CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of U.S. Provisional Patent Application No. 61/445,171, filed on February 22, 2011, the entirety of which is hereby incorporated by reference and made a part of this specification.

BACKGROUND

Technical Field

[0002] The present disclosure generally relates to the field of transfer of thermal energy and, more particularly, to removal of thermal energy from a heat-generating device.

Description of the Related Art

[0003] Heat-generating devices, such as vertical-cavity surface-emitting lasers (VCSELs), light-emitting diodes (LEDs), laser diodes, microprocessors and the like, generate thermal energy or heat when in operation. Regardless of which type of heat-generating device the case may be, heat generated by such a heat-generating device must be removed or dissipated from the heat- generating device in order to achieve optimum performance of the heat- generating device and keep the heat-generating device within its safe operating temperature. With the form factor of heat-generating devices and the applications they are implemented in becoming ever more compact, it is imperative to effectively dissipate the high-density heat generated in a small footprint area to ensure safe and optimum operation of heat-generating devices operating under such conditions.

[0004] Many metal-based water-cooled and air-cooled cooling packages have been developed for use in compact packages to dissipate heat generated by the various types of heat-generating devices mentioned above. For instance, heat exchangers and heat pipes made of a metallic material with high thermal conductivity, such as copper, silver, aluminum or iron, are commercially available. However, most metal-based heat exchangers and heat pipes experience oxidation, corrosion and/or crystallization after long periods of operation. Such fouling factors significantly reduce the heat transfer efficiency of metal-based heat exchangers and heat pipes. Other problems associated with the use of metal-based cooling packages include, for example, issues with overall compactness of the package, corrosion of the metallic material in water-cooled applications, difficulty in manufacturing, etc. Yet, increasing demand for higher power density in small form factor motivates the production of a compact cooling package with fewer or none of the aforementioned issues.

[0005] Heat-generating devices, such as vertical-cavity surface-emitting lasers (VCSELs), light-emitting diodes (LEDs), laser diodes, microprocessors and the like, generate thermal energy or heat when in operation. Regardless of which type of heat-generating device the case may be, heat generated by such a heat-generating device must be removed or dissipated from the heat- generating device in order to achieve optimum performance of the heat- generating device and keep the heat-generating device within its safe operating temperature. With the form factor of heat-generating devices and the applications they are implemented in becoming ever more compact, it is imperative to effectively dissipate the high-density heat generated in a small footprint area to ensure safe and optimum operation of heat-generating devices operating under such conditions.

[0006] Many metal-based water-cooled and air-cooled cooling packages have been developed for use in compact packages to dissipate heat generated by the various types of heat-generating devices mentioned above. For instance, heat exchangers and heat pipes made of a metallic material with high thermal conductivity, such as copper, silver, aluminum or iron, are commercially available. However, most metal-based heat exchangers and heat pipes experience oxidation, corrosion and/or crystallization after long periods of operation. Such fouling factors significantly reduce the heat transfer efficiency of metal-based heat exchangers and heat pipes. Other problems associated with the use of metal-based cooling packages include, for example, issues with overall compactness of the package, corrosion of the metallic material in water-cooled applications, difficulty in manufacturing, etc. Yet, increasing demand for higher power density in small form factor motivates the production of a compact cooling package with fewer or none of the aforementioned issues.

SUMMARY

[0007] Various embodiments of the present disclosure pertain to a silicon- based thermal energy transfer apparatus, or a cooling package, that remove thermal energy from a heat-generating device. The novel and non-obvious silicon-based thermal energy transfer apparatus eliminates problems with oxidation, corrosion and/or crystallization after long periods of operation as experienced by metal-based cooling packages. Other problems associated with the use of metal-based cooling packages such as issues with overall compactness of the package, corrosion of the metallic material in water- cooled applications, and difficulty in manufacturing may also be eliminated or minimized.

[0008] With a thermal conductivity of at least 900 W/(m-K), diamond serves as a much better thermal conductor than most commercially available metal and metal alloys. With a layer of diamond coating on the surface of the silicon-based thermal energy transfer apparatus, such that the heat- generating device is in direct contact with the layer of diamond when bonded, mounted, attached or otherwise fastened to the layer of diamond of the silicon-based thermal energy transfer apparatus, heat from the heat- generating device can quickly and widely spread across the layer of diamond to allow much higher efficiency in heat dissipation than existing technologies. [0009] In one aspect, a thermal energy transfer apparatus that removes thermal energy from a heat-generating device may comprise: a silicon-based manifold having an internal cavity, a first primary side, and a second primary side opposite the first primary side. The second primary side may have at least one coolant inlet port and at least one coolant outlet port that are connected to the internal cavity of the manifold. The at least one coolant inlet port may be at a position directly opposite a position on the diamond layer where the heat-generating device is received. The apparatus further comprises a diamond layer covering at least a portion of the first primary side of the manifold such that the heat-generating device is in direct contact with the diamond layer when the heat-generating device is received on the first primary side of the manifold.

[0010] In one embodiment, the silicon-based manifold may comprise a silicon-based first plate and a silicon-based second plate. The first plate may have a first primary side and a second primary side opposite the first primary side. The first primary side of the first plate may be the first primary side of the manifold, the second primary side of the first plate may have a recess. The first plate may have an opening connecting the first primary side and the recess on the second primary side of the first plate such that a coolant flowing in the internal cavity of the manifold directly contacts the diamond layer. The second plate may have a first primary side as the second primary side of the manifold and a second primary side opposite the first primary side. The first primary side may have the at least one coolant inlet port and the at least one coolant outlet port. The second primary side may have a recess such that the opening in the first plate and the recess on the second primary side of the second plate form the internal cavity of the manifold when the first plate and the second plate are mated together with the second primary side of the first plate facing the second primary side of the second plate. At least the first primary side of the silicon-based first plate may have a surface roughness of a root mean squared (RMS) value of 2 microns or less.

[0011] In another embodiment, the silicon-based manifold may comprise a silicon-based first plate and a silicon-based second plate. The first plate may have a first primary side and a second primary side opposite the first primary side. The first primary side of the first plate may be the first primary side of the manifold on which the diamond layer is deposited. The second primary side of the first plate may have a recess. The second plate may have a first primary side as the second primary side of the manifold and a second primary side opposite the first primary side. The first primary side of the second plate may have the at least one coolant inlet port and the at least one coolant outlet port. The second primary side of the second plate may have a recess such that the recess on the second primary side of the first plate and the recess on the second primary side of the second plate form the internal cavity of the manifold when the first plate and the second plate are mated together with the second primary side of the first plate facing the second primary side of the second plate. At least the first primary side of the silicon-based first plate has a surface roughness of an RMS value of 2 microns or less.

[0012] I n one embodiment, the diamond layer may have a thickness in a range between ΙΟμηι and 500μηι.

[0013] I n one embodiment, the diamond layer may cover a substantial portion of the first primary side of the manifold.

[0014] I n another aspect, a thermal energy transfer apparatus that removes thermal energy from a heat-generating device may comprise: a silicon-based base plate, a silicon-based first fin structure and a silicon-based second fin structure. The silicon-based base plate may have a first primary side, a second primary side opposite the first primary side, a first groove on the first primary side, and a second groove on the first primary side parallel to the first groove. Each of the first and second fin structures respectively may have a first primary side and a second primary side opposite the first primary side. Each of the first and second fin structures respectively may further have, between the first primary side and the second primary side, a top edge, a bottom edge opposite the top edge, a front edge, and a back edge opposite the front edge.

[0015] The first primary side, the top edge, the second primary side, and the bottom edge of the first fin structure may have a contiguous layer of diamond thereon. The first primary side, the top edge, the second primary side, and the bottom edge of the second fin structure may have a contiguous layer of diamond thereon. The bottom edge of the first fin structure may be received in the first groove, and the bottom edge of the second fin structure may be received in the second groove. The first groove and the second groove may be distanced from each other such that when the heat-generating device is received between the first fin structure and the second fin structure the heat- generating device is in direct contact with the layer of diamond on the first fin structure and with the layer of diamond on the second fin structure.

[0016] In one embodiment, the bottom edge of at least one of the first fin structure and the second fin structure may be V-shaped. At least one of the first groove and the second groove may be a V-shaped groove.

[0017] In one embodiment, at least one of the first and second fin structures may comprise at least one coolant inlet port on one of the respective edges, at least one coolant outlet port on one of the respective edges, and a coolant flow channel therein that connects the at least one coolant inlet port and the at least one coolant outlet port to allow a coolant to flow through the respective fin structure.

[0018] In one embodiment, the at least one of the first and second fin structures may comprise a silicon-based first half-fin structure and a silicon- based second half-fin structure that are configured in a fashion described below. [0019] The first half-fin structure may have a first primary side as the first primary side of the respective fin structure, a second primary side opposite the first primary side, a top edge as half of the top edge of the respective fin structure, a bottom edge as half of the bottom edge of the respective fin structure, a front edge as half of the front edge of the respective fin structure, and a back edge as half of the back edge of the respective fin structure. The second primary side of the first half-fin structure may have a recess. The first primary side of the first half-fin structure may have an opening connecting the first primary side of the first half-fin structure and the recess on the second primary side of the first half-fin structure such that the coolant flowing in the coolant flow channel of the respective fin structure is in direct contact with the layer of diamond.

[0020] The second half-fin structure may have a first primary side as the second primary side of the respective fin structure, a second primary side opposite the first primary side, a top edge as half of the top edge of the respective fin structure, a bottom edge as half of the bottom edge of the respective fin structure, a front edge as half of the front edge of the respective fin structure, and a back edge as half of the back edge of the respective fin structure. The second primary side of the second half-fin structure may have a recess. The first primary side of the second half-fin structure may have an opening connecting the first primary side of the second half-fin structure and the recess on the second primary side of the second half-fin structure such that the coolant flowing in the coolant flow channel of the respective fin structure is in direct contact with the layer of diamond.

[0021] In one embodiment, at least the first primary side of the silicon-based first half-fin structure may have a surface roughness of an RMS value of 2 microns or less.

[0022] In another embodiment, at least one of the first and second fin structures may comprise a silicon-based first half-fin structure and a silicon- based second half-fin structure that are configured in a fashion described below.

[0023] The first half-fin structure may have a first primary side as the first primary side of the respective fin structure, a second primary side opposite the first primary side, a top edge as half of the top edge of the respective fin structure, a bottom edge as half of the bottom edge of the respective fin structure, a front edge as half of the front edge of the respective fin structure, and a back edge as half of the back edge of the respective fin structure. The second primary side of the first half-fin structure may have a recess.

[0024] The second half-fin structure may have a first primary side as the first primary side of the respective fin structure, a second primary side opposite the first primary side, a top edge as half of the top edge of the respective fin structure, a bottom edge as half of the bottom edge of the respective fin structure, a front edge as half of the front edge of the respective fin structure, and a back edge as half of the back edge of the respective fin structure. The second primary side of the second half-fin structure may have a recess such that the coolant flow channel of the respective fin structure is formed when the first half-fin structure and the second half-fin structure are mated together with the second primary side of the first half-fin structure facing the second primary side of the second half-fin structure.

[0025] In one embodiment, at least the first primary side of the silicon-based first half-fin structure has a surface roughness of an RMS value of 2 microns or less.

[0026] In one embodiment, the layer of diamond on at least one of the first fin structure and the second fin structure may have a thickness in a range between ΙΟμηι and 500μηι.

[0027] In one aspect, a method may comprise: polishing a first primary side of a silicon wafer; forming a layer of diamond on the first primary side of the silicon wafer; micromachining a second primary side of the silicon wafer that is opposite the first primary side to form at least one recess on the second primary side; cutting the silicon wafer to provide a first half-structure such that a first primary side of the first half-structures is covered by a respective layer of diamond and a second primary side of the first half-structure has a respective one of the at least one recess; and bonding a silicon-based second half-structure with the first half-fin structure to form a silicon-based manifold, the second half-structure having at least one coolant inlet port and at least one coolant outlet port through which a coolant flows in and out of the manifold, respectively.

[0028] In one embodiment, polishing the first primary side of the silicon wafer may comprise polishing the first primary side of the silicon wafer such that the first primary side of the silicon wafer has a surface roughness of an RMS value of 2 microns or less.

[0029] In one embodiment, forming the layer of diamond on the first primary side of the silicon wafer may comprise forming, on the first primary side of the silicon wafer, a layer of diamond having a thickness in a range between ΙΟμηι and 500μηι.

[0030] In one embodiment, micromachining the second primary side of the silicon wafer to form at least one recess on the second primary side may comprise micromachining the second primary side of the silicon wafer to form at least one recess on the second primary side such that at least a portion of the layer of diamond is exposed on the second primary side of the wafer. Furthermore, cutting the silicon wafer to provide the first half-structure such that a first primary side of the first half-structures is covered by a respective layer of diamond and a second primary side of the first half-structure has a respective one of the at least one recess may comprise cutting the silicon wafer to provide the first half-structure such that the first primary side of the first half-structures is covered by the respective layer of diamond and the second primary side of the first half-structure has a respective one of the at least one recess that exposes the respective layer of diamond on the second primary side of the first half-structure.

[0031] I n one embodiment, the method may further comprise: attaching a heat-generating device to the manifold such that the heat-generating device is in direct contact with the layer of diamond on the first primary side of the first half-structure; and flowing the coolant into the manifold through the coolant inlet port and out of the manifold through the coolant outlet port to remove a portion of heat from the heat-generating device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] I n the detailed description that follows, embodiments are described as illustrations since various changes and modifications will become apparent to those skilled in the art from the following detailed description. The use of the same reference numbers in different indicates similar or identical items. It is appreciable that the figures are not necessarily in scale as some components may be shown as out of proportion than the size in actual implementation in order to clearly illustrate the concept of the present disclosure.

[0033] Figure 1 is a three-dimensional view of a thermal energy transfer apparatus that removes thermal energy from a heat-generating device in accordance with one embodiment of the present disclosure. [0034] Figure 2 is another three-dimensional view of the thermal energy transfer apparatus of Figure 1 in accordance with one embodiment of the present disclosure.

[0035] Figure 3 is a cross-sectional view of the thermal energy transfer apparatus of Figure 1 in accordance with one embodiment of the present disclosure.

[0036] Figure 4 is a cross-sectional view of the thermal energy transfer apparatus of Figure 1 in accordance with another embodiment of the present disclosure.

[0037] Figure 5 is a three-dimensional view of a fin structure of a thermal energy transfer apparatus that removes thermal energy from a heat- generating device in accordance with one embodiment of the present disclosure.

[0038] Figure 6A is a cross-sectional view of line BB of the fin structure of Figure 5 in accordance with one embodiment of the present disclosure.

[0039] Figure 6B is a side view of line CC of the fin structure of Figure 6A in accordance with one embodiment of the present disclosure.

[0040] Figure 7A is a cross-sectional view of line BB of the fin structure of Figure 5 in accordance with another embodiment of the present disclosure.

[0041] Figure 7B is a side view of line CC of the fin structure of Figure 7A in accordance with one embodiment of the present disclosure. [0042] Figure 8 is a three-dimensional view of a fin structure of a thermal energy transfer apparatus that removes thermal energy from a heat- generating device in accordance with another embodiment of the present disclosure.

[0043] Figure 9A is a cross-sectional view of line DD of the fin structure of Figure 8 in accordance with one embodiment of the present disclosure.

[0044] Figure 9B is a side view of line EE of the fin structure of Figure 9A in accordance with one embodiment of the present disclosure.

[0045] Figure 10 is a side view of a thermal energy transfer apparatus that removes thermal energy from a heat-generating device in accordance with another embodiment of the present disclosure.

[0046] Figure 11 is a three-dimensional view of the thermal energy transfer apparatus of Figure 10 in accordance with one embodiment of the present disclosure.

[0047] Figure 12 is a flowchart of a process of fabricating a thermal energy transfer apparatus that removes thermal energy from a heat-generating device in accordance with one embodiment of the present disclosure.

DETAILED DESCRIPTION

Overview

[0048] The present disclosure describes embodiments of a thermal energy transfer apparatus that removes thermal energy from a light-emitting device.

While aspects of described techniques relating to a thermal energy transfer apparatus that removes thermal energy from a light-emitting device can be implemented in any number of different applications, the disclosed embodiments are described in context of the following exemplary configurations.

Illustrative First Thermal Energy Transfer Apparatus

[0049] Figure 1 illustrates a three-dimensional view of a thermal energy transfer apparatus 100 that removes thermal energy from a heat-generating device 101 when the heat-generating device 101 is bonded, mounted, attached or otherwise fastened to the thermal energy transfer apparatus 100. The heat-generating device 101 may be, for example, a VCSEL or a microprocessor chip.

[0050] The thermal energy transfer apparatus 100 comprises a silicon-based manifold 110. The manifold 110 has an internal cavity 108 (not visible in Figure 1 but partially visible in Figure 2), a first primary side (i.e., the top surface of the manifold 110 which faces the heat-generating device 101 in Figure 1), and a second primary side opposite the first primary side (i.e., the bottom surface of the manifold 110 which is not visible in Figure 1). In one embodiment, the silicon-based manifold 110 comprises a silicon-based first plate 103 and a silicon-based second plate 104. Detailed description of the silicon-based first plate 103 and the silicon-based second plate 104 will be provided below with reference to Figures 3 and 4. [0051] The thermal energy transfer apparatus 100 further comprises a diamond layer 102. The diamond layer 102 covers at least a portion of the first primary side of the manifold 110 such that the heat-generating device 101 is in direct contact with the diamond layer 102 when the heat-generating device 101 is received on the first primary side of the manifold 110. For example, as shown in Figure 1, the diamond layer 102 may cover substantially the entire first primary side of the manifold 110. When the heat-generating device 101 is bonded, mounted, attached or otherwise fastened to the diamond layer 102 of the thermal energy transfer apparatus 100, heat from the heat-generating device 102 can quickly and widely spread across the layer of diamond since diamond has excellent thermal conductivity, i.e., 900-2,320 W/(m-K). As such, heat from the heat-generating device 102 can be better dissipated by the manifold 110 in addition to being radiated and convected to the ambience. This technique results in much higher efficiency in heat dissipation than existing cooling package technologies.

[0052] Figure 2 illustrates another three-dimensional view of the thermal energy transfer apparatus 100 of Figure 1 in accordance with one embodiment of the present disclosure.

[0053] The second primary side of the manifold 110 may have at least one coolant inlet port and at least one coolant outlet port that are connected to the internal cavity 108 of the manifold 110. The number and location of each of the at least one coolant inlet port and the at least one coolant outlet port are designed so as to enhance heat transfer to a coolant flowing through the manifold 110. In one embodiment, as shown in Figure 2, the second primary side of the manifold 110 has one coolant inlet port 105 and four coolant output ports 106A, 106B, 106C and 106D. To optimize the heat transfer efficiency, the at least one coolant inlet port, e.g., the coolant inlet port 105, is at a position directly opposite a position on the diamond layer 102 where the heat-generating device 101 is received. Detailed description about the location of the coolant inlet port 105 will be provided below with reference to Figures 3 and 4.

[0054] In other embodiments, there may be more coolant inlet port than shown in Figure 2. Even with more than one coolant inlet port, the at least one coolant inlet port may be designed to be positioned directly opposite a position on the diamond layer 102 where the heat-generating device 101 is bonded, mounted, attached or otherwise fastened to the diamond layer 102.

[0055] The coolant output ports 106A, 106B, 106C and 106D surround the coolant inlet port 105 so that the coolant flowing into the manifold 110 has to spread out in four directions, thus absorbing the heat spread by the diamond layer 102 along the way, in order to flow out of the manifold 110 from the coolant output ports 106A, 106B, 106C and 106D. In other embodiments, there may be fewer or more coolant output ports than shown in Figure 2, and those coolant output ports may be at different positions on the second primary side of the manifold 110. [0056] Figure 3 illustrates a cross-sectional view of the thermal energy transfer apparatus 100 of Figure 1 in accordance with one embodiment of the present disclosure.

[0057] In one embodiment, as shown in Figure 3, the first plate 103 has a first primary side, i.e., the top side shown in Figure 3, and a second primary side opposite the first primary side, i.e., the bottom side shown in Figure 3. The first primary side of the first plate 103 is the first primary side of the manifold 110 on which the diamond layer 102 is deposited. The second primary side of the first plate 103 has a recess.

[0058] The second plate 104 has a first primary side, i.e., the bottom side shown in Figure 3, as the second primary side of the manifold 110 and a second primary side opposite the first primary side, i.e., the top side shown in Figure 3. The first primary side of the second plate 104 has the at least one coolant inlet port, e.g., the coolant inlet port 105, and the at least one coolant outlet port, e.g., the coolant outlet ports 106A, 106B, 106C and 106D. The second primary side of the second plate 104 has a recess.

[0059] As shown in Figure 3, the coolant inlet port 105 is directly below the heat-generating device 101. This allows a coolant 107 flowing into the manifold 110 through the coolant inlet port 105 to impinge on the second primary side of the first plate 103 which is directly below the heat-generating device 101. This has been shown experimentally to result in optimal heat transfer from the heat-generating device 101 to the coolant 107. Furthermore, with at least a portion of the heat from the heat-generating device 101 spread across the diamond layer 102, this amount of heat can be more uniformly transferred from the diamond layer 102 to the first plate 103, and subsequently to the coolant 107 as the coolant 107 flows through the manifold 110 before exiting the coolant outlet ports 106A, 106B, 106C and 106D.

[0060] The recess on the second primary side of the first plate 103 and the recess on the second primary side of the second plate 104 form the internal cavity 108 of the manifold 110 when the first plate 103 and the second plate 104 are mated together with the second primary side of the first plate 103 facing the second primary side of the second plate 104.

[0061] In one embodiment, the first plate 103 and the second plate 104 are each micromachined from a single-crystal silicon wafer. I n another embodiment, the first plate 103 and the second plate 104 are each micromachined from a poly-crystal silicon wafer. The first plate 103 and the second plate 104 may be made from the same wafer or different wafers.

[0062] In one embodiment, at least the first primary side of the first plate 103 is polished to have a surface roughness of a root mean squared (RMS) value of 2 microns or less. I n another embodiment, both the first primary side and the second primary side of the first plate 103 are polished to have a surface roughness of an RMS value of 2 microns or less. [0063] As the diamond layer 102 is deposited or otherwise formed on the first primary side of the first plate 103, a highly polished surface on the first primary side of the first plate 103, i.e., having a low surface roughness RMS value, helps the formation of the diamond layer 102 having mirror-polished surfaces.

[0064] Having a highly polished surface on the second primary side of the first plate 103 supports a laminar flow of the coolant 107 in the internal cavity 108 of the manifold 110. Laminar flow of the coolant 107 results in better heat transfer by convection compared to the case of turbulent flow. If the coolant 107 has a turbulent flow, e.g., at least partly due to the second primary side of the first plate 103 having rough surface finish, not only convective heat transfer is less than desirable with a turbulent flow but air pockets may likely form between the coolant 107 and the second primary side of the first plate 103 and further degrade heat transfer to the coolant 107.

[0065] In one embodiment, the diamond layer 102 covers a substantial portion of the first primary side of the manifold. For example, as shown in Figures 1 and 3, the diamond layer 102 covers substantially the entire first primary side of the manifold 110, which is the first primary side of the first plate 103. In other embodiments, the diamond layer 102 covers only a portion of the first primary side of the first plate 103 such that the heat- generating device 101 directly contacts the diamond layer 102, not the first primary side of the first plate 103. I n other words, the dimensions Wl and W2 of the diamond layer 102, as shown in Figure 3, may be different in different embodiments.

[0066] In one embodiment, the diamond layer 102 has a thickness, shown as the dimension D2 in Figure 3, in a range between ΙΟμηι and 500μηι. The dimension D2 may be the same as or different from the thickness of the first plate 103, shown as the dimension Dl in Figure 3.

[0067] Figure 4 illustrates a cross-sectional view of the thermal energy transfer apparatus 100 of Figure 1 in accordance with another embodiment of the present disclosure.

[0068] The embodiment of the thermal energy transfer apparatus 100 shown in Figure 4 and the embodiment of the thermal energy transfer apparatus 100 shown in Figure 3 are similar. In the interest of brevity, features of the embodiment of the thermal energy transfer apparatus 100 shown in Figure 4 that are similar to those of the embodiment of the thermal energy transfer apparatus 100 shown in Figure 3 will not be repeated herein.

[0069] The main difference between the embodiment of the thermal energy transfer apparatus 100 shown in Figure 4 and the embodiment of the thermal energy transfer apparatus 100 shown in Figure 3 is that the first plate 103 has an opening connecting the first primary side and the recess on the second primary side of the first plate 103. This way, the diamond layer 102 is exposed to the coolant 107 and, accordingly, the coolant 107 flowing in the internal cavity 108 of the manifold 110 directly contacts the diamond layer 102 to transfer heat away from the diamond layer 102. Given that heat in the diamond layer 102 can be directly transferred to the coolant 107 without having to traverse through the thickness of the first plate 103, as in the case shown in Figure 3, it is believed the embodiment of the thermal energy transfer apparatus 100 shown in Figure 4 can better transfer heat away from the heat-generating device 101 than the embodiment shown in Figure 3.

[0070] In one embodiment, the first plate 103 and the second plate 104 are each micromachined from a single-crystal silicon wafer. I n another embodiment, the first plate 103 and the second plate 104 are each micromachined from a poly-crystal silicon wafer. The first plate 103 and the second plate 104 may be fabricated from the same wafer or different wafers. After the formation of the diamond layer 102 on the first primary side of the first plate 103, the second primary side of the first plate 103 is etched to create an opening in the first plate 103 to expose the diamond layer 102 on the second primary side of the first plate 103.

[0071] In one embodiment, at least the first primary side of the first plate 103 is polished to have a surface roughness of a root mean squared (RMS) value of 2 microns or less. As the diamond layer 102 is deposited or otherwise formed on the first primary side of the first plate 103, a highly polished surface on the first primary side of the first plate 103, i.e., having a low surface roughness RMS value, helps the formation of the diamond layer 102 having mirror-polished surfaces. Having a highly polished surface on the diamond layer 102 supports a laminar flow of the coolant 107 in the internal cavity 108 of the manifold 110.

[0072] In one embodiment, the diamond layer 102 covers a substantial portion of the first primary side of the manifold. For example, as shown in Figures 1 and 4, the diamond layer 102 covers substantially the entire first primary side of the manifold 110, which is the first primary side of the first plate 103. In other embodiments, the diamond layer 102 covers only a portion of the first primary side of the first plate 103 such that the heat- generating device 101 directly contacts the diamond layer 102, not the first primary side of the first plate 103. I n other words, the dimensions W3 and W4 of the diamond layer 102, as shown in Figure 4, may be different in different embodiments.

[0073] In one embodiment, the diamond layer 102 has a thickness, shown as the dimension D3 in Figure 4, in a range between ΙΟμηι and 500μηι.

Illustrative Second Thermal Energy Transfer Apparatus

[0074] Figure 5 illustrates a three-dimensional view of a fin structure 200 of a thermal energy transfer apparatus that removes thermal energy from a heat-generating device in accordance with one embodiment of the present disclosure.

[0075] The fin structure 200 has a first primary side and a second primary side opposite the first primary side. Between the first primary side and the second primary side, the fin structure 200 has a top edge, a bottom edge opposite the top edge, a front edge, and a back edge opposite the front edge.

[0076] As shown in Figure 5, the fin structure 200 comprises a silicon-based first half-fin structure 208 and a silicon-based second half-fin structure 209. Detailed description of the silicon-based first half-fin structure 208 and the silicon-based second half-fin structure 209 will be provided below with reference to Figures 6A, 6B, 7A and 7B.

[0077] The first primary side, the top edge, the second primary side, and the bottom edge of the first fin structure 200 have a contiguous layer of diamond 210 coated thereon. That is, at least a portion of each of the first primary side, the top edge, the second primary side, and the bottom edge of the first fin structure 200 is covered by a portion of the layer of diamond 210. In one embodiment, substantially the entire first primary side, the top edge, the second primary side, and the bottom edge of the first fin structure 200 are covered by the layer of diamond 210.

[0078] In one embodiment, the bottom edge of the fin structure 200 and is V-shaped. In other embodiments, the bottom edge and at least one other edge of the fin structure 200 are V-shaped. For example, the top edge, bottom edge, front edge and back edge of the fin structure 200 may be V- shaped. [0079] Figure 6A illustrates a cross-sectional view of the fin structure 200 of Figure 5 in accordance with one embodiment of the present disclosure. Figure 6B illustrates a side view of the fin structure 200 of Figure 6A in accordance with one embodiment of the present disclosure.

[0080] In one embodiment, the fin structure 200 comprises at least one coolant inlet port on one of the respective edges, at least one coolant outlet port on one of the respective edges, and a coolant flow channel therein that connects the at least one coolant inlet port and the at least one coolant outlet port to allow a coolant to flow through the fin structure 200.

[0081] The first half-fin structure 208 has a first primary side, i.e., the top side shown in Figure 6A, as the first primary side of the fin structure 200, and a second primary side opposite the first primary side, i.e., the bottom side shown in Figure 6A. Between the first primary side and the second primary side, the first half-fin structure 208 has a top edge as half of the top edge of the fin structure 200, a bottom edge as half of the bottom edge of the fin structure 200, a front edge as half of the front edge of the fin structure 200, and a back edge as half of the back edge of the fin structure 200. The second primary side of the first half-fin structure 208 has a recess 201 that forms half of the coolant inlet port, the coolant flow channel, and the coolant outlet port.

[0082] The second half-fin structure 209 has a first primary side, i.e., the bottom side shown in Figure 6A, as the second primary side of the fin structure 200, and a second primary side opposite the first primary side. Between the first primary side and the second primary side, the second half- fin structure 209 has a top edge as the other half of the top edge of the fin structure 200, a bottom edge as the other half of the bottom edge of the fin structure 200, a front edge as the other half of the front edge of the fin structure 200, and a back edge as the other half of the back edge of the fin structure 200. The second primary side of the second half-fin structure 209 has a recess 202 that forms the other half of the coolant inlet port, the coolant flow channel, and the coolant outlet port.

[0083] The coolant flow channel of the fin structure 200 is formed when the first half-fin structure 208 and the second half-fin structure 209 are mated together with the second primary side of the first half-fin structure facing the second primary side of the second half-fin structure.

[0084] In one embodiment, the first half-fin structure 208 and the second half-fin structure 209 are each micromachined from a single-crystal silicon wafer. In another embodiment, the first half-fin structure 208 and the second half-fin structure 209 are each micromachined from a poly-crystal silicon wafer. The first half-fin structure 208 and the second half-fin structure 209 may be made from the same wafer or different wafers.

[0085] In one embodiment, at least the first primary side of the first half-fin structure 208 is polished to have a surface roughness of an RMS value of 2 microns or less. In another embodiment, the first primary side and the second primary side of the first half-fin structure 208 are polished to have a surface roughness of an RMS value of 2 microns or less. Alternatively or additionally, at least the first primary side of the second half-fin structure 209 is polished to have a surface roughness of an RMS value of 2 microns or less. Alternatively or additionally, the first primary side and the second primary side of the second half-fin structure 209 are polished to have a surface roughness of an RMS value of 2 microns or less. Benefits of having a highly polished surface have been described above and thus, in the interest of brevity, will not be repeated herein.

[0086] In one embodiment, the layer of diamond 210 on the first fin structure 200 has a thickness T2 in a range between ΙΟμηι and 500μηι. The dimension T2 may be the same as or different from the thickness Tl of the first half-fin structure 208 and the second half-fin structure 209.

[0087] Figure 7A illustrates a cross-sectional view of the fin structure 200 of Figure 5 in accordance with another embodiment of the present disclosure. Figure 7B illustrates a side view of the fin structure 200 of Figure 7A in accordance with one embodiment of the present disclosure.

[0088] The embodiment of the fin structure 200 shown in Figures 7A, 7B and the embodiment of the fin structure 200 shown in Figures 6A, 6B are similar. In the interest of brevity, features of the embodiment of the fin structure 200 shown in Figures 7A, 7B that are similar to those of the embodiment of the sin structure 200 shown in Figures 6A, 6B will not be repeated herein. [0089] The main difference between the embodiment of the fin structure 200 shown in Figures 7A, 7B and the embodiment of the fin structure 200 shown in Figures 6A, 6B is that either or both of the first half-fin structure 208 and the second half-fin structure 209 have an opening connecting its first primary side and the recess on its second primary side. This way, the layer of diamond 210 is exposed to the coolant and, accordingly, the coolant flowing in the coolant flow channel of the fin structure 200 directly contacts the layer of diamond 210 to transfer heat away from the layer of diamond 210. Given that heat in the layer of diamond 102 can be directly transferred to the coolant without having to traverse through the thickness of the respective half-fin structure, it is believed the embodiment of the fin structure 200 shown in Figures 7 A, 7B can better transfer heat away from a heat-generating device that is bonded, mounted, attached or otherwise fastened to the layer of diamond 210 than the embodiment shown in Figures 6A, 6B.

[0090] In one embodiment, the first half-fin structure 208 and the second half-fin structure 209 are each micromachined from a single-crystal silicon wafer. In another embodiment, the first half-fin structure 208 and the second half-fin structure 209 are each micromachined from a poly-crystal silicon wafer. The first half-fin structure 208 and the second half-fin structure 209 may be fabricated from the same wafer or different wafers. After the formation of the layer of diamond 210 on the first primary side of the first half-fin structure 208, the second primary side of the first half-fin structure 208 is etched to create an opening in the first half-fin structure 208 to expose the layer of diamond 210 on the second primary side of the first half-fin structure 208. A similar fabrication process may be carried out for the second half-fin structure 209.

[0091] In one embodiment, at least the first primary side of the first half-fin structure 208 is polished to have a surface roughness of an RMS value of 2 microns or less. In another embodiment, the first primary side and the second primary side of the first half-fin structure 208 are polished to have a surface roughness of an RMS value of 2 microns or less. Alternatively or additionally, at least the first primary side of the second half-fin structure 209 is polished to have a surface roughness of an RMS value of 2 microns or less. Alternatively or additionally, the first primary side and the second primary side of the second half-fin structure 209 are polished to have a surface roughness of an RMS value of 2 microns or less. Benefits of having a highly polished surface have been described above and thus, in the interest of brevity, will not be repeated herein.

[0092] In one embodiment, the layer of diamond 210 has a thickness, shown as the dimension T3 in Figures 7A, 7B, in a range between ΙΟμηι and 500μηι.

[0093] Figure 8 is a three-dimensional view of a fin structure 300 of a thermal energy transfer apparatus that removes thermal energy from a heat- generating device in accordance with another embodiment of the present disclosure. [0094] The fin structure 300 comprises a silicon-based fin structure 311. The fin structure 311 has a first primary side and a second primary side opposite the first primary side. Between the first primary side and the second primary side, the fin structure 311 has a top edge, a bottom edge opposite the top edge, a front edge, and a back edge opposite the front edge.

[0095] The first primary side, the top edge, the second primary side, and the bottom edge of the first fin structure 311 have a contiguous layer of diamond 312 coated thereon. That is, at least a portion of each of the first primary side, the top edge, the second primary side, and the bottom edge of the first fin structure 311 is covered by a portion of the layer of diamond 312. In one embodiment, substantially the entire first primary side, the top edge, the second primary side, and the bottom edge of the first fin structure 311 are covered by the layer of diamond 312.

[0096] In one embodiment, the bottom edge of the fin structure 311 and is V-shaped. In other embodiments, the bottom edge and at least one other edge of the fin structure 311 are V-shaped. For example, the top edge, bottom edge, front edge and back edge of the fin structure 311 may be V- shaped.

[0097] In one embodiment, the fin structure 311 is micromachined from a single-crystal silicon wafer. I n another embodiment, the fin structure 311 is micromachined from a poly-crystal silicon wafer. [0098] In one embodiment, at least the first primary side of the fin structure 311 is polished to have a surface roughness of an RMS value of 2 microns or less. I n another embodiment, the first primary side and the second primary side of the fin structure 311 are polished to have a surface roughness of an RMS value of 2 microns or less. Alternatively, the first primary side, the second primary side, the top edge and the bottom edge of the fin structure 311 are polished to have a surface roughness of an RMS value of 2 microns or less. Benefits of having a highly polished surface have been described above and thus, in the interest of brevity, will not be repeated herein.

[0099] In one embodiment, the layer of diamond 312 on the fin structure 311 has a thickness in a range between ΙΟμηι and 500μηι.

[00100] Figure 9A is a cross-sectional view of the fin structure 300 of Figure 8 in accordance with one embodiment of the present disclosure. Figure 9B is a side view of the fin structure 300 of Figure 9A in accordance with one embodiment of the present disclosure.

[00101] Figure 10 is a side view of a thermal energy transfer apparatus 400 that removes thermal energy from a heat-generating device in accordance with another embodiment of the present disclosure. Figure 11 is a three- dimensional view of the thermal energy transfer apparatus 400 of Figure 10 in accordance with one embodiment of the present disclosure.

[00102] The thermal energy transfer apparatus 400 removes thermal energy from one or more heat-generating device 414. Although there are a fixed number of heat-generating devices 414 shown in Figures 10 and 11, in various embodiments the number of the heat-generating devices 414 may be greater or smaller than that shown in Figures 10 and 11.

[00103] The thermal energy transfer apparatus 400 comprises a silicon-based base plate 413 and a plurality of silicon-based fin structures including a silicon- based first fin structure and a silicon-based second fin structure. In one embodiment, least one of the plurality of silicon-based fin structures of the apparatus 400 may be the fin structure 200 shown in Figures 5, 6A, 6B, 7A and 7B. I n another embodiment, least one of the plurality of silicon-based fin structures of the apparatus 400 may be the fin structure 300 shown in Figures 8, 9A and 9B. For illustrative purpose only, the fin structure 300 is shown as each of the plurality of fin structures of the apparatus 400 in Figures 10 and 11.

[00104] The silicon-based base plate 413 has a first primary side, a second primary side opposite the first primary side, and a plurality of parallel grooves. For example, a first groove on the first primary side is parallel to a second groove on the first primary side of the base plate 413.

[00105] The bottom edge of each of the plurality of fin structures is received in a respective one of the grooves. The groove are distanced from each other such that when a respective heat-generating device 414 is received between two neighboring fin structures the heat-generating device 414 is in direct contact with the layer of diamond 312 on each of the two fin structures 300. [00106] In one embodiment, the bottom edge of at least one of the fin structures is V-shaped. At least one of the grooves is a V-shaped groove to receive the V-shaped bottom edge of the fin structure.

Illustrative Fabrication Process

[00107] Figure 12 illustrates a flowchart of a process 500 of fabricating a thermal energy transfer apparatus that removes thermal energy from a heat- generating device in accordance with one embodiment of the present disclosure.

[00108] At 502, the process 500 polishes a first primary side of a silicon wafer. At 504, the process 500 forms a layer of diamond on the first primary side of the silicon wafer. At 506, the process 500 micromachines a second primary side of the silicon wafer that is opposite the first primary side to form at least one recess on the second primary side. At 508, the process 500 cuts the silicon wafer to provide a first half-structure such that a first primary side of the first half-structures is covered by a respective layer of diamond and a second primary side of the first half-structure has a respective one of the at least one recess. At 510, the process 500 bonds a silicon-based second half- structure with the first half-fin structure to form a silicon-based manifold, the second half-structure having at least one coolant inlet port and at least one coolant outlet port through which a coolant flows in and out of the manifold, respectively. Accordingly, the process 500 may be utilized to fabricate the components of the manifold 110 and the components of the fin structure 200 described above.

[00109] I n one embodiment, the first primary side of the silicon wafer is polished such that the first primary side of the silicon wafer has a surface roughness of an RMS value of 2 microns or less.

[00110] I n one embodiment, on the first primary side of the silicon wafer, a layer of diamond is formed and has a thickness in a range between ΙΟμηι and 500μηι.

[00111] I n one embodiment, the second primary side of the silicon wafer is micromachined to form at least one recess on the second primary side such that at least a portion of the layer of diamond is exposed on the second primary side of the wafer. Furthermore, the silicon wafer is cut to provide the first half-structure such that the first primary side of the first half-structures is covered by the respective layer of diamond and the second primary side of the first half-structure has a respective one of the at least one recess that exposes the respective layer of diamond on the second primary side of the first half-structure.

[00112] I n one embodiment, the process 500 further comprises: attaching a heat-generating device to the manifold such that the heat-generating device is in direct contact with the layer of diamond on the first primary side of the first half-structure; and causing the coolant to flow into the manifold th rough the coolant inlet port and out of the manifold through the coolant outlet port to remove a portion of heat from the heat-generating device.

Conclusion

[00113] The above-described techniques pertain to silicon-based thermal energy transfer heat-generating devices. The novel and non-obvious silicon- based thermal energy transfer apparatus eliminates problems with oxidation, corrosion and/or crystallization after long periods of operation as experienced by metal-based cooling packages. Other problems associated with the use of metal-based cooling packages such as issues with overall compactness of the package, corrosion of the metallic material in water-cooled applications, and difficulty in manufacturing may also be eliminated or minimized.

[00114] Although the techniques have been described in language specific to structural features and/or methodological acts, it is to be understood that the appended claims are not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing such techniques. Furthermore, although the techniques have been illustrated in the context of cooling package for a VCSEL and a microprocessor chip, the techniques may be applied in any other suitable context such as, for example, cooling package for laser diodes and LEDs.