JP2019004064A - Multi-beam semiconductor laser element and multi-beam semiconductor laser device - Google Patents

Abstract

To provide a multi-beam semiconductor laser element and a multi-beam semiconductor laser device which are capable of independently activating multiple beams with a narrow pitch and stability.SOLUTION: A multi-beam semiconductor laser element (semiconductor chip) 20 comprises a semiconductor layer formed over a semiconductor substrate 21, and including an n-type clad layer 22, an active layer 23, a p-type first clad layer 24 and a p-type second clad layer 25. The semiconductor chip 20 comprises: a plurality of ridge parts 27 formed on the p-type second clad layer 25, extending along a light outgoing direction from a front end face to a rear end face, and arrayed in order along a direction orthogonal to the light outgoing direction; a plurality of conductive layers 30 and 31 formed on the plurality of ridge parts 27 respectively; and a concave part 32 formed on a face to be joined to a submount of the second conductive layer 31 along the light outgoing direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a multi-beam semiconductor laser element and a multi-beam semiconductor laser device.

Conventionally, there has been known a multi-beam semiconductor laser device in which a multi-beam semiconductor laser element (semiconductor chip) having a plurality of emitters (light emitting points) is joined to a submount by junction down mounting. In such a multi-beam type semiconductor laser device, multiple beams are independently driven, and an electrically isolated electrode must be formed on each ridge corresponding to each of the plurality of emitters. There is.
For example, in Patent Document 1, in a multi-beam semiconductor laser device, the width of solder formed on the surface of the submount electrode (electrode width) is larger than the width of the conductive layer (electrode width) formed on the upper surface of the surface electrode of the semiconductor chip. A point of widening the solder width) is disclosed. In this way, by making the solder width wider than the electrode width, even if extra solder is generated during fusion bonding, the extra solder is spread over the entire solder area that is not in contact with the electrode, and local protrusion is suppressed. However, it is difficult to generate solder balls. This prevents the solder balls from coming into contact with the adjacent emitter electrode and causing a short circuit.

JP 2014-22481 A

However, in the multi-beam type semiconductor laser device, in recent years, a further narrow pitch (for example, a beam pitch of 40 μm or less) has been demanded. As the distance between the emitters adjacent to each other becomes shorter, it becomes more difficult to make the solder width wider than the electrode width, and thus it becomes difficult to suppress the generation of solder balls during fusion bonding.
Accordingly, an object of the present invention is to provide a multi-beam semiconductor laser element and a multi-beam semiconductor laser device that can stably perform independent beam driving with a narrow pitch.

  In order to solve the above problems, one aspect of a multi-beam semiconductor laser device according to the present invention includes a semiconductor layer formed on a semiconductor substrate and including a first cladding layer, an active layer, and a second cladding layer. A multi-beam semiconductor laser element, which is formed in the second cladding layer, extends from the front end surface to the rear end surface along the light emission direction, and is arranged in order along the direction orthogonal to the emission direction. A plurality of ridges formed on the plurality of ridges, a plurality of conductive layers formed on the plurality of ridges, and a surface to be bonded to a submount of the conductive layer along the light emitting direction. And a recessed portion formed.

  As described above, since the concave portion is formed on the surface of the conductive layer to be joined to the submount, when the conductive layer and the submount are joined via solder during mounting, excess solder is added to the concave portion. Can be stored. Therefore, it can suppress that excessive solder is pushed outside and becomes a solder ball. Therefore, it can suppress that the formed solder ball contacts the electrode of the adjacent emitter, etc., and can suppress the short circuit between the adjacent emitters appropriately. As a result, independent driving of the laser can be performed stably. Further, even if the solder width is not widened, excess solder can be accommodated by the concave portion, so that a narrow pitch can be accommodated.

In the multi-beam semiconductor laser element, the conductive layer includes a first conductive layer and a second conductive layer formed on the first conductive layer, and the concave portion includes the second conductive layer. It may be formed in a layer.
As described above, when the conductive layer has at least a two-stage structure of the first conductive layer and the second conductive layer, the second conductive layer is shifted from above the ridge portion, and stress is hardly applied to the ridge portion during mounting. it can. As a result, the polarization angle rotation and the relative difference between the beams of the polarization angle due to the stress can be reduced, and the optical characteristics can be stabilized. Further, in this case, since the second conductive layer is positioned above the ridge portion, the second conductive layer approaches the adjacent emitter, but a concave portion is formed in the second conductive layer. Therefore, the formation of solder balls at the time of mounting can be appropriately suppressed, and a short circuit between the emitters can be appropriately suppressed.

Furthermore, in the multi-beam semiconductor laser element, the concave portion may be formed with a closed portion on at least one of the front end surface side and the rear end surface side.
In this case, it is possible to prevent the solder drawn into the concave portion during mounting from being pushed out from the end surface of the concave portion. Thereby, it is possible to avoid a situation in which the solder pushed out from the end surface of the concave portion shields the laser light emission surface.

In the multi-beam semiconductor laser element, an opening may be formed on a side surface of the concave portion. Here, the side surface of the concave portion is a surface facing the direction orthogonal to the direction in which the concave portion extends. Thus, by forming the opening on the side surface of the concave portion, the air in the concave portion can be extracted from the opening, and the solder can be easily drawn into the concave portion.
Further, in the multi-beam semiconductor laser device, the opening is a side close to the electrically conducting ridge portion among two side surfaces facing in a direction orthogonal to the light emitting direction. It may be formed on the side surface. In this case, even when the solder drawn into the concave portion is pushed out from the opening, the solder comes into contact with an electrically conducting electrode or the like, and between adjacent emitters. There is no electrical short circuit.

In the multi-beam semiconductor laser element, a recess corresponding to the recess may be formed in at least one of the semiconductor substrate and the semiconductor layer. As described above, when the concave portion is formed on the surface serving as the base of the conductive layer, the concave portion reflecting the shape of the concave portion is reflected on the outermost surface of the conductive layer by arranging the conductive layer so as to cover the concave portion. Can be formed.
Further, in the multi-beam semiconductor laser device, the periphery of the concave portion on the surface to be bonded to the submount of the conductive layer is made of a material having poor solder wettability with respect to the inner surface of the concave portion. May be. In this case, the solder can easily be drawn into the concave portion, and the formation of solder balls can be suppressed more appropriately.

  According to another aspect of the present invention, there is provided a multi-beam semiconductor laser device including a multi-beam semiconductor laser element and a submount on which the multi-beam semiconductor laser element is mounted via a solder layer. In the semiconductor laser device, the multi-beam semiconductor laser element is formed on a semiconductor layer including a first cladding layer, an active layer, and a second cladding layer formed on a semiconductor substrate, and the second cladding layer. A plurality of ridge portions that extend along the light emission direction from the front end surface to the rear end surface and that are arranged in order along the direction orthogonal to the emission direction, and on each of the plurality of ridge portions, respectively. A plurality of conductive layers formed, and the submount is formed corresponding to each of the plurality of ridge portions, and the submount is interposed through the solder layer. Comprising a plurality of electrode portions which are bonded to the conductive layer, the concave portion on at least one of the contact with the solder layer surface of the contact with the solder layer surface and the electrode portion of the conductive layer is formed.

As described above, since the concave portion is formed on at least one of the surface of the conductive layer in contact with the solder layer and the surface of the electrode portion in contact with the solder layer, the conductive layer and the submount are joined via solder during mounting. In addition, excess solder can be stored in the concave portion. Therefore, it can suppress that excessive solder is pushed outside and becomes a solder ball. Therefore, it can suppress that the formed solder ball contacts the electrode of the adjacent emitter, etc., and can suppress the short circuit between the adjacent emitters appropriately. As a result, independent driving of the laser can be performed stably. Further, even if the solder width is not widened, excess solder can be accommodated by the concave portion, so that a narrow pitch can be accommodated.
Furthermore, in the multi-beam semiconductor laser device, the width of the solder layer may be equal to or smaller than the width of the conductive layer in a direction orthogonal to the light emission direction. Thereby, it can respond to the further narrow pitch.

According to another aspect of the present invention, there is provided a multi-beam semiconductor laser device including a semiconductor layer including a first cladding layer, an active layer, and a second cladding layer formed on a semiconductor substrate. A method of manufacturing a semiconductor laser device, wherein the second cladding layer extends in a light emitting direction from a front end surface to a rear end surface, and is arranged in order along a direction orthogonal to the emitting direction. Forming a ridge portion; forming a conductive layer on each of the plurality of ridge portions; and forming a concave portion along a light emitting direction on a surface of the conductive layer to be bonded to a submount. And a step of performing.
As a result, a multi-beam semiconductor laser element capable of stably performing independent driving of the beam with a narrow pitch can be manufactured.

  According to the present invention, even when the distance between adjacent ridge portions is small, it is possible to suppress short-circuit defects due to solder balls between the ridge portions. Accordingly, it is possible to realize a multi-beam semiconductor laser element and a multi-beam semiconductor laser device that can stably perform independent beam driving with a narrow pitch.

1 is an overall configuration diagram of a multi-beam semiconductor laser device according to an embodiment. It is sectional drawing which shows the structure of a multi-beam type semiconductor laser element. It is a top view which shows an example of a recessed part. It is a top view which shows an example of a recessed part. It is a side view which shows an example of a recessed part. It is a conceptual diagram of a concave part. It is a conceptual diagram of a concave part. It is an example of the manufacturing method of a recessed part. It is a figure for demonstrating the short circuit defect between adjacent emitters. It is sectional drawing which shows another example of a multi-beam type semiconductor laser apparatus. It is sectional drawing which shows another example of a multi-beam type semiconductor laser apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The embodiment described below is an example as means for realizing the present invention, and should be appropriately modified or changed according to the configuration and various conditions of the apparatus to which the present invention is applied. It is not limited to the embodiment. In the drawings described below, the same or functionally similar components are denoted by the same reference numerals, and repeated description thereof is omitted. Further, each drawing is shown for easy understanding when referred to in conjunction with the following description, and is not necessarily drawn to scale.

FIG. 1 is a diagram illustrating a configuration example of a multi-beam type semiconductor laser device (hereinafter simply referred to as “semiconductor laser device”) 100 according to the present embodiment. The semiconductor laser device 100 according to this embodiment can be used as a light source of an image printing apparatus such as a laser printer or a copying machine.
The semiconductor laser device 100 includes a submount 10 and a multi-beam semiconductor laser element (hereinafter referred to as “semiconductor chip”) 20.
The submount 10 is a support substrate for supporting the semiconductor chip 20. The submount 10 can be made of a ceramic such as AlN or SiC. The semiconductor chip 20 is mounted on the submount 10 by a junction down method.

  In this embodiment, the semiconductor chip 20 is a four-beam semiconductor laser device having four emitters (light emitting points), and has a configuration in which a plurality of semiconductor layers including an active layer are stacked on a substrate. For example, in the semiconductor chip 20, at least an n-type cladding layer (first cladding layer), an active layer, a p-type cladding layer (second cladding layer), and a p-type contact layer are stacked in this order on an n-type semiconductor substrate. Can have different configurations. A specific configuration of the semiconductor chip 20 will be described later. The semiconductor chip 20 emits laser light having a predetermined oscillation wavelength from both end surfaces (upper and lower end surfaces in FIG. 1) when a predetermined injection current is supplied. The oscillation wavelength of the laser light emitted from the semiconductor chip 20 is not particularly limited.

  The submount 10 on which the semiconductor chip 20 is placed is bonded to the heat sink unit 40. The heat sink portion 40 is provided in the vicinity of the center portion of the circular surface of the disc-shaped stem 41. In the present embodiment, the submount 10 is joined to the heat sink portion 40 so that the emission direction of the laser light emitted from the semiconductor chip 20 coincides with the direction perpendicular to the circular surface of the stem 41. . Further, at this time, the submount 10 may be joined to the heat sink portion 40 so that the light emitting point of the semiconductor chip 20 is located at the approximate center of the circular surface of the stem 41.

The submount 10, the semiconductor chip 20, and the heat sink 40 are covered with a cylindrical cap 42 together with peripheral lead pins and wires. The cap 42 is attached for the purpose of protecting the semiconductor chip 20, the wire, and the like. A light extraction window 43 is provided in the opening formed in the center of the upper surface of the cap 42, and the laser light emitted from the upper end surface of the semiconductor chip 20 passes through the light extraction window 43 and is a semiconductor laser device. 100 is emitted to the outside.
The heat sink 40 is made of a highly heat radiating metal material (for example, Cu), and the heat generated by the semiconductor chip 20 during light emission is transmitted to the heat sink 40 via the submount 10 and radiated.

Next, a specific configuration of the semiconductor chip 20 will be described.
FIG. 2 is a principal cross-sectional view showing a specific configuration of the semiconductor chip 20. As shown in FIG. 2, the semiconductor chip 20 includes a semiconductor substrate 21 and a plurality of semiconductor layers stacked on the main surface of the semiconductor substrate 21. Here, the semiconductor substrate 21 may be a GaAs substrate, for example. In addition, the semiconductor layer includes an n-type cladding layer 22, an active layer 23, a p-type first cladding layer 24, and a p-type second cladding layer deposited by, for example, metal organic chemical vapor deposition (MOCVD). 25 and p-type contact layer 26. Here, the n-type cladding layer 22 corresponds to the first cladding layer, and the p-type first cladding layer 24 and the p-type second cladding layer 25 correspond to the second cladding layer.
The n-type cladding layer 22 is made of, for example, AlGaInP. The active layer 23 has, for example, a multi quantum well (MQW) structure in which barrier layers made of AlGaInP and well layers made of GaInP layers are alternately stacked. The p-type first cladding layer 24 and the p-type second cladding layer 25 are each made of, for example, AlGaInP, and the p-type contact layer 26 is made of, for example, GaAs.

The p-type second cladding layer 25 is formed with a plurality of ridge portions (mesa stripes) 27 having a convex cross-sectional shape and extending in parallel with each other. In the present embodiment, since the semiconductor chip 20 is a four-beam semiconductor laser element, four ridge portions 27 are formed in the p-type second cladding layer 25. In FIG. 2, two ridge portions 27 of the four ridge portions 27 are shown. Each of the plurality of ridge portions 27 corresponds to one emitter.
The ridge 27 extends along the light emission direction (resonator direction) from the front end surface to the rear end surface, and in the plane on the p-type second cladding layer 25, the light emission direction (resonator direction). ) Are formed side by side along a direction orthogonal to the above.
The p-type contact layer 26 is formed on each of the p-type second cladding layers 25 constituting the ridge portion 27. That is, the ridge portion 27 has a two-layer structure of the p-type second cladding layer 25 and the p-type contact layer 26.

  A passivation film (insulating oxide film) 28 made of, for example, silicon oxide is formed on the surface of the p-type second cladding layer 25 and the ridge portion 27. However, the passivation film 28 is not formed in the region that becomes the top (the lower surface in FIG. 2) of the ridge 27, and the p-type contact layer 26 is exposed at the top. A p-type surface electrode 29 ohmically connected to the p-type contact layer 26 is formed on the surface of the p-type contact layer 26 and the surface of the passivation film 28. The surface electrode 29 includes at least one of Ti, Cr, Mo, W, Ni, Pt, Cu, Ag, and Au. For example, the surface electrode 29 can be a multilayer metal film in which a Ti film, a Pt film, and an Au film are sequentially stacked from the side closer to the semiconductor substrate 21.

  A conductive layer is formed on the surface electrode 29. In the present embodiment, the conductive layer includes a first conductive layer (first-stage thick film electrode) 30 formed on the surface electrode 29 and a first conductive layer formed on a part of the first conductive layer 30. A second conductive layer (second-stage thick film electrode) 31 having a smaller area than the layer 30 is formed. The first conductive layer 30 and the second conductive layer 31 are gold (Au) layers formed by, for example, a plating method. Further, a concave portion 32 is formed on the surface (the lower surface in FIG. 2) to be joined to the submount 10 of the second conductive layer 31. Further, an n-type back electrode 33 is formed on the back surface (the top surface in FIG. 2) of the semiconductor substrate 21. The back electrode 33 can have the same configuration as the above-described front electrode 29.

  In the semiconductor chip 20, when a predetermined current is injected into the front surface electrode 29 and the back surface electrode 33, the active layer 23 under each of the four ridge portions 27 serves as a light emitting point, for example, a red color having an oscillation wavelength of 650 nm. Oscillates the laser beam. The red laser beam is emitted from both end faces (resonator end faces) of the semiconductor chip 20, which are surfaces orthogonal to the extending direction of the ridge 27, and the forward light thereof is the light of the cap 42 shown in FIG. The light is emitted to the outside of the CAN package through the extraction window 43.

  On the other hand, on the chip mounting surface (upper surface in FIG. 2) of the submount 10, there are four submount electrodes (electrode portions) 12 made of a multilayer metal film in which, for example, a Pt film and an Au film are sequentially laminated on a Ti film. Is formed. These four submount electrodes 12 are arranged corresponding to the ridge portions 27 of the semiconductor chip 20 when the semiconductor chip 20 is mounted on the submount 10. Specifically, each submount electrode 12 is disposed so as to face each second conductive layer 31.

A solder layer 13 made of, for example, AuSn is formed on each surface of the submount electrode 12. Here, the width of the solder layer 13 formed on the surface of the submount electrode 12 in the arrangement direction of the plurality of ridge portions 27 (in the plane on the p-type second cladding layer 25 and in the direction orthogonal to the resonator direction). Is equal to or less than the width of the second conductive layer 31. That is, when the width of the second conductive layer 31 is W and the width of the solder layer 13 is L, the relationship of W ≧ L is established.
The surface electrode 29 of the semiconductor chip 20 and the submount electrode 12 of the submount 10 are electrically connected by melting and bonding the solder layer 13 and the second conductive layer 31.

  As described above, in the present embodiment, the concave portion 32 is formed on the surface (joint surface) to be joined to the submount 10 of the second conductive layer 31. Therefore, excess solder of the solder layer 13 that can be generated during fusion bonding is stored in the concave portion 32 and is suppressed from being pushed out of the second conductive layer 31. That is, the formation of solder balls can be suppressed. Thereby, it can suppress that a solder ball contacts the electrode (for example, 1st conductive layer 30) of the emitter which adjoins, and can suppress that it short-circuits between the mutually adjacent emitters. As a result, each beam can be stably driven independently. In addition, a decrease in assembly yield can be suppressed.

  FIG. 3 is a plan view showing an example of the concave portion 32. FIG. 3 is a view of the second conductive layer 31 as viewed from above in FIG. As shown in FIG. 3, the concave portion 32 can be formed along the light emission direction (resonator direction) and closed at both ends. As described above, since the closed portions are formed at both ends of the concave portion 32 in the resonator direction, it is possible to prevent the solder drawn into the concave portion 32 during fusion bonding from being pushed out from the resonator end face side. it can. Thereby, the situation where the solder pushed out from the resonator end face side shields the laser emission surface can be avoided. In addition, the said obstruction | occlusion part may be formed only in any one of the front end surface side and the back end surface side.

Moreover, as shown in FIG. 4, the recessed part 32 may be formed with an opening 32a for venting air on its side surface. Here, the side surface of the concave portion 32 is a surface facing the direction orthogonal to the direction in which the concave portion 32 extends. Thus, by providing the opening 32a in the concave portion 32, the concave portion 32 can easily contain solder, and the formation of solder balls can be more appropriately suppressed. It should be noted that the position and size of the opening 32a are not limited to the position and size shown in FIG. 4, and can be any position and size. In FIG. 4, only one opening 32 a is provided at a substantially central position in the resonator direction, but a plurality of openings 32 a may be provided.
However, as shown in FIG. 5, the opening 32 a is located on the side close to the ridge 27 where the second conductive layer 31 is electrically conductive, of the two side surfaces facing in the direction orthogonal to the resonator direction. It is preferably formed on the side surface. In this case, even if the solder is pushed out together with air from the opening 32a, the problem of short circuit failure does not occur. As described above, when the opening 32a is formed on the side surface close to the ridge portion 27 where the second conductive layer 31 is electrically conductive, if both ends in the resonator direction are closed, for example, the side surface The entire surface may be open.

  Moreover, the recessed part 32 can be formed by arbitrary manufacturing methods. For example, the concave portion 32 can be formed by multistage plating. That is, the concave portion 32 can be formed by a photolithography process and a process of depositing a plating film only on the resist opening, and by a manufacturing method in which the area of the resist opening is narrowed toward the upper layer. Here, as shown in FIG. 2, when the cross-sectional shape orthogonal to the resonator direction of the concave portion 32 is a half-moon shape, etching for smoothing the step may be performed after the multi-step plating. The manufacturing method of the concave portion 32 is not limited to the above. For example, a method of performing wet etching by providing an etching stop layer, or forming a thick conductive layer, and then forming the concave portion in a photolithography process. It is also possible to use a method of opening the power range and then performing dry etching (ion milling or the like) or wet etching to dent the conductive layer in the resist opening.

Furthermore, the recessed part 32 can also be formed by another manufacturing method. For example, a recess (recess) is formed on the surface on which the second conductive layer 31 is formed, and the second conductive layer 31 is formed thereon, so that the recess 32 reflecting the shape of the recess is formed. You may make it form the 2nd conductive layer 31 which has.
FIG. 6 is a conceptual diagram when the concave portion 32 is formed by forming the recess 25 a in the p-type second cladding layer 25. As shown in FIG. 6, by forming the first conductive layer 30 on the p-type second cladding layer 25 in which the depression 25a is formed, the depression 30a reflecting the depression 25a is formed on the first conductive layer 30. Form. Then, by forming the second conductive layer 31 on the first conductive layer 30 in which the recess 30a is formed, the concave portion 32 reflecting the recess 30a may be formed in the second conductive layer 31. .

Instead of forming the depression 25a in the p-type second cladding layer 25, the depression 30a is formed by intermittently forming the first conductive layer 30 as shown in FIG. The concave portion 32 can be similarly formed by forming the concave recess 30a in the layer 30. In FIG. 6, the case where the depression 25 a is formed in the p-type second cladding layer 25 has been described. However, the depression is formed in the semiconductor substrate 21 and the semiconductor layer closer to the semiconductor substrate 21 than the p-type second cladding layer 25. The concave portion 32 may be formed on the surface of the second conductive layer 31 that is the outermost surface while maintaining the depression.
Thus, the cross-sectional shape orthogonal to the resonator direction of the concave portion 32 is not limited to the half-moon shape as shown in FIG. 2, but is a rectangular shape or a substantially rectangular shape as shown in FIGS. There may be. In addition, the said cross-sectional shape is not limited above, Arbitrary shapes may be sufficient.

Further, it is preferable that the periphery of the concave portion 32 on the joint surface of the second conductive layer 31 with the solder layer 13 is made of a material having poor solder wettability with respect to the inner surface of the concave portion 32. Here, the periphery of the concave portion 32 is a region other than the concave portion 32 on the surface of the second conductive layer 31.
In this case, for example, as shown in FIG. 8A, first, on the second conductive layer 31, a material 31a (for example, Pt, Pt, etc.) having lower wettability than the material (for example, Au) constituting the second conductive layer 31 is formed. Ti, Ni, etc.) are formed, the region other than the region where the concave portion 32 is formed is covered with a resist R, and the concave portion 32 is formed by etching. Then, if the resist R is removed, as shown in FIG. 8B, the material 31a having poor wettability may be disposed around the concave portion 32 on the joint surface.
Further, photolithography and etching may be further performed to remove the poorly wettable material 31a on the bottom surface of the second conductive layer 31, as shown in FIG.

  Thereby, the solder can be more easily drawn into the concave portion 32. Instead of disposing a material with poor wettability around the concave portion 32, the inner surface of the concave portion 32 may be coated with a material with good wettability around the concave portion 32. Further, the manufacturing method for facilitating the drawing of solder into the concave portion 32 is not limited to the above. For example, the surface modification of the inner surface of the concave portion 32 can be performed by plasma cleaning, excimer laser irradiation, or the like.

Hereinafter, a method for manufacturing the semiconductor laser device 100 according to the present embodiment will be described.
First, a method for manufacturing the semiconductor chip 20 will be described. In manufacturing the semiconductor chip 20, first, the MOCVD, LPE (Liquid Phase Epitaxy) method or the like is used to form an n-type cladding layer 22, an active layer 23, a p-type first cladding layer 24, and a p-type second cladding on the semiconductor substrate 21. The layer 25 and the p-type contact layer 26 are sequentially stacked.
Next, an oxide film is formed on the p-type contact layer 26, and the oxide film is patterned using photolithography and etching processes. The p-type second cladding layer 25 and the p-type contact layer 26 are formed along the pattern. Etch. Thereby, a plurality of (four in this embodiment) ridge portions 27 are formed.

  Next, a passivation film 28 is formed on the entire surface of the wafer, and the passivation film 28 formed in a region to be the upper surface of each ridge portion 27 is removed by photolithography and etching, and the p-type contact layer 26 in the region is exposed. Let Then, the surface electrode 29 is formed on the entire surface of the wafer and formed into a predetermined shape. Subsequently, the first conductive layer 30 and the second conductive layer 31 are formed in a predetermined shape on the surface electrode 29 by, for example, a gold plating method. At this time, the concave portion 32 is formed after the film formation of the second conductive layer 31 or at the same time. This completes the p-side process.

Next, the n-side process will be described. First, the wafer is fixed with the device surface (p side in this embodiment) facing down, and the back surface (n side in this embodiment) of the semiconductor substrate 21 is polished to a desired thickness. Then, the back electrode 33 is formed on the polished surface.
Finally, the semiconductor chip 20 according to the present embodiment is completed by turning the wafer into chips.
Note that a conductive layer (thick film electrode) may also be formed on the back electrode 33 after the back electrode 33 is formed. Thus, by forming a conductive layer also on the back electrode 33, an effect of reducing warpage of the wafer or chip resulting from the device surface side having an extremely multilayer and thick film structure can be obtained.

Next, a method for manufacturing the semiconductor laser device 100 will be described.
First, the solder layer 13 is formed in a predetermined shape on the submount electrode 12 of the submount 10. At this time, the width L of the solder layer 13 is equal to or less than the width W of the second conductive layer 31.
When the semiconductor chip 20 is mounted on the submount 10, the recognition pattern formed on the submount 10 and the recognition pattern formed on the semiconductor chip 20 are recognized using a CCD camera or the like. Then, the recognized patterns of both recognized are aligned, and the semiconductor chip 20 is mounted on the submount 10 by the junction down method. The submount electrode 12 of the submount 10 is formed at a position facing the second conductive layer 31 of the semiconductor chip 20, and the second conductive layer 31 is formed on the solder layer 13 formed on the submount electrode 12. By bonding, the surface electrode 29 of the semiconductor chip 20 and the submount electrode 12 are electrically connected.

  After the semiconductor chip 20 is bonded to the submount 10, the semiconductor chip 20 is bonded to the disc-shaped stem 41 that constitutes the semiconductor laser device 100 together with the submount 10. Specifically, the submount 10 to which the semiconductor chip 20 is bonded is bonded to a heat sink 40 provided on the stem 41 via solder or the like. Next, the front surface electrode 29 and the back surface electrode 33 of the semiconductor chip 20 can be energized by wire bonding. Finally, a cylindrical cap 42 is attached to the disk-shaped surface of the stem 41 and hermetically sealed by welding or the like. To do. The semiconductor laser device 100 is completed through the above steps.

  As described above, the multi-beam semiconductor laser element (semiconductor chip) 20 in this embodiment includes the n-type cladding layer 22, the active layer 23, the p-type first cladding layer 24, and the p-type formed on the semiconductor substrate 21. A plurality of ridge portions 27 extending in the direction of the resonator, formed in the p-type second cladding layer 25 corresponding to the plurality of emitters, and a plurality of ridge portions, respectively. A plurality of surface electrodes 29 respectively formed on the plurality of surface electrodes 29, and a plurality of conductive layers respectively formed on the plurality of surface electrodes 29. Here, the conductive layer can be configured to include a first conductive layer 30 formed on the surface electrode 29 and a second conductive layer 31 formed on the first conductive layer 30. A concave portion 32 is provided on the surface of the second conductive layer 31 to be joined to the submount.

  Thus, since the recessed part 32 is formed in the surface which should be joined to the submount of the 2nd conductive layer 31, the 2nd conductive layer 31 and the submount electrode of the submount 10 are interposed through the solder layer 13 at the time of mounting. When joining 12, excess solder of the solder layer 13 can be accommodated in the concave portion 32. Therefore, it can suppress that excessive solder is pushed outside and becomes a solder ball. Therefore, it can suppress that the formed solder ball contacts the electrode of the adjacent emitter, etc., and can suppress the short circuit between the adjacent emitters appropriately. As a result, independent driving of the laser can be performed stably. In addition, even if the solder width is not widened, excess solder can be accommodated by the concave portion 32, so that a narrow pitch can be accommodated.

By the way, in order to suppress the generation of solder balls, it is considered to make the solder width wider than the width of the conductive layer formed on the surface electrode of the semiconductor chip. In this case, excess solder generated during fusion bonding is pushed outward, but since the solder width is wider than the electrode width, the excess solder spreads over the entire solder region not in contact with the electrode, and the solder is locally localized. Protrusion is suppressed and solder balls are hardly generated. However, as a demand from the market, further narrowing of the pitch is required, and in such a narrow pitch semiconductor laser device, it is difficult to make the solder width wider than the electrode width. Therefore, it becomes difficult to appropriately suppress the formation of solder balls.
That is, as shown in FIG. 9, in the semiconductor laser device with a narrow pitch, when the second conductive layer 131 in which the concave portion 32 is not formed as in this embodiment is used, excessive solder becomes solder balls. An adjacent emitter electrode or the like (first conductive layer 30 in FIG. 9) comes into contact with the electrode and causes a short circuit.

On the other hand, in the present embodiment, the concave portion 32 is provided on the joint surface of the second conductive layer 31 with the submount 10 so that the second conductive layer 31 itself accommodates excess solder. Therefore, it is possible to appropriately suppress the formation of solder balls. Further, since the excessive solder can be accommodated by the concave portion 32 without taking a wide solder width, a narrow pitch of the semiconductor laser device can be realized. For example, even if the width L of the solder layer 13 is less than or equal to the width W of the second conductive layer, the formation of solder balls can be appropriately suppressed.
In this way, it is possible to realize narrow pitch and stable independent driving of the beam. In the present embodiment, the beam pitch, which is the distance between the ridge portions 27 adjacent to each other, can be set to 20 μm to 50 μm. Here, the cavity length is 300 μm to 600 μm, the width W of the second conductive layer is 7 μm to 10 μm, and the width of the concave portion is about 5 μm.
The thickness of the first conductive layer 30 is about 2 μm, the thickness of the second conductive layer 31 is about 5 μm, the thickness of the passivation film 28 is about 0.5 μm, the thickness of the surface electrode 29 is about 0.5 μm, solder The thickness of the layer 13 is about 3 μm.

In the present embodiment, the conductive layer formed on the surface electrode 29 has a two-stage structure of the first conductive layer 30 and the second conductive layer 31, and the second conductive layer 31 overlaps the ridge portion 27 in a plan view. It is formed in a position that does not become necessary. That is, the ridge portion 27 and the solder layer 13 do not overlap in a plan view, and have a structure in which there is a gap between the ridge portion 27 and the submount 10. This makes it difficult for the ridge 27 to be stressed when the semiconductor chip 20 and the submount 10 are assembled. As a result, the polarization angle rotation and the relative difference between the beams of the polarization angle due to the stress can be reduced, and the optical characteristics can be stabilized.
In this case, since the second conductive layer 31 is shifted from the upper side of the ridge 27, the second conductive layer 31 approaches the adjacent emitter. However, since the concave portion 32 is formed in the second conductive layer 31, the formation of solder balls at the time of mounting can be appropriately suppressed, and a short circuit between the emitters can be appropriately suppressed. That is, the necessity for the concave portion 32 increases as the conductive layer has a two-stage structure and the second conductive layer 31 is closer to the adjacent emitter.

  As described above, the semiconductor chip 20 according to the present embodiment includes the concave portion 32 that can store excess solder that may be generated when the semiconductor chip 20 and the submount 10 are joined via solder. Therefore, it is possible to realize a multi-beam type semiconductor laser device and a multi-beam type semiconductor laser device that can appropriately suppress the formation of solder balls, and can stably perform independent beam driving with a narrow pitch. it can.

(Modification)
In the above embodiment, the case where the conductive layer has the two-stage structure of the first conductive layer 30 and the second conductive layer 31 has been described. However, excessive solder is applied to the surface to be joined to the submount 10. The conductive layer may have a one-step structure as long as a concave portion that can be stored is formed.

In the above-described embodiment, the case where the concave portion 32 is formed in the second conductive layer 32 has been described. However, the concave portion that can store excess solder that may be generated during bonding is not necessarily formed on the semiconductor chip 20 side. You don't have to. For example, as shown in FIG. 10, a concave portion may be formed on the submount 10 side.
FIG. 10 shows an example in which a concave portion 14 is formed on the surface of the submount 10 in contact with the solder layer 13 in the submount electrode 12. Also in this case, the same effect as the above-described embodiment can be obtained. That is, the concave portion that can store excess solder that can be generated during bonding is in contact with the surface of the semiconductor chip 20 that contacts the solder layer 13 of the second conductive layer 31 and the solder layer 13 of the submount electrode 12 of the submount 10. It may be formed on at least one of the surfaces.
In addition, when forming the recessed part 14 in the submount electrode 12, as shown in FIG. 11, by forming the submount electrode 12 on the submount 10 in which the depression 10a is formed, You may make it form the concave-shaped part 14 reflecting the hollow 10a.

  DESCRIPTION OF SYMBOLS 10 ... Submount (support substrate), 12 ... Submount electrode (electrode part), 13 ... Solder layer, 20 ... Multi-beam type semiconductor laser element (semiconductor chip), 21 ... Semiconductor substrate, 22 ... N-type clad layer, 23 ... active layer, 24 ... p-type first cladding layer, 25 ... p-type second cladding layer, 26 ... p-type contact layer, 27 ... ridge portion, 28 ... passivation film, 29 ... surface electrode, 30 ... first conductive layer , 31 ... second conductive layer, 32 ... concave portion, 33 ... back electrode, 100 ... multi-beam type semiconductor laser device

Claims (10)

A multi-beam type semiconductor laser device comprising a semiconductor layer formed on a semiconductor substrate and including a first cladding layer, an active layer, and a second cladding layer,
A plurality of ridges formed in the second cladding layer, extending from the front end face to the rear end face along the light emitting direction, and arranged in order along the direction orthogonal to the emitting direction;
A plurality of conductive layers respectively formed on the plurality of ridges;
A multi-beam type semiconductor laser device comprising: a concave portion formed along a light emission direction on a surface of the conductive layer to be bonded to the submount. The conductive layer includes a first conductive layer and a second conductive layer formed on the first conductive layer,
The multi-beam semiconductor laser element according to claim 1, wherein the concave portion is formed in the second conductive layer.   3. The multi-beam semiconductor laser element according to claim 1, wherein the concave portion has a closed portion formed on at least one of the front end surface side and the rear end surface side. 4.   4. The multi-beam semiconductor laser device according to claim 1, wherein an opening is formed on a side surface of the concave portion. 5.   The opening is formed on a side surface close to the electrically conducting ridge portion, out of two side surfaces facing in a direction orthogonal to the light emitting direction. The multi-beam type semiconductor laser device according to claim 4.   6. The multi-beam semiconductor laser element according to claim 1, wherein a concave portion corresponding to the concave portion is formed in at least one of the semiconductor substrate and the semiconductor layer.   The periphery of the concave portion on the surface to be joined to the submount of the conductive layer is made of a material having poor solder wettability with respect to the inner surface of the concave portion. The multi-beam semiconductor laser element according to any one of 6. A multi-beam semiconductor laser device comprising: a multi-beam semiconductor laser element; and a submount on which the multi-beam semiconductor laser element is mounted via a solder layer,
The multi-beam semiconductor laser element is
A semiconductor layer formed on a semiconductor substrate and including a first cladding layer, an active layer, and a second cladding layer;
A plurality of ridges formed in the second cladding layer, extending from the front end face to the rear end face along the light emitting direction, and arranged in order along the direction orthogonal to the emitting direction;
A plurality of conductive layers respectively formed on the plurality of ridge portions,
The submount is
A plurality of electrode portions formed respectively corresponding to the plurality of ridge portions, and joined to the conductive layer via the solder layer;
A multi-beam semiconductor laser device, wherein a concave portion is formed on at least one of a surface of the conductive layer in contact with the solder layer and a surface of the electrode portion in contact with the solder layer.   9. The multi-beam semiconductor laser device according to claim 8, wherein a width of the solder layer is equal to or smaller than a width of the conductive layer in a direction orthogonal to the light emission direction. A method of manufacturing a multi-beam type semiconductor laser device comprising a semiconductor layer formed on a semiconductor substrate and including a first cladding layer, an active layer, and a second cladding layer,
Extending the second cladding layer from the front end surface to the rear end surface along the light emitting direction, and forming a plurality of ridges arranged in order along the direction orthogonal to the emitting direction; and
Forming a conductive layer on each of the plurality of ridges;
Forming a concave portion along a light emitting direction on a surface of the conductive layer to be bonded to the submount, and a method of manufacturing a multi-beam type semiconductor laser device.

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