JP7319507B2 - Light-emitting device manufacturing method and light-emitting device - Google Patents

Description

The present invention relates to a method for manufacturing a light emitting device and a light emitting device.

A semiconductor laser is formed by laminating a semiconductor layer on a substrate for growth. method may be adopted.
For example, for the purpose of improving cleavability, a method of removing a growth substrate after bonding a semiconductor layer to a support substrate with better cleavability (Patent Document 1, etc.), cracks caused by a difference in thickness of a semiconductor layer For the purpose of suppressing the occurrence of , a method of removing the growth substrate after bonding a semiconductor layer to a support substrate provided with a step has been proposed (Patent Document 2, etc.).

JP 2002-299739 JP 2009-123939

In semiconductor lasers, the higher the output, the greater the amount of heat generated.
An object of the present invention is to provide a method for manufacturing a light-emitting device and a light-emitting device capable of improving heat dissipation.

The present application includes the following inventions.
(1) preparing a wafer having a laser device structure formed on the upper side of a conductive first substrate and a top electrode formed on the top surface of the device structure;
bonding the upper electrode side of the wafer to a second substrate;
thinning the wafer by removing a portion of the first substrate;
forming a lower surface electrode on the lower surface of the thinned first substrate;
obtaining a laser element by singulating the wafer;
A method of manufacturing a light-emitting device, comprising mounting the laser element on a submount with the lower electrode facing the submount.
(2) A light-emitting device comprising a submount and a laser element,
The laser element is
a conductive first substrate and a device structure of a laser formed on the upper side of the first substrate;
a bottom electrode formed on the bottom surface of the first substrate;
a top electrode formed on the top surface of the device structure;
a conductive second substrate that is bonded to the top electrode and is thicker than the first substrate;
The submount is a light emitting device joined to face the lower surface electrode.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a light-emitting device and a light-emitting device which can aim at the improvement of heat dissipation can be provided.

4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; 4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; FIG. 4 is a schematic plan view showing a method for manufacturing the light emitting device of Example 1; 4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; 4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; 4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; FIG. 4 is a schematic plan view showing a method for manufacturing the light emitting device of Example 1; 4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; 4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; 4A to 4C are schematic cross-sectional views showing a method for manufacturing the light emitting device of Example 1; FIG. 3 is a schematic cross-sectional view showing a laser device of a comparative example; 5 is a graph showing voltage-current curves of the laser device of Example 1 and the laser device of Comparative Example. 2 is a schematic cross-sectional view showing a light emitting device of Example 2; FIG. FIG. 11 is a schematic cross-sectional view showing a light emitting device of Example 3;

The embodiments shown below are examples for embodying the technical idea of the present invention, and are not intended to limit the present invention. Also, the sizes and positional relationships of members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, the same names and reference numerals basically indicate the same or homogeneous members, and overlapping descriptions will be omitted as appropriate.

[Method for manufacturing light-emitting device]
A method for manufacturing a light-emitting device according to one embodiment includes:
providing a wafer having a laser device structure formed on the top side of a conductive first substrate and a top electrode formed on the top surface of the device structure;
bonding the upper electrode side of the wafer to a second substrate;
thinning the wafer by removing a portion of the first substrate;
forming a lower surface electrode on the lower surface of the thinned first substrate;
obtaining a laser element by singulating the wafer;
Mounting the laser element on a submount with the lower electrode facing the submount.

In this way, by thinning the wafer on which the laser device structure is formed and mounting it on the submount, the light emitting point (that is, the active layer) of the laser device, which is the heat source, can be brought closer to the submount. Therefore, heat can be easily released to the submount, and the thermal resistance of the laser element can be reduced. Furthermore, since it is not necessary to provide an insulating film between the light emitting point of the laser element and the submount, the thermal resistance of the laser element can be further reduced.
In addition, by removing a part of the first substrate and thinning the wafer, the light emitting point can be separated from the submount compared to the case where the first substrate is completely removed. This eliminates the need for the light emitting end face of the laser element to protrude greatly from the submount in consideration of mounting accuracy errors. can be done. Therefore, heat from the light emitting facet and its vicinity can be easily released to the submount, and the thermal resistance of the laser element can be reduced.

(wafer preparation)
A wafer is provided having a laser device structure formed on the upper side of a conductive first substrate and a top electrode formed on the upper surface of the device structure.
First, as shown in FIG. 1A, an arbitrary laser element structure 12 is crystal-grown on a conductive first substrate 11 .
Examples of the conductive first substrate 11 include a compound semiconductor substrate such as a GaN substrate and a GaAs substrate, an elemental semiconductor substrate such as silicon, and the like. Among them, a crystalline substrate having a cleavage property is preferable. Here, having cleavability refers to having an easy-cleavage face that is easily cleaved. For example, when the first substrate 11 is a GaN substrate, the M plane (ie, (10-10) plane) is the easy-cleavage plane. In this case, it is preferable to form the element structure 12 with the C-plane (that is, the (0001) plane), which is a plane perpendicular to the M-plane, as the main plane. In the step of preparing the wafer, the thickness of the first substrate is, for example, 50 μm to 2 mm. The first substrate 11 may have unevenness on its surface, or may have an off-angle. The off angle is preferably within 1 degree, for example.

A semiconductor laminate is formed as a laser device structure. The semiconductor laminate has, for example, an n-side semiconductor layer, an active layer, and a p-side semiconductor layer in order from the first substrate side. The n-side semiconductor layer and the p-side semiconductor layer include an n-type semiconductor layer and a p-type semiconductor layer, respectively, and may partially have an undoped layer. The active layer has, for example, a multiple quantum well structure or a single quantum well structure. The semiconductor laminate can be formed by epitaxial growth on the first substrate. Materials constituting the semiconductor laminate include III-V group compound semiconductors such as GaN-based semiconductors, GaP-based semiconductors, _{and GaAs -} based semiconductors. x, 0≤y, x+y≤1) nitride semiconductor is used.

A waveguide is formed in the semiconductor laminate by a known method. For example, by photolithography and etching processes, a part of the semiconductor stack is removed so that a striped ridge is formed on the upper surface of the semiconductor stack, that is, the surface of the p-side semiconductor layer. Thereby, a waveguide can be formed.

Then, an upper electrode is formed on the upper surface of the element structure of the laser.
The upper electrode is electrically connected to the p-side semiconductor layer. The upper surface electrode includes, for example, a first p-electrode in contact with the upper surface of the p-side semiconductor layer and a second p-electrode as a pad electrode arranged on the first p-electrode for external connection. The first p-electrode is preferably formed on the upper surface of the p-side semiconductor layer corresponding to the waveguide, and may be formed only on the upper surface of the ridge. The second p-electrode may be arranged only on the ridge, or may be formed on the ridge over the upper surface of the p-side semiconductor layer.

The upper electrode is formed of a single layer film or laminated film of metal or alloy such as palladium, platinum, nickel, gold, titanium, tungsten, copper, silver, zinc, tin, indium, chromium, aluminum, iridium, rhodium, etc. be able to. A conductive oxide film such as ITO may be used. In this electrode, the uppermost layer can be gold in order to facilitate bonding with a second substrate, which will be described later. Alternatively, in order to perform liquid phase diffusion bonding, the uppermost layer may be formed of a laminated structure film having a low melting point material such as tin and an alloying material such as nickel directly below it. This allows, for example, liquid phase diffusion bonding in which tin melts at about 232° C. and forms a Ni ₃ Sn ₄ alloy with nickel. By using liquid phase diffusion bonding, it is possible to expand the bonding area to areas other than the ridge during bonding, which will be described later.
For example, the film thickness of the first p-electrode is 10 nm to 1000 nm, and the film thickness of the second p-electrode is 1000 nm to 1 μm.

Before and after forming the upper electrode, it is preferable to form an insulating film on regions other than the contact region between the upper electrode and the semiconductor layer, for example, the upper surface and side surfaces of the p-side semiconductor layer. In the case of a laser device structure using a nitride semiconductor, a ridge is formed on the upper surface of the device structure, and an insulating film with a relatively low refractive index is formed on the region other than the ridge, thereby efficiently transmitting light to the optical waveguide. can be locked up. The insulating film can be formed of an insulating film such as an oxide, nitride, or oxynitride of Zr, Si, V, Nb, Hf, Ta, Al, Ce, In, Sb, Zn, or the like. As the insulating film having a relatively low refractive index, it is preferable that the insulating film has a large refractive index difference with the semiconductor layer (for example, GaN), and examples of such a material include SiO ₂ . The film thickness is, for example, about 100 nm to 1500 nm.
Further, in the case of a laser device using a nitride semiconductor, a material having a relatively high thermal resistance such as an oxide film may be used as an electrode material or an insulating film. In this case, in junction-down mounting, these materials with high thermal resistance are arranged between the laser element and the submount, thereby impeding heat dissipation. Therefore, by mounting the lower surface electrode (n-electrode) side of the first substrate in the wafer on which the laser device structure is formed on the submount, the thermal resistance can be further reduced than in the case of junction-down mounting. . Furthermore, as will be described later, when a substrate having an electrical resistivity lower than that of the first substrate (for example, a Si substrate doped with boron) is used as the second substrate, the thick first substrate of the second substrate The electric resistance can be lowered and the driving voltage of the laser element can be reduced as compared with the case where the laser element having the junction down is mounted.
Therefore, these two effects, that is, thermal resistance reduction and voltage reduction, can further improve the efficiency of the laser device.

(Lamination of Wafer to Second Substrate)
The second substrate to be bonded to the laser element structure is preferably one that can be cleaved together with the first substrate and/or the laser element structure, and therefore is preferably made of a material having cleavability. . In other words, a crystalline substrate having an easy-cleavage plane is preferable. In consideration of the fact that the second substrate is energized after the laser element is mounted, the substrate is preferably conductive, and more preferably has low electrical resistance, for example, lower electrical resistance than the GaN substrate. Examples of the second substrate include a Si substrate and a GaAs substrate. A Si substrate is preferable from the viewpoint of manufacturing a laser element at low cost.

The second substrate preferably has a conductive layer on at least one surface, that is, the surface facing the device structure of the laser. The conductive layer can be formed of a single-layer film or a laminated film of metals or alloys such as palladium, platinum, nickel, gold, titanium, tungsten, copper, silver, zinc, tin, indium, chromium, aluminum, iridium, and rhodium. can. A conductive oxide film such as ITO may be used. Among others, in order to facilitate bonding, the uppermost surface is preferably made of the same material as the uppermost surface of the upper electrode of the element structure, more preferably gold. A conductive layer can also be formed on the other surface opposite to the one surface. When wires are to be connected to the other surface of the second substrate, it is preferable to provide a conductive layer whose top layer is made of a material such as gold that has excellent adhesion to the wires.
From the viewpoint of ensuring strength, the thickness of the second substrate is set to be thicker than that of the first substrate after thinning the wafer, which will be described later. The thickness of the second substrate is preferably thick enough to reduce the influence of warpage caused by the first substrate, and specifically, it is preferably about 300 μm to 500 μm. After thinning the first substrate, which will be described later, the second substrate can also be polished. The thickness of the second substrate after polishing is also thicker than that of the first substrate after thinning, and is preferably 100 μm to 1000 μm, preferably 200 μm to 700 μm.

Such a second substrate is attached to the device structure of the laser. That is, the upper electrode formed on the upper surface of the element structure of the laser faces the conductive layer of the second substrate, and the two are connected. At this time, the first substrate and the second substrate are aligned so that their cleavage directions are parallel, that is, the easy-cleavage surfaces of the first substrate and the easy-cleavage surfaces of the second substrate are parallel. It is preferable to stick them together. However, as in Example 1, which will be described later, the easy-cleavage plane of the first substrate is perpendicular to the principal surface, while the easy-cleavage plane of the second substrate is not perpendicular to the principal plane but inclined to the principal plane. , so they do not have to be exactly parallel. Thereby, the first substrate can also be cleaved by cleaving the second substrate. It is more preferable that the easy-cleavage plane of the device structure of the laser is also parallel to the easy-cleavage planes of the first substrate and the second substrate. Furthermore, since the cavity facets of the laser element are preferably formed by cleavage, it is preferable to align the facets cleaved by the easy-cleavage planes to the cavity facets. For this reason, it is preferable to use a GaN substrate as the first substrate and a Si substrate as the second substrate. Note that the easy-cleavage surfaces of the first substrate and the second substrate are parallel to each other to the extent that the first substrate can be cleaved by cleaving the second substrate. For example, a deviation of about ±0.2 degrees is allowed.
If there is a metal layer such as an electrode at the dividing position, the metal layer may stretch and adhere to the dividing surface during division. For this reason, it is preferable that none of the upper surface electrode, the lower surface electrode, and the conductive layer exist at the division position, particularly at the division position for forming the cavity facet. In order to obtain such a positional relationship, it is preferable to form the upper surface electrode, the lower surface electrode, and the conductive layer while avoiding the planned division positions.
As a bonding method, liquid phase diffusion bonding, solid phase diffusion bonding, heat pressure welding, or the like can be used. For example, when heat pressure welding is used, substantially no deformation of the electrode surface occurs. Therefore, when the upper surface electrode on the upper surface of the device structure is formed, for example, on the upper surface of the ridge, the most convex top portion of the upper surface electrode on the ridge and the conductive layer of the second substrate are bonded. , and other portions may become voids. When the second substrate is left as will be described later, it is considered preferable to use diffusion bonding such as solid-phase diffusion bonding, which has a stronger bonding force than thermal pressure bonding.

(Wafer thinning)
A portion of the first substrate is removed from below to thin the wafer. Removal preferably utilizes polishing and/or dry etching. When performing polishing, in order to suppress the influence of warping of the wafer, the second substrate side is temporarily attached to a temporary substrate that is thicker than the second substrate with wax or the like, and part of the first substrate is removed. is preferred. A material of the temporary substrate is, for example, sapphire, and its thickness is, for example, about 2 mm.

As described in the above-mentioned Patent Document 2, for example, a thermal decomposition layer that is thermally decomposed by laser irradiation is arranged between the first substrate and the element structure, and the first substrate is thermally decomposed to form the element structure. If the method of peeling from the layer is used, there is concern that the active layer may be damaged by heat during thermal decomposition. On the other hand, in this embodiment, the thinning of the wafer is performed by polishing and/or dry etching. This makes it possible to eliminate the need for laser irradiation that causes such thermal damage.

Chemical mechanical polishing (CMP) and/or dry etching may be combined with the final finishing of mechanical polishing.
It is preferable to thin the first substrate to, for example, 0.5 μm to 8 μm by polishing, dry etching, or the like. For example, it is thinned to about 3 μm. Moreover, the shortest distance from the lower surface of the first substrate after thinning to the active layer (particularly the well layer) is preferably 2 μm to 9.5 μm. This makes it difficult for the emitted laser light to hit the submount.

(Formation of bottom electrode)
A lower surface electrode is formed on the surface of the wafer that has been thinned (the surface of the first substrate opposite to the laser device structure). The bottom electrode may be of the same material and/or laminate structure as the top electrode, or may be of a different material and/or laminate structure. The film thickness of the electrode can be appropriately set depending on the material used. The lower electrode is formed of a single-layer film or laminated film of metals or alloys such as palladium, platinum, nickel, gold, titanium, tungsten, copper, silver, zinc, tin, indium, chromium, aluminum, iridium, rhodium, etc. be able to. The film thickness of the lower electrode is, for example, 100 nm to 5 μm.
If a temporary substrate is provided in the previous step, it is preferably removed after forming the lower electrode. Moreover, the second substrate may be thinned to an arbitrary thickness, if necessary. Thinning of the second substrate facilitates separation of the wafer into individual pieces in the subsequent process.

When thinning the second substrate, it is preferable to form a conductive layer on the surface (other surface) of the second substrate subjected to the thinning treatment in an arbitrary step after thinning. The conductive layer here may be of the same material and/or laminated structure as the conductive layer on one surface of the second substrate, the lower electrode, or the upper electrode, or may be of a different material and/or laminated structure. The conductive layer on the other side is used for connecting to a wire or the like for energization after mounting the obtained light emitting device on a circuit board or the like.

(Singulation of wafer)
After forming the bottom electrode on the bottom surface of the first substrate, the first substrate and the second substrate are singulated together. The separation into individual pieces is usually performed by dividing for forming the cavity facets and dividing in the direction intersecting the cavity facets, and either of the divisions may be performed first. For example, dividing grooves are formed in at least one of the first substrate and the second substrate. When grooves are formed in both the first substrate and the second substrate, the grooves are formed so that the grooves of the first substrate and the grooves of the second substrate are arranged on the same line in plan view. preferably. If at least one of the first substrate and the second substrate contains an opaque material, it is difficult to arrange the respective grooves on the same line in plan view. Therefore, it is more preferable to form the groove only on the second substrate. Since the device structures of the first substrate and the laser are thin films, it is possible to divide the wafer by forming grooves only in the second substrate. The film thickness of the wafer excluding the second substrate is made thinner than the second substrate. The grooves can be formed using, for example, a laser scribing device. The groove may be formed in a line shape or broken line shape. If the second substrate has cleavability, the grooves are preferably broken lines along the easy-cleavage plane. When forming a line-shaped groove across the wafer, if it does not perfectly match the easy-cleavage plane, the dividing direction tends to meander. This is because the gap is cleaved in the direction along the easy-cleavage plane. After forming the groove, the first substrate and the second substrate are cleaved together along the groove. This cleavage can be performed by applying a blade or the like to the surface opposite to the grooved surface.
The direction that intersects the resonator facets can be a direction that intersects the resonator facets at about 90±1 degrees.
Such two-way division singulates the wafer into laser devices.

After forming the cavity facets, it is preferable to form reflecting mirrors on the light emitting side surface and the light reflecting side surface on the opposite side in an optional step. For example, it is possible to perform the first division step of forming the cavity facets, perform the reflection mirror formation step, and then perform the second division step in the direction intersecting the cavity facets. The reflecting mirror can be formed of an oxide film, a nitride film, an oxynitride film, a combination thereof, or the like. For example, it can be formed of a dielectric multilayer film made of SiO ₂ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ , Nb ₂ O ₅ , SiN, AlN, SiON, AlON, or the like. Reflecting mirrors can be formed with good reproducibility if the resonator facets are formed by cleavage.

(Mounting process to submount)
While the laser element structure is kept attached to the second substrate, the bottom electrode of the laser element faces the submount, and the singulated laser element can be mounted on the submount. The submount is preferably made of a material with good heat dissipation, such as SiC, AlN, or the like.
The mounting here is performed using a conductive bonding material such as AuSn eutectic solder, for example.

[Light emitting device]
The light emitting device 30 comprises a submount 22 and a laser element, as shown in FIG. 1J. The laser device includes a conductive first substrate 11a, a semiconductor laminate 12 which is a laser device structure formed on the upper side of the first substrate 11a, and a lower surface electrode formed on the lower surface of the first substrate 11a. It has an electrode 20, a first p-electrode 14 and a second p-electrode 16 which are upper electrodes formed on the upper surface of the semiconductor laminate 12, and a second substrate 17a joined to the upper electrodes. The first substrate 11 is thinner than the second substrate 17a, and the submount 22 faces the n-electrode 20 and is joined to the laser element by a joining member 24 such as AuSn eutectic solder.
As a result, the light emitting point of the laser element can be brought closer to the submount, so heat can be easily released to the submount, and the thermal resistance of the laser element can be reduced. Furthermore, since it is not necessary to provide an insulating film between the light emitting point of the laser element and the submount, the thermal resistance of the laser element can be further reduced.
In addition, since a part of the first substrate remains, the light emitting point can be separated from the submount compared to the case where the first substrate is absent. As a result, the light emitting end face does not need to protrude from the submount, or the amount of protrusion can be reduced. Therefore, the thermal resistance of the laser element can be reduced.
The light emitting device 30 can have a structure having a gap 19 between the second p-electrode 16 and the conductive layer 18 facing the element structure of the second substrate 17a (19 in FIG. 1J, 59 in FIG. 4). , and a structure without voids (FIG. 5).
The device structure of the laser can have striped ridges 13 (FIG. 1J). Moreover, it may further have a mesa-shaped ridge 53 (FIGS. 4 and 5).
Further, insulating films 15 can be arranged on both sides of the ridge 13 on the top surface of the semiconductor stack 12 .
Needless to say, the structure and material of each member described in the manufacturing method of the light emitting device can be adopted for each member of the light emitting device 30 .

Example 1: Manufacturing method of light-emitting device (wafer preparation)
First, as shown in FIG. 1A, a semiconductor laminate 12 was formed by sequentially forming an n-side semiconductor layer, an active layer, and a p-side semiconductor layer on the +C plane of a GaN substrate having a diameter of 50.8 mm as a first substrate 11. . In this case, _{InxAlyGa1 -xyN} (0≤x≤1, 0≤y≤1, 0≤x+y≤1) was used as _each layer. After that, a striped ridge 13 (35 μm wide, 270 nm deep) was formed on the upper surface of the p-side semiconductor layer.

Next, as shown in FIGS. 1B and 1C, a first p-electrode 14 made of an ITO film having a width of 32 μm and a thickness of 200 nm was formed on substantially the entire surface of the ridge 13 . After that, an insulating film 15 made of SiO ₂ having a thickness of 200 nm was formed on the side surface of the ridge 13 from the upper surface of the p-side semiconductor layer. Subsequently, a second p-electrode 16 (for example, Ni/Pd/Au/Pt/Au (film thickness: 8 nm/200 nm/400 nm/200 nm/700 nm)) electrically connected to the first p-electrode 14 is connected to the first p-electrode 14. 14 and formed over the insulating film 15 .

(Lamination of Wafer to Second Substrate)
As shown in FIG. 1D, a Si substrate having a plane orientation of {100}, an electrical resistivity of 0.005 Ω·cm or less, and a thickness of 400 μm was prepared as the second substrate 17 . Note that the plane orientation {100} indicates that the plane orientation of the main surface is {100}.
A film of Pt/Au (200 nm/700 nm) is formed on one surface of the second substrate 17 using a sputtering device, and this is provided as a conductive layer 18 .

Gold, which is the uppermost layer of the conductive layer 18 of the second substrate 17, and gold, which is the uppermost layer of the second p-electrode 16, which is the upper electrode of the laser device structure on the wafer, are thermally compressed at 7 kN and 280° C., A metal bond (Au—Au heat pressure bonding) was formed, and the wafer was bonded to the second substrate 17 . In this bonding, since the metal surface is not substantially deformed, the upper surface of the second p-electrode 16 formed on the ridge 13 and the first p-electrode 14 may have a Air gaps 19 are created on both sides of the resulting protrusion.
Further, during this bonding, alignment was performed so that the {111} plane of the Si substrate, which was the second substrate 17, was substantially aligned with (parallel to) the m-plane of the first substrate 11 of the wafer. However, since the {111} plane of the second substrate 17 is not perpendicular to the {100} plane of the main surface of the substrate but inclined, the {111} plane of the second substrate 17 and the m The faces are not strictly parallel.

(Wafer thinning)
As shown in FIG. 1E, a portion of the first substrate 11 in the thickness direction was removed to thin the wafer.
The bonded second substrate 17 side was temporarily bonded to a sapphire substrate having a thickness of 2 mm with wax in order to suppress warpage of the wafer when the thickness of the first substrate 11 was reduced. polished until At this time, CMP was used as the final polishing finish. The in-plane distribution of the thickness was within ±1.0 μm in the substrate of φ50.8 mm.

(Formation of bottom electrode)
As shown in FIGS. 1F and 1G, a film of Ti/Pt/Au (6 nm/200 nm/300 nm) is formed on the polished surface (n-side semiconductor layer side) of the thinned first substrate 11a using a sputtering apparatus. Then, an n-electrode 20 was formed as a lower surface electrode.

After that, the temporarily attached sapphire substrate was peeled off. Subsequently, the first substrate 11 side was similarly temporarily attached to a sapphire substrate having a thickness of 2 mm with wax, and the second substrate 17 having a thickness of 400 μm was polished to a thickness of 75 μm as shown in FIG. 1H. By this polishing, the second substrate 17 can be made to have a thickness suitable for cleaving at the time of singulation in the post-process. After polishing the second substrate 17, the sapphire substrate that was temporarily attached was peeled off, and a Pt/Au (200 nm/700 nm) film was formed on the polished surface of the thinned second substrate 17a using a sputtering device. , a conductive layer 21 used for wire bonding after mounting was formed.
In this way, a structure was formed in which the first substrate 11 is energized through the second substrate 17 when mounted.

(Singulation of wafer)
Grooves were formed in each of the first substrate 11 and the second substrate 17 of the obtained bonded structure on the same line in plan view, for example, on the dotted line X in FIG. 1G, using a laser scribing device. After the grooves were formed, both substrates were cleaved along the grooves using a substrate breaking device to form cavity facets of laser devices.
After that, a dielectric multilayer film is formed on the facets of the resonator, and the substrate having a bonded structure cleaved at the facets of the resonator is cut in a direction perpendicular to the facets of the resonator, for example, in the direction of the dotted line Y in FIG. 1G, using a substrate breaking device. After grooves were formed with a laser scribing device, the substrate was cut and individualized into chips as shown in FIG. 1I to obtain laser elements 23 .

(Mounting process to submount)
As shown in FIG. 1J, the laser element 23, which is separated into individual pieces by being bonded to the second substrate 17, is mounted on a submount 22 made of SiC via a bonding member 24 made of eutectic solder, and the n-electrode of the laser element 23 is mounted. The light emitting device 30 was obtained by mounting with the 20 side facing each other.

[Evaluation of Light Emitting Device]
(Thermal resistance reduction effect)
The thermal resistance of the light emitting device 30 obtained as described above and the light emitting device 40 of the comparative example shown in FIG. 2 were measured. The light emitting device 40 of the comparative example does not have a bonded structure, is substantially the same as the light emitting device 30 of Example 1 except that the substrate 41 is thicker than the first substrate 11a and the laser element is junction-down mounted. It has a similar configuration.
In the laser device 23 of Example 1, the thickness of the first substrate 11a is 5 μm, and the thickness of the second substrate 17a is 75 μm.
Also, the laser device of the comparative example has the semiconductor laminate 12 on one main surface side of the substrate 41 and has the striped ridge 13 like the laser device 23 of the first example. An electrode similar to the n-electrode 20 of the laser device 23 of the first embodiment is formed on the other main surface of the substrate 41 . A first p-electrode 44 (ITO film with a thickness of 200 nm, thermal conductivity: 8 W/(m·K)), an insulating film 15 and a second p-electrode 16 similar to those in Example 1 are formed on the surface of the semiconductor laminate 12. This laser element is mounted on a submount 22 similar to that of the first embodiment with a bonding member 24 made of AuSn eutectic solder.

Each of the light-emitting device 30 of Example 1 and the light-emitting device 40 of the comparative example was mounted in a package and subjected to transient thermal resistance measurement using a cooling method (static method) to estimate the thermal resistance of each material. As a result, the thermal resistance of the package and the submount did not differ greatly between Example 1 and the comparative example, but the thermal resistance of the laser element in the light emitting device of Example 1 was lower than that of the comparative example. (-0.52 K/W).
In the laser device of the comparative example, a p-electrode with low thermal conductivity (ITO film with a thickness of 200 nm, thermal conductivity: 8 W/ (m K)) and an insulating film (SiO ₂ film with a thickness of 200 nm, thermal conductivity: 1 W/(m K)). n-electrodes with high Therefore, it can be explained that a low thermal resistance value was obtained as a result.

(voltage reduction effect)
The light emitting device 30 of Example 1 described above and the light emitting device 40 of the comparative example shown in FIG.
Current-voltage measurement results are shown in FIG.
According to FIG. 3, in the light emitting device of Example 1, a voltage lower than that of the light emitting device using the laser element of the comparative example was measured (-0.17 V @ 3.0 A).

The laser device of the comparative example includes a substrate 41 (thickness: 80 μm, electrical resistivity: 0.01 Ω·cm), whereas the laser device of Example 1 includes a first substrate 11a having a thickness of 5 μm and a thickness of 75 μm. A good voltage reduction effect was exhibited by using the second substrate 17a (electric resistivity: ≤0.005Ω·cm) made of Si.

Example 2 Method of Manufacturing Light Emitting Device In Example 2, a Si substrate with a plane orientation of {111} was used as the second substrate. The {110} plane perpendicularly intersecting the {111} plane was used as the cleavage plane.
As a result, a cleavage plane substantially perpendicular to the {111} plane of the main surface of the second substrate was obtained.
In addition, in Example 2, the light emitting device was manufactured in substantially the same manner as in Example 1 except for the plane orientation of the second substrate. I can expect it.

Example 3 Method for Manufacturing Light Emitting Device In the light emitting device 50 of Example 3, as shown in FIG. 4, the element structure of the wafer is not a striped ridge, but the ridge side faces are projected from the upper surface of the second semiconductor layer. It was fabricated in the same manner as in Example 1, except that a mesa-shaped ridge 53 having grooves spaced apart by 5 μm was used.
When the wafer having this element structure is bonded to the second substrate 17 as in the first embodiment, the bonding areas of the two are different. That is, in Example 3, since the semiconductor laminate 52 as the device structure has a mesa-shaped ridge structure, the height of the ridge is the same as that of the ridge except for the groove with a width of 5 μm from the side surface of the ridge, and the first p-electrode 14 (film 200 nm-thickness ITO film) and the insulating film 15 (200 nm-thickness SiO ₂ film) are also equal, the height of the entire second p-electrode 56 (120 μm-wide) is equal except for the 5-μm-wide trench. Almost the entire surface of the electrode 56 can be bonded to the conductive layer 18 of the second substrate 17 by thermal pressure welding.
As a result, the gap 59 was only the groove portion with a width of 5 μm from the side surface of the ridge. As a result, as compared with the first embodiment, an improvement in bonding strength between the first substrate 11 and the second substrate 17 can be expected.

Example 4 Manufacturing Method of Light Emitting Device In the light emitting device 60 of Example 4, both the second p-electrode 56, which is one of the upper electrodes of the device structure, and the conductive layer 18 on the second substrate 17a are the uppermost layers. were formed in the same manner as in Example 3, except that Ni/Sn (500 nm/1100 nm) films were further formed on the Au. As shown in FIG. 5, these substrates were bonded together by thermocompression bonding to form a NiSn bonding layer 57 in the same manner as in Example 1, thereby bonding the two substrates together.
As a result, the gap of 5 μm width from the side surface of the ridge, which was generated in Example 3, can be filled by liquid phase bonding with NiSn. Therefore, this light emitting device 60 can have a larger junction area than the third embodiment. As a result, an improvement in bonding strength can be expected.

11, 11a: first substrate 12, 52: semiconductor laminate (laser element structure)
13, 53: ridges 14, 44: first p-electrode (upper surface electrode)
15: insulating film 16, 56: second p-electrode (upper surface electrode)
17, 17a: second substrate 18, 21: conductive layer 19, 59: gap 20: n-electrode (lower surface electrode)
22: submount 23: laser element 24: bonding members 30, 40, 50, 60: light emitting device 41: substrate 57: NiSn bonding layer

Claims (10)

providing a wafer having a laser device structure formed on the top side of a conductive first substrate and a top electrode formed on the top surface of the device structure;
bonding the upper electrode side of the wafer to a second substrate;
thinning the wafer by removing a portion of the first substrate;
forming a lower surface electrode on the lower surface of the thinned first substrate;
obtaining a laser element by singulating the wafer;
A method of manufacturing a light-emitting device, comprising mounting the laser element on a submount with the lower electrode facing the submount. 2. The method of manufacturing a light-emitting device according to claim 1, wherein in the step of obtaining the laser elements, grooves for division are formed in the second substrate to singulate the wafer. 3. The method of manufacturing a light-emitting device according to claim 2, wherein in the step of obtaining the laser element, the groove for division is formed in a broken line shape in a plan view. 4. The method of manufacturing a light emitting device according to claim 1, wherein in the step of thinning the wafer, a portion of the first substrate is removed by polishing and/or dry etching. wherein the first substrate and the second substrate are crystalline substrates each having an easy-cleavage plane;
1-, wherein in the step of bonding the wafer to the second substrate, the wafer is bonded to the second substrate such that the easy-cleavage surface of the first substrate and the easy-cleavage surface of the second substrate are arranged in parallel. 5. The method for manufacturing the light-emitting device according to any one of 4. 6. The method of manufacturing a light emitting device according to claim 1, wherein the first substrate is a GaN substrate, and the second substrate is a Si substrate. 7. The method according to any one of claims 1 to 6, wherein in the step of preparing the wafer, the element structure has a striped ridge on its upper side, and the wafer further has an insulating film formed on the upper surface of the element structure on both sides of the ridge. A method for manufacturing a light-emitting device according to any one of claims 1 to 3. A light emitting device comprising a submount and a laser element,
The laser element is
a first substrate that is a conductive GaN substrate;
a laser device structure formed on the upper side of the first substrate;
a bottom electrode formed on the bottom surface of the first substrate;
a top electrode formed on the top surface of the device structure;
a second substrate, which is a Si substrate, bonded to the upper electrode;
the first substrate is thinner than the second substrate;
The light-emitting device, wherein the submount is joined to face the lower surface electrode. The light emitting device according to claim 8, wherein the second substrate has an electrical resistivity lower than that of the first substrate. The element structure has a striped ridge on the upper side,
10. The light emitting device according to claim 8, further comprising an insulating film provided on the upper surface of the element structure on both sides of the ridge.