JP5095091B2 - Laser device manufacturing method - Google Patents

Description

  The present invention relates to a laser device used for optical discs, inspections, illuminations, etc., and more particularly to a method for manufacturing a short wavelength laser device such as a gallium nitride based semiconductor laser device.

  Group III nitride semiconductors (hereinafter referred to as “gallium nitride semiconductors”) such as GaN, AlGaN, GaInN, and AlGaInN emit light at a short wavelength because they have a larger energy band gap than AlGaInAs semiconductors and AlGaInP semiconductors. In addition, since it is a direct transition type, it has a feature that it is a semiconductor material having excellent luminous efficiency. For this reason, these gallium nitride semiconductors are semiconductor light emitting devices such as semiconductor laser devices capable of emitting light in the wavelength range from ultraviolet to green and light emitting diodes (LEDs) capable of covering a wide emission wavelength range from ultraviolet to red. It is attracting attention as a material that constitutes, and is widely considered for applications such as high-density optical discs, full-color displays, and the environment and medical fields.

Since this gallium nitride based semiconductor has higher thermal conductivity than GaAs based semiconductors, it is expected to be applied as an element operating at high temperature and high output. Further, arsenic (As) is used in AlGaAs semiconductors and cadmium (Cd) is used in ZnCdSSe semiconductors, whereas gallium nitride semiconductors contain such harmful materials. Moreover, since the toxicity of ammonia (NH ₃ ) used as a raw material is less than that of arsine (AsH ₃ ), which is a raw material for AlGaAs-based semiconductors, the burden on the environment is small.

  By the way, the gallium nitride semiconductor laser device has a problem of deterioration of the laser light emitting end face. In this regard, it is assumed that the pressure-sensitive adhesive used in the pressure-sensitive adhesive sheet used in the manufacturing process or the organic matter present in the air in the manufacturing process is the generation source and is deposited on the laser light emitting end face as follows.

  In the manufacturing process of a gallium nitride based semiconductor laser chip, a wafer on which a plurality of gallium nitride based semiconductor laser chips are manufactured is divided to form a laser beam emitting end face into a bar shape (hereinafter referred to as “laser bar”). To do. In the chip dividing step of further dividing the laser bar into individual gallium nitride based semiconductor laser chips, the laser bar is once attached to the adhesive sheet. Next, a scribe line is formed on the laser bar using a diamond scriber or the like. Further, the laser bar is divided into chips. At this time, since the adhesive sheet is attached to the laser bar, the divided gallium nitride-based semiconductor laser chips are not separated. However, the adhesive of the adhesive sheet adheres to the gallium nitride semiconductor laser chip.

  The gallium nitride semiconductor laser chips thus divided are separated one by one from the adhesive sheet, and after a chip test, they are fixed to the stem. Further, by attaching a lid, the inside of the package is hermetically sealed, and the laser device is completed. Prior to hermetic sealing, other components such as the submount, stem, and lid may be attached with organic substances in the air in the manufacturing process. Possible sources of organic substances in the atmosphere include microorganisms, humans, building materials, and greases and oils used in manufacturing equipment.

  Adhering contaminants are vaporized and drift inside the package of the completed laser device. The vaporized contaminant causes a photochemical reaction by a photochemical vapor deposition (CVD) effect by a short wavelength laser beam emitted from the gallium nitride semiconductor laser chip, and contains Si (silicon) or C (carbon) as a main component. It becomes a photochemical reaction substance. This photochemical reaction material is deposited on the laser light emitting end face having the highest light intensity. Such a phenomenon is caused by a laser having an oscillation wavelength (emission wavelength) of 550 nm or less, which has a high energy per photon and easily promotes a chemical reaction, in particular, a laser using a gallium nitride semiconductor laser chip having an oscillation wavelength of 420 nm or less. In the device it becomes prominent.

  As described above, when the photochemical reaction material is deposited on the laser light emitting end face, the light absorption at the laser light emitting end face is increased and the reflectance is changed. As a result, the laser drive current required to obtain the same output increases, and the life of the laser becomes very short.

  In order to avoid such a problem, the gallium nitride semiconductor laser chip is irradiated by irradiating the stem to which the gallium nitride semiconductor laser chip is fixed with ultraviolet light or by irradiating plasma generated by an ECR (Electron Cyclotron Resonance) method. In addition, a method of hermetically sealing with a lid after removing contaminants attached to the lid has been proposed (see Patent Document 1).

In addition, the stem to which the gallium nitride semiconductor laser chip is fixed is hermetically sealed with a lid in an ozone atmosphere, and then irradiated with ultraviolet rays to remove contaminants attached to the gallium nitride semiconductor laser chip and the lid. A method has been proposed (see Patent Document 2).
JP 2004-40051 A JP 2004-273908 A

  When the technique according to Patent Document 1 described above is used, components such as a stem and a gallium nitride semiconductor laser chip are taken out from the processing apparatus after ultraviolet or plasma irradiation, and the components are exposed to the atmosphere. There was a problem that it was re-contaminated with contaminants before sealing. In particular, there is a process using an Ag paste containing a large amount of an organic solvent between the irradiation process of ultraviolet light or plasma and the hermetic sealing process, or between the irradiation process of ultraviolet light or plasma and the hermetic sealing process. Recontamination becomes noticeable when the exposure time is long.

  Further, when hermetic sealing is performed in an ozone atmosphere using the technique disclosed in Patent Document 2, it is used for solder in which a gallium nitride semiconductor laser chip and a stem are joined by ozone or a gallium nitride semiconductor laser chip. As a result of oxidation of the electrodes, the characteristics are deteriorated or the lifetime is reduced as a problem different from the removal of the pollutants. On the other hand, a sufficient effect cannot be obtained by simply irradiating ultraviolet rays without hermetic sealing in an ozone atmosphere, especially when the continuous operation is performed at an environmental temperature of 60 ° C. (increasing drive current value). ) Will occur.

  The present invention has been made in view of such problems, and package components such as a laser chip, a stem, and a lid without deteriorating solder and electrodes used in a gallium nitride based semiconductor laser chip. An object of the present invention is to provide a method of manufacturing a laser device having a long life by removing contaminants adhering to the surface and suppressing the deposition of photochemical reaction materials on the laser light emitting end face during the operation of the laser chip.

  (1) The present invention includes a step of fixing a laser chip inside a package provided with a window, a step of hermetically sealing the inside of the package, and the package from the window while being heated to 70 ° C. Is a method of manufacturing a laser device, characterized by having a step of irradiating light with a wavelength of 420 nm or less inside. The inside of the package is, for example, a space generated between a stem to which a laser chip is fixed and a lid joined to the stem. If it is 70 degreeC or more, since it exceeds the boiling point of some substances considered as a pollutant so that it may mention later, they vaporize inside a package. In this state, the vaporized contaminant is decomposed and removed by irradiation with light having a wavelength of 420 nm or less (hereinafter referred to as “ultraviolet light”). As a result, it is possible to remove contaminants present in a portion where ultraviolet rays or the like do not reach sufficiently. Moreover, according to this manufacturing method, since the process of irradiating ultraviolet rays etc. is performed after airtight sealing, there is no recontamination. Therefore, it is possible to prevent the laser from being deteriorated during the operation of the laser chip.

  (2) The present invention is a method of manufacturing a laser device, wherein the laser device is heated to 280 ° C. or lower in the step of irradiating the ultraviolet ray or the like. Since this condition is below the melting point of a solder material such as AuSn, it is possible to perform irradiation with ultraviolet rays or the like while keeping the laser chip fixed to the package.

  (3) The present invention provides the method for manufacturing a laser device, wherein the wavelength of the light is 150 nm or more and 290 nm or less. If the wavelength is 150 nm or more, the window can be transmitted, and if the wavelength is 290 nm or less, the contaminant is decomposed by breaking the siloxane bond in the siloxane-based material considered as a contaminant. Can do.

  (4) The present invention is a method for manufacturing a laser device, characterized in that dry air or inert gas is sealed inside the package. This makes it difficult for metals such as solder materials and electrodes used in the package to be oxidized or corroded.

  (5) The present invention is the method for manufacturing a laser device, wherein the dew point of the enclosed gas is −10 ° C. or lower. This makes it difficult for metals such as solder materials and electrodes used in the package to be oxidized or corroded.

  (6) The present invention is the method for manufacturing a laser device, wherein the window portion is made of quartz glass, quartz or sapphire, or a material using these as a base material. Since these materials have good ultraviolet transmittance, irradiation with ultraviolet rays or the like from the outside can reach the inside of the package without being absorbed by the window portion.

  (7) The present invention is the laser device manufacturing method, wherein the laser chip fixed to the laser device has an emission wavelength of 420 nm or less. The light in this wavelength region has an action of decomposing organic substances, and as a result, a photochemical reaction substance is deposited on the laser light emitting end face, so that the manufacturing method of the present invention is effective.

  (8) The present invention is the method for manufacturing a laser device, wherein the laser chip fixed to the laser device is a gallium nitride based semiconductor laser chip. Gallium nitride semiconductor laser chips are small and have high efficiency as light sources for blue, purple, and near ultraviolet light.

  In the present invention, the inside of a hermetically sealed laser chip package is irradiated with ultraviolet rays or the like in a heated state, whereby contaminants are vaporized and decomposed and removed by irradiation with ultraviolet rays or the like. It is also possible to remove pollutants present in areas that do not reach enough. Moreover, according to this manufacturing method, since the process of irradiating ultraviolet rays etc. is performed after airtight sealing, there is no recontamination. Therefore, no photochemical reaction material is deposited on the laser light emitting end face during the operation of the laser device, so that increase in light absorption and reflectance fluctuation are suppressed, and the laser chip drive current is stabilized over a long period of time. Can be realized.

  Hereinafter, a gallium nitride based semiconductor laser device that is the best mode for carrying out the present invention will be described. However, suppression of characteristic deterioration due to deposition of a photochemical reaction material on the laser light emitting end surface, which is a problem of the present invention, is a problem common to laser devices having a wavelength of 550 nm or less, particularly 420 nm or less. Therefore, the present invention is also applicable to other laser devices such as an SHG laser that generates light having a wavelength of about 405 nm using a laser having a wavelength of about 810 nm and an SHG (Second Harmonic Generation) element. In addition, other lasers that are currently under development and are expected to have superior characteristics over gallium nitride semiconductor laser devices in the future, such as laser devices using organic substances and zinc oxide semiconductors The present invention can also be applied to an apparatus.

(Structure of semiconductor laser device)
Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1A is a front view of the laser chip fixing holder 300 and the lid 330, and FIG. 1B is a top view.

  In the semiconductor laser device 340, the inside of the package composed of the stem 320 and the lid 330 is hermetically sealed by joining the laser chip fixing holder 300 and the lid 330. The laser chip fixing holder 300 is obtained by fixing a gallium nitride based semiconductor laser chip 350 on a block portion 321 of a stem 320 via a submount 310. One end of the lid 330 is open, and a window 330A is provided at the other end. The lid 330 is made of a metal such as copper or iron, and the window 330A is made of quartz or quartz glass that can transmit laser light emitted from the gallium nitride based semiconductor laser chip 350 and ultraviolet light emitted from the outside, glass, Made of plastic, sapphire, etc.

  Referring to FIG. 1A, a gallium nitride based semiconductor laser chip 350 includes an n-type GaN substrate 301, a laminated body 302 made of a plurality of gallium nitride based semiconductor layers formed on the n-type GaN substrate 301, and a laminated structure. It comprises a p-side electrode 303 formed on the surface of the body 302, an n-side electrode (inner layer) 304A and an n-side electrode (outer layer) 304B formed in this order from the side closer to the n-type GaN substrate 301. The n-side electrode (outer layer) 304B is fixed to the surface side of the submount 310 via solder 312 (Au: 70 wt%, Sn: 30 wt%) made of Au70Sn30.

  The submount 310 is formed by forming metal multilayer films 307 and 308 on the front surface side and the back surface side of the SiC plate, respectively. The metal multilayer films 307 and 308 are formed by laminating, for example, titanium (Ti), platinum (Pt), and gold (Au) in this order from the side in contact with the SiC plate of the submount 310. The back surface side of the submount 310 is fixed to the block portion 321 of the stem via solder 313 (main component Sn, Ag: 3 wt%, Cu: 0.5 wt%) made of SnAg3Cu0.5. The submount 310 has a role of radiating heat generated in the gallium nitride based semiconductor laser chip 350.

  The p-side electrode 303 is connected to the pin 316 via the wire 314A, the n-side electrode (inner layer) 304A is the n-side electrode (outer layer) 304B, the solder 312 made of Au70Sn30, the metal multilayer 307, and the pin 311 via the wire 314B. Is electrically connected. Further, insulating rings 311A and 316A are provided between the stem 320 and the pins 311 and 316, respectively. The pins 311 and 316 and the stem 320 and the block portion 321 of the stem which is a part of the stem 320 are provided. The gap is electrically insulated from the stem 320 using insulating rings 311A and 316A. Current is supplied from the pins 311 and 316 to the gallium nitride based semiconductor laser chip 350. The pin 322 is electrically connected to the stem 320.

(Structure of gallium nitride semiconductor laser chip)
Next, the structure of the gallium nitride based semiconductor laser chip 350 will be described. FIG. 2 shows a front view of the gallium nitride based semiconductor laser chip 350. The stacked body 302 includes an n-type GaN contact layer 402, an n-type AlGaN cladding layer 403, an n-type GaN guide layer 404, an InGaN multiple quantum well active layer 405, which are sequentially formed on the surface of the n-type GaN substrate 301. The p-type AlGaN evaporation prevention layer 406, the p-type GaN guide layer 407, the p-type AlGaN cladding layer 408, the p-type GaN contact layer 409, and the SiO ₂ insulating film 410.

The p-type AlGaN cladding layer 408 and the p-type GaN contact layer 409 are provided with striped ridges 306 extending in the resonator direction. That is, the gallium nitride based semiconductor laser chip 350 shown in FIG. 2 has a ridge stripe structure. Further, an SiO ₂ insulating film 410 for current confinement is provided between the p-side electrode 303 and the p-type AlGaN cladding layer 408 and the p-type GaN contact layer 409 except for the ridge 306 portion.

  Note that the material used for the gallium nitride based semiconductor layer in the stacked body 302 is not limited to the above-described materials, but other gallium nitride based semiconductors, for example, p-type AlGaInN is used for the p-type cladding layer, and multiple quantum wells are used. GaInNAs or GaInP may be used for the active layer. Further, the n-type AlGaN cladding layer 403 or the p-type AlGaN cladding layer 408 may have a multilayer structure or a multiple quantum well structure. Furthermore, a crack prevention layer such as an InGaN layer may be inserted between the n-type GaN contact layer 402 and the n-type AlGaN cladding layer 403. Further, a buffer layer may be inserted between the n-type GaN substrate 301 and the n-type GaN contact layer 402. Further, the ridge 306 extending in a stripe shape in the resonator direction is not only the p-type AlGaN cladding layer 408 and the p-type GaN contact layer 409, but also the p-type GaN guide layer 407, the p-type AlGaN evaporation prevention layer 406, and the InGaN multiple layers. The quantum well active layer 405 may be formed by being dug up to somewhere.

  Further, in the first embodiment, the n-type GaN substrate 301 is used to manufacture the gallium nitride based semiconductor laser chip 350, but the substrate material is not limited to GaN, and a mixture of InN, AlN or GaN, InN, and AlN. It may be a crystal semiconductor, or a sapphire, spinel, SiC, Si, or a III-V group semiconductor such as GaAs or GaP other than a gallium nitride semiconductor.

(Gallium nitride semiconductor laser chip manufacturing process)
Below, the manufacturing process of the laser apparatus of Embodiment 1 is demonstrated.

  First, from a plurality of gallium nitride semiconductor layers as shown in FIG. 2 on the n-type GaN substrate 301 by appropriately using a well-known technique generally used for manufacturing a gallium nitride semiconductor laser chip. A wafer on which the laminated body 302 and the p-side electrode 303 are formed is manufactured. The p-side electrode 303 is Pd (15 nm) / Mo (15 nm) / Au (200 nm) from the side close to the p-type GaN contact layer 409.

  Next, polishing or etching is performed from the back side of the n-type GaN substrate 301 to reduce the thickness of the wafer from the initial 350 μm to about 40 to 150 μm. Thereafter, Ti (30 nm) / Al (150 nm) is formed from the side close to the n-type GaN substrate 301 as the n-side electrode (inner layer) 304A, and Mo (8 nm) / Pt (as the n-side electrode (outer layer) 304B is formed. 15 nm) / Au (250 nm).

The wafer on which the multilayer body 302, the p-side electrode 303, the n-side electrode (inner layer) 304A, and the n-side electrode (outer layer) 304B are formed is cleaved, and a vacuum evaporation method or an ECR sputtering method is applied to the cleaved surface. By performing end face coating made of a transparent dielectric such as Al ₂ O ₃ (not shown), the laser light emitting end face of the gallium nitride based semiconductor laser chip 350 is formed. At this time, the wafer is cleaved so that the resonator length of the gallium nitride based semiconductor laser chip 350 is 600 μm. Incidentally, the laser light emitting end face may be formed by etching instead of cleaving the wafer.

(Chip splitting process of gallium nitride semiconductor laser chip)
The laser bar obtained by cleaving the wafer in this way is further divided into gallium nitride based semiconductor laser chips 350. In FIG. 3A showing the scribing process which is the first half of the chip dividing process, the laser bar 140 attached to the adhesive sheet 150 is set in a scribing device (not shown), and a diamond scriber in the scribing device, etc. The scribe line 141 is formed using There is a possibility that the adhesive of the adhesive sheet 150 may adhere to and remain on the divided gallium nitride semiconductor laser chip 350. Next, in the breaking process, which is the latter half of the chip splitting process, as shown in FIG. 3 (b), the adhesive sheet 150 is stretched in the direction indicated by the arrows 151 and 152 perpendicular to the scribe line 141, so that the laser bar The individual gallium nitride based semiconductor laser chip 350 is divided from 140. Since the gallium nitride based semiconductor laser chip 350 is affixed to the adhesive sheet 150, it does not fall apart. As the chip dividing step, a dicing method, a laser ablation method, or the like, which is a method that does not use a diamond scriber, may be used.

  The gallium nitride based semiconductor laser chip 350 thus obtained is subjected to characteristic evaluation by pulse current drive in the chip state, and non-defective chips having a threshold current value smaller than the reference value are selected.

(Mounting process of gallium nitride semiconductor laser chip)
The gallium nitride based semiconductor laser chip 350 thus obtained is fixed (mounted) on the block portion 321 of the stem. Below, the mounting process implemented using the die-bonding method which adheres using a solder material is demonstrated.

  As shown in FIG. 4A, the submount 310 is placed on a support portion 261 in a mounting apparatus filled with a nitrogen atmosphere, and the surface of the submount 310 has a sheet thickness of about 200 μm and a sheet shape. A solder 312 made of Au70Sn30 having a melting point of 280 ° C. is placed. Next, the submount 310 is heated to a temperature slightly higher than the melting point of the solder 312 made of Au70Sn30. When the solder 312 made of Au70Sn30 is melted, the gallium nitride based semiconductor laser chip 350 obtained by the above method is colleted 270. Then, the n-side electrode (outer layer) 304B side is placed in contact with the solder 312 made of Au70Sn30. Further, while appropriately applying the load F, the gallium nitride based semiconductor laser chip 350 and the submount 310 are well adapted to the solder 312 made of Au70Sn30, cooled to solidify the solder 312 made of Au70Sn30, and nitrided on the submount 310. The gallium semiconductor laser chip 350 is fixed.

  Next, as shown in FIG. 4B, the stem 320 is placed on the support portion 261 in the mounting apparatus, and the solder 313 made of SnAg3Cu0.5 having a melting point of 220 ° C. is placed on the block portion 321 of the stem. Then, the stem block 321 is heated to a temperature slightly higher than the melting point of the solder 313 made of SnAg3Cu0.5, and when the solder 313 made of SnAg3Cu0.5 is melted, the gallium nitride based semiconductor laser obtained by the above method is used. The submount 310 to which the chip 350 is fixed is sucked by the collet 270 and placed on the stem block 321 so that the metal multilayer film 308 formed on the back surface faces the stem block 321 side. Further, the submount 310 to which the gallium nitride based semiconductor laser chip 350 is fixed and the stem block portion 321 are well adapted to the solder 313 made of SnAg3Cu0.5 while appropriately applying the load F. Thereafter, the stem block portion 321 is cooled to solidify the solder 313 made of SnAg3Cu0.5, and the gallium nitride semiconductor laser chip 350 fixed to the stem block portion 321 via the submount 310 is obtained.

  Here, after the gallium nitride based semiconductor laser chip 350 is once taken out from the mounting device to the atmosphere, it is set in a wire bonding device (not shown) filled with a nitrogen atmosphere. Here, as shown in FIG. 1A, the p-side electrode 303 and the pin 316 are electrically connected by a wire 314A, and the n-side electrode (inner layer) 304A and the pin 311 are connected to the n-side electrode (outer layer) 304B, Electrical connection is established via solder 312 made of Au70Sn30, metal multilayer 307, and wire 314B.

  In the first embodiment, a Pd / Mo / Au multilayer film is used as the material of the p-side electrode 303. However, in addition to Pd, for example, Co, Cu, Ag, Ir, Sc, Au, Cr, Mo, La, and La W, Al, Tl, Y, La, Ce, Pr, Nd, Sm, Eu, Tb, Ti, Zr, Hf, V, Nb, Ta, Pt, Ni and compounds thereof may be used. In addition to Au, Ni, Ag, Ga, Sn, Pb, Sb, Zn, Si, Ge, Al and their compounds may be used, and the thickness of each layer is not limited to the above-described values. In the first embodiment, the Ti / Al multilayer film is used as the material of the n-side electrode (inner layer) 304A, but Hf may be used in addition to Ti. Each layer thickness is not limited to the value shown in the first embodiment.

  In the first embodiment, SiC is used as the material of the submount 310. However, a material having good thermal conductivity such as AlN, GaAs, Si, and diamond can be used.

  Further, the solder material provided on the surface of the submount 310 (the metal multilayer film 307 side) is not limited to Au70Sn30, but may be Au80Sn20 (Au: 80% by weight, Sn: 20% by weight) which is a eutectic point. Any solder material such as SnAgCu, In, or PbSn may be used. Furthermore, the ratio of Au and Sn is not limited also in AuSn solder. Also, the solder material between the back surface of the submount 310 (the metal multilayer film 308 side) and the block portion 321 of the stem is not limited to SnAg3Cu0.5, but AuSn, In, PbSn, Ag paste, and other conductive materials. Any of pastes can be used. Further, the ratio of Sn, Ag, and Cu in the solder made of SnAg3Cu0.5 may be changed, and the ratio is not limited. The melting point of the solder material provided on the surface of the submount 310 (metal multilayer film 307 side) is higher than the melting point of the solder material between the back surface of the submount 310 (metal multilayer film 308 side) and the block portion 321 of the stem. Alternatively, both sides can be die bonded simultaneously as a solder material having the same melting point.

  The stem 320 including the stem block portion 321 is made of a metal mainly composed of Cu or Fe, and a Ni film / Au film or a Ni film / Cu film / Au film is sequentially formed on the surface thereof by a plating method.

(Airtight sealing process)
Next, in the hermetic sealing device 280 shown in FIG. 5, the laser chip fixing holder 300 is placed on the base 281 of the hermetic sealing device 280 filled with dry air having a dew point of −20 ° C., and the lid 330 is placed. It is placed in a jig 282 and overlapped with the laser chip fixing holder 300. The laser chip fixing holder 300 and the lid 330 are fused and hermetically sealed by a resistance heating method in which a current is passed between the base 281 and the jig 282 to manufacture the semiconductor laser device 340. Thereby, the inside of the package of the gallium nitride based semiconductor laser chip 350 is cut off from the external atmosphere.

  The gas enclosed in the package is not limited to dry air, and may be an inert gas such as dry nitrogen, helium, neon, argon, krypton, or a mixed gas of dry inert gas and dry air or oxygen. .

(UV irradiation process)
Next, the semiconductor laser device 340 is put in the ultraviolet irradiation device 200 shown in FIG. 6 and heated to 200 ° C. by a heater, and the wavelength 185 nm and the wavelength 254 nm are passed through the window 330A of the lid 330 in the semiconductor laser device 340. Ultraviolet rays 202 are irradiated for 10 minutes from a mercury lamp 201 that emits ultraviolet rays. The illuminance of the mercury lamp 201 was 5 mW / cm ² .

  In order to perform this process effectively, it is desirable to use a material that can transmit the ultraviolet rays satisfactorily, particularly quartz or quartz glass, as the window portion 330A. In that case, light having a wavelength of 150 nm or more can be transmitted.

  Here, regarding the photolysis of a siloxane-based substance that is a candidate for a contaminant, the center of the light absorption wavelength of the siloxane bond (Si—O) that forms the skeleton is around 270 nm, and the siloxane bond is formed by light having a wavelength of 290 nm or less. Decomposition is promoted due to the excited state. Therefore, decomposition is promoted by light having a wavelength of 290 nm or less, such as light from the mercury lamp 201 (wavelength 185 nm and wavelength 254 nm). Even when light having a wavelength longer than 290 nm is irradiated, decomposition of the siloxane-based material is promoted because a bond between Si and a side chain (such as Si—C) is in an excited state. A siloxane-based material is considered to be a main component of a pollutant because a substance mainly composed of solid silicon oxide is generated as a photochemical reaction substance after decomposition.

  Regarding the photodecomposition of an organic substance having a carbon bond, which is another candidate for a pollutant, the decomposition of the C—C bond forming the skeleton is accelerated by light having a wavelength of 290 nm to 420 nm. Conversely, if an organic substance having a carbon bond becomes a polymer higher than the original organic substance by a photochemical reaction such as polymerization or cross-linking, it becomes a solid residue as a photochemical reaction substance. Therefore, such an organic substance having a carbon bond is also contaminated. It can be a substance.

  As described above, the light source is not limited to the mercury lamp 201 and may be any halogen lamp, ultraviolet laser, ultraviolet LED, excimer lamp, or the like as long as it has a wavelength of 420 nm or less. Also, the illuminance and time are not limited to the above. Note that in a laser device using a gallium nitride semiconductor laser chip with an oscillation wavelength of 420 nm or less, a photochemical reaction material is deposited on the laser light emitting end face. It is estimated that it is effective to use ultraviolet rays.

  In this way, by irradiating the semiconductor laser device 340 with the ultraviolet rays 202, the pollutants evaporated by heating are decomposed. Although the laser light emission end face is also exposed to ultraviolet rays, the ultraviolet irradiation area is the entire hermetically sealed space and is sufficiently larger than the laser light emission end face, so that the photochemical reaction material to the laser light emission end face in this ultraviolet irradiation step The deposition of is negligible. As a result, it is possible to obtain an element having a long life without any photochemical reaction material being deposited on the laser light emitting end face during driving of the element, and without deterioration of characteristics such as an increase in driving current during operation.

  By performing the ultraviolet irradiation step by heating, the contaminants are easily vaporized, and the effect of the ultraviolet irradiation can be promoted. Here, the boiling points of typical siloxane-based materials that are candidates for contaminants are 1,1,3,3-tetramethyldisiloxane = 70 ° C., pentamethyldisiloxane = 86 ° C., hexamethyldisiloxane = 101 ° C., octamyltriloxaneex ° C, Octamethylcyclotetrasiloxane = 175 ° C, Decamethycyclopentasyloxane = 211 ° C, Dodecamethylcyclohexasiloxane = 245 ° C. In addition, the boiling point of a typical organic substance having a carbon bond that is a candidate for pollutants is benzene = 80 ° C., methyl ethyl ketone = 80 ° C., toluene = 110 ° C., butanol = 117 ° C., xylene = 140 ° C., decane = 174 ° C., Butyl acetate = 100-150 ° C., Dodecane = 213 ° C., Tetradecane = 254 ° C., Cyclohexylate = 177 ° C., 2-Ethylhexylate = 199 ° C., Phosphate ester = 215 ° C. These contaminants may be generated from greases and oils used in humans, microorganisms, building materials, manufacturing equipment, and pressure-sensitive adhesives used in pressure-sensitive adhesive sheets. It may also occur when polymer contaminants are decomposed than those listed here. By heating to the boiling point of these substances and irradiating with ultraviolet rays or the like, it is possible to effectively remove the vaporized contaminants. Therefore, for example, in order to remove a siloxane-based substance, the heating temperature is preferably 70 ° C. or higher, more preferably 101 ° C. or higher, and further preferably 153 ° C. or higher. If it is 70 degreeC or more, it can remove effectively also about organic substances which have carbon bonds, such as benzene.

(Aging test)
An aging test was performed on the five semiconductor laser devices 340 that oscillate at an emission wavelength of 405 nm manufactured as described above, and the long-term stability of the drive current value was examined. At this time, the aging test was performed under an APC (Automatic Power Control) driving condition of an environmental temperature of 60 ° C., an optical output value of 30 mW, and a direct current (DC). FIG. 7 shows the test result of the obtained semiconductor laser device 340 of the first embodiment.

  FIG. 7 shows the relationship between the aging time and the drive current value for the five semiconductor laser devices 340 of the first embodiment. As shown in FIG. 7, in the semiconductor laser device 340 that has performed the ultraviolet irradiation process at 200 ° C., the drive current value is substantially maintained at the initial value even when the aging time is up to 4000 hours. In addition, the five semiconductor laser devices 340 manufactured have a small variation in driving current value of about 10 mA, and the driving current values are uniform after the long-term aging test.

(Embodiment 2)
As the second embodiment, five semiconductor laser devices were manufactured in the same conditions as in the first embodiment except that the temperature of the ultraviolet irradiation process was set to 70 ° C. However, a heater is not used for heating to 70 ° C., and a temperature rise accompanying the lighting of the mercury lamp 201 is used.

  The five semiconductor laser devices of the second embodiment manufactured in this way were also subjected to an aging test in the same manner as the semiconductor laser device 340 of the first embodiment, and the long-term stability of the drive current value was examined. At this time, the aging test was performed under an APC driving condition of an environmental temperature of 60 ° C., an optical output value of 30 mW, and a direct current (DC). FIG. 8 shows the test results of the obtained semiconductor laser device of the second embodiment.

  FIG. 8 shows the relationship between the aging time and the drive current value for the five semiconductor laser devices of the second embodiment. With respect to the semiconductor laser device of the second embodiment in which the ultraviolet irradiation process is performed at room temperature, a slight increase in the drive current value with the aging time is observed. If the lifetime is 1.4 times the initial drive current value, the lifetime is longer than 4000 hours in which the test was performed.

(Comparative Example 1)
As Comparative Example 1 for the method of manufacturing the semiconductor laser device 340 of the first embodiment, five semiconductor laser devices having the same manufacturing conditions as those of the semiconductor laser device 340 of the first embodiment except that the ultraviolet irradiation process is not performed were manufactured. .

  The five semiconductor laser devices of the comparative example thus manufactured were also subjected to an aging test in the same manner as the semiconductor laser device 340 of the embodiment, and the long-term stability of the drive current value was examined. At this time, the aging test was performed under an APC driving condition of an environmental temperature of 60 ° C., an optical output value of 30 mW, and a direct current (DC).

  The test results of the obtained semiconductor laser device of Comparative Example 1 are shown in FIG. FIG. 9 shows the relationship between the aging time and the drive current value for the five semiconductor laser devices of Comparative Example 1. In the semiconductor laser device of Comparative Example 1 in which the ultraviolet irradiation process is not performed, the drive current value increases significantly when the aging time is long, and the drive current value varies among the five manufactured semiconductor laser devices. Is big.

(Comparative Example 2)
As a comparative example 2 for the method of manufacturing the semiconductor laser device 340 of the first embodiment, a semiconductor laser device having the same manufacturing conditions as the semiconductor laser device 340 of the first embodiment except that the dew point of the sealed gas is 0 ° C. 5 were produced.

  The five semiconductor laser devices of Comparative Example 2 manufactured in this way were also subjected to an aging test in the same manner as the semiconductor laser device 340 of the first embodiment, and the long-term stability of the drive current value was examined. At this time, the aging test was performed under an APC driving condition of an environmental temperature of 60 ° C., an optical output value of 30 mW, and a direct current (DC).

  The test results of the obtained semiconductor laser device of Comparative Example 2 are shown in FIG. FIG. 10 shows the relationship between the aging time and the drive current value for the five semiconductor laser devices of Comparative Example 2. Three of the five pieces stopped operating in the middle, and when the cause of the failure was investigated, it was found that the electrode was corroded. Thus, the failure situation in Comparative Example 2 is due to electrode corrosion, which is different from the deterioration in Comparative Example 1.

(Cause of differences in characteristics)
In order to investigate the cause of the difference in characteristics between the first embodiment, the second embodiment, and the comparative example 1, the semiconductor laser devices of the first embodiment, the second embodiment, and the comparative example 1 are deposited on the laser light emitting end face. The material was analyzed by Auger electron spectroscopy. From the laser light emitting end face of Comparative Example 1, carbon showing organic deposition and silicon showing silicon compound deposition were detected at a concentration 10 times or more that of the gallium nitride based semiconductor laser chip of the first embodiment. In the second embodiment, about twice as much carbon and silicon as in the first embodiment were detected. From the above, the long-term stability of the good drive current value was not obtained in the semiconductor laser device of Comparative Example 1 because the photochemical reaction material containing carbon or silicon on the laser light emitting end face of the gallium nitride based semiconductor laser chip 350 was obtained. This is considered to be due to deposition, which caused an increase in light absorption and a change in reflectivity, resulting in characteristic deterioration such as an increase in drive current value.

(Other embodiments)
In the above-described embodiment, the can type package including the stem 320 and the lid 330 is used. However, the present invention is not limited to the can type package. For example, a carrier type package may be used. Further, a semiconductor element other than the gallium nitride based semiconductor laser chip 350, such as a light receiving element, may be fixed to the stem 320.

  In the embodiment described above, the window portion 330A is provided on the lid 330. However, if the window portion can emit light from the laser chip and irradiate light with a wavelength of 420 nm or less from the outside, the package can be used. For example, it may be provided on the stem.

  In the above-described embodiment, the semiconductor laser device 340 has been described. However, the present invention can also be applied to other semiconductor device devices using a gallium nitride semiconductor laser chip, such as a laser coupler and an optical pickup device.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

2A and 2B are a front view and a top view illustrating a configuration of the semiconductor laser device according to the first embodiment. 1 is a front view showing a configuration of a gallium nitride based semiconductor laser chip in a first embodiment. FIG. 3 is a schematic diagram of a chip dividing process in the first embodiment. FIG. 3 is a schematic diagram of a mounting process in the first embodiment. FIG. 3 is a schematic diagram of an airtight sealing process in the first embodiment. FIG. 3 is a schematic diagram of an ultraviolet irradiation process in the first embodiment. FIG. 3 is a correlation diagram between an aging time and a drive current value of the semiconductor laser device in the first embodiment. FIG. 10 is a correlation diagram between an aging time and a drive current value of the semiconductor laser device in the second embodiment. 6 is a correlation diagram between an aging time and a drive current value of the semiconductor laser device in Comparative Example 1. FIG. 6 is a correlation diagram between an aging time and a drive current value of a semiconductor laser device in Comparative Example 2. FIG.

Explanation of symbols

140 Laser bar 141 Scribe line 150 Adhesive sheet 151, 152 Stretching direction 200 Ultraviolet irradiation device 201 Mercury lamp 202 Ultraviolet 261 Support portion 270 Collet 280 Airtight sealing device 281 Base 282 Jig 300 Laser chip fixing holder 301 n-type GaN substrate 302 Laminated body 303 p-side electrode 304A n-side electrode (inner layer)
304B n-side electrode (outer layer)
306 Ridge 307 Metal multilayer film 308 Metal multilayer film 310 Submount 311 Pin 311A Insulation ring 312 Solder made of Au70Sn30 313 Solder made of SnAg3Cu0.5 314A Wire 314B Wire 316 pin 316A Insulation ring 320 Stem 321 Stem block 322 Pin 330 Body 330A window 340 semiconductor laser device 350 gallium nitride semiconductor laser chip 402 n-type GaN contact layer 403 n-type AlGaN cladding layer 404 n-type GaN guide layer 405 InGaN multiple quantum well active layer 406 p-type AlGaN evaporation prevention layer 407 p-type GaN guide layer 408 p-type AlGaN cladding layer 409 p-type GaN contact layer 410 SiO ₂ insulating film

Claims (7)

A step of fixing the laser chip on the stem, and a lid having a window portion attached to the stem in a dry air or inert gas atmosphere to form a package, thereby hermetically sealing the inside of the package process and, within the package throughout the have a step of irradiating the light of the following wavelength 420nm to the entire space of the interior of the package from the window portion in a state of being heated above 101 ° C., a light source for irradiating said light mercury lamp, A method of manufacturing a laser device, wherein the method is a halogen lamp, an ultraviolet LED, or an excimer lamp .   2. The method of manufacturing a laser device according to claim 1, wherein in the step of irradiating the light, the laser device is heated to 280 ° C. or lower.   2. The method of manufacturing a laser device according to claim 1, wherein the wavelength of the light is 150 nm or more and 290 nm or less.   The method for manufacturing a laser device according to claim 1, wherein a dew point of the dry air or the inert gas is −10 ° C. or lower.   4. The method of manufacturing a laser device according to claim 1, wherein the window portion is made of quartz glass, quartz, sapphire, or a material using these as a base material.   The method for manufacturing a laser device according to claim 1, wherein the laser chip has an emission wavelength of 420 nm or less.   The method of manufacturing a laser device according to claim 1, wherein the laser chip is a gallium nitride based semiconductor laser chip.

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