A high aspect ratio microchannel heat sink and its preparation method and application

Abstract

The present invention belongs to the field of chip heat dissipation technology, and relates to a high aspect ratio microchannel heat sink and its preparation method and application. The heat sink is provided with a microchannel for cooling the working medium in and out, the microchannel has a high aspect ratio, and a plurality of staggered ribs are arranged in the microchannel, and the radial cross section of the rib gradually decreases from both ends to the middle along the axial direction. The heat sink provided by the present invention can improve the heat dissipation performance of the microchannel.

Description

Technical Field

[0001] The invention belongs to the technical field of chip heat dissipation, and relates to a high aspect ratio microchannel heat sink and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] According to the inventor's research, the existing microfluidic structure mainly uses silicon as the manufacturing material, and adopts a simple rectangular cross-section channel or cylindrical rib structure. As the heat flux density of the power chip increases sharply, due to the small contact area between the coolant and the channel wall, the simple structure of the microfluidic channel can no longer meet the increasing heat dissipation needs, and structural improvements are urgently needed to achieve better heat dissipation effects. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, an object of the present invention is to provide a high aspect ratio microchannel heat sink and a preparation method and application thereof. The heat sink provided by the present invention can improve the heat dissipation performance of the microchannel.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] On the one hand, a high aspect ratio microchannel heat sink is provided, wherein a microchannel for cooling medium to enter and exit is provided in the heat sink, wherein the microchannel has a high aspect ratio, wherein a plurality of staggered ribs are arranged in the microchannel, wherein the radial cross-section of the ribs gradually decreases from both ends to the middle along the axial direction.

[0007] The present invention can increase the heat exchange area by providing a microchannel with a high aspect ratio and providing ribs that are narrow in the middle and wide at both ends, and coordinates the staggered arrangement of the ribs to improve the heat dissipation performance of the microchannel in the heat sink.

[0008] When silicon is used as a microfluidic material for microwave power components, its parasitic effects will affect the grounding of the microwave power chip, thereby affecting the performance of the microwave chip and even causing the microwave chip to self-excite or burn out. In addition, the thermal conductivity of silicon is relatively low. Silicon-based microfluidics are limited by their thermal conductivity and are prone to insufficient heat dissipation, resulting in heat accumulation. Moreover, as a third-generation wide bandgap semiconductor, silicon carbide will become the mainstream of high-performance chip substrate materials in the fields of radio frequency in the future. The thermal expansion coefficient of silicon carbide is 4.7×10 -6 / K, the thermal expansion coefficient of silicon is 2.5×10 -6 / K, the thermal expansion coefficient of silicon carbide is close to twice that of silicon. If the silicon-based microfluidic channel is assembled with the silicon carbide substrate chip, the probability of thermal mismatch is high, which has a great negative impact on the electrical performance and reliability of the RF microsystem components. Therefore, further, the material of the heat sink is silicon carbide. As a microfluidic channel material, silicon carbide can not only improve the thermal conductivity of the microfluidic channel, but also reduce parasitic effects and prevent thermal mismatch when assembled with the silicon carbide chip.

[0009] Research shows that in order to achieve efficient heat dissipation of hundreds of watts per square centimeter or even kilowatts per square centimeter, the width of the microchannel needs to be in the order of tens of micrometers (10-90μm), and the aspect ratio of the channel needs to exceed 5:1, that is, the high aspect ratio described in the present invention. However, the current ordinary processing technology is difficult to meet the requirements, making it difficult to achieve the processing of high aspect ratio microchannels. In addition, due to the limitations of etching principles, current etching technology cannot directly process the rib column structure that is narrowed in the middle.

[0010] Therefore, on the other hand, a preparation method of the above-mentioned high aspect ratio microfluidic channel heat sink is provided, providing two substrates, each substrate having a groove, and arranging a plurality of staggered half ribs in the groove to obtain a half heat sink; the depth of the groove in the half heat sink is equal to the height of the half rib, and the radial cross-section of the half rib gradually decreases from the bottom of the groove to the opening of the groove; the two half heat sinks are spliced ​​so that the grooves of the two half heat sinks are aligned and the half ribs of the two half heat sinks are aligned, and assembled by wafer bonding to obtain the result.

[0011] In a third aspect, an application of the high aspect ratio microchannel heat sink in chip heat dissipation.

[0012] The beneficial effects of the present invention are:

[0013] 1. The present invention arranges ribs with narrow middle and wide ends in the microchannel, which reduces the flow resistance of the cooling medium and increases the heat dissipation contact area in the microchannel. The staggered arrangement enhances the disturbance of the coolant in the microchannel, and has a large depth-to-width ratio, which significantly improves the cooling efficiency of the microchannel, reduces the pressure drop of the cooling medium in the microchannel, and reduces power consumption.

[0014] 2. The present invention selects silicon carbide as the heat sink material, which has smaller parasitic effects, greater thermal conductivity, and better thermal compatibility with silicon carbide chips compared to silicon.

[0015] 3. The present invention proposes a preparation method for processing complex microfluidic channel structures with high aspect ratios on silicon carbide materials. Compared with the traditional method of etching microfluidic channel structures on a single substrate, the new preparation method greatly improves the upper limit of the aspect ratio of the microfluidic channels that can be processed, and significantly reduces the difficulty of processing complex microstructures, providing a solution for silicon carbide-based microfluidic channel processing, high aspect ratio microfluidic channel processing, and complex microfluidic structure processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 This is a schematic structural diagram of a high aspect ratio microchannel heat sink according to Example 1 of the present invention;

[0018] Figure 2 A cross-sectional view of the internal structure of a microchannel heat sink with a high aspect ratio according to Example 1 of the present invention;

[0019] Figure 3 A three-dimensional cross-sectional view of the internal structure of a high aspect ratio microchannel heat sink according to Example 1 of the present invention;

[0020] Figure 4 This is a schematic diagram of the structure of a single-leaf hyperbolic rib column according to Example 1 of the present invention;

[0021] Figure 5 This is a simplified schematic diagram of a single-leaf hyperbolic rib column structure according to Embodiment 2 of the present invention;

[0022] Figure 6 It is a side view schematic diagram of a silicon carbide substrate before wafer bonding during the preparation process of Example 3 of the present invention;

[0023] Figure 7 This is a schematic diagram of the process before and after wafer bonding of a silicon carbide substrate during the preparation process of Example 3 of the present invention. DETAILED DESCRIPTION

[0024] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] As introduced in the background technology, the existing heat sink microchannel has poor heat dissipation. In order to solve the above technical problems, the present invention proposes a high aspect ratio microchannel heat sink and a preparation method and application thereof.

[0027] A typical embodiment of the present invention provides a high aspect ratio microchannel heat sink, in which a microchannel for cooling medium to enter and exit is opened, and the microchannel has a high aspect ratio. A plurality of staggered ribs are arranged in the microchannel, and the radial cross-section of the ribs gradually decreases from both ends to the middle along the axial direction.

[0028] The present invention can increase the heat exchange area by providing a microchannel with a high aspect ratio and providing ribs that are narrow in the middle and wide at both ends, and coordinates the staggered arrangement of the ribs to improve the heat dissipation performance of the microchannel in the heat sink.

[0029] In some embodiments of this implementation, the heat sink is made of silicon carbide. Using silicon carbide as the microchannel material can not only improve the thermal conductivity of the microchannel, but also reduce parasitic effects and prevent thermal mismatch when assembling with the silicon carbide chip.

[0030] In some embodiments of this implementation mode, the wall surface of the rib column is a single-leaf hyperbolic surface. This structure has a smoother transition from top to bottom, a larger convection heat exchange area and a smaller flow resistance.

[0031] In some embodiments of this implementation mode, the radial cross section of the rib column is circular, which has a larger surface area and can reduce the pressure drop of the cooling medium in the microchannel.

[0032] In some examples of this embodiment, the heat sink is a cubic block structure, which is convenient for assembly with the chip.

[0033] In some embodiments of this implementation mode, the surface of the heat sink is metallized to reduce the influence of parasitic effects on chip grounding, ensure reliable grounding of the chip, and avoid self-excitation or burning of the chip.

[0034] Another embodiment of the present invention provides a method for preparing the above-mentioned high aspect ratio microfluidic channel heat sink, providing two substrates, each substrate having a groove, and arranging a plurality of staggered half ribs in the groove to obtain a half heat sink; the depth of the groove in the half heat sink is equal to the height of the half rib, and the radial cross-section of the half rib gradually decreases from the bottom of the groove to the opening of the groove; the two half heat sinks are spliced ​​so that the grooves of the two half heat sinks are aligned and the half ribs of the two half heat sinks are aligned, and assembled by wafer bonding to obtain the heat sink.

[0035] The present invention greatly improves the upper limit of the depth-to-width ratio of the microchannel that can be processed through wafer bonding assembly, and reduces the difficulty of processing ribs that are narrow in the middle and wide at both ends.

[0036] In some examples of this implementation, the process of preparing the semi-heat sink is: chemically mechanically polishing one side of the substrate, coating with photoresist, drying, exposing and developing photolithography to form a patterned mask, and then etching the substrate using a plasma etching process.

[0037] In some examples of this implementation mode, the etched surface of the semi-heat sink is subjected to secondary chemical mechanical grinding and polishing, and then splicing and wafer bonding assembly are performed after cleaning.

[0038] In one or more embodiments, the secondary chemical mechanical polishing is performed to polish the surface to a roughness of not less than 2 nm.

[0039] In some embodiments of this implementation mode, after wafer bonding and assembly, the whole surface is metallized to reduce the influence of parasitic effects on chip grounding, ensure reliable grounding of the chip, and avoid self-excitation or burning of the chip.

[0040] The present invention provides a better preparation method, the steps of which are as follows:

[0041] 1) Prepare two silicon carbide substrates of the same size. The size of the silicon carbide substrate can be determined according to the size of the target chip or microsystem in the actual application.

[0042] 2) Chemical mechanical polishing, photoresist coating, drying, exposure and development photolithography are performed on one side of the two silicon carbide substrates to form a patterned mask, and then the silicon carbide substrates are etched using a plasma etching process to form a staggered semi-single-leaf hyperbolic rib column structure that is narrow on the top and wide on the bottom.

[0043] 3) The etched surfaces of the two silicon carbide substrates are subjected to secondary chemical mechanical grinding and polishing, with the surface roughness required to reach more than 2nm, and are cleaned to remove impurities such as surface metal and organic matter.

[0044] 4) The two silicon carbide substrates with half a single-leaf hyperboloid rib column structure are precisely spliced ​​and merged into a complete single-leaf hyperboloid rib column structure. The temperature (1100℃~1400℃) and pressure (1MPa~4MPa) are maintained at a certain temperature. The two silicon carbide substrates are bonded into an integrated structure through wafer bonding technology so that the bonding surface reaches sufficient bonding strength. After wafer bonding assembly, the depth-to-width ratio of the complete microfluidic channel is twice that before bonding, realizing the processing of single-leaf hyperboloid complex structure microfluidic channels with a large depth-to-width ratio.

[0045] 5) The surface of the microfluidic heat sink after bonding and assembly is metallized to reduce the influence of parasitic effects on chip grounding, ensure reliable grounding of the chip, and avoid self-excitation or burning of the chip.

[0046] Wet etching and dry etching are two basic technologies for preparing rib-column structures that are narrow at the top and wide at the bottom. Compared with wet etching, dry etching has the characteristics of high control accuracy, good uniformity of large-area etching, and less pollution. The main methods of dry etching include laser direct writing, reactive ion etching (RIE) etching, and inductively coupled plasma (ICP) etching. Among them, ICP etching technology is a high-density, low-pressure etching technology that can accurately control the etching morphology through parameter adjustment and has the advantages of low damage and high precision. The present invention adopts ICP etching technology and utilizes chlorine-containing gas (such as BCl 3 ), oxygen-containing gas (O 2 ) and a carrier gas (such as Ar) are used for etching. During the etching process, firstly, appropriate ICP source power and RF bias power are set, and then the cavity pressure (Cavity Pressure) of the reaction chamber is gradually reduced by gradually reducing the flow rate of the chlorine-containing gas, thereby gradually reducing the selectivity in the etching process, and completing the etching processing of a semi-single-leaf hyperboloid rib column structure with a narrow upper part and a wide lower part. This method can accurately control the etching morphology, and finally obtain a semi-single-leaf hyperboloid rib column structure with a narrow upper part and a wide lower part, a controllable curvature, a smooth side wall, and a flat bottom.

[0047] A third embodiment of the present invention provides an application of the above-mentioned high aspect ratio microchannel heat sink in chip heat dissipation.

[0048] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0049] Example 1

[0050] A silicon carbide-based high aspect ratio single-blade hyperbolic rib microchannel heat sink, such as Figures 1 to 4 As shown, it includes an inlet 1, a flow channel 2, a single-leaf hyperboloid rib column 3, and an outlet 4. The coolant enters the flow channel 2 from the inlet 1, flows through the single-leaf hyperboloid rib column 3 arranged inside, and finally flows out from the outlet 4 to complete the chip heat dissipation process.

[0051] When the coolant flows through the single-leaf hyperbolic rib column 3, the single-leaf hyperbolic rib column 3 provides a larger heat dissipation contact area than the traditional cylindrical rib column microfluidic structure, thereby improving the convective heat transfer efficiency; in addition, the single-leaf hyperbolic rib columns 3 are staggered, which increases the disturbance to the coolant and promotes the full mixing of the fluid, and the full mixing of the fluid significantly improves the heat transfer coefficient; in addition, since the cross-sectional diameter of the single-leaf hyperbolic rib column 3 gradually decreases from the upper and lower sides to the middle part, it is beneficial to reduce the pressure drop loss, and the circular cross-section is also beneficial to reduce the friction factor; in addition, silicon carbide substrate is used as the raw material, and since silicon carbide has high thermal conductivity, the thermal conductivity of the microchannel heat dissipation structure is improved, and the heat exchange capacity between the channel wall and the liquid in the channel is enhanced; in addition, thanks to the advanced preparation method proposed in the present invention, the above-mentioned microfluidic heat dissipation structure has a larger depth-to-width ratio than the traditional microfluidic structure, which greatly improves the heat dissipation performance of the microchannel.

[0052] Example 2

[0053] A silicon carbide-based simplified single-leaf hyperboloid rib microchannel heat sink with a high aspect ratio is the same as that in Example 1, except that the single-leaf hyperboloid rib in Example 1 is simplified. The simplified structure is as follows: Figure 5 shown.

[0054] Example 3

[0055] A method for preparing a silicon carbide-based single-blade hyperbolic rib microchannel heat sink with a high aspect ratio, the steps are as follows:

[0056] 1) Prepare two silicon carbide substrates of the same size. In this embodiment, 10×10 mm is selected. In actual applications, the size can be determined according to the target chip or microsystem size.

[0057] 2) Chemical mechanical polishing, photoresist coating, drying, exposure and development photolithography are performed on one side of the two silicon carbide substrates to form a patterned mask, and then the silicon carbide substrate is etched by plasma etching process to form a half single-leaf hyperbolic rib column structure with narrow upper and wide lower sides, such as Figure 6 shown.

[0058] Using ICP etching technology, using BCl 3 , O 2 During the etching process, the ICP power is first set to 1375W and the RF bias power is set to 240W, and then the cavity pressure (Cavity Pressure) of the reaction chamber is gradually reduced by gradually reducing the flow rate of the chlorine-containing gas, thereby gradually reducing the selectivity in the etching process, and completing the etching processing of the semi-single-leaf hyperbolic rib column structure with a narrow upper part and a wide lower part.

[0059] 3) The etched surface of the silicon carbide substrate is subjected to secondary chemical mechanical grinding and polishing, and the surface roughness is required to reach more than 2nm. Before bonding, the sample needs to undergo a hydrophilic surface treatment, including wet cleaning and plasma treatment. Wet cleaning is carried out in sequence with acetone, alcohol, piranha liquid (SPM), standard cleaning solution No. 1 (SC1), diluted hydrofluoric acid solution and deionized water to remove surface metal, organic matter and other impurities. Subsequently, the silicon carbide surface is activated using oxygen plasma, which can also eliminate carbon contamination on the wafer surface and further reduce the surface roughness.

[0060] 4) After the above-mentioned surface treatment, two silicon carbide substrate etched surfaces are used for direct bonding, and the two silicon carbide substrates with half a single-leaf hyperboloid rib column structure are precisely spliced ​​and merged into a complete single-leaf hyperboloid rib column structure. The bonded sample is loaded with pressure (3MPa), and finally annealed in a high temperature environment (1200°C) of conventional atmosphere to obtain a direct bonding sample of SiC and SiC. The airtightness and mechanical properties of the bonded sample meet the application requirements. The silicon carbide microfluidic channel heat dissipation structure with a complex structure of single-leaf hyperboloid rib columns has been completed. The aspect ratio of the assembled microfluidic channel is twice that before bonding, achieving a high aspect ratio. The assembly process for wafer bonding is as follows: Figure 7 shown.

[0061] 5) The assembled microfluidic heat sink is subjected to overall surface metallization treatment to reduce the influence of parasitic effects on the grounding performance of the chip, ensure reliable grounding of the chip, and avoid self-excitation or burning of the chip.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high aspect ratio microchannel heat sink, characterized in that: A microchannel for cooling medium to enter and exit is provided in the heat sink, the microchannel has a high aspect ratio, and the aspect ratio of the channel must exceed 5:

1. A plurality of staggered ribs are provided in the microchannel, and the radial cross section of the ribs gradually decreases from both ends to the middle along the axial direction; The heat sink is made of silicon carbide; The wall surface of the rib column is a single-leaf hyperbolic surface; The radial cross section of the rib column is circular.

2. The high aspect ratio microchannel heat sink according to claim 1, characterized in that: The heat sink has a cubic block structure.

3. The high aspect ratio microchannel heat sink according to claim 1, characterized in that: The surface of the heat sink is metallized.

4. A method for preparing a high aspect ratio microchannel heat sink according to any one of claims 1 to 3, characterized in that: Two substrates are provided, each substrate is provided with a groove, and a plurality of staggered half-ribs are arranged in the groove to obtain a semi-heat sink; the depth of the groove in the semi-heat sink is equal to the height of the half-rib, and the radial cross-section of the half-rib gradually decreases from the bottom of the groove to the opening of the groove; the two semi-heat sinks are spliced ​​so that the grooves of the two semi-heat sinks are aligned and the half-ribs of the two semi-heat sinks are aligned, and the semi-heat sinks are assembled by wafer bonding to obtain the semi-heat sink.

5. The method for preparing a high aspect ratio microchannel heat sink according to claim 4, characterized in that: The process of preparing the semi-heat sink is: chemically mechanically polishing one side of the substrate, coating with photoresist, drying, exposing and developing by photolithography to form a patterned mask, and then etching the substrate by plasma etching process to obtain the semi-heat sink.

6. The method for preparing a high aspect ratio microchannel heat sink according to claim 4, characterized in that: The etched surface of the semi-heat sink is subjected to secondary chemical mechanical grinding and polishing, and then splicing and wafer bonding assembly are carried out after cleaning.

7. The method for preparing a high aspect ratio microchannel heat sink according to claim 6, characterized in that: Secondary chemical mechanical grinding and polishing to a surface roughness of not less than 2nm.

8. The method for preparing a high aspect ratio microchannel heat sink according to claim 4, characterized in that: After wafer bonding and assembly, the entire surface is metallized.

9. Application of the high aspect ratio microchannel heat sink according to any one of claims 1 to 3 in chip heat dissipation.

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