

<Group 13 nitride crystal substrate>
Further, the group 13 nitride crystal substrate according to the present embodiment is the group 13 nitride crystal substrate 1210 (see FIGS. 4-4 and 8) manufactured in the sixth step described above.

  FIG. 8 is a view (plan view) of group 13 nitride crystal substrate 1210 as seen from the main surface side. As shown in FIG. 8, the group 13 nitride crystal substrate 1210 manufactured in the sixth step has a hexagonal domain having a c-plane as a main surface and a boundary region 1107 having many crystal defects in the main surface as a boundary. 1106 is included.

  The domain 1106 is considered to be formed by propagation of properties of the domain 106 and the boundary region 107 when the group 13 nitride crystal 1200 is grown on the group 13 nitride crystal substrate 1100 in the fifth step. Accordingly, since the size of the domain 1106 is equal to the size of the domain 106, the size of the domain 1106 can be controlled by controlling the interval between the growth start regions 105 in the first step.

  FIG. 9 is a diagram (plan view) showing an example of a group 13 nitride crystal substrate 1210 having a different domain 1106 size. In the first step, when the gap between the growth start regions 105 (see FIG. 3-1) is wide, the size of the domain 1106 can be made larger than that shown in FIG. 8 as shown in FIG. .

  As described above, when the interval between the growth start regions 105 (see FIG. 3-1) is 1 mm or more, the interval between parallel sides of the hexagonal side of the domain 1106 is 1 mm. That's it.

  As a preferred embodiment, in the hexagonal shape of the domain 1106, the interval between the parallel sides of the hexagonal sides is 5 mm or more, more preferably 10 mm or more, and further preferably 25 mm or more.

  According to the present embodiment, the shape of each domain 1106 can be made uniform. Thus, when a device process is performed on each domain 1106, device processing can be performed using a mask having a uniform shape and size without changing the mask shape for each domain 1106. it can. Therefore, the device processing process can be made efficient.

  Since the size of the group 13 nitride crystal substrate 1210 is determined by the size of the base substrate 101 used in the first step, the outer diameter is larger than 2 inches, such as φ3 inches, φ4 inches, and φ6 inches. It is possible to make it the same size as the single crystal substrate (underlying substrate 101) used in general.

  Further, according to the present embodiment, the curvature radius of the group 13 nitride crystal substrate 1210 can be set to 20 m or more by the above-described steps.

  As described above, according to the present embodiment, since the group 13 nitride crystal growth start region is arranged so as to be located at the lattice point of the triangular lattice, the manufacturing efficiency of the hexagonal group 13 nitride crystal is improved. In addition, the strain of the group 13 nitride layer can be reduced by controlling the arrangement of lattice points. Thereby, there is an effect that it is possible to provide a method for producing a group 13 nitride crystal, a method for producing a group 13 nitride crystal substrate, a group 13 nitride crystal, and a group 13 nitride crystal substrate with a large diameter and little warpage. .

  Next, other embodiments of the method for producing a group 13 nitride crystal and the method for producing a group 13 nitride crystal substrate will be described.

(Second Embodiment of Manufacturing Method)
Next, a second embodiment will be described with reference to FIGS. 10-1 to 10-4.

  FIG. 10A is a diagram (a cross-sectional view) for explaining an example of the first step in the second embodiment. First, a group 13 nitride film 202 is formed on the main surface of the base substrate 201 as shown in FIG. Then, as shown in (c), a pattern 203 is formed on the group 13 nitride film 202 with a resist or the like. Next, as shown in (d), a mask 204 is formed on the surface of the group 13 nitride film 202 and the pattern 203. Thereafter, as shown in (e), the resist pattern 203 is removed, and a mask is formed in a region other than the resist pattern 203. In this way, the surface of the group 13 nitride film 202 exposed from the opening of the mask 204 can be used as the group 13 nitride crystal growth start region 205.

  In the above description, the constituent materials of the masks 103 and 204 are not particularly limited. However, as a preferred embodiment, tungsten, tantalum, alumina, YAG, MgO, silicon nitride, or the like can be used. The masks 103 and 204 can be formed on the group 13 nitride films 102 and 202 by sputtering or the like.

  FIG. 10B is a diagram (cross-sectional view) for explaining an example of the second to third steps performed after the first step described above with reference to FIG. As shown in FIG. 5F, the group 13 nitride crystal 206 starts crystal growth in the plurality of growth start regions 205 formed on the group 13 nitride film 202. As shown in (f), the group 13 nitride crystal 206 first grows in a hexagonal pyramid shape, and then grows in a hexagonal column shape so as to enlarge the c-plane as shown in (g). (Second step)

  Then, as shown in (h), the c-plane is further enlarged so as to cover the surface of the mask 204, and as shown in (i), the group 13 nitride crystals 206 grown from the adjacent growth start regions 205 are mutually connected. Are concatenated. (Third step)

  Further, by further growing the group 13 nitride crystal 206, as shown in (j), a group 13 nitride crystal layer 2100 in which a plurality of group 13 nitride crystals 206 are connected can be obtained. In this case, if the group 13 nitride crystal 206 is sufficiently grown, the surface of the group 13 nitride crystal layer 2100 can be smoothed as shown in (j).

  FIG. 10C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps performed after the third step described above with reference to FIG. Similar to the process described above with reference to FIG. 4-3, the fourth process (see (k) in the figure), the fifth process (see (l) and (m) in the figure), and the sixth process (in the figure (n) )) Is performed.

  FIG. 10-4 is a perspective view of the group 13 nitride crystal substrate 2210 obtained by the sixth step. As shown in FIG. 10-4, in group 13 nitride crystal substrate 2210 (2210a to 2210g), group 1nitride crystal domains 1206 grown from adjacent growth start regions are arranged.

(Third Embodiment of Manufacturing Method)
Next, a third embodiment will be described with reference to FIGS. 11-1 to 11-4.

  FIG. 11A is a diagram (cross-sectional view) for explaining an example of a first step in the third embodiment. First, a group 13 nitride film 302 is formed on the main surface of the base substrate 301 as shown in FIG. Then, as shown in (c), a plate having a through hole is placed on the group 13 nitride film 302 as a mask 303. In this manner, the surface of the group 13 nitride film 302 exposed from the through hole can be used as the group 13 nitride crystal growth start region 305.

  In the above description, the constituent material of the plate-like mask 303 is not particularly limited, but tungsten, tantalum, sapphire, alumina, YAG, MgO, silicon nitride, or the like can be used.

In the above description, the surface of the base substrate 101, 201, 301 may be exposed in the region other than the growth start region. In such a case, the constituent material of the base substrates 101, 201, and 301 is preferably a material that suppresses generation of group 13 nitride nuclei on the base substrates 101, 201, and 301 in the second step. As an example, as a constituent material of the base substrates 101, 201, and 301, an oxide substrate such as sapphire or MGal ₂ O ₄ is preferable.

  FIG. 11B is a diagram (cross-sectional view) for explaining an example of the second to third steps performed after the first step described above with reference to FIG. As shown in FIG. 4D, the group 13 nitride crystal 306 starts crystal growth in the plurality of growth start regions 305 formed on the group 13 nitride film 302. As shown in (d), the group 13 nitride crystal 306 first grows in a hexagonal pyramid shape, and then grows in a hexagonal column shape so as to enlarge the c-plane as shown in (e). (Second step)

  Then, as shown in (f), the c-plane is further enlarged so as to cover the surface of the mask 303, and as shown in (g), the group 13 nitride crystals 306 grown from the adjacent growth start regions 305 are mutually connected. Are concatenated. (Third step)

  Further, by further growing a group 13 nitride crystal 306, as shown in (h), a group 13 nitride crystal layer 3100 in which a plurality of group 13 nitride crystals 306 are connected can be obtained. In this case, if the group 13 nitride crystal 306 is sufficiently grown, the surface of the group 13 nitride crystal layer 3100 can be smoothed as shown in FIG.

  FIG. 11C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps performed after the third step described above with reference to FIG. Similar to the process described above with reference to FIG. 4-3, the fourth process (see (i) in the figure), the fifth process (see (j) and (k) in the figure), and the sixth process (see (l) in the figure). )) Is performed.

  FIG. 11-4 is a perspective view of the group 13 nitride crystal substrate 3210 obtained by the sixth step. As shown in FIG. 11-4, in group 13 nitride crystal substrate 3210 (3210a to 3210g), group 13 nitride crystal domains 1306 grown from adjacent growth start regions are arranged.

(Fourth Embodiment of Manufacturing Method)
Next, a fourth embodiment will be described with reference to FIGS. 12-1 to 12-4.

  FIG. 12A is a diagram for explaining an example of a first step in the fourth embodiment. First, as shown in FIG. 2B, a group 13 nitride film 402 is formed on the main surface of the base substrate 401. Then, as shown in (c), a resist pattern 403 is formed on the group 13 nitride film 402 by photolithography or the like. Then, using a technique such as dry etching, the group 13 nitride film 402 other than the portion covered with the resist pattern 403 is removed as shown by the arrow in (c). In this way, the surface of the base substrate 401 is exposed as shown in FIG. Thereafter, as shown in (e), the resist pattern 403 is removed, and the group 13 nitride film 402 protected by the resist pattern 403 can be used as the growth start region 405.

  12-2 is a diagram (cross-sectional view) for explaining an example of the second to third steps performed after the first step described above with reference to FIG. 12-1. As shown in FIG. 5F, the group 13 nitride crystal 406 starts crystal growth in a plurality of growth start regions 405 formed on the base substrate 401. As shown in (f), the group 13 nitride crystal 406 grows in a hexagonal column shape with the growth start region 405 as a seed crystal so as to enlarge the c-plane. (Second step)

  Then, as shown in (g), the c-plane further expands so as to cover the surface of the base substrate 401, and as shown in (h), a group 13 nitride crystal grown from the adjacent growth start region 405. 406 are connected to each other. (Third step)

  Further, by further growing a group 13 nitride crystal 406, a group 13 nitride crystal layer 4100 in which a plurality of group 13 nitride crystals 406 are connected can be obtained as shown in (i). In this case, if the group 13 nitride crystal 406 is sufficiently grown, the surface of the group 13 nitride crystal layer 4100 can be smoothed as shown in (i).

  FIG. 12C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps performed after the third step described above with reference to FIG. Similar to the process described above with reference to FIG. 4-3, the fourth process (see (j) in the figure), the fifth process (see (k) and (l) in the figure), and the sixth process (in the figure (m) )) Is performed.

  FIG. 12-4 is a perspective view of the group 13 nitride crystal substrate 4210 obtained by the sixth step. As shown in FIG. 12-4, in group 13 nitride crystal substrate 4210 (4210a to 4210g), group 1nitride crystal domains 1406 grown from adjacent growth start regions are arranged.

(Fifth Embodiment of Manufacturing Method)
Next, a fifth embodiment will be described with reference to FIGS. 13-1 to 13-4.

  FIGS. 13-1 is a figure (sectional drawing) explaining an example of the 1st process in 5th Embodiment. In the first step, a group 13 nitride film is formed through a lift-off mask with a through hole formed on the base substrate 501, the lift-off mask is removed, and the remaining group 13 nitride film is formed. Can be used as a growth start region.

First, as shown in FIG. 2B, a lift-off mask 502 such as SiO _{2 is formed} on the base substrate 501. After that, a resist pattern 503 is formed by photolithography or the like as shown in (c), and an opening is formed in the lift-off mask material 502 such as SiO ₂ by using a dry etching method or the like as shown by an arrow in the figure. To do. Thereafter, the resist pattern 503 is removed as shown in (d), and then a group 13 nitride film 504 is formed as shown in (e). Then, the lift-off mask 502 is removed, and the group 13 nitride film 504 on the base substrate 501 can be formed as the growth start region 505 by being formed in the opening of the lift-off mask 502.

  FIG. 13B is a diagram (a cross-sectional view) for explaining an example of the second to third steps performed after the first step described above with reference to FIG. As shown in FIG. 5F, the group 13 nitride crystal 506 starts crystal growth in a plurality of growth start regions 505 formed on the base substrate 501. As shown in (f), the group 13 nitride crystal 506 grows in a hexagonal column shape with the growth start region 505 as a seed crystal so as to enlarge the c-plane. (Second step)

  Then, as shown in (h), the c-plane further expands so as to cover the surface of the base substrate 501, and as shown in (i), a group 13 nitride crystal grown from the adjacent growth start region 505. 506 are connected to each other. (Third step)

  Further, by further growing a group 13 nitride crystal 506, a group 13 nitride crystal layer 5100 in which a plurality of group 13 nitride crystals 506 are connected as shown in (j) can be obtained. In this case, if the crystal growth of each group 13 nitride crystal 506 is sufficiently performed, the surface of the group 13 nitride crystal layer 5100 can be smoothed as shown in (j).

  FIG. 13C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps performed after the third step described above with reference to FIG. Similar to the process described above with reference to FIG. 4-3, the fourth process (see (k) in the figure), the fifth process (see (l) and (m) in the figure), and the sixth process (in the figure (n) )) Is performed.

  FIG. 13-4 is a perspective view of the group 13 nitride crystal substrate 5210 obtained by the sixth step. As shown in FIG. 13-4, in group 13 nitride crystal substrate 5210 (5210a to 5210g), group 1nitride crystal domains 1506 grown from adjacent growth start regions are arranged.

(Sixth Embodiment of Manufacturing Method)
Next, a sixth embodiment will be described with reference to FIGS. 14-1 to 14-4.

  Further, the first step according to another preferred embodiment includes a step of stacking a group 13 nitride crystal on a base substrate, and a surface of the stacked group 13 nitride crystal with a mask having a plurality of through holes. A surface of the group 13 nitride crystal exposed from these through holes is defined as a growth start region. Next, a specific example of the present embodiment will be described with reference to FIG.

  FIG. 14A is a diagram (cross-sectional view) for explaining an example of the first step in the sixth embodiment. In the first step, as shown in FIG. 5B, a plate with a through hole may be placed on the base substrate 601 and used as a lift-off mask 602. In this case, as shown in (c), a group 13 nitride film 603 is formed on the base substrate 601 and the mask 602. Thereafter, as shown in (d), the mask 602 is removed from the base substrate 601, and the group 13 nitride film 603 formed on the bottom of the through hole can be used as the growth start region 605.

  Note that the constituent material of the mask 602 is not particularly limited, but may include at least one of tungsten, tantalum, sapphire, alumina, YAG, MgO, silicon nitride, quartz, and the like as the constituent material. preferable.

  FIG. 14B is a diagram (cross-sectional view) for explaining an example of second to third steps performed after the first step described above with reference to FIG. As shown in FIG. 5E, the group 13 nitride crystal 606 starts crystal growth in a plurality of growth start regions 605 formed on the base substrate 601. As shown in (e), the group 13 nitride crystal 606 grows in a hexagonal column shape with the growth start region 605 as a seed crystal so as to enlarge the c-plane. (Second step)

  Then, as shown in (f), the c-plane further expands so as to cover the surface of the base substrate 601, and as shown in (g), a group 13 nitride crystal grown from the adjacent growth start region 605. 606 are connected. (Third step)

  Further, by further growing a group 13 nitride crystal 606, a group 13 nitride crystal layer 6100 in which a plurality of group 13 nitride crystals 606 are connected as shown in (h) can be obtained. In this case, if the group 13 nitride crystal 606 is sufficiently grown, the surface of the group 13 nitride crystal layer 6100 can be smoothed as shown in FIG.

  FIG. 14C is a diagram (a cross-sectional view) for explaining an example of the fourth to sixth steps performed after the third step described above with reference to FIG. Similar to the process described above with reference to FIG. 4-3, the fourth process (see (i) in the figure), the fifth process (see (j) and (k) in the figure), and the sixth process (see (l) in the figure). )) Is performed.

  FIG. 14-4 is a perspective view of the group 13 nitride crystal substrate 6210 obtained by the sixth step. As shown in FIG. 14-4, in group 13 nitride crystal substrate 6210 (6210a to 6210g), group 1nitride crystal domains 1606 grown from adjacent growth start regions are arranged.

(Seventh Embodiment of Manufacturing Method)
Next, a seventh embodiment will be described with reference to FIGS. 15-1 to 15-4.

  FIG. 15A is a diagram (cross-sectional view) for explaining an example of the first step in the seventh embodiment. In the first step, the growth start region of the group 13 nitride crystal may be formed by a flux method.

For example, Ga 702 is placed on a sapphire base substrate 701 as shown in FIG. Then, as shown in (c), the base substrate 701 is heated in an atmosphere of sodium (Na) vapor and nitrogen gas (N ₂ ). Then, Ga in Ga 702 is liquefied, sodium (Na) and nitrogen (N ₂ ) in the gas phase are dissolved in this liquid Ga to form a mixed melt 703, and GaN 705 is crystal-grown. The GaN 705 thus crystal-grown can be used as a group 13 nitride crystal growth start region.

Note that as a preferred embodiment of the first step by the flux method, the pressure of the nitrogen gas is 775 ° C., and the heating temperature of the base substrate 701 is 3 MPa. Thereby, GaN 705 can be crystal-grown efficiently. However, the pressure of nitrogen gas and the heating temperature of the base substrate 701 are not limited to this, and may be other pressure values and temperatures.

  FIG. 15B is a diagram (cross-sectional view) for explaining an example of the second to third steps performed after the first step described above with reference to FIG. As shown in FIG. 5E, the group 13 nitride crystal 706 starts crystal growth in a plurality of growth start regions 705 formed on the base substrate 701. As shown in FIG. 4E, the group 13 nitride crystal 706 grows in a hexagonal column shape with the growth start region 705 as a seed crystal so as to enlarge the c-plane. (Second step)

  Then, as shown in (f), the c-plane further expands so as to cover the surface of the base substrate 701, and as shown in (g), the group 13 nitride crystal grown from the adjacent growth start region 705. 706 are connected to each other. (Third step)

  Further, by further growing a group 13 nitride crystal 706, a group 13 nitride crystal layer 7100 in which a plurality of group 13 nitride crystals 706 are connected as shown in (h) can be obtained. In this case, if the group 13 nitride crystals 706 are sufficiently grown, the surface of the group 13 nitride crystal layer 7100 can be smoothed as shown in FIG.

  FIG. 15C is a diagram (cross-sectional view) for explaining an example of the fourth to sixth steps performed after the third step described above with reference to FIG. Similar to the process described above with reference to FIG. 4-3, the fourth process (see (i) in the figure), the fifth process (see (j) and (k) in the figure), and the sixth process (see (l) in the figure). )) Is performed.

  FIG. 15-4 is a perspective view of the group 13 nitride crystal substrate 7210 obtained by the sixth step. As shown in FIG. 15-4, in group 13 nitride crystal substrate 7210 (7210a to 7210g), group 1nitride domains 1706 grown from adjacent growth start regions are arranged.

Example 1
First, the 1st process in Example 1 is demonstrated using FIG. 12 (FIGS. 12-1 thru | or FIG. 12-4). In this example, a gallium nitride crystal was manufactured as a group 13 nitride crystal.

  In this example, a c-plane sapphire substrate having a diameter of 100 mm was used as the base substrate 401 as shown in FIG. First, as shown in FIG. 12B, gallium nitride (GaN) was epitaxially grown on the sapphire substrate 401 by MOCVD to form a GaN layer (group 13 nitride crystal layer) 402. The epitaxial growth of GaN by MOCVD was performed by a general two-step growth in which a low-temperature GaN buffer layer was grown and then a high-temperature GaN layer was grown.

  Next, as shown in FIG. 12-1 (c), a resist pattern 403 was formed on the GaN layer 402 by photolithography. The resist pattern 403 was a circle having a diameter of 200 μm as shown in FIG. The resist pattern 403 is arranged in a regular triangular lattice position so that the sides forming the lattice form an angle of 30 ° with the a-axis of the GaN layer 402. The interval between adjacent growth start regions 405 was 12 mm.

  Then, dry etching was performed as indicated by the arrow in FIG. 12-1 (c), and the GaN layer 402 other than the portion covered with the resist pattern 403 was removed by etching as illustrated in FIG. 12-1 (d). .

  Thus, after exposing the surface of the sapphire substrate 401 as shown in FIG. 12-1 (d), the resist pattern 403 was removed. Then, as shown in FIG. 12A, the portion of the GaN layer 402 protected by the resist pattern 403 was used as a growth start region 405.

  Next, the 2nd process thru | or 4th process in Example 1 are demonstrated with reference to FIG. In this example, the second to fourth steps were performed by the flux method using the crystal manufacturing apparatus 1 shown in FIG.

  First, the pressure vessel 11 was peeled off from the crystal manufacturing apparatus 1 at the valve 21 portion and placed in a glove box in an Ar atmosphere. Next, the base substrate 401 manufactured in the first step was placed in a reaction vessel 12 made of YAG having an inner diameter of 150 mm. Next, gallium (Ga) and sodium (Na) were charged into the reaction vessel 12. In this example, the molar ratio of gallium to sodium was 0.25: 0.75.

  And after installing the reaction container 12 in the pressure vessel 11, the pressure vessel 11 was sealed, the valve | bulb 21 was closed, and the inside of the reaction vessel 12 was interrupted | blocked from the external atmosphere. In addition, since a series of work is performed in the glove box of high-purity Ar gas atmosphere, the inside of the pressure vessel 11 is filled with Ar gas.

  Next, the pressure vessel 11 was taken out of the glove box and incorporated in the crystal production apparatus 1. That is, the pressure vessel 11 was installed at a predetermined position where the heater 13 was provided outside, and was connected to a nitrogen and argon gas supply pipe 14 at the valve 21 portion.

  Then, the valve 21 and the valve 18 are opened, Ar gas is introduced from the Ar gas supply pipe 20 into the gas supply pipe 14, the pressure is adjusted by the pressure control device 19, and the total pressure in the pressure-resistant vessel 11 is set to 2 MPa. Closed.

  Next, nitrogen gas was introduced from the nitrogen gas supply pipe 17, the pressure was adjusted by the pressure control device 16, the valve 15 was opened, and the total pressure in the pressure-resistant vessel 11 was set to 4 MPa. That is, the partial pressure of nitrogen in the internal space 23 of the pressure vessel 11 is 2 MPa. Thereafter, the valve 15 is closed and the pressure control device 16 is set to 8 MPa.

  Next, the heater 13 was energized to raise the temperature of the reaction vessel 12 to the crystal growth temperature. In this example, the crystal growth temperature was 880 ° C. At the crystal growth temperature, gallium and sodium in the reaction vessel 12 are melted to form a mixed melt 25. The temperature of the mixed melt 25 is the same as the temperature of the reaction vessel 12. Moreover, when the heater 13 is heated in this way, the gas in the pressure vessel 11 is heated and the volume expands. Here, since the pressure value is set to 8 MPa in the pressure control device 16 as described above, the total pressure of the gas in the pressure vessel 11 is 8 MPa. The nitrogen partial pressure is 4 MPa.

  Next, the valve 15 is opened and a nitrogen gas pressure is applied at 8 MPa. This is because the partial pressure of nitrogen in the pressure vessel 11 is maintained at 4 MPa even when nitrogen is consumed by crystal growth of gallium nitride. Holding in this state for 300 hours, nitrogen is continuously dissolved in the mixed melt 25, and a GaN crystal 406 made of gallium and nitrogen is formed on the base substrate 401 as shown in FIGS. 12-2 (f) to (i). Thus, the GaN crystal layer 4100 was manufactured.

After 300 hours, the heater 13 was turned off, and the temperature of the mixed melt 25 was lowered to room temperature.
When the pressure vessel 11 was opened after the pressure of the gas in the pressure vessel 11 was lowered, the GaN crystal layer 4100 was grown on the base substrate 401 in the reaction vessel 12. Further, as shown in FIG. 12-2 (j), the GaN crystal layer 4100 was peeled off cleanly because the portion of the growth start region 405 formed on the base substrate 401 was cracked.

  The GaN crystal layer 4100 had a diameter slightly larger than 100 mm, which was the diameter of the base substrate 401, and a thickness of 5 mm. The main surface of the GaN crystal layer 4100 was a c-plane in a hexagonal crystal structure.

  The surface of the grown GaN crystal layer 4100 was polished and subjected to surface treatment. When observed with a fluorescence microscope, it was found that the contrast changed in the vicinity of the connected GaN crystal 406, that is, in the boundary region 407, and a plurality of hexagonal domains 406 were formed on the c-plane (see FIG. 7). . Further, when the surface of the GaN crystal layer 4100 was etched with phosphoric acid, many etch pits were observed in the boundary region 407 of each domain 406. Further, the GaN crystal layer 4100 had no cracks, and the radius of curvature exceeded 20 m.

  Further, when the cross section of the GaN crystal layer 4100 was observed with a microscope, the GaN crystal 406 grown from the growth start region 405 was united (connected) with the GaN crystal 406 grown from the adjacent growth start region 405, and one GaN crystal was obtained. A history of forming the layer 4100 was observed. This is presumably because the crystal growth surface slightly changes at the location where the GaN crystal 406 is connected, and the way in which impurities are incorporated changes.

  The fifth step and the sixth step were performed using the GaN crystal layer 4100 subjected to the same crystal growth step and surface treatment as a substrate. In the fifth step of this example, crystal growth was performed by the flux method as in the second step.

  As shown in FIG. 6, in this example, a GaN crystal layer 4100 was installed in the reaction vessel 12, and a GaN crystal 4200 was grown on the substrate. The crystal growth conditions are the same as those in the second step except that the growth time is 600 hours.

  After the fifth step, the grown GaN crystal 4200 was epitaxially grown on the GaN crystal layer 4100, and its thickness was 10 mm.

  Next, as shown in FIG. 12-3 (m), the grown GaN crystal 4200 was externally ground and sliced parallel to the c-plane to obtain a plurality of GaN crystal substrates 4210 (4210a-). Thereafter, the surface of the GaN crystal substrate 4210 was polished and subjected to surface treatment to manufacture a GaN crystal substrate 4210 having a diameter of 100 mm.

When the surface of the GaN crystal substrate 4210 was etched with phosphoric acid, etch pits were formed side by side in a hexagonal outer peripheral shape (see FIG. 8). In the hexagonal domain 1406 formed by the etch pit rows or boundary regions 1407, almost no etch pits were formed. In this domain 1406, among the hexagonal sides, the interval between the parallel sides was about 12 mm. Further, the radius of curvature of the GaN crystal substrate 4210 exceeded 20 m. Furthermore, the Si concentration in the crystal was below the detection limit (2 × 10 ¹⁷ cm ⁻³ ) of SIMS analysis.

As described above, the GaN crystal substrate 4210 manufactured in the present example includes a plurality of hexagonal domains that are bounded by a region having many crystal defects in the c-plane. The distance between the sides is 1 mm or more, and the silicon concentration in the crystal is less than 2 × 10 ¹⁷ cm ⁻³ and has an outer diameter greater than 2 inches.

  In addition, the GaN crystal substrate 4210 manufactured in this example is a self-supporting substrate having a radius of curvature of 20 m or more and a c-plane as a main surface in addition to the same characteristics as the above-described group 13 nitride crystal.

(Example 2)
In this example, the fifth step was performed by the HVPE method. The other steps were the same as in Example 1. As a result, the thickness of the manufactured GaN crystal substrate was 1 mm. The various characteristics of the manufactured GaN crystal substrate were the same as those of the GaN crystal substrate 4210 of Example 1, but the Si concentration in the GaN crystal was 1 × 10 ¹⁸ cm ⁻³ .

Thus, the GaN crystal substrate manufactured in this example has a silicon concentration in the crystal of 2 × 10 ¹⁷ cm ⁻³ or more, a curvature radius of 20 m or more, and an outer diameter larger than 2 inches. And a self-supporting substrate having a c-plane as a main surface.

(Example 3)
In this example, a GaN crystal substrate was manufactured in the same process as in Example 1 except that Ca was added to the mixed melt 25 during crystal growth in the second and fifth steps. did. As a result, the various characteristics of the manufactured GaN crystal substrate were the same as those of the GaN crystal substrate 4210 of Example 1, but Ca was detected in the GaN crystal in SIMS analysis.

  Thus, the GaN crystal substrate manufactured in this example contains at least one element of calcium (Ca), barium (Ba), and strontium (Sr).

As described above, the GaN crystal substrate manufactured in this example has a silicon concentration in the crystal of 2 × 10 ¹⁷ cm ⁻³ or more, and at least one of calcium, barium, and strontium in the crystal. And a curvature radius of 20 m or more, an outer diameter larger than 2 inches, and a c-plane as a main surface.

  As described above, the group 13 nitride crystal substrate manufactured according to the present embodiment is a self-supporting substrate with small warpage and little distortion, and thus can be used as a high-quality substrate for LEDs and electronic devices.

DESCRIPTION OF SYMBOLS 11 Pressure-resistant container 12 Reaction container 13 Heater 14 Gas supply pipes 15, 18, 21 Valves 16, 19 Pressure control device 17 Nitrogen supply pipe 20 Argon supply pipe 22 Pressure gauge 23 Internal space of pressure-resistant container 24 Base 25 Mixed melt 101, 201 , 301, 401, 501, 601, 701 Base substrate 105, 205, 305, 405, 505, 605, 705 Growth start region 106, 206, 306, 406, 506, 606, 706 Group 13 nitride crystal 107, 407, 1107, 1407 Border region 1100, 2100, 3100, 4100, 5100, 6100, 7100 Group 13 nitride crystal layer 1106, 1206, 1306, 1406, 1506, 1606, 1706 Domain 1200, 2200, 3200, 4200, 5200, 6200, 7200 Group 13 Nitride crystal 1210, 2210, 3210, 4210, 5210, 6210, 7210 Group 13 nitride crystal substrate

JP 2005-12171 A

Chemistry of Materials Vol. 9 (1997) 413-416

Claims (10)

A first step of disposing a group 13 nitride crystal growth start region on the main surface of the base substrate so as to be a lattice point position of a triangular lattice;
A second step of growing the group 13 nitride crystal by aligning the crystal orientation from each growth start region;
A third growth of the group 13 nitride crystal layer is formed on the main surface of the base substrate by continuing the crystal growth and connecting the plurality of group 13 nitride crystals grown from the adjacent growth start regions. Process,
A fourth step of separating the group 13 nitride crystal layer and the base substrate in the cooling process of the group 13 nitride crystal layer;
Only including,
In the first step, the triangular lattice is an equilateral triangular lattice in which lattice point intervals are equal to each other, and the hexagonal group 13 nitride grown from the side constituting the equilateral triangular lattice and the growth start region is formed. The angle formed by the a-axis of the crystal is 30 °,
In the second step or the third step, the group 13 nitride crystal is grown by a flux method. The base substrate used in the first step is a large crystal substrate than two inches in diameter, according to claim 1, characterized in, that the distance between the growth initiation region between said adjacent is 1mm or more A method for producing a group 13 nitride crystal. The first step includes
Laminating a group 13 nitride crystal on the base substrate;
Placing a mask having a plurality of through holes corresponding to the positions of the lattice points on the surface of the laminated group 13 nitride crystal,
Making the surface of the group 13 nitride crystal exposed from the through hole the growth start region,
The method for producing a group 13 nitride crystal according to claim 1 or 2 . Wherein the mask used in the first step, tungsten, tantalum, sapphire, alumina, YAG, MgO, be included as a constituent material at least any one of silicon nitride, according to claim 3, wherein A method for producing a group 13 nitride crystal. Wherein as the base substrate, process for producing a Group 13 nitride crystal according to any one of claims 1 to 4, characterized in that a single crystal substrate of oxide used in the first step. Sodium is used as a flux in the flux method, according to any one of claims 1 to 5, characterized in that gallium is used as the Group 13 element used as a raw material of the group 13 nitride crystal A method for producing a group 13 nitride crystal. A group 13 nitride crystal produced by the method for producing a group 13 nitride crystal according to any one of claims 1 to 3 is used as a substrate, and a group 13 nitride crystal is further grown on the substrate. And a fifth step of
A sixth step of manufacturing a crystal substrate using the group 13 nitride crystal grown in the fifth step;
A method for producing a group 13 nitride crystal substrate, comprising: 8. The group 13 nitride crystal substrate according to claim 7 , wherein, in the fifth step, the group 13 nitride crystal is grown on the substrate by an HVPE (halogenated vapor phase epitaxy) method. Production method. 8. The method for producing a group 13 nitride crystal substrate according to claim 7 , wherein in the fifth step, the group 13 nitride crystal is grown on the substrate by a flux method. The group 13 nitride crystal substrate according to claim 9 , wherein sodium is used as a flux in the flux method, and gallium is used as a group 13 element used as a raw material of the group 13 nitride crystal. Production method.

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