CN1921243A - Nitride semiconductor laser element and method for manufacturing the same - Google Patents
Nitride semiconductor laser element and method for manufacturing the same Download PDFInfo
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- CN1921243A CN1921243A CN 200610121688 CN200610121688A CN1921243A CN 1921243 A CN1921243 A CN 1921243A CN 200610121688 CN200610121688 CN 200610121688 CN 200610121688 A CN200610121688 A CN 200610121688A CN 1921243 A CN1921243 A CN 1921243A
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Abstract
A substrate with a nitride semiconductor layer is cleaved to form resonator end faces, on which a coating film is formed so as to make a nitride semiconductor laser bar. This is divided into nitride semiconductor laser elements. Prior to forming the coating film on the resonator end face, the resonator end face is exposed to a plasma atmosphere generated from the gas containing nitrogen gas. When a ratio of nitrogen to gallium in the surface of the resonator end face before the exposure is represented by ''a'', an average value of ratios of nitrogen to gallium inside from the surface of the resonator end face before the exposure is represented by ''b'', a ratio of nitrogen to gallium in the surface of the resonator end face after the exposure to the first plasma atmosphere is represented by ''d'', and an average value of ratios of nitrogen to gallium inside from the surface of the resonator end face after the exposure is represented by ''e'', the value ''g'' that is expressed by g=(b.d)/(a.e) is set to a value that satisfies g>=0.8.
Description
Technical field
The present invention relates to have the semiconductor Laser device and the manufacture method thereof of nitride semiconductor layer.
Background technology
In recent years, require CD to have increasing memory capacity, and follow higher density.In order to cater to this demand, adopt the BD (Blu-ray Disc) and the HD-DVD (high definition DVD) of blue semiconductor laser to obtain standardization, the device such as decoder that meets described standard has been realized commercialization.The disks needs that meet these standards have the blue semiconductor laser of high reliability, thereby are implemented on the two-layer CD with higher density high speed writing information.
Be used for duplicate on conventional CD or the DVD or the AlGaAs of writing information system or InGaAlP based semiconductor laser comprise be positioned on the resonator end face by such as SiO
2, Al
2O
3Or Si
3N
4The coat film that constitutes of dielectric, be used to prevent deterioration or optical damage as the resonator end face of laser beam exiting surface.Yet, if EB (electron beam) evaporator (evaporator) or sputter equipment are used on as the nitride semi-conductor laser of blue semiconductor laser deposit coat film as it is, then the COD level is low, the critical power that COD (calamitous optical damage) promptly may take place is low, thereby reliability is very low.Therefore, must improve paint-on technique.Notice that COD is meant the phenomenon of the crystal melting of the formation semiconductor Laser device that the absorption of laser beam is caused owing to exiting surface.
JP-A-2002-335053 discloses a kind of method of making semiconductor laser, wherein, the resonator end face of the semiconductor Laser device that will form by cleavage is exposed in the argon plasma atmosphere, thereby removes on the resonator end face natural oxide film of formation naturally by the argon particle that is in plasmoid.Therefore, improve the coat film that is formed on the resonator end face and the adhesion between the resonator end face, thereby improved the reliability of resonator end face.In addition, also propose after cleavage, to heat semiconductor surface, removing attached to the moisture of described semiconductor surface etc., thereby further improve its reliability.
JP-A-2002-335053 propose semiconductor laser fabrication method adopted, be exposed in the process of argon plasma atmosphere, do not apply voltage to diode laser bar and support thereof, therefore, argon ion can not attracted under the effect of electrical potential difference on the diode laser bar (laser bar), thus the resonator end face of bump diode laser bar.In other words, it is not so-called reverse sputtering (countersputtering).In this case, the ion that arrives at the resonator end face of diode laser bar is considered to have the energy of tens of keV.This energy of ion is enough to remove moisture attached to the diode laser bar surface, carbon, natural oxide film etc. by its plasma, and this energy is considered to the resonator end face of diode laser bar is caused damage hardly.
The inventor has carried out elementary analysis to the resonator end face that is exposed to argon plasma atmosphere, is exposed to the effect of argon plasma atmosphere with research.As a result, the inventor finds not observe carbon and oxygen after being exposed to argon plasma atmosphere, and when not being exposed to argon plasma atmosphere, has then observed carbon and oxygen.Viewed carbon and oxygen are contemplated as falling with in natural oxide film, moisture or the pollutant, and described natural oxide film, moisture or pollutant form after the resonator end face in time till the formation coat film by cleavage and be attached.When on the resonator end face, carrying out heat treatment, rather than when being exposed to argon plasma atmosphere, obtained similar result.
From this result, we can say, should after removing carbon and oxygen, form coat film from the resonator end face, improving semiconductor Laser device, and, can or be exposed to argon plasma atmosphere by heat treatment and realize so formation coat film.
Yet,, found the following fact according to the experiment that the inventor did.That is to say, although being exposed to argon plasma atmosphere is effective for removing carbon and oxygen from the resonator end face, but, if described semiconductor Laser device is a nitride semiconductor Laser device, comprise that so the surface of the semiconductor Laser device of resonator end face will be subjected to the influence of described exposure.
The details of this experiment is as follows.Make two samples of nitride semiconductor Laser device.One of sample is exposed to argon plasma atmosphere, and another sample then is not exposed to argon plasma atmosphere.Each sample is carried out ageing test, before ageing test and measure the COD level of each sample afterwards.Figure 11 shows two samples before aging and through the variation of COD level after 200 hours aging.One of sample has the Al that is formed on the resonator end face after being exposed to argon plasma atmosphere
2O
3Coat film.Another sample is through cleavage but be not exposed under the state of argon plasma atmosphere and have the Al that is formed at the resonator end face
2O
3Coat film.Aging condition comprises 70 ℃ ambient temperature, the power of 60mW, APC (automated power control) drives and CW (continuous wave) drives.In addition, measure CO D level under the condition of 50ns, 50% duty factor, room temperature and impulsive measurement.
Can understand from Figure 11, just aging COD level before, promptly initial COD level, the sample that is exposed to argon plasma atmosphere is lower than another sample.This is considered to because be exposed to argon plasma atmosphere the resonator end mask is had some influences.
In addition, after being exposed to argon plasma atmosphere and not being exposed to two samples aging of argon plasma atmosphere, the COD level before the COD level is all aging descends to some extent.Yet the sample that is exposed to argon plasma atmosphere has the COD level higher than the sample that is not exposed to argon plasma atmosphere.In other words, after aging, put upside down relation between two COD levels.Therefore, we can say, suppressed deterioration by being exposed to argon plasma atmosphere, thereby improved reliability by the aging COD level that causes.
The reason of this point is thought as follows.In the nitride semiconductor Laser device that is not exposed to argon plasma atmosphere, exist a kind of by the impurity in the resonator end face such as natural oxide film etc. cause can be between resonator end face and coat film cause the compound interface state of non-light emission at the interface.Therefore, the heating in the ageing process has caused the deterioration of resonator end face.On the contrary, in the nitride semiconductor Laser device that is exposed to argon plasma atmosphere, compare with the situation that does not have argon plasma atmosphere, the non-light emission at the interface that has reduced between resonator end face and coat film is compound.Therefore, in ageing process, only generate heat seldom, thereby reduced the deterioration in the resonator end face, thereby the COD level has only deterioration seldom.
In other words, have the advantage that reduces the horizontal deterioration of COD though be exposed to argon plasma atmosphere, it also has the shortcoming that reduces initial COD level.When needs high power nitride semiconductor Laser device, the reduction of initial COD level may be a serious problem.For example, with regard to the semiconductor Laser device with characteristic shown in Figure 11, the semiconductor Laser device that is exposed to argon plasma atmosphere is difficult to realize being in the above high power of initial COD level of 200mW.
May cause some infringements to the resonator end face though be exposed to argon plasma atmosphere as mentioned above,, up to the present also not to the details of infringement or the research of particular content.Therefore, the inventor studies it, and finds to be exposed to the reduction that argon plasma atmosphere has caused the nitrogen content in the resonator end face that is made of nitride-based semiconductor.To be illustrated its details hereinafter.
With regard to nitride semiconductor Laser device, on the resonator end face, carry out sputter etching from the surface to inside, meanwhile, adopt the atomic quantity ratio between AES (Auger electron spectroscopy) method measurement gallium and the nitrogen.In being exposed to surperficial zone, GaN implements described measurement.Figure 12 shows the sample that is not exposed to argon plasma atmosphere and is exposed to the measurement result of the sample of argon plasma atmosphere.The longitudinal axis is corresponding to the ratio of number of nitrogen atoms and gallium atomic quantity, and transverse axis is corresponding to the time span of sputter etching.This specification hereinafter in the middle of, the statement of ratio of nitrogen to gallium all is meant the ratio of atomic quantity at every turn.Here, one minute sputter etching is corresponding to the degree of depth of about 3nm.From Figure 12, be appreciated that the reduction that is exposed to argon plasma atmosphere and caused the ratio of nitrogen to gallium of nitride semiconductor Laser device end face (at the zero point of the transverse axis of Figure 12).
In addition, with regard to another nitride semiconductor Laser device, on the resonator end face, carry out sputter etching, meanwhile, adopt the atomic quantity ratio between AES method measurement gallium and the nitrogen from the surface to inside.Figure 13 shows the sample that is not exposed to argon plasma atmosphere and is exposed to the measurement result of the sample of argon plasma atmosphere.The degree of depth that transverse axis rises corresponding to the surface of self-resonance device end face, and the longitudinal axis is corresponding to ratio of nitrogen to gallium.Also be appreciated that from Figure 13 and be exposed to the reduction that argon plasma atmosphere has caused the end face ratio of nitrogen to gallium of nitride semiconductor Laser device.
As mentioned above, on the surface of the nitride semiconductor Laser device that is exposed to argon plasma atmosphere, ratio of nitrogen to gallium has reduced, and its reason is considered to be by being excited the removal of the nitrogen with high vapour pressure that the impact of argon ion causes.In addition, this reason may comprise that also being exposed to argon plasma atmosphere has caused that nitrogen is removed from the surface of resonator end face and reduces, thereby makes the resonator end face become the state that existing gallium surpasses nitrogen.Owing to make ratio of nitrogen to gallium significantly unbalance as balanced stoichiometric proportion with 1: 1, therefore, non-smooth launching centre increase, it has caused causing the increase of the calorific value of the rapid deterioration of end face.For this reason, the state of removing nitrogen depends on the time span that is exposed to argon plasma atmosphere, microwave power, treatment temperature etc.
As shown in figure 11, the sample that is exposed to argon plasma atmosphere has the initial COD level lower than the sample that is not exposed to argon plasma atmosphere.This point is considered to be caused by following reason: nitrogen has caused increasing of non-smooth launching centre and non-light to launch the increase of compound probability from being removed of resonator end face, thereby calorific value is increased.
In addition, in the manufacture method of the semiconductor laser that JP-A-2002-335053 proposes, before forming coat film, diode laser bar is heated, thereby evaporation and removal are attached to the moisture on the end surface.Usually adopt with diode laser bar be heated above room temperature temperature this technology evaporate moisture or improve the quality of coat film.Yet, with regard to nitride semi-conductor laser, find that this heating process has caused nitrogen to be removed from the resonator end face, thereby reduced the COD level.
Summary of the invention
The object of the present invention is to provide a kind of method of making nitride semiconductor Laser device, wherein, can remove the impurity that is formed on the resonator end face such as natural oxide film, to improve reliability, and, can reduce collateral damage, promptly reduce from described resonator end face to get on to denitrogenate, to improve initial COD level described resonator end face.
Method according to manufacturing nitride semiconductor Laser device of the present invention comprises: the nitride semiconductor layer that forms nitride semiconductor layer on substrate forms step; And cleavage formed the described substrate of described nitride semiconductor layer thereon, thereby forms the cleavage step of two resonator end faces that are parallel to each other.Described method also comprises described resonator end face is exposed to first exposing step in the middle of first plasma atmosphere that is generated by the mist of nitrogen or inert gas and nitrogen.In first exposing step, ratio of nitrogen to gallium when be illustrated in the surface that is exposed to described resonator end face before first plasma atmosphere with " a " in, be illustrated in before the described exposure mean value with " b " from the ratio of nitrogen to gallium of the inside on the surface of described resonator end face, be illustrated in the ratio of nitrogen to gallium in the surface that is exposed to described resonator end face after described first plasma atmosphere with " d ", when being illustrated in after the described exposure mean value from the ratio of nitrogen to gallium of the inside on the surface of described resonator end face, will be made as the value that satisfies g 〉=0.8 by the value " g " of g=(bd)/(ae) expression with " e ".
In addition, the method according to manufacturing nitride semiconductor Laser device of the present invention also comprises second exposing step that described resonator end face is exposed to second plasma atmosphere that is generated by inert gas that is between described cleavage step and described first exposing step.
In addition, the method according to manufacturing nitride semiconductor Laser device of the present invention also comprises: after described first exposing step, form and prevent that the resonator end face is subjected to the end face coated film of optical damage.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, end face coated film is made of the oxide of Al, Ti, Si, Y, Nb, Ta or Zr.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, end face coated film is made of the nitride of Al or Si.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, the two all has the end face coated film that is made of same material two resonator end faces.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, end face coated film forms by electron cyclotron resonace sputtering method or high-frequency sputtering.In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, the underlayer temperature in first exposing step is in 150-500 ℃ the scope.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, the underlayer temperature in first exposing step is in 200-400 ℃ the scope.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, the underlayer temperature in second exposing step is in 150-500 ℃ the scope.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, the underlayer temperature in second exposing step is in 200-400 ℃ the scope.
In addition, nitride semiconductor Laser device according to the present invention is made by said method.
In addition, the manufacture method according to nitride semiconductor Laser device of the present invention comprises: the nitride semiconductor layer that forms nitride semiconductor layer on substrate forms step; Cleavage has formed the described substrate of described nitride semiconductor layer thereon, thereby forms the cleavage step of two resonator end faces that are parallel to each other; And the coat film that forms coat film on described resonator end face forms step.Described method comprises that also being in described cleavage step and described coat film forms and described resonator end face is exposed to first exposing step in the middle of first plasma atmosphere that is generated by the gas that contains nitrogen between the step.
In addition, in manufacture method, in from first exposing step to the time of finishing coat film formation step, the resonator end face is not exposed in the middle of the air according to nitride semiconductor Laser device of the present invention.
In addition, in manufacture method, generate first plasma atmosphere by the gas that only contains nitrogen according to nitride semiconductor Laser device of the present invention.
In addition, in manufacture method, generate first plasma atmosphere by the gas that contains nitrogen and argon according to nitride semiconductor Laser device of the present invention.
In addition, in manufacture method according to nitride semiconductor Laser device of the present invention, in first exposing step, on the resonator end face, form contain constitute described coat film element film.
In addition, in manufacture method, in first exposing step, the substrate that has formed nitride semiconductor layer on it is heated to is in the 100-500 ℃ of temperature in the scope according to nitride semiconductor Laser device of the present invention.
In addition, in manufacture method, in first exposing step, the resonator end face is exposed in the scope that time span in first plasma atmosphere is in 30 seconds to 20 minutes according to nitride semiconductor Laser device of the present invention.
In addition, in manufacture method, generate first plasma atmosphere by electron cyclotron resonace according to nitride semiconductor Laser device of the present invention.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, in first exposing step, the microwave power of electron cyclotron resonace is in 200-800 watt the scope.
In addition, in manufacture method according to nitride semiconductor Laser device of the present invention, described coat film one of them is to be made of the nitride of oxide, Al or the Si of Al, Ti, Si, Y, Nb, Ta, Zr, Hf or Zn or the nitrogen oxide of Al or Si at least.
In addition, also comprise second exposing step that described resonator end face is exposed to second plasma atmosphere that the mist by inert gas or inert gas and nitrogen generates that is between described cleavage step and described first exposing step according to the method for manufacturing nitride semiconductor Laser device of the present invention.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, the inert gas in second exposing step is an argon.
In addition, in manufacture method, in second exposing step, the substrate that has formed nitride semiconductor layer on it is heated to is in the 100-500 ℃ of temperature in the scope according to nitride semiconductor Laser device of the present invention.
In addition, in manufacture method, in second exposing step, the resonator end face is exposed in the scope that time span in second plasma atmosphere is in 30 seconds to 20 minutes according to nitride semiconductor Laser device of the present invention.
In addition, in manufacture method, generate second plasma atmosphere by electron cyclotron resonace according to nitride semiconductor Laser device of the present invention.
In addition, in the manufacture method according to nitride semiconductor Laser device of the present invention, in second exposing step, the microwave power of electron cyclotron resonace is in 200-800 watt the scope.
Description of drawings
Fig. 1 observes along the direction that is parallel to cavity length, according to the cross section of the nitride semiconductor laser rod of first embodiment of the invention.
Fig. 2 is from observing perpendicular to the direction of cavity length, according to the end view of the nitride semiconductor laser rod of first embodiment.
Fig. 3 shows the general structure of ECR sputter equipment.
Fig. 4 shows the general structure according to the nitride semiconductor laser device of first embodiment.
Fig. 5 be presented at aging before and afterwards, according to the curve chart of the COD level of the nitride semiconductor Laser device of first embodiment.
Fig. 6 be presented at aging before and afterwards, according to the curve chart of the COD level of another nitride semiconductor Laser device of first embodiment.
Fig. 7 shows ratio of nitrogen to gallium and from according to the surface of the resonator end face of the nitride semiconductor Laser device of first embodiment curve chart to the relation its inner degree of depth.
Fig. 8 is the curve chart of the relation between the relative quantity of the nitrogen that shows that the voltage ratio of nitrogen and argon gas and resonator end face are interior.
Fig. 9 be presented at aging after, the relative quantity of nitrogen and the curve chart of the relation between the COD level in the resonator end face.
Figure 10 be show the temperature of nitride semiconductor laser rod when it is exposed to plasma atmosphere and wear out after the COD level between the curve chart of relation.
Figure 11 is presented at the before aging and aging curve chart of the COD level of conventional nitride semiconductor Laser device afterwards.
Figure 12 is the interior ratio of nitrogen to gallium of the sputter face of the conventional nitride semiconductor Laser device of demonstration and the curve chart of the relation between the sputtering time.
Figure 13 be show ratio of nitrogen to gallium and from the surface of the resonator end face of conventional nitride semiconductor Laser device to the curve chart of the relation its inner degree of depth.
Embodiment
First embodiment
The first embodiment of the present invention is described hereinafter with reference to the accompanying drawings.Fig. 1 is the front view of observing from the direction that is parallel to cavity length according to the nitride semiconductor laser rod of first embodiment, Fig. 2 is the end view from the described nitride semiconductor laser rod of observing perpendicular to the direction of cavity length, Fig. 3 shows the general structure of ECR sputter equipment, and Fig. 4 shows the general structure of nitride semiconductor laser device.
As shown in Figure 1, nitride semiconductor laser rod 10 comprises: n type GaN substrate 11 forms n-AlGaInN resilient coating 21, n-AlGaInN coating 22, n-AlGaInN guide layer 23, AlGaInN multiple quantum well active layer 24, p-AlGaInN guide layer 25, p-AlGaInN coating 26 and p-AlGaInN contact layer 27 in order from substrate 11 1 sides on described n type GaN substrate 11.Suitably adjust the ratio of mixed crystal in each layer, although itself and the present invention do not have substantial the contact.Notice that active layer 24 can contain the V group element such as As or P of about 0.01-10%.
At least in the part of p-AlGaInN guide layer 25, p-AlGaInN coating 26 and p-AlGaInN contact layer 27, form the banded ridge 12 that extends along the resonator direction.The width of described band is in the scope of about 1.2-2.4 μ m, and its representative value is about 1.5 μ m.
Form the p electrode 32 that contacts with p-AlGaInN contact layer 27, under the p electrode 32 except that the part of ridge 12, form insulator film 31.By this way, make nitride semiconductor laser rod 10 have so-called ridge band (ridge stripe) structure.In addition, the rear side at nitride semiconductor laser rod 10 forms n electrode 33.
Nitride semiconductor laser rod 10 is to comprise that by making with diamond pen patterning method or break method the above-mentioned layer that is formed on the substrate and the nitride semiconductor wafer cleavage of electrode obtain.The surface that obtains by this cleavage is exactly a resonator end face 13 and 14 parallel to each other shown in Figure 2.
In addition, as shown in Figure 2, form low reflection coat film 34 being positioned on the resonator end face 13 of bright dipping side, on the resonator end face 14 of light reflection side, form height reflection coat film 37 with about 95% reflectivity with about 5% reflectivity.Low reflection coat film 34 and high reflection coat film 37 prevent resonator end face 13 and 14 oxidations, and the control reflectivity prevents that resonator end face 13 and 14 is subjected to optical damage.
Next, will be described hereinafter the formation of low reflection coat film 34 and high reflection coat film 37, and preliminary treatment.
At first, explanation is used to form the device of low reflection coat film 34 and high reflection coat film 37.Employing has the device of vacuum mechanism, for example ECR as shown in Figure 3 (electron cyclotron resonace) sputter equipment 50, form these coat films, described device can realize continuing to be exposed to plasma atmosphere, and forms coat film under situation about not being exposed in the middle of the air.
With reference to figure 3, with the structure of explanation ECR sputter equipment 50.ECR sputter equipment 50 has film and forms 70 two major parts of stove 60 and plasma generation chamber.Film forms stove 60 and is furnished with air inlet 61, target 62, heater 63, sample stage 64, shutter 65 and exhaust outlet 66.Sample stage 64 supports the nitride semiconductor laser rod 10 that is attached on the support (not shown), and its orientation makes and form coat film on resonator end face 13 or resonator end face 14.Exhaust outlet 66 is furnished with the vacuum pump (not shown), thereby by exhaust outlet 66 gas that film forms in the stove 60 is discharged.Target 62 is electrically connected with RF (radio frequency) power supply 67.In addition, plasma generation chamber 70 is furnished with air inlet 71, microwave entrance 72, microwave introducing window 73 and solenoid 74.When introducing window 73 by microwave, the gas of introducing from air inlet 71, producing plasma from microwave entrance 72 introducing microwaves.
Before forming low reflection coat film 34 and high reflection coat film 37, it is oxidized that film forms the inside of stove 60.The reason of implementing oxidation in this stove is as described below.
Adopt ECR sputter equipment 50 to form coat film and be achieved in that the target 62 that sputter is made of the metallic target material such as aluminium or silicon usually, and described material is reacted with oxygen that is in plasmoid and nitrogen, thereby form the oxide of described target material and the film of nitride on the surface that is positioned over the nitride semiconductor laser rod on the sample stage 64.In addition, before forming coat film, also the resonator end face to be exposed to plasma atmosphere, to remove natural oxide film etc.
In this case, both not oxidation also not the target material that is in metallic state of nitrogenize be attached to the inside that film except the near surface of nitride semiconductor laser rod 10 forms stove 60.In addition, the surface of target 62 also exposes with the metallic state of target material.When the inside of film formation stove 60 is in this kind state, the resonator end face is exposed in the middle of the plasma atmosphere.So film forms the inwall of stove 60 and the target material that is in metallic state on the target 62 carries out sputter to being attached to, and makes it to be attached on the surface of the nitride semiconductor laser rod 10 that comprises the resonator end face.
After forming low reflection coat film 34 and high reflection coat film 37, apply RF voltage from RF power supply 67 to target 62, with sputtering target 62.But, when the resonator end face is exposed to plasma atmosphere, do not apply RF voltage.But target 62 still has been subjected to sputter, because do not applying under the RF voltage condition, the generation of plasma can produce about several volts low-voltage in target 62.Although the self-generating current potentials in the target 62 are approximately several volts, and apply the RF voltage condition and compare 62 of targets and be subjected to a small amount of sputter.And in some cases, the target material that is in metallic state that is attached to the inwall of film formation stove 60 also has been subjected to sputter.
If only produced by argon gas the resonator end face is exposed to wherein plasma atmosphere, the target material such as aluminium or silicon to target 62 carries out sputter so, thereby forms the film of the target material that is in metallic state on resonator end face 13 and 14.After the aluminium that is in metallic state or silicon have absorbed light from the oscillation wavelength scope of nitride semiconductor Laser device, to be heated, thereby cause that COD damages (breakdown), described nitride semiconductor Laser device obtains by cutting apart nitride semiconductor laser rod 10.Therefore, if it is present in resonator end face 13 and 14, will cause the remarkable reduction of COD level.
In addition, if generated plasma, film that nitride by the target material with pettiness light absorption constitutes rather than that constitute by metal will be formed by the mist of argon gas and nitrogen.Nitride film has strong stress, therefore, if it is formed on resonator end face 13 and 14, will cause adverse effect to the characteristic of nitride semiconductor Laser device.Particularly, owing to do not have good quality at the film that does not apply under the RF voltage condition formation naturally, therefore, it is not suitable as coat film.
Can form the inwall of stove 60 and the surface of target 62 by the pre-oxidation film, prevent this sputter of target 62 when being exposed to plasma atmosphere.If target 62 is surperficial oxidized, self-generating voltage is step-down so, thereby makes the quantitative change of the material that is subjected to sputter little.In addition, if target material is aluminium, aluminium oxide Al so
2O
3Have low-down sputtering raste, promptly compare with the aluminium that is in metallic state, it is hardly by sputter.Even it is by sputter, can not cause the reduction of COD level, because what be attached to nitride semiconductor laser rod 10 is not metal but can not causes the oxide of light absorption.
As the method for oxidation furnace inwall, two kinds of methods as described below are arranged.In a kind of method therein, form the stove 60 inner plasmas that only produce that produce by oxygen at film.Thereby make film form the inwall of stove 60 and the surface oxidation of target 62.
In another approach, from air inlet 61 in film forms stove 60, provide the mist of argon gas and oxygen, the ratio of the oxygen that contains in the described mist make target 62 with the oxide state by sputter, afterwards, apply RF voltage to target 62.So, from target 62 target materials with the oxide state by sputter, the surface of nitride semiconductor laser rod 10 not only, the whole inwall that film forms stove 60 is all covered by the metal of the oxide of target material rather than target material.Can improve the flow of oxygen gradually by when applying RF voltage with firm power to target 62, and the lip-deep electromotive force of monitoring target 62 and learn this ratio of oxygen.When the ratio of the flow of oxygen and oxygen increased, detected electromotive force reduced rapidly under a certain flow.This shows that the oxidation of target 62 becomes than faster to the sputter of target 62 by argon, and the surface of target material has obtained sufficient oxidation.Therefore, if when applying RF voltage, the supply of oxygen is faster than this flow, so will be from target 62 with oxide state sputter target material, and the inwall that makes target 62 and film form stove 60 is coated with the oxide of target material.
Note, must before nitride semiconductor laser rod 10 being put into film formation stove 60, perhaps after nitride semiconductor laser rod 10 being put into film formation stove 60, under the state of sealing shutter 65, implement this technology.
Next, for get on from the resonator end face 13 and 14 that is placed on the nitride semiconductor laser rod 10 on the sample stage 64 in the film formation stove 60 removing natural oxidizing film, moisture or pollutant, will comprise that the surface of the nitride semiconductor laser rod 10 of resonator end face 13 and 14 is exposed to plasma atmosphere.This condition is shown in following table 1.Though in the present embodiment, only produce plasma atmosphere by nitrogen or by the mist that contains nitrogen, with the removal of minimizing nitrogen,, in comparison example 1, also show the situation that only generates plasma atmosphere by argon gas.
[table 1]
| Example 1 | Example 2 | Comparison example 1 | |
| Plasma atmosphere | Nitrogen only | The mixture of nitrogen and argon gas | Argon gas only |
| Argon flow [sccm] | 0 | 20 | 40 |
| Nitrogen flow [sccm] | 20 | 5.5 | 0 |
| Microwave power [W] | 500 | 500 | 500 |
| Stove back pressure [Pa] | 4.8×10 -2 | 8.3×10 -2 | 1.4×10 -1 |
| Process time [min] | 5 | 5 | 5 |
| Technological temperature | Room temperature | Room temperature | Room temperature |
Under the conditions shown in Table 1, in ECR sputter equipment 50, provide gas, and apply the microwave that makes plasma generation by air inlet 61 and air inlet 71.Afterwards, when the shutter 65 under just being positioned at the nitride semiconductor laser rod 10 that is placed on film formation stove 60 is opened, the resonator end face 13 resonator end faces 14 of described nitride semiconductor laser rod 10 are exposed to plasma atmosphere, thereby remove natural oxide film.In this case, it is 0 watt with the power setting that is connected to the RF power supply 67 of target 62.
Next, on resonator end face 13 and 14, form low reflection coat film 34 and high reflection coat film 37 respectively.In this embodiment, on the resonator end face 13 of light exit side, form as low reflection coat film 34 by Al
2O
3The film that constitutes.At first, provide argon gas to ECR sputter equipment 50, in it, provide oxygen with the flow of 6-7sccm with the flow of 40sccm.Afterwards, apply the microwave that generates plasma, apply RF voltage to the target 62 that constitutes by aluminium.Afterwards, the argon of plasmoid is subjected to the attraction of target 62, and bump target 62, makes aluminium be scattered and combines with the oxygen that is in plasmoid.If shutter 65 is opened in this state, will on the resonator end face 13 of nitride semiconductor laser rod 10, form so by Al
2O
3The low reflection coat film 34 that constitutes.In this case, the film internal pressure that forms stove 60 is set to about 1 * 10
-1Pa, microwave power are set to 500 watts, and RF power supply 67 is set to 500 watts.
The time span that shutter 65 is opened is set to certain value, makes low reflection coat film 34 become the thickness corresponding to the expection reflectivity.Can calculate this time span according to following explanation.At first, go up formation at pseudo-body (dummy) in advance and have the film of same material, and calculate the thickness of this film by the reflectivity of this film with low reflection coat film 34.Afterwards, the film of deriving according to the thickness of film and the time span of being opened by shutter 65 forms the described time span of speed calculation.Usually the thickness that is positioned at the coat film on the light exit side is adjusted, made described coat film have antiradar reflectivity.In this embodiment, with Al
2O
3Thickness be set to 80nm, make reflectivity become 5%.If the system of monitoring film thickness is provided in the process that forms low reflection coat film 34, so can be according to opening and closing from the signal controlling shutter 65 of described monitoring system.
Next, on the resonator end face 14 of light reflection side, form high reflection coat film 37.In this embodiment, high reflection coat film 37 comprises from resonator end face 14 1 sides by this protective layer that forms in proper order 35 and reflector 36.A plurality of layers of alternately being formed by the material with different refractivity usually in reflector 36 constitute, to obtain about 95% high reflectance.Here, protective layer 35 is by Al
2O
3Constitute, reflector 36 is made of following nine layers that form in order from resonator end face 14 1 sides: SiO
2, TiO
2, SiO
2, TiO
2, SiO
2, TiO
2, SiO
2, TiO
2And SiO
2
After forming low reflection coat film 34, do not forming under the situation of taking out in the stove 60 upset nitride semiconductor laser rod 10 from film.Afterwards, make resonator end face 14 point to shutter 65 1 sides, and be exposed in the plasma atmosphere that is produced by the gas that comprises nitrogen, its residing operation is identical with the situation that forms low reflection coat film 34 on the resonator end face 13 of light exit side.So, formed the layer in protective layer 35 and reflector 36.The thickness that height is reflected each layer of coat film 37 is configured such that the entire emission rate becomes the value of expection reflectivity.Here; the thickness of protective layer 35 is set to the reflectivity in reflector 36 is risen hardly the 6nm of influence, and the layer thickness in reflector 36 is set to 70nm, 45nm, 70nm, 45nm, 70nm, 45nm, 70nm, 45nm and 140nm in order from resonator end face 14 1 sides.Note, also not having what problem if in a single day when upset, nitride semiconductor laser rod 10 is formed taking-up the stove 60 from film.
The nitride semiconductor laser rod 10 that has successfully formed low reflection coat film 34 and high reflection coat film 37 as mentioned above thereon is divided into nitride semiconductor Laser device.As shown in Figure 4, nitride semiconductor Laser device 49 is installed on the subbase seat 42 that constitutes by AlN, SiC etc., each subbase seat 42 is installed on the stem stem 41.At last, by lead 44 nitride semiconductor Laser device 49 is connected to pin 43, pin 43 is provided with on the face of the stem stem 41 that subbase seat 42 has been installed thereon, adopts cap 46 in airtight mode it to be sealed, thereby has finished nitride semiconductor laser device 40.Installed on it on face of the opposite stem stem 41 of the face of subbase seat 42 two lead-in wire pins 45 have been set.In addition, cap 46 is provided with windowpane 47, can be penetrated by described windowpane 47 by nitride semiconductor Laser device 49 emitted laser bundles.
Make the sample of three nitride semiconductor laser devices 40 as mentioned above.The plasma atmosphere that only by nitrogen gas generation the resonator end face is exposed to wherein of first example in the first sample employing table 1 is made.Second sample is to adopt the argon gas of example 2 and the mixture of nitrogen to make, and the 3rd sample is to adopt the only nitrogen of comparison example 1 to make.Afterwards, under initial condition and after 200 hours aging, measure the COD level of three samples.The result has been shown among Fig. 5 and the table 2.Fig. 5 shows the COD level of these samples of marking and drawing in the plane, in described plane, transverse axis is corresponding to ageing time, and the longitudinal axis is corresponding to the COD level.Ambient temperature be 70 ℃, APC drive implement under the condition for the power of 60mW aging.Have in impulsive measurement under the condition of the width of 50ns and 50% duty ratio, at room temperature measure CO D level.
[table 2]
| Example 1 | Example 2 | Comparison example 1 | |
| Plasma atmosphere | Nitrogen only | The mixture of nitrogen and argon gas | Argon gas only |
| Initial value [mW] | 700 | 600 | 200 |
| After 200 | 600 | 500 | 120 |
Be appreciated that under the initial condition and after aging that by this result example 1 and example 2 have all been obtained the comparison COD level higher than example 1.This reason is considered to be: owing to contain nitrogen being used for producing the gas that sample with example 1 and example 2 is exposed to plasma atmosphere wherein, therefore, reduced the removal of nitrogen from resonator end face 13 and 14.In addition, with example 1 and example 2 relatively, under initial condition and after aging, example 1 has all been obtained the COD level higher than example 2.This reason is considered to be: owing in plasma, also contain argon, thus the resonator end face in the example 2 13 and 14 has been caused infringement.In example 1, plasma atmosphere only contains nitrogen, does not contain argon, thereby it does not cause damage to resonator end face 13 and 14.Therefore, reduced the removal of nitrogen, thereby obtained high COD level than comparison example 1 and example 2.
In addition, owing to after aging, kept high COD level, suggestion is exposed to the plasma atmosphere that is produced by the gas that contains nitrogen by the mode identical with only being exposed to the plasma atmosphere that produced by argon gas, removes natural oxide films, moisture, pollutant etc. from resonator end face 13 and 14 thus.
According to The above results, measured the amount of the nitrogen in the resonator end face 13 and 14 that is exposed to the plasma atmosphere that satisfies above-mentioned three conditions by the AES measurement, to confirm that being exposed to the plasma atmosphere that is generated by the gas that contains nitrogen has reduced the removal of nitrogen from resonator end face 13 and 14.The result is as shown in table 3.Here, to be shown in after the cleavage just the nitrogen content in the per unit area in the resonator end face 13 and 14 be 100% o'clock value to the scale of nitrogen.
[table 3]
| Example 1 | Example 2 | Comparison example 1 | |
| Plasma atmosphere | Nitrogen only | The mixture of nitrogen and argon gas | Argon gas only |
| The amount of nitrogen in the resonator end face | 96％ | 90％ | 77％ |
The amount of nitrogen is a minimum value in the comparison example 1, is maximum in the example 1.Therefore, can confirm that exist relatedly between the amount of the nitrogen in the resonator end face 13 and 14 of nitride semiconductor Laser device and the COD level, wherein the former is big more, the latter is high more.In addition, from discovering of the inventor, the nitrogen of plasmoid is easy to be attached to resonator end face 13 and 14, but only by being exposed to mode wherein, the nitrogen of molecular state can not be attached to resonator end face 13 and 14, and therefore, it can not prevent the reduction of COD level.
Next, after initial condition and 200 hours aging, measure the COD level of another nitride semiconductor laser device 40.Utilize another nitride semiconductor Laser device 49 to make nitride semiconductor laser device 40, the resonator end face of described nitride semiconductor Laser device 49 is exposed to the plasma atmosphere that generates under the conditions shown in Table 4.In example 3, only generate plasma atmosphere by nitrogen.In comparison example 2, only generate plasma atmosphere by argon gas.
[table 4]
| Example 3 | Comparison example 2 | |
| Plasma atmosphere | Nitrogen only | Argon gas only |
| Argon flow [sccm] | 0 | 40 |
| Nitrogen flow [sccm] | 20 | 0 |
| Microwave power [W] | 500 | 500 |
| Stove back pressure [Pa] | 0.5×10 -2 | 1.4×10 -1 |
| Process time [min] | 5 | 5 |
| Technological temperature | Room temperature | Room temperature |
Aging condition is that 70 ℃ of ambient temperatures, power 60mW and APC drive.The COD measuring condition is 50ns, duty ratio 50%, room temperature and impulsive measurement.The result has been shown among Fig. 6 and the table 5.Fig. 6 is the curve chart of planar marking and drawing, and in described plane, transverse axis is corresponding to ageing time, and the longitudinal axis is corresponding to the COD level.
[table 5]
| Example 3 | Comparison example 2 | |
| Plasma atmosphere | Nitrogen only | Argon gas only |
| Initial value [mW] | 600 | 200 |
| After 200 | 500 | 150 |
From this result, be appreciated that generating by nitrogen under the situation of the plasma atmosphere that is used to expose that the COD level almost is three times by the situation of argon gas generation plasma atmosphere.
In the process of carrying out AES (Auger electron spectroscopy) measurement, these two nitride semiconductor Laser devices 49 from resonator end towards etched inside are to measure the amount of nitrogen.Fig. 7 shows the result.Fig. 7 is the curve chart of planar marking and drawing, wherein, the degree of depth that transverse axis (X-axis) rises corresponding to self-resonance device end face, the longitudinal axis (Y-axis) is corresponding to ratio of nitrogen to gallium (atomic quantity ratio).In Fig. 7, the part of X=0 is resonator end face 13 and the low interface of reflecting between the coat film 34 that is made of GaN.For example, the part of X=2nm is represented from this interface inside 2nm place, and has indicated the ratio of nitrogen to gallium here.
Next, the method for the relative quantity of the nitrogen that the surface that the resonator end face that calculates nitride semiconductor Laser device in this manual is described is interior.
1) carrying out AES on the resonator end face without the nitride semiconductor Laser device that exposes measures.
1-1) determine the resonator end face the surface in ratio of nitrogen to gallium (a).
1-2) in playing the depth bounds of 2-4.5nm, the surface of self-resonance device end face calculates the mean value (b) of ratio of nitrogen to gallium.
1-3) the value (c=a/b) of calculating by obtaining divided by the value that obtains among the 1-2 (b) with the value (a) that obtains among the 1-1.
2) carrying out AES on the resonator end face of the nitride semiconductor Laser device through exposing measures.
2-1) determine the ratio of nitrogen to gallium (d) that the resonator end face is interior.
2-2) in playing the depth bounds of 2-4.5nm, the surface of self-resonance device end face calculates the mean value (e) of ratio of nitrogen to gallium.
2-3) calculate the value (f=d/e) that obtains divided by the value that obtains among the 2-2 (e) by the value (d) that will obtain among the 2-1.
3) calculate the value (g=f/c) that obtains divided by the value that obtains among the 1-3 (c) by the value (f) that will obtain among the 2-3.In this manual, the value (g) that obtains by this way is defined as the relative quantity of the nitrogen in the resonator end face.
Be appreciated that from this definition the relative quantity of nitrogen in the surface of resonator end face is based on the ratio of nitrogen to gallium in the face that is not exposed to plasma atmosphere.Therefore, if finished the exposure of nitride semiconductor Laser device, and can't obtain without the nitride semiconductor Laser device that exposes, so can be by the nitride semiconductor Laser device of scribing (scribe) cleavage through exposing, to form new end face, can measure ratio of nitrogen to gallium in the described new end face as benchmark.What will record in this face by this method, compares as the result of benchmark and through the measurement result in the face that exposes.Therefore, even without without the sample that exposes, also can measure the relative quantity of the nitrogen in the resonator end face.
Based on the aforementioned calculation method, determine the relative quantity of the nitrogen in the resonator end face surface of sample shown in Figure 7.At first, adopt the result of the sample that is not exposed to argon plasma atmosphere shown in Figure 13 as benchmark.In the sample that is not exposed to argon plasma atmosphere shown in Figure 13, the ratio of nitrogen to gallium (a) in the surface of resonator end face (X=0 among Figure 13) is 1.185, and the mean value of the ratio of nitrogen to gallium in the depth bounds of described surface 2-4.5nm (b) is 1.011.Therefore, c=a/b=1.185/1.011 ≈ 1.172.
Like the sample implementation of class of comparison example shown in Figure 72, calculate.Ratio of nitrogen to gallium (d) in the surface of resonator end face is 0.908, and the mean value of the ratio of nitrogen to gallium in the depth bounds of described surface 2-4.5nm (e) is 1.055.Therefore, f=d/e=0.908/1.055 ≈ 0.861.Therefore, the relative quantity (g) of the nitrogen in the resonator end face of the sample of comparison example 2 is as follows: g=f/c=0.861/1.172 ≈ 0.73=73%.
In addition, with regard to the sample of example 3, the ratio of nitrogen to gallium (d) in the surface of resonator end face is 1.222, and the mean value (e) that the ratio of nitrogen to gallium in the depth bounds of 2-4.5nm is played on the surface of self-resonance device end face is 1.062.Therefore, f=d/e=1.222/1.062 ≈ 1.150.Therefore, the relative quantity (g) of the nitrogen in the resonator end face of example 3 is as follows: g=f/c=1.150/1.172 ≈ 0.98=98%.
Like this, in the sample that is exposed to the plasma atmosphere that is only generated by argon gas of comparison example 2, compare before with exposure, the relative quantity of nitrogen has reduced to 73% in the resonator end face.On the other hand, in the sample that is exposed to the plasma atmosphere that is only generated by nitrogen of example 3, the relative quantity of nitrogen is 98%, and it is near the same value before exposing.Therefore, expose required plasma atmosphere, can under the situation of the nitrogen in not reducing the resonator end face of nitride semiconductor Laser device, remove removing natural oxidizing thing etc. so if only generate by nitrogen.In addition, after being exposed to plasma atmosphere, can realize high initial COD level and reducing by the relative quantity that keeps the nitrogen in the resonator end face by the aging COD changing down that causes.
Next, when changing in the nitrogen that in being used in the gas that generates the required plasma atmosphere of exposure, is comprised and the scope of partial pressure ratio at 0-100% of argon gas, make the sample of nitride semiconductor Laser device.Afterwards, measure the relative quantity of the nitrogen in the resonator end face that calculates each sample based on AES.Fig. 8 shows the result.Fig. 8 is the curve chart of planar marking and drawing, and in described plane, transverse axis is corresponding to the voltage ratio of nitrogen and argon gas, and the longitudinal axis is corresponding to the relative quantity of the nitrogen in the resonator end face.Be appreciated that from Fig. 8 existence is related between the relative quantity of nitrogen in the voltage ratio of nitrogen that is used for generating the gas that exposes required plasma atmosphere and argon gas and resonator end face.If the former increases, the latter also increases.Therefore, can be by controlling the relative quantity of the nitrogen in the nitrogen that contains in the described gas and the voltage ratio between the argon gas control resonator end face.
Similarly, when changing in the nitrogen that in being used in the gas that generates the required plasma atmosphere of exposure, is comprised and the scope of voltage ratio at 0-100% of argon gas, be manufactured on the sample of the nitride semiconductor Laser device of the relative quantity that has different nitrogen in the resonator end face.Afterwards, under the condition of 70 ℃ of ambient temperatures, power 60mW and APC driving, described sample is implemented 200 hours ageing test.Fig. 9 shows the result.In Fig. 9, transverse axis is corresponding to the relative quantity of the nitrogen in the resonator end face, and the longitudinal axis is corresponding to the COD level after aging.The relative quantity that is appreciated that the nitrogen in the resonator end face by Fig. 9 with aging after the COD level between exist related; If the former increases, the latter also increases.Therefore, in order to realize high COD level and low deterioration ratio, must after exposing, keep the high relative quantity of nitrogen in the resonator end face.In addition, be appreciated that so aging COD level afterwards will significantly reduce if the relative quantity of the nitrogen in the resonator end face becomes less than 80%.For this reason, the relative quantity of wishing the nitrogen in the resonator end face is 80% or higher.
In an embodiment of the present invention, when the resonator end face being exposed to the plasma atmosphere that is generated by the gas that contains nitrogen, nitride semiconductor laser rod 10 can be under the room temperature or be heated.If it is heated, can improve the efficient of nitrogen to the deposit of resonator end face.In addition, can also improve the removal efficient of natural oxide film etc.In ECR sputter equipment 50, by heater 63 nitride semiconductor laser rod 10 is heated to 200 ℃, and only is exposed in the plasma atmosphere that generates by nitrogen.With regard to the nitride semiconductor laser device 40 that adopts the nitride semiconductor Laser device of making by this nitride semiconductor laser rod 10 49, measure CO D level before 200 hours aging and afterwards.Figure 10 shows the result.In Figure 10, transverse axis is corresponding to the temperature that is exposed to plasma atmosphere, and the longitudinal axis is corresponding to the COD level.Figure 10 also show aging after, be exposed to the measurement result of COD level of the nitride semiconductor laser device of the plasma atmosphere that only generates by nitrogen under the room temperature under the same conditions.Aging condition is as follows.Ambient temperature is 70 ℃, and the power during APC drives is 60mW.The measuring condition of COD level is that the width under the room temperature is 50ns, and duty ratio is 50% impulsive measurement.Be appreciated that from Figure 10 when the exposure implemented to the plasma atmosphere that only contains nitrogen, the COD level has obtained further raising under heated condition.
Next, measure relation between the amount of nitrogen of the temperature of the nitride semiconductor laser rod 10 when being exposed to plasma atmosphere and resonator end face 13 and 14 by the AES method of measurement.The result is as shown in table 6.It is 100% o'clock value that the scale of this nitrogen is shown in after the cleavage just the nitrogen content in the per unit area in the resonator end face 13 and 14.
[table 6]
| Component | Room temperature | 200℃ | |
| Plasma atmosphere | Nitrogen only | Nitrogen only | |
| The amount of nitrogen in the resonator end face | 96％ | 99％ |
As can be understood from Table 6, when implementing the exposure to the plasma atmosphere that only contains nitrogen under to nitride semiconductor laser rod 10 heated state, can more effectively reduce the removal of nitrogen from resonator end face 13 and 14.This heating-up temperature preferably is in 100-500 ℃ the scope, more preferably is in 150-500 ℃ the scope.In addition, 200-400 ℃ scope preferably many.This is because if temperature is higher than 500 ℃, electrode part is graded possible breakdown (broken down) so, makes that voltage may raise when nitride semiconductor Laser device 49 provides electric power.
In addition, in an embodiment of the present invention, the resonator end face is exposed in the plasma atmosphere that is generated by the gas that contains nitrogen.As the ECR sputter equipment, can adopt a kind of device of being furnished with special exposure chamber (not shown), described special exposure chamber is arranged in plasma shown in Figure 3 and generates between chamber 70 and the film formation stove 60.In this ECR sputter equipment, special exposure chamber is connected to the film that is under the high vacuum state forms stove, thereby under high vacuum state, form mobile nitride semiconductor laser rod 10 between the stove in special exposure chamber and film, and can not be exposed in the external environment condition.This special exposure chamber does not have target, but is furnished with the RF plasma source as plasma source.In addition, film formation stove is furnished with the target that is connected to the RF power supply.Owing to dispose described ECR sputter equipment by this way, therefore needn't form and implement oxidation within the stove at film.
In having the ECR sputter equipment of said structure, in special exposure chamber, make the resonator end face 13 and 14 of nitride semiconductor laser rod 10 be exposed to the plasma atmosphere that only contains nitrogen, afterwards, nitride semiconductor laser rod 10 is transferred to the film that is under the high vacuum state forms in the stove.In film forms stove, on resonator end face 13 and 14, form Ta with 50nm thickness
2O
5Film.Employing is made nitride semiconductor laser device 40 by the nitride semiconductor Laser device 49 that this nitride semiconductor laser rod 10 obtains, and the enforcement test identical with above-mentioned test.Thereby, with regard to the amount and COD level of the nitrogen of resonator end face, obtained similar result, wherein, the characteristic that is obtained is better than being exposed to the situation of the plasma atmosphere that only contains argon gas.
In this embodiment, the microwave power that is used to generate plasma preferably is in 200-800 watt the scope.If power is lower than 200 watts, nitrogen just can not be attached on resonator end face 13 and 14, and can not fully remove natural oxide film, moisture, pollutant etc.If power is higher than 800 watts,, also can remove nitrogen from resonator end face 13 and 14 even in the plasma that only generates by nitrogen.This reason is considered to be: be included in nitrogen ion in the plasma and caused infringement to resonator end face 13 and 14.
In addition, the time span that is exposed to plasma atmosphere preferably is in 30 seconds to 20 minutes the scope.If described time span is shorter than 30 seconds, can not fully remove natural oxide film, moisture, pollutant etc. from resonator end face 13 and 14.If described time span was longer than 20 minutes, promptly be used in the microwave power that generates plasma and be in 200-800 watt the scope, also can remove nitrogen, thereby cause not wishing the result that obtains from resonator end face 13 and 14.
In addition, if adopt the mist contain nitrogen, might adopt the inert gas (for example helium, neon, krypton or xenon) except that argon so or adopt the mist of two or more inert gases as generating the gas that the resonator end face is exposed to plasma atmosphere wherein.Notice that the inert gas in this specification is meant helium, neon, argon, krypton and xenon.
Second embodiment
Next, will describe second embodiment of the invention in detail.Second embodiment and first embodiment are similar, except will in two stages the resonator end face being exposed to the plasma atmosphere.
In this embodiment, in two stages the resonator end face is exposed in the middle of the plasma atmosphere.The resonator end face is exposed in the middle of the plasma atmosphere that only generates in the phase I, is exposed in the middle of the plasma atmosphere that only generates by nitrogen in second stage by argon gas.Table 7 shows the example of condition under this situation.
[table 7]
| Phase I | Second stage | |
| Plasma atmosphere | Argon gas only | Nitrogen only |
| Argon flow [sccm] | 40 | 0 |
| Nitrogen flow [sccm] | 0 | 40 |
| Microwave power [W] | 300 | 700 |
| Stove back pressure [Pa] | 1.4×10 -1 | 1×10 -1 |
| Processing time [min] | 1 | 10 |
| Treatment temperature | Room temperature | Room temperature |
According to this embodiment, the resonator end face 13 and 14 from nitride semiconductor laser rod 10 in the phase I is removed natural oxide film etc., and has also removed nitrogen.In second stage, the resonator end face 13 and 14 that was once got on by it except nitrogen has absorbed nitrogen once more.Therefore, mainly utilize nitrogen to keep the amount of the nitrogen in resonator end face 13 and 14, rather than utilize it to remove natural oxide film etc.Being exposed to the resonator end face 13 of the plasma atmosphere under the condition shown in the table 7 and the relative quantity of nitrogen in 14 the surface is 98%, and it is near the same value before exposing.
In addition, table 8 shows another example that makes the resonator end face be exposed to the residing exposure condition of plasma atmosphere in the present embodiment.Here, the temperature of nitride semiconductor laser rod is made as 300 ℃ in the time of will being exposed to plasma atmosphere.
[table 8]
| Phase I | Second stage | |
| Plasma atmosphere | Argon gas only | Nitrogen only |
| Argon flow [sccm] | 20 | 0 |
| Nitrogen flow [sccm] | 0 | 40 |
| Microwave power [W] | 300 | 700 |
| Stove back pressure [Pa] | 1.1×10 -1 | 7.3×10 -2 |
| Processing time [min] | 10 | 10 |
| | 300 | 300 |
As for the nitride semiconductor laser rod 10 that is exposed to the plasma atmosphere that is under the condition shown in the table 8, measure the amount of the nitrogen in resonator end face 13 and 14, the result is 98%, it is near the same value before exposing.It is 100% o'clock value that the scale of this nitrogen is shown in after the cleavage just the nitrogen content in the per unit area in the resonator end face 13 and 14.
Under each of two kinds of above-mentioned conditions, in the resonator end face of nitride semiconductor Laser device, obtain with first embodiment similarly about the amount of nitrogen and the result of COD level.
In this embodiment, the microwave power in the phase I preferably is in 200-800 watt the scope.If this power is lower than 200 watts, can not fully remove natural oxide film, moisture, pollutant etc. from resonator end face 13 and 14.If power is higher than 800 watts, will in second stage, be exposed to the quantity that to recover nitrogen in the plasma atmosphere that only contains nitrogen even make from resonator end face 13 and 14 a large amount of nitrogen of removing so.
The time span that is exposed to plasma atmosphere in phase I preferably is in 30 seconds to 20 minutes the scope.If described time span is shorter than 30 seconds, can not fully remove natural oxide film, moisture, pollutant etc. from resonator end face 13 and 14.If time span was longer than 20 minutes, will fully remove nitrogen from resonator end face 13 and 14 so, in second stage, be exposed to the quantity that can not recover nitrogen in the plasma atmosphere that only contains nitrogen even make.
When in the phase I, nitride semiconductor laser rod 10 being exposed to plasma atmosphere, can make nitride semiconductor laser rod 10 be in room temperature or to its heating.Yet if the temperature of nitride semiconductor laser rod 10 becomes 500 ℃ or higher, grade may be breakdown for electrode part so, makes that voltage may raise when nitride semiconductor Laser device 49 provides electric power, thereby cause not wishing the result that obtains.
Microwave power in the second stage preferably is in 200-800 watt the scope.If power is lower than 200 watts, just be difficult to compensate nitrogen on the degree of amount of the nitrogen in the resonator end face 13 and 14 that can recover to be lowered in the phase I.If power is higher than 800 watts,, also can remove nitrogen from resonator end face 13 and 14 even in the plasma atmosphere that only generates by nitrogen.This reason is considered to be the infringement that caused by the nitrogen ion in the plasma atmosphere.
In addition, the time span that is exposed to plasma in the second stage preferably is in 30 seconds to 20 minutes the scope.If time span is shorter than 30 seconds, just be difficult to compensate nitrogen on the degree of quantity of the nitrogen in the resonator end face 13 and 14 that can recover to be lowered in the phase I.If time span was longer than 20 minutes,, also can remove nitrogen from resonator end face 13 and 14 even in the plasma atmosphere that only generates by nitrogen.
In addition, when in second stage, the nitride semiconductor laser rod being exposed to plasma atmosphere, can make the nitride semiconductor laser rod be in room temperature or to its heating.Even, also can obtain about suppressing to remove the effect of the present invention of nitrogen from resonator end face 13 and 14 not to the heating of nitride semiconductor laser rod.If to nitride semiconductor laser rod heating, heating-up temperature preferably is in 100-500 ℃ the scope, more preferably is in 200-400 ℃ the scope.If heating-up temperature is higher than 500 ℃, grade may be breakdown for electrode part so, makes that voltage may raise when nitride semiconductor Laser device 49 provides electric power.
In this embodiment, when in the phase I, the resonator end face being exposed to plasma atmosphere, can adopting inert gas beyond the argon as the gas that generates plasma atmosphere, rather than adopt argon gas only.Perhaps, can adopt the mist of inert gas and nitrogen.
In addition, in the present embodiment, can divide the three or more stages that the resonator end face is exposed in the middle of the plasma atmosphere, and be not limited to two stages, be to be generated by the gas that contains nitrogen as long as be used for the plasma atmosphere that final stage exposes.In each stage, except above-mentioned gas, can adopt the mist of inert gas and nitrogen to realize plasma atmosphere.In addition, described inert gas can contain the inert gas of two or more.
Note, in first and second embodiment, should be implemented in the formation coat film at least at the resonator end face 13 of bright dipping side and in the past the resonator end face was exposed to the plasma that produces by the gas that contains nitrogen, to obtain described effect.This be because, the optical density in the resonator end face of light reflection side 14 are lower than the optical density in the resonator end face 13 of light exit side, thereby the heat generation in the resonator end face 14 of light reflection side is lower, its possibility that causes COD to damage is very little.Yet, because the possibility that in the resonator end face 14 of light reflection side, exists COD to damage.Therefore, preferably also expose resonator end face 14 on the light reflection side.
In addition, in the present invention, importantly: after being exposed to the plasma atmosphere that generates by the gas that contains nitrogen, on the resonator end face, form coat film not being exposed under the airborne situation.Therefore, if after being exposed to the plasma atmosphere that generates by the gas that contains nitrogen, be not exposed under the airborne situation, forming the coat film that covers whole resonator end face, so, after this, exposing nitride semiconductor Laser device does not just have problems.Therefore, also may additionally form another coat film.So, might form the multiple coating film that constitutes by multiple material, thereby improve the flexibility of design nitride semiconductor Laser device.Therefore, can after forming protective layer 35, be exposed under the airborne situation, in another device, forming the reflector 36 of high reflection coat film 37.
In addition, as the material of low reflection coat film 34 and high reflection coat film 37, might adopt the nitrogen oxide (oxide nitride) of nitride, Al or Si of oxide, Al or Si of Al, Ti, Si, Y, Nb, Ta, Zr, Hf or Zn or the fluoride of Mg or Ca.
In addition, in first or second embodiment, can adopt EB (electron beam) evaporator rather than ECR sputter equipment to form coat film.If the EB evaporator is furnished with plasma generating equipment, in stove, does not implement oxidation so and do not have problems yet.With regard to the EB evaporator, plasma gas generating portion (generation plot) and target can be separated each other.Therefore, can not exist plasma gas to cause that target is by sputter and there is material to be attached to possibility on the sample.
In addition, might adopt RF (radio frequency) sputter equipment rather than ECR sputter equipment.If adopt the RF plasma method to make the nitrogen that is in plasmoid, will generate the nitrogen that much is in state of atom, described nitrogen is attached to the resonator end face easily.Therefore, can effectively prevent the removal of nitrogen.The RF plasma method has adopted the high frequency of 13.56MHz to generate the gas that is in plasmoid, and it adopts the circumnutation (cyclotron movement) that is caused by magnetic field unlike the ecr plasma method.Except this point, form the similar of the method for coat film and ecr plasma method.
In addition, resonator end face 13 and 14 is not limited to form by cleavage, and it can be by such as the vapor phase etchant of RIE (reactive ion etching) method or ICP (inductively coupled plasma) method or the etching minute surface (etched mirror) that adopts the wet etching of KOH (potassium hydroxide) solution etc. to form.Owing to when implementing etching, observed the removal of nitrogen, therefore, also can apply the present invention to the etching minute surface and without any problem.
Claims (28)
1. method of making nitride semiconductor Laser device, described method comprises:
The nitride semiconductor layer that forms nitride semiconductor layer on substrate forms step; And
Cleavage has formed the described substrate of described nitride semiconductor layer thereon, thereby forms the cleavage step of two resonator end faces that are parallel to each other, wherein
Described method also comprises first exposing step that described resonator end face is exposed to first plasma atmosphere that is generated by the mist of nitrogen or inert gas and nitrogen, in described first exposing step, ratio of nitrogen to gallium when be illustrated in the surface that is exposed to described resonator end face before described first plasma atmosphere with " a " in, be illustrated in before the described exposure mean value with " b " from the ratio of nitrogen to gallium of the inside on the surface of described resonator end face, be illustrated in the ratio of nitrogen to gallium in the surface that is exposed to described resonator end face after described first plasma atmosphere with " d ", when being illustrated in after the described exposure mean value from the ratio of nitrogen to gallium of the inside on the surface of described resonator end face, will be made as the value that satisfies g 〉=0.8 by the value " g " of g=(bd)/(ae) expression with " e ".
2. method according to claim 1, wherein, described method also comprises being in and described resonator end face is exposed to second exposing step in the middle of second plasma atmosphere that is generated by inert gas between described cleavage step and described first exposing step.
3. method according to claim 1, wherein, formation avoided described resonator end face to be subjected to the end face coated film of optical damage after described method also was included in described first exposing step.
4. method according to claim 3, wherein, described end face coated film is made of the oxide of Al, Ti, Si, Y, Nb, Ta or Zr.
5. method according to claim 3, wherein, described end face coated film is that the nitride by Al or Si constitutes.
6. method according to claim 3, wherein, the two all has the end face coated film that is made of same material described two resonator end faces.
7. method according to claim 3, wherein, described end face coated film forms by electron cyclotron resonace sputtering method or high-frequency sputtering.
8. method according to claim 1, wherein, the described substrate temperature in described first exposing step is in 150-500 ℃ the scope.
9. method according to claim 1, wherein, the described substrate temperature in described first exposing step is in 200-400 ℃ the scope.
10. method according to claim 2, wherein, the described substrate temperature in described second exposing step is in 150-500 ℃ the scope.
11. method according to claim 2, wherein, the described substrate temperature in described second exposing step is in 200-400 ℃ the scope.
12. nitride semiconductor Laser device by method manufacturing according to claim 1.
13. a method of making nitride semiconductor Laser device, described method comprises:
The nitride semiconductor layer that forms nitride semiconductor layer on substrate forms step;
Cleavage has formed the described substrate of described nitride semiconductor layer thereon, thereby forms the cleavage step of two resonator end faces that are parallel to each other; And
The coat film that forms coat film on described resonator end face forms step, wherein
Described method comprises that also being in described cleavage step and described coat film forms and described resonator end face is exposed to first exposing step in the middle of first plasma atmosphere that is generated by the gas that contains nitrogen between the step.
14. method according to claim 13 wherein, forming in the time period of step to finishing coat film from first exposing step, is not exposed to described resonator end face in the middle of the air.
15. method according to claim 13, wherein, described first plasma atmosphere is generated by the gas that only contains nitrogen.
16. method according to claim 13, wherein, described first plasma atmosphere is generated by the gas that contains nitrogen and argon.
17. method according to claim 13 wherein, in described first exposing step, does not form the film that comprises the element that constitutes described coat film on described resonator end face.
18. method according to claim 13 wherein, in described first exposing step, is heated to temperature in the scope that is in 100-500 ℃ with the described substrate that has formed described nitride semiconductor layer on it.
19. method according to claim 13 wherein, in described first exposing step, is exposed to described resonator end face in the scope that time span in described first plasma atmosphere is in 30 seconds to 20 minutes.
20. method according to claim 13 wherein, generates described first plasma atmosphere by electron cyclotron resonace.
21. method according to claim 20, wherein, in described first exposing step, the microwave power of described electron cyclotron resonace is in 200-800 watt the scope.
22. method according to claim 13, wherein, the nitride of one of them oxide by Al, Ti, Si, Y, Nb, Ta, Zr, Hf or Zn, Al or the Si at least of described coat film or the nitrogen oxide of Al or Si constitute.
23. method according to claim 13 also comprises being in described resonator end face being exposed to second exposing step in the middle of second plasma atmosphere that is generated by the mist of inert gas and nitrogen between described cleavage step and described first exposing step.
24. method according to claim 23, wherein, the described inert gas in described second exposing step is an argon.
25. method according to claim 23 wherein, in described second exposing step, is heated to temperature in the scope that is in 100-500 ℃ with the described substrate that has formed described nitride semiconductor layer on it.
26. method according to claim 23 wherein, in described second exposing step, is exposed to described resonator end face in the scope that time span in described second plasma atmosphere is in 30 seconds to 20 minutes.
27. method according to claim 23 wherein, generates described second plasma atmosphere by electron cyclotron resonace.
28. method according to claim 27, wherein, in described second exposing step, the microwave power of described electron cyclotron resonace is in 200-800 watt the scope.
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| CN107113061A (en) * | 2014-09-30 | 2017-08-29 | 祥茂光电科技股份有限公司 | Semiconductor laser diode with integrated heating region |
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| US7668218B2 (en) | 2007-02-20 | 2010-02-23 | Nichia Corporation | Nitride semiconductor laser element |
| US7701995B2 (en) | 2007-07-06 | 2010-04-20 | Nichia Corporation | Nitride semiconductor laser element |
| KR101461672B1 (en) * | 2008-02-11 | 2014-11-13 | 엘지전자 주식회사 | Semiconductor laser diode package system and Method the same |
| US9972968B2 (en) * | 2016-04-20 | 2018-05-15 | Trumpf Photonics, Inc. | Passivation of laser facets and systems for performing the same |
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| US6618409B1 (en) * | 2000-05-03 | 2003-09-09 | Corning Incorporated | Passivation of semiconductor laser facets |
| JP2002043691A (en) * | 2000-07-25 | 2002-02-08 | Matsushita Electric Ind Co Ltd | Nitride semiconductor laser device and its manufacturing method |
| JP4977931B2 (en) * | 2001-03-06 | 2012-07-18 | ソニー株式会社 | GaN semiconductor laser manufacturing method |
| US6812152B2 (en) * | 2001-08-09 | 2004-11-02 | Comlase Ab | Method to obtain contamination free laser mirrors and passivation of these |
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| JP5285835B2 (en) * | 2005-07-13 | 2013-09-11 | 株式会社東芝 | Semiconductor device and manufacturing method thereof |
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| JP4860210B2 (en) | 2012-01-25 |
| CN101383481A (en) | 2009-03-11 |
| JP2007059732A (en) | 2007-03-08 |
| CN101383481B (en) | 2010-09-29 |
| CN100431229C (en) | 2008-11-05 |
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