JP6900798B2 - Multi-beam type semiconductor laser element and multi-beam type semiconductor laser device - Google Patents

Description

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

Conventionally, a multi-beam type semiconductor laser device in which a multi-beam type semiconductor laser element (semiconductor chip) having a plurality of emitters (light emitting points) is bonded to a submount by junction down mounting is known. In such a multi-beam type semiconductor laser device, multi-beam independent driving is performed, and electrodes corresponding to each of a plurality of emitters need to be electrically isolated electrodes. There is.
For example, in Patent Document 1, in a multi-beam type semiconductor laser device, the width of solder formed on the surface of a submount electrode (electrode width) is larger than the width of a conductive layer formed on the upper surface of a surface electrode of a semiconductor chip (electrode width). The point of widening the solder width) is disclosed. By making the solder width wider than the electrode width in this way, even if excess solder is generated during melt bonding, the excess solder is spread over the entire solder region that does not come into contact with the electrodes, and local protrusion is suppressed. However, it makes it difficult for solder balls to be generated. This prevents the solder balls from coming into contact with the electrodes of the adjacent emitters and causing a short circuit.

Japanese Unexamined Patent Publication No. 2014-22481

However, in recent years, the multi-beam type semiconductor laser apparatus is required to have a narrower pitch (for example, a beam pitch of 40 μm or less). As the distance between the emitters adjacent to each other becomes closer, it becomes difficult to make the solder width wider than the electrode width, so that it becomes difficult to suppress the generation of solder balls at the time of melt bonding.
Therefore, an object of the present invention is to provide a multi-beam type semiconductor laser device and a multi-beam type semiconductor laser device capable of stably driving a beam independently at a narrow pitch.

In order to solve the above problems, one aspect of the multi-beam type semiconductor laser device according to the present invention includes a semiconductor layer including a first clad layer, an active layer and a second clad layer formed on a semiconductor substrate. A multi-beam type semiconductor laser device, which is formed in the second clad layer and extends from the front end face to the rear end face along the light emission direction, and is arranged in order along the direction orthogonal to the light emission direction. A plurality of ridge portions formed by the above, a plurality of conductive layers formed on the plurality of ridge portions, and a surface to be joined to a submount of the conductive layer, formed along the light emission direction. It includes a concave portion that is, a, that has an opening formed on a side surface of the concave portion.

In this way, since the concave portion is formed on the surface to be joined to the submount of the conductive layer, when the conductive layer and the submount are joined via solder at the time of mounting, excess solder is applied to the concave portion. Can be stored. Therefore, it is possible to prevent the excess solder from being extruded to the outside and becoming a solder ball. Therefore, it is possible to prevent the formed solder balls from coming into contact with the electrodes or the like of adjacent emitters, and to appropriately suppress short circuits between the emitters adjacent to each other. As a result, the independent drive of the laser can be stably performed. Further, even if the solder width is not wide, the excess solder can be stored by the concave portion, so that it is possible to cope with a narrow pitch.
Further, an opening is formed on the side surface of the concave portion. Here, the side surface of the concave portion is a surface facing the direction orthogonal to the extending direction of the concave portion. By forming the opening on the side surface of the concave portion in this way, the air in the concave portion can be evacuated from the opening, and the solder can be easily drawn into the concave portion.

Further, in the multi-beam type semiconductor laser device, the conductive layer includes a first conductive layer and a second conductive layer formed on the first conductive layer, and the concave portion is the second conductive layer. It may be formed in layers.
In this way, 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 can be shifted from above the ridge portion to make it difficult for stress to be applied to the ridge portion at the time of mounting. it can. As a result, it is possible to reduce the rotation of the polarization angle due to the stress and the relative difference between the beams of the polarization angle, and it is possible to stabilize the optical characteristics. Further, in this case, since the second conductive layer is located at a position where the upper part of the ridge portion is displaced, 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 the short circuit between the emitters can be appropriately suppressed.

Further, in the above-mentioned multi-beam type semiconductor laser device, the concave portion may have a closed portion formed on at least one of the front end face side and the rear end face side.
In this case, it is possible to prevent the solder drawn into the concave portion during mounting from being extruded from the end face of the concave portion. As a result, it is possible to avoid a situation in which the solder extruded from the end surface of the concave portion shields the emission surface of the laser beam.

Et al is, in the multi-beam semiconductor laser device described above, the opening of the two opposing sides in a direction perpendicular to the emission direction of the light, to the ridge portion are electrically conductive It may be formed on the side surface on the near side. In this case, even if the solder drawn into the concave portion is pushed out from the opening, the solder will come into contact with an electrically conducting electrode or the like, and will be between adjacent emitters. There is no electrical short circuit.

Further, in the above-mentioned multi-beam type semiconductor laser device, a recess corresponding to the concave portion may be formed on at least one of the semiconductor substrate and the semiconductor layer. In this way, when the concave portion is formed on the surface that is the base of the conductive layer, the concave portion that reflects the shape of the concave portion is formed 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 type semiconductor laser device, 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. It may have been done. In this case, the solder is easily drawn into the concave portion, and the formation of solder balls can be suppressed more appropriately.

Further, one aspect of the multi-beam type semiconductor laser device according to the present invention is a multi-beam type including a multi-beam type semiconductor laser element and a submount in which the multi-beam type semiconductor laser element is mounted via a solder layer. A semiconductor laser device, the multi-beam type semiconductor laser device is formed on a semiconductor layer including a first clad layer, an active layer, and a second clad layer formed on a semiconductor substrate, and the second clad layer. Further, a plurality of ridge portions formed along the emission direction of light from the front end face to the rear end surface and arranged in order along the direction orthogonal to the emission direction, and a plurality of ridge portions on the plurality of ridge portions, respectively. A plurality of formed conductive layers are provided, and the submount is formed corresponding to each of the plurality of ridge portions, and a plurality of electrode portions bonded to the conductive layer via the solder layer are provided. 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, and an opening is formed on a side surface of the concave portion .

In this way, 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, when the conductive layer and the submount are joined via solder at the time of mounting. In addition, excess solder can be stored in the concave portion. Therefore, it is possible to prevent the excess solder from being extruded to the outside and becoming a solder ball. Therefore, it is possible to prevent the formed solder balls from coming into contact with the electrodes or the like of adjacent emitters, and to appropriately suppress short circuits between the emitters adjacent to each other. As a result, the independent drive of the laser can be stably performed. Further, even if the solder width is not wide, the excess solder can be stored by the concave portion, so that it is possible to cope with a narrow pitch.
Further, in the above-mentioned multi-beam type semiconductor laser apparatus, the width of the solder layer may be equal to or less than the width of the conductive layer in a direction orthogonal to the light emission direction. As a result, it is possible to cope with further narrowing of the pitch.

Further, one aspect of the method for manufacturing a multi-beam type semiconductor laser device according to the present invention is a multi-beam type including a semiconductor layer including a first clad layer, an active layer and a second clad layer formed on a semiconductor substrate. A method for manufacturing a semiconductor laser device, which is a method of manufacturing a plurality of semiconductor laser devices, in which a plurality of semiconductor laser elements are stretched in the second clad layer from a front end face to a rear end face along an emission direction of light, and are arranged in order along a direction orthogonal to the emission direction. A step of forming a ridge portion, a step of forming a conductive layer on each of the plurality of ridge portions, and a concave portion formed along the light emitting direction on a surface to be joined to a submount of the conductive layer. a step of, only including, in the step of forming the concave portion, forming an opening in the side surface of the concave portion.
This makes it possible to manufacture a multi-beam type semiconductor laser device capable of stably driving the beam independently at a narrow pitch.

According to the present invention, even when the distance between the ridge portions adjacent to each other is narrow, it is possible to suppress short-circuit defects due to solder balls between the ridge portions. Therefore, it is possible to realize a multi-beam type semiconductor laser device and a multi-beam type semiconductor laser device capable of stably driving the beam independently at a narrow pitch.

It is an overall block diagram of the multi-beam type semiconductor laser apparatus in this embodiment. It is sectional drawing which shows the structure of the multi-beam type semiconductor laser element. It is a top view which shows an example of the concave part. It is a top view which shows an example of the concave part. It is a side view which shows an example of the concave part. It is a conceptual diagram of a concave part. It is a conceptual diagram of a concave part. This is an example of a method for manufacturing a concave portion. It is a figure for demonstrating the short circuit defect between adjacent emitters. It is sectional drawing which shows another example of the multi-beam type semiconductor laser apparatus. It is sectional drawing which shows another example of the 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 a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions. It is not limited to the embodiment. Further, in the drawings described below, the same or functionally similar components are designated by the same reference numerals, and the repeated description thereof will be omitted. Further, each drawing is shown for easy understanding when referred to together with the following description, and is not necessarily drawn at a certain ratio of scale.

FIG. 1 is a diagram showing 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 in this embodiment can be used as a light source for an image printing device such as a laser printer or a copying machine.
The semiconductor laser device 100 includes a submount 10 and a multi-beam type 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, for example, a ceramic such as AlN or SiC. The semiconductor chip 20 is mounted on the submount 10 by a junction down method.

In the present embodiment, the semiconductor chip 20 is a 4-beam semiconductor laser device including four emitters (light emitting points), and has a configuration in which a plurality of semiconductor layers including an active layer are laminated on a substrate. For example, in the semiconductor chip 20, at least an n-type clad layer (first clad layer), an active layer, a p-type clad layer (second clad layer), and a p-type contact layer are laminated in this order on an n-type semiconductor substrate. Can have a different configuration. The specific configuration of the semiconductor chip 20 will be described later. When a predetermined injection current is supplied, the semiconductor chip 20 emits laser light having a predetermined oscillation wavelength from both end faces (upper and lower end faces in FIG. 1). The oscillation wavelength of the laser beam emitted by the semiconductor chip 20 is not particularly limited.

The submount 10 on which the semiconductor chip 20 is mounted is joined to the heat sink portion 40. The heat sink portion 40 is provided near the central portion of the circular surface of the disk-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 beam 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 substantially at the center of the circular surface of the stem 41.

The submount 10, the semiconductor chip 20, and the heat sink portion 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 central portion 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. It is emitted to the outside of 100.
The heat sink portion 40 is made of a highly heat-dissipating metal material (for example, Cu), and the heat generated by the semiconductor chip 20 at the time of light emission is transferred to the heat sink portion 40 via the submount 10 and dissipated.

Next, a specific configuration of the semiconductor chip 20 will be described.
FIG. 2 is a cross-sectional view of a main part 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 laminated on the main surface of the semiconductor substrate 21. Here, the semiconductor substrate 21 can be, for example, a GaAs substrate. Further, the semiconductor layer includes, for example, an n-type clad layer 22, an active layer 23, a p-type first clad layer 24, and a p-type second clad layer deposited by a metal organic chemical vapor deposition (MOCVD) method. 25 and p-type contact layer 26 are included. Here, the n-type clad layer 22 corresponds to the first clad layer, and the p-type first clad layer 24 and the p-type second clad layer 25 correspond to the second clad layer.
The n-type clad layer 22 is made of, for example, AlGaInP. The active layer 23 is composed of, for example, a multi-quantum well (MQW) structure in which barrier layers made of AlGaInP and well layers made of GaInP layers are alternately laminated. The p-type first clad layer 24 and the p-type second clad 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 clad layer 25 has a convex cross-sectional shape, and a plurality of ridge portions (mesa stripes) 27 extending in parallel with each other are formed. In the present embodiment, since the semiconductor chip 20 is a 4-beam semiconductor laser device, four ridge portions 27 are formed on the p-type second clad layer 25. In FIG. 2, two ridge portions 27 out of the four ridge portions 27 are shown. Each of these plurality of ridge portions 27 corresponds to one emitter.
The ridge portion 27 extends from the front end face to the rear end face along the light emission direction (resonator direction), and in the plane on the p-type second clad layer 25, the light emission direction (resonator direction). ) Are arranged in order along the direction orthogonal to).
The p-type contact layer 26 is formed on each upper portion of the p-type second clad layer 25 constituting the ridge portion 27. That is, the ridge portion 27 has a two-layer structure of a p-type second clad layer 25 and a 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 clad layer 25 and the ridge portion 27. However, the passivation film 28 is not formed in the region that becomes the top (lower surface in FIG. 2) of the ridge portion 27, and the p-type contact layer 26 is exposed at the top. A p-type surface electrode 29 ohmic-connected to the p-type contact layer 26 is formed on the surface of the p-type contact layer 26 and on the surface of the passivation film 28. The surface electrode 29 is configured to contain 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 laminated from the side closest to the semiconductor substrate 21.

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

In the semiconductor chip 20, when a predetermined current is injected into the front electrode 29 and the back electrode 33, the active layer 23 below each of the four ridge portions 27 becomes a light emitting point, and the semiconductor chip 20 has a red color having an oscillation wavelength of, for example, 650 nm. Oscillate a laser beam. Then, the red laser beam is emitted from both end faces (resonator end faces) of the semiconductor chip 20 which is a plane orthogonal to the extending direction of the ridge portion 27, and the front light thereof is the light of the cap 42 shown in FIG. It is emitted to the outside of the CAN package through the take-out window 43.

On the other hand, on the chip mounting surface (upper surface of FIG. 2) of the submount 10, four submount electrodes (electrode portions) 12 composed of, for example, a multilayer metal film in which a Pt film and an Au film are sequentially laminated on a Ti film are formed. It 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 arranged so as to face each second conductive layer 31.

Further, a solder layer 13 made of, for example, AuSn or the like 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 (the direction orthogonal to the resonator direction in the plane on the p-type second clad layer 25). 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 melt-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 (bonding surface) to be bonded to the submount 10 of the second conductive layer 31. Therefore, the excess solder of the solder layer 13 that may be generated at the time of melt bonding is stored in the concave portion 32 and is suppressed from being pushed out to the outside of the second conductive layer 31. That is, the formation of solder balls can be suppressed. As a result, it is possible to prevent the solder balls from coming into contact with the electrodes or the like of the adjacent emitters (for example, the first conductive layer 30), and to prevent electrical short circuits between the emitters adjacent to each other. As a result, the independent drive of each beam can be stably performed. 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 viewed from above in FIG. As shown in FIG. 3, the concave portion 32 is formed along the light emission direction (resonator direction), and both ends thereof can be closed. By forming the closed portions at both ends of the concave portion 32 in the resonator direction in this way, it is possible to prevent the solder drawn into the concave portion 32 from being extruded from the resonator end face side at the time of melt joining. it can. As a result, it is possible to avoid a situation in which the solder extruded from the end face side of the resonator shields the laser emitting surface. The closed portion may be formed only on either the front end face side or the rear end face side.

Further, as shown in FIG. 4, the concave portion 32 may be formed with an opening 32a for venting air on the side surface thereof. Here, the side surface of the concave portion 32 is a surface facing the concave portion 32 in a direction orthogonal to the extending direction. By providing the opening 32a in the concave portion 32 in this way, the concave portion 32 can easily contain the solder, and the formation of the solder ball can be suppressed more appropriately. The position and size of the opening 32a are not limited to the position and size shown in FIG. 4, and may be any position and size. In FIG. 4, only one opening 32a is provided at a substantially central position in the resonator direction, but a plurality of openings 32a may be provided.
However, as shown in FIG. 5, the opening 32a is located on the side of the two side surfaces facing in the direction orthogonal to the resonator direction, which is closer to the ridge portion 27 in which the second conductive layer 31 is electrically conductive. It is preferably formed on the side surface. In this case, even when the solder is extruded from the opening 32a together with the air, the problem of short circuit failure does not occur. In this way, when the opening 32a is formed on the side surface on the side close to the ridge portion 27 in which the second conductive layer 31 is electrically conductive, if both ends in the resonator direction are closed, for example, the above side surface. The entire surface of the may be open.

Further, the concave portion 32 can be formed by any manufacturing method. For example, the concave portion 32 can be formed by multi-stage plating. That is, the concave portion 32 can be formed by a manufacturing method in which the photolithography step and the step of forming a plating film only on the opening of the resist are repeated and the area of the resist opening is narrowed toward the upper layer. Here, as shown in FIG. 2, when the cross-sectional shape of the concave portion 32 orthogonal to the resonator direction is a half-moon shape, etching may be performed to smooth the stages after multi-stage plating. The method for producing the concave portion 32 is not limited to the above. For example, a method of providing an etching stop layer for wet etching or a method of forming a thick conductive layer and then forming the concave portion in a photolithography step. 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 of the resist opening.

Further, the concave portion 32 can be formed by another manufacturing method. For example, by forming a recess (recess) on the surface on which the second conductive layer 31 is formed and forming the second conductive layer 31 on the recess, the concave portion 32 reflecting the shape of the recess can be formed. The second conductive layer 31 to have may be formed.
FIG. 6 is a conceptual diagram in the case where the recess 25a is formed in the p-type second clad layer 25 to form the concave portion 32. As shown in FIG. 6, by forming the first conductive layer 30 on the p-type second clad layer 25 on which the recess 25a is formed, the recess 30a reflecting the recess 25a is formed in 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. ..

In addition, instead of forming the recess 25a in the p-type second clad layer 25, as shown in FIG. 7, the recess 30a is formed by intermittently forming the first conductive layer 30, or the first conductive layer 30 is formed. The concave portion 32 can also be formed in the same manner by forming the concave recess 30a in the layer 30. Further, in FIG. 6, the case where the recess 25a is formed in the p-type second clad layer 25 has been described, but the recess is formed in the semiconductor layer closer to the semiconductor substrate 21 than the semiconductor substrate 21 or the p-type second clad layer 25. The concave portion 32 may be formed on the surface of the second conductive layer 31, which is the outermost surface, while maintaining the recess.
As described above, the cross-sectional shape of the concave portion 32 orthogonal to the resonator direction is not limited to the crescent shape as shown in FIG. 2, but is a rectangular shape or a substantially rectangular shape as shown in FIGS. 6 and 7. There may be. The cross-sectional shape is not limited to the above, and may be any shape.

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, which has a lower wettability than the material (for example, Au) constituting the second conductive layer 31). (Ti, Ni, etc.) is formed, the region other than the concave portion 32 forming region is covered with the resist R, and the concave portion 32 is formed by etching. Then, if the resist R is removed, as shown in FIG. 8B, a material 31a having poor wettability can be arranged around the concave portion 32 on the joint surface.
Further, photolithography and etching may be further performed to remove the material 31a having poor wettability on the bottom surface of the second conductive layer 31, as shown in FIG. 8C.

This makes it easier to draw the solder into the concave portion 32. Instead of arranging a material having poor wettability around the concave portion 32, the inner surface of the concave portion 32 may be covered with a material having good wettability with respect to the periphery of 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 inner surface of the concave portion 32 can be modified 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 or LPE (Liquid Phase Epitaxy) method is used to form an n-type clad layer 22, an active layer 23, a p-type first clad layer 24, and a p-type second clad on a semiconductor substrate 21. The layer 25 and the p-type contact layer 26 are sequentially laminated and formed.
Next, an oxide film is formed on the p-type contact layer 26, the oxide film is patterned using a photolithography and etching process, and the p-type second clad layer 25 and the p-type contact layer 26 are formed along the pattern. Etch. As a result, a plurality of (4 in this embodiment) ridge portions 27 are formed.

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

Next, the process on the n side will be described. First, the wafer is fixed with the device surface (p side in this embodiment) facing downward, and the back surface (n side in this embodiment) of the semiconductor substrate 21 is polished to a desired thickness. Then, the back surface electrode 33 is formed on the polished surface.
Finally, the semiconductor chip 20 according to the present embodiment is completed by converting the wafer into chips.
After forming the back surface electrode 33, a conductive layer (thick film electrode) may be formed on the back surface electrode 33 as well. By forming the conductive layer on the back surface electrode 33 in this way, it is possible to obtain the effect of reducing the warpage of the wafer or chip due to the extremely multi-layered and thick film structure on the device surface side.

Next, a method of manufacturing the semiconductor laser device 100 will be described.
First, the solder layer 13 is formed into 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, a recognition pattern formed on the submount 10 and a recognition pattern formed on the semiconductor chip 20 are recognized by using a CCD camera or the like. Then, the recognition patterns of the two recognized patterns are aligned, and the semiconductor chip 20 is mounted on the submount 10 by a junction-down method. The submount electrodes 12 of the submount 10 are formed at positions facing the second conductive layer 31 of the semiconductor chip 20, and these second conductive layers 31 are formed on the solder layer 13 formed on the submount electrode 12. By joining, 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 together with the submount 10 to the disk-shaped stem 41 constituting the semiconductor laser device 100. Specifically, the submount 10 to which the semiconductor chip 20 is bonded is bonded to the heat sink 40 provided on the stem 41 via solder or the like. Next, the front electrode 29 and the back electrode 33 of the semiconductor chip 20 can be energized by wire bonding, and finally, a cylindrical cap 42 is attached to the disk-shaped surface of the stem 41 and airtightly sealed by welding or the like. To do. Through the above steps, the semiconductor laser device 100 is completed.

As described above, the multi-beam type semiconductor laser device (semiconductor chip) 20 in the present embodiment includes the n-type clad layer 22, the active layer 23, the p-type first clad layer 24 and p formed on the semiconductor substrate 21. A semiconductor layer including the type second clad layer 25, a plurality of ridge portions 27 extending in the resonator direction, and a plurality of ridge portions formed on the p-type second clad layer 25 corresponding to the plurality of emitters, respectively. A plurality of surface electrodes 29 formed on the 27 and a plurality of conductive layers each formed on the plurality of surface electrodes 29 are provided. 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.

In this way, since the concave portion 32 is formed on the surface to be joined to the submount of the second conductive layer 31, the submount electrodes of the second conductive layer 31 and the submount 10 are formed via the solder layer 13 at the time of mounting. When joining with 12, the excess solder of the solder layer 13 can be stored in the concave portion 32. Therefore, it is possible to prevent the excess solder from being extruded to the outside and becoming a solder ball. Therefore, it is possible to prevent the formed solder balls from coming into contact with the electrodes or the like of the adjacent emitters, and to appropriately suppress short circuits between the emitters adjacent to each other. As a result, the independent drive of the laser can be stably performed. Further, since the excess solder can be stored by the concave portion 32 without widening the solder width, it is possible to cope with a narrow pitch.

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, the excess solder generated during melt bonding is extruded to the outside, but since the solder width is wider than the electrode width, the excess solder spreads over the entire solder region that does not come into contact with the electrodes, and the solder is localized. The protrusion is suppressed and solder balls are less likely to occur. However, as a demand from the market, further narrowing of the pitch is required, and it is difficult to make the solder width wider than the electrode width in such a narrow pitch semiconductor laser apparatus. Therefore, it becomes difficult to appropriately suppress the formation of solder balls.
That is, as shown in FIG. 9, when the second conductive layer 131 in which the concave portion 32 is not formed as in the present embodiment is used in the narrow pitch semiconductor laser apparatus, the excess solder becomes a solder ball. It comes into contact with the electrodes of adjacent emitters (first conductive layer 30 in FIG. 9) and short-circuits.

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 sub mount 10, and the second conductive layer 31 itself is configured to store excess solder. Therefore, the formation of solder balls can be appropriately suppressed. Further, since the excess solder can be stored by the concave portion 32 without widening the solder width, it is possible to realize a narrow pitch of the semiconductor laser device. For example, even if the width L of the solder layer 13 is equal to or less than 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 a narrow pitch and a stable independent drive 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 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, and solder. The thickness of the layer 13 is about 3 μm.

Further, 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 is planarly overlapped with the ridge portion 27. It is formed in a position where it does not become. That is, the ridge portion 27 and the solder layer 13 do not overlap in a plane, and have a structure in which there is a gap between the ridge portion 27 and the submount 10. As a result, stress can be less likely to be applied to the ridge portion 27 when the semiconductor chip 20 and the submount 10 are assembled. As a result, it is possible to reduce the rotation of the polarization angle due to the stress and the relative difference between the beams of the polarization angle, and it is possible to stabilize the optical characteristics.
Further, in this case, since the second conductive layer 31 is located at a position deviated from above the ridge portion 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 the short circuit between the emitters can be appropriately suppressed. That is, the conductive layer has a two-stage structure, and the closer the second conductive layer 31 is to the adjacent emitter, the greater the need for the concave portion 32.

As described above, the semiconductor chip 20 in the present embodiment includes a concave portion 32 capable of accommodating 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, can stably drive the beam independently at a narrow pitch, and can be performed. it can.

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

Further, in the above embodiment, the case where the concave portion 32 is formed on the second conductive layer 32 has been described, but the concave portion capable of accommodating the excess solder that may be generated at the time of joining 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 the concave portion 14 is formed on the surface of the submount electrode 12 of the submount 10 in contact with the solder layer 13. Also in this case, the same effect as that of the above-described embodiment can be obtained. That is, the concave portion capable of accommodating excess solder that may be generated at the time of joining is in contact with the surface of the semiconductor chip 20 in contact with the solder layer 13 of the second conductive layer 31 and the surface of the submount 10 in contact with the solder layer 13 of the submount electrode 12. It suffices if it is formed on at least one of the surfaces.
When the concave portion 14 is formed on the submount electrode 12, as shown in FIG. 11, the submount electrode 12 is formed on the submount 10 in which the recess 10a is formed, so that the submount electrode 12 is formed. The concave portion 14 reflecting the recess 10a may be formed.

10 ... Submount (support substrate), 12 ... Submount electrode (electrode portion), 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 clad layer, 25 ... p-type second clad layer, 26 ... p-type contact layer, 27 ... ridge portion, 28 ... passion 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 (9)

A multi-beam type semiconductor laser device having a semiconductor layer including a first clad layer, an active layer, and a second clad layer formed on a semiconductor substrate.
A plurality of ridge portions formed in the second clad layer, which extend from the front end face to the rear end face along the light emission direction and are formed in order along the direction orthogonal to the emission direction.
A plurality of conductive layers each formed on the plurality of ridge portions, and
The surface to be joined to the submount of the conductive layer is provided with a concave portion formed along the light emitting direction .
A multi-beam type semiconductor laser device characterized in that an opening is formed on a side surface of the concave portion. The conductive layer includes a first conductive layer and a second conductive layer formed on the first conductive layer.
The multi-beam type semiconductor laser device according to claim 1, wherein the concave portion is formed in the second conductive layer. The multi-beam type semiconductor laser device according to claim 1 or 2, 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. The opening is characterized in that it is formed on the side surface of the two side surfaces facing in a direction orthogonal to the light emission direction, which is closer to the electrically conductive ridge portion. The multi-beam type semiconductor laser device according to any one of claims 1 to 3. The multi-beam type semiconductor laser device according to any one of claims 1 to 4 , wherein a recess corresponding to the concave portion is formed on at least one of the semiconductor substrate and the semiconductor layer. From claim 1, 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. 5. The multi-beam type semiconductor laser device according to any one of 5. A multi-beam type semiconductor laser device including a multi-beam type semiconductor laser element and a submount in which the multi-beam type semiconductor laser element is mounted via a solder layer.
The multi-beam type semiconductor laser element is
A semiconductor layer including a first clad layer, an active layer and a second clad layer formed on a semiconductor substrate,
A plurality of ridge portions formed in the second clad layer, which extend from the front end face to the rear end face along the light emission direction and are formed in order along the direction orthogonal to the emission direction.
It is provided with a plurality of conductive layers, each of which is formed on the plurality of ridge portions.
The submount
A plurality of electrode portions formed corresponding to the plurality of ridge portions and bonded to the conductive layer via the solder layer are provided.
A 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 .
A multi-beam type semiconductor laser device characterized in that an opening is formed on a side surface of the concave portion. The multi-beam type semiconductor laser device according to claim 7 , wherein the width of the solder layer is equal to or less than the width of the conductive layer in a direction orthogonal to the light emission direction. A method for manufacturing a multi-beam type semiconductor laser device having a semiconductor layer including a first clad layer, an active layer, and a second clad layer formed on a semiconductor substrate.
A step of extending the second clad layer from the front end face to the rear end face along the light emission direction and forming a plurality of ridge portions arranged in order along the direction orthogonal to the emission direction.
A step of forming a conductive layer on each of the plurality of ridge portions, and
To the surface to be bonded to a submount of the conductive layer, viewed including the steps of forming a concave portion, a along the emitting direction of the light,
A method for manufacturing a multi-beam type semiconductor laser device , which comprises forming an opening on a side surface of the concave portion in the step of forming the concave portion.

Images