JP2008244281A - Manufacturing method for nitride semiconductor laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a nitride semiconductor laser element which method suppresses a deterioration in the characteristics and reliability of the nitride semiconductor laser element to enable carrying out junction-down bonding in a stable manner. <P>SOLUTION: The manufacturing method for the nitride semiconductor laser element includes a first step of manufacturing a nitride semiconductor substrate which has four or more recessions extending in a strip-like shape and three of more projections extending in a strip-like shape and on which a support portion growth region containing recessions and projections formed alternately one another and a ridge portion growth region containing no recession and projection are arranged alternately; a second step of laminating a plurality of nitride semiconductor layers sequentially on the surface of the nitride semiconductor substrate to manufacture a nitride semiconductor layer laminated structure in which an uppermost face located above the projections of the support portion growth region is projected up higher than a flat portion of an uppermost face located above the ridge portion growth region; and a third step of eliminating part of the surface of the nitride semiconductor layer laminated structure above the ridge portion growth region in a strip-like manner to form a ridge portion projecting upward on part of the nitride semiconductor layer laminated structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a nitride semiconductor laser device, and in particular, a nitride semiconductor capable of suppressing a decrease in characteristics and reliability of a nitride semiconductor laser device and performing stable junction-down junction. The present invention relates to a method for manufacturing a laser element.

  Junction down junction is known as a technique for improving the heat dissipation of a semiconductor laser device including a semiconductor laser element. Here, the junction-down junction is a method of joining the surface on which the ridge portion is formed to the submount.

  FIG. 7 is a schematic cross-sectional view of a conventional AlGaInAs-based semiconductor laser device disclosed in Patent Document 1. In FIG. Here, the conventional semiconductor laser device includes an n-type buffer layer 202, an n-type cladding layer 203, a light emitting layer 204, a p-type first cladding layer 205, a p-type second cladding layer 206 on an n-type GaAs substrate 201. The intermediate layer 207 and the p-type contact layer 208 are sequentially stacked.

  In this conventional semiconductor laser element, the ridge portion 212 and the dummy ridge portion 213 are formed by using a photolithography technique and an etching technique.

  Further, in this conventional semiconductor laser device, a current blocking layer 209 made of a semiconductor is formed in a portion excluding the upper surface of the ridge portion 212, and the p-type of the upper surface of the ridge portion 212 is formed on the current blocking layer 209. A p-side electrode 210 in contact with the contact layer 208 is formed. An n-side electrode 211 is formed on the back surface of the n-type GaAs substrate 201.

  In this conventional semiconductor laser device, the uppermost surface 210a of the p-side electrode 210 above the dummy ridge portion 213 is higher than the uppermost surface 210b of the p-side electrode 210 above the ridge portion 212 by a height h.

  When the semiconductor laser device having such a configuration is joined to a base such as a submount by junction down, the uppermost surface 210a of the p-side electrode 210 above the dummy ridge portion 213 serves as a support portion that contacts the base. Since the uppermost surface 210b of the p-side electrode 210 above the portion 212 does not contact the base, the stress applied to the ridge portion 212 can be reduced, so that the nitride semiconductor laser element caused by the stress applied to the ridge portion 212 can be reduced. Characteristic deterioration can be suppressed.

Further, in Patent Document 2, processing is performed so as to form at least one concave portion that is a region dug into the surface of the substrate and a hill portion that is a region that is not dug, and on the processed surface. A method of forming a dummy ridge portion extending along the longitudinal direction of the ridge portion, one on each side of the nitride semiconductor laser device, by growing a nitride semiconductor thin film is disclosed.
JP 2004-319987 A JP-A-2005-353808

  In general, nitride semiconductors are known to have more defects than GaAs semiconductors, and in particular, p-type nitride semiconductors are known to have many defects. Therefore, when the technique described in Patent Document 1 is applied to a nitride semiconductor laser device, defects may be exposed by etching the p-type nitride semiconductor layer to form a ridge portion.

  When a current block layer made of a semiconductor is formed on the upper surface of the p-type nitride semiconductor layer where this defect is exposed, a current block layer with many defects and poor crystallinity is formed. Therefore, when the p-side electrode is formed on the upper surface of the current blocking layer, there is a problem that a nitride semiconductor laser element with good reliability cannot be obtained due to current leakage.

  In addition, the nitride semiconductor laser element is more likely to generate kinks than other semiconductor laser elements such as GaAs, and the ridge portion is required to produce a high-power nitride semiconductor laser element such as 130 mW or 200 mW. It is necessary to narrow the width.

  However, the ridge portion formed with such a narrow width is easily damaged by being subjected to a slight pressure in the manufacturing process or the like, and is liable to deteriorate the characteristics and reliability of the nitride semiconductor laser device.

  Further, in the nitride semiconductor laser element disclosed in Patent Document 2, the dummy ridge portion may be destroyed when the junction down junction is made to a base such as a submount.

  In view of the above circumstances, an object of the present invention is to provide a nitride semiconductor laser device capable of suppressing a decrease in characteristics and reliability of the nitride semiconductor laser device and capable of performing a junction-down junction stably. It is to provide a manufacturing method.

  The present invention includes a support portion growth region in which four or more concave portions extending in a strip shape and three or more convex portions extending in a strip shape are formed, and the concave portions and the convex portions are alternately formed, and the concave portions and the convex portions are provided. A first step of producing a nitride semiconductor substrate having a surface in which ridge portion growth regions that are not formed are alternately arranged, and sequentially laminating a plurality of nitride semiconductor layers on the surface of the nitride semiconductor substrate To produce a nitride semiconductor layer stacked structure in which the uppermost surface located above the convex portion of the support portion growth region protrudes upward rather than the flat portion of the uppermost surface located above the ridge portion growth region. In the second step, a part of the surface of the nitride semiconductor layer stacked structure above the ridge growth region is removed in a strip shape, so that a ridge protruding upward from a part of the nitride semiconductor layer stacked structure is formed. 3rd process to form It includes a method for manufacturing a nitride semiconductor laser device.

  Here, in the method for manufacturing a nitride semiconductor laser device of the present invention, the width of the opening of the recess is preferably 3 μm or more, and the width of the upper surface of the protrusion is preferably 10 μm or more and 50 μm or less.

  In the method for manufacturing a nitride semiconductor laser device of the present invention, the depth of the recess is preferably 1.8 μm or more.

In the method for manufacturing a nitride semiconductor laser device of the present invention, the off-angle in the direction parallel to the longitudinal direction of the concave portion on the surface of the nitride semiconductor substrate is θ _p, and the off-direction in the direction perpendicular to the longitudinal direction of the concave portion is When the angle is θ _v , θ _p is 0.2 ° or more and 1 ° or less, θ _v is 0.2 ° or less, and (θ _v / θ _p ) is 0.7 or less. preferable.

  In the method for manufacturing a nitride semiconductor laser device according to the present invention, the absolute value of the difference between the maximum value and the minimum value of the upper surface width of the convex portion is preferably 5 μm or less in each of the support portion growth regions. .

  The method for manufacturing a nitride semiconductor laser device of the present invention preferably includes a step of covering the ridge portion with a metal film.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the nitride semiconductor laser element which can suppress the fall of the characteristic and reliability of a nitride semiconductor laser element, and can perform junction down junction stably is provided. it can.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

  FIG. 1 shows a schematic cross-sectional view of an example of the nitride semiconductor laser device of the present invention. Here, the nitride semiconductor laser element of the present invention has four or more concave portions 11 extending in a strip shape and three or more convex portions 12 extending in a strip shape, and the concave portions 11 and the convex portions 12 are alternately formed one by one. A plurality of nitrides are formed on the surface of the n-type nitride semiconductor substrate 10 in which the supporting portion growing regions 13 and the ridge portion growing regions 14 in which the concave portions 11 and the convex portions 12 are not formed are alternately arranged. A nitride semiconductor layer stacked structure 15 formed by sequentially stacking semiconductor layers is formed, and an insulating film 19 and a p-side electrode 20 are sequentially formed on the surface of the nitride semiconductor layer stacked structure 15, Furthermore, the metal film 21 is formed on the surface of the p-side electrode 20. An n-side electrode 22 is formed on the back surface of the nitride semiconductor substrate 10. The side of the ridge portion 16 located above the ridge portion growth region 14 is filled with an insulating film 19.

  In the nitride semiconductor laser device having such a configuration, a nitride semiconductor layer (supported above the convex portion of the support growth region 13 rather than the uppermost surface of the ridge 16 positioned above the ridge growth region 14). The uppermost surface of the part 17) protrudes upward. Here, the surface of the metal film 21 located above the support portion 17 is higher than the surface of the metal film 21 located above the ridge portion 16 by H.

  Thus, in the nitride semiconductor laser device manufactured according to the present invention, three or more support portions 17 projecting upward from the uppermost surface of the ridge portion 16 are formed.

  Therefore, when the nitride semiconductor laser device manufactured according to the present invention is used, even when a load is applied from the surface on which the n-side electrode 22 is formed when the junction down junction is performed on the submount. Since it is possible to suppress damage to the ridge portion 16 due to contact with the submount, according to the present invention, it is possible to suppress deterioration in characteristics and reliability of the nitride semiconductor laser device.

  Further, since the submount and the junction down junction can be performed on the surface of the metal film 21 covering the uppermost surfaces of the three or more support portions 17, the conventional Patent Document 2 in which the junction down junction is performed above the one support portion 17. Compared with the nitride semiconductor laser element, the junction area to the submount can be increased, so that the junction-down junction can be stably performed.

  In the present specification, “upper” means the direction in which the nitride semiconductor layers constituting the nitride semiconductor layer stacked structure 15 are stacked.

  An example of a method for manufacturing the nitride semiconductor laser element shown in FIG. 1 will be described below with reference to FIGS.

  First, the nitride semiconductor substrate 10 shown in FIG. 2 is produced. Here, FIG. 2A shows a schematic plan view of the nitride semiconductor substrate 10, and FIG. 2B shows a schematic cross-sectional view of the nitride semiconductor substrate 10. Hereinafter, an example of a method (first step) for producing the nitride semiconductor substrate 10 will be described.

First, 1.5 μm is formed on the entire surface of the n-type GaN substrate with the C-plane as the main surface and an off angle of 0.3 ° in the <1-100> direction and 0.1 ° in the <11-20> direction. A thick SiO ₂ film is sputter deposited.

Next, a mask pattern made of a plurality of strip-like photoresists extending in the <1-100> direction is formed on the SiO ₂ film by using a photolithography technique and an etching technique. Here, the mask pattern made of a photoresist is a pattern in which a mask-formed region made of a strip-like photoresist and a strip-like opening region between them are alternately arranged. In the pattern corresponding to the support growth region 13, the width of the band-shaped opening area between the masks made of a band-shaped photoresist is 5 μm, and the opening area is 7 periods at an interval of 30 μm in the <11-20> direction. It is a pattern in which the array is a set. The pattern corresponding to the ridge growth region 14 extends in the <1-100> direction in which the distance from the support growth region 13 to the next support growth region 13 is 185 μm in the <11-20> direction. It is a mask pattern made of a strip-like photoresist.

Then, using a dry etching technique such as RIE (Reactive Ion Etching), the SiO ₂ film and the n-type GaN substrate are etched to form a strip-shaped recess 11 dug into the surface of the n-type GaN substrate to a depth of 5 μm. And a support-growth region 13 having a belt-like convex part 12 with a width of 30 μm that is not dug. After the above etching, all the photoresist on the SiO ₂ film is removed.

Thereafter, the SiO ₂ film is removed using an HF (hydrogen fluoride) aqueous solution (hydrofluoric acid) or the like as an etchant, whereby the nitride semiconductor substrate 10 shown in FIG. 2 is manufactured.

In the above, the method for forming the SiO ₂ film is not limited to sputtering deposition, and for example, an electron beam deposition method or a plasma CVD (Chemical Vapor Deposition) method can be used. In the above, as a method of forming the recess 11, for example, dry etching or wet etching may be used, or the recess 11 may be formed by mechanically digging the surface of the n-type GaN substrate. Alternatively, the recess 11 may be formed by digging a nitride semiconductor thin film such as GaN, InGaN, AlGaN or InAlGaN on the surface of the n-type GaN substrate.

  For example, as shown in FIG. 2, the period of the concave portion 11 and the convex portion 12 in the support portion growth region 13 is configured such that the concave portion 11 and the convex portion 12 are alternately arranged and starts at the concave portion 11 and ends at the concave portion 11. Further, the support portion growth region 13 may be one cycle of recesses / convex portions / recesses, or may be composed of a plurality of cycles. Moreover, the opening part of the recessed part 11 and the upper surface of the convex part 12 may have a respectively different width | variety.

  As shown in FIG. 2, the width W1 of the opening of the recess 11 formed on the surface of the nitride semiconductor substrate 10 is preferably 3 μm or more. In addition, the depth D1 of the recess 11 formed on the surface of the nitride semiconductor substrate 10 is preferably 1.8 μm or more. When the width W1 of the opening of the recess 11 formed on the surface of the nitride semiconductor substrate 10 or the depth D1 of the recess 11 is less than 1.8 μm, the nitride semiconductor layer is formed on the surface of the nitride semiconductor substrate 10. This is because the concave portion 11 is buried in the process of forming the nitride semiconductor layer laminated structure 15 by laminating the layers, and the support portion 17 protruding upward from the ridge portion 16 tends not to be obtained.

  As shown in FIG. 2, the width W2 of the upper surface of the convex portion 12 formed on the surface of the nitride semiconductor substrate 10 is preferably 10 μm or more and 50 μm or less. When the width W2 of the upper surface of the convex portion 12 is less than 10 μm, the width of the support portion 17 formed by stacking the nitride semiconductor layers becomes narrow, and thus the support portion 17 is damaged during the manufacturing process. There is. When the width W2 of the upper surface of the convex portion 12 exceeds 50 μm, the entire tip of the nitride semiconductor layer formed on the upper surface of the convex portion 12 does not cause edge growth, which will be described later, and the ridge portion growth region 14 is not preferable because it tends to have a flat portion between edge growths like the surface of the nitride semiconductor layer formed on the surface 14.

Further, the surface of the nitride semiconductor substrate 10, and _p an off-angle in a direction parallel to the longitudinal direction theta of the recess 11, when the off-angle in the direction orthogonal to the longitudinal direction of the recess 11 and the theta _v, theta _p is It is preferably 0.2 ° or more and 1 ° or less, θ _v is 0.2 ° or less, and (θ _v / θ _p ) is 0.7 or less.

For example, on the surface of nitride semiconductor substrate 10, the off angle θ _{p in the} direction parallel to the longitudinal direction of recess 11 is 0.1 °, and the off angle θ _{v in the} direction perpendicular to the longitudinal direction of recess 11 is 1 °. In this case, the surface of each support portion 17 rises to the left or falls to the right, and when viewed as the entire support portion growth region 13, it has a shape like a saw blade. When the junction 17 is bonded to the submount with the support portion 17 having such a shape, the nitride semiconductor laser element and the submount are obliquely bonded, and the nitride semiconductor laser element emits laser light. Due to variations in the diffusion of the generated heat, large distortion occurs in the ridge portion. Therefore, from the viewpoint of solving such a problem and from the viewpoint of edge growth and surface morphology, which will be described later, on the surface of the nitride semiconductor substrate 10, the off angle in the direction parallel to the longitudinal direction of the recess 11 is defined as θ _p. When the off-angle in the direction perpendicular to the longitudinal direction is θ _v , θ _p is 0.2 ° or more and 1 ° or less, θ _v is 0.2 ° or less, and (θ _v / θ _p ) Is preferably 0.7 or less.

  Further, in each of support portion growth regions 13 on the surface of nitride semiconductor substrate 10, the absolute value of the difference between the maximum value and the minimum value of the upper surface width of convex portion 12 is preferably 5 μm or less. When the absolute value of the difference between the maximum value and the minimum value of the upper surface width of the convex portion 12 in each support portion growth region 13 is 5 μm or less, the height of the support portion 17 tends to be equal. is there. Accordingly, when the junction down junction is performed on the submount by using three or more support portions 17 having such an equivalent height, the breakage of the support portion 17 at the junction down junction is easily suppressed. It tends to be possible to more stably junction down junction of the semiconductor laser device.

In the present invention, the nitride semiconductor substrate 10 has a composition formula of, for example, Al _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z ≠ 0). A substrate made of a nitride semiconductor can be used. Further, about 10% or less of the nitrogen atoms of the nitride semiconductor constituting the nitride semiconductor substrate 10 may be substituted with atoms such as As, P, or Sb (however, in the nitride semiconductor substrate 10, hexagonal The crystal system is maintained). The nitride semiconductor substrate 10 may be doped with Si, O, Cl, S, C, Ge, Zn, Cd, Mg, Be, or the like. Further, when the nitride semiconductor substrate 10 is n-type, it is preferably doped with Si, O or Cl. Further, as the surface of the nitride semiconductor substrate 10 on which the nitride semiconductor layers are stacked, for example, C plane {0001}, A plane {11-20}, R plane {1-102}, M plane {1-100 } Or {1-101} plane is preferably used.

  A nitride semiconductor layer stacked structure is manufactured by sequentially stacking a plurality of nitride semiconductor layers on the surface of the nitride semiconductor substrate 10 manufactured as described above (second step).

FIG. 3 is a schematic enlarged cross-sectional view of an example of the nitride semiconductor layer stacked structure 15 produced on the surface of the nitride semiconductor substrate 10. Here, in the nitride semiconductor layer stacked structure 15, for example, the nitride semiconductor substrate 10 is placed in a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, and a thickness of 0.2 μm is formed on the surface of the nitride semiconductor substrate 10. n-type GaN layer 101, n-type Al _0.05 Ga _0.95 N layer 102 having a thickness of 2 μm, n-type GaN guide layer 103 having a thickness of 0.02 μm, MQW active layer 104 having a period of 12 nm, thickness 0.01 μm p-type Al _0.02 Ga _0.98 N carrier blocking layer 105, 0.02 μm thick p-type GaN guide layer 106, 0.55 μm thick p-type Al _0.05 Ga _0.95 N layer 107 and 0.1 μm thick The p-type GaN contact layer 108 is sequentially grown by MOCVD.

  FIG. 4 is a schematic cross-sectional view of an example of a wafer after the nitride semiconductor layer stacked structure 15 is formed on the surface of the nitride semiconductor substrate 10.

  Here, as shown in FIG. 4, on the uppermost surface located above the ridge growth region 14 of the nitride semiconductor substrate 10, a ridge formation portion 25 having a flat surface and a ridge formation portion 25. Edge growth portions 26, which are regions raised from the ridge forming portion 25, are formed at both ends. In this specification, the crystal growth in which the end portion is raised in this way is referred to as edge growth, and the region where the edge growth occurs is referred to as an edge growth portion. Further, the step H 1 from the surface of the ridge forming portion 25 that becomes a flat portion to the highest portion of the edge growth portion 26 depends on the manufacturing conditions of the nitride semiconductor substrate 10 and the forming conditions of the nitride semiconductor layer stacked structure 15. However, it can be, for example, 1 μm or more and 3 μm or less.

  First, the process of forming the edge growth portion 26 will be described taking the edge growth portion 26 above the ridge growth region 14 as an example. Here, description will be made assuming that the width of the ridge growth region 14 is 185 μm similar to the above.

  When the epitaxial growth of the nitride semiconductor layer is started on the surface of the nitride semiconductor substrate 10, atoms and molecules as raw materials for the nitride semiconductor layer adhere to the surface of the nitride semiconductor substrate 10 and cause migration or the like to cause the nitride semiconductor. The surface of the substrate 10 is moved. However, since the atoms and molecules attached to the ridge growth region 14 do not flow into the recess 11 and are fixed at the end of the ridge growth region 14 until the embedding of the recess 11 proceeds to a certain extent. Edge growth begins to occur from the end of the growth region 14, and when the formation of the nitride semiconductor layer stacked structure 15 is completed, an edge growth portion 26 having a width of, for example, 20 μm to 30 μm is formed.

  Thus, when the formation of the nitride semiconductor layer stacked structure 15 is completed with the edge growth portion 26 formed on the entire surface of the nitride semiconductor substrate 10, the nitride semiconductor layer stack on the ridge forming region 14 is completed. A ridge forming portion 25 having a flat surface with good surface morphology is obtained on the surface of the structure 15 except for the edge growth portion 26. In the ridge forming portion 25 having a good surface morphology, the occurrence of edge growth makes it difficult for atoms and molecules to flow into the concave portion 11 due to migration or the like, thereby enabling uniform crystal growth.

  Next, the case where a nitride semiconductor layer grows on the convex part 12 of the support part growth region 13 will be described. The width of the upper surface of the convex portion 12 is narrower than that of the ridge portion growth region 14, but when epitaxial growth of the nitride semiconductor layer on the surface of the nitride semiconductor substrate 10 is started, the width of the upper surface of the convex portion 12 is also increased. Atoms and molecules are attached, and the attached atoms and molecules move by migration or the like. However, until the embedding of the concave portion 11 proceeds to a certain extent, atoms and molecules attached to the ridge growth region 14 cannot flow into the concave portion 11 and the width of the upper surface of the convex portion 12 is narrowed. As a result, edge growth starts from both ends of the upper surface of the convex portion 12, and edge growth from both ends of the convex portion 12 interferes with each other in the process of growing the nitride semiconductor layer, and eventually the edge grows over the entire surface on the convex portion 12. The growth is generated, and the thick support portion 17 is formed. As described above, in order to cause edge growth on the entire surface of the convex portion 12, the width W2 of the upper surface of the convex portion 12 shown in FIG. 2 is preferably 10 μm or more and 50 μm or less.

Further, the surface morphology of the nitride semiconductor layer stacked structure 15 is affected by the off-angle of the nitride semiconductor substrate 10. When the off angle θ _{p in the} direction parallel to the longitudinal direction of the concave portion 11 of the nitride semiconductor substrate 10 is 0.2 ° or more, edge growth tends to occur, but the off angle θ _p is 1 °. If it exceeds, surface morphology due to the nitride semiconductor substrate 10 such as polishing scratches on the surface of the nitride semiconductor substrate 10 is likely to appear, so the above-mentioned off angle θ _p is 0.2 ° or more and 1 ° or less. Is preferred.

Further, the off angle θ _{v in the} direction orthogonal to the longitudinal direction of the recess 11 of the nitride semiconductor substrate 10 affects the degree of edge growth. When the off angle θ _v exceeds 0.2 °, the in-plane of the wafer and it tends to occur a distribution in the height of the bulge by the edge growth in, the surface morphology tend to occur problems such as easily deteriorate, it is preferable that the off angle theta _v is 0.2 ° or less .

Furthermore, when the off angle θ _{p in the} direction parallel to the longitudinal direction of the concave portion 11 of the nitride semiconductor substrate 10 and the off angle θ _{v in the} direction orthogonal to each other satisfy the relationship (θ _v / θ _p ) ≦ 0.7. The edge growth occurs, and the nitride semiconductor layer laminated structure 15 having a good surface morphology tends to be obtained.

  The effect of edge growth and surface morphology due to the off-angle of the surface of the nitride semiconductor substrate 10 described above is affected by the movement of atoms and molecules due to migration during epitaxial growth due to the off-angle of the surface of the nitride semiconductor substrate 10. It is thought to be affected.

  FIG. 5 shows a schematic cross-sectional view of an example of a laser bar in which the nitride semiconductor laser elements shown in FIG. 1 are connected horizontally. Here, the ridge portion 16 is formed by removing a part of the surface of the nitride semiconductor layer stacked structure 15 above the ridge portion growth region 14 in a strip shape (third step).

  More specifically, first, a portion corresponding to the ridge portion 16 is protected at the center of the ridge forming portion 25 of the wafer shown in FIG. The ridge portion 16 is produced by etching both sides of the ridge. In the present embodiment, the ridge portion 16 has a height of 0.4 μm and a width of the upper surface of the ridge portion 16 of 1.2 μm so as to be parallel to the concave portion 11 along the <1-100> direction. It is formed as a forward mesa shape with a bottom width of 1.5 μm.

  The ridge portion 16 is preferably formed at a position separated from both end portions of the ridge forming portion 25 by 10 μm or more in the width direction (a direction orthogonal to the longitudinal direction of the concave portion 11). In the edge growth portion 26, the layer structure of the nitride semiconductor layer stacked structure is not easily designed as a result of edge growth. Therefore, when the ridge portion 16 is formed in a region less than 10 μm in the width direction from both ends of the ridge formation portion 25. May cause variations in the characteristics of the nitride semiconductor laser device.

  When the ridge portion 16 is manufactured, the support portion 17 is preferably covered with a mask so that it is not etched. This is because if the support portion 17 is etched, the height difference H1 between the ridge portion 16 and the support portion 17 becomes small.

  Next, as shown in FIG. 5, the surface portion excluding the upper surface of the ridge portion 16 is protected by the insulating film 19, and then the p-side electrode 20 and the metal film 21 are sequentially laminated.

Here, the insulating film 19 can be formed by the following method, for example. First, after the ridge portion 16 is formed on the nitride semiconductor layer stacked structure 15, a mask made of a photoresist is formed only on the upper surface of the ridge portion 16, and then an insulating film 19 made of silicon nitride is formed using a sputtering method or the like. Form. Then, after the insulating film 19 is formed, the photoresist is removed. Here, silicon nitride is used as the insulating film 19, but as other materials, at least one oxide or nitride selected from the group consisting of Si, Ti, Zr, Ta and Al, or Silicon oxide such as SiO ₂ can be used.

  The insulating film 19 preferably covers the surface of the nitride semiconductor layer stacked structure 15 continuously except for the upper surface of the ridge portion 16. For example, in the present embodiment, the support portion growth region 13 is a region in which the concave portion 11 and the convex portion 12 are formed in a concentrated manner, but the upper portion of the concave portion 11 sandwiched between the convex portions 12 is nitride. The semiconductor layer is not formed and is a groove. For this reason, the support portions 17 are separated from each other, but it is preferable that the grooves above the recesses 11 are embedded or covered with an air bridge to prevent leakage of current from the grooves between the support portions 17. can do.

  The p-side electrode 20 is formed on the upper surface of the ridge portion 16 and the upper surface of the insulating film 19. The p-side electrode 20 is preferably formed over the entire surface of the nitride semiconductor layer stacked structure 15 on the side where the ridge portion 16 is formed. This is because the p-side electrode 20 has a function of promoting the growth of the metal film 21 in addition to the function as an electrode for injecting current into the ridge portion 16. In order to effectively express the function of promoting the growth of the metal film 21 in the p-side electrode 20, it is preferable that the material of the uppermost surface of the p-side electrode 20 is the same metal as that of the metal film 21. For example, when Au is used for the metal film 21, as the p-side electrode 20, for example, the uppermost surface such as Pd / Mo / Au, Ni / Au, Pd / Pt / Au, or Pd / Au is made of Au. It is preferred to use a configuration. When the metal film 21 is made of at least one type of plating selected from the group consisting of Au, Ag, and Au, or a single metal such as Ag, Cu, Al, or Mo, the uppermost surface of the p-side electrode 20 For example, a metal such as Ag, Cu, Al, or Mo can be used.

  As the plating used to form the metal film 21, for example, cyan gold plating or sulfite gold plating can be used, but sulfite gold plating is particularly preferable because it is hard to cause deformation because of its high hardness. In addition, when the gold plating is applied, the particles on the plating surface become finer, which is preferable because the adhesion to the submount becomes good.

  Such p-side electrode 20 and metal film 21 can be formed as follows, for example. First, the insulating film 19 is formed on the surface of the nitride semiconductor layer stacked structure 15, and then the p-side electrode 20 is formed by EB (Electron Beam) vapor deposition. Subsequently, a metal film 21 having a thickness of, for example, 5 μm is formed by electrolytic plating.

  As a method for forming the metal film 21, in addition to the above-described electrolytic plating, for example, electroless plating, alloy plating, EB vapor deposition, sputtering, ECR (Electron cyclotron Resonance) method, or the like can be used.

  The thickness of the metal film 21 is preferably 1 μm or more. In the present invention, a step is generated between the upper surface of the support portion 17 and the upper surface of the ridge portion 16 due to edge growth, so that the support is provided when the nitride semiconductor laser element is bonded to the submount by junction down bonding. This is because the characteristics of the nitride semiconductor laser element may vary due to the fact that the solder does not flow uniformly into the ridge portion 16 that is recessed from the portion 17 and a cavity is formed.

  Further, after the formation of the p-side electrode 20 and the metal film 21, the thickness of the nitride semiconductor substrate 10 is reduced to, for example, 80 μm or more and 200 μm or less by polishing or etching the back surface of the nitride semiconductor substrate 10. be able to. An n-side electrode 22 having a configuration of Hf / Al, for example, is formed on the rear surface of the nitride semiconductor substrate 10 by an EB vapor deposition method or the like.

  Further, as the n-side electrode 22, in addition to the Hf / Al configuration, for example, Hf / Al / Mo / Au, Hf / Al / Pt / Au, Hf / Al / W / Au, Hf / Au, or A configuration such as Hf / Mo / Au may be used. Further, as the n-side electrode 22, a configuration in which Hf is replaced with Ti or Zr in the above configuration may be used.

  Further, the laser bar shown in FIG. 5 has a <1-100> direction in which the wafer after the ridge portion 16, the p-side electrode 20, the metal film 21 and the n-side electrode 22 are formed becomes the longitudinal direction of the ridge portion 16. It is formed by cleaving in a direction orthogonal to The cleavage plane exposed by this cleavage forms the resonator end face, and a waveguide Fabry-Perot resonator having a resonator length of, for example, 400 μm is formed. In the present invention, it is needless to say that the resonator length is limited to 400 μm, and can be in the range of 300 μm to 1000 μm, for example.

  The cavity end face formed as described above corresponds to the {1-100} plane of the nitride semiconductor crystal. Cleaving is performed in a state where a ruled line is formed on the entire back surface of the wafer by a diamond cutter and a predetermined pressure is applied to the wafer. Further, a ruled line may be formed by a diamond cutter only on a part of the wafer, for example, only at the edge of the wafer, and it may be cleaved starting from this. The formation of the resonator end face may be performed by etching.

Thus, after forming the resonator end faces before and after the waveguide type Fabry-Perot resonator, SiO ₂ films and TiO ₂ films are alternately deposited on both sides of the end faces of the resonators, respectively, and the reflectance is 70%. The dielectric multilayer film can be formed. One of the two resonator end faces formed is a laser beam emitting surface, and the reflectance of the dielectric multilayer film formed on the resonator end surface serving as the laser beam emitting surface is set to 5%, for example. The reflectance of the dielectric multilayer film formed on the resonator end face may be 95%, for example. Needless to say, the reflectance of the dielectric multilayer film is not limited to the above. Further, the configuration of the dielectric multilayer film is not limited to a laminate in which SiO ₂ films and TiO ₂ films are alternately laminated. For example, a laminate of SiO ₂ films and Al ₂ O ₃ films, etc. It may be used.

  Further, the laser bar having the configuration shown in FIG. 5 is cut along the direction parallel to the longitudinal direction of the ridge portion 16 along, for example, the broken line 31 shown in FIG. An element can be manufactured.

  Here, as a method of dividing, for example, a laser bar is set on the stage with the surface on which the n-side electrode 22 is formed on the upper side, and a scribe line is formed on the surface of the n-side electrode 22 which becomes the back surface of the laser bar by a diamond cutter or the like. Insert. Then, with a predetermined pressure applied to the laser bar, a blade having a sharp tip shape is applied to the scribe line, and the pressure is applied using a braking device to divide the laser bar along the scribe line. Thereby, the plurality of nitride semiconductor laser elements are divided into chips. This method is called a scribing method. In addition, the width of the recess 11 may be widened so that the portion desired to be divided on the surface of the nitride semiconductor substrate 10 is included in the opening of the recess 11. The nitride semiconductor laser element may be divided so that at least one support portion 17 is included on both sides of the ridge portion 16 of the nitride semiconductor laser element.

  In addition to the above scribing method, a method of dividing the laser bar by forming scratches or grooves on the surface of the n-side electrode 22 can also be used. Also, a dicing method in which the surface of the n-side electrode 22 is scratched or cut using a wire saw or a thin blade or the like, a laser that uses the excimer laser light irradiation and subsequent rapid cooling as a scribe line. A scribing method or a laser ablation method in which grooving is performed by irradiating and evaporating a laser beam having a high energy density can be used.

  FIG. 6 is a schematic cross-sectional view showing an example of a state in which the nitride semiconductor laser device having the configuration shown in FIG. 1 manufactured according to the present invention is joined to a submount by junction down junction.

  As a method for junction down junction of the nitride semiconductor laser element having the configuration shown in FIG. 1 to the submount, for example, the following method is available. First, the submount 32 is installed in the mounting device, and the solder 33 is melted on the submount 32. Next, the surface on the side where the ridge portion 16 of the nitride semiconductor laser element is formed from the upper surface side of the melted solder 33. The nitride semiconductor laser element is placed on the solder 33 so that the surface of the submount 32 faces the surface of the submount 32. Then, a load is applied from the surface on which the n-side electrode 22 of the nitride semiconductor laser element is formed, and the nitride semiconductor laser element is brought into close contact. Thereafter, the solder 33 is solidified by cooling. In this manner, the nitride semiconductor laser element can be junctioned down to the submount.

  Here, in the nitride semiconductor laser device manufactured according to the present invention, for example, the metal film 21 is formed, so that the cavity is not filled with the solder 33 above the recessed ridge portion 16. Even if it occurs, the heat generated in the nitride semiconductor layer immediately below the ridge portion 16 can be conducted to the submount 32 through the metal film 21 with good thermal conductivity, so that the nitride semiconductor laser device has a high performance. Even if it is an output, it can thermally radiate well. Therefore, it is possible to avoid the problem of heat dissipation that increases with the increase in the output of the nitride semiconductor laser element.

  In the above, as the material of the submount 32, SiC or AlN is preferably used. In the above, the material of the solder 33 is preferably an alloy of gold and tin. In this case, the ratio (mass ratio) of gold and tin is preferably 70:30.

  In addition, when expressing a crystal plane and a direction, it should be expressed by adding a bar on a required number, but since there are restrictions on expression means, in this specification, the required number is used. Instead of the expression with a bar on top, the symbol “-” is added in front of the required number.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be suitably used for manufacturing a nitride semiconductor laser element that is bonded by junction down bonding.

It is typical sectional drawing of an example of the nitride semiconductor laser element of this invention. (A) is a typical top view of an example of the nitride semiconductor substrate used for this invention, (b) is typical sectional drawing of the nitride semiconductor substrate shown to (a). In the present invention, it is a schematic enlarged cross-sectional view of an example of a nitride semiconductor layer laminated structure produced on the surface of a nitride semiconductor substrate. In this invention, it is typical sectional drawing of an example of the wafer after forming the nitride semiconductor layer laminated structure on the surface of the nitride semiconductor substrate. FIG. 2 is a schematic cross-sectional view of an example of a laser bar in which the nitride semiconductor laser elements shown in FIG. 1 are connected horizontally. FIG. 2 is a schematic cross-sectional view showing an example of a state in which the nitride semiconductor laser element having the configuration shown in FIG. 1 is joined to a submount by junction down junction. FIG. 6 is a schematic cross-sectional view of a conventional AlGaInAs-based semiconductor laser element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Nitride semiconductor substrate, 11 recessed part, 12 convex part, 13 support part growth region, 14 ridge part growth region, 15 nitride semiconductor layer laminated structure, 16 ridge part, 17 support part, 19 insulating film, 20 p side electrode , 21 Metal film, 22 n-side electrode, 25 Ridge formation part, 26 Edge growth part, 31 Broken line, 32 Submount, 33 Solder, 101 n-type GaN layer, 102 n-type Al _0.05 Ga _0.95 N layer, 103 n-type GaN Guide layer, 104 MQW active layer, 105 p-type Al _0.02 Ga _0.98 N carrier block layer, 106 p-type GaN guide layer, 107 p-type Al _0.05 Ga _0.95 N layer, 108 p-type GaN contact layer, 201 n-type GaAs substrate, 202 n-type buffer layer, 203 n-type cladding layer, 204 light-emitting layer, 205 p-type first cladding layer, 206 p-type second cladding layer, 207 Intermediate layer, 208 p-type contact layer, 209 current blocking layer, 210 p-side electrode, 210a, 210b, top surface, 211 n-side electrode, 212 ridge portion, 213 dummy ridge portion.

Claims (6)

A supporting portion growth region having four or more concave portions extending in a strip shape and three or more convex portions extending in a strip shape, and alternately forming the concave portions and the convex portions, and the concave portions and the convex portions are formed. A first step of producing a nitride semiconductor substrate having a surface in which ridge growth regions that are not formed are alternately arranged;
By sequentially laminating a plurality of nitride semiconductor layers on the surface of the nitride semiconductor substrate, the convex portion of the support portion growth region is more than the uppermost flat portion located above the ridge portion growth region. A second step of producing a nitride semiconductor layer stacked structure in which the uppermost upper surface protrudes upward;
By removing a part of the surface of the nitride semiconductor layer stacked structure above the ridge growth region in a strip shape, a ridge part protruding upward is formed in a part of the nitride semiconductor layer stacked structure A third step;
A method for manufacturing a nitride semiconductor laser device, comprising:   2. The method for manufacturing a nitride semiconductor laser device according to claim 1, wherein the width of the opening of the concave portion is 3 μm or more, and the width of the upper surface of the convex portion is 10 μm or more and 50 μm or less.   The method for manufacturing a nitride semiconductor laser device according to claim 1, wherein the depth of the concave portion is 1.8 μm or more. When the off-angle in the direction parallel to the longitudinal direction of the concave portion on the surface of the nitride semiconductor substrate is θ _p and the off-angle in the direction orthogonal to the longitudinal direction of the concave portion is θ _v ,
The θ _p is 0.2 ° or more and 1 ° or less, θ _v is 0.2 ° or less, and (θ _v / θ _p ) is 0.7 or less. 4. A method for producing a nitride semiconductor laser device according to any one of 3 above.   5. The absolute value of the difference between the maximum value and the minimum value of the width of the upper surface of the convex portion is 5 μm or less in each of the support portion growth regions. A method for manufacturing a nitride semiconductor laser device.   6. The method for manufacturing a nitride semiconductor laser device according to claim 1, further comprising a step of covering the ridge portion with a metal film.

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