JP5511545B2 - Semiconductor laser element - Google Patents

Description

  The present invention relates to a semiconductor laser device, and more particularly to a protection structure for a ridge waveguide in a ridge type semiconductor laser device.

  Conventionally, Patent Document 1 discloses a semiconductor laser element in which a protective layer having a higher upper surface is provided on both sides of a ridge waveguide in order to protect the ridge waveguide.

JP 2003-298190 A

  By the way, in the said prior art, it is thought that the terminal electrically connected to a ridge waveguide is arrange | positioned on a protective layer. In this case, since the terminal is positioned at the top, there is a risk that the terminal may be damaged when the element is adsorbed in the manufacturing stage, or a foreign object may be adsorbed to the terminal when the element is fixed with an adhesive tape for cleavage. is there. Such flaws and foreign matter on the terminal may cause poor connection of wire bonding and poor recognition in image recognition.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a semiconductor laser device capable of protecting the ridge waveguide and the terminal.

  In order to solve the above problems, a semiconductor laser device according to the present invention includes an active layer disposed above a semiconductor substrate, a ridge waveguide disposed above the active layer and extending in one direction within the plane, and the active layer A pedestal portion disposed above the ridge waveguide in an in-plane direction; an electrode portion disposed above the ridge waveguide; and the pedestal portion electrically connected to the electrode portion. And a protective part arranged at a position different from the terminal part above the pedestal part. The upper end of the protection part is located above the electrode part and the terminal part.

  According to the present invention, the protection portion can protect the ridge waveguide and the terminal.

1 is a cross-sectional view of a semiconductor laser device according to a first embodiment of the present invention. FIG. 3 is a plan view of the semiconductor laser element according to the same embodiment. It is a figure showing the manufacturing process of the semiconductor laser element concerning the embodiment. It is a figure following FIG. 2A. It is a figure following FIG. 2B. It is a figure following FIG. 2C. It is a block diagram showing the module for optical communication carrying the semiconductor laser element concerning the embodiment. It is sectional drawing of the semiconductor laser element which concerns on 2nd Embodiment of this invention. It is sectional drawing of the semiconductor laser element which concerns on 3rd Embodiment of this invention. FIG. 3 is a plan view of the semiconductor laser element according to the same embodiment. It is a figure showing the manufacturing process of the semiconductor laser element concerning the embodiment. It is a figure following FIG. 6A. It is a figure following FIG. 6B. It is a figure following FIG. 6C. It is a figure following FIG. 6D.

  Embodiments of a semiconductor laser device of the present invention will be described with reference to the drawings. In the following description, numerical values such as material names and thicknesses of the respective layers of the semiconductor laser element are merely examples.

[First Embodiment]
1A and 1B are a sectional view and a plan view of the semiconductor laser device according to the first embodiment of the present invention. The semiconductor laser device of this embodiment is configured as a ridge type semiconductor laser device, and its oscillation wavelength is in the 1.3 μm band. In this semiconductor laser device, on a semiconductor substrate 1 made of n-type InP (indium phosphide), an n-type buffer layer 2 made of n-type InP, an n-type cladding layer 3 made of n-type InP, and an n-type InAlAs ( Indium aluminum arsenic) layer 4, an active layer 5 having a strained multiple quantum well structure including an InGaAlAs (indium gallium aluminum arsenide) well layer and an InGaAlAs barrier layer, a p-type InAlAs layer 6, and a p-type cladding layer made of p-type InP 7, a p-type hetero barrier reduction layer 8 made of p-type InGaAsP (indium gallium arsenide phosphorus), and a p-type contact layer 9 made of p-type InGaAs (indium gallium arsenide) are formed in this order. The material of the active layer 5 is an InGaAlAs material, but may be an InGaAsP material.

  A central portion in the width direction (left-right direction in FIG. 1B) of the upper layer portion 19 including the p-type cladding layer 7, the p-type hetero barrier reduction layer 8, and the p-type contact layer 9 is arranged in the front-rear direction (vertical direction in FIG. 1B). Two extending grooves are formed side by side in the width direction. A portion of the p-type cladding layer 7 sandwiched between the two grooves is a ridge waveguide 10, and a portion outside the two grooves is a pedestal portion 7 b. The ridge waveguide 10 extends linearly from end to end in the front-rear direction. The pedestal 7b is disposed away from the ridge waveguide 10 both in the width direction. The ridge waveguide 10 and the pedestal portion 7 b are disposed above the active layer 5. Note that the upper side of the active layer 5 may not be in contact with the active layer 5.

  A silicon oxide film 11 is formed on the surface of the etched upper layer portion 19. Furthermore, on the silicon oxide film 11, by deposition of Au, an electrode portion 12 located above the ridge waveguide 10, a terminal portion 13 located above one pedestal portion 7b, and both pedestal portions 7b An Au plated electrode 15 located above is formed. Specifically, the electrode portion 12 is electrically connected to the ridge waveguide 10 through an opening formed in the silicon oxide film 11. The terminal portion 13 is a pad for wire bonding and is formed in a circular shape. The electrode part 12 and the terminal part 13 are electrically connected via a connection part 23 formed along the inner surface of the groove. The Au plating electrode 15 is disposed away from the terminal portion 13 so as to be insulated from the terminal portion 13.

  On the Au plating electrode 15, a protective portion 14 made of Au plating deposited by electrolytic plating technology is formed. The protection unit 14 is deposited by energizing the Au plating electrode 15. For this reason, the Au plating electrode 15 is provided with a connection portion 45 for electrical connection with the Au plating electrode 15 of another adjacent semiconductor laser element before cleavage. The protection part 14 is formed relatively thick by electrolytic plating technology, and its upper end is located above the electrode part 12 and the terminal part 13.

  Each protection portion 14 is formed in a U shape with the ridge waveguide 10 side open, and is arranged to be line-symmetric with respect to the ridge waveguide 10 as an axis. The two sides constituting the U-shaped protection part 14 extend from the side closer to the ridge waveguide to the side farther from the side. Specifically, these sides extend while curving from the side near the ridge waveguide and outside in the front-rear direction toward the side far from the ridge waveguide and toward the center in the front-rear direction. Are connected to each other. The terminal portion 13 is located inside the U-shaped protection portion 14. That is, the range around the terminal portion 13 excluding the ridge waveguide 10 side is surrounded by the protection portion 14. The two side parts constituting the protection part 14 are respectively arranged on the front side and the rear side of the terminal part 13 so as to sandwich the terminal part 13 in the front-rear direction.

  Further, as shown in FIG. 1B, a multilayer reflective film 17 is formed on the front and rear cleavage surfaces of the semiconductor laser element. The multilayer reflective film 17 contains alumina, amorphous silicon, and silicon oxide.

  According to the semiconductor laser device described above, since the ridge waveguide 10 and the terminal portion 13 are protected by the protection portion 14, it is possible to suppress crystal chipping of the ridge waveguide 10, scratches on the terminal portion 13, and foreign matters. is there. As a result, it is possible to suppress poor connection of wire bonding to the terminal portion 13 and recognition failure in image recognition.

  In addition, since the protection portion 14 is formed above each pedestal portion 7b, the entire element is easily kept horizontal when being sucked by a nozzle or the like. Further, the stress generated in the element is made uniform. Each protection part 14 is preferably arranged so as to be line symmetric with respect to the ridge waveguide 10 as an axis.

  In addition, since the protective portion 14 includes a portion extending from the side closer to the ridge waveguide 10 to the side farther from the ridge waveguide 10, it is possible to disperse stress generated in the vicinity of the ridge waveguide 10 toward the side away from the ridge waveguide 10. is there.

  Further, since the protective portion 14 extends while being curved, the stress generated in the element is suppressed from being concentrated on a part of the protective portion 14. Moreover, since the protective part 14 is made of a metal such as Au, the chipping of the protective part 14 itself is suppressed by the ductility of the metal.

  In addition, since the two side portions constituting the protection portion 14 are respectively positioned on the front and rear sides of the terminal portion 13, the material of the multilayer reflection film 17 is formed on the terminal portion 13 when the multilayer reflection film 17 is formed. It is possible to suppress adhesion. That is, since the multilayer reflection film 17 is formed on the entire cleaved surface before and after the semiconductor laser element, there is a possibility that the material of the multilayer reflection film 17 protruding from the edge may go around the element upper surface. Therefore, by providing the protective part 14 as described above, it is possible to suppress the material of the multilayer reflective film 17 from adhering to the surface of the terminal part 13. As a result, it is possible to suppress poor connection of wire bonding to the terminal portion 13 and recognition failure in image recognition.

  When current was injected into the semiconductor laser device described above, laser oscillation occurred at a threshold current of 11 mA, and an oscillation spectrum was observed at a wavelength of 1301 nm. Further, the overall yield including basic characteristics, reliability, appearance inspection, and image recognition of the semiconductor laser element alone is 70% in the conventional semiconductor laser element not provided with the protection section 14, whereas the protection section 14 In the semiconductor laser device of the present embodiment including

  2A to 2D are views showing a manufacturing process of the semiconductor laser device according to the first embodiment.

  First, as shown in FIG. 2A, an n-type buffer layer 2 made of n-type InP having a thickness of 200 nm is formed on a semiconductor substrate 1 made of n-type InP by a well-known metal organic chemical vapor deposition method. An active layer having a strained multiple quantum well structure including an n-type cladding layer 3 made of 500 nm n-type InP, an n-type InAlAs layer 4 having a thickness of 30 nm, an InGaAlAs well layer having a thickness of 5 nm, and an InGaAlAs barrier layer having an thickness of 8 nm. 5, a p-type InAlAs layer 6 with a thickness of 30 nm, a p-type cladding layer 7 made of p-type InP with a thickness of 1600 nm, a p-type heterobarrier reduction layer 8 made of p-type InGaAsP with a thickness of 30 nm, and a thickness A p-type contact layer 9 made of 200 nm p-type InGaAs is stacked in this order.

  Next, as shown in FIG. 2B, a part of the upper layer portion 19 including the p-type cladding layer 7, the p-type hetero barrier reduction layer 8, and the p-type contact layer 9 is formed by a well-known photolithography technique (photoresist film). Etching to the middle or the whole of the p-type cladding layer 7 is performed by an etching technique using a mask. Thereby, the p-type cladding layer 7 is formed with the ridge waveguide 10 extending linearly in the front-rear direction and the pedestal portion 7b that is separated from the ridge waveguide 10 in the width direction. The width of the ridge waveguide 10 is 1.5 μm.

  Next, as shown in FIG. 2C, a silicon oxide film 11 having a thickness of 300 nm is deposited on the surface of the etched upper layer portion 19 by a CVD method. Thereafter, a part of the silicon oxide film 11 above the ridge waveguide 10 is removed by dry etching using the photoresist film as a mask, and a part of the upper surface of the ridge waveguide 10 is exposed.

  Next, as shown in FIG. 2D, on the surface of the silicon oxide film 11, an electrode portion 12 electrically connected to the ridge waveguide 10 by vapor deposition of Au, a terminal portion 13 for wire bonding, A connection part 23 that connects the electrode part 12 and the terminal part 13 and an Au plating electrode 15 for forming the protection part 14 are formed.

  Next, a protective portion 14 made of 2 μm Au plating is formed on the Au plating electrode 15 by electrolytic plating technology. The upper end of the protection part 14 is formed higher than the electrode part 12 and the terminal part 13. The specific configuration of the protection unit 14 is as described above. Further, the lower surface of the semiconductor substrate 1 is polished to form an n-electrode 16. Thereby, the cross-sectional structure shown in FIG. 1A is completed.

  Thereafter, the semiconductor substrate 1 is cleaved in a bar shape for each resonator length of 200 μm, and a multilayer reflective film 17 is formed on the cleaved end face. In addition, the semiconductor substrate 1 is cleaved and formed into chips every width of 400 μm. Thereby, the ridge type semiconductor laser device as shown in FIGS. 1A and 1B is completed.

  FIG. 3 is a block diagram showing an optical communication module on which the semiconductor laser device according to this embodiment is mounted. The optical communication module includes a semiconductor laser element 100, a photodiode 101, a thermistor 102, and a driver IC 103. The driver IC 103 drives the semiconductor laser element 100 according to the input data 104, whereby the semiconductor laser element 100 outputs an optical signal 105. As a result of evaluating the optical dynamic characteristics of the module for optical communication, a modulation spectral line width of 2.5 nm was obtained at a relaxation oscillation frequency of 19 GHz and a modulation signal frequency of 10 GHz.

[Second Embodiment]
FIG. 4 is a sectional view of a semiconductor laser device according to the second embodiment of the present invention. About the structure which overlaps with the said embodiment, detailed description is abbreviate | omitted by attaching | subjecting the same number. In the semiconductor laser device of this embodiment, an Au plating heat dissipating portion 20 for heat dissipation of the ridge waveguide 10 is provided on the electrode portion 12 disposed above the ridge waveguide 10. The Au plating heat radiation portion 20 is made of Au plating deposited by electrolytic plating technology, and is formed together with a part of the protection portion 14. Specifically, the Au plating heat dissipating part 20 is formed together with the lower part 14a of the protection part 14, and then electrolytic plating is performed again only on the lower part 14a to form the upper part 14b. The upper end of the protection part 14 formed in this way is located above the Au plating heat dissipation part 20. Thereby, the Au-plated heat radiating part 20 is protected by the protection part 14 together with the ridge waveguide 10 and the terminal part 13.

[Third Embodiment]
5A and 5B are a sectional view and a plan view of a semiconductor laser device according to the third embodiment of the present invention. About the structure which overlaps with the said embodiment, detailed description is abbreviate | omitted by attaching | subjecting the same number. In the semiconductor laser device of this embodiment, a ridge protective layer 18 as a spacer layer made of non-doped InP is formed on the p-type contact layer 9. Therefore, the ridge protective layer 18 is located above the ridge waveguide 10. A terminal portion 13 and an Au plating electrode 15 are disposed above the ridge protective layer 18. Further, an Au plating heat dissipating part 20 is provided on the electrode part 12 disposed above the ridge waveguide 10. The Au plating heat radiation part 20 is made of Au plating deposited by electrolytic plating technology, and is formed together with the protection part 14. Here, since the Au plating electrode 15 is provided above the ridge protection layer 18, the upper end of the protection part 14 formed together with the Au plating heat dissipation part 20 is located above the Au plating heat dissipation part 20. Become. Thereby, the Au-plated heat radiating part 20 is protected by the protection part 14 together with the ridge waveguide 10 and the terminal part 13.

  6A to 6E are views showing a manufacturing process of the semiconductor laser device according to the third embodiment. First, as shown in FIG. 6A, a ridge protective layer 18 made of non-doped InP having a thickness of 700 nm is stacked on the p-type contact layer 9.

  Next, as shown in FIG. 6B, the ridge protective layer 18 is patterned into a stripe shape by photolithography, and an opening 18a having a width of 25 μm extending in the front-rear direction is formed at the center in the width direction. At this time, the upper surface of the p-type contact layer 9 made of p-type InGaAs is exposed at the bottom of the opening 18a.

  Next, as shown in FIG. 6C, a part of the bottom of the opening 18a is further etched to the middle or the whole of the p-type cladding layer 7, thereby extending linearly in the front-rear direction to the p-type cladding layer 7. The ridge waveguide 10 and the pedestal portion 7b that is separated from the ridge waveguide 10 in the width direction are formed.

  Next, as shown in FIG. 6D, a silicon oxide film 11 having a thickness of 300 nm is deposited on the surface of the ridge protective layer 18 and the inner surface of the opening 18a by the CVD method. Thereafter, a part of the silicon oxide film 11 above the ridge waveguide 10 is removed by dry etching using the photoresist film as a mask, and a part of the upper surface of the ridge waveguide 10 is exposed.

  Next, as shown in FIG. 6E, on the surface of the silicon oxide film 11, an electrode portion 12 electrically connected to the ridge waveguide 10 by deposition of Au, a terminal portion 13 for wire bonding, A connection part 23 that connects the electrode part 12 and the terminal part 13 and an Au plating electrode 15 for forming the protection part 14 are formed.

  Next, a resist mask is formed so that the electrode portion 12 and the Au plating electrode 15 are exposed, and the Au plating heat radiation portion 20 and the protection portion 14 made of 2 μm Au plating are formed together by an electrolytic plating technique. . The upper end of the protection part 14 is formed higher than the Au plating heat dissipation part 20 and the terminal part 13. The specific configuration of the protection unit 14 is as described above. Further, the lower surface of the semiconductor substrate 1 is polished to form an n-electrode 16. Thereby, the cross-sectional structure shown in FIG. 5A is completed.

  Thereafter, the semiconductor substrate 1 is cleaved in a bar shape for each resonator length of 200 μm, and a multilayer reflective film 17 is formed on the cleaved end face. In addition, the semiconductor substrate 1 is cleaved and formed into chips every width of 400 μm. Thereby, the ridge type semiconductor laser device as shown in FIGS. 5A and 5B is completed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made by those skilled in the art.

  DESCRIPTION OF SYMBOLS 1 Semiconductor substrate, 2 n-type buffer layer, 3 n-type cladding layer, 4 n-type InAlAs layer, 5 active layer, 6 p-type InAlAs layer, 7 p-type cladding layer, 7b base part, 8 p-type hetero barrier reduction layer, 9 p-type contact layer, 10 ridge waveguide, 11 silicon oxide film, 12 electrode part, 13 terminal part, 14 protective part, 14a lower part, 14b upper part, 15 Au plated electrode, 16 n electrode, 17 multilayer reflective film, 18 ridge Protective layer, 18a opening, 19 upper layer part, 20 Au plating heat radiation part, 23 connection part, 45 connection part, 100 semiconductor laser element, 101 photodiode, 102 thermistor, 103 driver IC, 104 input data, 105 optical signal.

Claims (9)

An active layer disposed above the semiconductor substrate;
A ridge waveguide disposed above the active layer and extending in one direction in the plane;
A pedestal disposed above the active layer and spaced in the in-plane direction from the ridge waveguide;
An electrode portion disposed above the ridge waveguide;
A terminal portion electrically connected to the electrode portion and disposed above the pedestal portion;
A protective part disposed at a position different from the terminal part above the pedestal part, and an upper end of the protective part is located above the electrode part and the terminal part; and
Equipped with a,
The protective portion extends in an in-plane direction while being curved,
A semiconductor laser device. The pedestal is disposed in both the width direction of the ridge waveguide,
The protection part is formed above each pedestal part,
The semiconductor laser device according to claim 1. Each of the protection portions is arranged to be symmetric about the ridge waveguide.
The semiconductor laser device according to claim 2. The protective portion includes a portion extending from a side near the ridge waveguide to a side far from the ridge waveguide.
The semiconductor laser device according to claim 1. The protective part includes a portion located in the extending direction of the ridge waveguide with respect to the terminal part,
The semiconductor laser device according to claim 1. The protective part is made of metal.
The semiconductor laser device according to claim 1. A heat dissipating part disposed above the ridge waveguide and the electrode part;
The upper end of the protection part is located above the heat dissipation part,
The semiconductor laser device according to claim 1. The protective part includes an upper part and a lower part,
One of the upper part and the lower part is formed together with the heat dissipation part,
The semiconductor laser device according to claim 7 . A spacer layer is disposed between the pedestal part and the protection part,
The protection part is formed together with the heat dissipation part,
The semiconductor laser device according to claim 7 .

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