JP2013182965A - Manufacturing method, surface light-emitting laser element, surface light-emitting laser array, optical scanner, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a surface light-emitting laser capable of improving yield.SOLUTION: The manufacturing method of a surface light-emitting laser includes the steps of: laminating a plurality of semiconductor layers on a substrate; forming a truncated square pyramid-shape mesa corresponding to a light-emitting part; and forming a p-side electrode 113 that has a T-shape formed by a square part 113a and a rectangular part 113b when seen from a direction orthogonal to the substrate (z-axis direction), the square part 113a covering a part of a top face of the mesa and the rectangular part 113b covering two ridges of the mesa adjacent to each other.

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 a step of laminating at least a first semiconductor multilayer reflective film of a first conductivity type, an active region, and a second semiconductor multilayer reflective film of a second conductivity type on a substrate; Forming a post by removing a semiconductor film from the semiconductor multilayer reflective film to a part of the first semiconductor multilayer reflective film, and forming a first on the first semiconductor multilayer reflective film exposed at the bottom of the post A step of forming an insulating film; a step of forming a second insulating film on the first insulating film; and a second semiconductor multilayer reflective film on the top of the post on the second insulating film. And a method of manufacturing a surface emitting semiconductor laser having a step of forming an electrode pad.

  Patent Document 2 discloses a semiconductor multilayer formed by sequentially laminating at least a first-conductivity-type semiconductor multilayer reflector, an active layer, and a second-conductivity-type semiconductor multilayer reflector on a semiconductor substrate. A step of forming a film, a step of forming a mask on the semiconductor multilayer film with different inclinations of edges depending on the orientation, a step of etching the semiconductor multilayer film with the mask to form a mesa structure, and a mesa structure A method of manufacturing a vertical cavity surface emitting semiconductor laser device including a step of forming a covering insulating film is disclosed.

  Patent Document 3 discloses a step of immersing a semiconductor substrate whose surface is GaAs in a solution containing at least hydrofluoric acid, a step of washing the surface of the semiconductor substrate with water to make it hydrophilic, and a semiconductor while maintaining the hydrophilicity of the surface of the semiconductor substrate. Etching with an etching solution capable of etching at least GaAs using the resist mask, a step of removing water on the substrate surface, a step of forming a resist mask using a photoresist on the semiconductor substrate And a step of forming a step structure in which the side surface extending in the reverse mesa direction has a forward taper shape is disclosed.

  In Patent Document 4, a laminated film having a lower semiconductor multilayer reflector, a lower spacer layer, an active layer, an upper spacer layer, and an upper multilayer reflector is formed on a compound semiconductor substrate, and the laminated film is dry-etched. In the method of manufacturing a surface emitting laser having a step of processing into a mesa structure, the stacked film includes an etching stop layer and an oxygen introduction layer in contact with the etching stop layer, and the oxygen introduction layer is being etched. A method for manufacturing a surface emitting laser is disclosed in which a gas containing oxygen atoms is introduced and etching is stopped at an etching stop layer.

  In Patent Document 5, a mesa shape and a bonding pad region are simultaneously formed by a dry etching method, and in this case, the mesa side wall portion wiring width connecting the mesa bottom portion to the mesa bottom portion of the surface emitting laser array element which is a convex portion is disclosed. A method of manufacturing a surface emitting laser array that is formed wider than the width of a wiring formed on a mesa bottom that is a recess 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 device having a mesa-shaped light emitting portion in which a plurality of semiconductor layers are stacked, and a light emission region on the top surface of the mesa surrounded by an electrode. Laminating the plurality of semiconductor layers; forming a truncated pyramid-shaped mesa; forming the electrode covering a part of the upper surface of the mesa and two adjacent ridgelines in the truncated pyramid; A method of manufacturing a surface emitting laser element including

  According to the manufacturing method of the present invention, the yield 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 a longitudinal cross-sectional view of one light emission part. FIG. 9A and FIG. 9B are diagrams for explaining the substrate of the surface emitting laser array. FIGS. 10A and 10B are views (No. 1) for describing a method of manufacturing a surface emitting laser array, respectively. It is FIG. (2) for demonstrating the manufacturing method of a surface emitting laser array. It is a figure for demonstrating the etching depth H. FIG. FIGS. 13A and 13B are views (No. 3) for describing the method for manufacturing the surface emitting laser array, respectively. It is a figure for demonstrating the square frustum of a mesa. It is a figure for demonstrating the film thickness T of a protective film. It is FIG. (4) for demonstrating the manufacturing method of a surface emitting laser array. It is a figure for demonstrating the resist pattern. It is FIG. (1) for demonstrating a non-mask area | region. It is FIG. (2) for demonstrating a non-mask area | region. FIG. 6 is a diagram (part 1) for explaining the positional relationship between the upper surface of the mesa and the non-mask region; FIG. 6 is a diagram (part 2) for explaining the positional relationship between the upper surface of the mesa and the non-mask region; It is FIG. (5) for demonstrating the manufacturing method of a surface emitting laser array. It is a figure for demonstrating the shape of a p side electrode. It is FIG. (6) for demonstrating the manufacturing method of a surface emitting laser array.

  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, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the 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 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.

  Each light emitting portion is a surface emitting laser (VCSEL) having an oscillation wavelength band of 780 nm. As shown in the longitudinal sectional view of FIG. 8 as an example, a substrate 101, a buffer layer 102, a lower semiconductor DBR 103, a lower spacer layer 104, An active layer 105, an upper spacer 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. FIG. 8 is a schematic diagram for easy understanding, and the relationship between the thicknesses of the respective layers is not accurate.

  The surface of the substrate 101 is a mirror-polished surface, and as shown in FIG. 9A, 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. 9B, 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. 8, the buffer layer 102 is laminated on the + z side surface of the substrate 101 and is a layer 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 laminated on the + z side of the lower spacer layer 104, and has three quantum well layers and four barrier layers. Each quantum well layer is made of Al _0.12 Ga _0.88 As, and each barrier layer is made of 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 24 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.

  A selective oxidation layer 108 made of p-AlAs is provided at a position optically separated from the resonator structure in the upper semiconductor DBR 107 by λ / 4.

  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 laminate is formed by crystal growth by metal organic vapor phase epitaxy (MOCVD) or molecular beam epitaxy (MBE) (see FIG. 10A).

Here, 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. ing. 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) On the surface of the contact layer 109, a resist pattern 120a for defining the outer shape of a mesa structure (hereinafter abbreviated as “mesa”) and a resist for masking a region where an electrode pad is formed A pattern 120b and the like are formed (see FIG. 10B).

(3) The stacked body is etched using the resist pattern 120a and the resist pattern 120b as an etching mask by an ECR (Electron Cyclotron Resonance) method using an Cl ₂ gas or an ICP (Inductively Coupled Plasma) method, using the resist pattern 120a and the resist pattern 120b as an etching mask. A mesa in which the oxide layer 108 is exposed on the side surface is formed. Here, the bottom surface of the etching is positioned in the middle of the lower semiconductor DBR 103. The mesa formed here has a side surface inclined with respect to the z-axis. The degree of this inclination can be controlled by appropriately changing process conditions such as gas flow rate during dry etching, plasma discharge power, and substrate temperature.

  (4) Immerse in an acetone solution and remove the etching mask by ultrasonic cleaning (see FIG. 11). The mesa formed here has a quadrangular frustum shape. The inclination angle of the side surface of the mesa with respect to the x-axis is θ. Further, the height (etching depth) of the mesa is set to H (see FIG. 12).

  The angle θ is desirably in the range of 65 ° to 85 °. When the angle θ is smaller than 65 °, the degree of freedom of the design rule regarding the distance between two adjacent mesas is reduced. If the angle θ is greater than 85 °, the step coverage of the wiring is insufficient and the risk of disconnection increases. A more desirable range of the angle θ is 70 ° to 76 °. Here, as an example, H = 3.4 μm and θ = 73 °.

  (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. 13A). 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 protective film 111 made of SiO ₂ is formed as an interlayer insulating film using a plasma CVD method (see FIG. 13B). A SiN film or a SiON film may be formed as the interlayer insulating film. Here, the length L1 of the side extending in the y-axis direction on the upper surface of the mesa and the length L2 of the side extending in the x-axis direction are set (see FIG. 14). In addition, the thickness of the protective film 111 covering the side surface of the mesa is T (see FIG. 15).

  The thickness T of the protective film 111 is desirably in the range of 100 nm to 400 nm. When the film thickness T is less than 100 nm, the wiring capacity increases and the operation speed decreases. Further, if the film thickness T is larger than 400 nm, there is a possibility that crystal defects are induced in the protective film 111 due to internal stress. A more desirable range of the film thickness T is 150 nm to 300 nm. Here, as an example, T = 200 nm.

  (7) A resist pattern for forming a contact hole for the p-side electrode 113 is formed on the upper surface of the mesa.

  (8) The protective film 111 is etched using BHF (buffered hydrofluoric acid) using the resist pattern as an etching mask.

  (9) The etching mask is removed (see FIG. 16).

  (10) A resist pattern 124 having openings (non-mask regions) corresponding to the p-side electrode 113, wiring members, electrode pads, and the like is formed by photolithography (see FIG. 17).

  As shown in FIG. 18, the opening (non-mask region) corresponding to the p-side electrode 113 includes a square part 124a, a rectangular part 124b, and a lead part 124c. A portion composed of the square portion 124a and the rectangular portion 124b has a T shape. The square portion 124a has a mask region that becomes a light emission region at the center.

  The length of the side extending in the y-axis direction of the square portion 124a is L3, and the length of the side extending in the x-axis direction is L4. The length of the side (long side) extending in the y-axis direction of the rectangular portion 124b is L6, and the length of the side (short side) extending in the x-axis direction is L7. Then, L6−L3 = 2 × L5.

  Here, the relationship of L3 <L1, L4 <L2, L5 <L1, L3 <L2, L4> L1 is satisfied.

  In addition, as shown in FIG. 19, d1, d2, and d3 are defined, and when the alignment accuracy in this (photolithography process) is a, d1 ≧ a, d2 ≧ a, d3 ≧ a + T + H × tan It is set so as to satisfy the relationship of (90−θ) and L5 ≧ 2a + T + H × tan (90 ° −θ °). Therefore, L3-L1 (= 2 × d1) ≧ 2a, L2-L4 (= 2 × d2) ≧ 2a, L6-L3 (= 2 × L5) ≧ 2 × {2a + T + H × tan (90−θ)}, L7 The relationship of (= d2 + d3) ≧ 2a + T + H × tan (90 ° −θ °) is satisfied.

  Here, a double-sided aligner (model number MA-6) manufactured by SUSS is used as the exposure apparatus. In this case, the alignment accuracy a is 0.8 μm.

  By satisfying the above relationships, the square portion 124a does not cover the side surface of the mesa even when the alignment of the wiring pattern is shifted to the maximum, and the mesa on the lead-out side (here, + x side) of the wiring member. Since the two ridge lines are completely covered with the rectangular portion 124b, the risk of inducing crystal defects due to internal stress to the electrode material is reduced. Therefore, the risk of disconnection failure can be greatly reduced.

  By the way, if d1 = a, d2 = a, d3 = a + T + H × tan (90−θ), and L5 = 2a + T + H × tan (90 ° −θ °), the resist pattern 124 is on the + x side and the −y side. FIG. 20 shows the case of the most misalignment, and FIG. 21 shows the case of the resist pattern 124 most misaligned on the −x side and the + y side.

  (11) Evaporate the electrode material on the p side. As the electrode material on the p side, a multilayer film made of Cr / AuZn / Au or a multilayer film made of Ti / Pt / Au is used. The thickness of the p-side electrode material was 700 nm to 900 nm. The material of the wiring and the material of the electrode pad are the same as the electrode material on the p side.

  (12) The resist pattern 124 is removed using an organic solvent, and a p-side electrode 113, a wiring pattern, an electrode pad, and the like are formed (see FIG. 22). A region surrounded by the p-side electrode 113 is a light emission region. Note that the p-side electrode 113 is formed only on the mesa serving as the light emitting portion.

  Here, as an example, as shown in FIG. 23, a square portion 113a of the p-side electrode 113 covers a part of the upper surface of the mesa, and a rectangular portion 113b of the p-side electrode 113 covers two adjacent ridge lines of the mesa. Yes.

  (13) 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. 24). Here, the n-side electrode 114 is a multilayer film made of AuGe / Ni / Au.

  (14) Ohmic conduction is established between the p-side electrode 113 and the n-side electrode 114 by annealing. Thereby, the mesa becomes a light emitting part.

  (15) Cut for each chip.

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

  By manufacturing in this way, the yield can be improved.

  By the way, generally, there is a step of forming a wiring member as one of the manufacturing steps of the surface emitting laser element. In this process, wiring has to be performed across a large step from the top surface of the mesa to the bottom surface of the mesa, which may cause disconnection and poor reliability due to insufficient step coverage of the wiring.

  When the p-side electrode is formed on the entire surface of the mesa side wall as in the manufacturing method disclosed in Patent Document 1, crystal defects are induced in the surface emitting laser element due to the internal stress of the p-side electrode, and the reliability is improved. There was a risk of decline.

  As disclosed in Patent Document 2 and Patent Document 3, even when the mesa is tapered, the wiring coverage is not sufficient, the film thickness is reduced on the side of the mesa, and disconnection and wiring reliability are caused. There was a risk of lowering

  In the manufacturing method disclosed in Patent Document 4, not only the number of steps for forming polyimide is increased and the cost is increased, but also crystal defects are induced in the surface emitting laser element due to internal stress, and reliability may be lowered. was there.

  Moreover, in the method of securing the coverage of the mesa side wall by evaporating the wiring material obliquely, burrs are generated at the end of the wiring formed in the mesa bottom region of the recess, and this wiring burrs become particles in the subsequent process. There was a risk of causing a short circuit. Furthermore, when oblique deposition is performed by a self-revolving type deposition method in order to obtain a uniform in-plane film thickness distribution, a rectangular mesa causes a shadowing time out of the deposition time, so that the effect of improving step coverage is obtained. Was difficult.

  In the manufacturing method disclosed in Patent Document 5, when the alignment accuracy is shifted to the limit during the photolithography process of wiring formation, the electrode member may cover the mesa side surface other than the wiring drawing direction.

  In the present embodiment, the p-side electrode 113 includes a square portion 113a and a rectangular portion 113b, and the outer dimension of the square portion 113a is smaller than the mesa upper surface dimension. In the photolithography process when forming the p-side electrode 113, even if the position of the resist pattern 124 is deviated by the upper limit of the alignment accuracy, the p-side electrode 113 is positioned on the mesa side surface except in the direction in which the wiring member is drawn. There is no covering. Thus, the generation of crystal defects due to the internal stress of the wiring member can be suppressed. In addition, the long side dimension of the rectangular portion 113b is larger than the mesa upper surface dimension. Therefore, the two ridge lines in the drawing direction of the wiring member can be reliably covered with the electrode material, and the risk of disconnection of the wiring member can be dramatically reduced.

  As apparent from the above description, the method for manufacturing the surface emitting laser element of the present invention is implemented in the method for manufacturing the surface emitting laser array 100 described above.

  As described above, the surface emitting laser array 100 according to the present embodiment forms a plurality of square frustum-shaped mesas corresponding to the plurality of light emitting units in the step of laminating a plurality of semiconductor layers on the substrate 101. When viewed from the process, the direction orthogonal to the substrate 101 (z-axis direction), it is a T-shape composed of a square portion 113a and a rectangular portion 113b. The square portion 113a covers a part of the upper surface of the mesa and the rectangular portion 113b It is manufactured through a process of forming a p-side electrode 113 that covers two adjacent ridgelines in the mesa.

  In this case, the yield can be improved. Therefore, a highly reliable surface emitting laser array can be supplied at low cost.

  According to the optical scanning device 2010 according to the present embodiment, each light source has the surface-emitting laser array 100, so that highly accurate optical scanning can be performed stably.

  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.

  In addition, since the color printer 2000 according to the present embodiment includes the optical scanning device 2010, it is possible to stably form a high-quality image as a result.

  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.

  In the above embodiment, the case where the mesa has a quadrangular pyramid shape has been described, but the present invention is not limited to this. In short, the mesa may be a truncated pyramid shape.

  Moreover, although the said embodiment demonstrated the case where the p side electrode 113 consisted of the square part 113a and the rectangular part 113b, it is not limited to this. For example, the square portion 113a may be a substantially square portion.

  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.

  In the above embodiment, instead of the surface emitting laser array 100, a surface emitting laser element manufactured in the same manner as the surface emitting laser array 100 and having one light emitting portion may be used.

  In the above embodiment, the case where the optical scanning device 2010 is used in a printer has been described. However, the optical scanning device 2010 may be used in an image forming apparatus other than a printer, for example, a copier, a facsimile, or a multifunction machine in which these are integrated. it can.

  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.

  The medium may be a printing plate known as CTP (Computer to Plate). That is, the optical scanning device 2010 is also suitable for an image forming apparatus that directly forms an image on a printing plate material by laser ablation to form a printing plate.

  Further, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that can give reversibility to color development by 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 Layer 108a ... Oxide 108b ... Current passing region 109 ... Contact layer 113 ... P-side electrode 113a ... Square part (first part) 113b ... Rectangular part (second part) 114 ... n side Electrodes 124... Resist pattern (photomask) 2000. , 2105d ... scanning lens (part of scanning optical system), 2106a, 2106b, 210 c, 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 2008-34637 A JP 2006-013366 A JP 2007-150170 A JP 2005-191343 A JP 2009-302113 A

Claims (9)

A method of manufacturing a surface-emitting laser element having a mesa-shaped light emitting portion in which a plurality of semiconductor layers are stacked, and a light emission region on the top surface of the mesa surrounded by an electrode,
Laminating the plurality of semiconductor layers on a substrate;
Forming a truncated pyramidal mesa;
Forming the electrode covering a part of the upper surface of the mesa and the two adjacent ridgelines in the truncated pyramid. The electrode has a first portion that covers a part of the top surface of the mesa and a second portion that covers two adjacent ridgelines in the truncated pyramid,
In the step of forming the electrode, the length L1 of the side extending in the first direction on the upper surface of the mesa, the length L2 of the side extending in the second direction orthogonal to the first direction, the first length of the electrode in the first direction The length L3 of the side extending in the first direction of the part, the length L4 of the side extending in the second direction, the one side end of the second part and the one side end of the first part of the electrode The electrode satisfying the relationship of L3 <L1, L4 <L2, L5 <L1, L3 <L2, L4> L1 is formed using the distance L5 to the portion. The manufacturing method as described. The step of forming the electrode includes a photolithography step using a photomask having a non-mask region having the same shape as the electrode,
The non-mask region includes an alignment accuracy a in the photolithography process, a height H of the mesa, a rising angle θ of a side surface of the mesa, a length L6 of a long side of the second portion of the electrode, a short length L3-L1 ≧ 2a, L2-L4 ≧ 2a, L6-L3 ≧ 2 × {2a + T + H × tan (90−θ)} using the side length L7 and the thickness T of the protective film covering the side surface of the mesa The manufacturing method according to claim 2, wherein a relationship of L7 ≧ 2a + T + H × tan (90 ° −θ °) is satisfied.   4. The outer shape of the first portion of the electrode when viewed from a direction orthogonal to the substrate is a square shape, and the outer shape of the second portion is a rectangular shape. 5. Manufacturing method.   A surface-emitting laser element manufactured by the manufacturing method according to claim 1. A surface emitting laser array having a plurality of light emitting portions,
The surface emitting laser array by which the said several light emission part was manufactured with the manufacturing method as described in any one of Claims 1-4. An optical scanning device that scans a surface to be scanned with light,
A light source having the surface-emitting laser element according to claim 5 or the surface-emitting laser array according to claim 6;
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 7, wherein the at least one image carrier is scanned with light modulated according to image information.   The image forming apparatus according to claim 8, wherein the image information is multicolor color image information.

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