JP2012151324A - Semiconductor laser device and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser device which secures adequate heat radiation characteristics while reducing heat stress, and to provide a manufacturing method of the semiconductor laser device.SOLUTION: A semiconductor laser device 100 according to one embodiment of this invention has a planar lightwave circuit (PLC) substrate 11, a PLC electrode 12, a solder bump 14, and a laser diode (LD) 15. The PLC electrode 12 is formed on the PLC substrate 11 and an opening 18 is formed at a part of the PLC electrode 12. The LD 15 is disposed above the PLC electrode 12. The solder bump 14 is formed between the PLC electrode 12 and the LD 15. A surface of the PLC substrate 11, which is exposed through the opening 18, does not contact with the solder bump 14.

Description

  The present invention relates to a semiconductor laser device and a manufacturing method thereof, and more particularly to a semiconductor laser device and a manufacturing method thereof that suppress deterioration of semiconductor laser characteristics due to mounting.

  With the recent development of technology, optical communication systems are growing dramatically. In particular, in order to increase the utilization efficiency of the fiber, techniques such as speeding up of optical signals and increasing the number of wavelengths have been developed. Along with this technical progress, demands for components used in optical communication systems are becoming stricter year by year. On the other hand, with the progress of FTTH (Fiber To The Home), the cost reduction of the parts used is also an important issue. Recently, there is an increasing demand for higher speeds in FTTH. As a result, the initial transmission rate was about 100 Mbps, but recently a transmission rate of 2.4 Gbps has been realized. Furthermore, a transmission rate of 10 Gbps is about to be realized.

  As described above, in a situation where a transmission rate of several Gbps is required, it is essential to employ a laser diode that oscillates in a single mode. Therefore, DFB-LD (Distributed FeedBack-Laser Diode) is generally used. Further, in order to efficiently couple the signal emitted from the DFB-LD to the optical fiber, position alignment at the submicron level is necessary. As a result, the cost for alignment becomes large, which is a big problem in reducing the cost. As means for solving such a problem, there is a method of mounting an LD (Laser Diode) on a PLC (Planar Lightwave Circuit) by passive alignment (Patent Document 1). According to this method, the time required for alignment becomes unnecessary, so that the cost can be greatly reduced.

  Here, a normal semiconductor device on which an LD is mounted will be described. In addition, the structure currently disclosed by patent document 1 is assumed here as a structure of PLC which mounts LD. FIG. 8 is a perspective view showing a configuration of a normal semiconductor laser device 400. As shown in FIG. 8, the normal semiconductor laser device 400 includes a PLC electrode 42 and an LD mounting base 43 formed on a PLC substrate 41. The LD 45 is mounted on the PLC electrode 42 and the LD mounting base 43. In FIG. 8, the LD 45 is mounted so that the upper surface side is located on the PLC electrode 42 side. In FIG. 8, the LD back surface side electrode E4 formed in the LD 45 is displayed.

  FIG. 9 is a front view of the end surface portion 46 of FIG. In an ordinary semiconductor laser device 400, as shown in FIG. 8, the LD 45 and the PLC electrode 42 are joined via solder bumps 44. The LD 45 is mounted such that the surface on the side closer to the active layer 47 is on the PLC electrode 42 side. That is, the LD 45 is mounted such that the LD upper surface side electrode E3 is positioned on the PLC electrode 42 side. At this time, the active layer 47 is mounted such that the extending direction (oscillation direction) is along the longitudinal direction of the LD mounting base 43.

  Then, the manufacturing method of the normal semiconductor laser apparatus 400 is demonstrated. 10A and 10B are perspective views showing a manufacturing process of a normal semiconductor laser device 400. FIG. First, the PLC electrode 42 and the LD mounting base 43 are formed on the PLC substrate 41 (FIG. 10A). Then, solder bumps 44 are formed on the PLC electrode 42 (FIG. 10B). For the solder bumps 44, for example, solder made of AuSn is used.

  Then, the LD 45 is placed on the solder bump 44. Thereafter, heat is applied to the PLC substrate 41 to melt the solder bumps 44 and then cooled. For example, the temperature at the time of melting the solder bump 44 is 290 ° C., and the temperature at the time of cooling is room temperature (about 25 ° C.). As a result, the LD 45 and the PLC electrode 42 are joined by the solder bump 44. As a result, the LD 45 is mounted on the PLC substrate 41, and the ordinary semiconductor laser device 400 shown in FIG. 8 is obtained.

  In addition, a method has been proposed in which two bonding layers are provided between the LD and the mount to reduce stress on the LD (Patent Document 2). Further, a structure in which a part of the back electrode of the LD is removed has been proposed (Patent Document 3).

Japanese Patent No. 2823044 JP 2004-335860 A JP 2006-210775 A

  However, the inventor has found that a module in which an LD is mounted on a PLC has the following problems. A module in which an LD is mounted on a PLC has an advantage that it can be produced at a low cost, but has a disadvantage that a sub-mode suppression ratio (hereinafter referred to as SMSR) yield is poor. This drawback is caused by mounting a stress-sensitive DFB-LD on a PLC substrate by solder bonding. Hereinafter, the mechanism in which this defect occurs will be briefly described. Hereinafter, unless otherwise specified, LD refers to DFB-LD.

As shown in FIG. 9, the surface of the LD 45 on the active layer 47 side (upper surface side electrode E <b> 3) is in contact with the solder bump 44. Therefore, the active layer 47 of the LD 45 receives the stress resulting from the thermal contraction of the solder bump 44 from the PLC substrate 41 side. Generally, the thermal expansion coefficient of solder is larger than the thermal expansion coefficient of the PLC board. For example, when the solder is made of AuSn, the thermal expansion coefficient is 17.5 × 10 ⁻⁶ [/ ° C.]. When the main material of the PLC substrate is Si, its thermal expansion coefficient is 2.4 × 10 ₋₆ [/ ° C.]. Therefore, when the solder is cooled to room temperature after the LD mounting is completed, the solder contracts more than the PLC substrate.

  FIG. 11A is a front view of a normal semiconductor laser device 400 when the solder bumps 44 are melted. When the solder bump 44 is melted, no stress acts on the LD 45 as shown in FIG. 11A. On the other hand, FIG. 11B is a front view of a normal semiconductor laser device 400 when the solder bumps 44 are cooled. When the solder bumps 44 are cooled, the solder bumps 44 are thermally contracted. Therefore, as shown in FIG. 11B, the LD 45 generates a tensile stress σ toward the PLC substrate 41. Therefore, the LD 45 is bent and the active layer 47 is affected by the stress σ.

  When stress is applied to the active layer of the LD, the refractive index of the active layer changes, and the oscillation state of the LD becomes unstable. As a result, the SMSR deteriorates and the SMSR yield decreases. That is, in order to improve the SMSR yield in LD solder mounting, it is necessary to reduce the stress that pulls the LD toward the PLC substrate.

  As a method for reducing the stress applied to the active layer, a structure in which a part of the PLC electrode is removed (hereinafter, the structure is referred to as a hollow electrode structure) may be used. Thereby, the area of the solder bonded to the PLC substrate can be reduced, and the tensile stress applied to the active layer in the direction of the PLC substrate can be reduced. FIG. 12 is a perspective view of a semiconductor laser device 500 having a hollow electrode structure. In FIG. 12, the solder bumps 44 and the LD 45 on the PLC electrode 52 are omitted for easy viewing of the PLC electrode 52. The hollow electrode structure is a structure in which the part of the PLC electrode where the LD active layer is disposed is removed. The PLC electrode 52 is divided into PLC electrodes 52a and 52b with a portion where the LD active layer is disposed directly above. The surface of the PLC substrate 41 between the PLC electrodes 52a and 52b is covered with Si or Si oxide. The other configuration of the semiconductor laser device 500 is the same as that of the normal semiconductor laser device 400 shown in FIG.

  FIG. 13 is a front view of the semiconductor laser device 500 when the solder bumps 44 are cooled. Since the surface of the PLC substrate 41 between the PLC electrodes 52a and 52b is covered with Si or Si oxide, the solder bumps 44 are not bonded to this portion. As a result, the stress σ is generated only in the portion where the solder bump and the PLC electrodes 52a and 52b are in contact with each other. That is, since the solder bump 44 immediately below the active layer is not bonded to the PLC electrode, it is possible to reduce the stress applied to the active layer.

  However, although the semiconductor laser device 500 having the hollow electrode structure can reduce the stress applied to the LD 45, this structure has a disadvantage in that optical characteristics are deteriorated due to an increase in LD temperature. As described above, the bonding area between the solder bump 44 and the PLC electrode 52 in the semiconductor laser device 500 is smaller than the bonding area between the solder bump 44 and the PLC electrode 42 in the normal semiconductor laser device 400 shown in FIG. In the semiconductor laser device 500, the exhaust heat path of the heat generated from the LD is narrow, and the heat dissipation characteristics are deteriorated as compared with the normal structure. Therefore, in the semiconductor laser device 500, the heat generated from the LD stays around the LD, and the operating temperature of the LD rises. As a result, the light output of the semiconductor laser device 500 decreases. Further, air enters the solder non-contact portion 72 shown in FIG. In general, air has very poor heat dissipation characteristics, and promotes deterioration of heat dissipation characteristics in the hollow electrode structure.

  In the technique described in Patent Document 2, a bonding layer must be formed on the LD itself. This complicates the LD manufacturing process. In the technique described in Patent Document 3, the LD is mounted with the back surface, which is the surface far from the active layer, facing the mount side. Therefore, the heat from the active layer as a heat source cannot be sufficiently dissipated to the mount side.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor laser device capable of ensuring sufficient heat dissipation characteristics while reducing thermal stress, and a manufacturing method thereof.

  A semiconductor laser device according to one embodiment of the present invention includes a substrate, an electrode formed over the substrate and partially having an opening, a semiconductor laser disposed over the electrode, the electrode, and the semiconductor laser A solder bump formed between the substrate and the surface of the substrate exposed through the opening and the solder bump are not in contact with each other.

  In one embodiment of the present invention, there is provided a method for manufacturing a semiconductor laser device, wherein an electrode having an opening is partially formed on a substrate, a solder bump is formed on the electrode, and the semiconductor laser is formed on the solder bump. The upper surface of the substrate is melted and then cooled to join the semiconductor laser and the electrode, and the solder bump is melted and exposed through the opening. , And then cooled and contracted to be in non-contact with the exposed surface of the substrate.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductor laser apparatus which can ensure sufficient thermal radiation characteristic, reducing a thermal stress, and its manufacturing method can be provided.

1 is a perspective view showing a configuration of a semiconductor laser apparatus 100 according to a first embodiment. 2 is a front view of an end surface portion 16 of the semiconductor laser apparatus 100 according to the first embodiment. FIG. FIG. 6 is a perspective view showing a manufacturing process of the semiconductor laser device 100 according to the first embodiment. FIG. 6 is a perspective view showing a manufacturing process of the semiconductor laser device 100 according to the first embodiment. 3 is a top view of the PLC electrode 12 of the semiconductor laser apparatus 100 according to the first embodiment. FIG. FIG. 5 is a cross-sectional view of the semiconductor laser device 100 taken along line VV in FIG. 1. 4 is a top view of a PLC electrode 22 of a semiconductor laser device 200 according to a second embodiment. FIG. FIG. 6 is a top view of a PLC electrode 32 of a semiconductor laser device 300 according to a third embodiment. 2 is a perspective view showing a configuration of a normal semiconductor laser device 400. FIG. 3 is a front view of an end surface portion 46 of a normal semiconductor laser device 400. FIG. 6 is a perspective view showing a manufacturing process of a normal semiconductor laser device 400. FIG. 6 is a perspective view showing a manufacturing process of a normal semiconductor laser device 400. FIG. It is a front view of the normal semiconductor laser apparatus 400 when the solder bump 44 is melted. It is a front view of the normal semiconductor laser apparatus 400 when the solder bump 44 is cooled. It is a perspective view of the semiconductor laser apparatus 500 which has a hollow electrode structure. It is a front view of the semiconductor laser apparatus 500 when the solder bump 44 is cooled.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

Embodiment 1
The semiconductor laser device according to the first embodiment will be described. FIG. 1 is a perspective view showing the configuration of the semiconductor laser apparatus 100 according to the first embodiment. As shown in FIG. 1, in the semiconductor laser device 100, a PLC electrode 12 and an LD mounting base 13 are formed on a PLC substrate 11. The LD 15 is mounted on the PLC electrode 12 and the LD mounting base 13. In FIG. 1, the LD 15 is mounted so that the upper surface side is located on the PLC electrode 12 side. In FIG. 1, the LD back surface side electrode E2 formed in LD15 is displayed.

  FIG. 2 is a front view of the end surface portion 16 of FIG. In the semiconductor laser device 100, as shown in FIG. 2, the LD 15 and the PLC electrode 12 are joined via the solder bumps 14. The LD 15 is mounted such that the surface on the side closer to the active layer 17 is on the PLC electrode 12 side. That is, the LD 15 is mounted such that the LD upper surface side electrode E1 is positioned on the PLC electrode 12 side. At this time, the active layer 17 is mounted so that the extending direction (oscillation direction) is along the longitudinal direction of the LD mounting base 13.

  Next, a method for manufacturing the semiconductor laser device 100 will be described. 3A and 3B are perspective views showing the manufacturing process of the semiconductor laser device 100. FIG. First, the PLC electrode 12 and the LD mounting base 13 are formed on the PLC substrate 11 (FIG. 3A). Then, solder bumps 14 are formed on the PLC electrode 12 (FIG. 3B). For the solder bump 14, for example, solder made of AuSn is used.

  Then, the LD 15 is placed on the solder bump 14. Thereafter, heat is applied to the PLC substrate 11 to melt the solder bumps 14 and then cooled. For example, the temperature at the time of melting the solder bump 14 is 290 ° C., and the temperature at the time of cooling is room temperature (about 25 ° C.). As a result, the LD 15 and the PLC electrode 12 are joined by the solder bump 14. Thereby, the LD 15 is mounted on the PLC substrate 11, and the semiconductor laser device 100 shown in FIG. 1 is obtained.

  Next, the PLC electrode 12 will be described in detail. The semiconductor laser device 100 according to the present embodiment secures heat dissipation characteristics while reducing the thermal stress applied to the LD 15 by devising the shape of the PLC electrode 12. FIG. 4 is a top view of the PLC electrode 12 according to the first exemplary embodiment. A dotted line frame 19 in FIG. 4 schematically shows the position of the active layer 17 of the LD 15.

  As shown in FIG. 4, an opening 18 is formed in the PLC electrode 12. FIG. 4 shows an example in which the openings 18 are formed in rows in the extending direction of the active layer 17 immediately below the active layer 17. The surface of the PLC substrate 11 where the opening 18 is formed is covered with Si or Si oxide. In addition, arrangement | positioning of the opening part 18 shown in FIG. 4 is only an illustration, and the 1 or more opening part 18 should just be formed. The opening 18 may be formed at a position that is not directly under the active layer.

  FIG. 5 is a cross-sectional view of the semiconductor laser device 100 taken along line VV in FIG. In FIG. 4, the VV line passes through the opening 18. As shown in FIG. 5, the semiconductor laser device 100 includes a solder contact portion 1 where the LD 15 and the PLC electrode 12 are joined. Since the solder contact portion 1 has a high heat dissipation characteristic, the heat generated from the LD 15 can be sufficiently dissipated by the presence of the solder contact portion 1 periodically.

  Further, since the surface of the PLC substrate 11 in the opening 18 is covered with Si or Si oxide, the solder bumps 14 do not adhere to the PLC substrate 11. Therefore, there is a solder non-contact portion 2 in which a gap is generated between the LD 15 and the PLC substrate 11 by the opening 18. Since the solder non-contact portions 2 are periodically present, the influence of the thermal contraction of the solder bumps 14 can be alleviated and the tensile stress applied to the LD 15 can be reduced.

  That is, according to this configuration, both high heat dissipation characteristics and reduction of thermal stress can be achieved. Therefore, according to the semiconductor laser device 100, it is possible to provide a semiconductor laser device capable of ensuring sufficient heat dissipation characteristics while reducing thermal stress, and a method for manufacturing the same.

Embodiment 2
Next, a semiconductor laser device according to the second embodiment will be described. The semiconductor laser device 200 according to the second embodiment has a configuration in which the PLC electrode 12 of the semiconductor laser device 100 is replaced with a PLC electrode 22. Other configurations and manufacturing methods of the semiconductor laser device 200 are the same as those of the semiconductor laser device 100. Therefore, only the configuration of the PLC electrode 22 will be described below. FIG. 6 is a top view of the PLC electrode 22 according to the second embodiment. A dotted line frame 29 in FIG. 6 schematically shows the position of the active layer 17.

  In the PLC electrode 22, minute openings 28 are formed in two rows in the extending direction of the active layer 17 with the active layer 17 interposed therebetween. According to the PLC electrode 22, similarly to the PLC electrode 12, it is possible to alternately form joint portions and solder non-contact portions. That is, the PLC electrode 22 can exhibit the same effects as the PLC electrode 12. Therefore, according to the semiconductor laser device 200, similarly to the semiconductor laser device 100, it is possible to provide a semiconductor laser device that can secure sufficient heat dissipation characteristics while reducing thermal stress and a method for manufacturing the same.

  Note that the configuration of the PLC electrode 22 shown in FIG. 6 is merely an example. Therefore, the number of rows of the openings 28 is not two, but can be any number. Further, the row of the openings 28 may be formed immediately below the active layer 17.

Embodiment 3
Next, a semiconductor laser device according to the third embodiment will be described. The semiconductor laser device 300 according to the third embodiment has a configuration in which the PLC electrode 12 of the semiconductor laser device 100 is replaced with a PLC electrode 32. Other configurations and manufacturing methods of the semiconductor laser device 300 are the same as those of the semiconductor laser device 100. Therefore, only the configuration of the PLC electrode 32 will be described below. FIG. 7 is a top view of the PLC electrode 32 according to the third embodiment. Note that a dotted frame 39 in FIG. 7 schematically shows the position of the active layer 17.

  In the PLC electrode 32, minute openings 38 are formed in a mosaic shape (in a staggered pattern). According to the PLC electrode 32, similarly to the PLC electrodes 12 and 22, the joint portions and the solder non-contact portions can be alternately formed. That is, the PLC electrode 32 can exhibit the same effects as the PLC electrodes 12 and 22. Therefore, according to the semiconductor laser device 300, similarly to the semiconductor laser devices 100 and 200, it is possible to provide a semiconductor laser device that can secure sufficient heat dissipation characteristics while reducing thermal stress and a method for manufacturing the same.

Other Embodiments The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. For example, in the above-described embodiment, the shape of the opening is rectangular, but the shape of the opening is not limited to the above example. That is, the shape of the opening can be other shapes such as an arbitrary polygon such as a circle or a triangle. Further, the arrangement and the number of openings are not limited to the examples shown in the above embodiments. That is, as long as sufficient heat dissipation characteristics can be ensured while reducing thermal stress, the openings can be arranged at arbitrary positions and an arbitrary number of openings can be provided.

  In the above-described embodiment, solder made of AuSn is used for the solder bump, but solder made of another material can be used.

  A part or all of the above embodiment can be described as in the following supplementary notes, but is not limited thereto.

  (Supplementary note 1) a substrate, an electrode formed on the substrate and partially having an opening, a semiconductor laser disposed above the electrode, and a solder formed between the electrode and the semiconductor laser A semiconductor laser device comprising: a bump; wherein the surface of the substrate exposed through the opening and the solder bump are in non-contact.

  (Supplementary note 2) The semiconductor laser device according to supplementary note 1, wherein a surface of the semiconductor laser closest to the active layer is opposed to the electrode through the solder bump.

  (Supplementary note 3) The semiconductor laser device according to Supplementary note 1 or 2, wherein a thermal expansion coefficient of the solder bump is larger than a thermal expansion coefficient of the substrate.

  (Supplementary Note 4) The semiconductor laser device according to any one of Supplementary Notes 1 to 3, wherein the plurality of openings are formed as a row arranged in an extending direction of the active layer.

  (Supplementary note 5) The semiconductor laser device according to supplementary note 4, comprising one or a plurality of the columns.

  (Supplementary note 6) The semiconductor according to supplementary note 5, wherein a part of the plurality of columns and the other columns are formed to face each other across a region immediately below the active layer. Laser device.

  (Supplementary note 7) The semiconductor laser device according to supplementary note 5, wherein any one of the one column or the plurality of the columns is formed immediately below the active layer.

  (Supplementary Note 8) A part of the plurality of columns except the one formed immediately below the active layer and the other columns are formed to face each other across the region immediately below the active layer. 8. The semiconductor laser device according to appendix 7, wherein:

  (Supplementary note 9) The semiconductor laser device according to any one of supplementary notes 1 to 3, wherein the plurality of openings are formed in a mosaic shape.

  (Supplementary note 10) The semiconductor laser device according to supplementary note 9, wherein a part of the plurality of openings is formed immediately below the active layer.

  (Additional remark 11) The semiconductor laser as described in any one of additional remark 1 thru | or 10 further provided with the base for semiconductor laser mounting formed between the said board | substrate around the said solder bump, and the said semiconductor laser. apparatus.

  (Supplementary note 12) The semiconductor laser device according to any one of Supplementary notes 1 to 11, wherein a surface of the substrate exposed through the opening is covered with silicon or a silicon oxide film.

  (Supplementary note 13) An electrode having a partial opening is formed on a substrate, a solder bump is formed on the electrode, a semiconductor laser is disposed above the solder bump, and the solder bump is melted. Then, by cooling, the semiconductor laser and the electrode are joined, and the solder bumps are brought into contact with the surface of the substrate exposed through the opening by melting, and then cooled and contracted. A semiconductor laser device that is in non-contact with the exposed surface of the substrate.

DESCRIPTION OF SYMBOLS 1 Solder contact part 2 Solder non-contact part 11, 41 Board | substrate 12, 22, 32, 42, 52, 52a, 52b PLC electrode 13, 43 LD mounting base 14, 44 Solder bump 15, 45 LD
16, 46 End face part 17, 47 Active layer 18, 28, 38 Opening part 72 Solder non-contact part 100, 200, 300, 400, 500 Semiconductor laser device E1, E3 Upper surface side electrode E2, E4 Back surface side electrode

Claims (10)

A substrate,
An electrode formed on the substrate and partially having an opening;
A semiconductor laser disposed above the electrode;
A solder bump formed between the electrode and the semiconductor laser,
The surface of the substrate exposed through the opening and the solder bump are not in contact with each other.
Semiconductor laser device. The semiconductor laser is
The surface closest to the active layer is opposed to the electrode via the solder bump,
The semiconductor laser device according to claim 1. The thermal expansion coefficient of the solder bump is larger than the thermal expansion coefficient of the substrate,
The semiconductor laser device according to claim 1 or 2. A plurality of the openings are formed as a row arranged in the extending direction of the active layer,
The semiconductor laser device according to claim 1. Comprising one or more of said columns,
The semiconductor laser device according to claim 4. A part of the plurality of the columns and the other columns are formed so as to face each other with a region immediately below the active layer interposed therebetween,
The semiconductor laser device according to claim 5. Any one of the one row or the plurality of the rows is formed immediately below the active layer,
The semiconductor laser device according to claim 5. A part of the plurality of columns except for those formed immediately below the active layer and the other columns are formed to face each other with a region immediately below the active layer interposed therebetween. To
The semiconductor laser device according to claim 7. A plurality of the openings are formed in a mosaic shape,
The semiconductor laser device according to claim 1. Forming an electrode partially having an opening on the substrate;
Forming solder bumps on the electrodes;
A semiconductor laser is disposed above the solder bump,
By melting the solder bump and then cooling, the semiconductor laser and the electrode are joined,
The solder bump is brought into contact with the surface of the substrate exposed through the opening by melting, and is then brought into non-contact with the exposed surface of the substrate by being cooled and contracted.
Manufacturing method of semiconductor laser device.

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