JP2013187516A - Manufacturing method, surface light-emitting laser element, surface light-emitting laser eye, optical scanner, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a surface light-emitting laser element capable of improving yield.SOLUTION: A manufacturing method of a surface light-emitting laser element includes the steps of: forming a plurality of semiconductor layers on a substrate 101; etching a part of the plurality of semiconductor layers to form a mesa; forming a protective layer 111 on the mesa; forming an inclined member 124 that contacts the protective layer 111 covering a part of an inclined surface of the mesa, and has an inclined surface inclined to the substrate 101; forming a wiring member on the inclined surface of the inclined member 124; and removing the inclined member 124.

Description

  The present invention relates to a manufacturing method, a surface emitting laser element, a surface emitting laser array, an optical scanning apparatus, and an image forming apparatus. More specifically, the manufacturing method for manufacturing a surface emitting laser element, and the surface emitting manufactured by the manufacturing method. The present invention relates to a laser element and a surface emitting laser array, an optical scanning device having the surface emitting laser element or the surface emitting laser array, and an image forming apparatus including the optical scanning device.

  BACKGROUND ART A vertical cavity surface emitting laser (VCSEL) is a semiconductor laser element that emits light in a direction perpendicular to a substrate, and is an edge emitting that emits light in a direction parallel to the substrate. Compared with conventional semiconductor laser devices, it has the following features: (1) low price, (2) low power consumption, (3) small size and high performance, and (4) easy two-dimensional integration. Yes.

  For example, Patent Document 1 discloses that a first conductor layer whose upper surface indicates a first conductivity type, a second conductor layer whose upper surface indicates a second conductivity type different from the first conductivity type, and sides of the upper surface of the first conductor layer An insulating layer that covers at least a part of the edge and at least a part of the edge of the upper surface of the second conductor layer and has an inclined portion that descends toward the upper surface of the first conductor layer, and one end of the first conductor A first electrode formed on the layer and having the other end formed on the inclined portion; a second electrode formed on the second conductor layer; and a peripheral electrode formed on the insulating layer; A terminal electrode for applying a voltage to one conductor layer; and a third electrode formed on the insulating layer and the first and second electrodes and connecting the first electrode and the terminal electrode via the second electrode. An electrode structure characterized by this is disclosed.

  In Patent Document 2, a second electrode is formed on the upper surface of the light emitting region, has an opening above the current path narrowing portion, and forms a current path that passes through the current path narrowing portion and reaches the first electrode. And a third electrode formed on the periphery of the multilayer structure, and a plurality of conductors interconnecting the second and third electrodes above the shallow portion of the recess, A surface-emitting semiconductor light-emitting element that emits light in a direction perpendicular to the first and second main surfaces is disclosed.

  However, it has been difficult to improve the yield by the conventional manufacturing method.

  The present invention relates to a method of manufacturing a surface emitting laser element in which a mesa-shaped light emitting portion in which a plurality of semiconductor layers are stacked and an electrode are electrically connected by a wiring member, and the plurality of semiconductors on a substrate Forming a layer; etching a part of the plurality of semiconductor layers to form the mesa; forming a protective layer on the mesa; and an inclined surface inclined with respect to the substrate Forming a member in contact with the protective layer covering a part of the slope of the mesa, forming the wiring member on the inclined surface of the inclined member, and removing the inclined member. A method of manufacturing a surface emitting laser element including the same.

  In the present specification, “inclined surface” means a surface that is simply inclined, and includes not only one or a plurality of planes but also one or a plurality of curved surfaces.

  According to the manufacturing method of the present invention, the manufacturing yield of the surface emitting laser element can be improved.

1 is a diagram illustrating a schematic configuration of a color printer according to an embodiment of the present invention. FIG. 2 is a diagram (part 1) for describing the optical scanning device in FIG. 1; FIG. 3 is a second diagram for explaining the optical scanning device in FIG. 1; FIG. 3 is a third diagram for explaining the optical scanning device in FIG. 1; FIG. 4 is a diagram (part 4) for explaining the optical scanning device in FIG. 1; It is a figure for demonstrating a surface emitting laser array. It is a figure for demonstrating the arrangement | sequence state of a some light emission part. It is AA sectional drawing of FIG. It is the figure which expanded a part of FIG. FIGS. 10A and 10B are diagrams for explaining the substrate of the surface emitting laser array. FIGS. 11A and 11B are views (No. 1) for describing a method for manufacturing a surface emitting laser array, respectively. FIGS. 12A and 12B are views (No. 2) for describing the method for manufacturing the surface emitting laser array, respectively. FIGS. 13A and 13B are views (No. 3) for describing the method for manufacturing the surface emitting laser array, respectively. FIGS. 14A and 14B are views (No. 4) for describing the method of manufacturing the surface emitting laser array, respectively. It is FIG. (5) for demonstrating the manufacturing method of a surface emitting laser array. 6 is a diagram for explaining a surface emitting laser array of Comparative Example 1. FIG. 6 is a diagram for explaining a surface emitting laser array of Comparative Example 2. FIG. 10 is a diagram for explaining a surface emitting laser array of Comparative Example 3. FIG. It is a figure for demonstrating a disconnection. It is a figure for demonstrating the modification 1 of a surface emitting laser array. It is the figure which expanded a part of FIG. It is a figure for demonstrating the modification 2 of a surface emitting laser array. It is a figure for demonstrating a surface emitting laser element. It is a figure for demonstrating the modification 1 of a surface emitting laser element. It is a figure for demonstrating the modification 2 of a surface emitting laser element. 6 is a diagram for explaining a surface emitting laser element of Comparative Example 1. FIG. 6 is a diagram for explaining a surface emitting laser element of Comparative Example 2. FIG. 10 is a diagram for explaining a surface emitting laser element of Comparative Example 3. FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a color printer 2000 according to an embodiment.

  The color printer 2000 is a tandem multi-color printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and includes an optical scanning device 2010, four photosensitive drums (2030a, 2030b, 2030c, 2030d), four cleaning units (2031a, 2031b, 2031c, 2031d), four charging devices (2032a, 2032b, 2032c, 2032d), four developing rollers (2033a, 2033b, 2033c, 2033d), transfer A belt 2040, a transfer roller 2042, a fixing device 2050, a paper feed roller 2054, a paper discharge roller 2058, a paper feed tray 2060, a paper discharge tray 2070, a communication control device 2080, and a printer control device 209 that comprehensively controls the above-described units. And and the like.

  The communication control device 2080 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The printer control device 2090 includes a CPU, a program described in a code decodable by the CPU, a ROM storing various data used when executing the program, a RAM that is a working memory, an amplification circuit And an A / D conversion circuit for converting analog data into digital data. Then, the printer control device 2090 notifies the optical scanning device 2010 of multi-color image information (black image information, cyan image information, magenta image information, yellow image information) received from the host device via the communication control device 2080. To do.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, and the cleaning unit 2031a are used as a set, and constitute an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, and the cleaning unit 2031b are used as a set, and constitute an image forming station (hereinafter also referred to as “C station” for convenience) that forms a cyan image.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, and the cleaning unit 2031c are used as a set, and constitute an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, and the cleaning unit 2031d are used as a set, and constitute an image forming station (hereinafter also referred to as “Y station” for convenience) that forms a yellow image.

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is a surface to be scanned. Each photosensitive drum is rotated in the direction of the arrow in the plane in FIG.

  Each charging device uniformly charges the surface of the corresponding photosensitive drum.

  The optical scanning device 2010 scans the surface of the corresponding charged photosensitive drum with light modulated for each color based on multicolor image information from the printer control device 2090. Thereby, a latent image corresponding to the image information is formed on the surface of each photosensitive drum. The latent image formed here moves in the direction of the corresponding developing device as the photosensitive drum rotates. The configuration of the optical scanning device will be described later.

  As each developing roller rotates, toner from a corresponding toner cartridge (not shown) is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, the toner moves only to a portion irradiated with light on the surface and adheres to the surface. In other words, each developing roller causes toner to adhere to the latent image formed on the surface of the corresponding photosensitive drum so as to be visualized. Here, the toner-attached image (toner image) moves in the direction of the transfer belt 2040 as the photosensitive drum rotates.

  The yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 2040 at a predetermined timing, and are superimposed to form a color image.

  Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is disposed in the vicinity of the paper feed tray 2060. The paper feed roller 2054 takes out the recording paper one by one from the paper feed tray 2060. The recording paper is sent out toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the toner image on the transfer belt 2040 is transferred to the recording paper. The recording paper on which the toner image is transferred is sent to the fixing device 2050.

  In the fixing device 2050, heat and pressure are applied to the recording paper, thereby fixing the toner on the recording paper. The recording paper on which the toner is fixed is sent to the paper discharge tray 2070 via the paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070.

  Each cleaning unit removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum. The surface of the photosensitive drum from which the residual toner has been removed returns to the position facing the corresponding charging device again.

  Next, the configuration of the optical scanning device 2010 will be described.

  2 to 5 as an example, the optical scanning device 2010 includes four light sources (2200a, 2200b, 2200c, 2200d), four coupling lenses (2201a, 2201b, 2201c, 2201d), four openings. Plate (2202a, 2202b, 2202c, 2202d), four cylindrical lenses (2204a, 2204b, 2204c, 2204d), optical deflector 2104, four scanning lenses (2105a, 2105b, 2105c, 2105d), six folding mirrors ( 2106a, 2106b, 2106c, 2106d, 2108b, 2108c) and a scanning control device (not shown).

  Here, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of each photosensitive drum is described as the X-axis direction, and the rotation axis direction of the optical deflector 2104 is described as the Z-axis direction.

  In the following, for convenience, in each optical member, a direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and a direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  The light source 2200a, the coupling lens 2201a, the aperture plate 2202a, the cylindrical lens 2204a, the scanning lens 2105a, and the folding mirror 2106a are optical members for forming a latent image on the photosensitive drum 2030a.

  The light source 2200b, the coupling lens 2201b, the aperture plate 2202b, the cylindrical lens 2204b, the scanning lens 2105b, the folding mirror 2106b, and the folding mirror 2108b are optical members for forming a latent image on the photosensitive drum 2030b.

  The light source 2200c, the coupling lens 2201c, the aperture plate 2202c, the cylindrical lens 2204c, the scanning lens 2105c, the folding mirror 2106c, and the folding mirror 2108c are optical members for forming a latent image on the photosensitive drum 2030c.

  The light source 2200d, the coupling lens 2201d, the aperture plate 2202d, the cylindrical lens 2204d, the scanning lens 2105d, and the folding mirror 2106d are optical members for forming a latent image on the photosensitive drum 2030d.

  Each coupling lens is disposed on the optical path of light emitted from the corresponding light source, and makes the light substantially parallel light.

  Each aperture plate has an aperture and shapes the light through the corresponding coupling lens.

  Each cylindrical lens forms an image of the light that has passed through the opening of the corresponding aperture plate in the vicinity of the deflection reflection surface of the optical deflector 2104 in the sub-scanning corresponding direction.

  The optical deflector 2104 has a two-stage polygon mirror. Each polygon mirror has four deflecting reflecting surfaces. The first-stage (lower) polygon mirror deflects the light from the cylindrical lens 2204a and the light from the cylindrical lens 2204d. The second-stage (upper) polygon mirror reflects the light from the cylindrical lens 2204b and the cylindrical lens 2204c. Are arranged such that the light from each is deflected. Note that the first-stage polygon mirror and the second-stage polygon mirror rotate with a phase shift of approximately 45 ° from each other, and writing scanning is alternately performed in the first and second stages.

  The light from the cylindrical lens 2204a deflected by the optical deflector 2104 is irradiated onto the photosensitive drum 2030a through the scanning lens 2105a and the folding mirror 2106a to form a light spot.

  The light from the cylindrical lens 2204b deflected by the optical deflector 2104 is irradiated to the photosensitive drum 2030b through the scanning lens 2105b and the two folding mirrors (2106b and 2108b), and a light spot is formed. The

  The light from the cylindrical lens 2204c deflected by the optical deflector 2104 is irradiated to the photosensitive drum 2030c through the scanning lens 2105c and the two folding mirrors (2106c and 2108c), and a light spot is formed. The

  The light from the cylindrical lens 2204d deflected by the optical deflector 2104 is applied to the photosensitive drum 2030d through the scanning lens 2105d and the folding mirror 2106d, thereby forming a light spot.

  The light spot on each photosensitive drum moves in the longitudinal direction of the photosensitive drum as the optical deflector 2104 rotates. The moving direction of the light spot on each photosensitive drum is the “main scanning direction”, and the rotating direction of the photosensitive drum is the “sub-scanning direction”.

  An optical system disposed on the optical path between the optical deflector 2104 and each photosensitive drum is also called a scanning optical system.

  Each light source has a surface emitting laser array 100 as shown in FIG. 6 as an example. In the following description, it is assumed that the laser oscillation direction is the z-axis direction, and two directions orthogonal to each other in a plane orthogonal to the z-axis are the x-axis direction and the y-axis direction.

  The surface-emitting laser array 100 includes 32 light emitting units arranged two-dimensionally, and 32 electrode pads provided around the 32 light emitting units and corresponding to each light emitting unit. . Each electrode pad is electrically connected to the corresponding light emitting portion by a wiring member.

  As shown in FIG. 7, the 32 light emitting units have the same light emitting unit interval (“d2” in FIG. 7) when all the light emitting units are orthogonally projected onto a virtual line extending in the x-axis direction. Has been placed. In this specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

  FIG. 8 is a cross-sectional view taken along line AA in FIG. FIG. 9 shows an enlarged view of a part of FIG.

  Each light emitting unit is a surface emitting laser (VCSEL) having an oscillation wavelength band of 780 nm. As shown in FIG. 9, the substrate 101, the buffer layer 102, the lower semiconductor DBR 103, the lower spacer layer 104, the active layer 105, the upper spacer A layer 106, an upper semiconductor DBR 107, a contact layer 109, a p-side electrode 113, an n-side electrode 114, and the like are included. Note that FIG. 9 is a schematic diagram for easy understanding, and the relationship between the thicknesses of the layers is not accurate.

  The surface of the substrate 101 is a mirror-polished surface, and as shown in FIG. 10A, the normal direction of the mirror-polished surface (main surface) is crystal orientation with respect to the crystal orientation [1 0 0] direction. [1 1 1] An n-GaAs single crystal substrate inclined 15 degrees (θ = 15 degrees) in the A direction. That is, the substrate 101 is a so-called inclined substrate. Here, as shown in FIG. 10B, the crystal orientation [0 −1 1] direction is arranged in the + x direction and the crystal orientation [0 1 −1] direction is arranged in the −x direction.

  Returning to FIG. 9, the buffer layer 102 is a layer formed on the + z side surface of the substrate 101 and made of n-GaAs.

The lower semiconductor DBR 103 is stacked on the + z side of the buffer layer 102 and has a low refractive index layer made of n-Al _0.9 Ga _0.1 As and a high refractive index made of n-Al _0.3 Ga _0.7 As. It has 40.5 pairs of layers. Between each refractive index layer, in order to reduce an electrical resistance, a composition gradient layer having a thickness of 20 nm in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer includes 1/2 of the adjacent composition gradient layer, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ. When the optical thickness is λ / 4, the actual thickness D of the layer is D = λ / 4n (where n is the refractive index of the medium of the layer).

The lower spacer layer 104 is laminated on the + z side of the lower semiconductor DBR 103 and is a layer made of non-doped Al _0.6 Ga _0.4 As.

The active layer 105 is stacked on the + z side of the lower spacer layer 104 and is an active layer having a triple quantum well structure made of Al _0.15 Ga _0.85 As / Al _0.3 Ga _0.7 As.

The upper spacer layer 106 is stacked on the + z side of the active layer 105 and is a layer made of non-doped Al _0.6 Ga _0.4 As.

  A portion composed of the lower spacer layer 104, the active layer 105, and the upper spacer layer 106 is also called a resonator structure, and the thickness thereof is set to be an optical thickness of one wavelength. The active layer 105 is provided at the center of the resonator structure at a position corresponding to the antinode in the standing wave distribution of the electric field so that a high stimulated emission probability can be obtained.

The upper semiconductor DBR 107 is laminated on the + z side of the upper spacer layer 106, and has a low refractive index layer made of p-Al _0.9 Ga _0.1 As and a high refractive index made of p-Al _0.3 Ga _0.7 As. It has 25 pairs of layers. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer is provided in which the composition is gradually changed from one composition to the other composition. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

  In one of the low refractive index layers in the upper semiconductor DBR 107, a selective oxidation layer 108 made of AlAs is inserted with a thickness of 30 nm. The selective oxidation layer 108 is inserted in the second pair of low refractive index layers from the upper spacer layer 106.

  The contact layer 109 is stacked on the + z side of the upper semiconductor DBR 107 and is a layer made of p-GaAs.

  Note that a structure in which a plurality of semiconductor layers are stacked over the substrate 101 as described above is also referred to as a “stacked body” for convenience in the following.

  Next, a method for manufacturing the surface emitting laser array 100 will be described.

  (1) The stacked body is formed by crystal growth by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) (see FIG. 11A). Here, an example using the MOCVD method is shown.

Trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as Group III materials, and phosphine (PH ₃ ) and arsine (AsH ₃ ) are used as Group V materials. Further, carbon tetrabromide (CBr ₄ ) and dimethyl zinc (DMZn) are used as the raw material for the p-type dopant, and hydrogen selenide (H ₂ Se) is used as the raw material for the n-type dopant.

  (2) A resist pattern 120 or the like for defining the outer shape of a mesa structure (hereinafter abbreviated as “mesa” for convenience) is formed on the surface of the contact layer 109 (see FIG. 11B).

(3) The stacked body is etched using the resist pattern 120 as an etching mask by an ECR (Electron Cyclotron Resonance) method using an Cl ₂ gas, or an ICP (Inductively Coupled Plasma) method, and at least the selectively oxidized layer 108 is formed. Form a mesa exposed on the side. Here, the bottom surface of the etching is positioned in the middle of the active layer 105. The mesa formed here has a side surface inclined with respect to the z-axis.

  (4) Immerse in an acetone solution and remove the etching mask by ultrasonic cleaning (see FIG. 12A). The mesa formed here has a quadrangular frustum shape.

  (5) The laminated body is heat-treated in water vapor. As a result, Al (aluminum) in the selectively oxidized layer 108 is selectively oxidized from the outer peripheral portion of the mesa, and an unoxidized region 108b surrounded by the Al oxide 108a remains in the central portion of the mesa. (See FIG. 12B). In other words, a so-called oxidized constriction structure is formed that restricts the drive current path of the light emitting part only to the central part of the mesa. The non-oxidized region 108b is a current passing region.

  (6) A resist pattern in which only a region corresponding to a separation groove (hereinafter referred to as “separation groove”) is exposed is formed by photolithography.

  (7) An isolation groove is formed using an ICP dry etching method.

  (8) The resist pattern is removed.

  (9) The laminate is placed in a heating chamber and held in a nitrogen atmosphere at a temperature of 380 to 400 ° C. for 3 minutes. As a result, oxygen or water adhering to the surface in the atmosphere or a natural oxide film due to a small amount of oxygen or water in the heating chamber becomes a stable passive film.

(10) A protective layer 111 made of SiN, SiON, or SiO ₂ is formed by vapor phase chemical deposition (CVD) (see FIG. 13A).

  (11) Open a window for the p-side electrode contact on the top of the mesa. Here, after masking with a photoresist, the opening at the top of the mesa is exposed to remove the photoresist, and the protective layer 111 is etched and opened with BHF (buffered hydrofluoric acid) ( (See FIG. 13B). At the same time, the protective layer 111 on the bottom surface of the separation groove is also removed.

  (12) In order to form an inclined member on which the p-side electrode (wiring member) is formed, the photoresist is applied and then patterned according to the shape of the p-side electrode (wiring member). Bake at ℃. The baked resist pattern becomes the inclined member 124 (see FIG. 14A). Here, as an example, as shown in FIG. 14A, the upper surface of the inclined member 124 (surface on which the wiring member is formed) is an inclined surface having an inclination angle θ with respect to the x axis, and the inclination is the mesa side surface. More lenient than. The inclined surface is simply an inclined surface, and may include one or more curved surfaces as well as one or more flat surfaces.

  The baking temperature is not limited to 130 to 150 ° C., and may be any temperature that does not deform when patterning a photoresist in the “step of forming a p-side electrode” described later. Also, the control of the resist pattern shape is easier than the mesa shape control by dry etching.

  The upper surface of the inclined member 124 needs to have a shape suitable for preventing disconnection. Therefore, the upper surface of the inclined member 124 is (a) not having a concave shape inside, but having a shape in which metal atoms adhere continuously, and (b) the inclination angle θ is smaller than 80 °. It is necessary to satisfy.

  If the upper surface of the inclined member 124 is recessed inward, metal atoms are unlikely to adhere to the recess during vapor deposition, and disconnection is likely to occur. Also, if the inclination angle is 80 ° or more, the wiring material at the mesa bottom is very sparse, and disconnection is likely to occur when measuring the output.

  (13) A square resist pattern having a side of 10 μm is formed in a region to be a light emitting portion on the upper part of the mesa, and a p-side electrode material is deposited. As the electrode material on the p side, a multilayer film made of Ti / Pt / Au is used. The film thickness of the p-side electrode (wiring member) is desirably 500 nm or more in order to maintain the strength.

  (14) Lift off the electrode material of the light emitting portion, perform oxygen plasma treatment, remove the resist, and form the p-side electrode (wiring member) 113 (see FIG. 14B). A gap 125 exists between the p-side electrode (wiring member) 113 and the protective layer 111 that protects the side surface of the mesa.

  (15) After polishing the back side of the substrate 101 to a predetermined thickness (for example, about 100 μm), an n-side electrode 114 is formed (see FIG. 15). Here, the n-side electrode 114 is a multilayer film made of AuGe / Ni / Au.

  (16) Ohmic conduction is established between the p-side electrode (wiring member) 113 and the n-side electrode 114 by annealing. Thereby, each mesa becomes a light emission part.

  (17) Cut by chip by scribing and braking.

  Then, through various post-processes, the surface emitting laser array 100 is obtained.

  When 3000 surface emitting laser arrays 100 were manufactured using the above manufacturing method and their output characteristics were measured, it was confirmed that no disconnection occurred in all the surface emitting laser arrays 100. Further, no wiring was peeled between the protective layer 111 and the electrode pad during wire bonding.

  Subsequently, a plurality of comparative examples will be described. In the following, differences from the surface emitting laser array 100 of the present embodiment will be mainly described, and the same reference numerals are used for the same or equivalent components as those of the above-described embodiment, and the description will be simplified. Or shall be omitted.

  FIG. 16 shows a conventional surface emitting laser array 502 in which a p-side electrode (wiring member) 113 and a protective layer 111 protecting the side surface of the mesa are in close contact as Comparative Example 1. When 3000 surface emitting laser arrays 502 were manufactured using a conventional manufacturing method and the output characteristics thereof were measured, disconnection was confirmed in 25 surface emitting laser arrays 502.

  FIG. 17 shows a conventional surface emitting laser array 503 in which the periphery of the mesa is surrounded by polyimide 121 as Comparative Example 2. When 3000 surface emitting laser arrays 503 were manufactured using a conventional manufacturing method, many peelings were observed between the polyimide 121 and the electrode pads during wire bonding.

  Furthermore, when the lifetimes of the surface-emitting laser array 503 and the surface-emitting laser array 100 of the present embodiment were compared, the surface-emitting laser array 100 had a longer lifetime.

  FIG. 18 shows a conventional surface emitting laser array 504 in which a wiring member is formed at the same height as the upper surface of the mesa as Comparative Example 3. When 3000 surface emitting laser arrays 504 were manufactured using a conventional manufacturing method and the size of the oxidized constriction region was measured with an IR microscope, the size of the variation was about 2 in the surface emitting laser array 100 of the present embodiment. It was twice.

  By the way, since the light emitting part has a height of several μm, when the p-side electrode (wiring member) is formed by vapor deposition, if the rising angle of the light emitting part (the inclination angle of the mesa side surface with respect to the x-axis direction) is large, the light emitting part Disconnection is likely to occur due to the fact that metal atoms do not adhere to the bottom of the substrate, and the yield decreases. The wiring member forming method by vapor deposition is a generally used method, and the wiring member can be easily formed. However, unlike the chemical vapor deposition method (CVD method), the metal atoms forming the wiring member in the vapor deposition behave linearly, so that the rising angle of the light emitting portion is larger than the angle at which the metal atoms fly to the substrate surface. When it becomes larger, as indicated by the symbol A in FIG. 19 as an example, metal atoms do not adhere to the vicinity of the mesa bottom, and disconnection is likely to occur.

  On the other hand, it is conceivable to control the rising angle of the light emitting portion to be small during dry etching, but it is difficult to control the rising angle of the light emitting portion by dry etching, and the rising angle is uniform over the entire substrate surface. It is difficult to ensure sex.

  Further, as disclosed in Patent Document 1, it is conceivable to eliminate the step by filling the step of the light emitting portion with polyimide so that the disconnection does not occur. However, this method has a short life due to the stress caused by the polyimide. There was an inconvenience. Moreover, since polyimide has poor adhesion to the p-side electrode (wiring member), there is a disadvantage that the wiring member is easily peeled off during wire bonding.

  In addition, as in Patent Document 2, it is conceivable to partially etch the periphery of the light emitting part and form a wiring member at the same height as the light emitting part. In some cases, the portion was not opened, and the warpage of the substrate increased. In this case, when forming the oxidized constriction structure, a gap is formed between the substrate and the inter-substrate holding member, and a non-uniform temperature distribution is generated on the substrate. As a result, there is a disadvantage that the oxidized constriction region varies greatly in the plane, resulting in a significant decrease in yield.

  As described above, according to the method of manufacturing the surface emitting laser array according to the present embodiment, the step of forming the plurality of semiconductor layers on the substrate 101 and the mesa are formed by etching a part of the plurality of semiconductor layers. A step of forming a protective layer 111 on the mesa, a step of forming an inclined member 124 having an inclined surface inclined with respect to the substrate 101 in contact with the protective layer 111 covering a part of the inclined surface of the mesa, It includes a step of forming a p-side electrode (wiring member) 113 on the inclined surface of the member 124 and a step of removing the inclined member 124.

  In the surface emitting laser array 100 manufactured by this manufacturing method, a gap 125 is provided between the p-side electrode (wiring member) 113 and the protective layer 111 that protects the side surface of the mesa in each light emitting portion.

  In this case, disconnection and peeling of the wiring member can be suppressed, and the manufacturing yield can be improved. Therefore, it is possible to reduce the price of the surface emitting laser array 100.

  According to the optical scanning device 2010 according to the present embodiment, since each light source has the surface emitting laser array 100, it is possible to reduce the price without reducing the scanning accuracy.

  In addition, since the surface emitting laser array 100 includes a plurality of light emitting units, a plurality of optical scans can be performed simultaneously, and the speed of image formation can be increased.

  Further, according to the color printer 2000 according to the present embodiment, since the optical scanning device 2010 is provided, it is possible to reduce the price without deteriorating the image quality.

  By the way, in the surface emitting laser array 100, since the intervals between the light emitting portions when the respective light emitting portions are orthogonally projected onto the virtual line extending in the sub-scanning corresponding direction are equal intervals d2, the lighting timing is adjusted to adjust the light emitting portions on the photosensitive drum. Then, it can be considered that the configuration is the same as that in the case where the light emitting units are arranged at equal intervals in the sub-scanning direction.

  For example, if the distance d2 is 2.65 μm and the magnification of the optical system of the optical scanning device 2010 is doubled, high-density writing of 4800 dpi (dots / inch) can be performed. Of course, the number of light emitting portions in the direction corresponding to the main scanning is increased, the arrangement of the arrays in which the pitch d1 (see FIG. 7) in the direction corresponding to the sub scanning is narrowed to further reduce the interval d2, and the magnification of the optical system is decreased. For example, higher density can be achieved and higher quality printing becomes possible. Note that the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light emitting unit.

  In this case, the color printer 2000 can print without reducing the printing speed even if the writing dot density increases. Further, when the writing dot density is the same, the printing speed can be further increased.

  By the way, in the color printer 2000, color misregistration may occur due to manufacturing error or position error of each component. Even in such a case, if each light source of the optical scanning device 2010 includes the surface emitting laser array 100, the color misregistration can be reduced by changing the light emitting unit to be lit.

  In the above embodiment, the case where a photoresist is used as the material of the inclined member 124 has been described. However, the present invention is not limited to this. For example, glass may be used as the material of the inclined member 124. In this case, for example, the inclined member 124 may be formed by a so-called SOG (spin-on-glass) method. The SOG method is excellent in film thickness controllability. Then, after forming the p-side electrode (wiring member) 113, the glass (inclined member 124) is removed with hydrofluoric acid, whereby the p-side electrode (wiring member) 113 and the protective layer 111 protecting the side surface of the mesa are formed. A gap 125 is formed between them. Also in this case, the surface emitting laser array 100 can be manufactured with a high yield as in the above embodiment.

  Moreover, although the said embodiment demonstrated the case where the height (dimension of the z-axis direction) of the space | gap 125 was substantially equal to the height of a mesa, it is not limited to this. As an example, like the surface emitting laser array 501 shown in FIG. 20, the height of the gap 125 may be lower than the height of the mesa. This surface emitting laser array 501 has the same characteristics as the surface emitting laser array 100. An enlarged view of a part of FIG. 20 is shown in FIG.

  Moreover, although the said embodiment demonstrated the case where the cross-sectional shape of the p side electrode (wiring member) 113 of the part which forms the space | gap 125 was a straight line, it is not limited to this. As an example, the cross-sectional shape of the p-side electrode (wiring member) 113 in the part forming the gap 125 is a polygon (including the case where each side is a curve) as in the surface emitting laser array 502 shown in FIG. It may be a part. The surface emitting laser array 502 can operate at a higher speed than the conventional surface emitting laser array. Further, the cross-sectional shape of the p-side electrode (wiring member) 113 in the portion where the gap 125 is formed may be a curve.

  Moreover, although the said embodiment demonstrated the case where the oscillation wavelength of each light emission part was a 780 nm band, it is not limited to this. The oscillation wavelength of each light emitting unit may be changed according to the characteristics of the photoreceptor.

  Moreover, although the said embodiment demonstrated the case where a surface emitting laser array had 32 light emission parts, it is not limited to this.

  Further, in the above embodiment, instead of the surface emitting laser array 100, as shown in FIG. 23 as an example, one light emitting portion is provided to protect the p-side electrode (wiring member) 113 and the side surface of the mesa. Alternatively, a surface emitting laser element 200 in which a gap 125 is provided between the protective layer 111 and the protective layer 111 may be used. The surface emitting laser element 200 can be manufactured in the same manner as the surface emitting laser array 100. When 3000 surface emitting laser elements 200 were manufactured using the above manufacturing method and their output characteristics were measured, it was confirmed that no disconnection occurred in all the surface emitting laser elements 200. Further, there was no peeling between the protective layer 111 and the electrode pad during wire bonding.

  Also in this case, as an example, like the surface emitting laser element 201 shown in FIG. 24, the height of the gap 125 may be lower than the height of the mesa. In addition, as an example, a cross-sectional shape of the p-side electrode (wiring member) 113 in a portion where the gap 125 is formed is a polygon (including a case where each side is a curve) as in the surface emitting laser element 202 shown in FIG. ). The surface emitting laser element 202 can operate at a higher speed than the conventional surface emitting laser element. Further, the cross-sectional shape of the p-side electrode (wiring member) 113 in the portion where the gap 125 is formed may be a curve.

  FIG. 26 shows a conventional surface emitting laser element 203 in which a p-side electrode (wiring member) 113 and a protective layer 111 protecting the side surface of the mesa are in close contact as a surface emitting laser element of Comparative Example 1. Yes. When 3000 surface emitting laser elements 203 were manufactured using a conventional manufacturing method and their output characteristics were measured, disconnection was confirmed in 20 surface emitting laser elements 203.

  FIG. 27 shows a conventional surface emitting laser element 204 in which the periphery of the mesa is surrounded by polyimide 121 as the surface emitting laser element of Comparative Example 2. When 3000 surface emitting laser elements 204 were manufactured using a conventional manufacturing method, many peelings were observed between the polyimide 121 and the electrode pads during wire bonding.

  Further, when the lifetimes of the surface emitting laser element 201, the surface emitting laser element 202, and the surface emitting laser element 203 were compared, the surface emitting laser element 203 had the shortest lifetime.

  FIG. 28 shows a conventional surface emitting laser element 205 in which a wiring member is formed at the same height as the upper surface of the mesa as the surface emitting laser element of Comparative Example 3. When 3000 surface emitting laser elements 205 were manufactured using a conventional manufacturing method and the size of the oxidized constriction region was measured with an IR microscope, the size of the variation was determined by the surface emitting laser element 200, the surface emitting laser element 201, and It was about twice that of the surface emitting laser element 202.

  Further, the surface emitting laser array 100, the surface emitting laser element 200, and the modified examples thereof can be used for applications other than the image forming apparatus. In that case, the oscillation wavelength may be a wavelength band such as a 650 nm band, an 850 nm band, a 980 nm band, a 1.3 μm band, and a 1.5 μm band depending on the application.

  By the way, it is preferable that the groove | channel between two light emission parts shall be 5 micrometers or more for the electrical and spatial separation of each light emission part. This is because if it is too narrow, it becomes difficult to control etching during production. Further, the mesa size (length of one side) is preferably 10 μm or more. This is because if it is too small, heat will be accumulated during operation and the characteristics may be deteriorated.

  Further, in the above embodiment, instead of the surface emitting laser array 100, a surface emitting laser array manufactured by the same manufacturing method as the surface emitting laser array 100 and having a plurality of light emitting units arranged one-dimensionally may be used. good.

  In the above embodiment, the case of the color printer 2000 as the image forming apparatus has been described. However, the present invention is not limited to this. For example, a laser printer that forms a monochrome image may be used.

  For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. 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 equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal 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.

  DESCRIPTION OF SYMBOLS 100 ... Surface emitting laser array, 101 ... Substrate, 102 ... Buffer layer, 103 ... Lower semiconductor DBR, 104 ... Lower spacer layer, 105 ... Active layer, 106 ... Upper spacer layer, 107 ... Upper semiconductor DBR, 108 ... Selective oxidation 108a ... oxide, 108b ... current passing region, 109 ... contact layer, 111 ... protective layer, 113 ... p-side electrode, 114 ... n-side electrode, 121 ... polyimide, 124 ... inclined member, 125 ... gap, 200, 201, 202 ... surface emitting laser element, 501 ... surface emitting laser array, 2000 ... color printer (image forming apparatus), 2010 ... optical scanning device, 2030a, 2030b, 2030c, 2030d ... photosensitive drum, 2104 ... optical deflector, 2105a, 2105b, 2105c, 2105d ... scanning lens (part of scanning optical system), 2 06a, 2106b, 2106c, 2106d, 2108b, 2108c ... Folding mirror (part of scanning optical system), 2200a, 2200b, 2200c, 2200d ... Light source, 2201a, 2201b, 2201c, 2201d ... Coupling lens, 2202a, 2202b, 2202c , 2202d... Aperture plate, 2204a, 2204b, 2204c, 2204d... Cylindrical lens.

JP 2008-004670 A Japanese Patent No. 4050028

Claims (10)

A method of manufacturing a surface-emitting laser element in which a mesa-shaped light emitting portion in which a plurality of semiconductor layers are stacked and an electrode are electrically connected by a wiring member,
Forming the plurality of semiconductor layers on a substrate;
Etching part of the plurality of semiconductor layers to form the mesa;
Forming a protective layer on the mesa;
Forming an inclined member having an inclined surface inclined with respect to the substrate in contact with the protective layer covering a part of the inclined surface of the mesa;
Forming the wiring member on the inclined surface of the inclined member;
And a step of removing the inclined member.   The manufacturing method according to claim 1, wherein the inclined surface of the inclined member is one flat surface or a curved surface.   The manufacturing method according to claim 1, wherein the inclined surface of the inclined member includes a plurality of flat surfaces or curved surfaces.   The manufacturing method according to claim 1, wherein the wiring member has a thickness of 500 nm or more. In a surface emitting laser element in which a mesa-shaped light emitting portion in which a plurality of semiconductor layers are stacked and an electrode are electrically connected by a wiring member,
A surface-emitting laser element having a gap between the wiring member and a side surface of the mesa.   6. The surface emitting laser element according to claim 5, wherein the wiring member in the portion forming the gap has a straight or curved cross-sectional shape.   6. The surface emitting laser element according to claim 5, wherein the wiring member in the portion forming the gap has a polygonal cross section.   A surface emitting laser array in which the surface emitting laser elements according to any one of claims 5 to 7 are integrated. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface emitting laser element according to claim 7 or the surface emitting laser array according to claim 8;
An optical deflector for deflecting light from the light source;
A scanning optical system that condenses the light deflected by the optical deflector onto the surface to be scanned. At least one image carrier;
An image forming apparatus comprising: the optical scanning device according to claim 9, wherein the at least one image carrier is scanned with light modulated according to image information.