JP2002246679A - Semiconductor laser element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element where yield can be improved and an original laser characteristic can be displayed and to provide the manufacturing method. SOLUTION: In multiple element main bodies 10 formed on a substrate 11, exposure areas 102 are installed with a separation position 101 when they are divided into bar shapes as a center. The exposure areas 102 are those where the insulating film 19 and the electrodes 22 to 25 of the element main body 10 are removed by wet etching and the like, and width W is not less than 10 μm. Since a scriber is not brought into contact with the insulating film 19 and the electrodes 22 and 25 even if the scriber is put in the separation position 101 at the time of division, it is prevented that they stick to a separation face being a resonator end face and smoothness is deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device composed of a compound semiconductor and a method of manufacturing the same, and more particularly to a semiconductor laser device manufactured by forming a large number on a common substrate and then separating the same. It relates to the manufacturing method.

[0002]

2. Description of the Related Art A semiconductor laser is a light emitting element that oscillates by flowing a forward current through a pn junction of a semiconductor layer and recombining electrons and holes. It is used for various applications such as video disk pickup, optical disk memory, and laser printer. The semiconductor used as the material is also a II-VI group or III-V group semiconductor compound, and each has many variations.

The semiconductor laser has a p-layer laminated on a substrate.
It has a structure in which a functional layer composed of a semiconductor layer of n-type and n-type is sandwiched between a p-side electrode and an n-side electrode. An insulating layer is provided. The insulating layer is generally made of silicon oxide (Si
This is a thin film made of an insulating material such as O ₂ ) or silicon nitride (SiN _x ), and is provided to secure electrical insulation from the surroundings or to limit a current injection region.

[0004]

The semiconductor laser device is manufactured by dividing a large number of laser chips formed simultaneously on one substrate. Specifically, a groove is formed between the chips by scribing with a diamond cutter such as a dicer or a scriber from the back side of the substrate, and the substrate is cleaved by applying an external force. First, a substrate on which a large number of semiconductor laser elements are formed in a matrix form, as shown in FIG.
The semiconductor laser device 1010 is separated into parallel bars 1100. The end face at this time corresponds to the resonator end face of the semiconductor laser device 1010.

However, when the substrate is separated into bars 1100, the surface pattern of the insulating film, the electrode, etc., at the separation position, often lacks due to the originally inferior adhesion, and is often damaged by the stress at the time of cleavage. . Such a defective portion of the insulating film or electrode reduces the adhesion of the reflective film that adheres to the end face and coats the end face, and the deterioration progresses, thereby shortening the life of the element. In addition, the end surface roughness sometimes adversely affects device characteristics such as a decrease in slope efficiency and an increase in threshold current.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor laser device capable of improving yield and exhibiting intrinsic laser characteristics and a method of manufacturing the same. It is in.

[0007]

According to the semiconductor laser device of the present invention, there is provided an element body having a cavity end face on a side surface, and an exposed region having a predetermined width between the cavity end face in a surface area of the element body. And an insulating film provided to be

The method for manufacturing a semiconductor laser device according to the present invention comprises:
A step of integrally forming the plurality of element bodies with a separation position corresponding to the cavity end face position therebetween; and at least a surface of each of the plurality of integrally formed element bodies, between the separation position. The method includes a step of forming an insulating film so that an exposed region having a predetermined width is present, and a step of individually separating element bodies along a separation position.

In the semiconductor laser device and the method of manufacturing the same according to the present invention, the device separation position is provided in the exposed region of each device body. Since the exposed area is not covered with an insulating layer,
When the element is separated, the insulating layer is not cut.
Therefore, the insulating layer does not adhere to the separation surface serving as the resonator end face.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
1 shows a configuration of a semiconductor laser according to the embodiment.
This semiconductor laser is manufactured by forming a plurality of element bodies 10 having a laser structure on a substrate, and then dividing the substrate into individual laser chips by dividing the substrate into individual element bodies 10. The element body 10 includes a buffer layer 12 on a substrate 11.
, N-side contact layer 14, n-type cladding layer 1 made of nitride III-V compound semiconductor
5, an active layer 16, a p-type cladding layer 17, and a p-side contact layer 18 are laminated, and the entire surface thereof is covered with an insulating layer 19. On the p-side contact layer 18, a p-side electrode 22 and a contact electrode 24 are provided.
On the side contact layer 14, an n-side electrode 23 and a contact electrode 25 are provided so as to be conductive through the insulating layer 19, respectively. In this semiconductor laser, the opposing surface perpendicular to the device extension direction is the cavity end surface. In this case, the insulating layer 19, the p-side electrode 22, and the n-side electrode 2
3 and contact electrodes 24, 25 are provided between the resonator end face and an exposed area 102.

In the exposed region 102, at least the insulating film 19 among the components of the element body 10 has been removed. In this case, the semiconductor layer is exposed by removing the insulating film 19 and the electrode portions 22 to 25. This exposed area 102
When the element body 10 is divided into bars in the manufacturing process, it is provided to prevent the insulating film 19 and the electrode portions 22 to 25 from being directly divided at the separation positions. The width of the exposed area 102 at this time varies strictly according to the blade width of the scriber and the accuracy of the separation position, as described later, but is, for example, about 5 μm.

Next, a method of manufacturing the semiconductor laser will be described.

(Formation of Laser Structure) FIG. 2 shows an arrangement of a laser structure of a semiconductor laser device according to the present embodiment on a substrate, and FIG. 3 shows a cross section taken along line II of FIG. This element body 10 is provided with a buffer layer 12 on a substrate 11.
Are arranged periodically, and a large number are formed at a time. The element body 10 before separation has an elongated shape so that a large number can be obtained as shown by a dotted line in the figure.

First, as shown in FIG. 4, a buffer layer 12 made of a nitride III-V compound semiconductor is grown on a substrate 11, and the nitride III A base layer 13, an n-side contact layer 14, an n-type cladding layer 15, an active layer 16, a p-type cladding layer 17, and a p-side contact layer 18 made of a -V compound semiconductor are sequentially grown.

More specifically, for example, a buffer layer 12 made of GaN is grown to a thickness of 30 nm on a substrate 11 made of sapphire having a thickness of 400 μm, and a base layer 13 made of GaN is formed.
Is grown 1.5 μm. Subsequently, an n-type contact layer 14 (4.5 μm in thickness) made of n-type GaN doped with silicon (Si) as an n-type impurity, and an n-type clad layer 15 made of n-type AlGaN doped with silicon as an impurity
(Thickness: 1.0 μm), Ga _1-x In _x N and Ga _1-y
Active layer 16 having multiple quantum well structure of In _y N
(Thickness: 50 nm), magnesium (M
g), a p-type clad layer 17 (0.8 μm thick) made of p-type AlGaN and a p-side contact layer 18 (0.1 μm thick) made of p-type GaN doped with magnesium as an impurity are sequentially grown. . As a growth method, for example, MOCVD (Metal Organic Chemical Vapor
or Deposition) method is used.

At this time, for example, trimethylaluminum gas ((CH
_{3) 3} Al), as a source gas of gallium (raw material as the gas trimethylgallium gas _{Ga) ((CH 3) 3} Ga) or triethyl gallium gas _{((C 2 H 5) 3} Ga), indium (In) Trimethyl indium gas ((CH ₃ ) ₃ In), ammonia (NH ₃ ) as a source gas for nitrogen (N), monosilane gas (SiH ₄ ) as a source gas for silicon, and bis = methylcyclo as a source gas for magnesium Pentadienyl magnesium gas (MeCp ₂ Mg) or bis cyclopentadienyl magnesium gas (Cp ₂ Mg) is used.

Further, the p-side contact layer 18, the p-type cladding layer 17, the active layer 16, the n-type cladding layer 15, and a part of the n-side contact layer 14 are selectively etched, so that the n-side contact layer 14 is formed on the surface. Expose. Thereafter, an insulating layer 19 made of an insulating material such as silicon dioxide (SiO ₂ ) or silicon nitride (SiN _x ) is formed on the entire exposed surface of the semiconductor layer thus formed. As a method of forming the insulating layer 19, for example, in addition to a normal sputtering method and a vapor deposition method, ECRCVD (Electron Cyclot
ron Resonance Chemical Vapor Deposition (Electron Cyclotron Resonance Chemical Vapor Deposition) or ECR sputtering may be used.

Next, as shown in FIG. 5, a resist film 20 having a thickness of, for example, 1 μm is formed on the entire surface of the insulating layer 19 by spin coating.

Next, as shown in FIG.
An opening 20a is formed in the insulating layer 19, and an opening 19a is formed in the insulating layer 19 by using the opening 20a as a mask, for example, using a hydrofluoric acid-based etchant.

Next, as shown in FIG. 7, after a nickel film or a platinum film is formed by, for example, an evaporation method so as to cover the entire surface of the substrate 11, an appropriate metal (for example,
A gold) film is formed, and a metal layer 21 is formed. Nickel or platinum makes good ohmic contact with the group III nitride compound. As a result, the surface of the p-side contact layer 18 exposed from the opening 19 a is covered with the metal layer 21.

Next, as shown in FIG. 8, the resist film 20 is removed using an organic solvent such as acetone.
At this time, at the same time, the portion of the metal layer 21 in contact with the resist film 20 is selectively removed (lift-off method), leaving only the portion of the metal layer 21 provided on the p-side contact layer 18. . Subsequently, the remaining metal layer 21 is subjected to a heat treatment to be alloyed to form a p-side electrode 22.
And

Next, similarly to the formation of the p-side electrode 22,
The n-side electrode 23 is formed as shown in FIG. That is, a resist film (not shown) is provided again on the entire surface of the substrate 11, and an opening 19b is formed in a region of the insulating layer 19 on the n-side contact layer 14 in the same manner as the opening 19a. continue,
For example, titanium, aluminum, platinum, and gold are sequentially deposited on the entire surface to form an n-side electrode 23.

Finally, for example, titanium and gold are selectively deposited on the p-side electrode 22 and the insulating layer 19 around the p-side electrode 22 to form a contact electrode 24. At the same time, n
The contact electrode 25 is formed on the side electrode 23 and the surrounding insulating layer 19. Thereby, the element body 10
Is formed. The contact electrodes 24 and 25 reinforce the adhesion of the p-side electrode 22 and the n-side electrode 23, respectively, and serve as a bonding pad for mounting the semiconductor laser device on a package and a die bonding electrode for the package. Can be used.

(Formation of Exposed Surface) The element body 10 thus formed is a continuous element row extending in the direction in which the p-side electrode 22 extends (the direction perpendicular to the paper surface in FIG. 3). I have. As shown in FIG. 9, this is divided perpendicularly to the spreading direction at a separation position 101 represented by a dashed line,
Although the bar is cut into a plurality of rod-shaped bars 100, an exposed region 102 is formed before the bar 100 in this embodiment.

Here, the exposed region 102 is formed as a region having a width W centered on a predetermined separation position 101 on the substrate 11. Note that the scriber separation position accuracy is ±
Since the width W is about 5 μm, the width W of the exposed region 102 needs to be set to 10 μm or more as 5 μm or more from the separation position 101. However, if the width W is large, the element body 10
And the drive voltage may be increased.
Therefore, the width W of the exposed region 102 is preferably set to 15 μm or less on both sides from the separation position 101.

Then, as in the formation of the electrodes, the substrate 1
A resist film (not shown) serving as a mask is formed on the entire surface of the substrate 1, a position corresponding to the exposed region 102 of the resist film is opened, and wet etching is performed to remove the insulating film 19 and the electrode portions 22 to 25. Thereby, the element body 10
The exposed region 102 is patterned in a stripe shape on the substrate. Therefore, the exposed region 102 is formed by the buffer layers 12 to p.
Only the semiconductor layer of the side contact layer 18 is laminated, and the surface of the semiconductor layer (here, the n-side contact layer 14 and the p-side contact layer 18) is exposed.

(Separation of Laser Structure) The thickness of the substrate 11 is 4
00 μm, and it is difficult to obtain a flat separation surface with this thickness. For this purpose, first, the element body 10 of the substrate 11
The surface on the opposite side is polished to make the substrate 11
Thin to a thickness in the range of 90 μm. Next, scribing is performed from the back surface of the substrate 11 at a separation position 101 predetermined in the exposure region 102, and a crack is formed in the substrate 11 along the separation position 101 using a scriber or the like. Further, when a force is applied to the separation position 101 to split the substrate 11, the substrate 11 is divided with a precision equal to the blade width of the scriber to form the bar 100. At this time, the insulating layer 19 and the electrodes 22 to
Since 25 is not directly divided, these defective portions do not adhere to the separation surface.

This separation surface is a surface perpendicular to the extending direction (resonator length direction) of the element body 10 and serves as a resonator end surface functioning as a reflecting mirror (see FIG. 1). In the subsequent steps, the bar 100 is further divided into the element bodies 10 and, if necessary, an AR (Anti
Reflection) coating is applied to make individual laser chips.

In the laser chip manufactured in this manner, the above-described separation surface is used as the cavity end surface, and since this surface is smooth, the slope efficiency does not decrease and the threshold current does not increase. In this way, the intrinsic characteristics of the semiconductor laser device are maintained, and at the same time, the variation among individuals is reduced. Further, since the resonator end face is smooth, AR
The adhesion of the coat film is improved, and the laser life can be extended.

According to the present embodiment, the substrate 11 is divided by forming the exposed region 102 having a width of 5 μm or more on both sides of the separation position 101 as a center.
It is possible to prevent the insulating layer 19 and the electrode portions 22 to 25 from adhering to the separation surface such as a defective portion and to make the separation surface a smooth surface. Therefore, the yield of the laser chip manufactured in this way can be improved, and the characteristics can be improved.

[Second Embodiment] FIG. 10 shows the configuration of a semiconductor laser according to a second embodiment. In this semiconductor laser, a plurality of laser structures 50 are formed on a substrate, and the substrate is divided into individual laser chips to form individual laser chips in the same manner as the semiconductor laser described in the first embodiment. It is made with. Note that, in the semiconductor laser of the present embodiment, the components are the same as those of the semiconductor laser of the first embodiment except that the n-side electrode 53 is provided on the back side of the conductive substrate 11. , Are given the same reference numerals.

In the laser structure 50, the n-side electrode 53 is
1, the entire surface of the substrate 11 is formed of a semiconductor layer having a function as a laser.
Further, in this case, the p-type cladding layer 17 and the p-side contact layer 18 are formed as narrow band-shaped ridges, and the current is confined to this width.

In order to prevent the insulating film 19 and the electrodes 22 and 53 from coming into contact with the scriber when the laser structure 50 is divided into bars, an exposed region 102 is provided here as well. In the exposed region 102, the semiconductor film is exposed by removing the insulating film 19 and the electrodes 22, 53.

Such a semiconductor laser has a laser structure 5
After a plurality of 0s are formed on the substrate, they are divided in the same manner as in the first embodiment, and are manufactured as a large number of laser chips. Therefore, in addition to FIG. 10 described above, also in this embodiment, a manufacturing method thereof will be described with reference to FIG.

First, a buffer layer 12 made of a nitride III-V compound semiconductor is grown on a substrate 11 made of, for example, GaN, and the buffer layer 12 is used as a nucleus to form a nitride III-V compound. The base layer 13 made of a semiconductor and the p-side contact layer 18 are sequentially grown. Furthermore,
A part of the p-side contact layer 18 and a part of the p-type cladding layer 17 are selectively etched to be processed into a band-shaped ridge portion thinner than the lower layer portion. Next, the insulating layer 19 is formed on the entire exposed surface of the semiconductor layer thus formed. afterwards,
As in the first embodiment, a striped opening 1 is formed in a portion of the insulating layer 19 on the p-side contact layer 18.
9a is formed. Next, the p-side electrode 22 is formed on the insulating layer 19 in the same manner as in the first embodiment. Further, an n-side electrode 53 is formed on the back side of the substrate 11. Thereby, a laser structure 50 is formed. The laser structure 50 thus formed is a continuous element row extending in the direction in which the p-side electrode 22 extends (the direction perpendicular to the plane of FIG. 10).

Then, the insulating film 19, the p-side electrode 22 and the n-side electrode 53 are removed by etching, and the exposed region 102 is patterned in a stripe shape in a region having a width W around a predetermined separation position 101. The n-side electrode 53 may be patterned at the same time as the formation of the exposed region 102 by providing a mask in the region of the exposed region 102 at the time of formation.

Next, scribing is performed at a separation position 101 defined in the exposure region 102 in advance, and a crack is formed in the substrate 11 along the separation position 101 using a scriber or the like. Further, when a force is applied to the separation position 101 to split the substrate 11, the substrate 11 is divided with a precision equal to the blade width of the scriber to form the bar 100. At this time, the insulating layer 19 or p
Since the side electrode 22 and the n-side electrode 53 are not directly divided, these defective portions do not adhere to the separation surface. This separation plane is a plane perpendicular to the spreading direction (resonator length direction) of the laser structure 50, and serves as a resonator end face that functions as a reflecting mirror (see FIG. 10). At this time, in a subsequent step, the bar 100 is further divided, and individual laser chips are manufactured.

According to the present embodiment, the exposed areas 102 having a width of 5 μm or more are formed on both sides of the substrate 11 with the separation position 101 as the center, and the substrate 11 is split. The insulating film 19, the p-side electrode 22 and the n-side electrode 53 are prevented from adhering to the substrate, and this surface can be made a smooth surface. Therefore, the yield of the laser chip manufactured in this way can be improved, and the characteristics can be improved.

As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the embodiments, and various modifications are possible. For example, in the above embodiment, a sapphire substrate and a GaN substrate are used as the substrate 11, but any type of substrate may be used.
For example, the present invention can be applied to a SiC substrate, a Si substrate, a GaAs substrate, and the like.

The element body 1 described in the above embodiment is
0 and the laser structure 50 are examples of a semiconductor laser device made of a group III-V nitride semiconductor.
The present invention can be widely applied to laser devices using other semiconductor materials and semiconductor laser devices having other structures.

[0042]

As described above, according to the semiconductor laser device and the method of manufacturing the same of the present invention, an exposed region having a predetermined width exists between the insulating film and the end face of the resonator in the surface region of the device body. Therefore, when an element formed integrally in the manufacturing process is separated, a separation position can be provided in the exposed region, and the insulating layer does not adhere to the separation surface corresponding to the resonator end face, and a smooth surface is formed. A cavity facet is formed. Accordingly, it is possible to maintain the intrinsic characteristics of the semiconductor laser device represented by the slope efficiency and to prolong the life associated with the improvement in the adhesion of the AR coat film. At the same time, variations in characteristics between individuals can be reduced, and the yield can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a view for explaining a laser structure forming step of the semiconductor laser device of FIG. 1;

FIG. 3 is a sectional view of the semiconductor laser device of FIG. 1;

FIG. 4 is a cross-sectional view for explaining a manufacturing process of the semiconductor laser device of FIG. 1;

FIG. 5 is a cross-sectional view subsequent to the step of FIG. 4;

FIG. 6 is a sectional view following the step of FIG. 5;

FIG. 7 is a sectional view following the step in FIG. 6;

FIG. 8 is a cross-sectional view subsequent to the step of FIG. 7;

FIG. 9 is a view for explaining a separation step of the semiconductor laser device of FIG. 1;

FIG. 10 is a diagram illustrating a configuration of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 11 is a view for explaining a problem in the separation of a conventional semiconductor laser device.

[Explanation of symbols]

10, 50: Element body, 11: Substrate, 12: Buffer layer, 13: Underlayer, 14: n-side contact layer, 15: n
Type clad layer, 16 ... active layer, 17 ... p-type clad layer,
18 ... p-side contact layer, 19 ... insulating layer, 20 ... resist film, 21 ... metal layer, 22 ... p-side electrode, 23, 53 ... n
Side electrodes, 24, 25: Contact electrode, 100: Bar, 101: Separation position, 102: Exposed area

Claims (6)

[Claims] 1. An element body having a resonator end face on a side face, and an insulating film provided in a surface area of the element body so that an exposed area having a predetermined width exists between the resonator end face. A semiconductor laser device. 2. An electrode is provided on a surface of the element body,
2. The semiconductor laser device according to claim 1, wherein an exposed region having a predetermined width also exists between the electrode and the resonator end face. 3. The semiconductor laser device according to claim 1, wherein the width of the exposed region is 5 μm or more. 4. The device according to claim 1, wherein the electrodes are provided on a front surface and a back surface of the element body, respectively, and an exposed region having a predetermined width exists between each of the two electrodes and the end face of the resonator. 2. The semiconductor laser device according to 1. 5. A step of integrally forming a plurality of element bodies with a separation position corresponding to a resonator end face position therebetween; and at least a surface of each of the integrally formed element bodies, A semiconductor, comprising: a step of forming an insulating film so that an exposed region having a predetermined width exists between the separation position and the semiconductor device; and a step of individually separating the element main bodies along the separation position. Laser element manufacturing method. 6. The method according to claim 5, wherein the width of the exposed region is 5 μm or more.