JP6547552B2 - C-plane GaN wafer and C-plane GaN wafer manufacturing method - Google Patents

Description

  The present invention relates to a C-plane GaN wafer and a C-plane GaN wafer manufacturing method. C-plane GaN wafers are mainly used as substrates for nitride semiconductor devices.

The nitride semiconductor is also referred to as a nitride-based III-V compound semiconductor, a group III nitride-based compound semiconductor, a GaN-based semiconductor, etc. And the like, including compounds in which part or all of Ga of GaN is substituted with another periodic table group 13 element (B, Al, In). The nitride semiconductor has a wurtzite crystal structure belonging to a hexagonal system.
A nitride semiconductor device is a semiconductor device in which the main part of the device structure is formed of a nitride semiconductor, and includes a light emitting device such as an LED or LD (laser diode) and an electronic device such as a HEMT or a MOSFET.

The C-plane GaN wafer is a single crystal wafer composed only of GaN, and its main surface is parallel to the C plane or slightly inclined from the C plane.
The C plane of GaN includes a (0001) plane which is a gallium polar plane and a (000-1) plane which is a nitrogen polar plane. The main surface of the C-plane GaN substrate has a gallium polar surface on one side and a nitrogen polar surface on the opposite side. In the manufacture of nitride semiconductor devices, a device structure is usually formed by epitaxially growing a nitride semiconductor thin film on the gallium polar surface of a C-plane GaN wafer.

In Patent Document 1 (Japanese Patent Laid-Open No. 2008-28259), a single crystal GaN is sliced to obtain a wafer, and then a wet etching is performed by wet etching before polishing and planarizing the main surface of the wafer. A C-plane GaN wafer fabrication method is disclosed for removal.
Patent Document 2 (Japanese Patent Laid-Open No. 2007-153712) discloses, as a method of roughening the nitrogen-polar surface of a C-plane GaN wafer, a method of wet-etching after polishing and planarizing the nitrogen-polar surface.
Patent Document 3 (Japanese Patent Laid-Open No. 2011-121803) discloses that after the nitrogen polar surface of a C-plane GaN wafer is polished and planarized, the non-volatile organic matter can be attached and then wet etching can be more uniformly roughened. It is done.
The nitrogen polarity surface of the C-plane GaN wafer roughened by wet etching becomes a matte surface. When the gallium polar face is mirror finished and the nitrogen polar face is matted, these two main surfaces can be visually distinguished (Patent Document 4).

JP 2008-28259 A JP 2007-153712 A JP, 2011-121803, A Unexamined-Japanese-Patent No. 2007-297263

The inventors of the present invention tried to wet-etch the as-sliced nitrogen polar surface to perform a matte finish in order to more efficiently manufacture a C-plane GaN wafer having the nitrogen polar surface as a matte surface. However, the result was not good and uneven appearance was clearly observed on the nitrogen polarity surface after etching. As a result of examination by SEM, it was found that smooth portions and rough portions are mixed in this nitrogen polar surface, and the ratio of the mixed portions is not uniform in the surface, which is the cause of the appearance unevenness.
Furthermore, wet organic etching was performed after depositing nonvolatile organic matter on the nitrogen-polar surface of as slice, and the results were similar.

  The present invention has been completed in the course of experiments and studies conducted by the present inventors in order to solve the above problems, and its main purpose is to suppress the appearance unevenness of the nitrogen polar surface, which is considered to be a matte surface. It is an object of the present invention to provide a planar GaN wafer and a method of manufacturing such a C-plane GaN wafer.

Embodiments of the present invention include the following.
(1) A C-plane GaN wafer in which the nitrogen polar surface is a matte surface, and the area of the smooth region on the nitrogen polar surface is A _S and the area of the rough region on the nitrogen polar surface is A _r A C-plane GaN wafer characterized in that the area ratio A _S / (A _S + A _r ) is less than 3%.
(2) The C-plane GaN wafer according to (1), in which projections uneven in shape and size are irregularly arranged in the rough region.
(3) The C-plane GaN wafer according to (1) or (2), which has a facet growth region and a C-plane growth region on the nitrogen polar surface.
(4) A method of manufacturing a C-plane GaN wafer in which the nitrogen polar surface is a matte surface, which is (i) the first main surface which is the main surface on the [0001] side and the main surface on the [000-1] side. A first step of preparing a GaN wafer having a second main surface; and (ii) forming a rough area and a smooth area by wet etching on the second main surface of the GaN wafer prepared in the first step. And (iii) the second main surface after the second step has been carried out, is subjected to a treatment to deposit non-volatile organic matter, and then is wet-etched to form the smooth region formed in the second step. A third step of roughening.
(5) The method according to (4), wherein the second main surface of the GaN wafer prepared in the first step is an as-sliced surface, and the second step includes wet etching the as-sliced surface.
(6) the C-plane area of A _S of smooth regions in the N-polar surface is a matte surface of the GaN wafer, when the area of the crude region in the nitrogen-polar surface was A _r, the area ratio of the smooth region A _S / ( The production method according to (4) or (5) above, wherein A _S + A _r ) is less than 3%.
(7) The manufacturing method according to (6), wherein the C-plane GaN wafer has a facet growth region and a C-plane growth region on a nitrogen polar surface which is the mat surface.
(8) A method of manufacturing a C-plane GaN wafer in which the nitrogen polar surface is a matte surface, the first main surface being the main surface on the [0001] side and the second main surface being the main surface on the [000-1] side. A method of manufacturing, comprising: a wafer preparation step of preparing a GaN wafer having a surface; and a wet etching step including etching the second major surface of the prepared GaN wafer with an aqueous ammonia solution at room temperature.
(9) the C-plane area of A _S of smooth regions in the N-polar surface is a matte surface of the GaN wafer, when the area of the crude region in the nitrogen-polar surface was A _r, the area ratio of the smooth region A _S / ( The production method according to the above (8), wherein A _S + A _r ) is less than 3%.

  According to the present invention, there are provided a C-plane GaN wafer in which the appearance unevenness of the nitrogen polar surface, which is a matte surface, is suppressed, and a method of manufacturing the C-plane GaN wafer.

FIG. 1 shows the appearance of a C-plane GaN wafer, FIG. 1 (a) is a perspective view, and FIG. 1 (b) is a side view. FIG. 2 is a drawing for explaining how a facet growth region and a C-plane growth region are formed on the main surface of a C-plane GaN wafer. FIG. 3 is an SEM image of the nitrogen polar surface of a C-plane GaN wafer. FIG. 4 is a plan view for explaining nine positions on the nitrogen polarity surface where the area ratio of the smooth area is measured. FIG. 5 is an optical image of the nitrogen polar surface of a C-plane GaN wafer. FIG. 6 is an optical image of the nitrogen polar surface of a C-plane GaN wafer. FIG. 7 is an SEM image of the nitrogen polar surface of a C-plane GaN wafer.

Preferred embodiments of the present invention are described in detail below.
1. C-plane GaN Wafer The C-plane GaN wafer according to the present invention typically has a disk shape, as shown in FIG. 1 (a) is a perspective view, and FIG. 1 (b) is a side view.
Referring to FIG. 1, C-plane GaN wafer 10 has gallium polar surface 11 which is the main surface on the [0001] side, nitrogen polar surface 12 which is the main surface on the [000-1] side, and side surface 13. doing.
The diameter of the C-plane GaN wafer 10 is 45 mm or more, and usually 305 mm or less. Typical diameters are 45-55 mm (about 2 inches), 95-105 mm (about 4 inches), 145-155 mm (about 6 inches), 195-205 mm (about 8 inches), and so on.

The C-plane GaN wafer is required to have a strength that does not cause handling problems, so its thickness is preferably 250 μm or more, more preferably 300 μm or more. Depending on the diameter, it can also be thicker.
Chamfering for smoothing the boundary between the gallium polarity surface 11 and the side surface 13 can be appropriately performed as needed. The same applies to the boundary between the nitrogen polarity surface 12 and the side surface 13.
The C-plane GaN wafer 10 can further be provided with an orientation flat that indicates the crystal orientation.

The main surface of the C-plane GaN wafer 10 may be parallel to the C-plane of the GaN crystal or may be slightly inclined from the C-plane. The angle of this inclination is called off angle.
The inclination direction in the case of inclining the gallium polar face from the C face can be arbitrarily determined according to the purpose, but preferably, it is a direction within ± 5 degrees centered on the <10-10> direction, or 11-20> A direction within a range of ± 5 degrees centered on the direction. The absolute value of the off angle is usually 0.1 degrees or more, preferably 0.2 degrees or more, and usually 10 degrees or less.

The gallium polar surface 11 of the C-plane GaN wafer 10 is a main surface used for epitaxial growth of a nitride semiconductor, and is mirror-finished. For example, the RMS roughness of the gallium polar surface 11 measured by AFM is usually less than 5 nm, preferably less than 2 nm, more preferably less than 1 nm in a measurement range of 10 μm × 10 μm.
On the other hand, the nitrogen polarity surface 12 is a matte surface. In the nitrogen polar surface 12, Ra is preferably 0.1 μm to 5 μm.

On the nitrogen polarity surface 12 of the C-plane GaN wafer 10, there is a rough region which is a region in which fine protrusions gather without gaps. Since the projections in the rough area are formed by wet etching, they are not uniform in shape and size, and irregular in arrangement. One of the advantages of the wet etching method is that the cost of the process of finishing the nitrogen polar surface can be kept low because the number of wafers that can be processed at one time is relatively large.
Although it is desirable that only the rough region is present on the nitrogen polar surface 12 of the C-plane GaN wafer 10, the presence of a smooth region which is a flat region without projections can be tolerated if it is slight.
The area ratio A _S / (A _S + A _r ) of the smooth area in the nitrogen polar plane [where, A _S is the area of the smooth area and A _r is the area of the rough area] is less than 3%, preferably Is less than 2%, even less than 1%, even less than 0.5%, even less than 0.2% (including 0%).

The area ratio of the smooth area in the nitrogen polarity plane can be determined, for example, using a digital microscope (model number: VHX-900) manufactured by Keyence Corporation.
Specifically, an optical image of a nitrogen polar surface is acquired with a resolution of about 3 μm ² (about 1.7 μm square to about 1.8 mm square) in size of one pixel. Then, it is determined whether each pixel belongs to the smooth area or the rough area. Then, the ratio of the number of pixels belonging to the smooth area to the total number of pixels can be regarded as the area ratio of the smooth area.

The attribution of each pixel can be determined as follows.
For example, in an optical image obtained using epi-illumination, smooth areas appear bright and bright, while coarse areas are relatively dark. This is because the smooth area reflects the illumination light in the direction of the imaging device, while the rough area scatters the illumination light.
Therefore, a threshold is set to the luminance of the pixel of the optical image as a criterion, and all the pixels are pixels whose luminance reaches the threshold (first group; bright pixels) and pixels which do not reach (second group; dark pixel) Divided into two groups. That is, it is binarization. Then, when the color of the pixels belonging to the first group is changed to white and the color of the pixels belonging to the second group is changed to black, the original image is converted to a binarized image.
By comparing the binarized image with the original image, the above-described setting of the threshold is adjusted so that the smooth area recognized in the original image corresponds to the white portion in the binarized image. Then, the ratio of the number of pixels belonging to the first group to the total number of pixels is the same as the area ratio of the smooth area.
In an optical image obtained using epi-illumination, the difference in brightness between the smooth area and the rough area is quite clear, so slight differences in the set threshold do not cause large fluctuations in measurement results. Therefore, the area ratio of the smooth area can be determined with good reproducibility.

The C-plane GaN wafer 10 can be made n-type conductive by doping with n-type impurities such as oxygen, silicon, germanium and the like.
In another aspect, the C-plane GaN wafer 10 can be made insulator by doping with iron.
In still another aspect, the C-plane GaN wafer 10 can be made p-type conductive by doping with p-type impurities such as magnesium and zinc.

In one example, a facet growth region and a C-plane growth region may exist in the gallium polar surface 11 of the C-plane GaN wafer 10. The same applies to the nitrogen polarity surface 12.
The facet growth region and the C-plane growth region are structures found in a C-plane GaN wafer cut out of a c-axis grown GaN crystal in a growth mode in which pits are generated on the growth surface (the surface of the GaN crystal in the middle of growth). is there.
FIG. 2A shows a state in which a pit is generated on the growth surface of the c-axis-grown GaN crystal. Thereafter, as shown in FIG. 2 (b), when the growth is continued so as to maintain the presence of the pits, a GaN crystal including a facet growth portion fg and a C-plane growth portion cg is formed. The facet growth portion fg is a portion formed by growth on the inclined facet, and the C-plane growth portion cg is a portion formed by growth on the C-plane facet.

  When the GaN crystal including the facet growth portion fg and the C-plane growth portion cg is sliced, as shown in FIG. 2C, a C-plane substrate having a facet growth region Rf and a C-plane growth region Rc on the main surface is obtained. The facet growth region Rf is a region in which the facet growth portion fg is exposed, and the C-plane growth region Rc is a region in which the C-plane growth portion cg is exposed. The facet growth portion fg and the C-plane growth portion cg are exposed to the gallium polarity surface and the nitrogen polarity surface.

The impurity concentration and the carrier concentration are usually different between the facet growth region and the C-plane growth region.
For example, since oxygen is hardly taken into the C-plane growth portion of the GaN crystal, the concentration in the facet growth region is higher than that in the C-plane growth region. In an extreme case, the oxygen concentration in the facet growth region may exceed 1 × 10 ¹⁸ cm ⁻³ while the oxygen concentration in the C-plane growth region may be less than 1 × 10 ¹⁷ cm ⁻³ .
In contrast, silicon tends to have a higher concentration of C-plane growth regions than facet growth regions.
From the difference between the impurity concentration and the carrier concentration, the surface properties may not be the same between the facet growth region and the C-plane growth region. The properties of the surface include the adsorption of organic substances and the resistance to etching.

The C-plane GaN wafer according to the embodiment can be used as a substrate for manufacturing various nitride semiconductor devices. The device structure is formed by vapor phase epitaxial growth of one or more nitride semiconductors on a C-plane GaN wafer. As a preferable vapor phase epitaxial growth method, MOCVD method, MBE method, pulse vapor deposition method etc. suitable for thin film formation are exemplified.
Specific examples of nitride semiconductor devices include light emitting diodes, light emitting devices such as laser diodes, rectifiers, bipolar transistors, field effect transistors, electronic devices such as HEMTs (High Electron Mobility Transistors), temperature sensors, pressure sensors, radiation sensors, There are semiconductor sensors such as visible-ultraviolet light detectors, surface acoustic wave (SAW) devices, vibrators, resonators, oscillators, micro electro mechanical system (MEMS) parts, voltage actuators, solar cells, and the like.

2. FIELD OF THE INVENTION Another aspect of the present invention relates to a method of manufacturing a C-plane GaN wafer, and more particularly to a method of manufacturing a C-plane GaN wafer in which the nitrogen polar surface is a matte surface.
The C-plane GaN wafer manufacturing method according to the embodiment includes first to third steps shown in the following (i) to (iii).
(I) In the first step, a GaN wafer having a first main surface which is a [0001] side main surface and a second main surface which is a [000-1] side main surface is prepared.
(Ii) In the second step, rough and smooth regions are formed by wet etching on the second main surface of the GaN wafer prepared in the first step.
(Iii) In the third step, the second main surface after the second step has been carried out is treated to adhere non-volatile organic matter and then subjected to wet etching to form in the second step Roughen the smooth area.

In the first step, a GaN wafer can be prepared, for example, by slicing separately grown bulk GaN crystals parallel or substantially parallel to the C-plane. The growth method of the bulk GaN crystal is not limited, and may be HVPE method, Na flux method, ammonothermal method, or any combination of these methods. The bulk GaN crystal may be a crystal grown c-axis in a growth mode in which a pit is generated on the growth surface by the HVPE method.
The GaN wafer thus prepared has a first main surface which is a main surface on the [0001] side and a second main surface which is a main surface on the [000-1] side. The first major surface is a gallium polar surface, and the second major surface is a nitrogen polar surface.

In the second step, the GaN wafer prepared in the first step is subjected to wet etching. As an etching liquid used by wet etching, alkaline aqueous solutions, such as NaOH aqueous solution and KOH aqueous solution, or the mixed liquid of hydrochloric acid and a hydrogen-peroxide solution is illustrated preferably.
By wet etching, the second main surface of the GaN wafer, that is, the nitrogen polar surface is roughened, but the entire area is not rough, and rough and smooth areas are formed. In order to reduce the area ratio of the smooth region, the second main surface may be mirror-polished and a non-volatile organic material may be attached before the second step. However, there is a disadvantage that the number of steps increases.

In the third step, the second main surface after the second step has been performed is subjected to a process of depositing a non-volatile organic substance and then subjected to wet etching. Thereby, the smooth area formed on the second main surface in the second step is roughened.
The non-volatile organic substance mentioned here is preferably a polymer compound, and specific examples include latex rubber, polystyrene, polycarbonate and wax. In order to attach these non-volatile organic substances to the second main surface of the GaN wafer, an organic solvent in which the non-volatile organic substances are dissolved or dispersed may be applied to the second main surface and dried. Preferred examples of combinations of organic solvents and nonvolatile organic substances include isopropyl alcohol and wax, acetone and wax, acetone and polystyrene, acetone and polycarbonate, acetone and latex rubber and the like.

An ammonia solution is preferably exemplified as an etching solution used in wet etching.
For example, after the process of depositing the wax, if etching is performed for 40 hours or more using an aqueous ammonia solution at normal temperature, it is possible to make substantially all of the smooth area present on the second main surface a rough area.

The timing to process the first main surface (gallium polar surface) which is the main surface on the [0001] side of the GaN wafer prepared in the first step is not particularly limited, and it is before and after the second step It may be any, and may be before or after the third step.
Examples of processing that can be performed on the first main surface include grinding and lapping (any one or both) for planarization, and CMP and etching (any one for removing damaged layers formed during planarization). Or both), CMP and etching (either or both) for planarization after planarization and the like.

In one example, the process of attaching the non-volatile organic substance to the second main surface (nitrogen polar surface) of the GaN wafer included in the third step is processing (grinding, polishing, CMP of the first main surface (gallium polar surface) Etc.).
Specifically, after the second step, a step of processing the first main surface of the GaN wafer is arranged, and in the step of processing the first main surface, wax is applied to the second main surface (nitrogen polar surface) The wax is used as an adhesive to fix the GaN wafer on a flat plate. When processing of the first major surface is complete, the wax is softened to remove the GaN wafer from the plate and then the second major surface is wet etched. If necessary, the GaN wafer can be cleaned with an organic solvent prior to wet etching to remove excess wax deposited on the second major surface.

3. Experimental Results The results of experiments conducted by the present inventors are described below.
3.1. Experiment 1 (comparative example)
The bulk GaN crystal c-axis grown in the growth mode in which pits are generated on the growth surface by the HVPE method is sliced approximately parallel to the C plane to obtain a disk-shaped C-plane GaN wafer having a diameter of 100 mm. A facet growth region and a C-plane growth region were present on the main surface of this C-plane GaN wafer.
The as-sliced C-plane GaN wafer was subjected to a cleaning process including ultrasonic cleaning, and then dried once, and then a process of depositing non-volatile organic matter on the nitrogen polar surface was performed. In the process of depositing the non-volatile organic matter, the C-plane GaN wafer was dipped in a dispersion of latex rubber dispersed in acetone and dried.
Next, the C-plane GaN wafer was immersed in a 48 wt% KOH aqueous solution at 100 ° C. for 30 minutes to etch the nitrogen polar surface.
After etching, the C-plane GaN wafer was attached to a flat ceramic plate. At the time of affixing, a nitrogen polarity surface of the C-plane GaN wafer was adhered to the surface of the ceramic plate using a wax [Shift Wax 679 manufactured by Nikshin Seiko Co., Ltd.].
Next, grinding, lapping and CMP were sequentially applied to the gallium polar surface of the C-plane GaN wafer attached to the ceramic plate.

After the CMP process, the wax was softened, the C-plane GaN wafer was removed from the ceramic plate, washed with isopropanol, and then washed with an aqueous solution of hydrofluoric acid.
As a result of SEM observation of the nitrogen polar surface of the C-plane GaN wafer completed in this way, a rough area and a smooth area were observed as shown in FIG. The rough region is a portion where protrusions are densely packed, and the smooth region is a flat portion where no protrusions are observed (in the SEM image of FIG. 3, a portion where dark color appears is a smooth region).
The projections in the rough area are not uniform in shape and size, and their arrangement is irregular.
The smooth area is at a lower position than the protrusions, which suggests that the surface is etched and smoothed.

Next, on each of nine places (the distance between adjacent measurement points is 2 cm) selected as P _{1 to} P ₉ shown in FIG. 4 on the nitrogen polar face, the area ratio A _S / of the smooth area (A _S + A _r ) [where, A _S is the area of the smooth region and A _r is the area of the rough region] was examined.
In order to obtain the area ratio of the smooth area, first, an optical image was obtained with a resolution of a pixel size of 1.8 μm × 1.6 μm using a digital microscope (model number: VHX-900) manufactured by Keyence Corporation (model: Total number of pixels: 1.92 million, corresponding to about 6 mm ² in area). An example of the optical image is shown in FIG.
Then, using the luminance as a determination criterion, it was determined whether each pixel constituting the optical image belongs to the smooth region or the rough region. Then, the ratio of the number of pixels belonging to the smooth area was regarded as the area ratio of the smooth area.
The results are as shown in Table 1. The area ratio of the smooth area was 0.1% at a low area ratio, but reached 4.4% at a high area ratio. In addition, unevenness in appearance was observed due to non-uniform light transmittance of the wafer in the plane.

3.2. Experiment 2 (comparative example)
In Experiment 2, a C-plane GaN wafer was manufactured in the same manner as Experiment 1 except for the following two points.
The first point is that a surfactant is added to the cleaning solution used in the ultrasonic cleaning when cleaning the as-sliced C-plane GaN wafer before the KOH aqueous solution etching.
The second point is that the drying of the C-plane GaN wafer after the cleaning process is changed from natural drying to forced drying.
For the completed C-plane GaN wafer, in the same manner as in Experiment 1, the area ratio A _S / (A _S + A _r ) of the smooth area at nine locations on the nitrogen polar plane [where, A _S is the area of the smooth area , _Ar is the area of the rough region].
The results are as shown in Table 1. In the C-plane GaN wafer fabricated in Experiment 2, the area ratio of the smooth region in the nitrogen polarity plane was slightly higher than that prepared in Experiment 1.

3.3. Experiment 3 (Example)
In Experiment 3, after the CMP process, the wax is softened, the C-plane GaN wafer is removed from the ceramic plate, and the procedure is the same as in Experiment 2 until the cleaning with isopropanol is performed. The wafer was immersed in a 30 wt% aqueous ammonia solution for 41 hours at room temperature. After that, hydrofluoric acid cleaning was performed in the same manner as in Experiment 2 to complete a C-plane GaN wafer.
The area ratio A _S / (A _S + A _r ) of the smooth area at nine locations on the nitrogen polar plane of the C-plane GaN wafer produced in the same manner as in Experiment 1, where A _S is the area of the smooth area , _Ar is the area of the rough region]. As a reference, an optical image of the nitrogen polar surface at one of the measurement points is shown in FIG.

The results are as shown in Table 1. In the C-plane GaN wafer fabricated in Experiment 3, the area ratio of the smooth region was 0.0% at all nine locations. Furthermore, although it measured additionally in places other than said 9 places, the area ratio of the smooth area was 0.0% also in any place.
This indicates that the smooth region formed by the previous KOH etching was roughened by the later ammonia etching. An SEM image of the nitrogen polarity surface of the C-plane GaN wafer manufactured in Experiment 3 is shown in FIG.
The C-plane GaN wafer produced in Experiment 3 had smaller unevenness in appearance than the C-plane GaN wafer produced in Experiment 1 and the C-plane GaN wafer produced in Experiment 2.

  Arithmetic mean roughness Ra of the nitrogen polarity surface of the C-plane GaN wafer manufactured in Experiment 3 was measured using a stylus type roughness tester [SURFCOM 130A manufactured by Tokyo Seimitsu Co., Ltd., and pickup E-DT- according to JIS 0601 (1994 edition)]. It was 0.9 micrometer when it measured using SE19A. The measurement conditions were a measurement length of 10 mm, a measurement speed of 0.6 mm / sec, and a cutoff value of 0.8 mm.

3.4. Experiment 4 (comparative example)
In the above-mentioned Experiment 1, the process of attaching the non-volatile organic matter to the nitrogen-polar surface of the as-slice was performed. On the other hand, in Experiment 4, the nitrogen polar surface was ground and flattened before the process of depositing the non-volatile organic matter. A C-plane GaN wafer was fabricated in the same manner as in Experiment 1 except for this.
For the completed C-plane GaN wafer, in the same manner as in Experiment 1, the area ratio A _S / (A _S + A _r ) of the smooth area at nine locations on the nitrogen polar plane [where, A _S is the area of the smooth area , _Ar is the area of the rough region].
The results are as shown in Table 1. In the C-plane GaN wafer manufactured in Experiment 4, the area ratio of the smooth region is in the order of 3% in many places, and the appearance unevenness is higher than the C-plane GaN wafer manufactured in Experiment 3. It was big too.

  As mentioned above, although this invention was concretely explained according to the embodiment, each embodiment is shown as an example and does not limit the range of the present invention. Each embodiment described in the present specification can be variously modified without departing from the spirit of the invention, and is combined with the features described by the other embodiments within the feasible range. Can.

10 C-plane GaN wafer 11 Gallium polar surface 12 Nitrogen polar surface 13 Side surface

Claims (10)

A C-plane GaN wafer in which the nitrogen polarity surface is a matte surface,
Only the rough region exists on the nitrogen polar surface,
The rough area is an area in which fine protrusions gather without gaps.
The crude region, C-plane GaN wafer, wherein Rukoto protrusion shape and size is not uniform is not arranged irregularly. A method of manufacturing a C-plane GaN wafer, wherein the nitrogen polar surface is a matte surface,
(I) a first step of preparing a GaN wafer having a first main surface which is a main surface on the [0001] side and a second main surface which is a main surface on the [000-1] side;
(Ii) forming a rough area and a smooth area by wet etching on the second main surface of the GaN wafer prepared in the first step;
(Iii) The second main surface after the second step has been carried out is subjected to treatment for depositing nonvolatile organic matter, and then wet etching is carried out to roughen the smooth region formed in the second step The third step to
A manufacturing method characterized by including. The second major surface of the GaN wafer prepared in the first step is an as-sliced surface,
The manufacturing method according to claim 2 , wherein the as-sliced surface is subjected to wet etching in the second step. An epi-illumination is used to acquire an optical image of the nitrogen polar surface with a resolution of about 3 μm ² for one pixel size, and luminance is used as a criterion for each pixel in either the smooth or rough region of the nitrogen polar surface. The manufacturing method according to claim 2 or 3 , wherein the ratio of the number of pixels belonging to the smooth area to the total number of pixels constituting the optical image is less than 1% when it is determined to belong. The manufacturing method according to claim 4 , wherein the C-plane GaN wafer has a facet growth region and a C-plane growth region on a nitrogen polar surface which is the matte surface. The method according to any one of claims 2 to 5, wherein the non-volatile organic substance is a wax.
. A method of manufacturing a C-plane GaN wafer in which the nitrogen polar surface is a matte surface, having a first main surface which is a main surface on the [0001] side and a second main surface which is a main surface on the [000-1] side. Ga
Preparing a N wafer, and the second major surface of the prepared GaN wafer,
And D. a wet etching step including a process of depositing non-volatile organic matter and then etching with an aqueous ammonia solution at room temperature. An epi-illumination is used to acquire an optical image of the nitrogen polar surface with a resolution of about 3 μm ² for one pixel size, and luminance is used as a criterion for each pixel in either the smooth or rough region of the nitrogen polar surface. The manufacturing method according to claim 7 , wherein the ratio of the number of pixels belonging to the smooth area to the total number of pixels constituting the optical image is less than 1% when it is determined to belong. Wherein the GaN wafer to prepare a wafer preparation step has a smooth region on said second main surface, the manufacturing method according to claim 7 or 8. The method according to any one of claims 7 to 9, wherein the non-volatile organic substance is a wax.
.

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