JP2007088503A - Semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device using a uniform ridge having a forward taper-type ridge and highly symmetric property. <P>SOLUTION: A mask pattern 11 is formed on a substrate 10 and an isotropic wet etching which does not have dependency is performed on the face orientation of crystal including at least a ä111} B face. Then, the selective etching which is selectively carried out is performed on the face orientation including at least the ä111} B face. Therefore, the substrate 10 having a ridge 10a where both sides are constituted of the ä111} B faces is manufactured by those two types of etchings. Thus, an SDH structure is formed on the substrate 10, and a semiconductor light emitting device is manufactured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device using a substrate having a forward tapered ridge portion in which two inner angles between an upper surface and a side surface are obtuse angles.

  Semiconductors using III-V compound semiconductors such as gallium arsenide (GaAs), aluminum arsenide (AlAs), indium arsenide (InAs), indium phosphide (InP), gallium phosphide (GaP), and gallium antimonide (GaSb) Lasers have an oscillation wavelength ranging from red to infrared at room temperature, and are expected to be applied to devices such as high-density optical disc light sources, optical communication devices, and laser pointers.

  In application to such a device, it is desired to further reduce the threshold current, and as one method for realizing this, an SDH (Separate Double Heterostructure) structure has been proposed. According to this, for example, a refractive index waveguide structure having an internal current confinement mechanism can be obtained by crystal growth once on a structural substrate such as a ridge substrate (Patent Document 1, Non-Patent Document 1 and Non-patent document 2). In addition, since selective growth is used, high-quality crystals can be grown on the steps and the slopes of the structure substrate.

  Conventionally, as such a structural substrate, a substrate having an inverted tapered ridge portion has been used. The reverse taper type ridge portion refers to a wedge-shaped one whose inner angle between the upper surface and the side surface is an acute angle and whose cross-sectional shape is symmetrical. When manufacturing a substrate having this reverse taper type ridge portion, a stripe-shaped ridge portion is usually formed in parallel with the <011> direction which is the reverse mesa direction, so that a normal anisotropic etchant is used. By selectively performing wet etching with respect to the crystal orientation, a ridge portion having a uniform ridge width could be obtained relatively easily.

However, in the substrate having the reverse taper type ridge portion, the height of the ridge portion is not uniform, and the height is different particularly on both side surfaces of the ridge portion. It was difficult to produce as. Due to the inclination of the top surface of the ridge, the semiconductor layer that grows in a self-aligned manner on both sides tends to have a non-uniform structure, and the position of the current blocking layer formed on both sides of the active layer is shifted or distorted in shape. Has occurred. Therefore, there is a problem that laser characteristics such as threshold current and oscillation wavelength are likely to vary and yield is poor.
Japanese Patent Laid-Open No. 61-183987 Electronics Letters Vol.32 No.7 (1996) pp.664 IEEE J. Quantum Electron. Vol.28 (1992) p4

  Therefore, a substrate having a forward taper type ridge has been studied. The forward taper type ridge portion means that the inner angle between the upper surface and the side surface is an obtuse angle and the cross-sectional shape is a trapezoid. Such a forward taper type ridge portion is formed by etching using, for example, a sulfuric acid-based etchant. However, when sulfuric acid-based etchants are used, the etching rate is high, or the etchant must be prepared with a high-accuracy mixing ratio, which makes it difficult to control the etching, resulting in large variations in the ridge width. It was. For this reason, the width of the active layer formed on the ridge portion also varies widely. In addition to this, the side surface of the ridge portion does not become a non-crystal growth surface on which crystals are difficult to grow, but also has a growth surface, and the forward taper type m has the same characteristics as the above-mentioned reverse taper type. There was a problem that it would vary.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide an SDH structure formed on a substrate having a forward tapered ridge portion having high symmetry and high structural uniformity. An object of the present invention is to provide a semiconductor light emitting device that is highly reliable and can be stably produced.

  A semiconductor light-emitting device according to the present invention has an SDH structure formed on a substrate having a forward tapered ridge portion in which two inner angles between the upper surface and the side surface are obtuse angles, and the ridge portion of the substrate. Are formed by two different types of wet etching.

  In the semiconductor light emitting device according to the present invention, the ridge portion includes a substrate formed by two different types of wet etching, so that there is little misalignment in the SDH structure and high reliability.

  According to the semiconductor light emitting device of the present invention, since the SDH structure is constructed on the substrate in which the ridge portion is formed by two kinds of different wet etching, the threshold current and the oscillation caused by the shape nonuniformity for each device. Wavelength variation is prevented, reproducibility is high, and productivity is high.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a method for manufacturing a substrate according to a first embodiment of the present invention for each step. Here, a method for manufacturing a substrate having a forward tapered ridge portion used for a semiconductor light emitting element such as a semiconductor laser or a light emitting diode will be described.

  First, as shown in FIG. 1A, for example, it is made of GaAs (gallium arsenide) to which zinc (Zn) is added as a p-type impurity, and has a thickness with a (100) plane as a main surface (with respect to the main surface). A substrate 10 having a thickness of 350 μm, for example, is prepared. Next, a mask pattern 11 is formed on the main surface of the substrate 10 corresponding to the formation region of the ridge portion (see FIG. 1C). Specifically, the mask pattern 11 is formed as follows, for example.

First, a silicon oxide (SiO ₂ ) film having a thickness of 150 nm is formed on the (100) surface of the substrate 10 by a vapor deposition method such as CVD (Chemical Vapor Deposition) method or electtonic gun vapor deposition method. A multilayer inorganic material film is formed by laminating a 10 nm silicon nitride (SiN _x ) film, and a resist film (not shown) having a thickness of 1 μm is formed on the inorganic material film by spin coating. Next, a resist film (not shown) is processed by photolithography into, for example, a large number of stripes extending in the <110> direction of the substrate 10, and this resist film is used as a mask, for example, RIE (Reactive Ion Etching). ) Or a soluble solution such as hydrogen fluoride (HF) is used to selectively remove the laminated film. Thereafter, a resist film (not shown) is removed. Thereby, the mask pattern 11 is formed.

  Note that the width of the mask pattern 11 (the width in the direction perpendicular to the extending direction) is determined in consideration of the fact that the width of the ridge portion 10a becomes equal to or less than the width of the mask pattern 11 by side etching in an etching process described later. The predetermined value is determined according to the width of the portion 10a (for example, 10 μm when the width of the upper surface of the ridge portion 10a is 4 μm). Further, the interval between stripes is set to 100 μm, for example.

  The mask pattern 11 may be any pattern that can withstand subsequent etching, and may be formed of, for example, a single layer film of silicon oxide or silicon nitride. It is also conceivable that the mask pattern 11 is composed of an organic material film such as a resist film. In that case, the adhesion between the substrate 10 and the mask pattern 11 is low, and when the substrate 10 is etched, Side etching easily proceeds from the interface with the substrate 10. Therefore, it is preferable that at least a portion of the mask pattern 11 that is in contact with the substrate 10 is formed of an inorganic material film, and it is more preferable if the mask pattern 11 is formed by a method that can improve adhesion to the substrate 10 such as an evaporation method. preferable.

  After the mask pattern 11 is formed, as shown in FIG. 1B, the first etchant having no selectivity to the constituent elements of the substrate 10 is used up to the vicinity of the desired ridge shape with respect to the substrate 10. The first wet etching was performed. This first wet etching is isotropic etching and is performed so as not to depend on the crystal plane orientation including at least the {111} B crystal plane (hereinafter referred to as {111} B plane). The process is completed before etching until the side surface of the ridge portion becomes a stable {111} B surface.

As the first etchant, for example, sulfuric acid (H ₂ SO ₄ ), hydrogen peroxide solution (H ₂ O ₂ ), and water (H ₂ O) are mixed with sulfuric acid: hydrogen peroxide solution: water = 30: 10: 500. A liquid mixture mixed at a volume ratio of This sulfuric acid-based etchant affects the shape of the side surface of the ridge portion depending on the temperature, but if used at about room temperature, for example, 20 ° C., a ridge shape having no problem can be obtained.

  Here, etching proceeds from a portion of the substrate 10 that is not covered with the mask pattern 11, and side etching also proceeds in a direction perpendicular to the <110> direction. However, as described above, the mask pattern 11 is formed of an inorganic material film to enhance the adhesion with the substrate 10, so that the side etch is prevented from progressing at these interfaces. Accordingly, the drum-shaped ridge portion 10b is formed as a whole.

  After performing the first wet etching, as shown in FIG. 1C, an element that can become a cation among the constituent elements of the substrate 10 (for example, Ga in the case of GaAs) is selectively etched. Using the second etchant, the substrate 10 is subjected to a second wet etching that causes a {111} B surface, which is an amorphous growth surface, to appear on the side surface of the ridge portion 10a. This second wet etching is selective etching that is selectively performed on the substrate 10 with respect to a plane orientation including at least the {111} B plane. Here, the non-crystal growth surface refers to a surface where the crystal growth rate is extremely slow and substantially no crystal grows.

  As the second etchant, for example, a citric acid aqueous solution in which citric acid and water are mixed at a volume ratio of 1: 1, and a hydrogen peroxide solution, a citric acid aqueous solution: hydrogen peroxide solution = 450: 150 volume. A mixed solution mixed in a ratio is used. When this citric acid-based etchant is used, the etching automatically stops when the {111} B surface appears on the side surface of the ridge portion 10a, and the side etching does not proceed any more immediately below the mask pattern 11. Thereby, for example, the forward tapered ridge portion 10a extended in the <110> direction having a {111} B side surface, a top surface width of 4 μm, and a height of 3.5 to 4.0 μm is provided. It is formed with high accuracy. Note that the citric acid-based etchant has a property that the selectivity of the etching element is lowered when the temperature is high. Therefore, in order to make the side surface of the ridge portion 10a the {111} B surface, The temperature is preferably set in the range of 0 ° C. or higher and 7 ° C. or lower, and more preferably 5 ° C. or lower.

  For the second wet etching, in addition to the citric acid-based etchant described above, one that forms a complex with an element that can be a cation among the constituent elements of the substrate 10 can also be used. Examples of such an etchant include tartaric acid, acetic acid, oxalic acid, formic acid, succinic acid and malic acid which are carboxylic acids.

  After the second wet etching, as shown in FIG. 1D, the mask pattern 11 is removed by performing dry etching such as RIE or wet etching using a solution such as a soluble chemical. Thereby, the substrate 10 having a desired ridge shape can be obtained.

  When forming the ridge portion 10a, it is preferable to adjust the height of the ridge portion 10a to be, for example, 2.0 μm or more. This is because, for example, in order to manufacture a semiconductor laser having an SDH structure using this substrate 10, the height of the ridge portion 10a is required to be 2.0 μm or more. In addition, the width of the upper surface of the ridge portion 10a is preferably adjusted to be, for example, 10 μm or less. This is because if the width of the ridge portion 10a is 10 μm or less, the width of the active layer laminated thereon can be set to about 3.0 μm, and a low threshold can be achieved.

  As shown in FIG. 2A, when only the first wet etching is performed on the inorganic material film using the mask pattern 11, the shape of the ridge portion becomes a drum shape, and the depth of the ridge portion. Since the etching proceeds in the direction, a favorable forward taper type ridge portion cannot be formed. In addition, when only the second wet etching is performed on the inorganic material film using the mask pattern 11, the etching is smoothly performed with the {111} B surface as the side surface of the ridge from the start of etching to a depth of about 1.5 μm. move on. However, if the etching is further advanced, as shown in FIG. 2B, the {111} B surface appears in other regions other than the ridge portion that has been etched flat until then, and is flat. The basal plane cannot be obtained. Incidentally, as described above, in the production of the SDH type laser, the minimum condition is that the height of the ridge portion 10a of the substrate 10 is 2.0 μm or more. In addition, when the thickness is 1.8 μm or less, it is substantially impossible to manufacture such a light emitting element.

  As described above, in order to obtain the substrate 10 having the forward tapered ridge portion 10a which is an object of the present invention, it is effective to perform a combination of two different types of wet etching as in the present embodiment. I understand.

  3A to 3D show the shape of the ridge portion when etching is performed using the mask pattern 12 made of a resist film. When only the first wet etching is performed, as shown in FIG. 3A, the side etching proceeds and the ridge portion becomes a forward tapered shape. Neither is it chemically stable. Further, as the etching proceeds, as shown in FIG. 3B, the ridge side surface tends to bend, and this method tends to cause variations in the shape of the ridge portion. When only the second wet etching is performed, as shown in FIG. 3C, a {111} B surface appears in a region other than the ridge portion, and a flat base surface cannot be obtained. . In addition, when the second wet etching is performed after the first wet etching, the shape of the ridge portion tends to be a bell shape as shown in FIG. 3D, and a flat surface is not formed. There is a case. Of course, the curved side surface of the ridge is not chemically stable.

  Thus, it can be seen that the shape of the obtained ridge portion differs depending on the material constituting the mask patterns 11 and 12 even when the same etchant is used. As described above, this is due to the difference in adhesion to the substrate 10, and it is considered that the mask pattern 12 made of an organic material film is more easily side-etched.

  Thus, according to the substrate manufacturing method of the present embodiment, two different types of wet etching, that is, the first wet etching and the second wet etching are sequentially performed. The surface can be stably a {111} B surface, and the forward tapered ridge portion 10a can be formed in a highly symmetric shape with good dimensional design.

  In particular, if at least a portion of the mask pattern 11 that is in contact with the substrate 10 is formed of an inorganic material film, the adhesion between the substrate 10 and the mask pattern 11 can be increased, and the interface between the substrate 10 and the mask pattern 11 can be increased. Therefore, it is possible to prevent side etching from proceeding. Therefore, both side surfaces of the ridge portion 10a can be more stably set as {111} B surfaces.

  Further, if the inorganic material film of the mask pattern 11 is formed by the vapor deposition method, the adhesion between the substrate 10 and the mask pattern 11 can be further improved, and both side surfaces of the ridge portion 10a can be more stably {111 } B side can be used.

(Modification)
In the first embodiment, the case where the substrate 10 is composed of GaAs doped with zinc as a p-type impurity has been described. However, GaAs doped with an n-type impurity such as silicon (Si), or undope not doped with an impurity. The substrate 10 can be manufactured in the same manner by using -GaAs.

  Further, any one of aluminum arsenide (AlAs), indium arsenide (InAs), indium phosphide (InP), gallium phosphide (GaP), and gallium antimonide (GaSb), or at least one of these In the case of a mixed crystal of Al and gallium arsenide, it can be produced similarly. Also for these, both the ones to which p-type impurities or n-type impurities are added and those to which no impurities are added can be applied.

  Further, a case where a mixed crystal containing at least one of gallium arsenide, aluminum arsenide, indium arsenide, indium phosphide, gallium phosphide, and gallium antimonide can be similarly manufactured. Of course, this case can also be used regardless of whether or not impurities are added.

[Second Embodiment]
The second embodiment of the present invention relates to a method for manufacturing a semiconductor light emitting device using the method for manufacturing a substrate according to the first embodiment, and a semiconductor light emitting device obtained thereby. The semiconductor light emitting device according to the present embodiment is embodied by the manufacturing method of the present embodiment, and will be described below.

  4A to 4D show a method for manufacturing a semiconductor light emitting element according to this embodiment for each process. Here, a semiconductor laser having an SDH structure will be described as an example. Here, the SDH structure refers to a refractive index waveguide structure in which a current confinement mechanism is provided by a discontinuous semiconductor layer formed using a structural substrate such as a substrate having a ridge portion. In the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

First, as shown in FIG. 4A, the substrate 10 having the ridge portion 10a is manufactured in the same manner as in the first embodiment. Next, a first conductive clad layer 21 made of, for example, p-type Al _x Ga _1-x As is epitaxially grown on the substrate 10 by MOCVD (Metal Organic Chemical Vapor Deposition) method. . At this time, the first conductivity type cladding layer 21 hardly grows on the side surface of the ridge portion 10a which is the {111} B surface of the non-crystal growth surface, and is separated from each other on the upper surface and both sides of the ridge portion 10a. Formed. Further, on the upper surface of the ridge portion 10a, the same {111} B surface as the side surface of the ridge portion 10a is formed at the end portion of the first conductivity type cladding layer 21, and grows as if the side surface of the ridge portion 10a is extended. .

Subsequently, as shown in FIG. 4B, by performing continuous MOCVD, that is, by switching the source gas supplied for each layer, the light guide layer 22 is formed on the first conductivity type cladding layer 21 as necessary. The active layer 23 is further grown. For the light guide layer 22, for example, an AlGaAs mixed crystal having a higher aluminum concentration than that of the active layer 23 to widen the energy gap is used. For the active layer 23, for example, an Al _y Ga _1-y As mixed crystal (x > Y) is used. Even when the light guide layer 22 and the active layer 23 are grown, the light guide layer 22 and the active layer 23 are hardly grown on the {111} B plane, and are divided on the upper surface of the ridge portion 10a and both sides thereof.

Next, as shown in FIG. 4C, a second conductivity type cladding layer 24 made of, for example, an n-type Al _x Ga _1-x As mixed crystal is formed on the active layer 23. Here, the thickness of the second conductivity type cladding layer 24 is adjusted so that the triangle on the upper surface of the ridge portion 10a is closed during the growth. Both ends of the active layer 23 are closed by the second conductivity type cladding layer 24, and current confinement and lateral light confinement are performed. In this way, an SDH structure is formed.

After the SDH structure is formed, as shown in FIG. 4D, a cap layer 25 made of n-type GaAs having a high impurity concentration, for example, and a different conductivity type, for example, p-type Al _x Ga, are formed thereon. _An auxiliary current confinement layer 26 made of _1-x As is formed. After that, the portion corresponding to the upper center of the ridge portion 10a of the auxiliary current confinement layer 26 is selectively removed in the stripe direction in which the ridge portion 10a is extended to form the conduction groove 26a. Further, an electrode (not shown) in ohmic contact with the cap layer 25 is formed on the auxiliary current confinement layer 26 through the conduction groove 26a. Further, an electrode (not shown) is provided on the back surface of the substrate 10. Thereby, the semiconductor light emitting device of the present embodiment is obtained.

  As described above, in this embodiment, since the SDH structure is constructed on the substrate 10 in which the forward tapered ridge portion 10a is formed with a highly symmetrical shape and good dimensional design, the width of the ridge portion 10a is And the thickness of the first conductivity type cladding layer 21 can control the width of the active layer 23 grown on the ridge portion 10a with high accuracy. Therefore, it is possible to reliably form a semiconductor light emitting device having a narrow resonance region.

  In addition, since the side surface of the ridge portion 10a is stably a {111} B surface, the symmetry of the semiconductor layer formed by being divided on both sides of the ridge portion 10a can be increased. Therefore, a semiconductor light emitting device having a stable threshold current and oscillation wavelength can be obtained. In particular, although not described here, when a current blocking layer is provided on both sides of the active layer 23 grown on the ridge portion 10a, the symmetry of the current blocking layer can be increased, so that a higher effect can be obtained. Obtainable.

[Third Embodiment]
The third embodiment of the present invention relates to a method for manufacturing another semiconductor light emitting device using the method for manufacturing a substrate according to the first embodiment and another semiconductor light emitting device obtained thereby. Here, a semiconductor laser having an SDH structure will be described as an example. The semiconductor light emitting device according to the present embodiment is embodied by the manufacturing method of the present embodiment, and will be described below. Moreover, in the following description, the same code | symbol is attached | subjected to the part same as 1st Embodiment, and the description is abbreviate | omitted.

  6 to 8 show the semiconductor laser manufacturing method according to the present embodiment for each process. First, the substrate 10 is manufactured in the same manner as in the first embodiment. However, in the present embodiment, the thickness of the mask pattern 11 is in the range of 250 nm to 1 μm, preferably in the range of 300 nm to 500 nm. Specifically, for example, the mask pattern 11 is formed by an inorganic material film in which a silicon oxide film having a thickness of 350 nm to 400 nm and a silicon nitride film having a thickness of 10 nm to 15 nm are sequentially stacked by an evaporation method.

  If the thickness of the mask pattern 11 is too thin, the stress between the mask pattern 11 and the substrate 10 is reduced with the decrease in the contact area between the mask pattern 11 and the upper surface of the ridge portion 10a when performing the second wet etching. As a result, the waviness is generated in the mask pattern 11 and the adhesion between the mask pattern 11 and the substrate 10 is changed. As shown schematically in FIG. 5, the side surface of the ridge portion 10a is uneven. Because it ends up. Further, if the mask pattern 11 is too thick, the mask pattern 11 is cracked and the shape of the ridge portion 10a varies due to chipping or the like. Therefore, in the present embodiment, by setting the thickness of the mask pattern 11 within the above-described range, the period of unevenness formed on the side surface of the ridge portion 10a is increased and flattened, and variation in shape due to chipping or the like is achieved. Is to prevent.

  If the thickness of the mask pattern 11 is 1 μm or less, the etching of the mask pattern 11 does not require a long time, and even when the substrate 10 is mass-produced, the manufacturing cost and the like are not affected.

After the substrate 10 is fabricated, as shown in FIG. 6, a buffer layer having a thickness of 0.6 μm made of p-type GaAs doped with zinc as a p-type impurity, for example, as in the second embodiment. 31, p-type Al _s Ga _1-s As doped with zinc as a p-type impurity (where 0 <s <1) mixed crystal having a thickness of 500 nm, a first conductivity type cladding layer 32, and zinc as a p-type impurity A p-type Al _t Ga _1-t As (provided that t <s) mixed crystal having a thickness of 35 nm and an Al _u Ga _1-u As (provided that u <t) mixed crystal An active layer 34 having a thickness of 7 nm is sequentially grown. Subsequently, for example, a light guide layer 35 having a thickness of 35 nm made of an n-type Al _t Ga _1-t As mixed crystal to which silicon is added as an n-type impurity, and n-type Al _s to which silicon is added as an n-type impurity. The lower layer portion 36a of the second conductivity type cladding layer 36 (see FIG. 8) made of Ga _1-s As mixed crystal is grown sequentially. The lower layer portion 36a is grown on the ridge portion 10a until the side surfaces meet. In addition, the thickness of the lower layer part 36a is 500 nm, for example. Each of these layers is divided and formed on the upper surface of the ridge portion 10a and on both sides thereof, as in the second embodiment.

After growing the lower layer portion 36a of the second conductivity type cladding layer 36, as shown in FIG. 7, for example, a current block made of a p-type Al _s Ga _1-s As mixed crystal to which zinc is added as a p-type impurity. The layer 37 is grown by adjusting the thickness so as to cover the side surface of the active layer 34. Here, since the side surface of the ridge portion 10a extended in the <110> direction of the substrate 10 is flat or nearly flat, the shape of each layer grown thereon also follows that, and the current blocking layer 37 is flat. It is formed with high quality and high positional accuracy. Therefore, the side surface of the active layer 34 is covered with the current blocking layer 37 with high accuracy.

After the current blocking layer 37 is formed, a 500 nm thick _first layer made of, for example, an n-type Al _s Ga _1-s As mixed crystal in which silicon is added as an n-type impurity is formed on the current blocking layer 37 and the lower layer portion 36a. The upper layer portion 36b of the two-conductivity-type cladding layer 36 is grown. At this time, when the growth proceeds to a thickness that reaches a portion where the side surfaces of the lower layer portion 36a intersect, the substrate 10 grows on the entire surface. After the upper layer portion 36b of the second conductivity type cladding layer 36 is grown, a cap layer 38 having a thickness of 6000 nm made of, for example, n-type GaAs doped with silicon at a high concentration as an n-type impurity is grown thereon. .

  After that, on the cap layer 38, for example, an alloy of gold (Au) and germanium (Ge), nickel (Ni), and gold are sequentially deposited to form the n-side electrode 39. Further, on the back side of the substrate 10, for example, nickel, platinum (Pt), and gold are sequentially deposited to form the p-side electrode 40. Thereby, a semiconductor laser having an SDH structure is completed.

  The semiconductor laser manufactured in this way operates as follows.

  In this semiconductor laser, when a predetermined voltage is applied between the n-side electrode 39 and the p-side electrode 40, a current is injected into the active layer 34 formed on the ridge portion 10a, and electron-hole recombination occurs. Causes luminescence. Here, the ridge portion 10a of the substrate 10 is formed using the mask pattern 11 having a thickness in the range of 250 nm to 1 μm, the occurrence of waviness on the upper surface of the ridge portion 10a is prevented, and the side surface is flat or It ’s close. Therefore, there is little variation in the formation position of each semiconductor layer grown on the substrate 10, and both side surfaces of the active layer 34 formed on the ridge portion 10 a are accurately covered with the current blocking layer 37. Therefore, the reactive current is prevented from flowing from the light guide layer 33 to the light guide layer 35 or vice versa, and the threshold current, the operating voltage, the oscillation wavelength, and the like are further stabilized.

  Although not specifically shown here, for example, the mask pattern 11 made of the silicon oxide film 11b is formed on the substrate 10 by changing the thickness of the silicon oxide film 11b variously from 250 nm to 380 nm. On the other hand, when the first etching and the second wet etching were performed, the mask pattern 11 did not swell during the second wet etching, and no swell occurred on the upper surface of the ridge portion 10a. Further, the side surface of the ridge portion 10a was flat. Further, after that, when a crystal was grown on the substrate 10, a flat desired surface morphology could be obtained.

  Thus, according to the present embodiment, the first wet etching and the second wet etching are performed using the mask pattern 11 having a thickness in the range of 250 nm to 1 μm, and the ridge portion 10 a is formed on the substrate 10. Since it is formed, it is possible to effectively prevent waviness in the mask pattern 11 during etching and the occurrence of unevenness on the side surface of the ridge portion 10a. Therefore, variation in shape in the ridge portion 10a can be suppressed, and the substrate 10 can be manufactured with high reproducibility. As a result, the yield of the substrate 10 can be improved.

  Further, when the semiconductor laser having the SDH structure is manufactured using the substrate 10, the variation in the formation position of each semiconductor layer can be reduced, and the current block is surely covered on both sides of the active layer 34. The layer 37 can be formed with high accuracy. Therefore, a highly reliable semiconductor laser having stable characteristics can be obtained. In addition, the yield of the semiconductor laser can be improved. As a result, when this semiconductor laser is applied to a device such as an optical integrated circuit, optical communication or a light source of an optical recording medium, the degree of freedom of application is increased, and the speed, weight, area, and area of the device are reduced. Power consumption can be realized. Also, it can be easily applied to consumers or portable devices.

(Application examples)
In the third embodiment, the mask pattern 11 is composed of an inorganic material film. However, as shown in FIG. 9, an organic material film 11b such as a resist film is further formed on the inorganic material film 11a. The mask pattern 11A may be configured to include The thickness of the mask pattern 11A is preferably in the range of 250 nm to 1 μm, and more preferably in the range of 300 nm to 500 nm.

  As the organic material film 11b, for example, a resist film used when patterning an inorganic material film to form the mask pattern 11 can be used. In that case, for example, after patterning, a part of the resist film is etched so that the total thickness of the inorganic material film 11a and the remaining resist film is 250 nm to 1 μm. Further, if the total thickness of the inorganic material film 11a and the resist film formed by coating is 1 μm or less, the whole can be made into the organic material film 11b without being removed at all.

  As described above, even when the mask pattern 11A having a structure in which the inorganic material film 11a and the organic material film 11b are sequentially stacked from the substrate 10 side is used, the mask pattern 11A undulates during etching, as in the third embodiment. Along with this, it is possible to effectively prevent the ridge portion 10a from waviness and the side surface from being uneven. In addition, since part or all of the resist film removing step can be omitted, the manufacturing cost can be reduced.

  Although not specifically shown here, even in the case of using the mask pattern 11A in which the resist film 11c having a thickness of 250 nm is stacked on the silicon oxide film 11b having a thickness of 150 nm, the second wet etching is performed. The mask pattern 11A did not swell, and no swell occurred on the upper surface of the ridge portion 10a. Further, the side surface of the ridge portion 10a was flat. Further, after that, when a crystal was grown on the substrate 10, a flat desired surface morphology could be obtained.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the method for manufacturing the substrate having the forward tapered ridge portion 10a formed with the {111} B surface is described. However, the present invention does not depend on the use of the substrate and has the same shape. Widely applicable to structural substrates. In general, wet etching often has crystal orientation dependence depending on the type of etchant. Among them, an etchant having no orientation dependency is selected for a specific crystal plane, and the first wet etching is performed. On the contrary, an etchant exhibiting selectivity for the specific crystal plane is selected to select the second etchant. Any material that performs wet etching may be used, and the present invention is not limited to the etchant in this embodiment.

  In the second and third embodiments, the specific configuration of the semiconductor laser has been described. However, the present invention grows a plurality of crystal layers on a substrate having a forward tapered ridge portion 10a. The present invention can also be applied to semiconductor lasers having other configurations. For example, although the light guide layer 22 is provided in the second embodiment, it may not be provided. In addition, a buffer layer may be inserted between the substrate 10 and the first conductivity type cladding layer 21 as in the third embodiment.

  Furthermore, in the second and third embodiments, each layer is grown on the substrate 10 by MOCVD, but other vapor phase growth methods such as MBE (Molecular Beam Epitaxy) method are used. You may make it grow by.

  In addition, in the second and third embodiments, the semiconductor laser is described as a specific example as the semiconductor device, but the present invention can also be applied to other semiconductor devices. For example, when manufacturing a field effect transistor, it can apply when forming a recess.

It is sectional drawing showing each process of the manufacturing method of the board | substrate which concerns on the 1st Embodiment of this invention. It is sectional drawing for demonstrating the characteristic part of the manufacturing method of the board | substrate which concerns on the 1st Embodiment of this invention. It is another sectional view for explaining the characteristic part of the manufacturing method of the substrate concerning the 1st embodiment of the present invention. It is sectional drawing showing each process of the manufacturing method of the semiconductor light-emitting device concerning the 2nd Embodiment of this invention. It is a fragmentary sectional perspective view for demonstrating the part which can be improved of the manufacturing method of the board | substrate which concerns on the 1st Embodiment of this invention. It is sectional drawing showing the manufacturing method of the semiconductor laser which concerns on the 3rd Embodiment of this invention. FIG. 7 is a cross-sectional view illustrating a process following FIG. 6. FIG. 8 is a cross-sectional diagram illustrating a process following the process in FIG. 7. It is sectional drawing showing the example of 1 structure of the mask pattern used in manufacture of the semiconductor laser concerning the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 10a ... Ridge part, 11, 11A ... Mask pattern, 21, 32 ... 1st conductivity type clad layer, 22, 33, 35 ... Light guide layer, 23, 34 ... Active layer, 24, 36 ... 2nd Conductive cladding layer, 25, 38 ... cap layer, 26 ... auxiliary current confinement layer, 26a ... conducting groove, 31 ... buffer layer, 37 ... current blocking layer, 39 ... n-side electrode, 40 ... p-side electrode

Claims (7)

A semiconductor light emitting device in which an SDH structure is formed on a substrate having a forward tapered ridge portion in which two inner angles between an upper surface and a side surface are obtuse angles,
2. A semiconductor light emitting device according to claim 1, wherein the ridge portion of the substrate is formed by two different types of wet etching.   As the two different types of wet etching, a first wet etching for etching up to a desired ridge shape and a second wet etching for causing an amorphous growth surface to appear on the side surface of the ridge portion are performed. The semiconductor light emitting device according to claim 1.   2. The semiconductor light emitting element according to claim 1, wherein the ridge portion has a {111} B crystal plane on the side surface.   2. The semiconductor light emitting element according to claim 1, wherein the ridge portion has a height of 2.0 μm or more and a top surface width in a direction perpendicular to the height direction is 10 μm or less.   2. The semiconductor light emitting device according to claim 1, wherein the substrate is made of gallium arsenide (GaAs).   The substrate may be any one of aluminum arsenide (AlAs), indium arsenide (InAs), indium phosphide (InP), gallium phosphide (GaP), and gallium antimonide (GaSb), or at least one of these. 2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is composed of a mixed crystal of one kind and gallium arsenide (GaAs).   The substrate includes at least one of gallium arsenide (GaAs), aluminum arsenide (AlAs), indium arsenide (InAs), indium phosphide (InP), gallium phosphide (GaP), and gallium antimonide (GaSb). 2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is composed of a mixed crystal.

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