JP2019064870A - Composite substrate - Google Patents

Abstract

To provide a substrate for forming a semiconductor layer, such as an AlN crystal, an AlN film or (AlGa) N, capable of reducing cracks and breakages and improving crystal quality, and a substrate capable of suppressing a cost.SOLUTION: A composite substrate 10 has an AlN layer 11 having a (001) plane direction on a sapphire substrate surface 141 having a (001) plane direction. The ratio of the diffraction line intensity of (002) plane of the AlN layer 11 to that of (006) plane of the sapphire substrate 13 by an X ray 2θ/θ scan is 10% or more, and the ratio of the tilt half value width of (002) plane of the AlN layer 11 to that of (006) plane of the sapphire substrate 13 by X ray measurement is within 5 times. The thickness of the AlN layer 11 is 50 nm or more and 1000 nm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite substrate in which an AlN layer is disposed on the surface of a sapphire substrate.

In the present invention, a substrate made of α-alumina (Al ₂ O ₃ ) single crystal (hereinafter referred to as sapphire) is referred to as a sapphire substrate.

  A crystal layer made of a group III nitride semiconductor such as gallium nitride (GaN), aluminum nitride (AlN), or aluminum gallium nitride (AlGaN) is a light emitting diode or a laser diode that emits short wavelength light of blue band to ultraviolet band. It attracts attention as a functional layer which constitutes a light emitting device and a power transistor. Also, AlN is a material expected to be used as a heat dissipating material utilizing high heat conductivity.

These crystal layers are formed on a substrate such as α-alumina (Al ₂ O ₃ ) single crystal (hereinafter referred to as sapphire) or SiC single crystal by vapor phase growth means such as molecular beam epitaxial method or metal organic chemical vapor deposition method. It has been proposed to deposit multiple semiconductor thin film layers using In particular, a sapphire substrate is an excellent substrate material in terms of size, supply capability and cost, but direct formation of a semiconductor thin film layer on a sapphire substrate is very difficult and has not been achieved yet. Therefore, it is often used to once form an AlN buffer layer by MOCVD method or MOPVD method and then form a semiconductor thin film layer thereon. However, the AlN buffer layer and the semiconductor thin film layer formed in this way do not have sufficient crystal quality, and suffer from many problems such as a decrease in light emission efficiency of the semiconductor device, shortening of the life, or yield loss due to the occurrence of cracking. ing.

  In order to solve the problem, in Patent Document 1, the film formation method is devised to reduce the threading dislocations in the AlN buffer layer and to improve the crystallinity. In Patent Document 2, heat treatment is performed in an atmosphere of carbon and nitrogen to form aluminum oxynitride (AlON) on sapphire, and an aluminum nitride layer is further formed thereon to improve the crystallinity of the aluminum nitride buffer layer. I am trying. However, even if these techniques are used, the solution to the above problems is not sufficient, which hinders the spread of light emitting elements having a wavelength of 200 to 300 nm, in which aluminum gallium nitride based semiconductor elements are essential.

  In addition, it has been attempted to use AlN single crystal itself as a substrate. That is, after crystal growth of an AlN single crystal by a vapor phase growth method such as sublimation or halide vapor phase growth (HVPE) using a single crystal such as sapphire or SiC as a seed substrate, or a liquid phase method such as flux method, An AlN single crystal substrate is manufactured by a process such as polishing. However, in this case, there is a problem that the quality of the AlN single crystal is not sufficient or the price is high, and it has not been widely used.

WO 2013/005789 A1 JP 2005-104829

  An AlN single crystal substrate has attracted attention as a substrate material for forming a light emitting device such as a light emitting diode or a laser diode emitting short wavelength light of blue band to ultraviolet band and a functional layer constituting a power transistor or a functional layer. However, as described in the prior art, there are some problems.

  That is, when an AlN buffer layer is formed by MOCVD method or MOPVD method and a semiconductor thin film layer is formed thereon, the crystal quality is not sufficient, and the luminous efficiency of the semiconductor element is reduced, the life is shortened, or the occurrence of crack is generated. Problems such as yield loss due to

  In addition, the method of forming aluminum oxynitride (AlON) on sapphire by heat treatment in an atmosphere of carbon and nitrogen, and further forming an aluminum nitride layer thereon, has not accumulated technology to the industrial level, and the industrial level There is a problem that it does not lead to use in

  In addition, when using AlN single crystal itself as the substrate, AlN single crystal is produced by sublimation method, HVPE method, or flux method, but there are problems in terms of crystal quality or cost, and It has not been reached.

  In view of the above problems, the object of the present invention is to provide a substrate for forming a semiconductor layer such as AlN crystal, AlN film or (AlGa) N with reduced cracks and cracks and improved crystal quality, And providing a substrate that can reduce costs.

  The present invention was made in order to solve such problems, and is a composite substrate in which an AlN layer having a (001) plane orientation is formed on a sapphire substrate surface having a (001) plane orientation of the surface. The ratio of the diffraction line intensity of the (002) plane of the AlN layer to the diffraction line intensity of the (006) plane of the sapphire substrate by the line 2θ / θ scan is 10% or more, and It is characterized in that the ratio of the half width at half maximum of the (002) plane of the AlN layer to the half width at half width of the (006) plane is within 5 times. As a result, cracks and cracks are reduced on the composite substrate of the present invention, precipitation of AlN with different phases and orientations is suppressed, and a semiconductor layer such as an AlN crystal, an AlN film or (AlGa) N with improved crystal quality is manufactured. be able to. Further, if a semiconductor layer such as an AlN film or (AlGa) N is directly formed on the composite substrate of the present invention, it is possible to reduce the cost because AlN single crystal growth and its processing become unnecessary.

  The term "tilt" is a term used to indicate local variation in the surface orientation of the formed surface, and in the ω rocking curve by X-ray measurement, an angular width at which 50% of the strength of the rocking curve is 50% of the maximum strength. Is usually used as an index, and is used here as the half-width tilt.

  As a desirable mode of the present invention, it is desirable that a ratio of a twist half width of the (100) plane of the AlN layer to a twist half width of the (100) plane of the sapphire substrate by X-ray measurement is within 5 times. As a result, it is possible to form on the composite substrate of the present invention a semiconductor layer such as a high quality AlN crystal, an AlN film, or (AlGa) N in which the precipitation of AlN of different phases and different orientations is suppressed and the crystal quality is improved.

  Twist is a term that indicates local variation in crystal orientation with respect to the direction perpendicular to the forming surface, that is, the cross-sectional direction, and one specific surface having a surface orientation perpendicular to the surface orientation of the forming surface is selected. The rocking curve measurement is performed by X-ray measurement, and the angular width at which the strength becomes 50% of the maximum strength of the rocking curve, ie, the rocking curve half width is usually used as an index. . The (100) plane with respect to the (001) plane orientation of the sapphire surface and the (100) plane with respect to the (001) plane of the AlN layer formation surface are respectively orthogonal to each other.

  Another means for solving the problem is a composite substrate in which an AlN layer having a (001) plane orientation is formed on the surface of a sapphire substrate having a (110) plane orientation of the surface, The ratio of the diffraction line intensity of the (002) plane of the AlN layer to the diffraction line intensity of the (110) plane of the sapphire substrate is 10% or more, and the half width of the tilt of the (110) plane of the sapphire substrate by X-ray measurement. The ratio of the half width at half maximum of the (002) plane of the AlN layer to the above is five times or less. As a result, cracks and cracks are reduced on the composite substrate of the present invention, precipitation of AlN with different phases and orientations is suppressed, and a semiconductor layer such as an AlN crystal, an AlN film or (AlGa) N with improved crystal quality is manufactured. be able to. Further, if a semiconductor layer of (AlGa) N or the like is formed directly on the composite substrate of the present invention, it is possible to reduce the cost because AlN single crystal growth and its processing become unnecessary.

  As a desirable mode of the present invention, it is desirable that a ratio of a twist half width of the (100) plane of the AlN layer to a twist half width of the (006) plane of the sapphire substrate by X-ray measurement is within 5 times. As a result, it is possible to form on the composite substrate of the present invention a semiconductor layer such as a high quality AlN crystal, an AlN film, or (AlGa) N in which the precipitation of AlN of different phases and different orientations is suppressed and the crystal quality is improved.

  As a desirable mode of the present invention, it is desirable that the thickness of the AlN layer is 50 nm or more and 1000 nm or less. As a result, on the composite substrate of the present invention, a semiconductor layer such as an AlN crystal, an AlN film, or (AlGa) N of good quality can be formed with good surface smoothness.

  By using the composite substrate according to the present invention, it is possible to form a semiconductor layer such as an AlN crystal, an AlN film or (AlGa) N with reduced cracks and cracks and improved crystal quality, and to suppress the cost. Can.

FIG. 1 schematically shows the cross section of the composite substrate of the present embodiment. FIG. 2 shows a 2θ / θ scan of XRD when the diffraction intensity of the sapphire (006) plane in Example 1 is 100. FIG. 3 shows the diffraction line intensity area of the AlN (002) plane. FIG. 4 shows a 2θ / θ scan of XRD when the diffraction intensity of the sapphire (110) plane in Example 4 is 100. FIG. 5 illustrates the X-ray ω rocking curve and the tilt half width of the AlN (002) plane. FIG. 6 shows an example of the production flow of the composite substrate of the present embodiment. FIG. 7 schematically shows a heating unit at the time of nitriding treatment. FIG. 8 is a plan view showing the relationship between a nitrided substrate and carbon in Example 1.

  The object of the present embodiment is to provide a substrate for forming a semiconductor layer such as AlN crystal, AlN film or (AlGa) N with reduced cracks and cracks and improved crystal quality, and can suppress costs. It is provision of a substrate. The cost can be significantly reduced as compared to a freestanding AlN single crystal substrate. That is, this is because it does not include steps such as AlN single crystal growth to a thickness of 500 μm or more and processing for forming a freestanding substrate.

  In addition, semiconductor layers such as AlN crystal, AlN film or (AlGa) N can be formed by crystal growth or film formation using the AlN layer of the composite substrate in which the AlN layer is formed on the sapphire substrate surface. . However, this is not enough, and deterioration of crystal quality such as generation of cracks and cracks due to the state of AlN layer, precipitation of AlN crystal with different plane orientation, generation of subgrain boundary, or broadening of tilt and twist, etc. It will be Therefore, the inventors have clarified the conditions of the composite substrate that can improve the quality of the semiconductor layer such as the above-mentioned AlN crystal, AlN film or (AlGa) N, and have completed the invention.

  FIG. 1 schematically shows a cross section of a composite substrate 10 according to the present embodiment. The AlN layer 11 is disposed on the surface 141 of the sapphire substrate 13. Here, the plane orientation of the sapphire substrate surface 141 is the (001) plane or the (110) plane, and the plane orientation of the formation surface 12 of the AlN layer 11 is the (001) plane in any case. The AlN layer 11 may be disposed on the front and back two surfaces 141 and 142 of the sapphire substrate 13, but it is desirable to be disposed on one of the surfaces. Usually, the formation of a semiconductor layer such as an AlN crystal, an AlN film, or (AlGa) N is performed only on one surface, and thus it is meaningless to form on two surfaces.

  FIG. 2 is a 2θ / θ scan diagram of X-rays when the AlN layer 11 of the present invention is disposed on the sapphire substrate surface 141 whose surface orientation is the (001) plane. The X-ray target is Cu. An AlN layer 11 in which the plane orientation of the formation surface 12 is the (001) plane is formed, and the intensity of the diffraction line 111 of the AlN (002) plane is 10% or more with respect to the diffraction line intensity of the diffraction line 131 of the sapphire (006) plane. It is characteristic that there is. By setting the AlN layer 11 having such properties to the composite substrate 10 disposed on the sapphire substrate surface 141, even if a semiconductor layer such as an AlN crystal, an AlN film, or (AlGa) N is formed on the composite substrate 10. It was found that warpage, cracks, or AlN crystal precipitation different in plane orientation did not occur.

  In addition, the plane orientation of the sapphire substrate surface 141 does not have to completely match the (001) plane, and an off angle of about 20 deg or less may be attached. In this case, diffraction lines 131 and 111 from the sapphire (006) surface and the AlN (002) surface can be obtained by performing 2θ / θ scanning after the axial application. Further, the plane orientation of the sapphire (001) plane and the plane orientation of the AlN (001) plane do not have to completely coincide with each other, and a deviation may occur.

  Alternatively, the intensity ratio can be determined by the area ratio of diffraction lines. FIG. 3 is an enlarged view of the diffraction line of the AlN (002) surface that appears in the 2θ / θ scan. The strength area 113 of the hatched portion is taken as the strength of the AlN (002) plane. The diffraction line of the sapphire (006) plane and other diffraction lines are similarly expanded to obtain the area, and the ratio of intensities can be calculated.

  FIG. 4 is a 2θ / θ scan diagram of X-rays when the AlN layer 11 of the present invention is disposed on the sapphire substrate surface 141 whose surface orientation is the (110) plane. The X-ray target is Cu. An AlN layer 11 in which the plane orientation of the formation surface 12 is the (001) plane is formed, and the diffraction line intensity of the diffraction line 111 of the AlN (002) plane is 10 with respect to the diffraction line strength of the diffraction line 132 of the sapphire (110) plane. It is characterized by being at least%. In the case of the AlN layer 11 having such a property, even if a semiconductor layer such as an AlN crystal, an AlN film or (AlGa) N is formed thereon, no crack, crack, or AlN crystal precipitation with different plane orientations occurs. There was found.

  Further, the plane orientation of the surface 141 of the sapphire substrate does not have to be completely coincident with the (110) plane, and an off angle of about 20 deg or less may be attached. In this case, diffraction lines 132 and 111 from the sapphire (110) surface and the AlN (002) surface can be obtained by performing 2θ / θ scanning after the axial application. Further, the plane orientation of the sapphire (110) plane and the plane orientation of the AlN (001) plane do not have to completely coincide with each other, and a deviation may occur.

  Furthermore, the intensity ratio of the sapphire (110) plane to the AlN (002) plane may be determined from the ratio of the diffraction line intensity area as illustrated in FIG.

  In the composite substrate 10 of the present invention, the half width at half maximum of the AlN (002) plane of the AlN layer 11 arranged on the sapphire substrate 13 having the (001) plane surface orientation of the surface 141 is the half width at half of the sapphire (006) plane. It is desirable to be within 5 times in comparison. In the composite substrate 10 of the present invention, the AlN layer 11 disposed on the sapphire substrate 13 whose surface orientation is the (110) plane is the half tilt width of the AlN (002) plane is the tilt half width of the sapphire (110) plane. It is desirable that it is within 5 times compared with. Thus, even when a semiconductor layer such as an AlN crystal, an AlN film, or (AlGa) N is formed thereon using any of the composite substrates 10, a semiconductor such as an AlN crystal, an AlN film, or (AlGa) N formed The tilt of the layer can be improved.

  As an example of the X-ray ω rocking curve, an X-ray ω rocking curve 114 of the AlN (002) plane of the AlN layer 11 is shown in FIG. Since the angle range showing 50% strength to the maximum rocking curve strength is the half width and the ω rocking curve of the (002) plane which is the plane orientation of the forming surface 12, in this case the tilt half of the AlN (002) plane The value range 115 is obtained. It is understood that the smaller the half width is, the smaller the variation in the crystal orientation of the formed surface, that is, the smaller the number of defects and the better the quality as a crystal.

  However, the half width of the tilt is susceptible to the X-ray apparatus performance, particularly the monochromaticity and parallelism of the X-ray, and it is difficult to evaluate in absolute value. Therefore, based on the tilt half width of the sapphire substrate 13 as a base, the inventors relatively compare the tilt half width of the AlN layer 11 disposed on the surface 141, and compare the comparison value with the composite substrate 10 Improve the quality of semiconductor layer such as AlN crystal, AlN film or (AlGa) N by relating to the quality of semiconductor layer such as AlN crystal, AlN film, AlN film or (AlGa) N formed using I found that I could do it.

  That is, if the tilt half width of the AlN (002) plane of the AlN layer is within 5 times the half width of the sapphire (006) plane or the (110) plane, AlN alone can be formed on the composite substrate 10 of this embodiment. The tilt half-width of the AlN single crystal obtained by crystal growth becomes narrower than that of the AlN layer 11, and the crystal quality close to that of the sapphire substrate can be obtained. When the AlN film is formed on the composite substrate 10 of the present embodiment by sputtering, the half-width of the tilt of the formed AlN film is extremely small compared to the case where the AlN film is formed directly on the sapphire substrate. It is shown that the crystallinity of the AlN film is excellent.

  In the composite substrate 10 of the present embodiment, when the AlN layer 11 having the (001) plane orientation of the formation surface 12 is disposed on the sapphire substrate surface 141 having the (001) plane orientation, AlN (100) is disposed. It is desirable that the half width at half maximum of the surface is within 5 times as large as that of the sapphire (100) surface. In the composite substrate 10 of the present embodiment, when the AlN layer 11 having the (001) plane orientation of the formation surface 12 is disposed on the sapphire substrate 141 having the (110) plane orientation, AlN (100 It is desirable that the half width at half maximum of the face is within 5 times as large as that of the sapphire (006) face. As a result, even if a semiconductor layer such as an AlN crystal, an AlN film, or (AlGa) N is formed on any of the composite substrates 10, the crystal quality can be improved.

  The twist half width can usually be determined by in-plane measurement of X-rays. That is, X-rays are incident at a minute angle of 1 deg or less with respect to the sample surface, while the detector is centered on the sample and in the same plane as the sample surface and perpendicular to the surface orientation of the sample surface Rotate to an angle that causes diffraction to the specific reflective surface. For example, in the case of an AlN layer in which the formation plane orientation is a (001) plane, the AlN (100) plane is a plane orientation perpendicular to the (001) plane, and thus can be a specific reflection plane. Although the twist evaluation was performed using the (100) plane, it may be used if it has a plane orientation perpendicular to the (001) plane such as an AlN (110) plane. When the target is Cu, the diffraction angle of the AlN (100) surface is 33.2 deg. In this state, when the sample is rotated by φ rotation, that is, rotated so as to rotate in a plane, diffraction occurs and diffraction lines appear when the rotation angle becomes coincident with the X-ray incident angle of the AlN (100) surface. Since the formed AlN (001) plane has a six-fold axis, when φ is rotated by one rotation, ie, 360 degrees, six diffraction lines appear at intervals of 60 degrees. Among them, one having a good diffraction, ie, a large diffraction line intensity, is selected, a φ rocking curve is drawn, and its half width, ie, a twist half width is determined. The φ rocking curve is also a curve similar to the ω rocking curve shown in FIG.

  The twist half width can be determined by the same measurement for sapphire, but in the case of the composite substrate 10, the back surface 142 in which the sapphire is exposed on the surface or another sapphire substrate manufactured under the same conditions is used. Measure. In the case of in-plane measurement, since the penetration depth of X-rays is shallow, it is difficult to obtain good diffraction of the sapphire substrate when incident from the side 141 on which the AlN layer 11 is formed.

  The twist half width is also susceptible to the apparatus performance and measurement conditions such as X-ray monochromaticity and parallelism, as with the tilt half width, and it is difficult to evaluate in absolute value. Therefore, the inventors evaluated the twist half-width of the AlN layer 11 disposed on the surface 141 with a relative ratio based on the twist half-width of the sapphire substrate as a base, and formed using the composite substrate 10 It has been found that the quality of the semiconductor layer such as AlN crystal, AlN film or (AlGa) N can be improved by relating to the quality of the semiconductor layer such as AlN crystal, AlN film or (AlGa) N.

  That is, in the AlN layer 11 disposed on the sapphire substrate 13 whose surface orientation is the (001) plane, the half width of twist of the AlN (100) plane is within 5 times that of the sapphire (100) plane, The AlN layer 11 disposed on the sapphire substrate 13 whose surface orientation is the (110) plane is within 5 times the half width of the AlN (100) plane compared to that of the sapphire (006) plane. The twist half-width of the AlN single crystal obtained by growing AlN single crystal on the composite substrate 10 of the invention becomes narrower than that of the AlN layer 11, and a crystal quality close to that of the sapphire substrate 13 can be obtained. When an AlN film is formed by sputtering on the composite substrate 10 of the present invention, the X-ray twist half-width of the formed AlN film exhibits an extremely small value as compared with the case where it is directly formed on a sapphire substrate. It was found that the crystallinity of the AlN film formed by sputtering was excellent.

  The thickness of the AlN layer 11 in the composite substrate 10 of the present invention can be determined by an analytical instrument such as SIMS or ESCA. Further, it may be measured by an optical method using light interference.

  Hereinafter, although an example for producing the composite substrate of this embodiment is shown, you may produce the composite substrate which has a structure of this embodiment by another method.

  A production flow is illustrated in FIG. The main steps are a) a step of applying to a base alumina substrate on which a rare earth-containing material is based, b) a step of drying, c) a step of heat treating the applied substrate in the air, and d) a nitriding step. Part or all of this step may be repeated. The feature of this manufacturing method is to form AlN by replacing oxygen in the sapphire substrate and nitrogen in the atmosphere in the nitriding process. Therefore, the crystallinity of the sapphire substrate can be easily maintained, and the composite substrate having the features of the present embodiment can be easily manufactured. Since sapphire and AlN have different crystal structures, local rearrangement occurs, but large rearrangements that cause planar defects and line defects are less likely to occur. Further, the rare earth-containing material is oxidized by the heat treatment in air in step c) to form a rare earth oxide. The rare earth oxide is not necessarily essential for obtaining the composite substrate of the present embodiment, and in that case, only the step d) of nitriding treatment may be performed. However, it is desirable that the rare earth oxide function as an auxiliary during the nitriding treatment and be utilized to promote a desired AlN layer formation reaction.

  First, a raw material containing a rare earth element is coated on a sapphire substrate whose surface has a (001) plane orientation or a (110) plane orientation. Although the spin coating method which can be easily applied is used, it is not limited thereto, and may be performed by a spraying method, a vapor deposition method, a sputtering method or the like. Moreover, you may carry out by the atmosphere containing a rare earth at the process of nitriding-processing mentioned later, without coating. In addition, the sapphire substrate does not have to completely match the surface orientation with the above-mentioned plane orientation, and may have an off angle of about 20 deg or less.

  In spin coating, it is necessary to use a solution. As a raw material, an ethanol solution of rare earth nitrate and a rare earth MOD solution manufactured by High Purity Chemical Laboratory can be exemplified. The MOD solution is obtained by dissolving the organic salt of the rare earth element in a solution mainly composed of xylene. Since the volatility is high, reaggregation of the raw material after application can be prevented. A coated layer was formed by spin coating a rare earth nitrate ethanol solution or a rare earth MOD solution on a sapphire substrate rotated at 1000 to 3000 rpm for 20 to 120 seconds. An aqueous solution can also be used if attention is paid to reaggregation. In the case of the vapor deposition method or the sputtering method, rare earth materials in the form of oxides or metals can be used.

  When using a salt as a raw material, in order to oxidize rare earths, it is preferable to heat-process in air. This heat treatment can suppress the mixing of other types of anions. The heat treatment temperature is preferably 500 ° C. to 1,400 ° C., more preferably 600 ° C. to 1000 ° C., although it depends on the type of salts. In this temperature range, the smoothness of the substrate surface is maintained, and the coating solution is completely pyrolyzed, and even inorganic salts and organic salts can be made into rare earth oxides.

  The nitriding treatment is performed by heating a sapphire substrate coated with a rare earth element in nitrogen. This will be described using FIG. FIG. 7 schematically shows the heating unit. The heating furnace is composed of a carbon heater 25, a sample mount 23, and a chamber 28 covering the whole. A gas exhaust port 26 and a gas introduction port 27 are provided in the chamber 28, and the gas exhaust port 26 is connected to a rotary pump (not shown) and a diffusion pump (not shown), and can be degassed It has become. Further, nitrogen gas can be introduced through the gas inlet 27.

  The alumina plate 24 is placed on the sample placement table 23, and the substrate 20 to be nitrided and the carbon 21 are placed thereon. At the same time, a substantially airtight alumina pot 22 was placed on the alumina plate 24 so as to cover the entire nitrided substrate 20 and the entire carbon 21. The term “substantially sealed” means that the sealing property is not sufficient to completely shut off the gas flow, but is a sealing property to the extent that the gas flow can be suppressed to some extent. Further, when arranging the rare earth-containing raw material in the nitriding treatment, as in the case of the carbon 21, it is arranged so as to cover it with a substantially closed mortar. Furthermore, in the case where the rare earth-containing material or carbon is attached and disposed, it is attached to the inside of the alumina plate 24 and / or the alumina bowl 22.

  Although the atmosphere is maintained in the closed type heating furnace and the substantially closed mortar in the present embodiment, the present invention is not limited thereto. If the amount of carbon and the amount of rare earth element can be controlled, a gas flow or an open heating unit may be used.

  Although heating temperature is based also on the kind of rare earth elements, it is 1400-1800 degreeC, More preferably, it is 1500-1700 degreeC. Below this temperature, the formation of the AlN layer is not sufficient, and the composite substrate 10 having the features of the present embodiment can not be obtained. On the other hand, if the temperature is too high, the sapphire substrate itself is degraded or aluminum oxynitride (AlON) is generated, and it is difficult to obtain the composite substrate 10 having the features of the present embodiment.

  Further, carbon 21 is disposed in the vicinity of the substrate 20 subjected to the nitriding treatment. As described above, it may be attached to the alumina plate 24 and / or the alumina bowl 22. The amount of carbon is different depending on the processing size and the processing conditions, so it can not be generally stated. If the amount is too small, the nitriding treatment can not be sufficiently performed, and the composite substrate 10 having the features of the present embodiment can not be obtained. On the other hand, if the amount is too large, the reaction of formation of AlN rapidly occurs, causing tilt, deterioration of half width of twist, deterioration of surface flatness, or precipitation of AlN having different plane orientation. It becomes difficult to get. It is necessary to adjust the amount of carbon in consideration of the conditions such as the nitriding temperature, time, nitrogen concentration, and the area of the nitrided substrate.

  There is no particular limitation on the arrangement method of carbon and the form of carbon, but since the in-plane uniformity of the AlN layer 11 is affected, it is necessary to devise to be as uniform as possible. FIG. 8 shows an example of the arrangement. Powdered carbon 21 was evenly arranged in a ring around the 2 inch φ sized nitrided substrate 20. At this time, the carbon 21 was disposed with a slight gap so that the nitrided substrate 20 and the carbon 21 were not in direct contact with each other. If a desired composite substrate can be obtained, it may be arranged in one place or may be applied to a holder such as a mortar and the like. In addition, block or rod-like carbon may be disposed. Although carbon is used as the raw material in this embodiment as an example, a raw material containing a carbon atom such as an organic substance may be used, and furthermore, a gas containing a carbon atom may be used.

  By this process, the AlN layer 11 is formed on the surface of the sapphire substrate 13. Most of the rare earths applied to the surface of the sapphire substrate disappear due to the nitriding treatment. It is thought that nitrides or carbides are formed, gasified and disappear. Although a part is taken in near the sapphire surface 141 in the composite substrate 10 and remains, it is a very small amount, and the composite substrate 10 having the features of the present embodiment can be obtained.

Example 1
A MOD solution containing Eu at a concentration of 2 wt% was applied by spin coating at 2000 rpm for 20 seconds on a sapphire substrate 13 having a (001) plane orientation of a surface with a size of 2 inches φ. After coating, the coating was dried on a hot plate at 150 ° C. for 10 minutes, and then heat-treated in air at 600 ° C. for 2 hours. After the heat treatment, it was placed on an alumina plate 24 of 100 mm square, and 50 mg of powdered carbon 21 was further arranged in a ring around the substrate 20 as shown in FIG. As shown in FIG. 7, the whole was covered with an alumina mortar 22 having a size of 75 mm square and a height of 30 mm, and then installed on the sample installation table 23. The nitriding treatment furnace is a resistance heating type electric furnace using carbon as a heater. Before heating, the gas was degassed to 0.03 Pa using a rotary pump and a diffusion pump, and after flowing nitrogen gas to 100 kPa (atmospheric pressure), the flow of nitrogen gas was stopped. The nitriding treatment was performed at a treatment temperature of 1650 ° C., for a treatment time of 24 hours, and at a temperature rising / falling speed of 600 ° C./hour. The processed substrate was transparent.

  The nitrided substrate 20 taken out after the treatment was transparent. Four 15 mm square samples were cut out from the vicinity of the center, and X-ray measurement was performed using one of them. First, when 2θ / θ scanning was performed in the range of 15 to 80 deg with a Cu-targeted X-ray, as shown in FIG. 2, the sapphire (006) surface, the AlN (002) surface and the AlN (004) surface were Diffraction lines were observed, and AIN diffraction lines having different phases and different plane orientations did not appear. The intensity of AlN (002) diffraction line relative to the intensity of sapphire (006) diffraction line was 56%. The half width of the tilt measured with the X-ray ω rocking curve was 0.041 deg for the sapphire (006) plane, while 0.193 deg for the AlN (002) plane and 3 for the half width of the sapphire (006) plane It was tripled. In addition, when in-plane measurement was performed by rotating the sample 360 degrees in the plane using sapphire (100) face and AlN (100) face, six diffraction lines were obtained at 60 deg intervals on both the sapphire back surface 141 and the AlN layer 11. It was seen. It can be seen that the AlN layer 11 is a single crystal when considered together with the 2θ / θ scan. Further, while the half width of the sapphire (100) plane was 0.120 deg, the half width of the AlN (100) plane was 1.4 times as 0.173 deg.

  The thickness of the AlN layer was examined by ESCA using another sample of 15 mm square cut out near the center. As a result, it was found that the film thickness was about 500 nm.

Example 2
An AlN single crystal formed by forming an AlN single crystal on the composite substrate 10 as the composite substrate 10 of the present embodiment using one of the 15 mm square samples cut out in Example 1 by the flux method under the following conditions went. The material (composition: Si 35.7 wt%, C 2.3 wt%, Al 6 2.0 wt% weight: 300 g) was placed in a yttria-stabilized zirconia crucible and placed in the heating region of a high frequency heating furnace. A stirring jig made of yttria-stabilized zirconia, in which the composite substrate 10 prepared in Example 1 and cut out to 15 mm square was fixed with the AlN formation surface 12 of the AlN layer facing downward, was disposed immediately above the material. After the material temperature was raised to 1600 ° C. in a nitrogen atmosphere for melting, the solution was kept stirring for 5 hours with a stirring blade to saturate the solution with nitrogen. Thereafter, the composite substrate was brought into contact with the solution surface, and while rotating at 100 rpm, AlN single crystals were grown for 2 hours on the composite substrate. After crystal growth was completed, the composite substrate was separated from the solution and cooled to room temperature. An AlN single crystal with a thickness of 8 μm was formed on the composite substrate after cooling.

  When X-ray measurement was performed on the AlN single crystal growth surface of this sample in the same measurement system as in Example 1, only diffraction lines of AlN (002) and AlN (004) appeared in 2θ / θ scan, and tilt was observed. The half width was 0.063 deg, and the twist half width was 0.132 deg, which was better than the AlN layer 11 of the composite substrate 10, and showed values close to the tilt and twist half widths of the sapphire substrate. Thus, it was found that by using the composite substrate 10 as a substrate, it is possible to form an AlN single crystal in a good quality state.

Example 3
An AlN film was formed by reactive sputtering on the composite substrate 10 using one of the 15 mm square samples cut out in Example 1 as the composite substrate 10 of the present embodiment. Subsequently, using Al as a target and maintaining nitrogen gas and Ar gas flowing, the degree of vacuum is maintained at 0.23 Pa, sputtering is performed at a substrate heating temperature of 300 ° C. for 8 hours, and an AlN film is formed to a thickness of 1 μm. It formed.

  In the polarization microscope observation, the AlN layer 11 of the composite substrate 10 before the sputtering showed a substantially uniform film property although there was some light and shade. Although defects such as cracks and dislocations were not observed, a hexagonal pattern of about 10 μm in size was locally observed in the film. It seems to be a region where AlN formation has progressed from the periphery.

  The surface of the sputtered AlN film was observed with a polarization microscope, and it was found that some light and shade observed in the AlN layer 11 of the composite substrate 10 disappeared completely and became a uniform surface. In addition, no cracks or defects were observed, and the local hexagonal pattern disappeared to such an extent that visual recognition was difficult. Thus, it was found that by using the composite substrate 10 as a substrate, it is possible to form a semiconductor layer such as an AlN film or (AlGa) N in a good state.

  When this sample was subjected to X-ray measurement in the same measurement system as in Example 1, only diffraction lines of AlN (002), AlN (004) and sapphire (006) appeared in 2θ / θ scan, and The diffraction line intensity of the AlN (002) plane was 210.8% as compared to the diffraction line intensity of the sapphire (006) plane. Although the half width of the tilt is 0.474 deg, and the half width of the twist is 0.583 deg, which is wider than the AlN layer 11 of the composite substrate 10, it is an AlN film formed by the sputtering method that a good quality AlN film is not obtained Given some things, it can be judged as a good result.

Comparative Example 1
An AlN film having a thickness of 1 μm was formed by reactive sputtering under the same conditions as in Example 3 using a 15 mm square sapphire substrate whose surface had a (001) plane orientation as a substrate. Microscopic observation of the sputtered AlN film surface revealed that there were innumerable linear cracks intersecting at an angle of 60 deg or 120 deg and could not be used as a substrate.

  When this sample was subjected to X-ray measurement in the same measurement system as in Example 1, only diffraction lines of AlN (002), AlN (004) and sapphire (006) appeared in 2θ / θ scan. However, the diffraction line intensity of the AlN (002) plane was 98.8% lower than the diffraction line intensity of the sapphire (006) plane, which is lower than that of Example 3. In addition, the ω rocking curve half width is 1.96 deg, and the twist half width is 2.41 deg, which are also extremely broad compared to Example 3.

Example 4
A composite substrate was produced in the same manner as in Example 1 except that a sapphire substrate having a (110) plane was used as the surface orientation of the surface with a size of 2 inches φ. However, carbon was supplied by being attached to the alumina plate 24 and the alumina mortar 22 by pretreatment. That is, 80 mg of powdery carbon is uniformly dispersed on the entire surface of a 2-inch diameter alumina disc placed on an alumina plate and then placed, and then an alumina mortar 22 is placed on the alumina plate 24 to form a nitrogen atmosphere. It heat-treated on condition of 1600 degreeC and 12 hours inside. As a result, the powdered carbon placed on the alumina disc was evaporated and then adhered to the inside of the alumina crucible and to the alumina plate. Using these alumina plates 24 and alumina pots 22, nitriding treatment was carried out using carbon adhered to them as a carbon supply reduction. The nitriding treatment was performed at 1600 ° C. for 48 hours. The processed substrate was transparent.

  A 15 mm square sample cut out from near the center was cut out and subjected to X-ray measurement. First, when 2θ / θ scanning was performed in the range of 15 to 80 deg with a Cu-targeted X-ray, diffraction lines of the sapphire (110) surface and the AlN (002) surface appeared as shown in FIG. On the other hand, AlN diffraction lines and sapphire diffraction lines having different phases and different plane orientations did not appear. The intensity of AlN (002) diffraction line relative to the intensity of sapphire (110) diffraction line was 20%. Also, according to X-ray ω rocking curve measurement, the tilt half width is 0.035 deg for the sapphire (110) surface, while the half tilt width for the AlN (002) surface is 0.155 deg for the AlN (002) surface. Of the sapphire (110) plane was 4.4 times the half width of the tilt. In addition, when the sample was rotated 360 degrees in the plane using sapphire (006) plane and AlN (100) plane, in-plane measurement was performed. Six diffraction lines were observed at. It can be seen that the AlN layer 11 is a single crystal when considered together with the 2θ / θ scan. In addition, the half width of the sapphire (006) plane was 0.104 deg, while the half width of the AlN (100) plane was 2.4 times as 0.250 deg. Further, when the thickness of the AlN layer 11 was determined by ESCA, it was about 300 nm.

  When an AlN film formation was tried also by AlN single crystal growth by a flux method and sputtering method using this composite substrate 10, almost the same results as in Example 2 and Example 3 were obtained. However, it has been found that a semiconductor layer such as an AlN crystal, an AlN film, or (AlGa) N, which is free of cracks and cracks and has further improved crystal quality, is formed.

  The composite substrate of the present embodiment can also be used as a light emitting device, a substrate for a semiconductor device, or a substrate for growing a single crystal such as AlN. Further, it can also be used as a high thermal conductivity substrate, a substrate for surface acoustic wave or a piezoelectric substrate.

10 composite substrate 11 AlN layer 111 diffraction line 112 of AlN (002) plane diffraction line 113 of AlN (004) plane diffraction line intensity area of AlN (002) plane 114 X-ray ω rocking curve 115 AlN (002) plane 002) plane half tilt width 12 AlN formation plane 13 sapphire substrate 131 diffraction line of sapphire (006) plane 132 diffraction line of sapphire (110) plane 141 sapphire surface 142 sapphire back surface 20 nitrided substrate 21 carbon 22 alumina bowl 23 sample Installation table 24 Alumina plate 25 Carbon heater 26 Gas exhaust 27 Gas inlet 28 Chamber

Claims (5)

  A composite substrate in which an AlN layer having a (001) plane orientation is formed on a sapphire substrate surface having a plane orientation of (001) on the surface, which is a diffraction of the (006) plane of the sapphire substrate by X-ray 2θ / θ scanning. The ratio of the diffraction line intensity of the (002) plane of the AlN layer to the line intensity is 10% or more, and the (002) plane of the AlN layer to the half width of the tilt of the (006) plane of the sapphire substrate by X-ray measurement. The composite substrate characterized in that the ratio of the half width of the tilt is within 5 times.   The composite substrate according to claim 1, wherein a ratio of a twist half width of the (100) plane of the AlN layer to a twist half width of the (100) plane of the sapphire substrate by X-ray measurement is 5 or less. .   A composite substrate in which an AlN layer having a (001) plane orientation is formed on a sapphire substrate surface having a (110) plane orientation of the surface, which is a diffraction of the (110) plane of the sapphire substrate by X-ray 2θ / θ scanning. The ratio of the diffraction line intensity of the (002) plane of the AlN layer to the line intensity is 10% or more, and the (002) plane of the AlN layer to the half width of the tilt of the (110) plane of the sapphire substrate by X-ray measurement. The composite substrate characterized in that the ratio of the half width of the tilt is within 5 times.   The composite substrate according to claim 3, wherein a ratio of a twist half width of the (100) plane of the AlN layer to a twist half width of the (006) plane of the sapphire substrate by X-ray measurement is 5 times or less. .   The composite substrate according to any one of claims 1 to 4, wherein a thickness of the AlN layer is 50 nm or more and 1000 nm or less.