JP2010235347A - Method for producing group iii nitride semiconductor free-standing substrate and substrate for growing group iii nitride semiconductor layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a group III nitride semiconductor free-standing substrate by a simple process and at a low cost and a substrate for growing a group III nitride semiconductor layer. <P>SOLUTION: In the method for producing the group III nitride semiconductor free-standing substrate 14, a first group III nitride semiconductor layer 12 containing In is epitaxially grown on a substrate 10 at a first growing temperature, a second group III nitride semiconductor layer 13 is epitaxially grown on the grown first group III nitride semiconductor layer 12 at a second growing temperature higher than the first growing temperature and then the free-standing substrate 14 consisting of a second group III nitride semiconductor is produced by exfoliating the grown second group III nitride semiconductor layer 13 from the substrate. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

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

  Nitride semiconductor materials have a sufficiently large forbidden band width and a direct transition type between band transitions. Therefore, application to a short wavelength light emitting element has been actively studied. In addition, application to electronic devices is also expected due to the high saturation drift velocity of electrons and the use of a two-dimensional carrier gas by heterojunction.

  Nitride semiconductor layers constituting these elements are formed by metal-organic vapor phase epitaxy (MOVPE), molecular beam vapor phase epitaxy (MBE), hydride vapor phase epitaxy (HVPE). : Hydride Vapor Phase Epitaxy) or other vapor phase growth method is used to perform epitaxial growth on the base substrate. However, since there is no underlying substrate having a lattice constant matching with this nitride semiconductor layer, it is difficult to obtain a high-quality growth layer, and the obtained nitride semiconductor layer contains many crystal defects. . Since this crystal defect becomes a factor that hinders improvement in device characteristics, so far, studies have been actively conducted to reduce the crystal defect in the nitride semiconductor layer.

  As a method for obtaining a group III element nitride-based crystal with relatively few crystal defects, a method of forming a low temperature deposition buffer layer (buffer layer) on a dissimilar substrate such as sapphire and forming an epitaxial growth layer thereon is known. It has been. In the crystal growth method using this low-temperature deposition buffer layer, first, AlN or GaN is deposited on a substrate such as sapphire at around 500 ° C. to form an amorphous film or a continuous film partially including polycrystal. This is heated to around 1000 ° C. to partially evaporate and crystallize to form high-density crystal nuclei. Using this as a growth nucleus, a GaN film with relatively good crystallinity can be obtained. However, even if a method for forming a low temperature deposition buffer layer is used, there are considerable crystal defects such as threading dislocations and hole pipes, and it is not sufficient to obtain a high-performance device that is currently desired. It was.

  Therefore, a method for forming a semiconductor multilayer film constituting an element portion on a group III nitride semiconductor substrate such as GaN as a substrate for crystal growth has been actively studied. Hereinafter, such a substrate for crystal growth is referred to as a free-standing substrate. For example, as a technique for obtaining a GaN free-standing substrate, ELO (Epitaxial Lateral Overgrowth) technology is known. ELO is a technique for obtaining a GaN layer with few dislocations by forming a mask having a stripe-shaped opening on a base substrate and laterally growing from the opening. In Patent Document 1, it is proposed that a GaN layer is formed on a sapphire substrate using this ELO technique, and then the sapphire substrate is removed by etching or the like to obtain a GaN free-standing substrate.

  On the other hand, FIELO (Face-Initiated Lateral Overgrowth) technology (see Non-Patent Document 1) has been developed as a technique that further develops the technique of ELO. This technique is common to ELO in that selective growth is performed using a silicon oxide mask, but differs in that facets are formed in the mask opening. By forming facets, the propagation direction of dislocations is changed, and threading dislocations reaching the upper part of the epitaxial growth layer are reduced. By using this method, a high-quality GaN free-standing substrate with relatively few crystal defects can be obtained by growing a thick GaN layer on a base substrate such as sapphire and then removing the base substrate.

  As another technique, Patent Document 2 discloses a technique for obtaining a GaN free-standing substrate using a gap. In this method, after forming a GaN layer on a sapphire C-plane ((0001) plane) substrate, a titanium film is formed thereon. Next, the substrate is heat-treated in an atmosphere containing hydrogen gas or a hydrogen-containing compound gas to form voids in the GaN layer. Thereafter, by forming a new thick GaN layer on the GaN layer, a high-quality GaN free-standing substrate with less warpage can be obtained.

JP-A-11-251253 JP 2003-178984 A

A. Usui et al. , Jpn. J. et al. Appl. Phys. Vol. 36 (1997) p. L. 899-L. 902

  With the prior art as described above, a relatively high-quality group III nitride semiconductor free-standing substrate such as GaN can be obtained, but dissimilar substrates such as sapphire can be removed, peeled off, metal films, pattern formation, etc. Therefore, there is a problem in that the manufacturing process becomes high. Therefore, at present, for example, a GaN free-standing substrate is used for a GaN-based semiconductor laser diode or the like, and a group III nitride semiconductor free-standing substrate is used only for a device with a particularly high added value.

  The present invention has been made in view of the above problems, and a manufacturing method and a group III nitride semiconductor layer growth substrate capable of manufacturing a group III nitride semiconductor self-supporting substrate at a low cost by a simple process are provided. The purpose is to provide.

  In order to achieve the above object, at least a first group III nitride semiconductor layer containing In is epitaxially grown at a first growth temperature on a base material, and then the grown first III is formed. A second group III nitride semiconductor layer is epitaxially grown on the group nitride semiconductor layer at a second growth temperature higher than the first growth temperature, and the grown second group III nitride semiconductor layer is formed. A method of manufacturing a group III nitride semiconductor free-standing substrate is provided, wherein a free-standing substrate made of a second group III nitride semiconductor is manufactured by peeling from the base material.

As described above, a first group III nitride semiconductor layer containing In is grown, and a second nitride semiconductor layer is grown on the first group III nitride semiconductor layer at a higher temperature, thereby growing a high-quality second nitride semiconductor layer. The first group III nitride semiconductor layer functions as a good release layer when the temperature drops after growth, and the second semiconductor layer can be easily peeled off, so that a free-standing substrate can be obtained efficiently. it can. In addition, since the second group III nitride semiconductor layer can be grown with good crystallinity because it is grown on the epitaxially grown single crystal first group III nitride semiconductor layer, the epitaxial growth method is limited. Therefore, a thick second group III nitride semiconductor layer that can be a free-standing substrate can be efficiently grown.
As described above, according to the manufacturing method of the present invention, it is not necessary to form a metal film or a mask pattern as the peeling layer, and only the group III nitride semiconductor layer containing In is grown. A group III nitride semiconductor free-standing substrate can be manufactured at low cost.

At this time, the first group III nitride semiconductor layer containing In is preferably a layer of In _x Ga _1-x N (x> 0).
If it is a layer of In _x Ga _1-x N (x> 0), it can be grown relatively easily on the base material, and is suitable for producing a GaN free-standing substrate according to the present invention.

At this time, it is preferable that the first group III nitride semiconductor layer containing In is grown by MOVPE and the second group III nitride semiconductor layer is grown by HVPE.
Thus, with the MOVPE method, the first group III nitride semiconductor layer containing good In can be grown at a relatively low temperature on substrates having different thermal expansion coefficients. The thick second group III nitride semiconductor layer can be grown efficiently.

At this time, it is preferable that after the buffer layer is grown on the base material, the first group III nitride semiconductor layer containing In is epitaxially grown on the grown buffer layer.
In this way, by growing the buffer layer, distortion due to thermal expansion of the base material is not easily transmitted to the first nitride semiconductor layer even at high temperatures, and the second nitride semiconductor layer grown thereon is also better. Of good quality.

The second group III nitride semiconductor layer is preferably a GaN layer.
The present invention is preferable because it is difficult to manufacture, and a high-value-added, high-quality GaN free-standing substrate can be manufactured at low cost.

At this time, after the first group III nitride semiconductor layer containing In is grown, a GaN layer is grown on the grown first group III nitride semiconductor layer containing In by the MOVPE method. Preferably, a GaN layer is grown as the second group III nitride semiconductor layer on the grown GaN layer by HVPE.
Thus, by growing a GaN layer with good crystallinity by the MOVPE method on the first group III nitride semiconductor layer containing In, and then growing a thick GaN layer by the HVPE method, the crystallinity can be further increased. A GaN free-standing substrate with good quality can be efficiently manufactured.

Also provided is a group III nitride semiconductor free-standing substrate manufactured by the method for manufacturing a group III nitride semiconductor free-standing substrate of the present invention.
As described above, the group III nitride semiconductor free-standing substrate manufactured by the manufacturing method of the present invention is inexpensive and high-quality free-standing substrate.

Further, the present invention is a substrate for epitaxially growing a group III nitride semiconductor layer, and at least a group III nitride containing In on the surface of the base material on the side on which the group III nitride semiconductor layer is epitaxially grown Provided is a substrate for growing a group III nitride semiconductor layer, characterized by having a semiconductor single crystal layer.
With such a group III nitride semiconductor layer growth substrate, a high-quality group III nitride semiconductor layer can be grown on a single crystal layer of a group III nitride semiconductor containing In, and subsequent peeling is also possible. Since it is easy, a high-quality group III nitride semiconductor free-standing substrate can be easily manufactured.

At this time, it is preferable to have a GaN layer grown by the MOVPE method on the single crystal layer of the group III nitride semiconductor containing In.
If the MOVPE method has a GaN layer grown at a relatively low temperature to the extent that peeling does not occur, a higher quality GaN layer is grown thickly and efficiently on the GaN layer. Therefore, a higher-quality group III nitride semiconductor free-standing substrate can be manufactured.

  As described above, according to the manufacturing method or the group III nitride semiconductor layer growth substrate of the present invention, a high-quality group III nitride semiconductor free-standing substrate can be manufactured at a low cost by a simple process.

It is a flowchart which shows an example of the embodiment of the manufacturing method of the group III nitride semiconductor self-supporting substrate of this invention. It is the schematic which shows an example of the board | substrate for group III nitride semiconductor layer growth of this invention. It is the schematic which shows another example of the board | substrate for group III nitride semiconductor layer growth of this invention.

  The gist of the present invention is to use a group III nitride semiconductor layer containing thermally weak In as a release layer. Since one type of nitride semiconductor can be used as the release layer, it is possible to incorporate the release layer in a partly simpler process compared to the prior art and perform the release.

Hereinafter, an example of the embodiment of the method for manufacturing a group III nitride semiconductor free-standing substrate and the substrate for growing a group III nitride semiconductor layer according to the present invention will be described in detail with reference to the drawings. Is not to be done.
FIG. 1 is a flowchart showing an example of a method for producing a group III nitride semiconductor free-standing substrate of the present invention. 2 and 3 are schematic views showing an example of a group III nitride semiconductor layer growth substrate of the present invention.

As shown in FIG. 2, the substrate for growing a group III nitride semiconductor layer 15 of the present invention is a single group III nitride semiconductor containing In on the surface of the base material 10 on the side on which the group III nitride semiconductor layer is epitaxially grown. A crystal layer 12 is provided.
With such a group III nitride semiconductor layer growth substrate, a high-quality group III nitride semiconductor layer can be grown on the single crystal layer of group III nitride semiconductor containing In, and the temperature drop after the growth Thus, the group III nitride semiconductor single crystal layer 12 containing In functions as a release layer, and thus a group III nitride semiconductor free-standing substrate can be easily manufactured. In addition, since the outermost layer is a single crystal, the group III nitride semiconductor layer can be epitaxially grown with good crystallinity on it, and the type and growth method of the group III nitride semiconductor to be grown are not limited. Further, as shown in FIG. 2, a buffer layer 11 may be formed on a base material 10, and a single crystal layer 12 of a group III nitride semiconductor containing In is provided thereon, so that a single crystal of higher quality can be obtained. Since the layer is formed, defects in the group III nitride semiconductor layer to be grown can be further reduced, which is preferable.

Further, as shown in FIG. 3, the substrate 15 for group III nitride semiconductor layer growth has a GaN layer 16 grown by the MOVPE method on the single crystal layer 12 of group III nitride semiconductor containing In. Is preferred.
If the MOVPE method has a thin GaN layer grown at a relatively low temperature to the extent that peeling does not occur, a higher quality GaN layer is thickly and efficiently grown on the GaN layer. Therefore, a higher-quality group III nitride semiconductor free-standing substrate can be manufactured. The thickness of the GaN layer grown by this MOVPE method is not particularly limited, but if it is 1 μm or less, it is preferable because the cost is not high and peeling does not easily occur.

In the method for manufacturing a group III nitride semiconductor free-standing substrate of the present invention, a substrate to be a base material 10 is first prepared as shown in FIG.
It does not specifically limit as a board | substrate to prepare, For example, a sapphire board | substrate can be prepared.

Next, as shown in FIG.1 (b), it is preferable to grow the buffer layer 11 on the prepared base material 10. FIG. The buffer layer 11 is not particularly limited, and two or more layers may be grown. For example, GaN, AlN, or the like can be grown by the MOVPE method or the like.
In this way, by growing the buffer layer, the strain due to the thermal expansion of the base material is not easily transmitted to the first nitride semiconductor layer even at high temperatures, and a high-quality layer is formed and grown on the second layer. A better nitride semiconductor layer with reduced defects is formed.

Next, as shown in FIG. 1C, the first group III nitride semiconductor layer 12 containing In is epitaxially grown on the buffer layer 11 of the base material 10 at the first growth temperature. The substrate for growing a group III nitride semiconductor layer 15 is prepared.
The first group III nitride semiconductor layer grown at this time is not particularly limited as long as it contains In. For example, an In _x Ga _1-x N (x> 0) layer is epitaxially grown by the MOVPE method. Is preferred. If it is a layer of In _x Ga _1-x N (x> 0), it can be grown on the substrate relatively easily.
In addition, as the In concentration in the first group III nitride semiconductor layer 12, a higher In concentration is preferable because more excellent peeling occurs.

  At this time, if the MOVPE method is used as a method for growing the first group III nitride semiconductor layer 12 containing In, the first In containing good In at a relatively low temperature on a substrate having a different thermal expansion coefficient. This is preferable because a group III nitride semiconductor layer can be grown. Also, the first growth temperature is not particularly limited and can be set to, for example, 600 ° C. to 800 ° C. The lower the temperature, the better the group III nitride semiconductor layer is formed on the substrate.

Next, as shown in FIG. 1D, the second group III nitride semiconductor layer 13 is formed on the grown first group III nitride semiconductor layer 12 containing In at a temperature higher than the first growth temperature. The epitaxial growth is performed at the second growth temperature.
Since In contained in the first group III nitride semiconductor layer is vulnerable to heat, the second group III nitride semiconductor layer functions as a good buffer layer when grown at a high temperature, and is a single crystal. Since it can be grown on one group III nitride semiconductor layer, a group III nitride semiconductor layer with reduced defects can be grown.

At this time, the second group III nitride semiconductor layer 13 is not particularly limited and may be a layer of AlGaN or AlN, but is preferably a GaN layer.
The present invention is preferable because it is difficult to manufacture, and a high-value-added, high-quality GaN free-standing substrate can be manufactured at low cost.

At this time, the method for growing the second group III nitride semiconductor layer is not particularly limited, but it is preferably grown by the HVPE method.
If the HVPE method is used, a thick group III nitride semiconductor layer can be efficiently grown.

Also, a GaN layer 16 is grown on the grown first group III nitride semiconductor layer 12 containing In by the MOVPE method, and a group 15 nitride semiconductor layer growth substrate 15 as shown in FIG. 3 is produced. Preferably, a GaN layer is grown on the GaN layer 16 as the second group III nitride semiconductor layer 13 by the HVPE method.
In this way, a GaN layer is grown on the first group III nitride semiconductor layer containing In by MOVPE method at a relatively low temperature with good crystallinity, and a thick GaN layer is grown thereon by HVPE method. Thus, since a thick layer of GaN can be grown on a layer having the same composition, it can be grown with better crystallinity. The thickness of the GaN layer 16 grown by the MOVPE method at this time is not particularly limited, and if it is 1 μm or less, it is preferable because it can be grown without causing high cost and without causing peeling.
In addition, as a thin layer grown by this MOVPE method, other than GaN can be grown and is not particularly limited, but a layer having the same composition as the layer grown as the second group III nitride semiconductor layer can be grown. preferable.

Next, as shown in FIG. 1E, the grown second group III nitride semiconductor layer 13 is peeled off from the base material 10, whereby the freestanding substrate 14 made of the second group III nitride semiconductor is formed. To manufacture. At this time, even when the temperature is lowered after the second group III nitride semiconductor layer 13 is grown, it can be peeled off naturally, or even if it is not naturally peeled off when the temperature is lowered, it can be easily peeled even after the temperature is lowered.
As described above, since the first group III nitride semiconductor layer containing In functions as a release layer, a complicated process such as formation of a metal film or pattern formation as in the related art is not necessary, and a single process as described above is performed. Since the second group III nitride semiconductor layer grown with good crystallinity on the crystal can be naturally peeled, a high-quality group III nitride semiconductor free-standing substrate can be efficiently obtained by a simple method.

  The group III nitride semiconductor free-standing substrate 14 manufactured by the manufacturing method of the present invention as described above is a group III nitride semiconductor free-standing substrate that is inexpensive and has good crystallinity.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
First, a GaN first buffer layer is grown on a sapphire substrate at a low temperature of about 500 to 600 ° C. on a sapphire substrate by MOVPE using TMGa, TMIn, and NH ₃ as raw materials, and then the growth temperature is increased to 1000 to 1100 ° C. A second buffer layer was grown.
Thereafter, the growth temperature was lowered to about 600 to 800 ° C., and an InGaN / GaN multiple quantum well structure was grown as the first group III nitride semiconductor layer. After the MOVPE wafer was cleaned, a thick GaN film was grown at 1000 ° C. as a second group III nitride semiconductor layer by charging into the HVPE apparatus. In the HVPE apparatus, it is possible to grow a GaN layer at a high speed of, for example, about 100 (μm / h) using GaCl and NH ₃ which are halides of group III elements as raw materials. In this example, a thick GaN layer of about 800 μm was grown at such a growth rate, and when the wafer was taken out of the HVPE apparatus, the sapphire substrate and the thick GaN layer were easily peeled off, and a GaN free-standing substrate was formed. Obtained.
As a result of intensive studies by the inventors, it was found that the higher the In concentration in the InGaN layer grown by the MOVPE method, the better the peeling.

(Comparative example)
As in the example, except that an InGaN / GaN multiple quantum well structure was not grown, a thick GaN layer was grown on the GaN buffer layer not containing In by an HVPE apparatus.
In this case, when the film thickness of about 100 μm was grown, a crack occurred and the wafer was broken.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

10 ... base material, 11 ... buffer layer,
12... First Group III nitride semiconductor layer containing In,
13 ... Second group III nitride semiconductor layer, 14 ... Free-standing substrate,
15 ... Group III nitride semiconductor layer growth substrate,
16: GaN layer.

Claims (9)

  At least a first group III nitride semiconductor layer containing In on the substrate is epitaxially grown at the first growth temperature, and then the second group III nitride semiconductor layer is grown on the grown first group III nitride semiconductor layer. The group III nitride semiconductor layer is epitaxially grown at a second growth temperature higher than the first growth temperature, and the grown second group III nitride semiconductor layer is peeled off from the base material to form a second III A method of manufacturing a group III nitride semiconductor free-standing substrate, comprising manufacturing a free-standing substrate made of a group nitride semiconductor. 2. The group III nitride semiconductor free-standing substrate according to claim 1, wherein the first group III nitride semiconductor layer containing In is a layer of In _x Ga _1-x N (x> 0). Production method.   The first group III nitride semiconductor layer containing In is grown by a MOVPE method, and the second group III nitride semiconductor layer is grown by an HVPE method. The manufacturing method of the group III nitride semiconductor free-standing substrate of description.   The first group III nitride semiconductor layer containing In is epitaxially grown on the grown buffer layer after the buffer layer is grown on the substrate. The manufacturing method of the group III nitride semiconductor free-standing substrate as described in any one of Claims.   The method for producing a group III nitride semiconductor free-standing substrate according to any one of claims 1 to 4, wherein the second group III nitride semiconductor layer is a GaN layer.   After the first group III nitride semiconductor layer containing In is grown, a GaN layer is grown on the grown first group III nitride semiconductor layer containing In by the MOVPE method. 6. The group III nitriding according to claim 1, wherein a GaN layer is grown as the second group III nitride semiconductor layer on the GaN layer formed by HVPE. Method for manufacturing a semiconductor substrate.   A group III nitride semiconductor self-supporting substrate manufactured by the method for manufacturing a group III nitride semiconductor self-supporting substrate according to any one of claims 1 to 6.   A substrate for epitaxially growing a group III nitride semiconductor layer, wherein a single crystal layer of a group III nitride semiconductor containing In is formed on at least a surface of a substrate on a side on which the group III nitride semiconductor layer is epitaxially grown A substrate for growing a group III nitride semiconductor layer, comprising:   9. The substrate for growing a group III nitride semiconductor layer according to claim 8, comprising a GaN layer grown by a MOVPE method on the single crystal layer of the group III nitride semiconductor containing In. .

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