TWI452617B - Process for smoothening iii-n substrates - Google Patents

Description

Method for smoothing a Group III nitride substrate

The present invention relates to a method of smoothing, in particular for the grinding and/or polishing of materials comprising a III-N surface, in particular a III-N substrate or a III-N template comprising a foreign substrate. Here, N represents nitrogen; III represents at least one element selected from the group consisting of aluminum, gallium, and indium (hereinafter, abbreviated as (Al, Ga, In) in the main group III of the periodic system). The invention further relates to a III-N substrate and a III-N template comprising a foreign substrate. These III-N substrates and III-N templates are well suited for use as substrates or templates for the manufacture of electronic devices/electronic components.

Mechanical polishing and/or chemical mechanical polishing has long been commercially used as a standard method for planarizing and smoothing semiconductor substrate surfaces such as GaAs surfaces. To achieve this, the smooth and flat and defect-free substrate surface is a prerequisite for subsequent epitaxial or photolithography steps for fabricating microelectronic devices/elements or optoelectronic devices/elements. A polishing method for a GaN substrate having a c-plane orientation is known for Ga-polar ([0001]-directional) surface and N-polar ([000 ]-directionality) The chemical stability of the surface varies. Thus, the Ga surface (ie [0001]) is almost chemically inert at room temperature, N-surface (ie [000] ]) is affected by various etchants such as aqueous NaOH solution or aqueous KOH solution. Furthermore, the Ga-surface is clearly harder than the N-surface.

Weyher et al. (Chemical Polishing of Bulk and Epitaxial GaN, Journal of Crystal Growth 182 (1997) 17) provides a polishing method for polishing N-surfaces (Note: Interactions between subsequent N-surface or Ga-surface results, eg Referring to J. Weyher et al., "Defects in GaN Single Crystals and Homogeneous Epitaxial Structures", Journal of Crystal Growth 281 (205, 135)) involves a mechanical polishing step using a diamond slurry followed by a KOH and/or NaOH aqueous solution. CMP step. However, the Ga-surface is not suitable for this method, and the Ga-surface has a higher importance for subsequent epitaxy (see, for example, Miskys et al., "MOCVD epitaxy on a freestanding HVDE-GaN-substrate", Fris.phys.stat.sol. (a) 176 (1999, 443)). Weyher et al. did not indicate a hard material for abrasive particles.

The method described by Porowsky et al. ("Mechanical-chemical polishing of crystals and epitaxial layers of GaN and Ga _1-x-y Al _x In _y N", US 6,399,500) corresponds to the prior art of Weyher et al. But it has not been explicit to suggest the polarity of the polished surface. Hard materials for abrasive particles have not been indicated.

Tavernier et al. ("Chemical Mechanical Polishing of Gallium Nitride", Electrochemical and Solid State Letters 5 (2002) G61) report the use of ruthenium oxide as a CMP treatment method for abrasive particles, which can only be successfully applied to the nitrogen surface of GaN. Not suitable for the Ga surface.

Karouta et al. ("Final Polishing of Ga Polar GaN Substrates Using Reactive Ion Etching", Journal of Electronic Materials 28 (1999) 1448) proposes a method of polishing the Ga surface of GaN using chemical ion etching (RIE), in which the crystal The diamond slurry has been pretreated in the previous mechanical polishing step. An additional disadvantage of the RIE method is that it is extremely cumbersome, and ion irradiation causes damage to the crystal lattice near the surface region.

Kim et al. ("Manufacturing Method for GaN Substrate", US 6,211,089) report a method of polishing a GaN substrate comprising a step of mechanical polishing using a diamond slurry and a boron carbide plate, wherein the polishing damage is also used, The RIE method of the aforementioned disadvantages and the additional end-annealing method.

Xu et al. ("High Surface Quality GaN Wafers and Methods of Making Same", US 6,951,695) illustrate the chemical mechanical polishing of Al _x Ga _y In _z - end via the use of cerium oxide or alumina abrasive particles in an acidic or alkaline solution. Method of (0001)-Al _x Ga _y In _z N-surface. Further deduction of the crystal structure damage caused by the mechanical polishing in the front of the CMP step by using the diamond slurry (or another niobium carbide, boron carbide or alumina slurry), and the crystals caused by the CMP treatment, are further derived from the description. Structural damage can be eliminated or reduced by subsequent wet chemical etching steps, such as the use of 180 ° C hot phosphoric acid, which is technically cumbersome.

Kato et al. ("The polishing composition of a semiconductor substrate and a method of manufacturing a semiconductor substrate using the same", Japanese Patent Application No. 2003-100373) describes a slurry composition for polishing GaN, which is composed of hard abrasive grains ( For example, diamonds are composed of a mixture of soft abrasive particles such as cerium oxide. In the polishing procedure, the slurry is maintained at a temperature between 10 ° C and 80 ° C. It is extremely cumbersome in the art of high temperature polishing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for smoothing, in particular for polishing a III-N surface, which method can also be successfully applied to an almost chemically inert surface of a III-N crystal on the one hand [ie (Al, Ga, In). On the other hand, the damage to the crystal lattice is reduced as much as possible, so that a III-N substrate and a III-N template having an improved surface structure can be provided.

This object can be attained by a method of preparing a smoothed surface comprising a material comprising a III-N compound on a surface to be smoothed, wherein cubic boron nitride (cBN) is used as the abrasive material. The smoothing method specifically includes a grinding method and/or a polishing process including, in particular, the surface of the III-N material. Surprisingly, it has been found that the use of the particulate material cBN, on the one hand, achieves an effect on the almost chemically inert and hard (Al, Ga, In) N (Al, Ga, In) surface, on the other hand reduces the lattice Damaged. The reason is presumed to be because the cubic boron nitride (cBN) has the hardness most suitable for the special polished III-N material, and the best effect is obtained by the opposite effect of the hardness. Such cBN materials are, for example, harder than ruthenium oxide, so that substantial polishing can be achieved on the surface of the (Al, Ga, In) which is almost chemically inert and hard when polished. On the other hand, cBN materials have a lower hardness than diamonds, thus reducing damage to the crystal lattice.

Note that a CMP polishing liquid containing, for example, cerium oxide, cerium nitride, aluminum, zirconia, cerium oxide, boron nitride, diamond, hard carbon or the like as an abrasive material, is described in JP-A-2001-085373. However, this material is used to polish germanium wafers. The purpose of JP-A-2001-085373 is directed to wet abrasive grains containing an organic surfactant, and the abrasive particles are easily dispersed in water to obtain a higher polishing rate ratio of the tantalum oxide film to the tantalum nitride film. Thus, when polishing the III-N surface, it is not possible to reveal any hints that can solve a particular problem.

The smoothing of cubic boron nitride (cBN) as the abrasive material according to the present invention is preferably carried out toward the III polarity (e.g., Ga polarity) surface [0001] of the III-N material because the present chemically inert surface is available. The special effects of the invention. However, the smoothing according to the invention may additionally or additionally be based on the N-polar surface of the III-N material [000 ]get on.

A slurry which is particularly suitable for polishing is a water-soluble suspension additionally containing one or more substances selected from the group consisting of ammonia, potassium hydroxide, sodium hydroxide, hydrogen peroxide and an organic base.

In a preferred embodiment, the freestanding III-N substrate or III-N template is ground and/or polished, the template comprising a foreign substrate, a III-N upper layer and, optionally, III-N or other One or more intermediate layers formed by the material. The material of the foreign substrate is preferably selected from the group consisting of sapphire, tantalum carbide, gallium nitride, aluminum nitride, gallium arsenide, zinc oxide, antimony, lithium aluminate, and lithium gallate.

In order to further improve the crystal quality of the preferred embodiment, particularly to improve the crystal quality of the surface, the surface of the free-standing III-N substrate having an exact orientation of c-, a-, m- or r-plane, or toward c-, a- The m- or r-plane misdirected from 0.1 to 30 degrees is ground and/or polished. More preferably, the ground and/or polished surface has an exactly oriented III-polar (e.g., Ga-polar) c-plane, or a plane has an error toward the exact oriented III-polar (e.g., Ga-polar) c-plane. Oriented from 0.1 to 1 degree.

The suitable average particle size of the cBN abrasive material is, for example, in the range of from 0.1 micrometer to 20 micrometers, preferably from 0.5 micrometer to 10 micrometers, and still more preferably in the range of from 1 micrometer to 6 micrometers.

If the polishing procedure comprises a plurality of steps, in particular 2, 3, 4, 5 or 6 polishing steps, wherein the average particle size of the cubic boron nitride particles in the individual successive steps is decreased, the efficacy and effect of the polishing treatment are further improved. A particularly preferred combination of polishing steps consists in two consecutive steps or preferably three consecutive steps, the average particle size of the cBN being greater than 4 to 7 microns, respectively (first step), 2 microns to less than 4 microns (second step) And from 0.5 microns to less than 2 microns (optional third step), the particular average particle size is about 6 microns, about 3 microns and about 1 micron, respectively, wherein the "about" representation represents a tolerance of ± 0.5 microns.

It is further preferred to carry out the grinding treatment before the polishing treatment. It is preferred to use cubic boron nitride as an abrasive in the grinding treatment.

With a specially selected smoothing agent cBN, even with large-size III-N substrates or III-N plates with a diameter of at least 40 mm, a unique combination of opposite properties can be achieved, in other words excellent smoothing, including surface roughness The excellent uniformity is a combination of crystal quality that is highly preserved due to the small, substantially insignificant crystal damage. In particular, having a very low surface roughness uniformity across the surface of the substrate or on the surface of the wafer is a combined measurement of the properties achievable by the present invention. Thus, the uniform distribution of the rms value of the surface roughness according to the present invention, and particularly the rms on the entire wafer surface (except for the edge except for the 5 mm edge) can be used as a meaningful parameter, for example, mapping the wafer surface with a white light interferometer. This property can be measured, where the standard deviation of the rms value is a measure of the uniformity of the surface roughness. According to the present invention, a large-sized III-N substrate or a III-N template is provided, where the standard deviation of the rms value is 5% or less in the mapping on the smoothed surface by white light interferometry.

For example, the aforementioned disclosure by Miskys et al. as a comparison of the importance of the surface roughness uniformity of the present invention, as indicated in accordance with the present invention, indicates that the surface roughness uniformity can be indicated by a uniform distribution of rms values on the wafer surface. According to the prior art, even if the Ga-polar surface of the GaN layer is subjected to a cumbersome polishing process, the polishing process includes four 10 minute polishing steps, using diamond abrasive grains of 15, 7, 3, and 0.25 sizes, and including another use of super The long polishing step of the fine polishing material (0.04 micron size) after this polishing treatment, although the surface is smooth, leaves a micro scratch on the polished surface, which subsequently becomes the main nucleation site of GaN growth, After the epitaxial growth above these scratch locations, significant surface defects are detected.

For excellent crystal quality measurements, special measurements obtained from rocking curve mapping and/or micro-Raman mapping are appropriate. Thus parallel to the parallel plane of the growth plane obtained by the smoothing treatment of the present invention, the freestanding III-N substrate and the III-N template according to the present invention are measured in a rocking curve map to be half-maximum (half width). The full width standard deviation is 5% or less, preferably 3% or less, and more preferably 2% or less. In addition, or at the same time, on the surface parallel to the growth surface obtained by the smoothing method of the present invention, the free-standing III-N substrate and the III-N template according to the present invention are in the micro-Raman mapping, in the E ₂ -photon half The standard deviation of the full width measured by the maximum (half width) is 5% or less, preferably 3% or less, and more preferably 2% or less.

The standard deviation measurement method can perform individual rocking curve mapping measurement or micro-Raman measurement through a plurality of, for example, 100 measurement points, determine the standard deviation, form a full width average value of all the measured values in half maximum, and determine by ordinary statistical evaluation. The standard deviation from the mean.

According to the present invention, it is preferred to produce a III-N substrate or III-N template having a diameter of at least 2 吋 (about 5 cm), at least 3 吋 (about 7.6 cm), or at least 4 吋 (about 10 cm) or more. .

The preferred use of the smoothing treatment according to the present invention for a III-polar (e.g., Ga-polar) surface, the III-N substrate or III-N template is preferably fabricated in accordance with the present invention, wherein the white light interferometer mapping, The parameters described by the rocking curve mapping and/or the micro-Raman mapping are also applicable/effective for III-polar (eg Ga-polar) surfaces. More preferably, the parameters are effective/applicable to both surfaces, i.e., a III-polar surface (e.g., a Ga-polar surface) and an N-polar surface, respectively.

In the foregoing definition, N represents nitrogen and III represents at least one element of Group III of the periodic system of elements. The element III must be selected from the group consisting of elements consisting of Al, Ga and In, alone or in combination. Therefore, the corresponding general formula is Al _x Ga ₁ In _z N, where 0 x 1,0 y 1,0 z 1 and x+y+z=1. Examples of possible III-N compounds are quaternary compounds such as (Al, Ga, In) N, ternary compounds such as (Al, Ga) N, (Ga, In) N and (Al, In) N or binary compounds. Such as GaN or AlN. All of the reasonable atomic ratios are possible for the group III elements in the parentheses as exemplified above, that is, the individual elements are from 0 atom% to 100 atom% (for example, (Al, Ga) N = Al _x Ga _1-x N, Where 0 x 1). (Al, Ga) N and GaN are particularly preferred. The following examples are intended to apply not only to the III-N compound examples indicated herein, but also to all possible III-N compounds. In addition to the III-N substrate, the invention is also advantageously applied to a III-N template comprising a substrate as described above, a III-N upper layer, and optionally III-N or other One or more intermediate layers formed by the material, and the III-N surface are correspondingly smoothed. The III-N composition of the thin and thick layers, the substrate and the template can be selected separately. The compositions may be the same or different. The invention is particularly applicable to III-N substrates, III-N substrates and III-N templates which have been prepared by epitaxial method, preferably by vapor phase epitaxy, such as by MOVPE, especially by HVPE. The III-N compound is preferably crystalline, especially a single crystal.

Simple illustration

Further details of the present invention will be exemplified with the preferred embodiments and examples, but the examples and examples are by way of illustration and not limitation, and FIG. (Inventive) and comparison of surface roughness (rms) values of GaN wafers after mechanical polishing with diamond-containing slurry (comparative example), and Figure 2 is suitable for measuring rms values using white light interferometry The principle of surface research.

Detailed description of the preferred embodiment

The polishing process can be carried out commercially using a conventional polishing machine, wherein in the preferred embodiment, the support plate and the wafer fixed thereon are rotated, and the wafer is additionally oscillated in the radial direction during polishing. The polishing plate on which the polishing cloth is fixed and the wafer are pressed against each other during polishing, wherein the slurry is dropped on the polishing cloth.

The slurry is an aqueous based dispersion containing cBN as the abrasive particles. In order to obtain an optimum smooth surface, a plurality of polishing steps are performed in which the average grain size of cBN is reduced from one polishing step to the next. Possible fractionation in three subsequent polishing steps is an average particle size of 6 microns, 3 microns, and 1 micron.

Conditioning the polishing cloth in the polishing round or before or during the polishing round (for example, using Rohm and Hass's "DiaGrid" pad conditioner from Feldkirchen, Germany) cloth).

The polished (Al, Ga, In) N-wafer or (Al, Ga, In)-N template is produced by various vapor phase methods or solution growth methods. Immediately after the forming step, additional mechanical processing steps (one or more) selected from the following steps may be performed prior to the polishing process: - circular grinding, - flat and/or nicked grinding, - wire saw, - Etching rounding, - grinding, wherein the grinding step described later comprises a continuous plurality of partial steps using an abrasive having a decreasing average particle size. For example, tantalum carbide diamond or cubic boron nitride can be used as the abrasive.

Used to map wafer surfaces using a white light interferometer, where the standard deviation of rms values is used as a measure of surface roughness uniformity, and the wafer surface can be divided into orthogonal distances of up to 5 mm from each other within the grating. Considering the margin of 5 mm boundary, surface scanning is now performed on each grating, where the scanning area is at least 1% of the grating size. The rms value can be determined in a standard manner using commercially available white light interferometers using white light.

The crystal quality of the treated surface can be measured by technology, for example by X-ray diffraction, for example, corresponding to the diffraction of a particular lattice plane, the spatial distribution of the X-ray diffraction curve at the absolute value of the half maximum (half width). And / or the full width of the spatial distribution. The crystal quality uniformity at the growth plane or growth plane can be determined using a so-called rocking curve mapping (recording of Ω scans recorded at different locations on the surface of the sample) that have been recorded on parallel planes of the growth plane or growth plane. For example, when grown in the [0001] direction, the reflection of the (0002) lattice plane can be used for Ω scanning. The crystal quality uniformity in the growth direction can be determined by the standard deviation of the full width average of the (0002) Ω scan of the individual substrates that have been obtained from the corresponding bulk crystals in the half maximum (half width).

The second method for determining crystal quality uniformity is Raman mapping. Thus, for example, E ₂ in a plane parallel to the growth plane one scan - measurement in photon half maximum (half width) and the frequency of the full width parallel to the standard deviation of the uniformity of the crystal quality of the growth surface.

The micro-Raman measurement system uses a laser laser wavelength of 532 nm (frequency multiplying Nd:YAG laser) and a laser power of 3 mW (for example, using a Labram 800 HR spectrometer from Jobin Yvon), in which the laser system is used. The microscope was used to focus on the template to a beam diameter of about 1 micron. When scanning on the surface, the increment in the x direction and the y direction is, for example, about 2.5 mm. Use the appropriate margin, for example 2 mm from the wafer surface. When scanning over the surface of the wafer perpendicular to the surface, the increment in the z direction is about 10 microns. The frequency and full width of the E ₂ -photon at half maximum (half width) were determined by Lorentz linear analysis.

Example: As a polishing machine, PT 350 Premium of I-B-S Fertigungs-und Vertriebs-GmbH was used. A GaN-wafer having a (0001) directionality has been adhered to the N-polar back side of the heated support plate using a hot melt wax (Thermowax), wherein the support plate is again cooled to room temperature until the processing procedure is resumed. The polishing cloth was adhered to the polishing plate by a polyurethane-based hardness cloth (Rohm and Haas SUBA IV). cBN slurry (cBN slurry W69S1 6 micron / 3 micron HVY, distributor Dieter Manfred B Duel, Wittenberg, Germany) dripped at a flow rate of about 5 ml/min. The cBN slurry was used in two separate polishing steps, using 6 micron and 3 micron cBN abrasive particles (average particle size, respectively). The polished plate and the polished sample were rotated at ~30 min ^-1 and ~20 min ^{-1 respectively} . In addition, the sample is eccentrically fixed and oscillates in the radial direction. The compressive force during polishing was about 1.700 g/cm 2 .

The Ga-polar surface of the thus polished wafer and the Ga-polar surface of the wafer polished using the same conditions but using diamond slurry (average particle size of 6 μm and 3 μm) utilize a commercially available white light interferometer (Caixinxin) The field of view (Zygo New View) is compared. The performance of the measurement is further detailed as follows.

Figure 1 shows a comparison of the average surface roughness (rms value) after mechanical polishing with cBN slurry and diamond slurry.

As collected from Figure 1, the diamond slurry was compared using cBN slurries in each polishing step, and a relatively low surface roughness was obtained from Figure 1 relative to the average, especially the lower standard deviation of absolute rms values collected. . Here, the rms value is determined in an area of 350 x 260 square microns.

GaN surface analysis, in particular measurement of coarseness, including standard measurements of rms values measured using commercially available white light interferometers (new field of view).

The principle of a white light interferometer is shown in Figure 2 (source: zygoLOT). The measurement principle is based on a combination of a microscope and an interferometer. Here, the white light source is split into two beams, one of which is reflected by a reference mirror and the other beam is reflected by the sample. The two partial beams then overlap. Due to the undulating topography of the sample surface, the different optical path lengths of the beams are collected, and the interference pattern is obtained, and the interference pattern is analyzed by frequency domain analysis (FDA). The use of white light allows analysis of interference of multiple wavelengths of light. The relative position between the reference mirror and the sample surface can be dislocated using a piezoelectric actuator.

By analyzing the interference signal, the vertical relationship of up to 0.1 nm is obtained by accurately determining the relative relationship between the changes in the optical path between the mirror and the sample. The sample reflectance of 0.4% is sufficient for measurement, so even weak reflection surfaces can be measured.

The micro-Raman measurement used to determine the frequency and full width of the E ₂ -photon at half maximum (half width) can be determined by using the commercially available Labram 800 HR spectrometer from Joe Bianyifan as follows: - Laser laser wavelength 532 nm (Double-frequency Nd:YAG-laser), - laser power 3 mW, - focused on the sample by lightning rays using a microscope optics to a beam diameter of about 1 micron.

The spectrometer is additionally calibrated using a tantalum plasma line. The measured value can be performed in the backscattering geometry, where the polarization measurement is selected, so E ₂ -photons can be detected [surface scan: z(yx/y)-z; slit surface scan: y(xx)-y ]. When scanning on the surface, the increment in the x and y directions is about 2.5 mm. The margin of the edge of the wafer is 2 mm. When scanning on the open surface of the wafer on the vertical surface, the increment in the z direction is about 10 microns. The frequency and full width of the E ₂ -photon at half maximum (half width) were determined by Lawrence linear analysis.

Figure 1 shows a comparison of surface roughness (rms) values of GaN wafers after mechanical polishing using cBN-containing slurries (invention) and using diamond-containing slurries (comparative examples), and Figure 2 is suitable for Surface study principle for measuring rms values using white light interferometry.

Claims (23)

A method of preparing a smoothed surface of a Group III nitrogen (III-N) compound material, comprising polishing a surface of a material to be smoothed by a slurry in the form of an aqueous suspension comprising cubic boron nitride abrasive particles, the surface A compound comprising a III-N, wherein III represents at least one element of Group III of the periodic system, selected from the group consisting of Al, Ga, and In; wherein the polishing procedure comprises a plurality of successive polishing steps, wherein the abrasive particles are in at least one subsequent step It has a continuously reduced average particle size. The method of claim 1, wherein the slurry contains at least one selected from the group consisting of ammonia, potassium hydroxide, sodium hydroxide, hydrogen peroxide, and an organic base. The method of claim 1, wherein the material is selected from the group consisting of a free-standing III-N substrate and a III-N template, wherein the III-N template comprises an external A substrate, an upper III-N layer, and at least one intermediate layer, optionally formed of III-N or another material. The method of claim 3, further comprising subjecting the surface to be smoothed to a grinding treatment with a slurry comprising one of cubic boron nitride abrasive grains. The method of claim 3, wherein the material of the foreign substrate is selected from the group consisting of sapphire, tantalum carbide, gallium nitride, aluminum nitride, gallium arsenide, zinc oxide, antimony, lithium aluminate, and gallium. A group consisting of lithium acid. The method of claim 3, wherein the freestanding III-N substrate or the III-N template has a surface to be smoothed, respectively, by a correctly oriented c-, a-, m- or r-plane Defined, or defined by a plane having an erroneous orientation of 0.1 to 30 degrees toward the c-, a-, m-, or r-plane. The method of claim 3, wherein the freestanding III-N substrate or the III-N template has a surface to be smoothed, respectively, defined by a correctly oriented III-polar c-plane, or It is defined by a plane that is oriented 0.1 to 1 degree toward the III-polar c-plane. The method of claim 1, wherein the average particle size of the abrasive particles is in the range of 4 micrometers to 7 micrometers, 2 micrometers to 4 micrometers, and 0.5 micrometers to 2 micrometers, respectively, in three consecutive polishing steps. The method of claim 8, wherein the average particle size in each of the three successive polishing steps is about 6 microns, about 3 microns, and about 1 micron, respectively. The method of claim 1, further comprising performing a grinding process prior to the buffing process. The method of claim 10, wherein cubic boron nitride is used as the abrasive. The method of claim 1, wherein the slurry containing cubic boron nitride is applied toward the III-polar surface [0001] of the III-N material. A freestanding III-N substrate, wherein III represents at least one element of Group III of the periodic system selected from the group consisting of Al, Ga, and In, the substrate having a diameter greater than 40 mm, wherein white light interferometry is utilized In the on-surface mapping, the standard deviation of the rms values is 5% or less, one or both of which is the standard deviation of the full width measured at the half maximum in the rocking curve mapping on the surface parallel to the growth surface. For 5% or less, in the micro-Raman mapping on the surface parallel to the growth surface, the standard deviation of the full width measured at the E ₂ -photon half maximum is 5% or less. An optical device comprising an optical component, an electronic component or an optoelectronic component formed on a III-N substrate, wherein the substrate comprises a substrate as in claim 13 of the patent application. A free standing III-N substrate, wherein III represents at least one element of Group III of the periodic system, selected from the group consisting of Al, Ga, and In, the substrate having a diameter greater than 40 mm, wherein the free standing III-N The surface of the substrate has been smoothed by a slurry comprising an aqueous suspension of cubic boron nitride abrasive and smoothed by polishing comprising a plurality of successive polishing steps, wherein the abrasive has a continuous in at least one subsequent step The reduced average particle size, either or both, in the rocking curve map parallel to the surface of the growth surface, the standard deviation of the full width measured at the half maximum is 5% or less, parallel to the growth surface In the micro-Raman mapping on the surface, the standard deviation of the full width measured at the E ₂ -photon half maximum is 5% or less. A freestanding III-N substrate according to claim 15 wherein one of the surfaces of the freestanding III-N substrate has a correctly oriented c-, a-, m- or r-plane, or has a facing c- The a-, m- or r-plane is misoriented to a plane of 0.1 to 30 degrees. A freestanding III-N substrate according to claim 15 wherein the surface of the freestanding III-N substrate has a correctly oriented III-polar c-plane or a correctly oriented III-polar c-plane Misdirected to a plane of 0.1 degrees to 1 degree. A freestanding III-N substrate according to claim 15 wherein the smoothed surface is a III-polar surface of the III-N material [0001]. A III-N template, wherein III represents at least one element of Group III of the periodic system, selected from the group consisting of Al, Ga, and In, wherein the template comprises a foreign substrate, a III-N upper layer, and optionally At least one intermediate layer formed by III-N or another material having a diameter greater than 40 mm, wherein the standard deviation of the rms value is 5% or less in the surface mapping using white light interferometry, one of which or In the rocking curve mapping parallel to the surface of the growth surface, the standard deviation of the full width measured at the half maximum is 5% or less, in the micro-Raman mapping on the surface parallel to the growth surface, The standard deviation of the full width measured at the E ₂ -photon half maximum is 5% or less. For example, in the III-N template of claim 19, wherein the standard deviation of the full width measured at the half maximum is 5% or less in the rocking curve map parallel to the surface of the growth surface. An optical device comprising an optical component, an electronic component or an optoelectronic component formed on a III-N template, wherein the template comprises a board as in claim 19 of the scope of the patent application. A III-N template, wherein III represents at least one element of Group III of the periodic system, selected from the group consisting of Al, Ga, and In, wherein the template comprises a foreign substrate, a III-N upper layer, and optionally At least one intermediate layer formed of III-N or another material having a diameter greater than 40 mm, wherein the surface of the upper layer of the III-N has been passed through a slurry in the form of an aqueous suspension comprising cubic boron nitride abrasive And smoothed by polishing comprising a plurality of successive polishing steps, wherein the abrasive has a continuously reduced average particle size in at least one subsequent step, either or both, on a surface parallel to the growth surface In the rocking curve map, the standard deviation of the full width measured at the half maximum is 5% or less, and is measured in the micro-Raman mapping on the surface parallel to the growth surface at the E ₂ -photon half maximum. The standard deviation of the full width is 5% or less. Such as the sample of claim 22, wherein the foreign substrate It is formed of a material selected from the group consisting of sapphire, tantalum carbide, gallium nitride, aluminum nitride, gallium arsenide, zinc oxide, antimony, lithium aluminate, and lithium gallate.