JP2011049583A - Nitride semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor light-emitting device that achieves uniformity of characteristics within a wafer surface and improves the yield. <P>SOLUTION: A nitride semiconductor light-emitting device includes a substrate 10 and a nitride semiconductor layer 13 laminated on top of the substrate 10. The substrate 10 has a defect concentration region 11 and a low defect region 12 that is a region excluding the defect concentration region 11. In a portion of the substrate 10 including the defect concentration region 11, a trench region 14 is provided that is deeper than the surface of the low defect region 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a substrate such as a nitride semiconductor laser device and a manufacturing method thereof, and a nitride semiconductor light emitting device formed by laminating a nitride semiconductor layer on the substrate and a manufacturing method thereof.

  A semiconductor laser device that oscillates in the ultraviolet to visible region has been prototyped using nitride semiconductor materials typified by GaN, AlN, InN, and mixed crystals thereof. As the substrate, a GaN substrate is often used and has been energetically studied in each research institution. At present, a semiconductor laser element having a sufficient lifetime has not been obtained, and further life extension is required. It is known that the lifetime of this semiconductor laser element strongly depends on the density of defects (in this specification, vacancies, interstitial atoms, dislocations, etc.) existing in the GaN substrate. . However, it is difficult to obtain a substrate with a low defect density, which is said to be effective in extending the life, and has been actively studied.

As an example, Non-Patent Document 1 reports that the following method is used for manufacturing a GaN substrate. A SiO ₂ mask pattern having a periodic stripe-like opening having a thickness of 0.1 μm formed on a GaN substrate having a thickness of 2.0 μm grown on the sapphire substrate by MOCVD (Metalorganic Chemical Vapor Deposition). Then, a 20 μm thick GaN layer is formed again by MOCVD to obtain a wafer. This is a technique called ELOG (Epitaxially Lateral Overground), which is a technique for reducing defects by utilizing lateral growth.

Further, a GaN layer having a thickness of 200 μm is formed by HVPE (Hydride Vapor Phase Epitaxy), and a GaN substrate having a thickness of 150 μm is manufactured by removing the underlying sapphire substrate. Next, the surface of the obtained GaN substrate is polished flat. The substrate thus obtained includes a defect concentration region and a low defect region in the substrate surface. In general, the defect concentration region having a lot of defects on a part of the SiO _2, are often divided into the remaining low-defect regions on SiO _2.

Applied Physics Letter. Vol. 73 No. 6 (1998) p. 832-834

  However, when a nitride semiconductor layer is grown on a substrate including a defect-concentrated region and a low-defect region by MOCVD or the like, the characteristics of the semiconductor laser device manufactured therefrom vary, greatly reducing the yield.

  As a result of earnest research to elucidate the cause of variations in the characteristics of semiconductor laser elements when the nitride semiconductor layer is grown on a substrate containing defect-concentrated regions and low-defect regions by MOCVD etc. It has been found that the cause is that the film surface has poor surface flatness and an uneven surface morphology. This is because when a nitride semiconductor layer (in particular, an InGaN layer called an active layer) is grown on the uneven film, the layer thickness and composition differ in the plane depending on the unevenness, and greatly deviate from the set value. Furthermore, it was found that the uneven surface morphology greatly depends on the shape of the defect concentration region of the nitride semiconductor layer. In other words, the growth direction and growth mode of the thin film strongly depend on the shape of the defect concentration region, and if the shape of the defect concentration region is not uniform, the flatness of the film surface deteriorates and the surface morphology becomes uneven. It was. By growing a thin film such as an active layer on the uneven surface, the characteristics of the element vary.

  The experiment that led to the above consideration will be described. First, a case where a nitride semiconductor layer is grown on a substrate having a defect concentration region and a low defect region will be described. FIG. 15A is a sectional view of a conventional semiconductor laser device, and FIG. 15B is a top view of FIG. Reference numeral 10 denotes a substrate having a defect concentration region and a low defect region, 11 is a defect concentration region, 12 is a low defect region, 13 is a nitride semiconductor layer, and 13a is a surface of the nitride semiconductor layer.

  When the nitride semiconductor layer is grown on the substrate 10 as it is (without pretreatment on the substrate or the like), the defect concentration region has poor crystallinity compared to the low defect region, and a growth surface different from the low defect region appears. The growth rate is greatly different from that of low defect areas. For this reason, the growth rate of the defect concentration region is slower than that of the low defect region, and almost no growth occurs.

  FIG. 16A is a top view at the time of growth of a nitride semiconductor layer having a linear defect concentration region, and FIG. 16B is an upper surface at the time of growth of a nitride semiconductor layer having a point-like defect concentration region. FIG. Since almost no growth occurs in the defect concentration region, the growth proceeds in the direction of arrow A starting from the defect concentration region x, and the growth proceeds in the direction of arrow B starting from the defect concentration region y. When growth occurs in two different directions as described above, the layer thickness changes at the meeting portion and other regions, and the surface flatness deteriorates.

  FIG. 17 is a diagram in which the roughness is measured in the vertical direction [11-20] and the horizontal direction [1-100] in the linear defect concentration region. The roughness was measured using DEKTAK3ST manufactured by A SUBSIDIARY OF VEECO INSTRUMENTS INC. The measurement conditions are a measurement length of 600 μm, a measurement time of 3 s, a stylus pressure of 30 mg, and a horizontal resolution of 1 μm / sample. Among the measured 600 μm width, the difference in height between the highest part and the lowest part reaches 200 nm. However, a groove having a large defect concentration area is excluded.

  It was also found that the meeting part was a non-light emitting region. From the above, it can be said that the difference in the layer thickness of each layer within the wafer surface is a cause of variation in element characteristics.

  In view of the above-described problems, an object of the present invention is to provide a substrate that improves the yield by making the characteristics in the wafer surface uniform, and a nitride semiconductor light emitting device stacked on the substrate.

  In order to achieve the above object, the substrate of the present invention is a substrate having a defect concentration region and a low defect region which is a region excluding the defect concentration region, and the low defect region is included in a portion including the defect concentration region. A digging region dug out from the surface of is formed.

  In this way, by digging a portion including the defect concentration region, the growth direction becomes uniform, the surface flatness is improved, the characteristics in the wafer surface are made uniform, and the yield can be improved.

  Furthermore, the substrate of the present invention is characterized in that a digging region is formed in the low defect region more than the surface of the low defect region. At this time, the digging region formed in the low defect region may be formed on both sides of the digging region formed in the portion including the defect concentration region.

  In this way, the digging area dug into the low-defect area prevents the influence of a wide range when the low-defect area contains abnormal growth points such as areas with different defects or growth surfaces. be able to.

  Furthermore, the substrate of the present invention is characterized in that the distance from the end of the digging region formed in the portion including the defect concentration region to the end of the defect concentration region is 5 μm or more.

  Further, the substrate of the present invention is a substrate having a defect concentration region and a low defect region which is a region excluding the defect concentration region, and is dug into only the low defect region from the surface of the low defect region. A digging region is formed.

  As described above, by forming the dug region only in the low defect region, the propagation of the abnormal growth region can be stopped, and the surface flatness can be improved.

  In the substrate of the present invention, the digging region formed only in the low defect region is preferably formed on one side or both sides of the defect concentration region.

Furthermore, the substrate of the present invention is characterized in that the distance from the end of the dug area formed only in the low defect area to the end of the defect concentration area is 5 μm or more.

  The substrate of the present invention is characterized by comprising gallium nitride.

In the substrate of the present invention, the defect concentration region is linear or dot-shaped.
And when a defect concentration area | region is linear, it is preferable that the linear defect concentration area | region is extended in the [1-100] direction.

  Furthermore, in the substrate of the present invention, the digging depth of the digging region is 0.5 μm or more and 50 μm or less.

  In addition, a nitride semiconductor light emitting device according to the present invention includes any one of the above-described substrates and a nitride semiconductor layer stacked on the substrate.

  Furthermore, the nitride semiconductor light emitting device of the present invention is characterized in that the nitride semiconductor layer has a ridge portion that is a laser light waveguide region, and the ridge portion is formed at least 5 μm away from the end of the digging region. And

  Furthermore, the nitride semiconductor light emitting device of the present invention is characterized in that an n-type electrode is formed on the lower surface of the substrate and a p-type electrode is formed on the upper surface of the nitride semiconductor layer.

  The present invention also relates to a method of manufacturing a substrate having a defect concentration region and a low defect region excluding the defect concentration region, where a portion including the defect concentration region is dug more than the surface of the low defect region. The present invention relates to a method for manufacturing a substrate, which includes a step of forming an embedded digging region.

  Furthermore, the method for manufacturing a substrate according to the present invention is characterized in that the low defect region includes a step of forming a dug region that is dug more than the surface of the low defect region. At this time, a step of forming the digging region formed in the low defect region on both sides of the digging region formed in the portion including the defect concentration region may be included.

  Furthermore, in the substrate manufacturing method of the present invention, the portion including the defect concentration region so that the distance from the end of the digging region formed in the portion including the defect concentration region to the end of the defect concentration region is 5 μm or more. Includes a step of forming a digging region.

  The present invention also relates to a method of manufacturing a substrate having a defect concentration region and a low defect region excluding the defect concentration region, and the substrate is dug only in the low defect region than the surface of the low defect region. The present invention relates to a method for manufacturing a substrate, which includes a step of forming an embedded digging region.

  Furthermore, the substrate manufacturing method of the present invention includes a step of forming a dug region formed only in the low defect region on one side or both sides of the defect concentration region.

  Further, the substrate manufacturing method of the present invention includes a step of forming the digging region so that the distance from the end of the digging region formed only in the low defect region to the end of the defect concentration region is 5 μm or more. It is characterized by being.

  In the substrate manufacturing method of the present invention, it is preferable that the step of forming the digging region dug out from the surface of the low defect region is performed using vapor phase etching. As the vapor phase etching, reactive ion etching (RIE) is preferably exemplified.

  Further, in the substrate manufacturing method of the present invention, the substrate is gallium nitride.

  Furthermore, in the substrate manufacturing method of the present invention, when the defect concentration region is linear, a substrate in which the linear defect concentration region extends in the [1-100] direction is used.

  The present invention also relates to a method for manufacturing a nitride semiconductor light emitting device, comprising a step of forming a nitride semiconductor layer on a substrate obtained by the above method for manufacturing a substrate.

  In the method for manufacturing a nitride semiconductor light emitting device according to the present invention, the nitride semiconductor layer includes a step of forming a ridge portion which is a laser light waveguide region at a distance of 5 μm or more from the end of the digging region. And

  Furthermore, the method for manufacturing a nitride semiconductor light emitting device of the present invention includes a step of forming an n-type electrode on the lower surface of the substrate and forming a p-type electrode on the upper surface of the nitride semiconductor layer. .

  When the substrate has a defect concentration region and a low defect region which is a region excluding the defect concentration region, the substrate is provided by providing a digging region that is dug more than the surface of the low defect region at a predetermined position of the substrate. The growth direction of the nitride semiconductor layer laminated thereon is made uniform, the surface flatness is improved, the characteristics in the wafer surface are made uniform, and the yield can be improved.

  In addition, by providing a digging region at a predetermined position of the substrate, it is possible to release strain inherent in the nitride semiconductor layer stacked on the substrate, and to prevent generation of cracks.

(A) It is sectional drawing of the nitride semiconductor laser element of Example 1. FIG. FIG. 2B is a top view of FIG. It is sectional drawing which shows the layer structure of the nitride semiconductor layer. (A) It is an example of the top view which expanded the defect concentration area vicinity. (B) It is an example of the top view which expanded the defect concentration area vicinity. (C) It is an example of the top view which expanded the defect concentration area vicinity. (A) It is a top view of the board | substrate of Example 1. FIG. (B) It is sectional drawing of Fig.4 (a). (A) It is a figure which shows the surface flatness of a [11-20] direction. (B) It is a figure which shows the surface flatness of a [1-100] direction. (A) It is a top view at the time of the growth of the nitride semiconductor layer which has a linear defect concentration area | region. (B) It is a top view at the time of the growth of the nitride semiconductor layer which has a dotted | punctate defect concentration area | region. It is a figure which shows the correlation of the digging depth X and a yield. (A) It is a top view of the board | substrate which has a linear defect concentration area | region. (B) It is a top view of the board | substrate which has a dot-shaped defect concentration area | region. It is a figure which shows the correlation of the distance Y and a yield. 6 is a top view of a substrate having a spot-like defect concentration region in Example 2. FIG. (A) It is a top view of the board | substrate of Example 3. FIG. (B) It is sectional drawing of Fig.11 (a). (A) It is a top view at the time of the growth of the nitride semiconductor layer when it does not have a digging region. (B) It is a top view at the time of the growth of the nitride semiconductor layer in the case of having a digging region. (A) It is a top view of the board | substrate of Example 4. FIG. (B) It is sectional drawing of Fig.13 (a). (A) It is sectional drawing of the nitride semiconductor laser element of Example 4. FIG. (B) It is a top view of Fig.14 (a). (A) It is sectional drawing of the conventional semiconductor laser element. (B) It is a top view of Fig.15 (a). (A) It is a top view at the time of the growth of the nitride semiconductor layer which has the conventional linear defect concentration area | region. (B) It is a top view at the time of the growth of the nitride semiconductor layer which has the conventional point-like defect concentration area | region. (A) It is a figure which shows the surface flatness of the [11-20] direction of the conventional nitride semiconductor laser element. (B) It is a figure which shows the surface flatness of the [1-100] direction of the conventional nitride semiconductor laser element.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  In this specification, when the index indicating the plane and orientation of the crystal is negative, it is a rule of crystallography that the absolute value is indicated with a horizontal line, but in this specification, such notation is used. Since it is not possible, a negative sign is used in front of the absolute value to indicate a negative exponent.

  In the present invention, the substrate may be a free-standing GaN substrate after removing the substrate described in the conventional example, or may be used as it is without removing the substrate sapphire. That is, consider a case where a substrate having a defect concentration region and a low defect region is used on the surface of the substrate before the nitride semiconductor laser thin film is grown by the MOCVD method.

  1A is a cross-sectional view of a nitride semiconductor laser device, and FIG. 1B is a top view of FIG. In the n-type GaN substrate 10, a defect concentration region 11 exists, and a portion other than the defect concentration region 11 is a low defect region 12.

In this specification, the defect concentration region refers to a large number of etch pits as a result of etching by immersing a substrate or a nitride semiconductor layer formed on the substrate in a solution obtained by heating a mixed acid of sulfuric acid and phosphoric acid to 250 ° C. Refers to a region where defects (or dislocations, etc.) are extremely concentrated. On the other hand, the low defect region refers to a region of EPD (etch pit density) of 10 ⁴ to 10 ⁵ / cm ² . The EPD in the defect concentration region is two orders of magnitude larger than this. As a method for measuring EPD, vapor phase etching such as RIE (Reactive Ion Etching) may be used, or it can be measured by stopping growth in a MOCVD furnace and exposing it to a high temperature (about 1000 ° C.). . As the measuring means, AFM (atomic force microscope), CL (cathode luminescence), microscopic PL (photo luminescence), or the like can be used.

A nitride semiconductor layer (epitaxial growth layer) 13 is formed on the substrate 10. In addition, a dug region 14 is formed in the substrate 10 so as to include the defect concentration region 11. The dug area 14 is an area dug by RIE. A ridge portion 15 having a laser optical waveguide structure, a SiO ₂ layer 16 for current confinement, and a p-type electrode 17 are formed on the top surface of the nitride semiconductor layer 13. An n-type electrode 18 is formed on the lower surface of the substrate 10.

  In this specification, the distance between the center of the ridge 15 and the end of the digging region 14 is represented by d. In FIG. 1A, d = 40 μm.

FIG. 2 is a cross-sectional view showing the layer configuration of the nitride semiconductor layer 13. The nitride semiconductor layer 13 includes an n-type Al _0.062 Ga _0.938 N first clad layer (layer thickness 2.3 μm) 21 and an n-type Al _0.1 Ga _0.9 N second layer on an n-type GaN layer (layer thickness 3.5 μm) 20. Cladding layer (layer thickness 0.2 μm) 22, n-type Al _0.062 Ga _0.938 N third cladding layer (layer thickness 0.1 μm) 23, n-type GaN guide layer (layer thickness 0.1 μm) 24, InGaN / GaN-3MQW Active layer (InGaN / GaN layer thickness = 4 nm / 8 nm) 25, p-type Al _0.3 Ga _0.7 N evaporation prevention layer (layer thickness 20 nm) 26, p-type GaN guide layer (layer thickness 0.05 μm) 27, p-type Al _0.062 A Ga _0.938 N clad layer (layer thickness 0.5 μm) 28 and a p-type GaN contact layer 29 (layer thickness 0.1 μm) are sequentially stacked.

  As shown in FIG. 1B, the linear defect concentration region 11 extends in the [1-100] direction. The shape of a linear defect viewed from the top may differ depending on the defect concentration density and type, and examples of the shape of the defect concentration region are shown in FIGS. There are a line-shaped defect concentration region (FIG. 3A), a hole-like defect concentration region (FIG. 3B), a state where minute hole-shaped defect concentration regions are densely packed (FIG. 3C), and the like. . The order of the holes and the linear core here is about 1 nm to several tens of μm. This embodiment will be described using the case of FIG. In addition, the same effect is produced in the cases of FIGS.

Next, a manufacturing method will be described. As described in the conventional example, the method for manufacturing the GaN substrate 10 in which the defect concentration region is linear is formed by growing a base GaN layer having a thickness of 2.5 μm on the sapphire substrate by MOCVD and periodically A SiO ₂ mask pattern (period 20 μm) having a stripe-shaped opening is formed, and a GaN layer having a thickness of 15 μm is formed again by MOCVD to obtain a wafer. Since no film grows on SiO ₂ , growth starts from the opening. When the film thickness is thicker than the SiO _2, it is grown in the lateral direction from the opening over SiO _2. The films grown from the left and right in the central portion of SiO ₂ are associated with each other, and the associated portion becomes a defect concentration region 11 having a high defect density. Since SiO ₂ is formed in a linear shape, the defect concentration region 11 is also formed in a linear shape. Here, the width of the defect concentration region 11 is about 40 μm, and the interval between the defect concentration regions 11 is about 400 μm.

  Although a method for manufacturing a substrate using the ELOG method is described here, other manufacturing methods can also be used. Any method can be used as long as a nitride semiconductor layer is grown on a substrate having a defect-concentrated region and a low-defect region. Even if the substrate is sapphire, a SiC, GaN, GaAs, Si substrate, A spinel substrate, a ZnO substrate, or the like may be used.

Next, EB deposition of SiO ₂ or the like with a film thickness of 400 nm is performed on the entire surface of the substrate 10, and then a stripe having a width of 60 μm so as to include a defect concentration region in the [1-100] direction with a resist by a general photolithography process. Form a window. Thereafter, the SiO ₂ and GaN substrate 10 are etched by ICP or RIE. The etching depth of the GaN substrate 10 is 4 μm. Thereafter, the substrate processing before the growth of the nitride semiconductor layer 13 is completed by removing SiO ₂ with an etchant such as HF.

  The substrate 10 thus obtained is shown in FIG. 4A is a top view of the substrate 10, and FIG. 4B is a cross-sectional view of FIG. 4A. Reference numeral 14a denotes a region etched by RIE so as to include the defect concentration region 11, and the depth thereof is indicated by X. In this specification, as an etching method, vapor phase etching may be used, or a liquid phase etchant may be used.

Then, the nitride semiconductor layer 13 is laminated on the substrate 10 to form the ridge portion 15, the SiO ₂ layer 16, the p electrode 17, and the n electrode 18.

  As described above, when the defect concentration region 11 of the substrate 10 is dug by RIE and the nitride semiconductor layer 13 is laminated on the substrate 10, the surface flatness of the dug region 14 is very rough, as shown in FIG. The roughness of the conventional nitride semiconductor laser device (see FIG. 17) was the same level. However, as shown in FIG. 5B, the height difference between the highest and lowest portions in the 600 μm width measured in the non-digged region other than the dug region 14 was 20 nm or less. However, the recess of the groove portion of the defect concentration region 11 shown in FIG.

  The reason for this will be described with reference to FIG. 6A is a top view at the time of growth of the nitride semiconductor layer 13 having the linear defect concentration region 11, and FIG. 6B is a top view of the nitride semiconductor layer 13 having the point-like defect concentration region 11. It is a top view at the time of growth. Unlike the case where the growth direction varies in the plane depending on the shape of the defect concentration region 11 as shown in FIG. 16, the growth direction is almost the same as shown by arrows C and D in FIG. The meeting part due to the difference in growth direction will not occur. For this reason, the thickness of each layer becomes uniform without variation in the plane.

  Further, as shown in FIGS. 6A and 6B, the in-plane growth direction can be made uniform without depending on the shape of the defect concentration region 11 by the digging region 14, so that the surface flatness is improved. It is effective to improve.

By forming the ridge portion 15 in this very flat region, the in-plane distribution of element characteristics can be suppressed and the yield can be drastically improved. The semiconductor laser device thus obtained was subjected to a life test at 60 ° C. and 30 mW by APC driving. The life shown here refers to the time when I _op (current value when the light output is 30 mW) before the life test is 1.5 times as long as the life test. The light emission wavelength of each element was 405 ± 5 nm. Fifty elements were randomly picked from each wafer, and the number of semiconductor laser elements whose lifetime exceeded 3000 hours was examined as a yield.

  As a result, the yield exceeded 80%. When the nitride semiconductor layer 13 was grown as it was on the substrate 10 shown in the conventional example, the yield was 30% or less. Thus, it can be said that improvement of the surface flatness (except for the dug region 14) of the nitride semiconductor layer 13 makes it possible to make the thickness and composition of each layer in the wafer uniform, leading to an improvement in yield.

  Next, the depth X of the digging region 14 shown in FIG. 4 will be examined. FIG. 7 shows the correlation between the digging depth X and the yield. In FIG. 7, the digging depth X is only shown up to 5 μm, but in the case of the depth of more than that, the yield exceeded 80%. When the digging depth X is less than 0.5 μm, the digging region is immediately filled when the n-type GaN as the base grows, and the poor surface flatness of the digging region 14 is propagated. The surface flatness other than the digging region 14 is deteriorated. In addition, when X = 50 μm or more, the substrate is usually ground and polished for element separation, but it has been found that cracks and the like occur during this step, thereby reducing the yield. For this reason, the digging depth X is preferably 0.5 μm or more and 50 μm or less.

  Next, the position of the dug area 14 will be considered. FIG. 8A is a top view of the substrate 10 having a linear defect concentration region, and FIG. 8B is a top view of the substrate 10 having a dotted defect concentration region. As shown in FIGS. 8A and 8B, Y is the distance from the end of the defect concentration region 11 to the end of the digging region 14. Here, although the distance Y is different at both ends in the width direction of the defect concentration region 11, the shorter one is defined as the distance Y.

  FIG. 9 shows the correlation between the distance Y and the yield. When the distance Y is less than 5 μm, the poorly crystallized portion of the defect concentration region 11 cannot be completely included in the digging region 14 and is included in other than the digging region 14, so that the yield decreases. It was. Therefore, the distance Y is preferably 5 μm or more.

  Next, the position of the ridge portion 15 will be examined. The position of the ridge portion 15 is defined by the distance d shown in FIG. When the distance d is less than 5 μm, the layer thickness varies depending on edge growth (the growth rate of the end portion of the unexcavated region increases and the layer thickness increases), which is not preferable. Therefore, there is no problem if the distance d is 5 μm or more.

  In the nitride semiconductor laser device of the conventional example, 5 to 7 cracks were found in the 1 cm square area in the nitride semiconductor layer 13. This is considered to be caused by a strain caused by a difference in lattice constant between the AlGaN cladding layer and the GaN layer included in the nitride semiconductor layer 13 or a difference in thermal expansion coefficient. As described above, when a crack exists, the nitride semiconductor device including the crack in the chip remarkably deteriorates the characteristics and decreases the yield.

  In contrast, in the nitride semiconductor laser device of the present embodiment, there were zero cracks in a 1 cm square area. Thus, when this embodiment is used, cracks in nitride semiconductor layer 13 can be significantly reduced. This is presumably because the strain inherent in the nitride semiconductor layer 13 is released by the presence of the digging region 14.

  In the present embodiment, a case where the defect concentration region 11 is point-like will be described. The process, structure, and the like are the same as those of the first embodiment except that the defect concentration region 11 of the substrate 10 is point-like.

  When the digging region 14 is not formed as in the conventional example, the nitride semiconductor layer 13 grows in a circular shape from the defect concentration region 11, and the flatness is greatly deteriorated at the meeting portion. As a result of measuring the surface roughness, the surface height difference reached 200 nm.

  FIG. 10 is a top view of the substrate 10 having the dot-like defect concentration region 11. The surface flatness can be improved by forming the digging region 14 in a line including the point-like defect concentration region 11.

  As a result of measuring the surface flatness of the wafer produced by the method of Example 1, the height difference of the surface was 20 nm or less. The yield was almost the same as in Example 1. Moreover, it is preferable that the depth X, the distance Y, and the distance d of the digging region are the same as those in the first embodiment.

  In the present embodiment, a description will be given of a semiconductor laser element in which a digging is formed in addition to the digging region 14 including the defect concentration region 11. Except for the position of the digging area of the substrate 10, the process, structure, and the like are the same as those of the first embodiment.

  FIG. 11A is a top view of the substrate of Example 3, and FIG. 11B is a cross-sectional view of FIG. As the digging region, there are a digging region 14 including the defect concentration region 11 and a digging region 14 a formed in the low defect region 12.

  The purpose of the digging region 14a is to prevent the influence of a low-defect region from spreading over a wide range when an abnormally growing portion such as a region having a different defect or growth surface is included. 12A is a top view when the nitride semiconductor layer 13 is grown without the digging region 14a, and FIG. 12B is a plan view when the nitride semiconductor layer 13 is grown with the digging region 14a. It is a top view. As shown in FIG. 12 (a), if defects or the like are present irregularly in the low defect region 12, abnormal growth occurs because the defect is not dug, and the defect extends to the low defect region 12 over a wide range. . However, it has been found that by forming the dug region 14a also in the low defect region 12, it is possible to prevent propagation of abnormal growth as shown in FIG. That is, the abnormal growth occurring in the low defect region 12a in FIG. 12B also stops propagating by the digging region 14a, and the low defect region 12b can maintain a region with high surface flatness.

  The abnormal growth that occurred in the low-defect region 12a did not propagate to the low-defect region 12b and the level difference in surface flatness was suppressed to 20 nm or less. The width of the digging region 14a was 3 μm or more. If the width is 3 μm or less, the digging region 14a is buried and there is no effect of stopping abnormal growth. On the other hand, when the width is larger than 200 μm, the area of the low defect region 12 is narrowed, so that the region for forming the p-electrode 17 and the like is narrowed, which is not preferable.

  Further, the digging depth X of the digging region 14a is preferably 0.5 μm or more and 50 μm or less for the same reason as in the first embodiment.

  Note that a plurality of the digging regions 14a may be provided between the digging regions 14, and the effect is the same regardless of where the digging regions 14a are formed as long as the formation positions are within the low defect region.

  In the present embodiment, the surface flatness of the nitride semiconductor layer 13 is not created by digging the defect concentration region 11 using an etching method such as RIE, but by creating digging regions at both ends of the defect concentration region 11. This improves the in-plane yield of the characteristics of the semiconductor laser device significantly. The process, structure, and the like are the same as those of the first embodiment except for the position of the digging area of the substrate 10.

  FIG. 13A is a top view of the substrate of Example 4, and FIG. 13B is a cross-sectional view of FIG. Excavation regions 14 b are provided on both sides of the defect concentration region 11. For example, the digging region 14b can have a width of 20 μm and a depth of 3 μm. Reference numeral 12c denotes a low defect region between the dug regions 14b and is referred to as a ridge portion formation region. The ridge portion forming region refers to a region in which a ridge portion that is an optical waveguide region is formed when the nitride semiconductor layer 13 is grown on the substrate 10 and a nitride semiconductor laser device is further formed.

  A nitride semiconductor layer 13 is epitaxially grown on the substrate 10 of FIG. Then, a nitride semiconductor laser device is fabricated on the wafer. FIG. 14A is a cross-sectional view of the nitride semiconductor laser device of Example 4, and FIG. 14B is a top view of FIG. As in FIG. 1A, when the distance between the center of the ridge portion 15 and the end of the digging region 14b is represented by d, d = 100 μm.

  When the digging region 14b is provided on both sides of the defect concentration region 11 of the substrate 10 and the nitride semiconductor layer 13 is grown on the substrate 10 as in the present embodiment, the digging region including the defect concentration region 11 is provided. The surface flatness of the region sandwiched between 14b is very rough.

  However, the surface flatness of the ridge portion forming region 12c shown in FIG. 13 is the highest and lowest portions of the 600 μm width measured for the surface flatness even after the nitride semiconductor layer 13 is epitaxially grown. The height difference was 20 nm or less. This is probably because the propagation of the abnormal growth region can be stopped by the same action as that of the digging region 14a in FIG. Therefore, it was found that the surface flatness can be improved by forming the dug region 14b in the low defect region 12 so as to include the defect concentration region 11 without dug the defect concentration region 11. Thereby, the in-plane distribution of element characteristics can be suppressed and the yield can be dramatically improved.

  The yield was almost the same as in Example 1. Moreover, it is preferable that the depth X, the distance Y, and the distance d of the digging region are the same as those in the first embodiment.

  Further, as a condition for suppressing the level difference in surface flatness to 20 nm or less, the width of the dug region 14b is preferably 3 μm or more and 150 μm or less. When the width is 3 μm or less, the digging region 14 b is buried, and the abnormal growth of the defect concentration region 11 propagates to the low defect region 12. On the other hand, when the width is larger than 150 μm, the area of the low defect region 12 is narrowed, and accordingly, the region for forming the p-electrode 17 and the like is narrowed.

  Further, in the nitride semiconductor laser device of the present embodiment, there were zero cracks in a 1 cm square area. Thus, when this embodiment is used, cracks in nitride semiconductor layer 13 can be significantly reduced. The reason is the same as the reason described in the first embodiment.

  It is an object of the present invention to provide a substrate and a nitride semiconductor light emitting device that improve the yield by uniformizing the characteristics in the wafer plane during the production of the substrate and the nitride semiconductor light emitting device. Another object of the present invention is to prevent the occurrence of cracks by releasing the strain inherent in the nitride semiconductor layer.

DESCRIPTION OF SYMBOLS 10 Substrate 11 Defect concentration area 12 Low defect area 13 Nitride semiconductor layer 14 Excavation area 15 Ridge part

Claims (31)

A substrate having a defect concentration region and a low defect region which is a region excluding the defect concentration region,
A substrate, wherein a digging region is formed in a portion including the defect concentration region, which is dug more than a surface of the low defect region.   2. The substrate according to claim 1, wherein a digging region is formed in the low defect region so as to be dug more than a surface of the low defect region.   The substrate according to claim 2, wherein the digging region formed in the low defect region is formed on both sides of the digging region formed in a portion including the defect concentration region.   The substrate according to any one of claims 1 to 3, wherein a distance from an end of a dug area formed in a portion including the defect concentration area to an end of the defect concentration area is 5 µm or more. A substrate having a defect concentration region and a low defect region which is a region excluding the defect concentration region,
A substrate characterized in that a digging region dug out from the surface of the low defect region is formed only in the low defect region.   The substrate according to claim 5, wherein the digging region is formed on one side of the defect concentration region.   The substrate according to claim 5, wherein the digging region is formed on both sides of the defect concentration region.   The substrate according to claim 5, wherein a distance from an end of the digging region to an end of the defect concentration region is 5 μm or more.   The substrate according to claim 1, wherein the substrate is made of gallium nitride.   The substrate according to claim 1, wherein the defect concentration region is linear.   The substrate according to claim 10, wherein the linear defect concentration region extends in a [1-100] direction.   The substrate according to claim 1, wherein the defect concentration region has a dot shape.   The substrate according to any one of claims 1 to 12, wherein a digging depth of the digging region is 0.5 µm or more and 50 µm or less.   A nitride semiconductor light emitting device comprising: the substrate according to claim 1; and a nitride semiconductor layer laminated on the substrate.   15. The nitridation according to claim 14, wherein the nitride semiconductor layer has a ridge portion that is a laser light waveguide region, and the ridge portion is formed at a distance of 5 μm or more from an end of the digging region. Semiconductor light emitting device.   The nitride semiconductor light emitting device according to claim 14, wherein an n-type electrode is formed on a lower surface of the substrate, and a p-type electrode is formed on an upper surface of the nitride semiconductor layer. A method of manufacturing a substrate having a defect concentration region and a low defect region which is a region excluding the defect concentration region,
A method of manufacturing a substrate, comprising a step of forming a digging region that is dug more than a surface of the low defect region in a portion including the defect concentration region.   The method for manufacturing a substrate according to claim 17, further comprising a step of forming a digging region dug in the low defect region from a surface of the low defect region.   19. The substrate according to claim 18, further comprising a step of forming a digging region formed in the low defect region on both sides of a digging region formed in a portion including the defect concentration region. Manufacturing method.   Forming the digging region in the portion including the defect concentration region so that the distance from the end of the digging region formed in the portion including the defect concentration region to the end of the defect concentration region is 5 μm or more. The substrate manufacturing method according to claim 17, wherein the substrate is contained. A method of manufacturing a substrate having a defect concentration region and a low defect region which is a region excluding the defect concentration region,
A method for manufacturing a substrate, comprising a step of forming a digging region which is dug more than the surface of the low defect region only in the low defect region.   The method for manufacturing a substrate according to claim 21, further comprising a step of forming the digging region on one side of the defect concentration region.   22. The method for manufacturing a substrate according to claim 21, further comprising a step of forming the digging region on both sides of the defect concentration region.   24. The step of forming the digging region is included so that the distance from the end of the digging region to the end of the defect concentration region is 5 μm or more. The manufacturing method of the board | substrate of description.   The method for manufacturing a substrate according to any one of claims 17 to 24, wherein the step of forming the digging region is performed using vapor phase etching.   The method for manufacturing a substrate according to claim 25, wherein reactive ion etching (RIE) is used as the vapor phase etching.   The method for manufacturing a substrate according to any one of claims 17 to 26, wherein the substrate is a substrate made of gallium nitride.   The substrate according to any one of claims 17 to 27, wherein the defect concentration region is a substrate, and the linear defect concentration region is a substrate extending in a [1-100] direction. Production method.   A method for manufacturing a nitride semiconductor light emitting device, comprising a step of forming a nitride semiconductor layer on a substrate obtained by the method for manufacturing a substrate according to any one of claims 17 to 28.   30. The nitride semiconductor according to claim 29, wherein the nitride semiconductor layer includes a step of forming a ridge portion that is a laser light waveguide region at a distance of 5 μm or more from an end of the digging region. Manufacturing method of light emitting element.   31. The nitride semiconductor according to claim 29, further comprising forming an n-type electrode on the lower surface of the substrate and forming a p-type electrode on the upper surface of the nitride semiconductor layer. Manufacturing method of light emitting element.

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