JP2018195749A - Semiconductor laser element and method of manufacturing the same - Google Patents

Abstract

To provide a semiconductor laser element capable of reducing man hours and improving a yield, and to provide a method of manufacturing the same.SOLUTION: In a semiconductor laser element 1 in which a striped waveguide 31 is formed by a semiconductor lamination film 10 laminated on an upper surface 2c of a substrate 2, and that emits laser light from one end surface of the waveguide 31, a groove 43 extending in a direction crossing the waveguide 31 is provided on a lower surface 2d of the substrate 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor laser element that emits laser light and a method for manufacturing the same.

  A semiconductor laser element typified by a laser diode having a nitride-based semiconductor that is a compound of a group III element such as Al, Ga, In or the like and a group V element N is a light emitting element because of its band structure and chemical stability. And power devices. In light source applications of optical information recording devices such as optical disk drives, reliability has been ensured and costs have been reduced through the adoption of GaN substrates, improvements in crystal growth technology, improvements in device structure and wafer process technology, and so on. Yes. In addition, since nitride-based semiconductors have a short oscillation wavelength, they are used in white LEDs and the like as phosphor excitation light sources.

  In recent years, the use of blue laser light and green laser light made of nitride semiconductors has attracted attention as next-generation applications such as directional lights, projectors, and televisions. Since these applications require visibility, high radiation quality of laser light is required. However, since the substrate is transparent in a normal nitride semiconductor, light leaks from the substrate due to stray light from the active layer. For this reason, there is a problem that ripples occur particularly in the FFP (Far Field Pattern) in the vertical and horizontal mode.

  A semiconductor laser device for preventing ripples is disclosed in Patent Document 1. FIG. 25 shows a side sectional view of this semiconductor laser device. The semiconductor laser element 101 has a semiconductor multilayer film 110 including an active region 114 in which a nitride semiconductor is laminated on a substrate 102. A stripe-shaped ridge stripe (not shown) is provided on the semiconductor stacked film 110. A stripe-shaped waveguide is formed by the active region 114 into which current is injected from the ridge stripe. An electrode 123 and an electrode 124 are provided on the semiconductor laminated film 110 and the back surface of the substrate 102, respectively.

  The semiconductor laser device 101 has a filter structure 106 on the end face including the emission part of the waveguide. The filter structure 106 is formed of a multilayer film having angle dependency and wavelength dependency with respect to the electromagnetic beam.

  The active region 114 generates a first wavelength region coherent first electromagnetic beam 107 and a second wavelength region incoherent second electromagnetic beam 108 during the operating mode. The coherent first electromagnetic beam 107 radiated from the emission part of the waveguide composed of the active region 114 passes through the filter structure part 106.

  The second electromagnetic beam 108 is emitted from a region that is different from the emission part of the first electromagnetic beam 107 and includes the substrate 102. At this time, the second electromagnetic beam 108 is attenuated by the filter structure 106. As a result, only the first coherent electromagnetic beam 107 is emitted from the semiconductor laser element 101, and the ripple of FFP can be prevented.

  In the semiconductor laser device 101, a semiconductor multilayer film 110 is laminated on a first main surface of a wafer-like substrate 102, and a ridge stripe and an electrode 123 are formed on the semiconductor multilayer film 110. An electrode 124 is formed on the second main surface of the wafer-like substrate 102. Next, the substrate 102 is cut in a direction perpendicular to the ridge stripe to form a bar-shaped intermediate. Next, after the filter structure 106 is formed on the end face of the intermediate body that forms the end face of the waveguide, the filter structure 106 is cut in parallel to the ridge stripe and separated into individual pieces.

Japanese Patent Laying-Open No. 2015-111724 (pages 21-30, FIG. 3A)

  However, according to the conventional semiconductor laser device 101, since the filter structure 106 having a complicated structure is formed on the bar-shaped intermediate body, there is a problem that the number of steps is increased. In addition, since the number of steps for the bar-shaped intermediate body increases, defects due to the handling of the intermediate body increase, and the yield of the semiconductor laser device 101 decreases.

  It is an object of the present invention to provide a semiconductor laser device that can reduce the number of steps and improve the yield and a method for manufacturing the same.

  In order to achieve the above object, the present invention provides a semiconductor laser device in which a striped waveguide is formed by a semiconductor laminated film laminated on an upper surface of a substrate, and laser light is emitted from one end surface of the waveguide. A groove extending in a direction crossing the waveguide is provided on the lower surface of the substrate.

  According to the present invention, in the semiconductor laser device configured as described above, an electrode is provided on the lower surface of the substrate, and a metal film for forming the electrode is disposed on the inner wall of the groove.

  According to the present invention, in the semiconductor laser device configured as described above, a film containing an oxide is provided between the metal film on the inner wall of the groove and the substrate.

  According to the present invention, in the semiconductor laser device having the above structure, an uneven portion is provided on the side wall of the groove.

  According to the present invention, in the semiconductor laser device configured as described above, the groove is separated from the end face of the waveguide by 10 μm or more in the longitudinal direction of the waveguide.

  According to the present invention, in the semiconductor laser device configured as described above, the depth of the groove is smaller than the thickness of the substrate and larger than 1/10 of the thickness of the substrate.

  According to the present invention, in the semiconductor laser device configured as described above, the depth of the groove is greater than 1/3 of the thickness of the substrate.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor laser device that emits laser light from one end face of a striped waveguide formed by a semiconductor laminated film laminated on a substrate.
An epitaxial growth step of epitaxially growing the semiconductor multilayer film on the first main surface of the wafer-like substrate;
A stripe portion forming step of forming a stripe-like stripe portion in the semiconductor laminated film;
A first electrode forming step of forming a first electrode on the stripe portion;
A groove forming step of forming a groove extending in a direction intersecting the stripe portion by laser scribing on a second main surface of the wafer-shaped substrate facing the first main surface;
A second electrode forming step of forming a second electrode on the second main surface in which the groove is formed;
A first cutting step of cutting the substrate in a direction perpendicular to the stripe portion at a position different from the groove to form a bar-shaped intermediate;
An end face coat film forming step of forming an end face coat film on the cut surface of the first cutting step;
A second cutting step of cutting the intermediate body on which the end face coating film is formed in parallel with the stripe portion;
It is characterized by having.

  According to the present invention, in the method of manufacturing a semiconductor laser device having the above-described configuration, a chip dividing groove forming step for forming a chip dividing groove parallel to the stripe portion on the second main surface, and the stripe on the first main surface. A bar dividing groove forming step for forming a bar dividing groove orthogonal to the portion, the substrate is cut by cleaving on the bar dividing groove by the first cutting step, and the substrate is divided by the second cutting step. It is characterized by cutting by cleaving on the groove.

  According to the present invention, in the method of manufacturing a semiconductor laser device having the above structure, the chip dividing groove is formed by laser scribing in the chip dividing groove forming step, and the chip dividing groove forming step and the groove forming step are continuously performed. A debris removing step of removing debris by laser scribing is provided before the second electrode forming step.

  According to the present invention, in the method of manufacturing a semiconductor laser device having the above-described structure, the groove is separated from the bar dividing groove by 10 μm or more in the longitudinal direction of the stripe portion.

  According to the present invention, in the method of manufacturing a semiconductor laser device having the above structure, a film containing an oxide is formed on the inner wall of the groove by the groove forming step, and the second electrode is formed on the film by the second electrode forming step. The metal is arranged.

  According to the present invention, in the method of manufacturing a semiconductor laser device having the above-described structure, the unevenness is formed on the side wall of the groove by changing the sweep speed of the laser scribe.

  According to the semiconductor laser device of the present invention, since the semiconductor laminated film is laminated on the upper surface of the substrate and the groove extending in the direction intersecting the waveguide is provided on the lower surface, the ripple of the FFP in the vertical transverse mode can be prevented. At this time, since the groove can be formed on the wafer-like substrate, the number of steps of the semiconductor laser element can be reduced and the yield can be improved.

  According to the manufacture of the semiconductor laser device of the present invention, the epitaxial growth step of epitaxially growing the semiconductor multilayer film on the first main surface of the wafer-shaped substrate, the stripe portion forming step of forming the stripe-shaped stripe portion on the semiconductor multilayer film, and the wafer Forming a groove extending in a direction intersecting the stripe portion by laser scribing on the second main surface of the substrate. For this reason, a groove can be formed in the second main surface of the wafer-like substrate to prevent vertical and horizontal mode FFP ripples. Therefore, the number of steps of the semiconductor laser element can be reduced and the yield can be improved.

The perspective view which shows the semiconductor laser element of 1st Embodiment of this invention. The top view which shows the semiconductor laser element of 1st Embodiment of this invention The front view which shows the laminated structure of the active layer of the semiconductor laser element of 1st Embodiment of this invention Side surface sectional drawing which shows the light-shielding groove | channel of the semiconductor laser element of 1st Embodiment of this invention. Process drawing which shows the manufacturing process of the semiconductor laser element of 1st Embodiment of this invention. The front view which shows the epitaxial growth process of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the p side lower layer electrode formation process of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the stripe part formation process of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the embedding layer formation process of the manufacturing method of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the p side upper layer electrode formation process of the semiconductor laser element of 1st Embodiment of this invention The perspective view which shows the chip | tip division | segmentation groove | channel formation process of the semiconductor laser element of 1st Embodiment of this invention. The bottom view which shows the chip | tip division | segmentation groove | channel formation process of the semiconductor laser element of 1st Embodiment of this invention. The perspective view which shows the light-shielding groove | channel formation process of the semiconductor laser element of 1st Embodiment of this invention. The bottom view which shows the light-shielding groove | channel formation process of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the n side electrode formation process of the semiconductor laser element of 1st Embodiment of this invention The perspective view which shows the bar | burr division groove formation process of the semiconductor laser element of 1st Embodiment of this invention The top view which shows the bar | burr division groove formation process of the semiconductor laser element of 1st Embodiment of this invention The perspective view which shows the 1st cutting process of the semiconductor laser element of 1st Embodiment of this invention. The top view which shows the 1st cutting process of the semiconductor laser element of 1st Embodiment of this invention. The perspective view which shows the end surface coating film formation process of the semiconductor laser element of 1st Embodiment of this invention The perspective view which shows the bar | burr division groove formation process of the semiconductor laser element of 2nd Embodiment of this invention The top view which shows the bar | burr division groove formation process of the semiconductor laser element of 2nd Embodiment of this invention The perspective view which shows the wafer after the light-shielding groove | channel formation process of the semiconductor laser element of 3rd Embodiment of this invention. The bottom view which shows the wafer after the light-shielding groove | channel formation process of the semiconductor laser element of 3rd Embodiment of this invention Side sectional view showing a conventional semiconductor laser device

<First Embodiment>
Embodiments of the present invention will be described below with reference to the drawings. The arrows and crystal orientations shown in the drawings correspond to the crystal orientations of the substrate 2, respectively. 1 and 2 are a perspective view and a top view of the semiconductor laser device of the first embodiment. The semiconductor laser device 1 includes, for example, a nitride-based semiconductor multilayer film 10 epitaxially grown on an upper surface 2c made of a (0001) plane of a substrate 2 made of n-type GaN having a thickness of 130 μm. The substrate 2 may be mixed with impurities whose content of each element is 1% or less.

  Although the growth surface of the upper surface 2c of the substrate 2 is the (0001) plane (C plane), the (1-100) plane (M plane) or the (11-20) plane (A plane) may be used as the growth plane. . Further, the substrate 2 may be formed of other materials such as SiC.

  The semiconductor laminated film 10 includes a lower contact layer 11, a lower cladding layer 12, a lower guide layer 13, an active layer 14, an evaporation preventing layer 15, an upper guide layer 16, an upper cladding layer 17, and an upper contact layer 18 on the upper surface 2 c of the substrate 2. It is formed by laminating in order.

The lower contact layer 11 is formed of n-type GaN having a thickness of 0.1 to 10 μm (for example, 4 μm). The lower cladding layer 12 is formed of n-type Al _x1 Ga _1-x1 N (0 <x1 <1) having a thickness of 0.5 to 3.0 μm (for example, 2 μm). The lower guide layer 13 is formed of n-type Al _x2 Ga _1-x2 N (0 ≦ x2 <1, x2 <x1) having a film thickness of 0.2 μm or less (for example, 0.1 μm).

As shown in FIG. 3, the active layer 14 has a multiple quantum well (MQW) structure in which four barrier layers 14a and three quantum well layers 14b are alternately stacked. The quantum well layer 14b is formed by, for example, a thickness of _{4nm In x3 Ga 1-x3 N} . The barrier layer 14a is made of, for example, In _x4 Ga _1-x4 N (x3> x4) with a thickness of 8 nm. As an example of x3 and x4, x3 = 0.05 to 0.15 and x4 = 0 to 0.1 can be set.

In FIG. 2, the evaporation prevention layer 15 provided on the active layer 14 is formed of p-type Al _y1 Ga _1-y1 N (0 <y1 <1) having a film thickness of 0.02 μm or less (for example, 0.01 μm). The The upper guide layer 16 is formed of p-type Al _y2 Ga _1-y2 N (0 ≦ y2 <1, y2 <y1) having a film thickness of 0.2 μm or less (for example, 0.01 μm). The upper cladding layer 17 is formed of p-type Al _y3 Ga _1-y3 N (0 <y3 <1, y3> y2) having a film thickness of 0.01 to 1 μm (for example, 0.05 μm).

  The upper contact layer 18 is provided on the convex portion of the upper clad layer 17 that forms a ridge stripe 30 described later, and is formed of p-type GaN having a film thickness of 0.01 to 1 μm (for example, 0.05 μm).

  A striped ridge stripe 30 (stripe portion) extending in the <1-100> direction perpendicular to the emission surface 1 a is provided on the upper portion of the semiconductor laminated film 10. The ridge stripe 30 is formed by being dug up to an intermediate position in the thickness direction of the upper clad layer 17. A stripe-shaped waveguide 31 is formed by the region of the active layer 14 facing the ridge stripe 30.

A p-side lower layer electrode 22 is provided on the upper surface of the ridge stripe 30. The p-side lower layer electrode 22 is mainly composed of Pd or Ni and is in ohmic contact with the upper contact layer 18. A buried layer 21 is provided on the semiconductor laminated film 10 except on the ridge stripe 30. The buried layer 21 is formed of an insulating material such as SiO _{2 having a} thickness of 0.1 to 0.3 μm (for example, 0.15 μm). Both side surfaces of the ridge stripe 30 are covered with the buried layer 21, and light confinement in the operation mode can be performed.

  A p-side upper layer electrode 23 for injecting carriers from the upper surface of the ridge stripe 30 is formed on the upper contact layer 18 and the buried layer 21. The p-side upper layer electrode 23 is formed of, for example, a Mo / Au laminate, a Ti / Pt / Au laminate, or the like.

  Note that the p-side lower layer electrode 22 may be omitted. At this time, since the p-side upper layer electrode 23 is in ohmic contact with the upper contact layer 18, it is formed of, for example, a Pd / Mo / Au laminate, a Ni / Au laminate, or the like.

  An n-side electrode 24 for injecting carriers is formed on the lower surface 2 d of the substrate 2. The n-side electrode 24 is in ohmic contact with the substrate 2. The n-side electrode 24 is formed of, for example, a Hf / Al laminate, a Ti / Al laminate, or the like. A pad electrode 25 is provided on the n-side electrode 24 for facilitating connection and fixing of the semiconductor laser element 1 to the submount. The pad electrode 25 is formed of, for example, a Mo / Pt / Au laminate or the like.

An end face coating film 26 (see FIG. 20) is provided on the emission surface 1a and the opposing surface 1b facing the <1-100> direction of the semiconductor laser element 1. The end face coating film 26 on the emission surface 1a is formed of a low reflection film such as Al ₂ O ₃ . The end face coating film 26 on the opposing surface 1b is formed of a highly reflective film in which, for example, nine layers of Al ₂ O ₃ and Ta ₂ O ₅ are alternately laminated. The waveguide 31 forms a resonator by the end face coating film 26 on the emission surface 1a and the opposing surface 1b. Thus, when current is injected from the p-side upper layer electrode 23 into the active layer 14 via the ridge stripe 30, laser light is emitted from the emission portion 31 a on the end face of the waveguide 31.

  The lower surface 2d of the substrate 2 is provided with a plurality of light shielding grooves 43 (grooves) by laser scribing as will be described in detail later. The light shielding groove 43 extends in the <11-20> direction orthogonal to the stripe-shaped waveguide 31 formed by the ridge stripe 30.

  The light shielding groove 43 may extend in a direction that is not orthogonal as long as it intersects the ridge stripe 30 and the waveguide 31. Further, the number of light shielding grooves 43 may be one.

  FIG. 4 is a side sectional view of the light shielding groove 43. A metal film 24 a and a metal film 25 a that form the n-side electrode 24 and the pad electrode 25 are disposed on the inner wall of the light shielding groove 43. In addition, a film 27 containing an oxide formed during laser scribing of the light shielding groove 43 is disposed between the metal film 24 a and the substrate 2.

  The stray light incident on the substrate 2 from the waveguide 31 is shielded by the light shielding groove 43, and the laser light leaking from the substrate 2 can be reduced. At this time, since the metal films 24a and 25a are arranged on the inner wall of the light shielding groove 43, the stray light can be reflected or absorbed, and the laser light leaking from the substrate 2 can be reduced. In addition, since the coating 27 containing oxide is provided on the inner wall of the light shielding groove 43, the adhesion strength of the n-side electrode 24 can be improved.

  The metal films 24 a and 25 a may not be provided on the inner wall of the light shielding groove 43. At this time, the stray light incident on the substrate 2 is refracted on the light shielding groove 43, and the laser light reaching the emission surface 1a can be reduced.

  When the depth of the light shielding groove 43 is larger than 1/10 of the thickness of the substrate 2, about 10% of stray light can be shielded. Further, it is more preferable that the depth of the light shielding groove 43 is larger than 1/3 of the thickness of the substrate 2 because 30% or more of stray light can be shielded. At this time, if the depth of the light shielding groove 43 is made larger than the thickness of the substrate 2, the substrate 2 is divided and the strength of the semiconductor laser device 1 is significantly reduced. Accordingly, the depth of the light shielding groove 43 is made smaller than the thickness of the substrate 2.

  FIG. 5 is a process chart showing the manufacturing process of the semiconductor laser device 1. The semiconductor laser device 1 includes an epitaxial growth step, a p-side lower layer electrode forming step, a stripe portion forming step, a buried layer forming step, a p-side upper layer electrode forming step, a polishing step, a chip dividing groove forming step, a light shielding groove forming step, a debris removing step, The n-side electrode forming step, the pad electrode forming step, the bar dividing groove forming step, the first cutting step, the end face coating film forming step, and the second cutting step are sequentially performed.

  In the following description, an intermediate body in the process of a wafer may be simply referred to as “wafer 50”. Further, the intermediate body in the middle of the bar-like process obtained by dividing the wafer 50 may be simply referred to as “bar 51”.

  FIG. 6 is a front view showing an epitaxial growth step. In the epitaxial growth process, the semiconductor multilayer film 10 is epitaxially grown on the first main surface 2a of the wafer-like substrate 2 made of n-type GaN by MOCVD (Metal Organic Chemical Vapor Deposition) or the like.

  That is, the lower contact layer 11, the lower cladding layer 12, and the lower guide layer 13 are sequentially grown on the first main surface 2 a of the substrate 2. Then, four barrier layers 14 a and three quantum well layers 14 b (see FIG. 3) are alternately grown on the lower guide layer 13 to obtain the active layer 14. Subsequently, the evaporation preventing layer 15, the upper guide layer 16, the upper cladding layer 17, and the upper contact layer 18 are sequentially grown on the active layer 14.

  When the semiconductor laminated film 10 is formed by the MOCVD method, trimethyl gallium, ammonia, trimethyl aluminum, trimethyl indium, silane, and biscyclopentadienyl magnesium can be used as raw materials, and hydrogen and nitrogen can be used as carrier gases. .

  The upper surface 2c (see FIG. 1) of the substrate 2 of the semiconductor laser element 1 is the same surface as the first main surface 2a, and the lower surface 2d (see FIG. 1) is the second main surface 2b opposite to the first main surface 2a. Is the same plane.

  FIG. 7 is a front view showing the p-side lower layer electrode forming step. In the p-side lower layer electrode forming step, the p-side lower layer electrode 22 is formed on the upper contact layer 18 of the wafer 50 by vacuum deposition, sputtering, or the like.

  FIG. 8 is a front view showing the stripe portion forming step. In the stripe portion forming step, a resist 5 is formed by photolithography in a region where the ridge stripe 30 is to be formed on the p-side lower layer electrode 22 of the wafer 50. The resist 5 is formed in a stripe shape extending in a direction (<1-100> direction) perpendicular to the emission surface 1a (see FIG. 1).

Next, RIE (Reactive Ion Etching) is performed with SiCl ₄ gas, Cl ₂ gas, Ar gas, or the like, and the non-formed portion of the resist 5 is etched. As a result, a striped ridge stripe 30 (stripe portion) composed of the convex portion at the upper end of the upper cladding layer 17, the upper contact layer 18 and the p-side lower layer electrode 22 is formed. By forming the ridge stripe 30, a striped waveguide 31 (see FIG. 1) is obtained below the ridge stripe 30.

  The stripe portion forming step may be performed by dry etching such as the above RIE or wet etching.

Further, for example, a mask layer of SiO ₂ may be provided in the formation region of the ridge stripe 30 instead of the resist 5. At this time, a resist can be provided by photolithography in a region where the ridge stripe 30 is not formed, and after forming the SiO ₂ film, the resist and the SiO ₂ on the resist can be removed to form a mask layer. The removal of the mask layer can be performed using an etchant such as buffered hydrofluoric acid.

FIG. 9 is a front view showing a buried layer forming step. In the buried layer forming step, a buried layer 21 such as SiO ₂ is formed on the upper surface of the resist 5 (see FIG. 8), both side walls of the ridge stripe 30 and the upper clad layer 17 by sputtering or the like. Then, the buried layer 21 on the resist 5 is removed together with the resist 5 to expose the p-side lower layer electrode 22.

  FIG. 10 is a front view showing the p-side upper layer electrode forming step. In the p-side upper layer electrode forming step, a p-side upper layer electrode 23 (first electrode) is formed on the upper surfaces of the p-side lower layer electrode 22 and the buried layer 21 disposed on the top of the ridge stripe 30 by vacuum deposition, sputtering, or the like. A plurality of p-side upper layer electrodes 23 are provided in a pattern according to the arrangement of the semiconductor laser elements 1 formed in a chip shape by dividing the wafer 50.

  Next, in the polishing step, the second main surface 2b of the substrate 2 is polished to reduce the thickness of the substrate 2 to about 80 to 150 μm (for example, 130 μm). Thereby, the wafer 50 and the bar 51 (see FIG. 18) can be easily divided in a first cutting process and a second cutting process described later. The substrate 2 may be physically polished with an abrasive or chemically polished with a chemical.

  11 and 12 are a perspective view and a bottom view showing the chip dividing groove forming step. In the chip dividing groove forming step, a plurality of chip dividing grooves 42 are formed on the second main surface 2b of the substrate 2 of the wafer 50 by laser scribing. The chip dividing grooves 42 extend in the <1-100> direction parallel to the ridge stripes 30 and are arranged between the ridge stripes 30.

  The chip dividing groove 42 is used for dividing the wafer 50 into a plurality of bars 51 (see FIG. 18) in a first cutting process described later, and then separating the bars 51 into chips in the second cutting process. For this reason, the chip dividing grooves 42 are arranged at positions based on the ridge stripes 30 such as the center between the ridge stripes 30. Thus, a desired chip can be obtained with a high yield when dividing the bar 51 into chips.

  The chip dividing groove 42 is more preferably formed to a depth of about 5 to 60 μm from the second main surface 2 b of the substrate 2. As a result, it is possible to prevent the chip dividing groove 42 from being too shallow and difficult to divide, or from being too deep to damage the wafer 50 during handling. The chip dividing groove 42 is formed in a straight line extending between both end faces of the wafer 50 in the <1-100> direction. Thereby, it is possible to reduce cracking in an unintended direction when dividing the bar 51 (see FIG. 18) into the chip-shaped semiconductor laser device 1.

  13 and 14 are a perspective view and a bottom view showing the light shielding groove forming step (groove forming step). In the light shielding groove forming step, a plurality of light shielding grooves 43 are formed on the second main surface 2b of the substrate 2 of the wafer 50 by laser scribing. The light shielding groove 43 extends in the <11-20> direction orthogonal to the ridge stripe 30, and one or a plurality of light shielding grooves 43 are provided corresponding to each semiconductor laser element 1 separated into chips.

  As described above, the depth of the light shielding groove 43 is smaller than the thickness of the substrate 2, preferably 1/10 or more of the thickness of the substrate 2, more preferably 1/3 or more. Further, by appropriately selecting the laser output or the sweep speed in laser scribing, the aspect ratio of the light shielding groove 43 can be reduced and cracks on the light shielding groove 43 can be reduced. Furthermore, if the width of the light shielding groove 43 is larger than the width of the chip dividing groove 42, cracks on the light shielding groove 43 can be further reduced.

  Further, when the light shielding groove 43 is formed by laser scribing, a film 27 (see FIG. 4) containing oxide or metal is formed on the inner wall of the light shielding groove 43 by using a laser having a pulse width of the order of nanoseconds. .

  Furthermore, the width of the light shielding groove 43 can be periodically varied by changing the sweep speed of the laser pulse having a pulse width of nanosecond order at a repetition frequency of several tens of kHz. As a result, irregularities (not shown) such as periodic wavy shapes can be formed on the side walls of the light shielding grooves 43 in the longitudinal direction. By providing the concavo-convex portion, stray light that has entered the substrate 2 can be diffusely reflected, and light leaking from the substrate 2 can be further reduced.

  Next, in the debris removal step, debris generated by forming the chip dividing grooves 42 and the light shielding grooves 43 by laser scribing is removed. The debris adheres to the second main surface 2b of the substrate 2 along the chip dividing groove 42 and the light shielding groove 43, and contains a group III metal such as Ga, Al, In or the like as a main component.

  The debris removal step is performed by wet etching, and the wafer 50 is immersed in an acid or alkali etchant to dissolve and remove the debris. Although there is no restriction | limiting in particular in an etchant, For example, the thing containing acids, such as nitric acid, a sulfuric acid, hydrochloric acid, phosphoric acid, and the thing containing alkalis, such as sodium hydroxide and potassium hydroxide, are mentioned. When the etchant corrodes the p-side upper layer electrode 23 or the like, the wafer 50 may be immersed in the etchant after the portion is covered with a resist or the like.

Note that debris may be removed by dry etching using a chlorine-based gas (SiCl ₄ , Cl ₂ or the like), Ar gas, or the like.

  FIG. 15 is a front view showing an n-side electrode forming step and a pad electrode forming step. In the n-side electrode forming step, the n-side electrode 24 (second electrode) is formed on the second main surface 2b of the substrate 2 of the wafer 50 by vacuum evaporation or sputtering.

  When the n-side electrode 24 such as Hf / Al or Ti / Al is formed on the second main surface 2b, the Hf / Al or Ti / Al metal film 24a (FIG. 4) is also formed on the inner wall of the light shielding groove 43. Reference) is formed. When the n-side electrode 24 is formed, heat treatment is performed in order to reduce the contact resistance between the substrate 2 and the n-side electrode 24 and ensure ohmic contact.

  In the pad electrode forming step, the pad electrode 25 is formed on the n-side electrode 24 by vacuum deposition or sputtering. When the pad electrode 25 such as Mo / Pt / Au is formed on the n-side electrode 24, the Mo / Pt / Au metal film 25a (see FIG. 4) is also formed on the inner wall of the light shielding groove 43.

  16 and 17 are a perspective view and a top view showing the bar dividing groove forming step. In the bar dividing groove forming step, a plurality of bar dividing grooves 41 are formed on the semiconductor laminated film 10 of the wafer 50 by diamond points. The bar dividing groove 41 is formed at one end of the substrate 2 in the <11-20> direction, extends in the <11-20> direction orthogonal to the ridge stripe 30, and is disposed between the p-side upper layer electrodes 23.

  By forming the bar dividing groove 41 only at one end of the substrate 2, it is possible to reduce the man-hours compared to forming the bar dividing groove 41 on the entire wafer 50. In a first cutting step to be described later, the wafer 50 is divided on the bar dividing grooves 41, and the side walls of the bar dividing grooves 41 form the emission surface 1a and the opposing surface 1b (see FIG. 2) of the semiconductor laser element 1. Therefore, the interval between the bar dividing grooves 41 is the resonator length of the waveguide 31 (see FIG. 2) of the semiconductor laser device 1, and the resonator length is formed to about 415 μm, for example.

  The bar dividing groove 41 may be formed by laser scribing. At this time, it is more desirable to perform the above-mentioned debris removing process after the bar dividing groove forming process.

  18 and 19 are a perspective view and a top view showing the first cutting step. In the first cutting process, a blade is applied into each bar dividing groove 41 of the wafer 50 to perform cleavage, thereby forming a plurality of bars 51 that are bar-shaped intermediates. Thereby, as described above, the resonator end face of the waveguide 31 (see FIG. 2) is formed by the cleavage plane.

  At this time, if cleavage occurs from the bar dividing groove 41 on the upper surface of the wafer 50 toward the light shielding groove 43 on the lower surface, the end face of the resonator is not formed flat. For this reason, the light shielding groove 43 is formed at a position that does not overlap the bar dividing groove 41. When the light shielding groove 43 is separated from the bar dividing groove 41 by 10 μm or more in the longitudinal direction of the ridge stripe 30, the bar dividing groove 41 can be reliably cleaved perpendicular to the (0001) plane. Thereby, when the semiconductor laser element 1 is separated into pieces, the light shielding groove 43 is separated from the end face of the waveguide 31 by 10 μm or more in the longitudinal direction of the waveguide 31.

  It is more desirable to form the light shielding groove 43 at a position overlapping the p-side upper layer electrode 23 in plan view. Thereby, the appearance inspection of the separated semiconductor laser element 1 can be easily performed.

  FIG. 20 is a perspective view showing the end coat film forming step. In the end face coat film forming step, the end face coat film 26 is formed on the resonator end faces at both ends of the bar 51 by vacuum deposition or sputtering. As described above, the end surface coating film 26 on the emission surface 1a (see FIG. 2) is formed of a low reflection film, and the end surface coating film 26 on the opposing surface 1b (see FIG. 2) is formed of a high reflection film. Thereby, it is possible to efficiently emit light from the emitting portion 31a (see FIG. 1) and to protect the surfaces of both end faces.

  Next, in a 2nd cutting process, a blade is applied in each chip | tip division | segmentation groove | channel 42 of the bar | burr 51, it cleaves, and it divides into several chip shape. Thereby, the semiconductor laser device 1 shown in FIG. 1 is obtained.

  According to the present embodiment, the semiconductor laminated film 10 is laminated on the upper surface 2c of the substrate 2, and the light shielding groove 43 (groove) extending in the direction intersecting the waveguide 31 is provided on the lower surface 2d. Can be prevented. At this time, the light shielding groove 43 can be formed on the wafer-like substrate 2, and the step of forming the filter structure 106 (see FIG. 25) in a bar state as in the conventional example can be omitted. Therefore, the number of steps of the semiconductor laser element 1 can be reduced, the yield can be improved, and the cost of the semiconductor laser element 1 can be reduced.

  In addition, since the metal film 24a that forms the n-side electrode 24 is disposed on the inner wall of the light shielding groove 43, a laser that leaks from the substrate 2 by reflecting or absorbing stray light incident on the substrate 2 from the waveguide 31 by the metal film 24a. Light can be reduced.

  In addition, since the coating 27 containing an oxide is provided between the metal film 24 a on the inner wall of the light shielding groove 43 and the substrate 2, the adhesion strength of the n-side electrode 24 can be improved.

  Further, when the uneven portion is provided on the side wall of the light shielding groove 43, the laser light leaking from the substrate 2 due to diffuse reflection of the stray light incident on the substrate 2 can be further reduced.

  Further, since the light shielding groove 43 is separated from the end face of the waveguide 31 by 10 μm or more in the longitudinal direction of the waveguide 31, the end face of the resonator can be formed flat.

  Further, by making the depth of the light shielding groove 43 smaller than the thickness of the substrate 2 and larger than 1/10 of the thickness of the substrate 2, laser light leaking from the substrate 2 can be surely reduced.

  Further, by making the depth of the light shielding groove 43 larger than 1/3 of the thickness of the substrate 2, the laser light leaking from the substrate 2 can be more reliably reduced.

  Further, an epitaxial growth step of epitaxially growing the semiconductor multilayer film 10 on the first main surface 2a of the wafer-like substrate 2, a stripe portion forming step of forming a stripe-shaped ridge stripe 30 (stripe portion) on the semiconductor multilayer film 10, and a wafer A light shielding groove forming step (groove forming step) for forming a light shielding groove 43 extending in a direction intersecting the ridge stripe 30 by laser scribing on the second main surface 2b of the substrate 2 in the form of a plate.

  Thereby, the light shielding groove 43 can be formed in the second main surface 2b of the wafer-like substrate 2 to prevent the FFP ripple in the vertical transverse mode. For this reason, the process of forming the filter structure 106 (see FIG. 25) in the bar state as in the conventional example can be omitted. Therefore, the number of steps of the semiconductor laser element 1 can be reduced and the yield can be improved.

  Further, a chip dividing groove forming step for forming a chip dividing groove 42 parallel to the ridge stripe 30 on the second main surface 2b of the substrate 2, and a bar division orthogonal to the ridge stripe 30 on the first main surface 2a of the substrate 2 A bar dividing groove forming step for forming the groove 41. Thereby, the wafer 50 can be easily divided by cleavage on the bar dividing groove 41, and the bar 51 can be easily divided by cleavage on the chip dividing groove 42.

  At this time, the bar dividing grooves 41 and the chip dividing grooves 42 may be provided on the same surface of the wafer 50, but it is more preferable to provide them on different surfaces as in this embodiment. If the bar dividing groove 41 and the chip dividing groove 42 are provided on the same surface of the wafer 50, a shock wave generated when cleaving in the first cutting step may propagate to the chip dividing groove 42 and the wafer 50 may be broken in an unintended direction. . For this reason, by providing the bar dividing grooves 41 and the chip dividing grooves 42 on different surfaces of the wafer 50, the yield of the semiconductor laser device 1 can be improved.

  In addition, a chip split groove 42 is formed by laser scribing, a chip split groove forming process and a light shielding groove forming process are continuously performed, and a debris removing process for removing debris by laser scribing is provided before the second electrode forming process. Yes. Thereby, the chip dividing groove 42 and the light shielding groove 43 can be easily formed continuously, and the man-hour can be reduced as compared with the case where the chip dividing groove 42 is formed by diamond points. Note that the light shielding groove forming step may be performed before the chip dividing groove forming step.

  Further, since the debris removing process is performed on the wafer 50, the debris can be removed without contaminating the resonator end face. In particular, in the semiconductor laser device 1 of a nitride semiconductor, electrons and holes are non-radiatively recombined through surface levels formed by contamination of the cavity end face and absorb emitted light to generate heat. Then, the heat generation generates a narrow band gap, which causes further light absorption and heat generation, causing a decrease in light emission intensity and destruction of the resonator end face. For this reason, contamination of the cavity end face can be prevented and the reliability of the semiconductor laser device 1 can be improved.

  In addition, since debris on the second main surface 2b of the substrate 2 is removed before the n-side electrode 24 and the pad electrode 25 are formed, adhesion of debris to the n-side electrode 24 and the pad electrode 25 can be prevented. it can. Further, the possibility of corrosion of the n-side electrode 24 and the pad electrode 25 by the etchant when removing the debris can be eliminated.

  Further, since the light shielding groove 43 is separated from the bar dividing groove 41 by 10 μm or more in the longitudinal direction of the ridge stripe 30, the resonator end face can be formed flat.

  In addition, a film 27 containing oxide is formed on the inner wall of the light shielding groove 43 by the light shielding groove forming process, and the metal of the n-side electrode 24 is disposed on the film 27 by the second electrode forming process. As a result, the stray light incident on the substrate 2 is reflected by the metal film 24a, so that the laser light leaking from the substrate 2 can be reduced and the adhesion strength of the n-side electrode 24 can be improved.

  Further, in the light shielding groove forming step, the unevenness can be easily formed on the side wall of the light shielding groove 43 by changing the sweep speed of the laser scribe.

Second Embodiment
Next, FIGS. 21 and 22 are a perspective view and a top view showing the bar dividing groove forming step of the semiconductor laser device 1 of the second embodiment. For convenience of explanation, the same reference numerals are given to the same parts as those in the first embodiment shown in FIGS. In the present embodiment, the configuration of the bar dividing groove 41 is different from that of the first embodiment. Other parts are the same as those in the first embodiment.

  In the bar dividing groove forming step, a plurality of bar dividing grooves 41 are formed on the semiconductor laminated film 10 of the wafer 50 by diamond points. The bar dividing grooves 41 are arranged between the p-side upper layer electrodes 23 in the <1-100> direction of the substrate 2, and a plurality of bar dividing grooves 41 are intermittently provided in the <11-20> direction avoiding the ridge stripe 30.

  Thereby, although a man-hour increases compared with 1st Embodiment, it can cleave in the direction intended in the 1st cutting process easily and reliably. Although the bar dividing grooves 41 are arranged between the ridge stripes 30, the number of man-hours may be reduced by providing each of the plurality of ridge stripes 30.

<Third Embodiment>
Next, FIGS. 23 and 24 are a perspective view and a bottom view showing the wafer 50 after the light shielding groove forming step of the semiconductor laser device 1 of the third embodiment. For convenience of explanation, the same reference numerals are given to the same parts as those in the first embodiment shown in FIGS. In the present embodiment, the configuration of the chip dividing groove 42 is different from that of the first embodiment. Other parts are the same as those in the first embodiment.

  The chip dividing grooves 42 intermittently extend in the <1-100> direction parallel to the ridge stripe 30 and are arranged between the ridge stripes 30. Thereby, it is possible to reduce the possibility that the wafer 50 is broken compared to the first embodiment.

  At this time, the interval between the non-formed portions of the chip dividing groove 42 is formed smaller than the interval between the bar dividing grooves 41 (see FIG. 16). Thereby, the chip | tip division | segmentation groove | channel 42 can be reliably provided on the bar 51 (refer FIG. 18).

  Further, by providing the chip dividing groove 42 while avoiding the light shielding groove 43, the cracks on the light shielding groove 43 can be reduced.

  In the first to third embodiments, the semiconductor laser device 1 is formed in a ridge shape in which the side surface of the striped ridge stripe 30 is sandwiched between the buried layers, but has a striped strip portion for injecting current into the active layer 14. As long as it has a structure, the semiconductor laser element 1 may have another structure.

For example, a RiS (Ridge by Selective Re-growth) type semiconductor laser device in which a mask such as SiO ₂ having a striped window portion is provided on the upper clad layer and the upper clad layer is regrown in the window portion. Also good. Further, a BH (Buried Heterostructure) type semiconductor laser device in which the lower cladding layer, the active layer, and the upper cladding layer are formed in a stripe shape and sandwiched between embedded layers such as SiO ₂ may be used.

  Although the semiconductor laser device in which the nitride semiconductor laminated structure is formed on the gallium nitride substrate has been specifically described above, the scope of the present invention is not limited to this. The manufacturing method of the present invention can also be applied to semiconductor laser elements of other materials. In addition, when applied to semiconductor laser elements of other materials, it is needless to say that materials suitable for the substrate, semiconductor laminated film, electrode, insulating film, etc. need to be used.

  The present invention can be used for a semiconductor laser element typified by a laser diode. In particular, it can be applied to a semiconductor laser element made of a nitride-based semiconductor, and can be used for a light source such as a directional light, a projector, and a television.

DESCRIPTION OF SYMBOLS 1,101 Semiconductor laser element 1a Emission surface 1b Opposite surface 2,102 Substrate 2a 1st main surface 2b 2nd main surface 2c Upper surface 2d Lower surface 5 Resist 10 Semiconductor laminated film 11 Lower contact layer 12 Lower clad layer 13 Lower guide layer 14 Active Layer 14a barrier layer 14b quantum well layer 15 evaporation prevention layer 16 upper guide layer 17 upper cladding layer 18 upper contact layer 21 buried layer 22 p-side lower layer electrode 23 p-side upper layer electrode 24 n-side electrode 24a, 25a metal film 25 pad electrode 26 End coating film 27 Coating 30 Ridge stripe 31 Waveguide 31a Emitting portion 41 Bar dividing groove 42 Chip dividing groove 43 Light shielding groove 50 Wafer 51 Bar 106 Filter structure 107, 108 Electromagnetic beam 110 Semiconductor laminated film 114 Active region 123, 124 Electrode

Claims (13)

  In a semiconductor laser device in which a stripe-shaped waveguide is formed by a semiconductor laminated film laminated on the upper surface of a substrate and laser light is emitted from one end surface of the waveguide, the lower surface of the substrate is crossed with the waveguide. A semiconductor laser device comprising a groove extending.   2. The semiconductor laser device according to claim 1, wherein an electrode is provided on a lower surface of the substrate, and a metal film for forming the electrode is disposed on an inner wall of the groove.   3. The semiconductor laser device according to claim 2, wherein a film containing an oxide is provided between the metal film on the inner wall of the groove and the substrate.   4. The semiconductor laser device according to claim 1, wherein an uneven portion is provided on a side wall of the groove.   5. The semiconductor laser device according to claim 1, wherein the groove is separated from an end face of the waveguide by 10 μm or more in a longitudinal direction of the waveguide.   6. The semiconductor laser device according to claim 1, wherein the depth of the groove is smaller than the thickness of the substrate and larger than 1/10 of the thickness of the substrate.   8. The semiconductor laser device according to claim 7, wherein the depth of the groove is larger than 1/3 of the thickness of the substrate. In a method of manufacturing a semiconductor laser element that emits laser light from one end face of a striped waveguide formed by a semiconductor laminated film laminated on a substrate,
An epitaxial growth step of epitaxially growing the semiconductor multilayer film on the first main surface of the wafer-like substrate;
A stripe portion forming step of forming a stripe-like stripe portion in the semiconductor laminated film;
A first electrode forming step of forming a first electrode on the stripe portion;
A groove forming step of forming a groove extending in a direction intersecting the stripe portion by laser scribing on a second main surface of the wafer-shaped substrate facing the first main surface;
A second electrode forming step of forming a second electrode on the second main surface in which the groove is formed;
A first cutting step of cutting the substrate in a direction perpendicular to the stripe portion at a position different from the groove to form a bar-shaped intermediate;
An end face coat film forming step of forming an end face coat film on the cut surface of the first cutting step;
A second cutting step of cutting the intermediate body on which the end face coating film is formed in parallel with the stripe portion;
A method for manufacturing a semiconductor laser device, comprising:   A chip dividing groove forming step for forming a chip dividing groove parallel to the stripe portion on the second main surface, and a bar dividing groove forming step for forming a bar dividing groove orthogonal to the stripe portion on the first main surface. The substrate is cut by cleaving on the bar dividing groove by the first cutting step, and the substrate is cut by cleaving on the chip dividing groove by the second cutting step. The manufacturing method of the semiconductor laser element of description.   In the chip dividing groove forming step, the chip dividing groove is formed by laser scribing, the chip dividing groove forming step and the groove forming step are continuously performed, and debris by laser scribing is performed before the second electrode forming step. The method for manufacturing a semiconductor laser device according to claim 9, further comprising a debris removing step for removing.   11. The method of manufacturing a semiconductor laser device according to claim 9, wherein the groove is separated from the bar dividing groove by 10 μm or more in a longitudinal direction of the stripe portion.   9. A film including an oxide is formed on an inner wall of the groove by the groove forming step, and a metal of the second electrode is disposed on the film by the second electrode forming step. The method for manufacturing a semiconductor laser device according to claim 11.   13. The method of manufacturing a semiconductor laser device according to claim 8, wherein in the groove forming step, the unevenness is formed on the side wall of the groove by changing a laser scribe sweep speed.

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