JP5531584B2 - Surface emitting laser manufacturing method, surface emitting laser, surface emitting laser array element, optical scanning device, and image forming apparatus - Google Patents

Description

  The present invention relates to a surface emitting laser manufacturing method, a surface emitting laser, a surface emitting laser array element, an optical scanning device, and an image forming apparatus.

  A VCSEL (Vertical Cavity Surface Emitting Laser) is a semiconductor laser that emits light in a direction perpendicular to the substrate to be formed. It is less expensive than an edge-emitting semiconductor laser and can be two-dimensionally arrayed. Since it can be performed relatively easily and has high performance, it is used in applications such as light sources for optical communication such as optical interconnection, light sources for optical pickups, and light sources for image forming apparatuses such as laser printers. .

  A surface emitting laser is, for example, a lower DBR (Distributed Bragg Reflector) reflector made of an n-type semiconductor multilayer film, a lower spacer layer, a multiple quantum well active layer, an upper spacer layer, a p-type semiconductor multilayer film on an n-type GaAs substrate. The upper DBR reflecting mirror and the contact layer are sequentially stacked by epitaxial growth, and a mesa structure is formed by etching the stacked semiconductor layer in a predetermined region in a direction perpendicular to the substrate surface of the n-type GaAs substrate. An insulator film is formed on the side surface of the structure and the etched region, and laser light is emitted from a light emitting surface opened on the upper surface of the mesa structure. A surface-emitting laser array in which such surface-emitting lasers are integrated one-dimensionally or two-dimensionally is called a surface-emitting laser array.

  The surface-emitting laser formed in this way is expected to have a structure in which a current confinement layer is formed between a part of the upper RBR reflecting mirror or between the upper reflecting mirror and the upper spacer layer. Such a current confinement layer is also called a selective oxidation type VCSEL because it forms a current confinement structure by selectively oxidizing the periphery of an AlAs layer formed by crystal growth. Such a selective oxidation type VCSEL can reduce a threshold current value, power consumption, etc., and can obtain favorable laser characteristics.

  In such a surface emitting laser, since the active layer has a structure sandwiched between a lower DBR reflecting mirror and an upper DBR reflecting mirror made of a semiconductor multilayer film having high thermal resistance, the temperature of the active layer is increased by laser oscillation. Tend to be higher. When the temperature of the surface emitting laser is increased, the light output is saturated and the light output is lowered.

  In addition, the semiconductor layer formed on the n-type GaAs substrate is a layer containing a large amount of Al, and is easily oxidized due to the influence of moisture and the like, and various measures are taken to improve reliability. ing.

  In Patent Document 1, an element isolation groove that reaches the substrate is formed in a chip dividing line, a side surface of the lower BDR reflector is exposed, and a passivation film made of a dielectric is formed in a region including the side surface of the lower BDR reflector. A method of dividing into chips after forming is disclosed.

  Further, in Patent Document 2, an element isolation groove that reaches the substrate is formed in a chip dividing line, a side surface of the lower BDR reflector is exposed, and a metal film is formed in a region including the side surface of the lower BDR reflector. A method is disclosed.

  Patent Document 3 discloses a method of using AlAs having a lower thermal resistance than AlGaAs as a low refractive index layer of the lower DBR as a method of suppressing the temperature rise of the active layer.

  Patent Document 4 discloses a structure in which a heat dissipation layer is provided in order to dissipate heat generated during laser oscillation and stabilize characteristics. The heat dissipation layer is formed in the vicinity of the multiple quantum well active layer in the lower DBR reflector made of an n-type semiconductor multilayer film. The thickness of several layers of the low refractive index layers in the lower DBR reflector is changed to a laser. When the oscillation wavelength is λ, the optical length is formed to be thicker than λ / 4.

  Incidentally, the surface emitting lasers described in the cited documents 1 to 4 have the following problems.

  FIG. 1 shows a cross-sectional structure of a conventional surface-emitting laser, FIG. 1 (a) is a cross-sectional view showing one chip of a surface-emitting laser array, and FIG. It is an enlarged view in the area | region 1A of 1 (a).

  The surface emitting laser includes a buffer layer 411 on an n-type GaAs substrate 410, a lower DBR reflecting mirror 412 made of a laminated film of an n-type semiconductor, a spacer layer 413, an active layer 414 having a multiple quantum well structure, a spacer layer 415, a current A confinement layer 416, an upper DBR reflecting mirror 417 made of a laminated film of a p-type semiconductor, and a contact layer 418 are laminated. After the mesa structure 430 is formed, the current confinement layer 416 is selectively oxidized to form a peripheral portion. A selective oxidation region 416a and a non-oxidized current confinement region 416b are formed. A protective film 421 is formed on the side surface of the mesa structure 430, the surface etched to form the mesa structure 430, the side surface of the element isolation groove 431, and the like. The p-side electrode 422 is formed on the protective film 421 in contact with the contact layer 418, and an opening region 423 is formed on the contact layer 418 in the upper surface portion of the mesa structure 419. An n-side electrode 424 is formed on the back surface of the n-type GaAs substrate 410. In the surface-emitting laser having such a configuration, laser current is oscillated by passing a current through the n-side electrode 424 and the p-side electrode 422, and light is emitted from the opening region 423.

  The element isolation groove 431 is formed until the substrate surface of the n-type GaAs substrate 410 is exposed, and is separated from adjacent chips by the element isolation groove 431. The protective film 421 is formed on the side surface of the element isolation trench 431 and plays a role as a passivation film.

By the way, the surface emitting semiconductor laser having such a structure has many layers made of III-V group compound semiconductors containing a large amount of Al, such as AlGaAs, and these layers are altered by the oxidation of Al by moisture or the like. It's easy to do. For example, the DBR reflector is formed by alternately laminating several tens of low refractive index layers and high refractive index layers. As the low refractive index layer, Al _0.9 Ga _0.1 As is used. In this case, Al _0.3 Ga _0.7 As is used as the high refractive index layer. For this reason, Al _0.9 Ga _0.1 As used as the low refractive index layer has a large Al composition and is easily affected by moisture and the like.

  For this reason, in the method disclosed in Patent Document 1, when the dielectric film to be formed has pinholes or the like, moisture or the like enters through the pinholes and oxidizes the semiconductor film. In particular, in a high temperature and high humidity environment, it is extremely difficult to ensure reliability.

  Further, in the method disclosed in the cited document 2, when a metal film to be formed has a pinhole, moisture or the like enters through the pinhole. For this reason, although it is described that it is possible to cope with the problem by forming the metal film into two layers, forming the two metal films increases the number of steps, leading to an increase in manufacturing cost.

  Further, in the method disclosed in Patent Document 3, although the heat dissipation effect is enhanced by forming the low refractive index layer of the DBR reflector with AlAs, the moisture resistance is lower than that of AlGaAs, and the pin is attached to the passivation film or the like. When holes are generated, the reliability of the surface emitting laser is lowered due to the intrusion of moisture or the like.

  In addition, in the method disclosed in Patent Document 4, since the low refractive index layer in the lower DBR reflecting mirror is formed thick, the heat dissipation effect can be enhanced, but the film thickness of the low refractive index layer having a high Al composition. Therefore, when moisture or the like enters, oxidation is more likely to spread, and the reliability of the surface emitting laser is reduced.

By the way, the passivation film is mainly made of SiO ₂ or SiN as the dielectric, and is generally formed by plasma CVD (P-CVD). However, the SiO ₂ film or SiN film formed by plasma CVD tends to cause pinholes, and it is extremely difficult to obtain an SiO ₂ film or SiN film without pinholes.

  In order to obtain a film without pinholes, it is conceivable to form a passivation film in two layers. However, when a film is formed, the film to be formed is easily affected by the base, and the first layer If pinholes are present in the film, the second-layer film tends to be formed with the influence of the pinholes, which is not sufficient as a method for obtaining a film without pinholes. Furthermore, in order to prevent the influence of the first layer film as much as possible, a method of forming the second layer film after roughening the surface of the first layer film can be considered, but in order to roughen the surface of the first layer film, After the formation of the first layer, it is necessary to remove the first layer from the chamber and perform an etching process, pure water cleaning, or the like, which may damage the first layer. Further, when such a process is performed, the number of processes increases, the throughput decreases, and the manufacturing cost increases.

  The present invention has been made in view of the above, and provides a highly reliable surface-emitting laser having a configuration that prevents intrusion of moisture and the like, and has a particularly high heat dissipation effect even at high temperatures and high humidity. An object of the present invention is to provide a highly reliable surface-emitting laser, and further to provide a highly reliable surface-emitting laser array, optical scanning device, and image forming apparatus. It is.

The present invention is different from a lower reflector formed by alternately laminating semiconductor films having different refractive indexes on a surface of a semiconductor substrate, an active layer made of a semiconductor film, and a current confinement layer made of a semiconductor film. By etching a part of the semiconductor film formed by the semiconductor layer forming step of forming the upper reflecting mirror formed by alternately laminating the semiconductor films of refractive index by epitaxial growth and the semiconductor layer forming step, A mesa structure forming step for forming a mesa structure, an element isolation groove forming step for forming an element isolation groove by etching the semiconductor film formed by the semiconductor layer formation step to the surface of the semiconductor substrate, and the element isolation groove An insulator protective film forming step of forming an insulator protective film made of an insulator on the wall surface of the metal, and a metal protective film made of a metal material on the insulator protective film A metal film forming step of forming, was closed, the lower refractive layers in the bottom DBR is formed of AlAs, after the device isolation trench forming step, the lower reflector at the wall of the device isolation trench It has an oxide film forming step of forming an oxide film by oxidizing the wall surface of the low refractive index layer, and an insulator protective film forming step is performed after the oxide film forming step .

The present invention also provides a lower reflector formed by alternately stacking semiconductor films having different refractive indexes on the surface of a semiconductor substrate, an active layer made of a semiconductor film, a current confinement layer made of a semiconductor film, Etching a part of the semiconductor film formed by the semiconductor layer forming step of forming an upper reflector formed by alternately stacking semiconductor films of different refractive indexes by epitaxial growth, and the semiconductor layer forming step; A mesa structure forming step for forming a mesa structure, an element isolation groove forming step for forming an element isolation groove by etching the semiconductor film formed by the semiconductor layer forming step to the surface of the semiconductor substrate, and the element An insulator protective film forming step of forming an insulator protective film made of an insulator on a wall surface of the separation groove; and a metal made of a metal material on the insulator protective film A metal film forming step of forming a Mamorumaku, wherein the low refractive index layer in the lower reflector is formed by a AlAs, after the device isolation trench forming step, said at wall surface of the device isolation trench bottom the surface of the wall of the low refractive index layer of the reflection mirror is passivated by oxidation treatment, has a higher oxide film formed engineering of forming an oxide film serving as the AlxAsyOz layer and AlxOy layer on the wall surface, said oxide film An insulator protective film forming step is performed after the forming step.

  In the present invention, the surface-emitting laser has an upper electrode connected to the upper reflector side and a lower electrode formed on the back surface of the semiconductor, and the upper electrode and the metal protective film include the metal It is characterized by being formed simultaneously in the film forming step.

The present invention also provides a lower reflector formed by alternately laminating semiconductor films having different refractive indexes on the surface of a semiconductor substrate, and an active layer made of a semiconductor material on the lower reflector. A current confinement layer in which a current confinement structure is formed by oxidizing a partial region of a semiconductor material on the active layer and a semiconductor film having a different refractive index are alternately laminated on the current confinement layer. has an upper reflector formed by a part of the semi-conductor film to form a mesa structure by etching, the lower electrode on the semiconductor substrate, an upper electrode is connected to the upper reflector In a surface-emitting laser that emits laser light substantially perpendicularly to the semiconductor substrate surface by passing a current between the upper electrode and the lower electrode, the lower portion on the semiconductor substrate In the projection mirror, the active layer, the current confinement layer, and the upper reflecting mirror, an element isolation groove for element isolation is formed, and an insulator protection made of an insulator is formed on a wall surface of the element isolation groove. A metal protective film made of a metal material is formed on the film and the insulator protective film, and the low refractive index layer in the lower reflecting mirror is formed of AlAs, A part or all of the low refractive index layer is a layer having an odd multiple of λ / 4 and a film thickness of 3λ / 4 or more when the emission wavelength of the surface-emitting laser is λ, After forming the isolation groove, an oxide film is formed by oxidizing the surface of the wall surface of the lower refractive index layer of the lower reflecting mirror on the wall surface of the element isolation groove, and the insulator protective film is JP that you have been formed on the oxide film To.
The present invention also provides a lower reflector formed by alternately laminating semiconductor films having different refractive indexes on the surface of a semiconductor substrate, and an active layer made of a semiconductor material on the lower reflector. A current confinement layer in which a current confinement structure is formed by oxidizing a partial region of a semiconductor material on the active layer and a semiconductor film having a different refractive index are alternately laminated on the current confinement layer. And forming a mesa structure by etching a part of the semiconductor film, the lower electrode is connected to the semiconductor substrate, and the upper electrode is connected to the upper reflector, In a surface-emitting laser that emits laser light substantially perpendicularly to the semiconductor substrate surface by passing a current between the upper electrode and the lower electrode, the lower portion on the semiconductor substrate In the projection mirror, the active layer, the current confinement layer, and the upper reflecting mirror, an element isolation groove for element isolation is formed, and an insulator protection made of an insulator is formed on a wall surface of the element isolation groove. A metal protective film made of a metal material is formed on the film and the insulator protective film, and the low refractive index layer in the lower reflecting mirror is formed of AlAs, A part or all of the low refractive index layer is a layer having an odd multiple of λ / 4 and a film thickness of 3λ / 4 or more when the emission wavelength of the surface-emitting laser is λ, After forming the isolation groove, the surface of the low-refractive index layer of the lower reflecting mirror on the wall surface of the element isolation groove is passivated by oxidation treatment to form an AlxAsyOz layer and an AlxOy layer on the wall surface. With a film formed Ri, the insulator protective film is characterized by being formed on the oxide film.

  Further, the present invention is characterized in that the metal protective film is formed of a multilayer film.

  Further, the present invention is characterized in that the metal protective film has the same film configuration as the upper electrode.

  The present invention is characterized in that a plurality of the surface emitting lasers described above are arranged on the same semiconductor substrate.

The present invention also provides an optical scanning device that scans a surface to be scanned with a light beam, the light source unit having the surface-emitting laser array element described above, and a deflecting unit that deflects the light beam from the light source unit; characterized by comprising a scanning optical system that condenses on the surface to be scanned with the light beam deflected by the polarization direction means.

  The present invention further includes at least one image carrier and at least one optical scanning device according to claim 11 that scans the at least one image carrier with a light beam containing image information. It is characterized by that.

  According to the present invention, the image is a color image.

  According to the present invention, it is possible to provide a highly reliable surface-emitting laser having a configuration that prevents intrusion of moisture and the like, and a highly reliable surface-emitting laser that has a high heat dissipation effect even at high temperatures and high humidity. It is another object of the present invention to provide a highly reliable surface-emitting laser array, optical scanning device, and image forming apparatus.

Structure of a conventional surface emitting laser array Sectional drawing of the surface emitting laser array in 1st Embodiment Top view of surface-emitting type laser array in the first embodiment Top view of a surface emitting laser array having another configuration according to the first embodiment Sectional drawing of the surface emitting laser array of another structure in 1st Embodiment Manufacturing process diagram of surface-emitting type laser array in the first embodiment Sectional drawing of the surface emitting laser array in 2nd Embodiment Sectional drawing of the principal part of the surface emitting laser array in 2nd Embodiment Manufacturing process diagram of surface-emitting type laser array in the second embodiment Configuration of an image forming apparatus according to a third embodiment Schematic diagram of optical scanning device in third embodiment Schematic diagram of surface-emitting laser array element in the third embodiment Configuration of an image forming apparatus capable of color printing according to the third embodiment

Embodiments of the present invention will be described [First Embodiment]
The surface-emitting laser and the surface-emitting laser array in the first embodiment will be described. The surface emitting laser and the surface emitting laser array according to the present embodiment are formed of a III-V group compound semiconductor, and a current confinement structure is formed by selectively oxidizing a current confinement layer made of AlAs. It is a 780 nm band surface emitting laser.

(Surface emitting laser and surface emitting laser array)
The surface-emitting laser and the surface-emitting laser array in the present embodiment will be described with reference to FIGS. FIG. 2 shows a cross-sectional structure of the surface-emitting type laser array in the present embodiment, and FIG. 2B is an enlarged view of a region surrounded by a broken line 2A in FIG. FIG. 3 is a top view of the surface emitting laser array according to the present embodiment.

  The surface emitting laser in the present embodiment includes a buffer layer 11, a lower DBR reflecting mirror 12, a lower spacer layer 13, an MQW active layer 14, an upper spacer layer 15, an electric current constriction formed on an n-type GaAs substrate 10 by epitaxial growth. It has a layer 16, an upper DBR reflector 17 and a contact layer 18.

  The n-type GaAs substrate 10 is an inclined substrate, and a buffer layer 11 made of n-type GaAs is formed on the n-type GaAs substrate 10.

The lower DBR reflecting mirror 12 has an optical length of λ / 4 when the laser oscillation wavelength is λ, and has n-type Al _0.9 Ga _0.1 As and n-type Al _0.3 Ga _{0. .7} As is formed by alternately laminating 40.5 pairs, and Se (selenium) is doped as a dopant by 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁸ cm ⁻³ . The lower DBR reflecting mirror 12 is formed by laminating a low refractive index layer and a high refractive index layer, but a layer formed of n-type Al _0.9 Ga _0.1 As is a low refractive index layer. The layer formed of n-type Al _0.3 Ga _0.7 As is a high refractive index layer.

The lower spacer layer 13 is made of non-doped Al _0.6 Ga _0.4 As.

The MQW active layer 14 is formed of a multiple quantum well structure in which Al _0.12 Ga _0.88 As quantum well layers and Al _0.3 Ga _0.7 As barrier layers are alternately stacked.

The upper spacer layer 15 is made of non-doped Al _0.6 Ga _0.4 As.

  The current confinement layer 16 is formed of p-type AlAs and is selectively oxidized later to form a current confinement structure including a selective oxidation region 16a and a current confinement region 16b. The current confinement layer 16 is provided in an upper DBR reflector 17 to be described later, and has an optical length of λ / 4 away from the resonator region constituted by the lower spacer layer 13, the MQW active layer 14, and the upper spacer layer 15. It is formed in the position.

The upper DBR reflecting mirror 17 is formed by alternately stacking 24 pairs of p-type Al _0.9 Ga _0.1 As and p-type Al _0.3 Ga _0.7 As. The upper DBR reflecting mirror 17 is doped with Zn as a dopant by 5 × 10 ¹⁷ cm ^{−3 to} 6 × 10 ¹⁸ cm ⁻³ . The upper DBR reflecting mirror 17 is formed by laminating a low refractive index layer and a high refractive index layer, but a layer formed of p-type Al _0.9 Ga _0.1 As is a low refractive index layer. The layer formed of p-type Al _0.3 Ga _0.7 As is a high refractive index layer.

  The contact layer 18 is formed of a film made of p-type GaAs.

  In the semiconductor layer thus formed, the lower spacer layer 13, the MQW active layer 14, the upper spacer layer 15, the current confinement layer 16, the upper DBR reflector 17 and the contact layer 18 in a predetermined region are etched to form a mesa. The structure 30 is formed, and the AlAs layer which is the current confinement layer 16 is selectively oxidized.

Further, by isolating the buffer layer 11, the lower DBR reflector 12, the lower spacer layer 13, the MQW active layer 14, the upper spacer layer 15, the current confinement layer 16, the upper DBR reflector 17 and the contact layer 18, element isolation is achieved. An element isolation groove 31 is formed, and an insulator protective film 21 made of SiO ₂ or SiN is formed so as to cover the side surface of the mesa structure 30 and the wall surface of the element isolation groove 31.

  The p-side electrode 22 is formed on the insulator protective film 21 in contact with the contact layer 18 and is formed in ohmic contact with the contact layer 18. On the contact layer 18, an opening region 23 for emitting light on which the p-side electrode 22 is not formed is formed. The p-side electrode 22 is connected to the electrode pad 25 by a lead line 24 formed simultaneously with the p-side electrode 22.

  The n-side electrode 27 is provided on the back surface of the n-type GaAs substrate 10 and is formed in ohmic contact with the n-type GaAs substrate 10.

In the surface emitting laser according to the present embodiment, the metal protective film 26 is also formed on the insulator protective film 21 on the side surface of the element isolation groove 31. The metal protective film 26 can be formed at the same time as the p-side electrode 22 is formed, and is composed of a laminated film such as Ti / Pt / Au or Cr / AuZn / Au, and is vacuum deposited. Alternatively, the film is formed by EB (Electron Beam) vapor deposition or the like. The insulator protective film 21 is an insulating film made of SiO ₂ or SiN and has an amorphous structure. On the other hand, the metal protective film 26 is a film having a polycrystalline structure of columnar crystals. For this reason, since the metal protective film 26 is formed without being affected by the insulator protective film 21, pinholes in the insulator protective film 21 can be effectively blocked. In addition, since the metal protective film 26 is a multilayer film of different metals, the metal protective film 26 is further excellent in the effect of closing the pinholes.

  In the surface emitting laser according to the present embodiment, the lower DBR reflecting mirror 12 and the upper DBR reflecting mirror 17 are configured by laminating a high refractive index layer and a low refractive index layer. In order to reduce the electrical resistance at the interface between the low refractive index layer and the low refractive index layer, a composition gradient layer having a thickness of 20 nm in which the composition of AlGaAs is changed is formed at the interface between the high refractive index layer and the low refractive index layer. .

  2 and 3 show a surface-emitting laser array in which surface-emitting lasers are two-dimensionally arranged. As another configuration of the surface-emitting laser array in the present embodiment, FIG. 4 and FIG. 5 shows a surface emitting laser array in which surface emitting lasers are arranged one-dimensionally. 5 is a cross-sectional view taken along broken line 5A-5B in FIG. 4 and 5, the same reference numerals denote the same components as those shown in FIGS. 2 and 3.

(Method for manufacturing surface-emitting laser)
Next, a method for manufacturing the surface-emitting laser and the surface-emitting laser array in the present embodiment will be described with reference to FIG.

  First, as shown in FIG. 6A, an MOCVD (Metal Organic Chemical Vapor Deposition) or MBE (Molecular Beam Epitaxy: molecular beam) is formed on an n-type GaAs substrate 10 which is an inclined substrate. The buffer layer 11, the lower DBR reflecting mirror 12, the lower spacer layer 13, the MQW active layer 14, the upper spacer layer 15, the current confinement layer 16, the upper DBR reflecting mirror 17 and the contact layer 18 are sequentially formed by epitaxial growth.

The lower DBR reflecting mirror 12 includes 40.5 pairs of n-type Al _0.3 Ga _0.7 As serving as a high refractive index layer and n-type Al _0.9 Ga _0.1 As serving as a low refractive index layer alternately. It is formed by stacking. The lower spacer layer 13 is made of undoped Al _0.6 Ga _0.4 As, and the MQW active layer 14 is an Al _0.12 Ga _0.88 As quantum well layer and an Al _0.3 Ga _0.7 As barrier. A multiple quantum well structure is formed by alternately stacking layers, and the upper spacer layer 15 is formed of undoped Al _0.6 Ga _0.4 As. Furthermore, 24 pairs of p-type Al _0.3 Ga _0.7 As serving as a high refractive index layer and p-type Al _0.9 Ga _0.1 As serving as a low refractive index layer are alternately stacked as the upper DBR reflecting mirror 17. The contact layer 18 is formed of p-type GaAs. In the upper DBR reflector 17, a current confinement layer 16 made of p-type AlAs is formed in a region λ / 4 away from the resonator region made of the lower spacer layer 13, the MQW active layer 14 and the upper spacer layer 15. ing.

The MQW active layer 14 has a compressive strain composition, a GaInPAs quantum well active layer with three layers having a band gap wavelength of 780 nm, and a Ga _0.6 In _0.4 having a tensile strain of four layers lattice-matching. A wide band gap material (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P was used as a spacer layer (also referred to as a clad layer) formed by a P barrier layer and confining electrons. It may be a configuration. By adopting such a configuration, the band gap difference between the spacer layer and the quantum well active layer can be greatly increased as compared with the case where the spacer layer for confining carriers is formed of an AlGaAs system. A confinement effect can be obtained.

  Next, as shown in FIG. 6B, a resist pattern 41 is formed, and a mesa structure 30 is formed. Specifically, a photoresist is applied on the contact layer 18, and exposure and development are performed by an exposure apparatus, thereby forming a resist pattern 41 corresponding to the shape of the mesa structure 30. Thereafter, using the resist pattern 41 as a mask, the lower spacer layer 13, the MQW active layer 14, the upper spacer layer 15, the current confinement layer 16, the upper DBR reflector 17 and the contact layer 18 are etched by dry etching such as RIE. A mesa structure 30 is formed. The resist applied on the contact layer 18 is a positive resist and is exposed by contact exposure. As a result, the mesa structure 30 is formed in which the upper surface of the mesa is a square having sides of 20 μm to 25 μm. Note that the inclination angle of the side surface of the mesa structure 30 can be adjusted by adjusting the dry etching conditions. By making the taper shape 70 ° to 80 ° with respect to the substrate surface of the n-type GaAs substrate 10, p Disconnection of the lead electrode 24 and the like from the side electrode 22 can be prevented.

  Next, as shown in FIG. 6C, the resist pattern 41 is removed, and the current confinement layer 16 is selectively oxidized. Specifically, the selective oxidation causes the oxidation to proceed from the side surface of the current confinement layer 16 exposed by the mesa structure 30 by performing a heat treatment in a water vapor atmosphere. As a result, the peripheral portion of the mesa structure 30 is oxidized to form AlxOy, which is an insulator, and the selective oxidation region 16a is formed. A current confinement structure is formed by the selective oxidation region 16a and the non-oxidized current confinement region 16b in the central portion. The current confinement region 16b formed by this selective oxidation is formed in a substantially square shape of 5 μm × 5 μm.

  Next, as shown in FIG. 6D, an element isolation trench 31 is formed. Specifically, a resist pattern 42 (not shown) is formed on a region where the element isolation groove 31 is not formed by applying a photoresist, exposing with an exposure apparatus, and developing. Thereafter, the buffer layer 11, the lower DBR reflector 12, the lower spacer layer 13, the MQW active layer 14, the upper spacer layer 15, the current confinement layer 16, the upper DBR reflector 17 and the contact in the region where the resist pattern 42 is not formed. The element isolation trench 31 is formed by etching and removing the layer 18 by RIE or the like. In addition, the inclination angle of the side surface of the element isolation trench 31 can be adjusted by adjusting the dry etching conditions. By making the taper shape 70 ° to 80 ° with respect to the substrate surface of the n-type GaAs substrate 10, The step coverage in the metal protective film 26 can be improved.

  Next, as shown in FIG. 6E, an insulator protective film 21 is formed. Specifically, after the resist pattern 42 is removed, an insulator protective film 21 made of SiN is formed by P-CVD to a thickness of 150 to 300 nm, and then the resist is applied by applying a photoresist, exposing with an exposure apparatus, and developing. A pattern 43 is formed. The resist pattern 43 has an opening in a region where the scribe line 34 is formed in the contact hole 33 and the element isolation trench 31 on the contact layer 18 on the upper surface of the mesa structure 30. Thereafter, the insulator protective film 21 made of SiN in the openings of the resist pattern 43 is removed by wet etching with BHF (buffered hydrofluoric acid).

  Next, as shown in FIG. 6F, a p-side electrode 22, an electrode pad 25, a metal protective film 26, and an n-side electrode 27 are formed. Specifically, after removing the resist pattern 43, a resist pattern (not shown) is formed again by applying a photoresist, exposing with an exposure apparatus, and developing. This resist pattern is formed in a region where the p-side electrode 22, the electrode pad 25, and the metal protective film 26 are not formed. Thereafter, a metal film made of Cr (9 nm) / AuZn (18 nm) / Au (700 nm) is sequentially formed by EB vapor deposition. Thereafter, the p-side electrode 22, the electrode pad 25, and the metal protective film 26 are formed by removing the metal film on the region where the resist pattern (not shown) is formed by lift-off. Thereby, the metal protective film 26 and the p-side electrode 22 are formed simultaneously.

  Next, the back surface is polished until the thickness of the n-type GaAs substrate 10 becomes 100 μm to 300 μm, and a metal film made of Cr (9 nm) / AuGe (18 nm) / Au (250 nm) is sequentially stacked by EB vapor deposition. Thereby, the n-side electrode 27 is formed. Thereafter, the electrode is subjected to ohmic contact by annealing at 400 ° C. for 5 minutes.

  After that, the surface emitting laser and the surface emitting laser array in the present embodiment are manufactured by separating the elements along a scribe line 34 using a dicing saw or the like.

  The surface-emitting laser and the surface-emitting laser array according to the present embodiment are formed by laminating an insulator protective film 21 made of an insulator and a metal protective film 26 on the side surface of the element isolation groove 31. Even if pinholes or the like are present in the insulator protective film 21, since the pinholes are blocked in the metal protective film 26, moisture or the like can enter the semiconductor film having a high Al composition in the lower DBR reflector 12. Absent. Therefore, it is possible to prevent deterioration of the surface emitting laser and the surface emitting laser array even in a high temperature and high humidity environment, and the reliability can be improved.

In the above description, n-type Al _0.9 Ga _0.1 As is used for the low refractive index layer in the lower DBR reflecting mirror 12, but n-type AlAs may be used. Although n-type AlAs is a material that has a higher heat dissipation effect than n-type Al _0.9 Ga _0.1 As but is easily oxidized, the surface-emitting laser array according to the present embodiment protects an insulator made of an insulator. Since the film 21 and the metal protective film 26 are formed, a surface emitting laser and a surface emitting laser array that can prevent intrusion of moisture and the like, have a high heat dissipation effect, and have high reliability can be obtained. .

[Second Embodiment]
Next, a second embodiment will be described. The present embodiment is a surface-emitting laser and a surface-emitting laser array having configurations different from those of the first embodiment. The surface-emitting laser and the surface-emitting laser array in the present embodiment are formed of a III-V group compound semiconductor, and a current confinement structure is obtained by selectively oxidizing a layer made of AlAs that is a current confinement layer. Is formed and is a 780 nm band-emitting laser.

(Surface emitting laser and surface emitting laser array)
The present embodiment will be described with reference to FIG. FIG. 7A shows a cross-sectional structure of the surface-emitting type laser array in the present embodiment, and FIG. 7B shows an enlargement of the area 7A surrounded by the broken line in FIG. 7A. FIG.

  The surface emitting laser according to the present embodiment includes a buffer layer 111, a lower DBR reflector 112, a lower spacer layer 113, an MQW active layer 114, an upper spacer layer 115, a current confinement formed on an n-type GaAs substrate 110 by epitaxial growth. A layer 116, an upper DBR reflector 117, and a contact layer 118.

  The n-type GaAs substrate 110 is an inclined substrate, and a buffer layer 111 made of n-type GaAs is formed on the n-type GaAs substrate 110.

The lower DBR reflecting mirror 112 is formed by alternately stacking 40.5 pairs of n-type AlAs and n-type Al _0.3 Ga _0.7 As, and Se (selenium) as a dopant is 5 × It is doped with 10 ¹⁷ cm ^{−3 to} 2 × 10 ¹⁸ cm ⁻³ . The lower DBR reflecting mirror 112 is formed by laminating a low refractive index layer and a high refractive index layer, but a layer formed of n-type AlAs becomes a low refractive index layer, and n-type Al _0.3 Ga. A layer formed of _0.7 As becomes a high refractive index layer. In this embodiment, when the laser oscillation wavelength is λ, 37.5 pairs on the buffer layer 111 have a film thickness with an optical length of λ / 4, and the high refractive index layer and the low refractive index layer are In the three pairs close to the MQW active layer 114 and the lower spacer layer 113, the low refractive index layer made of n-type AlAs is formed with a film thickness with an optical length of 3λ / 4. In this manner, a region where the thick low refractive index layer is formed is referred to as a heat dissipation layer 151. The low refractive index layer in the heat dissipation layer 151 is preferably a thick film from the viewpoint of the heat dissipation effect, but may be any film thickness that allows the optical length to be an integral multiple of λ / 4. In addition, the number of low refractive index layers in the heat dissipation layer 151 may be more or less than three.

The lower spacer layer 113 is made of non-doped Al _0.6 Ga _0.4 As.

The MQW active layer 114 is formed of a multiple quantum well structure in which Al _0.12 Ga _0.88 As quantum well layers and Al _0.3 Ga _0.7 As barrier layers are alternately stacked.

The upper spacer layer 115 is made of non-doped Al _0.6 Ga _0.4 As.

  The current confinement layer 116 is formed of p-type AlAs and is selectively oxidized later to form a current confinement structure including a selective oxidation region 116a and a current confinement region 116b. The current confinement layer 116 is provided in an upper DBR reflecting mirror 117 described later, and has an optical length of λ / 4 away from a resonator region constituted by the lower spacer layer 113, the MQW active layer 114, and the upper spacer layer 115. It is formed in the position.

The upper DBR reflecting mirror 117 is formed by alternately stacking 24 pairs of p-type Al _0.9 Ga _0.1 As and p-type Al _0.3 Ga _0.7 As. The upper DBR reflecting mirror 117 is doped with Zn as a dopant by 5 × 10 ¹⁷ cm ^{−3 to} 6 × 10 ¹⁸ cm ⁻³ . The upper DBR reflecting mirror 117 is formed by laminating a low refractive index layer and a high refractive index layer, but a layer formed of p-type Al _0.9 Ga _0.1 As is a low refractive index layer. The layer formed of p-type Al _0.3 Ga _0.7 As is a high refractive index layer.

  The contact layer 118 is formed of a film made of p-type GaAs.

  In the semiconductor layer thus formed, the lower spacer layer 113, the MQW active layer 114, the upper spacer layer 115, the current confinement layer 116, the upper DBR reflector 117, and the contact layer 118 are etched in a predetermined region. After the structure 130 is formed, the AlAs layer that is the current confinement layer 116 is selectively oxidized.

Further, by isolating the buffer layer 111, the lower DBR reflector 112, the lower spacer layer 113, the MQW active layer 114, the upper spacer layer 115, the current confinement layer 116, the upper DBR reflector 117, and the contact layer 118, element isolation is achieved. An element isolation groove 131 is formed, and an insulator protective film 121 made of SiO ₂ or SiN is formed so as to cover the side surface of the mesa structure 130 and the wall surface of the element isolation groove 131.

  The p-side electrode 122 is formed on the insulator protective film 121 so as to be in contact with the contact layer 118 and is in ohmic contact with the contact layer 118. Note that an opening region 123 for emitting light on which the p-side electrode 122 is not formed is formed on the contact layer 118. The p-side electrode 122 is connected to the electrode pad 125 by a lead line formed simultaneously with the p-side electrode 122.

  The n-side electrode 127 is provided on the back surface of the n-type GaAs substrate 110 and is formed in ohmic contact with the n-type GaAs substrate 110.

In the surface emitting laser according to the present embodiment, the metal protective film 126 is also formed on the insulator protective film 121 on the side surface of the element isolation groove 131. The metal protective film 126 can be formed simultaneously with the formation of the p-side electrode 122, and is composed of a laminated film such as Ti / Pt / Au or Cr / AuZn / Au, and is vacuum deposited. Alternatively, the film is formed by EB (Electron Beam) vapor deposition or the like. The insulator protective film 121 is an insulating film made of SiO ₂ or SiN and is an amorphous structure film. On the other hand, the metal protective film 126 is a film having a polycrystalline structure of columnar crystals. For this reason, since the metal protective film 126 is formed without being affected by the insulator protective film 121, pinholes in the insulator protective film 121 can be effectively blocked. In addition, since the metal protective film 126 is a multilayer film of different metals, the metal protective film 126 is further excellent in the effect of closing the pinholes.

In the present embodiment, the low-refractive index layer is passivated in the exposed region of the wall of the element isolation groove 131 in the lower DBR reflecting mirror 112, and thereafter, the insulator protective film 121 and the metal A protective film 126 is formed. Here, the passivation treatment refers to introducing H ₂ O or O ₂ into the chamber and heat-treating the n-type GaAs substrate 110 on which the lower DBR reflector 112 is formed at a temperature of 370 ° C. to 400 ° C. Thus, a thickness of about several hundred nm of the exposed portions of the side surface and the wall surface of the AlAs layer which is a low refractive index layer is made into a stable oxide film. Specifically, an oxide film that becomes AlxOy or AlxAsyOz is formed by oxidizing AlAs constituting the low refractive index layer, and the oxide film thus formed by the passivation treatment has a dense structure. It is a film and can improve moisture resistance.

FIG. 8 is an enlarged view of a region where the heat radiation layer 151 is formed in the lower DBR reflecting mirror 112. The lower DBR reflecting mirror 112 has, on the n-type GaAs substrate 110 side, a low-refractive index layer 112a made of n-type AlAs with a film thickness of λ / 4 and a film thickness with an optical length of λ / 4. A high refractive index layer 112b made of n-type Al _0.3 Ga _0.7 As is laminated. On the other hand, in the MQW active layer 114 side, that is, in the region to be the heat dissipation layer 151, a low refractive index layer 151a made of n-type AlAs having a thickness of 3λ / 4 and a film having an optical length of λ / 4. A high refractive index layer 151b made of a thick n-type Al _0.3 Ga _0.7 As is laminated. The low refractive index layer thus formed is passivated to oxidize the AlAs layer exposed on the wall surface of the element isolation trench 131 and form an oxide film that becomes the AlxAsyOz layer 152 and the AlxOy layer 153. . At this time, depending on the degree of oxidation, the formed AlxOy layer 153 expands to protrude from the wall surface of the element isolation trench 131 (the oxidized portion becomes a convex state).

Thereafter, an insulator protective film 121 made of SiO ₂ or SiN is formed on the wall surface of the element isolation trench 131, and a metal protective film 126 is further formed thereon. Since the metal protective film 126 is formed on the insulator protective film 121, even if a pinhole 121 a or the like is generated in the insulator protective film 121, it can be effectively blocked by the metal protective film 126 formed of a metal multilayer film. it can.

  In the present embodiment, the low refractive index layer in the lower DBR reflecting mirror 112 is formed of AlAs, and the MQW active layer 114 side has a large thickness of the low refractive index layer, thereby obtaining a high heat dissipation effect. Can do. Thereby, a surface emitting laser array having a high heat dissipation effect and high reliability can be obtained.

(Method for manufacturing surface-emitting laser array)
Next, a method for manufacturing the surface emitting laser array in the present embodiment will be described with reference to FIG.

  First, as shown in FIG. 9A, a buffer layer 111, a lower DBR reflector 112, a lower spacer layer 113, an MQW active layer 114, an MOCVD or MBE are formed on an inclined n-type GaAs substrate 110. The upper spacer layer 115, the current confinement layer 116, the upper DBR reflecting mirror 117, and the contact layer 118 are sequentially formed by epitaxial growth.

The lower DBR reflecting mirror 112 includes 40.5 pairs of n-type Al _0.3 Ga _0.7 As serving as a high refractive index layer and n-type Al _0.9 Ga _0.1 As serving as a low refractive index layer alternately. It is formed by stacking. In this embodiment, when the laser oscillation wavelength is λ, 37.5 pairs on the buffer layer 111 have a film thickness with an optical length of λ / 4, and the high refractive index layer and the low refractive index layer are In the three pairs close to the lower spacer layer 113, the low refractive index layer made of n-type AlAs is formed with a film thickness with an optical length of 3λ / 4. The lower spacer layer 113 is made of undoped Al _0.6 Ga _0.4 As, and the MQW active layer 114 is made of an Al _0.12 Ga _0.88 As quantum well layer and an Al _0.3 Ga _0.7 As barrier. Multiple quantum well structures are formed by alternately stacking layers, and the upper spacer layer 115 is formed of undoped Al _0.6 Ga _0.4 As. Further, 24 pairs of p-type Al _0.3 Ga _0.7 As serving as a high refractive index layer and p-type Al _0.9 Ga _0.1 As serving as a low refractive index layer are alternately stacked as the upper DBR reflecting mirror 117. The contact layer 118 is formed of p-type GaAs. In the upper DBR reflector 117, a current confinement layer 116 made of p-type AlAs is formed in a region λ / 4 away from the resonator region made of the lower spacer layer 113, the MQW active layer 114, and the upper spacer layer 115. ing.

The MQW active layer 114 has a compressive strain composition, a GaInPAs quantum well active layer with three layers having a band gap wavelength of 780 nm, and a Ga _0.6 In _0.4 having a tensile strain of four layers lattice-matching. A wide band gap material (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P was used as a spacer layer (also referred to as a clad layer) formed by a P barrier layer and confining electrons. It may be a configuration. By adopting such a configuration, the band gap difference between the spacer layer and the quantum well active layer can be greatly increased as compared with the case where the spacer layer for confining carriers is formed of AlGaAs. A confinement effect can be obtained.

  Next, as shown in FIG. 9B, a resist pattern 141 is formed, and a mesa structure 130 is formed. Specifically, a photoresist is applied on the contact layer 118, and exposure and development are performed by an exposure apparatus, whereby a resist pattern 141 corresponding to the shape of the mesa structure 130 is formed. Thereafter, using the resist pattern 141 as a mask, the lower spacer layer 113, the MQW active layer 114, the upper spacer layer 115, the current confinement layer 116, the upper DBR reflector 117, and the contact layer 118 are etched by dry etching such as RIE. A mesa structure 130 is formed. The resist applied on the contact layer 118 is a positive resist and is exposed by contact exposure. As a result, the mesa structure 130 is formed in which the upper surface portion of the mesa is a square having sides of 20 μm to 25 μm. Note that the inclination angle of the side surface of the mesa structure 130 can be adjusted by adjusting dry etching conditions. By making the taper shape 70 ° to 80 ° with respect to the substrate surface of the n-type GaAs substrate 110, p Disconnection of the lead electrode from the side electrode 122 can be prevented.

  Next, as shown in FIG. 9C, the resist pattern 141 is removed, and the current confinement layer 116 is selectively oxidized. Specifically, the selective oxidation causes the oxidation to proceed from the side surface of the current confinement layer 116 exposed by the mesa structure 130 by performing a heat treatment in a water vapor atmosphere. As a result, the peripheral portion of the mesa structure 130 is oxidized to form an insulator AlxOy, thereby forming a selective oxidation region 116a. A current confinement structure is formed by the selective oxidation region 116a and the non-oxidized current confinement region 116b in the central portion. The current confinement region 116b formed by this selective oxidation is formed in a substantially square shape of 5 μm × 5 μm.

  Next, as shown in FIG. 9D, an element isolation trench 131 is formed. Specifically, a resist pattern 142 (not shown) is formed on a region where the element isolation groove 131 is not formed by applying a photoresist, exposing with an exposure apparatus, and developing. Thereafter, the buffer layer 111, the lower DBR reflecting mirror 112, the lower spacer layer 113, the MQW active layer 114, the upper spacer layer 115, the current confinement layer 116, the upper DBR reflecting mirror 117 and the contact in the region where the resist pattern 142 is not formed. The element isolation trench 131 is formed by etching and removing the layer 118 by RIE or the like. The inclination angle of the side surface of the element isolation trench 131 can be adjusted by adjusting dry etching conditions. By making the taper shape 70 ° to 80 ° with respect to the substrate surface of the n-type GaAs substrate 110, The step coverage in the metal protective film 126 can be improved.

Thereafter, a passivation process is performed to form an oxide film composed of the AlxAsyOz layer 152 and the AlxOy layer 153 on the AlAs layer in the lower DBR reflecting mirror 112 exposed on the wall surface of the element isolation trench 131. In the passivation process, an n-type GaAs substrate 110 in which an element isolation groove 131 is formed is placed in a chamber of an oxidation apparatus (iVOX 3001: manufactured by Epiquest) (the temperature of the substrate holder at this time is 200 ° C.) Water vapor is introduced for 1 second at a flow rate of 80 g / Hr. Thereafter, while introducing N ₂ gas at a flow rate of ₂ SLM, the substrate temperature is raised to 380 ° C., and this state is maintained for 3 minutes, whereby the passivation process shown in FIG. 8 is performed.

  Next, as shown in FIG. 9E, an insulator protective film 121 is formed. Specifically, after the resist pattern 142 is removed, an insulator protective film 121 made of SiN is formed by P-CVD to a thickness of 150 to 300 nm, and then the resist is applied by applying a photoresist, exposing with an exposure apparatus, and developing. A pattern 143 is formed. The resist pattern 143 has an opening in a region where the scribe line 134 is formed in the contact hole 133 and the element isolation trench 131 on the contact layer 118 on the upper surface of the mesa structure 130. Thereafter, the insulator protective film 121 made of SiN in the opening of the resist pattern 143 is removed by wet etching with BHF (buffered hydrofluoric acid).

  Next, as shown in FIG. 9F, a p-side electrode 122, an electrode pad 125, a metal protective film 126, and an n-side electrode 127 are formed. Specifically, after removing the resist pattern 143, a resist pattern (not shown) is formed again by applying a photoresist, exposing with an exposure apparatus, and developing. This resist pattern is formed in a region where the p-side electrode 122, the electrode pad 125, and the metal protective film 126 are not formed. Thereafter, a metal film made of Cr (9 nm) / AuZn (18 nm) / Au (700 nm) is sequentially formed by EB vapor deposition. Thereafter, the p-side electrode 122, the electrode pad 125, and the metal protective film 126 are formed by removing the metal film on the region where the resist pattern (not shown) is formed by lift-off. Thereby, the metal protective film 126 and the p-side electrode 122 are formed simultaneously.

  Next, the back surface is polished until the thickness of the n-type GaAs substrate 110 becomes 100 μm to 300 μm, and a metal film made of Cr (9 nm) / AuGe (18 nm) / Au (250 nm) is sequentially stacked by EB vapor deposition. Thereby, the n-side electrode 127 is formed. Thereafter, the electrode is subjected to ohmic contact by annealing at 400 ° C. for 5 minutes.

  Thereafter, the surface emitting laser array in the present embodiment is manufactured by separating the elements along a scribe line 134 with a dicing saw or the like.

  Since the surface emitting laser array in this embodiment is formed by laminating the insulator protective film 121 and the metal protective film 126 made of an insulator on the side surface of the element isolation groove 131, the insulator protective film Even if there is a pinhole or the like in 121, since the pinhole is blocked in the metal protective film 126, moisture or the like does not enter the semiconductor film having a high Al composition in the lower DBR reflector 112. Therefore, it is possible to prevent the deterioration of the surface emitting laser array even in a high temperature and high humidity environment, and the reliability of the surface emitting laser array can be improved.

  Further, in the surface emitting laser according to the present embodiment, n-type AlAs is used for the low refractive index layer in the lower DBR reflecting mirror 112, and further, the low heat dissipation layer 151 formed in the lower DBR reflecting mirror 112 is low. Since a thick n-type AlAs film is formed in the refractive index layer, the heat dissipation effect is also high.

[Third Embodiment]
Next, a third embodiment will be described. The present embodiment is an image forming apparatus using the surface emitting laser array element according to the present invention, that is, the surface emitting laser array element according to the first embodiment as a light source. This embodiment will be described with reference to FIG.

  A laser printer as an image forming apparatus according to the present embodiment includes an optical scanning device 200, a photosensitive drum 201, a charging charger 202, a developing roller 203, a toner cartridge 204, a cleaning blade 205, a paper feed tray 206, and a paper feed roller 207. A registration roller pair 208, a fixing roller 209, a paper discharge tray 210, a transfer charger 211, a paper discharge roller 212, and a charge removal unit 214.

  Specifically, in the rotation direction of the photosensitive drum 201, the charging charger 202, the developing roller 203, the transfer charger 211, the charge removal unit 214, and the cleaning blade 205 are arranged in the vicinity of the photosensitive drum 201 in this order.

  A photosensitive layer is formed on the surface of the photosensitive drum 201. Here, as shown in the figure, the photosensitive drum 201 is configured to rotate clockwise. The charging charger 202 has a function of uniformly charging the surface of the photosensitive drum 201.

  The optical scanning device 200 irradiates the surface of the photosensitive drum 201 charged by the charging charger 202 with light modulated based on image information from a host device such as a personal computer. By this light irradiation, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 201. The area where the latent image is formed on the surface of the photosensitive drum 201 moves in the direction in which the developing roller 203 is provided as the photosensitive drum 201 rotates. Details of the optical scanning device 200 will be described later.

  The toner cartridge 204 stores toner, and this toner is supplied to the developing roller 203. The developing roller 203 causes the toner supplied from the toner cartridge 204 to adhere to the latent image formed on the surface of the photosensitive drum 201 to visualize the image information on the surface of the photosensitive drum 201. Thereafter, as the photosensitive drum 201 rotates, the area where the toner is attached to the latent image on the surface of the photosensitive drum 201 moves in the direction in which the transfer charger 211 is provided.

  Recording paper 213 is stored in the paper feed tray 206. A paper feed roller 207 is disposed in the vicinity of the paper feed tray 206, and the paper feed roller 207 takes out the recording paper 213 one by one from the paper feed tray 206 and conveys it to the registration roller pair 208. The registration roller pair 208 is disposed in the vicinity of the transfer charger 211, temporarily holds the recording paper 213 taken out by the paper feeding roller 207, and exposes the recording paper 213 in accordance with the rotation of the photosensitive drum 201. It is sent out toward the gap between the body drum 201 and the transfer charger 211.

  To the transfer charger 211, a charge having a polarity opposite to that of the toner on the surface of the photoconductor 201 is applied in order to electrically attract the toner on the surface of the photoconductor drum 201 to the recording paper 213. The toner on the surface of the photosensitive drum 201 is transferred to the recording paper 213 by this charge, that is, an image formed by the toner is transferred to the recording paper 213. Thereafter, the recording paper 213 is sent to the fixing roller 209.

  In the fixing roller 209, heat and pressure are applied to the recording paper 213, whereby the toner is fixed to the recording paper 213. Here, the recording paper 213 on which the image is fixed is sent to the paper discharge tray 210 via the paper discharge roller 212 and is sequentially stacked on the paper discharge tray 210.

  The neutralization unit 214 neutralizes the surface of the photosensitive drum 201. The cleaning blade 205 removes toner (residual toner) remaining on the surface of the photosensitive drum 201. The removed residual toner is configured to be reusable. The surface of the photosensitive drum 201 from which the residual toner has been removed moves again in the direction in which the charging charger 202 is provided.

(Optical scanning device)
Next, the optical scanning device 200 will be described with reference to FIG.

  The optical scanning device 200 includes a light source unit 221, a coupling lens 222, an aperture plate (aperture) 223, a cylindrical lens 224, a polygon mirror 225, an fθ lens 226, a toroidal lens 227, two mirrors 228 and 229, and a shape planning unit. A main controller (not shown) that performs overall control is included.

  The light source unit 221 includes a surface emitting laser array in which a plurality of surface emitting semiconductor lasers in the first embodiment are formed.

  The coupling lens 222 is for making the light beam emitted from the light source unit 221 into substantially parallel light.

  The aperture plate 223 has an aperture and is for defining the beam diameter of the light beam from the coupling lens 222.

  The cylindrical lens 224 condenses the light beam that has passed through the aperture plate 223 on the reflection surface of the polygon mirror 225 via the mirror 228.

  The polygon mirror 225 is formed in a regular hexagonal column shape, and a mirror surface is formed so that the six side surfaces are reflective surfaces. The polygon mirror 225 is rotated at a constant speed in a direction indicated by an arrow by a motor (not shown), and the light beam is deflected at a constant angular velocity with this rotation.

fθ lens 226 has an image height proportional to the angle of incidence of the light beam from the polygon mirror 225, an image plane of the light beam polarized direction at a constant angular velocity by the polygon mirror 225 with respect to the main scanning direction equal Move fast.

  The toroidal lens 227 forms an image of the light flux from the fθ lens 226 on the surface of the photosensitive drum 201 via the mirror 229.

  As shown in FIG. 12, the light source unit 221 includes a surface emitting laser array LA in which surface emitting laser elements (VCSEL) are two-dimensionally arranged in an array. The surface emitting lasers are arranged with a predetermined sufficient interval in the main scanning direction, and the arrangement of the surface emitting lasers in the main scanning direction is arranged with a gap of d2 in the sub scanning direction. In this way, an array arranged in the main scanning direction while being shifted by an interval d2 in the sub scanning direction is formed for each pitch d1 in the sub scanning direction. By arranging in this way, it is possible to make the interval of the perpendiculars perpendicular to the sub-scanning direction from the center of each surface emitting laser equal (interval d2 is equal). Thus, by controlling the lighting timing of each surface emitting laser, the same configuration as when light sources are arranged at narrow regular intervals in the sub-scanning direction on the photosensitive drum 201 can be obtained. .

  For example, when the pitch d1 of the surface emitting semiconductor lasers in the sub-scanning direction is 26.5 μm and ten surface emitting semiconductor lasers are arranged in the main scanning direction, the distance d2 between the surface emitting semiconductor lasers. Is 2.65 μm. If the magnification in the optical system is set to double, writing dots can be formed on the photosensitive drum 201 at intervals of 5.3 μm. This corresponds to 4800 dpi (dots / inch), and high-density writing of 4800 dpi can be performed.

  Further, by increasing the number of surface emitting semiconductor lasers arranged in the main scanning direction, narrowing the pitch d1, and further narrowing the interval d2, it is possible to perform writing with higher density. Note that the writing interval in the main scanning direction can be easily controlled by controlling the lighting timing of the surface emitting semiconductor laser as the light source.

  In the optical scanning device and the image forming apparatus using the same according to the present embodiment, the surface emitting semiconductor laser according to the first embodiment having high reliability is used as the light source. Thus, it is possible to obtain an optical scanning apparatus and an image forming apparatus that have low power consumption, high speed, and high quality.

(Image forming apparatus for forming a color image)
Next, an image forming apparatus for forming a color image will be described with reference to FIG.

  This image forming apparatus is a color laser printer, which is a dandem color machine having a plurality of photosensitive drums for color images.

  This color laser printer includes a black (K) photosensitive drum K1, a charger K2, a developing unit K4, a cleaning unit K5, a transfer charging unit K6, a cyan (C) photosensitive drum C1, and a charging unit. C2, developing unit C4, cleaning unit C5, transfer charging unit C6, magenta (M) photosensitive drum M1, charging unit M2, developing unit M4, cleaning unit M5, transfer charging unit M6, yellow A photosensitive drum Y1 for (Y), a charger Y2, a developing device Y4, a cleaning unit Y5, a transfer charging unit Y6, an optical scanning device 200, a transfer belt 301, a fixing unit 302, and the like are provided.

  In this color laser printer, the optical scanning device 200 has a semiconductor laser for black, a semiconductor laser for cyan, a semiconductor laser for magenta, and a semiconductor laser for yellow. Each semiconductor laser is included in the present invention. It is comprised by the surface emitting semiconductor laser which concerns. The light beam from the black semiconductor laser is irradiated to the black photosensitive drum K1, the light beam from the cyan semiconductor laser is irradiated to the cyan photosensitive drum C1, and the light beam from the magenta semiconductor laser is magenta. The light beam from the yellow semiconductor laser is irradiated to the yellow photosensitive drum Y1, and the light beam from the yellow semiconductor laser is irradiated to the yellow photosensitive drum Y1.

  Each of the photosensitive drums K1, C1, M1, and Y1 rotates in the direction of the arrow, and in the order of the rotation direction, each of the chargers K2, C2, M2, and Y2, the developing devices K4, C4, M4, and Y4, for transfer. Charging means K6, C6, M6, Y6 and cleaning means K5, C5, M5, Y5 are arranged. Each of the chargers K2, C2, M2, and Y2 uniformly charges the surface of the corresponding photosensitive drum K1, C1, M1, and Y1. The charged surface of the photosensitive drums K1, C1, M1, and Y1 is irradiated with a light beam from the optical scanning device 200, and an electrostatic latent image is formed on the surface of the photosensitive drums K1, C1, M1, and Y1. It has become. Thereafter, toner images are formed on the surfaces of the photosensitive drums K1, C1, M1, and Y1 by the developing units K4, C4, M4, and Y4, and the transfer charging units K6, C6, M6, and Y6 corresponding to the toner images are formed. Thus, the toner images of the respective colors are transferred to the recording paper, and the image is fixed on the recording paper by the fixing unit 302. The cleaning means K5, C5, M5, and Y5 remove residual toner remaining on the surfaces of the corresponding photosensitive drums K1, C1, M1, and Y1.

  In this embodiment, the photosensitive drum is described as the image carrier. However, the image carrier may be an image forming apparatus using a silver salt film. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process similar to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by the same process as the printing process in the ordinary silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  Further, an image forming apparatus using a color developing medium (positive photographic paper) that develops color by the heat energy of a beam spot as an image carrier may be used. In this case, a visible image can be directly formed on the image carrier by optical scanning.

  As mentioned above, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

10 n-type GaAs substrate 11 buffer layer 12 lower DBR reflector 13 lower spacer layer 14 active layer (multiple quantum well layer)
15 Upper spacer layer 16 Current confinement layer 16a Selective oxidation region 16b Current confinement region 17 Upper DBR reflector 18 Contact layer 21 Insulator protective film 22 P-side electrode 23 Open region 24 Lead line 25 Electrode pad 26 Metal protective film 27 N-side electrode 30 Mesa structure 31 Element isolation groove

JP 2007-173513 A JP 2009-54855 A JP 2002-164621 A JP 2007-299897 A

Claims (11)

A lower reflector formed by alternately laminating semiconductor films having different refractive indexes on the surface of a semiconductor substrate, an active layer made of a semiconductor film, a current confinement layer made of a semiconductor film, and a semiconductor having a different refractive index A semiconductor layer forming step of forming an upper reflecting mirror formed by alternately stacking films by epitaxial growth;
A mesa structure forming step of forming a mesa structure by etching a part of the semiconductor film formed by the semiconductor layer forming step;
An element isolation groove forming step of forming an element isolation groove by etching the semiconductor film formed by the semiconductor layer forming step to the surface of the semiconductor substrate;
An insulator protective film forming step of forming an insulator protective film made of an insulator on the wall surface of the element isolation groove;
A metal film forming step of forming a metal protective film made of a metal material on the insulator protective film;
I have a,
The low refractive index layer in the lower reflecting mirror is made of AlAs,
After the element isolation groove forming step, an oxide film forming step for forming an oxide film by oxidizing the wall surface of the low refractive index layer of the lower reflecting mirror on the wall surface of the element isolation groove,
A method of manufacturing a surface-emitting laser, wherein an insulator protective film forming step is performed after the oxide film forming step . A lower reflector formed by alternately laminating semiconductor films having different refractive indexes on the surface of a semiconductor substrate, an active layer made of a semiconductor film, a current confinement layer made of a semiconductor film, and a semiconductor having a different refractive index A semiconductor layer forming step of forming an upper reflecting mirror formed by alternately stacking films by epitaxial growth;
  A mesa structure forming step of forming a mesa structure by etching a part of the semiconductor film formed by the semiconductor layer forming step;
  An element isolation groove forming step of forming an element isolation groove by etching the semiconductor film formed by the semiconductor layer forming step to the surface of the semiconductor substrate;
  An insulator protective film forming step of forming an insulator protective film made of an insulator on the wall surface of the element isolation groove;
  A metal film forming step of forming a metal protective film made of a metal material on the insulator protective film;
  Have
  The low refractive index layer in the lower reflecting mirror is made of AlAs,
  After the element isolation groove forming step, passivation is performed by oxidizing the wall surface of the lower refractive index layer of the lower reflecting mirror on the wall surface of the element isolation groove, and an AlxAsyOz layer and an AlxOy layer are formed on the wall surface. An oxide film forming step for forming an oxide film,
  A method of manufacturing a surface-emitting laser, wherein an insulator protective film forming step is performed after the oxide film forming step. The surface-emitting laser has an upper electrode connected to the upper reflector side and a lower electrode formed on the semiconductor back surface,
3. The surface emitting laser manufacturing method according to claim 1, wherein the upper electrode and the metal protective film are formed simultaneously in the metal film forming step. A lower reflector formed by alternately laminating semiconductor films of different refractive indexes on the surface of a semiconductor substrate;
On the lower reflector, an active layer made of a semiconductor material;
On the active layer, a current confinement layer in which a current confinement structure is formed by oxidizing a partial region of a semiconductor material;
On the current confinement layer, an upper reflector formed by alternately stacking semiconductor films having different refractive indexes;
Has a portion of the semi-conductor film to form a mesa structure by etching, the lower electrode on the semiconductor substrate, wherein the upper electrode is connected to the upper reflector, the upper electrode and the lower electrode In a surface emitting laser that emits a laser beam substantially perpendicular to the semiconductor substrate surface by passing a current between them,
In the lower reflector, the active layer, the current confinement layer, and the upper reflector on the semiconductor substrate, an element isolation groove for element isolation is formed,
On the wall surface of the element isolation groove, an insulator protective film made of an insulator and a metal protective film made of a metal material are formed on the insulator protective film ,
The low refractive index layer in the lower reflecting mirror is made of AlAs,
A part or all of the low refractive index layer in the lower reflecting mirror is a layer having an odd multiple of λ / 4 and a film thickness of 3λ / 4 or more when the emission wavelength of the surface emitting laser is λ. And
After forming the element isolation groove, an oxide film is formed by oxidizing the surface of the wall surface of the low refractive index layer of the lower reflecting mirror in the wall surface of the element isolation groove,
The insulator protective film, surface emitting laser characterized that you have formed on the oxide film.   A lower reflector formed by alternately laminating semiconductor films of different refractive indexes on the surface of a semiconductor substrate;
  On the lower reflector, an active layer made of a semiconductor material;
  On the active layer, a current confinement layer in which a current confinement structure is formed by oxidizing a partial region of a semiconductor material;
  On the current confinement layer, an upper reflector formed by alternately stacking semiconductor films having different refractive indexes;
  A mesa structure is formed by etching a part of the semiconductor film, a lower electrode is connected to the semiconductor substrate, an upper electrode is connected to the upper reflector, and the upper electrode is connected to the lower electrode. In a surface emitting laser that emits a laser beam substantially perpendicular to the semiconductor substrate surface by passing a current through
  In the lower reflector, the active layer, the current confinement layer, and the upper reflector on the semiconductor substrate, an element isolation groove for element isolation is formed,
  On the wall surface of the element isolation groove, an insulator protective film made of an insulator and a metal protective film made of a metal material are formed on the insulator protective film,
  The low refractive index layer in the lower reflecting mirror is made of AlAs,
  A part or all of the low refractive index layer in the lower reflecting mirror is a layer having an odd multiple of λ / 4 and a film thickness of 3λ / 4 or more when the emission wavelength of the surface emitting laser is λ. And
  After forming the element isolation groove, a passivation process is performed by oxidizing the wall surface of the low refractive index layer of the lower reflecting mirror on the wall surface of the element isolation groove, and an AlxAsyOz layer and an AlxOy layer are formed on the wall surface. Formed an oxide film,
  The surface-emitting laser, wherein the insulator protective film is formed on the oxide film. The metallic protective film surface emitting laser according to claim 4 or 5, characterized in that is formed by the multilayer film. The surface emitting laser according to claim 6 , wherein the metal protective film has the same film configuration as the upper electrode. Surface emitting laser according to any one of claims 4 to 7 is, surface emitting laser array device characterized by being arrayed on the same semiconductor substrate. An optical scanning device that scans a surface to be scanned with a light beam,
A light source unit comprising the surface emitting laser array element according to claim 8 ;
Deflecting means for deflecting the light beam from the light source unit;
A scanning optical system for focusing the light beam deflected by said polarization deflecting means on a surface to be scanned,
An optical scanning device comprising: At least one image carrier;
The optical scanning device according to claim 9 , wherein the at least one image carrier is scanned with a light beam including image information;
An image forming apparatus comprising: The image forming apparatus according to claim 10 , wherein the image is a color image.

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