JP2013175580A - Nitride single crystal with through hole, and method of manufacturing the same - Google Patents

Abstract

Provided is a method for producing a nitride single crystal having a through-hole, in which a through-hole of a specific size can be accurately formed with respect to a nitride single crystal having a large thickness.
SOLUTION: A single abrasive grain is interposed between a main surface 103 of a nitride single crystal 101 having a thickness of 100 to 1000 μm and a tool, and the nitride single crystal 101 and the tool of the tool are vibrated while ultrasonically vibrating the tool. The nitride single crystal 101 is punched in the thickness direction by pressing at least one of them, and nitride having a through hole 102 that forms a through hole 102 having a diameter in the range of 200 to 600 μm in 70% or more of the thickness direction. A method for producing a single crystal.
[Selection] Figure 1

Description

  The present invention relates to a nitride single crystal having a through hole and a method for producing the same.

  When a nitride crystal such as GaN is to be manufactured by an ammonothermal method or a liquid phase method, it is generally manufactured by growing a nitride crystal on the same type of crystal as a seed crystal. The seed crystal is usually a single crystal molded into a plate shape or a rod shape, and is used for growing a nitride crystal after being positioned in a reaction vessel. At this time, positioning and installation of the seed crystal are performed by various methods.

For example, in Patent Document 1, a small crystal of 12.6 to 48.4 mg is drilled with a high-power laser, and a wire is passed through the through hole and suspended in a reaction vessel. A method for growing a GaN crystal by a method is described (see Patent Document 1, Examples 1 to 5).
Patent Document 1 describes that a wire having a diameter of 130 μm is passed through the through-hole, but does not describe details such as the size and position of the through-hole formed in the crystal and processing conditions.

  Patent Document 2 describes a technique for crystallizing ZnO by a hydrothermal synthesis method, and FIG. 6C describes a perforated seed crystal. However, there is no detailed description of the hole size, processing method, and the like.

  In Patent Document 3, since a circular substrate of a self-standing nitride semiconductor has many crystal defects in the outer peripheral portion, a tool having a ring shape whose inner shape is a desired overall shape is provided for the reason of removing crystal defects in the outer peripheral portion. There is described a peripheral processing method characterized by hollowing out a desired nitride semiconductor substrate (wafer) having an overall shape corresponding to the shape inside the ring by the ultrasonic processing used. Here, in general, the wafer has a diameter of 50 mm or more, and the thickness of a ring-shaped tool used in the embodiment of Patent Document 3 is described as 1 mm (1000 μm). Is a large area processed hole having a width exceeding 1000 μm.

  In Patent Document 4, there is a description in [0058] that a hole for passing a wire through a seed crystal that is a nitride single crystal can be formed by a laser, a diamond drill, a polishing drill, or an ultrasonic drill. Here, the ultrasonic drill is a tool obtained by adding ultrasonic waves to a general drill (spiral blade), and usually uses ultrasonic waves to reduce cutting resistance. That is, the aspect in which the abrasive grains for cutting the nitride single crystal are free abrasive grains has not been disclosed or suggested.

JP-T-2006-513122 JP 2003-146799 A JP 2006-339431 A Special table 2010-509178 gazette

In the method of Patent Document 1, generation of processing heat due to laser processing is large, and there is a concern about the influence on the workpiece. In addition, since only the drilling of small crystals is described in the same document, large GaN with poor workability No suggestion could be made about the crystal drilling method.
In Patent Document 2, the material of a seed crystal that is a processed product is not a nitride. A nitride single crystal is harder than ZnO. For example, the hardness (Vickers) of GaN is about 17 times the hardness of ZnO. Therefore, even when referring to the aspect of drilling ZnO described in Patent Document 2, the method of forming a through hole having a specific size for a nitride single crystal having a specific thickness has not been known.
In Patent Document 3, since a tool having a ring shape is used, the bending of the inner mold of the tool is particularly suppressed, and it is not necessary to set precise machining conditions. Further, in Patent Document 3, it is assumed that the outer peripheral portion of the self-standing nitride semiconductor before processing is removed, and the accuracy of the cross section of the substrate on the side in contact with the outside of the ring-shaped tool is unknown. Furthermore, when processing a through-hole having a small area with a diameter of about 200 to 600 μm by the method of Patent Document 3, it is necessary to make the wall thickness of the ring-shaped tool very thin. There was no description of changing the size of the tool having the shape of. Therefore, in Patent Document 3, it is not assumed that a through-hole having a small area with a diameter of about 200 to 600 μm is processed. When drilling through holes with a small area of 200 to 600 μm in diameter by ultrasonic processing, it is clear that the processing conditions are completely different, and the processing conditions for setting the through holes are set by appropriately adjusting the conditions. However, it was not easy to make a through hole even if referring to Patent Document 3.
As a result of the inventors examining the method described in the above-mentioned patent document, it is difficult to accurately form a through hole of a specific size for a nitride single crystal having a large thickness. I found out. The problem to be solved by the present invention is to provide a method for producing a nitride single crystal having a through hole, which can accurately form a through hole of a specific size with respect to a nitride single crystal having a large thickness. is there.

  As a result of intensive studies, the inventors of the present invention have pressed the main surface of the nitride single crystal or the tool while ultrasonically vibrating the tool by interposing loose abrasive grains between the main surface of the nitride single crystal and the tool. Thus, it has been found that the above-mentioned problems can be solved by forming through holes having a specific range of diameters in the thickness direction of the nitride single crystal. As a result, the present invention having the following configuration has been provided.

[1] At least one of the nitride single crystal and the tool while free abrasive grains are interposed between the main surface of the nitride single crystal having a thickness of 100 to 1000 μm and the tool, and the tool is ultrasonically vibrated. The nitride single crystal is perforated in the thickness direction by pressing and forming a through-hole having a diameter in the range of 200 to 600 μm at 70% or more of the thickness direction. A method for producing a single crystal.
[2] The method for producing a nitride single crystal having a through hole according to [1], wherein the nitride single crystal is a single crystal of gallium nitride.
[3] The method for producing a nitride single crystal having a through-hole according to [1] or [2], wherein the loose abrasive is a slurry in which abrasive is dispersed in a lubricating liquid.
[4] The control is performed such that the ratio of the minimum diameter to the maximum diameter (minimum diameter / maximum diameter) of the through-hole is 0.5 to 1. ] The manufacturing method of the nitride single crystal which has a through-hole as described in any one of.
[5] Ratio of the area of the through hole in the surface of the nitride single crystal opposite to the tool side to the area of the through hole in the surface of the nitride single crystal on the tool side ( Any one of [1] to [4], wherein control is performed such that the area of the through hole on the surface opposite to the tool / the area of the through hole on the surface on the tool side is 0.5 to 1. A method for producing a nitride single crystal having through-holes according to one item.
[6] The penetration according to any one of [1] to [5], wherein the nitride single crystal is controlled so that a width of a drooping region on a surface on the tool side is within 100 μm. A method for producing a nitride single crystal having holes.
[7] The method according to any one of [1] to [6], wherein a control is performed so that a separation region having a width of 500 μm or less is formed on the surface of the nitride single crystal on the tool side. For producing a nitride single crystal having through-holes.
[8] The method for producing a nitride single crystal having a through hole according to any one of [1] to [7], wherein an area of a main surface of the nitride single crystal is 50 mm ² or more. .
[9] The nitride having a through hole according to any one of [1] to [8], wherein a through hole is formed in a region of 500 to 10,000 μm inward from the periphery of the nitride single crystal. A method for producing a single crystal.
[10] The through hole according to any one of [1] to [9], wherein a tool having a flat or convex shape at the bottom on the nitride single crystal side is used as the tool. The manufacturing method of the nitride single crystal which has.
[11] The through hole according to any one of [1] to [10], wherein the maximum width of an image projected onto the surface of the nitride single crystal side of the tool is 100 to 1500 μm. The manufacturing method of the nitride single crystal which has this.
[12] The method for producing a nitride single crystal having a through hole according to any one of [1] to [11], wherein the abrasive grains are SiC.
[13] The direction in which the tool is ultrasonically vibrated is a direction toward the main surface of the nitride single crystal, according to any one of [1] to [12], For producing a nitride single crystal having through-holes.
[14] The nitride single crystal having a through hole according to any one of [1] to [13], wherein a main surface of the nitride single crystal is a nonpolar plane or a semipolar plane. Production method.
[15] A nitride single crystal having a through-hole, which is manufactured by the manufacturing method according to any one of [1] to [14].

  According to the manufacturing method of the present invention, it is possible to manufacture a nitride single crystal having a through hole in which a through hole having a specific size is accurately formed with respect to a nitride single crystal having a large thickness.

It is a perspective view which shows the specific example of the nitride single crystal which has a through-hole formed in this invention. It is a top view of the nitride single crystal which has a cylindrical through-hole. It is a schematic diagram of the crystal manufacturing apparatus by the ammonothermal method that can be used for growing a nitride crystal on the nitride single crystal having a through hole of the present invention. It is the schematic of the surface of the nitride single crystal which has a through-hole seen from the surface direction of the nitride single crystal of the side which contacts a tool first. FIG. 5 is a schematic diagram of an a-a ′ cross section of the nitride single crystal 101 having the through hole 102 in FIG. 4. 2 is a schematic cross-sectional view of nitride single crystal 101 for explaining a separation region generated when through-hole 102 is formed. FIG. It is the schematic showing the positional relationship of the nitride single crystal, tool, and loose abrasive grain in the ultrasonic processing apparatus used in Examples 1-6. It is the schematic showing the positional relationship of the nitride single crystal in the blast apparatus used in the comparative example 1, the injection port, and a free abrasive grain.

Hereinafter, the nitride single crystal having a through hole of the present invention and a method for producing the same will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

In the following description, the “C plane” is a plane equivalent to the {0001} plane in a hexagonal crystal structure (wurtzite type crystal structure), and is a polar plane (0001) plane or (000-1) plane. Point to. In the group III nitride crystal, the C plane is a group III plane or a group V plane, and in gallium nitride, it corresponds to a Ga plane or an N plane, respectively. In the following description, the “M plane” refers to {1-100} plane, {01-10} plane, [-1010] plane, {−1100} plane, {0-110} plane, {10-10 } Non-polar planes comprehensively represented as planes, specifically (1-100) plane, (01-10) plane, (-1010) plane, (-1100) plane, (0-110). ) Plane and (10-10) plane. Further, in the following description, the “A plane” means {2-1-10} plane, {-12-10} plane, {-1-120} plane, {-2110} plane, {1-210} plane. , {11-20} plane, which is comprehensively represented as a plane, specifically, (2-1-10) plane, (-12-10) plane, (-1-120) plane, ( -2110) plane, (1-210) plane, and (11-20) plane.
In the present specification, the “semipolar plane” refers to a plane other than the [0001] plane and not m = 0 in the Miller index (hklm) in the hexagonal crystal structure. That is, it refers to a plane that is inclined with respect to the (0001) plane and is not a nonpolar plane. h, k, l and m are each independently preferably an integer of -5 to 5, more preferably an integer of -2 to 2, and preferably a low index surface. . As the semipolar plane, for example, (10-11) plane, (10-1-1) plane, (20-21) plane, (20-2-1) plane, (10-12) plane, (10-1- 2) plane, (11-22) plane, (10-13) plane, (11-24) plane, and the like.

[Method for producing nitride single crystal having through-hole]
The method for producing a nitride single crystal having a through-hole according to the present invention (hereinafter also referred to as the production method of the present invention) comprises free abrasive grains between the main surface of the nitride single crystal having a thickness of 100 to 1000 μm and the tool. The nitride single crystal is pressed in the thickness direction by pressing at least one of the nitride single crystal and the tool while ultrasonically vibrating the tool, and 70% or more of the thickness direction is 200 to 600 μm. A through-hole having a diameter within the range of is formed.
With such a configuration, a through hole having a specific size can be formed with high accuracy for a nitride single crystal having a large thickness.

The method for producing a nitride single crystal having a through hole according to the present invention is a method utilizing ultrasonic processing. In this specification, ultrasonic machining means that a tool having a desired shape is vibrated by applying ultrasonic waves, and the tool and the workpiece (in the present invention, a “nitride single crystal in which a through hole is formed”). This is a process of crushing the work piece by repeatedly applying the vibration wave from the tool to the work piece.
Since the preferred embodiment of the manufacturing method of the present invention does not require a mask for etching or the like, a nitride having a through-hole that can accurately form a through-hole of a specific size with respect to a nitride single crystal having a large thickness A single crystal can be easily produced. Moreover, in the preferable aspect of the manufacturing method of this invention, the through-hole corresponding to the shape of a tool (a rod etc.) is processable. Also, laser processing generates a lot of processing heat, and the thermal effect on the nitride single crystal in which the through-holes are formed increases. On the other hand, the preferred embodiment of the manufacturing method of the present invention generates relatively little processing heat. Therefore, it is possible to reduce the influence of heat on the nitride single crystal in which the through-hole is formed, so that the deterioration of the nitride single crystal can be prevented.
Hereinafter, the details of preferred embodiments of the materials used in the production method of the present invention and the conditions for forming the through holes will be described.

(Type and composition of nitride single crystal)
In the manufacturing method of the present invention, a nitride single crystal having a thickness of 100 to 1000 μm is used as the nitride single crystal in which the through hole is formed. In the manufacturing method of the present invention, since a through hole having a diameter in the range of 200 to 600 μm is formed in the nitride single crystal at 70% or more in the thickness direction, the nitride single crystal larger than the desired through hole is formed. Use crystals.
The nitride single crystal used in the manufacturing method of the present invention is formed with through holes of a specific size by the manufacturing method of the present invention. Thereafter, the obtained nitride single crystal having through-holes is placed in a reaction vessel, and a seed crystal (hereinafter referred to as “nitride crystal”) for growing a nitride crystal such as a group III nitride crystal thereon. It is sometimes referred to as “seed crystal in growth.”) It is preferably used.

The nitride single crystal used in the production method of the present invention is preferably a group III nitride single crystal because a more remarkable effect is seen.
Examples of the group III nitride single crystal include GaN, InN, AlN, InGaN, AlGaN, and AllnGaN. A single crystal containing at least Ga and N is preferable, GaN, AlGaN, and AllnGaN are more preferable, and GaN is more preferable. The nitride single crystal having a through-hole obtained by the manufacturing method of the present invention is used as a seed crystal in the growth of the nitride crystal, and the same material as the nitride crystal to be grown on the nitride single crystal is used. Is preferred. For example, when a GaN crystal is intended to grow on a seed crystal, it is preferable to select a GaN single crystal as a nitride single crystal having a through hole used as a seed crystal. That is, it is preferable to select a GaN single crystal as the nitride single crystal in which the through hole is formed.

The shape of the nitride single crystal is not particularly limited. Crystals having various shapes such as a cube, a rectangular parallelepiped, a cylinder, and a polygonal column can be used as the nitride single crystal. Preferred is a crystal having a large principal surface. The main surface here means a surface having the largest area in the crystal. The type of the main surface of the nitride single crystal is not particularly limited, and may be a polar surface, a nonpolar surface, or a semipolar surface. The nitride single crystal having through-holes obtained by the production method of the present invention preferably grows a nitride crystal on the surface including the main surface thereafter, on the main surface of the nitride single crystal having the through-holes More preferably, nitride crystals are mainly grown. Therefore, the plane orientation of the main surface of the nitride single crystal used in the manufacturing method of the present invention can also be determined in consideration of the nitride crystal to be finally used, the main surface and size of the wafer, and the like. In the production method of the present invention, the nitride single crystal having through-holes obtained by the production method of the present invention is grown by nitride crystal growth, wherein the main surface of the nitride single crystal is a nonpolar surface or a semipolar surface. From the viewpoint of easily growing a nitride crystal having a main surface that is a nonpolar surface or a semipolar surface, the main surface is more preferably an M surface or a semipolar surface.
Note that the main surface of the nitride single crystal before the through hole is formed and the main surface of the nitride crystal or wafer to be grown and used on the nitride single crystal finally having the through hole may be aligned. Although it is preferable, since the nitride crystal grown on the nitride single crystal having through-holes can be cut out in a desired direction and the wafer can be cut out, the main surfaces do not have to coincide.

In the production method of the present invention, the area of the main surface of the nitride single crystal is preferably 50 mm ² or more, more preferably 200 mm ² or more, and further preferably 400 mm ² or more. The maximum diameter of the nitride single crystal is preferably 10 mm or more, more preferably 20 mm or more, and further preferably 50 mm or more.

  In the manufacturing method of the present invention, the thickness of the nitride single crystal (typically, the thickness in the direction perpendicular to the main surface) is 100 to 1000 μm from the viewpoint of ease of handling and ease of forming through holes. The lower limit of the thickness of the nitride single crystal is preferably 200 μm or more, and more preferably 300 μm or more. The upper limit of the thickness of the nitride single crystal is preferably 600 μm or less, and more preferably 400 μm or less. The nitride single crystal may be not only a plate shape whose thickness direction is shorter than the vertical and horizontal directions but also a thick one such as a columnar shape.

  In the production method of the present invention, the production method of the nitride single crystal in which the through hole is formed is not particularly limited. For example, a single crystal manufactured by a hydride vapor phase epitaxy (HVPE) method, an ammonothermal method, a flux method, or the like can be used. In particular, it is preferable to use a nitride single crystal produced by an ammonothermal method in terms of low defect density and high crystallinity. Moreover, it is preferable that the surface of the produced nitride single crystal is smoothed by a method such as polishing or etching before being used in the production method of the present invention.

(Tools used for ultrasonic processing)
In the manufacturing method of the present invention, the tool used for ultrasonic machining is not particularly limited, and a tool used for known ultrasonic machining can be used. Conventionally, as an ultrasonic processing apparatus, for example, an ultrasonic processing apparatus described in JP-A-6-143099 is known, and ultrasonic vibration is generated from an ultrasonic vibration generating unit, for example, one or two or more horns ( Via the amplifier) and / or directly to the tool. Free abrasive grains are interposed between the ultrasonically vibrated tool and the nitride single crystal, and the tool is pressed against the workpiece with an appropriate pressure to use the shocking destructive force of ultrasonic waves. The shape is immersed in the nitride single crystal as it is. Abrasive grains that have entered between the tool and the nitride single crystal are subjected to a large impact at the tip of the tool, and the nitride single crystal is crushed little by little by the impact. Although the amount crushed by a single impact is negligible, increasing the number of repetitions as described above allows the tool tip surface shape to be engraved into the nitride single crystal with sufficient speed and accuracy for practical use. It will be followed.

Hereinafter, a tool used for ultrasonic machining will be described. In the present specification, unless otherwise specified, the term “tool” simply means “a member or region that penetrates a nitride single crystal when a through hole is formed”. In addition, a holding portion and a connecting portion (portion connected to the ultrasonic vibration generating portion) that do not penetrate the nitride single crystal are excluded.
The material of the tool is not particularly limited as long as it is not contrary to the gist of the present invention, but stainless steel, cast iron, aluminum or the like can be used. Among these, the material of the tool is preferably stainless steel from the viewpoint of tool wear and corrosion resistance.

  The length in the longitudinal direction of the tool is not particularly limited as long as a through-hole can be formed in the main surface of the nitride single crystal having a thickness of 100 to 1000 μm, but is preferably 1000 μm or more and preferably 3000 μm or more. It is more preferable, and it is especially preferable that it is 6000 micrometers or more. The length of the tool in the longitudinal direction is preferably 20000 μm or less, more preferably 15000 μm or less, and particularly preferably 10,000 μm or less.

  In the manufacturing method of the present invention, the maximum width of the projected image on the nitride single crystal side surface of the tool can be changed according to the size of the through hole to be formed, but is 100 μm or more. Is preferably 200 μm or more, and particularly preferably 300 μm or more. The maximum width of the projected image on the nitride single crystal side surface of the tool is preferably 1500 μm or less, more preferably 1000 μm or less, and particularly preferably 700 μm or less. When the tool is brought into perpendicular contact with the surface on the nitride single crystal side, the maximum width of the projected image matches the maximum width of the tool.

In the manufacturing method of the present invention, it is preferable to use a tool having a flat or convex shape at the bottom on the nitride single crystal side as the tool. Here, a tool having a concave shape (including a donut shape having a hole in the center) such as a ring-shaped tool as described in JP-A-2006-339431 is known. When a through-hole having a diameter of about 200 to 600 μm is formed on a thick nitride single crystal as in the manufacturing method of the present invention, it is more effective to use a tool whose bottom shape is flat or convex. It is preferable from the viewpoints of the transmission of powder and the discharge of chips.
Here, a tool whose bottom shape is a plane is specifically a shape whose tip is flat and cylindrical, or a shape where the apex of a cone whose tip is flat and tapered is cut in a plane, And a shape having a polygonal column shape at the tip. In addition, the tool having a convex bottom shape includes a shape in which the tip is a curved surface (such as a hemisphere) and a shape in which the tip is sharpened like a needle. Among these, in the manufacturing method of the present invention, a tool having a flat bottom portion is preferable, a tool having a flat tip and a cylindrical shape or a tool having a flat tip and a polygonal column is more preferable, and the tip is flat and circular. A columnar tool is particularly preferred.

(Free abrasive)
In the production method of the present invention, loose abrasive grains are interposed between the main surface of the nitride single crystal having a thickness of 100 to 1000 μm and the tool.
In the production method of the present invention, the loose abrasive grains are preferably a slurry in which abrasive grains are dispersed in a lubricating liquid.
Although there is no restriction | limiting in particular as said lubricating liquid, For example, water can be used. Although there is no restriction | limiting in particular about the mixing ratio (mass ratio) of the lubricating liquid in the said slurry, and a free abrasive grain, For example, it is preferable that it is 1: 9 or more, and it is more preferable that it is 3: 7 or more. The mixing ratio of the lubricating liquid and the free abrasive grains in the slurry is preferably 9: 1 or less, and more preferably 8: 2 or less. Furthermore, the mixing ratio of the lubricating liquid and free abrasive grains in the slurry is particularly preferably 6: 4.

The size of the free abrasive grains is not particularly limited as long as it is not contrary to the gist of the present invention, but the average primary particle diameter is preferably 1 μm or more, more preferably 7.5 μm or more, and 15 μm or more. It is particularly preferred. The size of the loose abrasive is preferably 200 μm or less, more preferably 100 μm or less, and particularly preferably 50 μm or less.
The material of the loose abrasive is not particularly limited as long as it is not contrary to the gist of the present invention, but it is preferable to use a material having a specific range of hardness according to the kind of the nitride single crystal. The loose abrasive is preferably made of a material having a Vickers hardness of 15000 MPa or more, more preferably a material of 17500 MPa or more, and particularly preferably a material of 20000 MPa or more. The loose abrasive is preferably made of a material having a Vickers hardness of 45000 MPa or less, more preferably a material of 40000 MPa or less, and particularly preferably a material of 30000 MPa or less.
For example, Si (Vickers hardness 9804 MPa), SiC (Vickers hardness 24510 MPa), B ₄ C (Vickers hardness 41000 MPa) or the like can be used as the material of the loose abrasive grains. Among them, when a group III nitride single crystal such as GaN is used as the nitride single crystal, SiC is preferable from the viewpoint of ease of forming a through hole and tool wear, and green silicon carbide abrasive grains (GC). It is more preferable from the viewpoint of friability. Note that the Vickers hardness of GaN is 14980 MPa.

(Conditions for ultrasonic processing)
The frequency of the ultrasonic wave applied to the tool is preferably 16 kHz or more, more preferably 20 kHz or more, and particularly preferably 23 KHz or more. The frequency of the ultrasonic wave applied to the tool is particularly preferably 25 KHz or less.
The output of the ultrasonic wave applied to the tool is preferably 10 W or more, more preferably 15 W or more, and particularly preferably 20 W or more from the viewpoint of bringing the aspect ratio of the through hole close to 1. The output of the ultrasonic wave applied to the tool is preferably 100 W or less, more preferably 50 W or less, and particularly preferably 30 W or less from the viewpoint of bringing the aspect ratio of the through hole close to 1.
The direction of ultrasonic vibration of the tool includes a direction parallel to the main surface of the nitride single crystal and a direction toward the main surface, but is a longitudinal direction of the tool and is a direction toward the main surface. It is preferable. Moreover, it is preferable to install the tool so that the direction in which the tool is ultrasonically vibrated is perpendicular to the surface of the nitride single crystal.

In the manufacturing method of the present invention, at least one of the nitride single crystal and the tool is pressed to form a through hole in the nitride single crystal. Among them, a method of fixing the nitride single crystal and pressing the tool is preferable.
Although there is no restriction | limiting in particular as the method of fixing the said nitride single crystal, For example, it can affix on arbitrary fixing plates, such as a carbon plate, using a wax.

The pressure applied when pressing the tool is not particularly limited, but is preferably 0.05 kg / cm ² or more, more preferably 0.1 kg / cm ² or more, and 0.2 kg / cm ^2. The above is particularly preferable. Pressure when pressing the tool, is preferably 0.8 kg / cm ² or less, more preferably 0.5 kg / cm ² or less, particularly not less 0.3 kg / cm ² or less preferable.
As another method of pressing the tool, constant pressure control is preferable.

The time for pressing at least one of the nitride single crystal and the tool to form a through hole in the nitride single crystal is not particularly limited, and depends on the thickness of the nitride single crystal, for example, 5 seconds. Preferably, it is 6 seconds or more, and more preferably 8 seconds or more. The time for forming the through hole in the nitride single crystal is preferably 60 seconds or less, more preferably 40 seconds or less, and particularly preferably 35 seconds or less.
The processing speed when pressing at least one of the nitride single crystal and the tool to form a through hole in the nitride single crystal is preferably 1 μm / sec or more, and preferably 5 μm / sec or more. It is more preferable that it is 10 μm / sec or more. The processing speed when forming a through hole in the nitride single crystal is preferably 50 μm / sec or less, more preferably 40 μm / sec or less, and particularly preferably 35 μm / sec or less.

(Through hole)
In the manufacturing method of the present invention, at least one through hole is formed in the nitride single crystal. The number of through holes formed in one nitride single crystal is preferably 1 to 6, more preferably 1 to 5, and still more preferably 1 to 4. When the nitride single crystal having through holes obtained by the manufacturing method of the present invention is used as a seed crystal in nitride crystal growth by the ammonothermal method, the number of through holes formed in one nitride single crystal is One is particularly preferable, and when using it as a seed crystal in the growth of a nitride crystal by a liquid phase method such as a chemical equilibrium method, two is particularly preferable from the viewpoint of preventing rotation. If a nitride single crystal provided with a plurality of through-holes is used as a seed crystal in the growth of nitride crystals, it is possible to grow a high quality crystal while suppressing the rotation and shaking of the seed crystal during crystal growth. In addition, by applying positioning means such as wires and hooks to each of the plurality of through holes provided, it becomes possible to perform more accurate positioning of the field where the nitride crystal grows in the reaction vessel, and the reaction temperature is reduced. This is preferable because setting and the like are easy. In addition, by fixing each of the multiple through-holes through wires or hooks, the inclination of the main surface can be fixed at an arbitrary inclination from parallel to vertical with respect to the vertical direction. Speed and quality can be controlled. On the other hand, if the number of through-holes is one, the manufacturing method of the present invention can be carried out more easily, and a wide area except for the through-holes can be secured, so that more nitride crystals are grown thereon. Can be used. When two or more through holes are formed in one nitride single crystal, the size of each through hole may be different or the same.

  The through-hole formed in the nitride single crystal is a hole starting from one surface of the nitride single crystal and ending with another surface. The through hole is not necessarily linear, but is preferably a linear hole having a certain diameter from the viewpoint of ease of formation. Moreover, although the through-hole may be formed on the main surface or may be formed on a surface other than the main surface, the case where it is formed on the main surface is preferable. The through hole preferably extends in a direction perpendicular to the main surface. FIG. 1 shows a specific example of a nitride single crystal 101 having a typical through hole that can be used as a seed crystal in nitride crystal growth in the present invention. The through hole 102 extends linearly in a direction perpendicular to the main surface 103.

4 and 5 show details of the through hole 102 formed by the method for producing a nitride single crystal having a through hole according to the present invention. FIG. 4 is a schematic view of the surface of a nitride single crystal having a through-hole, as viewed from the surface direction of the nitride single crystal having a through-hole on the side that first comes into contact with the tool (hereinafter sometimes referred to as a tool side). FIG. Around the through hole 102, a fringe 115 portion may be formed. Further, a work-affected layer 116 may be formed in the through hole 102. Preferably the depth d ₁₁₆ of the damaged layer is 150μm or less, and more preferably less 130 .mu.m.
FIG. 5 is a schematic diagram of the aa ′ cross section of the nitride single crystal 101 having the through hole 102 in FIG. 4.

As for the said through-hole formed with the manufacturing method of this invention, 70% or more of the thickness direction has a diameter in the range of 200-600 micrometers. 70% or more in the thickness direction preferably has a diameter of 200 μm or more, and more preferably 70% or more in the thickness direction has a diameter of 250 μm or more. Further, 70% or more in the thickness direction preferably has a diameter of 300 μm or less, more preferably 70% or more in the thickness direction has a diameter of 500 μm or less, and 70% or more in the thickness direction has a diameter of 420 μm or less. It is particularly preferred.
At this time, a portion having a diameter in the range of 200 to 600 μm of the through hole formed by the manufacturing method of the present invention is the average diameter w _102b of the through hole inside the nitride single crystal having the through hole in FIG. Preferably equal. In addition, the width of the through hole in the surface of the nitride single crystal having the through hole on the side opposite to the tool side is preferably equal to the average diameter w _102b of the through hole in the crystal.
The surface of the nitride single crystal having a through hole on the surface of the tool (synonymous with the surface of the nitride single crystal that first comes into contact with the tool; however, in the present invention, free abrasive grains are interposed between the tool and the nitride single crystal. In order to form a through-hole, the tool and the nitride single crystal do not need to be in contact with each other, which is synonymous with the surface of the nitride single crystal on the first approaching side of the tool. w _102a is preferably 200 μm or more, more preferably 300 μm or more, and particularly preferably 350 μm or more. Preferably has an average diameter w _102a of the through hole in the plane of the tool-side surface of the nitride single crystal is 600μm or less, more preferably 500μm or less, and particularly preferably in at most 420 [mu] m.
Here, in the nitride single crystal having a through-hole obtained by the manufacturing method of the present invention, a fine surface sag may be formed on the tool-side surface of the nitride single crystal having a through-hole. Therefore, the average diameter w _102a of the through hole in the plane of the surface of the tool side of the nitride single crystal having a through hole, when the surface sag occurs represents the length including the surface whose width w _115.
The minimum diameter of the through-hole on the tool side surface of the nitride single crystal having a through-hole is 200 μm or more, preferably 300 μm or more, and more preferably 400 μm or more.
The maximum diameter of the through hole is preferably 600 μm or less, more preferably 500 μm or less, and further preferably 400 μm or less. If the maximum diameter of the through-hole is 600 μm or less, the nitride single crystal having the through-hole obtained by the production method of the present invention is used as a seed crystal in nitride crystal growth by an ammono method or the like, and the nitride is formed thereon When the crystal is grown, the through hole is filled in the crystal growth process, and a high-quality nitride crystal can be grown.

In the manufacturing method of the present invention, it is preferable to control the width w _{115 of the} runner 115 on the tool-side surface of the nitride single crystal having the through-hole to be within 100 μm, and control to be within 50 μm. It is more preferable to control the distance to be within 10 μm.
On the other hand, in the manufacturing method of the present invention, it is preferable to control the depth d ₁₁₅ of the flank 115 on the surface on the tool side of the nitride single crystal having the through holes to be within 100 μm, and within 50 μm. It is more preferable to control so that it is within 10 μm.
Examples of the method for controlling the width and depth of the face 115 on the surface of the tool side of the nitride single crystal having the through holes include adjustment of the abrasive grain size, processing time, frequency, and tool length. The control method is not limited to such a mode.

On the other hand, it is preferable that the through-holes in the surface of the nitride single crystal having the through-holes on the surface opposite to the tool side have almost no surface runoff 115. That is, it is preferable that the average value w _102b of the width of the through hole in the surface of the nitride single crystal having the through hole on the side opposite to the tool side is equal to the distance between the side surfaces of the through holes.

In the manufacturing method of the present invention, the ratio of the minimum diameter length of the through hole in the surface of the tool side to the maximum diameter (minimum diameter / maximum diameter) (also referred to as aspect ratio) is 0.5 to 0.5. It is preferably controlled to be 1, more preferably controlled to be 0.6 to 1, and particularly preferably controlled to be 0.7 to 1. The method for controlling the ratio of the minimum diameter length to the maximum diameter length (minimum diameter / maximum diameter) of the through hole in the surface on the tool side includes adjustment of the abrasive grain size and the tool length. However, the control method is not limited to such a mode.
Further, in the manufacturing method of the present invention, the nitride single crystal tool having a through hole in the area of the through hole in the surface of the nitride single crystal having the through hole opposite to the tool side is provided. The ratio to the area of the through hole in the surface of the side surface (the area of the through hole on the surface opposite to the tool / the area of the through hole on the surface on the tool side) is controlled to be 0.5 to 1. It is more preferable, and it is more preferable to control so that it may become 0.6-1, and it is especially preferable to control so that it may become 0.7-1. A through-hole in the surface of the surface of the nitride single crystal having the through-hole in the area of the surface of the nitride single crystal having the through-hole on the surface opposite to the tool side. Examples of the method for controlling the ratio to the area include adjustment of the abrasive grain size and processing time, but the control method is not limited to such an embodiment.

The depth d ₁₀₂ of the through hole is synonymous with the thickness of the nitride single crystal 101 having the through hole at the position where the through hole is formed.

The position where the through hole is formed in the surface of the nitride single crystal having the through hole is preferably not too close to the periphery of the nitride single crystal having the through hole. The distance from the periphery of the nitride single crystal having a through hole to the hole end closest to the periphery of the nitride single crystal of the through hole is preferably more than 500 μm, more preferably more than 800 μm, more than 1000 μm. More preferably it is. If the seed crystal in the nitride crystal growth is manufactured so that the through-hole does not exist in a region within 500 μm inward from the periphery of the nitride single crystal having the through-hole, when the temperature is raised to grow the nitride crystal, It becomes easy to prevent the region between the through hole and the periphery from melting and the through hole from becoming a part of the periphery. By doing so, for example, when a nitride single crystal having a through-hole as a seed crystal in nitride crystal growth is placed in the reaction vessel through a wire through the through-hole, the situation where the seed crystal is detached from the wire and dropped off is further reduced. It becomes easy to prevent. On the other hand, the position of the through hole is preferably not too far from the peripheral edge of the nitride single crystal having the through hole. Nitride crystals that grow near the through-holes are often inferior in quality compared to nitride crystals that grow on other major surfaces, so that a single-crystal nitride through-hole with a through-hole used as a seed crystal is formed It is preferable to make a main surface region that is not made as wide as possible and to grow a high-quality nitride crystal thereon. From such a viewpoint, the distance from the periphery of the nitride single crystal having the through hole to the hole end farthest from the nitride single crystal periphery of the through hole is preferably 10000 μm or less, and preferably 5000 μm or less. More preferably, it is more preferably 2000 μm or less.
4 and 5, the distance from the peripheral edge 111 of the nitride single crystal having a through hole to the hole end closest to the peripheral edge of the nitride single crystal of the through hole is a length represented by w ₁₁₁ .

  Producing a seed crystal in the growth of a nitride crystal so that the through-hole exists only in the region of 500 to 10000 μm inward from the periphery of the nitride single crystal having a through-hole can easily prevent the seed crystal from dropping off at the time of temperature rise. Moreover, it is preferable because it is easy to grow a larger and better nitride crystal. For example, when a nitride single crystal having a cylindrical through hole is used as a seed crystal, as shown in FIG. 2, a peripheral vicinity region 112 from the peripheral edge 111 to the inner side of 500 μm and a central region from the peripheral edge 111 to the inner side of more than 10,000 μm If a through-hole is formed only in the intermediate region 113 without forming a through-hole in 114, the through-hole is maintained even if the vicinity of the periphery of the peripheral vicinity region 112 is melted during the temperature rise, and the central region 114 is included. Good quality nitride crystals can be grown in a wide area.

  The shape of the through hole in the plane of the main surface of the nitride single crystal having the through hole is not particularly limited. If the nitride single crystal having the through hole can be suspended through a wire, It may be a square or various other shapes. The shape of the through-hole in the plane of the main surface of the nitride single crystal having the through-hole can be changed by changing the projected image of the tool on the surface of the nitride single crystal having the through-hole. It can be processed into a shape. It is also possible to make the crystal orientation of the obtained nitride single crystal having through-holes clear.

(Peeling area)
In the manufacturing method of the present invention, a separation region having a width within 500 μm from the through hole is formed on the surface of the nitride single crystal having the through hole opposite to the tool side (that is, the width of the separation region is It is preferable to form a separation region having a width of 400 μm or less, and it is particularly preferable to form a separation region having a width of 300 μm or less. As shown in FIG. 6, the peeling region runs on the nitride single crystal having the through hole on the side opposite to the tool side in a direction crossing the traveling direction of the tool, and is inclined from the main surface around the through hole. It is a planar crack that exists as a rough surface. Specifically, by observing the cross section of the through hole with a microscope at a magnification of 100, a streak-like line is observed in the peeled area.
In FIG. 6, the width of the peeling region 117 is represented by w ₁₁₇ and is the length from the side wall of the through hole to the end point of the crack.
Further, when the peeling region 117 is formed in a donut shape around the through hole, the outer diameter thereof is preferably within 1500 μm, more preferably within 1300 μm, and particularly preferably within 1100 μm. .
On the other hand, the height (synonymous with depth or thickness) d ₁₁₇ of the peeling region 117 is not particularly limited, and is, for example, 300 μm or less from the surface on the tool side of the nitride single crystal having the through hole. Is preferably 200 μm or less, and more preferably 150 μm or less.
Examples of the method for controlling the width and height of the separation region include adjustment of surface orientation, cutting speed, output, and abrasive grain size, but the control method is not limited to such a mode. The generation mechanism of the peeling region 117 is not limited to any theory, but when the hole portion is thinned in the process of forming the through hole, the thinning is performed when the cutting speed of the tool exceeds the removal capability of the tool. It is considered that this occurs when pressure is applied to the workpiece (nitride single crystal).

(Treatment after through-hole formation)
After the through hole is formed, it is preferable to perform a surface treatment on a region including the through hole forming portion and its vicinity. Examples of the surface treatment method include chemical etching, polishing, buffing, and the like. Adopting chemical etching is preferable in terms of cost and simplicity. As a specific example of chemical etching, a method of etching at about 100 ° C. using a strong alkali solution such as a saturated KOH solution can be exemplified as a preferable method. Thus, by performing the surface treatment after forming the through hole, the work-affected layer generated by the formation of the through hole can be removed, and the quality of the nitride crystal grown thereon can be improved. .

[Crystal growth using a nitride single crystal having a through-hole obtained by the production method of the present invention]
(Positioning)
The nitride single crystal having a through-hole obtained by the production method of the present invention is preferably placed in a reaction vessel and a nitride crystal is preferably grown thereon. At this time, the nitride single crystal having a through hole is preferably positioned in the reaction vessel using positioning means. As the positioning means, a wire, a hook, or a combination thereof can be used, but a wire is preferably used. When using a wire, the nitride single crystal having a through hole is formed by inserting the wire into a through hole of the nitride single crystal having a through hole and holding the wire on a jig fixed to the reaction vessel or the side surface of the reaction vessel. Can be positioned. Positioning here refers to the case where a nitride single crystal having a through-hole used as a seed crystal in nitride crystal growth is fixed so as not to move, and the case where a nitride single crystal having a through-hole is in a limited region. It includes both of cases where it is possible to move. For example, two or more through holes are provided in a nitride single crystal having a through hole, a wire is inserted into each through hole, and the end of the wire is attached to a jig or reaction vessel side wall installed in the reaction vessel. By fixing, the nitride single crystal having the through hole can be fixed so as not to move. Further, by inserting a wire into one through-hole provided in the nitride single crystal having a through-hole, and connecting the end of the wire to a jig (for example, a seed rack) installed in the reaction vessel, the treatment can be performed. The nitride single crystal having through holes may be suspended from the tool so that the nitride single crystal having through holes can move within a certain region. Positioning the nitride single crystal having a through-hole within a certain region so that the nitride single crystal can move as in the latter can grow a more uniform nitride crystal on the nitride single crystal having a through-hole. Is preferable. Moreover, you may penetrate the nitride single crystal which has several through-holes in one wire.

  When using a wire, the diameter of the wire is preferably 100 μm or more, more preferably 150 μm or more, and even more preferably 200 μm or more. Moreover, it is preferable that the diameter of a wire is 1900 micrometers or less, It is more preferable that it is 1500 micrometers or less, It is further more preferable that it is 1000 micrometers or less. The diameter of the wire must be smaller than the diameter of the through hole of the nitride single crystal having the through hole, and the difference in diameter is preferably 10 μm or more, more preferably 50 μm or more, and 100 μm or more. More preferably, it is 1900 μm or less, more preferably 1500 μm or less, and even more preferably 1000 μm or less.

The strength of the wire is preferably 10 kg / mm ² or more, more preferably 15 kg / mm ² or more, and further preferably 20 kg / mm ² or more. Further, the upper limit value can be 400 kg / mm ² or less, for example. The wire is preferably made of a corrosion-resistant material, such as Pt, Pt alloy, W, W alloy, Ta, Ta alloy, Ti, Ti alloy, Nb, Nb alloy, Ni, Ni alloy, Ag, Ag alloy, A wire made of Au or an Au alloy can be preferably used.

  If a nitride single crystal having a through hole obtained according to the production method of the present invention is used as a seed crystal in nitride crystal growth, the seed crystal can be efficiently positioned by a simpler method as described above. When a seed crystal is fixed in a seed rack or holder as in the prior art, stress is applied to the seed crystal, which may cause distortion or cracking in the seed crystal. Such a problem can be solved by using a nitride single crystal as a seed crystal. In particular, in the case of a seed holder, the contact area with the seed crystal is large, and when the seed rack is taken into the crystal during the crystal growth process, the grown nitride crystal is caused by the difference in thermal expansion between the seed rack and the grown nitride crystal. It was sometimes damaged. Even if a wire that is too thick is used, there is a possibility of breakage, but if a wire of 2.0 mm or less is used, the probability of breakage can be greatly reduced and a good quality crystal can be grown. Also, if the seed crystal is fixed to the fixture, the nitride crystal cannot be grown from the surface of the seed crystal in contact with the fixture, but if positioning such as suspending the nitride single crystal having a through hole is performed. In addition, the entire surface of the seed crystal in the nitride crystal growth can be used effectively, and the yield can be improved. Furthermore, if a nitride single crystal having a through-hole obtained according to the present invention is used as a seed crystal, even a large crystal can be used as a seed crystal in the growth of nitride crystals. A thick wire can also be used. In addition, by widening the region other than the through holes, it is possible to grow a high-quality nitride crystal on the seed crystal.

(Crystal growth)
It is preferable to grow a nitride crystal by a solvothermal method or a liquid phase method on the nitride single crystal having a through-hole installed in the reaction vessel. At this time, it is preferable to grow a nitride crystal on the surface including the main surface of the nitride single crystal having a through hole. A nitride crystal can be grown so as to cover a through-hole of a nitride single crystal having a through-hole, and can be grown so as to cover a wire or the like inserted through the through-hole. . If the diameter of the through hole and the diameter of the wire are within the above preferable ranges, a good quality crystal can be grown without progressing breakage such as cracks from the portion grown so as to cover the through hole and the wire portion. The growth of the nitride crystal on the nitride single crystal having the through hole can be performed until the weight of the nitride crystal to be grown becomes, for example, 10 g or more, preferably 30 g or more, and more preferably 50 g or more. . The upper limit can be determined according to the load resistance of the wire hanging the nitride single crystal having a through hole, the size of the nitride crystal to be finally used, and the like. Growth of nitride crystals on nitride single crystals having through-holes suspended from the wire should be performed in such a range that the weight of the entire nitride crystal after growth does not exceed 1/4 of the load resistance of the wire. Is preferable, it is more preferably performed within a range not exceeding 1/6, and further preferably performed within a range not exceeding 1/10.

  The method of crystal growth is not particularly limited, and examples thereof include solvothermal methods such as ammonothermal method and hydrothermal synthesis method, liquid phase methods such as chemical equilibrium method, temperature difference method, and Na flux method. In the present invention, it is particularly preferable to use an ammonothermal method. “Amonothermal method” is a method for producing a desired material using a dissolution-precipitation reaction of raw materials using a solvent containing nitrogen such as an ammonia solvent in a supercritical state and / or a subcritical state. is there. When the ammonothermal method is applied to crystal growth, crystals are precipitated by generating a supersaturated state due to a temperature difference utilizing the temperature dependence of the solubility of the raw material in the solvent. For example, when ammonia is used as the solvent, crystal growth by the ammonothermal method is a reaction in a high-temperature and high-pressure supercritical ammonia environment, and nitrides into pure ammonia in a supercritical state (for example, group III) Since the solubility of (nitride) is extremely small, a mineralizer is used to improve the solubility and promote crystal growth. A single crystal nitride having a through-hole as a seed crystal, a nitrogen-containing solvent, a raw material, and a temperature and pressure in a reaction vessel containing a mineralizer are changed to a supercritical state and / or a subcritical state. It is preferable to include a step of growing a nitride crystal on the surface of the nitride single crystal having the through-holes under control.

  In the following, a method for producing a nitride crystal using the ammonothermal method will be described in detail, but the crystal growth process using the nitride single crystal having a through hole of the present invention as a seed crystal in nitride crystal growth is described here. It is not limited.

1) Mineralizer A mineralizer generally used in the ammonothermal method can be appropriately selected and used. The mineralizer used may be a basic mineralizer or an acidic mineralizer. Basic mineralizers include alkali metals, alkaline earth metals, compounds containing rare earth metals and nitrogen atoms, alkaline earth metal amides, rare earth amides, alkali nitride metals, alkaline earth metal nitrides, azide compounds, and other hydrazines. Class of salts. Preferably, it is an alkali metal amide, and specific examples include sodium amide (NaNH ₂ ), potassium amide (KNH ₂ ), and lithium amide (LiNH ₂ ). The acidic mineralizer is a compound containing a halogen atom, and examples thereof include ammonium halides. For example, ammonium chloride (NH ₄ Cl), ammonium iodide (NH ₄ I), ammonium bromide (NH ₄ Br) , Ammonium fluoride (NH ₄ F). In the present invention, it is preferable to use an acidic mineralizer containing ammonium halide. Instead of adding the ammonium halide as a mineralizer, it may be added as a hydrogen halide gas. The hydrogen halide gas reacts with ammonia in the reaction vessel to produce ammonium halide. As a mineralizer used here, 1 type may be used independently among the above, or multiple types may be mixed and used for it.

  When performing the crystal growth, aluminum halide, phosphorus halide, silicon halide, germanium halide, zinc halide, arsenic halide, tin halide, antimony halide, bismuth halide, etc. are used in a reaction vessel. May be present.

  The molar concentration of the halogen element contained in the mineralizer with respect to ammonia is preferably 0.1 mol% or more, more preferably 0.3 mol% or more, and further preferably 0.5 mol% or more. The molar concentration of the halogen element contained in the mineralizer with respect to ammonia is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less. If the concentration is too low, the solubility tends to decrease and the growth rate tends to decrease. On the other hand, when the concentration is too high, the solubility tends to be too high and the generation of spontaneous nuclei increases, or the degree of supersaturation becomes too high and control tends to be difficult.

2) Solvent As the solvent used in the ammonothermal method, a solvent containing nitrogen can be used. Examples of the solvent containing nitrogen include a solvent that does not impair the stability of the grown nitride single crystal. Examples of the solvent include ammonia, hydrazine, urea, amines (for example, primary amines such as methylamine, secondary amines such as dimethylamine, tertiary amines such as trimethylamine, and ethylenediamine. Diamine) and melamine. These solvents may be used alone or in combination.

  The amount of water and oxygen contained in the solvent is desirably as small as possible, and the content thereof is preferably 1000 ppm or less, more preferably 10 ppm or less, and further preferably 0.1 ppm or less. When ammonia is used as a solvent, the purity is usually 99.9% or more, preferably 99.99% or more, more preferably 99.999% or more, and particularly preferably 99.9999% or more. .

3) Raw material The raw material containing the element which comprises the nitride crystal which is going to grow on the seed crystal in nitride crystal growth is used. Preferred are polycrystal raw materials for group III nitride crystals and / or metals of group III elements, more preferably gallium nitride and / or gallium. The polycrystalline raw material need not be a complete nitride, and may contain a metal component in which the group III element is in a metal state (zero valence) depending on conditions. For example, when the crystal is gallium nitride Is a mixture of gallium nitride and metal gallium.
The method for producing the polycrystalline raw material is not particularly limited. For example, a nitride polycrystal produced by reacting a metal or an oxide or hydroxide thereof with ammonia in a reaction vessel in which ammonia gas is circulated can be used. In addition, as a metal compound raw material having higher reactivity, a compound having a covalent MN bond such as a halide, an amide compound, an imide compound, or galazan can be used. Furthermore, a nitride polycrystal produced by reacting a metal such as Ga with nitrogen at a high temperature and a high pressure can also be used.

  The amount of water or oxygen contained in the polycrystalline raw material used as the raw material is preferably small. The oxygen content in the polycrystalline raw material is usually 10,000 ppm or less, preferably 1000 ppm or less, particularly preferably 1 ppm or less. The ease of mixing oxygen into the polycrystalline raw material is related to the reactivity with water or the absorption capacity. The worse the crystallinity of the polycrystalline raw material, the more active groups such as NH groups exist on the surface, which may react with water and partially generate oxides or hydroxides. For this reason, it is usually preferable to use a polycrystalline material having as high crystallinity as possible. The crystallinity can be estimated by the half width of powder X-ray diffraction. The half width of the (100) diffraction line (2θ = about 32.5 ° for hexagonal gallium nitride) is usually 0.25 ° or less, preferably It is 0.20 ° or less, more preferably 0.17 ° or less.

4) Reaction vessel The ammonothermal method can be carried out in a reaction vessel.
The reaction vessel can be selected from those capable of withstanding high temperature and high pressure conditions when growing nitride crystals. Examples of the reaction vessel include those described in JP-T-2003-511326 (International Publication No. 01/024921 pamphlet) and JP-T-2007-509507 (International Publication No. 2005/043638 pamphlet). A mechanism that adjusts the pressure applied to the reaction vessel and its contents from the outside may be provided, or an autoclave that does not have such a mechanism may be used.

  The reaction vessel is preferably made of a material having pressure resistance and erosion resistance, and in particular, a Ni-based alloy, stellite (Deroro Stellite Company, Inc.) having excellent erosion resistance against solvents such as ammonia. It is preferable to use a Co-based alloy such as More preferably, it is a Ni-based alloy. Specifically, Inconel 625 (Inconel is a registered trademark of Huntington Alloys Canada Limited, the same applies hereinafter), Nimonic 90 (Nimonic is a registered trademark of Special Metals Wiggin Limited, the same applies hereinafter), RENE41 (Teledyne). Allvac, Inc.), Inconel 718 (Inconel is a registered trademark of Huntington Alloys Canada Limited), Hastelloy (registered trademark of Haynes International, Inc.), Waspaloy (registered trademark of United Technologies, Inc.).

  The composition ratio of these alloys depends on the temperature and pressure conditions of the solvent in the system, and the reactivity with the mineralizers and their reactants contained in the system and / or the oxidizing power / reducing power, pH conditions, What is necessary is just to select suitably. In order to use these as materials constituting the inner surface of the reaction vessel, the reaction vessel itself may be manufactured using these alloys, or a thin film may be formed as an inner cylinder and placed in the reaction vessel. The inner surface of the material of the reaction vessel may be plated.

  In order to further improve the corrosion resistance of the reaction vessel, the inner surface of the reaction vessel may be lined or coated using the excellent corrosion resistance of the noble metal. Moreover, the material of the reaction vessel can be a noble metal. Examples of the noble metal include Pt, Au, Ir, Ru, Rh, Pd, Ag, and alloys containing these noble metals as main components, and among these, it is preferable to use Pt having excellent erosion resistance.

  A specific example of a crystal manufacturing apparatus including a reaction vessel that can be used in a method for manufacturing a nitride crystal is shown in FIG. FIG. 3 is a schematic view of a crystal manufacturing apparatus that can be used in the present invention. In the crystal manufacturing apparatus shown in FIG. 3, crystal growth is performed in a capsule 20 loaded as a reaction vessel in the autoclave 1. The capsule 20 includes a raw material dissolution region 9 for dissolving the raw material and a crystal growth region 6 for growing crystals. A solvent and a mineralizer can be placed in the raw material dissolution region 9 together with the raw material 8, and the seed crystal 7 can be installed in the crystal growth region 6 by suspending it with a wire. Between the raw material dissolution region 9 and the crystal growth region 6, a partition baffle plate 5 is installed in two regions. The baffle plate 5 has a hole area ratio of preferably 2 to 60%, more preferably 3 to 40%. The material of the surface of the baffle plate is preferably the same as the material of the capsule 20 that is a reaction vessel. Further, in order to give more erosion resistance and to purify the crystal to be grown, the surface of the baffle plate is preferably Ni, Ta, Ti, Nb, Pd, Pt, Au, Ir, pBN, Pd, Pt, Au, Ir, and pBN are more preferable, and Pt is particularly preferable. In the crystal manufacturing apparatus shown in FIG. 3, the space between the inner wall of the autoclave 1 and the capsule 20 can be filled with the second solvent. Here, ammonia can be filled as the second solvent while filling the nitrogen gas from the nitrogen cylinder 13 through the valve 10 or confirming the flow rate from the ammonia cylinder 12 with the mass flow meter 14. In addition, the vacuum pump 11 can perform necessary pressure reduction. Note that the crystal production apparatus to be used does not necessarily include a valve, a mass flow meter, and a conduit.

  A lining can also be used to provide corrosion resistance by the autoclave. The lining material is preferably at least one metal or element of Pt, Ir, Ag, Pd, Rh, Cu, Au and C, or an alloy or compound containing at least one metal, More preferably, it is an alloy or compound containing at least one or more metals or elements of Pt, Ag, Cu and C, or at least one or more metals because it is easy to line. For example, Pt simple substance, Pt-Ir alloy, Ag simple substance, Cu simple substance, graphite, etc. are mentioned.

5) Manufacturing process A procedure for growing a nitride crystal by the ammonothermal method will be described. First, a nitride single crystal having a through hole as a seed crystal, a nitrogen-containing solvent, a raw material, and a mineralizer are put in a reaction vessel and sealed. Prior to introducing them into the reaction vessel, the reaction vessel may be deaerated. Moreover, you may distribute | circulate inert gas, such as nitrogen gas, at the time of introduction | transduction of material. The seed crystal is usually charged into the reaction vessel at the same time or after the raw material and the mineralizer are charged. The seed crystal is preferably fixed to a noble metal jig similar to the noble metal constituting the inner surface of the reaction vessel. After loading, heat deaeration may be performed as necessary.

  When the production apparatus shown in FIG. 3 is used, the capsule 20 is sealed with a seed crystal, a nitrogen-containing solvent, a raw material, and a mineralizer in the reaction container 20, and then the capsule 20 is sealed in a pressure-resistant container (autoclave). ) 1 is loaded, and the space between the pressure-resistant vessel and the reaction vessel is preferably filled with a second solvent to seal the pressure-resistant vessel.

  Thereafter, the whole is heated to bring the inside of the reaction vessel into a supercritical state or a subcritical state. In the supercritical state, the viscosity is generally low and it is more easily diffused than the liquid, but has the same solvating power as the liquid. The subcritical state means a liquid state having a density substantially equal to the critical density near the critical temperature. For example, in the raw material filling part, the raw material is melted in a supercritical state, and in the crystal growth part, the temperature is changed so that it becomes a subcritical state, and crystal growth using the difference in solubility between the supercritical state and the subcritical state raw material is also performed. Is possible.

  When in the supercritical state, the reaction mixture is generally maintained at a temperature above the critical point of the solvent. When an ammonia solvent is used, the critical point is a critical temperature of 132 ° C. and a critical pressure of 11.35 MPa. However, if the filling rate with respect to the volume of the reaction vessel is high, the pressure far exceeds the critical pressure even at a temperature below the critical temperature. In the present invention, the “supercritical state” includes such a state exceeding the critical pressure. Since the reaction mixture is enclosed in a constant volume reaction vessel, the increase in temperature increases the pressure of the fluid. In general, if T> Tc (critical temperature of one solvent) and P> Pc (critical pressure of one solvent), the fluid is in a supercritical state.

  Under supercritical conditions, a sufficient growth rate of nitride crystals can be obtained. The reaction time depends in particular on the reactivity of the mineralizer and the thermodynamic parameters, ie temperature and pressure values. During the synthesis or growth of the nitride crystal, the pressure in the reaction vessel is preferably 120 MPa or more, more preferably 150 MPa or more, and further preferably 180 MPa or more. The pressure in the reaction vessel is preferably 700 MPa or less, more preferably 500 MPa or less, further preferably 350 MPa or less, and particularly preferably 300 MPa or less. The pressure is appropriately determined depending on the filling rate of the solvent volume with respect to the temperature and the volume of the reaction vessel. Originally, the pressure in the reaction vessel is uniquely determined by the temperature and the filling rate, but in reality, additives such as raw materials and mineralizers, temperature non-uniformity in the reaction vessel, and free volume Depending on the presence of

  The lower limit of the temperature range in the reaction vessel is preferably 500 ° C or higher, more preferably 515 ° C or higher, and further preferably 530 ° C or higher. The upper limit value is preferably 700 ° C. or lower, more preferably 650 ° C. or lower, and further preferably 630 ° C. or lower. It is preferable that the temperature of the raw material melting region in the reaction vessel is higher than the temperature of the crystal growth region. The temperature difference (| ΔT |) between the crystal growth region and the raw material dissolution region is preferably 5 ° C. or more, and more preferably 10 ° C. or more, from the viewpoint of maintaining crystal quality and controlling spontaneous nucleation crystals. Preferably, it is 100 ° C. or less, more preferably 80 ° C. or less, and particularly preferably 60 ° C. or less. The optimum temperature and pressure in the reaction vessel can be appropriately determined depending on the type and amount of mineralizer and additive used during crystal growth.

  In order to achieve the above temperature range and pressure range in the reaction vessel, the injection rate of the solvent into the reaction vessel, that is, the filling rate, is the free volume of the reaction vessel, that is, the polycrystalline raw material and the seed crystal in the reaction vessel. Subtract the volume of the structure to install the reaction vessel from the volume of the reaction vessel, and if a baffle plate is installed, subtract the volume of the baffle plate from the reaction vessel volume to the boiling point of the remaining volume of solvent. Based on the liquid density, the content is usually 20 to 95%, preferably 30 to 80%, more preferably 40 to 70%.

  Nitride crystal growth in the reaction vessel is maintained in a subcritical or supercritical state of a solvent such as ammonia by heating and heating the reaction vessel using an electric furnace with a thermocouple. Is done. The heating method and the rate of temperature increase to a predetermined reaction temperature are not particularly limited, but are usually performed over several hours to several days. If necessary, the temperature can be raised in multiple stages, or the temperature raising speed can be changed in the temperature range. It can also be heated while being partially cooled.

  The “reaction temperature” is measured by a thermocouple provided so as to be in contact with the outer surface of the reaction vessel and / or a thermocouple inserted into a hole having a certain depth from the outer surface. It can be estimated in terms of temperature. The average value of the temperatures measured with these thermocouples is taken as the average temperature. Usually, an average value of the temperature of the raw material melting region and the temperature of the crystal growth region is defined as the average temperature.

  The reaction time after reaching a predetermined temperature varies depending on the type of nitride crystal, the raw material used, the type of mineralizer, and the size and amount of the crystal to be produced, but is usually several hours to several hundred days. be able to. During the reaction, the reaction temperature may be constant, or the temperature may be gradually raised or lowered. Further, the temperature difference (| ΔT |) may be changed during the reaction. After a reaction time for producing desired crystals, the temperature is lowered. The temperature lowering method is not particularly limited, but the heating may be stopped while the heating of the heater is stopped and the reaction vessel is installed in the furnace as it is, or the reaction vessel may be removed from the electric furnace and air cooled. If necessary, quenching with a refrigerant is also preferably used.

After the temperature of the outer surface of the reaction vessel or the estimated temperature inside the reaction vessel is below a predetermined temperature, the reaction vessel is opened. The predetermined temperature at this time is not particularly limited, and is usually −80 ° C. to 200 ° C., preferably −33 ° C. to 100 ° C. Here, the valve may be opened by connecting a pipe to the pipe connection port of the valve attached to the reaction vessel, leading to a vessel filled with water or the like. Further, if necessary, after sufficiently removing a solvent such as ammonia in the reaction vessel by making a vacuum state, etc., it is dried, and the nitride crystal produced by opening the lid of the reaction vessel and the unreacted raw material or Additives such as mineralizers can be removed.
In the case of manufacturing gallium nitride, JP 2009-263229 A can be preferably referred to for details of materials, manufacturing conditions, manufacturing apparatuses, and processes other than those described above. The entire disclosure of this publication is incorporated herein by reference.

[Nitride crystals]
If the nitride single crystal having a through-hole obtained by the production method of the present invention is used as a seed crystal in nitride crystal growth, a relatively large size nitride crystal can be produced. For example, a nitride crystal having a maximum diameter of 25 mm or more can be produced, preferably a nitride crystal having 50 mm or more can be produced, more preferably a nitride crystal having 75 mm or more can be produced. Is possible.

  The manufactured nitride crystal may be used in a form including a seed crystal and a wire. For example, a nitride single crystal having a through-hole that is a seed crystal in nitride crystal growth or a nitride crystal grown on the surface while including a wire is surface-treated, and is used again as a seed crystal in further nitride crystal growth It is possible. Since the obtained seed crystal is equipped with a wire, a new crystal growth reaction can be easily advanced by fixing the end of the wire to a jig in the reaction vessel or the reaction vessel wall surface. It is also possible to use the crystal after removing the wire by cutting the end of the crystal.

  The grown nitride crystal can be cut into a specific direction to form a wafer (nitride crystal substrate) having a desired main surface. For example, when a nitride crystal having a large and large-diameter M-plane is manufactured by the manufacturing method of the present invention, a large-diameter M-plane wafer can be obtained by cutting in a direction parallel to the M-plane. In addition, when a nitride crystal having a large-diameter semipolar surface is produced, a large-diameter semipolar surface wafer can be obtained by cutting in parallel to the semipolar surface. In addition, when it is desired to obtain a crystal having a particularly high crystal quality, a high-quality crystal can be obtained by cutting out so as to avoid a crystal formed in the vicinity of the through hole.

If a nitride single crystal having a through hole obtained by the production method of the present invention is used as a seed crystal in the growth of nitride crystals, a nitride crystal having a dislocation density of 1 × 10 ⁷ / cm ² or less can be produced. Preferably, a nitride crystal of 1 × 10 ⁵ / cm ² or less can be produced, and more preferably, a nitride crystal of 1 × 10 ³ / cm ² or less can be produced. In addition, a nitride crystal manufactured using a nitride single crystal having a through-hole obtained by the manufacturing method of the present invention as a seed crystal in nitride crystal growth preferably has a feature that the stacking fault density is small. .

  The grown nitride crystal and the above wafer are suitably used for devices such as light emitting elements and electronic devices. Examples of light-emitting elements using nitride crystals and wafers include light-emitting diodes, laser diodes, and light-emitting elements combining these with phosphors. In addition, examples of electronic devices using nitride crystals and wafers include high-frequency elements and high-voltage high-power elements. Examples of the high frequency element include a transistor (HEMT, HBT), and an example of the high breakdown voltage high output element includes a thyristor (IGBT). Since the nitride crystal and wafer of the present invention are characterized by high quality, they are suitable for any of the above applications.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
(1) A circular wafer (main surface area) having a length × width of 5 × 20 mm and a thickness of 530 μm with a main surface of (20-21) plane cut out from a hexagonal GaN single crystal grown by the HVPE method on a carbon plate A substrate of about 100 mm ² GaN single crystal) was fixed using wax. A slurry in which water and SiC powder having a particle diameter of 125 μm were mixed at a ratio of 6: 4 was applied to an arbitrary position including a position of 1 mm inward from the periphery on the substrate. An ultrasonic processing apparatus (product number SOM-121, manufactured by Shinoda Co., Ltd.) having a cylindrical processing tool made of stainless steel (specifically, SUS304) having a flat bottom surface of 300 μm in diameter and made of stainless steel having a length of 20 cm. ) Was pressed against the substrate so as to pass through the applied slurry. The processing tool applied vibration (ultrasound) of 24 kHz and 25 W in the vertical direction to the substrate. FIG. 7 shows the positional relationship among the nitride single crystal, the tool, and the free abrasive grains in the ultrasonic machining apparatus used in Example 1.

(2) After the slurry was discolored, the processing tool was separated from the substrate for several seconds to wait for the chips to be removed from between the tool and the substrate, and then the processing tool was pressed against the substrate again. These operations were repeated at intervals of several seconds until the slurry became a carbon color. The time required for drilling was 31 seconds, and the drilling speed was 17.1 μm / second.

(3) The processing tool was separated from the substrate, and the substrate was washed with water. After cleaning, the penetration of the hole was confirmed using a digital microscope (manufactured by KEYENCE, Inc., VHX-900), and a hole with an average diameter of 410 μm penetrated from the periphery to the inside at a position of 1 mm, and no crack was generated. . In addition, 70% or more of the through holes in the thickness direction had a diameter in the above average diameter range. The aspect ratio of the through hole was 0.93, and some chipping around the through hole was observed. Details of the shape of the obtained through hole are shown in Table 1, FIG. 4 and FIG.
The maximum diameter and the minimum diameter of the through hole were measured by the above digital microscope, and the aspect ratio (minimum diameter / maximum diameter of the through hole) was calculated based on the obtained value. The average diameter of the through holes inside the nitride single crystal having the through holes was measured and calculated by the following method.
The workpiece was broken along a straight line passing through the through-hole, and the diameter of the through-hole inside the crystal was measured from the cross section with a digital microscope. Five diameters of the through holes were measured at equal intervals in the thickness direction from the substrate surface, and the arithmetic average of the five points was taken as the average diameter of the through holes.
It was confirmed by the digital microscope that 70% or more of the through holes in the thickness direction had a diameter in the range of the average diameter of the through holes inside the nitride single crystal having the through holes. In addition, the average diameter of the through-holes in the nitride single crystal having through-holes may coincide with the average diameter W _102b of the through-holes in the surface surface opposite to the tool of the nitride single crystal having through-holes. confirmed.

[Example 2]
Ultrasonic processing was performed in the same manner as in Example 1 except that the output was 15 W.
The processing tool was separated from the substrate, and the substrate was washed with water. After cleaning, when the penetration of the hole was confirmed using a digital microscope (manufactured by KEYENCE, VHX-900), a hole with an average diameter of 374 μm penetrated from the periphery to the inside at a position of 1 mm, and no crack was generated. . In addition, 70% or more of the through holes in the thickness direction had a diameter in the above average diameter range. The aspect ratio of the through hole was 0.83, and there was little work-affected layer (chipping) around the through hole. The other features of the shape of the through hole were almost the same as in Example 1.

[Example 3]
(1) A circular wafer (main surface area) having a length × width of 5 × 20 mm and a thickness of 530 μm having a main surface of (10-10) plane cut out from a hexagonal GaN single crystal grown by HVPE on a carbon plate About 100 mm ² substrate was fixed with wax using the same manner as in Example 1. Water and SiC powder were added at a ratio of 6: 4 at any position including 1 mm inward from the periphery on the substrate. The mixed slurry was applied, and the processing tool applied with vibrations (ultrasonic waves) of 24 kHz and 25 W using the ultrasonic processing apparatus used in Example 1 was pressed against the substrate so as to pass the applied slurry. The SiC powder used had a primary particle size of 36 μm.

(2) After the slurry was discolored, the processing tool was separated from the substrate for several seconds to wait for the chips to be removed from between the tool and the substrate, and then the processing tool was pressed against the substrate again. This operation was repeated at intervals of several seconds until the slurry became a carbon color.

(3) The processing tool was separated from the substrate, and the substrate was washed with water. After cleaning, the penetration of the holes was confirmed using a digital microscope (manufactured by Keyence Corporation, VHX-900). As a result, holes with an average diameter of 402 μm penetrated from the periphery to the inside at a position of 1 mm, and no cracks were generated. In addition, 70% or more of the through holes in the thickness direction had a diameter in the above average diameter range. The aspect ratio of the hole was 0.95, and the work-affected layer (chipping) around the hole was remarkable. The other features of the shape of the through hole were almost the same as in Example 1.

[Example 4]
Ultrasonic machining was performed in the same manner as in Example 3 except that the output was 15 W.
The processing tool was separated from the substrate, and the substrate was washed with water. After cleaning, the penetration of the hole was confirmed using a digital microscope (manufactured by KEYENCE, VHX-900). As a result, a hole with an average diameter of 387 μm penetrated from the periphery to the inside at a position of 1 mm, and no crack was generated. In addition, 70% or more of the through holes in the thickness direction had a diameter in the above average diameter range. The aspect ratio of the hole was 0.87, and the work-affected layer (chipping) around the hole was remarkable. The other features of the shape of the through hole were almost the same as in Example 1.

[Example 5]
(1) A circular wafer (major surface area of about 1963.5 mm ² ) substrate having a diameter of 50 mm and a thickness of 530 μm having a (0001) plane as a main surface cut from a hexagonal GaN single crystal grown by the HVPE method on a carbon plate Was fixed with wax. As in Example 1, slurry mixed with water and SiC powder having a particle size of 125 μm at a ratio of 6: 4 was applied to any position including 1 mm from the periphery to the inside on the substrate. Using the ultrasonic processing apparatus used, the processing tool applied with vibrations (ultrasonic waves) of 24 kHz and 25 W was pressed against the substrate so as to pass the applied slurry.

(2) After the slurry was discolored, the processing tool was separated from the substrate for several seconds to wait for the chips to be removed from between the tool and the substrate, and then the processing tool was pressed against the substrate again. This operation was repeated at intervals of several seconds until the slurry became a carbon color.

(3) The processing tool was separated from the substrate, and the substrate was washed with water. After cleaning, when the penetration of the hole was confirmed using a digital microscope (manufactured by KEYENCE, VHX-900), a hole with an average diameter of 393 μm penetrated from the periphery to the inside at a position of 1 mm, and no crack was generated. In addition, 70% or more of the through holes in the thickness direction had a diameter in the above average diameter range. The aspect ratio of the hole was 0.95, and a work-affected layer (chipping) around the hole was somewhat observed. The other features of the shape of the through hole were almost the same as in Example 1.

[Example 6]
Ultrasonic machining was performed in the same manner as in Example 5 except that the output was 15 W.
The processing tool was separated from the substrate, and the substrate was washed with water. After cleaning, the penetration of the hole was confirmed using a digital microscope (manufactured by KEYENCE, VHX-900). As a result, a hole with an average diameter of 384 μm penetrated from the periphery to the inside at a position of 1 mm, and no crack was generated. In addition, 70% or more of the through holes in the thickness direction had a diameter in the above average diameter range. The aspect ratio of the hole was 0.87, and there was little work-affected layer (chipping) around the hole. The other features of the shape of the through hole were almost the same as in Example 1.

[Comparative Example 1]
(1) A circular wafer (major surface area of about 1963.5 mm ² ) substrate having a diameter of 50 mm and a thickness of 530 μm having a (0001) plane as a main surface cut from a hexagonal GaN single crystal grown by the HVPE method on a carbon plate The substrate was fixed using wax.

(2) The injection port of the blasting apparatus was installed at a position 1 cm from the substrate surface and 90 ° with respect to the substrate surface, and blasting was performed for 30 seconds. At this time, the abrasive grain size of the blast is 50 μm, and the pressure air is 0.4 MPa. Details of the blasting apparatus used are shown in FIG.

(3) Although a crater-like depression occurred on the substrate surface, no through hole was opened.

  The results obtained in each example and comparative example are summarized in Table 1 below. In addition, all the peeling area | regions formed in Examples 1-6 were confirmed by microscopic observation at 100 times.

<Example 7>
Using the apparatus shown in FIG. 3, GaN crystal growth was performed by the ammonothermal method according to the following procedure.

  Crystal growth was performed using the RENE41 autoclave 1 with an inner dimension of 70 mm in diameter and a length of 1050 mm as a pressure vessel, and a Pt-Ir capsule 20 with an inner dimension of 59 mm in diameter and a length of 950 mm as a reaction vessel. As a raw material, 1500 g of polycrystalline GaN particles were weighed and placed in the capsule lower region (raw material dissolution region 9 in FIG. 3). Next, sufficiently dried ammonium iodide having a purity of 99.999% and gallium fluoride having a purity of 99.999% were charged into the capsule as a mineralizer.

Further, a platinum baffle plate 5 was installed between the raw material dissolution region 9 at the lower part of the capsule and the crystal growth region 6 at the upper part. As a seed crystal, the nitride single crystal having a through hole manufactured in Example 1 was used. A platinum wire (strength 14 kg / mm ² ) having a diameter of 200 μm was passed through a through-hole having a diameter of 410 μm formed at a position of 1 mm inward from the periphery of the nitride single crystal having the through-hole. A platinum wire was tied to a seed support frame made of a platinum alloy, and a nitride single crystal having a through hole was fixed to be suspended. At this time, the nitride single crystal having a through hole was positioned so as to be near the center of the horizontal position of the support frame so as not to touch the seed support frame. After this seed support frame was placed in the crystal growth region, a cap with an ammonia-filled tube was connected to the top of the capsule by welding. After that, the inside of the capsule is vacuum deaerated using a vacuum pump through a tube, the inside of the capsule is purged with nitrogen gas five times, and then the capsule is numbered with a band heater installed on the outer wall of the capsule while being connected to the vacuum pump. The adsorbed gas and moisture in the capsule were removed by heating for a period of time.

  Subsequently, the capsule was filled with ammonia while being cooled with dry ice ethanol, the tube was sealed, and the capsule was sealed.

  The capsule 20 was inserted into the autoclave 1 and the autoclave lid was closed. After degassing the inside of the autoclave and purging with nitrogen gas multiple times, based on the flow control while cooling the autoclave with dry ice ethanol, the amount of ammonia that balances the amount of ammonia in the capsule is separated in the autoclave and the capsule. The gap was filled.

  Subsequently, the autoclave 1 was housed in an electric furnace composed of a heater divided into two parts in the vertical direction. The temperature of the crystal growth region of the autoclave measured by a thermocouple inserted at a depth of 19 mm from the outer wall of the autoclave was 585 ° C., and the temperature of the raw material dissolution region measured by a thermocouple inserted at a depth of 19 mm was 630 ° C. (temperature difference) (45 ° C .: average temperature 607 ° C.). After reaching the set temperature, the temperature was maintained for 20 days. The pressure in the autoclave was 210 MPa.

After completion of the crystal growth, the autoclave was cooled and ammonia outside the capsule and inside the capsule was discharged. The obtained nitride crystals were each suspended from a seed support frame by a platinum wire. In order to take out the obtained nitride crystal, the seed support frame was manually pulled up. The weight of the grown nitride crystal was 34.6 g. The platinum wire used for suspending the nitride single crystal having a through hole was partially buried in the obtained nitride crystal, but defects such as cracks that could be visually confirmed from the portion were not confirmed. The through hole was closed, and the occurrence of cracks that could be visually confirmed from here was not confirmed.
In addition, when the nitride single crystal having through holes manufactured in Examples 2 to 6 is used as a seed crystal in nitride crystal growth, crystal formation can be performed in the same manner as in Example 7, and the obtained nitride In the product crystal, the through-hole was blocked, and generation of cracks that could be visually confirmed was not confirmed.

101 Nitride single crystal (substrate)
102 Through-hole w _102a Average diameter of the through-hole in the plane of the surface of the nitride single crystal that first comes into contact with the tool w _102b Average diameter of the through-hole d inside the crystal d _102a Depth of the through-hole 103 Main nitride single crystal surface 111 nitride single crystal of the periphery w ₁₁₁ distance from the periphery of the nitride single crystal to bore end closest to the nitride single crystal periphery of the through hole 112 near the peripheral edge region 113 intermediate area 114 central region 115 side anyone w ₁₁₅ face anyone Width d ₁₁₅ Depth of surface dripping 116 Processed altered layer d ₁₁₆ Processed altered layer depth 117 Peeling area w ₁₁₇ Peeling area width d ₁₁₇ Peeling area height (depth)
201 Tool 202 Free abrasive grains (slurry dispersed in lubricating liquid)
203 Vibration direction of tool 204 Injection port 205 Abrasive grain (compressed air containing abrasive grains may be used)
DESCRIPTION OF SYMBOLS 1 Autoclave 2 Autoclave inner surface 3 Lining 4 Lining inner surface 5 Baffle plate 6 Crystal growth region 7 Seed crystal (seed)
8 Raw material 9 Raw material melting area 10 Valve 11 Vacuum pump 12 Ammonia cylinder 13 Nitrogen cylinder 14 Mass flow meter 20 Capsule 21 Capsule inner surface

Claims (15)

  A loose abrasive is interposed between the main surface of the nitride single crystal having a thickness of 100 to 1000 μm and the tool, and at least one of the nitride single crystal and the tool is pressed while ultrasonically vibrating the tool. The nitride single crystal having a through hole is formed by drilling the nitride single crystal in the thickness direction and forming a through hole having a diameter in the range of 200 to 600 μm at 70% or more of the thickness direction. Production method.   The method for producing a nitride single crystal having a through hole according to claim 1, wherein the nitride single crystal is a gallium nitride single crystal.   The manufacturing method of the nitride single crystal which has a through-hole of Claim 1 or 2 whose said free abrasive grain is the slurry by which the abrasive grain was disperse | distributed in the lubricating liquid.   It controls so that ratio (minimum diameter / maximum diameter) with respect to the length of the maximum diameter of the length of the minimum diameter of the said through-hole may be set to 0.5-1. A method for producing a nitride single crystal having a through hole.   The ratio of the area of the through hole in the surface of the nitride single crystal opposite to the tool side to the area of the through hole in the surface of the nitride single crystal on the tool side (opposite to the tool) The through-hole according to any one of claims 1 to 4, which is controlled so that the area of the through-hole on the surface on the side / the area of the through-hole on the surface on the tool side) is 0.5-1. A method for producing a nitride single crystal.   The manufacture of a nitride single crystal having a through-hole according to any one of claims 1 to 5, wherein a width of a fringe region on the surface on the tool side of the nitride single crystal is controlled to be within 100 µm. Method.   The nitride single crystal having a through hole according to any one of claims 1 to 6, which is controlled so that a separation region having a width of 500 µm or less is formed on a surface of the nitride single crystal on the tool side. Manufacturing method. The manufacturing method of the nitride single crystal which has a through-hole as described in any one of Claims 1-7 whose area of the main surface of the said nitride single crystal is 50 mm < ² > or more.   The manufacturing method of the nitride single crystal which has a through-hole as described in any one of Claims 1-8 which forms a through-hole in the area | region of 500-10000 micrometers inside from the periphery of the said nitride single crystal.   The manufacturing method of the nitride single crystal which has a through-hole as described in any one of Claims 1-9 using the tool in which the shape of the bottom part by the side of the said nitride single crystal is a plane or a convex type as the said tool.   The manufacturing method of the nitride single crystal which has a through-hole as described in any one of Claims 1-10 whose maximum width of the projection image to the surface at the side of the said nitride single crystal of the said tool is 100-1500 micrometers. .   The manufacturing method of the nitride single crystal which has a through-hole as described in any one of Claims 1-11 whose said abrasive grain is SiC.   The method for producing a nitride single crystal having a through hole according to any one of claims 1 to 12, wherein a direction in which the tool is ultrasonically vibrated is a direction toward a main surface of the nitride single crystal.   The manufacturing method of the nitride single crystal which has a through-hole as described in any one of Claims 1-13 whose main surface of the said nitride single crystal is a nonpolar surface or a semipolar surface.   A nitride single crystal having a through-hole, which is manufactured by the manufacturing method according to claim 1.

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