JP2008098362A - Semiconductor laser device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser whose contact resistance during element operation is small and the method of manufacturing the same. <P>SOLUTION: The method of manufacturing a semiconductor laser device includes a step (a) of laminating a first conductive type first clad layer 103, an active layer 104, a second conductive type second clad layer 105, a second conductive type contact layer 110, and a damage absorption layer 111 on a substrate 102 in this order, a step (b) of processing the second clad layer 105, the contact layer 110, and the damage absorption layer 111 and forming a stripe-shaped ridge, a step (c) of forming a current block layer 107 comprising a dielectric material in such a manner that the second clad layer 105 and the ridge are covered with the current block layer, a step (d) of forming a current injection region 116 by removing at least a portion of the current block layer 107 on the damage absorption layer 111, and a step (e) of removing the damage absorption layer 111 of the portion of the current injection region 116 on the contact layer 110 after the step (d). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device used as a light source in an optical disk device, an information processing device, and the like, and a manufacturing method thereof.

  With the progress of high-density recording of optical discs such as DVDs, not only reproduction but also recording DVD drives such as DVD-RAM or DVD-RW have been commercialized. And the recording double speed is steadily increasing.

  In order to cope with the high recording speed of such a recording DVD drive, development of a high-power semiconductor laser used as the light source is being actively carried out. Various proposals have been made as means for increasing the output power of semiconductor lasers. One of them is to efficiently release the heat generated during high-power operation by increasing the cavity length and increasing the chip area. Can be mentioned.

  However, when the chip area is increased, the number of chips per semiconductor laser wafer 1sl (one) is decreased, and the chip cost is increased.

Therefore, in place of the current blocking layer formed by epitaxial growth of a compound semiconductor layer such as AlInP in the past, a current blocking layer made of a dielectric film such as SiN or SiO ₂ is used, thereby reducing the number of times of crystal growth and reducing the cost. (See, for example, Patent Document 1).

  Here, the semiconductor laser device and its manufacturing method in the prior art shown in the first embodiment of Patent Document 1 will be described with reference to FIGS. FIG. 4D shows the structure of the semiconductor laser device described in the first embodiment of Patent Document 1, and FIGS. 4A to 4C show the manufacturing process. These are all cross-sectional views seen from the direction perpendicular to the longitudinal direction of the ridge-type stripe.

  First, as shown in FIG. 4A, an n-type cladding layer 12, a first guide layer 13, an active layer 14, a second guide layer 15, an electron barrier layer 16, and a first p-type cladding layer 17 are formed on a substrate 11. Then, the etching stop layer 18, the second p-type cladding layer 19 and the p-type contact layer 20 are laminated in this order from the bottom. For this purpose, epitaxial growth is sequentially performed using a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method).

  Thereafter, a photoresist is applied on the surface of the p-type contact layer 20, and a photoresist stripe pattern 21 is formed by photolithography.

  Next, as shown in FIG. 4B, using the stripe pattern 21 as a mask, the p-type contact layer 20 and the second p-type cladding layer 19 are sequentially etched to form a ridge.

Next, as shown in FIG. 4C, after removing the photoresist 21, a dielectric made of SiO ₂ or SiN is formed on the entire surface of the substrate by chemical vapor deposition (hereinafter referred to as CVD). A film 22 is formed.

  Next, using a photolithography technique, at least a part of the dielectric film 22 formed on the p-type contact layer 20 is removed by etching to form a current injection region. Subsequently, a p-side electrode 23 and an n-side electrode 24 are formed to complete the semiconductor laser wafer shown in FIG.

When the above manufacturing method is used, the number of crystal growths can be reduced by using a dielectric film such as SiO ₂ or SiN for the current blocking layer instead of the current blocking layer made of the semiconductor layer formed by epitaxial growth. Cost reduction can be realized.
JP 2006-49420 A

As described above, when a dielectric such as SiO ₂ or SiN is used as the current blocking layer, at least a part of the dielectric film formed on the p-type contact layer is removed by etching in the step of forming the current injection region. Then, the current injection region is opened. Next, a p-side electrode is formed on the p-type contact layer exposed through the opening.

  At this time, in order to reduce the contact resistance and operating voltage of the semiconductor laser as much as possible, it is indispensable to clean the interface between the p-type contact layer and the p-side electrode.

  In the manufacturing method described in the first embodiment of Patent Document 1 shown in FIGS. 4A to 4D, the dielectric film formed on the p-type contact layer when forming the current injection region As a method for etching and removing at least a part of the above, there are a dry etching technique and a wet etching technique.

  When the dry etching technique is used, the dielectric film can be etched with high dimensional accuracy. However, since dry etching is a physical phenomenon, sputter is the main cause of etching, crystal defects due to physical damage due to plasma during dry etching occur on the surface of the p-type contact layer in the current injection region. Such crystal defects cause device deterioration such as an increase in contact resistance and an increase in operating voltage.

  On the other hand, when the wet etching technique is used, crystal defects due to physical damage do not occur. However, since the p-type contact layer is the outermost surface of the wafer, it is exposed to the atmosphere for a long time, and a natural oxide film and a modified layer are formed on the surface of the p-type contact layer. For this reason, element degradation such as an increase in contact resistance and an increase in operating voltage is inevitable.

  Here, in order to remove crystal defects, natural oxide films, modified layers, and the like generated on the surface of the p-type contact layer, after etching the dielectric film, a wet etching technique is used to continuously remove the surface of the p-type contact layer. A method of removing it is conceivable.

  However, since etching is mainly performed by time control, it is difficult to control the etching amount in the direction perpendicular to the wafer uniformly and precisely within the wafer surface and between the wafers. As a result, the etching amount becomes excessive and the p-type contact layer 20 may disappear, which causes a decrease in yield. Therefore, the solution of this is a problem.

  In view of the above problems, an object of the present invention is to increase contact resistance and operate by suppressing crystal defects, natural oxide film, and residual layer on the surface of the p-type contact layer on the ridge in contact with the p-side electrode. It is an object to provide a semiconductor laser device in which deterioration of element characteristics such as voltage increase is suppressed and a method for manufacturing the same.

  To achieve the above object, a ridge stripe semiconductor laser device of the present invention includes a first conductivity type first cladding layer formed on a substrate, an active layer formed on the first cladding layer, A second conductivity type second cladding layer formed on the active layer and having a stripe-shaped ridge; a second conductivity type contact layer formed on the ridge; and a predetermined region on the contact layer. A damage absorbing layer; and a current blocking layer formed on the second cladding layer and having an opening on the contact layer.

  According to the semiconductor laser device of the present invention, since the damage absorbing layer is provided on the contact layer, the occurrence of damage such as crystal defects, natural oxide film and modified layer in the contact layer is prevented. In other words, in the manufacturing process, the contact layer is covered with the damage absorbing layer so that the damage as described above occurs in the damage absorbing layer. Thereafter, when at least a part of the damage absorbing layer is removed, a non-damaged contact layer can be obtained.

  The predetermined region where the damage absorbing layer is formed is preferably a region at both ends in the width direction of the ridge.

  The current blocking layer preferably covers at least a part of the top surface of the damage absorbing layer.

The current blocking layer is preferably made of a dielectric material. Furthermore, it is preferable that the dielectric material includes at least one of SiN, SiO ₂ and Al ₂ O ₃ .

  The current blocking layer is formed by a plasma CVD method or an atmospheric pressure CVD method using a dielectric material such as SiN, for example. At this time, compared with the case where the surface orientation is parallel to the main surface of the substrate, the adhesion of the dielectric film is better when the surface orientation is formed perpendicular to the main surface of the substrate. Get higher. Therefore, a current blocking layer is formed so as to leave at least part of the upper surface of the damage absorbing layer while leaving the damage absorbing layer on both ends of the contact layer. As a result, a part of the current blocking layer is formed on the top surface of the damage absorbing layer whose plane orientation is a plane perpendicular to the main surface of the substrate. The adhesion of the block layer can be improved.

  The current blocking layer may be peeled off from the semiconductor laser device due to stress applied to the ridge during cleavage or assembly. However, in the semiconductor laser device of the present invention, this problem is suppressed by improving the adhesion as described above.

  In order to secure a region for injecting current on the ridge and to ensure the effect of improving the adhesion of the current blocking layer, a damage absorbing layer is left in the region at both ends in the width direction of the ridge, It is preferable to provide a current blocking layer. Here, the width direction of the ridge is a direction perpendicular to the direction of the resonator of the semiconductor laser device and parallel to the main surface of the substrate.

The contact layer is preferably made of a compound semiconductor having a composition of Al _x Ga _1-x As (0 ≦ x ≦ 1).

  The damage absorbing layer preferably includes at least one layer made of a semiconductor material, an organic material, or a dielectric material.

The damage absorbing layer includes at least one compound semiconductor layer, and the compound semiconductor layer includes Al _x Ga _1-x As (0 ≦ x ≦ 1) or (Al _x Ga _1-x ) _y In _1-y. It is preferably made of a compound semiconductor having a composition of P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1).

  The contact layer and the damage absorbing layer are formed as layers made of such materials, for example. However, at this time, the contact layer and the damage absorbing layer are selected so as to have a high selectivity with respect to etching. For example, if AlGaAs is selected as the material for the contact layer and AlGaInP is selected as the material for the damage absorbing layer, a high selectivity to etching can be obtained because the material system is different. For this reason, it is possible to selectively remove the damage absorbing layer. Further, even when both the contact layer and the damage absorption layer are made of AlGaAs, high selectivity can be obtained by increasing the Al composition of the damage absorption layer, and selective etching is possible. This is because the etch rate generally increases as the Al composition increases.

The damage absorbing layer has a multilayer structure including two or more compound semiconductor layers, and the uppermost layer of the multilayer structure has a composition of Al _x Ga _1-x As (0 ≦ x ≦ 1). Preferably it consists of.

In this way, by forming the compound semiconductor layer having a thermodynamically stable composition of Al _x Ga _1-x As (0 ≦ x ≦ 1), evaporation of P in the manufacturing process is suppressed.

  The compound semiconductor layer is preferably formed directly on the contact layer.

  That is, it is preferable that the compound semiconductor layer is formed on the contact layer without interposing another layer. By doing so, the compound semiconductor layer grows continuously with respect to the contact layer, so that the interface between the contact layer and the compound semiconductor layer is kept clean.

  The plane orientation of the substrate surface is preferably a plane orientation inclined from the (100) plane. In this way, formation of natural superlattices can be prevented. The natural superlattice causes problems such as difficulty in controlling the oscillation wavelength, and thus it is desired to prevent the generation of the natural superlattice.

  Furthermore, the plane orientation inclined from the (100) plane is preferably the [011] direction. Thereby, formation of a natural superlattice can be prevented more reliably.

  Next, in order to achieve the above object, a method of manufacturing a semiconductor laser device according to the present invention includes a first conductivity type first cladding layer, an active layer, and a second conductivity type second cladding layer on a substrate. A step (a) of laminating a second conductivity type contact layer and a damage absorbing layer in this order, and a step of processing the second cladding layer, the contact layer and the damage absorbing layer to form a striped ridge ( b), a step (c) of forming a current blocking layer made of a dielectric material so as to cover the second cladding layer and the ridge after the step (b), and at least one of the current blocking layers on the damage absorbing layer. A step (d) of forming a current injection region by removing the portion, and a step (e) of removing the damage absorption layer in the portion of the current injection region on the contact layer.

  In the step (e), it is preferable to selectively remove the damage absorbing layer by a wet etching technique.

  In the step (e), it is preferable to remove the damage absorbing layer using the current blocking layer as a mask.

  According to the method for manufacturing a semiconductor laser device of the present invention, a damage absorbing layer is provided on the contact layer, and after the ridge is formed, the current blocking layer is formed, and the current injection region is formed, the damage absorbing layer is removed.

  Conventionally, physical damage may occur on the upper surface of the contact layer on the ridge due to plasma during dry etching performed for ridge formation or the like, and a natural oxide film and a modified layer may be generated by exposure to the atmosphere. there were. However, in the semiconductor laser device of the present invention, since the damage absorbing layer is formed on the contact layer, physical damage, natural oxide film and the like are generated on the damage absorbing layer. Since the damage absorbing layer is removed, physical damage and a natural oxide film do not occur on the upper surface of the contact layer, and the interface with an electrode to be formed on the contact layer later can be cleaned.

  For this reason, it is possible to suppress deterioration of element characteristics such as an increase in contact resistance and an increase in operating voltage between the contact layer and the electrode.

  If only the damage absorbing layer is selectively removed, the etching amount for that purpose can be controlled uniformly and precisely within the wafer surface and between the wafers. Therefore, the contact layer can be prevented from disappearing due to excessive etching.

  Further, by removing the damage absorbing layer using the current blocking layer as a mask, the portion of the damage absorbing layer corresponding to the current injection region can be surely removed.

  According to the semiconductor laser device and the method of manufacturing the same of the present invention, the use of the damage absorbing layer formed on the contact layer improves the element characteristics such as reduction of contact resistance and operating voltage, as well as in the wafer surface and the wafer. Thus, the current injection region can be formed with good uniformity, and the manufacturing yield is improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, a ridge stripe type red semiconductor laser device made of an AlGaInP-based material will be described as an example. However, the present invention is not limited to this and can be applied to various other ridge stripe type semiconductor laser devices. is there.

(First embodiment)
Hereinafter, a semiconductor laser device and a manufacturing method thereof according to the first embodiment of the present invention will be described. FIGS. 1A to 1G are schematic cross-sectional views showing the manufacturing process of the ridge stripe semiconductor laser device of this embodiment.

First, as shown in FIG. 1A, an n-type cladding layer made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is formed on an n-type substrate 102 (thickness of about 400 to 500 μm) made of GaAs by MOCVD. 103 (thickness of about 1 to 3 μm), active layer 104 made of a GaInP-based material (thickness of about 5 to 6 nm), p-type cladding layer 105 made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (thickness of 1 to 2 μm) P-type intermediate layer 109 (thickness of about 40 to 60 nm) made of Ga _0.5 In _0.5 P, and p-type contact layer 110 (thickness of about 0.1 to 0.3 μm) made of GaAs from below (n-type). The layers are formed in this order (from the substrate 102 side).

Further, a p-type damage absorbing layer 111 (thickness of about 10 to 100 nm) made of Ga _0.5 In _0.5 P is formed on the p-type contact layer 110, and further, an SiO ₂ film 113 (thickness 0.2) is formed thereon. About 0.6 μm).

Here, as the n-type substrate made of GaAs, a semiconductor substrate having a so-called off-angle is generally used. For example, in the case of a visible light semiconductor laser having an oscillation wavelength band of 650 nm, in order to suppress the formation of a natural superlattice (ordered structure) in the Ga _0.3 In _0.3 P layer, the (100) plane inclined about 10 ° in the [011] direction is the surface A substrate is used.

  The inclination angle is set so that a natural superlattice is not formed when the first cladding layer is epitaxially grown on the substrate, that is, when the crystal growth is performed so that the crystal axis is aligned with the substrate. Usually, it is preferably 5 ° or more and 20 ° or less.

  As a specific example, consider a case where an AlGaInP-based semiconductor layer (AlP, GaP, InP mixed crystal semiconductor) is epitaxially grown on a GaAs (100) substrate. In this case, a natural superlattice, that is, a structure in which GaP (AlP) and InP are periodically stacked is formed. When the natural superlattice is formed, the energy gap is reduced as compared with the normal state (the state without the natural superlattice), and the wavelength of the oscillating laser light becomes longer. For example, the wavelength of the oscillating red laser light is usually 650 nm, but becomes 685 nm.

  In the case of a mixed crystal semiconductor, the energy gap can be controlled by changing the composition ratio of components constituting the semiconductor. However, when the natural superlattice is formed, the energy gap change due to the crystal structure becomes dominant, and the energy gap cannot be controlled by changing the composition ratio. This means that the oscillation wavelength cannot be controlled.

  Therefore, in order to prevent formation of a natural superlattice, it is desirable that the plane orientation of the substrate surface is inclined from the (100) plane. Furthermore, formation of a natural superlattice can be reliably prevented when the direction is [011].

  However, in the present invention, the substrate off angle can be used without any particular limitation, and the n-type substrate 102 of this embodiment does not have an off angle.

  The active layer 104 may be an active layer having a multiple quantum well structure in which GaInP is a well layer and AlGaInP is a barrier layer.

Next, as shown in FIG. 1B, the SiO ₂ film 114 is processed by a photolithography technique and a dry etching technique to form a SiO ₂ stripe 114.

Next, as shown in FIG. 1C, the p-type cladding layer 105, the p-type intermediate layer 109, the p-type contact layer 110, and the p-type damage absorption layer 111 are dry-etched using the SiO ₂ stripe 114 as a mask. Do.

  As a result, the portion not masked by the stripe mask 114 is etched partway through the p-type cladding layer 105, and the ridge 105a is formed as the remaining p-type cladding layer 105 without being etched. Similar to the ridge 105a, the p-type intermediate layer 109, the p-type contact layer 110, and the p-type damage absorption layer 111 remain unetched on the ridge 105a in accordance with the shape of the stripe mask 114. Structure 120 is constructed.

  As a method of controlling the dry etching amount in this way, for example, there is a method of stopping etching by time control, that is, a method of performing etching for a predetermined time. Another example is a method in which monochromatic light is applied to the n-type substrate 102 and etching is performed while calculating the etching residual thickness from the relationship between interference intensity obtained from the reflected light and time. In this case, the etching may be stopped when the remaining etching thickness reaches a desired value.

  Also, anisotropic plasma etching is suitable as the dry etching technique in the present embodiment. Examples include methods using inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) plasma.

An etching gas is typically a mixed gas of SiCl ₄ and Ar. However, chlorine gas or boron trichloride gas may be used instead of SiCl ₄ .

The dry etching technique used in the first embodiment is an ICP method, and a mixed gas of SiCl ₄ and Ar is used as an etching gas.

Next, after removing the SiO ₂ stripe 114 using a fluorine chemical solution, as shown in FIG. 1D, an SiN film 107 having a thickness of 80 nm to 300 nm is grown by using, for example, a plasma CVD method. This SiN film 107 is a film that functions as a current blocking layer.

Here, instead of the SiN film 107, a film made of another material may be provided as the current blocking layer. Any material having an insulating property and a refractive index smaller than that of the p-type cladding layer 105 made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P can be used. Specific examples include SiO ₂ , Al ₂ O _3. A dielectric film such as Further, regarding the film thickness of the SiN film 107, 80 nm to 300 nm is a preferable value, but is not limited thereto.

  Examples of means for forming the above film include a CVD method (for example, plasma CVD, atmospheric pressure CVD, low pressure CVD and MOCVD) and a PVD method (sputtering and vapor deposition). Among these, in the case of the present embodiment, a plasma CVD method that can achieve high film thickness uniformity and is easy to form is particularly preferable. Here, the CVD method is an abbreviation for a chemical vapor deposition method, and the PVD method is an abbreviation for a physical vapor deposition method.

  Next, as shown in FIG. 1E, the SiN film 107 on at least a part of the ridge structure 120 is removed by wet etching using a photolithography technique. Thereby, the current injection region 116 is formed. In the present embodiment, the entire surface on the ridge structure 120 is the current injection region 116.

  Note that dry etching can be performed instead of wet etching.

Next, as shown in FIG. 1 (f), for example, a hydrochloric acid chemical solution that is a mixed solution of hydrochloric acid and water (with a volume content of hydrochloric acid in the chemical solution of, for example, 15 to 40%) is used. Etching using as a mask. Thereby, the p-type damage absorbing layer 111 made of Ga _0.5 In _0.5 P is removed by etching until reaching the p-type contact layer 110. At this time, since the p-type contact layer 110 made of GaAs is resistant to a hydrochloric acid chemical solution, the etching in the direction perpendicular to the surface of the n-type substrate 102 stops when this layer is exposed.

  In this embodiment, a hydrochloric acid-based chemical solution is used for wet etching of the p-type damage absorbing layer 111. However, the present invention is not limited to this, and any chemical solution having high etching selectivity can be used. That is, here, a chemical solution that has a high etching rate for the p-type damage absorbing layer 111 and a low etching rate for the p-type contact layer 110 and the SiN film 107 may be used. For example, a sulfuric acid chemical solution can be used. Moreover, also about hydrochloric acid type chemical | medical solution, the volume fraction of hydrochloric acid in a chemical | medical solution is not restricted to 15-40%, Other values may be sufficient.

  Further, the p-type damage absorbing layer 111 may be removed by dry etching instead of wet etching. At this time, a method with small plasma damage is desirable. For example, chemical dry etching is preferably used.

  Next, the p-side electrode 112 is formed so as to cover the p-type contact layer 110 and the SiN film 107 by vapor deposition. Further, the n-side electrode 101 is formed on the back surface of the n-type substrate 102 (the surface on the opposite side to where the n-type cladding layer is formed). As a result, a ridge stripe semiconductor laser wafer in which the structure shown in FIG. 1G is formed on the wafer is obtained. Thereafter, the laser device is completed through processes such as cleavage and light emitting end face coating.

  As described above, according to the present embodiment, the p-type damage absorbing layer 111 has the ridge structure 120 until the step of removing the SiN film 107 and forming the current injection region 116 (step of FIG. 1E). The uppermost layer in FIG. Since the manufacturing process proceeds in such a state, dry etching damage, a natural oxide film, a modified layer, and the like are likely to occur on the surface of the p-type damage absorbing layer 111, for example.

  However, the p-type damage absorbing layer 111 is removed by wet etching in the step of FIG. For this reason, the dry etching damage, natural oxide film, denatured layer, and the like generated here are removed, and the remaining in the semiconductor laser device is suppressed.

  Therefore, when the p-side electrode 112 is formed in the subsequent step of FIG. 1G, the interface between the p-side electrode 112 and the p-type contact layer 110 is kept clean. As a result, it is possible to suppress deterioration of device characteristics due to dry etching damage, remaining of a natural oxide film, a modified layer, and the like, specifically, an increase in contact resistance and an increase in operating voltage.

  In this embodiment, the p-type damage absorption layer 111 made of a GaInP-based material is used. Therefore, the wet etching rate is significantly different from that of the p-type contact layer 110 made of a GaAs-based material, and the p-type damage absorbing layer 111 can be selectively removed. Further, the etching amount at this time can be controlled uniformly and accurately within the wafer surface and between the wafers.

  However, for the p-type damage absorbing layer 111, a material having a composition such as GaP, InP, GaInP, AlInP, AlGaInP, or AlGaAs may be used instead of the GaInP-based material. Any material that can be selectively removed from the p-type contact layer 110 made of GaAs may be used.

In this embodiment, the thickness of the p-type damage absorbing layer 111 is 10 nm to 100 nm. However, this is also an example, and other values can be selected. In this embodiment, dry etching is used. Although the ridge structure 120 is formed, the present invention is not limited to this, and a method using both dry etching and wet etching can also be used.

  Furthermore, although this embodiment has been described as an example of a red semiconductor laser device made of an AlGaInP-based material, the present invention is not limited to this. For example, the present invention can be applied to various ridge stripe semiconductor laser devices using a mixed crystal compound semiconductor such as a blue semiconductor laser device made of an AlGaInN-based material using a compound semiconductor layer having a GaN composition as the p-type contact layer 110. .

(Example 1)
Next, the semiconductor laser device of the invention described in the first embodiment and the manufacturing method thereof will be described more specifically as Example 1 with reference to FIGS. However, as a matter of course, the present invention is not limited to this example.

First, as shown in FIG. 1A, an n-type cladding layer 103 (thickness) made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is formed on an n-type substrate 102 (thickness: 460 μm) made of GaAs by MOCVD. 2.5 μm), active layer 104 (thickness 5 nm) made of GaInP-based material, p-type cladding layer 105 (thickness 1.5 μm) made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, Ga _0.5 In _0.5 P A p-type intermediate layer 109 (thickness 40 nm) made of GaAs, a p-type contact layer 110 (thickness 0.23 μm) made of GaAs and a p-type damage absorbing layer 111 (thickness 50 nm) made of Ga _0.5 In _0.5 P The layers were stacked in this order (from the n-type substrate 102 side). Further thereon, a SiO ₂ film 113 (thickness 0.5 μm) was formed by plasma CVD.

  The n-type substrate 102 used here is not an off-angle substrate (tilted substrate).

Next, as shown in FIG. 1B, the SiO ₂ film 113 was processed by a photolithography technique and a dry etching technique to form a SiO ₂ stripe 114 having a width of 2 μm.

Next, as shown in FIG. 1C, dry etching using the SiO ₂ stripe 114 as a mask for the p-type cladding layer 105, the p-type intermediate layer 109, the p-type contact layer 110, and the p-type damage absorbing layer 111. To do. Thereby, the ridge 105a was formed, and the ridge structure 120 was obtained.

Here, the portions other than the ridge structure 120 were etched so as to leave the p-type cladding layer 105 with a thickness of 230 nm on the upper surface of the active layer 104. The etching is stopped by time control for this purpose. As a dry etching method, an ICP method using a mixed gas of SiCl ₄ and Ar as an etching gas was used.

Next, as shown in FIG. 1D, after removing the SiO ₂ stripe 114 using a fluorine-based chemical solution, a 100 nm thick SiN film 107 was grown by plasma CVD.

  Next, as shown in FIG. 1E, the SiN film 107 on at least a part of the ridge structure 120 was removed by wet etching using a photolithography technique. Thereby, a current injection region 116 was formed. Further, the p-type cladding layer 105 covering the p-type cladding layer 105 and the side surface of the ridge structure 120 functions as a current blocking layer.

  Next, as shown in FIG. 1F, the p-type damage absorbing layer 111 was etched using a mixed solution of hydrochloric acid and water until the p-type contact layer 110 was exposed. At this time, the volume content of hydrochloric acid in the mixed solution was 15%. In this step, the p-type contact layer 110 was not etched.

  Next, a p-side electrode 112 is formed by vapor deposition so as to cover the upper surface of the p-type contact layer 110, the side surface of the ridge structure 120, and the upper surface of the p-type cladding layer 105, and the n-side electrode is formed on the back surface of the n-type substrate 102. 101 was formed. Thus, the ridge stripe type semiconductor laser wafer shown in FIG.

  In this example, the p-type damage absorbing layer 111 formed on the p-type contact layer 110 was removed by wet etching, and then the p-side electrode 112 was formed. Therefore, it is possible to stably form a ridge stripe semiconductor laser device having a low contact resistance and a low operating voltage without leaving a natural oxide film or a modified layer at the interface between the p-type contact layer 110 and the p-side electrode 112. I was able to.

  In this embodiment, since the p-type damage absorbing layer 111 made of a GaInP-based material is used, the selection ratio with respect to wet etching using a hydrochloric acid-based chemical is sufficiently higher than that of the p-type contact layer 110 made of a GaAs-based material. large. For this reason, the p-type damage absorption layer 111 could be selectively removed while suppressing variations in the wafer surface and between wafers.

(Second Embodiment)
Next, a semiconductor laser device and a manufacturing method thereof according to the second embodiment of the present invention will be described with reference to the drawings. However, portions common to the first embodiment will be described briefly, and differences will be described in detail.

  Specifically, in the present embodiment, the p-type damage absorbing layer 111 is left near both ends of the p-type contact layer 110 in the width direction, and a current block is formed on at least a part of the p-type damage absorbing layer 111. By forming the layer, the adhesion of the current blocking layer is improved.

  2A to 2G are views for explaining a manufacturing process of the semiconductor laser device of the invention of this embodiment. In these drawings, the same reference numerals are used for components equivalent to those shown in FIGS.

  First, in this embodiment, the steps shown in FIGS. 2A to 2D corresponding to the steps shown in FIGS. 1A to 1D in the first embodiment are sequentially performed. Thereby, the n-type cladding layer 103, the active layer 104, the p-type cladding layer 105, the p-type intermediate layer 109, the p-type contact layer 110, and the p-type damage absorption layer 111 are formed on the n-type substrate 102 from the bottom (n-type A ridge structure 120 that is stacked in this order (from the substrate 102 side) and includes the ridge 105a is formed, and further, the ridge structure 120 and side surfaces, and the upper surface of the p-type cladding layer 105 other than the ridge 105a are formed. A structure in which the covering SiN film 107 is formed is obtained. The thickness, material, formation method, and the like of each layer may be the same as those in the first embodiment, for example.

  Next, as shown in FIG. 2E, the SiN film 107 on at least a part of the upper surface of the ridge structure 120 is removed by wet etching using a photolithography technique. At this time, part of the SiN film 107 is left on the ridge structure 120 at both ends in the width direction of the ridge structure 120 (direction perpendicular to the length direction of the ridge and parallel to the main surface of the n-type substrate 102). .

  Thereby, a current injection region 116a is formed as a portion where the SiN film 107 on the ridge structure 120 is removed.

The dry etching used at this time may be anisotropic etching such as reactive ion etching (hereinafter referred to as RIE), ICP, or ECR. As the etching gas, a CF-based gas such as a mixed gas of CF ₄ and CHF ₃ can be used.

In this embodiment, as a specific etching method, an RIE method using a mixed gas of CF ₄ , CHF _3, and O ₂ as an etching gas is used. The volume contents of CF ₄ and CHF _{3 in} the mixed gas are 1 to 10% and 30 to 50%, respectively. Further, the pressure is 40 to 60 Pa, and the stage temperature is 10 to 20 ° C. However, these are examples and are not limited, and may be set as appropriate. Further, wet etching can be performed instead of dry etching.

Next, as shown in FIG. 2F, etching is performed using a hydrochloric acid chemical solution (having a volume content of hydrochloric acid in the chemical solution of, for example, 15 to 35%) and the SiN film 107 as a mask. Thereby, the p-type damage absorbing layer 111 made of Ga _0.5 In _0.5 Pp is removed by etching until reaching the p-type contact layer 110. However, under the SiN film 107 remaining at both ends in the width direction on the ridge structure 120, the p-type damage absorption layer 111 remains without being etched, and has an opening in an inner region on the ridge structure 120. .

  Further, since the p-type contact layer 110 made of GaAs is resistant to a hydrochloric acid chemical solution, when this layer is exposed, etching in a direction perpendicular to the surface of the n-type substrate 102 is stopped.

  Immediately after the vertical etching is stopped in this way, the side surface 111x (formed by wet etching) near the center in the width direction of the ridge structure 120 in the p-type damage absorbing layer 111 remaining at both ends on the ridge structure 120. The side surface is an inclined curved surface. As a result, the opening formed in the p-type damage absorbing layer 111 has a shape that widens upward (on the side opposite to the n-type substrate 102).

  On the other hand, it is preferable to continue the wet etching until the side surface 111x becomes substantially planar, that is, until the (111) plane is exposed as a whole. In the portion of the side surface 111x of the p-type damage absorbing layer 111 where the (111) plane is exposed, the wet etching rate decreases. For this reason, the unexposed portion of the (111) plane is preferentially etched, and the side surface 111x can be made substantially flat.

  As a result, the area of the p-type contact layer 110 exposed by removing the p-type damage absorbing layer 111 can be controlled, and the area can be uniformly and accurately controlled within the wafer surface and between the wafers. it can. The wet etching amount in the direction perpendicular to the substrate surface may be selected as appropriate.

  Here, the volume content of hydrochloric acid in the hydrochloric acid-based chemical solution is set to 15 to 35%. However, the present invention is not limited to this, and other values may be set as appropriate. Furthermore, as in the first embodiment, other etching solutions such as a sulfuric acid chemical solution can be used.

  Furthermore, as in the first embodiment, dry etching such as chemical dry etching may be performed instead of wet etching.

  Next, as shown in FIG. 2G, a p-side electrode 112 is formed so as to cover the p-type contact layer 110 and the SiN film 107 by vapor deposition. Further, the n-side electrode 101 is formed on the back surface of the n-type substrate 102. Thereby, the ridge stripe type semiconductor laser device is completed.

  By the manufacturing process as described above, the same effect as in the first embodiment is realized. That is, by forming and removing the p-type damage absorbing layer 111, the interface between the p-type contact layer 110 and the p-side electrode 112 can be cleaned. As a result, it is possible to suppress deterioration of element characteristics such as an increase in contact resistance and an increase in operating voltage. In addition, since the p-type damage absorbing layer 111 made of GaInP-based material and the p-type contact layer 110 made of GaAs-based material can be wet-etched with a high selection ratio, the p-type damage absorbing layer 111 is selectively removed. In addition, it is possible to accurately and uniformly control within the wafer surface and between wafers.

  In the present embodiment, the p-type damage absorbing layer 111 is partially left on both ends of the p-type contact layer 110, and the SiN film 107, which is a current blocking layer, is formed so as to cover the p-type damage absorbing layer 111. For this reason, on the ridge structure 120, the SiN film 107 formed on a surface whose plane orientation is perpendicular to the main surface of the n-type substrate 102 exists, and this improves the adhesion of the SiN film 107. To contribute.

  Note that the material and thickness of the p-type damage absorbing layer 111 are not limited to those described above, and can be set as appropriate as in the first embodiment. Further, the semiconductor laser device of the red invention has been described as an example, but the present invention is not limited to this, as in the first embodiment.

(Example 2)
Next, the semiconductor laser device of the invention described in the second embodiment and the manufacturing method thereof will be described more specifically as Example 2 with reference to FIGS. However, it is natural that the present invention is not limited to this example.

First, as shown in FIG. 2A, an n-type cladding layer 103 (thickness) made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is formed on an n-type substrate 102 (thickness 450 μm) made of GaAs by MOCVD. 2 μm), active layer 104 (thickness 5 nm) made of GaInP-based material, p-type cladding layer 105 (thickness 1.4 μm) made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, and Ga _0.5 In _0.5 P A p-type intermediate layer 109 (thickness 50 nm), a p-type contact layer 110 (thickness 0.2 μm) made of GaAs and a p-type damage absorption layer 111 (thickness 50 nm) made of Ga _0.5 In _0.5 P are formed from the bottom (n The layers were formed in this order (from the mold substrate 102 side). Further thereon, a SiO ₂ film 113 (thickness 0.5 μm) was formed by plasma CVD.

  Note that the n-type substrate 102 used here is not a substrate having an off angle.

Next, as shown in FIG. 1B, the SiO ₂ film 113 was processed by a photolithography technique and a dry etching technique to form a SiO ₂ stripe 114 having a width of 2 μm.

Next, as shown in FIG. 1C, dry etching using the SiO ₂ stripe 114 as a mask for the p-type cladding layer 105, the p-type intermediate layer 109, the p-type contact layer 110, and the p-type damage absorbing layer 111. The ridge structure 120 including the ridge 105a was formed.

Here, the portions other than the ridge structure 120 were etched so as to leave the p-type cladding layer 105 with a thickness of 250 nm on the upper surface of the active layer 104. The etching is stopped by time control for this purpose. As a dry etching method, an ICP method using a mixed gas of SiCl ₄ and Ar as an etching gas was used.

Next, as shown in FIG. 2D, after removing the SiO ₂ stripe 114 using a fluorine chemical solution, a 200 nm thick SiN film 107 was grown by plasma CVD.

  Next, as shown in FIG. 2E, the SiN film 107 on at least a part of the ridge structure 120 was removed by wet etching using a photolithography technique. As a result, the SiN film 107 was left at both ends in the width direction on the ridge structure 120, and the current injection region 116a was formed in the portion where the SiN film 107 was removed. Further, the p-type cladding layer 105 that covers both end portions in the width direction on the ridge structure 120, the p-type cladding layer 105, and the side surface of the ridge structure 120 functions as a current blocking layer.

Here, RIE was used as a dry etching method, and a mixed gas of CF ₄ , CHF _3, and O ₂ was used as an etching gas. Further, as dry etching conditions, the volume contents of CF ₄ and CHF _{3 in} the mixed gas are 5% and 40% in order, the pressure is 50 Pa, and the stage temperature is 17 ° C.

  Next, as shown in FIG. 2F, as shown, a p-type damage absorbing layer 111 is formed using a mixed solution of hydrochloric acid and water and using the SiN film 107 as a mask until the p-type contact layer 110 is exposed. Etched. At this time, the volume content of hydrochloric acid in the mixed solution was 20%. In this step, the p-type contact layer 110 was not etched.

  Next, a p-side electrode 112 is formed by vapor deposition so as to cover the upper surface of the p-type contact layer 110, the side surface of the ridge structure 120, and the upper surface of the p-type cladding layer 105, and the n-side electrode 101 is formed on the back surface of the n-type substrate 102. Formed. Thus, a ridge stripe type semiconductor laser wafer shown in FIG.

  In this example, the p-type damage absorbing layer 111 formed on the p-type contact layer 110 was removed by wet etching, and then the p-side electrode 112 was formed. Therefore, it is possible to stably form a ridge stripe semiconductor laser device having a low contact resistance and a low operating voltage without leaving a natural oxide film or a modified layer at the interface between the p-type contact layer 110 and the p-side electrode 112. I was able to.

  In this embodiment, since the p-type damage absorbing layer 111 made of a GaInP-based material is used, the selection ratio with respect to wet etching using a hydrochloric acid-based chemical is sufficiently higher than that of the p-type contact layer 110 made of a GaAs-based material. large. For this reason, the p-type damage absorption layer 111 could be selectively removed while suppressing variations in the wafer surface and between wafers.

  Furthermore, in this embodiment, the p-type damage absorbing layer 111 is left on the p-type contact layer 110 (both end portions in the width direction on the ridge structure 120), and a part of the SiN film 107 is covered therewith. It has become. Therefore, the adhesion of the SiN film 107 is improved and the semiconductor laser device can be manufactured stably.

(Third embodiment)
Next, a semiconductor laser device and a manufacturing method thereof according to the third embodiment of the present invention will be described with reference to the drawings. However, here too, the parts common to the first or second embodiment will be described briefly, and the differences will be described in detail.

  Specifically, in the present embodiment, a damage absorption layer having a two-layer structure is used. Further, as in the second embodiment, a damage absorbing layer is left at both end portions in the width direction on the ridge, and a portion where the damage absorbing layer is covered with a SiN film is present. This will be described in detail below.

  3A to 3H are views for explaining the manufacturing process of the semiconductor laser device of the invention of this embodiment. In these drawings, the same reference numerals are used for components equivalent to those shown in FIGS.

First, in the step shown in FIG. 3A, an n-type cladding made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is formed on an n-type substrate 102 (thickness of about 400 to 500 μm) made of GaAs by MOCVD. A layer 103 (thickness of about 1 to 3 μm), an active layer 104 (thickness of about 5 to 6 nm) made of a GaInP-based material, and a p-type cladding layer 105 (thickness of 1 to 5) of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P P-type intermediate layer 109 (thickness of about 40 to 60 nm) made of Ga _0.5 In _0.5 P, p-type contact layer 110 (thickness of about 0.1 to 0.3 μm) made of GaAs from below (n The layers are formed in this order (from the mold substrate 102 side). These steps are the same as the steps shown in FIG. 1A in the first embodiment.

Next, a p-type first damage absorbing layer 111a (thickness of about 10 to 100 nm) made of Ga _0.5 In _0.5 P is formed on the p-type contact layer 110, and a p-type second made of GaAs is further formed thereon. A damage absorbing layer 111b is formed. As described above, the damage absorbing layer in the present embodiment has a two-layer structure including the first and second damage absorbing layers.

  Subsequently, an SiO 2 film 113 (thickness of about 0.2 to 0.6 μm) is formed on the p-type second damage absorption layer 111b.

  As described in the first embodiment, it is common to use a semiconductor substrate having a so-called off angle as an n-type substrate for forming a semiconductor laser device. However, also in this embodiment, the substrate off angle can be used without any particular limitation, and the n-type substrate 102 having no off angle is used.

  The active layer 104 can also be an active layer having a multiple quantum well structure in which GaInP is a well layer and AlGaInP is a barrier layer, as in the first embodiment.

Next, as shown in FIG. 3B, the SiO ₂ film 114 is processed by the photolithography technique and the dry etching technique to form the SiO ₂ stripe 114.

Next, as shown in FIG. 3C, with respect to the p-type cladding layer 105, the p-type intermediate layer 109, the p-type contact layer 110, the p-type first damage absorption layer 111a, and the p-type second damage absorption layer 111b. Dry etching is performed using the SiO ₂ stripe 114 as a mask. Thus, the portion of the p-type cladding layer 105 masked by the SiO ₂ stripe 114 becomes the ridge 105a, and the remaining portions of the p-type cladding layer 105, the p-type intermediate layer 109, the p-type contact layer 110, The ridge structure 120 is configured together with the p-type first damage absorption layer 111a and the p-type second damage absorption layer 111b. In other parts of the ridge structure 120, the p-type cladding layer 105 is etched halfway.

  Here, as a method for controlling the dry etching amount, a method based on time control and a method of performing etching while calculating the remaining etching thickness by applying monochromatic light to the n-type substrate 102 can be used as in the first embodiment. .

A suitable dry etching technique in this embodiment is anisotropic plasma dry etching, and examples include a method using ICP plasma or ECR plasma. As the etching gas, a mixed gas of SiCl ₄ and Ar or the like is used. Instead of the SiCl ₄ gas component, chlorine gas or boron trichloride gas can also be used. Here, the dry etching technique is an ICP method, and a mixed gas of SiCl ₄ and Ar is used as an etching gas.

Next, after removing the SiO ₂ stripe 114 using a fluorine chemical solution, as shown in FIG. 4D, an SiN film 107 having a thickness of 80 nm to 300 nm is grown by using, for example, a plasma CVD method. This SiN film 107 is a film that functions as a current blocking layer.

Here, a material different from the SiN film may be used for the current blocking layer. This is the same as in the first embodiment, and any material having an insulating property and a refractive index smaller than that of the p-type cladding layer 105 may be used. Specific examples include dielectric films such as SiO ₂ and Al ₂ O ₃ . Further, regarding the film thickness of the SiN film 107, 80 nm to 300 nm is a preferable value, but is not limited thereto.

  As for the means for forming the above film, various CVD methods and PVD methods can be used as in the first embodiment, and plasma CVD method that can realize high film thickness uniformity and easy film formation. Is particularly preferred.

  Next, as shown in FIG. 3E, the SiN film 107 on at least a part of the ridge structure 120 is removed by wet etching using a photolithography technique. At this time, as in the second embodiment, on both ends of the ridge structure 120 in the width direction (direction perpendicular to the length direction of the ridge structure 120 and parallel to the main surface of the n-type substrate 102), A part of the SiN film 107 is left.

  Thereby, a current injection region 116b is formed as a portion where the SiN film 107 on the ridge structure 120 is removed.

The dry etching used at this time may be anisotropic dry etching such as RIE, ICP, or ECR. As the etching gas, a CF-based gas such as a mixed gas of CF ₄ and CHF ₃ can be used.

In this embodiment, a RIE method is used as a specific example, and a mixed gas of CF ₄ , CHF _3, and O ₂ is used as an etching gas. Further, as dry etching conditions, the volume contents of CF ₄ and CHF _{3 in} the mixed gas are 1 to 10% and 30 to 50%, the pressure is 40 to 60 Pa, and the stage temperature is 10 to 20 ° C., respectively. However, these are examples and are not limited, and may be set as appropriate. Further, wet etching can be performed instead of dry etching.

Next, as shown in FIG. 3 (f), a hydrogen peroxide-based chemical solution that is a mixed solution of sulfuric acid, hydrogen peroxide solution, and water (the volume content of sulfuric acid in the chemical solution is 0.1 to 15%, and Etching is performed using the SiN film 107 as a mask. Thus, the p-type second damage absorption layer 111b made of GaAs is removed by etching until reaching the p-type first damage absorption layer 111a made of Ga _0.5 In _0.5 P. Since Ga _0.5 In _0.5 P is resistant to a hydrogen peroxide solution, the p-type second damage absorption in the direction perpendicular to the main surface of the n-type substrate 102 is caused by the exposure of the p-type first damage absorption layer 111a. Etching of layer 111b stops.

  Immediately after the etching in the vertical direction is stopped in this way, the side surface 111y (side surface formed by wet etching) near the center of the ridge structure 120 in the p-type second damage absorption layer 111b remaining at both ends on the ridge structure 120. ) Is an inclined curved surface. As a result, the opening formed in the p-type second damage absorbing layer 111b has a shape that widens upward (on the side opposite to the n-type substrate 102).

  On the other hand, it is preferable to continue the wet etching until the side surface 111y becomes substantially linear, that is, until the (111) plane is exposed as a whole. In the portion of the side surface 111y of the p-type second damage absorbing layer 111b where the (111) plane is exposed, the wet etching rate is reduced. For this reason, the unexposed portion of the (111) plane is preferentially etched, and the side surface 111y can be substantially flat.

  As a result, the area of the p-type first damage absorption layer 111a exposed by removing the p-type second damage absorption layer 111b can be controlled, and the control of the area within and between the wafers can be made uniform. It can be performed with high accuracy.

  The volume content of sulfuric acid and hydrogen peroxide solution in the hydrogen peroxide solution is not limited to the values shown above, and may be set as appropriate. Further, the chemical solution is not limited to the hydrogen peroxide solution, and other chemical solutions may be used. Any chemical solution having high etching selectivity, that is, a high etching rate for the p-type second damage absorbing layer 111b and a low etching rate for the p-type first damage absorbing layer 111a and the SiN curtain 107 can be used here.

  The wet etching amount in the direction perpendicular to the substrate surface may be selected as appropriate.

Next, as shown in FIG. 3 (g), a hydrochloric acid-based chemical solution (with a volume content of hydrochloric acid in the chemical solution of, for example, 15 to 35%, which can be set to other values) is used. Etching is performed using the mold second damage absorbing layer 111b as a mask. Thus, the p-type first damage absorption layer 111a made of Ga _0.5 In _0.5 Pp is removed by etching until reaching the p-type contact layer 110. However, the p-type first damage absorption layer 111a remains without being etched under the SiN film 107 remaining at both ends in the width direction on the ridge structure 120 and the p-type second damage absorption layer 111b below the ridge structure 120. There will be an opening in the area inside the structure 120.

  Further, since the p-type contact layer 110 made of GaAs is resistant to a hydrochloric acid chemical solution, when this layer is exposed, etching in a direction perpendicular to the surface of the n-type substrate 102 is stopped.

  Here, as in the etching of the p-type second damage absorption layer 111b shown in FIG. 3F, the p-type first remaining on both ends of the ridge structure 120 immediately after the etching in the vertical direction is stopped. A side surface 111z (side surface formed by wet etching) near the center of the ridge structure 120 in the damage absorbing layer 111a is an inclined curved surface.

  On the other hand, it is preferable to continue the wet etching until the side surface 111z becomes substantially planar. In the portion of the side surface 111z where the (111) surface is exposed, the wet etching rate is reduced. For this reason, the unexposed portion of the (111) plane is preferentially etched, and the side surface 111z can be made substantially flat.

  As a result, the area of the p-type contact layer 110 exposed by removing the p-type first damage absorbing layer 111a can be controlled, and the control of the area in the wafer plane and between the wafers can be performed uniformly and accurately. be able to.

  The chemical used for wet etching is not limited to a hydrochloric acid chemical. A chemical solution that can perform highly selective etching with a high etching rate for the p-type first damage absorbing layer 111a and a low etching rate for the p-type second damage absorbing layer 111b, the SiN film 107, and the p-type contact layer 110. If available, it can be used.

  The amount of wet etching in the direction perpendicular to the substrate surface may be appropriately selected according to the type and mixing ratio of the chemical solution.

  Further, dry etching can be used instead of wet etching. It is desired that plasma damage is small, and for example, chemical dry etching may be used.

  Next, as shown in FIG. 3H, a p-side electrode 112 is formed so as to cover the p-type contact layer 110 and the SiN film 107. Further, the n-side electrode 101 is formed on the back surface of the n-type substrate 102. Thereby, the ridge stripe type semiconductor laser device is completed.

  By the manufacturing process as described above, the same effects as those of the first embodiment can be obtained in the present embodiment. That is, the interface between the p-type contact layer 110 and the p-side electrode 112 can be cleaned by forming and removing the p-type first damage absorbing layer 111a and the p-type second damage absorbing layer 111b. As a result, it is possible to suppress deterioration of element characteristics such as an increase in contact resistance and an increase in operating voltage. Further, since the p-type first damage absorption layer 111a made of GaInP-based material and the p-type contact layer 110 made of GaAs-based material can be wet-etched with a high selection ratio, a p-type damage absorption layer is selectively formed. In addition to being able to be removed, it can be controlled with high accuracy and uniformity within the wafer surface and between wafers.

  Further, for the purpose of suppressing the evaporation of P from the p-type first damage absorption layer 111a made of GaInP-based material, a stable p-type second made of GaAs-based material is formed on the p-type first damage absorption layer 111a. A two-damage absorbing layer 111b is formed.

  By using such a damage absorbing layer having a two-layer structure, evaporation of P can be prevented. However, it is not limited to a two-layer structure, and a damage absorbing layer having a structure of three or more layers may be used.

When using a damage absorption layer having a structure of two or more layers, the lowermost layer is preferably a compound semiconductor having a composition of, for example, GaP, InP, GaInP, AlInP, AlGaInP, or AlGaAs. More generally, a composition such as Al _x Ga _1-x As (0 ≦ x ≦ 1) or (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1). A compound semiconductor layer having In this way, the damage absorbing layer on the p-type contact layer 110 made of a GaAs material can be selectively removed.

The uppermost layer is preferably a thermodynamically stable compound semiconductor such as GaAs or AlGaAs, that is, Al _x Ga _1-x As (0 ≦ x ≦ 1). If it does in this way, evaporation of P from a lower layer can be suppressed reliably.

  In the present embodiment, the p-type first damage absorbing layer 111a and the p-type contact layer 110 have significantly different wet etching rates. For this reason, the p-type first damage absorbing layer 111a can be selectively removed, and the etching amount can be controlled with high accuracy within the wafer surface and between the wafers.

  For this reason, both the etching residue of the p-type first damage absorbing layer 111a and the disappearance of the p-type contact layer 110 due to excessive etching can be reliably suppressed. As a result, the semiconductor laser device can be manufactured stably.

  Also in this embodiment, as in the second embodiment, the p-type first damage absorption layer 111a and the p-type second damage absorption layer 111b are left at both end portions in the width direction on the ridge structure 120. Since the SiN film 107 which is a current blocking layer is formed on this portion whose plane orientation is a direction perpendicular to the main surface of the n-type substrate 102, the adhesion is improved.

  It should be noted that the thicknesses of the layers shown in the present embodiment are merely illustrative and can be set without limitation.

  In the present embodiment, a red semiconductor laser device made of an AlGaInP-based material is taken as an example, but the present invention is not limited to this. For example, a blue semiconductor laser device made of an AlGaInN-based material using a compound semiconductor layer having a composition of GaN as a p-type contact layer may be used. In addition, various ridge stripe semiconductor laser devices using mixed crystal compound semiconductors are applicable.

(Example 3)
Next, the semiconductor laser device of the invention described in the third embodiment and the manufacturing method thereof will be described more specifically as Example 3 with reference to FIGS. However, it is natural that the present invention is not limited to this example.

First, as shown in FIG. 3A, an n-type cladding layer 103 (of Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is formed on an n-type substrate 102 (thickness: 470 μm) made of GaAs by MOCVD. Active layer 104 (thickness 5 nm) made of GaInP-based material, p-type cladding layer 105 (thickness 1.85 μm) made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, Ga _0.5 In _0.5 A p-type intermediate layer 109 (thickness 55 nm) made of P and a p-type contact layer 110 (thickness 0.2 μm) made of GaAs were laminated in this order from the bottom (from the n-type substrate 102 side). The n-type substrate 102 used here is not an off-angle substrate (tilted substrate).

  Next, the p-type first damage absorption layer 111a (thickness 25 nm) and the p-type second damage absorption layer 111b (thickness 25 nm) are sequentially stacked on the p-type contact layer 110 using the MOCVD method. Formed.

Further, an SiO ₂ film 113 (thickness 0.55 μm) was formed on the p-type second damage absorption layer 111b.

Next, as shown in FIG. 3B, the SiO ₂ film 113 was processed by a photolithography technique and a dry etching technique to form a SiO ₂ stripe 114 having a width of 2 μm.

Next, as shown in FIG. 3C, for the p-type cladding layer 105, the p-type intermediate layer 109, the p-type contact layer 110, the p-type first damage absorption layer 111a, and the p-type second damage absorption layer 111b. Then, dry etching using the SiO ₂ stripe 114 as a mask was performed to form a ridge structure 120 including the ridge 105a.

Here, the portions other than the ridge structure 120 were etched so as to leave the p-type cladding layer 105 with a film thickness of 300 nm on the upper surface of the active layer 104. The etching is stopped by time control for this purpose. As a dry etching method, an ICP method using a mixed gas of SiCl ₄ and Ar as an etching gas was used.

Next, as shown in FIG. 3D, after removing the SiO ₂ stripe 114 using a hydrofluoric acid chemical solution, a 130 nm thick SiN film 107 was grown on the entire surface of the substrate by plasma CVD.

  Next, as shown in FIG. 3E, the SiN film 107 on at least a part of the ridge structure 120 was removed by wet etching using a photolithography technique. Thereby, a current injection region 116b was formed. Further, the p-type cladding layer 105 covering the p-type cladding layer 105 and the side surface of the ridge structure 120 functions as a current blocking layer.

Here, dry etching was performed by the RIE method. The etching gas is a mixed gas of CF ₄ , CHF ₃ and O ₂ . As etching conditions, the volume contents of CF ₄ and CHF _{3 in} the mixed gas were 7% and 3% in order, the pressure was 45 Pa, and the stage temperature was 15 ° C.

  Next, as shown in FIG. 3F, a p-type first damage absorption layer 111a made of a GaInP-based material is exposed using a mixed chemical solution of sulfuric acid, hydrogen peroxide solution, and water, using the SiN film 107 as a mask. Until then, the p-type second damage absorbing layer 111b made of GaAs-based material was etched. At this time, the p-type second damage absorbing layer 111b is left at both end portions in the width direction on the ridge structure 120 by being masked by the SiN film 107. Further, the volume content of sulfuric acid in the chemical solution was set to 1%, and the volume content of the hydrogen peroxide solution was set to 1%.

  Next, as shown in FIG. 3G, a mixed chemical solution of hydrochloric acid and water is used and the p-type second damage absorbing layer 111b remaining on the ridge structure 120 is used as a mask to form the p-type contact layer 110. The p-type first damage absorbing layer 111a is etched until is exposed. A part of the p-type first damage absorbing layer 111a is left at both end portions in the width direction on the ridge structure 120. The volume content of hydrochloric acid in the chemical solution was 15%.

  Next, a p-side electrode 112 is formed by vapor deposition so as to cover the upper surface of the p-type contact layer 110, the side surface of the ridge structure 120, and the upper surface of the p-type cladding layer 105, and the n-side electrode 101 is formed on the back surface of the n-type substrate 102. Formed. Thus, a ridge stripe type semiconductor laser wafer shown in FIG.

  In this example, the p-type first damage absorption layer 111a and the p-type second damage absorption layer 111b formed on the p-type contact layer 110 were removed by wet etching, and then the p-side electrode 112 was formed. Therefore, it is possible to stably form a ridge stripe semiconductor laser device having a low contact resistance and a low operating voltage without leaving a natural oxide film or a modified layer at the interface between the p-type contact layer 110 and the p-side electrode 112. I was able to.

  Further, since the p-type first damage absorbing layer 111a made of GaInP-based material is formed on the p-type contact layer 110 made of GaAs-based material, the p-type contact layer 110 made of GaAs-based material is suppressed while suppressing variations in the wafer surface and between wafers. The mold first damage absorbing layer 111a could be selectively removed. At this time, the p-type contact layer 110 was not etched.

  Further, the SiN film 107 covers the p-type second damage absorption layer 111b left on the p-type contact layer 110, so that the adhesion of the SiN film 107 is improved.

  A p-type second damage absorbing layer 111b made of a thermodynamically stable GaAs-based material is formed on the p-type first damage absorbing layer 111a made of a GaInP-based material. Thereby, evaporation of P from the p-type first damage absorption layer 111a can be suppressed.

  According to the semiconductor laser device and the manufacturing method thereof of the present invention, a ridge stripe semiconductor laser device with a clean interface between the contact layer and the electrode can be obtained, and etching can be performed uniformly and with high precision within and between wafers. It can be controlled and is useful for improving the yield of the ridge stripe semiconductor laser and its manufacture.

FIGS. 1A to 1G are diagrams for explaining a ridge stripe semiconductor laser device and its manufacturing process according to the first embodiment. 2A to 2G are views for explaining a ridge stripe type semiconductor laser device according to the second embodiment and a manufacturing process thereof. FIGS. 3A to 3H are views for explaining a ridge stripe type semiconductor laser device and its manufacturing process according to the third embodiment. 4A to 4D are views showing a conventional ridge stripe type semiconductor laser device and a manufacturing method thereof.

Explanation of symbols

101 n-side electrode 102 n-type substrate 103 n-type cladding layer 104 active layer 105 p-type cladding layer 107 SiN film 109 p-type intermediate layer 110 p-type contact layer 111 p-type damage absorption layer 111a p-type first damage absorption layer 111b p Type second damage absorbing layer 111x Side surface 111y Side surface 111z Side surface 112 P-side electrode 113 SiO ₂ film 114 Stripes 116, 116a, 116b Current injection region

Claims (15)

A first cladding layer of a first conductivity type formed on a substrate;
An active layer formed on the first cladding layer;
A second cladding layer of a second conductivity type formed on the active layer and having a striped ridge;
A second conductivity type contact layer formed on the ridge;
A damage absorbing layer formed in a predetermined region on the contact layer;
A semiconductor laser device comprising: a current blocking layer formed on the second cladding layer and having an opening on the contact layer. In claim 1,
2. The semiconductor laser device according to claim 1, wherein the predetermined region is a region at both ends in the width direction of the ridge. In claim 1 or 2,
The semiconductor laser device, wherein the current blocking layer covers at least a part of an upper surface of the damage absorbing layer. In any one of Claims 1-3,
The semiconductor laser device, wherein the current blocking layer is made of a dielectric material. In claim 4,
The semiconductor laser device, wherein the dielectric material includes at least one of SiN, SiO _2, and Al ₂ O ₃ . In any one of Claims 1-5,
The contact layer is made of a compound semiconductor having a composition of Al _x Ga _1-x As (0 ≦ x ≦ 1). In any one of Claims 1-6,
The damage-absorbing layer includes at least one layer made of a semiconductor material, an organic material, or a dielectric material. In any one of Claims 1-7,
The damage absorbing layer includes at least one compound semiconductor layer,
The compound semiconductor layer has a composition of Al _x Ga _1-x As (0 ≦ x ≦ 1) or (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1). A semiconductor laser device comprising a compound semiconductor having In any one of Claims 1-8,
The damage absorbing layer has a multilayer structure including two or more compound semiconductor layers,
The uppermost layer of the multilayer structure is made of a compound semiconductor having a composition of Al _x Ga _1-x As (0 ≦ x ≦ 1). In claim 8 or 9,
The semiconductor laser device, wherein the compound semiconductor layer is formed directly on the contact layer. In any one of Claims 1-10,
2. A semiconductor laser device according to claim 1, wherein the surface orientation of the substrate surface is a surface orientation inclined from the (100) plane. In claim 11,
The semiconductor laser device characterized in that the plane orientation inclined from the (100) plane is the [011] direction. A step of laminating a first conductivity type first clad layer, an active layer, a second conductivity type second clad layer, a second conductivity type contact layer, and a damage absorption layer in this order on a substrate ( a) and
Processing the second cladding layer, the contact layer, and the damage absorbing layer to form a striped ridge (b);
After the step (b), a step (c) of forming a current blocking layer made of a dielectric material so as to cover the second cladding layer and the ridge;
(D) forming a current injection region by removing at least a part of the current blocking layer on the damage absorbing layer;
And (e) removing the damage absorbing layer in the portion of the current injection region on the contact layer after the step (d). In claim 13,
In the step (e), the damage absorbing layer is selectively removed by a wet etching technique. In claim 13 or 14,
In the step (e), the damage absorbing layer is removed using the current blocking layer as a mask.

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