JP4836258B2 - Semiconductor laser array manufacturing method, surface emitting semiconductor laser array, optical scanning apparatus, image forming apparatus, optical transmission module, and optical transmission system - Google Patents

Description

  The present invention relates to a semiconductor laser array manufacturing method, a surface emitting semiconductor laser array, an optical scanning device, an image forming apparatus, an optical transmission module, and an optical transmission system, and more specifically, a surface emitting semiconductor laser having a plurality of light emitting units. Semiconductor laser array manufacturing method for manufacturing array, surface emitting semiconductor laser array having a plurality of light emitting units, optical scanning device having the surface emitting semiconductor laser array, image forming apparatus including the optical scanning device, and surface emitting type The present invention relates to an optical transmission module having a semiconductor laser array, and an optical transmission system including the optical transmission module.

  In electrophotographic image recording, an image forming apparatus using a laser is widely used. In this case, the image forming apparatus includes an optical scanning device, and forms a latent image by rotating the drum while scanning laser light using a polygon scanner (for example, a polygon mirror) in the axial direction of the photosensitive drum. Is common. In the field of electrophotography, an image forming apparatus is required to increase image density in order to improve image quality and to increase image output speed in order to improve operability.

  As a method for achieving both high density and high speed, there is a method of making a light beam emitted from a light source into a multi-beam. For convenience, it was also considered to use a “VCSEL array”.

  In addition, surface emitting semiconductor lasers have many advantages such as lower manufacturing costs and easier integration by arraying than edge emitting semiconductor lasers. It is expected to be used in many fields such as connection and optical recording.

  A surface emitting semiconductor laser is, for example, a semiconductor laminate in which an n-type semiconductor multilayer reflector, a lower spacer layer, a multiple quantum well active layer, an upper spacer layer, and a p-type semiconductor multilayer reflector are sequentially laminated on an n-type GaAs substrate. Are etched vertically to form a plurality of mesas, the mesa side walls and the periphery are covered with an insulator, and laser light is emitted from the light emitting surface opened at the top of the mesa. The upper electrode provided on the mesa is connected to the electrode pad by wiring. The VCSEL array is a two-dimensionally integrated mesa structure laser oscillation section (light emitting section).

  By the way, among surface emitting semiconductor lasers, there is a so-called selective oxidation type VCSEL that is most promising from the viewpoint of laser characteristics such as a threshold current value and power consumption. This is because an oxidized layer (AlAs layer or an AlGaAs layer whose Al composition is extremely close to 1) is grown as a part of a distributed Bragg reflector (DBR) during crystal growth, and this oxidized layer is grown after crystal growth. By selectively oxidizing the layers, a so-called current confinement structure is created in the VCSEL structure.

  In Patent Document 1, a lower semiconductor multilayer mirror, a resonator structure including an active layer having an oscillation wavelength longer than 1.1 μm, and an upper semiconductor multilayer reflector are sequentially stacked on a semiconductor substrate. Thus, a semiconductor multilayer structure is formed, and at least from the surface of the semiconductor multilayer structure to the lower end of the active layer is formed as a columnar structure by etching removal, and the thickness h is 3 μm or more around the columnar structure. A surface emitting semiconductor laser device provided with a polyimide film is disclosed.

  The selective oxidation type VCSEL is easily deteriorated because distortion occurs in the oxide in the current confinement structure, and sufficient consideration is required in the manufacturing process. Further, in the selective oxidation VCSEL, the stress due to passivation or polyimide formed so as to surround the mesa may affect the element lifetime. In particular, in a VCSEL array, polyimide expands due to heat generated during operation, and a large force may be applied to the mesa. Therefore, in the selective oxidation type VCSEL, it is necessary to minimize the stress applied to the mesa.

  In the conventional selective oxidation type VCSEL manufacturing method, the step portion is flattened with polyimide to prevent disconnection of the wiring. In this case, wiring and electrode pad (bonding pad) portions are formed on the polyimide.

  However, the adhesion between polyimide and metal is poor, and film peeling or bonding failure may occur. In addition, bonding failure may occur due to the softness of the polyimide. In order to improve them, it is conceivable to increase the ultrasonic vibration applied during the bonding operation, but in this case, there is a risk of peeling of the interface between the metal of the electrode pad and the polyimide.

  Further, it is desired to reduce the pitch of the electrode pads in response to the demand for higher density, and the ball diameter is inevitably reduced as the wire diameter becomes smaller. If the ball diameter is reduced, the bonding area is also reduced, which further increases bonding defects.

  In order to suppress such disadvantages related to polyimide, there is a demand for realizing a VCSEL array having a structure that does not use polyimide.

  However, when the side wall of the mesa is almost vertical, if the stepped portion is not flattened with polyimide, vapor deposition on the side wall of the mesa is difficult by a normal vapor deposition method, and so-called wiring disconnection occurs.

  In Patent Document 2, a stacked structure including an active layer and a current confinement layer is formed on a substrate with an inclined structure, and an electrode is formed on the uppermost layer of the stack structure with respect to the current confinement portion of the current confinement layer. There is disclosed a surface emitting laser element that is provided with an offset, an insulating film is provided along an inclined surface on the obtuse angle side of a laminated structure, and a wiring for an electrode is formed on the surface of the insulating film. In this surface emitting laser element, the light output window of the electrode is provided closer to the first inclined surface, and the area of the electrode closer to the inclined surface on the acute angle side than the area closer to the inclined surface on the obtuse angle side. It is getting bigger. As a result, an increase in current injection amount, realization of a single transverse mode, prevention of occurrence of defective formation of insulating films and wirings, and the like are achieved.

JP 2002-270959 A JP 2005-150442 A

  However, in the surface emitting laser element disclosed in Patent Document 2, when an array is formed, the wiring can be taken out from each light emitting portion only from one direction, so that the wiring is complicated and the number of times the wiring is bent increases. There was an inconvenience. In addition, if the number of light emitting units is increased, such as 4 × 6 or 4 × 8, it may be necessary to pass two wires between two light emitting units adjacent to each other. Not suitable for.

  The present invention has been made under such circumstances, and a first object thereof is to manufacture a surface-emitting type semiconductor laser array in which disconnection of wiring is suppressed while maintaining a high-density arrangement of a plurality of light-emitting portions. Another object of the present invention is to provide a method for manufacturing a semiconductor laser array.

  A second object of the present invention is to provide a surface emitting semiconductor laser array capable of stably emitting a plurality of light beams at a high density.

  A third object of the present invention is to provide an optical scanning device capable of stably performing high-density and high-speed optical scanning.

  A fourth object of the present invention is to provide an image forming apparatus capable of stably forming a high quality image at high speed.

  A fifth object of the present invention is to provide an optical transmission module that can generate a stable optical signal.

  A sixth object of the present invention is to provide an optical transmission system capable of performing stable optical transmission.

  From a first viewpoint, the present invention is a semiconductor laser array manufacturing method for manufacturing a surface-emitting type semiconductor laser array having a plurality of light-emitting portions each connected to a corresponding electrode pad by wiring. Applying a photoresist to the surface of the stacked body in which a plurality of semiconductor layers are stacked; a light shielding pattern for shielding light, and a light transmittance adjacent to the first direction of the light shielding pattern toward the first direction. At least one first mesa structure pattern comprising a gradually increasing transmittance change pattern, a light shielding pattern for shielding light, and a second direction different from the first direction of the light shielding pattern, A plurality of mesa structure patterns including at least one second mesa structure pattern including a transmittance change pattern in which light transmittance gradually increases in the second direction. A step of irradiating light onto the surface coated with the photoresist through a mask arranged corresponding to the plurality of light emitting portions to form an etching mask on the surface of the laminate. It is a manufacturing method.

  According to this, at least one first mesa structure having a disconnection prevention structure only in the first direction when the wiring drawing direction is the first direction, and the wiring drawing direction is different from the first direction. A plurality of mesa structures including at least one second mesa structure having a step-break prevention structure only in the second direction in the second direction can be formed corresponding to the plurality of light emitting portions. In this case, each step break prevention structure can be provided so that two adjacent mesa structures do not interfere with each other and the wiring with the corresponding electrode pad is a simple wiring. Therefore, it is possible to manufacture a surface-emitting type semiconductor laser array in which disconnection of wiring is suppressed while maintaining a high-density arrangement of a plurality of light emitting units.

  From a second viewpoint, the present invention is a surface-emitting type semiconductor laser array manufactured by the semiconductor laser array manufacturing method of the present invention.

  According to this, each step break prevention structure can be provided so that two adjacent mesa structures do not interfere with each other and the wiring with the corresponding electrode pad is a simple wiring. Accordingly, it is possible to suppress the disconnection of the wiring while maintaining the high-density arrangement of the plurality of light emitting units, and as a result, it is possible to stably emit the plurality of light beams with high density.

According to a third aspect of the present invention, in the surface-emitting type semiconductor laser array having a plurality of light emitting portions each including a mesa structure , each of which is connected to a corresponding electrode pad by a wiring, the at least one first light emitting portion unwinding direction is the first direction, the drawing direction of the wires and at least one second light-emitting portion is a second direction, the first light emitting portion The mesa structure is formed only in the first direction, and includes a first inclined surface that is inclined from the upper surface toward the first direction, and the measurable structure includes the first inclined surface. The mesa structure of the second light emitting unit is formed only in the second direction, and is inclined from the upper surface toward the second direction. A step-break preventing structure including the second inclined surface; Serial is a surface-emitting type semiconductor laser array and having a side wall comprising a substantially vertical surface facing the second inclined surface.

According to this, it becomes possible to emit a light beam of multiple stable at a high density.

  According to a fourth aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned with a light beam, the light source unit including the surface emitting semiconductor laser array of the present invention; and the light beam from the light source unit is deflected. And a scanning optical system for condensing the light beam deflected by the polarizer on a surface to be scanned.

  According to this, since the light source unit includes the surface-emitting type semiconductor laser array of the present invention, high-density and high-speed optical scanning can be stably performed.

  According to a fifth aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the invention for scanning a plurality of light beams including image information on the at least one image carrier. An image forming apparatus.

  According to this, since at least one optical scanning device of the present invention is provided, as a result, a high-quality image can be stably formed at high speed.

  According to a sixth aspect of the present invention, there is provided an optical transmission module for generating an optical signal corresponding to an input electric signal, the surface emitting semiconductor laser array of the present invention; An optical transmission module comprising: a driving device that is driven according to the input electric signal.

  According to this, since the surface-emitting type semiconductor laser array of the present invention is provided, as a result, a stable optical signal can be generated.

  According to a seventh aspect of the present invention, an optical transmission module of the present invention; an optical transmission medium that transmits an optical signal generated by the optical transmission module; and an optical signal that passes through the optical transmission medium as an electrical signal. An optical transmission system comprising: a converter for converting.

  According to this, since the optical transmission module of the present invention is provided, as a result, stable optical transmission can be performed.

<< Semiconductor Laser Array Manufacturing Method >>
Hereinafter, as an embodiment of the method for producing a semiconductor laser array of the present invention, a method for producing a 780 nm band surface emitting semiconductor laser array will be described with reference to FIGS. In this specification, the laser oscillation direction is defined as the Z-axis direction, and two directions orthogonal to each other in a plane perpendicular to the Z-axis direction are described as the X-axis direction and the Y-axis direction.

(1) A lower reflector 2, a lower spacer layer 3, an active layer 4, an upper spacer layer 5 and selective oxidation are formed on the n-GaAs substrate 1 by crystal growth using metal organic chemical vapor deposition (MOCVD). Semiconductor layers such as the layer 6 and the upper reflecting mirror 7 are sequentially stacked (see FIG. 1A). Hereinafter, a structure in which these semiconductor layers are stacked is also referred to as a “semiconductor stacked body”.

  The n-GaAs substrate 1 is a so-called off-substrate (tilted substrate) whose main surface is inclined.

The lower reflecting mirror 2 has 40.5 pairs of a low refractive index layer made of n-Al _0.9 Ga _0.1 As and a high refractive index layer made of n-Al _0.3 Ga _0.7 As. is doing. The optical thickness of each refractive index layer is λ / 4 where λ is the oscillation wavelength. In addition, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided between the low refractive index layer and the high refractive index layer in order to reduce electrical resistance. It has been.

The lower spacer layer 3 is a layer made of Al _0.6 Ga _0.4 As.

The active layer 4 has a quantum well layer made of Al _0.12 Ga _0.88 As and a barrier layer made of Al _0.3 Ga _0.7 As.

The upper spacer layer 5 is a layer made of Al _0.6 Ga _0.4 As.

  The lower spacer layer 3, the active layer 4, and the upper spacer layer 5 form a resonator region. The optical thickness of this resonator region is λ.

The upper reflecting mirror 7 has 24 pairs of a low refractive index layer made of p-Al _0.9 Ga _0.1 As and a high refractive index layer made of p-Al _0.3 Ga _0.7 As. Yes. In addition, a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition is provided between the low refractive index layer and the high refractive index layer in order to reduce electrical resistance. It has been.

  The selective oxidation layer 6 is a layer made of AlAs, and is provided in the upper reflector 6 at a position λ / 4 away from the resonator region.

Here, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as the Group III material, and arsine (AsH ₃ ) gas is used as the Group V material. Further, carbon tetrabromide (CBr ₄ ) is used as a p-type dopant material, and hydrogen selenide (H ₂ Se) is used as an n-type dopant material.

(2) A photoresist 8 is applied to the surface of the stacked body, which is the surface of the semiconductor stacked body (the surface opposite to the substrate 1) (see FIG. 1B).

(3) The photoresist 8 is irradiated with light through a photomask.

  Here, it is assumed that a photomask is prepared in advance, and on the photomask, as an example, patterns (hereinafter referred to as “chip patterns”) 20 shown in FIG. . The chip pattern 20 includes, as an example, a pattern 22 (hereinafter referred to as “light emitting part pattern” for convenience) 22 shown in FIG. 3 according to the number of light emitting parts included in one chip (here, an example). Only 16).

  This photomask is a so-called gray scale mask. For example, when a stepper exposure machine is used, each light-emitting part pattern has a light scattering plate between the photomask and the lamp when irradiated with light in an out-of-focus state (shifted focus) or when a contact exposure machine is used. When inserted and irradiated with light, as shown in FIG. 3, the first pattern 22a having a light transmittance of 0% and the light transmittance that is adjacent to the first pattern 22a and further away from the first pattern 22a. The second pattern 22b is gradually increased.

In order to make the explanation easy to understand, in the chip pattern 20, the four light emitting portion patterns closest to the −X side are the four light emitting portion patterns on the first row and the four light emitting portion patterns on the + X side of the first row light emitting portion pattern. The light emitting part pattern is the second light emitting part pattern, the four light emitting part patterns on the + X side of the second light emitting part pattern are the third light emitting part pattern, and the third light emitting part pattern is on the + X side. The four light emitting unit patterns are referred to as a fourth row of light emitting unit patterns. And when it is necessary to distinguish each light emission part pattern, as shown in FIG. 4, for convenience, as shown in FIG. 4, the four light emission part patterns of the light emission part pattern in the first row are moved from the left side to the right side. a light emitting portion pattern ₂₂ 1-22 _4, the four light emitting portion pattern of the light emitting portion pattern of the second row, from the left in FIG toward the paper surface right, a light emitting portion pattern ₂₂ 5-22 _8, emission in the third column The four light-emitting part patterns of the light-emitting part patterns are light-emitting part patterns 22 _{9 to} 22 ₁₂ from the left to the right of the paper, and the four light-emitting part patterns in the fourth row of light-emitting part patterns to the right, and the light emitting portion pattern _{22 13-22 16.}

  Each light emitting portion pattern is arranged so that adjacent light emitting portions do not interfere with each other, and the wiring is advantageous for wiring with the corresponding electrode pad (see FIG. 5).

Here, the light emitting portion pattern _{22 1-22} 4, 22 ₆ and 22 _7, a second pattern 22b on the -X side of the first pattern 22a is provided. In the light-emitting portion patterns 22 ₅ and 22 _9, the second pattern 22b is provided on the -Y side of the first pattern 22a. In the light-emitting portion patterns 22 ₈ and _{22 12,} a second pattern 22b is provided on the + Y side of the first pattern 22a. In the light emitting part patterns 22 ₁₀ and 22 ₁₁ and the light emitting part patterns 22 _{13 to} 22 ₁₆ , the second pattern 22 b is provided on the + X side of the first pattern 22 a.

(4) The photoresist 8 is developed.

  As an example, as shown in FIGS. 6A to 6D, the film thickness of the developed photoresist varies depending on the light transmittance of the photomask. Accordingly, as an example, as shown in FIG. 7A, which is a cross-sectional view taken along the line AA of FIG. 7A and FIG. 7A, the photoresist remaining on the surface of the stacked body becomes the first pattern 22a. The corresponding part becomes a plane parallel to the laminate surface, and the part corresponding to the second pattern 22b becomes an inclined surface inclined with respect to the laminate surface.

Then, assuming that the developed photoresist corresponding to the light emitting portion pattern 22 _k (k = 1 to 16) is a resist 8 _k , here, the resists 8 ₁ to 8 ₄ , 8 ₆ and 8 ₇ are planar −X. adjacent to the side, an inclined surface which gradually decreases in the -X direction, the resist 8 ₅ and 8 _9, adjacent to the -Y side of the plane, an inclined surface which gradually decreases in the -Y direction, The resists 8 ₈ and 8 ₁₂ are adjacent to the + Y side of the plane and have an inclined surface that gradually decreases in the + Y direction. In the resists 8 ₁₀ and 8 ₁₁ and the resists 8 ₁₃ to 8 ₁₆ , the + X side of the plane Adjacent and have an inclined surface that gradually decreases in the + X direction.

  A portion corresponding to one chip of the semiconductor laminated body after development is shown in FIG. 9 which is a BB cross-sectional view of FIGS. Hereinafter, in order to make the description easy to understand, description will be made using a portion corresponding to one chip.

(5) Dry etching is performed using the photoresist 8 as an etching mask (see FIG. 10A).

  Here, as an example, the etching conditions are set so that when the photoresist is etched by 0.1 μm, the semiconductor stacked body is etched by 0.5 μm (so-called selectivity = 5). Thereby, a mesa structure having a shape in which one of the four side walls is an inclined surface and the three side walls are substantially vertical surfaces is formed.

  Thus, the mesa structure of the present embodiment is a mesa structure having a shape in which one side wall of a columnar structure that is a conventional mesa structure is an inclined surface. Therefore, it can be considered that the mesa structure of the present embodiment includes a columnar structure portion and an inclined structure portion. This inclined structure portion is a step-break preventing structure. Hereinafter, the mesa structure is abbreviated as “mesa”.

  As an example, the height of the mesa is 3 μm, and the size of the columnar structure is 16 μm × 16 μm. Therefore, for example, when the length of the bottom of the inclined structure portion is 3 μm, the inclination angle of the inclined surface of the inclined structure portion is 45 degrees. Needless to say, the dimensions of the columnar structure portion and the inclined structure portion are not limited to this, and can be arbitrarily changed in the design.

  By the way, the etching bottom surface should just exist in the place which exceeded the to-be-selected oxidation layer 6 at least. Therefore, here, the bottom surface of the etching is set to reach the lower spacer layer 3. As a result, the selectively oxidized layer 6 appears on the side wall of the mesa.

Hereinafter, for convenience, a mesa corresponding to the light emitting unit pattern 22 _k (k = 1 to 16) is referred to as a mesa M _k .

In the mesas M _{1 to} M ₄ , M _6, and M ₇ , the inclined structure portion includes an inclined surface that is adjacent to the −X side of the columnar structure portion and gradually decreases in the −X direction. In the mesas M ₅ and M ₉ , The inclined structure portion is adjacent to the −Y side of the columnar structure portion and includes an inclined surface that gradually decreases in the −Y direction. In the mesas M ₈ and M ₁₂ , the inclined structure portion is adjacent to the + Y side of the columnar structure portion, In the mesa M ₁₀ , M ₁₁ , and the mesas M _{13 to} M ₁₆ , the inclined structure portion is adjacent to the + X side of the columnar structure portion and gradually decreases in the + X direction. Includes face.

(6) The remaining photoresist 8 is removed (see FIG. 10B).

(7) The selective oxidation layer 6 whose side surfaces are exposed by etching is heat-treated in water vapor to partially oxidize the selective oxidation layer 6, and the drive current path is oxidized at the center of the selective oxidation layer 6. A so-called current confinement structure is formed to limit only to a region that is not (see FIG. 11A).

(8) An insulating film 11 made of SiO ₂ is formed as a passivation film (see FIG. 11B).

(9) Open the window of the P-side electrode contact at the top of the mesa (see FIG. 12A). Here, after masking with a photoresist, exposure was performed to remove the portion of the photoresist that would be the opening at the top of the mesa, and the insulating film 11 was etched and opened with BHF.

(10) The p-side electrode 12 is formed by a lift-off method. Specifically, portions other than the electrode are masked in advance with a photoresist, and after the electrode material is deposited, ultrasonic cleaning is performed in a solution in which the photoresist such as acetone is dissolved. As the material of the p-side electrode 12, a multilayer film made of Cr / AuZn / Au or a multilayer film made of AuZn / Ti / Au is used. The p-side electrode 12 has a window in the center of the mesa, and laser light is emitted from this portion.

(11) Each of the plurality of electrode pads 16 is formed at a predetermined position on the semiconductor stacked body. In addition, wirings 15 are formed from the p-side electrodes 12 through the respective inclined surfaces to the corresponding electrode pads 16 (see FIG. 12B).

Here, the wires are drawn in the −X direction in the mesas M _{1 to} M ₄ , M ₆ and M ₇ , and the wires are drawn in the −Y direction in the mesas M ₅ and M ₉ . Further, the mesa _{M 8} and _{M 12} + Y direction wiring is drawn out, the mesa _{M 10, M 11,} and _M 13 in _{~M 16} + X direction in the wiring is drawn out.

  As described above, each light emitting portion pattern 22 is arranged so that adjacent light emitting portions do not interfere with each other and wiring with the corresponding electrode pad is advantageous. It is possible to turn around. Further, even if the number of light emitting portions is large, all wiring is possible without arranging a plurality of wirings between two adjacent mesas. Accordingly, it is possible to reduce the interval between two adjacent mesas, and it is possible to manufacture a surface emitting semiconductor laser array that can cope with higher density.

(12) After polishing the back side of the substrate 1 to about 100 μm, the n-side electrode 14 is formed (see FIG. 13). The n-side electrode 14 is an ohmic contact by being a multilayer film made of AuGe / Ni / Au. Thereby, each mesa becomes the light emitting unit 17.

(13) Cut along dicing lines provided between the chips and separate each chip.

  A surface-emitting type semiconductor laser array 100 manufactured in this way is shown in FIG.

  The surface-emitting type semiconductor laser array 100 includes six light emitting portions having a structure for preventing disconnection only in the -X direction when the wiring drawing direction is in the -X direction, and the wiring drawing direction in the -Y direction and in the -Y direction. Only two light emitting parts having a structure for preventing disconnection, six light emitting parts having a structure for preventing disconnection only in the + X direction when the wiring drawing direction is + X direction, and the + Y direction when the wiring drawing direction is + Y direction Only two light emitting portions having a step-break prevention structure, and each is connected to a corresponding electrode pad by wiring. Further, there is one wire passing between adjacent light emitting units.

  As described above, according to the semiconductor laser array manufacturing method according to the present embodiment, the stacked body is etched from the surface of the stacked body, and the step of preventing disconnection is provided only in the -X direction when the wiring drawing direction is the -X direction. At least one mesa structure, at least one mesa structure having a disconnection prevention structure only in the -Y direction when the wiring drawing direction is -Y direction, and disconnecting only in the + X direction when the wiring drawing direction is + X direction And forming at least one mesa structure having a prevention structure and at least one mesa structure having a step-break prevention structure only in the + Y direction when the wiring drawing direction is + Y direction, corresponding to the plurality of light emitting portions. Yes.

  Each step-break prevention structure is arranged so that adjacent light emitting portions do not interfere with each other and wiring with corresponding electrode pads is advantageous. Therefore, it is possible to manufacture a surface-emitting type semiconductor laser array in which disconnection of wiring is suppressed while maintaining a high-density arrangement of a plurality of light emitting units.

  Moreover, since the columnar structure portion and the inclined structure portion having the step-break prevention structure are integrated, a large step-break prevention effect can be obtained.

  Further, since the inclined structure portion has an inclined surface from the upper surface of the columnar structure portion to the bottom surface of the etching, it does not affect the formation of the p-side electrode 12, and a normal semiconductor is formed in the formation process of the p-side electrode 12. The process can be used as is.

  In addition, since the columnar structure portion and the inclined structure portion are formed at the same time, an increase in the manufacturing process can be suppressed and high-precision processing can be performed. Since the columnar structure portion and the inclined structure portion can be formed by a normal semiconductor process, mass production is easy. That is, cost reduction can be achieved.

  In addition, since a gray scale mask is used as a photomask, it can be easily applied to a normal semiconductor process. Further, the step break prevention structure can be provided at an arbitrary position and in an arbitrary direction only by designing the photomask.

  In the above embodiment, the case where the number of light emitting units included in one chip is 16 has been described. However, the present invention is not limited to this. For example, a surface emitting semiconductor laser array having 40 (4 × 10) light emitting portions in one chip can be manufactured in the same manner.

Further, in the above embodiment, the active layer 4 has been described with a barrier layer made of _Al 0.12 _{Ga 0.88} quantum well layer made of As and _Al 0.3 _{Ga 0.7} As, thereto Without limitation, for example, a three-layer GaInPAs quantum well layer having a compressive strain composition and a band gap wavelength of 780 nm, and a Ga _0.6 having a four-layer tensile strain lattice-matched with the GaInPAs quantum well layer An active layer having an In _0.4 P barrier layer may be used. At this time, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having a wide band gap may be used as a cladding layer for confining electrons (a spacer layer in the above embodiment). Compared with the case where the clad layer is formed of AlGaAs, the band gap difference between the clad layer and the quantum well layer can be made extremely large.

  Moreover, although the said embodiment demonstrated the case where a surface emitting semiconductor laser array of a 780 nm band was manufactured, it is not limited to this.

  In the above embodiment, the MOCVD method is used as the crystal growth method. However, the present invention is not limited to this, and other crystal growth methods such as a molecular beam crystal growth method (MBE method) are used. You can also.

  Moreover, although the said embodiment demonstrated the case where a some light emission part was arrange | positioned at matrix form, it is not limited to this, For example, a some light emission part may be arranged in zigzag form.

  Moreover, in the said embodiment, in the 2nd pattern 22b of a light emission part pattern, you may change the light transmittance by changing the density of the light shielding block of a fixed magnitude | size (FIG. 15 (A)-FIG. 15 (D). )reference).

<Image forming apparatus>
Next, an embodiment of the image forming apparatus of the present invention will be described with reference to FIG. FIG. 16 shows a schematic configuration of a laser printer 500 as an image forming apparatus according to an embodiment of the present invention.

  The laser printer 500 includes an optical scanning device 900, a photosensitive drum 901, a charging charger 902, a developing roller 903, a toner cartridge 904, a cleaning blade 905, a paper feeding tray 906, a paper feeding roller 907, a registration roller pair 908, and a transfer charger 911. , A static elimination unit 914, a fixing roller 909, a paper discharge roller 912, a paper discharge tray 910, and the like.

  The charging charger 902, the developing roller 903, the transfer charger 911, the charge removal unit 914, and the cleaning blade 905 are each disposed near the surface of the photosensitive drum 901. Then, with respect to the rotation direction of the photosensitive drum 901, the charging charger 902, the developing roller 903, the transfer charger 911, the static elimination unit 914, and the cleaning blade 905 are arranged in this order.

  A photosensitive layer is formed on the surface of the photosensitive drum 901. Here, the photosensitive drum 901 rotates clockwise (in the direction of the arrow) within the plane in FIG.

  The charging charger 902 uniformly charges the surface of the photosensitive drum 901.

  The optical scanning device 900 irradiates the surface of the photosensitive drum 901 charged by the charging charger 902 with light modulated based on image information from a host device (for example, a personal computer). As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 901 on the surface of the photosensitive drum 901. The latent image formed here moves in the direction of the developing roller 903 as the photosensitive drum 901 rotates. The configuration of the optical scanning device 900 will be described later.

  The toner cartridge 904 stores toner, and the toner is supplied to the developing roller 903.

  The developing roller 903 causes the toner supplied from the toner cartridge 904 to adhere to the latent image formed on the surface of the photosensitive drum 901 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for convenience) moves in the direction of the transfer charger 911 as the photosensitive drum 901 rotates.

  Recording paper 913 is stored in the paper feed tray 906. A paper feed roller 907 is disposed in the vicinity of the paper feed tray 906, and the paper feed roller 907 takes out the recording paper 913 one by one from the paper feed tray 906 and conveys it to the registration roller pair 908. The registration roller pair 908 is disposed in the vicinity of the transfer roller 911, temporarily holds the recording paper 913 taken out by the paper feed roller 907, and the recording paper 913 is synchronized with the rotation of the photosensitive drum 901. It is sent out toward the gap between 901 and the transfer charger 911.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 911 in order to electrically attract the toner on the surface of the photosensitive drum 901 to the recording paper 913. With this voltage, the toner image on the surface of the photosensitive drum 901 is transferred to the recording paper 913. The recording sheet 913 transferred here is sent to the fixing roller 909.

  In the fixing roller 909, heat and pressure are applied to the recording paper 913, whereby the toner is fixed on the recording paper 913. The recording paper 913 fixed here is sent to the paper discharge tray 910 via the paper discharge roller 912 and sequentially stacked on the paper discharge tray 910.

  The neutralization unit 914 neutralizes the surface of the photosensitive drum 901.

  The cleaning blade 905 removes toner remaining on the surface of the photosensitive drum 901 (residual toner). The removed residual toner is used again. The surface of the photosensitive drum 901 from which the residual toner has been removed returns to the position of the charging charger 902 again.

<Optical scanning device>
Next, the configuration and operation of the optical scanning device 900 will be described with reference to FIGS. 17 and 18.

  The optical scanning device 900 includes a light source unit 121, a coupling lens 122, an aperture plate 123, an anamorphic lens 124, a polygon mirror 125, a deflector side scanning lens 126, an image plane side scanning lens 127, a processing device 140, and the like. I have. In FIG. 17, the horizontal direction on the paper is the main scanning direction, and the direction perpendicular to the paper is the sub-scanning direction.

  As shown in FIG. 18, the light source unit 121 includes a surface-emitting type semiconductor laser array 200 manufactured in the same manner as the semiconductor laser array manufacturing method described above, and can simultaneously output 16 light beams. In FIG. 18, illustration of the step-break prevention structure, electrode pads, and wiring is omitted.

  The coupling lens 122 turns the plurality of light beams output from the light source unit 121 into weak divergent light.

  The aperture plate 123 has an aperture and defines the beam diameter of a plurality of light beams from the coupling lens 122.

  The anamorphic lens 124 converts a plurality of light beams that have passed through the opening of the aperture plate 123 into parallel light in the main scanning direction and light beams that converge near the polygon mirror 125 in the sub-scanning direction.

  A plurality of light beams from the anamorphic lens 124 are respectively deflected by the polygon mirror 125, and then mutually deflected in the sub scanning direction on the surface of the photosensitive drum 901 by the deflector side scanning lens 126 and the image surface side scanning lens 127. It is condensed as a light spot at a position separated by a predetermined interval.

  The polygon mirror 125 is rotated at a constant speed by a polygon motor (not shown). Along with the rotation, the plurality of light beams are deflected at equal angular speeds, and each light spot on the photosensitive drum 901 is reflected. Moves at a constant speed in the main scanning direction.

  The processing device 140 generates image data based on image information from a host device (for example, a personal computer), and outputs a drive signal for the surface emitting laser array 200 corresponding to the image data to the light source unit 121.

  In the surface-emitting type semiconductor laser array 200, as shown in FIG. 18, the position of each light emitting unit in the sub-scanning direction when a perpendicular is drawn from a virtual line extending in the direction corresponding to the sub-scanning direction from the center of each light emitting unit. Since the relationship is equally spaced (interval C), it can be considered that the light source is arranged on the photosensitive drum 901 at equal intervals in the sub-scanning direction by adjusting the lighting timing. . For example, when the size of each light emitting unit is φ20 μm, the pitch in the direction corresponding to the main scanning direction is 40 μm, and the pitch in the direction corresponding to the sub-scanning direction is 40 μm, the interval C = 10 μm, and assuming that the magnification of the scanning optical system is 1, 2400 dpi (dot / inch) can be realized. Of course, if the number of light emitting portions in the direction corresponding to the main scanning direction is increased or the pitch in the direction corresponding to the sub-scanning direction is reduced to further reduce the interval C, the density can be further increased and the quality can be improved. Printing is possible. Note that the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light emitting unit.

  Therefore, the optical scanning device 900 according to the present embodiment has the surface-emitting type semiconductor laser array of the present invention that can stably emit a plurality of light beams at high density. It becomes possible to carry out stably.

  In addition, the laser printer 500 according to the present embodiment includes the optical scanning device 900 that can stably perform high-density and high-speed optical scanning. As a result, high-quality images can be stabilized at high speed. Can be formed.

  In the above embodiment, the case where the light source unit 121 includes the surface-emitting type semiconductor laser array 200 having 16 (= 4 × 4) light emitting units has been described. However, the present invention is not limited to this. For example, instead of the surface emitting semiconductor laser array 200, as shown in FIG. 19, a surface having 40 (= 4 × 10) light emitting portions manufactured in the same manner as the semiconductor laser array manufacturing method described above. A light emitting semiconductor laser array 300 may be used. In this case, 40 light beams can be emitted simultaneously, and the photosensitive drum 901 can be scanned at a higher density. In FIG. 19, the illustration of the step-break prevention structure is omitted.

  In the above-described embodiment, the case where the wavelength of the laser light emitted from each light emitting unit is in the 780 nm band has been described. However, the wavelength is not limited to this, and any wavelength corresponding to the sensitivity characteristic of the photosensitive drum 901 may be used. In this case, at least a part of the material constituting each light emitting part or at least a part of the structure of each light emitting part is changed according to the oscillation wavelength.

  In the above embodiment, the laser printer 500 is described as the image forming apparatus. However, the present invention is not limited to this. In short, an image forming apparatus provided with the optical scanning device of the present invention can stably form a high-quality image at a high speed.

  Even an image forming apparatus that forms a color image has a surface emitting semiconductor laser array according to the present invention, and uses an optical scanning device corresponding to a color image, thereby stabilizing a high-quality color image at high speed. Can be formed.

  As an example, as shown in FIG. 20, the image forming apparatus may be a tandem color machine corresponding to a color image and including a plurality of photosensitive drums. The tandem color machine includes a black (K) photosensitive drum K1, a charger K2, a developing device K4, a cleaning unit K5, a transfer charging unit K6, a cyan (C) photosensitive drum C1, and a charger. C2, developing unit C4, cleaning unit C5, transfer charging unit C6, magenta (M) photosensitive drum M1, charging unit M2, developing unit M4, cleaning unit M5, transfer charging unit M6, yellow (Y) photosensitive drum Y1, charging unit Y2, developing unit Y4, cleaning unit Y5, transfer charging unit Y6, optical scanning device 900, transfer belt 80, fixing unit 30 and the like.

  In this case, in the optical scanning device 900, the plurality of light emitting portions in the surface emitting semiconductor laser array of the present invention are divided into black, cyan, magenta, and yellow. The light beam from the black light emitting unit is irradiated to the photosensitive drum K1, the light beam from the cyan light emitting unit is irradiated to the photosensitive drum C1, and the light beam from the magenta light emitting unit is applied to the photosensitive drum M1. The light beam emitted from the light emitting section for yellow is applied to the photosensitive drum Y1. The optical scanning device 900 may include the surface emitting semiconductor laser array of the present invention for each color. Moreover, you may provide the optical scanning device of this invention for every color.

  Each photosensitive drum rotates in the direction of the arrow in FIG. 20, and a charger, a developer, a transfer charging unit, and a cleaning unit are arranged in the order of rotation. Each charger uniformly charges the surface of the corresponding photosensitive drum. The surface of the photosensitive drum charged by the charger is irradiated with a light beam by the optical scanning device 900, and an electrostatic latent image is formed on the photosensitive drum. Then, a toner image is formed on the surface of the photosensitive drum by the corresponding developing device. Further, the toner images of the respective colors are transferred onto the recording paper by the corresponding transfer charging means, and finally the image is fixed on the recording paper by the fixing means 30.

  In a tandem color machine, color misregistration of each color may occur due to mechanical accuracy or the like. However, since the optical scanning device 900 has the surface emitting semiconductor laser array of the present invention, a light emitting unit to be lit is provided. By selecting the color misregistration, it is possible to improve the color misregistration correction accuracy of each color.

  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.

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

<Optical transmission system>
FIG. 21 shows a schematic configuration of an optical transmission system 1000 according to an embodiment of the present invention. In this optical transmission system 1000, an optical transmission module 1001 and an optical reception module 1005 are connected by an optical fiber cable 1004, and one-way optical communication from the optical transmission module 1001 to the optical reception module 1005 is possible.

  The optical transmission module 1001 includes a light source 1002 including the surface emitting semiconductor laser array of the present invention, a drive circuit 1003 that modulates the light intensity of the laser light emitted from the light source 1002 in accordance with an electrical signal input from the outside, and have.

  The optical signal output from the light source 1002 is coupled to the optical fiber cable 1004, guided through the optical fiber cable 1004, and input to the optical receiving module 1005.

  The optical receiving module 1005 includes a light receiving element 1006 that converts an optical signal into an electric signal, and a receiving circuit 1007 that performs signal amplification, waveform shaping, and the like on the electric signal output from the light receiving element 1006.

  According to the optical transmission module 1001 according to the present embodiment, since the light source 1002 includes the surface-emitting type semiconductor laser array of the present invention, a plurality of light beams can be stably emitted with high density, and as a result, a stable optical signal. Can be generated.

  Also, according to the optical transmission system 1000 according to the present embodiment, the optical transmission module 1001 that can generate a stable optical signal is provided, so that low-power consumption, high-speed, and large-capacity optical transmission can be stabilized. Can be performed.

  In the present embodiment, a configuration example of unidirectional communication of a single channel is shown, but a configuration of bidirectional communication, a parallel transmission method, a wavelength division multiplex transmission method, or the like can also be adopted. In short, the light source 1002 only needs to include the surface-emitting type semiconductor laser array of the present invention.

  As described above, according to the semiconductor laser array manufacturing method of the present invention, it is possible to manufacture a surface emitting semiconductor laser array in which disconnection of wiring is suppressed while maintaining a high-density array of a plurality of light emitting portions. Is suitable. The surface-emitting type semiconductor laser array of the present invention is suitable for stably emitting a plurality of light beams at a high density. The optical scanning device of the present invention is suitable for stably performing high-density and high-speed optical scanning. The image forming apparatus of the present invention is suitable for stably forming a high quality image at high speed. The optical transmission module of the present invention is suitable for generating a stable optical signal. The optical transmission system of the present invention is suitable for performing stable optical transmission.

1A and 1B are views (No. 1) for explaining a semiconductor laser array manufacturing method according to an embodiment of the present invention. It is a figure for demonstrating a chip pattern. It is a figure for demonstrating a light emission part pattern. It is a figure for demonstrating the code | symbol attached | subjected in order to identify the light emission part pattern. It is a figure for demonstrating arrangement | positioning of each light emission part pattern. FIGS. 6A to 6D are diagrams for explaining the relationship between the light transmittance of the light emitting portion pattern and the film thickness of the photoresist after development, respectively. FIG. 7A is a diagram for explaining the shape of the photoresist after development, and FIG. 7B is a cross-sectional view taken along line AA in FIG. 7A. It is a figure for demonstrating a part of semiconductor laminated body after developing a photoresist. It is BB sectional drawing of FIG. FIGS. 10A and 10B are views (No. 2) for explaining the semiconductor laser array manufacturing method according to the embodiment of the invention. 11A and 11B are views (No. 3) for explaining the semiconductor laser array manufacturing method according to the embodiment of the invention. FIGS. 12A and 12B are views (No. 4) for describing the method of manufacturing the semiconductor laser array according to the embodiment of the invention. It is FIG. (5) for demonstrating the semiconductor laser array manufacturing method which concerns on one Embodiment of this invention. It is a figure for demonstrating the surface emitting semiconductor laser array manufactured by the semiconductor laser array manufacturing method which concerns on one Embodiment of this invention. FIG. 15A to FIG. 15D are diagrams for explaining the light emitting portion pattern and its light transmittance, respectively. It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is the schematic which shows the optical scanning device in FIG. It is a figure for demonstrating an example of the surface emitting semiconductor laser array contained in the light source unit in FIG. It is a figure for demonstrating the other example of the surface emitting semiconductor laser array contained in the light source unit in FIG. It is a figure for demonstrating schematic structure of a tandem color machine. It is a figure for demonstrating schematic structure of the optical transmission module and optical transmission system which concern on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 8 ... Photoresist, 15 ... Wiring, 16 ... Electrode pad, 17 ... Light emission part, 22 ... Light emission part pattern (pattern for mesa structure), 100 ... Surface emitting semiconductor laser array, 121 ... Light source unit, 125 ... Polygon mirror (deflector), 126 ... Deflector-side scanning lens (part of scanning optical system), 127 ... Image plane-side scanning lens (part of scanning optical system), 200 ... Surface emitting semiconductor laser array, DESCRIPTION OF SYMBOLS 300 ... Surface emitting semiconductor laser array, 500 ... Laser printer (image forming apparatus), 900 ... Optical scanning device, 901 ... Photosensitive drum (image carrier), 1000 ... Optical transmission system, 1001 ... Optical transmission module (optical transmission) Module), 1003... Drive circuit (drive device), 1004... Optical fiber cable (light transmission medium), 1006... Light receiving element (part of converter), 1007 (Part of the transducer) receiver circuit.

Claims (12)

A semiconductor laser array manufacturing method for manufacturing a surface-emitting type semiconductor laser array having a plurality of light emitting portions each connected to a corresponding electrode pad by wiring,
Applying a photoresist to the surface of a laminate in which a plurality of semiconductor layers are laminated on a substrate;
For at least one first mesa structure comprising a light shielding pattern that shields light and a transmittance change pattern that is adjacent to the first direction of the light shielding pattern and gradually increases in light transmittance toward the first direction. A pattern, a light shielding pattern that shields light, and a transmittance change pattern that is adjacent to a second direction different from the first direction of the light shielding pattern and in which the light transmittance gradually increases in the second direction. A plurality of mesa structure patterns including at least one second mesa structure pattern formed on the surface coated with the photoresist through a mask arranged corresponding to the plurality of light emitting portions. And a step of forming an etching mask on the surface of the laminated body.   The semiconductor laser array manufacturing method according to claim 1, wherein the plurality of light emitting units are arranged in a staggered pattern.   A surface-emitting type semiconductor laser array manufactured by the method for manufacturing a semiconductor laser array according to claim 1. In a surface-emitting type semiconductor laser array, each of which is connected to a corresponding electrode pad by wiring and has a plurality of light emitting portions including a mesa structure
Wherein the plurality of light emitting units, including at least one first light emitting portion out direction of the wiring is the first direction, the drawing direction of the wires and at least one second light-emitting portion is a second direction See
The mesa structure of the first light emitting unit is formed only in the first direction, and includes a first sloped surface that includes a first inclined surface that is inclined from the upper surface toward the first direction; A side wall including a substantially vertical surface facing the first inclined surface,
The mesa structure of the second light emitting unit is formed only in the second direction, and includes a second sloped surface that includes a second inclined surface that is inclined from the upper surface toward the second direction, and A surface emitting semiconductor laser array , comprising: a side wall including a substantially vertical surface facing the second inclined surface . 5. The surface emitting semiconductor laser array according to claim 4 , wherein the plurality of light emitting units are arranged in a staggered manner. The first wiring in the first direction from the light emitting unit is pulled out, said second light-emitting portion to claim 4 or 5, characterized in that the wiring is drawn in the second direction The surface emitting semiconductor laser array described. Vertical-cavity surface-emitting laser array according to any one of claims 4-6, characterized in that the wire passing between the two adjacent light-emitting portion is a one of the plurality of light emitting portions. An optical scanning device that scans a surface to be scanned with a light beam,
A light source unit including a surface-emitting type semiconductor laser array according to any one of claims 3-7;
A deflector for deflecting a light beam from the light source unit;
A scanning optical system for condensing the light beam deflected by the polarizer onto a surface to be scanned. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to claim 8 that scans a plurality of light beams including image information on the at least one image carrier. The image forming apparatus according to claim 9 , wherein the image information is color image information. An optical transmission module that generates an optical signal according to an input electrical signal,
A surface emitting semiconductor laser array according to any one of claims 3 to 7 ;
An optical transmission module comprising: a driving device that drives the surface-emitting type semiconductor laser array in accordance with the input electric signal. An optical transmission module according to claim 11 ;
An optical transmission medium for transmitting an optical signal generated by the optical transmission module;
A converter for converting an optical signal through the optical transmission medium into an electric signal;