KR100774458B1 - Semiconductor laser device and method for manufacturing the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device, wherein the semiconductor laser device includes a first material layer including a buffer layer sequentially formed on a substrate, a first contact layer, a first cladding layer, and a first waveguide layer. ; An active layer formed on the first material layer and generating light; A second material layer including a second waveguide layer sequentially formed on the active layer, a second cladding layer, and a second contact layer; A ridge formed by partially etching the second clad layer to protrude in a direction perpendicular to the active layer; A dielectric film formed to cover a side surface of the protruding ridge, an upper surface and a side surface of the second clad layer, and a first contact layer etched with a mesa structure; And a protrusion formed on the dielectric layer and formed to protrude in a direction perpendicular to the active layer to protect the ridge, wherein a height h1 from the substrate to an upper surface of the protrusion is defined as By making it higher than the height h2 up to two contact layers, it is possible to protect the ridge from external shocks that may be generated during the manufacturing process of the semiconductor laser device.

Ridge, Scribing, Cleavage, First and Second Protrusions

Description

Semiconductor laser device and its manufacturing method {SEMICONDUCTOR LASER DEVICE AND METHOD FOR MANUFACTURING THE SAME}

1 is a cross-sectional view schematically showing a conventional unit semiconductor laser device;

2A to 2G are cross-sectional views illustrating a method of manufacturing a unit semiconductor laser device according to an embodiment of the present invention;

3A to 3C are views for explaining a process of separating the unit semiconductor laser device shown in FIG. 2G.

<Description of the symbols for the main parts of the drawings>

100; A substrate 120; First material layer

122; Buffer layer 124; First contact layer

126; First cladding layer 128; First waveguide layer

140; Second material layer 144; Second waveguide

146; Second clad layer 147; Ridge

148; Second contact layer 160; Active layer

170, 180; First and second electrodes 190; Dielectric film

200; projection part

The present invention relates to a semiconductor laser device, and more particularly, to a semiconductor laser device having a ridge and a method of manufacturing the same.

Semiconductor laser devices have been used in places such as optical communication, multi-communication, and space communication because of their narrow frequency range and sharpness of light. In addition, high-speed laser printing, compact disc players (CDPs) and multi-function disc players ( It is used as a light source of an optical recording / reproducing apparatus such as a DVDP or a digital versatile disk player.

Recently, high density optical storage media such as HD-DVD (High Density DVD) or BD (Blu-ray Disc) having a storage capacity of several tens of GB or more have been put into practical use. As a pick-up light source for recording information on such a high density optical storage medium or reproducing the recorded information, a high power semiconductor laser device that emits light in the 410 nm wavelength band has been developed.

Referring to FIG. 1, a high power semiconductor laser device includes a buffer layer 22, a first contact layer 24, a first cladding layer 26, a first waveguide layer 28, and an active layer 60 on a substrate 10. ), The second waveguide layer 44 and the second cladding layer 46 are sequentially stacked, and the first electrode 70 is formed at a portion of the mesa (MESA) etched on one side of the first contact layer 24. ) Is formed. In addition, a ridge 47 protruding upward is formed on the second clad layer 46, and a second contact layer 48 is formed on an upper surface of the ridge 47. Dielectric layers 90 are formed on the side surfaces of the ridges 47 and the upper and side surfaces of the second cladding layer 46 to prevent surface leakage currents, and the upper surfaces of the second contact layers 48 and the dielectric films 90. On the upper surface of the second electrode 80 is formed to be electrically connected to the second contact layer 48.

Looking at the manufacturing process of the high-power semiconductor laser device having the structure as described above, first, the buffer layer 22, the first on the substrate 10 by using a metal organic chemical vapor deposition (MOCVD) method, etc. The contact layer 24, the first cladding layer 26, the first waveguide layer 28, the active layer 60, the second waveguide layer 44, the second cladding layer 46 and the second contact layer 48 Are grown to be sequentially stacked.

Next, in order to form the first electrode 70, a portion of the second contact layer 24 is etched until the first contact layer 24 is exposed, and a portion of the second clad layer 46 is etched to form the ridge 47. . When the process of forming the mesa structure and the ridge 47 is completed, the dielectric film 90 is formed to expose the first and second contact layers 24 and 48. When the process of the dielectric film 90 is completed, the first electrode 70 is formed on the exposed portion of the first contact layer 24 and the second electrode 80 is formed on the second contact layer 48. A plurality of unit semiconductor laser elements are formed on the substrate 10 by the above-described process.

When the formation of the unit semiconductor laser device is completed, one surface of the substrate 10 is polished through a lapping and polishing process, and then the scribing process of inverting the substrate 10 to process a scribing tip ( A chip bar having a predetermined resonator length is manufactured through a scribing process.

The cleavage plane is formed by the scribing process, and the cleavage plane is used as the light exit plane. Therefore, the cleaved surface must be not only perpendicular to the active layer 60 but also maintain a smooth surface state in order to lower the threshold current I _th and increase the output.

However, since the ridge 47 is protruded, the ridge 47 is easily exposed to external shock during the manufacturing process of the semiconductor laser device, and the ridge 47 and cleaved surface may be damaged by the external shock.

In particular, during the scribing process, the scribing force is concentrated on the protruding ridge 47 so that not only the ridge 47 is damaged but also a crack is generated and may proceed to the light exit surface.

Thus, damage to the ridge 47 and the light exit surface not only reduces the electrical characteristics of the semiconductor laser device such as the threshold current or the driving voltage, but also lowers the optical properties of the semiconductor laser device such as the shape or output of the spot and thus the yield of the semiconductor laser device. It is a factor that lowers the reliability.

The present invention has been made in view of the above-described point, and an object of the present invention is to provide a semiconductor laser device capable of protecting the ridge from an external impact or load that may be generated during a manufacturing process, and a method of manufacturing the same.

Another object of the present invention is to provide a semiconductor laser device capable of preventing damage to the cleaved surface, which is a light exit surface, and a manufacturing method thereof.

Still another object of the present invention is to provide a semiconductor laser device and a method of manufacturing the same, which can increase the yield and improve the reliability.

A semiconductor laser device according to the present invention for achieving the above object, the first and second material layer formed to face each other on the substrate; An active layer interposed between the first and second material layers and generating light; And a ridge formed to protrude in a direction perpendicular to the active layer in any one material layer selected from the first and second material layers. And a protrusion formed to protrude in a direction perpendicular to the active layer to protect the ridge in the selected material layer.

According to an embodiment of the present invention, the first material layer includes a buffer layer sequentially formed on the substrate, a first contact layer, a first cladding layer, and a first waveguide layer, and the second material layer And a second waveguide layer, a second cladding layer, and a second contact layer sequentially formed on the active layer, wherein the ridge is formed by partially etching the second cladding layer, and the second contact layer is formed of the ridge. It is formed on the upper surface.

The semiconductor laser device may further include: a first electrode formed to be electrically connected to the first contact layer on a mesa flat portion etched to expose a portion of the first contact layer; A second electrode formed on the second contact layer and the protrusion to be electrically connected to the second contact layer; And a dielectric film interposed between the second electrode and the second cladding layer, between the protrusion and the second cladding layer, and covering the first cladding layer.

Here, the height h1 from the substrate to the upper surface of the protrusion is higher than the height h2 from the substrate to the second contact layer. Further, the distance between the protrusion and the ridge is preferably less than 10 μm.

The protrusion may include a first protrusion formed at one side of the ridge; And a second protrusion formed on the other side of the ridge, and formed of at least one of an insulating film and a metal film.

The object as described above, a) forming a first material layer, an active layer and a second material layer sequentially stacked on the substrate; b) forming a ridge in the second material layer to protrude in a direction perpendicular to the active layer; c) forming protrusions on the second material layer to protect the ridges; And d) forming first and second electrodes to be electrically connected to each of the first and second material layers.

According to the method of manufacturing a semiconductor laser device according to an embodiment of the present invention, the step a) includes a1) sequentially forming a buffer layer, a first contact layer, a first cladding layer, and a first waveguide layer on the substrate. Forming; a2) forming the active layer on the first waveguide layer; a3) sequentially forming a second waveguide layer, a second cladding layer, and a second contact layer on the active layer; And a4) etching the exposed portion of the first contact layer to form a mesa flat portion.

The step b) may include etching the second clad layer and the second contact layer such that the ridge protrudes in a direction perpendicular to the active layer, and the step c) may include c1) the mesa. Forming a dielectric film on a flat portion, an upper surface of the second contact layer and the second clad layer; c2) removing a portion of the mesa flat portion and a dielectric layer on the ridge top surface to expose the first and second contact layers; And c3) forming first and second protrusions protruding from the dielectric layer in a direction perpendicular to the active layer so as to be positioned at both sides of the ridge.

The step d) may include d1) forming the first electrode on an exposed portion of the mesa flat portion to be electrically connected to the first contact layer; And d2) forming the second electrode on an upper surface of the second contact layer to be electrically connected to the second contact layer.

Hereinafter, a semiconductor laser device and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 2G, a semiconductor laser device according to an embodiment of the present invention includes first and second material layers 120 and 140 formed on the substrate 100 so as to face each other, and the first and second materials. The active layer 160 interposed between the layers 120 and 140 and the first and second electrodes 170 and 180 for applying current to the first and second material layers 120 and 140. And a ridge 147 formed in the second material layer 140 to protrude in a direction perpendicular to the active layer 160, and a protrusion 200 to protect the ridge 147.

The substrate 100 is preferably a sapphire substrate which is a hetero substrate, but may be a III-IV compound semiconductor layer substrate such as GaN or SiC.

The first material layer 120 includes a buffer layer 122, a first contact layer 124, a first cladding layer 126, and a first waveguide layer 128 sequentially stacked on the substrate 100. Include.

The buffer layer 122 is formed on the substrate 100 and is formed of an undoped GaN layer. However, the buffer layer 122 may be an n-type material layer made of an N-group III-V nitride compound semiconductor.

The first contact layer 124 is formed on the buffer layer 122 and is made of an n-GaN layer. A mesa flat portion 149 partially etched to the first contact layer 124 is formed at one side of the first contact layer 124.

The first cladding layer 126 is made of an n-AlGaN layer, but may also be an n-GaN layer.

The first waveguide layer 128 is preferably a n-GaN layer as a GaN-based III-V nitride compound semiconductor layer. The first waveguide layer 128 has a lower refractive index than the active layer 160 and a higher refractive index than the first cladding layer 126.

The second material layer 140 includes a second waveguide layer 144 sequentially stacked on the active layer 160, a second cladding layer 146, and a second contact layer 148. Electron blocking layer (EBL) to prevent electrons from moving to the first waveguide layer 144 and the second cladding layer 146 between the active layer 160 and the second waveguide layer 144. ) May be formed.

The second waveguide layer 144 is preferably a p-GaN layer as a GaN-based III-V nitride compound semiconductor layer. The second waveguide layer 144 has a lower refractive index than the active layer 160 and a higher refractive index than the second cladding layer 146.

The second cladding layer 146 is a layer corresponding to the first cladding layer 126 and is formed on the second waveguide layer 144. The second cladding layer 146 is made of a p-AlGaN layer, but may also be a p-GaN layer.

The second contact layer 148 is formed on the upper surface of the ridge 147, preferably made of a p-GaN layer.

The active layer 160 is a material layer in which light is generated by carrier recombination such as electron-holes supplied from the first and second material layers 140, and has a GaN-based structure having a multi quantum well (MQW) structure. The Group III-V nitride compound semiconductor layer is composed of an InGaN layer, which is a material layer containing indium (In) in a predetermined ratio, but may be a GaN-based Group III-V nitride compound semiconductor layer.

The first electrode 170 is an n-electrode for supplying current to the first contact layer 124, and is provided to the mesa plate portion 149 etched by the mesa structure of the first contact layer 124. Is formed.

The second electrode 180 is a p-electrode for supplying current to the second contact layer 148 and is formed to cover the top surface of the second contact layer 148.

The ridge 147 is for forming a ridge waveguide structure, and is formed to protrude in a direction perpendicular to the active layer 160 by etching both sides of the second clad layer 146. The ridge 147 may be finely formed to have a width smaller than 2 μm in order to maintain the single mode characteristic of the emitted light, lower the threshold current I _th , and increase the kink level.

The dielectric layer 190 is formed on the surfaces of the left and right second clad layers 146 and the side surfaces of the ridges 147 protruding from the ridges 147. The dielectric layer 190 may be formed of an oxide including at least one element selected from Si, Al, zr, Ta, and the like.

The protrusion 200 is to protect the ridge 147 from external impact or load that may be generated in the manufacturing process of the semiconductor laser device. In particular, the protrusion 200 is scribed to the ridge 147 during the scribing process. This is to prevent the concentration of scribing force. The protrusion 200 includes first and second protrusions 200a and 200b formed on one side and the other side of the ridge 147, respectively.

First and second protrusions 200a and 200b are interposed between the second electrode 180 and the dielectric layer 190. Since the first and second protrusions 200a and 200b are disposed on the dielectric layer 190, the first and second protrusions 200a and 200b may be formed not only of an insulating film such as a silicon oxide film or a silicon nitride film but also a metal film such as a Ti film, a Zr film, and a Si film. Do. In addition, the first and second protrusions 200a and 200b may be formed in a multilayer structure including an insulating film and a metal film.

The first and second protrusions 200a and 200b are formed higher than the ridge 147 based on the substrate 100. Since the first and second protrusions 200a and 200b are formed higher than the second contact layer 148 formed on the upper surface of the ridge 147, the scribing force transmitted through the substrate 100 may be increased. The first and second protrusions 200a and 200b are distributed more. In addition, even if the first and second protrusions 200a and 200b are not formed higher than the ridge 147, when the following equation 1 is satisfied, the ridge 147 is removed from the scribing force. It can be efficiently protected.

-0.7 μm <h1-h2 <10 μm

Here, h1 is the height from the substrate to the top surfaces of the first and second protrusions 200a and 200b, and h2 is the height from the substrate 100 to the top surface of the ridge 147.

In order to more efficiently disperse the scribing force, the distance d1 (d2) between the first and second protrusions 200a and 200b and the ridge 147m is preferably less than 10 μm.

Hereinafter, the manufacturing method of the semiconductor laser element which has the above structure is demonstrated in detail.

2A to 2F, a method of manufacturing a semiconductor laser device includes a) sequentially stacking a first material layer 120, an active layer 160, and a second material layer 140 on a substrate 100. Forming; b) forming a ridge 147 on the second material layer 140 to protrude in a direction perpendicular to the active layer 160; c) forming a protrusion in the second material layer 140 to protect the ridge 147; And d) forming the first and second electrodes 170 and 180 to be electrically connected to the first and second material layers 120 and 140, respectively.

Looking at step a) in more detail, as shown in Figure 2a, the first material layer to be sequentially stacked on the substrate 100 using a metal organic chemical vapor deposition (MOCVD, MOCVD) The buffer layer 122, the first contact layer 124, the first cladding layer 126, and the first waveguide layer 128 are grown in sequence, and the first waveguide layer 128 is formed. The active layer 160 is grown on the second layer, and the second waveguide layer 144, the second material layer 140, the second cladding layer 146, and the second contact layer 148 are formed on the active layer 160. To grow. Thereafter, a portion of the first contact layer 124 is exposed to form the mesa flat portion 149, as shown in FIG. 2B, the first contact layer 124 and the first cladding layer 126. ), The first waveguide layer 128, the active layer 160, the second waveguide layer 144, and the second cladding layer 146 are etched.

Referring to FIG. 2C, the step b) will be described in more detail. In order to form the ridge 147, a mask is formed on a portion corresponding to the ridge 147, and the second contact layer 148 and the second cladding layer are formed. Etch (146). By this process, the second contact layer 148 is formed only on the upper surface of the ridge 147.

Referring to step c) in more detail, as shown in FIG. 2D, the dielectric layer 190 may be formed on all surfaces of the mesa flat portion 149, the second contact layer 148, and the second clad layer 146. To form. As shown in FIG. 2E, a portion of the mesa flat portion 149 of the first contact layer 124 and the dielectric layer 190 on the second contact layer 148 are removed. Thereafter, as illustrated in FIG. 2F, the first and second protrusions 200a and 200b are positioned at both sides of the ridge 147 by the deposition or coating process, and protrude in a direction perpendicular to the active layer 160. It is formed on the dielectric film 190 so as to.

The manufacturing process of the first and second protrusions 200a and 200b will be described in more detail. An insulating film or a metal film is formed on the upper surfaces of the ridge 147 and the dielectric film 190, and both sides of the ridge 147 are formed. The first and second protrusions 200a and 200b are formed by patterning the insulating film or the metal film on the substrate.

Referring to FIG. 2G, the step d) will be described in more detail. First, a first electrode serving as a conductive film on an exposed portion of the mesa flat portion 149 is electrically connected to the first contact layer 124. 170). Next, the second electrode (eg, to cover the top surface of the second contact layer 148 and the top surfaces of the first and second protrusions 200a and 200b to be electrically connected to the second contact layer 148). 180).

A plurality of unit semiconductor laser devices are manufactured by the above-described process, and after the process is completed, a structure in which a plurality of unit semiconductor laser devices 101 are formed on the substrate 100 as shown in FIG. Is formed.

Referring to FIG. 3B, the substrate 100 is wrapped and polished to easily separate the plurality of unit semiconductor laser devices 101.

Thereafter, as shown in FIG. 3C, the substrate 100 is turned upside down to perform a scribing process. In this case, the scribing force transmitted from the substrate 100 is distributed to the first and second protrusions 200a (200b (see FIG. 2G)) and the ridges 147 (see FIG. 2G). As such, by dispersing the scribing force previously concentrated on the ridge 147 to the first and second protrusions 200a and 200b, damage to the ridge 147 and damage to the cleaved surface, which is a light exit surface, can be prevented. It becomes possible.

According to the present invention as described above, the first and second protrusions are provided on both sides of the ridge to protect the ridge from external shocks that may be generated during the manufacturing process of the semiconductor laser device.

In particular, the scribing force applied to the ridge is reduced by the first and second protrusions dispersing the scribing force during the scribing process. Therefore, the ridge can be prevented from being damaged by the scribing force, as well as the cleavage surface, which is the light exit surface, can be prevented from being damaged by the scribing force transmitted through the ridge.

Thus, by preventing the damage of the cleaved surface, which is the ridge and the light exit surface, not only can the yield of the semiconductor laser device be improved, but also the electrical and optical properties of the semiconductor laser device can be improved. It is possible to improve the reliability.

Claims (18)

A first material layer including a buffer layer, a first contact layer, a first cladding layer, and a first waveguide layer sequentially formed on a substrate; An active layer formed on the first material layer and generating light; A second material layer including a second waveguide layer sequentially formed on the active layer, a second cladding layer, and a second contact layer; A ridge formed by partially etching the second clad layer to protrude in a direction perpendicular to the active layer; A dielectric film formed to cover a side surface of the protruding ridge, an upper surface and a side surface of the second clad layer, and a first contact layer etched with a mesa structure; And And a protrusion formed on the dielectric layer and protruding in a direction perpendicular to the active layer to protect the ridge. And a height h1 from the substrate to an upper surface of the protrusion is higher than a height h2 from the substrate to the second contact layer. The method of claim 1, wherein the second contact layer, A semiconductor laser device, characterized in that formed on the upper surface of the ridge. The method of claim 2, A first electrode formed to be electrically connected to the first contact layer on a mesa flat portion etched to expose a portion of the first contact layer; And And a second electrode formed on the second contact layer and the protrusion to be electrically connected to the second contact layer. The method of claim 3, The substrate is a sapphire substrate, The active layer is an InGaN layer, The buffer layer is an undoped GaN layer, The first and second contact layers are n-GaN layer and p-GaN layer, respectively The first and second waveguide layers are n-GaN and p-GaN layers, respectively. And the first and second clad layers are n-AlGaN layers and p-AlGaN layers, respectively. delete The method according to any one of claims 2 to 4, The height from the substrate to the upper surface of the protrusion is defined as h1, and when the height from the substrate to the second contact layer is defined as h2, the following equation satisfies: Equation  -0.7 μm <h1-h2 <10 μm The method according to any one of claims 1 to 4, The distance between the protrusion and the ridge is less than 10㎛ semiconductor laser device. The said protruding part is in any one of Claims 1-4. A first protrusion formed on one side of the ridge; And And a second protrusion formed on the other side of the ridge. The said protruding part is in any one of Claims 1-4. A semiconductor laser device comprising at least one of an insulating film and a metal film. a) a first material layer comprising a buffer layer, a first contact layer, a first cladding layer and a first waveguide layer on the substrate, an active layer, a second waveguide layer, a second cladding layer and a second contact layer Sequentially forming a second material layer; b) etching a portion of the first contact layer to form a mesa flat portion; c) partially etching the second clad layer and the second contact layer to form a ridge to protrude in a direction perpendicular to the active layer; d) forming a dielectric film on top of the mesa flat portion, the second contact layer and the second clad layer, and removing a portion of the mesa flat portion and the dielectric film on the ridge top surface to expose the first and second contact layers; Making; e) forming first and second protrusions to protect the ridges on the dielectric layer in a direction perpendicular to the active layer; And and f) forming first and second electrodes to be electrically connected to the first and second material layers, respectively. delete delete The method of claim 10, And a height h1 from the substrate to an upper surface of the protrusion is greater than a height h2 from the substrate to the second contact layer. The method of claim 10, When the height from the substrate to the upper surface of the protrusion is defined as h1 and the height from the substrate to the second contact layer is defined as h2, the protrusion is formed to satisfy the following equation. The manufacturing method of the semiconductor laser element. Equation  -0.7 μm <h1-h2 <10 μm The method according to any one of claims 10, 13 and 14, And the protrusion is formed such that a distance between the protrusion and the ridge is less than 10 μm. delete The method of claim 10, And the first and second protrusions are formed of at least one of an insulating film and a metal film. The method of claim 17, wherein f), f1) forming the first electrode on an exposed portion of the mesa flat portion to be electrically connected to the first contact layer; And f2) forming the second electrode on an upper surface of the second contact layer to be electrically connected to the second contact layer.

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