JP2010034157A - Semiconductor laser manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser manufacturing method that suppresses the deterioration in ESD properties. <P>SOLUTION: The method of manufacturing the semiconductor laser 50 includes step S105 for forming a semiconductor laser bar 2, step S107 for forming a first coating 21 on a first end face 2a of the semiconductor laser bar 2, and step S113 for forming a second coating 23 on a second end face 2b of the semiconductor laser bar 2. The step S107 includes step S109 for forming a first dielectric layer 21a on the first end face 2a while irradiating ions, having energy exceeding 60 eV, toward the first end face 2a by an ion assist vapor deposition method. The step S113 includes step S115 for forming a second dielectric layer 23a on the second end face 2b while irradiating ions, having energy exceeding 90 eV, toward the second end face 2b by the ion assist vapor deposition method. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a semiconductor laser manufacturing method.

Patent Document 1 describes a method for manufacturing a semiconductor laser. In this method, an oxygen-free Si film is formed when a protective film is formed on the end face of a semiconductor laser by vacuum evaporation. Thereafter, an Al ₂ O ₃ film is formed on the Si film. According to this film forming sequence, damage to the end face of the semiconductor laser due to oxygen is suppressed. As a result, the occurrence of leakage current at the end face and the reduction of the COD (optical breakdown level) value are suppressed.

Patent Document 2 describes a method for manufacturing a semiconductor laser. In this method, a single layer of Al ₂ O ₃ is formed on the end face of the semiconductor laser as a low reflection film by vacuum deposition, and a stack of Al ₂ O ₃ and amorphous Si is formed on the end face of the semiconductor laser as a high reflection layer. is doing. When forming these low-reflection films and high-reflection layers, the film formation rate is reduced at the initial stage of each formation, and then the film formation rate is increased. According to this method, it is possible to prevent stray electrons, recoil electrons, and the like from damaging the end surface, and the scattered deposition material from damaging the end surface. As a result, the COD value at the end face increases.

Cited Document 3 describes a method for manufacturing a semiconductor laser. In this method, when the protective film is formed on the end surface of the semiconductor laser by the sputtering method, the output of the discharge power source of the sputtering apparatus is lowered at the initial stage of forming the protective film, and the output is gradually increased. According to this method, it is possible to suppress the end face from being electrically damaged by the voltage applied to the end face suddenly at the start of the plasma discharge or the plasma discharge from causing the end face to be roughened.
JP 2002-164609 A JP 2001-177179 A JP 2003-183824 A

  A coating (protective film) is formed on two opposite end faces of the semiconductor laser for the purpose of end face protection and light reflectance control.

  When the coating is formed on the end face of the semiconductor laser, the end face may be damaged. If the end face is damaged, there arises a problem that characteristics such as ESD characteristics (electrostatic breakdown characteristics) of the semiconductor laser deteriorate.

  However, Patent Document 1 and Patent Document 2 do not mention the ESD characteristics of the semiconductor laser. Further, Patent Document 3 does not mention the ESD characteristics of the semiconductor laser, and the semiconductor laser manufacturing method uses plasma discharge by a sputtering apparatus. Is inevitable.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a semiconductor laser manufacturing method capable of suppressing deterioration of ESD characteristics.

  The semiconductor laser manufacturing method according to the present invention includes a step of forming a semiconductor laser bar including an active layer for generating laser light, a step of forming a first coating on the first end face of the semiconductor laser bar, and a first step of the semiconductor laser bar. Forming a second coating on the second end face opposite to the one end face, and the step of forming the first coating irradiates ions having energy of 60 eV or more toward the first end face by an ion-assisted deposition method. However, the step of forming the first dielectric layer on the first end face includes the step of forming the second coating by irradiating ions having energy of 90 eV or more toward the second end face by an ion-assisted deposition method. However, the method includes a step of forming a second dielectric layer on the second end face.

  According to the semiconductor laser manufacturing method of the present invention, ions having energy of 60 eV or more are irradiated toward the first end face when the first dielectric layer is formed by the ion-assisted deposition method. As a result, the first dielectric layer becomes a dense film with few crystal defects. During the formation of the first dielectric layer, the entire first end face is covered and protected by this dense film. Further, when the second dielectric layer is formed by the ion-assisted vapor deposition method, ions having an energy of 90 eV or more are irradiated toward the second end face. As a result, the second dielectric layer becomes a dense film with few crystal defects. During the formation of the second dielectric layer, the entire second end face is covered and protected by this dense film. As a result, a semiconductor laser with high ESD characteristics can be obtained.

  In the method for manufacturing a semiconductor laser according to the present invention, the step of forming the first coating includes the step of forming a third dielectric layer having a refractive index different from that of the first dielectric layer on the first dielectric layer. The step of forming the second coating may further include the step of alternately forming the fourth dielectric layer and the fifth dielectric layer having different refractive indexes on the second dielectric layer. .

  Thereby, the light reflectance of the first coating and the second coating can be easily controlled, and the light reflectance of the second coating can be easily made higher than the light reflectance of the first coating.

  In the semiconductor laser manufacturing method according to the present invention, the first dielectric layer can be made of aluminum oxide, and the second dielectric layer can be made of aluminum oxide.

  In the semiconductor laser manufacturing method according to the present invention, the first dielectric layer is made of aluminum oxide, the second dielectric layer is made of aluminum oxide, the third dielectric layer is made of titanium oxide, and the fourth dielectric layer is made. The body layer can be made of titanium oxide, and the fifth dielectric layer can be made of aluminum oxide.

  In the method for manufacturing a semiconductor laser according to the present invention, the first coating may be a low reflection layer of the semiconductor laser.

  In the method for manufacturing a semiconductor laser according to the present invention, the second coating may be a highly reflective layer of the semiconductor laser.

  As described above, according to the present invention, there is provided a method for manufacturing a semiconductor laser capable of suppressing degradation of ESD characteristics.

  Hereinafter, a method for manufacturing a semiconductor laser according to an embodiment will be described in detail with reference to the accompanying drawings. Where possible, the same symbols are used for the same elements.

  FIG. 1 is a flowchart showing the main steps of the semiconductor laser manufacturing method according to this embodiment. As shown in the flowchart 100 of FIG. 1, the semiconductor laser manufacturing method according to the present embodiment mainly includes a step S101 of forming a semiconductor stack for a semiconductor laser on a semiconductor substrate, and a step of forming a P electrode and an N electrode. S103, cleaving the semiconductor substrate to create a semiconductor laser bar S105, forming a low-reflection layer on the first end face of the semiconductor laser bar, S107, forming a high-reflection layer on the second end face of the semiconductor laser bar, and A step S123 for separating the semiconductor laser bar into individual semiconductor laser elements is provided.

(Process S101)
In step S101, semiconductor lamination or etching for a semiconductor laser is performed on a semiconductor substrate. The semiconductor is stacked by, for example, metal organic vapor phase epitaxy. The semiconductor laminate includes, for example, two cladding layers and an active layer provided between these cladding layers. Thereby, a semiconductor epitaxial wafer is obtained.

  FIG. 2 is a cross-sectional view showing the semiconductor epitaxial wafer obtained in step S101. FIG. 2 shows an orthogonal coordinate system 17.

  As shown in FIG. 2, the semiconductor epitaxial wafer 1 has a stripe-shaped stripe portion 1a provided on the main surface of a semiconductor substrate 5 such as an n-type InP substrate and extending in the Y-axis direction. The stripe portion 1a is a trench. It is provided between the grooves T.

  The stripe portion 1a includes a mesa portion 6, a p-type block layer 9 made of, for example, p-type InP, and an n-type block layer 10 made of, for example, n-type InP.

  The mesa portion 6 is provided on the main surface of the semiconductor substrate 5. The mesa unit 6 includes an active layer 7 and a first upper clad layer 8 provided thereon and made of, for example, p-type InP. The mesa portion 6 has a forward mesa shape, and the widths of the active layer 7 and the first upper cladding layer 8 are gradually reduced. The thickness of the active layer 7 is, for example, 1 μm. The thickness of the first upper cladding layer 8 is, for example, 1 μm. The stripe width of the mesa unit 6 is, for example, 1 μm.

  The active layer 7 has, for example, an MQW (multiple quantum well) structure or an SQW (single quantum well) structure made of GaInAsP. The semiconductor substrate 5 or the lower cladding layer supplies electrons which are carriers to the active layer 7. The first upper cladding layer 8 supplies holes serving as carriers to the active layer 7. Electrons and holes are recombined in the active layer 7 to generate light. Since the semiconductor substrate 5 or the lower clad layer is formed of a material having a lower refractive index than the material of the active layer 7, it functions to confine light generated in the active layer 7 in the vicinity of the active layer 7. Since the first upper cladding layer 8 is formed of a material having a lower refractive index than the material of the active layer 7, it functions to confine light generated in the active layer 7 in the vicinity of the active layer 7.

  Current block regions are formed on both sides of the mesa unit 6 and on the semiconductor substrate 5. For example, the p-type block layer 9 is formed on both side surfaces of the mesa portion 6 and the semiconductor substrate 5. The n-type block layer 10 is formed on the p-type block layer 9. The p-type block layer 9 and the n-type block layer 10 embed the mesa portion 6. The p-type block layer 9 and the n-type block layer 10 confine current in the mesa unit 6.

  On the first upper cladding layer 8 and the n-type block layer 10, a second upper cladding layer 11 made of, for example, p-type InP is formed. Since the second upper cladding layer 11 is made of a material having a lower refractive index than the material forming the active layer 7, it functions to confine light generated in the active layer 7 in the vicinity of the active layer 7. On the second upper clad layer 11, a contact layer 13 made of, for example, GaInAs is formed.

An insulating layer 15 made of, for example, SiN or SiO ₂ is formed on the contact layer 13 and the trench groove T. In the insulating layer 15, a contact hole 15 h extending in the Y-axis direction is formed on the contact layer 13.

  A plurality of stripe portions 1 a are formed on the semiconductor substrate 5. These stripe portions 1a are arranged in the X-axis direction and extend in the Y-axis direction.

(Step S103)
In step S103, a P electrode 18 and an N electrode 19 are formed on the semiconductor epitaxial wafer 1 by vacuum vapor deposition or the like as shown in FIG. The P electrode 18 and the N electrode 19 are made of a metal such as Au, for example. The P electrode 18 is formed on the insulating layer 15 and is in ohmic contact with the second upper cladding layer 11 through the contact hole 15h. The N electrode 19 is formed on the back surface of the semiconductor substrate 5. The N electrode 19 may be formed after the back surface of the semiconductor substrate 5 is polished to thin the semiconductor substrate 5. In this way, a substrate product including a plurality of laser elements arranged in an array is completed.

(Step S105)
In step S105, the substrate product is cleaved to form a semiconductor laser bar. In order to cleave the substrate product, two scribing lines are made in the substrate product, for example using a scribing device. These marking lines are formed in a direction substantially orthogonal to the extending direction of the stripe portion 1a. The substrate product is cleaved by applying force to the semiconductor substrate 5 after forming the marking lines. This cleavage occurs on a plane substantially parallel to a plane (XZ plane) orthogonal to the direction in which the mesa portion 6 extends. Thereby, the semiconductor laser bar is completed.

  FIG. 3 is a perspective view of a part of the semiconductor laser bar. The semiconductor laser bar 2 has a plurality of stripe portions 1a extending in the Y-axis direction, and the stripe portions 1a are arranged in the X-axis direction. The semiconductor laser bar 2 has a first end face 2a and a second end face 2b which are formed by cleavage and face each other. One end face of the active layer 7 is exposed at the first end face 2a, and the other end face of the active layer 7 is exposed at the second end face 2b. The thickness Z2 and length Y2 of the semiconductor laser bar 2 are, for example, about 100 μm and 300 μm, respectively.

(Step S107)
In step S107, a low reflective layer as a first coating is formed on the first end face of the semiconductor laser bar. In order to form the low reflection layer, for example, Step S109 and Step S111 can be performed. In step S109, an aluminum oxide layer is formed on the first end face of the semiconductor laser bar by ion-assisted vapor deposition. In step S111, a titanium oxide layer is formed on the aluminum oxide layer.

  First, an ion assist vapor deposition apparatus used for the ion assist vapor deposition method will be described. FIG. 4 is a diagram schematically illustrating an example of an ion-assisted vapor deposition apparatus. The ion assist deposition apparatus 27 includes a vacuum chamber 29, an ion gun 31, an electron gun 33, a container 35 such as a hearth, and a support base 37 such as a top plate.

  The vacuum chamber 29 has a flange 29F. A vacuum pump is connected to the flange 29F. By this vacuum pump, the inside of the vacuum chamber 29 is maintained at a low pressure enabling vacuum deposition.

The ion gun 31 emits ions 31A such as argon ions (Ar ⁺ ), for example. The ion gun 31 is disposed to face the support base 37.

  The vapor deposition material is accommodated in the container 35. The electron gun 33 emits an electron beam 33A. The traveling direction of the electron beam 33 </ b> A is bent by, for example, a magnetic field and is incident on the container 35. The container 35 contains a vapor deposition material. When the electron beam 33A enters the container 35, the vapor deposition material in the container 35 is heated by the electron beam 33A. By this heating, the vapor deposition material is evaporated, and the evaporated material flux 35A is released from the container 35. The released raw material flux 35 </ b> A may be blocked as necessary using a shutter 36 provided in the vacuum chamber 29.

  The support base 37 has a dome shape, for example, and is disposed to face the ion gun 31 and the container 35. A plurality of jigs 39 for supporting the semiconductor laser bar 2 are arranged on the support base 37. The semiconductor laser bar 2 is disposed on the jig 39 with one of its end faces facing the ion gun 31 and the container 35, and the end face serves as a vapor deposition surface. An anode voltage is applied between the ion gun 31 and the semiconductor laser bar 2. The ions 31 </ b> A are accelerated in the direction of the semiconductor laser bar 2 by the anode voltage, and are irradiated on the end surface of the semiconductor laser bar 2. The kinetic energy of the ions 31A when the ions 31A reach the semiconductor laser bar 2 has a magnitude corresponding to the anode voltage. The support table 37 is rotatable around the axis 37C during the deposition. Thereby, when vapor deposition is performed on the plurality of semiconductor laser bars 2, the uniformity of the respective vapor deposition films is improved.

  When performing vacuum deposition by the ion-assisted deposition method, the raw material flux 35A is made to reach the deposition surface while irradiating the ions 31A toward the deposition surface of the semiconductor laser bar 2. Then, a vapor deposition film made of the raw material flux 35A is formed on the vapor deposition surface.

  A film thickness measuring instrument 38 may be disposed in the vacuum chamber 29. The film thickness measuring device 38 is, for example, an optical film thickness measuring device. The support base 37 has a hole portion 37h penetrating from the front surface to the back surface. A monitor glass plate 39 is arranged on the side opposite to the container 35 side from the hole 37 h so as to face the film thickness measuring device 38. When vacuum deposition is performed on the semiconductor laser bar 2, the ions 31 </ b> A and the raw material flux 35 </ b> A reach the monitor glass plate 39, and a deposited film is also formed on the monitor glass plate 39. The thickness of the deposited film can be measured by the film thickness measuring device 38.

  Further, in the chamber 12, a crystal resonator 41 for monitoring the thickness of the deposited film may be disposed. The crystal resonator 41 is disposed to face the ion gun 31.

(Step S109)
In step S109, an aluminum oxide layer is formed on the first end face of the semiconductor laser bar by ion-assisted vapor deposition. In this step, aluminum oxide is used as the vapor deposition material accommodated in the container 35. The semiconductor laser bar 2 is fixed to the jig 39 so that the first end face 2 a faces the ion gun 31 and the container 35. That is, the 1st end surface 2a turns into a vapor deposition surface.

5A and 5B are cross-sectional views of the semiconductor laser bar. In this step, the raw material flux 35A is made to reach the first end face 2a while irradiating the first end face 2a with ions 31A made of argon ions having energy of 60 eV (9.6 × 10 ⁻¹⁸ J) or more. The magnitude of the energy of the ions 31 </ b> A is adjusted by the magnitude of the anode voltage applied between the ion gun 31 and the semiconductor laser bar 2. Then, as shown in FIG. 5A, an aluminum oxide layer 21a that is a first dielectric layer is formed. In a preferred embodiment, the ions 31A are irradiated as an ion beam. The kinetic energy of ion particles in this ion beam is distributed, and the peak value of the kinetic energy spectrum is preferably located at 60 eV or more.

  As described above, when forming the aluminum oxide layer 21a, the ions 31A having an energy of 60 eV or more are irradiated toward the first end face 2a, so that the raw material flux 35A that has reached the first end face 2a has energy from the ions 31A. Considered to receive. As a result, the individual atoms constituting the aluminum oxide layer 21a are likely to move to a stable position, so the aluminum oxide layer 21a is considered to be a dense film with few crystal defects. Therefore, the entire first end face 2a is covered and effectively protected by the aluminum oxide layer 21a. As a result, a semiconductor laser with high ESD characteristics can be obtained.

  As already described, when forming the aluminum oxide layer 21a, the lower limit of the energy of the ions 31A irradiated toward the first end face 2a is preferably 60 eV or more. Moreover, it is preferable that the upper limit is 100 eV or less. This is because when the energy of the ions 31A is larger than 100 eV, the impact applied to the first end face 2a is increased.

  Moreover, the aluminum oxide layer can have a multilayer structure as shown below. For example, after the aluminum oxide layer 21a is formed on the first end face 2a while irradiating the ions 31A having energy of 60 eV or more toward the first end face 2a, the layer made of aluminum oxide has energy less than 60 eV. It is formed on the aluminum oxide layer 21a while irradiating the ions 31A toward the first end face 2a or without irradiating the ions 31A. Also in this case, the aluminum oxide layer 21a becomes the first dielectric layer. In addition, when the aluminum oxide layer has either a single layer structure or a multilayer structure, the thickness of the aluminum oxide layer 21a is preferably 50 nm or more. This is because the first end face 2a can be sufficiently protected.

  As a material constituting the first dielectric layer, for example, titanium oxide can be used in addition to aluminum oxide.

(Process S111)
In step S111, as shown in FIG. 5B, a titanium oxide layer 21b that is a third dielectric layer is formed on the aluminum oxide layer 21a. The titanium oxide layer 21b can also be formed by ion-assisted vapor deposition. When the titanium oxide layer 21b is formed by ion-assisted vapor deposition, titanium oxide is used as the vapor deposition material accommodated in the container 35. In addition, the titanium oxide layer 21b can be formed while irradiating ions 31A made of argon ions toward the first end face 2a. The energy of the ions 31A at this time can be set to 40 to 150 eV, for example. Note that the titanium oxide layer 21b may be formed by a vacuum deposition method without irradiating the ions 31A. The thickness of the titanium oxide layer 21b can be set to 40 to 50 nm, for example.

  The low reflection layer 21 includes an aluminum oxide layer 21a that is a first dielectric layer and a titanium oxide layer 21b that is a third dielectric layer. The refractive index of the titanium oxide layer 21b is different from the refractive index of the aluminum oxide layer 21a at the oscillation wavelength of the semiconductor laser. Therefore, the reflectance of the low reflective layer 21 can be easily controlled to a predetermined value. The reflectance of the low reflective layer 21 is, for example, 0.01 to 1 percent. The low reflective layer 21 also functions as a protective film that protects the first end face 2a.

  As a material constituting the third dielectric layer, a material other than titanium oxide can be used. For example, the combination (A, B) of the material (A) constituting the first dielectric layer and the material (B) constituting the third dielectric layer is, for example, (aluminum oxide, titanium oxide), for example, (oxidation) Titanium, aluminum oxide) and (titanium oxide, magnesium fluoride).

(Step S113)
In step S113, a highly reflective layer as a second coating is formed on the second end face of the semiconductor laser bar. In order to form the highly reflective layer, for example, Step S115, Step S117, Step S119, and Step S121 can be performed. In step S115, an aluminum oxide layer is formed on the second end face of the semiconductor laser bar by ion-assisted vapor deposition. In step S117, a titanium oxide layer is formed on the aluminum oxide layer. In step S119, an aluminum oxide layer is formed on the titanium oxide layer. In step S121, step S117 and step S119 are repeated a predetermined number of times.

(Step S115)
In step S115, an aluminum oxide layer is formed on the second end face of the semiconductor laser bar by ion-assisted vapor deposition. In this step, aluminum oxide is used as the vapor deposition material accommodated in the container 35. The semiconductor laser bar 2 is fixed to the jig 39 so that the second end face 2 b faces the ion gun 31 and the container 35. That is, the 2nd end surface 2b becomes a vapor deposition surface.

6A to 6D are cross-sectional views of the semiconductor laser bar. In this step, the raw material flux 35A is made to reach the second end face 2b while irradiating ions 31A made of argon ions having energy of 90 eV (1.4 × 10 ⁻¹⁷ J) or more toward the first end face 2b. Then, as shown in FIG. 6A, an aluminum oxide layer 23a that is a second dielectric layer is formed. In a preferred embodiment, the ions 31A are irradiated as an ion beam. The kinetic energy of ion particles of this ion beam is distributed, and the peak value of the kinetic energy spectrum is preferably located at 90 eV or more.

  As described above, when forming the aluminum oxide layer 23a, the ions 31A having an energy of 90 eV or more are irradiated toward the second end face 2b. Considered to receive. As a result, the individual atoms constituting the aluminum oxide layer 23a can easily move to a stable position, so the aluminum oxide layer 23a is considered to be a dense film with few crystal defects. Therefore, the entire second end face 2b is covered and effectively protected by the aluminum oxide layer 23a. As a result, a semiconductor laser with high ESD characteristics can be obtained.

  As already described, when forming the aluminum oxide layer 23a, the lower limit of the energy of the ions 31A irradiated toward the second end face 2b is preferably 90 eV or more. Moreover, it is preferable that the upper limit is 100 eV or less. This is because when the energy of the ions 31A is greater than 100 eV, the impact applied to the second end face 2b is increased. The energy of the ions 31A irradiated toward the second end face 2b when forming the aluminum oxide layer 23a is the energy of the ions 31A irradiated toward the first end face 2a when forming the aluminum oxide layer 21a. It is preferably higher than energy.

  Moreover, the aluminum oxide layer can have a multilayer structure as shown below. For example, after the aluminum oxide layer 23a is formed on the second end face while irradiating ions 31A having an energy of 90 eV or more toward the second end face 2b, an aluminum oxide layer 23a is further formed on the second end face 2b. It is formed on the aluminum oxide layer 23a while irradiating 31A toward the second end face 2b or without irradiating the ions 31A. Also in this case, the aluminum oxide layer 23a becomes the second dielectric layer. In addition, when the aluminum oxide layer has either a single layer structure or a multilayer structure, the thickness of the aluminum oxide layer 23a is preferably 50 nm or more. This is because the second end face 2b can be sufficiently protected.

  As a material constituting the second dielectric layer, for example, silicon oxide can be used in addition to aluminum oxide.

(Step S117)
In step S117, as shown in FIG. 6B, a titanium oxide layer 23b, which is a fourth dielectric layer, is formed on the aluminum oxide layer 23a. The titanium oxide layer 23b can be formed by ion-assisted vapor deposition. When the titanium oxide layer 23b is formed by ion-assisted vapor deposition, titanium oxide is used as a vapor deposition material accommodated in the container 35. The titanium oxide layer 23b can be formed while irradiating the ions 31A toward the second end face 2b. The energy of the ions 31A at this time can be set to 40 to 150 eV, for example. Note that the titanium oxide layer 23b may be formed by vacuum deposition without irradiating the ions 31A. The thickness of the titanium oxide layer 23b can be set to 120 to 160 nm, for example.

(Step S119)
In step S119, as shown in FIG. 6C, an aluminum oxide layer 23c, which is a fifth dielectric layer, is formed on the titanium oxide layer 23b. The aluminum oxide layer 23c can be formed by ion-assisted vapor deposition. When the aluminum oxide layer 23c is formed by ion-assisted vapor deposition, aluminum oxide is used as a vapor deposition material accommodated in the container 35. The aluminum oxide layer 23c can be formed while irradiating the ions 31A toward the second end face 2b. The energy of the ions 31A at this time can be set to 40 to 150 eV, for example. Note that the aluminum oxide layer 23c may be formed by vacuum deposition without irradiating the ions 31A. The thickness of the aluminum oxide layer 23c can be set to 190 to 230 nm, for example.

(Process S121)
In step S121, step S117 and step S119 are alternately repeated a predetermined number of times. That is, as shown in FIG. 5D, the titanium oxide layer 23b and the aluminum oxide layer 23c are alternately formed a predetermined number of times on the aluminum oxide layer 23c formed in step S119. The number of times the titanium oxide layer 23b and the aluminum oxide layer 23c are alternately formed is not particularly limited, and the layer formed last may be any of the titanium oxide layer 23b and the aluminum oxide layer 23c.

  The highly reflective layer 23 includes an aluminum oxide layer 23a that is a second dielectric layer, a titanium oxide layer 23b that is a fourth dielectric layer, and an aluminum oxide layer 23c that is a fifth dielectric layer. The reflectance of the high reflection layer 23 is higher than the reflectance of the low reflection layer 21 with respect to light having the oscillation wavelength of the semiconductor laser. The refractive index of the titanium oxide layer 23b is different from the refractive indexes of the aluminum oxide layers 23a and 23c at the oscillation wavelength of the semiconductor laser. Therefore, the reflectance of the highly reflective layer 23 can be easily controlled to a predetermined value. Further, the reflectance of the high reflection layer 23 can be easily made higher than that of the low reflection layer 21. The reflectance of the highly reflective layer 23 is, for example, 60 to 90 percent. The highly reflective layer 23 also functions as a protective film that protects the second end surface 2b.

  As a material constituting the fourth dielectric layer, a material other than titanium oxide can be used. In addition, as a material constituting the second dielectric layer and the fifth dielectric layer, a material other than aluminum oxide can be used. For example, the combination (C, D) of the material (C) constituting the second dielectric layer and the fifth dielectric layer and the material (D) constituting the fourth dielectric layer is (aluminum oxide, titanium oxide) In addition, for example, (silicon oxide, titanium oxide), (silicon oxide, amorphous silicon) can be used.

  Further, the order of the above-described step S107 and step S113 may be reversed.

(Step S123)
In step S123, the semiconductor laser bar is separated into individual semiconductor laser elements. In this way, the semiconductor laser element is completed.

  FIG. 7 is a perspective view of the semiconductor laser device obtained in this embodiment. As shown in FIG. 7, the semiconductor laser element 50 includes a laser body 2x, a low reflection layer 21 formed on the first end surface 2a, and a high reflection layer 23 formed on the second end surface 2b. Yes. The thickness Z50, length Y50, and width X50 of the semiconductor laser element 50 are, for example, 100 μm, 300 μm, and 250 μm, respectively.

  When a voltage is applied in the forward direction to the semiconductor laser element 50, current flows through the mesa portion 6 by the action of the p-type block layer 9 and the n-type block layer 10. As a result, light is generated in the active layer 7. The light generated in the active layer 7 reciprocates between the low reflection layer 21 and the high reflection layer 23 due to reflection in the low reflection layer 21 and the high reflection layer 23. The semiconductor laser element 50 oscillates and emits laser light from the first end face 2a.

  When electrostatic discharge occurs in the forward direction in the semiconductor laser element 50, a pulsed current flows in the forward direction in the semiconductor laser element 50. By this current injection, pulsed high-intensity light is generated in the active layer 7. This light reaches the low reflection layer 21 and the high reflection layer 23. At this time, if there is a defect in the first end surface 2a or the second end surface 2b, damage occurs in the defect in the first end surface 2a or the second end surface 2b. As a result, the characteristics of the semiconductor laser element 50 may deteriorate. In the semiconductor laser device 50 of the present embodiment, as described above, the first end surface 2a and the second end surface 2b are effectively protected by the aluminum oxide layer 21a and the aluminum oxide layer 23a, respectively. There are few defects in the two end faces 2b. Therefore, the ESD characteristics of the semiconductor laser element 50 are improved.

  Hereinafter, in order to further clarify the effects of the present invention, description will be made using examples and comparative examples.

Example 1
As Example 1, 20 semiconductor laser elements were produced. Twenty semiconductor laser elements of Example 1 were produced as follows.

  First, a semiconductor epitaxial wafer (see the semiconductor epitaxial wafer 1 in FIG. 2) similar to that in the above embodiment was prepared. Then, after forming a P electrode and an N electrode on the semiconductor epitaxial wafer, the substrate product was cleaved to create a semiconductor laser bar (see semiconductor laser bar 2 in FIG. 3).

  Next, a low reflection layer was formed on the first end face of the semiconductor laser bar by ion-assisted vapor deposition. The low reflection layer has a two-layer structure including a first dielectric layer and a third dielectric layer. The first dielectric layer and the third dielectric layer were formed while irradiating argon ions toward the first end face.

  FIG. 8 is a diagram illustrating the formation conditions of the first dielectric layer and the third dielectric layer of Example 1 by the forming material and the ion-assisted vapor deposition method. FIG. 9 is a diagram showing temporal changes in the anode voltage and the energy of argon ions irradiated on the first end face when the low reflective layer of Example 1 is formed.

As shown in FIGS. 8 and 9, the first dielectric layer, which is the first layer of the low reflection layer, was formed using Al ₂ O ₃ . An anode voltage of 75.0 V was applied between the ion gun and the semiconductor laser bar from 0 second (point A1) to point A2. Thereby, the energy of argon ion became 60.0 eV from 0 second (point B1) to point B2. Between point A1 and point A2, the shutter of the ion assist vapor deposition apparatus was opened for 259 seconds. Thus, a first dielectric layer having a thickness of 128.8 nm was formed on the first end face while irradiating argon ions having energy of 60.0 eV toward the first end face.

Subsequently, a third dielectric layer which is the second layer of the low reflection layer was formed. The third dielectric layer was formed by using the TiO _2. From point A3 to point A4, an anode voltage of 56.7 V was applied between the ion gun and the semiconductor laser bar. As a result, the energy of argon ions was 45.4 eV from point B3 to point B4. Between point A3 and point A4, the shutter of the ion-assisted vapor deposition apparatus was opened for 210 seconds. Thus, a third dielectric layer having a thickness of 42.8 nm was formed on the first dielectric layer while irradiating argon ions having energy of 45.4 eV toward the first end face.

  Next, a highly reflective layer was formed on the second end face of the semiconductor laser bar by ion-assisted vapor deposition. The highly reflective layer has a six-layer structure including a second dielectric layer, a plurality of fourth dielectric layers, and a plurality of fifth dielectric layers. The second dielectric layer, the fourth dielectric layer, and the fifth dielectric layer were formed while irradiating argon ions toward the second end face.

  FIG. 10 is a diagram illustrating the formation conditions of the second dielectric layer, the fourth dielectric layer, and the fifth dielectric layer of Example 1 by the forming material and the ion-assisted deposition method. FIG. 11 is a diagram showing temporal changes in the anode voltage and the energy of argon ions applied to the second end face when the highly reflective layer of Example 1 is formed.

As shown in FIGS. 10 and 11, the second dielectric layer, which is the first layer of the highly reflective layer, was formed using Al ₂ O ₃ . From 0 second (point C1) to point C2, an anode voltage of 112.5 V was applied between the ion gun and the semiconductor laser bar. Thereby, the energy of argon ion became 90.0 eV from 0 second (point D1) to point D2. Between the point C1 and the point C2, the shutter of the ion assist vapor deposition apparatus was opened for 441 seconds. Thus, a second dielectric layer having a thickness of 220.1 nm was formed on the second end face while irradiating argon ions having an energy of 90.0 eV toward the second end face.

Subsequently, the fourth dielectric layer and the fifth dielectric layer were alternately formed to form the second to sixth layers of the highly reflective layer. The fourth dielectric layer was formed by using TiO _2. The fifth dielectric layer was formed using Al ₂ O ₃ . An anode voltage of 68.8 V was applied between the ion gun and the semiconductor laser bar between points C3 and C8. Thereby, between the point D3 and the point D8, the energy of argon ion became 55.0 eV, respectively.

  Between the point C3 and the point C4, the shutter of the ion assist vapor deposition apparatus was opened for 293 seconds. Thus, a 140.7 nm fourth dielectric layer was formed while irradiating argon ions having energy of 55.0 eV toward the second end face. Next, the shutter of the ion assist vapor deposition apparatus was opened for 422 seconds between point C4 and point C5. Thereby, a 210.3 nm fifth dielectric layer was formed while irradiating argon ions having energy of 55.0 eV toward the second end face. Next, the shutter of the ion assist vapor deposition apparatus was opened for 290 seconds between points C5 and C6. Thus, a fourth dielectric layer of 138.8 nm was formed while irradiating argon ions having energy of 55.0 eV toward the second end face. Next, the shutter of the ion assist vapor deposition apparatus was opened for 416 seconds between point C6 and point C7. As a result, a 204.9 nm fifth dielectric layer was formed while irradiating argon ions having energy of 55.0 eV toward the second end face. Next, the shutter of the ion assist vapor deposition apparatus was opened for 270 seconds between points C7 and C8. Thus, a 128.4 nm fourth dielectric layer was formed while irradiating argon ions having energy of 55.0 eV toward the second end face.

  Next, the semiconductor laser bar was separated into individual semiconductor laser elements. In this way, 20 semiconductor laser elements were produced.

(Comparative Example 1)
As Comparative Example 1, 20 semiconductor laser elements were prepared. The semiconductor laser element of Comparative Example 1 differs from the semiconductor laser element of Example 1 only in the formation conditions of the low reflection layer and the high reflection layer.

  FIG. 12 is a diagram illustrating the formation conditions of the first dielectric layer and the third dielectric layer of Comparative Example 1 by the forming material and the ion-assisted deposition method. FIG. 13 is a diagram showing temporal changes in the anode voltage and the energy of argon ions irradiated on the first end face when the low reflective layer of Example 1 is formed.

The low reflective layer of Comparative Example 1 is formed of the same material as the low reflective layer of Example 1. However, the conditions for forming the first dielectric layer of the low reflective layer of Comparative Example 1 are different from those of Example 1. As shown in FIGS. 12 and 13, in Comparative Example 1, an anode voltage of 56.7 V was applied between the ion gun and the semiconductor laser bar from the point A1 _X to the point A2 _X. Thereby, the energy of the argon ion became 45.4 eV from the point B1 _X to the point B2 _X. Between the point A1 _X and the point A2 _X , the shutter of the ion assist vapor deposition apparatus was opened for 259 seconds. As a result, a first dielectric layer having a thickness of 128.8 nm was formed on the first end face while irradiating argon ions having energy of 45.4 eV toward the first end face.

  FIG. 14 is a diagram showing the formation conditions of the second dielectric layer, the fourth dielectric layer, and the fifth dielectric layer of Comparative Example 1 by the forming material and the ion-assisted deposition method. FIG. 15 is a diagram showing temporal changes in the anode voltage and the energy of argon ions irradiated on the second end face when the high reflection layer of Comparative Example 1 is formed.

The highly reflective layer of Comparative Example 1 is formed of the same material as the highly reflective layer of Example 1. However, the conditions for forming the second dielectric layer of the highly reflective layer of Comparative Example 1 are different from those of Example 1. As shown in FIGS. 14 and 15, in Comparative Example 1, an anode voltage of 68.8 V was applied between the ion gun and the semiconductor laser bar from the point C1 _X to the point C2 _X. Thereby, the energy of the argon ion became 55.0 eV from the point D1 _X to the point D2 _X. Between the point C1 _X and the point C2 _X , the shutter of the ion assist vapor deposition apparatus was opened for 441 seconds. Thus, a third dielectric layer having a thickness of 220.1 nm was formed on the second end face while irradiating argon ions having energy of 55.0 eV toward the second end face.

(Comparative Example 2)
As Comparative Example 2, 20 semiconductor laser elements were produced. The semiconductor laser device of Comparative Example 2 differs from the semiconductor laser device of Example 1 only in the conditions for forming the highly reflective layer. The highly reflective layer of Comparative Example 2 was the same as that of Comparative Example 1.

(Comparative Example 3)
As Comparative Example 3, 20 semiconductor laser elements were produced. The semiconductor laser device of Comparative Example 3 differs from the semiconductor laser device of Example 1 only in the conditions for forming the low reflection layer. The low reflective layer of Comparative Example 3 was the same as Comparative Example 1.

(ESD characteristics test)
About Example 1 and Comparative Examples 1-3, the ESD characteristic test of each 20 semiconductor laser elements was done. FIG. 16 is a flowchart showing main steps of the ESD characteristics test method.

  As shown in the flowchart 200 of FIG. 16, the ESD characteristic test method includes an initial test voltage setting step S201, a forward ESD test step S203, a laser characteristic deterioration determination step S205, and a test voltage A step S207 for raising and a step S209 for ending the ESD characteristic test are provided.

  In step S201, the amplitude value of the pulse voltage when performing the ESD test is set for each semiconductor laser element.

  In step S203, an ESD test in the forward direction of each semiconductor laser element is performed. Specifically, a capacitor having a capacity of 100 pF is connected to each semiconductor laser element via a resistor of 1.5 kΩ. After this capacitor is charged, each semiconductor laser element is discharged in the forward direction to apply a pulse voltage. Such a pulse voltage is applied five times.

  In step S205, it is determined whether or not the laser characteristics of each semiconductor laser element have deteriorated. This determination is made based on the voltage value when 10 μA flows in the reverse direction.

  If it is determined in step S205 that there is no deterioration in laser characteristics, the test voltage is increased in step S207. Then, steps S203, S205, and S207 are repeated until it is determined in step S203 that the laser characteristics have deteriorated. After it is determined in step S203 that the laser characteristics have deteriorated, application of the test voltage is stopped in step S209, and the ESD test is terminated.

  FIG. 17 is a diagram showing ESD characteristic test results for Example 1 and Comparative Examples 1 to 3. The horizontal axis of FIG. 17 shows the test voltage value applied to each semiconductor laser element during the ESD characteristic test, and the vertical axis of FIG. 17 shows the defect rate of the semiconductor laser elements of Example 1 and Comparative Examples 1 to 3. Show.

  As shown in FIG. 17, in the semiconductor laser device of Example 1, when the test voltages were 1.0 kV, 1.5 kV, and 2.0 kV, the defect rates were all 0%. When the test voltages were 2.5 kV and 3.0 kV, the defect rates were 5%, respectively. Thereby, it was found that the semiconductor laser element of Example 1 had high ESD characteristics.

  On the other hand, in the semiconductor laser elements of Comparative Examples 1 to 3, the defect rate was higher than that of the semiconductor laser element of Example 1 at any test voltage. Thereby, it was found that the semiconductor laser element of Example 1 had higher ESD characteristics than the semiconductor laser elements of Comparative Examples 1 to 3.

It is a flowchart which shows the main processes of the manufacturing method of the semiconductor laser which concerns on embodiment. It is sectional drawing which shows a semiconductor epitaxial wafer. It is a perspective view of a part of a semiconductor laser bar. It is a figure which shows typically an example of an ion assist vapor deposition apparatus. It is sectional drawing of a semiconductor laser bar. It is sectional drawing of a semiconductor laser bar. It is a perspective view of a semiconductor laser element. It is a figure which shows the formation conditions by the ion-assisted vapor deposition method of the 1st dielectric material layer of Example 1, and a 3rd dielectric material layer. It is a figure which shows the time change of the energy of the argon voltage irradiated to the anode voltage and the 1st end surface at the time of forming the low reflective layer of Example 1. FIG. It is a figure which shows the formation conditions by the formation material and ion assist vapor deposition of the 2nd dielectric material layer of Example 1, a 4th dielectric material layer, and a 5th dielectric material layer. It is a figure which shows the time change of the energy of the argon voltage irradiated to an anode voltage and a 2nd end surface at the time of forming the highly reflective layer of Example 1. FIG. It is a figure which shows the formation conditions by the ion-assisted vapor deposition method of the formation material and the 1st dielectric material layer of a comparative example 1, and a 3rd dielectric material layer. It is a figure which shows the time change of the energy of the argon ion irradiated to an anode voltage and a 1st end surface at the time of forming the low reflective layer of Example 1. FIG. It is a figure which shows the formation conditions by the formation material and ion assist vapor deposition of the 2nd dielectric material layer of a comparative example 1, a 4th dielectric material layer, and a 5th dielectric material layer. It is a figure which shows the time change of the energy of the argon ion irradiated to an anode voltage and a 2nd end surface at the time of forming the highly reflective layer of the comparative example 1. FIG. It is a flowchart which shows the main processes of an ESD characteristic test method. It is a figure which shows the ESD characteristic test result about Example 1 and Comparative Examples 1-3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Semiconductor laser bar, 2a ... 1st end surface, 2b ... 2nd end surface, 21 ... 1st coating (low reflection layer), 21a ... 1st dielectric material layer (aluminum oxide layer) , 23 ... second coating (high reflection layer), 23a ... second dielectric layer (aluminum oxide layer), 50 ... semiconductor laser, S105 ... step of forming the semiconductor laser bar 2, S107 A step of forming a first coating on the first end surface, a step of forming a first dielectric layer on the first end surface, a step of forming a second coating on the second end surface, S115 .. The step of forming the second dielectric layer 2 on the second end face.

Claims (6)

Forming a semiconductor laser bar including an active layer for generating laser light;
Forming a first coating on a first end face of the semiconductor laser bar;
Forming a second coating on a second end face opposite to the first end face of the semiconductor laser bar;
With
The step of forming the first coating includes a step of forming a first dielectric layer on the first end face while irradiating ions having energy of 60 eV or more toward the first end face by an ion-assisted deposition method. Including
The step of forming the second coating includes a step of forming a second dielectric layer on the second end face while irradiating ions having energy of 90 eV or more toward the second end face by ion-assisted deposition. A method of manufacturing a semiconductor laser, comprising: Forming the first coating further includes forming a third dielectric layer having a refractive index different from that of the first dielectric layer on the first dielectric layer;
The step of forming the second coating further includes a step of alternately forming a fourth dielectric layer and a fifth dielectric layer having different refractive indexes on the second dielectric layer. A method for manufacturing a semiconductor laser according to claim 1. The first dielectric layer is made of aluminum oxide,
3. The method of manufacturing a semiconductor laser according to claim 1, wherein the second dielectric layer is made of aluminum oxide. The first dielectric layer is made of aluminum oxide,
The second dielectric layer is made of aluminum oxide,
The third dielectric layer is made of titanium oxide,
The fourth dielectric layer is made of titanium oxide,
The method of manufacturing a semiconductor laser according to claim 2, wherein the fifth dielectric layer is made of aluminum oxide.   The method of manufacturing a semiconductor laser according to claim 1, wherein the first coating is a low reflection layer of the semiconductor laser. The method of manufacturing a semiconductor laser according to claim 1, wherein the second coating is a highly reflective layer of the semiconductor laser.

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