JP2009283588A - Method of manufacturing nitride-semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a nitride-semiconductor light emitting device that improves a yield by equalizing an emission wavelength of a nitride-semiconductor light emitting device to be manufactured. <P>SOLUTION: A light-emitting element is manufactured by using a substrate 50. The substrate is configured such that the closer to the center side, the synthetic off-angle becomes closer to 0° while the closer to the outside, the synthetic off-angle becomes larger when a wafer, obtained by using a prescribed manufacturing method, shows such characteristics that the closer to the center side, the shorter its emission wavelength is while the closer to the outside, the longer its emission wavelength is. By using such a substrate 50, it becomes possible to reduce unevenness in distribution of the emission wavelength of the wafer due to the characteristics of the manufacturing method, thereby improving a yield. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a nitride semiconductor light emitting device, and more particularly to a method for manufacturing a nitride semiconductor light emitting device by laminating a layer made of a nitride semiconductor on a nitride semiconductor substrate.

  A nitride semiconductor (eg, AlN, GaN, InN, AlGaN, InGaN, etc.), which is a so-called III-V group semiconductor composed of a group III element and a group V element, emits blue or blue-violet light from its band structure. Expected to be used as an element, it has already been used for light emitting elements such as light emitting diodes and laser elements.

  In addition, since a high-quality nitride semiconductor substrate has not been obtained so far, a nitride semiconductor laser device or the like has been manufactured using a heterogeneous substrate such as a sapphire substrate. However, since a different substrate such as a sapphire substrate has a cleavage direction different from that of a nitride semiconductor, there has been a problem that it is difficult to divide the wafer.

With respect to these problems, high-quality nitride semiconductor substrates can be obtained in recent years, and by using these substrates, a nitride semiconductor light emitting device in which the above-described problems are solved can be obtained. (See Patent Document 1).
JP 2007-294985 A

  However, even if a high-quality nitride semiconductor substrate is used, a chip obtained from one wafer is mounted depending on the characteristics of the manufacturing apparatus and manufacturing method (for example, the temperature distribution of the substrate during growth and the flow of raw materials). There arises a problem in that the characteristics of the nitride semiconductor light emitting device vary. In particular, since the emission wavelength varies from chip to chip, it is difficult to keep the emission wavelength of the obtained nitride semiconductor light emitting element within a predetermined range. Therefore, the yield of the nitride semiconductor light emitting device is poor.

  Accordingly, an object of the present invention is to provide a method for manufacturing a nitride semiconductor light emitting device in which the light emission wavelength of the nitride semiconductor light emitting device to be manufactured is made uniform and the yield is improved. Another object of the present invention is to equalize various characteristics such as an optical confinement factor and an operating voltage, not limited to the emission wavelength.

  In order to achieve the above object, a method for manufacturing a nitride semiconductor light emitting device according to the present invention includes a layered structure including a layer made of a nitride semiconductor on a main surface of a substrate by a predetermined manufacturing method. Based on the manufacturing method characteristics showing the distribution of characteristics in a plane parallel to the main surface of the substrate of the laminated structure, using the first manufacturing method of the adjustment substrate made of a nitride semiconductor, the predetermined manufacturing method, A nitride semiconductor device is manufactured using the second step of manufacturing the wafer by manufacturing the laminated structure on the main surface of the adjustment substrate obtained by the first step, and the wafer obtained by the second step. And a third step.

  Further, in the method for manufacturing a nitride semiconductor light emitting device having the above-described configuration, the manufacturing method characteristic indicates a distribution of emission wavelengths in a plane parallel to a main surface of the substrate of the stacked structure, The combined off angle of the portion corresponding to the portion where the emission wavelength becomes the shortest in the manufacturing method characteristics may be set to 0 °.

  Further, in the method for manufacturing a nitride semiconductor light emitting device having the above-described configuration, the combined off angle of the adjustment substrate other than the portion corresponding to the portion where the emission wavelength is the shortest in the manufacturing method characteristics is larger than 0 °. It doesn't matter.

  By adopting such a configuration, it is possible to reduce variation in emission wavelength distribution in the entire laminated structure manufactured on the adjustment substrate. Further, the adjustment substrate may be provided with a distribution of a combined off angle according to the distribution of the emission wavelength.

  Further, in the method for manufacturing a nitride semiconductor light emitting device having the above-described configuration, the manufacturing method characteristics are such that the emission wavelength becomes shorter toward the center side and the emission wavelength becomes longer toward the outside side, and the combined off angle of the adjustment substrate is The value may be close to 0 ° toward the center side and increase toward the outside side.

  Further, in the method for manufacturing a nitride semiconductor light emitting device having the above-described structure, the predetermined manufacturing method allows the raw material for manufacturing the stacked structure to flow from a predetermined direction and the main material of the substrate while the raw material flows. The laminated structure may be manufactured by rotating around the center of the surface.

  Further, in the method for manufacturing a nitride semiconductor light emitting device having the above-described structure, before the first step, the main surface of the test substrate having a uniform synthetic off angle is formed on the main surface using the predetermined manufacturing method. A fourth step of producing a laminated structure and obtaining the production method characteristics based on the produced laminated structure may be further provided. Further, the composite off angle of the main surface of the test substrate may be uniform at 0 ° in the plane.

  With such a configuration, it is possible to obtain precise manufacturing method characteristics, and it is possible to manufacture an adjustment substrate that is optimal for a predetermined manufacturing method. Therefore, in-plane variations in the characteristics of the nitride semiconductor light emitting element such as the emission wavelength can be made more uniform.

  Moreover, in the method for manufacturing a nitride semiconductor light emitting device having the above-described structure, the stacked structure may include at least one layer made of InGaN.

  By adopting such a configuration, the In concentration, which is a parameter that has a significant influence on various characteristics of the nitride semiconductor light emitting device such as the emission wavelength, the optical confinement coefficient, and the operating voltage, is set to the composite off angle of the adjustment substrate. It becomes possible to control easily by controlling.

  In the method for manufacturing a nitride semiconductor light emitting device according to the present invention, an adjustment substrate is manufactured based on the distribution of characteristics of the laminated structure manufactured by a predetermined manufacturing method, and a predetermined manufacturing method is provided on the main surface of the adjustment substrate. A nitride semiconductor light emitting device is manufactured using a wafer having a stacked structure formed by using the wafer. Therefore, it is possible to reduce variation in characteristics due to a predetermined manufacturing method using the adjustment substrate. In particular, it is possible to reduce variation in the emission wavelength of the obtained light-emitting element and to make the emission wavelength uniform. Therefore, the yield of the nitride semiconductor light emitting device can be improved.

Hereinafter, a nitride semiconductor laser element will be described as an example of the nitride semiconductor light emitting element, and a method for manufacturing the nitride semiconductor light emitting element in the present invention will be described. First, the basic configuration of the method for manufacturing a nitride semiconductor light emitting device in the present invention will be described.
<< Basic configuration >>
<Production method characteristics>
First, an example of a manufacturing method characteristic that is a distribution of characteristics according to a manufacturing method of a stacked structure manufactured over a substrate will be described. In addition, the distribution of emission wavelengths when a multiple quantum well structure is formed on a substrate is given as an example of the characteristics of the manufacturing method, and this example will be described below.

  FIG. 1 is a graph showing an example of fabrication method characteristics, and shows a measurement result of a PL (Photoluminescence) peak wavelength of a wafer 100 in which a multiple quantum well structure made of InGaN is fabricated on a {0001} plane of a 2-inch sapphire substrate. It is shown. Here, the multiple quantum well structure made of InGaN is the same as the structure shown in the configuration example of the nitride semiconductor laser chip described later. In this example, it is assumed that a multiple quantum well structure is formed using a MOCVD (Metal Organic Chemical Vapor Deposition) method.

  In the example shown in FIG. 1, the distribution is such that the emission wavelength from the multiple quantum well structure formed on the center side of the wafer 100 is shorter and the emission wavelength of the multiple quantum well structure formed on the outer side is longer. ing. In other words, when an InGaN multiple quantum well structure is fabricated using the fabrication method in this example, In is less likely to be captured toward the center side of the wafer, and In is more likely to be captured toward the outside.

  As a manufacturing method of such a wafer 100, for example, there is a manufacturing method shown in FIG. FIG. 2 is a schematic perspective view showing a method for manufacturing a wafer. In FIG. 2, for the sake of simplicity, illustration of the reactor, the susceptor, and the like is omitted. As shown in FIG. 2, in the manufacturing method of this example, growth is performed by flowing a raw material and a carrier gas from a predetermined direction (a direction substantially parallel to the main surface of the substrate 101) and rotating the substrate 101. When such a manufacturing method is used, a wafer 100 having manufacturing method characteristics as shown in FIG. 1 is obtained.

  Therefore, when a wafer is manufactured using this manufacturing method and a light emitting element is manufactured, the light emission wavelength of the light emitting element on which the chip obtained from the center side of the wafer is mounted becomes short, and the light emission on which the chip obtained from the outside of the wafer is mounted. The light emission wavelength of the element becomes longer.

  In the present invention, in order to reduce such variation in emission wavelength distribution, that is, variation in manufacturing method characteristics, a wafer is manufactured using a substrate having predetermined characteristics described later, and a light emitting element is manufactured. Note that in the case where manufacturing method characteristics are predicted in advance, the above-described process for checking manufacturing method characteristics may be simplified or eliminated.

  On the other hand, before manufacturing the light emitting element, a step of examining the distribution of the emission wavelength of the wafer 100, that is, the characteristics of the manufacturing method may be performed by using a method such as PL measurement as described above. Further, the light emission wavelength distribution of the wafer 100 may be examined by actually manufacturing and operating the light emitting elements and examining the light emission wavelengths of the respective light emitting elements. Further, the substrate used for the wafer 100 manufactured for examining the distribution of the emission wavelength may be a substrate other than the sapphire substrate. Further, the manufacturing method characteristics may be examined using a method other than the above-described method.

The InGaN multiple quantum well structure may be a structure including a barrier layer made of GaN and a well layer made of InGaN, or a barrier layer made of InGaN and a well layer made of InGaN having a larger In composition than the barrier layer. The structure may be used.
<Substrate characteristics>
Next, a method for reducing the variation in the emission wavelength distribution of the wafer 100 described above will be described. The method for manufacturing a nitride semiconductor light emitting device according to the present invention is a method for manufacturing a light emitting device by using a nitride semiconductor substrate having a synthetic off-angle corresponding to the distribution of the emission wavelength of the wafer 100 described above. It is. Here, the combined off angle is defined by the following formula (I). In addition, a GaN substrate is taken as an example of the nitride semiconductor substrate and will be described below.

Composite off angle = (A ² + B ² ) ^1/2 (I)
A represents the off angle in the <11-20> direction of the substrate, and B represents the off angle in the <1-100> direction of the substrate.

  FIG. 3 is a graph showing the relationship between the combined off-angle of the substrate and the emission wavelength. As shown in FIG. 3, the larger the combined off angle of the substrate, the shorter the emission wavelength of the light emitting structure formed thereon. That is, when the synthetic off-angle of the substrate is increased, the incorporation of In is suppressed, and when the synthetic off-angle of the substrate is decreased, the incorporation of In is promoted.

  The method for manufacturing a nitride semiconductor light emitting device of the present invention is to manufacture a light emitting device using a substrate having a non-uniform off angle. For example, when a wafer is manufactured using a manufacturing method in which In is less likely to be captured toward the center side of the substrate and In is more likely to be captured toward the outer side, the synthesis off angle is smaller toward the center side of the substrate and the synthesis off is performed toward the outer side. A substrate with a large corner is used. By manufacturing a nitride semiconductor light emitting device by such a method, it is possible to reduce variations in manufacturing method characteristics including variations in the emission wavelength distribution of the wafer.

  An example of this substrate will be described with reference to FIG. FIG. 4 is a schematic plan view showing an example of the substrate, and shows a GaN substrate whose main surface is a {0001} plane.

  In the example of the substrate described below, the off angle refers to an angle of deviation between the {0001} plane of the crystal and the main surface of the substrate. In addition, the off angle in a certain direction is expressed with a positive / negative sign, but the case where the positive / negative is different means that the inclination of the crystal with respect to the normal of the principal surface of the <0001> axis is different. And

  Further, in the present application, since the substrate having a non-uniform off angle is used, the crystal orientations of the various portions of the substrate are slightly different. However, these crystal orientation shifts are very small, and the orientations are almost uniform overall. Therefore, the case where the entire substrate is described is treated as having the same crystal orientation.

  As shown in FIG. 4A, the substrate 50 has a center off-angle substantially equal to 0 ° in both the <1-100> direction and the <11-20> direction. That is, the crystal plane near the center is the plane closest to the {0001} plane. Further, the off-angle varies monotonously along each direction. Here, for the sake of simplicity, only the <1-100> direction and the <11-20> direction are shown, but the same relationship applies to other directions.

  Further, as shown in FIG. 4B, the synthetic off angle of the substrate 50 becomes larger toward the outside, and the center side has a value substantially equal to 0 °. Therefore, if a light emitting structure is formed on the substrate 50, the wavelength becomes shorter because In is less likely to be taken in toward the outer side, and the wavelength is longer because In is more likely to be taken in toward the center side.

  Therefore, when a light emitting structure is formed on the substrate 50 using a manufacturing method for manufacturing the wafer 100 as shown in FIG. 1, In is captured due to the characteristics of the substrate 50 on the outside because In is easily captured due to the characteristics of the manufacturing method. In the center side where it is difficult to capture In due to the characteristics of the manufacturing method, In is easily captured due to the characteristics of the substrate 50.

  In this manner, by making the characteristics of the manufacturing method and the characteristics of the substrate 50 opposite to each other, it is possible to reduce variations in emission wavelength distribution caused by the characteristics of the manufacturing method due to the characteristics of the substrate 50. Accordingly, the light emission wavelength of a light-emitting element manufactured using this manufacturing method can be made uniform, and the yield of the light-emitting elements can be improved.

  Another example of the substrate will be described with reference to FIGS. 5 and 6 are schematic plan views showing an example of the substrate, and show a GaN substrate having a {0001} plane as the main surface, as in FIG.

  As shown in FIG. 5A, the substrate 51 shown in FIG. 5 has a value that is substantially equal to 0 ° at the center while the off-angle varies monotonously with respect to the <1-100> direction. On the other hand, in the <11-20> direction, which is a direction perpendicular to the <1-100> direction, there are slight variations in both A2 passing through the center of the substrate 51 and A1 and A3 deviating from the center. It becomes a substantially constant value. A1 and A3 are in symmetrical positions with A2 as an axis, and have different off-angle signs.

  Further, as shown in FIG. 5B, the combined off angle in the <1-100> direction of the substrate 51 increases toward the outside, and is approximately equal to 0 ° at the center. On the other hand, in the <11-20> direction, A2 is substantially constant at a value substantially equal to 0 °, and A1 and A3 are constant at a certain value.

  The substrate 52 shown in FIG. 6 is the same as the substrate 51 shown in FIG. However, as shown in FIG. 6A, in this example, the off-angle varies monotonously with respect to the <11-20> direction, and is substantially equal to 0 ° at the center. On the other hand, in the <1-100> direction, both B2 passing through the center of the substrate 52 and B1 and B3 deviating from the center have slight fluctuations, which are substantially constant values. Further, B1 and B3 are in symmetrical positions with respect to B2, and the off-angle signs are different.

  Further, as shown in FIG. 6B, the combined off angle in the <11-20> direction of the substrate 52 becomes larger toward the outside, and the center becomes a value substantially equal to 0 °. On the other hand, in the <1-100> direction, B2 is substantially constant at a value substantially equal to 0 °, and B1 and B3 are constant at a certain value.

  When the substrate 51 shown in FIG. 5 is used, it is possible to reduce variation in emission wavelength distribution mainly in the <1-100> direction. In the case where the substrate 52 shown in FIG. 6 is used, it is possible to reduce variation in emission wavelength distribution mainly in the <11-20> direction. Accordingly, it is possible to make the light emission wavelength of most of the light emitting devices manufactured uniform, and to improve the yield of the light emitting devices.

  Further, a substrate other than the substrates 50 to 52 shown in FIGS. 4 to 6 may be used. For example, a substrate in which the direction of single flow is a direction other than the substrate 51 shown in FIG. 5 or the substrate 52 shown in FIG. 6 may be used. Even when other substrates are used, it is possible to efficiently emit light if the portion where the emission wavelength is shortened due to the characteristics of the manufacturing method and the portion where the combined off angle of the substrate is approximately equal to 0 ° overlap. Variations in wavelength distribution can be reduced.

Further, in the case of manufacturing a wafer in which the portion where the emission wavelength is shortened from the center by using a method different from the above-described manufacturing method, the portion in which the combined off angle is 0 ° is similarly removed from the center. We will use it. By using such a substrate, variations in the emission wavelength distribution of the wafer can be reduced. Therefore, no matter how the emission wavelength distribution varies, it is possible to reduce variations by changing the characteristics of the substrate.

  Further, the off angle and the combined off angle of the substrates 50 to 52 shown in FIGS. 4 to 6 may vary nonlinearly or may vary linearly. Furthermore, it may be adapted to the distribution of the emission wavelength of the wafer. By configuring the substrates 50 to 52 in this way, it becomes possible to further uniform the emission wavelength.

  Further, the wafer manufacturing method is not limited to the MOCVD method. For example, an MBE (Molecular Beam Epitaxy) method or an HVPE (Hydride Vapor Phase Epitaxy) method can also be used. Further, a plurality of manufacturing methods may be used. Even when these manufacturing methods are used, variation in the distribution of the emission wavelength of the wafer can be reduced by controlling the synthesis off angle of the substrate.

  In the example described above, the case where the variation in the emission wavelength distribution is reduced has been described, but the variation in other characteristics can also be reduced. For example, in a plane of a layer (for example, an InGaN layer provided as a barrier layer of a quantum well structure or an optical guide layer) provided in the vicinity of a layer that emits light (for example, an InGaN layer provided as a well layer of a quantum well structure) Since the distribution of In concentration in is also made uniform, the band gap and refractive index of these layers can be made uniform, and the optical confinement coefficient can be made uniform. Therefore, it is possible to make the spread angle of light emitted from the obtained light emitting element uniform, particularly the spread angle in the direction perpendicular to the main surface of the substrate.

Furthermore, since the distribution of In concentration in the plane of a semiconductor layer (for example, an InGaN layer used as a contact layer) in contact with the metal layer that is an electrode is made uniform, the size of the energy barrier between the metal layer and the semiconductor layer is increased. Can be made uniform. Therefore, it is possible to make the operating voltage characteristics and the threshold voltage of the obtained light emitting element uniform.
<< Example >>
Next, an example of a nitride semiconductor laser element obtained by using the manufacturing method described above will be described. First, the configuration and manufacturing method of a laser chip mounted on this laser element will be described.
<Laser chip configuration>
The configuration of the nitride semiconductor laser chip will be described with reference to FIG. FIG. 7 is a schematic plan view and cross-sectional view showing the configuration of the nitride semiconductor laser chip. Here, FIG. 7A shows a schematic plan view of the nitride semiconductor laser chip, and FIG. 7B shows a schematic cross-sectional view taken along the line AA of FIG. 7A. Show.

  As shown in FIGS. 7A and 7B, the laser chip 1 includes an n-type cladding layer 3, an active layer 4, and a light guide on the {0001} plane of the substrate 2 from below to above. The layer 5, the cap layer 6, the p-type cladding layer 7 and the contact layer 8 are laminated. Each of these layers is epitaxially grown and stacked. In this example, a crystal that inherits the orientation relationship of the underlying crystal is growing. In the following description, when the structure is described using the crystal orientation relationship, the crystal orientation relationship is indicated.

  A part of the p-type cladding layer 7 protrudes in a direction substantially parallel to the <0001> direction, and the protruding portion extends in a direction substantially parallel to the <1-100> direction. A contact layer 8 is provided on the upper surface of the protruding portion of the p-type cladding layer 7, and an ohmic electrode 9 is formed on the upper surface of the contact layer 8. These protruding portions serve as current passage portions (ridge portions 10). A current blocking layer 11 is formed on the surface of the p-type cladding layer 7 that does not protrude, that is, the upper surface of the portion other than the ridge portion 10.

  A pad electrode 12 is formed on the upper surface of the ridge portion 10 and a part of the upper surface of the current blocking layer 11, and an n-side electrode 13 is formed on the lower surface of the substrate 2. Although not shown, a protective film is formed on the resonator end face (end face substantially perpendicular to the <1-100> direction) from which light is emitted or reflected.

In FIG. 7, the pad electrode 12 covers a part of the ridge portion 10 and does not cover the ridge portion 10 in the vicinity of the resonator end face, but the entire ridge portion 10 may be covered. Further, the protective film is made of SiO ₂ , TiO ₂ , Al ₂ O ₃ , AlN, ZrO _2, etc., and the reflectance of the protective film formed on the reflection side end surface is the protection formed on the output side end surface. It may be configured to be higher than the reflectance of the film.
<Laser chip fabrication method>
(Wafer preparation method)
Next, a method for manufacturing a laser chip will be described with reference to the drawings. First, an example of a method for manufacturing a wafer for manufacturing a laser chip will be described with reference to FIGS. FIG. 8 is a schematic cross-sectional view showing an example of a method for manufacturing a wafer, and shows a cross section similar to that of the laser chip shown in FIG.

  First, an n-type GaN substrate 2 having {0001} as the main surface and a thickness of about 100 μm and a combined off-angle controlled as described above is manufactured. Then, as shown in FIG. 8A, an n-type cladding layer 3 made of n-type AlGaN and having a thickness of about 1.5 μm is stacked with the {0001} plane of the substrate 2 as the growth surface. An active layer 4 is laminated on the upper surface of the n-type cladding layer 3. As shown in the schematic cross-sectional view showing the configuration of the active layer in FIG. 9, the active layer 4 includes a well layer 4a made of undoped InGaN and a thickness of about 3.2 nm, and a thickness of about 20 nm made of undoped GaN. And a multiple quantum well structure formed by alternately stacking a plurality of barrier layers 4b. Here, FIG. 9 shows a case where three well layers 4a and four barrier layers 4b are stacked. The barrier layer 4b may be made of InGaN.

  Further, an optical guide layer 5 made of undoped InGaN and having a thickness of about 75 nm is laminated on the active layer 4 having the multiple quantum well structure. A 20 nm cap layer 6 is laminated. A p-type cladding layer 7 made of p-type AlGaN and having a thickness of about 500 nm is laminated on the upper surface of the cap layer 6. Then, a contact layer 8 made of undoped InGaN and having a thickness of about 3 nm is laminated on the p-type cladding layer 7. FIG. 8A shows a state in which the above-described layers 3 to 8 are stacked on the growth surface of the substrate 2.

Then, a p-side ohmic electrode 9 composed of a Pt layer having a thickness of about 1 nm and a Pd layer having a thickness of about 30 nm is formed on the upper surface of the contact layer 8, and a thickness of about 230 nm is formed on the p-side ohmic electrode 9. An SiO ₂ layer 14 is formed. In this way, each layer is formed to obtain a structure as shown in FIG.

Next, the structure shown in FIG. 8B is etched to form the ridge portion 10. At this time, a striped photoresist (not shown) having a width of about 1.5 μm and extending in the <1-100> direction is formed in a portion where the ridge portion 10 is to be formed. Then, etching by the RIE method is performed using a CF ₄ gas. Then, only the SiO ₂ layer 14 and the ohmic electrode 9 of the part forming the photoresist remains, the SiO ₂ layer 14 and the ohmic electrode 9 of the portion not forming a photoresist is removed.

Then, the photoresist is removed and etching is performed by the RIE method using a chlorine-based gas such as Cl ₂ or SiCl ₄ . At this time, using the SiO ₂ layer 14 as a mask, the SiO ₂ layer 1
The contact layer 8 and the p-type cladding layer 7 in the portion where 4 is not formed are etched. Then, the etching is stopped when the p-type cladding layer 7 remains about 80 nm, and the SiO ₂ layer 14 used as a mask is removed. Then, as shown in FIG. 8C, a part of the p-type cladding layer 7 protrudes, and a ridge part in which the contact layer 8 and the ohmic electrode 9 are sequentially formed on the protruding part of the p-type cladding layer 7. A structure with 10 is obtained.

Next, an SiO ₂ layer having a thickness of 180 nm is formed on the structure shown in FIG. 8C, and a photoresist is formed on the SiO ₂ layer formed in a portion other than the ridge portion 10. Then, etching by RIE using CF ₄ gas is performed, and the SiO ₂ layer formed on the ridge portion 10 is removed to form the current blocking layer 11 made of the SiO ₂ layer. As a result, a structure as shown in FIG.

  Further, with respect to the structure shown in FIG. 8D, a Ti layer having a thickness of about 30 nm, a Pd layer having a thickness of about 140 nm, and a thickness of about 140 nm are formed so as to cover the ridge portion 10 surrounded by the current blocking layer 11. A plurality of 3 μm-thick pad electrodes 12 formed by sequentially forming a 2400 nm Au layer are formed. Then, an Al layer having a thickness of about 6 nm, a Pd layer having a thickness of about 10 nm, and an Au layer having a thickness of about 600 nm are sequentially formed on the surface opposite to the growth surface of the substrate 2. By forming the n-side electrode 13, a wafer 20 as shown in FIG. 10 is obtained. FIG. 10 is a schematic plan view and cross-sectional view showing the configuration of the wafer. The plan view shown in FIG. 10A shows the same plane as FIG. 7A, and the cross-sectional view shown in FIG. 10B shows the same cross section as FIG. 7B. It is a thing.

  As shown in FIG. 10, a plurality of ridge portions 10 are formed on the wafer 20, each extending in the <1-100> direction and having a continuous shape. Further, a plurality of pad electrodes 12 are formed along each ridge portion 10, and the wafer 20 is cleaved and divided to obtain the laser chip 1 as shown in FIG. As an example, the case where the pad electrode 12 is divided in advance so as to be formed one by one for each laser chip has been described, but the pad electrode 12 is formed so as to be continuous along each ridge portion 10. It does not matter if it is done.

In the wafer manufacturing method described above, the MOCVD method may be used to form the layers 3 to 8 made of nitride semiconductor, or the MBE method, the HVPE method, and other methods may be used. The electrode layers 9, 12, and 13 may be formed by using a forming method such as sputtering or vapor deposition. As the vapor deposition, electron beam vapor deposition may be used, or resistance heating vapor deposition may be used. Absent. Further, a method such as PECVD (Plasma Enhanced Chemical Vapor Deposition) or sputtering may be used to form the SiO ₂ layer 14 and the current blocking layer 11.

  Further, although the thickness of the substrate 2 is set to 100 μm, the stacking may be started with a thickness of about 400 μm in order to facilitate handling. In this case, polishing or the like may be performed at the latest before the n-side electrode 13 is formed, and the substrate 2 may be thinned to a thickness of about 100 μm.

  When the single-flow substrates 51 and 52 as shown in FIGS. 5 and 6 are used, the single-flow direction may be selected based on the arrangement of the wafer 20 shown in FIG. For example, when there are more chips obtained from the vicinity of both ends in the <1-100> direction than in the vicinity of both ends in the <11-20> direction, the substrate 52 that flows in the <1-100> direction is used. By selecting the direction of single flow in this way, the portion where the emission wavelength is slightly deviated from the portion where the wafer 20 is wasted overlap, so that the yield can be further improved.

(Wafer cutting method)
Next, a method of obtaining the laser chip 1 shown in FIG. 7 by cleaving and dividing the wafer 20 shown in FIG. 10 will be described with reference to FIG. FIG. 11 is a schematic plan view showing the configuration of bars and chips. The plan views shown in FIGS. 11A and 11B show the same plane as the planes shown in FIGS. 7A and 10A.

  As shown in FIG. 11A, first, the wafer 20 shown in FIG. 10 is cleaved along the <11-20> direction to obtain the bar 30. At this time, the bar 30 is cleaved to form two end surfaces (surfaces substantially parallel to the {1-100} surface), and these end surfaces become the resonator end surfaces. Further, the bar 30 is configured such that a plurality of laser chips are aligned in a line in the <11-20> direction.

Further, a protective film made of, for example, SiO ₂ , TiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ or the like is formed on the resonator end face of the obtained bar 30. Then, the protective film formed on one of the end faces is made of, for example, a large number of layers of about 10 layers, and the reflectance is increased, and the protective film formed on either one of the end faces is made of, for example, one layer The reflectivity is low as it consists of a few layers. Then, as shown in FIG. 11B, the laser chip 1 is obtained by dividing the obtained bar 30 along the <1-100> direction.

  In the cleavage from the wafer 20 to the bar 30 and the division from the bar 30 to the chip 1, grooves along the respective cleavage direction and the division direction are formed in the wafer 20 or the bar 30, and cleavage and It is also possible to perform division. The groove may be a solid line or a broken line, or may be formed using a diamond point or a laser. Further, a groove may be formed on the surface of the wafer 20 or the bar 30 where the pad electrode 12 or the current blocking layer 11 is formed, or it may be formed on the surface where the n-side electrode 13 is formed. It doesn't matter.

(Laser element)
Next, an example of a laser element provided with the laser chip 1 shown in FIG. 7 will be described with reference to FIG. FIG. 12 is a schematic perspective view showing an example of a laser element. As shown in FIG. 12, the laser element 40 includes a submount 43 to which the laser chip 1 is connected and fixed (mounted) by solder, a heat sink 42 connected to the submount 43, and a heat sink 42 connected to a predetermined surface. Stem 41, pins 44a and 44b that pass through a predetermined surface of stem 41 and a surface opposite to the predetermined surface and are insulated from stem 41, one pin 44a and a pad electrode of laser chip 1 12, and a wire 45 b that electrically connects the other pin 44 b and the submount 43.

  Although not shown in order to display the configuration of the laser element 40 in an easy-to-understand manner, the laser element 40 is connected to a predetermined surface of the stem 41, and is connected to the laser chip 1, the submount 43, the heat sink 42, and the pins 44a and 44b. A cap is provided that seals a portion protruding from a predetermined surface of the stem 41 and the wires 45a and 45b.

  Then, current is supplied to the laser chip 1 through the two pins 44 a and 44 b to oscillate, and laser light is emitted from the laser chip 1. At this time, the cap is provided with a window made of a material transparent to the emitted laser beam, and the laser beam is emitted through the window.

Note that the configuration of the laser element 40 shown in FIG. 12 is merely an example, and the configuration of the manufactured laser element is not limited to this. For example, a configuration that includes a detection unit configured to detect output of light emitted from a photodiode or the like and that outputs a predetermined amount of light from the laser chip 1 by feeding back the detection result to the power supply device may be employed. Absent. Further, the number of pins may be three, and one pin may be used as a common pin for the detection unit and the laser chip 1, and the remaining two pins may be connected to the laser chip and the detection unit, respectively.

In FIGS. 1, 4 to 6 and 10, the substrates 50 to 52 and the wafers 20 and 100 are shown as substantially circular for the sake of simplicity. However, the orientation flat surface for specifying the crystal orientation It does not matter as a shape including a notch.
<< Example of substrate manufacturing method >>
In addition, an example of a method for manufacturing the substrates 50 to 52 illustrated in FIGS. 4 to 6 will be described below. First, a single crystal ingot for cutting out a substrate will be described with reference to FIG. FIG. 13 is a schematic perspective view and a cross-sectional view of an ingot. In the ingot 60 shown in FIG. 13, for example, GaN is grown in the <0001> direction on a GaAs substrate (not shown) having a (111) plane as a main surface by using a vapor phase growth method such as the HVPE method. Thus, it is obtained by removing GaAs. Details of this manufacturing method are described in, for example, JP-A-2005-206424. Also, the illustration of the lower side of the ingot 60 that is the GaAs substrate side is omitted.

  The upper surface 60a of the ingot 60 manufactured using the method described above warps in a convex shape or a concave shape with respect to the <0001> direction. That is, the ingot 60 is a single crystal but slightly distorted. FIG. 13 shows an example in which the upper surface 60a warps in a concave shape. FIG. 13A shows a perspective view of the ingot 60, and FIG. 13B shows a cross-sectional view taken along the line BB of FIG. 13A. Moreover, the broken line in FIG.13 (b) has each shown about the <0001> direction of the crystal | crystallization.

  As shown in FIG. 13B, the central axis Ac of the ingot 60 is substantially parallel to the <0001> direction. However, as the distance from the central axis Ac increases, the <0001> direction of the crystal is inclined from the central axis Ac. For example, in C1 and C2 indicating the <0001> direction, the angle θ1 formed by C1 closer to the central axis Ac is smaller and the angle θ2 formed by C2 farther from the central axis Ac is larger.

  Further, FIG. 14 shows a schematic cross-sectional view in the case where such an ingot 60 is cut perpendicularly to the central axis Ac to obtain a substrate. FIG. 14A is a cross-sectional view of an ingot showing a cutting direction, and FIG. 14B is a cross-sectional view of a substrate obtained by cutting the ingot. 14 (a) and 14 (b) both show a cross section corresponding to FIG. 13 (b).

  As shown in FIG. 14A, a substrate 61 as shown in FIG. 14B is obtained by cutting perpendicularly to the central axis Ac. In the substrate 61, the central crystal plane coincides with the {0001} plane, and the synthetic off angle increases toward the outer side. Further, the sign of the off-angle becomes positive and negative across the central axis Ac. Therefore, by cutting the ingot 60 in this way, a substrate 61 similar to the substrate 50 shown in FIG. 4 described above can be produced.

  FIG. 15 shows a schematic cross-sectional view when the ingot is cut in a direction that is not perpendicular to the central axis Ac, for example, perpendicular to C1. FIG. 15A is a sectional view showing the cutting direction of the ingot, and FIG. 15B is a sectional view of the substrate. FIGS. 15A and 15B correspond to FIGS. 14A and 14B, respectively.

By cutting as shown in FIG. 15A, the portion where the combined off angle is 0 ° becomes the portion C1. Therefore, it is possible to obtain the substrate 62 in which the portion where the combined off angle is 0 ° is off the center. Therefore, it is possible to obtain a substrate in which a portion where the combined off angle is 0 ° is formed at an arbitrary position.

  Further, by cutting the ingot 60 from a direction that is not perpendicular to the central axis Ac in this way, a certain direction (direction perpendicular to C1 in a plane parallel to C1 (the cross section shown in FIG. 15B)). The substrate 62 can be obtained in which the off-angle varies and the off-angle variation is small in a direction perpendicular to a certain direction. That is, a single-flow substrate such as the substrates 51 and 52 shown in FIGS. 5 and 6 can be obtained.

  Further, depending on the angle of cutting and the degree of distortion of the ingot 60, the combined off-angle may not be the same in the direction perpendicular to the direction of single flow as in the substrates 51 and 52 shown in FIGS. Specifically, lines connecting the combined off-angles having substantially the same values (corresponding to A1 to A3 and B1 to B3 in FIGS. 5 and 6) have a curved shape that bulges in the direction of single flow. Even when such a substrate is used, an effect of reducing the manufacturing method characteristics can be obtained in the same manner as the substrates 51 and 52 shown in FIGS.

  By manufacturing the substrates 61 and 62 as described above, the characteristics of the substrates 61 and 62 can be arbitrarily adjusted. Therefore, regardless of the manufacturing method characteristics, variations in manufacturing method characteristics can be reduced, and the yield of the light-emitting elements obtained can be improved.

  For example, even if the manufacturing method characteristics are as shown in FIG. 16, variations in the manufacturing method characteristics can be reduced. FIG. 16 is a graph illustrating another example of the manufacturing method characteristics. In FIG. 16, the distribution of In concentration is shown as a manufacturing method characteristic.

  The manufacturing method characteristics of the wafer 103 shown in FIG. 16 are such that the In concentration at the end portion D is large, and the In concentration decreases as the end portion E facing the end portion D is approached. In addition, in the direction substantially perpendicular to the direction connecting the end portion D and the end portion E, the distribution of In concentration is constant or the variation is small. Although FIG. 16 shows an example of the case where it is constant, it may be changed.

  Such a wafer 103 can be produced, for example, by the method shown in FIG. FIG. 17 is a schematic perspective view showing a wafer manufacturing method, which is the same as FIG.

  As shown in FIG. 17, in this example, the raw material and the carrier gas are allowed to flow from a predetermined direction (a direction substantially parallel to the main surface of the substrate 104 and from the end D side toward the end E side). The growth is performed with the 104 kept stationary. By using such a manufacturing method, a wafer 100 having manufacturing method characteristics as shown in FIG. 16 can be obtained.

  When the manufacturing method characteristic is the wafer 103 in FIG. 16, for example, the combined off-angle at the end corresponding to the end E is the smallest, and the combined off-angle is increased toward the end corresponding to the end D. It is preferable to use a single-flow substrate. If such a substrate is used, it is difficult for In to be taken in due to the characteristics of the substrate at the end D where In is likely to be taken in due to the characteristics of the manufacturing method, and at the end E where it is difficult to take In due to the characteristics of the manufacturing method. In is likely to be taken in due to the characteristics of the substrate.

  Note that such a single-flow substrate cuts the ingot 60 in such a cutting direction that the angle formed between the cutting direction and the central axis Ac of the ingot 60 is larger than the cutting direction shown in FIG. It can be obtained by such a method. For example, such a substrate can be obtained by a method of cutting the ingot 60 at an angle that is substantially perpendicular to C2.

  The present invention relates to a method for manufacturing a nitride semiconductor light emitting device. In addition, the present invention is preferably applied to a nitride semiconductor laser element manufactured by laminating a layer made of a nitride semiconductor on a nitride semiconductor substrate.

These are the graphs which show an example of a production method characteristic. These are the typical perspective views which show the preparation methods of a wafer. These are the graphs which show the relationship between the synthetic | combination off angle of a board | substrate, and the light emission wavelength. These are typical top views which show an example of a board | substrate. These are typical top views which show an example of a board | substrate. These are typical top views which show an example of a board | substrate. These are a schematic plan view and a cross-sectional view showing a configuration of a nitride semiconductor laser chip. These are typical sectional drawings which show an example of the manufacturing method of a wafer. These are typical sectional drawings which show the structure of an active layer. These are the typical top view and sectional drawing shown about the structure of a wafer. These are typical top views shown about the composition of a bar and a chip. FIG. 3 is a schematic perspective view showing an example of a laser element. These are the typical perspective view and sectional drawing of an ingot. These are typical sectional views shown about an example in the case of cutting an ingot. These are typical sectional views shown about an example in the case of cutting an ingot. These are the graphs which show another example of a production method characteristic. These are the typical perspective views which show the preparation methods of a wafer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser chip 2 Substrate 3 N-type clad layer 4 Active layer 4a Well layer 4b Barrier layer 5 Optical guide layer 6 Cap layer 7 P-type clad layer 8 Contact layer 9 P-side ohmic electrode 10 Ridge part 11 Current block layer 12 Pad electrode 13 n-side electrode 14 SiO ₂ layer 20 wafer 30 bar 40 nitride semiconductor laser element 41 stem 42 heat sink 43 submount 44a, 44b pin 45a, 45b wire 50-52 substrate 60 ingot 60a upper surface 61, 62 substrate 100 wafer Ac central axis C1 , C2 <0001> direction

Claims (7)

Manufacturing method showing distribution of characteristics in a plane parallel to the main surface of the substrate of the stacked structure when a stacked structure including a layer made of a nitride semiconductor is formed on the main surface of the substrate by a predetermined manufacturing method Based on the characteristics, a first step of producing an adjustment substrate made of a nitride semiconductor,
Using the predetermined manufacturing method, a second step of manufacturing a wafer by manufacturing the laminated structure on the main surface of the adjustment substrate obtained by the first step;
A third step of manufacturing a nitride semiconductor device using the wafer obtained by the second step;
A method for producing a nitride semiconductor light emitting device comprising: The production method characteristic indicates a distribution of emission wavelengths in a plane parallel to the main surface of the substrate of the laminated structure,
2. The method of manufacturing a nitride semiconductor light emitting element according to claim 1, wherein a synthetic off angle of a portion of the adjustment substrate corresponding to a portion of the manufacturing method characteristic corresponding to the shortest emission wavelength is 0 °. .   3. The nitride semiconductor light-emitting element according to claim 2, wherein a synthetic off-angle of the adjustment substrate other than a portion corresponding to the shortest emission wavelength in the manufacturing method characteristics is greater than 0 °. Production method. The production method characteristics are such that the emission wavelength becomes shorter toward the center side and the emission wavelength becomes longer toward the outside side,
4. The method for manufacturing a nitride semiconductor light emitting element according to claim 3, wherein a synthetic off angle of the adjustment substrate is closer to 0 ° toward the center side and increases toward the outer side. 5.   In the predetermined manufacturing method, a raw material for manufacturing the stacked structure is flowed from a predetermined direction, and the center of the main surface of the substrate is rotated around an axis while the raw material flows to manufacture the stacked structure. The method for producing a nitride semiconductor light emitting device according to claim 4, wherein the method is a product. Before the first step,
The multilayer structure is fabricated using the predetermined fabrication method on the principal surface of the test substrate having a uniform composite surface off-angle, and the fabrication method characteristics are obtained based on the fabricated multilayer structure. The four steps
The method for manufacturing a nitride semiconductor light emitting device according to claim 1, further comprising:   The method for manufacturing a nitride semiconductor light-emitting element according to claim 1, wherein the stacked structure includes at least one layer made of InGaN.

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