Semiconductor laser chip adopting patterned metal substrate and preparation method of semiconductor laser chip

Abstract

The invention relates to a semiconductor laser chip adopting a patterned metal substrate and a preparation method of the semiconductor laser chip, and solves the problems that when an existing semiconductor laser chip adopts a gallium arsenide material as a chip substrate, the heat of a heat source generated by the chip substrate is high, and a traditional heat dissipation path is large in heat resistance and poor in heat dissipation efficiency during heat transfer. The etching groove is formed in the original chip substrate, the deposited metal layer is arranged in the etching groove to replace a part of gallium arsenide substrate material, and the metal material in the deposited metal layer is low in resistance and high in heat conductivity coefficient, so that the overall resistance value of the chip substrate is reduced, the heat of a heat source is reduced, and the electro-optical conversion efficiency is improved; the deposited metal layer is located on the lower side of the light-emitting unit, so that heat generated by the light-emitting unit can be conducted to the solder layer through the deposited metal layer and then transmitted to the heat sink, a heat transfer path is reconstructed, the thermal resistance of the deposited metal layer is low, the conduction thermal resistance on the whole heat transfer path can be reduced, and heat dissipation is enhanced.

Description

Technical Field

[0001] The invention relates to a semiconductor laser chip, in particular to a semiconductor laser chip using a patterned metal substrate and a preparation method thereof. Background Art

[0002] In the field of optics, the main electro-optical conversion component for converting electrical energy into light energy is a semiconductor laser chip. However, some semiconductor laser chips have requirements for electrodes, and generally require the chip to be packaged in a positive package. For example, for a semiconductor laser chip with a separated electrode design, the existing design scheme is to set the light-emitting unit 4 of the semiconductor laser chip on the chip substrate 3, and the chip substrate 3 is fixed on the heat sink 1 through the solder layer 2, and the entire chip is packaged in a positive package. The specific structure is as follows: Figure 1 As shown, however, with this arrangement, when the light emitting unit 4 transfers heat, the conduction thermal resistance in the vertical direction is relatively large, and the chip substrate 3 will also generate relatively high heat source heat.

[0003] The heat generated by semiconductor laser chips is mainly divided into three parts: non-radiative recombination, free carrier absorption and Joule heat. Among them, non-radiative recombination and free carrier absorption are related to the epitaxial structure design of the light-emitting unit 4, and Joule heat is mainly generated in the electrodes, the light-emitting unit 4 and the chip substrate 3. For a specific laser structure, the thermal resistance and resistance of the electrode and the active area epitaxial structure cannot be changed, so the focus of chip heat dissipation research is now on the chip substrate 3. However, at present, near-infrared semiconductor laser chips generally use gallium arsenide materials to make chip substrates 3, and gallium arsenide is a semiconductor material with high resistivity (for example, a typical n-type doped 1*10 20 cm -3 , 3.6*10 -3 The characteristics of low Ω∙cm) and low thermal conductivity (typical value 46 W / m∙K) not only generate additional Joule heat, but also have relatively poor thermal and current conduction properties.

[0004] When the semiconductor laser chip generates heat, the heat generated by the light-emitting unit 4 is transferred to the solder layer 2 through the gallium arsenide substrate, and then conducted to the heat sink 1 through the solder layer 2. The heat is guided by the heat sink 1 to the coolant inside it, and heat exchange occurs at the solid-liquid interface, and the coolant takes away the heat. This traditional heat dissipation path has the problems of large thermal resistance and poor heat dissipation efficiency during heat transfer due to the characteristics of the gallium arsenide substrate. Although the existing semiconductor laser chip adopts a new flip-chip packaging method to solve the problem of thermal conductivity characteristics, it still does not solve the problem of excessive heat from the chip substrate 3 heat source. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problems that when the existing semiconductor laser chip adopts gallium arsenide material as the chip substrate, the heat source generated by the chip substrate is high, and its heat dissipation path has large thermal resistance and poor heat dissipation efficiency during heat transfer, and to provide a semiconductor laser chip using a patterned metal substrate and a preparation method thereof.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: A semiconductor laser chip using a patterned metal substrate comprises a chip substrate and a plurality of light-emitting units located on the top of the chip substrate; the plurality of light-emitting units are evenly arranged along the length or width direction of the chip substrate, are arranged in parallel with each other, and a gap is arranged between two adjacent light-emitting units; a solder layer is arranged on the lower surface of the chip substrate, a heat sink is arranged on the lower surface of the solder layer, and the chip substrate is fixed to the upper surface of the heat sink through the solder layer, and the special features thereof are: The chip substrate is provided with a plurality of etching grooves, the depth direction of the etching grooves is arranged along the thickness direction of the chip substrate, the plurality of etching grooves are respectively located at the lower side of the plurality of light-emitting units and correspond to the positions of the light-emitting units; A deposited metal layer matching the shape of the etching grooves is respectively disposed in each of the etching grooves, and the bottom end surface of the deposited metal layer is flush with the lower surface of the chip substrate and contacts the upper surface of the solder layer; The depth of the etched groove is the same as the thickness of the chip substrate, and the top width is 10%-150% of the width of the light-emitting unit. The bottom of the light-emitting unit is in contact with the chip substrate and the deposited metal layer. Alternatively, the depth of the etched groove is not less than 50% of the thickness of the chip substrate, the top width is 10%-150% of the width of the light emitting unit, and the opening is arranged downward, and the bottom of the light emitting unit is connected to the top of the chip substrate.

[0007] Furthermore, the projection shape of the etching groove in a vertical plane perpendicular to the length direction of the light-emitting unit is a rectangle, an isosceles trapezoid or a step shape.

[0008] Furthermore, the depth of the etching groove is the same as the thickness of the chip substrate, the top width of the etching groove is greater than or equal to 10% of the width of the light-emitting unit and less than or equal to 50% of the width of the light-emitting unit, a plurality of etching grooves are arranged on the bottom surface of a light-emitting unit, the arrangement direction of the plurality of etching grooves is the same as the arrangement direction of the light-emitting unit and the plurality of etching grooves are arranged parallel to each other, and the distance between two adjacent etching grooves is 50%-100% of the top width of the etching groove; Alternatively, the depth of the etching groove is the same as the thickness of the chip substrate, the top width of the etching groove is greater than 50% of the width of the light-emitting unit and less than or equal to 150% of the width of the light-emitting unit, and one etching groove is arranged on the bottom surface of a light-emitting unit.

[0009] Furthermore, the depth of the etching groove is not less than 50% of the thickness of the chip substrate, the top width of the etching groove is greater than or equal to 10% of the width of the light-emitting unit and less than or equal to 50% of the width of the light-emitting unit, a plurality of etching grooves are arranged on the bottom surface of a light-emitting unit, the arrangement direction of the plurality of etching grooves is the same as the arrangement direction of the light-emitting unit and the plurality of etching grooves are arranged parallel to each other, and the distance between two adjacent etching grooves is 50%-100% of the top width of the etching groove; Alternatively, the depth of the etching groove is not less than 50% of the thickness of the chip substrate, the top width of the etching groove is greater than 50% of the width of the light-emitting unit and less than or equal to 150% of the width of the light-emitting unit, and an etching groove is provided on the bottom surface of a light-emitting unit.

[0010] At the same time, the present invention also provides a method for preparing a semiconductor laser chip using a patterned metal substrate as described above, which is special in that it includes the following steps: S1, prepare semiconductor laser chip; S2, removing a part of the chip substrate by etching on the chip substrate to form a plurality of etching grooves, wherein the plurality of etching grooves are respectively located at the lower sides of the plurality of light-emitting units and correspond to the positions of the light-emitting units; S3, filling metal materials in the multiple etching grooves by using a deposition technology to form multiple deposited metal layers; S4, after the deposition is completed, the lower surface of the chip substrate is polished so that the bottom end surface of the deposited metal layer is flush with the lower surface of the chip substrate, and the lower surface of the chip substrate remains flat as a whole; S5. Solder the lower surface of the chip substrate to the upper surface of the heat sink through the solder layer, and the bottom end surface of the deposited metal layer contacts the upper surface of the solder layer, thereby completing the preparation of the semiconductor laser chip using the patterned metal substrate.

[0011] Furthermore, in step S2, the etching method is dry etching or wet etching.

[0012] Furthermore, in step S3, the deposition technique is vacuum thermal evaporation deposition, vacuum electron beam evaporation deposition, magnetron sputtering deposition or ion beam sputtering deposition.

[0013] The beneficial effects of the present invention are: (1) The present invention provides a semiconductor laser chip using a patterned metal substrate. An etched groove is opened on the original chip substrate, and a deposited metal layer is arranged in the etched groove to replace part of the gallium arsenide substrate material. The metal material in the deposited metal layer has low resistance and high thermal conductivity. This design reduces the overall resistance value of the chip substrate and reduces the heat source, thereby improving the electro-optical conversion efficiency. The deposited metal layer is located at the lower side of the light-emitting unit, so that the heat generated by the light-emitting unit can be conducted to the solder layer through the deposited metal layer, and then to the heat sink, thereby reconstructing the heat transfer path. The deposited metal layer has low thermal resistance, so that the conduction thermal resistance on the entire heat transfer path can be reduced, thereby enhancing heat dissipation. In addition, compared with gallium arsenide, the deposited metal layer is a high conductive channel, which helps to adjust the current distribution in the active area.

[0014] (2) The present invention provides a method for preparing a semiconductor laser chip using a patterned metal substrate, which does not change the original semiconductor laser chip tape-out process, and the original process of the chip substrate is retained. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of an existing semiconductor laser chip; Figure 2 It is a schematic structural diagram of an embodiment of a semiconductor laser chip using a patterned metal substrate of the present invention; Figure 3 is a pie chart showing the percentage of Joule heat of a chip substrate in an embodiment of the present invention; Figure 4 This is a bar chart showing an example calculation distribution of Joule heat of a chip substrate in an embodiment of the present invention.

[0016] The following are the descriptions of the reference numerals: 1- heat sink, 2- solder layer, 3- chip substrate, 4- light emitting unit, 5- deposited metal layer. DETAILED DESCRIPTION

[0017] In order to make the purpose, advantages and features of the present invention more clear, the semiconductor laser chip using a patterned metal substrate and its preparation method proposed by the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following specific embodiments, the advantages and features of the present invention will be more clear.

[0018] Reference Figure 2The present invention provides a semiconductor laser chip using a patterned metal substrate, including a chip substrate 3 and a plurality of light-emitting units 4 located on the top of the chip substrate 3; the light-emitting units 4 are grown on the chip substrate 3 by crystal growth to form a whole. In this embodiment, the light-emitting units 4 are transistors, and the plurality of light-emitting units 4 are evenly arranged along the length or width direction of the chip substrate 3, and the plurality of light-emitting units 4 are arranged parallel to each other, and a gap is provided between two adjacent light-emitting units 4. A solder layer 2 is provided on the lower surface of the chip substrate 3, and a heat sink 1 is provided on the lower surface of the solder layer 2, and the chip substrate 3 is fixed to the upper surface of the heat sink 1 through the solder layer 2.

[0019] The heat sink 1 is the same as the traditional semiconductor laser chip, and adopts a liquid-cooled heat sink, which has good heat dissipation effect and is widely used in the existing chip production, without special customization, saving production costs. The semiconductor laser chip of the present invention using a patterned metal substrate has the same general structure as the traditional semiconductor laser chip, the difference is that a plurality of etching grooves are arranged on the chip substrate 3, and the depth direction of the etching grooves is arranged along the thickness direction of the chip substrate 3. A deposited metal layer 5 matching its shape is respectively arranged in the plurality of etching grooves, and the plurality of etching grooves are respectively located on the lower side of the plurality of light-emitting units 4 and correspond to the position of the light-emitting units 4. The bottom end surface of the deposited metal layer 5 is flush with the lower surface of the chip substrate 3 and contacts the upper surface of the solder layer 2, so that a patterned metal substrate is formed.

[0020] The etched groove can be processed by dry etching or wet etching, and the etched groove can be processed into different shapes. For example, the projection shape of the etched groove in the vertical plane perpendicular to the length direction of the light-emitting unit 4 can be a rectangle, an isosceles trapezoid or a step shape. In this embodiment, in order to facilitate processing, the projection shape of the etched groove is a rectangle.

[0021] The deposited metal layer 5 needs to be filled into the etched groove using a deposition technique. Common deposition techniques include vacuum thermal evaporation deposition, vacuum electron beam evaporation deposition, magnetron sputtering deposition or ion beam sputtering deposition. The material used for the deposited metal layer 5 is generally a metal material with high conductivity and low thermal resistance, such as copper, gold or other alloys. In this way, part of the gallium arsenide substrate material can be replaced. At this time, the deposited metal layer 5 deposited and filled into the etched groove will form a metal channel with low resistance and high thermal conductivity, which can effectively reduce the resistance value of the entire chip substrate 3, reduce the Joule heat, and thus improve the electro-optical conversion efficiency.

[0022] The upper end surface of the deposited metal layer 5 can be in contact with the bottom surface of the light-emitting unit 4 or there is a gap, that is, the depth of the etching groove is the same as the thickness of the chip substrate 3 or the depth of the etching groove is not less than 50% of the thickness of the chip substrate 3. If it is less than 50%, it will affect heat transfer.

[0023] After the etching groove is processed, its top width is generally 10%-150% of the bottom width of the light emitting unit 4. The top width of the etching groove is 50% of the bottom width of the light emitting unit 4. The top width of the etching groove and its depth have the following four corresponding relationships: The first type is that the depth of the etching groove is the same as the thickness of the chip substrate 3, the top width of the etching groove is greater than or equal to 10% of the width of the light-emitting unit 4 and less than or equal to 50% of the width of the light-emitting unit 4, and a plurality of etching grooves may be arranged on the bottom surface of a light-emitting unit 4, the layout direction of the plurality of etching grooves is the same as the layout direction of the light-emitting unit 4 and the plurality of etching grooves are arranged parallel to each other, and the distance between two adjacent etching grooves is 50%-100% of the top width of the etching groove; The second type is that the depth of the etching groove is the same as the thickness of the chip substrate 3, but the top width of the etching groove is greater than 50% of the width of the light-emitting unit 4 and less than or equal to 150% of the width of the light-emitting unit 4. In this case, one etching groove is correspondingly provided on the bottom surface of one light-emitting unit 4; The third type is that the depth of the etching groove is not less than 50% of the thickness of the chip substrate 3, the top width of the etching groove is greater than or equal to 10% of the width of the light-emitting unit 4 and less than or equal to 50% of the width of the light-emitting unit 4, a plurality of etching grooves are arranged on the bottom surface of a light-emitting unit 4, the layout direction of the plurality of etching grooves is the same as the layout direction of the light-emitting unit 4 and the plurality of etching grooves are arranged parallel to each other, and the distance between two adjacent etching grooves is 50%-100% of the top width of the etching groove; The fourth type is that the depth of the etching groove is not less than 50% of the thickness of the chip substrate 3, the top width of the etching groove is greater than 50% of the width of the light-emitting unit 4 and less than or equal to 150% of the width of the light-emitting unit 4, and an etching groove is correspondingly arranged on the bottom surface of a light-emitting unit 4.

[0024] This arrangement makes the corresponding relationship between the light emitting unit 4 and the etching groove more diverse, and during processing, the most suitable combination can be selected according to the processing capacity and actual conditions.

[0025] At the same time, the present invention also provides a method for preparing the semiconductor laser chip using the patterned metal substrate, comprising the following steps: S1, prepare semiconductor laser chip; S2, removing a part of the chip substrate 3 by dry etching or wet etching on the chip substrate 3 to form a plurality of etching grooves, wherein the plurality of etching grooves are respectively located at the lower sides of the plurality of light-emitting units 4 and correspond to the positions of the light-emitting units 4; S3, filling metal materials in the multiple etching grooves by vacuum thermal evaporation deposition, vacuum electron beam evaporation deposition, magnetron sputtering deposition or ion beam sputtering deposition to form multiple deposited metal layers 5; S4, after the deposition is completed, the bottom surface of the chip substrate 3 is polished so that the bottom end surface of the deposited metal layer 5 and the lower surface of the chip substrate 3 are located in the same plane, and the lower surface of the chip substrate 3 remains flat as a whole; S5. Solder the lower surface of the chip substrate 3 to the upper surface of the heat sink 1 through the solder layer 2, and the bottom end surface of the deposited metal layer 5 contacts the upper surface of the solder layer 2, thereby completing the preparation of the semiconductor laser chip using the patterned metal substrate.

[0026] The scheme of the present invention is carried out after the epitaxial structure growth process is completed, has no impact on the traditional chip tape-out process, belongs to post-processing, and does not need to change the traditional chip tape-out process due to the production of a patterned metal substrate.

[0027] In order to verify the heat dissipation capability of semiconductor laser chips using patterned metal substrates, the following experiments were designed: The control group uses a 940nm semiconductor laser chip with a traditional gallium arsenide substrate and a drive current of 1100A. The laser chip has two power supply modes: pulse current and continuous current. The continuous current mode with the highest heat generation is used for power supply. The optical power in this power supply mode is 1050W and the electro-optical conversion efficiency is 67.4%. The chip substrate is n-type doped with 1*10 20 cm -3 The calculation is performed using a gallium arsenide substrate as an example; According to Joule's law, the entire GaAs substrate will generate 261.36 W of Joule heat, while the sum of non-radiative recombination, free carrier absorption, and electrode Joule heat is 246.5 W, and the total heat is 507.86 W. Figure 3 As shown, its Joule heat accounts for more than 50% of the total heat.

[0028] The experimental group implemented local pattern metallization on the chip substrate at a ratio of 60%, such as Figure 4 As shown (J represents Joule heat, 0.6Cu represents 60% copper, and 0.4GaAs represents 40% gallium arsenide), the yellow bar represents Joule heat, and the blue bar represents the sum of non-radiative recombination, free carrier absorption and electrode Joule heat. It can be seen that the Joule heat of the chip substrate is reduced to 20.8% of the original total heat. This part of the reduced heat alone can push the electro-optical conversion efficiency to 75%.

[0029] The embodiments described above are merely descriptions of specific implementation methods of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A semiconductor laser chip using a patterned metal substrate, comprising a chip substrate (3) and a plurality of light-emitting units (4) located on the top of the chip substrate (3); the plurality of light-emitting units (4) are evenly arranged along the length or width direction of the chip substrate (3), are arranged parallel to each other, and a gap is provided between two adjacent light-emitting units (4); a solder layer (2) is provided on the lower surface of the chip substrate (3), a heat sink (1) is provided on the lower surface of the solder layer (2), and the chip substrate (3) is fixed to the upper surface of the heat sink (1) through the solder layer (2), characterized in that: The chip substrate (3) is provided with a plurality of etching grooves, the depth direction of the etching grooves being arranged along the thickness direction of the chip substrate (3), the plurality of etching grooves being respectively located at the lower side of the plurality of light-emitting units (4) and corresponding to the positions of the light-emitting units (4); A deposited metal layer (5) matching the shape of the etching grooves is respectively arranged in each of the plurality of etching grooves, and a bottom end surface of the deposited metal layer (5) is flush with the lower surface of the chip substrate (3) and in contact with the upper surface of the solder layer (2); The depth of the etched groove is the same as the thickness of the chip substrate (3), the top width is 10%-150% of the width of the light-emitting unit (4), and the bottom of the light-emitting unit (4) is correspondingly connected to the chip substrate (3) and the deposited metal layer (5); Alternatively, the depth of the etched groove is not less than 50% of the thickness of the chip substrate (3), the top width is 10%-150% of the width of the light emitting unit (4), and the opening is arranged downward, and the bottom of the light emitting unit (4) is connected to the top of the chip substrate (3).

2. A semiconductor laser chip using a patterned metal substrate according to claim 1, characterized in that: The projection shape of the etching groove in a vertical plane perpendicular to the length direction of the light-emitting unit (4) is a rectangle, an isosceles trapezoid or a stepped shape.

3. A semiconductor laser chip using a patterned metal substrate according to claim 2, characterized in that: The depth of the etching groove is the same as the thickness of the chip substrate (3); the top width of the etching groove is greater than or equal to 10% of the width of the light-emitting unit (4) and less than or equal to 50% of the width of the light-emitting unit (4); a plurality of etching grooves are arranged on the bottom surface of a light-emitting unit (4); the arrangement direction of the plurality of etching grooves is the same as the arrangement direction of the light-emitting unit (4); the plurality of etching grooves are arranged parallel to each other; and the distance between two adjacent etching grooves is 50%-100% of the top width of the etching grooves; Alternatively, the depth of the etching groove is the same as the thickness of the chip substrate (3), the top width of the etching groove is greater than 50% of the width of the light-emitting unit (4) and less than or equal to 150% of the width of the light-emitting unit (4), and one etching groove is provided on the bottom surface of one light-emitting unit (4).

4. The semiconductor laser chip using a patterned metal substrate according to claim 2, characterized in that: The depth of the etching groove is not less than 50% of the thickness of the chip substrate (3); the top width of the etching groove is greater than or equal to 10% of the width of the light-emitting unit (4) and less than or equal to 50% of the width of the light-emitting unit (4); a plurality of etching grooves are arranged on the bottom surface of a light-emitting unit (4); the arrangement direction of the plurality of etching grooves is the same as the arrangement direction of the light-emitting unit (4) and the plurality of etching grooves are arranged parallel to each other; and the distance between two adjacent etching grooves is 50%-100% of the top width of the etching grooves; Alternatively, the depth of the etching groove is not less than 50% of the thickness of the chip substrate (3), the top width of the etching groove is greater than 50% of the width of the light-emitting unit (4) and less than or equal to 150% of the width of the light-emitting unit (4), and one etching groove is provided on the bottom surface of one light-emitting unit (4).

5. A method for preparing a semiconductor laser chip using a patterned metal substrate as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: S1, prepare semiconductor laser chip; S2, removing a portion of the chip substrate (3) by etching on the chip substrate (3) to form a plurality of etching grooves, wherein the plurality of etching grooves are respectively located under the plurality of light-emitting units (4) and correspond to the positions of the light-emitting units (4); S3, filling metal material in the plurality of etched grooves by using a deposition technique to form a plurality of deposited metal layers (5); S4, after the deposition is completed, the lower surface of the chip substrate (3) is polished so that the bottom end surface of the deposited metal layer (5) is flush with the lower surface of the chip substrate (3), and the lower surface of the chip substrate (3) remains flat as a whole; S5. The lower surface of the chip substrate (3) is welded to the upper surface of the heat sink (1) via the solder layer (2), and the bottom end surface of the deposited metal layer (5) is in contact with the upper surface of the solder layer (2), thereby completing the preparation of a semiconductor laser chip using a patterned metal substrate.

6. The method for preparing a semiconductor laser chip using a patterned metal substrate according to claim 5, characterized in that: In step S2, the etching method is dry etching or wet etching.

7. The method for preparing a semiconductor laser chip using a patterned metal substrate according to claim 6, characterized in that: In step S3, the deposition technique is vacuum thermal evaporation deposition, vacuum electron beam evaporation deposition, magnetron sputtering deposition or ion beam sputtering deposition.

Images