KR20130113452A - Method for producing substrate for group iii nitride semiconductor element fabrication, method for producing group iii nitride semiconductor free-standing substrate or group iii nitride semiconductor element, and group iii nitride growth substrate - Google Patents

Abstract

In the case where the chromium layer is nitrided into the MOCVD growth furnace, by improving the area ratio of the triangular pyramidal chromium nitride crystals on the surface of the formed chromium nitride layer, the crystallinity of the crystal layer grown on the chromium nitride layer thereafter and Provided is a method of manufacturing a substrate for producing a III-nitride semiconductor device that can improve uniformity. A film forming step of forming a chromium layer on the underlying substrate for growth, and a nitride step of forming a chromium nitride layer by nitriding the chromium layer under predetermined conditions, and at least one group III nitride semiconductor layer on the chromium nitride layer. It is a manufacturing method of the group III nitride semiconductor element manufacture board | substrate which has a crystal layer growth process which epitaxially grows, The said chromium layer is the range whose film-forming speed in a sputtering particle amorphous region is 7-65 kPa / sec by sputtering method. In which the chromium nitride layer is formed in a gas atmosphere containing ammonia gas in a MOCVD growth furnace at a temperature of 1000 ° C. or higher, having a furnace pressure of 6.666 kPa or more and 66.66 kPa or less. Gas components other than ammonia gas in gas atmosphere are made into the carrier gas which consists of nitrogen gas and hydrogen gas, and the said carry The content of the nitrogen gas occupying the gas is characterized in that in the range of 60 to 100% by volume.

Description

A method for manufacturing a group III nitride semiconductor device manufacturing substrate, a method for manufacturing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor device, and a group III nitride growing substrate. GROUP III NITRIDE SEMICONDUCTOR FREE-STANDING SUBSTRATE OR GROUP III NITRIDE SEMICONDUCTOR ELEMENT, AND GROUP III NITRIDE GROWTH SUBSTRATE}

The present invention relates to a method for manufacturing a group III nitride semiconductor device manufacturing substrate, a method for manufacturing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor device, and a group III nitride growth substrate.

In general, for example, a group III nitride semiconductor element composed of a group III nitride semiconductor composed of Al, Ga, and N compounds is widely used as a light emitting element or an element for an electronic device. Such a group III nitride semiconductor is generally formed by a metal organic chemical vapor deposition (MOCVD) method on a crystal growth substrate made of, for example, sapphire.

However, since the lattice constants of the group III nitride semiconductor and the crystal growth substrate (generally sapphire) are significantly different, the crystal quality of the group III nitride semiconductor layer grown on the crystal growth substrate due to a potential caused by the difference in the lattice constant is generated. There is a problem that this decreases.

In order to solve this problem, in the prior art, for example, a method of growing a GaN layer on a sapphire substrate via a low-temperature polycrystalline or amorphous buffer layer is widely used. However, since the sapphire substrate has a low thermal conductivity and poor heat dissipation, and an electric current cannot flow through the insulation, an n-electrode and a p-electrode are formed on one surface of the nitride semiconductor device layer, and a current is taken in this configuration. Is difficult to shed and is inadequate for the production of high power light emitting diodes (LEDs).

For this reason, non-patent document 1 and patent document 1 attach a growth layer to another support substrate with high thermal conductivity electroconductively, and irradiate a GaN layer from the back surface of a sapphire substrate with laser light which has quantum energy larger than the energy gap of GaN, A method such as a laser lift-off method for thermally decomposing Ga and N to peel a sapphire substrate and a group III nitride semiconductor layer has been proposed. However, these systems have problems such as high cost of the laser lift-off device, and easy thermal damage to the device layer formed on the GaN layer to be peeled off.

Moreover, as another conventional technique, the technique by which the GaN layer was grown through the metal nitride layer on the sapphire substrate by patent documents 2-5 is disclosed. According to this method, the dislocation density of the GaN layer can be reduced in comparison with the above buffer layer technology, and it is possible to grow a high quality GaN layer. This is because the difference between the lattice constant and the coefficient of thermal expansion between the CrN film and the GaN layer as the metal nitride layer is relatively small. In addition, this CrN film can be selectively etched with a chemical etching solution, and is useful in a process of separating the growth substrate and the group III nitride semiconductor device layer by a chemical lift-off method.

In this patent document, as a suitable condition for the chromium nitride layer, the metal chromium layer formed on the sapphire substrate for growth in an HVPE (Hydride Vapor Phase Epitaxy) device is an atmosphere containing ammonia gas. A technique is disclosed in which a nitriding treatment is applied at a temperature of 1000 DEG C or higher to partially form a triangular pyramidal chromium nitride microcrystal shown in Fig. 1A on a substrate surface. The crystal structure of chromium nitride is rock salt type (cubic system), and the bottom of the triangular pyramid is (111) plane, and the bottom is [10-10], [01-10], [-1100] directions in the sapphire substrate (0001) plane. The orientation parallel to and toward the apex of the triangular pyramid from the center of the bottom becomes [111] as shown by the result of the X-ray diffraction 2θ-ω scan in FIG.

Japanese Patent Publication No. 2001-501778 International Publication No. 2006/126330 Japanese Patent Publication No. 2008-91728 Japanese Patent Publication No. 2008-91729 WO2007 / 023911 publication

 W. S. Wong et al., Appl. Phys. Lett. 72 (1998) 599.

As such, generally, nitriding of the chromium layer is performed in an HVPE apparatus. The reason for this is that the nitriding treatment in the HVPE apparatus is a hot-wall type, and since the ammonia gas is heated before mixing with the Group III chloride gas such as GaCl, which is a Group III raw material, the decomposition efficiency of the ammonia gas is increased. Good things are mentioned. However, thin film growth is indispensable for the formation of nitride semiconductor elements. In HVPE growth furnaces, thin film formation of nitride semiconductor layers is difficult, and it is necessary to transfer the MON furnace after forming a CrN layer in the HVPE furnace. However, at this time, there was a problem that epitaxial growth of the group III nitride semiconductor layer having good crystallinity on the CrN layer was difficult due to oxidation of the surface of the CrN layer or the like.

The present inventors applied nitriding treatment to the chromium layer in a MOCVD growth furnace so as to solve these problems, but found that the manufacturing conditions described in Patent Literatures 2 to 5 are some, but not sufficient, conditions. That is, as shown in Fig. 2 (a), not only chromium nitride microcrystals having a weak triangular pyramid shape but also flaky or amorphous microcrystals having various orientations close to a square are included. ) And FIG. 2 (c), there are cases where a difference in shape in the substrate surface on the underlying substrate is observed. In addition, it is implied from the result of the X-ray diffraction shown in FIG.

In order to grow a group III nitride semiconductor crystal layer having good crystallinity on the chromium nitride layer, the [111] orientation of the chromium nitride layer coincides in the direction perpendicular to the surface of the sapphire substrate for growth, and the chromium nitride layer. Since the orientation of the in-plane rotation is preferably provided to be a predetermined orientation in the sapphire (0001) plane, the formation of various microcrystals in the scaly or irregular shape may lower the crystallinity or uniformity of the crystal layer. .

An object of the present invention is to improve the area ratio occupied by a weak triangular pyramidal chromium nitride crystal on the surface of a formed chromium nitride layer when nitriding a chromium layer in a MOCVD growth furnace. It is providing the manufacturing method of the group III nitride semiconductor element manufacture board | substrate which can improve the crystallinity and uniformity of the crystalline layer grown, and the manufacturing method of a group III nitride semiconductor independence board | substrate or a group III nitride semiconductor element.

In order to achieve the above object, the present invention has the following structure.

(1) a film forming step of forming a chromium layer on a substrate for growth, a nitriding step of forming a chromium nitride layer by nitriding the chromium layer under predetermined conditions, and at least one group III nitride on the chromium nitride layer It is a manufacturing method of the group III nitride semiconductor element manufacturing substrate provided with the crystal layer growth process which epitaxially grows a semiconductor layer, The said chromium layer is sputtering by the sputtering method in the film-forming rate in the sputtering particle amorphous region in the range of 7-65 GPa / sec. The chromium nitride layer is formed in a gas atmosphere containing ammonia gas in a MOCVD growth furnace having a pressure in the furnace of 6.666 kPa or more and 66.66 kPa or less and a temperature of 1000 ° C. or more. Gas components other than ammonia gas in a gas atmosphere are carrier gas which consists of nitrogen gas and hydrogen gas, and the said carrier gas Content ratio is 60 to method for manufacturing a Group III nitride semiconductor device for manufacturing a substrate, characterized in that in the range of 100% by volume of nitrogen gas accounts.

(2) The manufacturing method of the group III nitride semiconductor element manufacturing substrate as described in said (1) whose area ratio which the chromium nitride microcrystal of a chromium nitride layer surface of the said chromium nitride layer has about trigonal pyramidal shape occupies is 70% or more.

(3) The chromium layer of the substrate for producing a group III nitride semiconductor device according to (1) or (2), wherein the chromium layer is intermittently formed on a plurality of substrates for growth so as to have an average film forming speed in a range of 1 to 10 Pa / sec. Manufacturing method.

(4) Group III according to the above (2) or (3), wherein the orientation of the lower side of the triangular pyramidal chromium nitride microcrystal is parallel to the group <11-20> direction (a-axis direction) of the group III nitride semiconductor layer. The manufacturing method of the board | substrate for manufacturing nitride semiconductor elements.

(5) The substrate for growth has a crystal structure of hexagonal or pseudo hexagonal system, and the substrate for producing a group III nitride semiconductor device manufacturing according to any one of (1) to (4), wherein the surface is a (0001) plane. Way.

(6) a film forming step of forming a chromium layer on a substrate for growth, a nitride step of forming a chromium nitride layer by nitriding the chromium layer under predetermined conditions, and at least one group III nitride on the chromium nitride layer. A group III nitride semiconductor self-supporting substrate having a crystal layer growth step of epitaxially growing a semiconductor layer and a separation step of separating the growth substrate and the group III nitride semiconductor by removing the chromium nitride layer by chemical etching; A method of manufacturing a group nitride semiconductor device, wherein the chromium layer is formed by a sputtering method so as to have a thickness of 50 to 300 kPa in the range of 7 to 65 kV / sec in the sputtered grain amorphous region, and the chromium nitride layer is Gas atmosphere containing ammonia gas in a MOCVD growth furnace with a pressure in the furnace of 6.666 kPa or more and 66.66 kPa or less and a temperature of 1000 ° C or higher. And a gas component other than ammonia gas in the gas atmosphere is a carrier gas composed of nitrogen gas and hydrogen gas, and the content ratio of nitrogen gas in the carrier gas is in the range of 60 to 100% by volume. A method of manufacturing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor element.

(7) The production of the group III nitride semiconductor self-supporting substrate or the group III nitride semiconductor element according to the above (6), wherein an area ratio of the chromium nitride microcrystals on the surface of the chromium nitride layer is occupied by a chromium nitride microcrystal having a triangular pyramidal shape of 70% or more. Way.

(8) The group III nitride semiconductor self-supporting substrate according to (6) or (7) or III, wherein the chromium layer is formed intermittently to form an average film forming speed on the plurality of growth substrates, respectively, in a range of 1 to 10 Pa / sec. Method of manufacturing a group nitride semiconductor device.

(9) Group III according to the above (7) or (8), wherein the orientation of the bottom side of the trigonal pyramidal chromium nitride microcrystal is parallel to the <11-20> direction (a-axis direction) group of the group III nitride semiconductor layer. A method for producing a nitride semiconductor self-supporting substrate or a group III nitride semiconductor device.

(10) The group III nitride semiconductor self-supporting substrate or group III according to any one of (6) to (9), wherein the growth base substrate has a hexagonal or pseudo hexagonal crystal structure and whose surface is (0001). Method of manufacturing nitride semiconductor device.

(11) In the III-nitride growth substrate having a substrate and a chromium nitride layer on the substrate, a chromium nitride microcrystal having a triangular pyramidal shape occupies 70% of the chromium nitride microcrystal on the surface of the chromium nitride layer. The group III nitride growth substrate characterized by the above.

According to the present invention, the formation of a chromium layer formed on a substrate for growth and a nitriding condition for nitriding the chromium layer in a MOCVD growth furnace are appropriately set, thereby forming a triangular pyramidal shape in the surface of the chromium nitride layer formed. III which can improve the ratio which chromium microcrystals occupy, and can improve the crystallinity and uniformity of the crystal layer of the group III nitride semiconductor layer and group III nitride semiconductor element structure layer which continue to grow on a chromium nitride layer by this. A method for producing a substrate for producing a group nitride semiconductor element, and a method for producing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor element can be provided.

1 (a) and 1 (b) show the results of surface SEM photographs and X-ray diffraction 2θ-ω scans of samples subjected to nitriding of a chromium layer sputtered on a sapphire substrate in an HVPE furnace, respectively. Indicates.
2 (a) to 2 (c) respectively show surface SEM photographs of samples in the case where the chromium layer sputtered on a sapphire substrate was nitrided in a MOCVD furnace under predetermined conditions, and FIG. The result of the X-ray diffraction 2θ-ω scan is shown.
Fig.3 (a)-(d) is typical sectional drawing for demonstrating the manufacturing method of the board | substrate for group III nitride semiconductor element manufacture which concerns on this invention.
4 (a) and 4 (b) are schematic perspective views of various sputtering apparatuses, and FIG. 4 (c) is a schematic sectional view of the sputtering apparatus shown in FIG. 4 (b).
5 (a) and 5 (b) are graphs for explaining the relationship between the film formation speed and the average film formation speed.
6 (a) and 6 (b) show the relationship between the deposition rate of the chromium layer and the formation rate of the chromium nitride microcrystals of the triangular pyramidal shape after the nitriding treatment, respectively, and the average triangular pyramidal shape after the nitriding treatment with the average deposition rate of the chromium layer. It is a graph which shows the relationship with the formation rate of the chromium nitride microcrystals.
7 (a) and 7 (b) show SEM images of the surface of the sample after nitriding treatment, and FIG. 7 (c) shows the results of the X-ray diffraction 2θ-ω scan.
8 (a) and 8 (b) each show SEM photographs showing the surface shape of the chromium layer when the chromium layer on the sapphire substrate is heat-treated in a hydrogen-nitrogen mixed gas atmosphere or a nitrogen gas atmosphere.
Fig. 9 (a) is a graph showing the relationship between the proportion of nitrogen in the carrier gas and the area ratio occupied by microcrystalline crystals in the shape of a triangular pyramid. Figs. 9 (b) to 9 (f) show surface SEM photographs of the samples after nitriding treatment, respectively. Indicates.
10 is a SEM photograph showing the pressure inside the furnace during nitriding treatment and the surface state of the chromium nitride layer after nitriding treatment.
11 shows a SEM photograph showing the surface state of the chromium nitride layer when the nitriding treatment temperature and treatment time are changed when the carrier gas is total nitrogen.
12 (a) to 12 (e) are schematic cross-sectional views for explaining a method for manufacturing a group III nitride semiconductor element manufacturing substrate, a group III nitride semiconductor independence substrate, and a group III nitride semiconductor element according to the present invention.
13 (a) and 13 (b) are graphs showing the relationship between the film formation speed and average film formation speed of the chromium layer and the half width of the X-ray locking curve of the GaN layer grown by the MOCVD method, respectively.
14 (a) and 14 (b) are diagrams showing the crystal orientation (epitaxial) relationship between the chromium nitride layer and the group III nitride semiconductor layer due to the difference in substrate type.
Fig. 15 is a graph showing the relationship between the thickness of the chromium layer and the half width of the X-ray locking curve of the GaN layer grown by the MOCVD method.
16 (a) and 16 (b) are SEM images of the surface of the sample after the X-ray diffraction 2θ-ω scan and the nitriding treatment, respectively.

EMBODIMENT OF THE INVENTION The manufacturing method of the board | substrate for manufacturing a group III nitride semiconductor element which concerns on this invention, and the manufacturing method of a group III nitride semiconductor independence board | substrate or a group III nitride semiconductor element are demonstrated, referring drawings. Here, the group III nitride semiconductor element manufacturing substrate in the present invention means that at least one group III nitride semiconductor layer is grown on a chromium nitride layer formed on a substrate for growth, and a group III nitride semiconductor independence substrate is used. After the growth of the group III nitride semiconductor layer having a thickness of several hundred μm or more on the chromium nitride layer formed on the substrate for growth substrate, the substrate for growth is separated. In addition, the group III nitride semiconductor element means that the device is separated by performing a device process such as electrode deposition on the group III nitride semiconductor element manufacturing substrate, or the group III nitride semiconductor on the group III nitride semiconductor independence substrate. An element structure layer is formed, and an element isolation | separation is performed by performing a device process, such as electrode deposition. Examples of the group III nitride semiconductors include, but are not limited to, GaN-based, InGaN-based, AlInGaN-based, AlGaN-based, and the like. In addition, in this specification, a "layer" may be a continuous layer and may be a discontinuous layer. "Layer" shows the state formed with thickness.

Fig.3 (a)-(d) is typical sectional drawing for demonstrating the manufacturing method of the board | substrate for group III nitride semiconductor element manufacture which concerns on this invention. In the step shown in Fig. 3A, a substrate 10 for growth is prepared. As an example, the growth base substrate 10 is a sapphire single crystal, and the surface 10a on the upper surface side of the growth base substrate is a (0001) plane. The sapphire single crystal is a rhombohedral crystal structure, and is a pseudo hexagonal system.

As the base substrate 10 for growth, a material other than sapphire may be used as long as the material has any crystal structure of a pseudo hexagonal system, a hexagonal system, and a cubic system. For example, it may be a template substrate in which an AlN epitaxial layer is formed on an AlN single crystal or various growth substrates.

In the step shown in FIG. 3B, the chromium layer 20 is formed on the surface 10a of the growth base substrate 10 at a predetermined speed. The chromium layer 20 is formed by a sputtering method, and the film formation rate in the sputtered particle amorphous region is in the range of 7 to 65 Pa / sec. Moreover, although the atmosphere at the time of sputtering is Ar gas of the range of 0.05-0.5 Pa of pressure, what is necessary is just to adjust a pressure range suitably according to an apparatus structure. Moreover, as a film-forming method of the chromium layer 20, RF (high frequency) or DC (direct current) sputtering method etc. are mentioned, The film thickness of the chromium layer 20 is formed so that it may become the range of 50-300 Hz.

As a sputtering apparatus, although a single-purchase board | substrate may be set in the opposing position which is equal to or smaller than a target area, in order to improve productivity, when forming into a film on many base substrates for growth, FIG. The substrate holding holder or the tray 130 is rotated and formed into a film by the capsule type shown in 4 (a) or the parallel flat plate type shown in FIG. 4 (b). In this case, as shown in FIG. 4C, since the substrate 110 periodically passes through the sputtered particle amorphous region 140 near the target 120, it is intermittently at the film formation rate shown in FIG. 5A. It will be formed. In order to suppress the unevenness of the film thickness in the batch, it is necessary to reduce the difference in the amount of film formation even in the case where each substrate is formed only by the same number of times, or even when the film formation rate is not suppressed by one time.

Here, from the case where the rotational speed of the substrate holder or the tray 130 is set to Arpm (Fig. 5 (a)), if the rotational speed is set to 2 times 2 x Arpm, the unit is as shown in Fig. 5 (b). Although the number of film formations per hour doubles, the time to stay in the region 140 is halved, so that the film thickness per unit time does not basically change even if the rotation speed is changed. Here, removing the film thickness in the film forming process time is called an average film forming speed.

An object of the present invention is to form a chromium nitride layer suitable for improving the crystallinity of a group III nitride semiconductor layer, and to form a triangular pyramid-shaped microcrystal, which is not indeterminate or square, but uniformly over the entire surface of the substrate. It is in doing it. The formation conditions of the chromium layer 20 and the nitriding conditions in the MOCVD growth furnace are described below.

A sapphire (0001) substrate is set in the parallel plate type RF sputtering apparatus shown in Fig. 4 (b), and the high frequency power supply is adjusted so that the average film forming speed is 0.25 to 10 kHz / second (film forming speed is 1.65 to 65.9 kHz / second). In the range, the sample which 120-micrometer film was formed into a chromium layer 20 was prepared. In addition, the rotation speed of the tray was 20 rpm.

Next, a sample was set in the MOCVD apparatus, and the content of ammonia gas was 25% by volume, flow rate 6 SLM (Standard Litter Per Minute: flow rate converted to a flow rate at 0 ° C and 1 atmosphere), and gas other than ammonia gas. The content of hydrogen is 20% by volume and the content of nitrogen is 55% by volume (the proportion of nitrogen gas in the carrier gas is about 73.3% by volume), and nitriding is performed at a substrate temperature of 1080 ° C. for 10 minutes at a pressure of 26.664 kPa. And chromium layer 20 were used as the chromium nitride layer 30 of FIG.3 (c). Here, the content rate of ammonia gas is the range of 5 volume% or more and 95 volume% or less. This is because when the content ratio is less than 5% by volume, the efficiency of nitriding decreases and the nitriding treatment time becomes long. If the volume exceeds 95% by volume, purge gas for preventing the inflow of ammonia gas cannot be sufficiently flowed for the protection of the device. In addition, the temperature increase rate was 30 degree-C / min in hydrogen and nitrogen mixed gas atmosphere, and supply of ammonia gas was started from the time point which became 600 degreeC. In the cooling process, supply of ammonia gas and hydrogen gas was stopped at the time of 600 degreeC, and it cooled in nitrogen gas atmosphere. 3 (c) and 3 (d) show the chromium nitride layer exaggerated as a continuum of about triangular cross section.

The surface of the nitrided sample was observed by SEM (scanning electron microscope), and the shape of chromium nitride microcrystals was observed, and the ratio of microtriangular microcrystals in the sample surface to the film formation rate and average film formation speed was measured. Investigated the relationship. Among the chromium nitride microcrystals formed in the sample surface, the proportion of the microtriangular microcrystals occupies a small percentage of the triangular pyramids. When the proportion of the microtriangular pyramids is small, the micrographs of the triangular pyramids are superimposed on the microcrystalline pyramids determined by the SEM image. Calculated. In addition, when the microtriangular microcrystals occupy most of the space, the mark is superimposed on the microcrystals determined to be nontriangular pyramidal shape, and the area ratio is calculated by image processing, and the microtriangular microcrystals occupy about 100%. I got the ratio. In addition, the criterion for the determination of the weak triangular pyramid was that the ridgeline can be observed in the vertex and the three directions from the contrast caused by the height of the SEM photograph. In addition, when a ridgeline was observed other than a coalescing part even if a microcrystal was not independently and plurality is continued, it was also included. Therefore, it is represented here as a "weak" triangular pyramid shape.

In addition, about each chromium film-forming speed | rate conditions, in-plane distribution is evaluated in four positions of 20 mm in all directions and 5 points in total from each center and center using two 2-inch diameter sapphire substrates, and 2 Ten points of evaluation were computed by the sum total. 6 (a) and 6 (b) show the maximum and minimum ranges of the area ratios occupied by the approximately triangular pyramid-shaped microcrystals at the positions of the ten points for the respective deposition rate conditions. When the film formation rate and the average film formation rate at the time of sputtering are slow, for example, a film formation rate of 1.65 kV / sec and an average film forming rate of 0.25 kV / sec shown in (I) of Figs. 6 (a) and 6 (b), Fig. 7 It can be seen that, after the nitriding treatment, a weak triangular pyramidal microcrystal was not formed after the nitriding treatment as shown in (a), and a large number of flaky and amorphous chromium nitride microcrystals occupied the quadrangular shape. In the SEM image of FIG. 7 (a), the proportion of microcrystalline pyramidal crystals was about 4%. On the contrary, in the case of the film formation rate and the average film forming speed at the time of sputtering being fast, for example, the film forming speed of 30 s / sec and the average film forming rate of 4.5 s / sec shown by (II) in Figs. 6 (a) and 6 (b), Fig. As shown in the SEM photograph of 7 (b), it can be seen that the shape of the triangular pyramid occupies most of the space after nitriding. The ratio of the microcrystalline triangular crystallites in the chromium nitride microcrystals of the SEM photograph of FIG. 7B was about 97%. In addition, although the black-and-white contrast of a SEM photograph adheres in FIG.7 (b) by the influence of the height of a large triangular pyramid shape, when a black part is not necessarily flat and a microcrystal with a smaller triangular pyramid shape is observed at a higher magnification. There are many. In the present invention, however, the area ratio is evaluated by the magnification of the SEM photograph of FIG. 7.

That is, in the film-forming process of the chromium layer 20 shown to FIG. 3 (b), the film-forming rate in the sputtering particle amorphous region 140 is 7 kV / sec or more, and an average film-forming speed is 1 kV / sec or more, and is close to a rectangle. Scaly and amorphous chromium nitride microcrystals are drastically reduced, and as shown in the SEM photograph of FIG. 7 (b), the area ratio occupied by the approximately triangular pyramidal microcrystals can be 70% or more, 90% or more, or 95% or more. Able to know. In addition, as a result of the X-ray diffraction 2θ-ω scan of the sample of Fig. 7 (b), which is an SEM photograph, as shown in Fig. 7 (c), the chromium nitride is oriented in the [111] direction perpendicular to the underlying substrate surface. The state in which CrN # 100 'orientation as shown in FIG. 2 (d) is present has been eliminated. When attempting to obtain a dense film quality, it is generally considered that the film forming speed should be slow. However, it has been found that the film forming speed is better in view of the satisfactory nitriding treatment for the purpose of the present invention.

Although the scientific reason for the morphological change of the microcrystals of the chromium nitride layer after such nitriding treatment is unclear, high-speed film formation leads to imperfections at the atomic level such as voids and public clusters in the metal chromium layer. As the diffusion rate in the chromium layer is increased, the AlN intermediate layer on the surface of the underlying sapphire substrate is efficiently formed, and triangular pyramid-shaped chromium nitride microcrystals having good orientation are obtained by inheriting the information of the AlN intermediate layer during solid phase epitaxial growth of chromium nitride. It can be considered to be formed. In addition, formation of an intermediate | middle layer is shown by FIG. 7 of Unexamined-Japanese-Patent No. 2008-110912.

However, as described later, the thickness of the chromium layer is in the range of 50 to 300 kPa (5 to 30 nm), and preferably in the range of 50 to 180 kPa. The time is less than 5 to 18 seconds, and the rotation speed of the substrate holding holder or the tray 130 is also limited, and at higher speeds, it becomes difficult to ensure the uniformity of the film thickness in the film formation. Is 8 mV / sec or less, and the film formation rate in the sputtered particle amorphous region 140 is preferably 65 mV / sec or less.

That is, in the case where the chromium layer is nitrided in the MOCVD apparatus and the group III nitride semiconductor layer is continuously grown in the MOCVD apparatus, in the film forming process of the chromium layer, the average film forming speed is preferably in the range of 1 Pa / sec or more to 10 Pa / sec. The average film forming speed is more preferably in the range of 1.8 kV / sec or more and 8 kV / sec, and more preferably in the range of 4 kV / sec or more and 8 kV / sec. The deposition rate in the sputtered particle amorphous region 140 is in the range of 7 ms / sec or more and 65 ms / sec or less.

Conventionally, nitriding of the chromium layer has been performed in an HVPE apparatus. This is because the nitriding treatment in the HVPE apparatus is hot wall type, and the ammonia gas is heated before mixing with the Group III chloride gas such as GaCl, which is a Group III raw material, but in the MOCVD apparatus, only the substrate portion is heated to suppress the gas phase reaction. It can be considered that since the structure is taken, the decomposition efficiency of ammonia gas is poor, and the supply of atomic nitrogen, which mainly contributes to nitriding, is less than that of the HVPE method. The decomposition rate of ammonia gas in the thermal equilibrium state is about 1% at 800 ° C and about 3% at 900 ° C. However, thin film growth is indispensable for the formation of nitride semiconductor elements, and it is difficult to form a thin film of the nitride semiconductor layer in the HVPE furnace, and after forming the CrN layer in the HVPE furnace, it is necessary to transfer it to the MOCVD furnace. Due to oxidation and the like, epitaxial growth having good crystallinity on the CrN layer was difficult.

In general, the decomposition reaction of ammonia,

2NH ₃ ⇔N ₂ + 3H ₂ (Equation 1)

Although expressed by the formula, it can be considered that when ammonia dissociates, atomic nitrogen and atomic hydrogen are once formed and atomic nitrogen has a dominant influence on the nitriding of the metal chromium layer.

As a support, after the metal chromium layer was formed on the sapphire substrate, the heating treatment was performed at 1080 DEG C for 10 minutes using only a mixed gas of hydrogen and nitrogen or nitrogen gas as a carrier gas, without supplying ammonia gas. In this case, as shown in Figs. 8A and 8B, the metal film aggregates to form an island-shaped discontinuous film of several μm in size, and most of the nitriding does not proceed and no chromium nitride microcrystals are formed. Is also estimated. 8 (a) shows a mixed gas of hydrogen and nitrogen, and FIG. 8 (b) shows a case of nitrogen gas. However, it can be seen that the form is slightly different due to the presence or absence of hydrogen gas.

Therefore, the difference in the nitriding state of the chromium layer when the mixing ratio of nitrogen and hydrogen gas which are carrier gases other than ammonia gas was changed was investigated. The thickness of the metal chromium layer on the sapphire substrate 10 was 120 kPa, the average film forming speed at the time of sputtering film formation was 1.8 kV / sec, and the film forming rate in the sputtered particle amorphous region 140 was 18.1 kV / second. Ammonia gas content was 25 vol%, flow rate was 6 SLM, the ratio of nitrogen gas in the mixed carrier gas of nitrogen and hydrogen was 0, 20, 44, 73, 100 volume% Nitriding was performed at 1080 占 폚 for 10 minutes to form the chromium nitride layer 30 shown in Fig. 3 (c). Moreover, supply of ammonia gas was started from the time point which became 600 degreeC with the temperature increase rate in 30 degreeC / min in hydrogen and nitrogen mixed gas atmosphere. The cooling process stopped supplying ammonia gas and hydrogen gas at the time of 600 degreeC, and cooled in nitrogen gas atmosphere.

SEM (Scanning Electron Microscope) on the surface of the center of each substrate of the nitrided sample (2 to 3 sheets of sapphire substrate with 2 inch diameters under each condition), 4 points at 20 mm from the center, and 5 points in total Was observed, and the shape of the chromium nitride microcrystals was observed. In addition, the calculation method of the area ratio which the microcrystalline crystal of a triangular pyramid shape occupies is as above-mentioned. Fig. 9A shows the relationship between the nitrogen content in the carrier gas and the area ratio occupied by the crystals of the triangular pyramid shape. Here, the range of the maximum value and minimum value of the sample observation point of each condition is shown. Although the ratio of nitrogen gas is especially low and the difference in the form of the chromium nitride in a sample surface is large, all cannot be illustrated, but a typical example is shown to FIG. 9 (b)-(f). In addition, the ratio of nitrogen gas in the above-mentioned mixed carrier gas is described in figure, respectively.

When the content of nitrogen in the carrier gas is 50 vol% or less, the irregularity of the formation area ratio of the chromium nitride microcrystalline in the shape of a triangular pyramidal shape at the position in the sample plane is large, but when the proportion of nitrogen in the carrier gas is 60 vol% or more, It can be seen that the gap in the sample surface is greatly reduced, and that the trigonal pyramidal chromium nitride microcrystals are uniformly formed in the plane and the area ratio is at least 70% or more. Furthermore, it can be seen that at 70 vol% or more, an approximately trigonal pyramidal chromium nitride microcrystal is formed in an area ratio of 90% or more over the entire surface.

Therefore, in the MOCVD growth furnace, in the nitriding process of the metal chromium layer, nitrogen and hydrogen are used as the carrier gas as a gas component other than ammonia in the gas atmosphere containing ammonia gas, and the content ratio of nitrogen is in the range of 60 to 100% by volume. The ratio of the area of the chromium nitride microcrystals having a triangular pyramidal shape to the chromium nitride microcrystals on the surface of the chromium nitride layer after nitriding is obtained by setting the deposition rate at the time of forming the above-described metal chromium layer 10 to a predetermined value or more. Can be more than 70%.

Although the scientific reason is not clear, it can be considered that when the pressure is constant, the ratio of hydrogen in the mixed gas of ammonia gas, nitrogen gas and hydrogen gas is lowered, and the reaction of Equation 1 is due to the accelerated decomposition of ammonia. have. As to the nitriding treatment in the HVPE furnace, the carrier gas is hydrogen, but it is heated until the ammonia gas reaches the metal chromium layer so as to uniformly form a triangular pyramidal chromium nitride microcrystal, Although the density of the atomic nitrogen produced by the decomposition reaction can be increased, a structure in which the substrate portion is heated in a spot with respect to the MOCVD furnace is taken, and since the decomposition efficiency of ammonia is low, the addition of nitrogen gas as in the present invention is effective. do.

Next, the pressure dependence in the furnace provided to nitriding state was investigated. A metal chromium layer having a thickness of 120 ANGSTROM was formed on the sapphire substrate 10 having a diameter of 2 inches by the sputtering method. The average film-forming speed at the time of sputtering film-forming was 1.8 kV / sec, and the film-forming speed | rate in the sputtering particle amorphous region 140 was 11.9 kPa / sec. The content of ammonia gas is 25% by volume, the flow rate is 6 SLM, the total gas is nitrogen gas as the carrier gas, and nitriding is performed at a substrate temperature of 1080 ° C for 10 minutes, and the chromium nitride layer 30 of FIG. Formed. The pressure in the furnace adjusted the conductance on the exhaust side and set the same pressure during the temperature raising, the nitriding, and the low temperature under the conditions of 6.666 KPa, 26.664 KPa, 66.66 Kpa, 73.326 KPa, and 99.99 KPa. In addition, the temperature increase rate was 30 degreeC / min in nitrogen gas atmosphere, and supply of ammonia gas was started from the point which became 600 degreeC. In the cooling process, the supply of ammonia gas was stopped when the temperature reached 600 ° C and cooled in a nitrogen gas atmosphere.

The result of having observed the form of the chromium nitride layer of the obtained sample surface by SEM is shown in FIG. In the furnace pressure of 99.99 kPa, the triangular pyramidal microcrystals are only partially formed and continued, but when the pressure is lowered to 73.326 kPa, microtriangular microcrystals start to appear, but the shape is still collapsing. If the pressure in the furnace is 66.66 kPa or less, the triangular pyramidal microcrystals are uniformly formed. Therefore, it is 66.66 kPa or less as an appropriate range of pressure in a furnace. Although it can be considered that the formation of uniform triangular pyramid-shaped microcrystals is possible even under the pressure range of the experiment, it is confirmed from problems such as an increase in the change in the growth pressure conditions of the group III nitride letter semiconductor layer which continues to grow. The lower limit of 6.666 kPa.

Next, the nitriding treatment temperature and treatment time dependence which are provided to nitriding state were investigated. A metal chromium layer having a thickness of 120 ANGSTROM was formed on the sapphire substrate 10 having a diameter of 2 inches by the sputtering method. The average film-forming speed at the time of sputtering film-forming was 1.8 kV / sec, and the film-forming speed | rate in the sputtering particle amorphous region 140 was 11.9 kPa / sec. The content of ammonia gas is 25% by volume, the flow rate is 6 SLM, the total nitrogen gas is used as the carrier gas, the substrate temperature is in the range of 900 ° C to 1080 ° C, and the processing time is in the range of 10 minutes to 40 minutes, The pressure in the furnace was 26.66 KPa. In addition, in a nitrogen mixed gas atmosphere, the temperature increase rate was raised to 30 ° C./min, and the supply of ammonia gas was started from the point where the temperature reached 600 ° C., followed by nitriding of the predetermined treatment time at the treatment temperature, and cooling at 30 ° C./min. It was cold at speed. In the cooling process, the supply of ammonia gas was stopped when the temperature reached 600 ° C and cooled in a nitrogen gas atmosphere.

11 shows the results of observing the form of the chromium nitride layer in the case of changing the nitriding treatment temperature and treatment time by SEM. In the case where the nitriding treatment temperature is 900 ° C., even when the treatment time is 10 minutes and 40 minutes, microcrystalline pyramidal crystals are not formed but are in the form of original patterns. In the case where the nitriding treatment temperature is 1000 ° C, some triangular pyramidal microcrystals start to form from the original pattern in the nitriding treatment of 10 minutes, and microtriangular microcrystals of the triangular pyramid are formed in the 40 minute treatment time. It can be seen that. It is understood that at a temperature of 1080 ° C for nitriding treatment, micro triangular pyramidal microcrystals are formed over the entire surface. In this case, it can be seen that when the treatment time is extended, the rearrangement of chromium nitride occurs on the surface, and the enlargement of microcrystals and discrete microcrystals become discrete. However, when the magnification is further increased at the time of SEM observation, microtriangular microcrystals having a small size are often present in discretely visible parts. From such a result, although the shape control of the chromium nitride layer is possible by changing the nitriding process time, the nitriding process temperature of 1000 degreeC or more is preferable for formation of a weak triangular pyramidal microcrystal.

As mentioned above, although suitable conditions regarding the formation conditions of the metal chromium layer 20 and the formation conditions of the chromium nitride layer 30 in a MOCVD furnace were shown, the growth of the group III nitride semiconductor layer performed continuously is a metal chromium. After the layer was subjected to nitriding at 1080 ° C., for example, in the case of GaN film formation, the substrate temperature was lowered to 900 ° C., and the ammonia gas flow rate, hydrogen gas flow rate, nitrogen gas flow rate, and pressure conditions were adjusted, followed by TMG (trimethyl). Gallium) is introduced into the furnace to form a GaN buffer layer indicated by reference numeral 40 in FIG. The supply of TMG is stopped once, the respective gas flow rates and pressure conditions are changed, the temperature is raised to 1050 ° C, and TMG is introduced into the furnace again to grow the GaN layer 50. When it grows to predetermined thickness, it cools by adjusting supply of TMG, atmospheric gas conditions, etc., and obtain a group III nitride semiconductor substrate. Moreover, supply of ammonia gas is continued to 600 degreeC during temperature-fall.

In addition, although the case of GaN was shown in this example, each layer of 40 and 50 of FIG. 3 (d) may be AlN, AlGaN, or the like. The layer 50 may be a multilayer structure having a semiconductor element structure.

As shown in FIG. 12, the chromium nitride layer 30 is selected by the process shown in FIG. 12 (c) for the board | substrate 90 (corresponding to FIG.3 (d)) of the III-nitride semiconductor element manufacture of FIG. It is selectively dissolved by an etchant, for example, a mixed solution of ammonium dicerium nitrate and perchloric acid or nitric acid, and the underlying substrate 10 for growth and the group III nitride semiconductor layers 40 and 50 are separated to free the group III nitride semiconductor. The substrate 150a can be obtained.

Further, the group III nitride semiconductor layer 60 is further grown on the group III nitride semiconductor element manufacturing substrate, whereby the group III nitride semiconductor element manufacturing substrate 90a shown in Fig. 12B can be obtained. In this case, the group III nitride semiconductor layer 60 may continue to grow in the MOCVD apparatus in which the group III nitride semiconductor layer 50 is grown, or once out of the MOCVD apparatus, and may be grown by another growth apparatus. Using this epitaxial substrate, the chromium nitride layer 30 is selectively dissolved in a step shown in FIG. 12 (d) by a selective etching solution, for example, a mixed solution of ammonium dicerium ammonium nitrate and perchloric acid or nitric acid, and grown. The group III nitride semiconductor self-supporting substrate 150b can be obtained by separating the substrate 10 and the group III nitride semiconductor layers 40, 50, and 60.

In addition, the group III nitride semiconductor layer 50 of the group III nitride semiconductor element fabrication substrate of FIG. 12 (a) or the group III nitride semiconductor layer 60 of FIG. 12 (b) is a multilayer structure having a semiconductor device structure. By dissolving the chromium nitride layer 30 selectively, as shown in FIG. 12, the underlying substrate 10 for growth can be removed, and the group III nitride semiconductor element 160 separated as shown in Fig. 12E can be obtained.

In addition, as a procedure for forming a semiconductor element, the device may be fabricated after first removing the underlying substrate for growth from the group III nitride semiconductor element manufacturing substrate, and may be processed on the growth surface side of the substrate for producing the group III nitride semiconductor element. For example, the substrate 70 for growth may be separated by dissolving the chromium nitride layer 30 after the formation of the electrode 70 or the like, or after the element separation processing, to form the electrode 80 or the like on the separation surface. good.

The foregoing has described a substrate for the fabrication of a group III nitride semiconductor device on which a group III nitride semiconductor layer is grown on a chromium nitride layer, a method for manufacturing a group III nitride semiconductor self-supporting substrate, and an embodiment of a group III nitride semiconductor device. Next, And the crystallinity of the Group III nitride semiconductor layer grown thereon.

As described above, the metal chromium layer 20 was formed on the sapphire substrate (10) substrate 10 by an RF sputtering method to a thickness of 120 kPa. At this time, the sample which prepared the average film forming speed and the film forming speed in the sputtering particle amorphous region 140 in the range of 0.25 to 10 kV / sec and 1.65 to 65.9 kV / sec, respectively was prepared.

Next, the sample was set in the MOCVD apparatus, and the metal chromium layer 20 was nitrided for 10 minutes at the substrate temperature of 1080C in the above-described order. At this time, the content of ammonia gas was 25 vol%, the flow rate was 6 SLM, the content of hydrogen was 20 vol% and the content of nitrogen was 55 vol% (ratio of nitrogen in carrier gas 73.3 vol%), and the total pressure was 26.664 KPa.

After the nitriding treatment, the substrate temperature was lowered to 900 ° C., and after a few minutes of temperature stability of the system, the TMG supply was started to grow the GaN buffer layer to about 2.5 μm. The total pressure at this time was 86.658 kPa, and the raw material gas composition ratio (common name V / III ratio) of group V (ammonia) and group III (Ga) was about 1000. Supply of TMG was stopped once, and the board | substrate temperature was heated up to 1050 degreeC for several minutes.

After waiting for a few minutes for the temperature of the system to stabilize, TMG was started to be supplied again, and the GaN layer was further grown by about 3 μm (total thickness of GaN was about 5.5 μm), and then the supply of TMG was stopped to start cooling. . The semiconductor substrate was obtained after stopping supply of ammonia gas and cooling to room temperature vicinity when the board | substrate temperature fell to 600 degreeC.

About the sample obtained, the full width at half maximum (FWHM) of the X-ray-diffraction-locking curve in the (0002) diffraction surface and the (10-12) diffraction surface was measured, and crystallinity was evaluated. As a result, as shown in Fig. 13 (a), the slower the deposition rate of the metal chromium layer in the sputtered particle amorphous region is, the larger the half width is obtained by (0002) diffraction and (10-12) diffraction, so that the crystallinity of the GaN growth layer is increased. It turns out that this falls.

FIG. 13 (b) shows the relationship between the average film formation speed of the metal chromium layer and the respective half-value widths. Similarly, when the average film formation speed becomes slow, it can be seen that the half-width of the X-ray diffraction becomes large and the crystallinity decreases.

Although the crystallinity required differs depending on the type of product and the required characteristics, the half width is preferably 600 arcsec or less, more preferably 400 arcsec or less, and more preferably narrower. Therefore, the deposition rate of the metal chromium layer in the sputtered particle amorphous region during the deposition of the metal chromium layer is appropriately 7 ms / sec or more, more preferably 11 ms / sec or more, still more preferably 25 ms / sec or more. In addition, the average film forming rate is preferably 1 Å / second or more, more preferably 1.8 Å / second or more, and further preferably 4 Å / second or more. The area ratio occupied by the microcrystalline pyramidal microcrystals of chromium nitride shown in Figs. 6 (a) and 6 (b) described above is 70% or more, more preferably 90% or more, even more preferably 95% or more. It meets the requirements.

The half width of the (0002) diffraction is an index relating to the fluctuation of the c-axis perpendicular to the GaN (0001) plane formed, and the smaller this value, the smaller the in-plane orientation gap. It is thought that the chromium nitride layer is not a scaly or irregular shape close to a square, but is a triangular pyramid-shaped one mainly, and has an orientation connecting the center and apex of the bottom of the triangular pyramid, and thus the c-axis fluctuation of GaN grown thereon is reduced. Can be.

On the other hand, the half width of the (10-12) diffraction is an index related to the rotational movement of the crystal orientation in the c plane, but the chromium nitride layer is not a scaly or irregular shape close to a square, but is mainly a triangular pyramid, and the base of the triangular pyramid is It is considered that it was provided in parallel with the m-axis (<10-10> direction group) in c plane of a sapphire substrate, and it can be considered that the rotational movement of the orientation in c plane of GaN grown on it was reduced.

The epitaxial relationship between the group III nitride semiconductor layers such as triangular pyramidal chromium nitride crystals and grown GaN (0001) on the sapphire (0001) plane as the base substrate is shown in Fig. 14 (a),

(0001) _Sapphire // (111) _CrN // (0001) _{Group III nitride semiconductor layer}

And

[1-100] _Sapphire // [10-1] _CrN // [11-20] _{Group III nitride semiconductor layer}

.

In the case of a template substrate having a hexagonal (0001) layer of AlN, GaN, SiC or the like formed on an AlN, SiC, GaN single crystal (0001) surface or various growth substrates, the epitaxial relationship is shown in FIG. As shown in 14 (b),

(0001) _{hexagonal crystal} // (111) _CrN // (0001) _{group III nitride semiconductor layer}

And

[11-20] _{hexagonal crystal} // [10-1] _CrN // [11-20] _{group III nitride semiconductor layer}

.

Therefore, the direction along the base of the triangular pyramid chromium nitride microcrystal is the <10-1> direction group, and the orientation of the <11-20> direction group of the group III nitride semiconductor crystal layer grown thereon is not dependent on the substrate type of the underlying substrate. , Always parallel.

Next, the relationship between the thickness of the metal chromium layer 10 and the crystallinity of the obtained group III nitride semiconductor layer will be described.

First, a sample was formed on the sapphire substrate 10 by sputtering to form a metal chromium layer 20 in the range of 0 kV (no chromium layer) to 500 kV. The average film formation speed at that time was 4.5 kV / sec, the film formation speed in the sputtered particle amorphous region was 29.7 kV / sec, and the rotation speed of the substrate tray 130 shown in Fig. 4B was 20 rpm.

Such a sample was set in a MOCVD apparatus, and nitriding treatment was performed on the metal chromium layer 20 for 10 minutes at 1080 ° C in the same manner as described above. At this time, the content rate of ammonia gas was 25 volume%, and the flow volume was 6 SLM. As carrier gas other than ammonia gas, total pressure was 26.664 kPa using total nitrogen gas.

Subsequently, after changing the furnace pressure, the substrate temperature was lowered to 900 ° C., and the system was waited for a few minutes to stabilize the temperature. Then, the supply of TMG was started to grow the GaN buffer layer to about 2.5 μm. The total pressure at this time was 86.658 kPa, and the raw material gas composition ratio (common name V / III ratio) of group V (N in ammonia) and group III (Ga) was about 1000. Here, supply of TMG was stopped and the board | substrate temperature was heated up to 1050 degreeC for several minutes.

After waiting for a few minutes for the temperature of the system to stabilize, TMG was started to be supplied again, and the GaN layer was further grown by about 3 μm (total thickness of GaN was about 5.5 μm), and then the supply of TMG was stopped to start cooling. . The supply of ammonia gas was stopped at the time when the substrate temperature dropped to 600 ° C, and cooled to near room temperature to obtain a group III nitride semiconductor substrate.

About the sample obtained, the half value width (FWHM) of the X-ray-diffraction-locking curve (XRD) was measured on the (0002) diffraction surface and the (10-12) diffraction surface, and crystallinity was evaluated. Although the result is shown in FIG. 15, in the range whose thickness of a chromium layer is 50 kPa or more and 300 kPa or less, the XRD half value width in both surfaces is 600 arcsec or less, and it is preferable at the crystallinity of a GaN layer, and is 60 kPa or more and 180 kPa or less. It is a more preferable range. In the case where the film thickness of the metal chromium layer was 0 GPa, the GaN buffer layer did not grow on the sapphire substrate during the GaN buffer growth at 900 ° C. This is presumed to be due to the lack of early growth nuclei.

When the nitride of the metal chromium layer in the MOCVD furnace and the GaN layer of the group III nitride semiconductor are grown, the appropriate range of the thickness of the metal chromium layer is shifted in a direction thinner than in the case of the HVPE method (Patent Document 3). Although it can be considered that the thing reflects the difference of the nitriding state between the manufacturing methods, the difference in the film-forming rate of GaN, the difference in the lateral growth by the surface migration of group III atom in a growth surface, etc., the detail is unknown.

Moreover, about the sample obtained, the selective etching evaluation of the chromium nitride layer was performed by the mixed solution of ammonium dicerium nitrate and perchloric acid heated at 80 degreeC, but when the thickness of a metal chromium layer is 40 GPa or less, etching does not advance. Without this, the GaN layer and the sapphire substrate could not be separated by chemical lift-off (CLO). On the other hand, when the thickness of the metal chromium layer was 50 GPa or more, the GaN layer could be separated by selective etching of the chromium nitride layer.

In the case of the thickness of the former, it is considered that the exposure ratio of the underlying sapphire substrate surface increases, and the GaN layer directly contacts the surface of the sapphire substrate when the GaN layer having the chromium nitride layer as the growth nucleus grows in the lateral direction. . In terms of chemical lift-off, the lower limit of the thickness of the metal chromium layer in the MOCVD method is 50 kPa or more.

As described above, the chemical lift-off in the MOCVD method is possible, and in order to improve the crystallinity of the group III nitride semiconductor layer, the deposition rate condition of the metal chromium layer, the gas species condition during the nitriding treatment, and the triangular pyramidal chromium Although the characteristics of the orientation relationship between the nitride microcrystals and the orientation relationship between the group III nitride semiconductor crystals and the thickness conditions of the metal chromium layer have been described, examples of representative embodiments are shown, and the present invention is not limited to this embodiment.

Example

(Example 1)

In the order described above, the film formation rate was 4.5 kV / sec (29.7 kV / sec in the sputtered particle amorphous region) by an RF sputtering method on a sapphire (0001) substrate having a 2-inch diameter, and was 120 kW thick. After the metal chromium layer was formed into a film, nitriding treatment was performed for 10 minutes at a substrate temperature of 1080 ° C in a MOCVD furnace. At that time, the content rate of ammonia gas was 25% by volume, and the flow rate was 6 SLM, a carrier gas other than ammonia gas, 20% by volume of hydrogen, and 55% by volume of nitrogen (nitrogen gas in carrier gas). Ratio was 73.3% by volume) and the total pressure was 26.664 kPa. Subsequently, the substrate temperature was lowered to 900 ° C., the GaN buffer layer was grown to about 2.5 μm, and the temperature was raised to 1050 ° C., and the GaN layer was grown to about 3 μm. In addition, the total pressure in the furnace during growth was 86.658 kPa, and the raw material gas composition ratio (common name V / III ratio) of group V (N in ammonia) and group III (Ga) was about 1000. After completion of growth, the mixture was cooled to around room temperature to obtain a group III nitride semiconductor substrate having a GaN epitaxial layer. As a result of evaluating the crystallinity by the half width of the X-ray locking curve (XRD) of the (0002) diffraction and the (10-12) diffraction of the GaN layer, the crystallinity was 290 arcsec and 330 arcsec, respectively. (Equivalent to the process to FIG. 12 (a))

Next, the board | substrate sample was set in the HVPE furnace, the temperature was raised at the temperature increase rate of about 30 degree-C / min in hydrogen atmosphere, and supply of ammonia gas was started when it became 600 degreeC. Wait for the system temperature to stabilize at 1040 ° C for about 5 minutes, start supplying hydrochloric acid (HCl) gas to the Ga source heated to 850 ° C, generate GaCl, mix it with ammonia gas in front of the substrate, and source gas Was supplied, and GaN thick film growth was started. In addition, the flow rate of ammonia gas is 1 SLM, the flow rate of hydrochloric acid (HCl) gas is 40 SCCM (Standard cm3 / min: atmospheric pressure 1.013 Pa, flow rate converted at 0 ° C), and the flow rate of hydrogen carrier gas is 3.3 SLM at V / III ratio. Was 25, and the total pressure was 101.3 kPa. After 5 hours of growth, a GaN thick film epitaxial substrate having a thickness of about 350 µm was obtained. (Equivalent to the process to FIG. 12 (b))

The sample was separated from the sapphire substrate by a selective etching of the chromium nitride layer in a mixed solution of ammonium dicerium nitrate and perchloric acid heated to 80 ° C. to obtain a freestanding substrate having a diameter of 40 mm. The half width of the XRD of the obtained self-supporting substrate was very good at 85 arcsec and 103 arcsec by (0002) diffraction and (10-12) diffraction, respectively. (Equivalent to the process up to FIG. 12 (d))

In addition, by growing an epitaxial layer of a device structure on a freestanding substrate, it is possible to manufacture optical devices such as laser diodes and electronic devices such as Schottky barrier diodes. As mentioned above, according to this invention, the self-supporting board | substrate of group III nitride semiconductor which has favorable characteristic can be obtained easily.

(Example 2)

A 120-inch-thick metal chromium layer was formed on the 2-inch diameter sapphire substrate by the RF sputtering method at an average film forming speed of 4.5 kV / sec. The sample was nitrided at a substrate temperature of 1080 ° C. for 10 minutes in a MOCVD furnace. Subsequently, the substrate temperature was lowered to 900 ° C., the GaN buffer layer was grown to about 2.5 μm, and then heated up to 1050 ° C. to grow the GaN layer to about 4 μm. Si (silicon) was added by n-type dopant to the GaN layer on the GaN buffer layer, and carrier density was made into 2 * 10 <^18> cm <^-3> .

Next, the light emitting layer of In _{0 .1} Ga _{0 .9} N / GaN of the MQW (multiple quantum well), was formed on while elevating the substrate temperature at 750 ℃ in the range of 850 ℃. Next, 20 nm of an Mg-doped p-type AlGaN electron block layer and 0.2 µm of an Mg-doped p-type GaN cladding layer were grown. Next, a p + type GaN contact layer having a carrier density of 5 x 10 ¹⁷ cm ^-3 was formed at about 100 Hz. The group III nitride semiconductor epitaxial substrate of the LED structure was obtained.

Dry etching was carried out from the epitaxial layer side of the obtained epitaxial substrate to the sapphire substrate, and the element isolation gap processing of 1 mm square was performed. This gap becomes a channel for chemical etching solution supply with the separation between the elements. Next, an Ag-based reflective layer and an ohmic electrode were formed on the p + GaN layer, and the p + type Si substrate on which the ohmic electrode was formed was bonded to Au + Au pressurized thermocompression bonding at 300 ° C.

Next, the chromium nitride layer was selectively etched in a mixed solution of dicerium ammonium nitrate and nitric acid heated to 80 ° C, the sapphire substrate was separated, and the LED structure layer was transferred to the Si support substrate side. After removing the GaN buffer layer by dry etching and forming the ohmic pad electrode of Ti / Al / Ni / Au on the n-GaN surface, the Si support substrate was cut | disconnected by dicer and the LED element of a vertical structure was produced. (This embodiment corresponds to the process reaching FIG. 12 (e) through FIG. 12 (a) and FIG. 12 (b).)

The characteristics of the bare chip state of the obtained blue LED element are as follows: when the forward current I _f is 350 mA, the forward voltage V _f is 3.3 V, the peak emission wavelength λ _p is 455 nm, and the output _Po is Was 320 mW, which was a very good result.

As described above, according to the present invention, a group III nitride semiconductor epitaxial substrate which can be continuously performed in the MOCVD furnace from the nitriding process to the epitaxial structure of the LED structure, and has good characteristics, and the group III nitride semiconductor element processed therein It can be obtained easily.

(Example 3)

An AlN (0001) template substrate was prepared in which an AlN epitaxial layer was formed directly on a 2 inch sapphire (0001) substrate. The AlN layer had a thickness of about 1 μm, and the half widths of the XRDs were 85 arcsec and 1283 arcsec in (0002) diffraction and (10-12) diffraction, respectively. A 90-Hz metal chromium layer was formed into a film by the RF sputtering method on condition of an average film forming speed of 4.5 kPa / sec.

The sample was set in a MOCVD furnace, the temperature was raised at a rate of 30 ° C / min, and nitriding was performed at 1050 ° C for 5 minutes. The nitriding treatment temperature and time are different from those on the sapphire substrate. In the case of the sapphire substrate, the AlN intermediate layer is formed between the chromium layer. However, if the substrate surface is AlN single crystal from the beginning, the formation is unnecessary and low temperature. This is because a triangular pyramidal chromium nitride layer is formed even for a short time. Moreover, ammonia gas supply was started from 600 degreeC, the content rate was 25 volume%, and the flow volume was 6 SLM. As a carrier gas other than ammonia gas, nitrogen gas was used and the total pressure was 26.664 kPa.

Subsequently, the substrate temperature was lowered to 900 ° C, temperature stabilization of the system, preparation of gas-based conversion, and the like were performed, and after about 3 minutes, TMG was started to supply, and a GaN buffer layer was formed by about 2.5 µm. The total pressure at this time was 650 Torr (86.658 KPa), and the raw material gas composition ratio (common name V / III ratio) of group V (N in ammonia) and group III (Ga) was about 1000. The supply of TMG was stopped here and the board | substrate temperature was heated up to 1050 degreeC for several minutes.

Waiting for a few minutes for the temperature of the system to stabilize, TMG was started to be supplied again, and the GaN layer was further grown by about 3 µm (the total thickness of GaN was about 5.5 µm), and then the supply of TMG was stopped to start cooling. . The supply of ammonia gas was stopped at the time when the substrate temperature dropped to 600 ° C, and cooled to near room temperature to obtain a group III nitride semiconductor substrate.

The half width of XRD was evaluated by (0002) diffraction and (10-12) diffraction, and the crystallinity of the obtained GaN layer was very good at 120 arcsec and 218 arcsec, respectively. In particular, it can be seen that the in-plane rotational orientation fluctuation of the used AlN template is not turned over and is greatly improved. Moreover, the fragment was cut out from the sample, and the chromium nitride layer was selectively etched in the mixed solution of dicerium ammonium nitrate heated at 80 degreeC, and nitric acid, and separation of the AlN template substrate and GaN layer was confirmed. (Equivalent to the process from FIG. 12 (a) through FIG. 12 (c))

An AlN (0001) template substrate having an XRD half-value width substantially equal to the above was separately prepared, and a 50 nm metal chromium layer was formed by RF sputtering under a condition of an average film forming speed of 4.5 mW / sec. Next, after the same nitriding treatment was applied in the MOCVD apparatus, cooling was performed without growing GaN, and the sample was taken out near the room temperature. Moreover, supply of ammonia gas was stopped at the stage which became 600 degrees C or less during cooling.

As a result of evaluating the sample by X-ray diffraction θ-2ω scan, it can be seen that the chromium nitride is in a [111] orientation perpendicular to the AlN (0001) plane as shown in Fig. 16A. In addition, SEM observation of the surface of the sample showed that a triangular pyramidal microcrystal was formed as shown in Fig. 16 (b), and there was also a very small difference in the direction of its base, which was in a state parallel to the <11-20> direction group of AlN. Able to know. Since such a state is realized, the in-plane rotational orientation fluctuations of the AlN (0001) template are alleviated in the chromium nitride layer, and the in-plane rotational orientation fluctuations of the GaN layer are greatly improved to obtain a substrate for producing a Group III nitride semiconductor device having good crystallinity. have.

(Comparative Example 1)

On the sapphire substrate, 120 상 에 of a metal chromium layer was formed on the sapphire substrate under the conditions of an average film forming speed of 0.5 kPa / sec and a film forming rate of 3.3 kPa / sec in the sputtered particle amorphous region. In the same manner as in Example 1, nitriding was performed for 10 minutes at a substrate temperature of 1080 ° C in a MOCVD furnace. Subsequently, the substrate temperature was lowered to 900 ° C., the GaN buffer layer was grown to about 2.5 μm, and the temperature was raised to 1050 ° C., and the GaN layer was grown to about 3 μm. It cooled to room temperature after completion | finish of growth, and obtained the semiconductor substrate which has a GaN epitaxial layer.

The crystallinity of the GaN layer of the sample was evaluated by the full width at half maximum of the X-ray locking curve (XRD) of (0002) diffraction and (10-12) diffraction. As a result, in Example 1, 764 arcsec and 1005 arcsec, respectively, In comparison with this, the half width has increased significantly.

(Comparative Example 2)

On the sapphire (0001) substrate, the metal chromium layer was formed into a film with a thickness of 25 kV and 500 kV by RF sputtering under conditions of an average film forming speed of 4.5 kV / sec and a film forming rate of 29.7 kV / sec in the sputtered grain amorphous region. At this time, the rotation speed of the board | substrate tray was 30 rpm. In the same manner as in Example 1, a nitriding treatment was performed at a substrate temperature of 1080 ° C. for 10 minutes in a MOCVD furnace. Subsequently, the substrate temperature was lowered to 900 ° C., the GaN buffer layer was grown to about 2.5 μm, and the temperature was raised to 1050 ° C., and the GaN layer was grown to about 3 μm. It cooled to room temperature after completion | finish of growth, and obtained the semiconductor substrate which has a GaN epitaxial layer.

As a result of evaluating the crystallinity of the GaN layer of the sample having the thickness of the metal chromium layer of 25 μs by the half width of the X-ray locking curve (XRD) of the (0002) diffraction and the (10-12) diffraction, the 538 arcsec, 633 arcsec. Moreover, in the sample of 500 micrometers in thickness, it became 838 arcsec and 1288 arcsec, respectively, and the crystallinity worsened compared with Example 1. FIG. In addition, although the crystallinity of the former sample was better than that of the metal chromium layer thickness of 500 kPa, the chromium nitride layer was not selectively etched in the mixed solution of ammonium dicerium nitrate and nitric acid heated to 80 ° C. Separation of the GaN layer was impossible.

As mentioned above, although this invention was demonstrated in detail, showing specific example about embodiment and an Example, this invention is not limited to embodiment and the Example of the said invention, All the changes in the range which does not deviate from the range of this invention. Or variations are possible.

(Industrial availability)

According to the present invention, the formation of a chromium layer formed on a substrate for growth and a nitriding condition for nitriding the chromium layer in a MOCVD growth furnace are appropriately set, thereby forming a triangular pyramidal shape in the surface of the chromium nitride layer formed. III which can improve the ratio which chromium microcrystals occupy, and can improve the crystallinity and uniformity of the crystal layer of the group III nitride semiconductor layer and group III nitride semiconductor element structure layer which continue to grow on a chromium nitride layer by this. A method for producing a substrate for producing a group nitride semiconductor element, and a method for producing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor element can be provided.

10: not substrate for growth
10a: surface on the surface side of the substrate
20: metal chromium layer
30: chromium nitride layer
40: group III nitride semiconductor buffer layer
50: group III nitride semiconductor layer
60: group III nitride semiconductor layer
70: electrode
80: electrode
90: Substrate for Manufacturing Group III Nitride Semiconductor Device
90a: Substrate for Manufacturing Group III Nitride Semiconductor Devices
110: not substrate for growth
120: sputtering target
130: substrate holder or substrate tray
140: sputtering particle amorphous region
150a: group III nitride semiconductor independence board
150b: group III nitride semiconductor independence board
160: group III nitride semiconductor device

Claims (11)

A film forming step of forming a chromium layer on the underlying substrate for growth;
A nitriding step of forming the chromium nitride layer by nitriding the chromium layer under predetermined conditions;
Crystal layer growth step of epitaxially growing at least one group III nitride semiconductor layer on the chromium nitride layer
As a method for producing a substrate for producing a group III nitride semiconductor device comprising:
The said chromium layer is formed into a film by the sputtering method so that the film-forming rate in a sputtered particle amorphous region may be 7-65 kPa / sec, and thickness may be 50-300 kPa,
The chromium nitride layer is formed in a gas atmosphere containing ammonia gas in a MOCVD growth furnace with a pressure in the furnace of 6.666 kPa or more and 66.66 kPa or less and a temperature of 1000 ° C. or higher. A carrier gas comprising a gas and a hydrogen gas, wherein the content ratio of nitrogen gas in the carrier gas is in the range of 60 to 100% by volume.
The method of claim 1,
A method for manufacturing a group III nitride semiconductor device manufacturing substrate, wherein an area ratio of the chromium nitride microcrystals on the surface of the chromium nitride layer occupies about 70% or more of the chromium nitride microcrystals having a weak triangular pyramid shape.
3. The method according to claim 1 or 2,
The chromium layer is formed intermittently on a plurality of growth substrates so as to have an average film forming speed in a range of 1 to 10 Pa / sec, respectively.
The method according to claim 2 or 3,
A method of manufacturing a substrate for manufacturing a Group III nitride semiconductor device, wherein the orientation of the bottom side of the triangular pyramidal chromium nitride microcrystal is parallel to the <11-20> direction (a-axis direction) group of the Group III nitride semiconductor layer.
5. The method according to any one of claims 1 to 4,
The substrate for growth has a crystal structure of hexagonal or pseudo hexagonal system, the surface is (0001) surface, the manufacturing method of the group III nitride semiconductor device manufacturing substrate.
A film forming step of forming a chromium layer on the underlying substrate for growth;
A nitriding step of forming the chromium nitride layer by nitriding the chromium layer under predetermined conditions;
A crystal layer growth step of epitaxially growing at least one Group III nitride semiconductor layer on the chromium nitride layer,
Separation step of separating the growth substrate and the group III nitride semiconductor by removing the chromium nitride layer by chemical etching
As a method for producing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor device comprising:
The chromium layer is formed by sputtering so that the film formation rate in the sputtered particle amorphous region is in the range of 50 to 300 kPa in the range of 7 to 65 kPa / sec,
The chromium nitride layer is formed in a gas atmosphere containing ammonia gas in a MOCVD growth furnace having a furnace pressure of 6.666 kPa or more and 66.66 kPa or less and a temperature of 1000 ° C. or more, and the gas components other than ammonia gas in the gas atmosphere are nitrogen gas and A carrier gas made of hydrogen gas, wherein the content ratio of nitrogen gas in the carrier gas is in the range of 60 to 100% by volume, wherein the group III nitride semiconductor self-supporting substrate or the group III nitride semiconductor element is produced.
The method according to claim 6,
A method for producing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor device, wherein an area ratio of the chromium nitride microcrystals on the surface of the chromium nitride layer is 70% or more.
8. The method according to claim 6 or 7,
The chromium layer is intermittently formed on a plurality of growth substrates so as to have an average film forming speed in a range of 1 to 10 Pa / second, respectively. A method of manufacturing a group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor element.
9. The method according to claim 7 or 8,
Fabrication of a Group III nitride semiconductor self-supporting substrate or a Group III nitride semiconductor element in which the orientation of the bottom of the triangular pyramidal chromium nitride microcrystal is parallel to the <11-20> direction (a-axis direction) group of the Group III nitride semiconductor layer. Way.
10. The method according to any one of claims 6 to 9,
The growth substrate has a hexagonal or pseudo hexagonal crystal structure, and the surface is a (0001) surface, the group III nitride semiconductor self-supporting substrate or a group III nitride semiconductor device manufacturing method.
As a group III nitride growth substrate having a substrate and a chromium nitride layer on the substrate:
A group III nitride growth substrate, characterized in that the area ratio of the chromium nitride microcrystals on the surface of the chromium nitride layer occupies about 70% or more of the chromium nitride microcrystals having a triangular pyramidal shape.

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