KR101752408B1 - nitride semiconductor device and method for forming cleavage plane of the same - Google Patents

Abstract

A nitride semiconductor device having a cleavage plane induction structure and a method of forming a cleavage plane thereof, the nitride semiconductor device including a substrate, a first semiconductor layer formed on the substrate, an active layer formed on the first semiconductor layer, a ridge A second semiconductor layer on which a cleavage plane inducing structure is formed on one side of the ridge, and an electrode formed on the ridge.

Description

[0001] The present invention relates to a nitride semiconductor device and a method of forming a cleavage plane thereof,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor device, and more particularly, to a nitride semiconductor device having a cleavage plane induction structure and a method of forming a cleavage plane thereof.

Generally, laser light of a semiconductor laser device is being put to practical use in places such as optical communication, multiple communication, and space communication.

Such a semiconductor laser device is used as a means for transferring, recording, and reading data in a communication field such as optical communication or an apparatus such as a compact disk player (CDP) or a digital versatile disk player (DVDP) Widely used.

Among them, a nitride semiconductor laser device is of particular interest because of its direct transition type in which the transition method has a high probability of laser oscillation and is capable of blue laser oscillation.

The semiconductor laser device basically has a structure having an active layer made of InGaN of a multi-layered quantum well (MQW) structure between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, It is determined to increase or decrease the In composition ratio of the active layer.

Such a semiconductor laser device has a structure in which an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer are sequentially formed on a sapphire or GaN substrate surface and a ridge stripe is formed in a part of the p- Lt; / RTI >

The conditions of the material used for each of the laser devices are such that the energy gap Eg of the semiconductor layer material must be larger than the energy gap of the active layer in order to confine carriers (electrons and holes) in the active layer to obtain an inversion distribution state, In order to confine light in the active layer, the refractive index of the material of the semiconductor layer can be made smaller than the refractive index of the active layer material.

The most widely used N-type semiconductor layer is composed of GaN or AlxGa1-xN doped with Si impurities. The active layer structure includes a quantum well (QW) layer and a quantum barrier (QB) Layer is a multi-quantum well (MQW) layer.

The material composition of the quantum well layer is mainly composed of InxGa1-xN (0 < x < 1) and the quantum barrier layer constituent is composed of InyGa1-yN (0? Y <1, x> y) having a lower In composition than the quantum well layer .

The P-type semiconductor layer is made of GaN or AlxGa1-xN doped with Mg impurities. Each semiconductor layer is composed of a superlattice structure for repeatedly growing GaN and AlxGa1-xN, or a bulk structure of GaN or AlxGa1-xN As shown in Fig.

Recently, as the demand and interest for large-capacity and highly integrated recording / reproducing of optical storage devices have increased, much research has been conducted.

In order to increase the recording density of optical storage, there is a technology for a semiconductor laser device for optical pickup having a short wavelength of 405 nm or shorter based on a GaN semiconductor and a technique for development of a high power laser device of 300 mW or higher in pulse driving for recording and reproduction Studies are underway.

Generally, in such a high output laser device, some energy of the laser is absorbed to the forward cleavage surface during the emission of the laser through facet portion of the front, and deterioration occurs frequently.

For this reason, the front cleavage surface undergoes a catastrophic optical damage (COD), which eventually leads to damage and breakage of the front cleavage surface, resulting in shortening the reliability and lifetime of the laser device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a nitride semiconductor device capable of stably and easily separating a nitride semiconductor device in the form of a chip bar while maintaining the size of a window region constant using a wall modification inducing structure and a method of forming a cleavage surface thereof.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the precise forms disclosed. .

A nitride semiconductor device according to the present invention comprises a substrate, a first semiconductor layer formed on the substrate, an active layer formed on the first semiconductor layer, a ridge formed on the active layer, A second semiconductor layer on which a cleavage plane inducing structure is formed, and an electrode formed on the ridge.

The cleavage plane inducing structure may have a height equal to the height of the ridge, and the cleavage plane inducing structure may be located on a region of the upper surface of the second semiconductor layer adjacent to the cleavage plane.

The cleavage plane inducing structure may have a first side located on the same surface as the cleavage plane, a second side parallel to and opposite to the first side, and a second side opposite to the first side, A third side surface that is perpendicular to the side surface and is connected to the first side and the second side surface; and a third side surface facing the third side surface and being spaced apart from the second side surface toward the first side surface, And a fourth side connected to the two side surfaces.

Here, the cleavage plane inducing structure is made of the same material as the ridge, and an insulating film or a metal film may be formed on the cleavage plane inducing structure.

The cleavage surface inducing structures may be disposed one at a time, and a top surface of the ridge may be formed to expose a part of the ridge surface, and the cleavage surface inducing structure may be positioned on the same line as the window.

The nitride semiconductor device and the method of forming a cleavage surface thereof according to the present invention include the steps of forming an epitaxial layer including a first semiconductor layer, an active layer, and a second semiconductor layer on a substrate; forming an epitaxial layer on the ridge region and the cleavage- Forming a ridge and a cleavage surface inducing structure by etching the epitaxial layer to a predetermined depth using the metal electrode as a mask; forming an insulating film on the entire surface of the epi layer including the ridge and cleavage surface inducing structure; Etching the metal electrode to expose a metal electrode formed on the ridge and cleavage surface induction structure; etching the metal electrode to form a window to expose a portion of the ridge and exposing the cleavage surface inducing structure; And forming a cleavage surface by performing a cutting process.

Here, the top surface of the cleavage plane inducing structure may be any one of an equilateral triangle, an isosceles triangle, a right triangle, an obtuse triangle, or a shape in which two triangles selected therefrom face each other.

Other objects, features and advantages of the present invention will become apparent from the detailed description of embodiments with reference to the accompanying drawings.

The nitride semiconductor device according to the present invention and the method for forming the cleavage plane thereof have the following effects.

Disclosed is a method for separating a window region into a predetermined size in a process of manufacturing a laser diode chip bar. The method can effectively reduce scattering of optical characteristics and reliability characteristics, and can produce a laser diode in a large quantity without deteriorating the yield. .

Further, when the cleavage plane of the high power laser diode having the window structure is formed, the cleavage plane having a constant window area can be easily formed.

Further, in the ridge forming process, since the cleavage surface inducing structure is formed at the same time, no additional process is required, and a window of a predetermined size can be simply formed.

These characteristics make it possible to effectively prevent the increase in the scattering of the reliability characteristics and the reduction in the yield, which may occur due to the failure to form the window region normally during the chip bar manufacturing process of the laser diode, thereby facilitating mass production.

Figs. 1A to 1K are a cross-sectional view and a plan view showing a manufacturing process sequence of a ridge type laser diode forming a window structure
2A to 2C are plan views showing a process of dividing a semiconductor wafer into a chip bar
Figs. 3A to 3C are diagrams showing a deviation of a cleavage plane by cracks
Figs. 4A to 4C are diagrams showing the formation of an abnormal window region in cleavage plane derailment
FIGS. 5A to 5K are cross-sectional views and plan views showing a manufacturing process sequence of a ridge type laser diode forming a window structure according to the present invention.
6A to 6C are plan views showing a process of dividing a semiconductor chip of a semiconductor laser device according to the present invention;
Fig. 7 is an enlarged sectional view of the semiconductor laser device according to the present invention
8A to 8C are views showing a process of forming a cleavage surface according to the present invention

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

Generally, in the case of a semiconductor laser device, a method of minimizing the current flow by increasing the bandgap by doping the region adjacent to the front cleavage plane of the semiconductor laser device is used in order to prevent deterioration of the front cleavage plane.

However, since the method of preventing the front cleavage surface deterioration is technically difficult, there is a tendency to complicate the entire manufacturing process of the semiconductor laser device, and the effect of preventing the front cleavage surface deterioration of the semiconductor laser device manufactured using the deterioration preventing method is sufficient I could not say.

In order to exhibit the above effect, there is also a method of etching the p-type ohmic electrode layer adjacent to the front cleaved surface of the semiconductor laser device to form a window structure having no electrode on the front cleavage surface to block the current flow .

1A to 1K are a cross-sectional view and a plan view showing a manufacturing process sequence of a ridge type laser diode forming a window structure.

First, as shown in FIG. 1A, a single crystal wafer 10 having a laser diode structure is prepared by an epitaxial growth method.

1B, a first mask layer 20 is formed on the wafer 10 to expose the ridge region of the wafer 10.

1C, a metal electrode layer for forming a p-type ohmic electrode is formed on the entire surface including the exposed ridge region, and a metal electrode 30 is formed in the ridge region by a lift-off process.

Next, as shown in FIG. 1D, the wafer is dry-etched to a predetermined depth using the metal electrode 30 as a mask to form a ridge.

Next, as shown in FIG. 1E, an insulating film 40 is formed on the entire surface including the ridge by a CVD method or a PVD method.

1F, a photoresist layer 50 is formed on the insulating layer 40 and hard baked. Thereafter, as shown in FIG. 1G, the photoresist layer 50 is dry-etched, Thereby exposing the insulating film 40 of the ridge region.

1H, the exposed insulating film 40 is etched-back to expose the metal electrode 30 in the ridge region, and then, as shown in FIG. 1I, In order to form a window, a second mask layer 60 is formed to expose the window region of the ridge.

Then, as shown in FIG. 1J, the metal electrode of the exposed window region is removed by wet etching to expose the ridge of the wafer 10, and then, as shown in FIG. 1K, the remaining second mask layer 60 are removed, the electrode on the ridge can form a partially removed window region.

In this manner, a semiconductor laser device can be manufactured by forming a window structure on the ridge top and then passing through a general laser diode process.

2A to 2C are plan views showing a process of dividing a semiconductor chip into semiconductor chips.

As shown in FIG. 2A, the ridges are formed side by side at regular intervals in one direction of the single crystal wafer, a p-type electrode pad is formed on each ridge, and a window region is formed between the p-type electrode pads have.

Then, as shown in FIG. 2B, one of the single crystal wafers is scratched by a scribing method.

At this time, the formed scratch must pass through the center between the adjacent p-type electrode pads.

The reason for this is that the window region formed between the p-type electrode pads is divided into half, resulting in a window region of two chip bars.

Thereafter, as shown in FIG. 2C, when the wafer is cut through the breaking method, a cleavage plane is formed, and a plurality of chip bars are formed.

As described above, in the separated chip bar, there is a window region in which a p-type ohmic electrode is not formed in the upper portion of the ridge, and this region is divided together with the chip bars positioned in the front and back.

As described above, in the case of the laser diode employing the window structure, the p-type contact epi layer is exposed at the upper part of the front cleavage surface, and the p-type ohmic electrode is formed only at the upper part of the ridge with a certain distance.

In the case of a semiconductor laser device formed by such a method, a semiconductor laser diode having constant characteristics is required to form a cleaved surface by sharing the front and rear chip bars halfway with each other in the window region.

However, in the laser diode having such a structure, it is very difficult for the division of the window region to be divided in half by the front and rear chip bars.

This is because, even if the chip bar is divided by scratching the area of the center by the scribing method, the delamination in the direction of the cleavage progression occurs when the cleavage plane is formed.

There are various causes of such deviation. Among them, a typical deviation is a slanting crack.

Figs. 3A to 3C are views showing delamination of a cleavage plane by a crack. Fig.

3A is a view showing a case where a chip bar manufacturing process of a laser diode is not properly performed due to a skewed crack.

Generally, various kinds of cracks are generated in the finished wafer, and as shown in Fig. 3A, a skewed crack may appear.

In this way, the slanting cracks generated in each part of the wafer cause the derailment in the cleavage plane forming process.

When the cleavage surface is formed, the cleavage proceeds from the scratch portion to the opposite side of the scratch. However, when the cleavage crack is encountered in the middle, the cleavage direction of the cleavage surface is deviated.

At this time, the size of the generated deviations is not controllable, and the manufactured chip bar also includes a step, so that a chip bar in which a window area does not occur may occur.

FIG. 3B is a photograph showing a chip bar in which a step due to an oblique crack is generated. As shown in FIG. 3B, a cleavage plane is deviated in a direction where the cleavage plane is bent in a region where there is a slanting crack, .

FIG. 3C shows a schematic diagram of a deviation generated from the start point of the scratch.

There is a case where a single side surface scratch of the wafer is formed by the scarification method and the cleaved surface is formed by deviating along the crystal direction without going straight to the desired direction at the end of the formed scratch and proceeding in a straight line.

The hypothetical line (ii) of the cleavage plane is a normal form, but (i) or (iii) occurs abnormally.

Regardless of the presence or absence of a crack, it is impossible to control the size of a deviation occurring at the end of the scratch, and the cleavage plane can be formed by being biased to one side.

In the case where a deviation occurs due to the above-mentioned reason, the size of the window region may be differently formed before and after the chip bar.

FIGS. 4A to 4C are diagrams showing the formation of an abnormal window region in the cleavage plane cleavage. FIG. 4A is an enlarged view of the window region and shows the predicted cleavage plane formation line.

As shown in FIG. 4A, (i) and (ii) show a virtual cleavage plane forming line, in the case of (i), a cleavage is made toward the center of the window region. In case (ii) Is a predicted line of cleavage formation.

(i), as shown in FIG. 4B, the window region is divided into a predetermined size above the ridge region of the front / rear chip bar.

However, the cleavage plane proceeding in the direction of (ii) has a window formed in a shape as shown in FIG. 4C, so that the size of the window region of the front / rear chip bar is varied, and in some cases, the window region is not generated on one side.

Due to these problems, the window region may be abnormally divided to cause the window region to be absent or the window region to have a large or small size.

This phenomenon increases scattering of the reliability characteristics of the high power laser diode and causes a phenomenon in which the optical characteristics of the chip become uneven when the size of the window region is formed to be long, which is a factor that hinders the yield and needs improvement.

In order to form the cleavage plane uniformly without cleaving the cleavage plane, there is a method of inducing the cleavage plane by grooving around the ridge through a semiconductor process, and a method of inducing cleavage direction by making a groove in the cleavage direction of the wafer at regular intervals during scribing , Which has the disadvantage that additional processing is required in addition to the general process.

The present invention can manufacture a laser diode having a constant window area size of a ridge type laser diode employing a window structure, and separating the ridge type laser diode into a chip bar shape and having constant characteristics.

In addition, the present invention provides a method of manufacturing a semiconductor device, which uses a conventional process method as it is without any additional semiconductor process for forming a groove around the ridge and forms a structure capable of guiding the direction of the cleaved surface, Type laser diode in which a region can be divided and held.

According to the present invention, when a ridge is etched, a cleavage surface inducing structure is formed on the left or right side of the ridge, and the cleavage progression direction is constantly guided when the cleavage surface is formed without further processing, Is kept constant.

5A to 5K are cross-sectional views and plan views showing a manufacturing process sequence of a ridge type laser diode forming a window structure according to the present invention.

First, as shown in FIG. 5A, a single crystal wafer 100 having a laser diode structure formed by an epitaxial growth method is prepared.

Next, as shown in FIG. 5B, a first mask layer 200 is formed on the wafer 100 to expose the ridge region of the wafer 100 and the cleavage plane inducing structure region.

5C, a metal electrode layer for forming a p-type ohmic electrode is formed on the entire surface including the exposed ridge region and the cleavage plane inducing structure, and a metal electrode (not shown) is formed on the ridge region and cleavage plane inducing structure region by a lift- 300 are formed.

Next, as shown in FIG. 5D, the wafer is dry-etched to a predetermined depth using the metal electrode 300 as a mask to form a ridge and a cleavage surface inducing structure.

Next, as shown in FIG. 5E, an insulating film 400 is formed on the entire surface including the ridge and the cleavage plane inducing structure by a CVD method or a PVD method.

5F, a photoresist layer 500 is formed on the insulating layer 400 and then hard baked. Thereafter, as shown in FIG. 5G, the photoresist layer 500 is dry-etched, Thereby exposing the insulating film 400 in the ridge region and the cleavage plane inducing structure region.

5H, the exposed insulating layer 400 is etched back to expose the metal electrode 300 of the ridge region and the cleavage plane inducing structure. Then, as shown in FIG. 5I, A second mask layer 600 is formed to expose a window region of the ridge and a cleavage surface inducing structure region to form a window in the ridge region and expose the cleavage surface inducing structure.

As shown in FIG. 5J, the exposed window regions and the metal electrodes of the cleavage plane inducing structure region are removed by wet etching to expose the ridge of the wafer 100 and the cleavage plane inducing structure. Then, as shown in FIG. 5K , And the remaining second mask layer 600 is removed, a cleavage surface inducing structure located at and around the window can be formed on the ridge.

Here, the cleavage plane inducing structure of the present invention has the same height as the height of the ridge because the cleavage plane inducing structure and etching depth for ridge formation are the same.

However, in some cases, the height of the ridge may be different from that of the cleavage plane induction structure.

The cleavage plane inducing structure is located on a region of the upper surface of the wafer adjacent to the cleavage plane, and is formed at a predetermined distance on one side of the ridge, and is preferably located on the same line as the window.

Also, the cleavage plane inducing structure has a shape in which the upper surface area becomes narrower toward the cleavage plane direction.

That is, the cleavage plane inducing structure includes a first side located on the same surface as the cleavage plane, a second side parallel to and opposed to the first side, and a second side perpendicular to the first and second sides, And a fourth side connected to the first side and the second side so that the gap between the third side and the third side becomes gradually narrower from the second side toward the first side, have.

Further, the cleavage plane inducing structure can be made of the same material as the ridge, and in some cases, other materials can be used, but the process is complicated.

Also, an insulating film or a metal film may be formed on the cleavage plane inducing structure, because the insulating film or the metal film formed on the cleavage plane inducing structure in the process is not completely removed.

However, in the present invention, it is not necessary to completely remove the insulating film or the metal film formed on the cleavage plane inducing structure.

The cleavage surface inducing structures may then be arranged one per ridge or one per multiple ridge.

And, the top surface of the cleavage plane inducing structure may be any one of an equilateral triangle, an isosceles triangle, a right triangle, and an obtuse triangle, or two triangles selected therefrom may face each other.

FIGS. 6A to 6C are plan views showing a process of dividing a semiconductor chip into semiconductor chips according to the present invention, and FIG. 7 is an enlarged sectional view of a semiconductor laser device according to the present invention.

6A to 6C show a process of forming a scratch on one side of a wafer through a scribing method and then separating the chip directly by a breaking method.

6A shows a cleavage surface inducing structure formed on a completed wafer at regular intervals. At this time, the cleavage surface inducing structures formed on the left or right sides of each ridge, So that it is uniformly divided by the chip bar before and / or after the window area.

These cleavage guide structures may be formed one per ridge, and one per two or three ridges.

6B and 6C show a process of dividing the chip bar without derailment by the cleavage surface guide structure of the present invention.

As shown in FIG. 7, the ridge type laser diode formed in accordance with the present invention has a ridge lower end, which is a light output portion, formed in the same manner as the conventional one, and a cleavage surface inducing structure is formed in the periphery of the ridge.

This cleavage plane induction structure is electrically disconnected and does not affect the optical output characteristics of the laser diode, but is used as a guiding structure for the cleavage plane.

The ridge structure formed in the ridge etching process is etched at the same height as the height of the etched ridge. The V-shape, in which the shape gradually narrows with respect to the progress direction of the cleavage plane, This is possible.

8A to 8C are views showing a process of forming a cleavage surface according to the present invention.

As shown in FIG. 8A, when a cleavage plane is formed in an abnormal direction, the cleavage plane inducing structure meets the cleavage plane inducing structure as shown in FIG. 8B, and the direction of the cleavage plane is bent toward the inside of the structure.

This makes it possible to fabricate a high power laser diode having a constant window area, thereby reducing scattering of optical output characteristics and reducing scattering of reliability characteristics, thereby improving yield.

As described above, according to the present invention, a window region can be separated into a certain size in a process of manufacturing a chip bar of a laser diode. By effectively reducing scattering of optical characteristics and reliability characteristics, a laser diode can be mass- There are advantages to be able to.

Further, when the cleavage plane of the high power laser diode having a window structure is formed, cleavage planes having a constant window area can be easily formed.

In addition, since the cleavage surface inducing structure is formed at the same time in the ridge forming process, a window having a constant size can be formed simply because no additional process is required.

Therefore, due to these characteristics, the present invention can effectively prevent the increase in scattering of the reliability characteristics and the yield reduction that may occur due to the window region being not normally formed in the process of manufacturing the chip bar of the laser diode, thereby facilitating mass production.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments but should be determined according to the claims.

Claims (13)

Board;
A first semiconductor layer formed on the substrate;
An active layer formed on the first semiconductor layer;
A second semiconductor layer formed on the active layer, wherein a ridge is formed in a predetermined region, and a cleavage plane inducing structure is formed in one side region of the ridge; And,
And an electrode formed on the ridge,
Wherein a top surface of the ridge is formed with a window to expose a part of the ridge surface, and the cleavage surface inducing structure is positioned on the same line as the window. The nitride semiconductor device according to claim 1, wherein the cleavage plane inducing structure has a height equal to a height of the ridge. The nitride semiconductor device according to claim 1, wherein the cleavage plane inducing structure is located on a region adjacent to the cleaved surface of the upper surface of the second semiconductor layer. The nitride semiconductor device according to claim 1, wherein the cleavage plane inducing structure is narrowed in the direction of the cleavage plane. The apparatus of claim 4, wherein the cleavage plane inducing structure comprises:
A first side positioned on the same surface as the cleavage surface;
A second side opposite and parallel to the first side;
A third side perpendicular to the first and second sides and connected to the first and second sides;
And a fourth side facing the third side and connected to the first side and the second side so that a distance between the second side and the third side decreases gradually from the second side toward the first side. . The nitride semiconductor device according to claim 1, wherein the cleavage plane inducing structure is made of the same material as the ridge. The nitride semiconductor device according to claim 1, wherein an insulating film or a metal film is formed on the cleavage plane inducing structure. The nitride semiconductor device according to claim 1, wherein the cleavage plane inducing structures are arranged one by one for at least one ridge. delete Forming an epi layer including a first semiconductor layer, an active layer, and a second semiconductor layer on a substrate;
Forming a metal electrode in the ridge region of the epi layer and the cleavage plane inducing structure region;
Forming a ridge and a cleavage plane inducing structure by etching the epi layer to a predetermined depth using the metal electrode as a mask;
Forming an insulating film on the entire surface of the epi layer including the ridge and cleavage plane inducing structure;
Exposing the metal electrode formed on the ridge and the cleavage plane inducing structure by etching the insulating film;
Etching the metal electrode to form a window that exposes a portion of the ridge, and exposing the cleavage surface inducing structure; And,
And forming a cleavage plane by performing a cutting process along the cleavage plane inducing structure. The method according to claim 10, wherein in the step of forming the ridge and the cleavage plane inducing structure by etching the epi layer to a predetermined depth using the metal electrode as a mask,
Wherein the cleavage plane inducing structure and the etch depth for forming the ridge are the same. 11. The method according to claim 10, wherein the cleavage plane inducing structure is formed at a predetermined distance from one side of the ridge and is located on the same line as the window. 11. The nitride semiconductor device according to claim 10, wherein the top surface of the cleavage plane inducing structure is one of an equilateral triangle, an isosceles triangle, a right triangle, and an obtuse triangle, or two triangles selected therefrom face each other Method of forming a cleavage surface.

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