JP2010278470A - Substrate for growing group-iii nitride semiconductor, epitaxial substrate for group-iii nitride semiconductor, group-iii nitride semiconductor element, stand-alone substrate for group-iii nitride semiconductor, and methods for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epitaxial substrate for group-III nitride semiconductors, a group-III nitride semiconductor element, and a stand-alone substrate for group-III nitride semiconductors, which produce good crystallinity not only for materials having growth temperatures at or below 1050°C, such as AlGaN, GaN, and GaInN, but also for high-Al Al<SB>x</SB>Ga<SB>1-x</SB>N compositions having high growth temperatures, and also to provide a substrate for growing group-III nitride semiconductors, for fabricating the same, and a method for efficient fabrication thereof. <P>SOLUTION: These are characterized by being provided with a crystal growth substrate, at least the surface region of which includes an aluminum-containing group-III nitride semiconductor, and a scandium nitride film formed on top of the surface region. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a group III nitride semiconductor growth substrate, a group III nitride semiconductor epitaxial substrate, a group III nitride semiconductor device, a group III nitride semiconductor free-standing substrate, and a method for manufacturing these.

  Generally, for example, a group III nitride semiconductor element composed of a group III nitride semiconductor composed of a compound of Al, Ga, etc. and N is widely used as a light emitting element or an electronic device element. Such a group III nitride semiconductor is currently generally formed by MOCVD on a crystal growth substrate made of, for example, sapphire.

  However, since the lattice constants of Group III nitride semiconductors and crystal growth substrates (generally sapphire) are greatly different, dislocations are generated due to the difference in lattice constants, and Group III nitrides grown on the crystal growth substrate. There exists a problem that the crystal quality of a semiconductor layer will fall.

In order to solve this problem, conventionally, for example, a method of growing a GaN layer on a sapphire substrate through a low-temperature polycrystalline or amorphous buffer layer has been widely used. However, since the thermal conductivity of the sapphire substrate is small and current cannot flow due to insulation, the n electrode and the p electrode are formed on one side of the sapphire substrate so that the current flows. In addition, because of its poor heat dissipation, it is not suitable for making high-power light-emitting diodes (LEDs).
For this reason, it is affixed to another support substrate that is conductive and has high thermal conductivity so that current can flow in the vertical direction, and laser light with quantum energy larger than the energy gap of GaN is formed on the sapphire substrate. A method such as a laser lift-off method is employed in which a GaN layer is irradiated and thermally decomposed into Ga and nitrogen to peel off the sapphire substrate and the group III nitride semiconductor layer.

  As other conventional techniques, Patent Documents 1 to 3 disclose techniques for growing a GaN layer on a sapphire substrate via a metal nitride layer. According to this method, the dislocation density of the GaN layer can be reduced as compared with the above technique, and a high-quality GaN layer can be grown. This is because the difference in lattice constant and thermal expansion coefficient between the GaN layer and the CrN layer, which is a metal nitride layer, is relatively small. Further, this CrN layer can be selectively etched with a chemical etching solution, and is useful in a process using a chemical lift-off method.

However, in a nitride semiconductor device for generating light in a shorter wavelength region than blue (for example, a wavelength of 400 nm or less), the shorter the wavelength of light to be generated, the more Al _x Ga ₁ of the nitride semiconductor device. _{-x It} is necessary to increase the Al composition x of the N layer. The growth temperature of Al _x Ga _1-x N whose Al composition generally exceeds 30 atomic% exceeds about 1050 ° C., which is the melting point of CrN. For this reason, when a group III nitride semiconductor layer containing Al _x Ga _1-x N whose Al composition generally exceeds 30 atomic% is grown on the CrN layer, CrN melts in a high temperature environment, and due to uneven distribution, It becomes difficult to remove by chemical etching, and chemical lift-off becomes difficult. This means that when the chemical lift-off method is adopted, the CrN layer can be used only when the value of the Al composition x of the Al _x Ga _1-x N layer of the nitride semiconductor device is approximately 0.3 or less, and is manufactured. It shows that the light emitting element has wavelength limitation. Therefore, when the chemical lift-off method is used in the element formation process, CrN cannot be used as a buffer layer for growing Al _x Ga _1-x N having a high growth temperature and a high Al composition. There has been a demand for a material suitable for the chemical lift-off method, which can be easily removed by chemical etching even when heat treatment at a temperature higher than 0 ° C. is performed.
It is conceivable to use a metal with a high melting point instead of CrN, but use a highly corrosive hydrofluoric acid etching solution to dissolve and remove high melting point metals (Zr, Hf, etc.) by chemical etching. There is a need to. When the above-mentioned hydrofluoric acid-based etching solution is used at the time of chemical lift-off, the corrosiveness to the substrate and the electrode is strong, and the protection measures are necessary, and the manufacturing cost is increased correspondingly, and the manufacturing process is free. The degree was considered to be low.

WO2006 / 126330 JP 2008-91728 A JP 2008-91729 A

The object of the present invention is to solve the above-mentioned problems, and not only for AlGaN, GaN, and GaInN having a growth temperature of 1050 ° C. or lower, but also for Al _x Ga _1-x N having a high Al composition and a high growth temperature. A group III nitride semiconductor epitaxial substrate, a group III nitride semiconductor device, a group III nitride semiconductor free-standing substrate, and a group III nitride for manufacturing them, which can employ the chemical lift-off method It is an object of the present invention to provide a substrate for semiconductor growth and a method for efficiently manufacturing them.

In order to achieve the above object, the gist of the present invention is as follows.
(1) A group III nitride semiconductor growth comprising a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al and a scandium nitride film formed on the surface portion. substrate.

  (2) The group III nitride semiconductor growth substrate according to (1) above, wherein the scandium nitride film has a crystal orientation of {111} in the plane orientation.

  (3) The group III nitride semiconductor growth substrate according to (1) or (2) above, wherein the surface orientation of the group III nitride semiconductor is {0001}.

  (4) The group III nitride semiconductor growth substrate according to any one of (1) to (3), wherein the scandium nitride film has a thickness of 3 to 100 nm.

  (5) The group III nitride semiconductor growth according to any one of (1) to (4) above, wherein a base substrate of the crystal growth substrate is any one of sapphire, Si, SiC, and GaN. Substrate.

  (6) The group III nitride semiconductor growth substrate according to any one of (1) to (5), wherein the at least surface portion is made of AlN.

  (7) The scandium nitride film includes a plurality of triangular pyramid-shaped microcrystalline portions, and the plurality of microcrystalline portions are uniformly formed on the surface portion. The group III nitride semiconductor growth substrate according to any one of to (6).

  (8) A Group III nitride comprising at least one Group III nitride semiconductor layer on the Group III nitride semiconductor growth substrate according to any one of (1) to (7) above Semiconductor epitaxial substrate.

  (9) A group III nitride half-body self-supporting substrate manufactured using the group III nitride semiconductor growth substrate according to any one of (1) to (7) above.

  (10) A Group III nitride semiconductor device manufactured using the Group III nitride semiconductor growth substrate according to any one of (1) to (7) above.

  (11) A step of forming a metal layer made of a Sc material on a crystal growth substrate made of a group III nitride semiconductor including at least a surface part of Al, and heating the metal layer in an atmospheric gas containing ammonia gas And a step of forming a scandium nitride film by performing a nitriding treatment, and a method for manufacturing a group III nitride semiconductor growth substrate.

  (12) A step of forming a metal layer made of an Sc material on a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al, and heating the metal layer in an atmospheric gas containing ammonia gas Forming a scandium nitride film by nitriding to produce a group III nitride semiconductor growth substrate, and at least one group III nitride semiconductor above the group III nitride semiconductor growth substrate. Forming a group III nitride semiconductor epitaxial substrate by epitaxially growing the layers, isolating the at least one group III nitride semiconductor layer, and forming a support substrate on the group III nitride semiconductor layer side And the group III nitride semiconductor layer and the crystal growth substrate are separated by chemical lift-off by selectively etching the scandium nitride film. A method for producing a group III nitride semiconductor device comprising the step of obtaining a compound semiconductor device.

  (13) A step of forming a metal layer made of an Sc material on a crystal growth substrate made of a group III nitride semiconductor including at least a surface part of Al, and heating the metal layer in an atmospheric gas containing ammonia gas Forming a scandium nitride film by nitriding to produce a group III nitride semiconductor growth substrate, and at least one group III nitride semiconductor above the group III nitride semiconductor growth substrate. A step of epitaxially growing a layer, and a step of selectively etching the scandium nitride film to separate the group III nitride semiconductor layer and the crystal growth substrate by chemical lift-off to obtain a group III nitride semiconductor free-standing substrate A method for manufacturing a group III nitride semiconductor free-standing substrate, comprising:

The substrate for group III nitride semiconductor growth of the present invention comprises a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al, and a scandium nitride film formed on the surface portion, Without significantly impairing the crystallinity of the group III nitride semiconductor layer Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) formed thereafter, and The group III nitride semiconductor layer can be easily peeled off from the crystal growth substrate by chemical lift-off.
Furthermore, at the time of chemical lift-off, the group III nitride semiconductor layer can be easily peeled from the crystal growth substrate by using an acidic solution as an etching solution. For example, an aqueous hydrochloric acid solution, an aqueous nitric acid solution, a mixed acid of sulfuric acid and nitric acid, an organic acid, or the like can be used as an etching solution, and an acidic solution in which only ScN is dissolved without dissolving a supporting substrate or an electrode material to be used. Can be appropriately selected.

Further, according to the present invention, by using the above-mentioned group III nitride semiconductor growth substrate, it is possible to remove the substrate by chemical lift-off, and the group III nitriding exceeds the wavelength limit when using a CrN material. covering things semiconductor material with a cover capable entire wavelength range (200nm~1.5μm), in other words, Al _x Ga _y in ₁ comprising from AlN grown at a high temperature of at least 1200 ° C. until InN grown at 500 ° C. before and after Group III nitride semiconductor epitaxial substrate with good crystallinity that can cover the growth temperature range of the entire composition region of _-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), III A group nitride semiconductor device and a group III nitride semiconductor free-standing substrate can be provided.

Furthermore, according to the present invention, a step of forming a metal layer made of Sc material on a crystal growth substrate made of a group III nitride semiconductor containing at least Al on the surface portion, and nitriding treatment is performed on the metal layer by comprising the step, crystals then formed III-nitride semiconductor layer _{Al x Ga y in 1-xy} N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) Thus, it is possible to manufacture a group III nitride semiconductor growth substrate that can easily separate the group III nitride semiconductor layer from the crystal growth substrate by chemical lift-off without significantly impairing the properties.

  In addition, the present invention provides a wavelength that can be covered with a group III nitride semiconductor material by exceeding the wavelength limit when using a CrN material by performing chemical lift-off using the above group III nitride semiconductor growth substrate. A group III nitride semiconductor epitaxial substrate, a group III nitride semiconductor element, and a group III nitride semiconductor free-standing substrate with good crystallinity that cover the entire band (200 nm to 1.5 μm) can be efficiently manufactured.

It is a schematic diagram which shows the cross-section of the board | substrate for nitride semiconductors according to this invention. It is a schematic diagram which shows the manufacturing process of the nitride semiconductor element structure according to this invention. It is a graph which shows the result of 2 (theta) / omega scan measurement by a X-ray-diffraction apparatus. 4 is a surface SEM photograph of a sample according to the present invention. 4 is a surface SEM photograph of a sample according to the present invention. 4 is a surface SEM photograph of a sample according to the present invention. 4 is a surface SEM photograph of a sample according to the present invention. It is the surface height image by AFM of the sample according to this invention. It is a graph which shows the emission spectrum of the sample according to this invention.

  Next, an embodiment of a group III nitride semiconductor growth substrate of the present invention will be described with reference to the drawings. Here, the group III nitride semiconductor epitaxial substrate in the present invention refers to a substrate in which at least one group III nitride semiconductor layer is grown on the group III nitride semiconductor growth substrate. A semiconductor element refers to a group III nitride semiconductor epitaxial substrate that has been subjected to a device process such as electrode deposition, and an element separated, and a group III nitride semiconductor free-standing substrate is at least This is obtained by growing a group III nitride semiconductor layer having a thickness of 50 μm or more on the group III nitride semiconductor growth substrate and then peeling the group III nitride semiconductor growth substrate. FIG. 1 schematically shows a cross-sectional structure of a group III nitride semiconductor growth substrate according to the present invention.

  A group III nitride semiconductor growth substrate 1 shown in FIG. 1 is a group III nitride semiconductor including at least a surface portion, and in FIG. 1, a surface portion 2 containing at least Al. A crystal growth substrate 3 having this surface portion, and a surface A nitride film 4 made of scandium nitride formed on the portion 2 and adopting such a configuration increases the crystallinity of the group III nitride semiconductor layer formed above the scandium nitride film 4. The crystal growth substrate 3 can be peeled off from the group III nitride semiconductor layer by chemical lift-off without damage. In addition, the hatching in a figure is given for convenience for description.

A group III nitride semiconductor growth substrate 1 is formed of at least one layer of Al _x Ga _1-x N (0 ≦ x ≦ 1) formed on the scandium nitride film 4, and two buffer layers in FIG. It is preferable to further include an initial growth layer 5 composed of 5a and 5b. This is to improve the crystallinity of the nitride semiconductor layer grown thereon. The Al composition of these buffer layers can be appropriately selected according to the material formed thereon. A small amount of In may be included.

  The crystal growth substrate 3 is, for example, a template having a group III nitride semiconductor 2 containing at least Al on a base substrate 6 made of a material used for growing a group III nitride semiconductor such as sapphire, Si, SiC, or GaN or AlGaN. It can be a substrate, a single crystal substrate of group III nitride semiconductor 2, or a surface nitrided sapphire substrate formed by nitriding the surface of sapphire. FIG. 1 shows a case where the crystal growth substrate 3 is an AlN template substrate having an AlN single crystal layer 2 on a sapphire substrate 6. The surface portion 2 made of a group III nitride semiconductor containing at least Al has an effect of reducing crystal defects in the AlGaN layer grown thereabove.

Crystal growth substrate 3, at least the surface portion 2, more preferably consisting of Al composition of 50 _{atom% Al x Ga 1-x N} (0.5 ≦ x ≦ 1), of more than 80 atomic% Al _x Ga ₁ More preferably, it consists of _-xN (0.8≤x≤1). This is because homoepitaxial growth occurs when the Al composition of the group III nitride semiconductor layer grown upward is equivalent, and a layer having good crystallinity with low dislocation defect density can be grown. Further, when the Al composition of the group III nitride semiconductor layer grown upward is higher than that of the group III nitride semiconductor layer, the effect of further reducing dislocation can be expected by compressive stress, and the growth temperature is the highest among group III nitride semiconductor materials. The surface portion 2 is most preferably made of AlN because it does not deteriorate during the growth of the group III nitride semiconductor layer grown thereon.

  The scandium nitride (ScN) film 4 can be obtained by nitriding a metal Sc film. The ScN material has an excellent physical property that it has a high melting point and can be dissolved and removed by using various acidic solutions as etching solutions. The ScN crystal has a rock salt structure, but when at least the surface portion 2 of the crystal growth substrate 3 is made of a group III nitride semiconductor material containing Al, the same three crystal structures as those of the group III nitride semiconductor containing Al are included. Arranged in the (111) plane orientation having a rotation axis, the lattice constant and linear expansion coefficient of the a axis are close to those of the group III nitride semiconductor containing Al. Unlike the case of using CrN, when ScN is formed directly on a sapphire substrate without using a group III nitride semiconductor material containing Al, the ScN orientation is poor due to the large lattice constant difference between ScN and sapphire. It is difficult to grow a high-quality group III nitride semiconductor layer thereon.

  The thickness of the scandium nitride film 4 is preferably 3 to 100 nm. If it is less than 3 nm, the scandium nitride film 4 is too thin to make it difficult for the etching solution to enter, or the thickness of the metal Sc layer becomes discontinuous by the nitriding treatment, and the surface of the crystal growth substrate that is the base substrate is exposed. In some cases, the group III nitride semiconductor layer directly grows on the crystal growth substrate, making chemical lift-off difficult. On the other hand, if it exceeds 100 nm, high crystallization due to solid phase epitaxy of the scandium nitride film itself cannot be expected, and the crystallinity of the group III nitride semiconductor layer thereon may deteriorate and defects may increase. is there. The scandium nitride film 4 can be formed by forming a metal Sc layer on the crystal growth substrate 3 using a method such as a sputtering method or a vacuum deposition method, and performing nitriding treatment.

  Although not shown in FIG. 1, a group III nitride semiconductor epitaxial growth substrate according to the present invention is provided by providing at least one group III nitride semiconductor layer on a group III nitride semiconductor growth substrate 1 having the above-described configuration. Can be obtained.

  Similarly, although not shown in FIG. 1, a group III nitride semiconductor free-standing substrate and a group III nitride semiconductor device according to the present invention can be obtained using the group III nitride semiconductor growth substrate 1 having the above-described configuration. it can.

  Next, an embodiment of a method for producing a group III nitride semiconductor growth substrate of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a group III nitride semiconductor growth substrate 1 of the present invention has a single metal layer made of a Sc material on a crystal growth substrate 3 made of a group III nitride semiconductor having at least a surface portion 2 containing Al. And forming the scandium nitride film 4 by nitriding the metal layer. By adopting such a configuration, the group III nitride semiconductor layer formed thereabove is formed. The crystal growth substrate 3 can be peeled off from the group III nitride semiconductor layer by chemical lift-off without greatly deteriorating the crystallinity.

For the base substrate 6, for example, sapphire, Si, SiC, GaN, AlGaN, AlN or the like can be used. In particular, sapphire or Si can be suitably used from the viewpoint of substrate procurement cost. The metal layer made of Sc material can be formed by sputtering. A vapor deposition method may be used, but a sputtering method is more preferable.
The nitriding treatment of the Sc material is a mixed gas containing ammonia and containing one or two of inert gas (one or more selected from rare gases such as N2, Ar, He, Ne) and hydrogen gas, or This can be done by heating in ammonia gas. Since the Sc material has sublimability, it is preferable to start flowing the mixed gas or ammonia gas from a temperature lower than the sublimation temperature in the temperature raising process. As a result, Sc is nitrided to become ScN, which becomes a stable material even at high temperatures. The mixed gas or ammonia gas may start to flow from room temperature, but if the mixed gas or ammonia gas starts to flow from around 500 ° C., which is the decomposition temperature of ammonia, waste of ammonia gas can be prevented, resulting in cost reduction. This is preferable. The maximum temperature of the heating temperature (base substrate surface temperature) is preferably 850 to 1300 ° C. When the temperature is lower than 850 ° C., nitriding may not be sufficiently performed. When the temperature exceeds 1300 ° C., the equipment life may be shortened by increasing the temperature. The heating is preferably performed at a temperature of 850 ° C. or higher for 1 to 120 minutes. If it is less than 1 minute, nitriding may not be sufficient, and if it exceeds 120 minutes, there is no particular effect, which is disadvantageous in terms of productivity. The kind of the inert gas is not particularly limited, and N, Ar, etc. can be used. The concentration of ammonia gas is preferably in the range of 0.01 to 100% by volume. If the amount is less than the lower limit, nitriding may not be sufficient. When the concentration of ammonia gas is too high, the surface roughness after nitriding may increase, and the concentration of ammonia gas is more preferably 0.01 to 90% by volume. Further, the mixed gas may contain 20% by volume or less of hydrogen.
Even if the above nitridation is not sufficient, a group III nitride semiconductor can be grown if it can be confirmed that at least the surface of the Sc material is ScN arranged in the (111) plane orientation.

It is preferable to further include a step of forming an initial growth layer 5 made of at least one buffer layer made of an Al _x Ga _1-x N material (0 ≦ x ≦ 1) on the scandium nitride film 4. In order to improve the crystallinity of the group III nitride semiconductor layer formed thereafter, the growth temperature is preferably in the range of 900 to 1300 ° C. The initial growth layer can be grown by a known growth method such as MOCVD method, HVPE method (hydride vapor phase epitaxy method), PLD method (pulse laser deposition method).

  The substrate for growing III nitride semiconductor 1 according to the present invention can be manufactured using the method described above.

  Next, as shown in FIG. 2 (a), the Group III nitride semiconductor epitaxial substrate 8 according to the present invention is manufactured at least above the Group III nitride semiconductor growth substrate 1 produced by the above-described method. By including the step of epitaxially growing a single group III nitride semiconductor layer 7 and having such a structure, temperature limitation (wavelength limitation) when using a CrN material to remove the crystal growth substrate 3 described later by chemical lift-off is provided. 3), a group III nitride semiconductor epitaxial substrate with good crystallinity that covers the growth temperature zone of the group III nitride semiconductor material in the entire composition range can be manufactured.

  It is preferable that the group III nitride semiconductor layer 7 includes growth using a MOCVD method, an HVPE method, a PLD method, an MBE method or the like at a maximum temperature in the range of 900 to 1300 ° C.

It is preferable to further include a step of forming an initial growth layer 5 made of at least one buffer layer made of an Al _x Ga _1-x N material (0 ≦ x ≦ 1) on the scandium nitride film 4. In order to improve the crystallinity of the group III nitride semiconductor layer 7 formed thereafter, the growth temperature is preferably in the range of 900 to 1300 ° C.

  The initial growth layer 5 may be a single layer, but two or more layers are preferable from the viewpoint of improving the crystallinity of the group III nitride semiconductor layer 7 formed thereafter. When the initial growth layer 5 has two layers, the first growth layer 5 includes a first buffer layer 5a and a second buffer layer 5b grown on the first buffer layer 5a. The growth temperature of the first buffer layer 5a is 900 to 1260 ° C. Preferably, the growth temperature of the second buffer layer 5b is in the range of 1000 to 1300 ° C., and the growth temperature of the first buffer layer 5a is lower than the growth temperature of the second buffer layer 5b. In the initial stage of growth for growing the first buffer layer 5a, growth is promoted at a relatively low temperature to promote the formation of a large number of initial growth nuclei to improve the crystallinity, and then the second buffer layer 5b is formed. This is because when the growth is performed, the crystallinity is improved and the flatness is improved by filling the grooves / dents formed between a large number of initial nuclei by increasing the growth temperature. Further, the buffer layer may have three or more layers. In that case, it is preferable to increase the growth temperature sequentially. When the initial growth layer 5 is a single layer, the growth temperature is preferably in the range of 1000 to 1300 ° C.

  The group III nitride semiconductor epitaxial substrate 8 according to the present invention can be manufactured using the method described above.

  Next, as shown in FIGS. 2 (a) and 2 (b), the manufacturing method of the group III nitride semiconductor device 9 of the present invention is applied to the group III nitride semiconductor epitaxial substrate 8 formed by the above-described method. On the other hand, the step of element isolation of at least one group III nitride semiconductor layer 7, the step of forming the support substrate 10 on the group III nitride semiconductor layer 7 side, and the selective etching of the scandium nitride film 4 make III The group nitride semiconductor layer 7 (the group III nitride semiconductor layer 7 and the buffer layer 5 in the case shown in FIG. 2B) and the crystal growth substrate 3 are separated by chemical lift-off, and the group III nitride semiconductor device 9 By adopting such a configuration, the temperature limit (wavelength limit) when using the CrN material for removing the crystal growth substrate 3 by chemical lift-off is exceeded, and the III of the entire composition range is obtained. Growth of group nitride semiconductor materials Covering degree band can crystallinity efficiently produced good III nitride semiconductor device.

  At least one group III nitride semiconductor layer 7 is, for example, an n-AlGaN layer 11, an AlInGaN-based quantum well active layer 12, and a p-AlGaN layer 13, as shown in FIGS. 2 (a) and 2 (b). be able to. It should be noted that the order of lamination of the group III nitride semiconductor layers 11, 12 and 13 may be reversed. In addition, the support substrate 10 is preferably formed using a material having heat dissipation properties.

  The group III nitride semiconductor device 9 according to the present invention can be manufactured using the method described above.

  Next, in the method for producing a group III nitride semiconductor free-standing substrate of the present invention, the step of epitaxially growing at least one group III nitride semiconductor layer above the group III nitride semiconductor growth substrate produced by the method described above. And a step of selectively etching the scandium nitride film 4 to separate the group III nitride semiconductor layer and the crystal growth substrate by chemical lift-off to obtain a group III nitride semiconductor free-standing substrate. By adopting, the growth temperature range of the group III nitride semiconductor material in the entire composition range exceeds the temperature limit (wavelength limit) when the CrN material is used to remove the crystal growth substrate 3 by chemical lift-off. A group III nitride semiconductor free-standing substrate that covers and has good crystallinity can be efficiently manufactured.

  The thickness of the group III nitride semiconductor layer is 50 μm or more. This is to ensure handling.

  The group III nitride semiconductor free-standing substrate according to the present invention can be manufactured using the method described above.

  The above description shows an example of a typical embodiment, and the present invention is not limited to this embodiment.

Example 1
An AlN single crystal layer (thickness: 1 μm) was grown on sapphire by MOCVD to produce an AlN (0001) template substrate as a nitride semiconductor growth substrate. On the obtained AlN template substrate, using the sputtering method, a film of Sc was formed in the thickness shown in Table 1, and then installed in a MOCVD apparatus, and a mixed gas of nitrogen gas and ammonia gas was shown in Table 1. Flowing at the indicated flow rate, the temperature was raised to the temperature shown in Table 1 (substrate surface temperature) in this atmosphere, and nitriding was performed at a pressure of 200 Torr while maintaining this temperature for 10 minutes. Then, it cooled to room temperature over 70 minutes, took out from the MOCVD apparatus, and obtained five samples of samples 1-1 to 1-5.

(Evaluation)
In order to confirm the crystallization and crystal orientation of the scandium nitride film, 2θ / ω scan measurement was performed on each of the five samples using an X-ray diffractometer. FIG. 3 shows measurement results, in which the horizontal axis represents an angle of 2θ, and the vertical axis represents the intensity of diffracted X-rays. In Samples 1-1 to 1-4, in addition to diffraction peaks from sapphire and AlN of the AlN template used as the base substrate, diffraction peaks of Sc111 (111) and (222) are seen. From this result, it was found that the Sc film is nitrided and ScN has a crystal orientation of (111).
In Sample 1-5 having a low nitriding temperature of 830 ° C., the X-ray diffraction peaks of ScN (111) and (222) were not observed, and (111) -oriented ScN was not formed.
Moreover, the result of having observed the surface of Samples 1-1 to 1-4 with a scanning electron microscope (SEM) at 100,000 times is shown in FIGS. In particular, in FIG. 4, a plurality of triangular pyramid-shaped projections exist on the surface of the scandium nitride film, and each projection has a substantially uniform size and is arranged without a gap. Such convex portions were uniformly distributed over the entire surface of the base substrate. The triangular pyramid group is composed of two types of base directions, and the base direction is along the <1-100> direction group of the underlying AlN (0001). The surfaces other than the bottom surface of the triangular pyramid are substantially {100} planes.
When Samples 1-1 to 1-4 were immersed in the following etching solution at room temperature, it was confirmed that the ScN film could be removed by all the etching solutions for all the four samples.
<Etching solution>
Hydrofluoric acid (46%), buffered hydrofluoric acid _{(NH 4 HF 2: 17.1%} , NHF 4: 18.9%), nitric acid (61%), hydrochloric acid (36%), sulfuric acid (96%), mixed acid of sulfuric acid and nitric acid (Sulfuric acid: Nitric acid = 9: 1), Malic acid, Citric acid, Tartaric acid (% is% by mass)
Thus, the ScN film of the present application can be removed with a wide range of acid solutions, and can be selected according to the support substrate, electrode, and bonding material to be used.

(Example 2)
Similarly to Example 1, a single metal layer having the metal species and thickness shown in Table 2 was formed on an AlN (0001) template substrate by sputtering. The sample thus formed was subjected to nitriding treatment in the same manner as in Example 1 under the conditions shown in Table 2. However, Sample 2-2 is a comparative example in which nitriding is not performed, and heat treatment was performed in hydrogen gas. Thereafter, a buffer layer (1 μm) made of an AlN material was further formed using the MOCVD method under the conditions shown in Table 2, and Samples 2-1 to 2-3 were obtained. The source gas for Al is TMA.

(Evaluation)
Table 3 shows the results of the X-ray rocking curve measurement on the AlN (0002) and (10-12) planes and the evaluation of surface flatness by AFM for the AlN buffer layers of Samples 2-1 to 2-3. Show. As shown in Table 3, the half width of the X-ray rocking curve of Sample 2-1 in which the metal nitride layer is ScN is substantially the same as Sample 2-3 in which the metal nitride layer is CrN, and Sample 2- The crystallinity of the AlN buffer layer 1 was almost the same as that of the sample 2-3 and was good.
A □ 850 μm SiO ₂ pattern was formed on Samples 2-1 to 2-3 as a mask, and the AlN buffer layer was etched by dry etching to form a groove portion exposing the metal nitride layer. Thereafter, a bonding layer containing Au was formed on the AlN buffer layer and bonded to the support substrate. As the support substrate, a material resistant to an aqueous solution during etching was selected. The combination of the support substrate and the etching solution is as shown in the following conditions 1 to 4.
Condition 1 Hydrofluoric acid: aqueous solution containing HF (46% by mass) (support substrate: Mo, bonding layer: Au-Sn)
Condition 2 Nitric acid: aqueous solution containing HNO ₃ (61% by mass) (support substrate: Si, bonding layer: Au-Au)
Condition 3 Hydrochloric acid: aqueous solution containing HCl (36% by mass) (support substrate: Si, bonding layer: Au-Au)
Condition 4 Cr etching solution: aqueous solution containing (NH ₄ ) 2Ce (NO ₃ ) ₆ (14 mass%), HNO ₃ (3 mass%)
(Support substrate: Si, bonding layer: Au-Au)
Under these conditions 1 to 4, the temperature of the aqueous solution was 25 ° C., and samples 2-1 to 2-3 were immersed for 24 hours.
The results are shown in Table 4. In Table 4, when the AlN buffer layer and the growth substrate could be separated, it was marked as ◯, and when they could not be separated, it was marked as x. Sample 2-1 can be lifted off under all conditions. In Sample 2-2, the metal Sc as the layer to be etched disappeared due to the sublimation of the metal Sc, and the AlN buffer layer was formed directly on the AlN template. In Sample 2-3, CrN was dissolved at a high temperature, and the entire surface could not be covered, and the AlN buffer layer was partially formed directly on the AlN template.

(Example 3)
As in Example 1, an Sc metal layer having a thickness shown in Table 5 was formed on an AlN (0001) template substrate by sputtering, and then nitriding was performed under the conditions shown in Table 5. One or two buffer layers made of an AlN material were formed on the sample thus formed under the conditions shown in Table 5 to obtain Samples 3-1, 3-2. The film forming conditions other than those listed in Table 5 are the same as in Example 2.

(Evaluation)
A sample surface photograph of the AFM of Sample 3-1 is shown in FIG. Atomic steps are observed, and it can be seen that a flat AlN layer is obtained at the atomic level. On the other hand, Sample 3-2 had large irregularities due to surface roughness, and measurement by AFM was difficult.

  Results of evaluating the X-ray rocking curve for the AlN buffer layers of Samples 3-1 and 3-2 in the same manner as in Samples 2-1 to 2-3, and the results of Ra measured by AFM Is shown in Table 6. In Sample 3-1, in which the AlN buffer layer on the metal layer is two layers, Ra is greatly improved as compared with Sample 3-2 in which the AlN buffer layer is one layer. By using two AlN buffer layers, the surface flatness of the AlN buffer layer can be improved.

Example 4
As in Example 1, a 15-nm-thick Sc metal layer was formed on an AlN (0001) template substrate having a diameter of 2 inches by sputtering, and then the pressure was 200 Torr and the substrate temperature was 1150 ° C. in a MOCVD apparatus. A nitriding treatment was performed for a minute. At this time, the mixing ratio of NH ₃ and N ₂ was 30 and 70 by volume%, respectively.
After nitriding, the substrate temperature is lowered to 1020 ° C., AlN is grown on the 80 nm scandium nitride film as the first buffer layer under the condition of 10 Torr pressure, and then the substrate temperature is raised to 1200 ° C. As a layer, an AlN layer was grown to 920 nm. The V / III ratio during AlN growth was 120, and the growth rate was about 1000 nm / hr.

  Subsequently, in the MOCVD furnace, the n-type AlGaN cladding layer is 2.5 μm, the AlInGaN / AlGaN MQW (multiple quantum well) light-emitting layer, the p-AlGaN electron blocking layer, the p-AlGaN cladding layer / contact layer (the total thickness of the p-type layer is 0.25 μm) was grown to obtain an ultraviolet LED structure epitaxial substrate.

  The epitaxial layer of this epitaxial substrate was grooved to the AlN template portion by dry etching in a grid pattern, and was primarily separated into individual LED chips. Next, an Rh ohmic electrode was formed on the p-type contact layer, and then bonded to the low resistivity p-type Si substrate through a AuSu bonding layer by a vacuum heating press method. Using the groove processed portion as an etching channel, the scandium nitride film was selectively dissolved using hydrochloric acid, and the growth substrate and the LED structure epitaxial portion were separated and transferred to the Si support substrate side. An ohmic electrode serving as a positive electrode is formed on the back side of the Si substrate.

At least a part of the AlN layer was removed by dry etching, and a Ti / Al based ohmic electrode was formed on the exposed n-type AlGaN cladding layer. Dicing was performed along the primary separation groove with a blade dicer and separated into LED chips. When the characteristics of the obtained vertical structure ultraviolet LED were evaluated, an emission spectrum having a peak wavelength of 326 nm was shown as shown in FIG. The light output was 2.5 mW when the forward drive current _If was 20 mA, which was a very good result for this wavelength band. When Cr was used, the substrate temperature at 1200 ° C. was recorded before reaching the ultraviolet LED structure epitaxial growth, and the subsequent processes were not completed, and an LED having this wavelength could not be produced.

(Example 5)
As in Example 1, a 15-nm-thick Sc metal layer was formed on an AlN (0001) template substrate having a diameter of 2 inches using a sputtering method, and then the pressure was 200 Torr and the substrate temperature was 1150 ° C. in a MOCVD apparatus. A nitriding treatment was performed for a minute. At this time, the mixing ratio of NH ₃ and N ₂ was 30 and 70 by volume%, respectively.
After nitriding, the substrate temperature is lowered to 1020 ° C., AlN is grown on the 80 nm scandium nitride film as the first buffer layer under the condition of 10 Torr pressure, and then the substrate temperature is raised to 1200 ° C. As a layer, an AlN layer was grown to 920 nm. The V / III ratio during AlN growth was 120, and the growth rate was about 1000 nm / hr. The source gas for Al is TMA.

  Further, after raising the substrate temperature to 1250 ° C., the supply amount of TMA was doubled while maintaining the V / III ratio, and an AlN layer having a thickness of 100 μm was formed over 48 hours. After cooling, taking out and immersing in hydrochloric acid, the scandium nitride film was selectively etched, and the growth AlN template substrate was peeled off to obtain an AlN single crystal self-supporting substrate having a diameter of 2 inches.

(Example 6)
As in Example 1, a 20-nm thick Sc metal layer was formed on an AlN (0001) template substrate having a diameter of 2 inches by sputtering, and was then applied in a MOCVD apparatus at a pressure of 200 Torr and a substrate temperature of 1200 ° C. A nitriding treatment was performed for a minute.
After the nitriding treatment, the substrate temperature was lowered to 900 ° C., GaN layer initial growth was performed for 10 minutes, and then GaN thick film growth (about 7 μm thickness) was performed for 2 hours at a substrate temperature of 1040 ° C. After cooling and taking out, the sample was set in an HVPE furnace and heated to a substrate temperature of 1040 ° C. at a rate of temperature increase of 20 ° C./min. In parallel with the substrate heating, the temperature of the Ga source portion is heated to 850 ° C. Note that the flow rate of the atmospheric gas was 300 sccm for N _{2 and} 100 sccm for H ₂ , and NH ₃ was set to 1000 sccm when the sample temperature rose to 600 ° C. After waiting for the system to stabilize at a substrate temperature of 1040 ° C. for about 5 minutes, supply of HCl to the Ga source at a flow rate of 40 sccm was started, and growth of GaN was started. After 2 hours, the supply of HCl was stopped, the growth was terminated, and cooling was performed at a cooling rate of 25 ° C./min. When the substrate temperature reached 600 ° C., the supply of NH ₃ gas was stopped. After cooling, the sample is immersed in hydrochloric acid, the scandium nitride film is selectively etched, the growth AlN template substrate is peeled off, and a GaN single crystal having a diameter of 2 inches and a thickness of 163 μm is self-supporting. A substrate was obtained.

  While the present invention has been described in detail with specific examples in the embodiments and examples, the present invention is not limited to the above-described embodiments and examples and does not depart from the scope of the present invention. All changes and modifications are possible within the scope.

The substrate for group III nitride semiconductor growth of the present invention comprises a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al, and a scandium nitride film formed on the surface portion, Without significantly impairing the crystallinity of the group III nitride semiconductor layer Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) formed thereafter, and The group III nitride semiconductor layer can be easily peeled off from the crystal growth substrate by chemical lift-off.
Furthermore, at the time of chemical lift-off, the group III nitride semiconductor layer can be easily peeled from the crystal growth substrate by using an acidic solution as an etching solution. For example, an aqueous hydrochloric acid solution, an aqueous nitric acid solution, a mixed acid of sulfuric acid and nitric acid, an organic acid, or the like can be used as an etching solution, and an acidic solution in which only ScN is dissolved without dissolving a supporting substrate or an electrode material to be used. Can be appropriately selected.

Further, according to the present invention, by using the above-mentioned group III nitride semiconductor growth substrate, it is possible to remove the substrate by chemical lift-off, and the group III nitriding exceeds the wavelength limit when using a CrN material. covering things semiconductor material with a cover capable entire wavelength range (200nm~1.5μm), in other words, Al _x Ga _y in containing from AlN grown at a temperature higher than 1200 ° C. until InN grown at 500 ° C. before and after Group III nitride semiconductor epitaxial substrate with good crystallinity that can cover the growth temperature range of the entire composition range of _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), A group III nitride semiconductor device and a group III nitride semiconductor free-standing substrate can be provided.

Furthermore, according to the present invention, a step of forming a metal layer made of Sc material on a crystal growth substrate made of a group III nitride semiconductor containing at least Al on the surface portion, and nitriding treatment is performed on the metal layer by comprising the step, crystals then formed III-nitride semiconductor layer _{Al x Ga y in 1-xy} N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) Thus, it is possible to manufacture a group III nitride semiconductor growth substrate that can easily separate the group III nitride semiconductor layer from the crystal growth substrate by chemical lift-off without significantly impairing the properties.

  In addition, the present invention provides a wavelength that can be covered with a group III nitride semiconductor material by exceeding the wavelength limit when using a CrN material by performing chemical lift-off using the above group III nitride semiconductor growth substrate. A group III nitride semiconductor epitaxial substrate, a group III nitride semiconductor element, and a group III nitride semiconductor free-standing substrate with good crystallinity that cover the entire band (200 nm to 1.5 μm) can be efficiently manufactured.

1 Group III nitride semiconductor growth substrate 2 Surface portion 3 Crystal growth substrate 4 Scandium nitride film 5 Initial growth layer 5a First buffer layer 5b Second buffer layer 6 Base substrate 7 Group III nitride semiconductor layer 8 Group III nitride Semiconductor epitaxial substrate 9 Group III nitride semiconductor device 10 Support substrate 11 n-AlGaN layer 12 AlInGaN quantum well active layer 13 p-AlGaN layer

Claims (13)

A crystal growth substrate having a surface portion made of a group III nitride semiconductor containing at least Al; and
A group III nitride semiconductor growth substrate comprising a scandium nitride film formed on the surface portion.   2. The group III nitride semiconductor growth substrate according to claim 1, wherein the scandium nitride film has a crystal orientation of {111}.   The group III nitride semiconductor growth substrate according to claim 1 or 2, wherein the surface orientation of the group III nitride semiconductor is {0001}.   The group III nitride semiconductor growth substrate according to any one of claims 1 to 3, wherein the scandium nitride film has a thickness of 3 to 100 nm.   5. The group III nitride semiconductor growth substrate according to claim 1, wherein a base substrate of the crystal growth substrate is any one of sapphire, Si, SiC, and GaN.   The group III nitride semiconductor growth substrate according to claim 1, wherein at least the surface portion is made of AlN.   The scandium nitride film has a plurality of triangular pyramid-shaped microcrystalline portions, and the plurality of microcrystalline portions are uniformly formed on the surface portion. The substrate for growing a group III nitride semiconductor according to any one of the above.   A group III nitride semiconductor epitaxial substrate comprising at least one group III nitride semiconductor layer on the group III nitride semiconductor growth substrate according to claim 1.   A group III nitride semiconductor free-standing substrate produced using the group III nitride semiconductor growth substrate according to claim 1.   A group III nitride semiconductor device manufactured using the group III nitride semiconductor growth substrate according to claim 1. Forming a metal layer made of an Sc material on a crystal growth substrate having a surface portion made of a group III nitride semiconductor containing at least Al; and
And a step of forming a scandium nitride film by heating the metal layer in an atmosphere gas containing ammonia gas and performing a nitridation treatment. . Forming a metal layer made of an Sc material on a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al; and
Heating the metal layer in an atmosphere gas containing ammonia gas, performing nitriding treatment to form a scandium nitride film, and producing a group III nitride semiconductor growth substrate;
A step of producing a group III nitride semiconductor epitaxial substrate by epitaxially growing at least one group III nitride semiconductor layer above the group III nitride semiconductor growth substrate; and
Isolating the at least one group III nitride semiconductor layer, and
Forming a support substrate on the group III nitride semiconductor layer side;
Separating the group III nitride semiconductor layer and the crystal growth substrate by chemical lift-off by selectively etching the scandium nitride film to obtain a group III nitride semiconductor device. A method for manufacturing a group III nitride semiconductor device. Forming a metal layer made of an Sc material on a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al; and
Heating the metal layer in an atmosphere gas containing ammonia gas, performing nitriding treatment to form a scandium nitride film, and producing a group III nitride semiconductor growth substrate;
Epitaxially growing at least one group III nitride semiconductor layer above the group III nitride semiconductor growth substrate; and
Separating the group III nitride semiconductor layer and the crystal growth substrate by chemical lift-off by selectively etching the scandium nitride film to obtain a group III nitride semiconductor free-standing substrate. A method for producing a group III nitride semiconductor free-standing substrate.

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