Laser Diode

Abstract

To provide a laser diode.SOLUTION: A laser diode comprises: an electronic substrate having a substrate thermal expansion coefficient; an epitaxial structure which is formed in the electronic substrate; and a composite multilayer metal plate which is provided below the electronic substrate, is provided in the state of overlapping each other, includes first and second metal layers being different in material, and has a modulated thermal expansion coefficient. The electronic substrate, which has an initial thickness when the epitaxial structure is grown, is coupled to the composite multilayer metal plate after it is thin-walled to a coupling thickness. The modulated thermal expansion coefficient of the composite multilayer metal plate and the substrate thermal expansion coefficient are approximate to each other. Thus, the heat radiation capacity and light emission efficiency of the laser diode can be increased.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to diodes and methods for manufacturing diodes, and in particular to laser diodes capable of emitting light and methods for manufacturing laser diodes. [Background technology]

[0002] Laser diodes are made of semiconductors and their epitaxial structure includes a distributed Bragg reflector (DBR) that can form an optical cavity that reflects photons, and have the advantage of being more efficient than other light-emitting diodes.

[0003] When a laser diode is in operation, the epitaxial structure generates a large amount of thermal energy which is then transferred to the original substrate below the epitaxial structure. Since the original substrate is generally made of gallium arsenide and has a relatively low thermal conductivity, there is a problem of poor heat dissipation. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of this, how to improve the structure of the laser diode in order to solve the above problems has become a goal that related parties strive to pursue. [Means for solving the problem]

[0005] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS In order to solve the above problems, the present invention provides a laser diode and a manufacturing method thereof, which can contribute to increasing the heat dissipation capability of the laser diode and improving its efficacy through its structural arrangement.

[0006] According to one embodiment of the present invention, a laser diode is provided, comprising: an original substrate having a substrate thermal expansion coefficient; an epitaxial structure formed on the original substrate; and a composite multi-layer metal plate disposed below the original substrate and including at least a first metal layer and a second metal layer which are stacked on top of each other and made of different materials, the composite multi-layer metal plate having a modulated thermal expansion coefficient, wherein the original substrate has an initial thickness when growing the epitaxial structure, and is bonded to the composite multi-layer metal plate after being thinned to a bonding thickness, and the modulated thermal expansion coefficient of the composite multi-layer metal plate is close to the thermal expansion coefficient of the substrate.

[0007] Thus, the composite multi-layer metal plate can increase the heat dissipation capacity of the laser diode, and the original substrate is thinned, so that the vertical distance of its heat conduction is shortened, and the time of heat energy conduction to the composite multi-layer metal plate can be accelerated. In addition, since the composite multi-layer metal plate includes a first metal layer and a second metal layer of different materials, the thickness is controlled so that the modulated thermal expansion coefficient is close to the thermal expansion coefficient of the substrate, so that separation due to the excessive difference in thermal expansion coefficients after bonding between the original substrate and the composite multi-layer metal plate can be avoided. In addition, bonding the composite multi-layer metal plate can effectively improve the light output efficiency.

[0008] According to the laser diode of the above embodiment, the laser diode may have a vertical cavity surface emitting laser diode structure.

[0009] According to the laser diode of the above embodiment, the material of the original substrate can be gallium arsenide, the epitaxial structure has an epitaxial thermal expansion coefficient, and the substrate thermal expansion coefficient is close to the epitaxial thermal expansion coefficient.

[0010] According to the laser diode of the above embodiment, the epitaxial structure may include a first reflector provided on the original substrate, an active layer provided on the first reflector, and a second reflector provided on the active layer.

[0011] According to the laser diode of the above embodiment, the first reflector may be stacked from a plurality of N-type reflective layers, and the second reflector may be stacked from a plurality of P-type reflective layers, and the number of the P-type reflective layers may be greater than the number of the N-type reflective layers.

[0012] According to the laser diode of the above embodiment, the laser diode may have an edge-emitting laser diode structure.

[0013] According to the laser diode of the above embodiment, the composite multilayer metal plate may further include a third metal layer, the second metal layer is disposed between the first metal layer and the third metal layer, and the third metal layer and the first metal layer are made of the same material.

[0014] In the laser diode of the embodiment, the thicknesses of the first metal layer and the third metal layer may be smaller than the thickness of the second metal layer.

[0015] According to the laser diode of the above embodiment, the material of the first metal layer and the third metal layer may be copper, and the material of the second metal layer may be nickel-iron alloy.

[0016] According to another embodiment of the present invention, there is provided a method for manufacturing a laser diode, the method including: an epitaxial structure growing step of forming an epitaxial structure on an original substrate having an initial thickness; an original substrate thinning step of performing a thinning process to thin the original substrate to a bonding thickness; and a composite multi-layer metal plate installation step of providing a composite multi-layer metal plate below the original substrate, the composite multi-layer metal plate including at least a first metal layer located between the original substrate and a second metal layer, and a second metal layer.

[0017] The manufacturing method of the laser diode may further include a mesa etching step of removing a part of the epitaxial structure, and an oxidation step of performing an oxidation process on the second reflector, the epitaxial structure including a first reflector, an active layer and a second reflector which are sequentially stacked on an original substrate, to form an oxidized portion which is hollow and has an inner edge.

[0018] According to the above-mentioned method for manufacturing a laser diode, in the original substrate thinning step, a temporary substrate may be attached above the epitaxial structure, and the thinning process may be performed by polishing.

[0019] According to the above-mentioned method for manufacturing a laser diode, the temporary substrate may be removed in the composite multi-layer metal plate installation step.

[0020] The method for manufacturing the laser diode may further include, after the step of providing the composite multi-layer metal plate, an electrode forming step of providing a P-type metal layer on the second reflector.

[0021] The method for manufacturing the laser diode may further include a metal pad forming step of forming a metal pad connected to the P-type metal layer. [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic front view showing a laser diode according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic perspective view showing a laser diode according to a second embodiment of the present invention. [Diagram 3] 10 is a block flow chart showing a method for manufacturing a laser diode according to a third embodiment of the present invention. [Figure 4] 4 is a manufacturing flow chart showing a method for manufacturing the laser diode of the third embodiment of FIG. 3; [Diagram 5] 4 is a schematic top view showing a laser diode manufactured by applying the manufacturing method of the laser diode of the third embodiment shown in FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. For clarity, many practical details are described in the following description. However, the reader should understand that these practical details are not intended to limit the present invention. That is, in some embodiments of the present invention, these practical details are not necessary. In addition, in order to simplify the drawings, some conventional structures and elements are simply and diagrammatically shown in the drawings. Also, duplicated elements may be represented by the same or similar numbers.

[0024] In addition, in this specification, the terms "first", "second", "third", etc. are merely used to describe different elements or components, but are not intended to limit the elements or components themselves, so a first element or component may be called a second element or component. In addition, the combinations of elements, components, mechanisms, and modules in this specification are not generally known, routine, or customary in this field, and it is not possible to determine whether the combination relationship can be easily completed by a person skilled in the art based on whether the elements, components, mechanisms, and modules themselves are known.

[0025] Please refer to FIG. 1, which is a front view of a laser diode 100 according to a first embodiment of the present invention. The laser diode 100 includes an original substrate 110, an epitaxial structure 120, and a composite multi-layer metal plate 130. The original substrate 110 has a substrate thermal expansion coefficient, and the epitaxial structure 120 is formed on the original substrate 110. The composite multi-layer metal plate 130 is disposed under the original substrate 110 and includes at least a first metal layer 131 and a second metal layer 132 that are stacked on top of each other and made of different materials, and has a modulated thermal expansion coefficient. The original substrate 110 has an initial thickness when growing the epitaxial structure 120, and is thinned to a bonding thickness before bonding to the composite multi-layer metal plate 130, and the modulated thermal expansion coefficient of the composite multi-layer metal plate 130 is close to the substrate thermal expansion coefficient.

[0026] Thus, the composite multi-layer metal plate 130 can increase the heat dissipation ability of the laser diode 100, and since the original substrate 110 has already been thinned, the vertical distance of the heat conduction is shortened, and the heat energy can be conducted to the composite multi-layer metal plate 130 quickly. In addition, since the composite multi-layer metal plate 130 includes the first metal layer 131 and the second metal layer 132 made of different materials, the thickness can be controlled so that the modulated thermal expansion coefficient is close to the thermal expansion coefficient of the substrate, so that the original substrate 110 and the composite multi-layer metal plate 130 are not separated due to the large difference in thermal expansion coefficient after bonding. In addition, bonding the composite multi-layer metal plate 130 can effectively improve the light output efficiency, especially the light output and the light conversion efficiency. The details of the laser diode 100 will be described in detail later.

[0027] The laser diode 100 of the first embodiment may have a Vertical-Cavity Surface-Emitting Laser (VCSEL) structure. Therefore, the epitaxial structure 120 may include a first reflector 121, an active layer 123, and a second reflector 122. The first reflector 121 is disposed on the original substrate 110, the active layer 123 is disposed on the first reflector 121, and the second reflector 122 is disposed on the active layer 123.

[0028] The first reflector 121 may be stacked with a plurality of N-type reflective layers 1211, and the material may be an N-type semiconductor doped with an N-type dopant. The active layer 123 may be a quantum well. The second reflector 122 may be stacked with a plurality of P-type reflective layers 1221, and the material may be a P-type semiconductor doped with a P-type dopant, and the number of layers of the P-type reflective layers 1221 may be greater than the number of layers of the N-type reflective layers 1211. In addition, the epitaxial structure 120 may include an oxide portion 124 located in the second reflector 122 and having an inner edge 1241. The epitaxial structure 120 of the laser diode 100 is well known and is not the focus of the present invention, so the details thereof will not be described in detail, and in other embodiments, the epitaxial structure is not limited by the above disclosure.

[0029] The original substrate 110 may be made of gallium arsenide (GaAs), and the substrate thermal expansion coefficient is about 5.73 ppm / K and the thermal conductivity coefficient is about 52 W / (mK), while the epitaxial structure 120 may have an epitaxial thermal expansion coefficient, and the epitaxial thermal expansion coefficient may be about 5.5 ppm / K to 5.8 ppm / K, so that the substrate thermal expansion coefficient is close to the epitaxial thermal expansion coefficient. The original substrate 110 may initially have an initial thickness of, for example, 430 μm, and the first reflector 121, the active layer 123, and the second reflector 122 are sequentially grown. Thereafter, the original substrate 110 may be thinned, for example by polishing, to reduce the initial thickness to a bonding thickness of, for example, less than 150 μm, and then bonded to the composite multilayer metal plate 130. In one embodiment, the bonding thickness may be 120 μm, and in another embodiment, the bonding thickness may be 100 μm, but is not limited thereto. Note that, the thinner the bonding thickness of the original substrate 110, the more it can contribute to improving the light output and light conversion efficiency.

[0030] The composite multi-layer metal plate 130 may further include a third metal layer 133, where the second metal layer 132 is disposed between the first metal layer 131 and the third metal layer 133, and the third metal layer 133 and the first metal layer 131 are made of the same material. The materials of the first metal layer 131 and the third metal layer 133 may be, for example, copper, and the material of the second metal layer 132 may be, for example, but not limited to, a nickel-iron alloy.

[0031] In addition, the thickness of the first metal layer 131 and the third metal layer 133 may be smaller than that of the second metal layer 132, and the ratio of the thickness of the first metal layer 131, the second metal layer 132 and the third metal layer 133 may be between 1:3:1 and 1:9:1. In this way, different modulated thermal expansion coefficients can be arranged according to the original substrate 110 made of different materials. For example, the modulated thermal expansion coefficient of the composite multilayer metal plate 130 can be about 5.8 ppm / K to 6.0 ppm / K, which is between plus and minus 5% with respect to the thermal expansion coefficient of the substrate, and the thermal conductivity coefficient can be about 180 W / (mK) to effectively dissipate heat, and the thermal resistance can be about 20% lower than that of a conventional laser diode. In addition, the resistivity of the composite multilayer metal plate 130 can be about 10 -11 Since the resistivity of the original substrate 110 made of gallium arsenide is about 0.01MΩ·cm to 100MΩ·cm, when the original substrate 110 is thinned and the composite multilayer metal plate 130 is attached, the resistance of the entire laser diode 100 is reduced, the current density is improved, and the light output can be effectively increased. In addition, the Young's modulus of the composite multilayer metal plate 130 is 130 Gpa, and the Young's modulus of the original substrate 110 made of gallium arsenide is 83 Gpa, so that the supporting epitaxial structure 120 can be strengthened by the composite multilayer metal plate 130.

[0032] Please refer to FIG. 2, which is a perspective schematic diagram showing a laser diode 200 according to a second embodiment of the present invention. The laser diode 200 also includes an original substrate 210, an epitaxial structure 220, and a composite multi-layer metal plate 230, and the composite multi-layer metal plate 230 may include a first metal layer 231, a second metal layer 232, and a third metal layer 233, but is different from the first embodiment in that the laser diode 200 may have an edge emitting laser diode structure (Edge Emitting Laser; EEL). Therefore, the epitaxial structure 220 may include, for example, an N-type buffer layer, an N-type cladding layer, a lower separated confinement hetero-structure layer (Separated Confinement Hetero-structure; SCH), an active layer, an upper separated confinement hetero-structure layer, a P-type cladding layer, and a contact layer, and may have a ridge structure. In addition, the original substrate 210 in the second embodiment may be indium phosphide (InP), and by adjusting the thicknesses of the first metal layer 231, the second metal layer 232 and the third metal layer 233 of the composite multilayer metal plate 230, the modulated thermal expansion coefficient of the composite multilayer metal plate 230 can be made close to the thermal expansion coefficient of the substrate.

[0033] Please refer to Figures 3, 4 and 5, Figure 3 is a block flow chart showing a method for manufacturing a laser diode S300 according to a third embodiment of the present invention, Figure 4 is a manufacturing flow chart showing the method for manufacturing a laser diode S300 of the third embodiment of Figure 3, and Figure 5 is a top view schematic diagram showing a laser diode 300 manufactured by applying the method for manufacturing a laser diode S300 of the third embodiment of Figure 3. The method for manufacturing a laser diode S300 includes an epitaxial structure growth process S01, an original substrate thinning process S02, and a composite multi-layer metal plate installation process S03.

[0034] In the epitaxial structure growth step S01, an epitaxial structure 320 is formed on an original substrate 310 having an initial thickness D1.

[0035] In the original substrate thinning step S02, a thinning process is carried out to thin the original substrate 310 to a bonding thickness D2.

[0036] In the composite multi-layer metal plate installation step S03, a composite multi-layer metal plate 330 including at least a first metal layer 331 located between the original substrate 310 and the second metal layer 332, and a second metal layer 332 is provided below the original substrate 310.

[0037] Therefore, by thinning the original substrate 310 and then attaching it to the composite multi-layer metal plate 330, the light emitting performance and heat dissipation ability of the laser diode 300 can be effectively improved.

[0038] The laser diode manufacturing method S300 may further include a mesa etching step S06 and an oxidation step S07. In the mesa etching step S06, a part of the epitaxial structure 320 is removed. In the oxidation step S07, the epitaxial structure 320 includes a first reflector 321, an active layer 323, and a second reflector 322 which are stacked on the original substrate 310 in order, and an oxidation process is performed on the second reflector 322 to form an oxidation part 324 which is hollow and has an inner edge 3241.

[0039] 3 and 4, first, an epitaxial structure growing step S01 is carried out to grow an epitaxial structure 320 on an original substrate 310, and in this case, the original substrate 310 has not yet been thinned, so that the initial thickness D1 is greater than the bond thickness D2. Then, an original substrate thinning step S02 is carried out to firstly attach a temporary substrate T1 onto the epitaxial structure 320, and then carry out a thinning process such as polishing, so that the temporary substrate T1 is positioned so that the polisher pinches the temporary substrate T1 instead of the epitaxial structure 320, and the epitaxial structure 320 is not destroyed.

[0040] A composite multi-layer metal plate installation step S03 may be performed later, and the composite multi-layer metal plate 330 may be provided under the original substrate 310, and the temporary substrate T1 may be removed. The composite multi-layer metal plate 330 may include a first metal layer 331, a second metal layer 332, and a third metal layer 333 stacked on each other in sequence, as in the first embodiment, and the first metal layer 331, the second metal layer 332, and the third metal layer 333 may be arranged in advance so that the modulated thermal expansion coefficient of the composite multi-layer metal plate 330 is close to the substrate thermal expansion coefficient of the original substrate 310.

[0041] The laser diode manufacturing method S300 may further include a die bond metal layer forming step S04 and an electrode forming step S05 after the composite multilayer metal plate installation step S03. In the die bond metal layer forming step S04, a die bond metal layer 350 used for die bonding later is formed under the composite multilayer metal plate 330. In the electrode forming step S05, a P-type metal layer 340 is provided on the second reflector 322, and the P-type metal layer 340 may be a hollow ring. Then, a mesa etching step S06 is also performed to etch a part of the first reflector 321, the active layer 323, and the second reflector 322 to form a mesa. Then, an oxidation step S07 may be performed to form an oxidation portion 324 in the second reflector 322. In another embodiment, the die bond metal layer may not be produced, and the die bond metal layer forming step may be omitted.

[0042] The manufacturing method S300 of the laser diode may further include a metal pad forming step S08 of forming a protective layer 380 having extinction properties, the material of which is, for example, polyphenylene oxide (PPO), and a metal pad 370 may be formed on the protective layer 380, the metal pad 370 is connected to the P-type metal layer 340, and the hollow portion of the P-type metal layer 340 is filled with a silicon nitride layer 360. Finally, the laser diode 300 as shown in FIG. 5 is formed.

[0043] As can be seen from the above description, the laser diode of the present invention has good performance and does not require an additional etch stop layer made of AlAs between the epitaxial structure and the original substrate, while retaining the original substrate, thus avoiding the current crowding effect caused by the high resistance of AlAs and the mismatch of the thermal expansion coefficient of AlAs and the modulated thermal expansion coefficient of the composite multi-layer metal plate.

[0044] Although the present invention has been disclosed by way of the above-mentioned embodiment, the present invention is not limited to the embodiment, and those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention is based on the contents specified in the following claims. [Explanation of symbols]

[0045] 100, 200, 300: Laser diode 110, 210, 310: Original board 120, 220, 320: Epitaxial structure 121, 321: First reflector 1211:N type reflective layer 122, 322: Second reflector 1221:P type reflective layer 123, 323: Active layer 124, 324: Oxidation part 1241, 3241: Common-law marriage 130, 230, 330: Composite multi-layer metal plate 131, 231, 331: first metal layer 132, 232, 332: second metal layer 133, 233, 333: Third metal layer 340:P type metal layer 350: Die bond metal layer 360: Silicon nitride layer 370: Metal pad 380:Protective layer S300: Laser diode manufacturing method S01: Epitaxial structure growth process S02: Original substrate thinning process S03: Composite multi-layer metal plate installation process S04: Die bond metal layer formation process S05: Electrode formation process S06: Mesa etching process S07: Oxidation process S08: Metal pad formation process D1: Initial thickness D2: Bond thickness T1: Temporary board

Claims

1. an original substrate having a substrate thermal expansion coefficient; an epitaxial structure formed on the original substrate; a composite multi-layer metal plate having a modulated thermal expansion coefficient, comprising a first metal layer, a second metal layer and a third metal layer disposed under the original substrate and stacked on top of each other, the second metal layer being disposed between the first metal layer and the third metal layer, the first metal layer and the second metal layer being made of different materials, and the third metal layer and the first metal layer being made of the same material, the first metal layer and the third metal layer being made of copper, and the second metal layer being made of a nickel-iron alloy; Equipped with The original substrate has an initial thickness when growing the epitaxial structure, and is thinned to a bonding thickness of less than 150 μm before being bonded to the composite multilayer metal plate, and the modulated thermal expansion coefficient of the composite multilayer metal plate is between plus and minus 5% with respect to the thermal expansion coefficient of the substrate.

2. 10. The laser diode of claim 1, wherein the laser diode has a vertical cavity surface emitting laser diode structure.

3. 3. The laser diode of claim 2, wherein the material of the original substrate is gallium arsenide, the epitaxial structure has an epitaxial thermal expansion coefficient, and the substrate thermal expansion coefficient is about 5.5 ppm / K to 5.8 ppm / K.

4. The epitaxial structure is a first reflector provided on the original substrate; an active layer provided on the first reflector; a second reflector provided on the active layer; 3. The laser diode of claim 2 .

5. 5. The laser diode of claim 4, wherein the first reflector is formed of a plurality of N-type reflecting layers, the second reflector is formed of a plurality of P-type reflecting layers, and the number of layers of the P-type reflecting layers is greater than the number of layers of the N-type reflecting layers.

6. 10. The laser diode of claim 1, wherein the laser diode has an edge-emitting laser diode structure.

7. 2. The laser diode of claim 1, wherein the thicknesses of the first metal layer and the third metal layer are less than the thickness of the second metal layer.

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