WO2024095448A1 - Substrat monocristallin de nitrure de gallium et son procédé de production - Google Patents

Substrat monocristallin de nitrure de gallium et son procédé de production Download PDF

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WO2024095448A1
WO2024095448A1 PCT/JP2022/041169 JP2022041169W WO2024095448A1 WO 2024095448 A1 WO2024095448 A1 WO 2024095448A1 JP 2022041169 W JP2022041169 W JP 2022041169W WO 2024095448 A1 WO2024095448 A1 WO 2024095448A1
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width
main surface
single crystal
gallium nitride
substrate
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PCT/JP2022/041169
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Japanese (ja)
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尚 松浦
拓司 岡久
俊佑 西野
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住友電気工業株式会社
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/38—Nitrides

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  • This disclosure relates to a gallium nitride single crystal substrate and a method for manufacturing the same.
  • JP 2020-033210 A Patent Document 1
  • JP 2018-030763 A Patent Document 2 disclose a method for manufacturing a gallium nitride single crystal substrate with low dislocation density by arranging a mask having a predetermined opening on a base substrate, growing a gallium nitride single crystal having a triangular cross-sectional facet structure from the opening, and bending and eliminating dislocations propagated from the base substrate.
  • Patent Document 3 JP 2008-277841 A discloses a method for manufacturing a gallium nitride single crystal substrate with uniform dislocation density and carrier concentration by growing a single crystal having the above-mentioned facet structure without using a mask, obtaining a gallium nitride single crystal having unevenness at the interface, and then continuing crystal growth under conditions that flatten the unevenness.
  • Patent Document 4 discloses a semi-insulating gallium nitride single crystal doped with an acceptor dopant species.
  • the gallium nitride single crystal substrate according to the present disclosure is a gallium nitride single crystal substrate having a circular main surface with a diameter of 50 mm or more, the percentage of the standard deviation/average value of the resistivity measured at 101 measurement points on the main surface is less than 50%, and the measurement points are set at 100 ⁇ m intervals on an imaginary line segment with a length of 10 mm arbitrarily provided on the main surface.
  • the gallium nitride single crystal substrate according to the present disclosure is a gallium nitride single crystal substrate having a circular main surface with a diameter of 50 mm or more, in which the percentage of the standard deviation/average value of resistivity measured at 101 first measurement points on the main surface and the percentage of the standard deviation/average value of resistivity measured at 101 second measurement points on the main surface are both 50% or less, the first measurement points are set at 100 ⁇ m intervals on an imaginary line segment of 10 mm length that includes the center of the main surface, and the second measurement points are set at 100 ⁇ m intervals on an imaginary line segment of 10 mm length that includes any one point that is 80% of the radius away from the center of the main surface.
  • the method for manufacturing a gallium nitride single crystal substrate according to the present disclosure is a method for manufacturing a gallium nitride single crystal substrate having a circular main surface with a diameter of 50 mm or more, and includes a step of growing a gallium nitride single crystal by placing a mask having a structure in which shielding portions and openings are repeated in the width direction on a base substrate, the width of one pitch formed by the width of the shielding portions and the width of the openings is less than 500 ⁇ m, and the percentage of the width of the openings relative to the width of one pitch is 50% or less.
  • FIG. 1 is a schematic diagram illustrating the structure of a mask used to obtain a gallium nitride single crystal substrate according to this embodiment.
  • FIG. 2 is an explanatory diagram illustrating 101 measurement points set on the main surface of the gallium nitride single crystal substrate according to the first embodiment to determine the standard deviation/average percentage of resistivity.
  • FIG. 3 is an explanatory diagram illustrating 101 first and second measurement points set on a main surface of a gallium nitride single crystal substrate according to the second embodiment to determine the percentage of the standard deviation/average value of resistivity.
  • FIG. 4 is a schematic diagram for explaining the application of the three-terminal guard method to a sample to be measured in order to obtain the resistivity.
  • FIG. 1 is a schematic diagram illustrating the structure of a mask used to obtain a gallium nitride single crystal substrate according to this embodiment.
  • FIG. 2 is an explanatory diagram illustrating 101 measurement points set on the main surface of the gallium nitride single crystal substrate according to
  • FIG. 5 is an explanatory diagram illustrating nine first measurement regions on a main surface set to determine a reference area in a gallium nitride single crystal substrate according to the first and second embodiments, and the coordinates (X, Y) of their center points.
  • FIG. 6 is an explanatory diagram illustrating a virtual lattice in which squares each measuring 2 mm on a main surface are arranged in parallel as many times as possible without overlapping each other, in order to determine the dislocation density of the gallium nitride single crystal substrate according to the first and second embodiments, and a second measurement region.
  • FIG. 7 is a flowchart showing an example of a method for manufacturing a gallium nitride single crystal substrate according to this embodiment.
  • FIG. 8 is a schematic cross-sectional view illustrating the state in which the mask of FIG. 1 is disposed on an underlying substrate.
  • Patent Document 1 teaches the manufacture of a gallium nitride single crystal substrate using a mask having a structure in which a shielding portion and an opening are repeated in the width direction, the width of one pitch consisting of the width of the shielding portion and the width of the opening is 800 ⁇ m or more, and the width of the opening is larger than the width of the shielding portion. This produces a gallium nitride single crystal substrate having both a region in which the dislocation density is 3 ⁇ 10 6 /cm 2 or less in the plane and a region in which the dislocation density is less than 1 ⁇ 10 6 /cm 2.
  • the gallium nitride single crystal substrate of Patent Document 1 has a region in which the dislocation density differs by about three times in the plane, so that the dislocation density varies greatly in each region in the plane.
  • the gallium nitride single crystal substrate of Patent Document 2 does not mention the in-plane dislocation density distribution, it is presumed that the dislocation density varies greatly in each region in the plane because it is manufactured using a mask in which the width of the opening is larger than the width of the shielding portion.
  • Patent Document 3 teaches the manufacture of a gallium nitride single crystal substrate with a uniform dislocation density, but because no mask is used, it is difficult to control the epitaxial growth of the gallium nitride single crystal as intended. It has been reported that the in-plane resistivity of a gallium nitride single crystal substrate depends on the dislocation density. For this reason, a gallium nitride single crystal substrate with a large variation in in-plane dislocation density tends to have a large variation in in-plane resistivity as well. A gallium nitride single crystal substrate with a large variation in in-plane resistivity is generally considered to deteriorate device characteristics. Therefore, a gallium nitride single crystal substrate that provides good device characteristics by making the in-plane resistivity uniform without variation has not yet been obtained, and its development is eagerly awaited.
  • the present disclosure aims to provide a gallium nitride single crystal substrate that can achieve uniform in-plane resistivity without variation and thus provide good device characteristics, and a method for manufacturing the same.
  • the present inventors have made intensive studies to solve the above problems and have completed the present disclosure.
  • the present inventors have focused on the structure of a mask used when epitaxially growing a gallium nitride single crystal. Specifically, in a mask having a structure in which a shielding portion and an opening are repeated in the width direction, the width of one pitch consisting of the width of the shielding portion and the width of the opening is narrowed (specifically, the width of one pitch is set to less than 500 ⁇ m), and the percentage of the width of the opening/the width of one pitch is set to 50% or less.
  • the gallium nitride single crystal has a high probability of annihilation of dislocations propagating from the base substrate, and the number of dislocations remaining inside the single crystal can be reduced compared to the conventional method.
  • a gallium nitride single crystal substrate is a gallium nitride single crystal substrate having a circular main surface with a diameter of 50 mm or more, the percentage of the standard deviation/average value of resistivity measured at 101 measurement points on the main surface is less than 50%, and the measurement points are set at 100 ⁇ m intervals on an imaginary line segment with a length of 10 mm arbitrarily provided on the main surface.
  • a gallium nitride single crystal substrate having such characteristics can achieve uniform in-plane resistivity without variation, and can provide good device characteristics.
  • a gallium nitride single crystal substrate is a gallium nitride single crystal substrate having a circular main surface with a diameter of 50 mm or more, in which the percentage of the standard deviation/average value of resistivity measured at 101 first measurement points on the main surface and the percentage of the standard deviation/average value of resistivity measured at 101 second measurement points on the main surface are both 50% or less, the first measurement points are set at 100 ⁇ m intervals on an imaginary line segment of 10 mm length including the center of the main surface, and the second measurement points are set at 100 ⁇ m intervals on an imaginary line segment of 10 mm length including any one point away from the center of the main surface by a length of 80% of the radius.
  • a gallium nitride single crystal substrate having such characteristics can achieve uniform in-plane resistivity without variation, and can provide good device characteristics.
  • the average resistivity is preferably 1.0 ⁇ 10 ⁇ 2 ⁇ cm or more.
  • the present disclosure can be applied to a gallium nitride single crystal substrate having a low resistivity due to the addition or non-addition of a dopant or a reduction in the amount of addition. This makes it possible to make the in-plane resistivity uniform without variation for a gallium nitride single crystal substrate having a low resistivity with an average resistivity of 1.0 ⁇ 10 ⁇ 2 ⁇ cm or more.
  • the average resistivity is preferably 1.0 ⁇ 10 7 ⁇ cm or more.
  • the present disclosure can be applied to a gallium nitride single crystal substrate that has been given semi-insulating properties by adding a dopant or the like. This makes it possible to make the in-plane resistivity uniform without variation for a gallium nitride single crystal substrate having semi-insulating properties with an average resistivity of 1.0 ⁇ 10 7 ⁇ cm or more.
  • the maximum dislocation density of the gallium nitride single crystal substrate is preferably less than 2.0 ⁇ 10 6 /cm 2. This makes it possible to provide a gallium nitride single crystal substrate with reduced dislocation density.
  • the diameter of the main surface is preferably 95 mm or more and 155 mm or less.
  • the present disclosure can be applied to large gallium nitride single crystal substrates whose main surface has a diameter of 95 mm or more and 155 mm or less. This makes it possible to achieve uniform in-plane resistivity without variation for large gallium nitride single crystal substrates.
  • the gallium nitride single crystal substrate preferably contains at least one dopant selected from the group consisting of manganese, iron, cobalt, nickel, and copper. This makes it possible to make the in-plane resistivity of the gallium nitride single crystal substrate to which the dopant has been added uniform without variation.
  • a method for manufacturing a gallium nitride single crystal substrate is a method for manufacturing a gallium nitride single crystal substrate having a circular main surface with a diameter of 50 mm or more, and includes a step of growing a gallium nitride single crystal by placing a mask having a structure in which shielding portions and openings are repeated in the width direction on a base substrate, the width of one pitch formed by the width of the shielding portions and the width of the openings is less than 500 ⁇ m, and the percentage of the width of the openings to the width of one pitch is 50% or less.
  • A-B refers to the upper and lower limits of a range (i.e., greater than or equal to A and less than or equal to B). If no unit is stated for A, and only B, the units of A and B are the same. Furthermore, when compounds are expressed in chemical formulas in this specification, if the atomic ratio is not specifically limited, this includes all conventionally known atomic ratios, and should not necessarily be limited to only those within the stoichiometric range.
  • the "main surface” of a gallium nitride single crystal substrate means both of the two circular faces of the GaN substrate.
  • GaN substrate if at least one of the two faces satisfies the scope of the claims of this disclosure, it falls within the technical scope of this disclosure.
  • the "face” used in the term “in-plane” means the “main surface.”
  • the diameter of the main surface of a GaN substrate is described as “50 mm,” this means that the diameter is approximately 50 mm (approximately 50 to 55.5 mm), or that it is 2 inches.
  • the diameter of the main surface can be measured using a conventionally known outer diameter measuring device such as a caliper.
  • the GaN substrate has a "circular" main surface.
  • the term “circular” referring to the shape of the main surface includes a geometric circular shape, as well as a shape in which the main surface does not form a geometric circular shape due to the formation of at least one of a notch, an orientation flat (hereinafter also referred to as “OF”), or an index flat (hereinafter also referred to as "IF”) on the periphery of the main surface.
  • shape in which the main surface does not form a geometric circular shape refers to a shape in which, among the line segments extending from any point on the periphery of the main surface to the center of the main surface, the length of the line segments extending from any point on the notch, OF, and IF to the center of the main surface is short.
  • shape in which the main surface does not form a geometric circular shape also includes a shape in which the lengths of all the line segments extending from any point on the periphery of the main surface to the center of the main surface are not necessarily the same due to the shape of the gallium nitride single crystal (hereinafter also referred to as "GaN single crystal”) that is the raw material of the GaN substrate.
  • GaN single crystal gallium nitride single crystal
  • the gallium nitride single crystal substrate (GaN substrate) is a GaN substrate having a circular main surface with a diameter of 50 mm or more.
  • the percentage of the standard deviation/average value of the resistivity measured at 101 measurement points on the main surface is less than 50%.
  • the measurement points are set at 100 ⁇ m intervals on a virtual line segment with a length of 10 mm arbitrarily provided on the main surface.
  • a GaN substrate having such characteristics can achieve uniform in-plane resistivity without variation, thereby providing good device characteristics.
  • the imaginary line segment with a length of 10 mm can be provided anywhere on the main surface as described above.
  • Anywhere" on the main surface means “anywhere" on the main surface.
  • This "anywhere” includes the center of the main surface and the central part including its vicinity, the outer periphery of the main surface and the outer periphery including its vicinity, and all of the intermediate parts between the central part and the outer periphery.
  • the imaginary line segment with a length of 10 mm can be set at any of the central part, the outer periphery, and the intermediate part of the main surface.
  • the GaN substrate falls within the technical scope of the GaN substrate according to the first embodiment when the resistivity is measured at 101 measurement points on any one of all imaginary line segments that can be set on the main surface, and the percentage of the standard deviation/average value of the resistivity is less than 50%.
  • the gallium nitride single crystal substrate (GaN substrate) is a GaN substrate having a circular main surface with a diameter of 50 mm or more.
  • the percentage of the standard deviation/average value of the resistivity measured at 101 first measurement points on the main surface and the percentage of the standard deviation/average value of the resistivity measured at 101 second measurement points on the main surface are both 50% or less.
  • the first measurement points are set at 100 ⁇ m intervals on a virtual line segment having a length of 10 mm including the center of the main surface.
  • the second measurement points are set at 100 ⁇ m intervals on a virtual line segment having a length of 10 mm including any one point that is 80% of the radius away from the center of the main surface.
  • a GaN substrate having such characteristics can have a uniform in-plane resistivity without variation, and can provide good device characteristics.
  • the inventors came up with the idea of epitaxially growing the GaN single crystal, which is the raw material of the GaN substrate, on the base substrate using a mask 11 having a structure in which shielding portions 11a and openings 11b are repeated in the width direction, as shown in FIG. 1.
  • FIG. 1 is a schematic diagram illustrating the structure of a mask used to obtain a gallium nitride single crystal substrate according to this embodiment.
  • the mask 11 is rectangular in plan view and has a structure in which shielding portions 11a and openings 11b are repeated in the width direction. Furthermore, the shielding portion 11a and the opening portion 11b have a structure that is continuous in the longitudinal direction of the mask 11.
  • the narrow pitch P (the pitch P is less than 500 ⁇ m) allows dislocations that have propagated from the GaN film in the base substrate and bent at the interface of the facet structure with a triangular cross section to collide with other dislocations that have similarly propagated from the GaN film in the base substrate and bent, thereby eliminating many of them.
  • the pitch P of the mask 11 is narrow, even if the dislocations do not disappear and remain in the GaN single crystal as clumps (in a dense dislocation state), the pitch of the clumps becomes small, so that the distribution of the number of dislocations (dislocation density) per unit area (for example, 1 cm 2 ) in the plane of the GaN substrate obtained from the GaN single crystal can be made uniform without variation.
  • the pitch width P of the mask 11 is wide (specifically, the pitch width P is 500 ⁇ m or more), the probability of collision between the bent dislocations described above decreases, so that many of the dislocations do not disappear and remain as they are in the GaN single crystal.
  • the pitch width P of the mask 11 when the pitch width P of the mask 11 is wide, the pitch of the clusters of dislocations remaining in the single crystal also becomes large, so that it is considered that the distribution of dislocation density within the plane of the GaN substrate obtained from the GaN single crystal varies greatly.
  • the percentage of the width P of the opening width W2/1 pitch of the mask 11 is set to 50% or less (i.e. W2 ⁇ W1), the number of dislocations propagating from the GaN film in the underlying substrate can be suppressed.
  • the percentage of the width P of the opening width W2/1 pitch of the mask 11 is set to 50% or less (i.e. W2 ⁇ W1), the number of dislocations propagating from the GaN film in the underlying substrate can be suppressed.
  • the percentage of the width P of the opening width W2/1 pitch of the mask 11 is set to 50% or less (i.e. W2 ⁇ W1)
  • the GaN substrate according to the first and second embodiments has a circular main surface with a diameter of 50 mm or more, as described above.
  • the diameter of the main surface is preferably 95 mm or more and 155 mm or less.
  • the diameter of the main surface of the GaN substrate is 2 inches or more, and preferably 4 to 6 inches.
  • the main surface is considered to have a circular shape before the OF, IF, etc. are formed, and the size (diameter) of the main surface is determined.
  • FIG. 2 is an explanatory diagram for explaining 101 measurement points on the main surface set to obtain the percentage of the standard deviation/average value of resistivity for the gallium nitride single crystal substrate according to the first embodiment.
  • the measurement points F0 are set at 100 ⁇ m intervals I on a virtual line segment having a length of 10 mm arbitrarily provided on the main surface.
  • 101 measurement points F0 are set in a row at intervals I of 100 ⁇ m in one direction on the main surface, so that the resistivity can be measured in a region of 10 mm in total length arbitrarily provided on the main surface.
  • the crystal orientation perpendicular to the OF is the [11-20] direction.
  • the measurement points F0 are set at intervals I of 100 ⁇ m on an imaginary line segment 10 mm long extending in the [11-20] direction from the OF toward the center O of the main surface.
  • the percentage of the standard deviation/average value of the resistivity measured at the 101 first measurement points on the main surface and the percentage of the standard deviation/average value of the resistivity measured at the 101 second measurement points on the main surface are both 50% or less.
  • FIG. 3 is an explanatory diagram for explaining the 101 first and second measurement points on the main surface set to obtain the percentage of the standard deviation/average value of the resistivity for the gallium nitride single crystal substrate according to the second embodiment.
  • the first measurement points F1 are set at 100 ⁇ m intervals I on a virtual line segment having a length of 10 mm that includes the center O of the main surface.
  • the second measurement points F2 are set at 100 ⁇ m intervals I on a virtual line segment having a length of 10 mm that includes any one point that is 80% of the radius away from the center O of the main surface. That is, in the GaN substrate 100 according to the second embodiment, 101 first measurement points F1 are set in a row at 100 ⁇ m intervals I in one direction on the main surface, so that the resistivity can be measured in a region of 10 mm in length including the center O of the main surface. Furthermore, 101 second measurement points F2 are set in a row at 100 ⁇ m intervals I in one direction on the main surface, so that the resistivity can be measured in a region of 10 mm in length including a point 80% of the radius away from the center O of the main surface.
  • a GaN substrate to be measured is prepared by obtaining a GaN substrate whose main surface is the (0001) plane of a GaN single crystal, for example, according to the manufacturing method described below.
  • a total of 101 first measurement points F1 are set at 100 ⁇ m intervals I on a 10 mm long imaginary line segment that includes the center O of the main surface
  • a total of 101 second measurement points F2 are set at 100 ⁇ m intervals I on a 10 mm long imaginary line segment that includes an arbitrary point 80% of the radius away from the center O of the main surface.
  • the center O of the main surface is set as the midpoint, and a total of 101 measurement points can be set at 100 ⁇ m intervals I on an imaginary line segment ranging from -5 mm to +5 mm in the [1-100] direction from the midpoint.
  • a point 80% of the radius away from the center O of the main surface in the [1-100] direction is set as the midpoint, and a total of 101 measurement points can be set at 100 ⁇ m intervals I on an imaginary line segment ranging from -5 mm to +5 mm in the [1-100] direction from the midpoint.
  • the resistivity is determined at the 101 first measurement points F1, and the average value and standard deviation of the resistivity are calculated. Furthermore, the resistivity is determined at the 101 second measurement points F2, and the average value and standard deviation of the resistivity are calculated.
  • FIG. 4 is a schematic diagram for explaining the application of the three-terminal guard method to a sample to be measured in order to obtain resistivity. That is, the resistivity at the first measurement point F1 and the second measurement point F2 can be measured by arranging ohmic electrodes 30 at 101 first measurement points F1 and 101 second measurement points F2, respectively, as shown in FIG. 4, which are composed of a ring-shaped guard electrode 31 arranged on the main surface of the front side (upper side in FIG.
  • a resist pattern corresponding to the shapes of the guard electrode 31 and the probe electrode 32 of the ohmic electrode 30 is prepared by photolithography. Then, Ti/Al/Au are sequentially evaporated and lifted off to form the ohmic electrode 30 on the front side of the GaN substrate 100.
  • a back electrode 33 is prepared on the back side of the GaN substrate 100 by the same method as that for preparing the guard electrode 31 and the probe electrode 32 on the front side of the GaN substrate 100 described above, thereby forming the ohmic electrode 30 on the back side of the GaN substrate 100.
  • a voltage is applied from the back electrode 33 using a semi-automatic prober (product name (model number): "HSP-150 (6 inch)", manufactured by Hisol) under conditions of a voltage application range of 0 to 10 V and a voltage application step of 1 V, and the current flowing through the probe electrode 32 is measured.
  • a microammeter product name (model number): "34465A", manufactured by Keysight) can be used to measure the current.
  • the standard deviation/average value percentage of the resistivity measured at the first measurement point F1 and the standard deviation/average value percentage of the resistivity measured at the second measurement point F2 are both 50% or less.
  • the standard deviation/average value percentage of the resistivity measured at the first measurement point F1 is preferably 35% or less, and more preferably 30% or less.
  • the standard deviation/average value percentage of the resistivity measured at the second measurement point F2 is preferably 45% or less, and more preferably 20% or less.
  • the resistivity (and the standard deviation/average value percentage of the resistivity) at the measurement point F0 of the GaN substrate 100 according to the first embodiment can be determined by arranging the above-mentioned ohmic electrodes 30 at 101 measurement points F0 arranged continuously at intervals I of 100 ⁇ m in one direction on the main surface, as described above.
  • the diameter of the GaN substrate 100 according to the second embodiment is 50 mm
  • 101 first measurement points F1 are set on a virtual line segment of 10 mm length extending from the center O of the main surface in the direction of a predetermined crystal orientation
  • 101 second measurement points F2 are set with a length of 10 mm extending from the center O of the main surface to a point 80% of the radius away in the same direction as the above crystal orientation
  • the measurement point of the end of the first measurement point F1 far from the center O of the main surface and the measurement point of the end of the second measurement point F2 close to the center O of the main surface will overlap.
  • this overlap is permitted as a method for determining the standard deviation/average percentage of the resistivity in the GaN substrate 100 according to the second embodiment. This is because the partial overlap of the measurement points as described above does not cause any inconvenience from the viewpoint of understanding the variation in resistivity within the surface of the GaN substrate 100.
  • the average value of the resistivity is preferably 1.0 ⁇ 10 ⁇ 2 ⁇ cm or more.
  • the average value of the resistivity is also preferably 1.0 ⁇ 10 2 ⁇ cm or more.
  • the GaN substrate according to the first and second embodiments can reduce the resistivity by adding or not adding a dopant or by reducing the amount of dopant added. This makes it possible to make the in-plane resistivity uniform without variation for a gallium nitride single crystal substrate having a low resistivity such that the average value of the resistivity is 1.0 ⁇ 10 ⁇ 2 ⁇ cm or more, which can contribute to good device characteristics.
  • the average value of the resistivity is preferably 1.0 ⁇ 10 7 ⁇ cm or more.
  • the GaN substrate according to the first and second embodiments can be applied to a gallium nitride single crystal substrate to which semi-insulating properties have been imparted by the addition of a dopant. The estimated mechanism by which semi-insulating properties can be imparted will be described later. This allows the in-plane resistivity to be uniform without variation for a gallium nitride single crystal substrate having semi-insulating properties with an average resistivity of 1.0 ⁇ 10 7 ⁇ cm or more, which can contribute to good device characteristics.
  • the average value described by the term "average resistivity” means, unless otherwise specified or explained, all of the average resistivity measured at the measurement point F0, the average resistivity measured at the first measurement point F1, and the average resistivity measured at the second measurement point F2.
  • the average resistivity of the GaN substrate is 1.0 ⁇ 10-2 ⁇ cm or more
  • the average resistivity measured at the measurement point F0 defined in the first embodiment, and the average resistivity measured at the first measurement point F1 defined in the second embodiment, and the average resistivity measured at the second measurement point F2 are all 1.0 ⁇ 10-2 ⁇ cm or more.
  • the maximum dislocation density of the GaN substrate according to the first and second embodiments is preferably less than 2.0 ⁇ 10 6 /cm 2.
  • the maximum dislocation density of the GaN substrate is more preferably 1.0 ⁇ 10 6 / cm 2 or less, and further preferably 9.0 ⁇ 10 5 /cm 2 or less. This makes it possible to provide a GaN substrate with reduced dislocation density.
  • dislocation and dislocation density refer to “threading dislocations” and “the number of threading dislocations per 1 cm2 of the main surface” that are identified by applying a multiphoton excitation photoluminescence method to the main surface, respectively.
  • the above-mentioned “threading dislocations” are known to be non-radiative recombination centers in GaN single crystals, and appear as dark spots when the main surface of a GaN substrate is observed using a multiphoton excitation microscope or the like.
  • the above-mentioned “threading dislocations” are not academically synonymous with crystal defects, but can be regarded as equivalent to crystal defects in this technical field. Below, a calculation method for determining the maximum value of the dislocation density of the GaN substrate will be specifically described.
  • dislocation density an area on the main surface where 100 dislocations exist is first set as a reference area (hereinafter also referred to as the "reference area") for calculating the dislocation density, and dislocation density (hereinafter also referred to as the "second dislocation density") is obtained in a unit area smaller than the reference area (for example, an area that is 30% of the reference area), and the average or maximum value is calculated. It has been found that the average and maximum values of dislocation density calculated in this case appropriately reflect the average and maximum values of dislocation density over the entire main surface of the GaN substrate.
  • FIG. 5 is an explanatory diagram illustrating nine first measurement regions on the main surface set to find the reference area in the gallium nitride single crystal substrate according to the first and second embodiments, and the coordinates (X, Y) of their center points.
  • FIG. 6 is an explanatory diagram illustrating a virtual lattice in which squares with sides of 2 mm are laid out on the main surface in such a way that the greatest number of them are arranged in parallel without overlapping each other, and a second measurement region, in order to find the dislocation density of the gallium nitride single crystal substrate according to the first and second embodiments.
  • the dislocation density of the GaN substrate according to the first and second embodiments can be found as follows, with reference to FIGS. 5 and 6.
  • the first measurement area A1 is a square area with one side of 100 ⁇ m.
  • the coordinates (X, Y) of the X-axis and the Y-axis of the center point C of the first measurement area A1 are (0, 0), (D/4-5, 0), (0, D/4-5), (-(D/4-5), 0), (0, -(D/4-5)), (D/2-10, 0), (0, D/2-10), (-(D/2-10), 0), and (0, -(D/2-10)).
  • the units of D and X and Y in the coordinates (X, Y) are mm.
  • the number of dislocations can be obtained by the following method. That is, a multiphoton excitation photoluminescence method is applied to the main surface 101 of the GaN substrate 100, and the first measurement area A1 set on the main surface 101 is observed using a multiphoton excitation microscope. The observation can be performed using, for example, an objective lens with a magnification of 5 times. In this case, an image (one field of view) displayed on an external monitor connected to the microscope corresponds to a range of 2.5 mm x 2.0 mm including the first measurement area A1 on the main surface 101 of the GaN substrate 100.
  • the number of dark spots that appear in an image obtained by electronically enlarging the central part of the image (a size of 0.1 mm x 0.1 mm that can be considered to be the first measurement area A1) is counted, that is, the number of dislocations.
  • a high-magnification image can be obtained by setting the magnification of the objective lens to 10 to 100 times, and further combining electronic magnification, the number of dark spots in the central part of the high-magnification image (a size of 0.1 mm x 0.1 mm that can be considered as the first measurement area A1) can be counted.
  • the total number of dark spots measured in the nine first measurement areas A1 is calculated, and this is converted into the number of dislocations per cm2 , thereby calculating the first dislocation density as the dislocation density measured in the nine first measurement areas A1.
  • the reference area can be calculated by dividing 100 by the first dislocation density.
  • the unit of the reference area can be, for example, ⁇ m2 .
  • a virtual lattice G is formed on the main surface 101 in which squares with sides of 2 mm are laid out in the greatest number of parallel rows without overlapping each other.
  • squares laid out in the greatest number of parallel rows without overlapping each other on the main surface 101 means that when the squares are laid out in the greatest number of parallel rows without overlapping each other on the main surface 101, if the squares overlap with the periphery of the main surface 101 and its outside, the squares are excluded from being elements that make up the virtual lattice G. This is because the number of dislocations varies greatly from substrate to substrate in the region near the periphery of the main surface 101 of the GaN substrate 100, including the periphery, and is generally not used as a material for semiconductor devices.
  • a second measurement area A2 is set in the center of each of the squares constituting the lattice G.
  • the second measurement area A2 has an area of 30% of the reference area.
  • the second measurement area A2 set in the squares constituting the lattice G is observed using the multiphoton excitation microscope described above. In this observation, the magnification of the objective lens is appropriately selected so that at least the size of the second measurement area A2 is included in the image (one field of view) displayed on an external monitor connected to this microscope.
  • the number of dark spots, i.e., dislocations, that appear in the second measurement area A2 observed using the multiphoton excitation microscope is counted, and the number of dislocations is converted to the number per cm2 to calculate the second dislocation density.
  • the size of the second measurement area A2 which is 30% of the reference area is 0.05 mm x 0.05 mm.
  • a high-magnification image (size of 0.125 mm x 0.1 mm) is projected on an external monitor using an objective lens with a magnification of 100 times, the number of dark spots in the central part (size of 0.05 mm x 0.05 mm) of the high-magnification image is counted, and the number of dark spots is converted into the number of dislocations per 1 cm2, whereby the second dislocation density can be calculated.
  • the above-mentioned observation is performed every time the GaN substrate 100 is moved at a pitch of 2 mm in the vertical and horizontal directions, and the second dislocation density is calculated for all the second measurement areas A2 set in the virtual lattice G on the main surface 101.
  • the average value and maximum value of the second dislocation density are obtained from the second dislocation density calculated for each of the second measurement areas.
  • the average value and maximum value of the second dislocation density can then be taken as the average value and maximum value of the dislocation density of the GaN substrate 100, respectively.
  • the GaN substrate according to the first and second embodiments preferably contains at least one dopant selected from the group consisting of manganese, iron, cobalt, nickel, and copper, thereby making it possible to make the in-plane resistivity of a low-resistivity or semi-insulating GaN substrate to which a dopant has been added uniform without variation.
  • Metal atoms such as manganese, iron, cobalt, nickel, and copper can be added as dopants to the GaN substrate to give it semi-insulation.
  • the average resistivity of the semi-insulating GaN substrate can be set to, for example, 1 ⁇ 10 7 ⁇ cm or more and 5 ⁇ 10 8 ⁇ cm or less.
  • the mechanism by which semi-insulation can be given i.e., high resistance is presumed to be as follows.
  • the residual carrier density at a shallow energy level is about 1 ⁇ 10 17 cm ⁇ 3 or less
  • a p-type dopant at a deep energy level for example Fe
  • the n-type dopant at a shallow energy level is compensated to give semi-insulation with a very low carrier density.
  • the resistivity of the GaN substrate can be reduced by adding a reduced amount of the above-mentioned metal atoms.
  • the GaN substrate with low resistivity can have an average resistivity of, for example, 1 ⁇ 10 2 ⁇ cm to 1 ⁇ 10 5 ⁇ cm.
  • the average resistivity can be set to 1 ⁇ 10 -2 ⁇ cm to 5 ⁇ 10 7 ⁇ cm even without adding a dopant metal.
  • the manufacturing method of the gallium nitride single crystal substrate (GaN substrate) according to this embodiment is preferably a manufacturing method for manufacturing at least one of the GaN substrates according to the first embodiment or the second embodiment described above.
  • the manufacturing method of the GaN substrate is a manufacturing method of a gallium nitride single crystal substrate having a circular main surface with a diameter of 50 mm or more, and includes a step of growing a gallium nitride single crystal by placing a mask having a structure in which a shielding portion and an opening are repeated in the width direction on a base substrate.
  • the width of one pitch consisting of the width of the shielding portion and the width of the opening is less than 500 ⁇ m, and the percentage of the width of the opening to the width of one pitch is 50% or less.
  • the above-mentioned GaN substrate manufacturing method preferably includes, for example, the steps shown in the flowchart of FIG. 7 from the viewpoint of manufacturing GaN substrates having the above-mentioned effects with a high yield.
  • FIG. 7 is a flowchart showing an example of a method for manufacturing a gallium nitride single crystal substrate according to this embodiment.
  • the above-mentioned GaN substrate manufacturing method preferably includes a step S10 (first step) of preparing a base substrate, a step S20 (second step) of arranging a mask having a structure in which a shielding portion and an opening are repeated in the width direction on the base substrate, a step S30 (third step) of growing a gallium nitride single crystal (GaN single crystal) having a triangular facet structure from the opening of the mask, and a step S40 (fourth step) of processing the gallium nitride single crystal (GaN single crystal) into a gallium nitride single crystal substrate (GaN substrate).
  • the step of growing a gallium nitride single crystal by arranging a mask having a structure in which a shielding portion and an opening are repeated in the width direction on the base substrate corresponds to the above-mentioned second step and third step.
  • a mask having a structure in which a shielding portion and an opening are repeated in the width direction on the base substrate corresponds to the above-mentioned second step and third step.
  • the first step is a step S10 of preparing a base substrate.
  • FIG. 8 is a schematic cross-sectional view illustrating the state in which the mask of FIG. 1 is placed on the base substrate.
  • a base substrate 20 consisting of a growth substrate 21 and a GaN film 22 placed on the growth substrate 21 is prepared.
  • the material of the growth substrate 21 is not particularly limited as long as it is a substrate on which the GaN film 22 can be grown.
  • a heterogeneous substrate using a material (heterogeneous material) different from GaN such as a sapphire substrate or a gallium arsenide (GaAs) substrate
  • a homogeneous substrate using GaN homogeneous material
  • Other examples of the growth substrate 21 include an aluminum nitride (AlN) substrate, a silicon carbide (SiC) substrate, a zirconium boride ( ZrB2 ) substrate, a silicon oxide/ aluminum oxide ( SiO2 / Al2O3 ) sintered body substrate, and a molybdenum (Mo) substrate.
  • AlN aluminum nitride
  • SiC silicon carbide
  • ZrB2 zirconium boride
  • SiO2 / Al2O3 silicon oxide/ aluminum oxide
  • Mo molybdenum
  • the second step is step S20 of arranging a mask having a structure in which a shielding portion and an opening are repeated in the width direction on the base substrate.
  • a mask 11 (see FIG. 1) having a structure (pattern) in which a shielding portion 11a and an opening 11b are repeated in the width direction is formed on the base substrate 20 using a conventionally known method, so that the mask 11 is arranged on the base substrate 20.
  • the pattern of the mask 11 has a width P of one pitch formed by the width W1 of the shielding portion 11a and the width W2 of the opening 11b that is less than 500 ⁇ m, and the percentage of the width W2 of the opening (width W2 of the opening/width P of one pitch) relative to the width P of one pitch is 50% or less (i.e., W2 ⁇ W1).
  • the pattern of the mask 11 has a width P of one pitch formed by the width W1 of the shielding portion 11a and the width W2 of the opening 11b that is preferably 10 to 400 ⁇ m, and the percentage of the width W2 of the opening/width P of one pitch is preferably 3 to 30%. This makes it possible to produce a GaN single crystal with smaller variations in dislocation density.
  • the mask 11 can be formed, for example, by the following method.
  • a chemical vapor deposition film e.g., a silicon-based chemical vapor deposition film
  • a method such as plasma CVD (Chemical Vapor Deposition).
  • a patterned resist is formed on the chemical vapor deposition film by a photolithography method, and etching is performed using the resist as an etching mask.
  • the third step is step S30 of growing a gallium nitride single crystal having a triangular cross-sectional facet structure from the opening 11b of the mask 11.
  • This step allows epitaxial growth of a GaN single crystal on the side of the base substrate 20 on which the mask 11 is formed.
  • a crystal growth method for a GaN single crystal having a triangular cross-sectional facet structure for example, a hydride vapor phase epitaxy (HVPE) method using metallic Ga as a gallium (Ga) source and ammonia (NH 3 ) gas as a nitrogen (N) source can be used.
  • HVPE hydride vapor phase epitaxy
  • the epitaxial growth of a GaN single crystal by the HVPE method can be performed, for example, as follows. First, the base substrate 20 is placed on a quartz sample holder in a hot-wall type reactor, and at least the GaN film 22 in the base substrate 20 is heated to about 1000° C. Next, hydrogen chloride (HCl) gas is sprayed onto metal Ga placed in an upstream boat in the reactor, using hydrogen (H 2 ) gas as a carrier gas, to generate gallium chloride (GaCl) gas. Furthermore, NH 3 gas is introduced into the reactor.
  • HCl hydrogen chloride
  • H 2 hydrogen
  • GaCl gallium chloride
  • NH 3 gas is introduced into the reactor.
  • the GaCl gas and NH 3 gas are supplied to the GaN film 22 in the base substrate 20 through the opening 11b of the mask 11, using H 2 gas as a carrier gas, to epitaxially grow a GaN single crystal on the side of the base substrate 20 on which the mask 11 is formed.
  • the thickness of the epitaxially grown GaN single crystal can be adjusted by controlling the amount or time of supplying GaCl gas and NH 3 gas.
  • GaCl gas partial pressure 6 ⁇ 10 2 to 1.5 ⁇ 10 4 Pa
  • NH3 gas partial pressure 6 x 102 to 1.5 x 104 Pa
  • GaCl gas flow rate 40 to 1000 SCCM
  • NH3 gas flow rate 40 to 1000 SCCM
  • the epitaxial growth of the above-mentioned GaN single crystal when growing a GaN single crystal to which a dopant has been added, 0.5 to 3 mass% of the metal atoms that will become the dopant are mixed with the metal Ga placed in the upstream boat in the above-mentioned reactor, and a mixed gas consisting of these and chlorine is generated, and the epitaxial growth of the GaN single crystal can be carried out in the same manner as the epitaxial growth of the GaN single crystal by the above-mentioned HVPE method.
  • the inside of the hot-wall type reactor is heated to 1300° C. or higher (preferably 1500° C. or higher) for one hour for heat treatment, and then the third step is carried out.
  • the fourth step is step S40, in which the GaN single crystal is processed into a GaN substrate.
  • the back surface of the GaN single crystal is first ground. This allows the mask 11 and the base substrate 20 to be removed from the GaN single crystal. Furthermore, the surface of the GaN single crystal is flattened by grinding, and then polished. This allows the GaN substrate to be manufactured having a circular main surface with a desired diameter. Conventionally known methods can be applied to grind the back surface of the GaN single crystal, and to grind and polish the surface of the GaN single crystal. Since the growth orientation of the GaN single crystal is usually the [0001] direction, the main surface of the GaN substrate may be the C-plane ((0001) plane) of the GaN single crystal. It is preferable that the main surface is a plane having an off angle of 0° or more and 2° or less from the (0001) plane.
  • the above steps allow the GaN substrate according to this embodiment to be manufactured.
  • the above manufacturing method allows the growth of a gallium nitride single crystal in which dislocations propagating from the base substrate are eliminated with a high probability, and the number of dislocations remaining inside the crystal is reduced compared to the conventional method. Furthermore, from the gallium nitride single crystal, a gallium nitride single crystal substrate with small in-plane dislocation density variation and small in-plane resistivity variation can be obtained. Therefore, the GaN substrate manufactured by the above manufacturing method can provide good device characteristics.
  • one GaN substrate was obtained by carrying out the following GaN substrate manufacturing method.
  • Example 1 Manufacturing of 2-inch (50.8 mm) diameter GaN substrate ⁇ Sample 11> (First step) A commercially available sapphire substrate having a diameter of 50.8 mm was obtained, and a GaN film was formed on the sapphire substrate by MOCVD (metal organic chemical vapor deposition) to prepare a base substrate. The main surface of the GaN film had a (0001) plane orientation.
  • MOCVD metal organic chemical vapor deposition
  • a mask having a structure in which a shielding portion and an opening are repeated in the width direction was formed on the GaN film side of the base substrate.
  • a plasma CVD method was applied to the GaN film side of the base substrate to form a chemical vapor deposition film (thickness 200 nm) made of silicon oxide, and then a resist patterned by a photolithography method was formed on the chemical vapor deposition film, and a mask was formed by etching using the resist as an etching mask.
  • the pattern of the mask has a width of 10 ⁇ m for one pitch consisting of the width of the shielding portion and the width of the opening, and the percentage of the width of the opening/width of one pitch is 30% (i.e., the width of the opening is 3 ⁇ m and the width of the shielding portion is 7 ⁇ m).
  • a GaN single crystal having a triangular facet structure was grown from the GaN film of the base substrate through the opening of the mask.
  • the base substrate was placed on a quartz sample holder in a hot-wall type reactor, and the reactor was heated to 1020°C.
  • GaCl gas and iron chloride gas generated by reacting HCl gas with Ga to which 1% Fe was added, and NH3 gas were supplied into the reactor.
  • the reactor was then held at 1020°C for 29 hours.
  • the growth pressure was set to 1.01 ⁇ 105 Pa
  • the partial pressure of GaCl gas was set to 6.52 ⁇ 102 Pa
  • the partial pressure of iron chloride gas was set to 6.52 Pa
  • the partial pressure of NH3 gas was set to 7.54 ⁇ 103 Pa
  • the partial pressure of HCl gas was set to 3.55 ⁇ 101 Pa.
  • the temperature inside the reactor was lowered to room temperature to obtain a GaN single crystal.
  • the GaN single crystal had a crystal growth surface along the (0001) plane and a thickness of 1 mm as measured with a stylus-type film thickness meter.
  • the back surface of the GaN single crystal was ground to remove the base substrate and mask from the back surface of the GaN single crystal.
  • the surface of the GaN single crystal was then flattened by grinding, followed by polishing to produce a GaN substrate of sample 11 having a circular main surface with a diameter of 50.8 mm (2 inches) and a thickness of 800 ⁇ m.
  • the main surface of the GaN substrate of sample 11 was the C-plane ((0001) plane) of the GaN single crystal.
  • a GaN substrate of sample 12 having a circular main surface and a diameter of 50.8 mm (2 inches), a thickness of 800 ⁇ m, was manufactured using the same method as sample 11, except that, for the pattern of the mask placed on the base substrate in the second step, the width of one pitch consisting of the width of the shielding portion and the width of the opening was 20 ⁇ m, and the percentage of the width of the opening/the width of one pitch was 15% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 17 ⁇ m).
  • sample 13 A GaN substrate of sample 13 having a circular main surface and a diameter of 50.8 mm (2 inches), a thickness of 800 ⁇ m, was manufactured using the same method as sample 11, except that in the second step, the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening, which was 50 ⁇ m, and the percentage of the width of the opening/the width of one pitch was 6% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 47 ⁇ m).
  • a GaN substrate of sample 14 having a circular main surface and a diameter of 50.8 mm (2 inches), a thickness of 800 ⁇ m, was manufactured using the same method as sample 11, except that, for the pattern of the mask placed on the base substrate in the second step, the width of one pitch consisting of the width of the shielding portion and the width of the opening was 100 ⁇ m, and the percentage of the width of the opening/the width of one pitch was 3% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 97 ⁇ m).
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 200 ⁇ m, and the percentage of the width of the opening/width of one pitch was 1.5% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 197 ⁇ m).
  • a GaN substrate of sample 15 having a diameter of 50.8 mm (2 inches), a thickness of 800 ⁇ m and a circular main surface was produced.
  • a GaN substrate of sample 16 having a circular main surface and a diameter of 50.8 mm (2 inches), a thickness of 800 ⁇ m, was manufactured using the same method as sample 11, except that, for the pattern of the mask placed on the base substrate in the second step, the width of one pitch consisting of the width of the shielding portion and the width of the opening was 400 ⁇ m, and the percentage of the width of the opening/the width of one pitch was 0.75% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 397 ⁇ m).
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 1000 ⁇ m, and the percentage of the width of the opening/width of one pitch was 60% (i.e., the width of the opening was 600 ⁇ m and the width of the shielding portion was 400 ⁇ m).
  • a GaN substrate of sample 1A having a circular main surface with a diameter of 50.8 mm (2 inches) and a thickness of 800 ⁇ m was produced.
  • Example 1B A GaN substrate of sample 1B having a circular main surface and a diameter of 50.8 mm (2 inches), a thickness of 800 ⁇ m, was manufactured by using the same method as sample 11, except that in the second step, no mask was placed on the base substrate, in the third step, the surface of the epitaxially grown GaN single crystal was flattened in accordance with the method disclosed in Patent Document 2, and in the third step, the reactor was held at 1,020° C. for 50 hours.
  • the dislocation density of the main surface was determined by the method described above, and the minimum and maximum values of the dislocation density and the variation in the dislocation density ((maximum value-minimum value)/maximum value (%)) were calculated.
  • the resistivity at 101 first and second measurement points was determined by the method described above, and the average value and variation in the resistivity at the first measurement points (standard deviation of resistivity/average value (%)) and the average value and variation in the resistivity at the second measurement points (standard deviation of resistivity/average value (%)) were calculated.
  • the results are shown in Table 1.
  • the GaN substrates of Samples 11 to 16 are examples, and the GaN substrates of Samples 1A and 1B are comparative examples.
  • Example 2 Production of 101.6 mm (4 inch) diameter GaN substrate ⁇ Sample 21>
  • the GaN substrate of sample 21 was produced by the same method as sample 11, except that in the first step, a GaN film was formed on a commercially available sapphire substrate having a diameter of 110 mm, thereby producing a GaN substrate having a diameter of 101.6 mm (4 inches) and a thickness of 1 mm and having a circular main surface.
  • a GaN substrate of sample 22 having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was manufactured using the same method as sample 21, except that, for the pattern of the mask placed on the base substrate in the second step, the width of one pitch consisting of the width of the shielding portion and the width of the opening was 20 ⁇ m, and the percentage of the width of the opening/width of one pitch was 15% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 17 ⁇ m).
  • the pattern of the mask placed on the base substrate was such that the width of one pitch consisting of the width of the shielding portion and the width of the opening was 50 ⁇ m, and the percentage of the width of the opening/width of one pitch was 6% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 47 ⁇ m), but by using the same method as sample 21, a GaN substrate of sample 23 having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was produced.
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 100 ⁇ m, and the percentage of the width of the opening/width of one pitch was 3% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 97 ⁇ m).
  • a GaN substrate of sample 24 having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was produced.
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 200 ⁇ m, and the percentage of the width of the opening/width of one pitch was 1.5% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 197 ⁇ m).
  • a GaN substrate of sample 25 having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was produced.
  • a GaN substrate of sample 26 having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was manufactured using the same method as sample 21, except that, for the pattern of the mask placed on the base substrate in the second step, the width of one pitch consisting of the width of the shielding portion and the width of the opening was 400 ⁇ m, and the percentage of the width of the opening/width of one pitch was 0.75% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 397 ⁇ m).
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 1000 ⁇ m, and the percentage of the width of the opening/width of one pitch was 60% (i.e., the width of the opening was 600 ⁇ m and the width of the shielding portion was 400 ⁇ m).
  • a GaN substrate of sample 2A having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was manufactured.
  • the dislocation density of the main surface was determined by the method described above, and the minimum and maximum values of the dislocation density, as well as the variation in dislocation density ((maximum value-minimum value)/maximum value (%)) were calculated. Furthermore, the resistivity at 101 first and second measurement points was determined by the method described above, and the average value and variation in the resistivity at the first measurement points (standard deviation of resistivity/average value (%)) and the average value and variation in the resistivity at the second measurement points (standard deviation of resistivity/average value (%)) were calculated. The results are shown in Table 2.
  • the GaN substrates of samples 21 to 26 are examples, and the GaN substrate of sample 2A is a comparative example.
  • Example 3 Production of 152.4 mm (6 inch) diameter GaN substrate ⁇ Sample 31>
  • the GaN substrate of sample 31 was produced by the same method as sample 11, except that in the first step, a GaN film was formed on a commercially available sapphire substrate having a diameter of 160 mm, thereby producing a GaN substrate having a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm and having a circular main surface.
  • a GaN substrate of sample 32 having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm was produced using the same method as sample 31, except that, for the pattern of the mask placed on the base substrate in the second step, the width of one pitch consisting of the width of the shielding portion and the width of the opening was 20 ⁇ m, and the percentage of the width of the opening/width of one pitch was 15% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 17 ⁇ m).
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 50 ⁇ m, and the percentage of the width of the opening/width of one pitch was 6% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 47 ⁇ m).
  • a GaN substrate of sample 33 having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm was produced.
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 100 ⁇ m, and the percentage of the width of the opening/width of one pitch was 3% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 97 ⁇ m).
  • a GaN substrate of sample 34 having a diameter of 152.4 mm (6 inches), a thickness of 1.2 mm, and a circular main surface was produced.
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 200 ⁇ m, and the percentage of the width of the opening/width of one pitch was 1.5% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 197 ⁇ m).
  • a GaN substrate of sample 35 having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm was produced.
  • the width of one pitch consisting of the width of the shielding portion and the width of the opening was set to 400 ⁇ m, and the percentage of the width of the opening/the width of one pitch was set to 0.75% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 397 ⁇ m).
  • a GaN substrate of sample 36 having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm was produced.
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 1000 ⁇ m, and the percentage of the width of the opening/width of one pitch was 60% (i.e., the width of the opening was 600 ⁇ m and the width of the shielding portion was 400 ⁇ m).
  • a GaN substrate of sample 3A having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm was produced.
  • the dislocation density of the main surface was determined by the method described above, and the minimum and maximum values of the dislocation density and the variation in the dislocation density ((maximum value-minimum value)/maximum value (%)) were calculated.
  • the resistivity at 101 first and second measurement points was determined by the method described above, and the average value and variation in the resistivity at the first measurement points (standard deviation of resistivity/average value (%)) and the average value and variation in the resistivity at the second measurement points (standard deviation of resistivity/average value (%)) were calculated.
  • the results are shown in Table 3.
  • the GaN substrates of samples 31 to 36 are examples, and the GaN substrate of sample 3A is a comparative example.
  • Example 4 Production of 152.4 mm (6 inch) diameter GaN substrate ⁇ Sample 41>
  • the GaN substrate of sample 41 was manufactured using the same method as sample 11, except that in the first step, a GaN film was formed on a commercially available sapphire substrate having a diameter of 160 mm, thereby producing a GaN substrate having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm, and in the third step, HCl gas was reacted with Ga to which 100 ppm of Fe had been added to generate GaCl gas and Fe3Cl gas, which were then supplied into the reaction furnace together with NH3 gas.
  • the width of one pitch consisting of the width of the shielding portion and the width of the opening was set to 20 ⁇ m, and the percentage of the width of the opening/width of one pitch was set to 15% (i.e., the width of the opening was 3 ⁇ m and the width of the shielding portion was 17 ⁇ m), but by using the same method as for sample 41, a GaN substrate of sample 42 having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm was produced.
  • the pattern of the mask placed on the base substrate had a width of one pitch consisting of the width of the shielding portion and the width of the opening set to 1000 ⁇ m, and the percentage of the width of the opening/width of one pitch was 60% (i.e., the width of the opening was 600 ⁇ m and the width of the shielding portion was 400 ⁇ m).
  • a GaN substrate of sample 4A having a circular main surface with a diameter of 152.4 mm (6 inches) and a thickness of 1.2 mm was produced.
  • the dislocation density of the main surface was determined by the method described above, and the minimum and maximum values of the dislocation density and the variation in the dislocation density ((maximum value-minimum value)/maximum value (%)) were calculated.
  • the resistivity at 101 first and second measurement points was determined by the method described above, and the average value and variation in the resistivity at the first measurement points (standard deviation of resistivity/average value (%)) and the average value and variation in the resistivity at the second measurement points (standard deviation of resistivity/average value (%)) were calculated.
  • the results are shown in Table 4.
  • the GaN substrates of Samples 41 to 42 are examples, and the GaN substrate of Sample 4A is a comparative example.
  • Example 5 Production of 101.6 mm (4 inch) diameter GaN substrate ⁇ Sample 51>
  • a heat treatment was performed by heating the inside of the reactor at 1300° C. for 1 hour using a heater installed in the reactor, thereby growing a GaN single crystal without adding Fe.
  • a GaN substrate of sample 51 having a diameter of 101.6 mm (4 inches), a thickness of 1 mm, and a circular main surface was manufactured.
  • sample 52 A GaN substrate of sample 52 having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was manufactured by using the same method as sample 51, except that the heat treatment was changed to heating the inside of the reactor at 1400° C. for 1 hour.
  • sample 53 A GaN substrate of sample 53 having a circular main surface with a diameter of 101.6 mm (4 inches) and a thickness of 1 mm was manufactured by using the same method as sample 51, except that the heat treatment was changed to heating the inside of the reactor at 1500° C. for 1 hour.
  • the dislocation density of the main surface was determined by the method described above, and the minimum and maximum values of the dislocation density, as well as the variation in dislocation density ((maximum value-minimum value)/maximum value (%)) were calculated. Furthermore, the resistivity was determined at 101 first and second measurement points by the method described above, and the average value and variation in resistivity at the first measurement points (standard deviation of resistivity/average value (%)) and the average value and variation in resistivity at the second measurement points (standard deviation of resistivity/average value (%)) were calculated. The results are shown in Table 5.
  • the GaN substrates of Samples 51 to 53 are all examples.
  • the GaN substrates of Samples 11 to 16 all had smaller variations in resistivity (standard deviation/average value (%) of resistivity) measured at measurement points (first measurement point and second measurement point) on the main surface than the GaN substrates of Samples 1A and 1B.
  • the GaN substrates of Samples 21 to 26 all had smaller variations in resistivity (standard deviation/average value (%) of resistivity) measured at measurement points (first measurement point and second measurement point) on the main surface than the GaN substrate of Sample 2A.
  • the GaN substrates of Samples 31 to 36 all had smaller variations in resistivity (standard deviation/average value (%) of resistivity) measured at measurement points (first measurement point and second measurement point) on the main surface than the GaN substrate of Sample 3A.
  • the GaN substrates of samples 41 and 42 all had smaller variations in resistivity (standard deviation/average value (%) of resistivity) measured at measurement points (first measurement point and second measurement point) provided on the main surface than the GaN substrate of sample 4A.
  • the variation in resistivity (standard deviation/average value (%) of resistivity) measured at the measurement points (first and second measurement points) on the main surface of the GaN substrate of Samples 11 to 16, Samples 21 to 26, Samples 31 to 36, Samples 41 to 42, and Samples 51 to 53 was 50% or less (especially less than 50%). From the above, it is suggested that the GaN substrates according to this embodiment of Samples 11 to 16, Samples 21 to 26, Samples 31 to 36, Samples 41 to 42, and Samples 51 to 53 can provide good device characteristics due to the uniform in-plane resistivity without variation.

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  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)

Abstract

L'invention concerne un substrat monocristallin de nitrure de gallium qui a une surface principale circulaire ayant un diamètre de 50 mm ou plus. Le pourcentage d'écart-type/valeur moyenne de la résistance spécifique mesurée à 101 points de mesure sur la surface principale est inférieur à 50 %. Les points de mesure sont agencés à des intervalles de 100 µm sur un segment de ligne virtuelle ayant une longueur de 10 mm arbitrairement disposée sur la surface principale.
PCT/JP2022/041169 2022-11-04 2022-11-04 Substrat monocristallin de nitrure de gallium et son procédé de production WO2024095448A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006273716A (ja) * 1997-10-30 2006-10-12 Sumitomo Electric Ind Ltd ＧａＮ単結晶基板の製造方法
JP2012142629A (ja) * 2005-06-10 2012-07-26 Cree Inc 炭化シリコン基板上のｉｉｉ族窒化物エピタキシャル層
JP2012246195A (ja) * 2011-05-30 2012-12-13 Hitachi Cable Ltd 半絶縁性窒化物半導体ウエハ、半絶縁性窒化物半導体自立基板及びトランジスタ、並びに半絶縁性窒化物半導体層の成長方法及び成長装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006273716A (ja) * 1997-10-30 2006-10-12 Sumitomo Electric Ind Ltd ＧａＮ単結晶基板の製造方法
JP2012142629A (ja) * 2005-06-10 2012-07-26 Cree Inc 炭化シリコン基板上のｉｉｉ族窒化物エピタキシャル層
JP2012246195A (ja) * 2011-05-30 2012-12-13 Hitachi Cable Ltd 半絶縁性窒化物半導体ウエハ、半絶縁性窒化物半導体自立基板及びトランジスタ、並びに半絶縁性窒化物半導体層の成長方法及び成長装置

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