JP2006270125A - Nitride based semiconductor device and process for forming nitride based semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for forming a nitride based semiconductor capable of forming a nitride based semiconductor layer of good crystallinity with little dislocation and little crystal defect caused by detachment on the upper surface of a substrate with small number of growth steps. <P>SOLUTION: The process for forming a nitride based semiconductor comprises a step for forming a mask layer 2 of SiN on the upper surface of a sapphire substrate 1 such that a part of the upper surface of the sapphire substrate 1 is exposed, a step for forming an AlGaN buffer layer 3 on the exposed upper surface of the sapphire substrate 1 and the upper surface of the mask layer 2, and a step for growing a GaN layer 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nitride-based semiconductor device and a method for forming a nitride-based semiconductor, and more specifically, GaN (gallium nitride), AlN (aluminum nitride), InN (indium nitride), BN (boron nitride), or TlN. (Thallium nitride) or III-V group nitride semiconductors (hereinafter referred to as nitride semiconductors) such as mixed crystals thereof, and at least one element of As, P and Sb in these mixed crystals The present invention relates to a nitride semiconductor device having a compound semiconductor layer made of a III-V nitride semiconductor such as a mixed crystal and a method for forming the nitride semiconductor.

  In recent years, semiconductor devices using GaN-based compound semiconductors have been actively developed as semiconductor devices used for semiconductor light emitting devices such as light emitting diode devices and electronic devices such as transistors. When manufacturing such a GaN-based semiconductor element, since it is difficult to manufacture a substrate made of GaN, a GaN-based semiconductor layer is epitaxially grown on a substrate made of sapphire, SiC, Si, GaAs, or the like.

In this case, since the lattice constant is different between a substrate such as sapphire and GaN, threading dislocations (lattice defects) extending in the vertical direction from the substrate exist in the GaN-based semiconductor layer grown on the substrate such as sapphire. . The dislocation density of this lattice defect is about 10 ⁹ cm ⁻² . Such dislocations in the GaN-based semiconductor layer cause deterioration of device characteristics and reliability of the semiconductor device.

  Thus, as a method for reducing dislocations in the GaN-based semiconductor layer as described above, selective lateral growth (ELO) has been conventionally proposed (see, for example, Non-Patent Document 1).

  10 to 12 are cross-sectional views for explaining a conventional method for forming a nitride-based semiconductor using selective lateral growth. Next, a conventional method for forming a nitride-based semiconductor using selective lateral growth will be described with reference to FIGS.

First, as shown in FIG. 10, an AlGaN buffer layer 102 having a film thickness of several tens of nm is formed on the C (0001) plane of the sapphire substrate 101, and then a 3 to 4 μm film is formed on the AlGaN buffer layer 102. A first GaN layer 103 made of GaN having a thickness is formed. Further, a striped (elongated) mask layer 104 made of SiO ₂ is formed on the first GaN layer 103 as a selective growth mask.

  Next, the second GaN layer 105 made of GaN having a thickness of 10 μm or more is grown by performing regrowth using the mask layer 104 as a selective growth mask. Here, since it is difficult for GaN to grow on the mask layer 104, the second GaN layer 105 at the initial growth stage selectively grows on the upper surface of the first GaN layer 103 exposed between the adjacent mask layers 104. . In this case, on the exposed upper surface of the first GaN layer 103, the second GaN layer 105 grows in the direction of arrow Y (c-axis direction) in FIG. As a result, a second GaN layer 105 having a facet structure with a triangular cross section as shown in FIG. 11 is grown on the exposed upper surface of the first GaN layer 103.

  Further, as the growth of the second GaN layer 105 on the upper surface of the first GaN layer 103 proceeds, the second GaN layer 105 also grows in the direction of arrow X (lateral direction) shown in FIG. The second GaN layer 105 is also formed on the mask layer 104 by the lateral growth of the second GaN layer 105.

  Furthermore, when the second GaN layer 105 is grown in the lateral direction, as shown in FIG. 12, the second GaN layers 105 having the facet structure are combined to form a continuous film. Thereby, the second GaN layer 105 having a flat upper surface is formed. In the vicinity of the surface of the planarized second GaN layer 105 formed in this way, threading dislocations are reduced.

  As described above, in the conventional method for forming a nitride-based semiconductor, threading dislocations in the second GaN layer 105 can be reduced by performing selective lateral growth of the second GaN layer 105. By forming a nitride-based semiconductor layer (not shown) on the second GaN layer 105 in which such dislocations are reduced, a nitride-based semiconductor layer having good crystallinity is formed on the sapphire substrate 101. Can do.

  However, in the conventional method for forming a nitride-based semiconductor using selective lateral growth, the first GaN layer 103 is formed on the sapphire substrate 101, the mask layer 104 is formed, and then the second GaN layer 105 is formed. Forming. Therefore, in order to obtain a nitride-based semiconductor layer having good crystallinity, it is necessary to grow the GaN layer twice, that is, the first GaN layer 103 and the second GaN layer 105. As a result, the conventional method using selective lateral growth has a disadvantage that the manufacturing process becomes complicated.

  In the conventional method using selective lateral growth, the surface of the first GaN layer 103 may be contaminated in the step of forming the mask layer 104. In this case, since the second GaN layer 105 is formed on the contaminated surface, the second GaN layer 105 is not formed well.

  Furthermore, since the above-described conventional method using selective lateral growth requires two GaN layers, the first GaN layer 103 and the second GaN layer 105, the total film of each layer formed on the sapphire substrate 101 is required. The thickness is increased, and as a result, the warpage of the wafer is increased.

Therefore, conventionally, in order to solve the above inconvenience, a method of forming a GaN layer in which dislocations are reduced by one growth is proposed in a method using selective lateral growth (for example, Patent Document 1, 2). In this conventional proposed method, after forming a SiO ₂ mask on a sapphire substrate, a low-temperature growth GaN buffer layer and a high-temperature growth GaN layer are formed thereon, thereby reducing dislocation in one growth. Form a layer.

According to this conventional proposed method, it is not necessary to form a GaN layer before forming the mask, so that the GaN layer under the mask is contaminated, and the total film thickness of each layer on the substrate. It is possible to solve the inconvenience that the warpage of the wafer increases due to the increase in the thickness. In addition, since the GaN layer is formed by one growth, it is possible to form a nitride-based semiconductor layer with few dislocations with a small number of growth steps. For this reason, the manufacturing process is not complicated.
Journal of Applied Electronic Properties, Vol. 4 (1998), pp. 53-58 and pp. 210-215 JP 2000-21789 A Japanese Patent Laid-Open No. 10-312971

However, in the conventional proposed methods described above, the low temperature growth GaN buffer layer is formed only within the opening of the SiO ₂ mask, not formed on the upper surface of the SiO ₂ mask. For this reason, when the high temperature growth GaN layer is grown in the lateral direction, the growth outermost surface of the high temperature growth GaN layer and the upper surface of the mask come into contact with each other. Withdrawal increases. Thus, when the separation becomes large, a new crystal defect is generated, and as a result, there is a problem that the number of defects in the GaN layer increases.

In the conventional proposed method described above, since the mask is made of SiO ₂ , oxygen atoms in SiO ₂ appear on the upper surface of the grown GaN layer. For this reason, when a nitride-based light emitting device is formed using the GaN layer as a base layer, there is a problem that the light emitting device does not emit light well.

In FIG. 4 of Patent Document 2 described above, as in Patent Document 1 described above, after forming a SiO ₂ mask directly on the substrate, a GaN layer with reduced dislocation is formed by one selective lateral growth. The technology to do is described. However, even in the technique disclosed in Patent Document 2, as in the case of Patent Document 1 described above, since the buffer layer is not formed on the upper surface of the SiO ₂ mask, the GaN layer is grown in the lateral direction. The outermost growth surface of the GaN layer comes into contact with the upper surface of the mask layer. For this reason, the detachment from the growth outermost surface of the GaN layer at this contact portion becomes large. As a result, new crystal defects are generated, and as a result, there arises a problem that defects in the GaN layer increase.

  As described above, conventionally, a nitride-based semiconductor layer with few dislocations can be formed with a small number of growth steps, but a nitride-based semiconductor layer with few crystal defects due to separation is formed. Was difficult.

The present invention has been made to solve the above problems,
One object of the present invention is to provide a method for forming a nitride-based semiconductor capable of forming a nitride-based semiconductor layer with few dislocations and few crystal defects due to detachment with a small number of growth steps. It is to be.

  Another object of the present invention is to provide a nitride-based semiconductor device having good device characteristics including a nitride-based semiconductor layer with few dislocations and few crystal defects due to separation.

  According to one aspect of the present invention, there is provided a method for forming a nitride-based semiconductor, comprising: forming a mask layer on an upper surface of a substrate so that a part of the upper surface of the substrate is exposed; A step of forming a buffer layer on the upper surface of the mask layer and a step of growing a nitride-based semiconductor layer thereafter are provided.

  In the method for forming a nitride semiconductor according to the above aspect, the nitride semiconductor layer is formed on the buffer layer by forming the buffer layer not only on the upper surface of the exposed substrate but also on the upper surface of the mask layer. Is grown, the growth outermost surface of the nitride-based semiconductor layer that grows laterally on the mask layer does not come into contact with the mask layer. This makes it difficult for the nitride-based semiconductor layer to be detached from the outermost growth surface, so that a nitride-based semiconductor layer with few defects can be formed. In addition, by forming the mask layer directly on the substrate, it is not necessary to form a nitride-based semiconductor before forming the mask layer, so that the number of nitride-based semiconductor layer growth steps can be reduced. As a result, a nitride-based semiconductor layer in which dislocations are reduced by lateral growth can be formed with a small number of growth steps. Therefore, in the present invention, it is possible to form a nitride-based semiconductor layer with good crystallinity with few dislocations and few defects due to separation with a small number of growth steps.

In the method for forming a nitride-based semiconductor according to the above aspect, the mask layer preferably includes any one of a nitride and a refractory metal. If configured in this manner, the mask layer is not a film containing oxygen like SiO ₂ , so that oxygen atoms constituting the mask layer appear on the surface of the nitride-based semiconductor layer and the device characteristics deteriorate. Does not occur. In this case, the mask layer preferably contains SiN. In this way, a nitride-based semiconductor layer with fewer defects can be formed by nitrogen (N) atoms of SiN. In this case, the mask layer may include a multilayer film in which any one of the nitride and the refractory metal is exposed on the outermost surface. With this configuration, there is no oxygen-containing film such as SiO ₂ on the top surface of the mask layer, so that oxygen atoms appear on the surface of the nitride-based semiconductor layer, resulting in inconvenience that device characteristics deteriorate. Absent.

  In the above case, the mask layer preferably has a stripe structure. When the mask layer having a stripe structure is used in this way, the number of facet coupling portions when the nitride-based semiconductor layer is grown in the lateral direction is reduced, so that the nitride-based semiconductor layer can be easily flattened. it can. Further, the coupling direction between the facets becomes the same direction, and the deviation of the plane orientation between the facets in the coupling portion is suppressed.

  In the above case, the angle formed between the upper surface of the substrate and the side surface of the mask layer is preferably an acute angle. Thus, if the angle formed between the upper surface of the substrate and the side surface of the mask layer is an acute angle, a nitride-based semiconductor layer with good crystallinity is formed thereon.

  In the above case, a step of growing a nitride-based semiconductor element layer having an element region on the nitride-based semiconductor layer may be further provided. According to this structure, a nitride semiconductor element layer having an element region is grown on a nitride semiconductor layer having few defects. Therefore, a nitride semiconductor element having good element characteristics can be easily obtained. Can be formed.

  A nitride-based semiconductor device according to another aspect of the present invention includes a mask layer formed on a top surface of a substrate so that a part of the top surface of the substrate is exposed, and a top surface of the exposed substrate and a top surface of the mask layer. A buffer layer formed above, a nitride-based semiconductor layer formed so as to cover the buffer layer, and a nitride-based semiconductor element layer having an element region formed on the nitride-based semiconductor layer .

  In the nitride semiconductor device according to the other aspect described above, the nitride semiconductor layer is grown on the buffer layer by forming the buffer layer not only on the exposed upper surface of the substrate but also on the upper surface of the mask layer. In this case, the growth outermost surface of the nitride-based semiconductor layer that grows laterally on the mask layer does not come into contact with the mask layer. This makes it difficult for the nitride-based semiconductor layer to be detached from the outermost growth surface, so that a nitride-based semiconductor layer with few defects can be obtained. In addition, by forming the mask layer directly on the substrate, it is not necessary to form the nitride-based semiconductor layer before forming the mask layer, so that the number of steps of growing the nitride-based semiconductor layer can be reduced. . Thus, a nitride-based semiconductor layer in which dislocations are reduced by lateral growth can be obtained with a small number of growth steps. If a nitride-based semiconductor element layer having an element region is grown on a nitride-based semiconductor layer with few defects due to the separation and reduced dislocations, good device characteristics can be easily obtained. It is possible to obtain a nitride-based semiconductor device having

In the nitride semiconductor device according to the other aspect described above, the mask layer preferably includes any one of a nitride and a refractory metal. If configured in this manner, the mask layer is not a film containing oxygen like SiO ₂ , so that it is effective that oxygen atoms constituting the mask layer appear on the surface of the nitride-based semiconductor layer and the device characteristics deteriorate. Can be prevented. In this case, the mask layer preferably contains SiN. In this way, a nitride-based semiconductor layer with fewer defects can be formed by nitrogen (N) atoms of SiN. In this case, the mask layer may include a multilayer film in which any one of the nitride and the refractory metal is exposed on the outermost surface. With this configuration, there is no oxygen-containing film such as SiO ₂ on the top surface of the mask layer, so that oxygen atoms appear on the surface of the nitride-based semiconductor layer, resulting in inconvenience that device characteristics deteriorate. Absent.

  In the above case, the mask layer preferably has a stripe structure. When the mask layer having a stripe structure is used in this way, the number of facet coupling portions when the nitride-based semiconductor layer is grown in the lateral direction is reduced, so that the nitride-based semiconductor layer can be easily flattened. it can. Further, the coupling direction between the facets becomes the same direction, and the deviation of the plane orientation between the facets in the coupling portion is suppressed.

  In the above case, the angle formed between the upper surface of the substrate and the side surface of the mask layer is preferably an acute angle. Thus, if the angle formed between the upper surface of the substrate and the side surface of the mask layer is an acute angle, a nitride-based semiconductor layer with good crystallinity is formed thereon.

  As described above, according to the present invention, it is possible to form a nitride-based semiconductor capable of forming a nitride-based semiconductor layer with few dislocations and few crystal defects due to separation with a small number of growth steps. A method can be provided.

  Further, it is possible to provide a nitride-based semiconductor element including a nitride-based semiconductor element layer having good element characteristics formed on a nitride-based semiconductor layer with few dislocations and few crystal defects due to separation. it can.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

  1 to 4 are a cross-sectional view and a perspective view for explaining a method for forming a nitride-based semiconductor according to an embodiment of the present invention. With reference to FIGS. 1 to 4, a method for forming a nitride-based semiconductor according to the present embodiment will be described.

First, as shown in FIGS. 1 and 2, a mask layer 2 made of SiN having a thickness of about 0.1 μm is formed as a selective growth mask on the C (0001) plane of the sapphire substrate 1. A plurality of mask layers 2 are formed in a stripe shape (stripe structure) at a pitch interval of about 7 μm. As a specific method for forming the mask layer 2, first, an SiN film (plasma chemical vapor deposition method) or an electron beam evaporation method is used on the entire surface of the sapphire substrate 1 on the C surface. (Not shown). Then, a striped mask pattern (not shown) made of a photoresist is formed on the SiN film. Further, by partially removing the SiN film using the mask pattern as a mask, using wet etching using HF (hydrofluoric acid) solution or dry etching using CF ₄ gas and O ₂ gas. Then, a striped mask layer 2 is formed.

  Note that the pitch width of 7 μm is when the width of the region where the mask layer 2 is formed and the width of the region where the mask layer 2 is not formed are 2 μm and 5 μm, 3 μm and 4 μm, 4 μm and 3 μm, respectively. Either 5 μm or 2 μm may be used. Moreover, the width | variety of ratios other than these may be sufficient.

Next, as shown in FIG. 3, an MOCVD method (Metal Organic Chemical Vapor Deposition method) or an HVPE method (Hydride Vapor Phase method) is formed on the upper surface of the sapphire substrate 1 on which the mask layer 2 made of SiN is formed. Al _x GaN _1-x buffer having a film thickness of about 10 nm to 100 nm (about 0.01 μm to 0.1 μm) at a growth temperature of about 500 ° C. to 700 ° C. using Epitaxy (halide vapor phase growth method) or the like. Layer 3 (0 ≦ x ≦ 1) is formed. Then, the GaN layer 4 is formed at a growth temperature of about 1000 ° C. to 1200 ° C. using the MOCVD method or the HVPE method.

  At this time, the AlGaN buffer layer 3 also grows on the mask layer 2 made of SiN. In this case, the high temperature growth GaN layer is difficult to grow on the AlGaN buffer layer 3 on the mask layer 2 made of SiN. Therefore, the high temperature growth GaN layer is selectively grown in the direction of arrow Y in FIG. 3 on the AlGaN buffer layer 3 on the sapphire substrate 1 exposed between the mask layers 2 made of SiN. Thereby, the slope of the (11-22) plane as shown in FIG. 3 is formed only on the AlGaN buffer layer 3 on the portion of the upper surface of the sapphire substrate 1 exposed between the mask layers 2 made of SiN. A GaN layer 4 having a triangular facet structure with an exposed cross-sectional shape is formed.

  As the growth of the GaN layer 4 further proceeds, the GaN layer 4 grows in the direction of arrow X (lateral direction) in FIG. By this lateral growth, the GaN layer 4 is also formed on the mask layer 2. Finally, the GaN layers 4 having facet structures are combined to form a continuous film having a flat upper surface as shown in FIG. In the present embodiment, the GaN layer 4 made of a continuous film having a flat top surface and a film thickness of about 8 μm is formed. The GaN layer 4 is an example of the “nitride-based semiconductor layer” in the present invention.

  In the present embodiment, as described above, the AlGaN buffer layer 3 is grown not only on the exposed upper surface of the sapphire substrate 1 but also on the upper surface of the mask layer 2, thereby forming the GaN on the AlGaN buffer layer 3. When the layer 4 is grown, the growth outermost surface of the GaN layer 4 that grows laterally on the mask layer 2 does not come into contact with the mask layer 2. This makes it difficult for the GaN layer 4 to be detached from the growth outermost surface, so that the GaN layer 4 with few defects due to the separation can be formed.

  In the present embodiment, by forming the mask layer 2 directly on the sapphire substrate 1, it is not necessary to form a GaN layer before forming the mask layer 2, thereby reducing the number of GaN layer growth steps. be able to. As a result, the GaN layer 4 in which dislocations are reduced by lateral growth can be formed with a small number of growth steps.

  Therefore, in the present embodiment, the GaN layer 4 having good crystallinity with few dislocations and few defects due to separation can be formed with a small number of growth steps.

In the present embodiment, the mask layer 2 is made of SiN, so that the oxygen atoms constituting the mask layer 2 are formed in the GaN layer as in the case where the mask layer 2 is formed of a film containing oxygen such as SiO _2. No inconvenience of appearing on the surface of 4 and deteriorating device characteristics.

  In this embodiment, the mask layer 2 is formed to have a stripe structure, so that the number of facet coupling portions when the GaN layer 4 is grown in the lateral direction is reduced. Can be made.

  FIG. 5 is a cross-sectional view showing a semiconductor laser device manufactured by using the nitride-based semiconductor forming method of this embodiment described above. Next, the structure and manufacturing process of the semiconductor laser device manufactured by using the nitride-based semiconductor forming method of this embodiment will be described with reference to FIG.

  As shown in FIG. 5, the structure of the semiconductor laser device of the present embodiment has a stripe-shaped (stripe structure) film thickness of about 0.1 μm directly on the upper surface of the sapphire substrate 1 at a predetermined interval. A mask layer 2 made of SiN is formed. An AlGaN buffer layer 3 having a film thickness of about 10 nm to 100 nm (about 0.01 μm to 0.1 μm) is formed on the upper surface of the sapphire substrate 1 located between the mask layers 2 and on the upper surface of the mask layer 2. Has been. On the AlGaN buffer layer 3, a GaN layer 4 having a planarized surface having a thickness of about 8 μm is formed.

  A first conductivity type contact layer 5 made of n-type GaN having a thickness of about 4 μm is formed on the GaN layer 4. On the first conductivity type contact layer 5, a first conductivity type clad layer 6 made of n-type AlGaN having a thickness of about 0.45 μm is formed. A multiple quantum well (MQW) light emitting layer 7 made of InGaN is formed on the first conductivity type cladding layer 6. A second conductivity type cladding layer 8 made of p-type AlGaN having a film thickness of about 0.45 μm is formed on the MQW light emitting layer 7. A second conductivity type contact layer 9 made of p-type GaN having a thickness of about 0.15 μm is formed on the second conductivity type cladding layer 8. An n-type first conductivity type electrode 10 is formed on the exposed upper surface of the first conductivity type contact layer 5. A p-type second conductivity type electrode 11 is formed on the upper surface of the second conductivity type contact layer 9.

  The first conductivity type contact layer 5, the first conductivity type cladding layer 6, the MQW light emitting layer 7, the second conductivity type cladding layer 8 and the second conductivity type contact layer 9 are the “nitride-based semiconductor element layer” of the present invention. Is an example.

  As a method of forming the semiconductor laser device of the present embodiment having the above-described structure, first, the sapphire substrate 1 is formed using the method of forming a nitride-based semiconductor of the present embodiment described with reference to FIGS. On top, a mask layer 2 made of SiN having a thickness of about 0.1 μm, an AlGaN buffer layer 3 having a thickness of about 10 nm to 100 nm (about 0.01 μm to 0.1 μm), and a thickness of about 8 μm. The GaN layers 4 having the above are sequentially formed.

Next, MOCVD, HVPE, or gas source MBE (Molecular) using trimethylaluminum, trimethylgallium, trimethylindium, NH ₃ , SiH ₄ (silane gas), Cp ₂ Mg (cyclopentadienylmagnesium) as a source gas. A first conductivity type contact layer 5 made of n-type GaN having a film thickness of about 4 μm, and an n-type having a film thickness of about 0.45 μm on the GaN layer 4 by using, for example, Beam Epitaxy; A first conductivity type cladding layer 6 made of AlGaN, a multiple quantum well (MQW) light emitting layer 7 made of InGaN, a second conductivity type cladding layer 8 made of p-type AlGaN having a thickness of about 0.45 μm, and about 0 A second conductivity type contact made of p-type GaN having a film thickness of 15 μm Layer 9 is formed sequentially.

  Then, a predetermined region of the first conductivity type contact layer 5 is exposed by etching a partial region from the second conductivity type contact layer 9 to the first conductivity type contact layer 5. An n-type first conductivity type electrode 10 is formed on a predetermined region of the exposed first conductivity type contact layer 5. Further, a p-type second conductivity type electrode 11 is formed in a predetermined region on the second conductivity type contact layer 9.

  In the semiconductor laser device of the present embodiment described above, the GaN layer 4 having good crystallinity formed by using the nitride-based semiconductor forming method of the present embodiment shown in FIGS. Each layer 5-9 is formed on the top. That is, as described above, the GaN layer 4 is laterally grown on the mask layer 2 by forming the AlGaN buffer layer 3 not only on the exposed upper surface of the sapphire substrate 1 but also on the upper surface of the mask layer 2. In this case, detachment from the growth outermost surface of the GaN layer 4 is unlikely to occur, so that the GaN layer 4 with few defects due to the detachment can be formed. Further, by forming the GaN layer 4 by selective lateral growth, dislocations on the surface of the GaN layer 4 are reduced. Thus, by forming each of the layers 5 to 9 on the GaN layer having good crystallinity with few defects due to separation and reduced dislocations, the layers 5 to 9 are good. Crystallinity can be realized. Thereby, in this embodiment, it is possible to obtain a semiconductor laser element having good element characteristics and high reliability.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and all modifications within the meaning and scope equivalent to the scope of claims for patent are included.

  For example, in the above-described embodiment, the sapphire substrate 1 is used as a substrate, but the present invention is not limited to this, and the same effect can be obtained by using a SiC substrate, a Si substrate, a GaAs substrate, or a spinel substrate.

Moreover, in the said embodiment, although the mask layer 2 was formed with SiN, this invention is not restricted to this, Even if it forms the mask layer 2 with nitride other than SiN, or a refractory metal, the same effect can be acquired. it can. In this case, the refractory metal preferably has a melting point of 1000 ° C. or higher. Further, the mask layer 2 may be a multilayer film in which a nitride such as SiN or a refractory metal is on the uppermost surface. In this case, the uppermost surface of the mask layer 2, since there is no film containing oxygen, such as SiO _2, does not occur inconvenience that oxygen atoms device characteristics deteriorate appear on the surface of the GaN layer 4.

  Moreover, in the said embodiment, although the cross section of the mask layer 2 which consists of SiN was made into the rectangular shape as shown in FIG. 1, this invention is not restricted to this, It is good also as another shape. For example, a mask layer 12 having a trapezoidal shape as shown in FIG. 6, a mask layer 22 having an inverted trapezoidal shape as shown in FIG. 7, or a mask layer 32 having a shape as shown in FIG. 8 may be used. Moreover, as shown in FIG. 9, it may be a mask layer 42 having a two-layer structure including a trapezoidal lower layer 42a and a rectangular upper layer 42b. Thus, the mask layer may have a multilayer structure. Further, it may be a mask layer having a structure in which the structures shown in FIGS. 1 and 6 to 9 are appropriately combined. In particular, as shown in FIG. 7 or FIG. 8, when the angle formed between the upper surface of the substrate 1 and the mask layer 22 or 32 is an acute angle, a GaN layer (nitride-based semiconductor) with good crystallinity is formed thereon. Layer 4) was formed.

  The sapphire substrate (substrate) 1, AlGaN buffer layer (buffer layer) 3, GaN layer (nitride-based semiconductor layer) 4, and layers (nitride-based semiconductor element layers) 5 to 9 in the above embodiment are GaN III-V nitride semiconductors such as (gallium nitride), AlN (aluminum nitride), InN (indium nitride), BN (boron nitride) or TlN (thallium nitride), or mixed crystals thereof, and mixtures thereof The crystal may be composed of a III-V group nitride semiconductor such as a mixed crystal containing at least one element of As, P, and Sb.

  In the above embodiment, the AlGaN buffer layer 3 and the GaN layer 4 are not doped with impurity elements. However, the present invention is not limited to this, and the AlGaN buffer layer 3 and the GaN layer 4 are doped with n-type impurities. It is good also as a layer of 1st conductivity type.

  In the above embodiment, the mask layer 2 is formed with a pitch width of 7 μm. However, the present invention is not limited to this, and the pitch width of the mask layer 2 may be other than 7 μm and may be a width of 1 μm or more and 30 μm or less. That's fine.

It is sectional drawing for demonstrating the formation method of the nitride type semiconductor by one Embodiment of this invention. It is a perspective view in the process shown in FIG. It is sectional drawing for demonstrating the formation method of the nitride type semiconductor by one Embodiment of this invention. It is sectional drawing for demonstrating the formation method of the nitride type semiconductor by one Embodiment of this invention. It is sectional drawing which showed the semiconductor laser element formed using the formation method of the nitride type semiconductor of this embodiment shown in FIGS. It is sectional drawing which showed the modification of the shape of the mask layer used for the formation method of the nitride-type semiconductor of this embodiment. It is sectional drawing which showed the modification of the shape of the mask layer used for the formation method of the nitride-type semiconductor of this embodiment. It is sectional drawing which showed the modification of the shape of the mask layer used for the formation method of the nitride-type semiconductor of this embodiment. It is sectional drawing which showed the modification of the shape of the mask layer used for the formation method of the nitride-type semiconductor of this embodiment. It is sectional drawing for demonstrating the formation method of the conventional nitride semiconductor. It is sectional drawing for demonstrating the formation method of the conventional nitride semiconductor. It is sectional drawing for demonstrating the formation method of the conventional nitride semiconductor.

Explanation of symbols

1 Sapphire substrate (substrate)
2 Mask layer 3 AlGaN buffer layer (buffer layer)
4 GaN layer (nitride semiconductor layer)
5 First conductivity type contact layer (nitride-based semiconductor element layer)
6 First conductivity type cladding layer (nitride-based semiconductor element layer)
7 MQW light emitting layer (nitride-based semiconductor element layer)
8 Second conductivity type cladding layer (nitride semiconductor element layer)
9 Second conductivity type contact layer (nitride semiconductor element layer)

Claims (13)

Forming a mask layer directly on the upper surface of the substrate such that a portion of the upper surface of the substrate is exposed;
Forming a buffer layer directly on the upper surface of the substrate exposed from the mask layer and on the upper surface of the mask layer;
And a step of growing a nitride-based semiconductor layer thereafter.   The method for forming a nitride-based semiconductor according to claim 1, wherein the mask layer includes any one of a nitride and a refractory metal.   The method for forming a nitride-based semiconductor according to claim 2, wherein the mask layer includes SiN.   4. The method for forming a nitride-based semiconductor according to claim 2, wherein the mask layer includes a multilayer film in which one of a nitride and a refractory metal is exposed on the outermost surface. 5.   The method for forming a nitride-based semiconductor according to claim 1, wherein the mask layer has a stripe structure.   The method for forming a nitride-based semiconductor according to claim 1, wherein an angle formed by the upper surface of the substrate and the side surface of the mask layer is an acute angle.   The method for forming a nitride-based semiconductor according to claim 1, further comprising a step of growing a nitride-based semiconductor element layer having an element region on the nitride-based semiconductor layer. A mask layer directly formed on the upper surface of the substrate so that a part of the upper surface of the substrate is exposed;
A buffer layer formed directly on the upper surface of the substrate exposed from the mask layer and on the upper surface of the mask layer;
A nitride-based semiconductor layer formed to cover the buffer layer;
A nitride-based semiconductor element comprising: a nitride-based semiconductor element layer having an element region formed on the nitride-based semiconductor layer.   The nitride semiconductor device according to claim 8, wherein the mask layer includes any one of a nitride and a refractory metal.   The nitride semiconductor device according to claim 9, wherein the mask layer includes SiN.   11. The nitride semiconductor device according to claim 9, wherein the mask layer includes a multilayer film in which one of nitride and a refractory metal is exposed on the outermost surface.   The nitride semiconductor device according to claim 8, wherein the mask layer has a stripe structure.   The nitride semiconductor device according to any one of claims 8 to 12, wherein an angle formed between an upper surface of the substrate and a side surface of the mask layer is an acute angle.

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