JP4884698B2 - Semiconductor device manufacturing method, semiconductor laser device, optical transmission module, and optical disk device - Google Patents

Description

  The present invention relates to a semiconductor device manufacturing method, a semiconductor laser device, an optical transmission module, and an optical disk device.

  In a semiconductor device having a quantum well structure, a transistor, or the like, electrodes are arranged to inject current into a semiconductor material and to make electrical contact with the outside. Usually, in order to inject a current into a semiconductor microstructure, a device has been devised in which an electrode on the microstructure is drawn out, a wider electrode region is provided, and a metal wire or the like is connected thereto. For example, the region other than the current injection region is embedded with an insulating resin or dielectric, or is embedded with a semiconductor layer having a conductivity type different from that of the current injection region, an electrode is drawn from the current injection region to the embedded region, and a metal wire or the like is provided. A wide electrode area that is easy to bond is secured. In addition, since many of the current injection regions are formed by processing a semiconductor layer into a mesa shape, the buried region also serves to eliminate a step due to the mesa and facilitate the extraction of the electrode.

  As a conventional semiconductor device, for example, there is a semiconductor laser device that emits laser light from a light emitting layer. This semiconductor laser device (not shown) generally has a so-called buried ridge structure. More specifically, in the semiconductor laser device, the active layer is sandwiched between the lower cladding layer and the upper cladding layer. A ridge stripe portion is formed on the upper clad layer to inject current into the stripe region of the active layer, and a current confinement layer is formed on both sides of the ridge stripe portion. .

  This buried ridge structure is fabricated as follows.

  First, after the first semiconductor crystal growth is performed, a lower cladding layer, an active layer, an upper cladding layer, and the like are stacked on the substrate, and then a part of the semiconductor layer on the substrate is etched to form a ridge-shaped stripe portion. Form.

  Then, a second semiconductor crystal growth is performed, and current confinement layers are stacked on both sides of the stripe portion.

  Further, a third semiconductor crystal growth is performed, and a contact layer is stacked on the stripe portion and the current confinement layer, thereby ensuring a wide contact layer region where the electrode is formed.

  As described above, the buried ridge structure has a problem that it is necessary to perform the semiconductor crystal growth process three times in total, and it is very difficult to reduce the cost.

  A so-called air ridge structure that solves this problem is described in Japanese Patent Application Laid-Open No. 2000-114660. As shown in FIG. 13, this air ridge structure has a merit that the current can be confined by using an insulator film or the like, and therefore there is an advantage that only one semiconductor crystal growth step is required.

  The semiconductor laser device having this air ridge structure is manufactured as follows.

  First, an n-AlGaAs lower cladding layer 502, an i-AlGaAs lower optical confinement layer 503, a quantum well active layer 504 composed of an InGaAs quantum well layer and a GaAsP barrier layer, an i-AlGaAs on an n-GaAs substrate 501 shown in FIG. An upper optical confinement layer 505, an AlGaAs layer for forming a p-AlGaAs upper cladding layer 506, and a GaAs layer for forming a p-GaAs contact layer 507 are sequentially stacked by metal organic chemical vapor deposition (MOCVD).

  Then, a part of the AlGaAs layer for forming the p-AlGaAs upper cladding layer 506 and the GaAs layer for forming the p-GaAs contact layer 507 are etched by a normal photolithography process and etching process. A ridge-shaped stripe portion 511 is formed.

Then, the whole surface is covered with an SiN _X, and remove only SiN _X on the contact layer 507, an insulating protective film 508 made of SiN _X, after expose the upper surface of the contact layer 507, a contact layer A p-side electrode 509 is formed on 507 and the insulating protective film 508.

  Next, the n-side electrode 510 is attached to the back surface of the n-GaAs substrate 501 (the surface opposite to the surface on which each semiconductor layer is laminated).

  Then, the entire wafer is cleaved into bars having a resonator width, and a low reflection film and a high reflection film (not shown) are formed on the two cleaved surfaces exposed, and further divided into chips. A semiconductor laser device is completed.

  According to this semiconductor laser device, since the width of the stripe portion 511 is as fine as about several μm, it is impossible to bond a metal wire used for normal current injection directly only on the upper surface of the stripe portion 511. Therefore, the upper surface of the contact layer 507 is exposed from the insulating protective film 508, and the p-side electrode 509 is formed on the contact layer 507 and the insulating protective film 508, whereby the p-side electrode 509 is removed from the stripe portion 511. A metal wire (not shown) is bonded at a portion drawn out on 508 so that current can be injected into the stripe portion 511.

  As another conventional semiconductor device, there is a GaAs heterojunction bipolar transistor described in Patent Document 2 (Japanese Patent Laid-Open No. 2003-1000076) as shown in FIG.

  The GaAs heterojunction bipolar transistor is manufactured as follows.

First, on the semi-insulating GaAs substrate 601 shown in FIG. 14, the GaAs layer for forming the n ⁺ -type GaAs subcollector layer 602 and the n-type GaAs collector layer 603 and the p ⁺ -type GaAs base layer 604 are formed. In order to form the GaAs layer, the AlGaAs layer for forming the n-type AlGaAs emitter layer 605, the GaAs layer for forming the n ⁺ -type GaAs first emitter contact layer 606, and the n ⁺ -type InGaAs second emitter contact layer 607 The InGaAs layers are epitaxially grown sequentially by MOCVD.

Next, a known photolithography process and an etching process are performed to expose the surfaces of the p ⁺ type GaAs base layer 604 and the n ⁺ type GaAs subcollector layer 602.

Next, an emitter ohmic contact electrode 613 made of WN _x is formed on the n ⁺ -type InGaAs second emitter contact layer 607, and a base ohmic contact electrode 612 made of Pt / Ti / Pt / Au is placed on the p ⁺ -type GaAs base layer 604. A collector ohmic contact electrode 611 made of AuGe / Ni / Au is formed on the n ⁺ -type GaAs subcollector layer 602 by sputtering and vapor deposition, respectively. Subsequently, an alloy process is performed to obtain an ohmic connection between the p ⁺ type GaAs base layer 604 and the n type GaAs collector layer 603.

  Next, an intermediate metal film 615 made of Ti / Pt / Au is formed on the base ohmic contact electrode 612, and an intermediate metal film 616 made of Ti / Pt / Au is formed on the emitter ohmic contact electrode 613. .

Next, the n ⁺ type GaAs subcollector layer 602, the n type GaAs collector layer 603, the p ⁺ type GaAs base layer 604, the n type AlGaAs emitter layer 605, the n ⁺ type GaAs first emitter contact layer 606, and the n ⁺ type InGaAs. In order to fill the step formed by the second emitter contact layer 607, a thermosetting resin 620 is formed. Photosensitive polyimide is used as the material of the thermosetting resin 620.

  The method for forming the thermosetting resin 620 will be described in detail. A polyimide precursor diluted with a solvent is applied onto a GaAs substrate 601 by spin coating, and the polyimide precursor is exposed and developed to obtain a desired material. A patterned polyimide precursor is formed. Then, the polyimide precursor is converted into a polyimide by heat treatment to obtain a thermosetting resin 620. The thermosetting resin 620 is designed so as not to overlap with the region where the collector ohmic contact electrode 611 is formed as much as possible.

  Next, an intermediate metal film 621 made of Ti / Pt / Au is formed on the collector ohmic contact electrode 611, and subsequently, wiring metal electrodes 618 and 619 for the respective ohmic connection electrodes are formed, whereby the heterojunction bipolar transistor is formed. Complete.

  In this heterojunction bipolar transistor, the wiring metal electrode 618 drawn out from the intermediate metal film 616 on the emitter ohmic contact electrode 613 and the wiring metal electrode 619 drawn out from the intermediate metal film 615 on the base ohmic contact electrode 612 are mesa-shaped semiconductors. Since it is pulled out from the upper part of the portion, it is formed on the thermosetting resin 620 formed to fill the step of the semiconductor layer so as not to be disconnected.

  Generally, in such a heterojunction bipolar transistor, in order to reduce the base-emitter junction area and reduce the base resistance, the mesa-shaped semiconductor portion is rectangular when viewed from above, and The mesa side surface parallel to the longitudinal direction of the rectangle has a reverse taper shape as shown in FIG. Furthermore, in order to reduce the cost of the bipolar transistor, it is necessary to reduce the chip area of the transistor, and when the electrode is drawn out from the upper part of the mesa-shaped semiconductor portion, it must be drawn across the mesa side surface. Also from this, embedding with the thermosetting resin is important.

  However, the semiconductor laser device of FIG. 13 has a problem in that the formed insulating protective film and the p-electrode are likely to be disconnected, making it difficult to manufacture, and low yield. Further, the insulating protective film 508 is partially removed by etching so that only the upper surface portion of the contact layer 507 is opened, and a pattern mask is formed with a resist or the like in order to expose the upper surface portion of the contact layer 507. It must be formed and protected except for the opening. For this purpose, a photolithography process is generally used, but it is necessary to use a photomask for this purpose, which increases the number of photomasks and alignment processes, reduces the alignment tolerance, and increases the cost and decreases the yield. was there. Further, the opening is only about the width of the lowermost portion of the ridge 511 due to the size of the ridge 511, and more than that, the opening, that is, the junction area between the p-electrode 509 and the contact layer 507 is increased. I can't earn. This is a major obstacle in improving the semiconductor laser device with better characteristics with less resistance.

Further, in the transistor of FIG. 14, a process of partially embedding an insulating material 620 such as a resin on the side surface of the mesa is necessary in order to pull out the electrodes 618 and 619 from the upper part of the mesa without being disconnected. Similarly to the above, in order to remove the insulating material in unnecessary portions, the pattern production process by the photolithography process increases, and there are problems such as a decrease in yield and an increase in manufacturing cost.
JP 2000-114660 A (see paragraphs 0013 to 0017, FIG. 1) Japanese Unexamined Patent Publication No. 2003-1000076 (see paragraph 0024, FIG. 4 (a))

  Accordingly, an object of the present invention is to provide a semiconductor device manufacturing method, a semiconductor laser device, an optical transmission module using the semiconductor laser device, and the semiconductor laser device capable of improving the yield and reducing the manufacturing cost. To provide an optical disk apparatus using this.

In order to solve the above problems, a method for manufacturing a semiconductor device of the present invention includes:
Laminating a semiconductor layer group consisting of a plurality of semiconductor layers on a semiconductor substrate;
Processing the semiconductor layer group so that at least a part of the semiconductor layer group has a flange that protrudes in a direction intersecting the direction from the semiconductor layer group toward the substrate;
Applying a positive-type photosensitive insulator on the surface of the processed semiconductor layer group;
Exposing the entire surface of the insulator from above;
Removing the insulator exposed by the exposure by development;
The development which is substantially below the collar part from at least a part of the upper surface of the semiconductor layer having the collar part to at least a part of the semiconductor layer exposed on the side of the collar part. Forming a thin film that covers at least a part of the region on the side surface of the insulator left by
Before forming the thin film, the insulator that is substantially under the collar part left by the development is set so that at least a part of the insulator projects outward from the bottom of the collar part by thermal expansion. It is characterized by including a step of deforming.

  A collar part here refers to the location of the shape where a certain semiconductor layer has projected sideways rather than the semiconductor layer under it. Further, the “processed surface of the semiconductor layer group” means an exposed surface of the processed semiconductor layer group, and includes not only the upper surface of the buttocks and the upper surface of portions other than the buttocks. It is a concept including the side surface of the part and the lower surface of the collar part.

According to the above configuration, when the thin film is pulled out from the semiconductor layer having the flange portion to the outside, it is possible to prevent the thin film from being disconnected through the side surface of the insulator. In the method of forming the insulator, since the insulator has a positive type photosensitivity, the insulator that has entered substantially below the collar portion by coating is not exposed to subsequent exposure to the entire surface. Absent. On the other hand, since the insulator on the upper surface of the semiconductor layer having the flange and the semiconductor layer exposed to the outside of the flange is exposed, only the insulator that has entered under the flange is left by development. be able to. Therefore, in the exposure process in the photolithography process in the manufacturing method of the present semiconductor device, a photomask for patterning is unnecessary, the process can be shortened, and pattern defects due to misalignment and the like do not occur. Therefore, the yield can be improved and the cost can be reduced.
In addition, since the insulator protrudes from substantially below the flange portion to the outside, the thin film on the insulator does not break without taking a special manufacturing method to improve side coverage. It can be formed from the upper surface of the semiconductor layer having the flange portion onto the semiconductor layer exposed to the outside under and outward of the flange portion. Therefore, a semiconductor device that can be manufactured at a lower cost and has a higher yield can be provided.
Here, the thin film means a film that is sufficiently thinner than the height of the step formed by the upper surface of the semiconductor layer having the flange and the semiconductor layer exposed outside the flange.

  The semiconductor device manufacturing method according to one embodiment includes a step of applying a lubricant before applying the insulator.

  According to this embodiment, the insulator is easily slipped by the lubricant, and the insulator is easily filled under the flange portion having a complicated structure, thereby improving the yield. Is possible. In addition, since the insulator easily slips even on the upper surface of the semiconductor layer having the flange portion, the thickness of the insulator to be removed in a later development process becomes thin. Therefore, defects due to the remaining of the insulator on the upper surface of the semiconductor layer having the flange portion after development can be reduced, and the yield can be improved.

In the manufacturing method of the semiconductor device of one embodiment,
The insulator is made of polyimide containing microscopic materials having thermal expansibility,
The step of deforming is a heat treatment.

  According to this embodiment, it is easy to provide a positive type photosensitivity because it is rich in insulation by using mainly polyimide among the resins as a material constituting the insulator. Thus, the desired shape can be easily processed by exposure and development. Therefore, the insulator having the shape as described above can be preferably manufactured. Furthermore, since the polyimide contains a minute material having a thermal expansion property, the volume can be easily increased by performing a heat treatment step, It can be easily deformed so that at least a part thereof protrudes outside the collar portion.

In the manufacturing method of the semiconductor device of one embodiment,
The substrate has a first conductivity type;
In the step of laminating the semiconductor layer group, as the semiconductor layer group, at least a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer are sequentially laminated from the substrate side,
The first semiconductor layer is formed to be a second conductivity type low concentration semiconductor layer having a doping concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
The second semiconductor layer and the third semiconductor layer are formed to be a second conductivity type high concentration semiconductor layer having a doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more,
In the step of processing the semiconductor layer group, the second semiconductor layer and the third semiconductor layer form a striped ridge structure on the upper surface of the first semiconductor layer, and the flange portion is formed by the third semiconductor layer. Etching the semiconductor layer group so that is formed,
In the step of forming the thin film, an electrode is formed as the thin film,
The high-concentration compound layer is formed at the interface between the electrode and the third semiconductor layer, and the low-concentration compound layer is formed at the interface between the electrode and the first semiconductor layer. A step of performing a heat treatment after the formation.

  Here, the first conductivity type refers to either the p-type or n-type conductivity type, and the second conductivity type refers to the other conductivity type of the p-type or n-type.

According to this embodiment, in the Schottky junction between the low concentration semiconductor layer having a doping concentration of 1 × 10 ¹⁷ cm ⁻³ or less and the electrode, sufficient current confinement can be obtained by the low concentration side compound layer. At the same time, in the ohmic junction between the high-concentration semiconductor layer having a doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more and the electrode, a lower contact resistance can be obtained by the high-concentration compound layer. Since the Schottky junction and the ohmic junction are further enhanced in this way, for example, low threshold current oscillation can be achieved without performing a current block layer burying regrowth process or an electrode contact layer crystal regrowth process. Provided is a method for manufacturing a semiconductor laser device that is capable of high output operation, has long-term reliability, and has excellent heat dissipation characteristics that can reduce costs by simplifying the manufacturing process. Therefore, it is possible to manufacture a semiconductor device that can obtain a sufficient current confinement property and excellent element reliability, and that can operate at high output with low power consumption.

In the manufacturing method of the semiconductor device of one embodiment,
The lowermost layer of the electrode is made of Ti,
In the step of performing the heat treatment, the low concentration side compound layer and the high concentration side compound layer are formed by heat treatment at 350 ° C. or higher and 430 ° C. or lower.

  According to this embodiment, when the temperature of the heat treatment is less than 350 ° C., the high concentration side compound layer and the low concentration side compound layer are not sufficiently formed, and when the temperature exceeds 430 ° C., Since the compound layer on the high concentration side has high resistance, a semiconductor device having good ohmic characteristics and Schottky junction characteristics can be provided by heat treatment in the above temperature range.

In the manufacturing method of the semiconductor device of one embodiment,
The lowermost layer of the electrode is made of Pt,
In the heat treatment step, the low concentration compound layer and the high concentration compound layer are formed by heat treatment at 350 ° C. or higher and 450 ° C. or lower.

  According to this embodiment, when the temperature of the heat treatment is less than 350 ° C., the high concentration side compound layer and the low concentration side compound layer are not sufficiently formed, and when the temperature exceeds 450 ° C., Pt Is excessively diffused in the semiconductor layer, and the characteristics of the semiconductor device are deteriorated. Therefore, a semiconductor device having good ohmic characteristics and Schottky junction characteristics can be provided by heat treatment in the above temperature range.

The semiconductor laser device of the present invention is
A semiconductor substrate made of a III-V compound semiconductor of the first conductivity type;
A lower clad layer made of a first-conductivity-type III-V compound semiconductor, an active layer made of a III-V compound semiconductor, and a second-conductivity type III-V compound semiconductor, which are sequentially stacked on the semiconductor substrate. A semiconductor layer group including at least a contact layer made of an upper cladding layer and a III-V group compound semiconductor of the second conductivity type,
At least a part of the semiconductor layer group has a striped ridge structure, and has a ridge that projects in a direction crossing the extending direction of the ridge structure,
And an insulator located on both sides of the ridge structure, not located on the upper surface of the collar, and positioned substantially below the collar .
The at least part of the upper surface of the semiconductor layer having the flange part to at least a part of the region on the semiconductor layer exposed outside the flange part, which is substantially below the flange part. A thin film covering at least a part of the region on the side surface of the insulator,
A part of the insulator protrudes from the bottom of the collar part to the outside, and the thickness of the insulator decreases as it projects from the bottom of the collar part to the outside. It is said.

  According to the above configuration, from at least a part of the upper surface of the semiconductor layer having the flange part to at least a part of the semiconductor layer exposed to the outside of the flange part, substantially below the flange part. It is possible to continuously coat the thin film without causing step breakage, including at least a part of the region on the side surface of the insulator. Therefore, the yield can be improved and the cost can be reduced.

In the semiconductor laser device of one embodiment,
The insulator is made of a polyimide containing minute matter that has been thermally expanded.

  According to this embodiment, the shape is rich in insulation, can be easily processed into a desired shape by a normal process, and further, the shape that protrudes from substantially below the collar portion due to the expansion of the minute object. The insulating material can be easily formed without requiring mask alignment.

In the semiconductor laser device of one embodiment,
The semiconductor layer group is partly located between the stripe-shaped ridge structure and the active layer, and the other part has a surface on the side of the stripe-shaped ridge structure. Including a ridge lower layer made of a conductive type III-V compound semiconductor,
The thin film extends from at least a part of the upper surface of the semiconductor layer having the flange to at least a part of the ridge lower layer exposed outside the flange. An electrode that covers at least a part of the region on the side surface of the insulator that is substantially below the part,
Current confinement is performed on the striped ridge structure by using a Schottky junction between the electrode and the ridge lower layer.

According to this embodiment, current confinement can be performed without providing an insulating layer such as silicon nitride (SiNx) or silicon oxide (SiO ₂ ) between the electrode and the ridge lower layer. Therefore, a semiconductor laser device that can be manufactured at low cost is provided.

  In addition, according to the above embodiment, since the crystal growth process is performed once, the number of crystal growth and processing processes can be reduced as compared with the buried ridge type that requires three crystal growth processes. Can be reduced.

In the semiconductor laser device of one embodiment,
The contact layer is located on top of the striped ridge structure;
The contact layer has a doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more,
The ridge lower layer has a doping concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
A low-concentration compound layer comprising at least one of the constituent elements of the electrode and at least one of the constituent elements of the ridge lower layer is formed at the interface between the electrode and the ridge lower layer,
A high-concentration compound layer made of at least one of the constituent elements of the electrode and at least one of the constituent elements of the contact layer is formed at the interface between the electrode and the contact layer.

According to this embodiment, in the ohmic junction between the contact layer having a doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more and the electrode, a lower contact resistance is obtained by the higher concentration compound layer, and doping is performed. In the Schottky junction between the ridge lower layer having a concentration of 1 × 10 ¹⁷ cm ⁻³ or less and the electrode, sufficient current confinement can be obtained by the low concentration compound layer. Since the ohmic junction and the Schottky junction are enhanced in this way, the crystal regrowth process of the buried layer (current blocking layer) for current confinement and the crystal of the contact layer for obtaining low contact resistance. Sufficient current constriction and low contact resistance can be realized without performing a separate regrowth process, and thermal and electrical reliability is improved. As described above, the manufacturing process is simplified, and the above-described electrodes having better heat dissipation characteristics are provided, so that oscillation is performed at a low threshold current, high output operation is possible, and long-term reliability is obtained. In addition, the cost can be reduced by simplifying the manufacturing process, and reliability and high output characteristics equivalent to or higher than those of a semiconductor laser device having a conventional structure can be realized with low power consumption.

In the semiconductor laser device of one embodiment,
The ridge lower layer is composed of a plurality of semiconductor layers including at least a ridge lower highly doped layer and a ridge lower lightly doped layer,
The ridge lower highly doped layer is located closer to the substrate than the ridge lower lightly doped layer,
The low doped layer below the ridge is formed of a III-V group compound semiconductor of a second conductivity type having a doping concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
The highly doped layer below the ridge is formed of a second conductivity type III-V group compound semiconductor having a doping concentration exceeding 1 × 10 ¹⁷ cm ⁻³ .

  According to this embodiment, the presence of the highly doped layer at the bottom of the ridge allows freedom according to the optical characteristic specifications required for the second conductivity type semiconductor layer without being restricted in consideration of the Schottky junction characteristics. It is possible to change the layer thickness, composition, etc., and to suppress an increase in element resistance, thereby further reducing power consumption.

  In the semiconductor laser device of one embodiment, the lowermost layer material of the electrode is made of Ti or Pt.

  According to this embodiment, the high-concentration compound layer and the low-concentration compound layer that can achieve both sufficient current confinement and low contact resistance can be formed simultaneously.

  An optical transmission module of the present invention includes the above-described semiconductor laser device.

  According to the above configuration, since the semiconductor laser device is used, the unit price of the module can be significantly reduced.

  An optical disk device of the present invention includes the above-described semiconductor laser device.

  According to the above configuration, since the semiconductor device laser device is used, the unit price of the device can be significantly reduced.

  As is clear from the above, according to the method for manufacturing a semiconductor device of the present invention, when the thin film is drawn from the upper surface of the semiconductor layer having the flange portion to the outer side, the semiconductor device is interposed on the side surface of the insulator. It is possible to prevent the thin film from being disconnected.

  In addition, since the insulator has a positive type photosensitivity, the insulator that has entered substantially below the collar portion by coating is not exposed by subsequent exposure to the entire surface, and has the collar portion. Since the insulator exposed on the upper surface of the semiconductor layer and the outside of the flange is exposed, only the insulator that has entered substantially below the flange by development can be left. Thus, in the exposure process in the photolithography process in the manufacturing method of the semiconductor device, a photomask for patterning is unnecessary, the process can be shortened, and pattern defects due to misalignment and the like do not occur. Therefore, the yield can be improved and the cost can be reduced.

  Further, according to the semiconductor laser device of the present invention, at least a part of the semiconductor layer exposed outside the collar part from at least a part of the upper surface of the semiconductor layer having the collar part. It is possible to continuously cover the thin film without any step breakage, including at least a part of the region on the side surface of the insulator, which is substantially below the flange portion. Therefore, it is possible to obtain a semiconductor laser device capable of improving the yield and reducing the cost.

  In addition, since the optical module of the present invention includes the semiconductor laser device, the yield can be improved, the manufacturing cost can be reduced, and the unit price of the module can be significantly reduced.

  In addition, since the optical disk device of the present invention includes the semiconductor laser device, the yield can be improved, the manufacturing cost can be reduced, and the unit price of the device can be significantly reduced.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 shows the structure of a semiconductor device according to the first embodiment of the present invention. In the first embodiment, the first conductivity type is n-type, and is hereinafter referred to as “n−”. Further, the second conductivity type is p-type, and is hereinafter referred to as “p−”.

Here, a semiconductor laser device is taken as an example of the semiconductor device. As shown in FIG. 1, the semiconductor laser device includes an n-GaAs substrate 101, an n-GaAs buffer layer 102, an n-Al _0.5 Ga _0.5 As first lower cladding layer 103, and an n-Al ₀ layer. _.489 Ga _0.511 As the second lower cladding layer _104, Al _{0.25 Ga 0.75} As lower guide layer 105, multiple strained quantum well active layer _106, Al _{0.25 Ga 0.75} As upper guide layer 107, p-Al _0.4 Ga _0.6 As first upper cladding layer 108, p-Al _0.548 Ga _0.452 As second upper cladding lower layer 109, p-Al _0.548 Ga _0.452 As second An upper cladding upper layer 110 and a p-In _0.34 Ga _0.66 As _0.4 P _0.6 etching stop layer 111 are sequentially stacked. On this etching stop layer 111, a p-Al _0.5 Ga _0.5 As third upper cladding layer 112 having a reverse mesa stripe shape, a p-GaAs first contact layer 113, and a p ^++- GaAs second contact layer 114 are formed. Furthermore, a p-electrode 116 is provided on the entire front surface, and an n-electrode 117 is provided on the back surface. The semiconductor laser device also has a mesa stripe portion 121a and mesa stripe side portions 121b on both sides of the mesa stripe portion 121a. The mesa stripe portion 121a has a flange 400 in a direction perpendicular to the direction in which the stripe extends, and polyimide 115 which is an insulator is filled substantially under the flange 400. The p-electrode 116 is formed so as to cover the upper surface of the second contact layer 114 and the etching stop layer 111 on the mesa stripe side portion 121b, including the side surface of the polyimide 115. ing. In addition, the flange 400 referred to here is a part of the p-GaAs first contact layer 113 and the p ^++- GaAs second contact layer 114 in the mesa stripe part 121a, and the p under the part thereof. —Al _0.5 Ga _0.5 As This indicates a portion having a shape projecting laterally from the third upper cladding layer 112.

Next, a method for manufacturing the semiconductor laser structure will be described with reference to FIGS. On an n-GaAs substrate 101 having a (100) plane, an n-GaAs buffer layer 102 (layer thickness 0.5 μm), an n-Al _0.5 Ga _0.5 As first lower cladding layer 103 (layer thickness 1.85 μm). ), N-Al _0.489 Ga _0.511 As second lower cladding layer 104 (layer thickness 0.1 μm), Al _0.25 Ga _0.75 As lower guide layer 105 (layer thickness 3 nm), In _0.072 Ga _0.928 As quantum well layer (layer thickness 4.6 nm, 2 layers) and Al _0.15 Ga _0.85 As barrier layer (layer thickness 21.5 nm, 7.9 nm, 21.5 nm from the substrate side) ) Alternately arranged, multi-strain quantum well active layer 106, Al _0.25 Ga _0.75 As upper guide layer 107 (layer thickness 0.1 μm), p-Al _0.4 Ga _0.6 As first Upper cladding layer 108 (layer thickness 0.1 μm, P-Al ranging concentration that corresponds to the substrate side 0.05 .mu.m is 4 × ¹⁰ 17 ^{cm -3,} 0.05μm is 8 × ¹⁰ 17 ^{cm -3} in the substrate opposite), the ridge lower layer and the ridge lower highly doped layer _0.548 Ga _0.452 As second upper cladding lower layer 109 (layer thickness 0.22 μm, doping concentration 8 × 10 ¹⁷ cm ⁻³ ), p-Al ₀ corresponding to the ridge lower layer and the lower ridge lower doped layer _.548 Ga _0.452 As second upper clad upper layer 110 (layer thickness 0.1 μm, doping concentration 1 × 10 ¹⁷ cm ⁻³ ), corresponding to the ridge lower layer and the ridge lower lightly doped layer as the first semiconductor layer P-In _0.1568 Ga _0.8432 As _0.4 P _0.6 etching stop layer 111 (layer thickness 15 nm, doping concentration is 1.0 × 10 ¹⁷ cm ⁻³ ), P-Al _0.5 Ga _0.5 As third upper cladding layer 112 corresponding to the upper cladding layer as the second semiconductor layer (layer thickness 1.28 μm, doping concentration 2.4 × 10 ¹⁸ cm ⁻³ ), A p-GaAs first contact layer 113 (layer thickness: 0.45 μm, doping concentration: 3.0 × 10 ¹⁸ cm ⁻³ ) corresponding to a contact layer as a third semiconductor layer and a p ^++- GaAs second contact layer 114 ( A semiconductor layer group having a layer thickness of 0.3 μm and a doping concentration of 1.0 × 10 ²⁰ cm ⁻³ ) is sequentially grown by a metal organic chemical vapor deposition (MOCVD) method.

The doping concentrations of the p-Al _0.5 Ga _0.5 As third upper cladding layer 112, the p-GaAs first contact layer 113, and the p ^++- GaAs second contact layer 114 are not limited to the above values. It may be 1.0 × 10 ¹⁸ cm ⁻³ or more.

  Further, in FIG. 2, a resist mask 118 (mask width 6 μm) is formed in a portion where a mesa stripe portion is to be formed by a photolithography process so that the stripe direction has a (01-1) direction.

Next, portions other than the resist mask portion 118 are etched to form mesa stripe portions 121a as shown in FIG. Etching is performed in two stages using a mixed aqueous solution of sulfuric acid and hydrogen peroxide (volume mixing ratio is sulfuric acid: hydrogen peroxide: water = 1: 8: 50, liquid temperature is 10 ° C.) and hydrofluoric acid, and etching is stopped. The process is performed up to just above the layer 111. InGaAsP makes use of the fact that the etching rate by hydrofluoric acid is very slow, and makes it possible to flatten the etching surface and control the width of the mesa stripe, and GaAs also has a very slow etching rate by hydrofluoric acid. In the etching with acid, almost only the third upper cladding layer 112 is etched, and the mesa stripe portion 121a has a shape having a flange 400 as shown in FIG. The flange 400 includes a part of the p-GaAs first contact layer 113 and the p ^++- GaAs second contact layer 114. The depth of etching is 2.03 μm, the width of the lowermost part of the mesa stripe is about 2.5 μm, and the width of the uppermost part is about 4.5 μm.

  After the etching, the resist mask 118 is removed, and an adhesion enhancer and a water-soluble polyimide precursor as a lubricant are sequentially applied to the entire surface and prebaked. Next, when a positive-type photosensitive polyimide material is applied and pre-baked again, as shown in FIG. 4, the polyimide material 115a is applied so as to cover the entire surface including the mesa stripe portion 121a. It is also filled under the collar 400.

  Here, the entire surface is exposed from the upper surface side. Since the polyimide material 115a has positive photosensitivity, it is substantially below the collar part 400 (in FIG. 4, below the collar part 400 of the mesa stripe part 121a and above the broken line, the third part The polyimide material 115a in the upper cladding layer 112 side) is not exposed, and the polyimide material 115a on the mesa stripe portion 121a and the etching stop layer 111 at other positions is exposed. In FIG. 4, the polyimide material 115a on the mesa stripe 121a side from the broken line portion is not exposed. Thereafter, development is performed to remove the exposed polyimide material 115a, so that only the polyimide material 115a in the portion indicated by the hatched portion in FIG. 5 remains.

  Next, heat treatment is performed to imidize the polyimide material 115a to form a resin. At this time, since the polyimide material 115a contains a minute object (not shown) having a property of increasing its volume when subjected to heat treatment, as shown in FIG. In response to this, it is deformed into a polyimide 115 having a shape projecting from the substantially lower side of the flange 400 to the side. The above-mentioned microscopic materials are, for example, thermally expandable microspheres in which low-boiling hydrocarbons are microencapsulated with a resin shell wall, thermally expandable graphite, and the like, which are approximately the same temperature as the heat treatment temperature for polyimide formation. When the heat is applied, the volume expands.

  Thereafter, a p-electrode 116 (corresponding to a thin film) made of Ti (layer thickness: 50 nm) / Pt (layer thickness: 50 nm) / Au (layer thickness: 300 nm) is formed on the entire surface. Thereafter, the back surface (the surface on which crystal growth is not performed) of the GaAs substrate 101 is etched to an overall thickness of about 100 μm, and AuGe (layer thickness: 100 nm) / Ni (layer thickness: 15 nm) is formed on the entire back surface. An n-electrode 117 made of / Au (layer thickness: 300 nm) is disposed, and heat treatment is performed at 390 ° C. for 1 minute. In this manner, the semiconductor laser device having the structure shown in FIG. 1 can be manufactured. The final chip state is then cleaved into a bar shape with the desired resonator length and width on a plane perpendicular to the mesa stripe direction, and a low reflection film and a high reflection film (see FIG. (Not shown) are formed and further divided into chips. Further, a metal wire (not shown) required for current injection is bonded onto the p electrode 116 in the mesa stripe side portion 121b.

  In the first embodiment, as shown in FIG. 9, the operation of a semiconductor laser device having characteristics of a threshold current of 12 mA and an external quantum efficiency of 0.95 was confirmed with a pulse current. This characteristic is the same as that of a conventional semiconductor laser device manufactured by performing crystal growth by metal organic vapor phase epitaxy three times, and the crystal growth necessary for this semiconductor laser device is only one time. In addition to being able to improve, the manufacturing process and cost could be greatly reduced. Further, although the collar 400 is provided, the space below the collar 400 is filled with the polyimide 115, so that the p-electrode 116 is disconnected from the upper surface of the second contact layer 114. It was possible to pull it out easily without letting it go. Also, in the polyimide forming process, since the polyimide 115 has positive photosensitivity and the entire surface is exposed using the flange 400, the manufacturing process and cost can be reduced. By eliminating the need for photomask alignment, the yield could be further increased. Furthermore, since the junction area between the p-electrode 116 and the second contact layer 114 can be increased as compared with a conventional semiconductor laser device having an air ridge structure, the element resistance can be reduced and the temperature characteristics can be reduced. It was possible to realize a semiconductor laser device with high reliability.

  Further, in the first embodiment, since the polyimide, that is, the insulator 115 has a minute material having a thermal expansion property, the minute material expands by the heat treatment process, and the insulator 115 becomes the flange portion. It is possible to project outward from substantially below 400. As a result, the p-electrode (thin film) 116 could be easily pulled out onto the etching stop layer 111 in the mesa stripe side portion 121b without being cut off from the upper surface of the second contact layer 114. Specifically, the microscopic material is preferably a thermally expandable microsphere in which a low boiling point hydrocarbon is microencapsulated with a resin shell wall, thermally expandable graphite, or the like. These are expanded in volume when heated, and can be easily mixed with other resins. Furthermore, in the first embodiment, since the heat treatment temperature at which the minute matter expands and the heat treatment temperature for polyimide formation are approximately the same, the heat treatment is only required once, and the cost can be reduced.

  In the first embodiment, since the insulator 115 protrudes, a p-electrode 116 is formed which can be pulled out from the upper surface of the second contact layer 114 without any step even when the electrode is deposited using a normal deposition method. can do. The p-electrode (total layer thickness: 400 nm) is sufficiently thinner than the height (2.03 μm) of the mesa stripe part having the collar part. Even with such a thin film, the insulator is disposed, Even if it has a part, the thin film could be pulled out from the upper part without being cut off.

  In the present invention, the insulator may be formed so as to be filled substantially under the collar portion without being deformed so as to expand.

  When the insulator 415 is not overhanging by using an insulator 415 that does not expand or hardly expand as in the modification shown in FIG. 6, formation of the p-electrode 416 using an oblique deposition method or a sputtering method is performed. By performing the above, it is possible to form the p-electrode 416 that can be extracted without being disconnected. In FIG. 6, the same constituent elements as those shown in FIG. 1 are denoted by the same reference numerals as those of FIG.

  Also, as shown in FIGS. 1 and 4, in the first embodiment, polyimide 115 is used as an insulator, and the polyimide material 115a as the base material may be made photosensitive by using an additive. Therefore, it is suitable for the above manufacturing method. Further, the viscosity and expansibility of the polyimide material 115a can be easily controlled with respect to the shape of the collar 400 and the shape of the insulator desired to be finally obtained. Further, the collar portion 400 has a structure that is vulnerable to external impacts. A resin is used for the insulator 115 disposed substantially below the collar portion 400 to reinforce the structure and provide a highly reliable semiconductor laser device. It can be.

  Further, in the first embodiment, the insulator 115 substantially below the flange 400 is sufficiently filled until it contacts the third upper cladding layer 112. That is, the insulator 115 is present in the vicinity of the third upper cladding layer 112 in the stripe ridge structure, and the metal 116 that is a p-electrode and the third upper cladding layer 112 are not in contact with each other.

  So far, the present inventors have studied a semiconductor laser device in which an insulating film is omitted from the conventional air ridge structure using a current confinement structure by a metal-semiconductor Schottky junction. It was found that since the electrode was in contact with the inner upper cladding layer, the oscillated laser beam was absorbed by the electrode, and sufficient efficiency could not be obtained.

  As described above, in the first embodiment, since the third upper cladding layer 112 and the p-electrode 116 are not in contact with each other, a highly efficient semiconductor laser device that does not receive laser light absorption by the p-electrode 116 is realized. I was able to. For this reason, restrictions in optical design have been relaxed, and the degree of freedom such as the composition and thickness of each semiconductor layer could be increased.

  Further, as in the modification shown in FIG. 7, there may be a gap 119 between the third upper cladding layer 112 and the insulator 715. In that case, optical confinement by air is performed in the vicinity of the third upper cladding layer 112, and therefore, the optical design of the semiconductor laser device may be performed in consideration of this. By doing so, the third upper cladding layer 112 made of a semiconductor layer due to the influence of the operating atmosphere temperature of the semiconductor laser element can be compared with the case where the insulator 715 is in contact with the third upper cladding layer 112. Since the gap 119 can absorb the stress caused by the difference in volume expansion coefficient with the insulator 715, a semiconductor laser device with higher reliability can be obtained. In FIG. 7, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those of FIG.

  In the first embodiment, a water-soluble polyimide precursor (not shown) is used as a lubricant. Compared with the case where this is not used, since the polyimide material 115a to be applied thereafter becomes slippery due to the lubricant, the polyimide material 115a can easily enter under the flange 400 and is easily filled. is there. Moreover, since the coating thickness of the polyimide material 115a can be reduced on the upper surface of the second contact layer 114, problems such as a residue in the removal of the polyimide material 115a in an exposed portion by subsequent development can be reduced. There is an effect that can.

In the first embodiment, current confinement is performed on the striped ridge 121a using a Schottky junction. Of course, the present invention can be applied to a more general insulating thin film, for example, an air ridge structure through silicon oxide (SiO ₂ ) or silicon nitride (SiN _x ), thereby improving the yield by preventing the electrode from being disconnected. Can be made sufficiently large. Specifically, although not shown, it is necessary to dispose the insulating thin film on the entire surface by vapor deposition or the like before producing the p-electrode, and to remove at least the insulating thin film on the second contact layer. If the insulating thin film is disconnected, the p-electrode cannot be extracted. Therefore, with the structure as in the first embodiment, the insulating thin film can also be extracted without causing the disconnection. It becomes possible.

  In addition, when current confinement is performed using a Schottky junction as in the first embodiment, a heat treatment is performed after the p electrode 116 is formed, so that the lowermost electrode material of the p electrode 116 If a compound layer is formed at the interface between the semiconductor layers 114 and 111, the Schottky junction property in the current confinement region and the ohmic junction property in the contact layer 114 are further strengthened, and current is injected only into the ridge portion 121a with low resistance. A ridge waveguide semiconductor laser device can be obtained.

In the first embodiment, the lowermost layer of the p-electrode 116 is made of Ti, and an alloying reaction is caused between Ti and the semiconductor layers 114 and 111 by heat treatment at 390 ° C. When Ti is deposited on the semiconductor layers 114 and 111 and then heated to about 400 ° C., the oxide layer formed on the surface of the semiconductor layers 114 and 111 is removed during the manufacturing process, and the doping concentration is 1 × 10 ¹⁷ cm. ^A stable Schottky junction can be obtained for a low concentration semiconductor layer of ⁻³ or less, that is, the etching stop layer 111. When Ti is formed on the InGaAsP layer 111 and the AlGaAs layer 110 as in the first embodiment and heated appropriately, a particularly thermally and electrically stable Schottky junction can be obtained. This is considered to be because a very thin Ti alloy layer as a low concentration compound layer is formed at the interface between the p electrode 116 and the low concentration semiconductor layer 111. The effect of obtaining a good Schottky junction is difficult to see.

For GaAs or InGaAs doped to 1 × 10 ¹⁸ cm ⁻³ or more, a low contact resistance can be realized by forming a TiAs layer in addition to the above-described oxide layer removal effect. The heat treatment temperature suitable for these reactions is 350 ° C. or higher and 430 ° C. or lower. When the temperature is lower than 350 ° C., the reaction of forming the compound layer by alloying does not proceed sufficiently, and when the temperature exceeds 430 ° C., the contact resistance gradually deteriorates in the ohmic junction. It is considered that the resistance deterioration at 430 ° C. or more is caused by the generation of the Ti _x Ga _1-x layer and the mixing of the metal material above the Ti. Also in the first embodiment, in consideration of the optimum heat treatment condition of the AuGe / Ni / Au electrode material on the back surface side, a heat treatment is performed at 390 ° C. for 1 minute between the p electrode 116 and the GaAs second contact layer 114. A high-concentration compound layer composed of the electrode material and the contact layer material was formed, and a desired ohmic junction was obtained.

  The lowermost layer of the p-electrode 116 may be Pt. In this case, a preferable heat treatment temperature is 350 ° C. or higher and 450 ° C. or lower. When the temperature of the heat treatment is less than 350 ° C., the high concentration side compound layer and the low concentration side compound layer are not sufficiently formed, and when the temperature exceeds 450 ° C., Pt diffuses too much into the semiconductor layer. Since the characteristics of the semiconductor device are deteriorated, a semiconductor device having good ohmic characteristics and Schottky junction characteristics can be provided by heat treatment in the above temperature range.

In the first embodiment, as the ridge lower layer, the etching stop layer 111 having the second conductivity type doping concentration of 1.0 × 10 ¹⁷ cm ⁻³ and the second upper cladding upper layer 110 are used. And the second upper cladding lower layer 109 having a second conductivity type doping concentration of 8 × 10 ¹⁷ cm ⁻³ , and between the second upper cladding upper layer 110 and the active layer 106. The second upper cladding lower layer 109 is located. As a result, the layer thickness, composition, etc. can be freely changed according to the optical characteristic specifications required by the second conductivity type semiconductor layer without being restricted in consideration of the Schottky junction characteristics, and the element resistance Can be suppressed, and further reduction in power consumption can be achieved. Of course, even if the etching stop layer 111 is not provided, the Schottky junction property is provided. However, when the etching stop layer 111 is provided, the Schottky junction property is further improved and a highly reliable semiconductor laser device is obtained. Can be realized. Furthermore, since the etching with high stripe width controllability using the etching stop layer 111 can be performed, the yield improvement effect can be obtained.

In the method of manufacturing the semiconductor device according to the first embodiment, in the Schottky junction between the etching stop layer 111 and the p electrode 116 having a doping concentration of 1 × 10 ¹⁷ cm ⁻³ , In the ohmic junction between the second contact layer 114 and the p-electrode 116 having a doping concentration of 1 × 10 ²⁰ cm ⁻³ , a sufficient current confinement is obtained by the compound layer, Lower contact resistance can be obtained. Since the Schottky junction and ohmic junction are further strengthened in this way, low threshold current oscillation and high output can be achieved without performing the current block layer burying regrowth step and the electrode contact layer crystal regrowth step. Operation is possible and long-term reliability is obtained. Furthermore, a method of manufacturing a semiconductor laser device having excellent heat dissipation characteristics that can reduce costs by simplifying the manufacturing process is provided. Therefore, it is possible to manufacture a semiconductor device that can obtain a sufficient current confinement property and excellent element reliability, and that can operate at high output with low power consumption.

  In the first embodiment, the total thickness of the p-electrode is 400 nm, but the thickness of the thin film is about 1/3 or more of the height of the step as in the mesa stripe portion. Thin film breakage due to steps is less likely to occur. However, the thinner the thickness, the lower the consumption of raw materials used for forming the thin film, and the lower the cost of the apparatus.

  In the first embodiment, the etching stop layer 111 is a semiconductor layer made of InGaAsP, but is not limited to this. In the etching in the first embodiment, since the etchant used for the second time is hydrofluoric acid, the etching stop layer may be GaAs.

  The stripe direction of the semiconductor laser device of the first embodiment is the (01-1) direction on the (100) plane, the so-called reverse mesa direction, but is not limited thereto. On the (100) plane, the stripe direction may be a (011) direction perpendicular to the above, that is, a so-called forward mesa direction. In the case of this modification, a cross-sectional view perpendicular to the stripe direction is as shown in FIG. 8, and the side surfaces of the first contact layer 813 and the second contact layer 814 become wider toward the substrate 101. Therefore, the p electrode 814 can be structured to be less likely to be disconnected. 8, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those of FIG. 1, and the description thereof is omitted.

  Further, in the semiconductor laser device of the first embodiment, the insulator 115 is made of polyimide containing a microscopic material having thermal expansion, and is deformed so as to protrude outward from substantially below the flange 400. Is a heat treatment step, but is not limited thereto. In the first embodiment, the heat treatment step serves as both the polyimide forming step and the deformation step. However, if the treatment temperatures are different, the heat treatment may be performed separately. In that case, it is preferable that the processing temperature of the deformation process is designed to be lower and the deformation process is performed prior to the polyimidization process. The minute object may be a swellable minute object, and in this case, the step of deforming may be a wetting step. Moreover, the said micro thing may have foamability. In that case, the surface of the insulator, that is, the surface on which the p-electrode is arranged becomes a smooth and perforated surface after foaming of the minute object, but the p-electrode is not cut off at least in a part of the region. This is not a problem as long as it is secured.

(Second Embodiment)
FIG. 10 is a cross-sectional view showing an optical transmission module 200 of the optical transmission system according to the second embodiment of the present invention. FIG. 11 is a perspective view showing a light source portion. In the second embodiment, the semiconductor laser device (laser chip) 201 described in the first embodiment is used as a light source, and a silicon (Si) pin photodiode is used as the light receiving element 202. In this optical transmission system, it is assumed that the other party that transmits and receives signals also includes the same optical transmission module as described above. The semiconductor laser device 201 has an emission wavelength of about 890 nm in the module mounted state.

  In FIG. 10, a pattern (not shown) of both positive and negative electrodes for driving a semiconductor laser is formed on a circuit board 206, and a recess 206a having a depth of 300 μm is provided in a portion where the laser chip 201 is mounted. . A laser mount (mounting material) 210 on which the laser chip 201 is mounted is fixed to the recess 206a with solder. As shown in FIGS. 10 and 11, the flat portion 213 of the positive electrode 212 of the laser mount 210 is electrically connected to a laser driving positive electrode portion (not shown) on the circuit board 206 by a wire 207a. The recess 206a has a depth that does not hinder the radiation of the laser beam, and the roughness of the surface does not affect the radiation angle.

  The light receiving element 202 is also mounted on the circuit board 206, and an electric signal is taken out by the wire 207b. In addition, an IC circuit 208 for laser driving / reception signal processing is mounted on the circuit board 206.

  Next, an appropriate amount of a liquid silicon resin 209 mixed with a light diffusing filler is dropped into a recess 206a, which is a portion where the laser mount 210 is fixed and mounted with solder. The silicon resin 209 stays in the recess 206a due to surface tension, covers the laser mount 210, and is fixed to the recess 206a. In the second embodiment, the recess 206a is provided on the circuit board 206 and the laser mount 210 is mounted. However, as described above, the silicon resin 209 remains on the surface of the laser chip 201 and its vicinity due to surface tension. The recess 206a is not necessarily provided.

  Thereafter, the silicon resin 209 is heated at 80 ° C. for about 5 minutes to be cured until it forms a jelly. Next, the entire surface is covered with a transparent epoxy resin mold 203. A lens portion 204 for controlling the emission angle is formed on the upper surface of the laser chip 201, and a lens portion 205 for condensing the signal light is integrally formed on the upper surface of the light receiving element 202 as a molded lens. . As described above, in this optical transmission system, it is assumed that the other party holds another optical transmission module and transmits and receives an optical signal. An optical signal emitted from the light source with information is received by the light receiving element of the counterpart optical transmission module, and an optical signal transmitted from the counterpart is received by the light receiving element 202.

  Next, the laser mount 210 will be described with reference to FIG. As shown in FIG. 11, a laser chip 201 is die-bonded to an L-shaped heat sink 211 using In glue. The laser chip 201 is the InGaAs semiconductor laser device described in the first embodiment, and the chip lower surface 201b is coated with a high reflection film, while the laser chip upper surface 201a is coated with a low reflection film. Has been. These reflective films also serve as protection for the end face of the laser chip.

  A positive electrode 212 is fixed to the base 211b of the heat sink 211 with an insulator so as not to be electrically connected to the heat sink 211. The positive electrode 212 and the electrode region 201c provided on the Schottky junction on the surface of the laser chip 201 are connected by a gold wire 207c. As described above, the laser mount 210 is fixed to the negative electrode (not shown) of the circuit board 206 of FIG. 10 by soldering, and the flat part 213 on the upper side of the positive electrode 212 and the positive electrode part of the circuit board 206 (see FIG. (Not shown) with a wire 207a. By forming such wiring, the optical transmission module 200 capable of obtaining the laser beam 214 by oscillation is completed.

  The optical transmission module 200 according to the second embodiment uses the single growth type semiconductor laser device 201 that can be manufactured at a low cost as described above. it can.

(Third embodiment)
FIG. 12 shows an example of the structure of an optical disc apparatus according to the third embodiment of the present invention. This optical disc apparatus is for writing data on the optical disc 301 and reproducing the written data. As the light emitting element used at that time, the quantum well in the semiconductor laser device of the first embodiment described above is used. A semiconductor laser device 302 that oscillates at 780 nm is provided by changing a layer such as an active layer. The process of forming the stripe ridge structure and the insulator is the same as in the first embodiment.

  This optical disk device will be described in more detail. At the time of writing, the signal light emitted from the semiconductor laser device 302 is converted into parallel light by the collimator lens 303, transmitted through the beam splitter 304, and the polarization state is adjusted by the λ / 4 polarizing plate 305, and then irradiated with laser light. The light is condensed by the objective lens 306 and irradiated onto the optical disc 301.

  On the other hand, at the time of reading, the optical disc 301 is irradiated with a laser beam carrying no data signal along the same path as at the time of writing. This laser beam is reflected on the surface of the optical disc 301 on which data is recorded, passes through the laser beam irradiation objective lens 306 and the λ / 4 polarizing plate 305, and then is reflected by the beam splitter 304 to change the angle by 90 °. The light is condensed by the reproduction light objective lens 307 and is incident on the signal detection light-receiving element 308. The data signal recorded by the intensity of the laser light incident in the signal detecting light receiving element 308 is converted into an electric signal, and is reproduced by the signal light reproducing circuit 309 to the original signal.

  Since the optical disk apparatus according to the third embodiment uses the semiconductor laser apparatus 302 with a manufacturing process and a manufacturing cost reduced as compared with the conventional semiconductor laser apparatus, an optical disk apparatus with a lower cost can be provided.

  Here, an example in which the semiconductor laser device 302 of the present invention is applied to a recording / reproducing optical disc device has been described. However, the present invention can also be applied to an optical disc recording device and an optical disc reproducing device that use the same wavelength band of 780 nm.

  Note that the compound semiconductor device of the present invention is not limited to the above-described examples. For example, the thickness and number of well layers and barrier layers of the semiconductor laser device are within the scope not departing from the gist of the present invention. Of course, various changes can be made.

It is sectional drawing of the surface perpendicular | vertical with respect to the stripe direction of the semiconductor laser apparatus concerning 1st Embodiment of this invention. It is sectional drawing of the surface perpendicular | vertical with respect to the stripe direction after completion | finish of resist mask preparation of the semiconductor laser apparatus concerning 1st Embodiment of this invention. It is sectional drawing of the surface perpendicular | vertical with respect to a stripe direction after the collar part formation of the mesa stripe part by etching of the semiconductor laser apparatus concerning 1st Embodiment of this invention. It is sectional drawing of a surface perpendicular | vertical with respect to a stripe direction when receiving the whole surface exposure from upper direction after the polyimide precursor application | coating formation of the semiconductor laser apparatus concerning 1st Embodiment of this invention. It is sectional drawing of the surface perpendicular | vertical with respect to the stripe direction after photosensitive polyimide precursor image development of the semiconductor laser apparatus concerning 1st Embodiment of this invention. In the semiconductor laser device according to the first embodiment of the present invention, the manufacturing method is changed, and the stripe direction of the modified example is manufactured by omitting the step of deforming the insulator filled in the substantially lower part of the flange part outward. It is sectional drawing of a surface perpendicular | vertical to. In the semiconductor laser device according to the first embodiment of the present invention, the manufacturing method is changed, and the stripe direction of the modified example manufactured so as to have a gap between the third upper cladding layer and the insulator is changed. It is sectional drawing of a perpendicular | vertical surface. In the semiconductor laser device according to the first embodiment of the present invention, the manufacturing method is changed, and the cross-section of the plane perpendicular to the stripe direction of the modified example in which the stripe direction is formed in the (011) direction, the so-called forward mesa direction FIG. It is a graph of the current-light output characteristic of the semiconductor device (semiconductor laser device) concerning this invention. It is the schematic of the optical transmission module used for the optical transmission system concerning 2nd Embodiment of this invention. It is a perspective view of the light source concerning the optical transmission system concerning a 2nd embodiment of the present invention. It is the schematic of the optical disk apparatus of 3rd Embodiment of this invention. It is the cross-sectional schematic of the surface perpendicular | vertical with respect to the stripe direction of the conventional semiconductor laser apparatus. It is the cross-sectional schematic of the surface perpendicular | vertical to the longitudinal direction of a rectangular mesa which shows the element structure of the conventional heterojunction bipolar transistor.

DESCRIPTION OF SYMBOLS 101 Substrate 102 Buffer layer 103 First lower cladding layer 104 Second lower cladding layer 105 Lower guide layer 106 Multiple strain quantum well active layer 107 Upper guide layer 108 First upper cladding layer 109 Second upper cladding lower layer 110 Second upper cladding Upper layer 111 Etching stop layer 112 Third upper cladding layer 113, 813 First contact layer 114, 814 Second contact layer 115, 415, 815 Polyimide 115a Polyimide material 116 p electrode 117 n electrode 118 resist mask 119 gap 121a mesa stripe Part 121b Mesa stripe side part 200 Optical transmission module 201 Laser chip 201a Laser chip upper surface 201b Chip lower surface 201c Electrode region 202 Light receiving element 203 Epoxy resin mold 204, 205 Part 206 circuit board 206a recess 207a, 207b wire 207c gold wire 208 circuit 209 silicon resin 210 laser mount 211 heat sink 211b base 212 positive electrode 213 flat part 214 laser beam 301 optical disk 302 semiconductor laser device 303 collimating lens 304 beam splitter 305 polarizing plate 306 Laser beam irradiation objective lens 307 Reproduction light objective lens 308 Signal detection light receiving element 309 Signal light reproduction circuit

Claims (14)

Laminating a semiconductor layer group consisting of a plurality of semiconductor layers on a semiconductor substrate;
Processing the semiconductor layer group so that at least a part of the semiconductor layer group has a flange that protrudes in a direction intersecting the direction from the semiconductor layer group toward the substrate;
Applying a positive-type photosensitive insulator on the surface of the processed semiconductor layer group;
Exposing the entire surface of the insulator from above;
Removing the insulator exposed by the exposure by development;
The development which is substantially below the collar part from at least a part of the upper surface of the semiconductor layer having the collar part to at least a part of the semiconductor layer exposed on the side of the collar part. Forming a thin film that covers at least a part of the region on the side surface of the insulator left by
Before forming the thin film, the insulator that is substantially under the collar part left by the development is set so that at least a part of the insulator projects outward from the bottom of the collar part by thermal expansion. The manufacturing method of the semiconductor device characterized by including the process to deform | transform. In the manufacturing method of the semiconductor device according to claim 1,
A method for manufacturing a semiconductor device, comprising: applying a lubricant before applying the insulator. In the manufacturing method of the semiconductor device according to claim 1,
The insulator is made of polyimide containing microscopic materials having thermal expansibility,
A method of manufacturing a semiconductor device, wherein the step of deforming is a heat treatment. In the manufacturing method of the semiconductor device according to claim 1,
The substrate has a first conductivity type;
In the step of laminating the semiconductor layer group, as the semiconductor layer group, at least a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer are sequentially laminated from the substrate side,
The first semiconductor layer is formed to be a second conductivity type low concentration semiconductor layer having a doping concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
The second semiconductor layer and the third semiconductor layer are formed to be a second conductivity type high concentration semiconductor layer having a doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more,
In the step of processing the semiconductor layer group, the second semiconductor layer and the third semiconductor layer form a striped ridge structure on the upper surface of the first semiconductor layer, and the flange portion is formed by the third semiconductor layer. Etching the semiconductor layer group so that is formed,
In the step of forming the thin film, an electrode is formed as the thin film,
The high-concentration compound layer is formed at the interface between the electrode and the third semiconductor layer, and the low-concentration compound layer is formed at the interface between the electrode and the first semiconductor layer. The manufacturing method of the semiconductor device characterized by including the process of heat-processing after formation. In the manufacturing method of the semiconductor device according to claim 4,
The lowermost layer of the electrode is made of Ti,
In the step of performing the heat treatment, the low concentration side compound layer and the high concentration side compound layer are formed by heat treatment at 350 ° C. or higher and 430 ° C. or lower. In the manufacturing method of the semiconductor device according to claim 4,
The lowermost layer of the electrode is made of Pt,
In the step of performing the heat treatment, the low concentration side compound layer and the high concentration side compound layer are formed by heat treatment at 350 ° C. or higher and 450 ° C. or lower. A semiconductor substrate made of a III-V compound semiconductor of the first conductivity type;
A lower clad layer made of a first-conductivity-type III-V compound semiconductor, an active layer made of a III-V compound semiconductor, and a second-conductivity type III-V compound semiconductor, which are sequentially stacked on the semiconductor substrate. A semiconductor layer group including at least a contact layer made of an upper cladding layer and a III-V group compound semiconductor of the second conductivity type,
At least a part of the semiconductor layer group has a striped ridge structure, and has a ridge that projects in a direction crossing the extending direction of the ridge structure,
And an insulator located on both sides of the ridge structure, not located on the upper surface of the collar, and positioned substantially below the collar .
The at least part of the upper surface of the semiconductor layer having the flange part to at least a part of the region on the semiconductor layer exposed outside the flange part, which is substantially below the flange part. A thin film covering at least a part of the region on the side surface of the insulator,
A part of the insulator protrudes from the bottom of the collar part to the outside, and the thickness of the insulator decreases as it projects from the bottom of the collar part to the outside. A semiconductor laser device. The semiconductor laser device according to claim 7, wherein
A semiconductor laser device, characterized in that the insulator is made of polyimide containing a thermally expanded fine substance. The semiconductor laser device according to claim 8, wherein
The semiconductor layer group is partly located between the stripe-shaped ridge structure and the active layer, and the other part has a surface on the side of the stripe-shaped ridge structure. Including a ridge lower layer made of a conductive type III-V compound semiconductor,
The thin film extends from at least a part of the upper surface of the semiconductor layer having the flange to at least a part of the ridge lower layer exposed outside the flange. An electrode that covers at least a part of the region on the side surface of the insulator that is substantially below the part,
A semiconductor laser device characterized in that current confinement is performed on the stripe ridge structure by using a Schottky junction between the electrode and the ridge lower layer. The semiconductor laser device according to claim 9, wherein
The contact layer is located on top of the striped ridge structure;
The contact layer has a doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more,
The ridge lower layer has a doping concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
A low-concentration compound layer comprising at least one of the constituent elements of the electrode and at least one of the constituent elements of the ridge lower layer is formed at the interface between the electrode and the ridge lower layer,
A semiconductor laser characterized in that a high concentration compound layer comprising at least one of the constituent elements of the electrode and at least one of the constituent elements of the contact layer is formed at the interface between the electrode and the contact layer. apparatus. The semiconductor laser device according to claim 9, wherein
The ridge lower layer is composed of a plurality of semiconductor layers including at least a ridge lower highly doped layer and a ridge lower lightly doped layer,
The ridge lower highly doped layer is located closer to the substrate than the ridge lower lightly doped layer,
The lower ridge lower doped layer is formed of a second conductivity type III-V group compound semiconductor having a doping concentration of 1 × 10 ¹⁷ cm ⁻³ or less,
2. The semiconductor laser device according to claim 1, wherein the highly doped layer under the ridge is formed of a second conductivity type III-V group compound semiconductor having a doping concentration exceeding 1 × 10 ¹⁷ cm ⁻³ . The semiconductor laser device according to claim 9, wherein
A semiconductor laser device characterized in that the lowermost layer material of the electrode is made of Ti or Pt. An optical transmission module comprising the semiconductor laser device according to claim 7. An optical disk device comprising the semiconductor laser device according to claim 7.

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