JP2017222548A - Production of group iii nitride crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production of a group III nitride single crystal while suppressing crack initiation in a substrate.SOLUTION: This group III nitride crystal manufacturing method comprises: a (i) step of preparing a seed crystal substrate having a base substrate, a plurality of point seeds comprising a group III nitride arranged on a first principal surface of the base substrate, a plurality of gaps arranged on the first principal surface and between the point seeds, and a plurality of grooves arranged in a second principal surface of the base substrate and arranged at positions not overlapping the plurality of gaps in a plane view; a (ii) step of bringing the point seeds into contact with a solution containing at least one III group element selected from gallium, aluminum and indium, and an alkaline metal in an atmosphere containing nitrogen, thereby growing the group III nitride crystal; and a (iii) step of separating the base substrate and the group III nitride crystal.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a method for producing a group III nitride crystal.

  Group III nitride single crystal semiconductors such as gallium nitride are attracting attention as materials for heterojunction high-speed electronic devices such as power semiconductors and semiconductor elements that emit blue and ultraviolet light. Blue laser diodes (LD) are applied to high-density optical discs and displays, and blue light-emitting diodes (LEDs) are applied to displays and illumination. In addition, the ultraviolet LD is expected to be applied to biotechnology and the like, and the ultraviolet LED is expected as an ultraviolet light source for fluorescent lamps.

A substrate of a group III nitride single crystal semiconductor (for example, gallium nitride) is usually formed by vapor phase epitaxial growth. For example, a substrate obtained by heteroepitaxially growing a group III nitride crystal on a base substrate made of sapphire is used. However, the sapphire substrate and the gallium nitride single crystal have a difference of 13.8% in the lattice constant and a difference of 25.8% in the linear expansion coefficient. For this reason, the gallium nitride single crystal thin film obtained by vapor phase epitaxial growth has insufficient crystallinity. The dislocation density of the crystal obtained by this method is usually 1 × 10 ⁸ cm ⁻² to 1 × 10 ⁹ cm ⁻² , and reduction of the dislocation density is an important issue. In order to solve this problem, efforts have been made to reduce the dislocation density, and for example, an ELOG (Epitaxial Lateral Overgrowth) method has been developed. According to this method, the dislocation density can be lowered to about 1 × 10 ⁵ cm ⁻² to 1 × 10 ⁶ cm ^−2, but the manufacturing process is complicated.

  On the other hand, a method of performing crystal growth in a liquid phase instead of vapor phase epitaxial growth has been studied. Conventionally, the equilibrium vapor pressure of nitrogen at the melting point of a group III nitride single crystal such as a gallium nitride single crystal or an aluminum nitride single crystal is 1000 MPa or more. Therefore, in order to grow gallium nitride in a liquid phase, 800 MPa at 1200 ° C. Conditions have been needed. In contrast, it has been clarified that a gallium nitride single crystal can be synthesized at a relatively low temperature and low pressure of 870 ° C. and 4 MPa by using a sodium flux method in which nitrogen is dissolved by utilizing a mixed melt with a sodium melt. .

  In addition, a mixture of gallium and sodium was melted at 800 ° C. and 5 MPa in a nitrogen gas atmosphere containing ammonium, and a single crystal having a maximum crystal size of about 1.2 mm was grown using this melt for 96 hours. It is obtained (for example, refer to Patent Document 1).

  In addition, after a gallium nitride single crystal layer is formed on a sapphire substrate by metal organic chemical vapor deposition (MOCVD), a single crystal is grown by liquid phase epitaxy (LPE). A method has also been reported.

  In these methods, there is a difference in thermal expansion coefficient between the base substrate made of sapphire and the group III nitride single crystal. Therefore, when a group III nitride single crystal is grown using a base substrate made of sapphire, the group III nitride single crystal is distorted or warped. As a result, the substrate is easily damaged during the group III nitride single crystal growth, and it becomes difficult to manufacture a device using the formed semiconductor substrate. Among them, as a method capable of producing a group III nitride single crystal substrate having only a good group III nitride single crystal and having a small warp, a base substrate composed of sapphire and a group III nitride single crystal substrate are manufactured. A manufacturing method including a step of creating a gap in between has been reported (for example, see Patent Document 2).

FIG. 2 is a schematic diagram illustrating an example of a main part of the configuration of the apparatus for producing a group III nitride crystal.
In a conventional method for producing a group III nitride single crystal by the sodium flux method, a mixed melt 101 of a group III metal melt and a sodium melt is placed in a crucible container 100, and a seed crystal substrate 102 is contained therein. Has been placed. The seed crystal substrate has a multilayer structure having a film 104 in which a group III nitride crystal is heteroepitaxially grown on a base substrate 103 as shown in FIG. In this seed crystal substrate 102, as shown in FIG. 6, the gap 106 may be formed on the base substrate 103. By arranging the crucible container 100, the mixed melt 101, and the seed crystal substrate 102 having the above-described configuration in an environment of 780 ° C. and nitrogen gas 4 MPa, the nitrogen dissolved in the mixed melt 101 is a group III nitride of the seed crystal substrate 102. The single crystal film 104 reacts with gallium in the mixed melt 101 to generate a gallium nitride single crystal 107 (FIG. 7) (the following formula (I)).
Ga + N → GaN (I)

JP 2009-234800 A JP 2008-308346 A

  However, even if the manufacturing method includes a gap between the base substrate and the group III nitride single crystal substrate, cracks occur without any ingenuity. This is because the yield strength decreases at the crystal bond, and the crystal breakage occurs due to the stress generated by the difference in expansion coefficient between the base substrate and the group III nitride single crystal substrate during the cooling process, and the base substrate breaks down. This is thought to be due to the seed being destroyed. In addition, this stress increases as the diameter of the substrate increases.

  Therefore, an object of the present disclosure is to provide a method for producing a group III nitride single crystal in which generation of cracks in the substrate is suppressed.

In order to achieve the above object, a method for producing a group III nitride crystal according to the present disclosure includes a base substrate,
A plurality of point seeds made of a group III nitride disposed on the first main surface of the base substrate;
A plurality of voids disposed on the first main surface and between the point seeds;
(I) preparing a seed crystal substrate having a plurality of grooves arranged on the second main surface of the base substrate and arranged at positions not overlapping with the plurality of voids in plan view;
In a nitrogen-containing atmosphere, a group III nitride crystal is grown by bringing the point seed into contact with a melt containing at least one group III element selected from gallium, aluminum, and indium and an alkali metal (ii) Process,
Separating the base substrate and the group III nitride crystal (iii);
including.

  According to the method for producing a group III nitride crystal according to the present disclosure, a group III nitride single crystal having no cracks can be grown.

(A)-(c) is a schematic sectional drawing which shows each process of (i)-(iii) of the manufacturing method of the group III nitride crystal which concerns on Embodiment 1. FIG. It is the schematic which shows an example of the principal part of a structure of the manufacturing apparatus of a group III nitride crystal. It is a top view which shows the image which looked at arrangement | positioning of a cylindrical type point seed from the C surface side. (A) And (b) is a figure showing the large size process of the group III nitride crystal manufacture in Embodiment 1. FIG. It is a figure which shows an example of the principal part of the manufacturing method of the conventional group III nitride crystal. It is a figure which shows an example of the principal part of the manufacturing method of the conventional group III nitride crystal. It is a figure which shows an example of the principal part of the manufacturing method of the conventional group III nitride crystal. It is a figure which shows an example of the manufacturing method of the group III nitride crystal in this indication. It is an enlarged view which shows the image of the groove processing of the base substrate in this indication.

The method for producing a group III nitride crystal according to the first aspect includes a base substrate,
A plurality of point seeds made of a group III nitride disposed on the first main surface of the base substrate;
A plurality of voids disposed on the first main surface and between the point seeds;
(I) preparing a seed crystal substrate having a plurality of grooves arranged on the second main surface of the base substrate and arranged at positions not overlapping with the plurality of voids in plan view;
In a nitrogen-containing atmosphere, a group III nitride crystal is grown by bringing the point seed into contact with a melt containing at least one group III element selected from gallium, aluminum, and indium and an alkali metal (ii) Process,
Separating the base substrate and the group III nitride crystal (iii);
including.

The method for producing a group III nitride crystal according to a second aspect is the first aspect, wherein in the step (ii),
The group III element may be gallium, the alkali metal may be at least one selected from sodium, lithium and potassium, and the group III nitride crystal may be a GaN crystal.

The method for producing a group III nitride crystal according to a third aspect is the first or second aspect, wherein in the step (i),
The plurality of point seeds may be formed by at least one of electric discharge machining from the first main surface side or laser machining from the second main surface side.

  The method for producing a group III nitride crystal according to a fourth aspect is any one of the first to third aspects, wherein in the step (i), the plurality of grooves penetrate the base substrate, The base substrate may be divided into a plurality of pieces.

  The III-nitride crystal manufacturing method according to the fifth aspect is the fourth aspect described above, and in the step (i), each of the divided base substrates may have an equilateral triangle shape.

The method for producing a group III nitride crystal according to a sixth aspect is the fifth aspect, wherein in the step (i), the width of the groove is
(1) It is not less than a value obtained by adding 0.0005% of the length of one side of the equilateral triangle to a value obtained by subtracting the temperature at the time of placement from the temperature at the time of crystal growth, and (2) the group III nitride to be grown It may be 70% or less of the height of the crystal.

  Hereinafter, a method for producing a group III nitride crystal according to an embodiment will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals. In all the drawings, the size, ratio, and the like of each component may be different from actual ones.

(Embodiment 1)
FIG. 1A to FIG. 1C are schematic cross-sectional views showing steps (i) to (iii) of the method for producing a group III nitride crystal according to the first embodiment.
As shown in FIG. 1A, the method for producing a group III nitride crystal according to the first embodiment includes a base substrate 103 and a group III nitride disposed on the first main surface 103a of the base substrate 103. A plurality of point seeds 108 made of a material, a plurality of gaps 106 disposed on the first main surface 103a and between the point seeds 108, and a second main surface 103b of the base substrate 103, And (i) a step of preparing a seed crystal substrate 1000 having a plurality of grooves 113 arranged at positions not overlapping with the plurality of gaps 106 in a plan view.

Further, in this manufacturing method, the point seed 108 is brought into contact with a melt (mixed melt) containing at least one group III element selected from gallium, aluminum and indium and an alkali metal in an atmosphere containing nitrogen. (Ii) to grow a group III nitride crystal 107.
The method further includes a step (iii) of separating the base substrate 103 and the group III nitride crystal 107.

  In the group III nitride crystal manufacturing method according to the first embodiment, the nitrogen-containing atmosphere is preferably a pressurized atmosphere in order to promote the supply of nitrogen and improve the reaction rate. The range of the said pressurization is a range of 0.1 MPa or more and 10 MPa or less, for example.

  In the manufacturing method according to the first embodiment, it is preferable to perform separation using a stress generated by the difference between the linear expansion coefficient of the base substrate 103 and the linear expansion coefficient of the group III nitride single crystal 107. As another method, separation by laser processing is possible, but the number of steps increases.

  The group III nitride crystal 107 has a crystal plane C plane as a growth plane.

  The crystal growth of the group III nitride crystal 107 has a growth dominant direction and grows naturally in a hexagonal column or hexagonal pyramid shape. The air gap 106 is formed by cutting off a part of the group III nitride single crystal film 104. The group III nitride single crystal film 104 remaining after processing forms a columnar shape having a circular or regular hexagonal growth surface when viewed from the upper surface in consideration of the crystal growth dominant direction. This cylindrical or regular hexagonal seed crystal is called a point seed 108. Various arrangements such as a 90 degree position relative to each other can be considered for the relative arrangement of the point seeds 108, but in consideration of the growth dominant direction of natural growth in a hexagonal column or hexagonal pyramid, the point seeds 108 are located at 60 degree positions. Preferably they are arranged. The plurality of gaps 106 are disposed between the plurality of point seeds 108. The period of the gap 106 and the point seed 108 is preferably 30 μm or more. When it is smaller than 30 μm, the adjacent point seeds 108 are bonded at the initial stage of growth, and there are many dislocations and the crystallinity is deteriorated.

  The void indicates a space observed in the crystal cross section, and means a space (for example, sub-μm order) or more space that can be observed by SEM (Scanning Electron Microscope). The period of the air gap is a distance between a plurality of air gaps, and means a pitch. This can be measured, for example, with an electron microscope. Note that the period of the voids can also be expressed by, for example, the mutual distance (pitch) of the growth points of the group III nitride crystal such as the surface of the point seed 108. Further, the period of the gap 106 can be adjusted according to the method of forming the growth point (for example, size, position, mutual distance). FIG. 3 shows a view of the arrangement of the point seeds 108 as viewed from the C-plane direction. Each circle in the figure is a cylindrical point seed 108. In the figure, the mutual distance between growth points is shown as a pitch.

  In the manufacturing method of the present disclosure, as the base substrate 103, for example, a sapphire substrate can be used. Although a group III nitride crystal substrate can be used for the base substrate 103, it is difficult to select a material that meets the manufacturing cost.

  In the production method of the present disclosure, the alkali metal constituting the mixed melt is at least one selected from sodium, lithium, and potassium. This is because, in materials other than alkali metals, it is difficult to divide nitrogen molecules in nitrogen gas supplied by pressurization into nitrogen atoms for crystal growth reaction.

  In the production method of the present disclosure, the mixed melt may further include an alkaline earth metal. The effect of suppressing polycrystallization may be obtained by including an alkaline earth metal.

  In the manufacturing method of the present disclosure, the gap 106 can be formed by, for example, laser processing from the second main surface 103 b side of the base substrate 103. If this is not possible, the gap 106 can be formed by electrical discharge machining from the growth surface side (first main surface 103a side) of the group III nitride single crystal film 104.

  In the substrate of the present disclosure, the diameter of the point seed 108 in FIG. 3 is processed to be 30 μm or more. When the diameter of the point seed 108 is smaller than 30 μm, initial nuclei cannot be formed on the point seed. In order to stably form initial nuclei, a sufficient growth area of the point seed 108 is required, and the diameter of the point seed 108 is more preferably 100 μm or more.

  Hereinafter, the method for producing a group III nitride crystal according to the first embodiment will be described with reference to an example.

  In this method, first, a group III nitride single crystal layer 104 having a gap 106 is formed on a base substrate 103. As the base substrate 103, for example, a sapphire substrate can be used. An example of a method for forming the group III nitride layer 104 having voids will be described below.

First, a first group III nitride single crystal layer represented by a composition formula Al _u Ga _v In _1-uv N (where 0 ≦ u ≦ 1, 0 ≦ v ≦ 1) is formed on a substrate. To do. The first group III nitride single crystal layer can be formed by, for example, MOCVD (Metal Organic Chemical Deposition), MBE (Molecular Beam Epitaxy), or HVPE (Hydrogen Vapor Phase Epitaxy).

  Next, a part of the group III nitride single crystal layer 104 is removed (the void 106 is formed) to form a point seed 108. The point seed 108 can be formed by laser processing from the base substrate 103 side or the growth surface side of the group III nitride single crystal film 104 or by electric discharge processing from the growth surface side of the group III nitride single crystal film 104.

  The upper surface of the point seed 108 is usually a C plane. As the shape of the point seed 108, a shape in which the seed crystals generated in the following steps are easily combined and the substrate is easily separated can be selected and formed into a dot shape.

  As a result, voids 106 are formed in the group III nitride single crystal layer 104 on the base substrate 103, and the group III nitride single crystal layer 104 remains in a columnar shape. The remaining point seed 108 of the group III nitride single crystal layer 104 is formed in a columnar shape or a regular hexagonal column shape by the above-described processing method. A base substrate on which a plurality of point seeds 108 and voids 106 are formed is referred to as a seed crystal substrate 102.

  Next, a process of further enlarging the seed crystal substrate 102 is performed. 4 (a) and 4 (b) are diagrams showing a large format process for manufacturing a group III nitride crystal in the first embodiment. First, a plurality of seed crystal substrates 102 are prepared, and in each substrate, the point seed 108 is avoided and the base substrate 103 is selectively cut at the gap 106 (FIG. 4A). 102 is arranged as a large-sized seed crystal substrate 110 having the same crystal orientation (FIG. 4B). FIG. 4B shows an example in which a hexagonal large-sized substrate 110 is configured by combining six seed crystal substrates 102. In FIG. 4A, it is assumed that the crystal orientations of the six seed crystal substrates 102 are aligned in the same direction, and an equilateral triangular substrate is cut out from each of the cut surfaces of a plurality of patterns. As shown in FIG. 4B, the diameter of the seed crystal substrate 102 cut out in the form of six triangles thus obtained is combined to increase the diameter. At this time, considering the crystal growth dominant direction in which the growth substrate naturally forms a regular hexagonal shape, the crystal can be most efficiently grown when the large-diameter substrate 110 has a regular hexagonal shape. . Therefore, the shape after cutting out the seed crystal substrate 102 may be, for example, a rectangle or a regular hexagon. However, it is most preferable to cut the seed crystal substrate 102 into a regular triangle that is easy to form a regular hexagon when combined.

  The six seed crystal substrates 102 processed into a regular triangle are arranged so as to form a regular hexagon in a direction in which the crystal orientations are aligned. For example, three of the six seed crystal substrates 102 in FIG. 4A are cut so that the apex of the equilateral triangle is positioned in the [1100] direction, and the remaining three in the [−1-100] direction. Cut so that the apex of the equilateral triangle is located. By alternately arranging three of each of the cut substrate 111 and the substrate 112 in the clockwise direction while fixing the orientation, the seed crystal substrate 110 having a large diameter with the crystal orientations aligned is obtained. be able to. The cutting process can be performed by laser processing or machining.

  When the seed crystal substrate 102 having an equilateral triangle shape is disposed, a gap 109 is provided between adjacent base substrates 103. The lower limit value of the width of the gap 109 to be provided is calculated from the thermal expansion coefficient of sapphire, the difference between the reaction temperature and room temperature, and the size of the seed crystal substrate 102. This is the length of a value obtained by adding the value obtained by subtracting the temperature at the time of crystal growth to 0.0005% of the length of one side of the seed crystal substrate 111 or the seed crystal substrate 112 having an equilateral triangle shape. This is the limit of contact between the substrates during thermal expansion. Further, the upper limit value of the width of the gap 109 to be provided is the width of the gap in which crystals grown in the a-axis direction from the point seed 108 can be combined, and this is calculated from the grown film thickness. The relationship between the thickness of the growth film 107 grown in the c-plane direction and the distance grown in the inter-substrate direction at that time is a ratio of 2.1: 2 from the crystal structure. In order for the substrates grown in the inter-substrate direction to be coupled to each other, the upper limit is the width of the gap having a length of 70% or less of the growth film thickness of the target growth film 107. In consideration of the above upper limit value and lower limit value, the gap 109 provided between the base substrates 103 when arranging the equilateral triangular seed crystal substrate 102 has a length of one side of the equilateral triangular seed crystal substrate 102. 0.0005%, which is not less than the length of the value obtained by subtracting the temperature at the time of crystal growth from the temperature at the time of crystal growth, and 70% or less of the height of the group III nitride crystal to be grown. Deploy. The gap 109 provided between the base substrates 103 when arranging the equilateral triangular seed crystal substrate 102 is 0.0005% of the length of one side of the equilateral triangular seed crystal substrate 102 at the time of crystal growth. When the length obtained by subtracting the temperature at the time of placement from the temperature is smaller than the length of the integrated value, the base substrates 103 come into contact with each other due to thermal expansion, and the base substrate 103 is displaced and the crystal orientation is disturbed. As a result, a highly crystalline substrate cannot be obtained. Further, when the gap 109 provided between the base substrates 103 when arranging the equilateral triangular seed crystal substrate 102 is larger than 70% of the target growth film thickness, the point seeds are not connected during the growth and are flat. Substrate growth cannot be performed.

  Next, the group III element selected in the mixed melt 101 containing at least one group III element selected from gallium, aluminum, and indium and an alkali metal in an atmosphere containing nitrogen (preferably a pressurized atmosphere of 10 MPa or less). By bringing the growth surface side surface of the group III nitride single crystal layer 104 made of the above nitride into contact, at least one group III element in the mixed melt 101 reacts with nitrogen dissolved by pressurization. Then, a group III nitride crystal is grown on the group III nitride single crystal layer 104. As the atmosphere containing nitrogen, for example, a nitrogen gas atmosphere or a nitrogen gas atmosphere containing ammonium can be applied. As the alkali metal, at least one selected from sodium, lithium and potassium, that is, one of them or a mixture thereof is used, and these are usually used in a flux state.

  FIG. 2 is a schematic diagram illustrating an example of a main part of the configuration of the apparatus for producing a group III nitride crystal. The mixed melt 101 in FIG. 2 is prepared, for example, by putting a material into the crucible 100 and heating it. In order to promote mixing, the crucible 100 may perform a rocking motion, a rotational motion, or a combination of both. After producing the mixed melt 101, a group III nitride single crystal grows by bringing the mixed melt 101 into a supersaturated state. The melting and crystal growth of the material are performed, for example, at a temperature of about 700 ° C. to 1100 ° C. and a pressure of about 0.1 Pa to 5 MPa. The mixed melt 101 may further contain an alkaline earth metal. As the alkaline earth metal, for example, calcium, magnesium, strontium, barium, beryllium and the like can be used. Use of these alkaline earth metals has an effect of suppressing the formation of polycrystals.

According to this method, III-nitride crystal represented by a composition formula _{Al s Ga t In 1-st} N ( provided that 0 ≦ s ≦ 1,0 ≦ t ≦ 1) is obtained. For example, a gallium nitride crystal can be obtained by using only gallium as a group III element as a material, and a composition formula Al _s Ga _1-s N (where 0 ≦ s) by using gallium and aluminum as a group III element as a material. A crystal represented by ≦ 1) is obtained.

  Next, the portion including the base substrate 103 and the portion including the group III nitride single crystal 107 are separated in the vicinity of the gap 106.

  By using the substrate having the gap 106 as the seed crystal substrate 102, the base substrate 103 can be separated from the group III nitride single crystal substrate 107. This separation step may be performed mechanically or may be performed using a stress generated by the difference between the linear expansion coefficient of the substrate and the linear expansion coefficient of the group III nitride single crystal. When utilizing the difference in linear expansion coefficient, for example, separation can be performed in a cooling step (including natural cooling) after the crystal growth step.

Example 1
The seed crystal substrate in the present disclosure is as shown in FIG. In this example, an experiment was performed in which a 4-inch substrate was divided into 6 sectors having a central angle of 60 degrees so that the point seed 108 was not included in the cut surface as an element verification experiment. The base substrate 103 constituting the seed crystal substrate to which the grown GaN substrate was bonded was a sapphire substrate having a diameter of 150 mm and a thickness of 1 mm. The group III nitride film including voids processed on the base substrate 103 is disposed in a regular hexagonal region inscribed in a circle having a diameter of 130 mm when viewed from the growth surface side. The cylindrical point seeds 108 in the group III nitride single crystal film 104 including the voids are arranged at positions of 60 degrees with respect to each other, and the pitch between the cylindrical point seeds 108 is 550 μm. The width of the gap between each of the six cut base substrates 103 was 300 μm.

  The crucible 100 was made of alumina and the inner diameter was 168 mm. The constituent elements of the mixed melt 101 of the Group III metal melt and the alkali metal melt were gallium as the Group III metal and sodium as the alkali metal, and the liquid height was 20 mm. The crystal substrate was held at 890 ° C. and 3 MPa, and a gallium nitride single crystal substrate was grown to a thickness of 1 mm. After the growth, the substrate was cooled to 25 ° C., and the growth substrate was peeled from the sapphire base substrate.

(Example 2)
Processing was performed so that the width of the gap between the six cut substrates was 500 μm, and the other conditions were the same as in Example 1.

(Example 3)
Processing was performed so that the width of the gap between the six cut substrates was 700 μm, and the other conditions were the same as in Example 1.

(Comparative Example 1)
Processing was performed so that the width of the gap between the six cut substrates was 1000 μm, and the other conditions were the same as in Example 1.

(Comparative Example 2)
Processing was performed so that the width of the gap between the six cut substrates was 100 μm, and the other conditions were the same as in Example 1.

  It was evaluated whether the growth substrate 107 can connect the point seed 108 under the above conditions. The results of presence / absence of point seed connection in the above examples and comparative examples are shown in Table 1 below.

  Note that the groove 113 does not penetrate the base substrate 103 and can be selectively formed in a groove shape provided in the second main surface 103b. When the point seeds 108 are arranged in an a-plane connection, the size of the point seeds 108 is the distance between the point seeds so that the peeling surface of the sapphire base substrate divided by low stress during cooling in the groove shape does not damage the point seeds 108. It is necessary to be less than half (FIGS. 8 and 9).

  In the seed crystal substrate 102 on which the point seed 108 is formed, the stress applied to the group III nitride crystal after growth as the area of the base substrate divided by the substrate is cut or the groove shape is processed. Becomes smaller and harder to break. At this time, the stress applied to the group III nitride crystal is reduced by reducing the length from the center of gravity of the region divided by cutting or groove shape processing to a point farthest from 10 mm. It becomes smaller than the proof stress and can be peeled without breaking the grown substrate. (Fig. 10)

  In addition, it is effective to suppress the warpage of the substrate in order to avoid the occurrence of cracks on the surface of the group III nitride crystal after growth due to the warpage of the substrate. As a method therefor, there is a method of increasing the thickness of the group III nitride crystal to be grown or increasing the thickness of the sapphire base substrate. In this case, there is no upper limit to the thickness, but as the group III nitride crystal becomes thicker, more raw material melt is required, and the inclusion of polycrystals and defects increases.

  It should be noted that the present disclosure includes appropriately combining any of the above-described various embodiments and / or examples, and each of the embodiments and / or examples. The effect which an Example has can be show | played.

  As described above, when the method for producing a group III nitride crystal according to the present disclosure is used, a group III nitride crystal applicable to a heterojunction high-speed electronic device such as a power semiconductor field or an optoelectronic device such as an LED or laser field. Can be obtained.

100 crucible container 101 mixed melt of group III metal melt and sodium melt 102 seed crystal substrate 103 base substrate 104 group III nitride single crystal layer 106 void 107 in group III nitride single crystal layer grown group III nitride Single crystal 108 Point seed 109 Gap 110 Large-diameter seed crystal substrate 111 Seed crystal substrate 112 cut for large-diameter seed crystal substrate 113 cut for large-diameter groove processing portion of base substrate 114 Peeling superior surface of group III nitride single crystal 115 Peeling superior surface of sapphire single crystal

Claims (6)

A base substrate;
A plurality of point seeds made of a group III nitride disposed on the first main surface of the base substrate;
A plurality of voids disposed on the first main surface and between the point seeds;
(I) preparing a seed crystal substrate having a plurality of grooves arranged on the second main surface of the base substrate and arranged at positions not overlapping with the plurality of voids in plan view;
In a nitrogen-containing atmosphere, a group III nitride crystal is grown by bringing the point seed into contact with a melt containing at least one group III element selected from gallium, aluminum, and indium and an alkali metal (ii) Process,
Separating the base substrate and the group III nitride crystal (iii);
A method for producing a group III nitride crystal containing In the step (ii),
The group III nitride crystal according to claim 1, wherein the group III element is gallium, the alkali metal is at least one selected from sodium, lithium and potassium, and the group III nitride crystal is a GaN crystal. Manufacturing method. In the step (i),
3. The group III nitride crystal according to claim 1, wherein the plurality of point seeds are formed by at least one of electrical discharge machining from the first principal surface side or laser machining from the second principal surface side. Production method.   4. The group III nitride crystal according to claim 1, wherein in the step (i), the plurality of grooves penetrate the base substrate and divide the base substrate into a plurality of parts. 5. Production method.   The method for producing a group III nitride crystal according to claim 4, wherein in the step (i), each of the divided base substrates has an equilateral triangle shape. In the step (i), the width of the groove is
(1) It is not less than a value obtained by adding 0.0005% of the length of one side of the equilateral triangle to a value obtained by subtracting the temperature at the time of placement from the temperature at the time of crystal growth, and (2) the group III nitride to be grown The method for producing a group III nitride crystal according to claim 5, wherein the height of the crystal is 70% or less.

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