CVD diamond heat dissipation structure of optical chip and preparation method of CVD diamond heat dissipation structure

Abstract

The invention provides a CVD diamond heat dissipation structure of an optical chip and a preparation method of the CVD diamond heat dissipation structure, and relates to the technical field of heat sink pieces. The heat sink sheet is arranged on the top packaging material gallium arsenide of the optical module chip; transverse intervals and longitudinal intervals are arranged between the heat sink sheets. And the heat sink sheets form a grid type structure. According to the invention, gallium arsenide is used as a photoetching substrate by means of electronic characteristics and photoelectric characteristics of gallium arsenide, and diamond is used as a heat sink to grow on an optical module chip by means of high thermal conductivity of diamond. The diamond heat sink is added on the optical module chip, so that the heat dissipation requirement of a high-power device can be met, the heat dissipation effect of the chip is remarkably improved, the temperature of the optical module chip is effectively reduced, and the loss of the device is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of heat sink chips, and particularly to a CVD diamond heat dissipation structure for an optical chip and a preparation method thereof. Background Art

[0002] During the operation of an optical chip, a large amount of heat is generated. As the power of the optical module continuously increases, more and more heat is generated, and the demand for heat dissipation also continuously increases. If the heat cannot be conducted in a timely and effective manner, the chip temperature will rise, which will in turn affect its performance and stability, cause losses to the optical module device, and affect its service life. Currently, the operating temperature of optical module devices on the market can reach 70°C to 85°C, while the temperature of high-power optical module devices during operation can easily reach over a hundred degrees Celsius. The accumulation of heat limits the working time and product performance by the heat dissipation efficiency. The optical modules on the market mainly rely on the convective exchange of air for heat dissipation. Due to the enclosed structure of the optical module device, heat retention is easily formed, making it difficult to meet the heat dissipation requirements and restricting the maximum power and working time of the optical module device. The heat dissipation capacity of existing optical module devices is difficult to meet the heat dissipation requirements of high-power operation of optical modules and the future market.

[0003] Since gallium arsenide has good electronic and optoelectronic properties, it is an excellent substrate for lithography. Diamond is the material with the highest known thermal conductivity in nature, and its thermal conductivity can even reach more than 2000 W / mk. This property gives diamond a significant advantage in heat dissipation efficiency. The high thermal conductivity of diamond and its excellent mechanical, acoustic, optical, electrical, and chemical properties make it have obvious advantages in the heat dissipation problem of high-power optoelectronic devices. However, natural diamonds are very rare, limited in size, and extremely expensive. If diamond materials are made into heat sinks by chemical vapor deposition and applied to optical module devices, the heat dissipation capacity of optical module devices can be greatly improved.

[0004] In summary, it is necessary to design a diamond heat sink chip that is beneficial to improving the heat dissipation capacity of an optical chip. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a CVD diamond heat dissipation structure for an optical chip and a preparation method thereof, which can enhance its heat dissipation capacity, meet the heat dissipation requirements of high-power operation of optical module devices, extend its working time, reduce the loss of the device, and thus extend the service life of the product.

[0006] To achieve the above purpose, the present invention provides the following solutions: A CVD diamond heat dissipation structure for an optical chip includes: multiple heat sink chips; The heat sink is disposed on the top encapsulation material gallium arsenide of the optical module chip; a lateral spacing and a longitudinal spacing are provided between each of the heat sinks; each of the heat sinks forms a grid structure.

[0007] Preferably, the material of the heat sink is diamond, the specification of the heat sink is designed as 0.6mm * 0.2mm * 16μm, the number of the heat sinks is 8; the lateral spacing of the heat sinks is 0.1mm, the minimum longitudinal spacing is 0.1mm, and the channel depth of the heat sink is 8μm.

[0008] A preparation method of a CVD diamond heat dissipation structure of the optical chip as described above includes: Measuring the size of the top encapsulation material gallium arsenide of the optical module chip; Designing the specification, shape, number, spacing and channel depth of the heat sink according to the size of the top encapsulation material gallium arsenide of the optical module chip; Performing photolithography on the top encapsulation material gallium arsenide of the optical module chip; Performing etching on the top encapsulation material gallium arsenide of the optical module chip; Removing the photoresist on the top encapsulation material gallium arsenide of the optical module chip; Based on the designed specification, number, spacing and channel depth of the heat sink, preparing a diamond film by chemical vapor deposition technology to obtain the heat sink disposed on the top encapsulation material gallium arsenide of the optical module chip; Performing quality inspection on the prepared heat sink.

[0009] Preferably, the size of the optical module chip is 3mm * 0.5mm * 1mm.

[0010] Preferably, performing photolithography on the top encapsulation material gallium arsenide of the optical module chip includes: For optical module chips with different processes, selecting acetone solvent or using automatic spraying for coating; Controlling the residual solvent concentration of the photoresist film at 15% to 30% for soft baking; the time and temperature of soft baking are adjusted according to the concentration and amount of the residual solvent; Fabricating the corresponding mask plate according to the designed specification and shape of the heat sink, and performing alignment exposure to transfer the pattern of the mask plate to the photoresist; Checking the clarity of the pattern shape generated on the photoresist, and determining whether to perform post-baking operation according to the nature of the photoresist used in the product and whether the quality of the generated pattern meets the required resolution of the product; Performing development operation on the photoresist by rotary spraying method; Performing hard baking operation on the photoresist and performing heat treatment.

[0011] Preferably, an etching process is performed on the gallium arsenide, which is the top encapsulation material of the optical module chip, including: Determine the depth of the channel for diamond growth according to the designed specifications and channel depth of the heat sink wafer; Use Cl 2 / BCl 3 / Ar as the etching gas for etching; among them, Cl 2 is the main etching gas, and BCl 2 and Ar are adjusting gases; the bias power for etching is set to 75W to 150W, the ICP power is set to 300W to 400W, and the Cl 2 flow rate is set to 5sccm to 7sccm; the etching time is 12min to 20min.

[0012] Preferably, the method for removing the photoresist on the gallium arsenide, which is the top encapsulation material of the optical module chip, is the dry photoresist removal technology of the ashing process, and O 2 .

[0013] Preferably, based on the designed specifications, quantity, spacing, and channel depth of the heat sink wafer, a diamond film is prepared by chemical vapor deposition technology to obtain a heat sink wafer disposed on the gallium arsenide, which is the top encapsulation material of the optical module chip, including: For heat sink wafers with different specifications, quantities, spacings, and channel depths, select the thin film preparation process according to the actual product plan; Pretreat the surface of the substrate, slightly grind the gallium arsenide channel of the wafer with diamond paste to cause damage to the surface of the substrate, then ultrasonically clean it with acetone for 10 min to remove the surface oxide layer, dry the substrate with dry air, and place it in the cavity of an antenna-coupled stainless steel resonant cavity type MPCVD device to deposit a diamond film; Control the methane concentration at 2.5%, control the methane flow rate at 8sccm to 12sccm, the hydrogen flow rate at 320sccm to 480sccm, control the working pressure at 10kpa to 16kpa, control the substrate temperature at 850°C to 950°C, and control the working time at 7h to 9h.

[0014] Preferably, a quality inspection is performed on the prepared heat sink wafer, including: Use an atomic force microscope for quality inspection; the quality inspection includes the uniformity of the diamond film, the overall pattern shape, and the growth height.

[0015] According to the specific embodiments provided by the present invention, the following technical effects of the present invention are disclosed: The present invention provides a CVD diamond heat dissipation structure for an optical chip and a preparation method thereof. By virtue of the electronic and optoelectronic characteristics of gallium arsenide, it is used as a lithography substrate, and by virtue of the high thermal conductivity of diamond, it is used as a heat sink and grown on the optical module chip. Taking the diamond heat sink in a grid structure as an example, on the top layer of gallium arsenide of a 3mm * 0.5mm * 1mm optical module chip, 8 diamond heat dissipation sheets of 0.6mm * 0.2mm * 16μm are embedded. On the premise that the room temperature is 20°C and the operating temperature of the optical module chip is 60°C, the optical module chip can increase the heat dissipation power by about 1 time. Therefore, adding diamond heat dissipation sheets on the optical module chip can meet the heat dissipation requirements of high-power devices, significantly improve the heat dissipation effect of the chip, effectively reduce the temperature of the optical module chip, and thus reduce the loss of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic diagram of the specific position of the CVD diamond heat sink and its heat dissipation structure provided by the embodiment of the present invention in the optical module; Figure 2 It is a schematic diagram of the CVD diamond heat sink and its heat dissipation structure provided by the embodiment of the present invention.

[0018] Description of the reference numerals: 1. Upper shell of the optical module; 2 - Heat sink; 3. Optical module chip; 4. Lower shell of the optical module; 5. Gallium arsenide of the top layer packaging material. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0020] The object of the present invention is to provide a CVD diamond heat dissipation structure for an optical chip and a preparation method thereof, which can meet the heat dissipation requirements of high-power devices, significantly improve the heat dissipation effect of the chip, effectively reduce the temperature of the optical module chip, and thus reduce the loss of the device.

[0021] To make the above objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] As Figure 1 and Figure 2 shown, the present invention provides a CVD diamond heat dissipation structure for an optical chip, including: multiple heat sink chips 2; the heat sink chips 2 are disposed on the top encapsulation material gallium arsenide 5 of the optical module chip 3; there are horizontal and vertical spacings between the respective heat sink chips 2; the respective heat sink chips 2 form a grid-like structure. The material of the heat sink chips 2 is diamond, the specification of the heat sink chips 2 is designed to be 0.6 mm * 0.2 mm * 16 μm, the number of the heat sink chips 2 is 8; the horizontal spacing of the heat sink chips 2 is 0.1 mm, the minimum vertical spacing is 0.1 mm, and the channel depth of the heat sink chips 2 is 8 μm. Exemplarily, the optical module chip 3 is disposed between the upper housing 1 of the optical module and the lower housing 4 of the optical module.

[0023] In this embodiment, the size, quantity, and heat dissipation structure of the diamond heat sink are designed according to the size of the optical chip in the optical module. The corresponding shape is opened on the gallium arsenide on the top layer of the optical module chip using photolithography technology, and then the required channels are etched on the gallium arsenide using etching technology. After that, the degluing operation is carried out, and the etched channels are used as the substrate for chemical vapor deposition of diamond, thereby generating a diamond heat sink with a heat dissipation structure. Finally, quality inspection is carried out to obtain a complete CVD diamond heat dissipation structure for the optical chip. The diamond heat sink should be designed and planned for its size and quantity according to the actual chip size of the optical module and the heat dissipation requirements of the product solution. The heat dissipation structure of the diamond heat sink is a grid-type heat dissipation structure. Different optical modules should design the heat dissipation structure of the product according to the actual size of the optical chip and the diamond heat sink and the heat dissipation requirements of the product solution. The photolithography technology should determine the shape and thickness of the photoresist according to the size of the diamond heat sink and the heat dissipation structure determined. When using photolithography technology, isopropyl methyl ketone or acetone solvent should be selected for spin coating according to the actual packaging process of the optical chip. When using photolithography technology, the spin coating method or the automatic spraying method should be selected for spin coating according to the shape and size of the diamond heat sink and the heat dissipation structure determined. The residual solvent concentration of the photolithography technology should be controlled and adjusted according to the actual designed size of different diamond heat sinks and heat dissipation structures. The size and shape of the mask plate in the photolithography technology should be made according to the shape and size of the diamond heat sink and the heat dissipation structure determined. Whether to use post-baking in the photolithography technology should be determined according to the standing wave effect generated by different products, whether the photoresist is positive, and the requirements of the product. The development operation in the photolithography technology should determine whether to use the spin spraying method or the immersion method for development according to the shape and size of the diamond heat sink and the heat dissipation structure determined. The hardening film operation should be carried out according to the size and thickness of the photoresist designed and made actually in the photolithography technology. The gallium arsenide on the top layer of the optical module chip should be subjected to the above operations according to the material on the top layer in the process packaging of the actual optical chip. The dry etching technology is used in the etching technology, and the channel size of the etching is determined according to the shape and size of the diamond heat sink and the heat dissipation structure determined.

[0024] Specifically, the preparation process of the CVD diamond heat dissipation structure of an optical chip in this embodiment is as follows: Step 1: Measure the size of the gallium arsenide on the top layer of the optical chip. Specifically, different optical module chips have different sizes, and the gallium arsenide on their top layer needs to be measured and planned to design a diamond heat sink with a suitable size. In this solution, the general optical module chip size of 3mm * 0.5mm * 1mm is selected for design and production.

[0025] Step 2: Design the size and heat dissipation structure of the diamond heat sink. Different optical chips have different sizes and shapes. According to the size and shape of the optical chip determined in Step 1, design a diamond heat sink and its heat dissipation structure. Considering that the optical module chip mainly dissipates heat through the convective movement of air, in order to increase the heat dissipation area and air flow, design a grid-type heat dissipation structure. Specifically, 8 cuboids with a cross-section of 0.6 mm * 0.2 mm * 16 μm are evenly distributed, with a minimum horizontal interval of 0.1 mm and a minimum vertical interval of 0.1 m, and the designed channel depth is 8 μm. Specifically, different products can design the heat sink according to the product plan and actual heat dissipation requirements.

[0026] Step 3: Perform photolithography on the top-layer gallium arsenide of the optical chip. After surface treatment of the top-layer gallium arsenide of the optical chip, spin-coat with methyl isobutyl ketone (MIBK), and the coating thickness is about 8 μm. Specifically, for optical chips with different processes, acetone solvent can also be selected or automatic spraying can be used for coating. Control the residual solvent concentration of the photoresist film at 15% to 30% for soft baking, and adjust the soft baking time and temperature according to the concentration and amount of the residual solvent. Make the corresponding mask according to the size and shape determined in Step 2 and perform alignment exposure to transfer the pattern of the mask to the photoresist. Considering that different products will produce different standing wave effects, specifically, it should be determined whether to perform post-baking according to whether the product uses positive photoresist and the product requirements. Considering the clarity of the pattern, use the spin spray method for development operation. Specifically, for different products and their different heat sinks, the immersion development method can also be used for heat sinks with simple patterns. To ensure that the photoresist is firm and intact, perform a hardening film operation, further heat treatment, to enhance the adhesion and etching resistance of the photoresist, but attention should be paid to temperature control to avoid damaging the photoresist.

[0027] Step 4: Perform etching on the top-layer gallium arsenide of the optical chip. Existing etching processes include wet etching and dry etching. Considering that wet etching is a chemical reaction with isotropic characteristics and is not easy to control the etching morphology and etching accuracy, while dry etching can control the etching rate and directionality by controlling the plasma density and plasma energy, which is beneficial to the formation of the heat sink and the improvement of heat dissipation performance. Therefore, dry etching is selected to process the top-layer gallium arsenide. According to the size and depth of the heat sink determined in Step 2 and Step 3, 8 μm needs to be etched as the channel for diamond growth. Use Cl 2 / BCl 3 / Ar as the etching gas for etching. Specifically, Cl 2 is the main etching gas, and BCl 2 and Ar are the adjusting gases. Considering the etching rate and etching success rate, set the bias power to 75 W to 150 W, the ICP power to 300 W to 400 W, and Cl2 Etch at a flow rate of 5 sccm to 7 sccm for an etching time of 12 min to 20 min. Specifically, different products have different heat sink wafers and required depths, and various data should be adjusted according to the actual product plan and depth requirements to fabricate the required structure.

[0028] Step Five: Remove the photoresist on the gallium arsenide. Considering that there may be residues when using wet photoresist stripping for hardened photoresist, use a dry photoresist stripping technology that employs the ashing process. The gas selected is O 2 , to remove the photoresist on the top layer of the gallium arsenide. Specifically, for products with photoresist that has not undergone the hardening step, wet photoresist stripping can also be used according to the specific process steps and product plan. Specifically, for photoresists of different materials, CF 4 gas can also be selected for dry photoresist stripping.

[0029] Step Six: Prepare a diamond film using chemical vapor deposition technology. According to the size and shape of the heat sink wafer determined in Step Two, deposit a 12-μm diamond film in the etched gallium arsenide channel. Considering the diameter and thickness of the required heat sink wafer, use microwave plasma chemical vapor deposition (MPCVD) to deposit the diamond film. Specifically, for heat sink wafers of different sizes and depths, other thin film preparation processes can be selected according to the actual product plan. Pretreat the substrate surface. Gently grind the gallium arsenide channel of the wafer with a size of 10 mm × 5 mm using diamond paste to cause damage to the substrate surface, then ultrasonically clean it with acetone for 10 min to remove the surface oxide layer, dry it with dry air, and place it in the cavity of an antenna-coupled stainless steel resonant cavity type MPCVD device to deposit the diamond film. Considering the depth of the required heat sink wafer, control the methane concentration at about 2.5%, control the methane flow rate at 8 sccm to 12 sccm, the hydrogen flow rate at 320 sccm to 480 sccm, control the working pressure at 10 kPa to 16 kPa, control the substrate temperature at 850 °C to 950 °C, and control the working time at 7 h to 9 h. Using microwave plasma chemical vapor deposition can obtain a relatively fast deposition rate and high product quality within a certain range. Specifically, for diamond film heat sink wafers of different sizes and depths, various data should be adjusted according to the more specific product plan to obtain the best parameter indicators.

[0030] Step Seven: Conduct quality inspection. Use an atomic force microscope (AFM) for quality inspection, including the uniformity of the diamond film, the overall pattern shape, the growth height, etc. The quality of the diamond film formation will directly affect the heat dissipation capacity and the adhesion stability of the diamond film.

[0031] In the present specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0032] In this article, specific examples are used to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A CVD diamond heat dissipation structure for an optical chip, characterized in that: include: Multiple heat sinks; The heat sink sheet is arranged on gallium arsenide, the top packaging material of the optical module chip; a transverse spacing and a longitudinal spacing are arranged between each of the heat sink sheets; each of the heat sink sheets forms a grid structure.

2. The CVD diamond heat dissipation structure of the optical chip according to claim 1, characterized in that: The heat sink sheet is made of diamond, the specifications of the heat sink sheet are designed to be 0.6mm*0.2mm*16μm, and the number of the heat sink sheets is 8; the lateral spacing of the heat sink sheets is 0.1mm, the minimum longitudinal spacing is 0.1mm, and the channel depth of the heat sink sheet is 8μm.

3. A method for preparing a CVD diamond heat dissipation structure of an optical chip as claimed in any one of claims 1 to 2, characterized in that: include: Measure the size of gallium arsenide, the top packaging material of the optical module chip; Design the specifications, shape, quantity, spacing and trench depth of the heat sink according to the size of GaAs, the top packaging material of the optical module chip; Perform photolithography on gallium arsenide, the top packaging material of the optical module chip; Etch the gallium arsenide, the top packaging material of the optical module chip; Remove the photoresist on the gallium arsenide packaging material on the top layer of the optical module chip; Based on the designed specifications, quantity, spacing and channel depth of the heat sink, a diamond film is prepared by chemical vapor deposition technology to obtain a heat sink disposed on gallium arsenide, the top packaging material of the optical module chip; Perform quality inspection on the prepared heat sink.

4. The method for preparing the CVD diamond heat dissipation structure of the optical chip according to claim 3, characterized in that: The size of the optical module chip is 3mm*0.5mm*1mm.

5. The method for preparing the CVD diamond heat dissipation structure of the optical chip according to claim 3, characterized in that: Photolithography of GaAs, the top packaging material of the optical module chip, including: For optical module chips with different processes, choose acetone solvent or use automatic spraying for glue coating; The residual solvent concentration of the photoresist film is controlled to be between 15% and 30% for soft baking; the time and temperature of the soft baking are adjusted according to the concentration and amount of the residual solvent; According to the specifications and shape of the designed heat sink, a corresponding mask is made, and alignment exposure is performed to transfer the pattern of the mask to the photoresist; Check the clarity of the graphics produced on the photoresist, and decide whether to perform post-baking operation based on the properties of the photoresist used in the product and whether the quality of the graphics produced meets the resolution required by the product; Developing the photoresist using a rotary spray method; The photoresist is hardened and then heated.

6. The method for preparing the CVD diamond heat dissipation structure of the optical chip according to claim 3, characterized in that: Etch the GaAs top layer packaging material of the optical module chip, including: Determine the depth of the diamond growth channel according to the designed specifications and channel depth of the heat sink; Cl2 / BCl3 / Ar is used as etching gas for etching; wherein Cl2 is the main etching gas, BCl2 and Ar are regulating gases; the etching bias power is set to 75W to 150W, the ICP power is set to 300W to 400W, and the Cl2 flow rate is set to 5sccm to 7sccm; the etching time is 12min to 20min.

7. The method for preparing the CVD diamond heat dissipation structure of the optical chip according to claim 3, characterized in that: The method for removing the photoresist on the gallium arsenide top packaging material of the optical module chip is the dry degumming technology of the Ashing process, and O2 is selected as the degumming gas.

8. The method for preparing the CVD diamond heat dissipation structure of the optical chip according to claim 3, characterized in that: Based on the designed specifications, quantity, spacing and channel depth of the heat sink, a diamond film is prepared by chemical vapor deposition technology to obtain a heat sink disposed on the top packaging material of the optical module chip, gallium arsenide, including: For heat sinks of different specifications, quantities, spacing and channel depths, the film preparation process is selected according to the actual product solution; The substrate surface was pretreated by lightly grinding the GaAs channel with diamond paste to damage the substrate surface, and then ultrasonically cleaning with acetone for 10 minutes to remove the surface oxide layer. The substrate was dried with dry air and placed in the cavity of an antenna-coupled stainless steel resonant cavity MPCVD device to deposit a diamond film. Control the methane concentration at 2.5%, control the methane flow rate at 8 sccm to 12 sccm, control the hydrogen flow rate at 320 sccm to 480 sccm, control the working pressure at 10 kPa to 16 kPa, control the substrate temperature at 850°C to 950°C, and control the working time at 7h to 9h.

9. The method for preparing a CVD diamond heat dissipation structure of an optical chip according to claim 3, characterized in that: Perform quality inspection on the prepared heat sink, including: Atomic force microscopy was used for quality inspection; the quality inspection included uniformity of the diamond film, overall pattern shape, and growth height.

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