JP7044309B2 - Nitride semiconductor templates and nitride semiconductor devices - Google Patents

Description

The present invention relates to nitride semiconductor templates and nitride semiconductor devices.

A light emitting diode (LED) that emits light in the ultraviolet wavelength band is formed by laminating a nitride semiconductor layer containing aluminum (Al) on a base substrate, and has a nitride semiconductor film containing Al as the base substrate. Nitride semiconductor templates may be used. In such a nitride semiconductor template, a nitride semiconductor film containing Al (for example, an aluminum nitride (AlN) film) is formed on a dissimilar substrate such as a sapphire substrate or a silicon carbide (SiC) substrate with a thickness of several hundred nm to several tens of μm. It is made up of. Regarding such a nitride semiconductor template, it has been proposed to improve the quality of a nitride semiconductor film such as a thin AlN film on a substrate by annealing treatment (see, for example, Non-Patent Document 1).

H. Miyake et al., "Annealing of an AlN buffer in N2-CO for growh of a high-quality AlN film on sapphire", Applied Physics Express 9 (16), 55

However, under the treatment conditions of the annealing treatment by the above-mentioned conventional technique, the annealing treatment cannot be performed efficiently, and if the treatment conditions are changed to improve the efficiency, the surface state of the nitride semiconductor film after the annealing treatment is changed. It may cause deterioration.

An object of the present invention is to provide a technique capable of efficiently obtaining a high-quality nitride semiconductor template and a nitride semiconductor device using the template.

According to one aspect of the invention
A method for manufacturing a nitride semiconductor template in which a nitride semiconductor layer is formed on a substrate.
A first layer forming step of epitaxially growing a first layer made of a nitride semiconductor containing aluminum on the substrate.
An annealing step in which the first layer is annealed in an inert gas atmosphere,
A second layer made of a nitride semiconductor containing aluminum is formed by epitaxial growth by vapor phase growth on the first layer after the annealing step, and the nitride semiconductor layer is formed by the first layer and the second layer. The second layer forming process that constitutes
A method for manufacturing a nitride semiconductor template comprising the above is provided.

According to another aspect of the invention.
A nitride semiconductor template in which a nitride semiconductor layer is formed on a substrate.
The nitride semiconductor layer is
A first layer formed on the substrate and made of a nitride semiconductor containing aluminum, the surface on the side of the substrate is a nitrogen polar surface, and the surface facing the nitrogen polar surface is a group III polar surface. ,
A second layer formed on the group III polar plane in the first layer and made of a nitride semiconductor containing aluminum is provided.
A nitride semiconductor template is provided in which the first layer and the second layer are distinguished by the difference in impurity concentration.

According to the present invention, a high-quality nitride semiconductor template and a nitride semiconductor device using the template can be efficiently obtained.

It is sectional drawing which shows the schematic structural example of the nitride semiconductor template which concerns on one Embodiment of this invention. It is a schematic diagram which shows a specific example of the growth apparatus used for manufacturing the nitride semiconductor template which concerns on one Embodiment of this invention. It is sectional drawing which shows the outline of the manufacturing procedure of the nitride semiconductor template which concerns on one Embodiment of this invention. It is explanatory drawing which shows a specific example of the relationship between the state about the dislocation of the surface of the AlN film constituting the 1st layer, and the annealing treatment condition in the nitride semiconductor template which concerns on one Embodiment of this invention. It is explanatory drawing which shows a specific example of the relationship between the state about the dislocation of the surface of the AlN film constituting the 2nd layer, and the annealing treatment condition in the nitride semiconductor template which concerns on one Embodiment of this invention.

<Findings obtained by the inventor>
An LED that emits light in the ultraviolet wavelength band (hereinafter, simply referred to as "ultraviolet LED") includes a single crystal AlN substrate, a nitride semiconductor template having a nitride semiconductor film containing aluminum (Al), and the like as its base substrate. Used.
A single crystal AlN substrate is generally realized by growing an AlN film having a thickness of several mm to several cm on a different type substrate by a sublimation method and then removing the different type substrate, and the dislocation density on the surface is 1 × 10. Low dislocations of ⁵ pieces / cm ² or less have been obtained. However, it is still difficult to realize a large substrate size of 1 inch or more in diameter, and because impurities are mixed in, it absorbs a lot in the ultraviolet region, so sufficient products can be obtained in terms of productivity and characteristics of the ultraviolet LED. It cannot be said that it is.
On the other hand, the nitride semiconductor template is formed by forming a nitride semiconductor film containing Al, such as an AlN film, on a dissimilar substrate such as a sapphire substrate or a SiC substrate with a thickness of several hundred nm to several tens of μm. Since the thickness of the nitride semiconductor film is thin, cracks are unlikely to occur and it is easy to increase the diameter. Since the growth method can be used, it is more advantageous than the single crystal AlN substrate using the sublimation method in terms of increasing the diameter and transparency.
Therefore, for the ultraviolet LED, it is conceivable to use a nitride semiconductor template as the base substrate in consideration of the large diameter, transparency, and the like.

By the way, in the nitride semiconductor templates realized so far, when the thickness of the nitride semiconductor film containing Al is thin (several μm thickness), the dislocation density on the surface becomes high (for example, 1 × 10). ( ⁹ pieces / cm over ² ), and when the dislocation density is as low as 1 × 10 ⁸ pieces / cm ² units or less, it is necessary to process the seed substrate as the base, or the nitride semiconductor film containing Al. Since it is necessary to increase the thickness (for example, more than 20 μm), there is a problem that cracks are likely to occur.
In order to solve such a problem, Non-Patent Document 1 discloses a method of improving the quality of a thin AlN film on a sapphire substrate by annealing. That is, in Non-Patent Document 1, after growing an AlN film of about 300 nm on a sapphire substrate, the substrate and the AlN film are annealed at a high temperature of 1600 ° C. or higher in an _N2 -CO mixed atmosphere. It is described that the dislocation density of the AlN film is reduced to 1 × 10 ⁸ pieces / cm ² units. The reason why the _N2 -CO mixed atmosphere is used for the annealing treatment of the AlN film is to suppress deterioration (white turbidity of the surface) of the AlN surface during the annealing treatment.

However, in a general MOVPE method or HVPE method growth apparatus, it is not assumed that a gas containing carbon monoxide (CO) is allowed to flow. Therefore, in order to apply the method disclosed in Non-Patent Document 1, it is necessary to prepare an annealing device capable of flowing CO gas different from the growth device. Further, for example, when the growth apparatus is configured so that CO gas can be introduced, the purity of the nitride semiconductor film to be grown may decrease due to the inclusion of impurities such as carbon (C) and oxygen (O). I am concerned.
On the other hand, as a result of a follow-up test by the present inventor, an annealing treatment for a nitride semiconductor film containing Al was performed at 1600 ° C. in a nitrogen gas (N ₂ ) atmosphere that can be realized by a general MOVPE method or HVPE method growth device. It was found that in the above case, since the annealing treatment was not performed in the _N2 -CO mixed atmosphere, the surface of the nitride semiconductor film was deteriorated.

Based on these facts, as a result of diligent studies, the present inventor may obtain a nitride semiconductor film containing Al on a surface that is rough to the extent that it is not suitable for regrowth on it at first glance. When a nitride semiconductor film containing additional Al is grown on the surface of the rough nitride semiconductor film under predetermined conditions, the rough surface can be mirrored, and the dislocation density of the regrowth surface can be further improved. We have come to obtain a new finding that the number of particles can be reduced to 1 × 10 ⁹ pieces / cm ² or less.

The present invention is based on the above-mentioned new findings found by the present inventor.

<One Embodiment of the present invention>
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(1) Configuration of Nitride Semiconductor Template First, a schematic configuration example of the nitride semiconductor template according to the present embodiment will be described.
FIG. 1 is a cross-sectional view showing a schematic configuration example of a nitride semiconductor template according to the present embodiment.

The nitride semiconductor template 10 given as an example in the present embodiment is used as a base substrate when manufacturing a semiconductor device (semiconductor device) such as an LED, and is configured as a substrate-like structure. Specifically, the nitride semiconductor template 10 includes a substrate 11 and a nitride semiconductor layer 12.

(substrate)
The substrate 11 functions as a support substrate for supporting the nitride semiconductor layer 12. In the following, the upper surface of the substrate 11 (the surface on the side of the nitride semiconductor layer 12) is referred to as the “front surface (or the first main surface)”, and the lower surface of the substrate 11 located on the opposite side thereof is referred to as the “back surface (or the first surface)”. The second main aspect) ".

The substrate 11 is made of, for example, a sapphire (Al ₂ O ₃ ) substrate, and is configured such that a surface inclined by 0.1 to 3 ° in the a-axis direction or the m-axis direction from the C surface ((0001) surface) is a surface. Has been done.

Further, the surface of the substrate 11 is, for example, a mirror surface. In other words, it is a so-called epiready surface on which a group III nitride semiconductor can be epitaxially grown. Specifically, the root mean square roughness (RMS) of the surface of the substrate 11 is, for example, 10 nm or less, preferably 1 nm or less. The term "RMS" as used herein means a value obtained by analyzing an image having a size of 5 μm × 5 μm with an atomic force microscope (AFM). On the other hand, the back surface of the substrate 11 is not particularly limited, but may be a mirror surface similar to the front surface side or a so-called lap surface which is a rough surface having random irregularities.

As the diameter size of the substrate 11, for example, one having a diameter of 2 to 8 inches is used. As a result, the nitride semiconductor template 10 corresponds to a large substrate size exceeding 1 inch diameter. Further, regarding the thickness of the substrate 11, from the viewpoint of suppressing the warp of the wafer after laminating the LED structure, it is preferable that the larger the diameter size of the wafer, the thicker the wafer, but it is conceivable that the thickness is, for example, 300 μm to 2 mm.

(Nitride semiconductor layer)
The nitride semiconductor layer 12 is a layer formed on the substrate 11 and made of a nitride semiconductor containing aluminum (Al). Examples of the nitride semiconductor containing Al include, but are not limited to, aluminum nitride (AlN). That is, if the nitride semiconductor containing Al is represented by In _{1-xy Al x} Gay N (0 ≦ x + y ≦ 1, 0 <x ≦ 1, 0 ≦ y ≦ 1), it is of AlN. Alternatively, it may be indium nitride (AlInN), aluminum gallium nitride (AlGaN), or aluminum gallium nitride indium (AlInGaN).
Further, the nitride semiconductor layer 12 is composed of a two-layer structure consisting of a first layer 13 located on the side facing the substrate 11 and a second layer 14 formed so as to overlap the first layer 13. There is.

The first layer 13 and the second layer 14 constituting the nitride semiconductor layer 12 are distinguished from each other by the difference in the impurity concentration. For example, when comparing the impurity concentrations of the first layer 13 and the second layer 14 based on the analysis result by the secondary ion mass spectrometry (SIMS), the first layer 13 near the substrate 11 has impurities. O is contained in a larger amount than that of the second layer 14.

The cause of such a difference in oxygen concentration between the first layer 13 and the second layer 14 is due to the difference in crystallinity of the nitride semiconductor containing Al during the growth of each layer. That is, since the dislocation density in the nitride semiconductor containing Al is high during the growth of the first layer 13, a large amount of oxygen is taken in by diffusion from the substrate 11 side or by mixing from the growth atmosphere during the growth. .. The concentration is, for example, about 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ . On the other hand, when the second layer 14 grows, the underlying first layer 13 is improved in quality (lower dislocation) by annealing as described later, so that the second layer 14 is also nitrided containing low dislocation Al. It becomes a layer of physical semiconductors. Therefore, during the growth of the second layer 14, although there is some oxygen diffusion from the first layer 13, the uptake of oxygen is suppressed as a whole. The oxygen concentration of the second layer 14 depends on the atmosphere of the growth apparatus, but is typically 1 × 10 ¹⁸ / cm ³ or less, for example.

Therefore, the nitride semiconductor layer 12 can be identified as having a two-layer structure of the first layer 13 and the second layer 14 by measuring the impurity concentration, and further, the first layer 13 and the second layer 12 can be specified. It is possible to specify where the interface position with the layer 14 exists. The impurity concentration may be measured by using, for example, the result of SIMS analysis, but other known methods may be used.

(First layer)
The first layer 13, which is one of the layers constituting the two-layer structure, is a layer formed by epitaxially growing a nitride semiconductor containing Al on the substrate 11, as described in detail later, and further has an inert gas atmosphere. It is a layer that has been annealed in. By being formed in this way, the first layer 13 is configured to have polarity in the growth direction. Specifically, most of the surface on the side of the substrate 11 is a nitrogen (N) polar surface, and most of the surface on the side facing the N polar surface (that is, the surface on the side of the second layer 14) is Group III polar. It is configured to be a surface. The surface of the first layer 13, which is the surface on the side of the second layer 14, may include a slight N-polar surface (for example, about 10% or less of the surface area). Even in that case, due to the property that the nitride semiconductor itself containing Al easily grows to Group III polarity at high temperature, the entire surface of the second layer 14 is exposed by growing the second layer 14, as will be described later. It becomes a group III polar plane.

Further, the surface of the first layer 13 (that is, the surface on the side of the second layer 14) is reduced in dislocation by being subjected to an annealing treatment. Specifically, for example, the average dislocation density on the surface is 1 × 10 ⁹ pieces / cm ² or less. Further, for example, the half width of (10-12) diffraction of the X-ray locking curve (XRC) measurement with respect to the surface using X-ray diffraction (XRD) is 600 seconds or less, more preferably 400 seconds or less.

However, since the first layer 13 has undergone the annealing treatment in an inert gas atmosphere, the surface may be deteriorated as compared with the case where the annealing treatment is not performed. Specifically, the surface roughness RMS is, for example, It is 1 to 50 nm.

The decrease in dislocation density and the increase in surface roughness in the nitride semiconductor containing Al due to the annealing treatment means that the constituent atoms in the nitride semiconductor containing Al or its surface move around relatively freely during the annealing treatment. It means that. Since there are many dangling bonds of constituent atoms in the dislocation part, it is originally in a state of higher energy than a perfect crystal. However, when the constituent atoms of the nitride semiconductor containing Al are allowed to move freely by performing an annealing treatment as described in detail later, a driving force for extinguishing dislocations is generated so as to reduce the energy of the entire crystal.
However, if such constituent atoms are allowed to move relatively freely, the surface of the nitride semiconductor containing Al becomes rough as described above. Therefore, conventionally, the annealing treatment under such conditions includes Al. It was never adopted as a method for reducing dislocations in nitride semiconductors.

Further, the first layer 13 is formed so as to have a thickness of a continuous film and a thickness at which cracks do not occur. Specifically, the first layer 13 is formed, for example, with a thickness of 100 to 800 nm. If the thickness of the first layer 13 is less than 100 nm, it may not be a continuous film, but if it is 100 nm or more, it can be formed as a continuous film. Further, if the thickness of the first layer 13 exceeds 800 nm, cracks may occur during the formation of the first layer 13 or during the subsequent annealing treatment, but if the thickness is 800 nm or less, the cracks are formed so as not to occur. can do. The first layer 13 is formed, for example, with a thickness of 100 to 800 nm, but it is particularly preferable that the first layer 13 is formed with a thickness of 200 to 800 nm.

(Second layer)
The second layer 14, which is the other layer constituting the two-layer structure, is a layer formed by epitaxially growing a nitride semiconductor containing Al on the surface of the first layer 13, as will be described in detail later. As described above, the entire area of the second layer 14 thus formed is a group III polar plane.

Further, since the second layer 14 is formed on the first layer 13 having a low dislocation, the second layer 14 has a low dislocation like the first layer 13. Specifically, for example, the average dislocation density on the surface thereof (that is, the surface opposite to the surface on the side of the first layer 13) is 1 × 10 ⁹ pieces / cm ² or less.

Moreover, since the second layer 14 is formed on the first layer 13 having low dislocations, cracks are unlikely to occur even if the second layer 14 is formed thick. If there are many dislocations in the underlying layer, it will be in the same state as if there are many cracks inside the underlying layer, so the layer formed on it will be vulnerable to stress and will be easily cracked. This is because if a low dislocation layer such as layer 13 is used as a base, weak portions in the second layer 14 formed on the layer are reduced and cracking is difficult.
Specifically, the second layer 14 is formed, for example, with a thickness of 100 nm to 20 μm. More preferably, the second layer 14 is formed, for example, with a thickness of 3 to 20 μm. The second layer 14 is configured as a crack-free layer even if the thickness is 3 μm or more.

Further, since the second layer 14 is grown on top of the first layer 13, the surface of the second layer 14 is flattened as compared with the case of only the first layer 13. Specifically, the surface roughness RMS of the surface of the second layer 14 is 10 nm or less, more preferably 1 nm or less.

(2) Method for Manufacturing Nitride Semiconductor Template Next, a procedure for manufacturing the nitride semiconductor template 10 having the above-described configuration, that is, a method for manufacturing the nitride semiconductor template according to the present embodiment will be described.

(Structure example of growth device)
Here, first, a configuration example of a growth device used for manufacturing the nitride semiconductor template 10 will be described.
FIG. 2 is a schematic diagram showing a specific example of a growth apparatus used for manufacturing a nitride semiconductor template according to the present embodiment.
The illustration shows a hydride vapor phase deposition apparatus (HVPE apparatus) as a specific example of the growth apparatus.

The HVPE apparatus 200 includes an airtight container 203 made of a heat-resistant material such as quartz or alumina and having a film forming chamber 201 inside. A susceptor 208 for holding the substrate 11 is provided in the film forming chamber 201. The susceptor 208 has a pocket 208p for accommodating the substrate 11 with the surface of the substrate 11 facing up. The susceptor 208 is connected to the rotation shaft 215 of the rotation mechanism 216, and the substrate 11 placed on the susceptor 208 is placed on the susceptor 208 while the substrate 11 is held upward by the gear provided on the back surface of the susceptor 208. It is configured to be rotatable in the circumferential direction (direction along the main surface).
The susceptor 208, the pocket 208p, and the rotation mechanism 216 are preferably made of carbon or carbon coated with SiC, boron nitride (BN), or the like, and the other members are made of high-purity quartz with few impurities. It is preferable to be configured. Further, it is preferable that the member in the region exposed to a high temperature of 1300 ° C. or higher is made of alumina instead of high-purity quartz.

At one end of the airtight container 203, a gas supply pipe 232b for supplying hydrogen chloride (HCl) gas into the film forming chamber 201, a gas supply pipe 232c for supplying ammonia (NH ₃ ) gas into the forming chamber 201, and A gas supply pipe 232d for supplying H ₂ gas, N ₂ gas or HCl gas is connected to the film forming chamber 201. The gas supply pipes 232b to 232d are provided with flow rate controllers 241b to 241d and valves 243b to 243d in this order from the upstream side. A gas generator 233b for accommodating solid Al as a raw material is provided downstream of the gas supply pipe 232b. The gas generator 233b is a nozzle that supplies aluminum chloride (AlCl or AlCl ₃ ) gas as a film-forming gas generated by the reaction of HCl gas and Al toward the substrate 11 or the like held on the susceptor 208. 249b is connected. On the downstream side of the gas supply pipes 232c and 232d, nozzles 249c and 249d that supply the film-forming gas supplied from these gas supply pipes toward the substrate 11 and the like held on the susceptor 208 are connected. The nozzles 249b to 249d are arranged so as to allow gas to flow in a direction intersecting the surface of the substrate 11 (in an oblique direction with respect to the surface).

On the other hand, at the other end of the airtight container 203, an exhaust pipe 230 for exhausting the inside of the film forming chamber 201 is provided. The exhaust pipe 230 is provided with a pump 231 (or a blower). A zone heater 207 for heating the substrate 11 and the like held in the gas generator 233b and the susceptor 208 to a desired temperature is provided on the outer periphery of the airtight container 203, and the temperature in the film forming chamber 201 is measured in the airtight container 203. Each temperature sensor 209 is provided. The vicinity of the gas generator 233b of the zone heater 207 (see A1 in the figure) is maintained at 600 to 800 ° C. or 400 to 600 ° C., whereby AlCl gas or AlCl ₃ gas is generated by the reaction between HCl gas and Al. Generated. Further, the vicinity of the susceptor 208 of the zone heater 207 (see A3 in the figure) is maintained at a temperature suitable for growth described later.

Each member included in the HVPE apparatus 200 is connected to a controller 280 configured as a computer, and is configured such that a processing procedure and processing conditions described later are controlled by a program executed on the controller 280.

In addition to the above-mentioned parts, the HVPE apparatus 200 includes a gas supply pipe 232a for supplying HCl gas into the film forming chamber 201, a flow rate controller 241a, a valve 243a, a gallium (Ga) melt or indium as a raw material ( In) A gas generator 233a, a nozzle 249a, etc. for accommodating the melt are provided, and gallium chloride (GaCl) gas or gallium chloride (GaCl) gas as a film forming gas generated by the reaction between the HCl gas and the Ga melt or the In melt is provided. Indium chloride (InCl) gas may be configured to be supplied toward the substrate 11 or the like held on the susceptor 208. Furthermore, a gas generator accommodating the Ga melt and the In melt may be provided separately, and the GaCl gas and the InCl gas may be supplied independently.

(Outline of manufacturing procedure)
Subsequently, a procedure for manufacturing a nitride semiconductor template using the HVPE apparatus 200 having the above-described configuration will be described by taking the case where the nitride semiconductor is AlN as an example. Hereinafter, the nitride semiconductor template 10 when the nitride semiconductor is AlN is referred to as “AlN template 10”.
FIG. 3 is a cross-sectional view showing an outline of a manufacturing procedure of a nitride semiconductor template according to the present embodiment.

The production of the AlN template 10 includes a substrate preparation step (step 1, hereinafter, the step is abbreviated as “S”), a first layer forming step (S2), an annealing step (S3), and a second layer forming step (S4). ) And then.

(S1: Substrate preparation process)
In the substrate preparation step (S1), the substrate 11 processed by the HVPE apparatus 200, that is, the substrate 11 that constitutes the AlN template 10, is prepared. Specifically, as the substrate 11, for example, a sapphire substrate having a surface inclined by 0.1 to 3 ° in the a-axis direction or the m-axis direction from the C surface is prepared. Since the optimum growth conditions of the AlN film may change slightly depending on the off direction of the substrate 11, it is effective to keep the off direction of the substrate 11 to be used constant in order to improve the reproducibility. If the off-angle is less than 0.1 °, the accuracy in the off-direction becomes low at the stage of polishing the sapphire substrate, and the off-direction may change for each substrate 11. Therefore, such a small off-angle It is preferable to avoid the substrate 11. Further, when the off-angle is larger than 3 °, a huge step is often formed on the surface of the finally obtained AlN template 10, so it is preferable to avoid the substrate 11 having such a large off-angle. ..

For the diameter size of the substrate 11, for example, one of the sizes of 2 to 8 inches in diameter is selected. The diameter size referred to here may be an actual inch size, but may be a customarily used size such as "2 inches" = 50 mm or "6 inches" = 150 mm.

(S2: First layer forming step)
After the substrate preparation step (S1), the first layer forming step (S2) is then performed. In the first layer forming step (S2), first, the substrate 11 prepared in the substrate preparation step (S1) is placed on the susceptor 208 of the HVPE apparatus 200 with its surface facing up.

Further, in the HVPE apparatus 200, solid Al as a raw material is stored in the gas generator 233b. Then, while rotating the susceptor 208 and heating and exhausting the inside of the film forming chamber 201, the H ₂ gas (or a mixed gas of H ₂ gas and N ₂ gas) is introduced into the film forming chamber 201 from the gas supply pipe 232d. ) Is supplied. Further, gas is supplied from the gas supply pipes 232b and 232c in a state where the inside of the film forming chamber 201 reaches a desired growth temperature and a desired growth pressure and the inside of the film forming chamber 201 has a desired atmosphere, and the substrate 11 is subjected to gas supply. AlCl gas or AlCl ₃ gas and NH ₃ gas are supplied as the film forming gas in the direction intersecting the surface. These film-forming gases may be mixed with a carrier gas composed of H ₂ gas, N ₂ gas or a mixed gas thereof and supplied.

As a result, as shown in FIG. 3A, the first layer 13 made of AlN is epitaxially grown and formed on the surface side of the substrate 11 by vapor phase growth. In this way, by forming the first layer 13 by epitaxial growth by vapor phase growth, the diameter of the AlN template 10 is increased (for example, a large substrate size of 2 inches or more) as compared with the case of forming by the sublimation method. It is advantageous in terms of realization) and ensuring transparency.

The surface of the substrate 11 on which the first layer 13 is formed is a mirror surface and does not have an uneven pattern on the surface. Therefore, in forming the first layer 13, voids due to the uneven pattern on the surface do not exist between the substrate 11 and the first layer 13.

The first layer 13 is formed so that the first layer 13 has a thickness that makes it a continuous film and the first layer 13 has a thickness that does not cause cracks. Specifically, as described above, for example, the first layer 13 is formed so that the thickness of the first layer 13 is 100 to 800 nm, particularly 200 to 800 nm.

Further, in the first layer forming step (S2), the first layer 13 crystallizes (that is, becomes a non-amorphous state) at the time when the growth to the above-mentioned thickness is completed (that is, the asgrown state before the annealing treatment). Under the conditions, the first layer 13 is formed. Specifically, the first layer 13 is formed by heating with the zone heater 207 so that, for example, the vicinity of the susceptor 208 of the HVPE apparatus 200 maintains a growth temperature of 1000 to 1300 ° C. (in FIG. 2). See A3). Then, the growth of the AlN film for forming the first layer 13 is carried out by adjusting the supply amounts of AlCl gas or AlCl ₃ gas and NH ₃ so that the growth rate is 0.5 to 500 nm / min. The supply amount ratio (so-called V / III ratio) of the N source and the Al source is 0.2 to 200. At this time, HCl gas may flow from the nozzle 249d in order to prevent parasitic AlN adhesion to the nozzles 249a to 249a, and the amount thereof is 0.1 to 100 with respect to AlCl gas or _AlCl3 gas. The ratio is.

The surface roughness RMS of the surface of the first layer 13 thus formed is, for example, about 0.3 to 10 nm at the time when the growth is completed (that is, the asgrown state before the annealing treatment). Further, the first layer 13 becomes polar in the growth direction, for example, the side of the substrate 11 becomes an N polar surface, and almost the entire surface on the opposite side (that is, the surface of the first layer 13) is a group III polar surface. It becomes a certain Al polar surface.

(S3: Annealing process)
By the way, since the first layer 13 is formed thin so as to have a thickness that does not cause cracks, there is a concern that the dislocation density will increase at the time of completion of growth (that is, in the asgrown state before the annealing treatment). To. Therefore, after the first layer forming step (S2), an annealing step (S3) is performed in order to improve the quality of the thin first layer 13 on the substrate 11.

In the annealing step (S3), the supply of AlCl gas or AlCl ₃ gas, NH ₃ gas and H ₂ gas into the film forming chamber 201 in the HVPE apparatus 200 is stopped, and N ₂ gas is supplied from all the gas supply pipes. By doing so, the atmosphere in the film forming chamber 201 is replaced with N ₂ gas. Then, after creating an _N2 gas atmosphere in the film forming chamber 201, while rotating the susceptor 208 and exhausting the inside of the film forming chamber 201, the zone heater 207 (see A3 in FIG. 2) is used to move the vicinity of the susceptor 208. Raise to the desired annealing temperature. In this way, in the annealing step (S3), the N ₂ gas atmosphere is applied to the first layer 13 formed on the substrate 11 without carrying out the substrate 11 from the film forming chamber 201 of the HVPE apparatus 200. Annealing process is performed with. That is, the annealing treatment is performed on the first layer 13 in an N ₂ gas atmosphere, which is an atmosphere that does not contain AlCl gas or AlCl ₃ gas, NH ₃ gas, and H ₂ gas. In this way, since the annealing treatment is performed in the N ₂ gas atmosphere, it is possible to suppress the mixing of impurities such as C and O into the first layer 13 during the annealing treatment, and it is also used in the first layer forming step (S2). It is also possible to realize an annealing process using the existing HVPE apparatus 200 as it is.

The annealing treatment performed in the annealing step (S3) is for improving the quality of the surface state (particularly, the state related to dislocations) of the first layer 13. Therefore, in the annealing step (S3), it is preferable to perform the annealing treatment under the condition that the average dislocation density on the surface of the first layer 13 after the annealing treatment is 1 × 10 ⁹ pieces / cm ² or less. Further, in the annealing step (S3), the annealing treatment is performed under the condition that the half width of the (10-12) diffraction of the XRC measurement on the surface of the first layer 13 after the annealing treatment is 600 seconds or less, more preferably 400 seconds or less. I do. This corresponds to the annealing treatment in the annealing step (S3) under the condition of mainly reducing the blade dislocations of the first layer 13. When the average dislocation density is 1 × 10 ⁹ pieces / cm ² or less, the half width of the (10-12) diffraction of the XRC measurement corresponds to about 400 seconds or less.

The state of the surface dislocations (for example, blade-like dislocations and spiral dislocations) of the AlN layer after the annealing treatment depends on the treatment temperature (annealing temperature) at the time of performing the annealing treatment, for example, as shown in FIG.
FIG. 4 is an explanatory diagram showing a specific example of the relationship between the state regarding dislocations on the surface of the AlN film constituting the first layer and the annealing treatment conditions.
The illustration shows a specific example of the relationship between the half-value width of (10-12) diffraction of XRC measurement using an XRD device (that is, the measurement results for both blade dislocations and spiral dislocations) and the annealing temperature (FIG. 4 (a)). (See), and also shows a specific example of the relationship between the half-value width of (0002) diffraction in the XRC measurement (that is, the measurement result for spiral dislocations) and the annealing temperature (see FIG. 4 (b)). Specifically, in the case of the figure, the thickness of the first layer 13 is 100 nm, 200 nm, 320 nm, 460 nm, 570 nm, 800 nm, 840 nm, or 1020 nm, and there is no annealing or the annealing temperature is 1500 to 1850. The temperature is ℃, the time of the annealing treatment is 1 hour, and the result of taking out the wafer from the HVPE apparatus 200 and performing the XRC measurement immediately after the annealing treatment, that is, before growing the second layer 14, is shown.

According to the measurement results shown in FIGS. 4 (a) and 4 (b), when no annealing treatment is performed, the average dislocation density on the surface of the first layer 13 is 1 ×, which is equivalent to that of the conventional AlN film. 10 ¹⁰ pieces / cm ² or more, and the half width of (0002) diffraction is as small as about 100 seconds, but the half width of (10-12) diffraction is as large as about 1000 seconds.
On the other hand, when the annealing treatment is performed, the XRC half width is changed especially by the annealing treatment at 1600 ° C. or higher. That is, by performing the annealing treatment at a temperature of 1600 ° C. or higher, the half width of the (0002) diffraction of the XRC measurement is increased as compared with the case where the annealing treatment is not performed, and the half width of the (10-12) diffraction is decreased. is doing.
In particular, focusing on the half width of (10-12) diffraction, the decrease is remarkable in the range of the annealing temperature in the range of 1600 to 1800 ° C., especially when the thickness of the first layer 13 is 800 nm or less, 600 seconds or less. It is a small half-value width of. Further, when the thickness of the first layer 13 is 320 nm or less, the temperature is in the range of 1600 to 1800 ° C., and when the thickness of the first layer 13 is 460 nm, the temperature is in the range of 1720 to 1800 ° C. (10-12). The half width of diffraction is 400 seconds or less, and under this condition, it is considered that the dislocation density is 1 × 10 ⁹ pieces / cm ² or less. When the annealing temperature is 1850 ° C. or higher, the half width of (10-12) diffraction deteriorates to 700 seconds or longer, and it is considered that the annealing temperature is too high and the dislocation density is conversely increasing. Be done.
Even when the annealing time was changed between 30 and 180 minutes, almost the same results were obtained.

From the above, in the annealing step (S3), as a specific condition for realizing the above-mentioned high quality of the first layer 13, for example, the thickness of the first layer 13 is in the range of 100 to 800 nm. The annealing treatment is performed in the temperature range of 1600 to 1800 ° C. and in a time of 30 to 180 minutes.
When the thickness of the first layer 13 is smaller than 100 nm, the surface is not flattened after the growth of the first layer 13, and the sapphire of the substrate 11 is etched during the annealing treatment to form the first layer 13. Since it peels off, it becomes difficult to obtain a high-quality film. Further, when the thickness of the first layer 13 is larger than 800 nm, it is difficult to set the half width of the (0002) diffraction of the XRC measurement to 600 seconds or less, as shown in FIG. This is a phenomenon that supports the idea that when the first layer 13 is thin, the constituent atoms of AlN move around relatively freely during the annealing treatment to reduce dislocations. That is, it can be explained that the reason why it is difficult to improve the quality of the AlN film when the first layer 13 is thick is that the degree of freedom of the constituent atoms in AlN is relatively reduced.
If the annealing treatment is performed at a temperature of less than 1600 ° C., the effect of the annealing treatment may not be sufficiently obtained, the surface condition of the first layer 13 may not be improved, and the annealing treatment may not be performed at a temperature of 1850 ° C. or higher. If this is done, the annealing treatment will be excessively performed, which will hinder the improvement of the surface condition of the first layer 13.
The same applies to the annealing treatment time, and if the annealing treatment is performed in a time of less than 30 minutes, the effect of the annealing treatment may not be sufficiently obtained, and the surface condition of the first layer 13 may not be improved in quality. Further, if the annealing treatment is performed for a time exceeding 180 minutes, the annealing treatment will be excessively performed, and there is a concern that the surface condition of the first layer 13 will be hindered from being improved in quality.

By the way, in the annealing step (S3), if the annealing treatment is performed under the condition that the quality of the AlN film can be sufficiently improved, the surface of the first layer 13 is deteriorated. Specifically, the surface of the first layer 13 may change as described below before and after the annealing treatment.

For example, regarding the surface roughness RMS of the surface of the first layer 13, the surface roughness RMS after the annealing step (S3) is the surface after the first layer forming step (S2) and before the annealing step (S3). Roughness is greater than RMS. Specifically, the surface roughness RMS of the surface of the first layer 13 after the first layer forming step (S2) and before the annealing step (S3) is 0.3 to 10 nm, whereas the annealing step (S3). ) The surface roughness RMS of the surface of the first layer 13 after that is changed to 1 to 50 nm.

Further, for example, regarding the half width of the (0002) diffraction or (0004) diffraction of the XRC measurement with respect to the surface of the first layer 13, the value after the annealing step (S3) is annealed after the first layer forming step (S2). It becomes larger than the value before the step (S3). Specifically, as shown in FIG. 4, the (0002) diffraction or (0004) diffraction of the XRC measurement with respect to the surface of the first layer 13 after the first layer forming step (S2) and before the annealing step (S3). The half width is 50 to 200 seconds when the thickness of the first layer 13 is at least 800 nm or less. On the other hand, the half width of the (0002) diffraction or (0004) diffraction of the XRC measurement on the surface of the first layer 13 after the annealing step (S3) is 100 to 600 for the annealing treatment at 1600 to 1800 ° C. Each value changes before and after the annealing process, such as seconds.
An increase in the half-value width of the (0002) diffraction or (0004) diffraction is generally considered to indicate an increase in the blade dislocation density. However, this is mainly an argument for crystals when the surface is flattened, and a different argument holds when the surface is rough. That is, when the surface is rough, even if dislocations do not exist, there is an additional degree of freedom in the atomic position on the surface or the orientation of the lattice plane, so that (0002) diffraction or (0004) diffraction can be performed. A large half-value range may be observed. Considering this, at least in the range where the annealing temperature is 1800 ° C. or lower, the increase in the half width of (0002) diffraction seen in FIG. 4 does not reflect the increase in the dislocation density of the first layer 13, and the surface surface. It is thought that it was due to the roughness. As will be described later, even if the second layer 14 having only a few hundred nm is grown on the first layer 13 after the annealing treatment, the half width of (0002) diffraction is before the annealing treatment when the surface is flattened. The fact that it recovers to the same extent as the above supports this inference (the dislocation density does not increase after the annealing treatment).

As described above, if the annealing treatment in the N ₂ gas atmosphere is performed so that the dislocations of the first layer 13 are lowered, the first layer 13 is deteriorated such as surface roughness. Therefore, conventionally, the annealing treatment in the N ₂ gas atmosphere has not been used.
However, even when the surface of the first layer 13 is deteriorated by the annealing treatment in the N ₂ gas atmosphere, when an additional AlN film is grown on the rough surface under the predetermined conditions described later, The present inventor has found that the rough surface can be mirrored and the dislocation density of the regrowth surface can be 1 × 10 ⁹ pieces / cm ² or less in the best case. Therefore, after the annealing step (S3), the second layer forming step (S4) is performed in order to superimpose the first layer 13 and grow the second layer 14 under predetermined conditions.

(S4: Second layer forming step)
In the second layer forming step (S4), the susceptor 208 is rotated and heated in the film forming chamber 201 without carrying out the substrate 11 on which the first layer 13 is formed from the film forming chamber 201 of the HVPE apparatus 200. And while exhausting, H ₂ gas (or a mixed gas of H ₂ gas and N ₂ gas) is supplied from the gas supply pipe 232d into the film forming chamber 201. Further, gas is supplied from the gas supply pipes 232b and 232c in a state where the inside of the film forming chamber 201 reaches a desired growth temperature and a desired growth pressure and the inside of the film forming chamber 201 has a desired atmosphere, and the substrate 11 is subjected to gas supply. AlCl gas or AlCl ₃ gas and NH ₃ gas are supplied as the film forming gas in the direction intersecting the surface. These film-forming gases may be mixed with a carrier gas composed of H ₂ gas, N ₂ gas or a mixed gas thereof and supplied.

As a result, as shown in FIG. 3B, the second layer 14 made of AlN is epitaxially grown and formed on the surface of the first layer 13 by vapor phase growth. By forming the second layer 14 by epitaxial growth by vapor phase growth in this way, the crystal structure of the second layer 14 becomes similar to the crystal structure of the first layer 13. That is, since the first layer 13 has low dislocations, the second layer 14 formed on the first layer 13 also has low dislocations. Specifically, for example, when the average dislocation density on the surface of the first layer 13 after the annealing treatment is the best, it is 1 × 10 ⁹ pieces / cm ² or less, so that the second layer 14 formed on the first layer 13 In the best case, the average dislocation density on the surface of the surface is 1 × 10 ⁹ pieces / cm ² or less. Further, due to the growth of the second layer 14, the entire surface becomes an Al polar surface which is a group III polar surface.

The second layer 14 is formed, for example, so that the thickness of the second layer 14 is 100 nm to 20 μm. Even if it is formed so thick, the second layer 14 is formed on the first layer 13 with low dislocations, so that cracks are unlikely to occur. If there are many dislocations in the underlying layer, it will be in the same state as if there are many cracks inside the underlying layer, so the layer formed on it will be vulnerable to stress and will be easily cracked. This is because if a low dislocation layer such as layer 13 is used as a base, weak portions in the second layer 14 formed on the layer are reduced and cracking is difficult. That is, with respect to the second layer 14 formed on the first layer 13, for example, even if the second layer 14 is formed with a thickness of 3 μm or more, which is generally considered to be likely to cause cracks, a crack-free layer (no cracks are present). It will be formed as a layer).

Further, in the second layer forming step (S4), the formation of the second layer 14 is maintained, for example, in the vicinity of the susceptor 208 of the HVPE apparatus 200, maintaining a growth temperature of 1000 to 1600 ° C, more preferably 1400 to 1600 ° C. The zone heater 207 (see A3 in FIG. 2) is used for heating so as to be in such a state. Then, the growth of the AlN film for forming the second layer 14 is carried out by adjusting the supply amounts of AlCl gas or AlCl ₃ gas and NH ₃ so that the growth rate is 0.5 to 500 nm / min. The supply amount ratio (so-called V / III ratio) of the N source and the Al source is 0.2 to 200. At this time, HCl gas may be flown from the nozzle 249d in order to prevent parasitic AlN adhesion to the nozzles 249a to 249a, and the amount thereof is 0.1 to 100 with respect to the _AlCl3 gas. do.

The surface roughness RMS of the surface of the second layer 14 thus formed is, for example, 10 nm or less, more preferably 1 nm or less.

That is, even if the surface of the first layer 13 is deteriorated, it is formed so as to be superimposed on the surface of the first layer 13 on the premise that the first layer 13 has a low dislocation. When the second layer 14 is grown to a thickness of 100 nm or more and at a growth temperature of 1000 to 1600 ° C., particularly at a growth temperature of 1400 to 1600 ° C., the surface of the second layer 14 can be mirrored. can. Furthermore, the dislocation density on the surface of the second layer 14 can be set to 1 × 10 ⁹ pieces / cm ² or less in the best case.

FIG. 5 is an explanatory diagram showing a specific example of the relationship between the state regarding dislocations on the surface of the AlN film constituting the second layer and the annealing treatment conditions, and is a half width at half maximum of (10-12) diffraction in the XRC measurement (that is,). A specific example of the relationship between the annealed dislocation (measurement results for both edge dislocations and spiral dislocations) and annealing temperature (see FIG. 5 (a)), and the half width of (0002) diffraction of the same XRC measurement (that is, measurement for spiral dislocations). A specific example of the relationship between the result) and the annealing temperature (see FIG. 5B) is shown.
The figure shows the XRC half width measured after growing the second layer 14 having a thickness of 300 nm on the first layer 13. More specifically, in the illustrated example, the thickness of the first layer 13 is 100 nm, 200 nm, 320 nm, 460 nm, 570 nm, 800 nm, 840 nm, or 1020 nm, and there is no annealing or the annealing temperature is 1500 to 1850 ° C. Yes, when the annealing treatment time is 1 hour, the result of XRC measurement is shown for the second layer 14 formed on the first layer 13 with a thickness of 300 nm.

According to the measurement result shown in FIG. 5A, when the annealing temperature of the first layer 13 is in the range of 1600 to 1800 ° C. and the thickness of the first layer 13 is 800 nm or less, the surface of the second layer 14 is formed. The half width of the (10-12) diffraction of the XRC measurement is 600 seconds or less. Further, according to the measurement result shown in FIG. 5 (b), the half width of (0002) diffraction under the corresponding conditions is 200 seconds or less, and the dislocation densities of both the blade dislocations and the spiral dislocations are under these conditions. It can be seen that it is kept low.
In particular, focusing on the half width of (10-12) diffraction, when the annealing temperature is in the range of 1600 to 1800 ° C. and the thickness of the first layer 13 is 320 nm or less, the annealing temperature is 1700 to 1800 ° C. In the range and when the thickness of the first layer 13 is 460 nm, the half width of the (10-12) diffraction of the XRC measurement is 400 seconds or less, and the dislocation density is 1 × 10 ⁹ pieces / cm. It is ² or less.
Even when the thickness of the second layer 14 is changed from 100 nm to 20 μm, almost the same result is obtained.

(Flow from S2 to S4)
As described above, in the production of the AlN template 10, in the present embodiment, the first layer forming step (S2), the annealing step (S3) and the second layer forming step (S4) are carried out by the same growth apparatus, HVPE. This is continuously performed using the device 200. That is, since it is performed continuously, after the annealing step (S3), the second layer forming step (S4) is performed without sandwiching the polishing step for the first layer 13.

Therefore, unlike the case of the method disclosed in Non-Patent Document 1, for example, it is not necessary to prepare an annealing device capable of flowing CO gas separately from the growth device. Furthermore, since the annealing treatment is performed in an _N2 gas atmosphere, it is possible to suppress impurities such as C and O from being mixed into the upper second layer 14, and the HVPE apparatus 200 that performs vapor phase growth can be used as it is. The former annealing process can also be realized.

(Products)
By going through each of the steps (S1 to S4) described above, the AlN template 10 of the present embodiment shown in FIG. 1 is manufactured.

In such an AlN template 10, after the first layer 13 is grown on the substrate 11, an annealing treatment is performed at a temperature of 1600 to 1800 ° C. in an _N2 gas atmosphere, and the second layer 14 is placed on the second layer 14 at a temperature of 100 nm or more. It was obtained by growing to a thickness and at a growth temperature of 1000 to 1600 ° C., particularly at a growth temperature of 1400 to 1600 ° C., whereby the surface of the second layer 14 was mirrored and had a low rearrangement. Is. That is, the AlN template 10 is only the HVPE device 200 (that is, with a simple device configuration that does not require an annealing device other than the growth device), and is, for example, a conventional product by the method disclosed in Non-Patent Document 1. It achieves the same or better surface quality and crystal quality.

Further, in the AlN template 10, the first layer 13 and the second layer 14 are continuously formed by using the same HVPE device 200, but during the growth of the first layer 13, the AlN template 10 is formed. Due to the high dislocation density of the substrate 11, a large amount of oxygen is taken in by diffusion from the substrate 11 side or by mixing from the growth atmosphere during growth. The concentration is about 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ . Since the first layer 13 itself is grown by the method conventionally used, the oxygen concentration is also about the same as that by the conventional method. On the other hand, when the second layer 14 grows, the first layer 13 as a base is improved in quality (lower dislocation) by annealing treatment, so that the second layer 14 also has low dislocation AlN. Therefore, during the growth of the second layer 14, although there is some oxygen diffusion from the first layer 13, the uptake of oxygen is suppressed as a whole. The oxygen concentration of the second layer 14 depends on the atmosphere of the HVPE device 200, but is typically 1 × 10 ¹⁸ / cm ³ or less.

The AlN template 10 thus obtained is used, for example, when manufacturing a semiconductor device (semiconductor device) such as an LED. That is, a nitride semiconductor device can be configured by laminating an n-type, p-type or undoped multilayer film on the AlN template 10 and growing and forming a nitride semiconductor laminated structure containing Al. .. Such a nitride semiconductor device can realize, for example, a Schottky diode, a pn junction diode, a light emitting diode or a transistor.

(3) Effects obtained by the present embodiment According to the present embodiment, one or more of the following effects can be obtained.

(A) According to the present embodiment, the AlN layer 12 of the AlN template 10 has a two-layer structure of the first layer 13 and the second layer 14, and the first layer 13 is annealed in an _N2 gas atmosphere. After that, the second layer 14 is regrown on the first layer 13, so that a high quality AlN template 10 can be efficiently obtained.

(B) In the AlN template 10 of the present embodiment, the AlN layer 12 on the substrate 11 has a two-layer structure of the first layer 13 and the second layer 14, and both the first layer 13 and the second layer 14 have a two-layer structure. It is formed by epitaxial growth by vapor phase growth. Therefore, as compared with the case of forming by, for example, the sublimation method, it is advantageous in terms of increasing the diameter of the AlN template 10 and ensuring transparency.

(C) Further, since the AlN template 10 of the present embodiment is annealed with respect to the first layer 13, the first layer 13 can be reduced in dislocation. Moreover, since the first layer 13 has low dislocations, the second layer 14 formed on the first layer 13 also has low dislocations. That is, since the AlN template 10 of the present embodiment achieves the low dislocation of the AlN layer 12 by the annealing treatment to the first layer 13, it is not necessary to increase the AlN growth thickness for the low dislocation, and the annealing treatment is performed. It is possible to achieve low dislocation on the surface of the AlN layer 12 with a thinner thickness (total thickness of the first layer 13 and the second layer 14) than in the case where the AlN layer 12 is not used, and the risk of cracks in the AlN layer 12 is reduced. be able to.
Moreover, since the second layer 14 is formed on the first layer 13 having low dislocations, cracks are less likely to occur even if the second layer 14 is formed thick. If there are many dislocations in the underlying layer, it will be in the same state as if there are many cracks inside the underlying layer, so the layer formed on it will be vulnerable to stress and will be easily cracked. This is because if a low dislocation layer such as layer 13 is used as a base, weak portions in the second layer 14 formed on the layer are reduced and cracking is difficult.

(D) Further, since the AlN template 10 of the present embodiment is annealed to the first layer 13 in an _N2 gas atmosphere, it is possible to suppress the mixing of impurities such as C and O, and the AlN film to be grown can be suppressed. It is possible to eliminate the concern that the purity of the gas will decrease.
Moreover, in the annealing treatment in the N ₂ gas atmosphere, it is possible to perform the annealing treatment using the HVPE apparatus 200 for growing the AlN film as it is, so that it is not necessary to prepare an annealing apparatus different from the HVPE apparatus 200. .. That is, in manufacturing the AlN template 10, it is feasible to continuously perform the first layer forming step (S2), the annealing step (S3), and the second layer forming step (S4) in the HVPE apparatus 200. The AlN template 10 can be manufactured very efficiently.

(E) If the annealing treatment in the N ₂ gas atmosphere is performed to the extent that the crystal layer has lower dislocations, deterioration such as surface roughness occurs. Therefore, conventionally, the annealing treatment in the N ₂ gas atmosphere has not been used. However, in the present embodiment, even if the surface of the first layer 13 is deteriorated by the annealing treatment in the N ₂ gas atmosphere, the second layer has additional AlN growth on the rough surface. Since the formation of 14 is performed under predetermined conditions, the surface of the second layer 14 can be mirrored, and the average dislocation density of the surface of the second layer 14, that is, the surface of the AlN layer 12 is 1 × 10 ⁹ pieces /. It can be cm ² or less. That is, even if the surface of the first layer 13 is roughened by the annealing treatment, the second layer 14 having a flat surface can grow on the first layer 13 whose dislocations have been reduced by the annealing treatment. This makes it possible to obtain a high quality AlN template 10.

<Other embodiments>
Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment and can be variously modified without departing from the gist thereof.

In the above-described embodiment, the case where the nitride semiconductor is AlN, that is, the case where the first layer 13 and the second layer 14 are formed by using AlN has been described as an example, but the present invention is limited thereto. There is no such thing. The first layer 13 and the second layer 14 are nitride semiconductors containing Al, for example, In _{1-xy Al x} Gay N (0 ≦ x + y ≦ 1, 0 <x ≦ 1, 0 ≦ y ≦ 1). ), AlN, AlInN, AlGaN, or AlInGaN, the same result as the example of the above-described embodiment can be obtained.

Further, in the above-described embodiment, the case where the annealing treatment is performed in an _N2 gas atmosphere in the annealing step (S3) has been described as an example, but the present invention is not limited thereto. That is, the annealing treatment performed in the annealing step (S3) contains GaCl gas, GaCl ₃ gas, AlCl gas, AlCl ₃ gas, InCl gas, InCl ₃ gas, HCl gas, Cl ₂ gas, NH ₃ gas and H ₂ gas. If the operation is performed on the first layer 13 in a non-existent atmosphere, even if the operation is performed using an inert gas different from the N ₂ gas such as argon or helium instead of the N ₂ gas. Often, even in that case, the same technical effect as in the case of the above-described embodiment is obtained.

Further, in the above-described embodiment, the case where the substrate 11 is a sapphire substrate has been described, but the present invention is not limited to this, and for example, the substrate 11 may be a SiC substrate or the like. However, when the substrate 11 is a SiC substrate, the optimum annealing temperature in the annealing step (S3) is in the range of 1600 to 2000 ° C.
Further, the surface of the substrate 11 is not limited to the C surface, but may be an R surface, an A surface or an M surface, or a surface inclined in the range of 0.1 to 3 ° from these surfaces.

Further, in the above-described embodiment, the case where the gas is flowed in the direction intersecting the main surface of the substrate 11 (the direction oblique to the main surface) in the HVPE apparatus 200 has been described, but the main surface of the substrate 11 is covered. The gas may flow in a direction along the main surface (a direction parallel to the main surface) or in a direction perpendicular to the main surface of the substrate 11.

Further, in the above-described embodiment, the case where the nitride semiconductor template 10 is manufactured by using the HVPE device 200 has been given as an example, but the present invention is not limited thereto. That is, if the growth apparatus used for manufacturing the nitride semiconductor template 10 is formed by epitaxially growing the first layer 13 and the second layer 14, for example, another vapor phase growth apparatus such as a MOVPE apparatus or sputtering. It may be carried out by using a growth apparatus other than the vapor phase growth method such as the method or the sodium flux method, and even in that case, the same technical effect as in the case of the above-described embodiment is obtained.

Further, in the above-described embodiment, a case where the first layer forming step (S2), the annealing step (S3), and the second layer forming step (S4) are continuously performed using the same HVPE apparatus 200 is given as an example. However, the present invention is not limited to this. That is, in the first layer forming step (S2), the annealing step (S3), and the second layer forming step (S4), each step is performed using a different device, or the same growth device is used for either two steps. You may use it to do it.

<Preferable Aspect of the Present Invention>
Hereinafter, preferred embodiments of the present invention will be described.

[Appendix 1]
According to one aspect of the invention
A method for manufacturing a nitride semiconductor template in which a nitride semiconductor layer is formed on a substrate.
A first layer forming step of epitaxially growing a first layer made of a nitride semiconductor containing aluminum on the substrate.
An annealing step in which the first layer is annealed in an inert gas atmosphere,
A second layer made of a nitride semiconductor containing aluminum is formed by epitaxial growth by vapor phase growth on the first layer after the annealing step, and the nitride semiconductor layer is formed by the first layer and the second layer. The second layer forming process that constitutes
A method for manufacturing a nitride semiconductor template comprising the above is provided.

[Appendix 2]
In the method for manufacturing a nitride semiconductor template according to Appendix 1, preferably.
As the substrate, a sapphire substrate having a surface inclined by 0.1 to 3 ° in the a-axis direction or the m-axis direction from the C surface is used.

[Appendix 3]
In the method for manufacturing a nitride semiconductor template according to Appendix 1 or 2, preferably.
As the substrate, a substrate having a diameter of 2 to 8 inches is used.

[Appendix 4]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 3, preferably.
The surface roughness RMS of the surface of the first layer after the annealing step is larger than the surface roughness RMS of the surface of the first layer after the first layer forming step and before the annealing step.
The surface roughness RMS is a value obtained by analyzing an image having a size of 5 μm × 5 μm with an atomic force microscope.

[Appendix 5]
In the method for manufacturing a nitride semiconductor template according to Appendix 4, preferably.
The surface roughness RMS of the surface of the first layer after the first layer forming step and before the annealing step is 0.3 to 10 nm.
The surface roughness RMS of the surface of the first layer after the annealing step is 1 to 50 nm.

[Appendix 6]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 5, preferably.
X-ray locking curve measurement (000) for the surface of the first layer after the annealing step.
2) The annealing treatment is performed under the condition that the half width of diffraction or (0004) diffraction becomes larger than the value after the first layer forming step and before the annealing step.

[Appendix 7]
In the method for manufacturing a nitride semiconductor template according to Appendix 6, preferably.
The half-value width of (0002) diffraction or (0004) diffraction of the X-ray locking curve measurement with respect to the surface of the first layer after the first layer forming step is 50 to 200 seconds.
The half width of the (0002) diffraction or (0004) diffraction of the X-ray locking curve measurement with respect to the surface of the first layer after the annealing step is 100 to 600 seconds.

[Appendix 8]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 7, preferably.
In the first layer forming step, the first layer is formed so that the thickness of the first layer becomes a continuous film and the thickness of the first layer does not cause cracks.

[Appendix 9]
In the method for manufacturing a nitride semiconductor template according to Appendix 8, preferably.
In the first layer forming step, the first layer is formed so that the thickness of the first layer is 100 to 800 nm.

[Appendix 10]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 9, preferably.
In the first layer forming step, the first layer is formed under the condition that the first layer is crystallized (= non-amorphous state) at the time of completion of growth (= asgrown state before annealing treatment).

[Appendix 11]
In the method for manufacturing a nitride semiconductor template according to Appendix 10, preferably.
In the first layer forming step, the first layer is formed at a growth temperature of 1000 to 1300 ° C.

[Appendix 12]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 11, preferably.
In the annealing step, the annealing treatment is performed under the condition that the average dislocation density on the surface of the first layer after the annealing step is 1 × 10 ⁹ pieces / cm ² or less.

[Appendix 13]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 12, preferably.
In the annealing step, the annealing treatment is performed under the condition that the half width of the (10-12) diffraction of the X-ray locking curve measurement on the surface of the first layer after the annealing treatment is 600 seconds or less.

[Appendix 14]
In the method for manufacturing a nitride semiconductor template according to Appendix 13, more preferably.
The annealing treatment is performed under the condition that the half width is 400 seconds or less.

[Appendix 15]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 14, preferably.
In the annealing step, the annealing treatment is performed under the condition of reducing the blade dislocations of the first layer.

[Appendix 16]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 15, preferably.
The substrate is a sapphire substrate,
In the annealing step, the annealing treatment is performed in a temperature range of 1600 to 1800 ° C.

[Appendix 17]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 15, preferably.
The substrate is a SiC substrate, and the substrate is a SiC substrate.
In the annealing step, the annealing treatment is performed in a temperature range of 1600 to 2000 ° C.

[Appendix 18]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 17, preferably.
In the annealing step, the annealing process is performed in a time of 30 to 180 minutes.

[Appendix 19]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 18, preferably.
In the annealing step, the annealing treatment is performed in a nitrogen gas atmosphere.

[Appendix 20]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 19, preferably.
In the annealing step, the annealing treatment is performed in an atmosphere that does not contain hydrogen and ammonia gas.

[Appendix 21]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 20, preferably.
In the annealing step, the annealing treatment is performed using an inert gas (argon, helium, etc.) different from the nitrogen gas instead of the nitrogen gas.

[Appendix 22]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 21, preferably.
In the second layer forming step, the second layer is formed under the condition that the surface roughness RMS of the second layer is 10 nm or less.

[Appendix 23]
In the method for manufacturing a nitride semiconductor template according to Appendix 22, more preferably.
The surface roughness RMS of the second layer is set to 1 nm or less.

[Appendix 24]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 23, preferably.
In the second layer forming step, the second layer is formed at a growth temperature of 1000 to 1600 ° C.

[Appendix 25]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 24, preferably.
In the second layer forming step, the second layer is formed so that the thickness of the second layer is 100 nm to 20 μm.

[Appendix 26]
In the method for manufacturing a nitride semiconductor template according to any one of Supplementary note 1 to 25, preferably.
The first layer forming step, the annealing step, and the second layer forming step are continuously performed using the same growth apparatus.

[Appendix 27]
In the method for manufacturing a nitride semiconductor template according to Appendix 26, preferably.
After the annealing step, the second layer forming step is performed without sandwiching the polishing step for the first layer.

[Appendix 28]
According to another aspect of the invention.
A nitride semiconductor template in which a nitride semiconductor layer is formed on a substrate.
The nitride semiconductor layer is
A first layer formed on the substrate and made of a nitride semiconductor containing aluminum, the surface on the side of the substrate is a nitrogen polar surface, and the surface facing the nitrogen polar surface is a group III polar surface. ,
A second layer formed on the group III polar plane in the first layer and made of a nitride semiconductor containing aluminum is provided.
A nitride semiconductor template is provided in which the first layer and the second layer are distinguished by the difference in impurity concentration.

[Appendix 29]
In the nitride semiconductor template according to Appendix 28, preferably.
The surface roughness RMS on the side of the first layer at the interface between the first layer and the second layer is 1 to 50 nm.

[Appendix 30]
In the nitride semiconductor template according to Appendix 28 or 29, preferably.
The first layer has a surface roughness RMS of 1 to 50 nm on the polar surface of Group III.
The surface roughness RMS of the surface of the second layer is 10 nm or less.

[Appendix 31]
In the nitride semiconductor template according to any one of the appendices 28 to 30, preferably.
The first layer has a thickness of 100 to 800 nm and has a thickness of 100 to 800 nm.
The second layer has a thickness of 100 nm to 20 μm.

[Appendix 32]
In the nitride semiconductor template according to any one of the appendices 28 to 31, preferably.
The second layer is a crack-free layer having a thickness of 3 μm or more.

[Appendix 33]
In the nitride semiconductor template according to any one of the appendices 28 to 32, preferably.
The average dislocation density on the surface of the second layer is 1 × 10 ⁹ pieces / cm ² or less.

[Appendix 34]
In the nitride semiconductor template according to any one of the appendices 28 to 33, preferably.
The entire surface of the second layer is a group III polar surface.

[Appendix 35]
In the nitride semiconductor template according to any one of the appendices 28 to 34, preferably.
The substrate does not have a surface unevenness pattern and
There are no voids due to the surface unevenness pattern between the substrate and the first layer.

[Appendix 36]
In the nitride semiconductor template according to any one of the appendices 28 to 35, preferably.
The first layer and the second layer are aluminum nitride and indium nitride represented by In _1-x-y Al _{x Gay} N (0≤x + y≤1, 0 <x≤1, 0≤y≤1). , Aluminum gallium nitride, or aluminum gallium nitride indium.

[Appendix 37]
According to still another aspect of the invention.
The nitride semiconductor template according to any one of claims 28 to 36,
A nitride semiconductor laminated structure formed by growing on the nitride semiconductor template,
Nitride semiconductor devices are provided.

[Appendix 38]
In the nitride semiconductor device according to Appendix 37, preferably.
The nitride semiconductor laminated structure is an n-type, p-type or undoped structure represented by In _{1-x-y Al x} Gay N (0≤x + y≤1, 0 <x≤1, 0≤y≤1). It is formed by laminating a multilayer film, and realizes a Schottky diode, a pn junction diode, a light emitting diode, or a transistor.

10 ... Nitride semiconductor template (AlN template), 11 ... Substrate, 12 ... Nitride semiconductor layer, 13 ... First layer, 14 ... Second layer, 200 ... HVPE device

Claims (5)

A nitride semiconductor template in which an aluminum nitride layer is formed on a substrate.
The aluminum nitride layer is
It is formed on the substrate to a thickness of 100 to 800 nm, which is a thickness that forms a continuous film and does not cause cracks, is made of aluminum nitride, and the surface on the side of the substrate is a nitrogen polar surface. The surface on the side facing the nitrogen polar surface is the aluminum polar surface, and the first layer having an average dislocation density of 1 × 10 ⁹ pieces / cm ² or less on the aluminum polar surface.
A second layer formed on the polar surface of aluminum in the first layer, made of aluminum nitride, and having an average dislocation density of 1 × 10 ⁹ pieces / cm ² or less on the surface is provided.
A nitride semiconductor template in which the first layer and the second layer are distinguished by the difference in impurity concentration. The nitride semiconductor template according to claim 1, wherein the surface of the first layer constituting the interface with the second layer is rougher than the surface of the second layer. The nitride semiconductor template according to claim 1 or 2, wherein the oxygen concentration in the second layer is smaller than the oxygen concentration in the first layer. The first layer has a surface roughness RMS of 1 to 50 nm on the polar surface of aluminum.
The nitride semiconductor template according to any one of claims 1 to 3 , wherein the second layer has a surface roughness RMS of 10 nm or less. The nitride semiconductor template according to any one of claims 1 to 4 .
A nitride semiconductor laminated structure formed by growing on the nitride semiconductor template,
Nitride semiconductor device.

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