Abstract:
Devices employing semiconductor die having hydrophobic coatings, and related cooling methods are disclosed. A device may include at least one semiconductor die electrically coupled to a substrate by electrical contact elements. During operation the semiconductor die and the electrical contact elements generate heat. By applying hydrophobic coatings to the semiconductor die and the electrical contact elements, a cooling fluid may be used to directly cool the semiconductor die and the electrical contact elements to maintain these components within temperature limits and free from electrical shorting and corrosion. In this manner, the semiconductor die and associated electrical contact elements may be cooled to avoid the creation of damaging localized hot spots and temperature-sensitive semiconductor performance issues.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of co-pending U.S. patent application Ser. No. 14/332,690, filed Jul. 16, 2014. The aforementioned related patent application is herein incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to thermal management devices, and more specifically, to methods and devices to provide cooling for electronic systems. 
         [0003]    Electronic devices perform tasks which are becoming more complicated and computationally intensive with each passing year. In response to the requirements placed on these electronic devices, semiconductor die need to perform at ever-increasing levels of performance. In order to provide the increasing performance, successive generations of electronic devices include semiconductor die having smaller design rules which enable higher data speeds with the tradeoff of generating more heat in successively smaller spatial volumes. Further, as semiconductor die become smaller, packaging and interconnection circuitry coupling the semiconductor die to the larger electrical device becomes more densely packed. This dense interconnection circuitry may become a physical obstacle to remove heat from the semiconductor die and contributes to the heat generated by the electrical device. Heat is often removed from the electrical device as materials making up the electrical device may be altered by temperatures above a certain threshold and these temperatures may adversely change electrical characteristics of the materials. For example, power leakage through transistors on logic circuitry may occur as the temperature is increased and data integrity issues may occur when memory cells are exposed to temperatures outside their operating range. Also, removing heat may reduce extreme temperature fluctuations in the electrical device which can damage components through expansion and contraction when power is cycled on and off. 
         [0004]    Conventional cooling approaches for semiconductor die include passive air convection, forced air conduction, and/or thermal sinks. However, these approaches are becoming less effective given the greater amounts of heat being generated in reduced spatial volumes. New cooling approaches for electronic devices are needed. 
       SUMMARY 
       [0005]    According to one embodiment, a method is disclosed. The method includes conductively coupling a first semiconductor die to a substrate with at least one electrical contact element. The method also includes applying a hydrophobic coating directly to the semiconductor die, substrate, and electrical contact element. The hydrophobic coating is selected to transfer heat from the semiconductor die to a cooling fluid. In this manner, the semiconductor die may be efficiently cooled. 
         [0006]    In another embodiment, a method is disclosed. The method includes applying power to at least one semiconductor die through at least one electrical contact element. The method also includes flowing a cooling fluid into contact with a hydrophobic coating attached to an exterior of the at least one semiconductor die and at least one electrical contact element. In this manner, local hot spots on the at least one semiconductor die may be prevented as efficient cooling is provided. 
         [0007]    In another embodiment, a method is disclosed. The method includes applying power to a plurality of semiconductor die and the at least one electrical contact and the at least one electrical contact element through a second level interconnect of a substrate. The plurality of semiconductor die is in a stacked arrangement to form a 3D chip stack. The method also includes directing a cooling fluid through an inlet port of an enclosure and into a chamber, wherein the chamber is formed by the enclosure. The plurality of semiconductor die is disposed within the chamber, and the enclosure is attached to the substrate. The method also includes flowing the cooling fluid into contact with a hydrophobic coating attached to an exterior of the plurality of semiconductor die. The method also includes flowing the cooling fluid out of the chamber through an outlet port of the enclosure. The hydrophobic coating comprises at least one of: phased-separated spinodal glass powder, ceramic particles, diatomaceous earth, organosilanes, fluorinated organic compounds, silicones, siloxanes, and sol-gel materials including metal oxides. In this manner, temperature swings may be minimized when the 3D chip stack is cyclically turned on and off to reduce a probability of cracks forming in the 3D chip stack associated with cyclical expansion and contraction. 
         [0008]    In another embodiment, an electrical assembly is disclosed. The electrical assembly comprises at least one semiconductor die. The electrical assembly also comprises a substrate configured to interface with an electrical source. The electrical assembly also comprises at least one electrical contact element conductively connecting the at least one semiconductor die to a substrate. The electrical assembly also comprises a hydrophobic coating attached to the at least one semiconductor die, substrate, and at least one electrical contact element. In this manner, the semiconductor die may be configured to be efficiently cooled by direct cooling. 
         [0009]    In another embodiment, an electrical assembly is disclosed. The electrical assembly includes at least one semiconductor die generating heat. The electrical assembly also includes at least one substrate electrically coupled to an electrical source. The electrical assembly also includes at least one electrical contact element conductively connecting the substrate and the at least one semiconductor die. The electrical assembly also includes a hydrophobic coating disposed on the at least one semiconductor die, at least one substrate, and at least one electrical contact element. The hydrophobic coating includes an inner surface in direct thermal conductive communication with the semiconductor die and an outer surface configured for direct convective heat transfer to a cooling fluid. In this manner, hot spots on the at least one semiconductor die may be prevented as efficient cooling is provided. 
         [0010]    In another embodiment, an electrical assembly is disclosed. The electrical assembly includes a substrate configured to interface with an electrical source. The electrical assembly also includes a plurality of semiconductor die. The plurality of semiconductor die including a first semiconductor die and a second semiconductor die. The substrate and the plurality of semiconductor die are in a stacked arrangement to form a 3D chip stack, and the first semiconductor die is disposed between the second semiconductor die and the substrate. The electrical assembly also includes at least one electrical contact element conductively connecting the first semiconductor die to the substrate and the second semiconductor die to at least one TSV (through silicon via) of the first semiconductor die. The electrical assembly also includes a hydrophobic coating attached to each of the plurality of semiconductor die, substrate, and electrical contact element. The electrical assembly also includes an enclosure secured to the substrate and forming a chamber containing the plurality of semiconductor die. The enclosure includes an inlet port and an outlet port configured for a cooling fluid to respectively enter and depart from the chamber. The hydrophobic coating includes an inner surface in direct conductive thermal communication with the semiconductor die and an outer surface arranged for direct convective thermal communication with the cooling fluid. In this manner, temperature swings may be minimized when the 3D chip stack may be cyclically turned on and off to reduce a probability of cracks forming in the electrical assembly associated with cyclical expansion and contraction. 
         [0011]    Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
         [0012]    It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and operation of the various embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]      FIGS. 1A and 1B  are a partial cutaway front side view and a partial cutaway right side view, respectively, of an exemplary electrical device including at least one semiconductor die electrically connected to a substrate using electrical contact elements and cooled by a cooling fluid as directed by an enclosure, wherein a hydrophobic coating is applied to the at least one semiconductor die, at least one electrical contact element, and substrate; 
           [0014]      FIG. 1C  is a top perspective view of the electrical device of  FIG. 1A  being cooled by the cooling fluid which is in communication with an exemplary pump and an exemplary heat exchanger; 
           [0015]      FIGS. 1D and 1E  are a front side view and left side view of the electrical device of  FIG. 1A  including the enclosure; 
           [0016]      FIG. 1F  is a bottom view of the enclosure of the electrical device of  FIG. 1D ; 
           [0017]      FIG. 1G  is an exploded top perspective view of the electrical device of  FIG. 1D ; 
           [0018]      FIG. 2  is a flow chart of an exemplary method for cooling the electrical assembly of the electrical device of  FIG. 1A ; 
           [0019]      FIG. 3  is a flow chart of an exemplary method for creating the electrical device of  FIG. 1A ; 
           [0020]      FIG. 4A  is a top perspective view of an exemplary wafer being diced by a saw to create the at least one semiconductor die of  FIG. 1A ; 
           [0021]      FIG. 4B  is a top perspective view of the at least one electrical contact element being conductively connected to a substrate; 
           [0022]      FIG. 4C  is a side view of a first semiconductor die being conductively connected to the substrate through the at least one electrical contact element; 
           [0023]      FIG. 4D  is a side view of a second semiconductor die being conductively connected to the substrate by TSVs (through silicon vias) of the first semiconductor die and the at least one electrical contact element; 
           [0024]      FIG. 4E  is a side view of a third semiconductor die being conductively connected to the substrate by TSVs (through silicon vias) of the first and second semiconductor dies and the at least one electrical contact element to create an electrical assembly of the electrical device of  FIG. 1A ; 
           [0025]      FIG. 4F  is a top perspective view of the electrical assembly of  FIG. 4E  created by the conductive connecting of  FIGS. 4B through 4E  with a masking layer applied to the substrate; 
           [0026]      FIG. 4G-1  is a top perspective view of the electrical assembly of  FIG. 4F  being immersed into a hydrophobic coating solution to apply the hydrophobic coating; 
           [0027]      FIG. 4G-2  is a top perspective view of the electrical assembly of  FIG. 4F  with the hydrophobic coating solution being sprayed thereon with an exemplary spray nozzle as an alternative to  FIG. 4G-1 ; 
           [0028]      FIG. 4G-3  is a schematic view of the electrical assembly of  FIG. 4F  with a hydrophobic coating being applied by an evaporation deposition process as an alternative to  FIG. 4G-1 ; 
           [0029]      FIG. 4G-4  is a schematic view of the electrical assembly of  FIG. 4F  with a hydrophobic coating being applied by a chemical vapor deposition process as an alternative to  FIG. 4G-1 ; 
           [0030]      FIG. 4H  is a top perspective view of the electrical assembly of  FIG. 4F  and the hydrophobic coating being rotated about an axis of rotation to create a more uniform thickness of the hydrophobic coating; 
           [0031]      FIG. 4I  is a top perspective view of the electrical assembly of  FIG. 4F  with the hydrophobic coating curing within an optional heating oven; 
           [0032]      FIG. 4J  is a top perspective view of an enclosure being attached to the substrate of the electrical assembly of  FIG. 4I ; 
           [0033]      FIG. 4K  is a side view of the second layer interconnect being conductively attached to the second surface of the substrate of the electrical assembly of  FIG. 4J ; and 
           [0034]      FIGS. 5A through 5C  are a top perspective view, front side view, and left side view, respectively, of another example of an exemplary electrical device comprising a semiconductor die conductively connected to a substrate with electrical contact elements and/or wire bonds, while being cooled by a cooling fluid, wherein the electrical device may have a hydrophobic coating applied which prevents direct contact between the cooling fluid and the substrate, single die, electrical contact elements, and wire bonds. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIGS. 1A and 1B  are a partial cutaway front side view and a partial cutaway right side view, respectively, of an exemplary electrical device  10 . The electrical device  10  may be optionally electrically connected to a circuit board  12  through a second layer interconnect  14 . The electrical device  10  may perform arithmetic, logic, and/or memory operations according to information exchanged through the second layer interconnect  14 . In the embodiment depicted in  FIG. 1A , the second layer interconnect  14  is shown as a plurality of solder balls  16  in a ball grid array configuration, but in other embodiments the second layer interconnect  14  could include, for example, a plurality of pins in a pin grid array, a plurality of wire bonds connecting a substrate  22  to the circuit board  12 , and/or a plurality of pads in a land grid array (LGA) configuration. The electrical device  10  may also receive electrical power through the second layer interconnect  14 . In this manner, the electrical device  10  may receive power and exchange data. 
         [0036]    The electrical device  10  includes an electrical assembly  18  which performs information processing for the electrical device  10 . The electrical assembly  18  comprises at least one semiconductor die  20 A- 20 C; a substrate  22 ; at least one electrical contact element  24 A- 24 C; and hydrophobic coating  26 . The semiconductor die  20 A- 20 C are electrically connected to the substrate  22  by the electrical contact elements  24 A- 24 C. Specifically, the second semiconductor die  20 B may be electrically connected by the electrical contact elements  24 A,  24 B and at least one TSV  25 A (“through silicon via”) to the substrate  22 . The third semiconductor die  20 C may be electrically connected by the electrical contact elements  24 A- 24 C and at least one TSV  25 A,  25 B to the substrate  22 . The substrate  22  receives electrical power from the circuit board  12  via the second layer interconnect  14  as discussed above. In this manner, the semiconductor die  20 A- 20 C receive electrical power to perform arithmetic, logic, and/or memory operations for the electrical device  10 . The semiconductor die  20 A- 20 C, the electrical contact elements  24 A- 24 C, and the substrate  22  contain conductive materials having electrical resistance and generate heat when carrying electrical current associated with the electrical power. 
         [0037]    The heat generated by the electrical assembly  18  is transferred by thermal conduction to the hydrophobic coating  26 . The hydrophobic coating  26  includes an inner surface  28 A attached to exterior surfaces of the semiconductor die  20 A- 20 C, the electrical contact elements  24 A- 24 C, and the substrate  22 . The hydrophobic coating  26  may also include an outside surface  28 B configured to transfer the heat through convective heat transfer from the hydrophobic coating  26  to a cooling fluid  30  in an ambient environment  32 . In this manner, the heat may be efficiently removed from the electrical assembly  18 . 
         [0038]      FIG. 1C  is a top perspective view of heat being removed from the electrical device  10  of  FIG. 1A  by the cooling fluid  30 . The electrical device  10  may also include an enclosure  34  which directs the cooling fluid  30  to and from the electrical assembly  18 . The enclosure  34  may be secured to the substrate  22  and may form a chamber  36  to contain the at least one semiconductor die  20 A- 20 C and the electrical contact elements  24 A- 24 C. The cooling fluid  30  may enter the chamber  36  through at least one inlet port  38 A of the enclosure  34  and may exit the chamber  36  through at least one outlet port  38 B. The cooling fluid  30  may be in communication with an exemplary pump  40  to ensure a sufficient flow rate of the cooling fluid  30  through the chamber  36  to maintain the electrical assembly  18  within a temperature range. The cooling fluid  30  may also be in communication with an exemplary heat exchanger  42 . The heat exchanger  42  may remove at least a portion of the heat from the cooling fluid  30  to enable the cooling fluid  30  to return to the chamber  36  at a determined temperature to control the temperature of the electrical assembly  18 . The cooling fluid  30  may be directed from the outlet port  38 B to the pump  40  and the heat exchanger  42 , and then to return to the inlet port  38 A with a fluid conduit  44 , for example, plastic tubing. By changing the flow rate of the cooling fluid  30  with the pump  40  and/or the temperature of the cooling fluid  30  departing the heat exchanger  42 , the temperature of the electrical assembly  18  may be maintained below a threshold temperature. In this manner, the temperature-sensitive characteristics of the semiconductor die  20 A- 20 C may be controlled to enable predictable performance of the electrical assembly  18 . 
         [0039]      FIGS. 1D and 1E  are a front side view and left side view of the electrical device  10  of  FIG. 1A  depicting the enclosure  34 , secured to the substrate  22 .  FIG. 1F  is a bottom view of the enclosure  34  of the electrical device  10  of  FIG. 1D  depicting an interface surface  46  which may be complementary to a mounting surface  48  of the substrate  22  to form a tight seal to restrict entry into and exit from the chamber  36 , except through the inlet port  38 A and the outlet port  38 B. The tight seal may include bonding material, for example, epoxy to secure the enclosure  34  to the substrate  22  or mechanical sealing means. In this manner, the enclosure  34  may be secured to the substrate  22 . 
         [0040]    Now that an introduction of the electrical device  10  has been provided, details of the associated components are provided in more detail in relation to  FIG. 1G , which is an exploded top perspective view of the electrical device  10 . The electrical device  10  includes the second layer interconnect  14 , the substrate  22 , the electrical contact elements  24 A- 24 C, the at least one semiconductor die  20 A- 20 C, the hydrophobic coating  26 , and the enclosure  34 . These are now discussed in sequence. 
         [0041]    The second layer interconnect  14  connects the electrical device  10  to the circuit board  12 . The second layer interconnect  14  may be, in one example depicted in  FIG. 1G , a ball grid array (BGA) comprising a plurality of solder balls to attach the electrical device  10  to pads  50  on the circuit board  12 . In other examples the second layer interconnect  14  may be in a pin grid array (PGA) utilizing metal pins to be inserted into holes in a socket that may be soldered to the circuit board  12 . In another example, the second layer interconnect  14  may be pads instead of the solder balls in which the pads are abutted against spring contacts in a socket secured to the circuit board  12 . In another example, the second layer interconnect  14  may be wire bonds instead of solder balls in which wires bonded to pads on the substrate  22 , and the circuit board  12 . The second layer interconnect  14  is made of a strong conductive material which may comprise, for example, copper, tin, gold, and/or aluminum. In this manner, the electrical assembly  18  can be attached to the circuit board  12 . 
         [0042]    It is noted that the second layer interconnect  14  may be free of the hydrophobic coating  26 , except in embodiments when the circuit board  12  is to be in contact with the cooling fluid  30 . In some embodiments where the circuit board  12  is to be in contact, then the hydrophobic coating  26  may also be applied to the second layer interconnect  14 . 
         [0043]    With continued reference to  FIG. 1G , the substrate  22  may serve as a structural foundation upon which the electrical device  10  is constructed and also may provide an electrical interface to a circuit board  12  through the second layer interconnect  14 . As a structural foundation, the substrate  22  may secure the at least one semiconductor die  20 A- 20 C to the circuit board  12  through the second layer interconnect  14  and the electrical contact elements  24 A- 24 C. The substrate  22  also provides an electrical interface between the second layer interconnect  14  and the electrical contact elements  24 A- 24 C which may be electrically connected to the at least one semiconductor die  20 A- 20 C. The substrate  22  may provide electrical pathways  54  separated and supported with dielectric material  56  to minimize crosstalk, electrical shorting, and power leakage. To provide the electrical pathways  54 , the substrate  22  may contain conductive material which may comprise, for example, copper, tin, gold, and/or aluminum. To provide the structural foundation and dielectric characteristics, the substrate  22  may also comprise, for example, thermoplastic, thermosets, ceramic, and/or composite material. In this manner, the substrate  22  may serve as a structural foundation and electrical interface. 
         [0044]    It is noted that the substrate  22  may contact the cooling fluid  30  at the mounting surface  48  of the substrate  22 . In order to protect the electrical contact element  24 A from the cooling fluid  30 , the hydrophobic coating  26  may be applied to the mounting surface  48 , for example, in order to prevent electrical crosstalk, electrical shorts and power loss. In this manner, the hydrophobic coating  26  may form a uniform layer preventing the cooling fluid  30  from contacting the electrical contact elements  24 A. The hydrophobic coating  26  may also seal the mounting surface  48  to prevent the cooling fluid  30  from entering into surface irregularities in the substrate  22 , which may cause small surface cracks to propagate and cause leaks. 
         [0045]    The electrical contact elements  24 A- 24 C conductively connect the at least one semiconductor die  20 A- 20 C to the substrate  22 . The electrical contact elements  24 A- 24 C may comprise, in one example depicted in  FIG. 1G , solder balls  58  which may conductively connect to electrical contacts (not shown) and through silicon vias (TSVs) of the semiconductor dies  20 A- 20 C. In another example, The electrical contact elements  24 A- 24 C may comprise wire bonds, in which wires bonded to electrical contacts on semiconductor die  20 A- 20 C are bonded to other semiconductor die  20 A- 20 C and/or the substrate  22 . The electrical contact elements  24 A- 24 C may comprise a strong conductive material, for example, copper, gold, silver, tin, and/or aluminum. The outside surface of the electrical contact elements  24 A- 24 C may have the hydrophobic coating  26  applied to prevent contact with the cooling fluid  30 . The cooling fluid  30  may cause electrical shorting, cross talk or power loss if not prevented by the hydrophobic coating  26  from contacting the electrical contact elements  24 A- 24 C. In this manner, the electrical contact elements  24 A- 24 C may conductively connect the at least one semiconductor die  20 A- 20 C to the substrate  22  while being protected from contact with the cooling fluid  30 . 
         [0046]    The semiconductor die  20 A- 20 C may perform the arithmetic, logic, and/or memory operations of the electrical device  10 . The semiconductor die  20 A- 20 C may comprise, for example, one or more of: a computer processor, an application-specific integrated circuit (ASICS), and/or a dynamic random access memory (DRAM). The at least one semiconductor die  20 A- 20 C may be manufactured, for example, using microlithography techniques on a silicon wafer. The semiconductor die  20 A- 20 C may be cut from one or more wafers and may comprise electrical components to perform arithmetic, logic, and/or memory operations. The semiconductor die  20 A,  20 B may respectively contain TSVs  25 A,  25 B to electrically connect the semiconductor die  20 A- 20 C in a 3D chip stack arrangement. In this manner, a footprint of the electrical device  10  on the printed circuit board  12  may be minimized and connection distances between the semiconductor die  20 A- 20 C minimized to increase processing speed. 
         [0047]    Further, the hydrophobic coating  26  may be attached to the external surface of the at least one semiconductor die  20 A- 20 C. The hydrophobic coating  26  may prevent the cooling fluid  30  from contacting electrical connection locations between the electrical contact elements  24 A- 24 C and the at least one semiconductor die  20 A- 20 C. The hydrophobic coating  26  may also prevent the cooling fluid  30  from penetrating into the semiconductor die  20 A- 20 C where materials could be vulnerable to corrosion, electrical cross talk, power loss, and electrical shorting. In this manner, the at least one semiconductor die  20 A- 20 C may be protected from the cooling fluid  30 . 
         [0048]    The enclosure  34  directs the cooling fluid  30  to and from the electrical assembly  18 . The enclosure  34  may be made from a strong material resistant to leakage of the cooling fluid  30 , may include a chemical composition inert to the cooling fluid  30 , and may include a melting point higher than operating temperatures of the electrical device  10 . In this regard, the enclosure  34  may comprise, for example, plastic and/or metal. The enclosure  34  may form the chamber  36  within which the at least one semiconductor dies  20 A- 20 C and the electrical contact elements  24 A- 24 C may be disposed. The enclosure  34  may include the at least one inlet port  38 A for the cooling fluid  30  to enter the chamber  36  and remove the heat from the electrical assembly  18  through convective heat transfer. The enclosure may also include the at least one outlet port  38 B for the cooling fluid  30  containing the heat from the electrical assembly  18  to depart from the chamber  36 . The enclosure  34  may be secured to the substrate  22  to prevent the cooling fluid  30  from entering and departing the chamber  36  without use of the inlet port  38 A and the outlet port  38 B. In this manner, the heat may be removed from the electrical assembly  18 . 
         [0049]    It is noted that the cooling fluid  30  may be a liquid or a gas. Preferably the cooling fluid  30  is a liquid possessing a relatively low viscosity to efficiently move through the chamber  36 , high thermal conductivity, high specific heat, and thermal stability at operating temperatures. The hydrophobic coating  26  may prevent contact between the cooling fluid  30  and electrical components of the electrical assembly  18  to enable the cooling fluid  30  to be electrically conductive. The cooling fluid  30  may comprise, for example, water, ethylene glycol, propylene glycol, perfluorinated hydrocarbons (e.g., Fluorinert™), synthetic hydrocarbons (e.g., polyalphaolefins), suspended nanoparticles, glycol, and/or any combination thereof. In this manner, the cooling fluid  30  may enter through the inlet port  38 A, receive heat generated by the electrical assembly  18 , and then exit the chamber  36  with the heat through the outlet port  38 B. 
         [0050]    With continued reference to  FIG. 1G , and also reference back to  FIG. 1A , the hydrophobic coating  26  may be attached to the at least one semiconductor die  20 A- 20 C, the electrical contact elements  24 A- 24 C, and the substrate  22  through a cohesive and/or adhesive bond. The hydrophobic coating  26  may comprise at least one of: phased-separated spinodal glass powder, ceramic particles, diatomaceous earth, organosilanes (RnSi(OR)4-n, wherein R is an alkyl, aryl, organofunctional group, fluorinated organic compound, and/or a methoxy, ethoxy, or acetoxy group), other fluorinated organic compounds, silicones, siloxanes, and sol-gel materials including metal oxides. The ceramic particles may, for example, include nanoparticles. The ceramic particles may also include at least one of, for example, aluminum oxide and zinc oxide. In some cases, the hydrophobic coating  26  may comprise at least one of: Nanomyte® coatings made by NEI Corporation of Somerset, N.J.; Ultra Ever Dry made by UltraTech International, Incorporated; Rust-Oleum® NeverWet® made by Rust-Oleum Corporation of Vernon Hills, Ill.; and HydroFoe™ superhydrophobic coating made by Lotus Leaf Coatings, Incorporated of Albuquerque, N. Mex. The hydrophobic coating  26  may include a wetting characteristic associated with an effective contact angle of at least ninety (90) degrees with a drop of water, and preferably more than one-hundred fifty (150) degrees. A thickness D 1  ( FIG. 1A ) of the hydrophobic coating  26  may be in a range from two (2) angstroms to seventy-five (75) microns to minimize an obstruction to the cooling fluid  30  traveling through the enclosure  34 . The hydrophobic coating  26  may prevent the cooling fluid  30  from contacting the at least one semiconductor die  20 A- 20 C, the electrical contact elements  24 A- 24 C, and the substrate  22 . Also, in some embodiments utilizing a solution-based coating application, the hydrophobic coating  26  also may be relatively inexpensive to apply as opposed to more expensive embodiments utilizing, for example, a vapor deposition process and/or an evaporative deposition process. In this manner, the hydrophobic coating  26  may be used as part of the electrical device  10  to enable efficient cooling of the semiconductor die  20 A- 20 C by the cooling fluid  30  while avoiding cross talk and electrical shorts related to contact of the cooling fluid  30  with the electrical contact elements  24 A- 24 C. 
         [0051]    The hydrophobic coating  26  may provide several benefits. First, the hydrophobic coating  26  may form a physical barrier to prevent the cooling fluid  30  from contacting the at least one semiconductor die  20 A- 20 C, the electrical contact elements  24 A- 24 C, and the substrate  22 . Secondly, the hydrophobic coating  26  may increase the efficiency of heat transfer, for example, by conducting heat from the inner surface  28 A to the outer surface  28 B, to the cooling fluid  30 . Thirdly, the hydrophobic coating  26  may be applied using various methods including a relatively low-cost, solution-based application instead of more expensive vapor deposition processes. In this manner, the hydrophobic coating  26  may provide efficient cooling to the semiconductor die  20 A- 20 C. 
         [0052]    Now that the components and embodiments of the electrical device  10  have been discussed,  FIG. 2  depicts a flow chart of an exemplary method  60  for cooling the electrical assembly  18  of the electrical device  10  of  FIG. 1C . The method  60  includes the operations  62 A and  62 B which are discussed below using the terminology discussed above. 
         [0053]    In this regard, the method  60  may include applying power to the at least one semiconductor die  20 A- 20 C through the electrical contact elements  24 A- 24 C and the TSVs  25 A,  25 B (operation  62 A of  FIG. 2 ). The method  60  may also include flowing the cooling fluid  30  into contact with the hydrophobic coating  26  attached to an exterior of the at least one semiconductor die  20 A- 20 C and the electrical contact elements  24 A- 24 C (operation  62 B of  FIG. 2 ). In this manner, efficient cooling may be provided to the at least one semiconductor die  20 A- 20 C. 
         [0054]    Next,  FIG. 3  depicts a flow chart of an exemplary method  64  for creating the electrical device  10  of  FIG. 1A . The method  64 , including the operations  66 A through  66 E, is discussed in detail with respect to  FIGS. 4A through 4K  below using the terminology discussed above. 
         [0055]    In this regard,  FIG. 4A  is a top perspective view of an exemplary wafer  68  being diced by a saw  70  to form the at least one semiconductor die  20 A- 20 C of  FIG. 1A  (operation  66 A of  FIG. 3 ). The wafer  68  may be provided with the electrical interconnection features of the at least one semiconductor die  20 A- 20 C, for example, by utilization of one or more microlithography processes. The saw  70  may be used to cut the wafer  68  into the semiconductor die  20 A- 20 C which may be used as a part of the electrical device  10 . It is noted that the semiconductor die  20 A- 20 C may originate from different ones of the wafers  68  and may have different electrical features to perform different arithmetic, logic, and/or memory operations. 
         [0056]    The method  64  may also include conductively coupling the at least one semiconductor die  20 A- 20 C to each other and to the substrate  22  using the electrical contact elements  24 A- 24 C (operation  66 B in  FIG. 3 ). In this regard, the electrical contact elements  24 A- 24 C may comprise solder balls  58 .  FIG. 4B  is a top perspective view of the electrical contact elements  24 A- 24 C being conductively connected to the substrate  22 . As shown in  FIG. 4B  the solder balls  58  may be precisely placed upon the substrate  22  using a ball placement system  72 . In one example, the ball placement system  72  may comprise a Koses KAM  750  solder ball attach machine manufactured by Korea Semiconductor System, Company, Limited of Bucheon City, Kyunggi-Do, Korea. 
         [0057]    Once the solder balls  58  are attached to precise contact locations of the substrate  22 , then the first semiconductor die  20 A may be conductively connected to the substrate  22  through the at least one solder balls  58  of the at least one electrical contact elements  24 A as shown in  FIG. 4C  using, for example, a robotic tool (not shown). The electrical contact elements  24 C enable an interstitial space  74 A to be disposed between the semiconductor dies  20 B,  20 C which may be later used for the cooling fluid  30  to flow and efficiently provide cooling to the semiconductor die  20 B,  20 C. It is noted that the solder balls  58  are connected to the at least one TSV  25 A of the first semiconductor die  20 A, so that at least a second semiconductor die  20 B may be conductively connected to the substrate  22 . 
         [0058]      FIGS. 4D and 4E  are side views of the second and third semiconductor dies  20 B,  20 C being conductively connected to the first semiconductor die  20 A and the substrate  22  using the electrical contact elements  24 A- 24 C and the TSVs  25 A,  25 C. This conductive coupling forms interstitial spaces  74 B,  74 C using similar manufacturing approaches discussed in relation to  FIGS. 4B and 4C . The interstitial spaces  74 A- 74 C may have a width D 2  (see  FIG. 1A ) in a range from one (1) micron to three (3) millimeters. In this manner, the electrical assembly  18  may be created. 
         [0059]    As shown in  FIG. 4F , a mask layer  75  may be applied to the second surface  85  of the substrate  22  in preparation for the hydrophobic coating  26  to be applied. The mask layer  75  may prevent, for example, the hydrophobic coating  26  from being attached to exterior areas of the substrate  22  where further electrical connections may be established. The mask layer  75  may be a conventional photoresist that may be removed in later stages of the method  64 . Using photoresist enables specific areas of the mask to be exposed to a microlithography stepper (not shown) or pattern generator (not shown) to protect specific areas of the substrate  22 . In the embodiment shown in  FIG. 4F , the second surface  85  is fully masked to prevent later attachment with the hydrophobic coating  26 . In this manner, the electrical assembly  18  may be readied for application of the hydrophobic coating  26 . 
         [0060]    The method  64  also includes applying the hydrophobic coating  26  to the at least one semiconductor die  20 A- 20 C; the at least one electrical contact element  24 A- 24 C; and the substrate  22  (operation  66 C of  FIG. 3 ). In this regard, and in one exemplary approach,  FIG. 4G-1  is a top perspective view of the electrical assembly  18  of  FIG. 4F  being immersed into a hydrophobic coating solution  76  which contains the hydrophobic coating  26 . The electrical assembly  18  may be then spun about an axis of rotation A 1  (see  FIG. 4H ) to even out the hydrophobic coating solution  76  to a more uniform thickness. In another approach, as depicted in  FIG. 4G-2 , the hydrophobic coating solution  76  may be sprayed on to the electrical assembly  18  using at least one spray nozzle  78 . The electrical assembly  18  may also be then spun relative to an axis of rotation A 1  (see  FIG. 4H ) to also even out the hydrophobic coating solution  76  to a more uniform thickness. 
         [0061]    The hydrophobic coating solution  76  may be cured to form the hydrophobic coating  26 . As shown in  FIG. 4I  the hydrophobic coating solution  76  may be cured by vaporizing solvents  80  within the hydrophobic coating solution  76  to leave a hydrophobic coating  26  applied to the semiconductor die  20 A- 20 C; the electrical contact elements  24 A- 24 C, and the substrate  22 . An optional heating oven  82  (shown in broken lines in  FIG. 4I ) may be used to accelerate the curing process. Alternatively, in some cases, curing may be accomplished at room temperature without the heating oven  82 . In this manner, a hydrophobic coating  26  may be applied. 
         [0062]    In another approach for applying the hydrophobic coating  26 ,  FIG. 4G-3  shows a schematic view of the electrical assembly  18  of  FIG. 4F  with the hydrophobic coating  26  being applied by an evaporation deposition device  100 . The evaporation deposition device  100  includes a low-pressure chamber  102  comprising a heater  104 , crucible  106 , vacuum pump  108 , fixture  110 , electron source  112 , and hydrophobic coating material  114 . The electronic assembly  18  may be placed in the low-pressure chamber  102  which may be pulled to near vacuum with the vacuum pump  108 . The electronic assembly  18  may be supported by the fixture  110  which may be moveable with an actuator  116 . The electron source  112  may form an electron beam  118  which is received by the hydrophobic coating material  114  within the crucible  106 . The hydrophobic coating material  114  may be evaporated and received by the electrical assembly  18  to form the hydrophobic coating  26 . The heater  104  may facilitate a more uniform thickness of the hydrophobic coating material  114  by providing a more uniform temperature of the electrical assembly  18 . In this manner, the hydrophobic coating  26  may be formed having a sub-nanometer thickness. 
         [0063]    In another approach for applying the hydrophobic coating  26 ,  FIG. 4G-4  shows a schematic view of the electrical assembly  18  of  FIG. 4F  with the hydrophobic coating  26  being applied by a chemical vapor deposition device  120 . The chemical vapor deposition device  120  includes at least one resistance heater  122 A- 122 C, a chamber  122 , a fixture  124 , and volatile precursors  126 . The one or more electrical subassemblies  18  may be supported in the chamber  122  by the fixture  124  as they are exposed to the volatile precursors  126  comprising the hydrophobic coating material  114 . The volatile precursors  126  enter the chamber  122  and react and/or decompose on the electrical assembly  18  to produce the hydrophobic coating  26 . The resistance heaters  122 A- 122 C may be proximate to the electrical assemblies  18  to initiate the reaction and/or decomposition of the volatile precursors  126  and facilitate a uniform distribution of the hydrophobic coating material  114  at the electrical assemblies  18 . In this manner, the hydrophobic coating  26  may also be formed having a sub-nanometer thickness. 
         [0064]    The method  64  may also include attaching the enclosure  34  to the substrate  22  (operation  66 D of  FIG. 3 ). Attachment as depicted in  FIG. 4J  may be made using, for example, an adhesive (for example, epoxy) or cohesive substance, mechanical interface means, or thermal bonding. The attachment of the enclosure  34  to the mounting surface  48  of the substrate  22  may prevent the cooling fluid  30  from entering or exiting the chamber  36  of the enclosure  34 , except through the inlet port  38 A and/or outlet port  38 B. The third semiconductor die  20 C may be spaced from the enclosure  34  by a distance D 3  ( FIG. 1A ) which may be the same or substantially the same as the thickness D 1  of the interstitial spaces  74 A- 74 C to facilitate flow of the cooling fluid  30  through the interstitial spaces  74 A- 74 C ( FIG. 4E ). In this manner, the cooling fluid  30  may be precisely directed to the electrical assembly  18  for cooling the semiconductor dies  20 A- 20 C. 
         [0065]    The method  64  may also include attaching the second layer interconnect  14  to the substrate  22  (operation  66 E of  FIG. 3 ). In this regard, the mask layer  75  may first be removed from the second surface  85  of the substrate  22 . Removal, for example, may include a conventional processing solution to remove the mask layer  75  from the second surface  85 . Once the mask layer  75  is removed, the second layer interconnect  14  may be attached.  FIG. 4K  is a side view of the second layer interconnect  14  being conductively attached to the second surface  85  of the substrate  22  of the electrical assembly  18 . The second layer interconnect  14  may comprise the solder balls  16 . The solder balls  16  may be precisely placed upon the second surface  85  of the substrate  22  using the ball placement system  72  discussed above. In this manner, the electrical device  10  may be created. 
         [0066]    Although the electrical device  10  has been discussed above, other embodiments are possible. In this regard,  FIGS. 5A through 5C  are a top perspective view, front side view, and left side view, respectively, of another example of an exemplary electrical device  10 ′ comprising a single semiconductor die  20 ′ conductively connected to a substrate  22 ′ with electrical contact elements  24 ′, and wire bonds  88 . The single semiconductor die  20 ′ may be cooled by the cooling fluid  30  which flows past. The single semiconductor die  20 ′, the electrical contact elements  24 ′ and the wire bonds  88  may have a hydrophobic coating  26 ′ applied which prevents direct contact between the cooling fluid  30  and the substrate  22 ′, the single semiconductor die  20 ′, the electrical contact elements  24 ′, and the wire bonds  88 . The hydrophobic coating  26 ′ may have similar dimensions, chemical makeup, and manufacturing application processes as discussed above for electrical device  10 . In this manner, the single semiconductor die  20 ′ may be efficiently cooled. 
         [0067]    The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. 
         [0068]    In the following, reference is made to embodiments presented in this disclosure. However, the scope of the present disclosure is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the following aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the invention” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s). 
         [0069]    Aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” 
         [0070]    The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
         [0071]    The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
         [0072]    Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. 
         [0073]    Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
         [0074]    Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. 
         [0075]    These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
         [0076]    The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0077]    The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.