WO2006077766A1 - 半導体レーザ装置及びその製造方法 - Google Patents
半導体レーザ装置及びその製造方法 Download PDFInfo
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- WO2006077766A1 WO2006077766A1 PCT/JP2006/300297 JP2006300297W WO2006077766A1 WO 2006077766 A1 WO2006077766 A1 WO 2006077766A1 JP 2006300297 W JP2006300297 W JP 2006300297W WO 2006077766 A1 WO2006077766 A1 WO 2006077766A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/223—Buried stripe structure
Definitions
- the present invention relates to a semiconductor laser device used as a light source for an optical disk device, an information processing device, and the like, and a method for manufacturing the same.
- the current distribution shape and the light distribution shape are controlled to increase the output. It is possible to improve the kink level, which is a problem. Also, by making the ridge top dimension almost the same as the bottom dimension, the thermal resistance during current injection can be reduced, and a low operating current can be realized.
- the substrate orientation is from the (100) plane to the [011] direction It is common to use a semiconductor substrate having an off-angle inclined by about 10 °.
- the ridge shape in a cross section perpendicular to the longitudinal direction (stripe direction) of the ridge becomes asymmetrical to the left and right reflecting the substrate off angle.
- the ridge shape in the cross section perpendicular to the longitudinal direction (stripe direction) of the ridge is a trapezoidal shape with low verticality of the wall surface. From the above points, it has been very difficult to improve the asymmetry and the perpendicularity of the ridge shape in the cross section perpendicular to the longitudinal direction of the ridge (stripe direction).
- ridge-type stripes have been formed using dry etching and wet etching in combination, and the ridge shape is perpendicular to the longitudinal direction of the ridge (stripe direction). It has been proposed (for example, see Patent Document 1 below). Since dry etching can be anisotropically etched, the vertical and symmetry of the cross section perpendicular to the longitudinal direction of the ridge (stripe direction) is higher than when forming a ridge-type stripe only by wet etching. An improved ridge shape is obtained. In addition, the wet etching after dry etching removes the damage layer generated by the plasma during dry etching.
- FIGS. Fig. 3 shows the structure of the semiconductor laser device described in Examples 1 and 3 of Patent Document 1
- Fig. 4 shows the manufacturing process.
- the cross-sectional view also shows the direction force perpendicular to the longitudinal direction of the ridge stripe. is there.
- Epitaxial growth is performed sequentially by the length method (hereinafter referred to as MOCVD method) (in FIG.
- a p-type intermediate layer (for example, a p-type GalnP intermediate layer) is deposited between the p-type cladding layer 307 and the p-type GaAs cap layer 309 (see FIG. Not shown).
- the ridge-type stripe pattern 313 may use a dielectric such as force Si 0 formed using a photoresist.
- the p-type GaAs cap layer 309 and the p-type cladding layer 307 are formed under the p-type cladding layer 307 using dry etching technology. Etching is performed to a position of 50 nm to 350 nm on the etching stop layer 306.
- wet etching is performed up to the p-type etching stop layer 306, and a ridge-type strut comprising a P-type AlGaAs cladding layer 307 and a p-type GaAs cap layer 309 is performed.
- an n-type current blocking layer 310 is deposited by MOCVD, and the current injection region, that is, p-type GaAs is deposited by wet etching.
- the current blocking layer on the cap layer 309 surface is removed.
- the p-type GaAs contact layer 311 is formed again by MOCVD, and the semiconductor laser wafer is completed (see Fig. 3 for the completed product).
- the AlGaAs-based infrared semiconductor laser device and the AlGalnP-based red semiconductor laser device are relatively perpendicular to each other in the cross section perpendicular to the longitudinal direction of the ridge (stripe direction).
- An improved ridge shape is obtained.
- the etching depth can be controlled by wet etching, and the plasma damage layer can be removed during dry etching.
- FIG. 6 is a cross-sectional view of the structure of the semiconductor laser device according to the second embodiment, and also shows the manufacturing process, and also shows the directional force perpendicular to the longitudinal direction of the ridge-type stripe.
- an n-type AlGaAs cladding layer 503, an active layer 504 having a quantum well structure, a p-type AlGaAs cladding layer 505, and a p-type etching stop Layer 506, p-type AlGaAs clad layer 507, and p-type GaAs cap layer 509 are sequentially grown epitaxially by the MOVPE method.
- a layer corresponding to the active layer 504 having a quantum well structure is not shown).
- a dielectric such as A10 is deposited on the surface of the p-type GaAs cap layer 509, and photolithography is performed.
- Ridge-type stripe pattern that also has dielectric force such as A10 by using Raffy technology
- the p-type etching stop layer 506 is a layer containing In having a band gap that does not absorb laser light, or a layer containing In having a layer thickness designed to obtain a quantum effect.
- AlGalnP or GalnP For example, AlGalnP or GalnP.
- Inductively coupled plasma is used for dry etching.
- P-type etching stop layer 506 uses a layer containing In, and its etching rate is significantly higher than that of p-type AlGaAs cladding layer 507 and p-type GaAs cap layer 509. descend. Therefore, in dry etching, etching can be stopped by the etching stop layer 506.
- a chemical liquid mainly composed of hydrofluoric acid is used as a dielectric such as A10.
- a current blocking layer 510 is formed by MOCVD.
- unnecessary portions of the current blocking layer 510 grown on the ridge stripe are removed by photolithography using a photoresist, and then p-type GaAs contact is formed by metal organic chemical vapor epitaxy (hereinafter referred to as MOVPE).
- MOVPE metal organic chemical vapor epitaxy
- FIG. 7 is a structure of the semiconductor laser device described in Patent Document 2
- FIG. 8 is a cross-sectional view showing a manufacturing process thereof as seen from a direction perpendicular to the longitudinal direction of the ridge type stripe.
- the SiO stripe 713 is formed by the luffy technique.
- a part of the In P clad layer 707 is etched to form a ridge stripe.
- the nP current blocking layer 705 and the n-type GaAs current blocking layer 706 are sequentially epitaxially grown.
- the SiO stripe 713 is removed and the entire surface of the substrate is removed by MOCVD.
- a type GaAs contact layer 710 is grown. Finally, a p-side electrode 711 and an n-side electrode 701 are formed to manufacture a semiconductor laser device.
- a ridge-type stripe can be formed only by dry etching, and in a cross section perpendicular to the longitudinal direction (stripe direction) of the ridge, the symmetry is high. A ridge shape is obtained.
- Patent Document 1 Japanese Patent Laid-Open No. 2003-69154
- Patent Document 2 Japanese Patent Laid-Open No. 2000-294877
- the ridge shape in a cross section perpendicular to the longitudinal direction (stripe direction) of the ridge is symmetrical with the semiconductor substrate facing down.
- the difference between the carrier distribution shape and the light distribution shape is reduced, the hole burning phenomenon is suppressed, and the lateral ridge shape asymmetry in the cross section perpendicular to the longitudinal direction (stripe direction) of the ridge is suppressed. Mode instability is eliminated.
- the shape of the ridge side wall surface is desirably a ridge-type stripe that is perpendicular to the surface of the semiconductor substrate and has a higher ridge height.
- the height of the ridge is low, laser light with a broad active layer force is absorbed by the P-type cap layer, etc., which tends to lead to deterioration of characteristics such as an increase in threshold current and a decrease in differential quantum efficiency.
- the width of the bottom of the ridge not only regulates the current path width but also the intensity of optical confinement, a ridge stripe semiconductor laser device is usually designed based on the width of the ridge bottom.
- the conventional process has a trapezoidal shape (forward mesa shape) where the ridge bottom dimensions are the same and the ridge top dimensions are narrowed, so that the contact resistance with the p-side electrode increases as the ridge top dimensions become smaller. Characteristics such as threshold values tend to decrease. Therefore, in order to avoid these problems, a high-power semiconductor laser with a large light spread of active layer strength requires the formation of a ridge-type stripe that does not reduce the width of the top surface of the ridge even if it has a high ridge height. Is done.
- the longitudinal direction (stripe direction) of the ridge is compared with the case of forming by only wet etching technology.
- a ridge shape with improved verticality and symmetry can be obtained, but side etching occurs at the top of the ridge due to wet etching for the purpose of etching depth control and plasma damage layer removal. Will fall.
- AlGalnP-based red semiconductor laser devices use a semiconductor substrate that generally has an off angle, specifically, a (100) plane inclined in the [0 11] direction. ) The symmetry of the ridge shape in the cross section perpendicular to the longitudinal direction (stripe direction) of the ridge is reduced.
- the wet etching chemical used does not etch the p-type GaAs cap layer 309, and only etches the p-type cladding layer 307.
- the p-type cladding layer 307 is made of AlGaAs in the case of an AlGaAs-based infrared semiconductor laser device, and is made of AlGalnP in the case of an AlGalnP-based red semiconductor laser device. Therefore, as shown in FIG. 4 (c), only the ridge side surface of the p-type cladding layer 303 is selectively etched, and the upper part of the p-type cladding layer 307 just below the p-type GaAs cap layer 309 is the desired ridge top dimension. A narrower overhang is formed with p-type GaAs cap layer 309 protruding on both sides of the ridge top portion.
- the n-type current blocking layer 310 is formed on a substrate having such a ridge shape in a cross section perpendicular to the longitudinal direction (stripe direction) of the ridge, the epitaxial growth is completely under the overhang. In other words, a cavity is formed, and the cavity remains in the completed semiconductor laser device without being lost even in the subsequent process.
- Such a cavity scatters oscillation light in the laser device, causes waveguide loss, and adversely affects device characteristics such as a decrease in differential quantum efficiency and an increase in threshold current and operating current.
- n-type AllnP when epitaxially grown, the n-type grown epitaxially is grown at the ridge skirt where multiple types of crystal planes are exposed.
- the crystallinity of the MnP current block layer decreases.
- the increase in the ridge size relative to the mask size and the decrease in the crystallinity of the n-type AllnP current blocking layer degrade the device characteristics such as non-uniformity in the horizontal emission angle of the laser beam and increase in threshold current and operating current.
- the source gas is insufficiently supplied, and the deposition rate is locally reduced, so that the coverage of the current blocking layer at the ridge skirt is lowered.
- a semiconductor layer such as n-type Alln P is used as the current blocking layer, a plurality of types of crystal planes are exposed on the ridge side wall formed by anisotropic dry etching. The epitaxial growth cannot be performed with good crystallinity, and the crystallinity of the current blocking layer is lowered.
- the SiN current blocking layer has low coverage at the ridge bottom that most affects the oscillation light close to the emission position.
- the crystallinity of the n-type AllnP current blocking layer is caused by nonuniformity in the horizontal emission angle of the laser beam, threshold This leads to deterioration of device characteristics such as increase in value current and operating current.
- the angle formed between the ridge side surface and the substrate surface at the lower edge of the ridge is close to 90 degrees. Stress concentrates in the vicinity of the bonding line between the side surface of the ridge and the etching stop layer, and cracks may occur at the bottom of the ridge starting from this portion. As a result, the performance of the laser device may be degraded.
- the above manufacturing method is limited to an AlGaAs infrared semiconductor laser device, and cannot be applied to an AlGalnP red semiconductor laser device.
- a thin GalnP etching stop layer is grown on an AlGaAs cladding layer, the composition, film thickness, and lattice irregularities are controlled. Deterioration in control and crystallinity is a problem, and stable production is difficult.
- the etching stop layer is provided! /, So that the dry etching depth cannot be controlled.
- the ridge height uniformity among the semiconductor laser devices decreases among a plurality of wafers.
- Example 2 of Patent Document 1 the angle formed between the ridge side wall surface and the substrate surface is increased, so that when a dielectric film such as SiN or SiO is applied to the current blocking layer, the ridge hem is not covered.
- the current block layer coverage at the ridge skirt may be reduced, and current leakage at the ridge skirt may occur.
- a semiconductor layer such as n-type AllnP is used as the current blocking layer, a plurality of crystal planes are exposed on the ridge side wall surface formed by anisotropic dry etching, so that the epitaxial has good crystallinity. It cannot grow and the crystallinity of the current blocking layer decreases.
- Example 2 of Patent Document 1 since the angle formed between the ridge side wall surface and the substrate surface is large, there is a risk of cracks occurring at the ridge hem.
- the present invention provides a ridge stripe type semiconductor laser device having an improved output having a ridge formation with excellent verticality and symmetry and a high kick level, and a method for manufacturing the same.
- a side wall protective layer is formed on the side wall surface of the ridge after dry etching over the ridge type stripe forming method using both dry etching and wet etching, and side etching of the ridge top during subsequent wet etching is performed.
- a ridge stripe semiconductor laser device of the present invention includes a first conductivity type cladding layer, an active layer, and a second conductivity type first cladding layer on a compound semiconductor substrate.
- a semiconductor laser comprising: an etching stop layer; a second conductivity type second cladding layer formed on a striped ridge; and a current blocking layer formed excluding at least a part of the ridge.
- each of both side surfaces of the ridge is substantially perpendicular to the semiconductor substrate surface and extends downward from the upper end of the ridge.
- a second surface having a substantially straight hem portion inclined surface force that is inclined downward toward the outside of the ridge at the ridge hem portion, and the first surface and the second surface are ,
- (bl) is a substantially stepped step surface that is substantially parallel to the semiconductor substrate surface and that extends outward from the ridge, and has a length of 0.2 m or less at the cross section.
- (b2) It is connected via a straight or curved curved intermediate surface that protrudes diagonally outward and bulges outward from the ridge, A ridge stripe semiconductor laser device in which a (111) plane of a semiconductor constituting the second cladding layer is exposed on the second surface.
- each of the first surface and the second surface is substantially straight in the shape of the ridge side surface.
- each of the two inclined surfaces is a substantially flat inclined surface, and when the first surface and the second surface are directly connected, the connection between these two surfaces is The cross-sectional shape has a refracting point, and the first surface and the second surface are connected via an intermediate surface (in this case, a stepped surface in this case) which is the third surface as in (bl) above.
- each connecting portion has a refraction point in the cross-sectional shape, and the third surface in (b2) above. Even when the surface is curved, the first surface and the second surface are straight flat surfaces.
- curved surfaces whose slope changes continuously as a whole such as curved surfaces whose cross-sectional shape is a continuous curve, such as the side wall surface of the cladding layer 307 in FIGS. 4 (c) and 4 (d), are excluded. It is burned.
- the (111) plane is exposed in an area of at least 50% or more of the second plane. This is preferable because the current blocking layer and the like can be epitaxially grown with good crystallinity.
- an angle formed by the first surface and the surface of the semiconductor substrate is 85 ° or more and 95 ° or less. It is preferable.
- the width near the ridge top end on the first surface is not so small compared to the width near the ridge bottom end on the first surface. It is possible to prevent the resistance from increasing or the characteristics such as the threshold from deteriorating. It is also preferable because the ridge height can be increased, the threshold current is increased and the differential quantum efficiency is prevented, the light spread from the active layer is large, and a high-power semiconductor laser can be obtained.
- the third intermediate surface protrudes outside the ridge in a cross-sectional shape perpendicular to the ridge stripe direction.
- the length of the step step surface substantially parallel to the surface of the semiconductor substrate is equal to or less than the thickness of the current blocking layer.
- the plane orientation of the surface of the semiconductor substrate is a plane orientation in which the (100) plane force is also inclined by a predetermined angle.
- the (100) plane inclination direction is the [011] direction.
- the predetermined angle is an angle at which a natural superlattice is not formed when the first cladding layer is epitaxially grown on the semiconductor substrate (growth so that the crystal axis is aligned with the substrate). In general, it is preferably 5 ° or more and 20 ° or less.
- a method for manufacturing a ridge stripe semiconductor laser device of the present invention includes a first conductivity type cladding layer, an active layer, and a second conductivity type first cladding layer on a compound semiconductor substrate, Except for the step of sequentially forming an etch stop layer and a second cladding layer of the second conductivity type, and a portion for forming a striped ridge, the second conductivity type second cladding layer is formed using a dry etching technique.
- This is a method for manufacturing a ridge stripe semiconductor laser device, in which etching is performed so that the (111) plane of the semiconductor constituting the second cladding layer is exposed on at least a part of the side surface of the ridge.
- the ridge stripe semiconductor laser device of the present invention at least 50% or more of the side surface of the ridge formed by the wet etching in the wet etching step (111). It is preferable to expose the surface.
- the side etch rate in the wet etching is reduced and stabilized, so the concentration of the chemical used for the wet etching, temperature, etc. Variation in etching rate due to variation can be suppressed, and ridge This is preferable because the shape of the hem can be easily controlled.
- wet etching is performed until the second surface is substantially linear in cross-sectional shape so that the (111) surface is exposed on almost the entire surface of the second surface. .
- the ridge stripe semiconductor laser device of the present invention in the cross section perpendicular to the stripe direction of the ridge, (thickness of the side wall protective layer) ⁇ (the thickness in the wet etching step)
- the amount of side etching of the second cladding layer of the second conductivity type is preferable.
- the plane orientation of the semiconductor substrate surface is a plane orientation inclined at a predetermined angle from the (100) plane.
- the inclination direction of the (100) plane is the [011] direction.
- the predetermined angle is an angle such that a natural superlattice is not formed when the first cladding layer is epitaxially grown on the semiconductor substrate (growth so that the crystal axis is aligned with the substrate). In general, it is preferably 5 ° or more and 20 ° or less.
- AlGalnP-based semiconductor layer AlGalnP-based semiconductor layer (A1P, GaP, InP mixed crystal semiconductor) on a GaAs (100) substrate.
- AlP AlP
- a red laser beam having a wavelength of 650 nm that oscillates becomes 685 nm.
- the energy gap can be changed accordingly by changing the composition ratio of the components constituting the semiconductor.
- the energy due to the crystal structure is changed.
- the gap change becomes dominant, and there is a disadvantage that even if the composition ratio is changed, a desired energy gap value, in other words, a desired oscillation wavelength cannot be controlled. Therefore, in order to prevent the formation of a natural superlattice, it is particularly preferable to use a (100) plane substrate whose semiconductor substrate surface is inclined at a predetermined angle in the [011] direction.
- the (100) surface force is formed on a compound semiconductor substrate having a surface orientation inclined at a predetermined angle as a first conductive type.
- a step of sequentially forming a cladding layer, an active layer, a second conductivity type first cladding layer, an etching stop layer, and a second conductivity type second cladding layer, and a portion where a stripe-shaped ridge is formed A step of etching the second conductivity type second clad layer halfway using a dry etching technique, and at least one layer on the ridge side surface of the ridge portion formed by the dry etching, Forming a sidewall protective layer having a different thickness on both sides of the ridge, and further etching the second conductivity type second cladding layer to the etching stop layer using a wet etching technique;
- the ridge is viewed from the [01-1] direction with the substrate facing down in a cross section perpendicular to the stripe direction of the ridge.
- the thickness of the sidewall protection layer formed on the right side of the ridge is the thickness of the sidewall protection layer formed on the left side of the ridge.
- etching is performed so that the (111) plane of the semiconductor constituting the second cladding layer is exposed on at least a part of the side surface of the ridge.
- the area of at least 50% or more of the side surface of the ridge formed by the wet etching is in the wet etching process. It is preferable to expose the (111) plane.
- the side etch rate in wet etching decreases and stabilizes. Therefore, the concentration and temperature of the chemical used in the wet etching are reduced. It is preferable because it can control the variation in etching speed due to the variation and facilitate the shape control of the ridge skirt.
- ⁇ Silicon etching amount of the second conductivity type second cladding layer in the wet etching step
- the surface shape of the substantially linear step step surface in the wafer surface which is substantially parallel to the surface of the semiconductor substrate and projecting to the outside of the ridge.
- a shape in which the third surface does not occur on the ridge side wall surface on the thickness side with the thinner layer thickness (a shape in which the first surface and the second surface are directly connected) can be stably formed in the wafer surface.
- the shape where the stepped surface bites into the inside of the ridge is particularly narrow due to the narrowing of the ridge, which narrows the current path, increases the resistance during laser operation, and tends to cause characteristic degradation such as an increase in value! /, .
- the inclination direction of the (100) plane is the [011] direction.
- a ridge stripe semiconductor laser device with improved element characteristics such as uniform horizontal radiation angle of laser light, improved differential quantum efficiency, and improved kink level, and A manufacturing method thereof can be provided. Furthermore, ridge-type stripes can be formed with good uniformity within and between wafers, and yield can be improved.
- FIG. 1 is a cross-sectional view showing the structure of an embodiment of a ridge stripe semiconductor laser device of the present invention.
- FIG. 2A is a cross-sectional view showing a manufacturing process of the ridge stripe type semiconductor laser device shown in FIG. 1 of the present invention.
- FIG. 2B is a process partial view of a cross section perpendicular to the stripe direction of the ridge of the process of various other embodiments of the present invention, corresponding to the process of (g) of FIG. 2A.
- FIG. 2C is a process cross-sectional view of another embodiment of the present invention, corresponding to the processes (f) to (i) in FIG. 2A.
- FIG. 2D is a partially enlarged view of the ridge and the vicinity of the skirt in the step (c) of FIG. 2A.
- FIG. 2E is a process cross-sectional view of another embodiment of the present invention, corresponding to the process after (c) in FIG. 2A.
- FIG. 2F is a process cross-sectional view of another embodiment of the present invention corresponding to the process after (c) in FIG. 2A.
- FIG. 2G is a partially enlarged view of the ridge and its vicinity in the (t-1) step of FIG. 2E.
- FIG. 2H is a partially enlarged view of the ridge and the vicinity of the skirt in the step (u-1) in FIG. 2F.
- FIG. 21 is a partially enlarged view of the ridge and the vicinity of the skirt in the step (t-5) of FIG. 2E.
- FIG. 2J is a partially enlarged view of the ridge and the vicinity of the skirt in the step (u-5) in FIG. 2F.
- FIG. 2K is a process cross-sectional view of another embodiment of the present invention corresponding to the process after (e) in FIG. 2A.
- FIG. 3 is a cross-sectional view showing the structure of an embodiment of a conventional ridge stripe semiconductor laser device.
- FIG. 4 is a sectional view showing a manufacturing process of the conventional ridge stripe type semiconductor laser device shown in FIG.
- FIG. 5 is a cross-sectional view showing the structure of an embodiment of a conventional ridge stripe semiconductor laser device.
- FIG. 6 is a cross-sectional view showing a manufacturing process of the conventional ridge stripe semiconductor laser device shown in FIG.
- FIG. 7 is a cross-sectional view showing the structure of an embodiment of a conventional ridge stripe semiconductor laser device.
- FIG. 8 is a sectional view showing a manufacturing process of the conventional ridge stripe semiconductor laser device shown in FIG.
- FIG. 1 is a cross-sectional view perpendicular to the longitudinal direction of the ridge of the ridge stripe semiconductor laser device according to the first embodiment
- FIG. 2A is a similar cross-sectional view showing the manufacturing process.
- the upper side, the lower side, or the upper side or the lower side of the semiconductor laser device is, for example, based on FIG.
- the side where 101 is present is referred to as the lower side and the lower side
- the side where the p-side electrode 112 is present is referred to as the upper side and the upper side.
- an n-type GaAs substrate 102 (thickness: 400 to 500 ⁇ m) is formed by MOCVD (metal organic chemical vapor deposition). Al Ga) In P cladding layer 10
- an SiO film 113 (thickness 0.
- the n-type GaAs substrate 102 used is, for example, a visible light semiconductor laser having an oscillation wavelength of 650 band, and suppresses the formation of a natural superlattice (ordered structure) in the Ga In P layer. l]
- a semiconductor substrate having a so-called off angle having a (100) plane inclined about 10 ° in the direction is used, but in the present invention, the substrate off angle can be used without any particular limitation.
- the substrate off-angle even when the substrate off-angle is inclined, the right-left symmetry of the ridge shape is substantially maintained in the cross section perpendicular to the stripe direction of the ridge as will be described later.
- the block layer can be formed without any problem.
- the active layer 104 may be an active layer having a multiple quantum well structure in which GalnP is a well layer and AlGalnP is a barrier layer.
- the p-type Ga In P etching stop layer 106 has a well layer of GalnP and a barrier of AK ⁇ alnP.
- It may be an etching stop layer having a multiple quantum well structure as a layer.
- the p-type Ga In P etching stop layer 106 does not absorb laser light.
- a ⁇ alnP can be used as long as it is a layer thickness with a band gap or a layer thickness designed to obtain a quantum effect!
- the SiO 2 film 113 in FIG. It is formed on the SiO stripe 114 by the technique and dry etching technique.
- the amount of dry etching is 65 to 95% of the ridge height, preferably 80 to 95%. Within this range, variation in the amount of side etching due to wet etching at the ridge skirt described later can be suppressed. If the area of the first surface formed by dry etching is too small, and as a result the area to be wet etched is too large, the amount of etching varies greatly depending on the state of the etchant (concentration, temperature, etc.). This is because the influence of the crystal plane described later is not dominant.
- the above numerical range of the dry etching amount and the ridge height refers to the relationship between the dry etching amount and the ridge height at the side surface of the ridge. That is, generally, as shown in FIG.
- the thickness of the portion remaining on the outer side of the ridge of the remaining second cladding layer 108 (that is, spreading laterally! /, The bottom portion) is In many cases, the part away from the side surface of the ridge tends to be thinner than the vicinity of the side surface of the ridge. Therefore, the reference ridge height when the amount of dry etching is in the range of 65 to 95% of the ridge height is that the upper edge force of the sidewall surface 121 after the first dry etching is also lower (the contact with the bottom surface 122 after the dry etching). The vertical distance to (part) was used as a reference.
- a method of stopping etching by time control a method of applying a monochromatic light to the substrate surface and obtaining interference intensity and time obtained from the reflected light.
- a method of applying a monochromatic light to the substrate surface and obtaining interference intensity and time obtained from the reflected light there is a method in which the etching is performed while calculating the remaining etching thickness and the etching is stopped when the desired film thickness is obtained.
- Examples of the dry etching technique that can be suitably employed in the present invention include anisotropic plasma etching, and examples of dry etching include inductively coupled plasma (hereinafter referred to as ICP) and electron 'cyclotron' resonance (The following are methods using ECR plasma.
- the etching gas is a force that uses a mixed gas of SiCl and Ar.
- chlorine gas trisalt-boron gas, or the like may be used.
- the dry etching technique used in the first embodiment is an ICP (Inductively Coupled Plasma) method, using a mixed gas of SiCl and Ar as an etching gas. Yes.
- ICP Inductively Coupled Plasma
- the volume content of SiCl in the mixed gas is 5-12%, semiconductor
- the temperature of the lower electrode on which the substrate is installed is 150 to 200 ° C
- the pressure in the chamber is 0.1 to 1 Pa
- the bias power of the lower electrode is 50 to 150 W
- the ICP power is 200 to 300 W, but this is not limited What is necessary is just to select suitably rather than a thing.
- the force by which the SiO film 115 having a thickness of 60 nm to 400 nm is grown to form the ridge side wall protective layer is not limited to this.
- the thickness of the SiO film 115 is not limited to this depending on the amount of side etching caused by the additional etching of the etching process or the amount of etching during wet etching using a hydrofluoric acid chemical solution that is appropriately performed for the purpose of surface treatment in each process. However, it may be selected appropriately.
- the SiO film 115 used in the first embodiment is not limited to this, and the side wall protection is not limited to this.
- etching chemical resistance As a material that can be used as a layer, high selectivity (etching chemical resistance) can be ensured with respect to the wet etching chemical used in the subsequent process, and an AalnP-based semiconductor layer and an intermediate product are not formed.
- a dielectric film such as SiN or A10, GaAs or AlGaAs can be used.
- examples of means for forming these films include a CVD method (eg, plasma CVD, atmospheric pressure CVD, MOCVD, etc.) and a PVD method (sputtering, vapor deposition, etc.).
- the plasma CVD method is particularly preferable because it enables film formation with uniform film thickness and facilitates film formation.
- the CVD method is an abbreviation for chemical vapor deposition
- the PVD method is an abbreviation for physical vapor deposition.
- the SiO film 115 used in the first embodiment is a single layer force.
- it may be composed of a plurality of layers as required.
- the SiO film 115 in the region other than the ridge side wall surface is dry-etched. Then, the SiO sidewall protective layer 116 is formed.
- a dry etching method capable of removing the SiO film 115 in a region other than the side surface of the ridge as appropriate such as a reactive ion etching method (hereinafter referred to as RIE method), an ICP method, and an ECR method is adopted.
- RIE method reactive ion etching method
- ICP method ICP method
- ECR method ECR method
- CF gas such as CF and CHF mixed gas is used as etching gas.
- the RIE method is adopted, and CF and CHF are used as etching gases.
- a mixed gas of 0 is used.
- the stage temperature is 10-20 ° C. It is not limited to this, but can be changed as appropriate.
- a hydrochloric acid-based chemical solution that is a mixture of tartaric acid, hydrochloric acid, and water (the volume content of tartaric acid in the chemical solution is 30 to 50%, the volume content of hydrochloric acid is
- the P-type (AlGa) InP second cladding layer 108 is used as a p-type GaInP etching stop layer 1
- the p-type Ga In P etching stop layer 106 is hydrochloric acid.
- this layer stops the etching in the direction perpendicular to the substrate surface.
- the end of the wet etching in the direction perpendicular to the substrate surface can be determined by visual observation of interference fringes in the etching region of the semiconductor substrate surface.
- the etching rate in the direction perpendicular to the substrate surface is extremely reduced, and the film thickness uniformity on the substrate surface is improved, so that the change in the interference fringes in the etching region is stopped. Therefore, it can be confirmed that the etching in the direction perpendicular to the substrate surface has stopped.
- the p-type (AlGa) InP second cladding layer 108 is wet-etched.
- a sulfuric acid chemical solution may be used.
- the SiO side wall protective layer 116 is highly resistant to hydrochloric acid chemicals, so
- the region where this layer is formed is not etched, and side etching does not occur at the top of the ridge side surface (that is, the first surface).
- the SiO side wall protective layer 116 is formed on the ridge side surface.
- the region (ridge skirt portion) isotropically etched.
- the wet etching is continued as it is until the two layers 116 are formed until the ridge side surface of the region (second ridge side wall surface 119: ridge skirt portion) is substantially linear.
- the wet etching process is performed until the second ridge side wall surface 119 (second surface) has a substantially straight inclined surface in cross-section, and this is clearly described as “additional etching”.
- the above-mentioned wet etching need not be performed in two stages.
- the wet etching may be performed until the second ridge side wall surface 119 has a substantially straight inclined surface in cross section. It should be noted that such an additional etching amount may be appropriately selected according to the kind of chemical solution and the mixing ratio.
- the SiO sidewall protective layer 116 is removed using a hydrofluoric acid chemical solution.
- the thickness of the SiO stripe 114 is changed from 100 to 100 for the SiO side wall protective layer 116.
- the thickness is set to 300 nm, only the SiO side wall protective layer 116 can be removed by stopping the etching with the hydrofluoric acid chemical solution by time control.
- a wet etching technique is used to remove the SiO side wall protective layer 116.
- the chemical dry etching method (hereinafter referred to as the CDE method) should be appropriately selected according to the material constituting the sidewall protective layer, which is not limited to wet etching.
- the SiO side wall protective layer 116 is selectively removed depending on the material constituting the side wall protective layer.
- the SiO stripe 114 is used as a mask by the MOCVD method.
- an n-type Al In P current blocking layer 107 is selectively grown to a thickness of 0.2 to 0.4 m.
- N-type GaAs cap selectively using SiO stripe 114 as mask by M0CVD
- Layer 111 is grown to a thickness of 0.1 to 0.2 / z m.
- the damage layer on the ridge side wall is not formed before the n-type Al In P current blocking layer 107 is grown.
- surface treatment is performed with a sulfuric acid chemical solution.
- the ridge side wall is 15 ⁇ ! It is etched in the range of ⁇ 40nm.
- the chemical solution for surface treatment may be a mixture of hydrochloric acid and water.
- the current blocking layer has a portion expressed as “a current blocking layer formed excluding at least a part of the ridge”. This is because the current is present on the upper surface of the ridge.
- the current blocking layer may be covered with a current block layer. Rather, the latter case is preferred.
- the SiO stripe 114 is removed with a hydrofluoric acid chemical solution or the like.
- a P-side electrode 112 and an n-side electrode 101 are formed by vapor deposition to complete a ridge stripe type semiconductor laser wafer.
- Examples of the material of the p-side electrode 112 include Ti / Pt / Au, and examples of the material of the n-side electrode 101 include AuGe / Ni / Au.
- force SiN or SiO using n-type Al In P current blocking layer 107 is used.
- a dielectric film such as 0.5 0.5 2 may also be used. In this case, growth of the n-type GaAs cap layer 111 is not necessary.
- the ridge-type stripe formed in Embodiment 1 has high verticality and symmetry, and is closer to the top of the ridge formed by dry etching.
- 118) and the surface of the n-type GaAs substrate 102 can be in the range of 85 to 95 °.
- the first surface (first ridge side wall surface) 118 and the second surface (second ridge side wall surface) 119 are indicated by (g) in FIG. 2A and (j) to (n) in FIG. 2B only. In other figures, it is difficult to see the figure, so the sign is omitted.
- the angle between the side surface of the ridge and the surface of the semiconductor substrate is the angle indicated by reference numeral 120 in (g), (h), and (i) of FIG.
- the semiconductor on the ridge side surface inside the ridge This is an angle formed between the first surface 118 and the second surface 119 and the semiconductor substrate surface, or a third surface between the first surface and the second surface.
- this definition also applies to the angle formed between the third intermediate surface and the semiconductor substrate surface.
- the reference numeral 120 is omitted, but the angle between the side surface of the ridge and the surface of the semiconductor substrate has the same definition. Used.
- the angle formed by the first surface (first ridge side wall surface) 118 and the surface of the semiconductor substrate 102 is substantially vertical, and more preferably in the range of 85 to 95 °.
- the ridge cross-sectional shape when the angle is less than 90 degrees within the above range, the ridge cross-sectional shape is a forward mesa shape, and when it is larger than 90 degrees, the ridge cross-sectional shape is slightly inverted mesa shape.
- the angle formed by the first ridge side wall surface 118 and the surface of the semiconductor substrate 102 is substantially vertical is preferably within a range including both ranges.
- the angle formed between the ridge inclined surface (second ridge side wall surface 119) closer to the ridge bottom formed by wet etching and the surface of the n-type GaAs substrate 102 is in the range of 40 to 65 °.
- the angle formed between the ridge inclined surface (second surface) closer to the bottom of the ridge and the surface of the n-type GaAs substrate 102 is on each side of the ridge side wall.
- the off-angle is about 10 °
- the angle is in the range of 40 to 50 ° on the one hand and 60 to 70 ° on the other hand.
- This angle is due to the fact that the (111) plane of (Al Ga) In P, which is the p-type second cladding layer 108, is mainly exposed at the ridge skirt. The reason is as follows
- the p-type second cladding layer 108 is epitaxially grown on the n-type GaAs substrate 102, the crystal of the P-type (Al Ga) In P second cladding layer 108 and the n-type GaAs substrate 102 The direction is
- the angle between the (100) plane and the (111) plane is about 50 °.
- Etching rate becomes dominant.
- the (100) plane is inclined about 10 ° in the [011] direction, so the (111) plane exposed on one side of the ridge is about 40 ° exposed on the opposite side (111). The surface is about 60 °.
- the second ridge sidewall surface 119 formed by wet etching is mainly the (111) plane.
- the first surface which is the most part of the ridge side wall surface, is a surface that is substantially perpendicular to the semiconductor substrate surface.
- the second surface of the skirt portion that is in contact with the substrate surface is against the substrate surface. Since the angular force is very slow, a dielectric film such as SiN or SiO is used as the current blocking layer.
- the current blocking layer is made of a dielectric film such as SiN or SiO at the bottom of the ridge.
- the supply of the source gas for forming the current does not become insufficient near the bottom of the ridge, and the coverage of the current blocking layer at the bottom of the ridge that most affects the oscillation light close to the light emission position is improved.
- the ridge inclined surface (second ridge side wall surface 119) closer to the ridge lower end becomes a substantially linear inclined surface in a cross-sectional shape perpendicular to the stripe direction of the ridge, Therefore, since the number of exposed crystal faces is reduced compared to the curved surface, the ridge of the n-type Al In P current blocking layer 107 grown epitaxially is used.
- the p-type Ga In P intermediate layer 109 is formed on the ridge top portion formed in the first embodiment.
- an overhang is formed at the ridge top (see, for example, FIG. 4C), and the n-type Al In P current blocking layer 107 is formed.
- the boundary force between the ridge side wall surface formed by dry etching and the ridge side wall surface formed by wet etching ie, the first ridge side wall surface 118 and the second ridge side wall surface 119
- the first ridge side wall surface and the second ridge side wall surface are connected to each other with an angle of force, that is, this boundary portion becomes a refracting portion, but p-type (AlGa)
- a surface force substantially parallel to the surface of the semiconductor substrate is also provided between the ridge inclined surface (second ridge side wall surface 119) and the upper ridge side wall surface (first ridge side wall surface 118), for example, as shown in FIG. 2B.
- (j) or (k) in FIG. 2B both are drawings of the process corresponding to process (g) in FIG. 2A), the force of protruding outside the ridge as shown by reference numeral 117,
- a step-like step (step step surface) force S having a surface substantially parallel to the surface of the semiconductor substrate may be formed (such as the step step surface (bl) of the third intermediate surface).
- the side etching amount (the amount of side etching) is different on both sides of the ridge in the cross-sectional shape perpendicular to the stripe direction of the ridge.
- the difference in the amount of side etching on both sides of the ridge is growing. Accordingly, in this case, the stepped step surface as shown in (1) of FIG. 2B, (m) of FIG. 2B, or (n) of FIG. 2B (both are drawings of the process corresponding to process (g) of FIG. 2A). 117 is formed.
- the dimensions a ⁇ a ′ and b ⁇ b ′ of the stepped step surface 117 are preferably as small as possible. Preferably it is 0. or less.
- a semiconductor substrate having an inclined off angle is used, as shown in (1) of FIG. 2B, (m) of FIG. 2B, and (n) of FIG.
- the dimensions cc, and d-d ' are different, but in any stepped step surface 117, the smaller the above dimensions are, the less preferable 0.2 ⁇ m or less, more preferably 0.1 ⁇ m or less. It is desirable to have it.
- the designed ridge width in the direction perpendicular to the stripe direction is 1.5 m.
- Intensity of the distribution of laser light Near Field Pattern, hereafter abbreviated as NFP
- the designed ridge bottom force is about 0.2 i um outside and the NFP intensity is 50%.
- Degree. Therefore, if the length of the stepped step surface is within this range (0.2 ⁇ m or less), a sharp change in the refractive index caused by the stepped step portion does not significantly affect the laser beam.
- the “refractive index change” refers to a difference in refractive index between the p-type second cladding layer 108 and the n-type current block layer 107.
- the step surface substantially parallel to the surface of the semiconductor substrate and substantially linear in the cross section is, for example, (j), (k), (1), (m) in FIG. 2B.
- the surface of the step 117 as shown in (n) is meant.
- such a stepped surface is sometimes simply referred to as a stepped step or a stepped step.
- the step step 117 shown in (j) of FIG. 2B is a step step projecting to the outside of the ridge side surface (the length of the left and right step steps is the same). This occurs when the amount of side etching (the amount of side etching) is smaller than the thickness of the sidewall protective layer in the wet etching process from (e) to (f) in FIG. 2A.
- the step 117 that digs inside the ridge is obtained when a semiconductor substrate without an inclined off angle is used. This occurs when the amount of side etching (amount of side etching) is larger than the thickness of the sidewall protective layer in the wet etching process.
- the ridge shape depends on the thickness of the sidewall protective layer and the amount of side etching generated on both sides of the ridge. It changes as follows.
- the ridge shape shown in (1) of FIG. 2B is the side etching with the larger side etching amount (the side etching amount is larger) out of the side etchings generated on both sides of the ridge in the wet etching process. Occurs when the amount is less than the thickness of the sidewall protective layer.
- the ridge shape shown in (n) of FIG. 2B is the side etching amount (side etching amount) of the side etching generated on both sides of the ridge in the wet etching process. This occurs when the other side etching amount larger than the thickness of the protective layer (the amount of side etching) is smaller than the thickness of the side wall protective layer.
- FIG. 2B is a cross-sectional view of a cross section perpendicular to the stripe direction of the ridge, similar to (g) of FIG. 2A, in another embodiment corresponding to the step g).
- a step 117 that has digged inside the ridge in the present invention, such a state is obtained, and the first ridge side wall surface 118 and the second ridge side wall surface 119 are formed on the third intermediate surface. It expresses that it is connected via a step which is one.
- Side etching amount (side etching amount) during wet etching on a straight line (straight line z in FIG. 2A (f)) substantially parallel to the surface of the semiconductor substrate at the position where the second ridge sidewall surface 119 is connected. was found to be constant. As described above, this is because the second ridge side wall surface 119 is aligned with the (111) surface during wet etching. This is due to the fact that the chucking speed is constant and stabilized. Therefore, (side etching amount) ⁇
- the size of the step step 117 is increased.
- the step step 117 is extended obliquely upward along the surface and the step step 117 is moved by etching.
- the controllability / stability of the ridge size decreases due to variations in the wet etching rate.
- the narrowing of the ridge narrows the current path, increases the resistance during laser operation, and tends to cause characteristic degradation such as an increase in threshold.
- the current blocking layer when this constriction exists as shown in FIG. 2B (), when the current blocking layer is formed, the current blocking layer may not be completely buried in the constricted portion, and a cavity may be formed.
- (side etching amount) ⁇ (side wall protective layer thickness) on both sides of the ridge wet etching stops in a shorter time as the distance between the lower end of the sidewall protection layer 116 and the etching stop layer 106 becomes shorter.
- the sidewall protection depends on the thickness of the sidewall protection layer 116. Examples thereof include a force for adjusting the distance between the lower end of the layer 116 and the etching stop layer 106, and adjusting the thickness of the side wall protective layer 116 according to the distance between the lower end of the side wall protective layer 116 and the etching stop layer 106.
- the dimensions a—a ′, b—b ′, c c ′, d—d ′ are preferably less than or equal to the current blocking layer thickness on the ridge sidewall surface.
- the angle between the first ridge side wall surface 118 and the surface substantially parallel to the surface of the semiconductor substrate is approximately 90 °, but the current block layer thickness is sufficiently large compared to the dimension of the step step 117.
- the strut is formed so as to leave a part of the p-type second cladding layer. After forming the eve-shaped ridge by dry etching, the sidewalls of the ridge are protected with SiO, etc.
- the P-type second cladding layer is removed by wet etching, stripe ridges with high vertical symmetry can be formed, and the carrier distribution shape and light distribution shape of the resulting semiconductor laser device The gap difference is reduced, the hole burning phenomenon is suppressed, and the kink level is improved.
- the ridge height can be increased, the laser light can be prevented from being absorbed by the GaAs cap layer and the like, and a high-power semiconductor laser with a large spread of light due to the active layer force can be obtained.
- cracks can be prevented by reducing the angle formed between the ridge and its lower layer.
- (side etching amount) ⁇ (side wall protective layer thickness) is set so that the ridge side wall surface 119 of the second surface protrudes outside the ridge. Can be formed stably.
- ⁇ side wall protective layer thickness
- 2E and 2F are cross-sectional views showing the manufacturing steps of the ridge stripe semiconductor laser device according to the second embodiment.
- the purpose of the second embodiment is to suppress the change in the refractive index due to the above step step 117 and to stably form the ridge size and shape.
- the second embodiment as shown in (b) of FIG.
- the steps to be formed are the same as those in Embodiment 1, the subsequent steps will be described. Also, the layer structure is the same as that in the first embodiment.
- Layer 108, p-type Ga In P intermediate layer 109, and p-type GaAs contact layer 110 are made of p-type (Al Ga
- FIG. 2D of the first embodiment the first post-dry-etch side wall surface 121 and the post-dry-etch bottom surface 122 are configured.
- FIG. 2D is an enlarged view of the ridge and its vicinity 125 in FIG. 2A (c).
- a dry etching shape is used and a sidewall protective film 116 is formed thereon as shown in FIGS. 2A (d) and 2 (e) and wet etching is performed, the surface of the semiconductor substrate is faced down.
- Step region 117 (first step) where the region under the sidewall protective layer 116 is substantially parallel to the surface of the semiconductor substrate
- the dimension of the step step 117 (the dimension in the lateral direction as shown in the figure) is preferably as small as possible, and is 0.2 m or less, more preferably 0.1 ⁇ m or less. It is desirable that If step step 117 is greater than or equal to 0, the refractive index changes sharply in the low-intensity region (intensity is 50% or less) of the laser light guided in the resonator. NFP is easily disturbed. If the NFP is disturbed, the distribution shape of the light emitted from the laser element (Far Field Pattern, hereinafter referred to as FFP) will also be deformed. In addition, there is a risk of abnormal data reading or data writing from the disk.
- step step 117 it is necessary to strictly control the formation of the step step 117 completely on the entire wafer.
- the dimension of the step step 117 on both sides of the ridge is different when viewed from the semiconductor substrate surface. Even if 0 is set to 0 m, a step 117 is always formed on the other side (see (o) and (p) in Fig. 2C).
- p-type (AlGa) In is used with the SiO stripe 114 as a mask.
- 2G and 2H are enlarged views of the portion 126 in FIG. 2E (t ⁇ l) and the portion 127 in FIG. 2F (u ⁇ 1) (the ridge and its vicinity).
- the ICP method is employed as the dry etching technique, and a mixed gas of SiCl and Ar is used as the etching gas.
- the shape of the ridge skirt is shown in Fig. 2E (t— 1)
- the volume content of SiCl in the mixed gas is 5
- the temperature of the lower electrode where the semiconductor substrate is installed is 150 to 200 ° C
- the pressure inside the chamber is 0.3 to 0.5 Pa
- the bias power of the lower electrode is 50 to 150 W
- the ICP power is 200 to 200
- the power to be 300 W is not limited to this, and dry etching conditions that provide a desired shape can be selected as appropriate.
- the etching conditions shown in Fig. 2F (u-l) the body of SiCl in the mixed gas
- volume content is 5 ⁇ 12%
- temperature of lower electrode where semiconductor substrate is installed is 150 ⁇ 200 ° C
- pressure inside chamber is 0.1 ⁇ 0.3Pa
- bias power of lower electrode is 50 ⁇ 150W
- ICP The power is 200 to 300W.
- the desired shape is not limited to this. Choose dry etching conditions as appropriate.
- Fig. 2G is an enlarged view of the vicinity of the ridge and its skirt region 126 in Fig. 2E (t-l).
- Fig. 2G shows the side wall surface 121 after the first dry etching substantially perpendicular to the semiconductor substrate surface and after the dry etching. After the dry etching, a side wall surface 123 after dry etching is formed between the bottom surfaces 122.
- the post-dry-etch side wall surface 123 serving as the third inclined intermediate surface may have a plurality of surface forces, and is an enlarged view of the vicinity of the ridge and its skirt region 127 in FIG. 2F (u ⁇ l).
- the side wall surface 124 after dry etching which is the third inclined intermediate surface in FIG.
- 2H it may be a shape in which a plurality of surfaces having a small width are gathered, that is, a curved surface (curved in the sectional view). If there are multiple post-dry-etch side wall surfaces that are the third inclined intermediate surface, the angle formed by the ridge side wall surface that is the third inclined intermediate surface and the semiconductor substrate surface is the p-type Ga In P etching stop. The shape is such that the closer to layer 106, the smaller. Curved field
- the angle formed between the ridge side wall surface and the semiconductor substrate surface is, in other words, smaller as the angle formed between the tangent at each position on the curve of the curve and the semiconductor substrate surface in the cross-sectional view is closer to the etching stop layer 106.
- this curve is a curve that is convex toward the inside of the ridge.
- the amount of dry etching is in the range of 65 to 95% of the ridge height, preferably in the range of 80% to 95%. Within this range, variations in the amount of side etching due to wet etching at the ridge skirt can be suppressed. Area of the first surface formed by dry etching If the area to be wet etched is too large as a result, the amount of etching varies greatly depending on the state of the etching solution (concentration, temperature, etc.).
- the above numerical range of the dry etching amount and the ridge height indicates the relationship between the dry etching amount and the ridge height at the side surface of the ridge. That is, in the second embodiment, as shown in FIG. 2G and FIG. 2H, the angle formed between the side wall surface of the ridge and the surface of the semiconductor substrate is determined by the P-type Ga In P etching stop layer 106.
- the reference ridge height when the amount of dry etching to form a surface substantially perpendicular to the surface of the semiconductor substrate is in the range of 65 to 95% of the ridge height is determined after the first dry etching.
- the height at the wall 121 was used as a reference.
- the reference ridge height when the amount of dry etching is in the range of 65 to 95% of the ridge height is based on the distance of the perpendicular that the ridge top force is lowered with respect to the surface of the etching stop layer 106.
- the amount of dry etching is 65 to 95% of the ridge height.
- the amount of dry etching, the numerical range of the ridge height, and the reference ridge height are the same as those in the first embodiment.
- the angle formed between the ridge side wall surface and the semiconductor substrate surface becomes smaller as it is closer to the P-type Ga In P etching stop layer 106.
- a method for obtaining such a desired dry etching amount a method of stopping etching by time control, a method of applying monochromatic light to the substrate surface, and the interference intensity and time obtained from the reflected light.
- a method of stopping etching by time control a method of applying monochromatic light to the substrate surface, and the interference intensity and time obtained from the reflected light.
- the etching is performed while calculating the remaining etching thickness and the etching is stopped when the desired film thickness is obtained.
- the dry etching technique that can be suitably employed is not limited to the ICP method described above, and is anisotropic.
- dry etching that is suitable for plasma etching, there is a method using electron 'cyclotron' resonance (hereinafter referred to as ECR) plasma.
- ECR electron 'cyclotron' resonance
- the etching gas a mixed gas of SiCl and Ar is used instead of the SiCl gas component.
- Chlorine gas or trisyl boron gas can be used.
- FIG. 2E (t— 2) and FIG. 2F (u— 2) as shown in FIG. 2E (t— 1) and FIG. 2F ( SiO films 128 and 129 having a thickness of 60 ⁇ m to 400 nm are grown on the entire surface (including the ridge side surface) of the intermediate obtained in u-1) by plasma CVD.
- the force obtained by growing the SiO films 128 and 129 having a thickness of 60 nm to 400 nm to form the ridge sidewall protective layer is as follows.
- the SiO film 128 in the region other than the ridge side wall in the next process is not limited to this, and
- the SiO film 128 and 129 thickness is limited to this
- SiO films 128 and 129 used in the second embodiment are not limited to this.
- a material that can be used as a side wall protective layer it can ensure high selectivity (etching chemical resistance) with respect to the wet etching chemical used in the subsequent process, and does not form an intermediate product with the A ⁇ alnP-based semiconductor layer.
- a material having high properties such as high film thickness controllability during film formation include dielectric films such as SiN and A10 in addition to SiO films, GaAs and
- Examples thereof include a semiconductor layer such as AlGaAs, a metal film having a property as described above, and an organic film, which can appropriately fulfill the role as a ridge sidewall protective layer.
- examples of means for forming these include a CVD method and a PVD method, but in this embodiment, it is possible to form a film with high film thickness uniformity and plasma that is easy to form.
- the CVD method is particularly preferable.
- the SiO films 128 and 129 used in the second embodiment have a single layer force.
- It may consist of a plurality of layers as required.
- the Si 0 films 128 and 129 in the region other than the ridge sidewall surface are removed by dry etching, and the SiO sidewall protective layer is removed. 130 and 13
- the SiO films 128 and 129 in regions other than the ridge side are removed as appropriate, such as RIE (Reactive Ion Etching), ICP, and ECR.
- a dry etching method can be employed. Etching gas CF and CHF
- CF gas such as 4 3 gas mixture is used.
- the RIE method is adopted, and CF and CHF are used as etching gases.
- a mixed gas of 0 is used.
- the force at which the stage temperature is 10 to 20 ° C.
- the present invention is not limited to this, and dry etching conditions that can remove the SiO film 115 in the region other than the side surface of the ridge can be adopted as appropriate.
- the mold (Al Ga) In P second cladding layer 108 is formed into a p-type Ga In P etching stop layer 106
- the p-type Ga In P etching stop layer 106 is resistant to hydrochloric acid chemicals.
- the end of the wet etching in the direction perpendicular to the substrate surface can be determined by visual observation of interference fringes in the etching region on the semiconductor substrate surface.
- the etching rate in the direction perpendicular to the substrate surface is extremely reduced, and the film thickness uniformity on the substrate surface is improved, so that the change in the interference fringes in the etching region is stopped. Therefore, it can be confirmed that the etching in the direction perpendicular to the substrate surface has stopped.
- the p-type (Al Ga) In P second cladding layer 108 is wet-etched.
- a sulfuric acid-based chemical solution may be used.
- SiO side wall protective layers 130 and 131 are highly resistant to hydrochloric acid chemicals
- the region where the side wall protective layer is formed on the side surface of the ridge is not etched, and side etching does not occur at the top portion of the ridge side wall (the portion that becomes the first surface).
- SiO sidewall protection is provided on the ridge side.
- Etching proceeds isotropically in the region where the two layers 130 and 131 are not formed (ridge skirt portion).
- the amount of side etching and the SiO side wall protective layers 130 and 131 are set so that the ridge side wall surfaces (second surface and third intermediate surface) protrude outward from the ridge on both sides of the ridge. Thickness adjust.
- the shape of the ridge side wall bites into the inside of the ridge, the ridge shape is the same as that in FIG. 2B (k) of the first embodiment.
- SiO sidewall protective layers 130 and 131 are formed!
- Si 0 sidewall protective layers 130 and 131 are formed !, and the ridge side surface of the region (second ridge side)
- the wall surfaces 133 and 135) are substantially linear.
- the wet etching process is performed until the second ridge side wall surfaces 133 and 135 have a substantially straight slope with a cross-sectional shape, and this is referred to as “additional etching” in order to make it easier to work.
- the wet etching which does not need to be performed in two stages, may be performed until the second ridge side wall surface 135 has a substantially straight inclined surface in cross-sectional shape.
- the additional etching amount may be appropriately selected according to the type of chemical solution (mixing ratio).
- the thickness of the SiO stripe 114 is changed to the SiO sidewall protective layers 130 and 131.
- SiO sidewall protective layers 130 and 131 can be removed by stopping the etching with the hydrofluoric acid chemical solution by time control.
- the wet etching is performed to remove the SiO side wall protective layers 130 and 131.
- the chemical dry etching method (hereinafter referred to as the CDE method) should be selected as appropriate depending on the material constituting the sidewall protective layer, which is not limited to wet etching.
- the SiO sidewall protective layer 130 depending on the material constituting the sidewall protective layer, the SiO sidewall protective layer 130
- n-type 114 as a mask, selectively form n-type Al In P current blocking layer 138 with a thickness of 0.2 to 0.4.
- an n-type GaAs cap layer 139 is grown to a thickness of 0.1 to 0. [0157] Before growing the n-type Al In P current blocking layer 107, the damage layer on the ridge side wall is removed.
- the chemical solution for surface treatment may be a mixture of hydrochloric acid and water.
- the current blocking layer has a portion expressed as “a current blocking layer formed excluding at least a part on the ridge”. This is because the current is present on the upper surface of the ridge.
- the current blocking layer may be covered with a current block layer. Rather, the latter case is preferred.
- a wedge stripe type semiconductor laser wafer is completed.
- Examples of the material of the p-side electrode 140 include Ti / Pt / Au, and examples of the material of the n-side electrode 141 include AuGe / NiIAu.
- force SiN or SiO using n-type Al In P current blocking layer 138 is used.
- a dielectric film such as 0.5 0.5 2 may also be used. In this case, the growth of the n-type GaAs cap layer 139 is not necessary.
- the third ridge side wall surface 121 and the second ridge side wall surface 135 have a third ridge side wall surface 135 as shown in FIGS. Inclined intermediate surfaces 134 and 136 are formed.
- FIG. 21 is an enlarged view of the ridge and its vicinity region 132 in FIG. 2E (t-5), and
- FIG. 2J is an enlarged view of the ridge vicinity region 133 in FIG. 2F (u-5).
- the third inclined intermediate surface 134 has a straight line shape
- the third inclined intermediate surface 136 has a curved shape (a curved shape convex toward the inside of the ridge), and each of them is inclined obliquely downward toward the outside of the ridge.
- the above-described effect can be obtained even when the width of the ridge skirt exceeds 0.2 ⁇ m.
- “Ridge hem The “width” means, for example, the horizontal distance from the first ridge side wall surface 121 to the portion where the second ridge side wall surface 135 is in contact with the etching stop layer 106 shown in FIG.
- the shape of the ridge side wall is projected to the outside of the ridge on both sides of the ridge, and the side etching amount and the thickness of the side wall protective layer are adjusted.
- Side wall surface dimension after dry etching of the third surface in the direction parallel to the surface) ⁇ (side wall protective layer thickness) (side etching amount) ⁇ 0.
- substrate thickness ⁇ (side wall protective layer thickness) ⁇ 0.
- the force is such that the ridge side wall surface protrudes to the outside of the ridge.
- a partial force of the bottom surface 122 after etching is also formed, and a step step 137 substantially parallel to the substrate surface is formed. If the length of the step 137 exceeds 0.2 m, the FFP may be deformed due to the disturbance of the NFP of the laser beam as described above. Therefore, it is desirable that the dimension of the third inclined intermediate surface in the direction parallel to the substrate surface and the length of the step step 137 be not more than 0, more preferably not more than 0.1 m. 2E (see FIG. 2H), as in FIG. 2E (see FIG. 2H), the dimension of the second wall surface 124 after dry etching in the direction parallel to the substrate surface, that is, [i ⁇ ]) ⁇ (SiO Side wall protective layer 131 thickness)-(Side etching amount)
- the thickness is 0.1 m or less.
- the side etching amount differs on both sides of the ridge. Considering the amount of side etching, on both sides of the ridge, (side wall surface dimension after dry etching of the third surface in the direction parallel to the substrate surface) ⁇ (side wall protective layer thickness) one (side etching amount) ⁇ 0
- the ridge side wall surface should protrude from the ridge. Is desirable.
- the n-type GaAs substrate 102 having an off angle in which the substrate orientation is inclined by 10 ° in the [110] direction from the (001) plane is used. It can be applied regardless of the off angle.
- FIG. 2K (w-1) to (w-6) and FIG. 2K (X) are cross-sectional views illustrating the manufacturing process of the stripe-strip type semiconductor laser device according to the third embodiment.
- the third embodiment is limited to the case where the n-type GaAs substrate 102 uses a semiconductor substrate having an off angle in which the substrate orientation is inclined in the [011] direction from the (100) plane.
- an intermediate step surface 117 is always obtained as shown in (1), (m), (n) of FIG. 2B and (p) of FIG. 2C, for example. Is formed.
- Embodiment 3 suppresses the formation of intermediate step surface 117 in Embodiment 1, thereby changing the refractive index generated near the connection between intermediate step surface 117 and second surface 119.
- the purpose is to form a ridge with good dimensional control and reproducibility.
- the steps up to the step of forming the sidewall protective layer 116 are the same as those in the first embodiment, and the subsequent steps will be described. Also, the layer structure is the same as in the first embodiment.
- the SiO film 115 in the region other than the ridge side wall is dry-etched.
- the SiO sidewall protective layer 116 is formed.
- the SiO sidewall protective layer 116 formed on both sides of the ridge is formed on the left side of the ridge.
- the layer formed on the right side of the ridge is the SiO side.
- a resist pattern 145 is formed by photolithography.
- the shape of the resist pattern 145 is not limited to this, and covers the entire SiO sidewall protective layer 116 or a portion closer to the lower edge of the ridge, and S
- the SiO side wall protective layer 116 is formed using a hydrofluoric acid chemical solution. After ⁇ is etched by a thickness of 20 nm to 50 nm to form a thin film, the resist pattern 145 is removed. Here, the SiO side wall protective layer 116 ⁇ after the thin film etching is applied to the SiO side
- the etching force corresponding to the thickness of Onm This amount of etching is not limited to this.
- 8 is small.
- Hydrofluoric acid chemicals for example, chemicals used when etching SiO stripe 114
- a chemical solution having a hydrofluoric acid concentration of about 1Z2 to 1Z10 is used, so the thickness of the SiO side wall protective layer 116 y can be adjusted without losing the SiO side wall protective layer 116 y by time control.
- part of the SiO stripe 114 is exposed from the resist pattern 145.
- the SiO stripe 114 of the exposed part is also etched.
- wet etching is performed on the thin film of the SiO sidewall protective layer 116 ⁇ .
- a chemical dry etching method (hereinafter referred to as a CDE method) should be selected as appropriate depending on the material constituting the sidewall protective layer, which is not limited to wet etching.
- the SiO side wall protective layer 116 ⁇ is selected according to the material constituting the side wall protective layer.
- An etching technique capable of selectively etching may be employed.
- the p-type Ga In P etching stop layer 106 is resistant to hydrochloric acid chemicals, so
- Embodiment 3 a mixed solution of tartaric acid, hydrochloric acid and water is used as the hydrochloric acid-based chemical solution, and the volume content of tartaric acid in the chemical solution is 30 to 50%, and the volume content of hydrochloric acid is 15 to 15%. 35%.
- the end of wet etching in the direction perpendicular to the substrate surface can be determined by visual observation of interference fringes in the etching region of the semiconductor substrate surface.
- the etching rate in the direction perpendicular to the substrate surface is extremely reduced, and the film thickness uniformity on the substrate surface is improved, so that the change in the interference fringes in the etching region is stopped. Therefore, it can be confirmed that the etching in the direction perpendicular to the substrate surface has stopped.
- the p-type (AlGa) InP second cladding layer 108 is wet-etched.
- a sulfuric acid-based chemical solution may be used.
- SiO sidewall protective layers 116 and 116 ⁇ are highly resistant to hydrochloric acid chemicals.
- SiO sidewall protective layers 116 ⁇ and 116 y are formed on the side surfaces of the ridge!
- Etching proceeds isotropically in the ridge skirt portion.
- the side surface is a curved inclined surface having a cross-sectional shape perpendicular to the stripe direction of the ridge. Therefore, the SiO side wall protective layers 116 and 116 ⁇ are formed!
- the second ridge side wall surface 147 has a substantially straight inclined surface with a cross-sectional shape, that is, a wet etching process portion which is performed until the (111) surface is exposed as a whole so that it can be easily rubbed. Force that is called “additional etching”
- the above wet etching does not have to be performed in two stages.
- the operation may be performed until the wall surface 147 has a substantially straight inclined surface with a cross-sectional shape.
- the additional etching amount may be appropriately selected according to the kind of chemical solution'mixing ratio.
- the SiO side wall protective layer 116 is formed using a hydrofluoric acid chemical solution.
- the thickness of the SiO stripe 114 is changed to the SiO sidewall protective layer 116 ⁇ and 11.
- SiO side wall protective layers 116 a and 116 y are removed by stopping the etching with the hydrofluoric acid chemical solution by time control.
- the removal of the SiO sidewall protective layers 116a and 116y is performed by a wet process.
- Etching technique is used, but CDE method should be selected according to the material composing the side wall protection layer which is not limited to wet etching.
- the SiO side wall protective layers 116a and 116y are selectively removed according to the material constituting the side wall protective layer.
- the n-type Al In P current blocking layer 148 is selectively formed to a thickness of 0.2
- an n-type GaAs carrier is selectively etched by MOCVD using the SiO stripe 114 as a mask.
- the top layer 149 is grown to a thickness of 0.1 to 0.2 m.
- surface treatment is performed with a sulfuric acid chemical solution.
- the ridge side wall is 15 ⁇ ! Etching is performed in the range of ⁇ 40nm.
- the chemical solution for surface treatment should be a mixture of hydrochloric acid and water.
- the current block layer has a portion expressed as "a current block layer formed excluding at least a part of the ridge". This is because the current is present on the upper surface of the ridge.
- the current blocking layer may be covered with a current block layer. Rather, the latter case is preferred.
- the SiO stripe 114 is formed with a hydrofluoric acid chemical solution or the like.
- the p-side electrode 150 and n-side electrode 151 are formed by vapor deposition, and the ridge stripe type half A conductor laser wafer is completed.
- the material of the p-side electrode 150 include Ti / Pt / Au
- examples of the material of the n-side electrode 151 include AuGe / Ni / Au.
- force SiN or SiO using n-type Al In P current blocking layer 148 is used.
- a dielectric film such as 0.5 0.5 2 may also be used. In this case, selective growth of the n-type GaAs cap layer 149 is unnecessary.
- the ridge-type stripe formed in Embodiment 3 has high verticality and symmetry, and the ridge side surface near the top of the ridge formed by dry etching and the surface of the n- type GaAs substrate 102 And the angle formed between the second ridge slope near the lower edge of the ridge formed by wet etching and the surface of the n-type GaAs substrate 102 is the ridge-type stripe formed in the first embodiment. Is equivalent to
- the third intermediate stepped surface is not formed at the boundary between the ridge sidewall surface formed by dry etching and the ridge sidewall surface formed by wet etching.
- the surface and the second surface are directly connected.
- an off-substrate when used, when the vertical (Al Ga) In P second cladding layer 108 is wet-etched,
- the amount of side etching that occurs under the SiO sidewall protective layers 116a and 116y is:
- a third intermediate stepped surface similar to that of the first embodiment may be formed between the first ridge side wall surface 146 and the second ridge side wall surface 147.
- the intermediate step with a shape that protrudes outside the ridge A ridge having a surface 152 and a small third intermediate step surface 152 with dimensions n—n ′ and o—o ′ can be formed with good dimensional controllability and reproducibility.
- a substantially linear inclined surface (second ridge side wall surface) is formed by wet etching at the ridge skirt that most affects oscillation light close to the emission position.
- the crystallinity of the current blocking layer composed of a semiconductor layer such as n-type MnP at the bottom of the ridge can be improved.
- current blocks composed of dielectric films such as SiN and SiO
- the coverage can be improved.
- power using an AlGalnP-based red semiconductor laser device is not limited to this, and the present invention can be applied to all ridge stripe semiconductor laser devices using mixed crystal compound semiconductors. It is.
- the ridge stripe semiconductor laser device according to the present invention emits laser light having a plurality of stripe ridges on the same substrate as well as a type having a single stripe ridge, and laser beams having different wavelengths. Needless to say, a laser device of a type that emits infrared light and red light, for example, is included.
- FIG. 2C are cross-sectional views showing processes corresponding to (f) to (i) of FIG. 2A when a semiconductor substrate having a specific inclined off-angle is used as the semiconductor substrate.
- the process before (o) in FIG. 2C is the same as the process shown in (a) to (e) of FIG. 2A, so (a) to (e) of FIG. 2A and (o) of FIG. ⁇ (R) will be quoted for explanation.
- an n-type (AlGa) InP cladding layer 103 (thickness) is formed on an n-type GaAs substrate 102 (thickness 450 m) by MOCVD. 2 / ⁇ ⁇ ), 0 & In P activity
- Ga In P etching stop layer 106 (thickness 10 nm), p-type (Al Ga) In P second cladding
- Layer 108 (thickness 1.2; z m), p-type Ga In P intermediate layer 109 (thickness 50 nm), and p-type GaAs
- a tact layer 110 (thickness 0.2 m) was sequentially formed.
- an S 10 film 113 (thickness 0.6 m) was formed on the p-type GaAs contact layer 110 by an atmospheric pressure CVD method.
- the n-type GaAs substrate 102 used has a substrate orientation of 10 in the [011] direction from the (100) plane.
- a SiO stripe 114 (width 2 m) was formed by a photolithography technique and a dry etching technique.
- the ICP method was used as the dry etching. Also, as an etching gas, with SiCl
- the product was 0 / o, the pressure in the chamber was about 0.6 Pa, the bias power of the lower electrode was 120 W, and the ICP capacity was 200 W.
- a 300 nm thick SiO film 115 is formed on the entire surface of the intermediate obtained in FIG. 2A (c) (including the ridge side surface) by plasma CVD. Grown up.
- the SiO film 115 in the region other than the side surface of the ridge is dry-etched.
- the SiO sidewall protective layer 116 was formed.
- CF and CHF in the mixed gas are used as dry etching conditions using a mixed gas of 4 and 0.
- the volume contents of 3 2 4 3 were 5% and 40%, respectively, and the pressure was 50 Pa.
- the purpose is to remove the SiO film 115 residue in regions other than the ridge sidewalls.
- Etching stop layer 106 is resistant to the hydrochloric acid chemicals, so this layer is not exposed.
- SiO side wall protective layer 116 is highly resistant to hydrochloric acid chemicals
- the region where the layer was formed was not etched, and side etching did not occur in the ridge top portion (first ridge sidewall 118).
- the SiO sidewall protective layer 116 is formed on the ridge sidewall surface.
- additional etching such as 200 nm etching in the direction perpendicular to the substrate surface when the material to be etched was used. Even if the additional etching is continued in this way, the p-type Ga In P etching stop layer 106 is formed.
- the inclined surface of the ridge skirt (second ridge side wall surface 119) has an almost linear inclination in the cross section perpendicular to the stripe direction of the ridge. A surface could be formed.
- the SiO sidewall is controlled by time control using a hydrofluoric acid chemical solution. Only the protective layer 116 was removed.
- the SiO stripe 114 is used as a mask by MOCVD.
- the surface treatment was performed with a sulfuric acid chemical solution (97% sulfuric acid). At this time, the ridge side wall was etched by about 25 ⁇ m on one side. Subsequently, the SiO stripe 114 is used as a mask by MOCVD.
- n-type GaAs cap layer 111 (thickness 0.17 m) was selectively grown.
- the SiO stripe 114 was removed using a hydrofluoric acid chemical solution.
- a p-side electrode 112 made of Ti / Pt / Au (thickness 50/100/50 nm) and an n-side electrode 101 made of AuGe I Ni I Au (thickness 100/50/400 nm) were formed by vapor deposition, A ridge stripe semiconductor laser wafer was completed.
- the obtained ridge-type stripe has high perpendicularity and symmetry, and the angle between the side of the ridge near the top of the ridge (first ridge side wall 118) and the surface of the n-type GaAs substrate 102 is It reached 86 °.
- the n-type GaAs substrate 102 having an off-angle of about 10 ° is used as the angle between the ridge side surface (second ridge side wall surface 119) closer to the bottom of the ridge and the n-type GaAs substrate 102 surface. Therefore, they differed on both sides of the ridge, becoming 40 ° and 62 °, respectively.
- the obtained ridge stripe semiconductor laser wafer was excellent in the perpendicularity of the ridge side surface to the substrate surface and the left-right symmetry of the ridge cross-sectional shape.
- the kink level reached the maximum value of 300 mW that can be measured with the measuring device used! /, It was confirmed that the kink level was over 300 mW at 25 ° C, V. Stable formation of ridge stripe semiconductor lasers with high performance was achieved.
- n-type GaAs cap layer 111 was not necessary, and the other conditions were the same, and n-type Al In P was used as the current blocking layer 107.
- the boundary between the ridge side surface formed by dry etching and the ridge side surface formed by wet etching becomes a refracting portion on one ridge side surface, and the first ridge side The side wall surface and the second ridge side wall surface were formed to be connected at an angle.
- a step step portion which is the third surface, is formed between the first ridge side wall surface and the second ridge side wall surface, and the dimension (g— g ') became 0.07 m.
- the side etching amount of the side etching that is larger in FIG. 2C (o) and (p), the second ridge side wall on the left side of the figure
- the side etching amount of the smaller side etching amount is equal to the thickness of the side wall protective layer. It is also the force applicable when it is smaller than the thickness.
- an n-type (AlGa) InP cladding layer 103 (thickness 2) is formed on an n-type GaAs substrate 102 (thickness 450 ⁇ m) by MOCVD. / ⁇ ⁇ ), ⁇ & In P active layer 104 (
- the n-type GaAs substrate 102 used has a substrate orientation of 10 in the [011] direction from the (100) plane.
- the ICP method was used as the dry etching. Also, as an etching gas, with SiCl
- the product was 0 / o, the pressure in the chamber was about 0.4 Pa, the bias power of the lower electrode was 100 W, and the ICP capacity was 250 W.
- a post-dry etching side wall surface 123 serving as a third inclined intermediate surface was formed between the first dry etching side wall surface 121 and the dry etching bottom surface 122.
- the above dry etching conditions were (1) lowering the etching gas concentration, (2) lowering the lower electrode power, and (3) lowering the pressure inside the chamber.
- an SiO film having a thickness of 300 nm is formed on the entire surface (including the ridge side surface) of the intermediate obtained in (t 1) of FIG. 2E by plasma CVD. Growing 128.
- the SiO side wall protective layer 130 was formed by removing the film by ching. [0220] Here, dry etching was performed using the RIE method. CF and CHF as etching gas
- CF and CHF in the mixed gas are used as dry etching conditions using a mixed gas of 4 and 0.
- the volume contents of 3 2 4 3 were 5% and 40%, respectively, and the pressure was 50 Pa.
- Etching stop layer 106 is resistant to the hydrochloric acid chemicals, so this layer is not exposed.
- SiO side wall protective layer 130 is highly resistant to hydrochloric acid chemicals
- the region where the layer was formed was not etched, and side etching did not occur in the ridge top portion (first ridge side wall surface 121).
- the SiO sidewall protective layer 130 is formed on the ridge sidewall surface.
- additional etching such as 1 OOnm etching in the direction perpendicular to the substrate surface when the layer was the material to be etched. Even if the additional etching is continued in this manner, the p-type Ga In P etching stop layer 106 is formed.
- the inclined surface of the ridge skirt (second ridge side wall surface 135) is almost straight in the cross section perpendicular to the stripe direction of the ridge.
- An inclined surface can be formed.
- the SiO stripe 114 is used as a mask by the MOCVD method.
- the surface treatment was performed with a sulfuric acid chemical solution (97% sulfuric acid). At this time, the ridge side wall was etched by about 25 ⁇ m on one side. Subsequently, the SiO stripe 114 is used as a mask by MOCVD.
- n-type GaAs cap layer 139 (thickness 0. m) was selectively grown.
- the SiO stripe 114 was removed using a hydrofluoric acid chemical solution.
- n-side electrode 141 (thickness 100/50/400 nm) made of AuGe / Ni / Au Then, a ridge stripe type semiconductor laser wafer was completed.
- the obtained ridge-type stripe has high perpendicularity and symmetry, and the angle between the side of the ridge near the top of the ridge (first ridge side wall 121) and the surface of the n-type GaAs substrate 102 is It reached 90 °.
- the n-type GaAs substrate 102 having an off angle of about 10 ° is used as the angle between the ridge side surface (second ridge side wall surface 135) closer to the ridge bottom and the n-type GaAs substrate 102 surface. Therefore, it is different on both sides of the ridge, and each is 40 ° (the second ridge side wall on the left side of the figure at (t 8) in Fig. 2E) and 62 ° (the right side of the figure at (t 8) in Fig. 2E) The second ridge side wall surface).
- the obtained ridge stripe semiconductor laser wafer was excellent in the perpendicularity of the ridge side surface to the substrate surface and the left-right symmetry of the ridge cross-sectional shape.
- the kink level reached the maximum value of 300 mW that can be measured with the measuring device used! /, It was confirmed that the kink level was over 300 mW at 25 ° C, V, and 300 mW. Stable formation of ridge stripe semiconductor lasers with high performance was achieved.
- SiN dielectric film is used as current blocking layer 138 instead of n-type Al In P
- n-type GaAs cap layer 139 was grown in the same manner. In this case, it is not necessary to grow the n-type GaAs cap layer 139.
- n-type Al In P was used as the current blocking layer 138.
- the boundary between the ridge side surface formed by dry etching and the ridge side surface formed by wet etching is on one ridge side surface. Became a refracted part, and the first ridge side wall surface and the second ridge side wall surface were formed to be directly connected at an angle.
- a third inclined intermediate surface 142 is formed between the first ridge side wall surface and the second ridge side wall surface, and the angle of the inclined intermediate surface 142 is 42 °.
- the dimension (p- ⁇ ') was 0.06 m, and the influence of the refractive index change due to the inclined intermediate surface was small, and a ridge could be formed.
- the side etching amount of the side etching that is larger ((t7), (t-8) in Fig. 2E) is the side etching amount of the second ridge sidewall on the left side of the figure).
- Side etching of the smaller side etching amount (the second ridge side wall on the right side of the figure in (t7), (t-8) in Fig.
- the force corresponds to (side wall dimension after the third dry etching in the direction parallel to the substrate surface) ⁇ (side wall protective layer thickness)-(side etching amount).
- an n-type (Al Ga) In P clad layer 103 (thickness 2) is formed on an n-type GaAs substrate 102 (thickness 450 ⁇ m) by MOCVD. / ⁇ ⁇ ), ⁇ & In P active layer 104 (
- the n-type GaAs substrate 102 used has a substrate orientation of 10 in the [011] direction from the (100) plane.
- an SiO stripe 114 (width 2 m) was formed by a photolithography technique and a dry etching technique.
- the ICP method was used as the dry etching. Also, as an etching gas, with SiCl
- a curved third post-etching side wall surface 124 that is convex in the ridge inner side direction is formed between the first ridge side wall surface 121 and the bottom surface 122 after dry etching. .
- the SiO film 129 in the region other than the side surface of the ridge is removed by dry etching.
- the SiO side wall protective layer 131 was formed by removing the film by ching.
- the dry etching conditions were CF and CF in the mixed gas.
- the volume content of CHF is 5% and 40%, respectively, the pressure is 50 Pa, and the stage temperature is 15
- the p-type Ga In P etching is performed on the second (Al Ga) In P second cladding layer 108 using a mixed chemical solution of tartaric acid, hydrochloric acid, and water.
- a mixed chemical solution of tartaric acid, hydrochloric acid, and water is the hydrochloric acid chemical solution.
- the etching in the direction perpendicular to the substrate surface was stopped by the exposure of this layer. By visually checking the interference fringes in the etching area, it was confirmed that etching was stopped in the direction perpendicular to the substrate surface.
- the volume contents of tartaric acid and hydrochloric acid in the chemical solution were 40% and 30%, respectively.
- the SiO side wall protective layer 131 is highly resistant to hydrochloric acid chemicals.
- the region where the layer was formed was not etched, and side etching did not occur in the ridge top portion (first ridge side wall surface 121).
- the region where the SiO sidewall protective layer 131 is not formed on the ridge sidewall surface is isotropic.
- the p-type (AlGa) InP second cladding layer is used as the material to be etched in order to form a substantially straight inclined surface (second ridge side wall surface 135) at the bottom of the ridge.
- the wet etching was continued for a time equivalent to lOOnm etching in the direction perpendicular to the substrate surface (additional etching) (see Fig. 2J). Even if the additional etching is continued in this way, the P-type Ga In P etching stop layer 106 is formed, so that the substrate
- the inclined surface of the ridge skirt (second ridge side wall surface 135) is the second ridge side wall surface 135 in the cross section perpendicular to the ridge stripe direction.
- Most of the straight line was a straight line, and an almost linear inclined surface could be formed.
- the boundary between the first ridge side wall surface 121 and the second ridge side wall surface 135 becomes a refracting portion on one ridge side surface, and the first ridge side wall surface and the second ridge side wall surface are directly angled. Connected and formed.
- a curved third inclined intermediate surface 143 was formed between the first ridge side wall surface and the second ridge side wall surface.
- an n-type Al In P current blocking layer 138 was selectively grown (thickness 0.3 m). In addition remove the damage layer on the ridge sidewall before growing the n-type Al In P current blocking layer 138
- n-type GaAs cap layer 139 (thickness 0. m) was selectively grown.
- the p-side electrode 140 (thickness 50/100/50 nm) made of Ti / Pt / Au and the n-side electrode 141 (thickness 100/50/400 nm) made of AuGe / Ni / Au are formed by vapor deposition.
- a ridge stripe type semiconductor laser wafer was completed.
- the obtained ridge-type stripe has high perpendicularity and symmetry, and the angle between the side of the ridge near the top of the ridge (first ridge side wall 121) and the surface of the n-type GaAs substrate 102 is It reached 87 °.
- the n-type GaAs substrate 102 having an off-angle of about 10 ° is used as the angle between the ridge side surface (second ridge side wall surface 135) closer to the bottom of the ridge and the n-type GaAs substrate 102 surface. Therefore, it is different on both sides of the ridge, 40 ° (in Fig. 2F (u-6) and (u-7), the second ridge side wall on the left side of the figure), 62 ° (Fig. 2F (u-6) ) And (u-7), the second ridge side wall on the right side of the figure.
- the obtained ridge stripe semiconductor laser wafer was excellent in the perpendicularity of the ridge side surface with respect to the substrate surface and the left-right symmetry of the ridge cross-sectional shape.
- the kink level reached the maximum value of 300 mW that can be measured with the measuring device used! /, It was confirmed that the kink level was over 300 mW at 25 ° C, V, and 300 mW. Stable formation of ridge stripe semiconductor lasers with high performance was achieved.
- SiN dielectric film is used as current blocking layer 138 instead of n-type Al In P
- n-type GaAs cap layer 139 was not necessary, and the other conditions were the same, and n-type Al In P was used as the current blocking layer 138.
- a ridge stripe semiconductor laser having the same performance as 0.5 0.5 can be stably formed.
- Example 3 the boundary between the ridge side surface formed by dry etching and the ridge side surface formed by wet etching becomes a refracting portion on one ridge side surface, and the first ridge side.
- the side wall surface and the second ridge side wall surface were formed by connecting directly with an angle.
- the first ridge side wall surface and the second ridge side wall surface In the meantime, a third inclined intermediate surface was formed, the angle of the inclined intermediate surface 143 was 45 °, and a ridge having a small refractive index change could be formed at the ridge skirt.
- the inclined intermediate surface 143 has a curved shape, and the angle of the inclined intermediate surface 143 is the inclined intermediate surface 143 at the connection point between the second ridge side wall surface 135 and the inclined intermediate surface 143. This is the angle between the tangent line and the surface of the semiconductor substrate.
- a semiconductor substrate having an inclined off angle as described in (1) of FIG. 2B is used.
- both sides of the ridge are used.
- the side etching amount of the larger side etching amount (the second ridge sidewall on the left side of the figure in (u-6) and (u-7) in Fig.
- an n-type (Al Ga) In P cladding layer 103 (thickness 2 m) is formed on an n-type GaAs substrate 102 (thickness 450 ⁇ m) by MOCVD.
- Ga In P active layer 104 (thickness
- a thickness of 0.6 m) was formed by atmospheric pressure CVD.
- the n-type GaAs substrate 102 used is an inclined substrate having an off angle with the substrate orientation inclined by 10 ° from the (100) plane in the [011] direction.
- a SiO stripe 114 width 2 m was formed by a photolithography technique and a dry etching technique.
- the ICP method was used as the dry etching. Also, as an etching gas, with SiCl
- the volume%, the internal pressure of the chamber was about 0.7 Pa, the lower electrode temperature was about 190 ° C, the lower electrode bias power was 120 W, and the ICP power was 200 W.
- a 300 nm thick SiO film 115 is formed on the entire surface of the intermediate obtained in FIG. 2A (c) (including the ridge side surface) by plasma CVD. Grown up.
- the SiO film 115 in the region other than the ridge side surface is dry-etched.
- 8 are formed.
- the dry etching conditions were CF and CF in the mixed gas.
- the volume content of CHF is 5% and 40%, respectively, the pressure is 50 Pa, and the stage temperature is 15
- the SiO sidewall protective layers 116 a and 116 ⁇ are also hydrofluoric acid.
- the thickness of SiO side wall protection layers 116a and 116 ⁇ is 0.12 m.
- a resist pattern 145 was formed by photolithography.
- the SiO side wall protective layer 116 is formed using a hydrofluoric acid chemical solution.
- the strike pattern 145 was removed.
- the p-type (Al Ga) In P second cladding layer 108 is formed into a p-type Ga In P using a mixed chemical solution of tartaric acid, hydrochloric acid and water.
- tartaric acid a mixed chemical solution of tartaric acid, hydrochloric acid and water.
- the p-type Ga In P etching stop layer 106 is the hydrochloric acid chemical solution.
- the etching in the direction perpendicular to the substrate surface was stopped by the exposure of this layer. By visually checking the interference fringes in the etching area, it was confirmed that etching was stopped in the direction perpendicular to the substrate surface.
- the volume contents of tartaric acid and hydrochloric acid in the chemical solution were 40% and 30%, respectively.
- SiO side wall protective layer 116a and ⁇ are highly resistant to hydrochloric acid chemicals.
- SiO sidewall protective layers 116 ⁇ and 116 y are formed on the ridge sidewall surface! / Territory
- the inclined surface of the ridge skirt (second ridge side wall surface 147) is the second ridge side wall surface 147 in the cross section perpendicular to the stripe direction of the ridge.
- Most of the upper side of the film was a straight line, and a substantially linear inclined surface could be formed.
- SiO 2 is controlled by time control using hydrofluoric acid chemical solution.
- the SiO stripe 114 is used as a mask by MOCVD.
- n-type Al In P current blocking layer 148 was selectively grown (thickness 0.3 m).
- an n-type GaAs cap layer 149 (thickness 0.17 m) was grown.
- p-side electrode 150 (thickness 50/100/50 nm) that also has Ti / Pt / Au force by evaporation method
- n-side electrode 151 (thickness 100/50/400 nm) made of AuGe / Ni / Au
- a ridge stripe type semiconductor laser wafer was completed.
- the obtained ridge-type stripe has high perpendicularity and symmetry, and the angle between the side of the ridge near the top of the ridge (first ridge side wall 146) and the surface of the n-type GaAs substrate 102 is It reached 90 °.
- the angle formed between the ridge side surface (second ridge side wall surface 147) closer to the lower edge of the ridge and the surface of the n-type GaAs substrate 102 is because an n-type GaAs substrate 102 having an off angle of 10 ° is used.
- the p-type Ga In P intermediate layer 109 and the p-type are formed on the ridge formed in this example.
- the obtained ridge stripe semiconductor laser wafer was excellent in the perpendicularity of the ridge side surface to the substrate surface and the left-right symmetry of the ridge cross-sectional shape.
- the kink level reached the maximum value of 300 mW that can be measured with the measuring device used! /, It was confirmed that the kink level was over 300 mW at 25 ° C, V, and 300 mW. Stable formation of ridge stripe semiconductor lasers with high performance was achieved.
- SiN dielectric film is used as current blocking layer 148 instead of n-type Al In P
- n-type GaAs cap layer 149 was not necessary, and the other conditions were the same, and n-type Al In P was used as the current blocking layer 148.
- a ridge stripe semiconductor laser having the same performance as 0.5 0.5 can be stably formed.
- the ridge stripe semiconductor laser device it is possible to improve the element characteristics such as uniformizing the horizontal emission angle of the laser beam, improving the differential quantum efficiency, and improving the kink level. Furthermore, a ridge-type stripe can be formed with good uniformity within the wafer surface and between wafers, and the yield can be improved. Therefore, it can be effectively used for a ridge stripe type semiconductor laser device. These semiconductor laser devices can be applied to rewritable optical disks and the like.
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Cited By (5)
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JP2009049389A (ja) * | 2007-07-20 | 2009-03-05 | Japan Aerospace Exploration Agency | 太陽電池の製造方法 |
JP2011049364A (ja) * | 2009-08-27 | 2011-03-10 | Sanyo Electric Co Ltd | 半導体レーザ素子およびその製造方法 |
WO2014068814A1 (ja) * | 2012-10-31 | 2014-05-08 | パナソニック株式会社 | 半導体発光装置およびその製造方法 |
US20210184427A1 (en) * | 2018-05-30 | 2021-06-17 | Nippon Telegraph And Telephone Corporation | Semiconductor Laser |
JP7251672B1 (ja) | 2022-03-30 | 2023-04-04 | 信越半導体株式会社 | 発光素子の製造方法 |
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US8138002B2 (en) * | 2008-08-21 | 2012-03-20 | Sony Corporation | Semiconductor light-emitting element, fabrication method thereof, convex part formed on backing, and convex part formation method for backing |
JP5660940B2 (ja) * | 2010-04-27 | 2015-01-28 | 住友電工デバイス・イノベーション株式会社 | 光半導体装置の製造方法 |
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JP2001230494A (ja) * | 2000-02-17 | 2001-08-24 | Mitsubishi Electric Corp | 半導体レーザ素子及びその製造方法 |
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US5264389A (en) * | 1988-09-29 | 1993-11-23 | Sanyo Electric Co., Ltd. | Method of manufacturing a semiconductor laser device |
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JP2000294877A (ja) | 1999-04-08 | 2000-10-20 | Nec Corp | 高出力半導体レーザ及びその製造方法 |
JP2000340887A (ja) | 1999-05-26 | 2000-12-08 | Sony Corp | 半導体レーザおよびその製造方法 |
US20020187557A1 (en) * | 2001-06-07 | 2002-12-12 | Hobbs Steven E. | Systems and methods for introducing samples into microfluidic devices |
JP2003069154A (ja) | 2001-06-11 | 2003-03-07 | Sharp Corp | 半導体レーザ素子およびその製造方法 |
JP2003298168A (ja) | 2002-03-29 | 2003-10-17 | Matsushita Electric Ind Co Ltd | 半導体装置及びその製造方法 |
JP2004014569A (ja) * | 2002-06-03 | 2004-01-15 | Toshiba Corp | 半導体レーザ及びその製造方法 |
JP2004342719A (ja) * | 2003-05-14 | 2004-12-02 | Toshiba Corp | 半導体レーザ装置及びその製造方法 |
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- 2006-01-12 JP JP2006519653A patent/JP4755090B2/ja active Active
- 2006-01-12 US US11/571,112 patent/US7852892B2/en active Active
- 2006-01-12 WO PCT/JP2006/300297 patent/WO2006077766A1/ja not_active Application Discontinuation
- 2006-01-12 CN CNA2006800005795A patent/CN101006624A/zh active Pending
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JP2001230494A (ja) * | 2000-02-17 | 2001-08-24 | Mitsubishi Electric Corp | 半導体レーザ素子及びその製造方法 |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2009049389A (ja) * | 2007-07-20 | 2009-03-05 | Japan Aerospace Exploration Agency | 太陽電池の製造方法 |
JP2011049364A (ja) * | 2009-08-27 | 2011-03-10 | Sanyo Electric Co Ltd | 半導体レーザ素子およびその製造方法 |
WO2014068814A1 (ja) * | 2012-10-31 | 2014-05-08 | パナソニック株式会社 | 半導体発光装置およびその製造方法 |
US9276379B2 (en) | 2012-10-31 | 2016-03-01 | Panasonic Intellectual Property Management Co., Ltd. | Semiconductor light emitting device and method for manufacturing same |
JPWO2014068814A1 (ja) * | 2012-10-31 | 2016-09-08 | パナソニックIpマネジメント株式会社 | 半導体発光装置およびその製造方法 |
US20210184427A1 (en) * | 2018-05-30 | 2021-06-17 | Nippon Telegraph And Telephone Corporation | Semiconductor Laser |
US11557876B2 (en) * | 2018-05-30 | 2023-01-17 | Nippon Telegraph And Telephone Corporation | Semiconductor laser |
JP7251672B1 (ja) | 2022-03-30 | 2023-04-04 | 信越半導体株式会社 | 発光素子の製造方法 |
WO2023190082A1 (ja) * | 2022-03-30 | 2023-10-05 | 信越半導体株式会社 | 発光素子の製造方法 |
JP2023149016A (ja) * | 2022-03-30 | 2023-10-13 | 信越半導体株式会社 | 発光素子の製造方法 |
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JPWO2006077766A1 (ja) | 2008-06-19 |
JP4755090B2 (ja) | 2011-08-24 |
US20090147814A1 (en) | 2009-06-11 |
TW200723622A (en) | 2007-06-16 |
CN101006624A (zh) | 2007-07-25 |
US7852892B2 (en) | 2010-12-14 |
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