Optical semiconductor components

Abstract

The optical semiconductor element of the present invention comprises: a substrate (11); a first ridge (12) formed on the substrate (11), having, from the bottom, a first first conductive type cladding layer (13), a first core layer (14), a first second conductive type cladding layer (15), and a first contact layer (16), and a first ridge groove (18) is arranged on both sides; and a first electrode (20) is in contact with the first contact layer (16) on the first ridge (12), does not extend to the first ridge groove (18), and includes a first solder layer (21).

Description

Technical Field

[0001] The present disclosure relates to a junction-down mounted optical semiconductor element. Background Art

[0002] Optical semiconductor elements such as semiconductor lasers are sometimes mounted junction-down for the purpose of high-speed operation (see, for example, Patent Document 1). Junction-down mounting has a smaller wiring inductance than wire bonding mounting, and thus enables high-speed operation.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2000-208859

[0004] However, in the optical semiconductor element, the area of ​​the electrode becomes larger, which hinders the high-speed operation. A solder electrode for bonding is formed on the submount on which the optical semiconductor element is mounted. Since it is difficult to form a fine solder electrode pattern on the submount, the area of ​​the solder electrode becomes larger. Therefore, the electrode of the optical semiconductor element must also be enlarged to match the solder electrode. As a result, the parasitic capacitance of the electrode becomes larger, and the optical semiconductor element cannot be operated at a high speed. Summary of the invention

[0005] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to obtain an optical semiconductor element capable of high-speed operation.

[0006] The optical semiconductor element involved in the present disclosure comprises: a substrate; a first ridge formed on the substrate, having a first first-conductivity type cladding layer, a first core layer, a first second-conductivity type cladding layer, and a first contact layer in order from the bottom, and a first ridge groove is arranged on both sides; a first electrode is in contact with the first contact layer on the first ridge, does not extend to the first ridge groove, and includes a first solder layer; a second ridge is formed on the substrate, is connected to the first ridge, has a second first-conductivity type cladding layer, a second core layer, a second second-conductivity type cladding layer, and a second contact layer in order from the bottom, and a second ridge groove is arranged on both sides; and a second electrode is in contact with the second contact layer on the second ridge, has an extension portion extending beyond the second ridge groove, and includes a second solder layer, the second core layer is an active layer that emits laser, and the first core layer is an absorption layer that modulates the laser from the second core layer.

[0007] According to the optical semiconductor element of the present disclosure, since the electrode including the layer formed of solder is formed on the ridge, it can operate at high speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a perspective view of the optical semiconductor element according to the first embodiment.

[0009] Figure 2(a) and (b) are a plan view and a cross-sectional view of the optical semiconductor element according to the first embodiment.

[0010] Figure 3 This is a cross-sectional view showing a first electrode of the optical semiconductor element according to the first embodiment.

[0011] Figure 4 (a) to (e) are cross-sectional views for explaining the method for manufacturing the optical semiconductor element according to the first embodiment.

[0012] Figure 5 This is a cross-sectional view of an example in which the optical semiconductor element according to the first embodiment is mounted on a submount with the junction facing downward.

[0013] Figure 6 This is a cross-sectional view of an optical semiconductor element according to the second embodiment.

[0014] Figure 7 It is a cross-sectional view of a modification of the optical semiconductor element according to the second embodiment.

[0015] Figure 8 (a) and (b) are a plan view and a cross-sectional view of the optical semiconductor element according to the third embodiment.

[0016] Fig. 9 This is a cross-sectional view of an example in which the optical semiconductor element according to the third embodiment is mounted on a submount with the junction facing downward.

[0017] Fig.10 (a) and (b) are a plan view and a cross-sectional view of the optical semiconductor element according to the fourth embodiment.

[0018] Fig.11 (a) to (d) are cross-sectional views for explaining a method for manufacturing an optical semiconductor element according to the fourth embodiment.

[0019] Fig.12 (a) and (b) are cross-sectional views for explaining the method for manufacturing the optical semiconductor element according to the fourth embodiment.

[0020] Fig.13 It is a cross-sectional view of an example in which the optical semiconductor element according to the fourth embodiment is mounted on a submount with the junction facing downward.

[0021] Fig.14 This is a perspective view of an optical semiconductor element according to the fifth embodiment.

[0022] Fig.15 (a) to (c) are a plan view and a cross-sectional view of an optical semiconductor element according to the fifth embodiment.

[0023] Fig.16(a) to (e) are cross-sectional views for explaining a method for manufacturing an optical semiconductor element according to the fifth embodiment.

[0024] Fig.17 (a) and (b) are cross-sectional views of an example in which the optical semiconductor element according to the fifth embodiment is mounted on a submount with the junction facing downward.

[0025] Fig.18 It is a top view of the optical semiconductor element involved in Embodiment 6.

[0026] Fig.19 This is a cross-sectional view of an example in which the optical semiconductor element according to the sixth embodiment is mounted on a submount with the junction facing downward.

[0027] Fig. 20 It is a plan view of a modification of the optical semiconductor element according to the sixth embodiment.

[0028] Fig.21 This is a perspective view of an optical semiconductor element according to the seventh embodiment.

[0029] Fig. 22 (a) to (c) are a plan view and a cross-sectional view of an optical semiconductor element according to the seventh embodiment. DETAILED DESCRIPTION

[0030] Implementation Method 1

[0031] The structure of the optical semiconductor element according to Embodiment 1 will be described. Figure 1 2 is a perspective view of the optical semiconductor element 10 according to the first embodiment. Figure 1 The directions of the x, y, and z axes are shown in Figure 1 In the figure, the thickness of the first electrode 20 is omitted. In the subsequent perspective views, the thickness of the electrode on the upper surface is also omitted. Figure 2 (a) is a plan view of the optical semiconductor element 10. Here, the plan view refers to the case of observing from above the z-axis. Figure 2 (b) is Figure 2 (a) is a cross-sectional view of the optical semiconductor element 10 taken along line AA.

[0032] The optical semiconductor element 10 includes a substrate 11. The substrate 11 is a semiconductor substrate formed of, for example, InP.

[0033] The optical semiconductor element 10 includes a first ridge 12. The first ridge 12 is formed on the substrate 11. The stripe direction of the first ridge 12 is Figure 2 The width of the first ridge 12 is, for example, 1 μm to 30 μm.

[0034] The first ridge 12 has, starting from the bottom, a first first-conductivity-type cladding layer 13, a first core layer 14, a first second-conductivity-type cladding layer 15, and a first contact layer 16. The first first-conductivity-type cladding layer 13 is a semiconductor layer of p-type or n-type conductivity, and is formed of InP. The first core layer 14 is an active layer having a quantum well structure, and is formed of InGaAsP. The first second-conductivity-type cladding layer 15 is a semiconductor layer of opposite conductivity to the first first-conductivity-type cladding layer 13, and is formed of InP. The first contact layer 16 is formed of conductive InGaAs. The first core layer 14 emits laser light. The laser light is modulated by the current flowing in the first core layer 14. The laser light is as Figure 1 As shown by the arrow in the figure, it is emitted from the end face.

[0035] First ridge grooves 18 are arranged on both sides of the first ridge 12. The positions of the first ridge grooves 18 are shown in the figure for explaining the manufacturing method. Figure 4 (b) of FIG. 1 . The width of the first ridge groove 18 is, for example, 2 μm to 20 μm, and the depth is, for example, 2 μm to 10 μm. An insulating film 17 is formed on the surface of the upper surface of the first ridge 12 except for a portion, and on the side and bottom surfaces of the first ridge groove 18. A resin film 19 is embedded in the first ridge groove 18. The resin film 19 is formed of BCB (benzocyclobutene), polyimide, or the like.

[0036] The optical semiconductor element 10 includes a first electrode 20. The first electrode 20 is in contact with the first contact layer 16 on the first ridge 12. The first electrode 20 does not extend to the first ridge groove 18, but is formed only on the upper portion of the first ridge 12. Figure 3 , which shows an enlarged view of only the first electrode 20. The first electrode 20 has a layer structure of Ti / Au / Ti / Pt / AuSn (solder) / Au or Ti / Pt / Au / Ti / Pt / AuSn (solder) / Au, etc. from the bottom. Among these layers, the Ti and Pt layers are thin films of less than 1 μm. The AuSn layer is the first solder layer 21. The film thickness of the first solder layer 21 is 1 μm to 10 μm. The top layer of Au is a thin film of less than 1 μm. Ti helps to improve the adhesion of the electrode, and Pt acts as a barrier metal. As a barrier metal, in addition to Pt, Ni, Ta, Cr, etc. can also be used. In addition, the top layer of Au has an anti-oxidation function on the surface of the first electrode 20.

[0037] The optical semiconductor element 10 includes a back surface electrode 23 on the surface below the substrate. The back surface electrode 23 is electrically connected to the first first-conductivity-type cladding layer 13 via the substrate 11 .

[0038] The depth (y-axis direction) of the optical semiconductor element 10 is, for example, 200 μm to 400 μm.

[0039] Next, use the section view ( Figure 4(a) to (e)) of the present invention describe a method for manufacturing the optical semiconductor element 10 .

[0040] First, prepare Figure 4 As shown in (a), the first ridge 12 is formed on the substrate 11 using a known semiconductor process technology. Figure 4 As shown in (b), an insulating film 17 is formed. Thus, the region of the first ridge groove 18 is determined. Figure 4 As shown in (c), the resin film 19 is embedded in the first ridge groove 18. Figure 4 As shown in (d) of FIG. 1 , the insulating film 17 on the first ridge 12 is etched to expose the first contact layer 16, and then the first electrode 20 is formed in contact with the first contact layer 16. Next, as shown in FIG. Figure 4 As shown in (e), the lower surface of the substrate 11 is ground to be thinned, and then the back electrode 23 is formed.

[0041] Next, use Figure 5 An example in which the optical semiconductor element 10 is mounted on the submount 25 with the junction facing downward will be described. Figure 5 2 is a cross-sectional view showing a state where the optical semiconductor element 10 is mounted on the submount 25. Figure 5 The weld lines are depicted in , but this is for illustration purposes and the weld lines do not have to lie in the xz plane.

[0042] The submount 25 includes a submount substrate 26, on which a first submount electrode 27 and a wire bonding electrode 29 are formed. The first submount electrode 27 and the wire bonding electrode 29 have a layer structure of Ti / Au or Ti / Pt / Au from the bottom. If a solder layer is formed on the first submount electrode 27, it is difficult to control the amount of solder, and therefore it is difficult to fine-tune the pattern of the first submount electrode 27. However, in this embodiment, since a solder layer is not formed on the first submount electrode 27, the pattern of the first submount electrode 27 can be fine-tune.

[0043] The optical semiconductor element 10 is bonded to the submount 25. The bonding is accomplished by the first electrode 20 and the first submount electrode 27. The first solder layer 21 of the first electrode 20 serves as a bonding agent.

[0044] The back surface electrode 23 and the wire bonding electrode 29 are wire-bonded.

[0045] As described above, according to the first embodiment, since the first electrode 20 including the first solder layer 21 is formed on the first ridge 12, the area of ​​the first electrode 20 is small. Therefore, the parasitic capacitance of the first electrode 20 is reduced, and the optical semiconductor element 10 can operate at a high speed. In addition, since the area of ​​the first electrode 20 is small, the amount of solder in the first solder layer 21 can be reduced, thereby suppressing the expansion of solder after the junction is mounted downward. In addition, since the resin film 19 having a lower dielectric constant than the semiconductor material is buried in the first ridge groove 18, the parasitic capacitance of the first electrode 20 can be reduced. In addition, since the optical semiconductor element 10 is mounted on the submount 25 with the junction facing downward, the inductance of the wiring is reduced. In addition, since the wire bonding operation is not required, it can be easily assembled. In addition, since the heat dissipation is improved, high-temperature and high-output operation can be performed. In addition, since the first electrode 20 includes the first solder layer 21, the first submount electrode 27 of the submount 25 does not require solder, and the area of ​​the first submount electrode 27 can be reduced.

[0046] In addition, it is easy to mount a plurality of optical semiconductor elements 10 on the submount. If the solder layer is not located at the first electrode 20 but at the electrode on the submount side, after mounting one optical semiconductor element 10, the solder used to join the submount side electrode of the second and subsequent optical semiconductor elements 10 melts. Therefore, it is not possible to mount a plurality of optical semiconductor elements on the submount one by one. However, in the optical semiconductor element 10 of the first embodiment, the first solder layer 21 exists on the first electrode 20, and since there is a layer formed of Au on the first solder layer 21, after mounting one optical semiconductor element, the AuSn of the first solder layer 21 reacts with the Au and becomes AuSn with a higher Au concentration. Since the higher the Au concentration, the higher the melting point of AuSn, the melting point of the first solder layer 21 after mounting becomes higher. Therefore, when mounting the second and subsequent optical semiconductor elements 10, the first solder layer 21 of the mounted optical semiconductor element 10 will not melt, and the optical semiconductor element 10 can be mounted easily.

[0047] Implementation Method 2

[0048] An optical semiconductor element according to Embodiment 2 will be described. The optical semiconductor element according to Embodiment 2 is different from Embodiment 1 in that the electrode on the ridge is T-shaped. The difference from Embodiment 1 will be mainly described here.

[0049] Figure 62 is a cross-sectional view of an optical semiconductor element 40 according to Embodiment 2. The first electrode 20a on the first ridge 12 is T-shaped. The first electrode 20a includes a lower electrode 42 and an upper electrode 43, and the width of the upper electrode 43 is wider than the width of the lower electrode 42. In this way, the shape in which the upper electrode 43 protrudes in two directions (x-axis direction) perpendicular to the stripe direction (y-axis direction) of the first ridge 12 relative to the lower electrode 42 when viewed from above is called a T-shaped shape.

[0050] As described above, according to the second embodiment, since the first electrode 20a is in a T-shape, the resistance of the first electrode 20a can be reduced, so that the optical semiconductor element can be operated at a high speed. In addition, the current loss is also small.

[0051] In addition, the first electrode may also be in a Γ-shaped shape. The so-called Γ-shaped shape is as follows: Figure 7 As shown, the upper electrode 43b is formed to protrude relative to the lower electrode 42b in only one direction (x-axis direction) perpendicular to the stripe direction (y-axis direction) of the first ridge 12 when viewed from above. In this case, the resistance of the first electrode 20b can also be reduced.

[0052] Implementation 3

[0053] An optical semiconductor element according to Embodiment 3 will be described. The optical semiconductor element according to Embodiment 3 is different from Embodiment 1 in that a structure for preventing one-side contact is formed. The differences from Embodiment 1 will be mainly described here.

[0054] Figure 8 (a) is a plan view of an optical semiconductor element 50 according to the third embodiment. Figure 8 (b) is Figure 8 (a) is a cross-sectional view of the optical semiconductor element 50 taken along line BB.

[0055] The optical semiconductor element 50 includes an insulator 51. The insulator 51 is formed in a region farther from the first ridge 12 than the first ridge groove 18 so that the height of the upper surface is equal to that of the first electrode 20. Here, the region farther from the first ridge 12 than the first ridge groove 18 refers to the region in the region where the first ridge 12 is located. Figure 8 In (a), the area on the left side of the first ridge 12 is indicated by R1, and the area on the right side of the first ridge 12 is indicated by R2.

[0056] Next, use Fig. 9 An example in which the optical semiconductor element 50 is mounted on the submount 52 with the junction facing downward will be described. Fig. 9 It is a cross-sectional view showing a state where the optical semiconductor element 50 is mounted on the submount 52 .

[0057] A third submount electrode 54 is formed on the submount 52. The third submount electrode 54 has a layer structure of Ti / Au or Ti / Pt / Au or the like from the bottom. The insulator 51 of the optical semiconductor element 50 is in contact with the third submount electrode 54.

[0058] As described above, according to Embodiment 3, since the insulator 51 is located on the left and right of the first ridge 12, the one-sided contact state that causes the optical semiconductor element 50 to tilt is prevented when mounted on the submount 52. That is, the insulator 51 functions as a structure for preventing one-sided contact.

[0059] In addition, although the insulator 51 is set to be on both sides of the first ridge 12, it can also be on only one side. In addition, a conductor such as metal can also be used as a structure. In particular, if the structure is formed at the same time as the first electrode 20, the number of manufacturing steps can be reduced. In the case of using a conductor in this way, when the junction is mounted downward, the conductor can also be joined to the third submount electrode 54 of the submount 52.

[0060] Implementation 4

[0061] The optical semiconductor element according to Embodiment 4 is described. The optical semiconductor element according to Embodiment 4 is different from Embodiment 3 in that the structure for preventing one-side contact is a recessed electrode formed in the recessed portion. The differences from Embodiment 3 are mainly described here.

[0062] Fig.10 (a) is a plan view of the optical semiconductor element 60 according to the fourth embodiment when viewed from above. Fig.10 (b) is Fig.10 (a) is a cross-sectional view of the optical semiconductor element 60 taken along CC.

[0063] The optical semiconductor element 60 includes a lower contact layer 65 between the substrate 11 and the first ridge 12. The lower contact layer 65 is electrically connected to the first first-conductivity-type cladding layer 13. The lower contact layer 65 is formed of InP having conductivity.

[0064] A recess 61 is formed in the optical semiconductor element 60. The position of the recess 61 is shown in FIG. Fig.11 The recess 61 is formed in a region farther from the first ridge 12 than the first ridge groove 18 so that the bottom surface 64 is in contact with the lower contact layer 65. The insulating film 17 is formed in the recess 61. The insulating film 17 has an opening in the bottom surface 64 of the recess 61.

[0065] The optical semiconductor element 60 includes a recessed electrode 62. The recessed electrode 62 is formed in the recessed portion 61 in such a manner that the height of the upper surface is equal to that of the first electrode 20. The recessed electrode 62 is electrically connected to the lower contact layer 65 at the bottom surface 64 of the recessed portion 61. That is, the recessed electrode 62 is electrically connected to the first first-conductivity-type cladding layer 13 via the lower contact layer 65. The recessed electrode 62 is formed of, for example, Au, and the uppermost portion has a layer structure of Ti / Pt / AuSn (solder) / Au, etc., from the bottom, similarly to the first electrode 20 of the first embodiment. The AuSn layer is a recessed solder layer 63 formed of solder.

[0066] The optical semiconductor element 60 includes an insulator 51. The insulator 51 is formed on the opposite side of the recessed electrode 62 across the first ridge 12. The insulator 51 is the same as the insulator 51 described in the third embodiment.

[0067] Next, use the section view ( Fig.11 (a)- Fig.12 (b)) A method for manufacturing the optical semiconductor element 60 is described.

[0068] First, prepare Fig.11 As shown in (a), a lower contact layer 65 is provided on the substrate 11 using a known semiconductor process technology, and a first ridge 12 is formed on the lower contact layer 65. Next, as shown in Fig.11 As shown in (b), the concave portion 61 is formed by etching. At this time, the bottom of the concave portion 61 is made to reach the middle of the lower contact layer 65. Fig.11 As shown in (c), an insulating film 17 is formed. Thus, the region of the first ridge groove 18 is determined. Fig.11 As shown in (d) of FIG. 1 , a resin film 19 is embedded in the first ridge groove 18. Next, as shown in FIG. Fig.12 As shown in (a), the recessed electrode 62, the first electrode 20, and the insulator 51 are formed. At this time, before the formation of the first electrode 20, the insulating film 17 on the first ridge 12 is etched to expose the first contact layer 16. Fig.12 As shown in (b), the lower surface of the substrate 11 is ground to be thinned.

[0069] Next, use Fig.13 An example in which the optical semiconductor element 60 is mounted on the submount 66 with the junction facing downward will be described. Fig.13 It is a cross-sectional view showing a state where the optical semiconductor element 60 is mounted on the submount 66 .

[0070] The third submount electrode 54 is formed on the submount 66. The optical semiconductor element 60 and the submount 66 are bonded together by the first electrode 20 and the first submount electrode 27, and the recessed electrode 62 and the third submount electrode 54. Here, the bonding agent is the first solder layer 21 of the first electrode 20 and the recessed solder layer 63 of the recessed electrode 62.

[0071] As described above, according to the fourth embodiment, since the recessed electrode 62 electrically connected to the first first conductive type cladding layer 13 is exposed to the upper side of the optical semiconductor element 60, when the optical semiconductor element 60 is mounted on the submount 66 with the junction facing downward, the recessed electrode 62 can be joined to the third submount electrode 54 without using a bonding wire. Therefore, the mounting is simple and the inductance of the wiring can be reduced. In addition, since the electrode for the bonding wire is not required, the submount 66 can be reduced. In addition, since the area of ​​the recessed electrode 62 is small, the amount of solder can also be reduced, so the spread of solder after the junction facing downward mounting can be suppressed.

[0072] In addition, the insulator 51 may not exist. In addition, a conductor such as metal may be used as a structure instead of the insulator 51. In particular, if the structure is formed simultaneously with the first electrode 20 and the upper part of the recessed electrode 62, the number of manufacturing steps can be reduced. In the case of using a conductor in this way, the conductor may be bonded to the third submount electrode 54 when the junction is mounted downward.

[0073] Implementation method 5

[0074] The structure of the optical semiconductor element according to the fifth embodiment will be described. Fig.14 It is a perspective view of an optical semiconductor element 70 according to the fifth embodiment. Fig.15 (a) is a plan view of the optical semiconductor element 70 . Fig.15 (b) is Fig.15 (a) is a cross-sectional view of the optical semiconductor element 70 at DD. Fig.15 (c) is Fig.15 1 is a cross-sectional view of the optical semiconductor element 70 at EE of (a). The optical semiconductor element 70 integrates a laser unit 84 and a modulator unit 85. Since the modulator unit 85 itself does not emit laser light, its function is different from that of the optical semiconductor element 10 of the first embodiment, but its structure is equivalent to that of the optical semiconductor element 10 of the first embodiment. The optical semiconductor element 70 is configured in the form of adding a laser unit 84 to the modulator unit 85.

[0075] The optical semiconductor element 70 includes a substrate 71. The substrate 71 is a semiconductor substrate formed of, for example, InP.

[0076] like Fig.15As shown in (b), the laser section 84 includes a second ridge 86. The second ridge 86 is formed on the substrate 71 in a manner connected to the first ridge 72. The stripe direction of the second ridge 86 is Fig.15 The second ridge 86 has a width in the range of, for example, 1 μm to 30 μm in the direction perpendicular to the paper surface of (b) (y-axis direction).

[0077] The second ridge 86 includes, in order from the bottom, a second first-conductivity-type cladding layer 87 , a second core layer 88 , a second second-conductivity-type cladding layer 89 , and a second contact layer 90 .

[0078] The second first-conductivity-type cladding layer 87 is a semiconductor layer of p-type or n-type conductivity, and is formed of InP. The second core layer 88 is an active layer having a quantum well structure, and is formed of InGaAsP. The second second-conductivity-type cladding layer 89 is a semiconductor layer of conductivity opposite to that of the second first-conductivity-type cladding layer 87, and is formed of InP. The second contact layer 90 is formed of InGaAs having conductivity. The second core layer 88 emits laser light. The laser light is CW (Continuous Wave) light.

[0079] Second ridge grooves 91 are arranged on both sides of the second ridge 86. The width of the second ridge groove 91 is, for example, 2 μm to 20 μm, and the depth is, for example, 2 μm to 10 μm. An insulating film 77 is formed on the surface except for a part of the upper surface of the second ridge 86, and on the side and bottom surfaces of the second ridge grooves 91. A resin film 79 is embedded in the second ridge grooves 91. The resin film 79 is formed of BCB (benzocyclobutene), polyimide, or the like.

[0080] The laser unit 84 includes a second electrode 92. The second electrode 92 contacts the second contact layer 90 on the second ridge 86. The second electrode 92 has an extension portion 94 that extends beyond the second ridge groove 91. The second electrode 92 has a layer structure of Ti / Au / Ti / Pt / AuSn (solder) / Au or Ti / Pt / Au / Ti / Pt / AuSn (solder) / Au from the bottom. Among these layers, the Ti and Pt layers are thin films of less than 1 μm. The AuSn layer is the second solder layer 93. The film thickness of the second solder layer 93 is 1 μm to 10 μm. The top layer of Au is a thin film of less than 1 μm. Ti helps to improve the adhesion of the electrode, and Pt acts as a barrier metal. As a barrier metal, Ni, Ta, Cr, etc. can also be used in addition to Pt. In addition, the top layer of Au has an anti-oxidation function on the surface of the second electrode 92.

[0081] like Fig.15 As shown in (c), the modulator section 85 includes a first ridge 72. The first ridge 72 is formed on the substrate 71. The stripe direction of the first ridge 72 is Fig.15The width of the first ridge 72 is, for example, 1 μm to 30 μm.

[0082] The first ridge 72 includes, in order from the bottom, a first first-conductivity-type cladding layer 73 , a first core layer 74 , a first second-conductivity-type cladding layer 75 , and a first contact layer 76 .

[0083] The first first conductivity type cladding layer 73 is a semiconductor layer of p-type or n-type conductivity, and is formed of InP. The first core layer 74 is an absorption layer having a quantum well structure, and is formed of AlGaInAs. The first second conductivity type cladding layer 75 is a semiconductor layer of opposite conductivity type to the first first conductivity type cladding layer 73, and is formed of InP. The first contact layer 76 is formed of InGaAs having conductivity. The first core layer 74 modulates the laser light from the second core layer 88 of the laser section 84. The modulation is performed by applying a voltage to the first first conductivity type cladding layer 73 and the first second conductivity type cladding layer 75. The modulated laser light is as shown in FIG. Fig.14 As shown by the arrow in the figure, it is emitted from the end face.

[0084] First ridge grooves 78 are arranged on both sides of the first ridge 72. The width of the first ridge groove 78 is, for example, 2 μm to 20 μm, and the depth is, for example, 2 μm to 10 μm. An insulating film 77 is formed on the surface except for a part of the upper surface of the first ridge 72, and on the side and bottom surfaces of the first ridge groove 78. A resin film 79 is embedded in the first ridge groove 78. The resin film 79 is formed of BCB (benzocyclobutene), polyimide, or the like.

[0085] The modulator portion 85 includes a first electrode 80. The first electrode 80 contacts the first contact layer 76 on the first ridge 72. The first electrode 80 does not extend to the first ridge groove 78, but is formed only on the upper portion of the first ridge 72. The first electrode 80 has a layer structure of Ti / Au / Ti / Pt / AuSn (solder) / Au or Ti / Pt / Au / Ti / Pt / AuSn (solder) / Au from the bottom. Among these layers, the Ti and Pt layers are thin films of less than 1 μm. The AuSn layer is the first solder layer 81. The film thickness of the first solder layer 81 is 1 μm to 10 μm. The top layer of Au is a thin film of less than 1 μm. Ti helps to improve the adhesion of the electrode, and Pt acts as a barrier metal. As a barrier metal, Ni, Ta, Cr, etc. can also be used in addition to Pt. In addition, the top layer of Au has an anti-oxidation function on the surface of the first electrode 80.

[0086] The optical semiconductor element 70 includes a back surface electrode 83 on the surface below the substrate. The back surface electrode 83 is electrically connected to the first first-conductivity-type cladding layer 73 and the second first-conductivity-type cladding layer 87 via the substrate 71 .

[0087] The depth (y-axis direction) of the laser unit 84 is, for example, 200 μm to 400 μm, and the depth of the modulator unit 85 is, for example, 100 μm to 300 μm.

[0088] Next, use the section view ( Fig.16 (a) to (e)) of the present invention describe a method for manufacturing the optical semiconductor element 70. Fig.16 The left side of (a) to (e) is the laser unit 84, and the right side is the modulator unit 85.

[0089] First, prepare Fig.16 As shown in (a), the first ridge 72 and the second ridge 86 are formed on the substrate 71 using a known semiconductor process technology. Fig.16 As shown in (b), an insulating film 77 is formed. Thus, the regions of the first ridge groove 78 and the second ridge groove 91 are determined. Fig.16 As shown in (c), the resin film 79 is embedded in the first ridge groove 78 and the second ridge groove 91. Fig.16 As shown in (d), after etching the insulating film 77 on the first ridge 72 and the second ridge 86 to expose the first contact layer 76 and the second contact layer 90, the first electrode 80 is formed in contact with the first contact layer 76, and the second electrode 92 is formed in contact with the second contact layer 90. Fig.16 As shown in (e), the lower surface of the substrate 71 is ground to be thinned, and then the back electrode 83 is formed.

[0090] Next, use Fig.17 (a) and (b) illustrate an example in which the optical semiconductor element 70 is mounted on the submount 95 with the junction facing downward. Fig.17 (a) and (b) are cross-sectional views showing a state where the optical semiconductor element 70 is mounted on the submount 95. Fig.17 (a) is a cross-sectional view of the laser unit 84, Fig.17 (b) is a cross-sectional view of the modulator section 85. Fig.17 In (a) and (b), a bonding wire and a wire bonding electrode 99 are depicted, but this is for illustration. In fact, only one bonding wire and one wire bonding electrode 99 are needed, and their positions can be appropriately selected. In addition, the number of bonding wires and wire bonding electrodes 99 can also be more than two.

[0091] The submount 95 includes a submount substrate 96, and a first submount electrode 97, a second submount electrode 98, and a wire bonding electrode 99 are formed on the submount substrate 96. The first submount electrode 97, the second submount electrode 98, and the wire bonding electrode 99 have a layer structure of Ti / Au or Ti / Pt / Au from the bottom. Since a solder layer is not formed on the first submount electrode 97, the pattern of the first submount electrode 97 can be made finer.

[0092] The optical semiconductor element 70 is bonded to the submount 95. The bonding is achieved by the first electrode 80 and the first submount electrode 97, and the second electrode 92 and the second submount electrode 98. The first solder layer 81 of the first electrode 80 and the second solder layer 93 of the second electrode 92 serve as bonding agents.

[0093] The back surface electrode 83 and the wire bonding electrode 99 are wire-bonded.

[0094] As described above, according to the fifth embodiment, the same effects as those described in the first embodiment can be obtained.

[0095] Furthermore, since the second electrode 92 has the extended portion 94 , the resistance is reduced, and therefore the loss of the current flowing in order to generate laser light in the laser portion 84 is reduced.

[0096] In addition, the extension portion 94 may not be located on both the left and right sides of the second ridge 86 but only on one side. In addition, the recessed electrode described in Embodiment 4 may be formed in the region of the modulator portion 85. In this case, since the first first-conductivity-type cladding layer 73 of the modulator portion 85 is electrically connected to the recessed electrode, the back electrode 83 may not exist.

[0097] Implementation 6

[0098] The optical semiconductor element according to Embodiment 6 will be described. The optical semiconductor element according to Embodiment 6 is different from Embodiment 5 in that the extended portion extends to the modulator portion and this portion functions as a structure. The differences from Embodiment 5 will be mainly described here.

[0099] Fig.18 It is a plan view of the optical semiconductor element 100 according to the sixth embodiment.

[0100] In the optical semiconductor element 100, the extended portion 107 of the second electrode 104 extends to the modulator portion 103. This extended portion functions as the structure described in the third embodiment.

[0101] Next, use Fig.19 An example in which the optical semiconductor element 100 is mounted on the submount 109 with the junction facing downward will be described. Fig.191 is a cross-sectional view showing a state where the optical semiconductor element 100 is mounted on the submount 109. Fig.18 FF.

[0102] The second submount electrode 110 of the submount 109 is formed in accordance with the shape of the second electrode 104 of the optical semiconductor element 100 . The second submount electrode 110 is bonded to the second electrode 104 .

[0103] As described above, according to the sixth embodiment, since the extension portion 107 extends to the left and right of the first ridge 72, a one-sided contact state that causes the optical semiconductor element 100 to tilt is prevented when mounted on the submount 109. That is, the extension portion 107 extending to the modulator portion 103 functions as a structure for preventing one-sided contact.

[0104] Furthermore, although the extended portion 107 extending to the modulator portion 103 is located on both the left and right sides of the first ridge 72 , it may be located on only one side.

[0105] In addition, if Fig. 20 As shown, the extension part 107 extending to the modulator part 103 may be in a key-shaped shape. The key-shaped shape means that the extension part 107 extending to the modulator part 103 side becomes thicker from the middle. In this way, the one-sided contact of the optical semiconductor element 100 can be prevented more stably.

[0106] Although the extension portion 107 extending to the modulator portion 103 is used as a structure for preventing one-sided contact, the insulator (or electrode) described in Embodiment 3 or the recessed electrode described in Embodiment 4 may be used. When the recessed electrode is used, the back surface electrode 83 may not exist.

[0107] Implementation 7

[0108] An optical semiconductor element according to Embodiment 7 will be described. The optical semiconductor element according to Embodiment 7 is different from Embodiment 5 in that a resin film is not formed in the ridge groove. This difference will be mainly described here.

[0109] Fig.21 It is a perspective view of an optical semiconductor element 120 according to the seventh embodiment. Fig. 22 (a) is a top view of the optical semiconductor element 120. Fig. 22 (b) is Fig. 22 (a) is a cross-sectional view at GG, Fig. 22 (c) is Fig. 221 is a cross-sectional view at HH of (a). Here, the optical semiconductor element 120 is integrated with a laser unit 124 and a modulator unit 125 in the same manner as the optical semiconductor element 70 of Embodiment 5. As shown in the figure, no resin film is formed in the first ridge groove 122 and the second ridge groove 126. In particular, the interior of the first ridge groove 122 is a cavity. The second electrode 127 is also formed in the second ridge groove 126 starting from above the second ridge 86 and extending to the expansion portion 128.

[0110] As described above, according to Embodiment 7, since no resin film is formed in the first ridge groove 122 and the second ridge groove 126, the manufacturing process for embedding the resin film can be reduced. In addition, since the dielectric constant can be lower than when the resin film is embedded, the parasitic capacitance of the first electrode 80 can be reduced.

[0111] In addition, as long as the interior of the first ridge groove 122 is a hollow, a resin film may be buried in the second ridge groove 126. In this case, the parasitic capacitance of the first ridge groove 122 may be reduced. In addition, the laser unit 124 and the modulator unit 125 may not be integrated, and the modulator unit 125 may not exist as in the first embodiment.

[0112] In addition, cases where the respective embodiments are appropriately combined, modified, or omitted are also included in the scope of the technical ideas shown in the embodiments.

[0113] Description of Reference Numerals

[0114] 10, 40, 50, 60, 70, 100, 120...optical semiconductor element; 11, 71...substrate; 12, 72...first ridge; 13, 73...first first conductive type cladding layer; 14, 74...first core layer; 15, 75...first second conductive type cladding layer; 16, 76...first contact layer; 18, 78, 122...first ridge groove; 20, 20a, 20, 80, 20b...first electrode; 21, 81...first solder layer; 42, 42b...lower electrode; 43, 4 3b...upper electrode; 61...recess; 62...recess electrode; 63...recess solder layer; 64...bottom surface; 65...lower contact layer; 86...second ridge; 87...second first conductive type cladding layer; 88...second core layer; 89...second second conductive type cladding layer; 90...second contact layer; 91, 126...second ridge groove; 92, 104, 127, 104b...second electrode; 93, 106...second solder layer; 94, 107, 128, 107b...extension portion.

Claims

1. An optical semiconductor element, wherein: The optical semiconductor element comprises: substrate; A first ridge is formed on the substrate, and has, from the bottom, a first first-conductivity-type cladding layer, a first core layer, a first second-conductivity-type cladding layer, and a first contact layer, and is provided with first ridge grooves on both sides; a first electrode, which contacts the first contact layer on the first ridge, does not extend to the first ridge groove, and includes a first solder layer; a second ridge formed on the substrate, comprising, from the bottom, a second first-conductivity-type cladding layer, a second core layer, a second second-conductivity-type cladding layer, and a second contact layer, and having second ridge grooves on both sides; and a second electrode which contacts the second contact layer on the second ridge, has an extended portion extending beyond the second ridge groove, and includes a second solder layer; The second core layer is an active layer that emits laser light. The first core layer is an absorption layer that modulates the laser light from the second core layer. The first ridge is connected to the second ridge in an emission direction of the laser light from the second core layer.

2. The optical semiconductor element according to claim 1, wherein The second solder layer is formed of AuSn, A layer made of Au exists on the second solder layer.

3. The optical semiconductor element according to any one of claims 1 to 2, wherein A structure having an upper surface having a height equal to that of the first electrode is formed in a region farther from the first ridge than the first ridge groove.

4. The optical semiconductor element according to claim 3, wherein A lower contact layer electrically connected to the first first-conductivity-type cladding layer is formed between the substrate and the first ridge. A concave portion is formed in a region farther from the first ridge than the first ridge groove, the concave portion being dug so as to contact the lower contact layer with its bottom surface. A recessed portion electrode is formed in the recessed portion, the upper surface height of the recessed portion electrode is equal to that of the first electrode, the recessed portion electrode is electrically connected to the first first-conductivity-type cladding layer through the bottom surface, and the recessed portion electrode includes a recessed portion solder layer, The structure is the recessed electrode.

5. The optical semiconductor element according to claim 4, wherein The concave solder layer is formed of AuSn, A layer made of Au exists on the recessed solder layer.

6. The optical semiconductor element according to claim 1 or 2, wherein A structure having an upper surface having a height equal to that of the first electrode is formed in a region farther from the first ridge than the first ridge groove. The structure is formed by extending the expansion portion.

7. The optical semiconductor element according to any one of claims 1, 2, 4 and 5, wherein The interior of the first ridge groove is a cavity.

8. The optical semiconductor element according to claim 3, wherein The interior of the first ridge groove is a cavity.

9. The optical semiconductor element according to claim 6, wherein The interior of the first ridge groove is a cavity.

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