JP2010251743A - Substrate for growing group-iii nitride semiconductor, group-iii nitride semiconductor device, free-standing substrate for group-iii nitride semiconductor, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group-III nitride semiconductor device, and a free-standing substrate for group-III nitride semiconductors and an epitaxial substrate for group-III nitride semiconductors, having good crystallinity for materials having growth temperatures at or below 1,050°C, such as AlGaN, GaN, and GaInN, and also for Al<SB>x</SB>Ga<SB>1-x</SB>N of high Al compositions having high growth temperatures; and to provide a method for efficiently manufacturing the same. <P>SOLUTION: These are provided with a crystal growth substrate, at least the surface region of which includes an Al-containing group-III nitride semiconductor, and a scandium nitride film formed by nitrogen treatment of Sc (scandium) 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 free-standing substrate, a group III nitride semiconductor element, and a method for manufacturing these.

  In general, for example, a group III nitride semiconductor element composed of a group III nitride semiconductor composed of a compound of N, Al, Ga, In or the like 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, as a conventional technique, for example, there is a method of growing a GaN layer on a sapphire substrate through a low-temperature polycrystalline or amorphous buffer layer, which is widely used. However, since the thermal conductivity of the sapphire substrate is small and current cannot flow due to insulation, an n-electrode and a p-electrode are formed on one side of the sapphire substrate and current is passed. It is unsuitable for making high-power light-emitting diodes (LEDs) because of its poor heat dissipation and poor heat dissipation.
For this reason, a laser beam having a quantum energy larger than the energy gap of GaN is formed on the sapphire substrate by switching to another support substrate that is conductive and has high thermal conductivity in order to pass current in the vertical direction. A method such as a laser lift-off method is employed in which the GaN layer is irradiated with thermal decomposition 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.

In either case, the sapphire substrate must be used because there is no III nitride free-standing substrate for epitaxial growth in device manufacturing or it is very expensive. Currently, GaN free-standing substrates are limited to blue-violet LD (laser diode) applications or special applications such as vertical Schottky barrier diodes. If a self-supporting substrate can be reduced in price even for higher output of LEDs, the advantage of having a vertical structure is great.
For example, as a conventional method for manufacturing a group III nitride free-standing substrate, as disclosed in Patent Document 4 and Non-Patent Document 1, in the case of a GaN free-standing substrate,
1) A method in which a GaN layer of about several μm is formed on a sapphire substrate by MOCVD, and then a thick film is grown by HVPE and peeled off by laser lift. 2) A GaAs (111) substrate is used as a growth substrate. Thick GaN film is grown by HVPE method, and the GaAs substrate itself is removed by etching after growth. 3) A GaN layer of about several μm is formed on the sapphire substrate by MOCVD method, and then Ti is deposited on it. A film is formed on the substrate, heat-nitrided and GaN-decomposed, and a TiN network mask and void are formed. Using the underlying GaN at the opening of the network as a seed, GaN is grown to a thick film by the HVPE method. There is a method in which voids at the growth interface promote peeling.
In the case of the above method 1), there is a problem that stress is applied between the part peeled off by laser irradiation and the close contact part, cracks are easily generated, and it is difficult to separate the GaN thick film with a large area and a high yield. . In the case of the method 2), there is a problem that As which is a harmful substance is mixed in the crystal. In the case of the above 3), since the crystal growth start portion is in an imperfect state in order to perform peeling at the interface, there is a problem that the crystal defect density of the obtained GaN thick film becomes high.
Therefore, both methods have problems in terms of quality and manufacturing cost.

WO2006 / 126330 JP 2008-91728 A JP 2008-91729 A JP 2003-178984 A

K. Motoki et al., “Preparation of Large Freestanding GaN Substrates by Hydride Vapor Phase Epitaxy Using GaAs as a Starting Substrate”, Jpn. J. Appl. Phys. 40 (2001) pp. L140-L143

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 figure which shows the nitridation and growth sequence of the sample according to this invention. It is a figure which shows the nitridation and growth sequence of the sample according to this invention. It is a graph which shows the relationship between nitriding temperature and sheet resistance.

  An object of the present invention is to solve the above-described problems, and does not require laser lift-off or chemical lift-off, and allows a group III nitride semiconductor layer and a crystal growth substrate to be separated from a group III nitride having good crystallinity. It is an object to provide a semiconductor free-standing substrate, a group III nitride semiconductor device, a group III nitride semiconductor growth substrate for manufacturing them, 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 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 nitriding under a condition in which nitridation is restricted, and a method for manufacturing a group III nitride semiconductor growth substrate.

  (2) A step of forming a metal layer made of 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 And a step of forming a scandium nitride film by performing nitriding treatment, wherein the maximum temperature of the nitriding treatment is in a range of 500 ° C. or more and less than 1000 ° C. A method for manufacturing a growth substrate.

  (3) The group III nitride semiconductor growth substrate according to (1) or (2), wherein the atmospheric gas containing ammonia gas is a mixed gas further containing at least one selected from an inert gas and a hydrogen gas. Manufacturing method.

  (4) The method for producing a group III nitride semiconductor growth substrate according to the above (1), (2) or (3), wherein the heating of the metal layer is performed at a temperature of 500 ° C. or higher for 0.1 to 120 minutes. .

(5) After the step of performing the nitriding treatment, a step of forming an initial growth layer made of at least one buffer layer made of Al _x Ga _1-x N (0 ≦ x ≦ 1) on the scandium nitride film. The method for producing a group III nitride semiconductor growth substrate according to any one of (1) to (4), further comprising:

  (6) 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 portion of Al, and heating the metal layer in an atmosphere containing ammonia gas A step of forming a scandium nitride film by performing nitriding under a condition in which nitridation is restricted, and producing a group III nitride semiconductor growth substrate, and at least above the group III nitride semiconductor growth substrate, One group III nitride semiconductor layer is epitaxially grown to produce a group III nitride semiconductor epitaxial substrate, and the group III nitride semiconductor epitaxial substrate is set to a temperature of 50 ° C. or less, and the group III nitride semiconductor layer and the crystal are grown. Separating the substrate, and separating the at least one group III nitride semiconductor layer into elements to obtain a group III nitride semiconductor element. Method of manufacturing a body element.

  (7) 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 atmosphere containing ammonia gas A step of forming a scandium nitride film by nitriding under a condition where the maximum temperature is 500 ° C. or more and less than 1000 ° C. to produce a group III nitride semiconductor growth substrate, and said group III nitride semiconductor Above the growth substrate, at least one group III nitride semiconductor layer is epitaxially grown to produce a group III nitride semiconductor epitaxial substrate. The group III nitride semiconductor epitaxial substrate is set to a temperature of 50 ° C. or less, and the group III nitride semiconductor epitaxial substrate is formed. Separating the nitride semiconductor layer and the crystal growth substrate, and separating the at least one group III nitride semiconductor layer into a device to obtain a group III nitride semiconductor device. A method for manufacturing a group III nitride semiconductor device.

(8) A step of forming an initial growth layer made of at least one buffer layer made of Al _x Ga _1-x N (0 ≦ x ≦ 1) on the scandium nitride film after the nitriding treatment. The method for producing a group III nitride semiconductor device according to (6) or (7), further comprising:

  (9) The initial growth layer includes a first buffer layer and a second buffer layer grown on the first buffer layer, and a growth temperature of the first buffer layer is in a range of 900 to 1260 ° C. The group III nitride semiconductor device according to (8), wherein the growth temperature of the two buffer layers is in the range of 1030 to 1300 ° C., and the growth temperature of the first buffer layer is equal to or lower than the growth temperature of the second buffer layer Manufacturing method.

  (10) 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 atmosphere containing ammonia gas A step of forming a scandium nitride film by performing nitriding under a condition in which nitridation is restricted, and producing a group III nitride semiconductor growth substrate, and at least above the group III nitride semiconductor growth substrate, One group III nitride semiconductor layer is epitaxially grown to obtain a group III nitride semiconductor epitaxial substrate, and the group III nitride semiconductor epitaxial substrate is set to a temperature of 50 ° C. or less, and the group III nitride semiconductor layer, the crystal growth substrate, A method for producing a group III nitride semiconductor free-standing substrate.

  (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 portion of Al, and heating the metal layer in an atmosphere containing ammonia gas A step of forming a scandium nitride film by nitriding under a condition where the maximum temperature is 500 ° C. or more and less than 1000 ° C. to produce a group III nitride semiconductor growth substrate, and said group III nitride semiconductor At least one group III nitride semiconductor layer is epitaxially grown above the growth substrate to obtain a group III nitride semiconductor epitaxial substrate, and the group III nitride semiconductor epitaxial substrate is set to a temperature of 50 ° C. or less, and the group III nitride is obtained. A method for producing a group III nitride semiconductor free-standing substrate comprising the step of separating a semiconductor layer and the crystal growth substrate.

(12) A crystal growth substrate including a group III nitride semiconductor including at least a surface portion of Al, and a scandium nitride film formed on the surface portion, wherein the scandium nitride film has a sheet resistance of 1 × 10 Group III nitride semiconductor growth substrate larger than ⁴ Ω / □.

  (13) The group III nitride semiconductor growth substrate according to (12), wherein the scandium nitride film partially contains metal scandium.

(14) In the above (12) or (13), further comprising an initial growth layer comprising at least one buffer layer comprising Al _x Ga _1-x N (0 ≦ x ≦ 1) on the scandium nitride film. The substrate for group III nitride semiconductor growth as described.

  (15) The group III nitride semiconductor growth substrate according to (12), (13) or (14), wherein the scandium nitride film has a thickness of 3 to 100 nm.

  (16) The group III nitride semiconductor growth according to any one of (12) to (15) above, wherein a base substrate of the crystal growth substrate is any one of sapphire, Si, SiC, and GaN. Substrate.

  (17) The group III nitride semiconductor growth substrate according to any one of (12) to (16), wherein the at least surface portion is made of AlN.

  (18) A Group III nitride semiconductor self-supporting substrate produced using the Group III nitride semiconductor growth substrate according to any one of (12) to (17).

  (19) A group III nitride semiconductor device manufactured using the group III nitride semiconductor growth substrate according to any one of (12) to (17).

  (20) a step of forming a metal layer made of Sc material on the crystal growth substrate, a step of nitriding the metal layer to form a scandium nitride film, and at least one layer on the scandium nitride film And a step of lowering the temperature of the group III nitride semiconductor layer to 50 ° C. or lower after epitaxial growth of the group III nitride semiconductor layer.

  (21) The method for peeling a group III nitride semiconductor layer according to (20), wherein the group III nitride semiconductor layer is slid from the crystal growth substrate after the temperature lowering step.

A substrate for group III nitride semiconductor growth according to the present invention includes a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al, and scandium nitridation obtained by nitriding an Sc layer formed on the surface portion. by comprising the object film, then formed by group III nitride semiconductor layer _{Al x Ga y in 1-xy} N of (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) The group III nitride semiconductor layer can be easily peeled off from the crystal growth substrate by lowering the temperature from the growth temperature of the group III nitride semiconductor layer to 50 ° C. or less without greatly impairing the crystallinity.
Furthermore, the gas used for forming the scandium nitride film is either ammonia gas, inert gas, or hydrogen gas, and is generally used as a growth gas for the group III nitride semiconductor layer by various growth methods. Therefore, no special equipment is required and the process is simple.

Further, according to the present invention, by using the group III nitride semiconductor growth substrate, the substrate can be removed without the need for chemical lift-off or laser lift-off, and a wavelength band that can be covered with a group III nitride semiconductor material. covering the full (200nm~1.5μm), in other _{words, Al x Ga y in 1-} xy N (0 ≦ x comprising of AlN is grown at a high temperature of above 1200 ° C. until InN grown at 500 ° C. before and after Provided a Group III nitride semiconductor free-standing substrate and a group III nitride semiconductor device with good crystallinity that can cover the growth temperature range of the entire composition range of ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) can do.

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) A group III nitride semiconductor growth substrate capable of easily peeling the group III nitride semiconductor layer from the crystal growth substrate without requiring chemical lift-off or laser lift-off without significantly degrading the properties. it can.

  In addition, the present invention covers the entire wavelength band (200 nm to 1.5 μm) that can be covered with a group III nitride semiconductor material without using chemical lift-off or laser lift-off, using the group III nitride semiconductor growth substrate. Thus, a group III nitride semiconductor free-standing substrate and a group III nitride semiconductor element with good crystallinity can be efficiently manufactured.

  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 free-standing substrate in the present invention is a group III nitride semiconductor layer having a thickness of 50 μm or more grown on the group III nitride semiconductor growth substrate. This is obtained by peeling off the 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 has a crystal growth substrate 3 made of a group III nitride semiconductor including at least a surface portion, and in FIG. And a nitride film 4 made of scandium nitride formed under limited conditions. By adopting such a configuration, the crystallinity of the group III nitride semiconductor layer formed above the scandium nitride film 4 can be improved. The crystal growth substrate 3 can be peeled off from the group III nitride semiconductor layer by cooling it to 50 ° C. or less from the growth temperature of the group III nitride semiconductor layer without significant damage. In addition, the hatching in a figure is given for convenience for description.

The 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 nitride film 4, and two buffer layers 5a in FIG. , 5b is preferably further included. 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.

  The crystal growth substrate 3 is, for example, a template substrate having a group III nitride semiconductor 2 containing at least Al on a base substrate 6 such as sapphire, Si, SiC or GaN, an AlN single crystal substrate, or nitriding the surface of sapphire. Thus, a surface sapphire nitride substrate can be formed. 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.

In the crystal growth substrate 3, at least the surface portion 2 is preferably made of Al _x Ga _1-x N (0.5 ≦ x ≦ 1) having an Al composition of 50 atomic% or more, and Al _x Ga ₁₋ of 80 atomic% or more. _x N and more preferably composed of (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. It is preferable that at least the surface portion 2 is made of AlN because it does not deteriorate during the growth of the group III nitride semiconductor layer grown thereon.

  The scandium nitride film 4 can be obtained by nitriding a metal Sc film to obtain a ScN film. It is important that the nitriding treatment be performed under conditions that limit nitriding. As a method for limiting the nitriding, (1) adjusting the nitriding temperature, (2) adjusting the ammonia concentration in the nitriding atmosphere, (3) adjusting the pressure and gas flow rate in the nitriding atmosphere, 4) Adjusting the nitriding time.

By nitriding under the conditions that limit the nitridation of the scandium (Sc) layer, scandium nitride is formed in a form that matches the crystal orientation of the growth substrate. Is sufficiently nitrided, but it is thought that metal scandium with insufficient nitridation remains at least near the interface between the growth substrate and the metal layer.
The coefficient of linear expansion of the metal Sc is 10.2 × 10 ⁻⁶ , which is about twice the expansion coefficient of the nitride semiconductor GaN, AlN or sapphire substrate, ScN. At the interface with the ScN or the interface with the III-nitride semiconductor layer, which is the underlying layer, stress is generated during the cooling process, and when taken out from the furnace, the III is easily peeled off by peeling or sliding from the growth substrate. A group nitride semiconductor layer is expected to be obtained.

  The thickness of the scandium nitride film 4 is preferably 3 to 100 nm. If the thickness is less than 3 nm, the scandium nitride film 4 is too thin, the thickness of the metal Sc layer becomes discontinuous by nitriding, and the surface of the crystal growth substrate, which is the base substrate, is exposed. In some cases, the group nitride semiconductor layer grows directly, making it difficult to peel off. 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 a scandium nitride film 4 by nitriding under a condition in which nitridation of the metal layer is limited. By adopting such a configuration, III formed above The crystal growth substrate 3 is peeled off from the group III nitride semiconductor layer by lowering the crystal growth substrate 3 to 50 ° C. or less from the growth temperature of the group III nitride semiconductor layer without significantly impairing the crystallinity of the group nitride semiconductor layer. Is made possible. It is important that the nitriding treatment be performed under conditions that limit nitriding. As a method for limiting the nitriding, (1) adjusting the nitriding temperature, (2) adjusting the ammonia concentration in the nitriding atmosphere, (3) adjusting the pressure and gas flow rate in the nitriding atmosphere, 4) Adjusting the nitriding time.

As the base substrate 6, sapphire, Si, SiC, GaN, or the like can be used. In particular, sapphire can be suitably used from the viewpoint of substrate procurement cost.
The metal layer made of Sc material can be formed by sputtering.
The nitriding treatment of the Sc material can be carried out by heating in ammonia gas or a mixed gas of ammonia gas and hydrogen gas and / or one or more inert gases. Here, examples of the inert gas include rare gases such as N ₂ , Ar, He, and Ne. 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 500 to 1300 ° C. When the temperature is lower than 500 ° C, the decomposition of ammonia is insufficient and nitriding may not be possible. When the temperature is higher than 1300 ° C, the equipment life may be shortened by increasing the temperature. However, in the case of 1000 ° C or higher, in order to limit nitriding, it is necessary to reduce the ammonia partial pressure in the nitriding atmosphere or shorten the nitriding time, and the maximum temperature of nitriding is 500 ° C or higher More preferably, the temperature is less than 1000 ° C. The heating is preferably performed at a temperature of 500 ° C. or higher in the range of 0.1 to 120 minutes. If it is less than 0.1 minutes, nitriding may not be sufficiently performed, and if it exceeds 120 minutes, there is no particular effect, which is disadvantageous in terms of productivity. The type of the inert gas is not particularly limited, and N ₂ , Ar, etc. can be used. The concentration of ammonia gas can be in the range of 0.01 to 100% by volume. If the amount is less than the lower limit, nitriding may not be sufficient. If the ammonia gas is too high, the surface roughness after nitriding may increase, and the ammonia gas concentration is more preferably 0.01 to 90% by volume. Further, the mixed gas may contain 20% by volume or less of hydrogen.

FIG. 5 shows the sheet resistance value when the nitriding temperature is changed after the sputter film is formed on the (0001) plane AlN template so that the Sc film thickness is 100 mm (10 nm) and 200 mm (20 nm). The measurement results are shown. The nitriding time was 10 minutes at each temperature. At this time, the flow rate ratio of ammonia gas: nitriding gas was 3: 7, and the pressure was 200 Torr. Regarding the color of the film, it is initially a metallic color (silver white), but from 500 ° C it is slightly grayish but has transparency, and from 1000 ° C it may be orange to yellow. I understood. As shown in FIG. 5, the sheet resistance value starts to become higher than the initial resistance value at 500 ° C., and the sheet resistance greatly increases up to 900 ° C., as shown in FIG. ^It becomes larger than ⁴ Ω / □, and more than 5 × 10 ⁵ Ω / □. When the nitriding temperature was further increased, the sheet resistance value again decreased from 1000 ° C., and gradually approached a predetermined value.

In the nitriding temperature range of 500 ° C. or higher and lower than 1000 ° C. in FIG. 5, the nitriding treatment can be performed under a condition that restricts nitriding, so that nitrogen-deficient ScN is formed and has insulating properties and visible light transmittance. The grayishness is thought to be due to the discrete and mixed metal Sc remaining in part. By epitaxially growing on the nitrided ScN under such nitridation-limited conditions, it is possible to lift off regardless of etching after the temperature is lowered from the growth temperature.
When the nitriding treatment is further performed at a higher temperature, the yellowish or orange color and the decrease in resistance value are interpreted as being completely converted to ScN (ScN is considered to be a conductive nitride). It was. In such a condition that becomes a complete ScN, it does not peel off naturally, and chemical lift-off by etching is required.
The above is a representative example. The state may change depending on other conditions such as Sc thickness, nitriding time, and atmosphere.

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 thick film layer 7 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 free-standing substrate manufacturing method of the present invention is at least one layer above the Group III nitride semiconductor growth substrate 1 manufactured by the method described above. The step of epitaxially growing the group III nitride semiconductor thick film layer 7 is provided.

  It is preferable that the group III nitride semiconductor thick film 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 thick film layer 7 formed thereafter, the growth temperature is preferably in the range of 900 to 1300 ° C.

  Although the initial growth layer 5 may be a single layer, it is preferable to use two or more layers from the viewpoint of improving the crystallinity of the Group III nitride semiconductor thick film 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.

  Further, the method for producing a group III nitride semiconductor free-standing substrate of the present invention comprises a step of epitaxially growing at least one group III nitride semiconductor layer above the group III nitride semiconductor growth substrate produced by the above-described method. Cooling the group III nitride semiconductor layer to a temperature not higher than 50 ° C. to separate the group III nitride semiconductor layer and the crystal growth substrate to obtain a group III nitride semiconductor free-standing substrate. By adopting such a configuration, the temperature limitation (wavelength limitation) in the case where the CrN material is used to remove the crystal growth substrate 3 by chemical lift-off exceeds the temperature limit (wavelength limitation) of the group III nitride semiconductor material in the entire composition range. A group III nitride semiconductor free-standing substrate with good crystallinity that covers the growth temperature zone 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.

Using the AlN template substrate obtained as described above, Sample 1-1 was produced under the conditions shown in Table 1. The procedure is described below.
Sc is deposited on an AlN template substrate by sputtering to a thickness of 20 nm, then placed in a MOCVD system, purged with nitrogen, and reduced in pressure to 200 Torr at a rate of 50 ° C / min. Started. FIG. 3A shows a nitriding / growth sequence in the temperature rise / growth. The horizontal axis represents elapsed time, and the vertical axis represents process temperature (substrate surface temperature). As shown in FIG. 3 (a), up to a temperature of 500 ° C., nitrogen gas was flowed at a flow rate of 3.5 SLM, and ammonia gas was started to flow from 500 ° C. in the middle of the temperature increase, thereby nitriding the Sc film. The flow rate ratio of nitrogen gas: ammonia gas at this time was set to the values shown in Table 1. The temperature was continuously raised, and when the temperature reached 900 ° C., the supply of ammonia gas was stopped, and the total flow rate was kept constant by replacing it with nitrogen gas at the same flow rate as the ammonia gas flow rate. The temperature was continuously raised to 1140 ° C, and after reaching 1140 ° C, the pressure was reduced from 200 Torr to 10 Torr, the atmosphere was changed from nitrogen gas to hydrogen gas, and the gas flow rate was changed to conditions suitable for AlN growth, then TMAl and ammonia Gas was supplied to start AlN epi growth. In order to obtain a thick film to obtain a free-standing substrate, the growth time was set to 24 hours. After completion of the growth, the temperature was lowered at a rate of 30 ° C./min, and the temperature was lowered to room temperature. Thus, Sample 1-1 was obtained.
When sample 1-1 was taken out from the MOCVD apparatus, peeling naturally occurred at the interface between the scandium nitride film and the AlN template used as the base substrate, and an AlN (0001) free-standing substrate having a thickness of about 50 μm was obtained. I was able to.

(Comparative Example 1)
A sample 1-2 was produced by the nitridation / growth sequence shown in FIG. 3B under the conditions shown in Table 1 using an AlN (0001) template substrate in the same manner as in Example 1. The procedure is described below.
Sc is deposited on an AlN template substrate by sputtering to a thickness of 10 nm, then placed in a MOCVD apparatus, purged with nitrogen, and reduced in pressure to 200 Torr at a rate of 50 ° C / min. Started. Nitrogen gas was flowed at a flow rate of 3.5 SLM up to a temperature of 500 ° C., and ammonia gas was started to flow from 500 ° C. during the temperature rising to nitrify the Sc film. At this time, the flow rate ratio of nitrogen gas: ammonia gas is the same as that of sample 1-1, but the temperature is raised to 1200 ° C. in a state where a mixed gas of ammonia and nitrogen is continuously flowed as shown in FIG. 3 (b). Further, nitriding was performed by holding at 1200 ° C. for 10 minutes. Then, the temperature is lowered to 1140 ° C in 2 minutes, the pressure is reduced from 200 Torr to 10 Torr, the atmosphere is changed from a mixed gas of nitrogen and ammonia to a mixed gas of hydrogen and ammonia, and the gas flow rate is changed to a condition suitable for the growth of AlN. Thereafter, TMAl was further supplied to start AlN epi growth. Similar to Sample 1-1, the growth time was 24 hours. After completion of the growth, the temperature was lowered at a rate of 30 ° C./min, and the temperature was lowered to room temperature. Thus, Sample 1-2 was obtained.
When sample 1-2 was taken out from the MOCVD apparatus, an integrated body in which a scandium nitride film and an AlN thick film were formed on an AlN template substrate was obtained, and a naturally exfoliated AlN self-supporting substrate could not be obtained. However, it was necessary to etch the scandium nitride film using hydrochloric acid or the like.

(Example 2)
An AlN single crystal layer having a surface orientation (0001) and a thickness of 1 μm was formed on a sapphire substrate having a 2 inch diameter by an MOCVD method (AlN template). Next, as shown in Table 2 (Sample 2-1), a 20 nm Sc metal film was formed on the surface of the AlN template by sputtering. The sample on which the Sc metal film was formed was set in an HVPE (hydride vapor phase epitaxy) apparatus. Nitridation / growth was performed according to the sequence shown in FIG. The sample on which the Sc metal film was formed was heated to 900 ° C. at a rate of 22 ° C./min in a nitrogen atmosphere (the flow rate was 300 sccm and continued to flow from the start to the end of cooling). When the substrate temperature reached 500 ° C., ammonia gas was started to flow at a flow rate of 1000 sccm, and held at 900 ° C. for 10 minutes to nitride the Sc and convert it to ScN. During this time, the temperature of the Ga source part is heated to 850 ° C. in parallel with the substrate heating. The Ga source part is purged with hydrogen gas at a flow rate of 100 sccm from the start of temperature rise to the end of cooling.
After maintaining at 900 ° C. for 10 minutes, HCl gas was started to flow into the Ga source at a flow rate of 80 sccm, and the generated GaCl was supplied to the substrate surface to start growth of the GaN initial growth layer. The growth time of the initial growth layer was 10 minutes. The supply of HCl gas was once stopped, and the temperature of the substrate was increased again at a rate of 22 ° C./minute up to 1040 ° C. in a mixed gas atmosphere of ammonia and nitrogen. After waiting for the temperature to stabilize, HCl gas was again flowed into the Ga source at a flow rate of 40 sccm, GaN growth was started, and a thick film was grown for 2 hours.
Thereafter, cooling was performed at a cooling rate of 30 ° C./min. When the substrate temperature decreased to 600 ° C., the supply of ammonia gas was stopped, and the sample was cooled to room temperature in a nitrogen atmosphere to obtain Sample 2-1.
The nitridation / growth sequence of Sample 2-1 is shown in FIG.
When the sample 2-1 was taken out of the HVPE furnace, the growth substrate and the GaN thick film layer were not separated only by tilting the sample 2-1, but the GaN thick film layer was slid with a slight force. It was possible to peel from the growth substrate with no cracks and the like. When the state of the peeled interface was observed, peeling was observed between the AlN template and ScN, and the ScN layer was attached to the GaN thick film side.
Since ScN dissolves in various acidic solutions, the GaN thick film side of Sample 2-1 was immersed in hydrochloric acid (36 wt%) for 5 minutes to completely remove the ScN layer and obtain a GaN free-standing substrate. As a result of measuring the thickness of the central portion of the GaN free-standing substrate, it was 157 μm.

(Comparative Example 2)
A 1 μm thick AlN single crystal layer with a plane orientation (0001) was fabricated by MOCVD on a 2-inch sapphire substrate (AlN template). Next, as shown in Table 2 (Sample 2-2), a 20 nm Sc metal film was formed on the surface of the AlN template by sputtering. A sample on which a Sc metal film was formed was prepared in the same manner as in Example 2 and set in an HVPE apparatus. Nitriding / growth was performed according to the sequence shown in FIG. 4B and the growth condition recipe shown in Table 2.
The temperature was raised to 1200 ° C. at a rate of 22 ° C./min in a nitrogen atmosphere (flow rate was 300 sccm and continued to flow from the start of temperature rise to the end of cooling). When the substrate temperature reached 500 ° C., ammonia gas was started to flow at a flow rate of 1000 sccm and held at 1200 ° C. for 10 minutes to nitride the Sc and convert it to ScN. During this time, the temperature of the Ga source part is heated to 850 ° C. in parallel with the substrate heating. The Ga source part is purged with hydrogen gas at a flow rate of 100 sccm from the start of temperature rise to the end of cooling.
Hold at 1200 ° C for 10 minutes, then cool down to 900 ° C, wait for the temperature to stabilize for about 5 minutes, start to flow HCl gas at a flow rate of 80 sccm to the Ga source, and supply the generated GaCl to the substrate surface By doing so, the growth of the GaN initial growth layer was started. The growth time of the initial growth layer was 10 minutes. The supply of HCl gas was once stopped, and the temperature of the substrate was increased again at a rate of 22 ° C./minute up to 1040 ° C. in a mixed gas atmosphere of ammonia and nitrogen. After waiting for the temperature to stabilize, HCl gas was again flowed into the Ga source at a flow rate of 40 sccm, GaN growth was started, and a thick film was grown for 2 hours.
Thereafter, cooling was performed at a cooling rate of 30 ° C./min. When the substrate temperature dropped to 600 ° C., the supply of ammonia gas was stopped, and the sample was cooled to room temperature in a nitrogen atmosphere to obtain Sample 2-2.
When the sample 2-2 was taken out from the HVPE apparatus, the GaN thick film was in full contact with the sample substrate and could not be peeled off. For peeling, it was necessary to etch the scandium nitride film using hydrochloric acid or the like.
In addition, when the thickness of the sample 2-2 was measured and the thickness of the GaN thick film part was calculated by subtracting the thickness of the sapphire substrate, it was 153 μm.

(Comparative Example 3)
A GaN thick film is grown under the same conditions as in Example 2 except that the metal species on the AlN template is Cr and the ammonia gas supply start temperature in the HVPE furnace is 600 ° C. 2-3 was obtained. The nitridation / growth conditions for Sample 2-3 are shown in Table 2, and the sequence is shown in FIG.
The GaN thick film of Sample 2-3 taken out from the HVPE apparatus after cooling was in close contact with the sample substrate and could not be peeled off regardless of etching.
This is consistent with a conventional report example (Japanese Patent Laid-Open No. 2008-110912).

(Comparative Example 4)
The same conditions as in Comparative Example 2 except that the metal species on the AlN template is Cr, the ammonia gas supply start temperature in the HVPE furnace is 600 ° C, and the maximum temperature of the nitriding treatment is 1080 ° C. Then, a thick GaN film was grown to obtain Sample 2-4. The nitriding / growth conditions for Sample 2-4 are shown in Table 2, and the sequence is shown in FIG.
The GaN thick film of Sample 2-4 taken out from the HVPE apparatus after cooling was in close contact with the sample substrate, and could not be peeled off regardless of etching.
This coincides with the above reported example that peeling is possible only by chemical lift-off using a dicerium ammonium nitrate etching solution.
As described above, the present invention can also be applied to the thick film growth of GaN by the HVPE method capable of growing the compound semiconductor layer at a high speed, and the self-standing substrate according to the present invention from Example 2 and Comparative Examples 2 to 4. It can be said that the manufacturing technique is an excellent technique in terms of cost.

  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.

A substrate for growing a group III nitride semiconductor of the present invention is a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al, and scandium nitride obtained by nitriding Sc (scandium) formed on the surface portion. Monomaku improve the crystallinity of the group III nitride upward is formed on the semiconductor layer _{Al x Ga y in 1-xy} N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) In addition, after the growth of the group III nitride semiconductor layer, the crystal growth substrate can be easily separated from the group III nitride semiconductor layer by setting the substrate temperature to 50 ° C. or less from the group III nitride semiconductor layer growth temperature. .

  Further, according to the present invention, by using the above-mentioned group III nitride semiconductor growth substrate, the growth temperature range of the group III nitride semiconductor material in the entire composition range is exceeded beyond the temperature limit when using the CrN material. A group III nitride semiconductor epitaxial substrate, a group III nitride semiconductor element, and a group III nitride semiconductor free-standing substrate that cover good crystallinity can be provided by a manufacturing method that does not require laser lift-off and chemical lift-off.

Furthermore, according to the present invention, by forming a scandium nitride film obtained by nitriding Sc (scandium) formed on a crystal growth substrate made of a group III nitride semiconductor including at least a surface portion of Al, a subsequent formation is performed. to improve 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) which is, and, a group III nitride After the growth of the crystal growth substrate from the nitride semiconductor layer to the group III nitride semiconductor layer, the growth of the group III nitride semiconductor can be easily separated by setting the substrate temperature to 50 ° C. or less from the growth temperature of the group III nitride semiconductor layer. Substrates can be manufactured.

  In addition, the present invention covers the growth temperature zone of the group III nitride semiconductor material in the entire composition range, exceeding the temperature limit when using the CrN material, using the group III nitride semiconductor growth substrate. Thus, it is possible to efficiently produce a group III nitride semiconductor epitaxial substrate, a group III nitride semiconductor element, and a group III nitride semiconductor free-standing substrate having good crystallinity.

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 thick film layer

Claims (21)

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
And a step of forming a scandium nitride film by heating the metal layer in an atmosphere gas containing ammonia gas and subjecting the metal layer to nitridation under a condition in which nitridation is limited. For manufacturing a substrate for growth of semiconductors. 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
A step of heating the metal layer in an atmospheric gas containing ammonia gas and performing a nitriding treatment to form a scandium nitride film, the maximum temperature of the nitriding treatment being 500 ° C. or more and 1000 ° C. A method for producing a substrate for growing a group III nitride semiconductor, characterized in that the range is less than the range.   3. The method for producing a group III nitride semiconductor growth substrate according to claim 1, wherein the atmospheric gas containing the ammonia gas is a mixed gas further containing at least one selected from an inert gas and a hydrogen gas.   The method for producing a group III nitride semiconductor growth substrate according to claim 1, 2 or 3, wherein the metal layer is heated at a temperature of 500 ° C or higher for 0.1 to 120 minutes. After the nitriding step, the method further includes forming an initial growth layer made of at least one buffer layer made of Al _x Ga _1-x N (0 ≦ x ≦ 1) on the scandium nitride film. The manufacturing method of the board | substrate for group III nitride semiconductor growth as described in any one of Claims 1-4. 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
Forming a scandium nitride film by heating the metal layer in an atmosphere containing ammonia gas and subjecting the metal layer to nitridation to form a scandium nitride film, and producing a group III nitride semiconductor growth substrate; ,
At least one group III nitride semiconductor layer is epitaxially grown above the group III nitride semiconductor growth substrate to produce a group III nitride semiconductor epitaxial substrate, and the group III nitride semiconductor epitaxial substrate is heated to 50 ° C. or less. Separating the group III nitride semiconductor layer and the crystal growth substrate as a temperature;
And a step of separating the at least one group III nitride semiconductor layer to obtain 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
A III-nitride semiconductor is formed by heating the metal layer in an atmosphere containing ammonia gas and performing a nitriding treatment under conditions where the maximum temperature is 500 ° C. or higher and lower than 1000 ° C. Producing a growth substrate;
At least one group III nitride semiconductor layer is epitaxially grown above the group III nitride semiconductor growth substrate to produce a group III nitride semiconductor epitaxial substrate, and the group III nitride semiconductor epitaxial substrate is heated to 50 ° C. or less. Separating the group III nitride semiconductor layer and the crystal growth substrate as a temperature;
And a step of separating the at least one group III nitride semiconductor layer to obtain a group III nitride semiconductor device. After the nitriding treatment, the method further includes forming an initial growth layer made of at least one buffer layer made of Al _x Ga _1-x N (0 ≦ x ≦ 1) on the scandium nitride film. A method for producing a group III nitride semiconductor device according to claim 6 or 7.   The initial growth layer includes a first buffer layer and a second buffer layer grown on the first buffer layer, and the growth temperature of the first buffer layer is in a range of 900 to 1260 ° C. The method of manufacturing a group III nitride semiconductor device according to claim 8, wherein the growth temperature of the first buffer layer is in the range of 1030 to 1300 ° C., and the growth temperature of the first buffer layer is equal to or lower than the growth temperature of the second buffer layer. 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
Forming a scandium nitride film by heating the metal layer in an atmosphere containing ammonia gas and subjecting the metal layer to nitridation to form a scandium nitride film, and producing a group III nitride semiconductor growth substrate; ,
At least one group III nitride semiconductor layer is epitaxially grown above the group III nitride semiconductor growth substrate to obtain a group III nitride semiconductor epitaxial substrate, and the group III nitride semiconductor epitaxial substrate is set to a temperature of 50 ° C. or lower. And a step of separating the group III nitride semiconductor layer from the crystal growth substrate. A method for manufacturing a group III nitride semiconductor free-standing substrate, comprising: 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
A III-nitride semiconductor is formed by heating the metal layer in an atmosphere containing ammonia gas and performing a nitriding treatment under conditions where the maximum temperature is 500 ° C. or higher and lower than 1000 ° C. Producing a growth substrate;
At least one group III nitride semiconductor layer is epitaxially grown above the group III nitride semiconductor growth substrate to obtain a group III nitride semiconductor epitaxial substrate, and the group III nitride semiconductor epitaxial substrate is set to a temperature of 50 ° C. or lower. And a step of separating the group III nitride semiconductor layer and the crystal growth substrate. A method for producing a group III nitride semiconductor free-standing substrate, 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, the scandium nitride film being a group III nitride semiconductor growth substrate having a sheet resistance greater than 1 × 10 ⁴ Ω / □.   The group III nitride semiconductor growth substrate according to claim 12, wherein the scandium nitride film partially contains metal scandium. The group III nitride according to claim 12 or 13, further comprising an initial growth layer formed of at least one buffer layer formed of Al _x Ga _1-x N (0 ≦ x ≦ 1) on the scandium nitride film. Semiconductor growth substrate.   The group III nitride semiconductor growth substrate according to claim 12, 13 or 14, wherein the scandium nitride film has a thickness of 3 to 100 nm.   16. The group III nitride semiconductor growth substrate according to claim 12, 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 any one of claims 12 to 16, wherein the at least surface portion is made of AlN.   A group III nitride semiconductor free-standing substrate produced using the group III nitride semiconductor growth substrate according to any one of claims 12 to 17.   A group III nitride semiconductor device manufactured using the group III nitride semiconductor growth substrate according to any one of claims 12 to 17. Forming a metal layer made of Sc material on the crystal growth substrate;
Nitriding the metal layer to form a scandium nitride film;
A group III nitride semiconductor layer from a crystal growth substrate comprising the step of epitaxially growing at least one group III nitride semiconductor layer on the scandium nitride film and then lowering the temperature to 50 ° C. or lower. Peeling method.   21. The method for peeling a group III nitride semiconductor layer according to claim 20, wherein the group III nitride semiconductor layer is slid from the crystal growth substrate after the temperature lowering step.

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