JP2006332364A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device and its manufacturing method wherein an occurrence of a warping caused by a mesa structure is restrained by an easier and universal method. <P>SOLUTION: One or plurality of mesa structures of an external form having steep cliffs on both sides of a flat top are formed on both faces of an upper face 11b and a lower face 11a of a semiconductor substrate 11. A mesa structure (first mesa structure) 13 formed on the lower face 11a of the semiconductor substrate 11 is such a mesa structure that has a so-called element function in which an active layer 12 is a light emitting layer, and a mesa structure (second mesa structure) 23 formed on the upper face 11b of the semiconductor substrate 11 is a dummy mesa structure having no active layer. The second mesa structure 23 is provided in such a mode that the warping of the semiconductor substrate 11 caused by an arrangement of the first mesa structure 13 is dissolved and mitigated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly to an improved device structure and a method for manufacturing the same, which are beneficially employed in a semiconductor laser having a mesa structure having an external structure having steep cliffs on both sides of a flat top. About.

  Conventionally, semiconductor lasers are used in various applications such as reading and writing information with optical recording media as a light source that emits light with a wavelength that is aligned in phase, distance measurement between automobiles, and more recently, It is also used as an information communication medium in optical communication. FIG. 16 shows a cross-sectional structure of an element structure that has been conventionally employed as such a semiconductor laser.

  As shown in FIG. 16, in this semiconductor laser, an epitaxial film 12 composed of a plurality of layers is formed by crystal growth on a substrate (semiconductor substrate) 11 composed of, for example, n-type GaAs (gallium, arsenic). It is configured. The layers constituting the epitaxial film 12 are composed of, for example, an n-type AlGaAs (aluminum, gallium, arsenic) cladding layer 12a, an n-type GaAs (gallium, arsenic) active layer 12b, and a p-type AlGaAs cladding layer 12c. That is, the epitaxial film 12 is formed in a stacked manner in such a manner that the active layer 12b is sandwiched between the clad layers 12a and 12c, whereby the active layer 12b becomes a pn junction layer (region) and the inversion distribution condition is satisfied. The light amplifying action for promoting laser oscillation is performed by the stimulated emission in the active layer 12b made of the pn junction.

Further, as is apparent from FIG. 16, the epitaxial film 12 composed of the cladding layer 12a, the active layer 12b, and the cladding layer 12c has a so-called mesa structure 13 having a steep cliff-like portion around a flat top. It is formed in the form that has. An insulating film 14 made of, for example, SiO ₂ (silicon oxide) is formed on the lower surface 11a of the substrate 11 including the mesa structure 13 in a form having a window (opening) 15 at a position corresponding to the mesa structure 13. Has been. Further, on the surface thereof, the window 15 is in contact with the epitaxial film 12 and is made of a multilayer film such as Cr / Pt / Au / Pt / Au or Ti / Pt / Au / Ti / Au. A lower electrode 16 is formed. On the other hand, an upper electrode 26 made of a multilayer film such as Au—Ge alloy / Ni / Au / Pt / Au is formed on the upper surface 11 b of the substrate 11. That is, in this semiconductor laser, current is supplied to the substrate 11 through the lower electrode 16 and the upper electrode 26. In addition, a solder layer for electrically and mechanically joining the substrate 11 serving as the laser bar to an appropriate pedestal is formed on the portion where the mesa structure 13 is formed, instead of the lower electrode 16. There is also. In addition, if necessary, an insulating film may be separately formed for separating a region in which current is passed through the substrate 11 and a region in which no current is passed.

  In any case, the semiconductor laser has the mesa structure 13 on one side (the lower surface 11a in the example of FIG. 16) as described above, and as a semiconductor laser corresponding to the portion where the mesa structure 13 is formed, The light emitting part is formed. Since these mesa structures 13 are usually formed at the same width and at equal intervals, the light emitting portions (light emission points) as the semiconductor lasers are also arranged at equal intervals according to this.

  Further, by making the semiconductor laser have such a mesa structure 13, current confinement can be enhanced through cliff-like portions formed on both sides of each mesa structure 13, and the mesa structure 13 When the solder layer is formed through the contact area, the contact area with the substrate 11 is also enlarged, and as a result, the adhesion between the substrate 11 and the pedestal is enhanced.

Next, an outline of an example of a method of manufacturing a semiconductor laser having such a mesa structure will be described with reference to FIGS.
When manufacturing such a semiconductor laser, first, as shown in FIG. 17A, on the lower surface 11a of the substrate 11 made of n-type GaAs, for example, a clad layer 12a made of n-type AlGaAs and an active material made of n-type GaAs. A layer 12b and a clad layer 12c made of p-type AlGaAs are stacked by crystal growth. Next, in the embodiment shown in FIG. 17B, the mesa structure 13 is formed by partially removing the epitaxial film 12 composed of the cladding layer 12a, the active layer 12b, and the cladding layer 12c, for example, by etching. Thereafter, as shown in FIG. 17C, an insulating film 14 is formed on the lower surface 11a of the substrate 11 including the mesa structure 13, and the mesa is further formed on the insulating film 14 by, for example, photolithography or etching. A window (opening) 15 corresponding to the top portion of the structure 13 is formed. Further, as shown in FIG. 18A, the surface of the insulating film 14 is contacted with the epitaxial film 12 through the window 15, for example, Cr / Pt / Au / Pt / Au or A lower electrode 16 made of a multilayer film such as Ti / Pt / Au / Ti / Au is formed. On the other hand, as shown in FIG. 18B, the upper electrode 26 made of, for example, a multilayer film of Au—Ge alloy / Ni / Au / Pt / Au is formed on the upper surface 11b of the substrate 11. When this semiconductor laser is used as, for example, a semiconductor laser array, as shown in FIG. 18 (c), in the form perpendicular to the extending direction of each mesa structure 13, a rod having a predetermined width, that is, The substrate 11 is cleaved as a laser bar, and an appropriate coating process is performed on the end surface that becomes the cleaved surface 11c.
JP-A-11-163267 JP 2003-273468 A

  As described above, a semiconductor laser having a mesa structure has excellent characteristics such as that the current confinement is increased or the contact area when a solder layer is formed is ensured through the mesa structure. Be able to. However, in the case of such a semiconductor laser, the following inconvenience due to this mesa structure cannot be ignored.

  That is, in the epitaxial film 12 in which the mesa structure is formed, the clad layer 12a, the active layer 12b, and the clad layer 12c are usually laminated so that lattice matching between the layers can be obtained in a high temperature (for example, 800 ° C.) atmosphere. The For this reason, in the process in which the epitaxial film 12 is cooled to room temperature, the substrate 11 serving as the laser bar is caused by a difference in thermal expansion coefficient between the epitaxial films 12 or between the epitaxial film 12 and the substrate 11. Distortion may occur. Moreover, such a semiconductor laser has a vertically asymmetric structure in which the film composition or film thickness is different between the upper surface 11b side and the lower surface 11a side including the above-mentioned electrodes as well as the mesa structure. In particular, the mesa structure is formed. In the portion to be formed, a film stress larger than usual is generated due to a step between the portion to be a mesa and the portion that is not. For this reason, in the end, the laser bar is warped in the form schematically shown in FIG. 19, and the yield is inevitably lowered particularly when the semiconductor laser is formed as the semiconductor laser array. .

  Conventionally, as a method for suppressing the warpage of the laser bar, for example, the method described in Patent Document 1 or the method described in Patent Document 2 has been taken, but there is still room for improvement in practice. It has become. Incidentally, in the method described in Patent Document 1, when a heat sink is heated and bonded to the upper surface and the lower surface of the laser bar, materials having different coefficients of thermal expansion are used as the heat sink to correct the warpage of the laser bar. However, this method does not eliminate the warpage of the laser bar itself, and cannot prevent damage to the semiconductor crystal due to such warpage. On the other hand, in the method described in Patent Document 2, the lattice constants of materials constituting the substrate serving as the laser bar and the epitaxial film laminated thereon are adjusted to intentionally cause lattice mismatch, thereby causing strain between layers. To control. However, this method is not a method that can be applied to all material systems for forming a laser bar because the combination of materials that can cause such lattice mismatch is limited.

Further, not only the semiconductor laser but also a semiconductor element having a mesa structure has the above-mentioned actual situation due to the mesa structure.
The present invention has been made in view of such circumstances, and provides a semiconductor device capable of suppressing the occurrence of warpage due to a mesa structure and a method for manufacturing the same by a simpler and more universal method. With the goal.

  In order to achieve such an object, according to the first aspect of the present invention, as the element structure of the semiconductor element, one or more mesa structures, which are external structures having steep cliffs on both sides of the flat top, are formed on the upper surface of the semiconductor substrate. And the structure formed on both sides of the lower surface was adopted.

  According to such a structure as a semiconductor element, the stress applied to the upper surface and the lower surface of the semiconductor element can be balanced through the mesa structure formed on both the upper surface and the lower surface of the semiconductor substrate. Thereby, generation | occurrence | production of the distortion in a semiconductor element can be suppressed, and by extension, generation | occurrence | production of the curvature of a semiconductor element can be suppressed now.

  In this case, the mesa structure formed on the upper surface and the lower surface of the semiconductor substrate, particularly the first mesa structure formed on one surface of the semiconductor substrate, as described in claim 2, is used. A mesa structure having an element function having an active layer can be used, and a second mesa structure formed on the other surface of the semiconductor substrate can be a dummy mesa structure having no active layer.

  As described above, when a mesa structure having an element function including an active layer is formed in such a semiconductor element, the semiconductor substrate has an asymmetric structure with different film compositions or film thicknesses on the upper surface side and the lower surface side. Further, since a difference in thermal expansion coefficient is generated between the semiconductor substrate and the material layer forming the element function, the distortion caused by these may occur in the semiconductor element. In this regard, by adopting the above structure in the semiconductor element, the stress applied to the upper surface and the lower surface of the semiconductor element can be balanced in such a manner that such strain is alleviated. Can be suppressed. In addition, since the second mesa structure is a dummy mesa structure, a high degree of freedom in manufacturing can be maintained for the same element structure.

Further, as the semiconductor element having the above structure, for example, according to the invention of claim 3,
A structure in which the first mesa structure and the second mesa structure are formed symmetrically across the semiconductor substrate.
Alternatively, as in the invention according to claim 4,
A structure in which the first mesa structure and the second mesa structure having the same width as the mesa structure are alternately formed across the semiconductor substrate.
Alternatively, as in the invention according to claim 5,
A structure in which at least one of a width and an arrangement interval as the first mesa structure and the second mesa structure is different from each other.
It is also effective to appropriately adjust the arrangement of the first mesa structure having the element function and the dummy second mesa structure. This makes it possible to balance the stress applied to the upper and lower surfaces of the semiconductor element according to the structure and film characteristics of the target semiconductor element. You will be able to.

In addition, about the structure of the said Claim 5, specifically, according to the invention of Claim 6,
A structure in which the width of the second mesa structure is formed wider than the width of the first mesa structure.
Or, according to the invention of claim 7,
A structure in which the width of the second mesa structure is narrower than the width of the first mesa structure.
Etc. can be adopted. And about these structures of Claim 6 or Claim 7, further, for example by the invention of Claim 8,
A structure in which the first mesa structure and the second mesa structure are formed in such a manner that the centers of the tops coincide with each other across the semiconductor substrate.
Alternatively, as in the invention according to claim 9,
A structure in which the first mesa structure and the second mesa structure are alternately formed across the semiconductor substrate.
And so on.

On the other hand, for the structure according to claim 5, for example, according to the invention according to claim 10,
A structure in which the first mesa structure and the second mesa structure are formed in different numbers.
In particular, in this case, according to the invention of claim 11,
A structure in which the second mesa structure is formed with a smaller number than the first mesa structure.
Or, according to the invention of claim 12,
A structure in which the second mesa structure is formed in a larger number than the first mesa structure.
Etc. can be adopted.

Similarly, the structure according to claim 5 is further structured as follows, that is, according to the invention according to claim 13,
A structure in which the second mesa structure is formed in a manner in which the width of the mesa structure is partially different from the center to the end of the semiconductor substrate.
Alternatively, as in the invention according to claim 14,
A structure in which the second mesa structure is formed in such a manner that the width of the mesa structure gradually increases from the center to the end of the semiconductor substrate.
Or, according to the invention of claim 15,
A structure in which the second mesa structure is formed in such a manner that the width of the mesa structure is gradually narrowed from the center to the end of the semiconductor substrate.
Or, according to the invention of claim 16,
A structure in which the second mesa structure is formed in a manner in which the arrangement interval is partially different from the center to the end of the semiconductor substrate.
Alternatively, as in the invention according to claim 17,
A structure in which the second mesa structure is formed in such a manner that the arrangement interval gradually increases from the center to the end of the semiconductor substrate.
Or, according to the invention of claim 18,
A structure in which the second mesa structure is formed in such a manner that the arrangement interval is gradually reduced from the central part to the end part of the semiconductor substrate.
Etc. can be adopted as appropriate.

  In any of these structures, the stress applied to the upper surface of the semiconductor element on which the second mesa structure is formed can be adjusted with a higher degree of freedom. In other words, even when the stress difference between the upper surface and the lower surface of the semiconductor element caused by the above-described strain is different, for example, in the plane of the semiconductor element, the formation mode or arrangement mode of the second mesa structure is adjusted as appropriate. This makes it possible to finely adjust the balance of stress applied to the upper surface and the lower surface of the semiconductor element.

  In addition, with respect to the semiconductor device according to any one of claims 2 to 18, both the first mesa structure and the second mesa structure are at the top, as in the invention according to claim 19. It is particularly effective to make the structure formed in a range of several tens nm to several μm.

  By adopting such a structure, current confinement through the first mesa structure and the second mesa structure is preferably enhanced. In addition, when forming a solder layer or the like for electrically and mechanically joining these mesas to the above-described pedestal or the like, the contact area with the solder layer is expanded and the adhesion is enhanced. It becomes like this. Furthermore, according to the structure, since these mesa structures can be easily formed by, for example, well-known etching or the like, the structure according to any one of claims 2 to 18 can be easily realized. Also become.

  In the semiconductor device according to any one of claims 2 to 19, as in the invention according to claim 20, the active layer in which the first mesa structure is sandwiched between clad layers is a light emitting portion. The present invention is particularly effective when applied to a laser bar in which such semiconductor lasers are arrayed on the semiconductor substrate.

  When such a laser bar is realized particularly with the structure according to the nineteenth aspect, the aspect ratio of “horizontal width: depth” of the laser bar may be set to “10: 1” to “10: 3”. desirable. Further, the laser bar usually has a width of about 10 mm and a light emission point of about 19 to 49 points. Accordingly, when the horizontal width of the laser bar is, for example, “10 mm”, if the emission point is set to, for example, “19” point, the horizontal width of the first mesa structure is about “200 μm” and the arrangement interval (pitch) is It is about “500 μm”. Further, in such a laser bar, the electrode structures on the upper surface and the lower surface are naturally different depending on the formation mode of the first and second mesa structures. In this way, even when the upper surface side and the lower surface side of the laser bar including each electrode are vertically asymmetrical, the use of each of the above structures allows fine adjustment of the balance of stress applied to the upper and lower surfaces. As a result, the warpage of the laser bar is suppressed. In addition, by suppressing the warpage of the laser bar in this way, the arrangement of the light emitting portions is also appropriately controlled, and as a result, improvement of the light collecting characteristics as a semiconductor laser can be expected.

  On the other hand, in the invention described in claim 21, as a method of manufacturing a semiconductor element in which one or more mesa structures which are external structures having steep cliffs on both sides of a flat top on one surface of a semiconductor substrate are formed. When forming the mesa structure on the semiconductor substrate, the mesa structure is also formed on the other surface of the semiconductor substrate, and the warpage of the semiconductor substrate is absorbed through adjustment of the formation mode of the mesa structure on the other surface. To do.

  According to such a manufacturing method, the warpage of the semiconductor substrate is absorbed through the adjustment of the formation mode of the mesa structure without being limited by the material composition or the like forming the semiconductor element. The semiconductor crystal is not damaged. That is, the semiconductor element having the mesa structure can be manufactured stably.

  Further, in the method for manufacturing a semiconductor device according to claim 21, as in the invention according to claim 22, the mesa structure formed on one surface of the semiconductor substrate has an element function including an active layer. The mesa structure for adjustment, which is formed on the other side of the semiconductor substrate, is a dummy mesa structure that does not have an active layer, so that any material can be used for this part. However, the degree of freedom as a manufacturing method is kept high for the above element structure.

  Also in the method for manufacturing a semiconductor device according to claim 22, as in the invention according to claim 23, the mesa structure including the active layer has the light emitting portion sandwiched between the active layer and the clad layer. As described above, a laser bar with reduced warpage can be produced with high yield by applying the method to a method of manufacturing a laser bar in which the semiconductor laser is arrayed on the semiconductor substrate. Become.

(First embodiment)
A first embodiment in which a semiconductor element and a manufacturing method thereof according to the present invention are applied to a semiconductor laser (laser bar) and a manufacturing method thereof will be described below with reference to FIGS.

FIG. 1 shows an element structure of a semiconductor laser according to this embodiment.
That is, this semiconductor laser also has the same basic structure as the light emitting portion as that of the semiconductor laser illustrated in FIG. 15, for example, a substrate (semiconductor substrate) 11 made of n-type GaAs (gallium, arsenic). On top of this, an epitaxial film 12 composed of a plurality of layers is laminated and formed by crystal growth. The layers constituting the epitaxial film 12 are, for example, an n-type AlGaAs (aluminum, gallium, arsenic) cladding layer 12a, an n-type GaAs (gallium, arsenic) active layer 12b, and a p-type AlGaAs (aluminum, gallium, arsenic) cladding layer. Each layer consists of 12c. That is, also in this case, the active layer 12b serving as the light emitting portion (light emitting point) is laminated and formed so as to be sandwiched between the clad layers 12a and 12c.

Further, the epitaxial film 12 composed of the clad layer 12a, the active layer 12b, and the clad layer 12c also has a steep cliff-like portion around the flat top, similarly to the semiconductor laser illustrated in FIG. The so-called mesa structure (first mesa structure) 13 is formed. In addition, the lower surface (one surface) 11a of the substrate 11 including the mesa structure 13 is provided with a window (opening) 15 at a position corresponding to the mesa structure 13 and is made of, for example, SiO ₂ (silicon oxide). A film 14 is formed. Further, on the surface thereof, the window 15 is in contact with the epitaxial film 12 and is made of a multilayer film such as Cr / Pt / Au / Pt / Au or Ti / Pt / Au / Ti / Au. A lower electrode 16 is formed.

  On the other hand, in the semiconductor laser according to this embodiment, as the element structure, a steep cliff-like portion is formed around the flat top on the upper surface (other surface) 11b of the substrate 11 as in the mesa structure 13. A mesa structure (second mesa structure) 23 is formed. This mesa structure 23 is a dummy mesa structure having no active layer. Here, the mesa structure 23 is disposed at positions that are vertically symmetrical with the mesa structure 13 with the substrate 11 interposed therebetween, and at equal widths and at equal intervals. For this reason, in the portions where the mesa structure 13 and the mesa structure 23 are formed, a large film stress is generated on the lower surface 11a and the upper surface 11b of the substrate 11 due to the step between the portion that becomes the mesa and the portion that does not. The stress applied to the lower surface 11a and the upper surface 11b of the substrate 11 is balanced. In the semiconductor laser according to this embodiment, the upper electrode 26 made of a multilayer film such as Au—Ge alloy / Ni / Au / Pt / Au is formed on the upper surface 11b of the substrate 11 so as to cover the mesa structure 23. The current is supplied to the substrate 11 through the lower electrode 16 and the upper electrode 26.

  Thus, in this embodiment, the stress applied to the substrate 11 is balanced through the mesa structures 13 and 23 formed on the lower surface 11a and the upper surface 11b of the substrate 11, respectively. For this reason, for example, the film composition including the distortion caused by the difference in thermal expansion coefficient between the substrate 11 and the epitaxial film 12 formed thereon, or the electrode structures on the upper surface 11b side and the lower surface 11a side of the substrate 11 are included. In addition, distortion caused by the asymmetric film thickness is naturally alleviated. For this reason, even when this semiconductor laser is formed as the laser bar described above, the warp as the laser bar is eliminated in the form schematically shown in FIG. 2 as a diagram corresponding to FIG. The production yield will be improved.

  The laser bar exemplified here is formed in a rod shape having a lateral width L shown in FIG. 2 of about 10 mm and a depth (not shown) of about 1 to 3 mm, and its aspect ratio, that is, a ratio of “horizontal width: depth”. Is “10: 1” to “10: 3”. Then, in the horizontal direction of such a laser bar, the light emitting point is normally formed by about 19 to 49 points through the mesa structure 13. Therefore, if a light emission point of “19” points is formed on a laser bar having a lateral width L of “10 mm”, the lateral width (mesa width) d of the mesa structure 13 shown in FIG. 1 is about “200 μm”. The arrangement interval (pitch) t is about “500 μm”. In this case, as the above mesa structures 13 and 23, the heights of the tops thereof are both set in the range of “several tens nm to several μm”, so that the stress applied to both surfaces of the substrate 11 is balanced. The inventors have confirmed that warpage as a laser bar is also preferably suppressed.

Next, a method for manufacturing a semiconductor laser (laser bar) having such an element structure will be described with reference to FIGS.
In this manufacturing, first, as shown in FIG. 3A, on the lower surface 11a of the substrate 11 made of n-type GaAs, for example, a clad layer 12a made of n-type AlGaAs, an active layer 12b made of n-type GaAs, and A clad layer 12c made of p-type AlGaAs is sequentially stacked by crystal growth.

Next, the epitaxial film 12 composed of the cladding layer 12a, the active layer 12b, and the cladding layer 12c formed on the lower surface 11a of the substrate 11 and the upper surface 11b of the substrate 11 are partially removed by, for example, anisotropic etching. As a result, the mesa structures 13 and 23 are formed in the manner shown in FIG. Here, as the etchant for the anisotropic etching, for example, H ₃ PO ₄ (phosphoric acid), H ₂ O ₂ (hydrogen peroxide), and (CH ₂ OH) ₂ (dimethyl ether) are “1: 1: 2”. A mixed solution mixed at a ratio of The depth of etching for forming these mesa structures 13 and 23, that is, the depth of mesa etching, is set in the range of “several tens nm to several μm”. In forming the mesa structure 23, the upper surface 11b of the substrate 11 may be directly etched in this way, or an appropriate film material may be deposited and etched.

Thereafter, as shown in FIG. 4A, an insulating film 14 made of, for example, a silicon oxide film (SiO ₂ ) is formed on the lower surface 11 a of the substrate 11 including the mesa structure 13. A window (opening) 15 is formed in a portion corresponding to the top portion of the mesa structure 13 by, for example, photolithography or etching. Then, the surface of the insulating film 14 is contacted with the epitaxial film 12 through the window 15 as shown in FIG. 4B, for example, Cr / Pt / Au / Pt / Au or A lower electrode 16 made of a multilayer film such as Ti / Pt / Au / Ti / Au is formed.

  On the other hand, as shown in FIG. 4C, an upper electrode 26 made of a multilayer film such as Au—Ge alloy / Ni / Au / Pt / Au is formed on the upper surface 11b of the substrate 11 including the mesa structure 23, for example. Form. Thereafter, in order to use this semiconductor laser as a semiconductor laser array (laser bar), as shown in FIG. 4D, a depth of about 1 to 3 mm is formed in a manner orthogonal to the extending direction of the respective mesa structures 13 and 23. The substrate 11 is cleaved into a rod shape having a shape, and an appropriate coating treatment is applied to the end surface that becomes the cleavage surface 11c to obtain the laser bar illustrated in FIG.

As described above, according to the semiconductor laser (laser bar) and the manufacturing method thereof according to this embodiment, the effects listed below can be obtained.
(1) A structure is formed in which a plurality of mesa structures 13 and 23 are formed on both sides of the lower surface 11a and the upper surface 11b of the semiconductor substrate 11, which are external structures having steep cliffs on both sides of the flat top. As a result, the stress balance can be achieved on both surfaces of the semiconductor substrate 11, and the occurrence of warpage as a laser bar can be suitably suppressed by this stress balance. In addition, by suppressing the occurrence of warpage in this way, the arrangement of the light emitting portions (light emitting points) is also appropriately controlled, and it is expected that the light condensing characteristics as a semiconductor laser or a semiconductor laser array can be improved. The production yield will be greatly improved.

(2) Further, since the warpage itself as a laser bar is suppressed, the semiconductor crystal is not damaged during the manufacturing process.
(3) Moreover, since the device structure itself is simple and effective in all material systems for forming the laser bar, the above structure can be applied to the manufacture of the laser bar with high universality.

  (4) Of the above mesa structures 13 and 23, the mesa structure 23 in particular has an active layer, that is, a dummy mesa structure having no element function. Although it can be used, the degree of freedom as a manufacturing method is kept high for the above element structure.

(5) Furthermore, since the mesa structure 23 itself and the mesa structure 13 can be formed by, for example, well-known etching or the like, the realization thereof is also easy.
(Second Embodiment)
Next, a second embodiment in which the semiconductor element according to the present invention is similarly applied to a semiconductor laser (laser bar) will be described with reference to FIG. 5 mainly focusing on differences from the first embodiment. To do. Note that the semiconductor laser according to the second embodiment is also provided with an insulating film, an electrode, and the like basically in accordance with the semiconductor laser according to the first embodiment illustrated in FIG. However, in FIG. 5, for convenience, the element structure of the semiconductor laser of the second embodiment is shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 5, even in the semiconductor laser device according to the second embodiment, a mesa structure (first mesa) having an element function formed on the lower surface 11a of the substrate (semiconductor substrate) 11 is used. In addition to the structure 13, a mesa structure (second mesa structure) 33 as a dummy is formed on the upper surface 11 b of the substrate 11.

  However, in this embodiment, as is clear from FIG. 5, the mesa structure 33 formed on the upper surface 11 b of the substrate 11 is different from the mesa structure 13 formed on the lower surface 11 a of the substrate 11. It is formed in a staggered manner. However, also in the same embodiment, the width (mesa width) and the arrangement interval (pitch) as the mesa structures 13 and 33 are set to be the same. Depending on the material of the substrate 11, the material of the mesa structure 33 serving as a dummy, and the film characteristics as an epitaxial film (mesa structure 13), the lower surface 11a and the upper surface 11b of the substrate 11 are rather affected by such an element structure. It becomes possible to balance the stress, and as a result, warpage as a laser bar can be suppressed.

  As described above, also by the semiconductor laser (laser bar) according to the second embodiment, the effects equivalent to or equivalent to the effects (1) to (5) according to the first embodiment described above. Can be obtained.

  Depending on the material or processing (manufacturing) method used for such a semiconductor laser (laser bar), the first or second embodiment can be modified as appropriate, for example, in the modes listed below. It is.

(First modification)
In the first embodiment, as illustrated in FIG. 1, the mesa structures 13 and 23 are formed on the lower surface 11a and the upper surface 11b of the substrate 11 so as to be vertically symmetrical with the substrate 11 interposed therebetween. Although the structures 13 and 23 have the same width (d), they may be structured as illustrated in FIG. 6 instead. For convenience, FIG. 6 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 6, the basic structure of the semiconductor laser (laser bar) according to this modification is the same as that of the first embodiment. That is, the mesa structures 13 and 23a are formed on the lower surface 11a and the upper surface 11b of the substrate 11 at the same upper and lower positions with the substrate 11 in between. However, in this modification, the lateral width of the mesa structure 23a formed on the upper surface 11b of the substrate 11 is made wider than the lateral width (d) of the mesa structure 13 formed on the lower surface 11a. Specifically, the width (d) of the mesa structure 13 formed on the lower surface 11a is about “200 μm”, whereas the width of the mesa structure 23a formed on the upper surface 11b is about “201 to 450 μm”, for example. More preferably, it is set to a range of about “250 to 300 μm”. Depending on the material of the substrate 11, the material of the mesa structure 23 a serving as a dummy, and the film characteristics as an epitaxial film (mesa structure 13), the lower surface 11 a and the upper surface 11 b of the substrate 11 are formed by using such an element structure. It becomes possible to balance the stress applied to the laser beam, and as a result, warpage as a laser bar can be suppressed.

(Second modification)
The first embodiment may have a structure opposite to that of the first modification, that is, a structure illustrated in FIG. For convenience, FIG. 7 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 7, the basic structure of the semiconductor laser (laser bar) according to this modification is the same as that of the first embodiment. That is, the mesa structures 13 and 23b are formed on the lower surface 11a and the upper surface 11b of the substrate 11 at the same upper and lower positions with the substrate 11 in between. However, in this modification, the lateral width of the mesa structure 23b formed on the upper surface 11b of the substrate 11 is made narrower than the lateral width (d) of the mesa structure 13 formed on the lower surface 11a. Specifically, the width (d) of the mesa structure 13 formed on the lower surface 11a is about “200 μm”, whereas the width of the mesa structure 23b formed on the upper surface 11b is about “10 to 199 μm”, for example. More preferably, it is set in a range of about “100 to 150 μm”. Depending on the material of the substrate 11, the material of the mesa structure 23 b serving as a dummy, and the film characteristics as the epitaxial film (mesa structure 13), the lower surface 11 a and the upper surface 11 b of the substrate 11 are formed by using such an element structure. It becomes possible to balance the stress applied to the laser beam, and as a result, warpage as a laser bar can be suppressed.

(Third Modification)
On the other hand, in the second embodiment, as illustrated in FIG. 5, the mesa structures 13 and 33 are formed on the lower surface 11 a and the upper surface 11 b of the substrate 11 in an alternating manner with the substrate 11 interposed therebetween. The mesa structures 13 and 33 have the same lateral width. However, instead of this, a structure as illustrated in FIG. 8 may be used. For convenience, FIG. 8 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 8, the basic structure of the semiconductor laser (laser bar) according to this modification is the same as that of the second embodiment. That is, mesa structures 13 and 33a are formed on the lower surface 11a and the upper surface 11b of the substrate 11 at alternate positions with the substrate 11 in between. However, in this modification, the lateral width of the mesa structure 33a formed on the upper surface 11b of the substrate 11 is made wider than the lateral width (d) of the mesa structure 13 formed on the lower surface 11a. Specifically, the width (d) of the mesa structure 13 formed on the lower surface 11a is about “200 μm”, whereas the width of the mesa structure 33a formed on the upper surface 11b is about “201 to 450 μm”, for example. More preferably, it is set to a range of about “250 to 300 μm”. Depending on the material of the substrate 11, the material of the mesa structure 33 a serving as a dummy, and the film characteristics as an epitaxial film (mesa structure 13), the lower surface 11 a and the upper surface 11 b of the substrate 11 are formed by using such an element structure. It becomes possible to balance the stress applied to the laser beam, and as a result, warpage as a laser bar can be suppressed.

(Fourth modification)
About 2nd Embodiment, it can also be set as the structure contrary to the said 3rd modification, ie, the structure illustrated in FIG. For convenience, FIG. 9 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 9, the basic structure of the semiconductor laser (laser bar) according to this modification is the same as that of the second embodiment. That is, mesa structures 13 and 33 b are formed at alternate positions on the lower surface 11 a and the upper surface 11 b of the substrate 11 with the substrate 11 interposed therebetween. However, in this modification, the lateral width of the mesa structure 33b formed on the upper surface 11b of the substrate 11 is made narrower than the lateral width (d) of the mesa structure 13 formed on the lower surface 11a. Specifically, the width (d) of the mesa structure 13 formed on the lower surface 11a is about “200 μm”, whereas the width of the mesa structure 33b formed on the upper surface 11b is about “10 to 199 μm”, for example. More preferably, it is set in a range of about “100 to 150 μm”. Depending on the material of the substrate 11, the material of the mesa structure 33 b serving as a dummy, and the film characteristics as the epitaxial film (mesa structure 13), the lower surface 11 a and the upper surface 11 b of the substrate 11 can be obtained by using such an element structure. It becomes possible to balance the stress applied to the laser beam, and as a result, warpage as a laser bar can be suppressed.

(5th modification)
On the other hand, in the first embodiment or the second embodiment, the number of mesa structures formed on the lower surface 11a and the upper surface 11b of the substrate 11 can be different. An example is shown in FIG. For convenience, FIG. 10 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 10, in this modification, the number of mesa structures 13 formed on the lower surface 11a of the substrate 11 while basically adopting the element structure according to the first or second embodiment. In contrast, the number of mesa structures 43 formed on the upper surface 11b of the substrate is reduced. Depending on the material of the substrate 11, the material of the mesa structure 43 serving as a dummy, and the film characteristics as the epitaxial film (mesa structure 13), the lower surface 11 a and the upper surface 11 b of the substrate 11 are formed by using such an element structure. It becomes possible to balance the stress applied to the laser beam, and as a result, warpage as a laser bar can be suppressed.

(Sixth Modification)
An element structure opposite to that of the fifth modification (FIG. 10) is shown in FIG. For convenience, FIG. 11 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 11, in this modification, the number of mesa structures 13 formed on the lower surface 11 a of the substrate 11 while basically taking the element structure according to the first or second embodiment. On the other hand, the number of mesa structures 53 formed on the upper surface 11b of the substrate is increased. Depending on the material of the substrate 11, the material of the mesa structure 53 serving as a dummy, and the film characteristics as the epitaxial film (mesa structure 13), the lower surface 11 a and the upper surface 11 b of the substrate 11 can be obtained by using such an element structure. It becomes possible to balance the stress applied to the laser beam, and as a result, warpage as a laser bar can be suppressed.

(Seventh Modification)
On the other hand, when the number of mesa structures formed on the lower surface 11a and the upper surface 11b of the substrate 11 is made different, especially for the mesa structure formed on the upper surface 11b of the substrate 11, the width (mesa width) and the arrangement interval are set to a plurality. The element structure set in the embodiment is also effective. An example is shown in FIG. For convenience, FIG. 12 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 12, in this modification, as the mesa structure formed on the upper surface 11b of the substrate 11, two kinds of mesas such as a mesa structure 63a and a mesa structure 63b having different widths (mesa widths) and arrangement intervals are used. The structure is adopted. Depending on the material of the substrate 11, the material of the mesa structures 63 a and 63 b serving as the dummy, and the film characteristics as the epitaxial film (the mesa structure 13), such an element structure allows the lower surface 11 a and The stress applied to the upper surface 11b can be balanced, and as a result, warpage as a laser bar can be suppressed.

(Eighth modification)
Further, when adopting mesa structures having different widths (mesa widths) and arrangement intervals as the mesa structures formed on the upper surface 11b of the substrate 11 as described above, for example, the structure illustrated in FIG. 13 is also effective. For convenience, FIG. 13 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 13, in this modification, the mesa structure formed on the upper surface 11 b of the substrate 11 has an aspect in which the width (mesa width) and the disposition interval sequentially increase from the center to both sides, or An element structure in which mesa structures 73a, 73b, and 73c to be the repetitive pattern are formed is adopted. Depending on the material of the substrate 11, the material of the mesa structures 73 a, 73 b, and 73 c serving as the dummy, and the film characteristics as the epitaxial film (mesa structure 13), the lower surface 11 a and the upper surface of the substrate 11 may be affected by such an element structure. The stress applied to 11b can be balanced, and as a result, warpage as a laser bar can be suppressed.

(Ninth Modification)
FIG. 14 shows an element structure opposite to that of the eighth modification (FIG. 13). For convenience, FIG. 14 is also shown as a diagram corresponding to FIG. 3B in the manufacturing process.

  As shown in FIG. 14, in this modification, the mesa structure formed on the upper surface 11 b of the substrate 11 has an aspect in which the width (mesa width) and the disposition interval are narrowed sequentially from the center to both sides, or An element structure in which mesa structures 83a, 83b, and 83c to be the repeated patterns are formed is adopted. Depending on the material of the substrate 11, the material of the dummy mesa structures 83a, 83b and 83c, and the film characteristics as the epitaxial film (mesa structure 13), the lower surface 11a and the upper surface of the substrate 11 may be affected by such an element structure. The stress applied to 11b can be balanced, and as a result, warpage as a laser bar can be suppressed.

(Other embodiments)
In addition, there are the following elements that can be changed in common with each of the above embodiments and each of the above modifications.

  -In particular, the dummy mesa structure formed on the upper surface 11b of the substrate 11 basically has some regularity through the first and second embodiments and the first to ninth modifications. Although various forms of arrangement in the form have been illustrated, the arrangement is not necessarily limited to these aspects, and the arrangement may be irregular. In short, it is only necessary that the stress applied to the lower surface 11a and the upper surface 11b of the substrate 11 can be balanced through the provision of the dummy mesa structure, and the warpage as a laser bar can be suppressed.

  In each of the above embodiments (the same applies to the above-described modifications), the lower electrode 16 formed on the lower surface side of the semiconductor substrate 11 and the upper electrode 26 formed on the upper surface side of the substrate 11 have different compositions. Although it is made of a multilayer film, these electrodes may be films made of the same composition.

  In each of the above-described embodiments (the same applies to the above-described modifications), a laser bar having a lateral width L (FIG. 2) of about 10 mm is passed through a mesa structure (first mesa structure) 13 formed on the lower surface 11a of the semiconductor substrate 11. In this example, the semiconductor laser array having “19” emission points is formed. However, the number of these emission points is arbitrary. In a laser bar having a width of about 10 mm, normally, 19 to 49 light emission points are formed as described above, and an arbitrary number of light emission points can be provided within this range. In this case, as the number of light emitting points increases, the width d of the mesa structure 13 and the arrangement interval (pitch) t shown in FIG. Further, the lateral width L as a laser bar is not limited to the above-described about 10 mm, and is arbitrary.

  In each of the above-described embodiments (the same applies to the above-described modified examples), a semiconductor laser (laser bar) having an active layer, that is, a mesa structure (first mesa structure) 13 having an element function as a light emitting unit is used. Although the case where the semiconductor element according to the invention is applied has been described, the semiconductor element to which the element structure of the invention can be applied is not limited to the semiconductor laser. In other words, the present invention can be applied to all semiconductor elements having a mesa structure, and by applying the present invention, it becomes possible to eliminate and mitigate the warpage of the substrate caused by the mesa structure.

  In this case, depending on the semiconductor element to be applied, both of the mesa structures formed on both sides of the semiconductor substrate may have an active layer and have an element function. Both of the formed mesa structures may be dummy mesa structures having no element function. In short, any structure in which the mesa structure is formed on both surfaces of the substrate in a manner in which the warpage of the semiconductor substrate is eliminated may be used. In that sense, for example, the semiconductor laser (laser bar) also removes the epitaxial film 12 depending on the depth of mesa etching and the film thickness of each layer, as illustrated in FIG. 15 as a diagram corresponding to FIG. Instead, for example, the mesa structure 13a may be formed in the same manner as or similar to the dummy mesa structure 23.

1 is a partial cross-sectional side view schematically showing an enlarged part of a first embodiment in which a semiconductor element according to the present invention is applied to a semiconductor laser (laser bar). FIG. 3 is a side view schematically showing the entire semiconductor laser (laser bar) according to the first embodiment in a reduced scale. (A) And (b) is sectional drawing which shows typically the manufacturing process of the semiconductor laser (laser bar) concerning the same 1st Embodiment. (A)-(c) is sectional drawing which shows the manufacturing process typically about the semiconductor laser (laser bar) concerning the said 1st Embodiment, (d) is a side view which shows the side structure finally cleaved. FIG. 5 is a cross-sectional view schematically showing a partially enlarged cross-sectional structure of a second embodiment in which the semiconductor element according to the present invention is applied to a semiconductor laser (laser bar), corresponding to FIG. Figure. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 1st modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 2nd modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 3rd modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 4th modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 5th modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 6th modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 7th modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacturing process about the 8th modification of each above-mentioned embodiment. Sectional drawing which expands a part of sectional structure typically as a figure corresponding to Drawing 3 (b) of a manufacture process about the 9th modification of each above-mentioned embodiment. The partial cross section side view which expands and partially schematically shows the further embodiment of each said embodiment (each modification is also included). The partial cross section side view which expands and a part typically shows about the conventional semiconductor laser (laser bar). (A)-(c) is sectional drawing which shows typically the manufacturing process of the conventional semiconductor laser (laser bar). (A)-(b) is sectional drawing which shows the manufacturing process typically about the conventional semiconductor laser (laser bar), (c) is a side view which shows the side structure finally cleaved. FIG. 6 is a side view schematically showing the whole of a conventional semiconductor laser (laser bar) in a reduced scale.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 11a ... Lower surface, 11b ... Upper surface, 11c ... Cleaved surface, 12 ... Epitaxial film, 12a, 12c ... Cladding layer, 12b ... Active layer, 13 ... Mesa structure (1st mesa structure), 23, 23a, 23b, 33, 33a, 33b, 43, 53, 63a, 63b, 73a to 73c, 83a to 83c ... mesa structure (second mesa structure), 14 ... insulating film, 15 ... window (opening), 16 ... bottom Electrode, 26 ... upper electrode.

Claims (23)

A semiconductor element in which one or more mesa structures, which are external structures having steep cliffs on both sides of a flat top, are formed on both upper and lower surfaces of a semiconductor substrate. The first mesa structure formed on one surface of the semiconductor substrate is a mesa structure having an element function including an active layer, and the second mesa structure formed on the other surface of the semiconductor substrate includes an active layer. The semiconductor element according to claim 1, wherein the semiconductor element has a dummy mesa structure. The semiconductor element according to claim 2, wherein the first mesa structure and the second mesa structure are formed symmetrically with the semiconductor substrate interposed therebetween. 3. The semiconductor element according to claim 2, wherein the first mesa structure and the second mesa structure are formed in such a manner that the mesa structures having the same width are alternately formed with the semiconductor substrate interposed therebetween. The semiconductor element according to claim 2, wherein the first mesa structure and the second mesa structure are formed such that at least one of a width and an arrangement interval as the mesa structure is different from each other. The semiconductor element according to claim 5, wherein the second mesa structure has a width wider than that of the first mesa structure. The semiconductor element according to claim 5, wherein the second mesa structure has a width narrower than a width of the first mesa structure. The semiconductor element according to claim 6, wherein the first mesa structure and the second mesa structure are formed in such a manner that the centers of the apexes coincide with each other across the semiconductor substrate. The semiconductor element according to claim 6, wherein the first mesa structure and the second mesa structure are alternately formed with the semiconductor substrate interposed therebetween. The semiconductor element according to claim 5, wherein the first mesa structure and the second mesa structure are formed in different numbers. The semiconductor element according to claim 10, wherein the second mesa structure is formed with a smaller number than the first mesa structure. The semiconductor element according to claim 10, wherein the second mesa structure is formed in a larger number than the first mesa structure. The semiconductor element according to claim 5, wherein the second mesa structure is formed in a mode in which a width of the mesa structure is partially different from a center portion to an end portion of the semiconductor substrate. The semiconductor element according to claim 5, wherein the second mesa structure is formed in such a manner that a width of the mesa structure is gradually increased from a center portion to an end portion of the semiconductor substrate. The semiconductor element according to claim 5, wherein the second mesa structure is formed in such a manner that a width of the mesa structure is gradually narrowed from a center portion to an end portion of the semiconductor substrate. The semiconductor element according to claim 5, wherein the second mesa structure is formed in a mode in which an arrangement interval is partially different from a center portion to an end portion of the semiconductor substrate. The semiconductor element according to claim 5, wherein the second mesa structure is formed in such a manner that an arrangement interval is gradually increased from a central portion to an end portion of the semiconductor substrate. The semiconductor element according to claim 5, wherein the second mesa structure is formed in such a manner that an arrangement interval is gradually narrowed from a center portion to an end portion of the semiconductor substrate. The semiconductor element according to any one of claims 2 to 18, wherein both the first mesa structure and the second mesa structure are formed such that a top height thereof is in the range of several tens of nanometers to several micrometers. . The first mesa structure forms a semiconductor laser in which the active layer sandwiched between cladding layers serves as a light emitting portion, and the semiconductor element is a laser bar in which the semiconductor lasers are arrayed on the semiconductor substrate. The semiconductor element as described in any one of Claims 2-19. A method of manufacturing a semiconductor device in which one or more mesa structures, which are external structures having steep cliffs on both sides of a flat top on one side of a semiconductor substrate, are formed,
When forming the mesa structure on the semiconductor substrate, the mesa structure is also formed on the other surface of the semiconductor substrate, and the warp of the semiconductor substrate is absorbed through adjustment of the formation mode of the mesa structure on the other surface. A method for manufacturing a semiconductor device, comprising: The mesa structure formed on one surface of the semiconductor substrate is a mesa structure having an element function having an active layer, and the adjustment mesa structure formed on the other surface of the semiconductor substrate is a dummy mesa having no active layer. The method for manufacturing a semiconductor element according to claim 21, wherein the structure is a structure. The mesa structure including the active layer is formed as a semiconductor laser that becomes a light emitting portion with the active layer sandwiched between cladding layers, and the semiconductor element is a laser bar in which the semiconductor laser is arrayed on the semiconductor substrate. The method for manufacturing a semiconductor element according to claim 22.

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