JP2003249724A - Nitride-based compound semiconductor laser device and manufacturing method thereof - Google Patents

Abstract

[Problem] To provide a nitride-based compound semiconductor laser device having good thermal resistance characteristics and a long lifetime, and a method of manufacturing the same. Of the chip surface in contact with the solder layer for fixing to the mount member, a portion immediately above or directly below the current injection region to the active layer and a dielectric film extending from the end face of the resonator in this portion. The ratio of the length in the laser resonator length direction to the covered portion is 20% or less. In manufacturing,
A bar-shaped chip body that becomes an individual laser diode chip after division is manufactured, and the chip body including a surface that becomes a resonator end surface of each laser diode chip is sandwiched between bar-shaped jigs. A dielectric film is provided on a surface to be a resonator end surface so that the end portion protrudes from a portion of the end portion of the jig that is in contact with the chip base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride-based compound semiconductor laser device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a semiconductor laser device, heat generated in a chip (hereinafter, also referred to as an LD chip) of a laser diode (hereinafter, also referred to as an LD) during its operation is efficiently dissipated to a supporting substrate to thereby cause a temperature of a light emitting portion. In order to suppress the characteristic deterioration due to the rise, a semiconductor LD chip is mounted on a mount member using a conductive bonding agent (hereinafter, also referred to as solder). For example, a method of mounting an LD chip of a nitride-based compound semiconductor can be roughly classified into three (A, B, C) described below. 19 to 21 are schematic sectional views of the semiconductor laser device of each mounting method.

FIG. 19 shows a semiconductor laser when an LD chip using an insulating substrate such as sapphire as a substrate is die-bonded with the insulating substrate side facing the submount (p-type electrode up) (A). FIG. 3 is a schematic sectional view of the device. In FIG. 19, reference numeral 1701 denotes an insulating substrate, 19
Reference numeral 02 is a nitride-based compound semiconductor growth layer grown on the insulating substrate 1701, 1302 is a semiconductor LD chip including the insulating substrate 1701 and the semiconductor growth layer 1902, 1905 is solder, and 1904 is a back surface and solder of the insulating substrate 1701. A metal multilayer film 1610 is formed on the semiconductor LD chip side to increase the fusion bonding strength of 1905, and 1610 is an active layer.

The semiconductor laser chip 1302 is die-bonded via a submount 1205 on which a metal multilayer film 1906 is formed and a solder 1905. 21
Reference numeral 1 is an n-type electrode, and 103 is a p-type electrode. The same mounting method can be used when an insulating GaN substrate is used as the insulating substrate. The semiconductor LD chip includes a substrate and a semiconductor growth layer, but when an electrode or a metal multi-layer film is formed on the substrate or the semiconductor growth layer, the electrode or the metal multi-layer film is also included.

In FIG. 20, a conductive material is used for the substrate, and the p-type electrode 103 and the conductive substrate 20 are provided on the semiconductor growth layer 1902 side.
The n-type electrode 211 is formed on the 01 side, and the conductive substrate 2001 is formed.
So that it faces the submount (p-type electrode up),
FIG. 22 is a schematic cross-sectional view of the semiconductor laser device when die bonding is performed (B). FIG. 21 similarly uses a conductive material for the substrate and the p-type electrode 10 on the semiconductor growth layer 1902 side.
3, the n-type electrode 211 is formed on the conductive substrate 2001 side,
FIG. 11 is a schematic cross-sectional view of the semiconductor laser device when die bonding is performed so that the semiconductor growth layer 1902 faces the submount 1205 (p-type electrode down) (C).

[0006] Here, die bonding generally refers to the following steps. Usually, the solder is provided in advance on the mount member, and this is heated above the melting point, and the laser chip aligned at the predetermined position is
The molten solder is pressed with a collet, and then the solder is cooled and solidified. Through this step, the semiconductor LD chip and the mount member are bonded together with good thermal conductivity.

[0007]

Before the semiconductor LD chip is die-bonded to the mount member, the resonator end face of the LD chip may be coated with a dielectric film such as TiO ₂ , Al ₂ O ₃ or SiO _2. However, during this process,
The dielectric material also wraps around the surfaces other than the resonator end surface, and the surfaces other than the resonator end surface are also coated. FIG. 22 is a schematic view of a nitride-based compound semiconductor LD chip covered with a dielectric film in which a part of a surface to be die-bonded (hereinafter referred to as a mount surface) is wrapped around. In FIG. 22, 220
Reference numeral 1 is a mount surface, 2202 is a dielectric film covering the mount surface, and 2203 is a boundary (edge) of the dielectric film 2202.
Since the dielectric film has a lower thermal conductivity than metal, the heat dissipation effect is reduced when the surface partially covered with the dielectric film faces the submount and is die-bonded using a solder material. In particular, when there is a warpage such as a nitride compound semiconductor LD chip, the contact area with the submount is reduced and the heat dissipation effect is further reduced, and the thermal characteristics (eg, thermal resistance value) of the LD, the life, etc. Was adversely affecting.

Regarding the typical thermal conductivity, the temperature is 27 ° C.
In the case of GaN, which is a nitride-based compound semiconductor,
W / mK, used as an electrode or metal multilayer film
u is 315, Pd is 75.5, Ni is 90.5, Al is 2
37, Mo is 138, Pt is 71.4 (unit is
All W / mK). On the other hand, it is a dielectric film for coating
Al₂O₃Is 17, SiO₂Is about 1 W / mK, and Ti
O₂, ZrO₂, Ta₂O _Five, TiON, MgF₂And so on
It is a level value and is less than half that of metal (40W /
The thermal conductivity is less than or equal to mK).

The reason why the LD chip of the nitride compound semiconductor is warped will be described below. When a nitride-based compound semiconductor is grown on a growth substrate having a material and composition different from that of the nitride-based compound semiconductor, the temperature drop after growth is caused by the difference in thermal expansion coefficient between the nitride-based compound semiconductor and the growth substrate. Strain occurs in the process and the like, and as a result, the LD substrate made of the growth substrate and the nitride-based compound semiconductor has a warp. The phenomenon of warpage also appears when GaN is used for the growth substrate. It is considered that this is because the composition of GaN, which is the growth substrate, and the nitride-based compound semiconductor, which is the semiconductor growth layer, do not completely match, and the crystallinity of the GaN substrate and the semiconductor growth layer are different. To be

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the prior art, and to provide a nitride compound semiconductor laser device having good thermal resistance and long life, and a manufacturing method thereof.

[0011]

In order to achieve the above object, according to the present invention, a laser diode chip made of a nitride compound semiconductor and having a cavity end face covered with a dielectric film, and a laser diode chip are supported. A laser device of a nitride-based compound semiconductor including a mount member and a solder layer located between the laser diode chip and the mount member and fixing the two is a region for injecting a current into an active layer on a chip surface in contact with the solder layer. Directly above or below
The ratio of the length in the laser cavity length direction to the portion of this portion covered with the dielectric film extending from the cavity end face is 0.
% And 20% or less.

Heat generation of the semiconductor LD chip mainly occurs around the current injection region from the p-type electrode to the active layer. here,
A dielectric film that covers the resonator end face (dielectric film for end face coating) extends to the chip surface (mounting surface) that is in contact with the solder layer, and the portion immediately above or below the current injection region is covered with the dielectric film. In the case where the laser cavity is present, the length of the portion covered with the dielectric film with respect to the portion directly above or directly below the current injection region is set to 20% or less with respect to the laser cavity length direction, so that the generated heat can easily escape. (Improvement of thermal resistance) and characteristics such as life can be improved.

The dielectric film covering the end face of the resonator is TiO 2.₂, S
iO₂, Al₂O₃, ZrO₂, Ta₂O _Five, TiON and
MgF₂Can be made of one or more of
It

All of these materials have a thermal conductivity of 40.
Although it is as low as W / mK or less, 80% or more of the portion of the mount surface directly above or directly below the current injection region to the active layer is in direct contact with the solder layer without being covered by the dielectric, so that heat dissipation is secured. The semiconductor laser device has excellent characteristics.

To achieve the above object, the present invention also provides a method of manufacturing a laser device of a nitride-based compound semiconductor, comprising a laser diode chip made of a nitride-based compound semiconductor and having a cavity end face covered with a dielectric film. Is a bar-shaped chip raw material that becomes individual laser diode chips after division, and sandwiches the chip raw material with a bar-shaped jig, and includes the chip raw material that includes the surface that becomes the cavity end face of each laser diode chip. A dielectric film is provided on the surface of the chip original, which is the end face of the resonator, in a state where the end of the body projects beyond the portion of the end of the jig that is in contact with the original chip.

According to this method, when the dielectric film is provided, the entire surface to be the cavity end face is exposed, while the surface to be the mounting surface of each laser diode chip is exposed.
The part apart from the surface which is the end face of the resonator is not exposed by contacting the jig. Therefore, it is possible to limit the extension of the dielectric film to the mount surface while providing the dielectric film on the entire surface that becomes the resonator end surface. To suppress the ratio of the length in the laser cavity length direction of the portion of the mount surface immediately above or below the current injection region to the active layer and the portion of this portion covered with the dielectric film to 20% or less. Is also easy. There is no restriction on the material of the jig, but it is easy to manufacture if a semiconductor having a cleavage property is used.

Here, a jig having a central portion in the thickness direction having ends projecting from both sides thereof is used, and a plurality of chip raw materials and a plurality of jigs are alternately arranged, and a resonator is used. It is also possible to align the heights of the surface of the chip raw material serving as the end surface and the surface of the central portion of the end portion of the jig so that the dielectric film is provided on the surface of the chip raw material serving as the resonator end surface.

By doing so, the dielectric film can be provided on a large number of raw materials of the chip at a time, which is efficient, and the length of the portion of the mount surface covered with the dielectric film can be made constant. As a result, the characteristics of the laser device can be made uniform.

In the present invention, the semiconductor laser device represents a semiconductor LD chip mounted on a mount member and integrated.

Further, the "portion immediately above or directly below the current injection region into the active layer" will be described below, but here, the case of a stripe electrode having an effect on lateral mode stability and the like will be taken as an example.

First, the "portion directly above the current injection region to the active layer" refers to one of the upper and lower surfaces of the LD chip in the semiconductor growth layer direction, which is closer to the active layer, and "to the active layer". The “portion immediately below the current injection region” refers to the portion of the surface farther from the active layer.

23 and 24 are a schematic view of a chip having an electrode stripe structure and a schematic view of a chip having a ridge stripe structure, respectively, showing an n-type substrate 2301, a semiconductor growth layer 1902, an active layer 1610, a cavity end face 101,
The “line showing the portion directly above the current injection region into the active layer” (cross section) 2303 of the region confined by the p-type electrode 103, the insulating film 104, the insulating film, etc., and the “activity of the region confined by the insulating film, etc. The area of a line (mounting surface portion) 106 indicating a portion immediately above or below the current injection region into the layer, a portion immediately above or immediately below the current injection region into the active layer 105 (currently above the current injection region) Part). Further, when the mount surface is on the p-type electrode side, the p-type electrode side is closer to the active layer, so the p-type electrode side is the “portion directly above the current injection region”, and the area of the “portion immediately above the current injection region” is , A portion immediately above the ridge or a portion (a portion surrounded by a dotted line in FIGS. 23 and 24) narrowed by an insulating film or the like.

FIG. 25 is a schematic view of a chip having a ridge stripe structure, in which the mount surface is on the n-type electrode side. At this time, the region “immediately above or immediately below the current injection region to the active layer” 105 (currently, the n-type electrode side is far from the active layer, so it is the region immediately below) means immediately above the ridge (p-type. ) Part (the part surrounded by the dotted line in FIG. 25). Further, also in the electrode stripe structure, the “portion immediately above or directly below the current injection region” can be considered in the same manner for electrodes having other shapes such as a circle and a rectangle.

Here, the length in the laser cavity length direction of the "portion immediately above or directly below the current injection region to the active layer" on the mount surface of the LD chip is "length α", and is defined by the end face coating dielectric film. The length of the covered portion in the laser cavity length direction is defined as “length β”. That is, in the mounting surface of the LD chip, the length in the laser cavity length direction of the “portion directly above or directly below the current injection region into the active layer” and the portion thereof covered with the end face coating dielectric film The ratio refers to “length β” / “length α” (= ratio γ).

FIGS. 26 and 27 are views for explaining the “length α” and the “length β”. FIG. 26 shows a case where the dielectric film is coated in parallel to the sides of the LD chip, and there is a “portion directly above or directly below the current injection region into the active layer” in parallel to the sides of the LD chip. is there. In FIG. 26, 101 is an end face of the laser resonator, 105 is “a portion immediately above or immediately below the current injection region into the active layer”,
Reference numeral 802 indicates a region covered with a dielectric film, 2601 indicates “length α”, 2602 indicates “length β”, and 2610 indicates the resonator length direction.

Further, in FIG. 27, the side of the LD chip is coated with a dielectric film shifted from the parallel position,
Further, there is a case where there is a “portion directly above or directly below the current injection region into the active layer”, which is displaced from the parallel position with respect to the side of the LD chip. In FIG. 27, reference numeral 2702 is a crossing point (a crossing point of the boundary) between a portion coated with the dielectric film and “a portion immediately above or directly below the current injection region to the active layer”, and 2701 is a boundary. A midpoint between intersecting points 2702, and 2703 is a line that passes through the midpoint 2701 and is parallel to the side of the end surface of the LD chip.
As described above, also in the case of FIG. 27, “length α” 2601 and “length β” 2602 can be considered as in FIG. 26.

Further, in the present invention, the mount member means a component for directly mounting the semiconductor LD chip, for example, a submount for a semiconductor light emitting element chip, or a holder without using the submount. When directly loaded on the (stem, frame or package), it refers to the supporting base of the stem, the frame or the package itself.

Further, in the present invention, the solder is a material for fixing the semiconductor LD chip and the mount member. For example, with Au-based solder having a relatively high melting point, Au
Sn, AuSi, AuGa, AuGe, AuSb, Au
In the case of Ni or a solder having a relatively low melting point, In-based solders such as In, InPb, InSn, InAg and InAgPb are used.
Etc., or Sn, SnPb, SnSb, SnAg,
There are solders containing Sn such as SnAgPb and SnPbSb, and solders containing Pb such as PbSb, PbAg and PbZn.

In the present invention, the mount surface means
When die bonding a semiconductor LD chip to a holder,
It refers to the surface of the semiconductor LD chip that faces the holder with the solder in between.

In the present invention, the term "nitride-based compound semiconductor" means a III-V-based compound semiconductor in which nitrogen is the main group V element. Specifically, nitrogen is a group V element. Indicates a semiconductor having a ratio of 51% or more and 100% or less.

For example, GaN αX_1-α (0.51 ≦ α ≦
1) (X is at least 1 of P, As, Sb, Bi, etc.)
Elements containing more than one type), BNβX_1-β (0.51 ≦ β ≦
1), AlNγX_1-γ (0.51 ≦ γ ≦ 1), AlδG
a_1-δNεX_1-ε (0 <δ <1, 0.51 ≦ ε ≦ 1),
InNζX_1-ζ (0.51 ≦ ζ ≦ 1), InηGa_1-η
NμX_1-μ (0 <η <1, 0.51 ≦ μ ≦ 1), Inν
GaξAl_1-ν_-ξNτX _1-τ (0 <ν <1, 0 <ξ <
1, 0.51 ≦ τ ≦ 1).

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, a nitride compound semiconductor laser device using a GaN substrate as a substrate
The first embodiment manufactured with the mold electrode up will be described.

FIG. 1 (a) is a schematic view from the back surface (GaN substrate side) of the nitride-based compound semiconductor LD chip before die bonding used in this embodiment, and FIG. 1 (b) is
It is a schematic diagram from the surface (growth layer side). In the figure, 101 is an end face of a laser resonator, 102 is a metal multilayer film formed on an n-type electrode, 103 is a p-type electrode, 104 is an insulating film, 1
Reference numeral 06 denotes a “line indicating a portion directly above or directly below the current injection region to the active layer” (dotted line), and 105 surrounded by this dotted line indicates “a portion immediately above or immediately below the current injection region to the active layer”. Show. In the case of p-type electrode up, the back surface side (metal multilayer film 102) of the nitride-based compound semiconductor LD chip becomes the mounting surface.

FIG. 2 is a schematic diagram of a cross section of a semiconductor LD chip. In FIG. 2, 201 is an n-type GaN substrate, and in order from the substrate side, an n-GaN contact layer 202,
n-AlGaN cladding layer 203, n-GaN guide layer 204, GaInN multiple quantum well active layer 205, p-A
lGaN evaporation prevention layer 206, p-GaN guide layer 20
7, p-AlGaN cladding layer 208, and p-GaN contact layer 209 are stacked. p-cladding layer 20
8 and the p-contact layer 209 are provided with striped ridges extending in the cavity direction, and the p-type electrode 10
3 between the p-AlGaN clad layer 208 and the p-GaN contact layer 209 except for the ridge portion.
04 are provided. Here, the p-type electrode 103 is p
N-type electrode 2 with Pd and Au from the side close to the contact
Reference numeral 11 denotes Hf and Al from the substrate side, and a metal multilayer film 102 (Mo and Au from the substrate side) is provided thereon.

In the present embodiment, the semiconductor LD chip was manufactured with the above-mentioned materials, but the material is not limited to the above-mentioned materials, and a nitride-based compound semiconductor (for example, p-AlGaInN for the clad layer 208, active layer for the clad layer 208) is used. 205 for GaI
nAs, GaInNP, etc.) may be used. Further, multiple quantum wells may be used for the clad layer, and an InGaN crack prevention layer may be inserted between the n-contact layer 202 and the n-clad layer 203. As described above, the semiconductor LD chip used in this embodiment has a so-called ridge stripe type structure.

The method of manufacturing the semiconductor laser device of this embodiment will be described below. First, an LD is formed on a semiconductor LD wafer by appropriately applying the process used for manufacturing a semiconductor element. Next, the thickness of the wafer is reduced to 4 by polishing or etching from the back surface side of the n-type GaN substrate 201.
Adjust to a thin thickness of about 0 to 200 μm. This is to facilitate division of the wafer into individual LD chips in a later step. In particular, when the end faces of the laser resonator are formed by division, it is desirable to adjust the thickness to a thin thickness of about 35 to 150 μm. In this embodiment, the thickness of the wafer was adjusted to 150 μm using a grinder, and then adjusted to about 100 μm using a polishing machine. The back surface of the wafer is flat because it is polished by a polishing machine.

Next, an n-type electrode 211 was formed on the back surface of the wafer. Here, the layer structure of the n-type electrode is Hf from the substrate side.
(30 nm), Al (150 nm), and a metal multi-layer film on top of that, Mo (8 nm), Au (150 nm) from the substrate side.
nm) in that order. The Hf / Al layer is n-type GaN
It is a layer for taking ohmic contact with the substrate, and Mo on it
Is a block layer that prevents the contamination of Au and Al, and Au mixes with solder at the time of mounting to firmly fix L.
It is a layer for die-bonding a D chip. The vacuum deposition method is suitable for forming such a thin metal film with good controllability of the film thickness, and although this method was used in the present embodiment as well, other methods such as an ion plating method and a sputtering method are used. May be.

Hereinafter, a laser diode wafer is referred to as an LD wafer, and a wafer obtained by dividing this into a bar shape is referred to as an LD bar. FIG. 3 is a schematic view of a nitride compound semiconductor LD wafer having a large number of semiconductor laser structures formed in the above process and an LD bar obtained by dividing the semiconductor LD wafer. In FIG. 3, 301 is a nitride-based compound semiconductor LD wafer, 1
Reference numeral 01 is a laser resonator end face, 103 is a p-type electrode, 104 is an insulating film, and 311 is an LD bar dividing line (A) for dividing into a bar shape.

Next, the wafer in this state is cleaved or etched in a direction perpendicular to the stripe direction to form a bar shape. Reference numeral 302 denotes an LD bar obtained by dividing a nitride compound semiconductor LD wafer. 312 is L for dividing into chips
It is a dividing line (B) for D chips. In this embodiment,
The LD bar dividing line (A) was controlled so that the resonator length 313 was 500 μm.

Then, an optical thin film coating is applied to the end faces of the laser resonator by vapor deposition. First, a jig for fixing the nitride compound semiconductor LD bar is prepared. FIG. 4 is a schematic view of a bar-shaped Si substrate (Si bar) having grooves. A groove 403 whose groove depth 402 is controlled is formed on the Si bar 40 by using a photolithography technique.
Make on both sides of the tip of 1. When the LD bar and the tip of this Si bar are aligned using a flat plate, since the groove of the Si bar is open, a dielectric film is deposited not only on the resonator end surface but also on the upper and lower surfaces of the LD chip. To be done. In the present embodiment, a Si bar having a groove depth of about 20 μm is used, and LD
Fix the bar and Si bar to the fixture with the tips aligned.

FIG. 5 is a schematic view of the nitride-based compound semiconductor LD bar fixed to the jig from the lateral direction, and FIG. 6 is a surface direction in which the nitride-based compound semiconductor LD bar fixed to the jig is vapor-deposited. It is a schematic diagram from. In FIG. 5, 501 is a nitride compound semiconductor LD bar, and 502 is this LD.
A bar-shaped Si substrate used as a jig for sandwiching the bar, 503 and 504 are fixing tools and screws for fixing the LD bar and the Si substrate, respectively, and 505 is a resonator end face of the LD bar and a jig (bar). Shows a step with the front end surface of the striped Si substrate). The bar-shaped Si substrate 502 is used for the purpose of preventing a portion other than the cavity end face of the laser element from being covered with the dielectric film. By the above operation, a step can be formed at the position of the resonator end surface of each LD bar to form the dielectric film.

On the other hand, FIG. 7 is a schematic side view of an LD bar which is fixed so as to cover the entire upper and lower surfaces of the LD bar by using a bar-shaped Si substrate 502 having no groove or the like formed at its tip. It is a figure. It is possible to prevent the mounting surface from being covered with the dielectric film by the method as shown in FIG. 7, but in this case, the dielectric film deposited on the resonator end face of the LD bar and S
Since the dielectric film deposited on the tip of the i-bar is integrated, the dielectric film covering the laser resonator end face is peeled off when the LD bar and the Si bar are separated after the dielectric film is deposited. The situation may occur. Therefore, it is preferable to deposit by a method of forming a step as shown in FIG.

Next, the vapor deposition of the dielectric film will be described in detail. The EB evaporation method was used to deposit SiO on the end face of one of the resonators.
_Two layers and a TiO ₂ layer are provided to form a multilayer film. The thickness of each layer is designed so as to satisfy a quarter wavelength condition with respect to the oscillation wavelength of the resonator, and three layers are alternately stacked to form a total of six layers. At this time, the wafer temperature was kept at 200 ° C. in order to increase the adhesion strength of the dielectric film. Then, the fixing tool is taken out from the EB vapor deposition apparatus, and the LD bar and the Si bar are separated.

In FIGS. 8 and 9, a dielectric film is provided by the method of FIG. 5 on a surface which becomes a resonator end face in which a part of the dielectric film wraps around the mount surface and the edge portion is covered. FIG. 3 is a schematic view from the p-type electrode side and a schematic view from the n-type electrode side of the obtained nitride compound semiconductor LD bar. 80
Reference numeral 2 is a region covered with a dielectric film. When measured with a scanning electron microscope or optical microscope, the groove depth of the Si bar was 2
Since it was 0 μm, the “length β”, which is an index of the region covered with the dielectric film, was also about 20 μm. Since the resonator length is 500 μm and the “length α” which is an index of the current injection region is also 500 μm, the “ratio γ” (= “length β) /“ length α ”) is 0.04. (4%).

After that, the LD bar was divided into individual semiconductor LD chips by a chip dividing process. 10 and 11 are a schematic view from the p-type electrode side and a schematic view from the n-type electrode side, respectively, of a nitride-based compound semiconductor LD chip in which a dielectric film is provided on the surface that becomes the resonator end face. . This step was performed as follows. First, the LD bar provided with the dielectric film was placed on the stage with the back side facing up, scratches were made while observing with an optical microscope, the positions were aligned, and a scribe line was placed at the diamond point on the back side. . Then, apply appropriate force to the LD bar,
By dividing along the scribe line, the nitride compound semiconductor LD chip shown in FIGS. 10 and 11 was produced.

Although the chip dividing step by the scribing method has been described here, a method of dividing the chip by inserting a scratch, a groove or the like from the back surface side of the substrate may be used. As another method, a dicing method in which a wire saw or a thin plate blade is used for scratching or cutting, irradiation heating with laser light such as excimer laser and subsequent rapid cooling causes cracks in the irradiation portion, and this is used as a scribe line. A laser scribing method, a laser ablation method of irradiating a laser beam having a high energy density and evaporating this portion to perform grooving may be used.

Next, the semiconductor L is formed by a die bonding method.
The D chip was mounted on the submount. 12 and 13
FIG. 3 is a schematic view of a nitride compound semiconductor laser device of this embodiment.

This step was carried out as follows. First, Ti (0.1 μm) / Pt (0.1 μm) / Au
(0.1 μm) (Au-on-Pt-on-Ti, the same applies hereinafter) is formed on the Fe submount 1205 having the metal multilayer films 1204 and 1206 on the surface thereof, and the In solder 1
201 was vapor-deposited. Semiconductor L due to rising solder
In order to prevent pn short circuit of D chip, solder 120
The thickness of 1 is preferably 0.5 to 20 μm, more preferably 0.5 to 5 μm.

Next, the submount 1205 is attached to the solder 12
When the solder 1201 melts by heating to 200 ° C., which is slightly higher than the melting point of 01, the semiconductor LD chip 1302
Is placed with the n-type electrode 211 and the metal multilayer film 102 facing down,
Further, the LD chip 1302 and the submount 1205 are soldered to the solder chip 120 while pressing the collet to apply a load appropriately.
I got used to 1. Then, cool and solder 1201
Was solidified.

Next, the support base 1210 of the stem 1301
A sheet-shaped PbSn solder 1202 is placed on the stem 1301 and the stem 1301 is slightly higher than the melting point of the solder 1202.
When the solder 1202 is melted by heating to ℃, the submount 1205 and the semiconductor LD chip 1302 fixed as described above are placed with the submount 1205 facing down, and the submount 1205 and the stem supporting base 1210 are placed.
The and 120 were well adapted to the solder 1202 to solidify the solder 1202. Then, wires 1207 and 1208 were connected to the pins 1209 of the stem and the support base 1210 from the surfaces of the p-type electrode 103 and the submount 1205 on the semiconductor growth layer 1203. In this way, the nitride-based compound semiconductor laser device shown in FIG. 13 was obtained.

The supporting substrate 1210 is Cu or Fe.
It is made of a metal mainly composed of Pd film / Au film and is sequentially plated on the surface. In addition, since a dielectric is used for the submount, it is possible to directly connect to the stem, package, external lead, etc. not only from the side of the submount that faces the semiconductor LD chip, but also from the side surface and the back surface. This leads to higher efficiency and simplification of the entire system.

240 nitride compound semiconductor laser devices were manufactured by the method of this embodiment. Regarding the characteristics (average of 240 laser diodes) of these semiconductor lasers, the “ratio γ” is 4%, the thermal resistance (Rth) is 32.5 (° C./W),
Device life (light output = 50mw, 60 ° C, DC, auto power control (hereinafter referred to as APC)) is 2620
It was time. Here, the thermal resistance is an index indicating the temperature rise of the laser element with respect to the input power, and the smaller this value, the smaller the temperature rise at the same input power, so that the proliferation of defects, the diffusion of dopants, etc. are suppressed. It is said that the device life is good.

For comparison, unlike the present embodiment, the ratio of the area covered by the dielectric film for end face coating to the area immediately above the electrode closer to the active layer (here, the p-type electrode) is 29%. Was manufactured, and using this chip, 230 nitride-based compound semiconductor laser devices were manufactured by the same method as this embodiment. The device characteristics (average value of 230 pieces) of these comparative examples have a thermal resistance of 61.4 (° C /
W), device life (light output = 50 mW, 60 ° C., DC, A
PC) was 780 hours.

Thus, the semiconductor laser device of this embodiment had better thermal resistance and element life characteristics than the comparative example.

The cause of the above difference can be inferred as follows. The dielectric film has poor wettability with the solder material, and when the solder material is die-bonded so that the surface coated with the dielectric film faces the submount surface,
The adhesion between the semiconductor LD chip and the submount is low, and the bondability is not strong. In particular, a nitride compound semiconductor L
When there is a warp such as a D chip, the semiconductor LD chip is easily peeled off from the submount due to a decrease in adhesion.
Moreover, since the thermal conductivity of the dielectric film portion is low, the heat dissipation effect is reduced (the thermal resistance is deteriorated), and the laser device is likely to reach a high temperature, which causes the diffusion of the dopant, the propagation of defects, and the deterioration of the dielectric on the end face. Etc., which adversely affects the life of the laser device. In this embodiment, since the adhesion of the dielectric film to the portion of the mount surface immediately above or below the current injection region is suppressed, the heat dissipation of the mount member and the semiconductor light emitting element chip is improved, and the thermal resistance is reduced. It is considered that it became favorable and the device life was improved.

Next, the reason why the effect is exhibited by setting the "ratio γ" to 0% or more and 20% or less will be described. FIG. 14 is a graph showing the relationship between the “ratio γ” and the thermal resistance (Rth). As can be seen from the graph of FIG. 14, in the range of the “ratio γ” from 0% to 20%, the thermal resistance increases as the “ratio γ” increases, but the degree of increase is small. On the other hand, when the “ratio γ” exceeds 20%, the thermal resistance sharply increases. When it exceeds 40%, the bonding strength suddenly weakens, and it becomes difficult to perform wire striking and the like, and accurate measurement cannot be performed. Therefore, plots of 40% or more are not made.

FIG. 15 is a graph showing the relationship between the "ratio γ" and the device life (light output = 50 mW, 60 ° C., APC). As can be seen from the graph of FIG. 15, the element life is long when the “ratio γ” is in the range of 0% to 20%.

The effect of improving the device characteristics in the above range is as follows.
The material used for the dielectric film is SiO ₂/ TiO₂Other than
However, for example, TiO₂, SiO₂, Al₂O₃, ZrO
₂, Ta₂O_Five, TiON, and these things
Similar observations were made with quality mixtures.

In this embodiment, the method of forming the double-sided electrode on the conductive substrate and die-bonding the conductive substrate side to the submount (p-type electrode up (α)) has been described. The forming method can be applied to other structures and mounting methods. Hereinafter, another embodiment of the present invention will be described. 16, FIG. 17 and FIG. 18 are schematic views of the main part of the semiconductor laser device of the second, third and fourth embodiments, respectively. In the second embodiment shown in FIG. 16, the p-type electrode is down (α), in the third embodiment shown in FIG. 17, the p-type electrode is up (β), and in the fourth embodiment shown in FIG. 18, the p-type electrode is down. The mounting method of (β) is adopted. In FIGS. 15, 17, and 18, 1
Reference numeral 610 indicates an active layer.

In the p-type electrode down (α) structure of FIG. 16, a double-sided electrode is formed on a conductive substrate (here, n-type GaN substrate 201), and the semiconductor growth layer 1203 side is placed on the submount 12.
It is produced by die bonding to 05. By the same method as that of the first embodiment, 220 nitride compound semiconductor laser devices having the p-type electrode down (α) structure of FIG. 16 were manufactured.
Regarding the characteristics (average value of 220 pieces) of these semiconductor lasers, the "ratio γ" is 6% and the thermal resistance is 34.1.
(° C / W), device life (light output = 50mW, 60 ° C, A
PC) was 2510 hours. "Ratio γ" and thermal resistance,
As a result of investigating the relationship between the chip and the sub-mount as in the first embodiment, by setting the “ratio γ” to 0% or more and 20% or less as in the first embodiment, The effect of improving fusion strength, thermal resistance, device life, etc. was obtained.

Further, as shown in FIG. 17, the insulating substrate 1
In the structure (p-type electrode up (β)) in which both electrodes are formed on the semiconductor growth layer 1203 side of 701 and the insulating substrate 1701 is die-bonded to the submount 1205,
Similarly to the first embodiment, the “ratio γ” is 0% or more and 2 or more.
By setting the content to 0% or less, the effect of improving the fusion strength, thermal resistance, and device life of the chip and the submount as obtained in the first embodiment was obtained.

Here, in the case of the p-type electrode down (α) structure shown in FIG. 16, a metal multilayer film is formed so as to cover the p-type electrode in order to increase the fusion strength between the semiconductor LD chip and the solder. It is preferable to form a metal multi-layer film in all the regions in contact with the solder layer.

In FIG. 18, 1610 is an active layer, and 18
Reference numeral 01 is an insulating substrate or conductive substrate, 1805 is an insulating submount, 1815 is a conductive submount, 1
Reference numeral 811 denotes a solder in which the conductive submount 1815 and the insulative submount 1805 are fused, and 1821 is a solder in which the n-type electrode 211 and the conductive submount 1815 are fused. An insulating substrate or a conductive substrate 1801 as shown in FIG. 18 is used to form both electrodes 103 and 211 on one side, and the n-type electrode 211 side is a conductive layer in which both surfaces are covered with a metal multilayer film. Submount 18
15 is sandwiched and fused to the insulating submount 1805 with solder 1811 and 1821, and the p-type electrode 103
In the same manner as in the first embodiment, the “ratio γ” is set to 0% even in the method (p-type electrode down (β)) of mounting on the insulating submount 1805 with the solder 1201 as usual.
By setting the amount to be not less than 20% and not more than 20%, the effects of improving the thermal resistance and the element life as obtained in the first embodiment were obtained.

In all of the above mounting methods, even when the polarities (p-type and n-type) of the semiconductor layer, the substrate, and the electrode closer to the active layer are reversed, the substrate and the growth layer are different in each structure. By optimizing the polarity, layer thickness, composition, etc., the same effect as that described in the first embodiment can be obtained.

In each of the above embodiments, the dielectric film T
Although iO ₂ and SiO ₂ were used, AlN, TiN, S
iN, ZrO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , TiON, Mg
It is also possible to use F ₂ or other oxide, fluoride, or nitride as the dielectric film. Even in that case, the thermal conductivity of the dielectric film is as low as 40 W / mK or less,
By applying the present invention, the same effect as that described in the first embodiment can be obtained.

Although only one end face coating is performed here, the present invention is also applied to the case where both end face coatings are performed, whereby the effect of improving the thermal characteristics and the life is exhibited.

In each embodiment, Fe is used for the submount, but the same effect can be obtained with other submounts.
In addition, other materials having a coefficient of thermal expansion larger than that of the nitride-based compound semiconductor, such as Ag, Cu, CuW, BeO, and Al.
_When it is replaced with ₂ O ₃ , GaAs, etc., compressive strain can be applied to the nitride-based compound semiconductor light emitting element chip, and the characteristics of the light emitting device can be improved. Furthermore, a material having a high thermal conductivity is preferable because it has excellent heat dissipation.

In each embodiment, In solder is used as the solder for adhering the semiconductor LD chip and the submount. However, solder having a low melting point such as InPb, InSn, InAg of In solder, InAgPb
Etc., or Sn, SnPb, SnSb, SnAg,
The same effect can be obtained by using Sn-containing solder such as SnAgPb and AnPbSb, or solder containing Pb such as PbSb, PbAg and PbZn, and epoxy resin or polyimide mixed with powder of Ag, Au and Cu. It is possible to obtain The solder may be formed by a coating method, a sputtering method, a printing method, a plating method or the like other than the vapor deposition method, and a sheet-shaped solder may be placed on the submount.

In each embodiment, PbSn is used as the solder for adhering the submount and the support, but the type of solder may be any of In-based, Sn-based, Au-based, Pb-based and the like. However, in order to avoid adverse effects on the solder already existing between the semiconductor LD chip and the submount, it is desirable that the melting point be lower than that of the existing solder. A vapor deposition method, a coating method, a sputtering method, a printing method, a plating method, or the like can also be adopted for forming the solder.

Further, in each embodiment, Pd /
Although Au was used, other than Pd, for example, Co, Cu, A
g, Ir, Sc, Au, Cr, Mo, La, W, Al,
Tl, Y, Ce, Pr, Nd, Sm, Eu, Tb, T
i, Zr, Hf, V, Nb, Ta, Pt, Ni and their compounds may be used, and other than Au, for example, Ni, A
g, Ga, In, Sn, Pb, Sb, Zn, Si, G
You may use e, Al, and its compound. The film thickness of the p-type electrode is not limited to the exemplified values.

In each of the embodiments, Hf / Al was used for the n-type electrode, but other than Hf, for example, Ti, Co, Cu, A
g, Ir, Sc, Au, Cr, Mo, La, W, Al,
Tl, Y, Ce, Pr, Nd, Sm, Eu, Tb, Z
r, V, Nb, Ta, Pt, Ni, Pd and their compounds may be used, and in addition to Al, for example, Au, Ni, A
g, Ga, In, Sn, Pb, Sb, Zn, Si, Ge
And its compounds may be used. The film thickness of the n-type electrode is not limited to the exemplified values.

Although the uppermost layer of the metal multilayer film on the mount surface is Au, other than this, for example, Pd, Co, C
u, Ag, Ir, Sc, Cr, Mo, La, W, Al,
Tl, Y, Ce, Pr, Nd, Sm, Eu, Tb, T
i, Zr, Hf, V, Nb, Ta, Pt, Ni, Ga,
Any of In, Sn, Pb, Sb, Zn, Si, Ge, Al, and alloys of these metals can be used as the uppermost layer. Even in that case, the "ratio γ" is 0% or more and 20
There is no difference in the effect obtained by setting it to be equal to or less than%.

The structure of the semiconductor LD chip is not limited to the illustrated one, but may be changed such as using another nitride compound semiconductor material as the substrate, and the material system of the semiconductor growth layer may be, for example, AlGaInN system, G
aInNAs system, GaInNP system, InGaAsP system,
InGaAlP series, AlGaN series, CdZnSe series, G
It is also possible to use other materials such as aAs and Si.

Further, on the submount loading surface,
A pad portion for wire bonding may be provided, or a mark for alignment during die bonding may be provided. The present invention can also be applied to a semiconductor laser device having a semiconductor LD chip having three or more electrodes, such as a so-called multi-beam laser.

Further, various kinds of films can be interposed between the solder layer and the submount substrate, as is known, for example, a film for improving the adhesion between the submount and the solder, A film for preventing a reaction between the submount and the solder, and a film for enhancing adhesion between these films and for preventing oxidation may be appropriately laminated. Instead of the exemplified metal pattern Au / Pt / Ti, Pt / Cr, Au / Mo, Au / Pt / Cr, Au
It is also possible to use / Mo / Ti or the like. Various films may be interposed between the solder, the bonding pad, and the submount for the same purpose.

[0076]

A laser diode chip made of a nitride compound semiconductor and having a cavity end face covered with a dielectric film,
A nitride-based compound semiconductor laser device comprising a mount member for supporting a laser diode chip, and a solder layer located between the laser diode chip and the mount member for fixing them together. The length in the laser cavity length direction of the portion of the contacting chip surface immediately above or directly below the current injection region to the active layer and the portion of this portion covered with the dielectric film extending from the cavity end facet When the ratio is 0% or more and 20% or less, the heat generated in the laser diode chip is efficiently transferred to the mount member, and the laser device has a good thermal resistance and a long life.

A dielectric film covering the end face of the resonator is formed of TiO 2.₂, S
iO₂, Al₂O₃, ZrO₂, Ta₂O _Five, TiON and
MgF₂Made of one or more of the
Taking advantage of the characteristics of
Can be given. The low thermal conductivity of each material
Due to the characteristics of the construction, there is no problem.

In a method of manufacturing a laser device of a nitride-based compound semiconductor, which comprises a laser diode chip made of a nitride-based compound semiconductor and having a cavity end face covered with a dielectric film, the laser device of the nitride-based compound semiconductor is divided into individual pieces after division as in the present invention. A bar-shaped chip prototype that serves as a laser diode chip is manufactured, and the chip prototype is sandwiched by bar-shaped jigs, and the end of the chip prototype including the surface that becomes the cavity end face of each laser diode chip is cured. If the dielectric film is provided on the surface of the chip raw material that will be the resonator end surface as a state in which the end portion of the tool protrudes from the portion that contacts the chip raw material, the entire surface of the surface that will be the resonator end surface will be dielectric. While providing the film, the extension of the dielectric film to the mount surface can be limited, and it is possible to provide a laser device having a good thermal resistance and a long life.

In particular, a jig having an end whose central portion in the thickness direction projects more than both sides thereof is used, and a plurality of chip raw materials and a plurality of jigs are alternately arranged, and the resonator end face is formed. By aligning the height of the surface of the raw material of the chip with the surface of the central part of the end of the jig and providing a dielectric film on the surface of the raw material of the chip that will be the end face of the resonator, many chips can be processed at once. (EN) A laser device having a uniform dielectric film can be provided on the original body for high efficiency, and the length of a portion of the mount surface covered with the dielectric film can be made constant, so that there is no variation in characteristics. It is possible.

[Brief description of drawings]

FIG. 1A is a back surface (GaN substrate side) of a nitride-based compound semiconductor LD chip used in a first embodiment of the present invention.
And (b) are schematic views from the surface (growth layer side).

FIG. 2 is a schematic view of a cross section of a nitride-based compound semiconductor LD chip.

FIG. 3 is a schematic diagram of a nitride compound semiconductor LD wafer and an LD bar during the manufacture of a nitride compound semiconductor LD chip.

FIG. 4 is a schematic view of a bar-shaped Si substrate used for manufacturing a nitride compound semiconductor LD chip.

FIG. 5 is a schematic view of a nitride-based compound semiconductor LD bar fixed to a jig from the lateral direction.

FIG. 6 is a schematic view of a nitride compound semiconductor LD bar fixed on a jig as viewed from the surface on which vapor deposition is performed.

FIG. 7 is a schematic view from the lateral direction of a nitride compound semiconductor LD bar fixed to a jig in another mode.

FIG. 8 is a schematic view from the p-type electrode side of a nitride-based compound semiconductor LD bar in which a dielectric film is provided on a surface that is an end face of a resonator.

FIG. 9 is a schematic view from the n-type electrode side of a nitride-based compound semiconductor LD bar in which a dielectric film is provided on a surface which is an end face of a resonator.

FIG. 10 is a schematic view from the p-type electrode side of a nitride-based compound semiconductor LD chip having a dielectric film provided on an end face of a resonator.

FIG. 11 is a schematic view from the n-type electrode side of a nitride-based compound semiconductor LD chip in which a dielectric film is provided on an end face of a resonator.

FIG. 12 is a schematic view of a nitride-based compound semiconductor laser device according to the first embodiment of the present invention.

FIG. 13 is a schematic view of a nitride-based compound semiconductor laser device according to the first embodiment of the present invention.

FIG. 14 is a diagram showing a relationship between “ratio γ” and thermal resistance Rth of a nitride compound semiconductor LD chip.

FIG. 15 is a diagram showing the relationship between the “ratio γ” and the device life of a nitride compound semiconductor LD chip.

FIG. 16 is a schematic view of a main part of a nitride-based compound semiconductor laser device according to a second embodiment of the present invention.

FIG. 17 is a schematic diagram of a main part of a nitride-based compound semiconductor laser device according to a third embodiment of the present invention.

FIG. 18 is a schematic diagram of a main part of a nitride-based compound semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 19 is a schematic view of a conventional semiconductor laser device.

FIG. 20 is a schematic view of a conventional semiconductor laser device.

FIG. 21 is a schematic view of a conventional semiconductor laser device.

FIG. 22 is a schematic view from the mount surface side of a conventional semiconductor LD chip in which a dielectric film is provided on an end face of a resonator, which is a problem to be solved by the present invention.

FIG. 23 is a schematic view of a nitride compound semiconductor LD chip of the present invention having an electrode stripe structure.

FIG. 24 is a schematic view of a nitride compound semiconductor LD chip of the present invention having a ridge stripe structure.

FIG. 25 is a schematic view of a nitride compound semiconductor LD chip of the present invention having a ridge stripe structure.

FIG. 26 is a diagram showing “length α” and “length β” in the present invention.

FIG. 27 is a diagram showing “length α” and “length β” in the present invention.

[Explanation of symbols]

101 End Facet of Laser Resonator 102 Metal Multilayer Film 103 p-Type Electrode 104 Insulating Film 105 Portion Immediately Above or Immediately Below Current Injection Region to Active Layer 106 Line 201 n Denoting Immediately Above or Immediately Below Current Injection Region to Active Layer Type GaN substrate 202 n-GaN contact layer 203 n-AlGaN cladding layer 204 n-GaN guide layer 205 GaInN multiple quantum well active layer 206 p-AlGaN evaporation prevention layer 207 p-GaN guide layer 208 p-AlGaN cladding layer 209 p- GaN contact layer 211 n-type electrode 301 Nitride-based compound semiconductor LD wafer 302 Nitride-based compound semiconductor LD bar 311 Nitride-based compound semiconductor LD bar dividing line (A) 312 Nitride-based compound semiconductor LD chip dividing line (B ) 313 Resonator length 401 Si bar 402 Groove depth 403 Groove 501 Nitride-based compound semiconductor LD bar 502 Bar-shaped Si substrate (jig) 503 Fixture 504 Screw 505 Step 802 between resonator end face of LD bar and tip end face of jig 802 Cover with dielectric film Area 1201 Solder 1202 Solder 1203 Semiconductor growth layer 1204 Metal multilayer film 1205 Submount 1206 Metal multilayer film 1207 Wire 1208 Wire 1209 Stem pin 1210 Stem support base 1301 Stem 1302 Semiconductor LD chip 1610 Active layer 1701 Insulating substrate 1801 Insulation Substrate or conductive substrate 1805 Insulating submount 1811 Solder 1815 Conductive submount 1821 Solder 1902 Semiconductor growth layer 1904 Metal multilayer film 1905 Solder 1906 Metal multilayer film 2001 Conductive substrate 2201 Mounting surface 202 Dielectric film 2203 Dielectric film boundary 2301 n-type substrate 2303 Line 2601 indicating a portion directly above or directly below the current injection region to the active layer Length α 2602 Length β 2610 Resonator length direction 2701 Boundary intersection 2702 Boundary Midpoint 2703 between the intersecting points of the line that passes through the midpoint between the intersecting points of the boundary and is parallel to the edge face of the LD chip.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5F073 AA11 AA74 AA83 CA07 CB02                       CB20 CB23 DA33 DA34 EA24                       EA28 FA14 FA15 FA18

Claims (4)

[Claims] 1. A laser diode chip made of a nitride-based compound semiconductor and having a cavity end face covered with a dielectric film,
In a nitride-based compound semiconductor laser device including a mount member supporting a laser diode chip and a solder layer located between the laser diode chip and the mount member and fixing the two, the active portion of the chip surface in contact with the solder layer The ratio of the length in the laser cavity length direction of the portion directly above or directly below the current injection region to the layer and the portion of this portion covered with the dielectric film extending from the cavity end face is 0% or more. And 20% or less, a laser device of a nitride compound semiconductor. 2. The dielectric film covering the cavity end face is TiO ₂ ,
The nitride compound semiconductor laser device according to claim 1, which is made of one or more materials selected from SiO ₂ , Al ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , TiON, and MgF ₂ . 3. A method for manufacturing a laser device of a nitride-based compound semiconductor, comprising a laser diode chip made of a nitride-based compound semiconductor and having a cavity end surface covered with a dielectric film. A bar-shaped chip raw material is manufactured, and the chip raw material is sandwiched by bar-shaped jigs, and the end of the chip raw material that includes the surface that becomes the cavity end face of each laser diode chip is the end of the jig. A method for manufacturing a laser device of a nitride-based compound semiconductor, comprising: providing a dielectric film on a surface of a chip raw material which is an end face of a resonator so as to project from a portion contacting the raw material chip. 4. A jig having a central portion in the thickness direction having ends projecting from both sides thereof is used, and a plurality of chip raw materials and a plurality of jigs are alternately arranged, and
The height of the surface of the chip raw material serving as the resonator end surface and the surface of the central portion of the end portion of the jig are aligned, and a dielectric film is provided on the surface of the chip raw material serving as the resonator end surface. Item 4. A method for manufacturing a laser device of a nitride compound semiconductor according to Item 3.