JP2012084613A - Semiconductor laser element, manufacturing method of the same and electronic information device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in device characteristics such as an operation current by protecting an inside metal electrode layer from oxidation so as to prevent increase in resistance value of the device.SOLUTION: By covering a portion including an end face in contact with air of an inside metal electrode layer 135 with dielectric films 140, 141, contact of the inside metal electrode layer 135 with air can be completely blocked. Accordingly, oxidation due to air contact of the inside metal electrode layer 135 as in the past can be prevented, so that deterioration in the inside metal electrode layer 135 due to oxidation can be inhibited and a highly reliable semiconductor laser element 200 can be achieved.

Description

  The present invention relates to a monolithic multi-wavelength semiconductor laser element having a plurality of laser parts formed on the same substrate, a method for manufacturing the same, and an electronic information device incorporating a pickup device using the semiconductor laser element in an information recording / reproducing part. About.

  In recent years, an optical pickup having a two-wavelength semiconductor laser device in which a semiconductor laser device for DVD with an emission wavelength of 650 nm band and a semiconductor laser device for CD with an emission wavelength of 780 nm band are used. In addition, an optical disk device that can reproduce the sound has been developed.

  FIG. 7 is a longitudinal sectional view schematically showing an example of a conventional monolithic two-wavelength laser element disclosed in Patent Document 1. In FIG.

  As shown in FIG. 7, a conventional monolithic two-wavelength laser element 100 having a non-hermetic package specification includes a first wavelength laser oscillation section 102 having a ridge portion and a second wavelength laser having a ridge portion on a substrate 101. A monolithic multi-wavelength laser element including an oscillating unit 103, wherein the first wavelength laser oscillating unit 102 and the second wavelength laser oscillating unit 103 are current blocking layers made of a semiconductor thin film in contact with the ridge portion. 131, an insulating layer 132 made of an insulating dielectric thin film made of a material having a refractive index lower than the refractive index of the material of the current blocking layer 131 in contact with the p-side electrode side of the current blocking layer 131, and the insulating layer An inner metal electrode layer 135 that contacts the p-side electrode side of 132 and an outer metal electrode layer 137 that contacts the p-side electrode side of the inner metal electrode layer 135 are provided. Reference numeral 134 denotes a p-type ohmic electrode.

  As described above, the monolithic two-wavelength laser element 100 includes, for example, a monolithic two-wavelength laser including the first wavelength laser oscillation unit 102 and the second wavelength laser oscillation unit 103 formed on a single GaAs substrate surface. In the element 100, the first wavelength laser oscillation unit 102 and the second wavelength laser oscillation unit 103 each have a real guide structure. For this reason, even when the first wavelength is in the 780 nm band and the second wavelength is in the 650 nm band, there is an advantage that the waveguide loss can be reduced and the operating current can be reduced compared to the conventional case.

  The substrate 101 is preferably made of a material containing GaAs. By using the substrate 101 containing such a material, there is an advantage that a crystal made of a desired material can be grown in a flat state with good crystallinity.

  The substrate 101 preferably has an off angle in the range of 5 to 25 degrees in the [110] direction from the (001) plane. This is to improve the laser element characteristics by adjusting the wavelength of the laser oscillation unit 103 of the second wavelength and improving the crystallinity of both the laser oscillation units 102 and 103 of the first wavelength and the second wavelength. The off angle is more preferably 10 to 20 degrees, and further preferably 13 to 18 degrees.

  The thickness of the current blocking layer 131 is preferably 0.05 μm or more, and more preferably 0.1 μm or more. Moreover, this film thickness is preferably 0.2 μm or less, and more preferably 0.17 μm or less. If this film thickness is less than 0.05 μm, the light confinement in the lateral direction of the ridge tends to be unstable, and the variation in optical characteristics tends to increase. Loss increases and operating current tends to increase.

  The current blocking layer 131 is preferably a current blocking layer made of a semiconductor thin film containing one or more materials selected from the group consisting of GaAs, α-Si, and Ge. By using the current blocking layer 131 containing such a material, the adhesiveness between the insulating dielectric thin film and the side surface of the ridge portion and the etch stop layer is improved, and the thin current blocking layer 131 absorbs light horizontally. This is because there is an advantage of stabilizing the shape of the radiation angle in the direction.

  The insulating layer 132 is preferably an insulating layer that is in contact with the p-side electrode side of the current blocking layer 131 and is made of an insulating dielectric thin film made of a material having a refractive index lower than that of the current blocking layer 131. . Since the refractive index of the insulating layer 132 is lower than the refractive index of the current blocking layer 131, there is an advantage that light confinement in the ridge lateral direction can be stabilized and waveguide loss can be reduced.

  The refractive index of the insulating layer 132 made of an insulating dielectric thin film having a low refractive index is preferably in the range of 1.0 to 2.0. That is, since the refractive index of the ridge material of the first wavelength laser part is generally in the range of 3.2 to 3.4, it is made of an insulating dielectric thin film in order to confine light in the laser oscillation part. It is desirable that the refractive index of the insulating layer 132 be smaller than that of the ridge portion material and the current blocking layer 131 described above. As the insulating layer 132 made of such an insulating dielectric thin film, a silicon nitride film or a silicon oxide film and a mixture thereof can be selected.

  The surface of the insulating layer 132 made of an insulating dielectric thin film preferably has an O composition and / or an N composition (including the total value of N and O 2) of 0 or more, particularly 0.00001 or more. More preferably. The O composition and / or N composition is preferably 0.001 or less, and more preferably 0.0005 or less. By doing so, there is an advantage that the adhesion between the insulating layer and the inner metal electrode layer containing Mo / Au as a material is improved, and the outer metal electrode layer containing Au as a material can be reliably formed.

  Furthermore, the film thickness of the underlying insulating layer made of an insulating dielectric thin film having a low refractive index is preferably 160 nm to 260 nm, and more preferably 180 nm to 240 nm in order to reduce the influence of unevenness due to the film thickness. . The film thickness of the insulating layer for the cover is preferably 250 nm to 350 nm, more preferably 280 nm to 330 nm as a result of considering the coverage of the end face portion and the adhesion to the inner metal electrode layer 135. .

  The inner metal electrode layer 135 preferably covers the entire surface of the insulating layer 132 on the laser emission direction side. By adopting such a structure, there is an advantage that the outer metal electrode layer 137 is formed on the entire surface of the inner metal electrode layer 135, heat dissipation from the laser oscillation unit is improved, and temperature characteristics and reliability are improved. .

  The inner metal electrode layer 135 is preferably an inner metal electrode layer containing a Mo / Au alloy and / or a Ti / Al alloy. By using the inner metal electrode layer 135 containing such a material, the heat conductivity is low, so that there is an advantage that heat dissipation can be improved.

  The outer metal electrode layer 137 is preferably an outer metal electrode layer containing Au as a material. By using the outer metal electrode layer 137 containing such a material, the thick outer metal electrode layer 137 can be easily formed by an electrolytic plating method, and it can be used with the brazing material when the element is mounted on the stem. There are advantages. The thickness of the outer metal electrode layer 137 is preferably in the range of 2.5 to 3 μm from the viewpoint of protection of the ridge portion and heat dissipation.

JP 2005-109089 A

  In the conventional monolithic two-wavelength laser element 100 of the non-hermetic package specification, the inner metal electrode layer 135 contains Mo / Au alloy or the like. In this case, since the end surface of the inner metal electrode layer 135 is in direct contact with the atmosphere, an oxidation reaction easily occurs when oxygen or moisture in the atmosphere comes into contact with the end surface of the inner metal electrode layer 135. In particular, when an element is exposed to severe conditions under high temperature and high humidity, oxidation rapidly proceeds from the end surface of the inner metal electrode layer 135, and the resistance value of the element increases, and the element such as operating current increases. There is a problem in that the characteristics are deteriorated and the element output can be lowered.

  The present invention solves the above-mentioned conventional problems, and by protecting the inner metal electrode layer from oxidation, it is possible to prevent an increase in the resistance value of the element and prevent deterioration of element characteristics such as operating current. An object of the present invention is to provide a semiconductor laser element that can be produced, a method for manufacturing the same, and an electronic information device in which a pickup device using the semiconductor laser element in an information recording / reproducing unit is incorporated.

  The semiconductor laser device of the present invention has one or more double heterostructures that are formed on a semiconductor substrate and oscillate at different wavelengths, and an electrode structure that is formed on each of the one or more double heterostructures. And the end surface part of the inner side metal electrode which comprises this electrode structure is covered and protected by the dielectric film, and the said objective is achieved by it.

  Preferably, the electrode structure in the semiconductor laser device of the present invention has a current blocking layer formed of a semiconductor thin film in contact with the ridge portion of the double heterostructure on each of the one or more double heterostructures, and the current An inner metal electrode formed on the blocking layer and on the one-conductive ohmic region of the double heterostructure; and an outer metal electrode formed on the inner metal electrode, including an end face of the inner metal electrode The portion is sandwiched between the dielectric films to protect the end face.

  Further preferably, in the semiconductor laser device of the present invention, the outer metal electrode is an Au layer, and the inner metal electrode is a Mo / Au layer.

  Further preferably, the inner metal electrode in the semiconductor laser device of the present invention is a Mo / Au electrode having a two-layer structure of an upper Au layer and a lower Mo layer.

Further preferably, the electrode structure in the semiconductor laser device of the present invention is a surface electrode of the semiconductor substrate, and is laminated from the top by Au / SiO ₂ / MoAu / SiO ₂ / AuZn.

  Further preferably, the dielectric film in the semiconductor laser device of the present invention has a dielectric film for a base and a dielectric film for a cover, and an end surface portion of the inner metal electrode constituting the electrode structure is The dielectric film for the base and the dielectric film for the cover are sandwiched from above and below.

  Further preferably, the thickness of the dielectric film for the base in the semiconductor laser device of the present invention is 160 nm to 260 nm.

  Further preferably, the thickness of the dielectric film for covering in the semiconductor laser device of the present invention is 250 nm to 350 nm.

Further preferably, the dielectric film in the semiconductor laser device of the present invention is a passivation film, and is any one of a SiO ₂ film, a SiO film, a SiN film, and a SiON film.

  Further preferably, the back electrode of the semiconductor substrate in the semiconductor laser device of the present invention is configured by being laminated from the bottom by Au / Pt / Ti / Ni / AuGe.

  Furthermore, the semiconductor laser device of the present invention preferably has a non-hermetic package structure.

  More preferably, the plurality of double heterostructures in the semiconductor laser device of the present invention include a first laser oscillation section having a first double heterostructure that oscillates at the first wavelength, and a second double heterostructure that oscillates at the second wavelength. And a second laser oscillation unit having a hetero structure.

  Still preferably, in a semiconductor laser device according to the present invention, the first laser oscillation unit is a CD laser oscillation unit, and the second laser oscillation unit is a DVD laser oscillation unit.

  The method for manufacturing a semiconductor laser device of the present invention has an electrode structure formed on each of one or a plurality of double heterostructures that oscillate at different wavelengths formed on a semiconductor substrate via a one-conductivity type ohmic region. In the method for manufacturing a semiconductor laser device, a step of forming a current blocking layer made of a semiconductor thin film in contact with the ridge portion of the double heterostructure on each of the one or more double heterostructures; Forming a first dielectric film on a portion; forming an inner metal electrode layer on the current blocking layer, the one conductivity type ohmic region and the first dielectric film; and Forming an outer metal electrode layer on a part, and forming a second dielectric film on the inner metal electrode layer including the end surface portion, the end surface of the inner metal electrode There is sandwiched from above and below with those which form the first dielectric film and the second dielectric layer so as to protect the said end face, the object is achieved.

  Preferably, in the method for manufacturing a semiconductor laser device of the present invention, the first dielectric film and the second dielectric film are the same material film.

  Further preferably, in the method of manufacturing a semiconductor laser device according to the present invention, a first laser oscillation unit having a first double heterostructure that oscillates at a first wavelength and a second double heterostructure that oscillates at a second wavelength are provided. A monolithic two-wavelength semiconductor laser element that forms a second laser oscillation section is manufactured.

  An electronic information device according to the present invention has a built-in pickup device using the semiconductor laser element according to the present invention as an information recording / reproducing unit, thereby achieving the above object.

  With the above configuration, the operation of the present invention will be described below.

  The present invention has a plurality of double heterostructures that are formed on a semiconductor substrate and that oscillates at different wavelengths, and an electrode structure formed on each of the plurality of double heterostructures. Covered and protected by a dielectric film.

  Thus, the end surface portion of the inner metal electrode layer constituting the electrode structure is covered and protected by the dielectric film. That is, the end surface (the lower Mo layer is exposed to the outside) of the inner metal electrode layer in contact with air is sandwiched and covered with a dielectric film. This makes it possible to completely block contact between the atmosphere and the Mo layer of the inner metal electrode layer. Therefore, it is possible to prevent oxidation of the inner metal electrode layer due to air contact as in the conventional case. For this reason, generation | occurrence | production of the deterioration by oxidation of Mo layer of an inner side metal electrode layer can be suppressed, and it becomes possible to obtain the semiconductor laser element excellent in reliability. Thus, by protecting the end surface portion of the inner metal electrode layer from oxidation, it is possible to prevent an increase in the resistance value of the element and prevent deterioration of element characteristics such as operating current.

  As described above, according to the present invention, even if the lower Mo layer in the end surface portion of the inner metal electrode layer constituting the electrode structure is exposed to the outside, the electrode structure is configured to be sandwiched and protected by the dielectric film. Thus, the end face portion of the inner metal electrode layer can be protected from oxidation. Therefore, the resistance value of the device can be prevented from increasing, and the device characteristics such as operating current can be prevented from deteriorating.

It is a longitudinal cross-sectional view which shows typically the example of a principal part structure of the monolithic two wavelength semiconductor laser element in embodiment of this invention. (A)-(d) is a principal part longitudinal cross-sectional view which shows each process (the 1) in the manufacturing method of the semiconductor laser element of the monolithic 2 wavelength of FIG. 1, respectively. (E)-(h) is a principal part longitudinal cross-sectional view which shows each process (the 2) in the manufacturing method of the semiconductor laser element of the monolithic 2 wavelength of FIG. 1, respectively. (I)-(l) is a principal part longitudinal cross-sectional view which shows each process (the 3) in the manufacturing method of the semiconductor laser element of the monolithic 2 wavelength of FIG. 1, respectively. (M)-(p) is a principal part longitudinal cross-sectional view which shows each process (the 4) in the manufacturing method of the semiconductor laser element of the monolithic 2 wavelength of FIG. 1, respectively. (A) And (b) is a longitudinal cross-sectional view which shows typically the modification of the semiconductor laser element of embodiment of this invention. It is a longitudinal cross-sectional view which shows typically an example of the conventional monolithic multiwavelength laser element currently disclosed by patent document 1. FIG.

  Hereinafter, embodiments of a semiconductor laser device and a method for manufacturing the same according to the present invention will be described in detail with reference to the drawings, and an electronic information device incorporating a pickup device using the semiconductor laser device in an information recording / reproducing unit will also be described. explain. In addition, each thickness, length, etc. of the structural member in each figure are not limited to the structure to illustrate from a viewpoint on drawing preparation.

  FIG. 1 is a longitudinal sectional view schematically showing an example of the configuration of the main part of a monolithic two-wavelength semiconductor laser device according to an embodiment of the present invention. In FIG. 1, the same components as those in the conventional configuration in FIG. 7 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 1, a semiconductor laser device 200 of a non-hermetic package specification according to this embodiment includes a laser oscillation unit 102A having a ridge portion (double heterostructure) that oscillates at a first wavelength on a substrate 101, and a second wavelength. A monolithic two-wavelength laser element having a laser oscillation portion 103A having a ridge portion (double heterostructure) for lasing, each of the first wavelength laser oscillation portion 102A and the second wavelength laser oscillation portion 103A. A current blocking layer 131 made of a semiconductor thin film in contact with the ridge, and a p-side formed on the current blocking layer 131 and a p-type ohmic electrode 134 as a one-conductive ohmic region on the ridge. An inner metal electrode 135A on the electrode side and an outer metal electrode 137 on the p-side electrode formed on the inner metal electrode 135A Electrode structure is provided with bets, the end face of the inner metal electrode 135A of the electrode structure is protected by being sandwiched vertically by a dielectric layer 140, 141.

  The first wavelength laser oscillation unit 102A and the second wavelength laser oscillation unit 103A have a real guide structure, and the first wavelength is a 780 nm band for CD and the second wavelength is a 650 nm band for DVD. Also in this case, there is an advantage that the waveguide loss can be reduced and the operating current can be reduced.

This electrode structure is a P electrode structure, and is formed by stacking Au / SiO ₂ / MoAu / SiO ₂ / AuZn from above. That is, from the top, this electrode structure is composed of the Au layer of the outer metal electrode 137A, the SiO ₂ film of the dielectric film 141 for the cover, the Mo / Au layer of the inner metal electrode 135A, and the SiO ₂ of the dielectric film 140 for the base. The film and the current blocking layer 131 are AuZn films. The underlying dielectric film 140 has a thickness of 160 nm to 260 nm, and the cover dielectric film 141 has a thickness of 250 nm to 350 nm. The dielectric films 140 and 141 are composed of SiO ₂ films, but may be any of SiO films, SiN films, and SiON films. On the other hand, the N-electrode structure on the back surface of the substrate 101 is an n-type ohmic electrode 138, which is formed by stacking Au / Pt / Ti / Ni / AuGe from below.

  The Mo / Au layer of the inner metal electrode 135A is a Mo / Au electrode having a two-layer structure of an upper Au layer and a lower Mo layer.

  Thus, by covering the portion including the end surface where the inner metal electrode layer 135 and the air contact with each other with the dielectric films 140 and 141, the contact between the atmosphere and the inner metal electrode layer 135 can be completely blocked. Therefore, since the oxidation of the inner metal electrode layer 135 due to air contact can be prevented as in the conventional case, the occurrence of deterioration due to the oxidation of the inner metal electrode layer 135 can be suppressed, and the semiconductor laser element 200 having excellent reliability can be obtained. be able to.

  Hereinafter, a method for manufacturing the semiconductor laser device 200 of the present embodiment having the above configuration will be described in detail.

  First, as shown in FIG. 2A, an MOCVD method (organometallic) is applied on an inclined n-type GaAs substrate 101 having a main surface inclined at an off angle of 15 degrees in the [110] direction from the (001) plane. A semiconductor laminated structure for the laser oscillation part for CD is formed by vapor phase epitaxy.

  That is, on the inclined n-type GaAs substrate 101, an n-type GaAs buffer layer 106, an n-type Al0.5Ga0.5As cladding layer 107, an n-type Al0.3Ga0.7As guide layer 108, and an MQW (multiple quantum well structure) active. Layer 109, p-type Al0.3Ga0.7As guide layer 110, p-type Al0.5Ga0.5As first cladding layer 111, p-type GaAs etching stop layer 112, p-type Al0.5Ga0.5As second cladding layer 113, and p The type GaAs cap layer 114 is sequentially formed in this order.

  Next, in order to form a semiconductor laminated structure for the DVD laser oscillation section, as shown in FIG. 2B, a line-shaped resist pattern (see FIG. 2) having a predetermined width is formed on the CD laser structure by photolithography. (Not shown). Using this resist pattern as a mask, p-type GaAs cap layer 114, p-type Al0.5Ga0.5As second cladding layer 113, p-type GaAs etching stop layer 112, p-type Al0.5Ga0.5As first cladding layer 111, Al0. The 3Ga0.7As guide layer 110, the active layer 109, the undoped Al0.3G a0.7As guide layer 108, the n-type Al0.5Ga0.5As cladding layer 107, and the n-type GaAs buffer layer 106 are wet-etched to obtain a substrate surface having a predetermined width. 115 is exposed.

  Subsequently, as shown in FIG. 2C, a semiconductor multilayer structure for a DVD laser oscillation unit is formed on the exposed substrate surface 115 by MOCVD.

  That is, an n-type GaAs buffer layer 116, an n-type GaInP buffer layer 117, an n-type (Al0.7Ga0.3) 0.5In0.5P cladding layer 118, an undoped (Al0.5Ga0.5) 0. 5In0.5P guide layer 119, active layer 120 made of MQW (multiple quantum well structure), undoped (Al0.5Ga0.5) 0.5In0.5P guide layer 121, p-type (Al0.7Ga0.3) 0.5In0 .5P first cladding layer 122, p-type GaInP etching stop layer 123, p-type (Al0.7Ga0.3) 0.5In0.5P second cladding layer 124, p-type GaInP intermediate layer 125 and p-type GaAs cap layer 126 Are sequentially formed in this order.

  After that, as shown in FIG. 2D, an unnecessary laminated portion formed on the CD laser oscillation portion laminated structure 102A in the semiconductor laminated structure for the DVD laser oscillation portion 103 is formed by photolithography and wet etching. Remove. At the same time, a laser oscillation part separation groove 127 reaching the substrate 101 is formed so as to electrically separate the CD laser oscillation part laminated structure 102A and the DVD laser oscillation part laminated structure 103A from each other, and the chip division groove 128 is also formed.

Next, as shown in FIG. 3 (e), a line shape having a width of 3 to 4 μm is formed on both the p-type GaAs cap layers 114 and 126 of the CD laser oscillation part laminated structure 102A and the DVD laser oscillation part laminated structure 103A. A SiO ₂ mask (not shown) is formed. The p-type second cladding layer 113 and the p-type cap layer 114 of the CD laser oscillation unit, and the p-type second cladding layer 124, the p-type GaInP intermediate layer 125, and the p-type GaAs cap layer 126 of the DVD laser oscillation unit are dried. Etching is processed to a predetermined ridge width, and the ridge shape is adjusted by wet etching. As a result, a ridge portion 129 of the CD laser oscillation portion 102 and a ridge portion 130 of the DVD laser oscillation portion 103 are formed.

  Further, as shown in FIG. 3F, the n-type GaAs having a layer thickness of 1.6 μm is embedded so as to bury the side surface of the ridge portion 129 of the CD laser oscillation section and the side surface of the ridge section 130 of the DVD laser oscillation section. A current blocking layer 131A is formed by MOCVD.

  Further, as shown in FIG. 3G, a line shape is formed above the groove 127 for electrically separating the CD laser oscillation unit 102 and the DVD laser oscillation unit 103 and above the chip dividing groove 128. A resist pattern (not shown) having an open window is formed on the CD laser oscillation unit 102 and the DVD laser oscillation unit 103 by photolithography. Using this resist pattern as a mask, only the n-type GaAs current blocking layer 131A formed on these grooves 127 and 128 is removed by wet etching.

  Further, as shown in FIG. 3H, a resist pattern 133 having a line shape is formed immediately above the ridges of the CD laser oscillation unit 102 and the DVD laser oscillation unit 103. Each n-type GaAs current blocking layer 131 is formed by removing the n-type GaAs current blocking layer 131a at the opening of the resist pattern 133 with a sulfuric acid-based etchant.

  Next, as shown in FIG. 4 (i), Au / AuZn is deposited by an electron beam deposition method. Thereafter, the resist pattern 133 is peeled off with an organic solvent. Subsequently, p-type GaAs cap layers 114 and 126 which are both P cap layers of the CD laser oscillation unit 102 and the DVD laser oscillation unit 103 are formed by lift-off, and a p-type ohmic electrode 134 (P-type alloy) is formed thereon. Electrode).

Thereafter, as shown in FIG. 4 (j), silicon dioxide is formed on the n-type GaAs current blocking layer 131 by plasma CVD as an insulating dielectric thin film material at a film forming temperature in the range of 150 to 400 degrees Celsius. A film (SiO ₂ film) is formed. The thickness of the insulating dielectric thin film such as a SiO ₂ film is preferably 160 to 260 nm, and more preferably 180 to 240 nm. In addition to the SiO ₂ film, the insulating dielectric thin film may be a SiO film, a SiN film, or a SiON film.

  Subsequently, a resist pattern is formed on the insulating dielectric thin film by photolithography. Using this resist pattern as a mask, the insulating dielectric thin film in the opening is removed with a buffered hydrofluoric acid solution to form an insulating dielectric thin film 140 having a predetermined shape as a dielectric film. Thereafter, the resist pattern is peeled off with an organic solvent.

The film formation temperature when forming an insulating layer (SiO ₂ film) as a passivation film made of a low refractive index insulating dielectric thin film 140 that hardly allows moisture to pass through is preferably 150 degrees Celsius or more. More preferably, it is 200 degrees Celsius or higher. The film forming temperature is preferably 400 degrees Celsius or less, and more preferably 250 degrees Celsius or less. When the film forming temperature is less than 150 degrees Celsius, the strain inherent in the insulating dielectric thin film 140 increases, and the thermal history such as the thermal history in the alloy process is affected by the difference in thermal expansion coefficient with the current blocking layer 131. Change tends to weaken the adhesion to the current blocking layer 131, and the insulating dielectric thin film 140 tends to peel off. When the film forming temperature exceeds 400 degrees Celsius, the density of the insulating dielectric thin film 140 is increased. And the hardness increases, the adhesiveness with the current blocking layer 131 is also weakened due to the difference in thermal expansion coefficient with the current blocking layer 131, and the insulating dielectric thin film 140 tends to peel off. .

  Further, as shown in FIG. 4 (k), an inner metal electrode layer 135a is formed on the entire surface of the p-type ohmic electrode 134 and the insulating dielectric thin film 140. Here, the inner metal electrode layer 135a is a Mo / Au electrode having a two-layer structure of an upper Au layer and a lower Mo layer by sputtering.

  Furthermore, as shown in FIG. 4L, a resist pattern 136 having a predetermined shape having a rectangular opening is formed on the CD-side laser oscillation unit 102 and the DVD-side laser oscillation unit 103 on the inner metal electrode layer 135a. .

  Further, as shown in FIG. 5M, the Au outer metal electrode layer 137A is formed only on the opening of the resist pattern 136 using the resist pattern 136 as a mask. When the Au outer metal electrode layer 137A is a thin layer having a thickness of less than 1 μm, it is necessary to form the Au outer metal electrode layer with a film thickness of 2 to 3 μm because it has insufficient heat dissipation from experimental investigation when mounted. The plating method includes an electroless plating method and an electrolytic plating method, but can be formed even if the base is not a metal. In the electroless plating method, it is difficult to perform film plating of a metal having a thickness of 1 μm or more. In the electroplating method, the base is formed only in a region where a current is applied, so that the base must be uniformly coated with a metal film.

  The step of forming the outer metal electrode layer 137A preferably includes the step of forming the outer metal electrode layer 137A by an electrolytic plating method. Thus, by forming the outer metal electrode layer 137A by the electrolytic plating method, there is an advantage that the outer metal electrode layer 137A having a predetermined thickness can be easily formed and can be formed on the entire surface of the predetermined inner metal electrode layer 135A. Because there is.

  Thereafter, as shown in FIG. 5 (n), a resist pattern (not shown) is formed by photolithography, and the Au outer metal such as the chip dividing groove 127 and the separation groove 128 is formed by wet etching using this resist pattern as a mask. The inner metal electrode layer 135 </ b> A is formed by removing peripheral portions other than those immediately below the electrode layer 137 </ b> A. Thereafter, the resist pattern is peeled off with an organic solvent.

Further, a silicon dioxide film (SiO ₂ film) is formed on the Au outer metal electrode layer 137A, the inner metal electrode layer 135A, and the insulating dielectric thin film 140 as a film to be the insulating dielectric thin film 141 by plasma CVD. Film. The thickness of the insulating dielectric thin film 141 is preferably 250 to 350 nm, and more preferably 280 to 330 nm.

  Further, as shown in FIG. 5 (o), a resist pattern (not shown) is formed on the film to be the insulating dielectric thin film 141 by photolithography, and buffered hydrofluoric acid dissolution is performed using this resist pattern as a mask. An insulating dielectric thin film 141 is formed by removing the film of the opening with a liquid. Thereafter, the resist pattern is peeled off with an organic solvent. By these insulating dielectric thin films 140 and 141, the end surface of the inner metal electrode layer 135A can be sandwiched vertically. Since the inner metal electrode layer 135A has a two-layer structure of Mo / Au, the upper Au layer is exposed, but the lower Mo layer can be protected by the insulating dielectric thin films 140 and 141.

  The obtained wafer is polished from the back side of the substrate so as to have a thickness of about 100 μm, and an n-type ohmic electrode 138 is formed on the back side of the substrate 101 as shown in FIG. Here, an AuGe / Ni / Ti / Pt / Au electrode was formed as the n-type ohmic electrode 138 by sputtering.

  The wafer on which the above-described two-wavelength laser oscillation units 102 and 103 are formed is divided into a plurality of bars, and a reflection film (not shown) is coated on the end face of each bar, and then divided into a plurality of chips. After the chip is mounted on the stem, the laser element characteristics are measured.

  As a result, the CD laser oscillation unit 102 had an oscillation wavelength of 782 nm and an operating current of 55 mA at an optical output of 7 mW. Further, the DVD laser oscillation unit 103 had an operating current of 70 mA, which was 656 nm, at an optical output of 7 mW. Regarding reliability, the vehicle ran well for 2000 hours or more.

  In short, the manufacturing method of the semiconductor laser device 200 of the present invention includes a laser oscillation portion 102A having a ridge portion (double heterostructure) that oscillates at the first wavelength on the substrate 101, and a ridge portion that oscillates at the second wavelength. A method of manufacturing a monolithic two-wavelength semiconductor laser device 200 having a laser oscillation unit 103A having a (double heterostructure), wherein the first wavelength laser oscillation unit 102A and the second wavelength laser oscillation unit 103A Forming a current blocking layer 131 made of a semiconductor thin film in contact with the ridge portion on each of them, and forming a dielectric film 140 as a first dielectric film on a part of the current blocking layer 131; The inner metal electrode layer 135A is formed on the surface including the current blocking layer 131, the p-type ohmic electrode 134, and the dielectric film 140. A step of forming an outer metal electrode layer 137A on the inner metal electrode layer 135A, and a step of forming a dielectric film 141 as a second dielectric film on the inner metal electrode layer 135A including the end surface portion. Then, the end surface portion of the inner metal electrode 135A is sandwiched and protected by the dielectric films 140 and 141 up and down.

  Therefore, according to the present embodiment, the end surface portion of the inner metal electrode layer 135 </ b> A constituting the electrode structure is covered and protected by the dielectric films 140 and 141. That is, the end face portion (the lower Mo layer is exposed to the outside) of the inner metal electrode layer 135A in contact with air is sandwiched and covered by the dielectric films 140 and 141. Thereby, contact between the atmosphere and the Mo layer of the inner metal electrode layer 135A can be completely blocked. Therefore, it is possible to prevent oxidation of the inner metal electrode layer 135A due to air contact as in the conventional case. For this reason, it is possible to suppress the occurrence of deterioration due to oxidation of the Mo layer of the inner metal electrode layer 135A, and it is possible to obtain the semiconductor laser element 200 having excellent reliability. Thus, by protecting the end surface portion of the inner metal electrode layer 135A from oxidation, it is possible to prevent an increase in the resistance value of the element and prevent deterioration of element characteristics such as operating current.

  In the present embodiment, the substrate 101 has a laser oscillation portion 102A having a ridge portion (double heterostructure) that oscillates at the first wavelength and a ridge portion (double heterostructure) that oscillates at the second wavelength. The monolithic two-wavelength semiconductor laser element 200 having the laser oscillation unit 103A and the manufacturing method thereof have been described. However, the present invention is not limited to this, and each of a plurality of double heterostructures that oscillate at different wavelengths formed on a semiconductor substrate. Also in the monolithic multi-wavelength semiconductor laser device having the electrode structure formed thereon and the method of manufacturing the same, the end face portion of the inner metal electrode 135A constituting the electrode structure is formed as a dielectric film 140, as a configuration of the present invention. 141 to protect the end surface portion of the inner metal electrode 135A by covering the upper and lower sides with the upper and lower surfaces. Of preventing oxidation of the end surface portion to prevent an increase of the resistance value of the element, it is possible to achieve the object of the present invention to prevent deterioration of device characteristics such as the operating current. Further, the present invention is not limited to the monolithic multi-wavelength semiconductor laser element and the manufacturing method thereof, and as shown in FIGS. 6A and 6B, the left and right CD laser oscillation units 102 and DVD laser oscillation units 103 in FIG. Also in the semiconductor laser element having the above and a manufacturing method thereof, as a configuration of the present invention, the end surface portion of the inner metal electrode 135A constituting the electrode structure is covered with the dielectric films 140 and 141 up and down, and the inner metal electrode 135A Protecting the end face portion prevents oxidation of the end face portion of the inner metal electrode 135A, prevents an increase in the resistance value of the element, and achieves the object of the present invention to prevent deterioration of element characteristics such as operating current. Can do.

  In addition, a pickup device using the semiconductor laser element 200 of the above embodiment as an information recording / reproducing unit is built in, and the information on the optical disk is read from the reflected light by irradiating the optical disk such as a CD or DVD, or the information on the optical disk. It is possible to obtain an electronic information device such as an information recording / reproducing apparatus. The optical element of the pickup device in this case is an optical functional element (for example, a hologram optical element) that causes the outgoing light to go straight and output, and also bends the incident light and makes it incident in a predetermined direction. Further, the electronic elements of the pickup device include a light emitting element (for example, a semiconductor laser element or a laser chip) for generating emitted light and a light receiving element (for example, a photo IC) for receiving incident light.

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  The present invention relates to a monolithic multi-wavelength semiconductor laser element having a plurality of laser parts formed on the same substrate, a method for manufacturing the same, and an electronic information device incorporating a pickup device using the semiconductor laser element in an information recording / reproducing part. In this field, even if the lower Mo layer at the end face of the inner metal electrode layer constituting the electrode structure is exposed to the outside, the inner metal electrode layer constituting the electrode structure is protected by being sandwiched by a dielectric film. As a result, the resistance value of the device can be prevented from increasing, and device characteristics such as operating current can be prevented from deteriorating.

101 n-type GaAs substrate 102 laser oscillation unit for CD 103 laser oscillation unit for DVD 104 terrace unit 105 insulating dielectric thin film 106 n-type GaAs buffer layer 107 n-type Al0.5Ga0.5As cladding layer 108 n-type Al0.3Ga0.7As Guide layer 109 Active layer 110 p-type Al0.3Ga0.7As guide layer 111 p-type Al0.5Ga0.5As first cladding layer 112 p-type GaAs etching stop layer 113 p-type Al0.5Ga0.5As second cladding layer 114 p-type GaAs Cap layer 115 n-type GaAs substrate surface 116 n-type GaAs buffer layer 117 n-type GaInP buffer layer 118 n-type (Al0.7Ga0.3) 0.5In0.5P cladding layer 119, 121 undoped (Al0.5Ga0.5) 0. 5In 0.5P guide layer 120 Active layer 122 p-type (Al0.7Ga0.3) 0.5In0.5P first cladding layer 123 p-type GaInP etching stop layer 124 p-type (Al0.7Ga0.3) 0.5In0.5P first 2 Cladding layer 125 p-type GaInP intermediate layer 126 p-type GaAs cap layer 127 laser part separation groove 128 chip division groove 129 ridge part of CD laser oscillation part 130 ridge part of DVD laser oscillation part 131 n-type GaAs current blocking layer 132 , 140, 141 Insulating dielectric thin film (dielectric film)
133, 136 resist pattern 134 p-type ohmic electrode (one conductivity type ohmic region)
135 inner metal electrode 137 outer metal electrode 138 n-type ohmic electrode

Claims (17)

  One or more double heterostructures that oscillate at different wavelengths formed on a semiconductor substrate, and an electrode structure formed on each of the one or more double heterostructures, and constitute the electrode structure A semiconductor laser device in which an end surface portion of an inner metal electrode is covered and protected by a dielectric film.   The electrode structure is formed on each of the one or more double heterostructures, a current blocking layer made of a semiconductor thin film in contact with the ridge portion of the double heterostructure, and on the current blocking layer and the double heterostructure The inner metal electrode formed on the inner metal electrode, and the outer metal electrode formed on the inner metal electrode. The portion including the end surface portion of the inner metal electrode is sandwiched vertically by the dielectric film to protect the end surface portion. The semiconductor laser device according to claim 1.   3. The semiconductor laser device according to claim 2, wherein the outer metal electrode is an Au layer, and the inner metal electrode is a Mo / Au layer.   4. The semiconductor laser device according to claim 3, wherein the inner metal electrode is a Mo / Au electrode having a two-layer structure of an upper Au layer and a lower Mo layer. _2. The semiconductor laser device according to claim 1, wherein the electrode structure is a surface electrode of the semiconductor substrate and is laminated by Au / SiO ₂ / MoAu / SiO ₂ / AuZn from above.   The dielectric film includes a dielectric film for a base and a dielectric film for a cover, and an end surface portion of an inner metal electrode constituting the electrode structure has the dielectric film for the base and the cover The semiconductor laser device according to claim 1, wherein the semiconductor laser device is sandwiched between upper and lower dielectric films.   The semiconductor laser device according to claim 6, wherein the underlying dielectric film has a thickness of 160 nm to 260 nm.   7. The semiconductor laser device according to claim 6, wherein the cover dielectric film has a thickness of 250 nm to 350 nm. The semiconductor laser device according to claim 1, wherein the dielectric film is a passivation film, and is any one of a SiO ₂ film, a SiO film, a SiN film, and a SiON film.   2. The semiconductor laser device according to claim 1, wherein the back electrode of the semiconductor substrate is formed by stacking Au / Pt / Ti / Ni / AuGe from below.   2. The semiconductor laser device according to claim 1, which has a non-hermetic package structure.   The plurality of double heterostructures include: a first laser oscillation unit having a first double heterostructure that oscillates at a first wavelength; and a second laser oscillation unit having a second double heterostructure that oscillates at a second wavelength. The semiconductor laser device according to claim 1.   13. The semiconductor laser device according to claim 12, wherein the first laser oscillation unit is a CD laser oscillation unit, and the second laser oscillation unit is a DVD laser oscillation unit. In a method of manufacturing a semiconductor laser device having an electrode structure formed on each of one or a plurality of double heterostructures lasing at different wavelengths formed on a semiconductor substrate via a one-conductivity type ohmic region,
On each of the one or more double heterostructures,
Forming a current blocking layer comprising a semiconductor thin film in contact with the ridge portion of the double heterostructure;
Forming a first dielectric film on a portion of the current blocking layer;
Forming an inner metal electrode layer on the current blocking layer, the one conductivity type ohmic region and the first dielectric film;
Forming an outer metal electrode layer on a portion of the inner metal electrode layer;
Forming a second dielectric film on the inner metal electrode layer including the end face portion,
A method of manufacturing a semiconductor laser device, wherein the first dielectric film and the second dielectric film are formed so that an end surface portion of the inner metal electrode is sandwiched from above and below to protect the end surface portion.   15. The method of manufacturing a semiconductor laser device according to claim 14, wherein the first dielectric film and the second dielectric film are the same material film.   Monolithic two-wavelength semiconductor laser forming a first laser oscillator having a first double heterostructure that oscillates at a first wavelength and a second laser oscillator having a second double heterostructure that oscillates at a second wavelength The method for manufacturing a semiconductor laser device according to claim 14, wherein the device is manufactured.   An electronic information device including a pickup device using the semiconductor laser device according to claim 1 in an information recording / reproducing unit.