KR20070099793A - Submount for light emitting device - Google Patents

Abstract

A submount for a light-emitting device is provided to prevent the short due to the overflow of solders by forming a barrier on a substrate to block the flow of the solder during a flip-chip bonding process. A submount(30) for a light-emitting device includes a substrate(31), a pair of bonding layers(34,36), a pair of solders(35,37), and a barrier(33). The pair of bonding layers(34,36) are separated from each other on the substrate(31). The pair of solders(35,37) are formed on the pair of bonding layers(34,36) respectively. The barrier(33) is formed on the substrate(31) to be placed between the pair of solders(35,37), and blocks the flow of the solders(35,37) which are melted during a flip-chip process.

Description

Submount for light emitting device

1 schematically shows a submount for a light emitting device and a ridge waveguide type laser diode coupled thereto according to an embodiment of the present invention.

2 shows an enlarged view of a portion of FIG. 1.

3 schematically shows a submount for a light emitting device and a ridge waveguide type laser diode coupled thereto according to another embodiment of the present invention.

4 and 5 schematically show a submount and a ridge waveguide type laser diode coupled thereto according to still other embodiments of the present invention, respectively.

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

10 ... laser diode 13,15 ... first and second electrodes

30,130,230,330 ... Submount 31 ... substrate

33 ... Barrier 34,36 ... Bonding Floor

35, 37 Solder 40 Step construction

The present invention relates to a submount for a light emitting device, and more particularly to a submount for a light emitting device coupled by a light emitting device and flip chip bonding.

In general, light emitting devices such as light emitting diodes (LEDs) and laser diodes (LDs) are combined with submounts by flip chip bonding technology for smooth heat dissipation. . The submount is provided with a solder which is melt-bonded with the electrodes of the light emitting element.

By the way, during the submount flip chip bonding with the light emitting device, a short circuit may occur due to the overflow of the molten solder, which may cause a decrease in reliability and performance of the light emitting device such as a laser diode.

Therefore, in order to improve reliability in the bonding process of the light emitting device and the submount, an improved submount design that can reliably prevent a short circuit due to the overflow of the molten solder is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and is intended to prevent a short circuit due to overflow of molten solder during flip chip bonding of a light emitting device and a submount. The purpose is to provide a mount.

Submount for a light emitting device according to the present invention for achieving the above object is a substrate; A pair of bonding layers formed on the substrate to be spaced apart from each other; A pair of solders formed on the pair of bonding layers, respectively; And a barrier formed on the substrate so as to be positioned between the pair of solders to block the flow of the molten solder during the flip chip process.

The barrier may be formed of a plurality of structures spaced apart from each other or single or embossed with respect to a surface of the substrate on which at least one bonding layer of the pair of bonding layers is formed.

The barrier may be formed by etching the substrate.

The light emitting element submount may be provided to be suitable as a submount of a ridge waveguide type laser diode.

In this case, a stepped structure may be formed at a position corresponding to the ridge of the ridge waveguide type laser diode of the substrate, and one bond layer and solder among the pair of bond layers and solder may be formed on the stepped structure.

The height of the stepped structure may be formed to be less than or equal to the height of the ridge of the laser diode.

The bottom width of the stepped structure may be formed to be equal to or larger than the ridge width of the laser diode.

The barrier is embossed or engraved with respect to a surface of the substrate on which another bonding layer of the pair of bonding layers is formed, and the stepped structure has a bottom surface having the same height as the surface of the substrate on which the other bond layers are formed. It may be formed to be located at or lower than.

The pair of bonding layers may be formed on the same height surface, and the barrier may be embossed or engraved with respect to the surface on which the pair of bonding layers are formed.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of a light emitting device submount and a light emitting device assembly employing the same according to the present invention.

A light emitting device assembly having a submount according to the present invention includes a light emitting device having two electrodes and a submount that is flip chip bonded to the light emitting device. The light emitting device may be a laser diode having at least one pair of electrodes, for example, a ridge waveguide type laser diode. In addition, the light emitting device may have another type of light emitting device having at least one pair of electrodes and flip-chip bonded to the submount. Hereinafter, embodiments of a submount for a light emitting device according to the present invention will be described with respect to a case where the light emitting device is a ridge waveguide type laser diode.

FIG. 1 schematically shows a light emitting device submount 30 and a ridge waveguide type laser diode 10 coupled thereto according to an embodiment of the present invention, and FIG. 2 shows an enlarged portion of FIG. FIG. 3 schematically shows a submount 130 for a light emitting device and a ridge waveguide type laser diode 10 coupled thereto according to another embodiment of the present invention.

1 to 3, the submounts 30 and 130 for light emitting devices according to the exemplary embodiment and the other exemplary embodiment of the present invention emit light having the first and second electrodes 13 and 15. A device such as a ridge waveguide type laser diode 10 is flip-chip bonded to emit heat generated when the laser diode 10 is operated. The substrate 31 is spaced apart from each other on the substrate 31. First and second bonding layers 36 and 34 formed on the first and second bonding layers 36 and 34, respectively, and formed on the first and second bonding layers 36 and 34, respectively; A barrier formed on the substrate 31 to be positioned between the first and second solders 37 and 35 to block the flow of the first or second solders 37 and 35 melted during the flip chip process. 33 is provided.

The ridge waveguide laser diode 10 may be, for example, a GaN series III-V nitride semiconductor laser. The ridge waveguide laser diode 10 may be configured as follows, for example. The first compound semiconductor layer is provided on the substrate. The substrate may be a III-V compound semiconductor layer substrate such as GaN or SiC, or a high resistivity substrate such as a sapphire substrate. The first compound semiconductor layer may be an n-type material layer or an undoped material layer made of a GaN-based III-V nitride compound semiconductor, and may be an n-GaN layer.

The first cladding layer and the resonance layer may be sequentially provided on the first compound semiconductor layer. The first cladding layer may be an n-AlGaN / GaN layer. The resonant layer may include a first wave guide layer, an active layer, and a second waveguide layer sequentially formed on the first cladding layer. The active layer is a material layer in which lasing occurs by carrier recombination such as electron-holes, and may be a GaN-based group III-V nitride compound semiconductor layer having a multi quantum well (MQW) structure. For example, the active layer may be an InxAlyGa1-x-yN (0 ≦ x ≦ 1, 0 ≦ y ≦ 1 and x + y ≦ 1) layer. In addition, the active layer may be a material layer containing indium (In) in a predetermined ratio in the GaN-based III-V nitride compound semiconductor layer, for example, an InGaN layer. The first and second waveguide layers may be n-GaN and p-GaN layers, respectively, as GaN-based III-V nitride compound semiconductor layers. The first and second waveguide layers have a lower refractive index than the active layer, and have a higher refractive index than the first cladding layer and the second cladding layer to be described later. The second cladding layer and the second compound semiconductor layer may be sequentially formed on the resonance layer.

The second cladding layer may include a protrusion in which a portion corresponding to the center of the resonance layer protrudes in the form of a ridge, and a portion thinner than the protrusion. The second compound semiconductor layer may be provided on an upper surface of the protrusion of the second clad layer. The second cladding layer may be the same material layer as the first cladding layer except that the doping material is p-type. The second compound semiconductor layer is a GaN-based group III-V nitride compound semiconductor layer, and may be a direct transition type doped with a p-type conductive impurity. For example, the second compound semiconductor layer may be a p-GaN layer. In addition, the second compound semiconductor layer may be an AlGaN layer or an InGaN layer containing a GaN layer, aluminum (Al), or indium (In) in a predetermined ratio, similar to the first compound semiconductor layer. The second cladding layer may be covered with a protective film having a channel communicating with the second compound semiconductor layer. The p-type electrode is provided on the passivation layer as the first electrode 13 in contact with the second compound semiconductor layer through the channel.

In the ridge waveguide type laser diode 10 having the above structure, the first compound semiconductor layer is formed stepwise so that the ridge 11 is positioned and the first portion 17 on which the first electrode 13 is formed. The second electrode 15 may be formed stepped so as to protrude from the second portion 18 on which the second electrode 15 is formed. The second electrode 15 may be formed on the stepped first compound semiconductor layer as an n-type electrode.

Bonding metal layers 21 and 23 may be formed on the first and second electrodes 13 and 15, respectively.

In this ridge waveguide type laser diode 10, the p-type electrode and the n-type electrode, that is, the first and second electrodes 13 and 15 are stepped from each other.

The submounts 30 and 130 are, for example, flip chip bonded with the ridge waveguide type laser diode 10 to dissipate heat generated during operation of the laser diode 10.

In the submounts 30 and 130, the substrate 31 may be made of an insulating material such as ceramic. The first and second bonding layers 36 and 34 may be made of a metal having excellent electrical conductivity and good adhesion to the first and second solders 37 and 35. The first and second bonding layers 36 and 34 may be formed of any one of Au, Ti, Pt, Cr, or at least two or more alloys such as Cr / Au, Ti / Pt / Au, and the like.

The first and second solders 37 and 35 are formed on the first and second bonding layers 36 and 34, respectively. The first and second solders 37 and 35 are used to bond the first and second electrodes 13 and 15 and the first and second bonding layers 36 and 34 of the laser diode 10 to each other. It can be made of an alloy excellent in meltability and thermal conductivity. The first and second solders 37 and 35 may include at least two or more alloys of Cr, Ti, Pt, Au, Mo, and Sn, for example, Au / Sn, Pt / Au / Sn, and Cr / Au. / Sn and the like.

The layer thicknesses of the first and second solders 37 and 35 are preferably formed in consideration of the positional difference in the vertical direction of the first and second electrodes 13 and 15 in the laser diode 10. Do. For example, as shown in FIGS. 1 and 3, the first portion 17 in which the ridge 11 is positioned and the first electrode 13 is formed is the second portion 18 in which the second electrode 15 is formed. When stepped so as to protrude more than), the second solder 35 bonded to the second electrode 15 may be formed thicker than the first solder 37 bonded to the first electrode 13. As another example, the second solder 35 may be formed to have the same or similar thickness as the first solder 37 by protruding the portion of the substrate where the second solder 35 is located.

The barrier 33 is a surface portion of the substrate 31 on which at least one bonding layer, for example, a second bonding layer 34, of the pair of bonding layers 36 and 34 is formed (hereinafter, referred to as a reference surface portion 32). It may be formed of a plurality of structures spaced apart from each other, single or embossed with respect to). The barrier 33 may be formed by etching the substrate 31.

1 shows an example in which the barrier 33 is formed of a plurality of structures, for example, six, spaced apart from each other at an embossed angle with respect to the reference plane portion 32. 3 shows an example in which the barrier 33 is formed of a plurality of structures, for example, five structures spaced apart from each other at a negative angle with respect to the reference plane portion 32. The barrier 33 may be formed in a single structure of embossed or engraved.

On the other hand, when applied to the ridge waveguide type laser diode 10, the submount 30, 130 according to the present invention, as shown in Figures 1 to 3, of the laser diode 10 of the substrate 31 It is more preferable that the stepped structure 40 is formed at a position corresponding to the ridge 11 so as to distribute the load applied to the ridge 11 so as to alleviate stress due to the load.

That is, the stepped structure 40 is formed on the substrate 31 such that the portion corresponding to the ridge 11 of the laser diode 10 becomes the bottom surface 38, and the first bond is formed on the stepped structure 40. Layer 36 and first solder 37 may be formed.

When the barrier 33 is embossed with respect to the reference plane portion 32 as in FIG. 1, the bottom surface 38 of the stepped structure 40, like the barrier 33, is the reference plane portion 32. Located at the same height as). When the barrier 33 is formed intaglio with respect to the reference surface portion 32 as in FIG. 3, the bottom surface 38 of the stepped structure 40, like the barrier 33, is the reference surface portion 32. It is located further down.

At this time, the height Hs of the stepped structure 40 is preferably smaller than or equal to the ridge height Hr of the laser diode 10. In addition, the bottom width Ws of the stepped structure 40 is preferably equal to or larger than the ridge width Wr of the laser diode 10. For example, the stepped structure 40 may be formed such that its bottom width Ws is at least 1.5 times the ridge width Wr of the laser diode 10.

In the case where the height Hs of the stepped structure 40 and the bottom surface width Ws of the stepped structure 40 are formed under the above conditions, the surface of the portion other than the ridge 11 of the first portion 17 ( 17a) comes into contact with the upper surface 39 of the stepped structure 40 to disperse the stress concentrated on the ridge 11 during flip chip bonding, thereby preventing performance degradation of the laser diode 10. can do. In addition, by using the barrier 33 and the stepped structure 40, the bonding force can be increased during the flip chip bonding of the laser diode 10 and the submount 30, so that the solders 37 and 35 and the laser diode can be increased. It is possible to improve the bonding quality between the (10).

In addition, using the submount 30 according to the present invention, the barrier 33 is provided between the two solders 37 and 35, so that the first and second solders 37 (melted during flip chip bonding) ( 35. That is, the overflow of the pn solder can be prevented, so that the short circuit of the laser diode 10 can be suppressed and the reliability is improved.

On the other hand, in the above, the submount 30 according to the present invention is distributed to the portion of the substrate 31 corresponding to the ridge 11 so as to distribute the load applied to the ridge 11 to alleviate stress caused by the load. Although the case where the stepped structure 40 is formed has been described and illustrated by way of example, as shown in FIGS. 4 and 5, the submounts 230 and 330 according to the present invention have a portion corresponding to the ridge 11. It may have a structure without the step structure 40 for load distribution. 4 and 5 show submounts 230 and 330 according to still another embodiment of the present invention, respectively, and the same reference numerals as in FIGS. 1 to 3 denote members having substantially the same or similar functions. Indicates.

In FIG. 4, an example in which the barrier 33 is formed of a plurality of structures, for example, five structures spaced apart from each other at an embossed position with respect to the reference surface portion 32 on which the second solder 35 is provided is shown. In FIG. 5, an example in which the barrier 33 is formed of a plurality of structures, for example, four spaced apart from each other at a negative angle with respect to the reference surface portion 32 on which the second solder 35 is provided is shown. The barrier 33 may be formed in a single structure of embossed or engraved.

In this case, as shown in FIG. 4, when the barrier 33 is embossed with respect to the reference surface portion 32, the surface portion on which the first solder 37 is provided is similar to the barrier 33. It is located at the same height as (32). In addition, when the barrier 33 is intaglio with respect to the reference plane portion 32 as shown in FIG. It is located lower than). At this time, the interval Hs' between the upper surface of the first solder 37 and the upper portion of the barrier 33 is preferably equal to or smaller than the height Hr of the ridge.

According to the submount for a light emitting device according to the present invention as described above, by forming a barrier on the substrate to be located between a pair of solder, it is possible to block the flow of solder during the flip chip bonding process. Therefore, it is possible to prevent a short circuit due to overflow of the molten solder during flip chip bonding of the light emitting element and the submount.

In addition, when the stepped structure is formed in a portion corresponding to the ridge of the ridge waveguide laser diode, the home audio may be distributed to the ridge during ridge waveguide laser diode and sub-mount flip chip bonding.

Claims (9)

A substrate; A pair of bonding layers formed on the substrate to be spaced apart from each other; A pair of solders formed on the pair of bonding layers, respectively; And a barrier formed on the substrate to be positioned between the pair of solders to block the flow of the molten solder during the flip chip process. The sub-light emitting device as claimed in claim 1, wherein the barrier is formed in a plurality of structures spaced apart from each other or single or embossed with respect to a surface of the substrate on which at least one bonding layer is formed. Mount. The submount of claim 2, wherein the barrier is formed by etching the substrate. 4. The submount for a light emitting element according to any one of claims 1 to 3, which is adapted to be suitable as a submount of a ridge waveguide type laser diode. The stepped structure according to claim 4, wherein a stepped structure is formed at a position corresponding to the ridge of the ridge waveguide type laser diode of the substrate, The submount for a light emitting device, characterized in that the one bond layer and the solder of the pair of bond layers and solder is formed on the stepped structure. 6. The submount of claim 5, wherein the height of the stepped structure is less than or equal to the height of the ridge of the laser diode. 6. The submount of claim 5, wherein the bottom width of the stepped structure is equal to or larger than the ridge width of the laser diode. The method of claim 5, wherein the barrier is embossed or engraved with respect to a surface of the substrate on which another bonding layer of the pair of bonding layers is formed, And the stepped structure is formed such that its bottom surface is located at the same height as or lower than the surface of the substrate on which the other bond layer is formed. The submount of claim 4, wherein the pair of bonding layers are formed on the same height, and the barrier is embossed or engraved with respect to the surface on which the pair of bonding layers are formed.

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