Patent Publication Number: US-9431380-B2

Title: Microelectronic assembly having a heat spreader for a plurality of die

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a divisional of application Ser. No. 13/741,743, filed Jan. 15, 2013, the entire disclosure of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field 
     This invention relates generally to semiconductor devices, and more specifically to heat spreaders in semiconductor device assemblies. 
     2. Related Art 
     To improve space efficiency, some semiconductor, or microelectronic, packages include one or more stacks of two or more integrated circuit die, to allow more circuitry to be packaged within a smaller area. However, a stack of die decreases an amount of area that is available for heat dissipation from each die. 
     A layout of most integrated circuits is optimized for circuit efficiency, and the layout may result in localized areas of a die that generate higher temperatures than other areas of the die. A heat spreader distributes heat from warmer area(s) of a die to cooler area(s) of the die, and may also accomplish heat dissipation from the die. To facilitate distribution and dissipation of heat, a heat spreader typically has high thermal conductivity. Many known heat spreaders also have high electrical conductivity. 
     A heat spreader may be placed between, and in thermal contact with, two or more die. This allows a single heat spreader to distribute heat from warmer area(s) to cooler area(s) of the two or more die. A heat spreader may be thermally coupled to a heat sink that is located outside a microelectronic device. The heat sink, in combination with the heat spreader, facilitates dissipation of heat from inside the microelectronic package to outside the microelectronic package. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example and is not limited by the accompanying figures, in which like references indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. 
         FIG. 1  is a perspective view of a microelectronic assembly including a stacked structure including a heat spreader sandwiched between two die, in accordance with one embodiment of the invention, and an outline of a microelectronic package. 
         FIG. 2  is a bottom plan view of the heat spreader and the two die of  FIG. 1 , showing a cut line  3 - 3 ′ and areas  4 ,  15  surrounding one through silicon via of the bottom die. 
         FIG. 3  is a cut view of the heat spreader and the two die of  FIG. 2 , along cut line  3 - 3 ′, and showing areas  27 ,  38 . 
         FIG. 4  is a top plan view of area  4  of the heat spreader including an opening in the heat spreader, and showing a cut line  5 - 5 ′. 
         FIG. 5  is a cut view of the portion of the heat spreader of  FIG. 4  along cut line  5 - 5 ′. 
         FIG. 6  is a cut view of the portion of the heat spreader of  FIG. 4  along cut line  5 - 5 ′ subsequent to deposition of an electrical insulating material in the opening. 
         FIG. 7  is a top plan view of the portion of the heat spreader of  FIG. 4  including the opening in the heat spreader, the electrical insulating material in the opening, and an insulated hole in the electrical insulating material, and showing a cut line  8 - 8 ′. 
         FIG. 8  is a cut view of the portion of the heat spreader of  FIG. 7  along cut line  8 - 8 ′, showing a first embodiment of the insulating material. 
         FIG. 9  is a cut view of the portion of the heat spreader of  FIG. 7  along cut line  8 - 8 ′, showing a second embodiment of the insulating material. 
         FIG. 10  is a cut view of a first die including a through silicon via, a heat spreader including an insulated hole, and a second die including a through silicon via. 
         FIG. 11  is a cut view of the first die, the heat spreader and the second die of  FIG. 10 , subsequent to being brought together to form a stacked structure. 
         FIG. 12  is a cut view of the stacked structure of  FIG. 11  subsequent to the through silicon vias and the insulated hole being filled with a continuous fill material. 
         FIG. 13  is a cut view of a first die including a through silicon via, a heat spreader including an insulated hole, a second die including a through silicon via, and a solder ball at the insulated hole. 
         FIG. 14  is a cut view of a first die including a through silicon via, a heat spreader including an insulated hole, a second die including a through silicon via, and an interconnect element at the insulated hole. 
         FIG. 15  is a top plan view of area  15  of the bottom die prior to formation of a heat spreader, showing a cut line  16 - 16 ′. 
         FIG. 16  is a cut view of  FIG. 15  along cut line  16 - 16 ′. 
         FIG. 17  is a top plan view of area  15  of the bottom die subsequent to deposition of a dielectric on a front side of the bottom die, showing a cut line  18 - 18 ′. 
         FIG. 18  is a cut view of  FIG. 17  along cut line  18 - 18 ′. 
         FIG. 19  is a top plan view of area  15  of the bottom die subsequent to selective removal of the dielectric on the front side of the bottom die, showing a cut line  20 - 20 ′. 
         FIG. 20  is a cut view of  FIG. 19  along cut line  20 - 20 ′. 
         FIG. 21  is a top plan view of area  15  of the bottom die subsequent to deposition of a metal on the front side of the bottom die, showing a cut line  22 - 22 ′. 
         FIG. 22  is a cut view of  FIG. 21  along cut line  22 - 22 ′. 
         FIG. 23  is a top plan view of area  15  of the bottom die subsequent to polish or etchback of the metal on the front side of the bottom die, showing a cut line  24 - 24 ′. 
         FIG. 24  is a cut view of  FIG. 23  along cut line  24 - 24 ′. 
         FIG. 25  is a top plan view of area  15  of the bottom die subsequent to selective removal of the dielectric on the front side of the bottom die, showing a cut line  26 - 26 ′. 
         FIG. 26  is a cut view of  FIG. 25  along cut line  26 - 26 ′. 
         FIG. 27  is an enlarged view of area  27  of  FIG. 3 , for an embodiment corresponding to  FIGS. 15-26 . 
         FIG. 28  is a top plan view of area  15  of the bottom die subsequent to deposition of a metal on a front side of the bottom die, showing a cut line  29 - 29 ′. 
         FIG. 29  is a cut view of  FIG. 28  along cut line  29 - 29 ′. 
         FIG. 30  is a top plan view of area  15  of the bottom die subsequent to selective removal of some of the metal, showing a cut line  31 - 31 ′. 
         FIG. 31  is a cut view of  FIG. 30  along cut line  31 - 31 ′. 
         FIG. 32  is a top plan view of area  15  of the bottom die subsequent to deposition of a dielectric onto the front side of the bottom die, showing a cut line  33 - 33 ′. 
         FIG. 33  is a cut view of  FIG. 32  along cut line  33 - 33 ′. 
         FIG. 34  is a top plan view of area  15  of the bottom die subsequent to selective removal of some of the dielectric, showing a cut line  35 - 35 ′. 
         FIG. 35  is a cut view of  FIG. 34  along cut line  35 - 35 ′. 
         FIG. 36  is a top plan view of area  15  of the bottom die subsequent to further selective removal of some of the dielectric, showing a cut line  37 - 37 ′. 
         FIG. 37  is a cut view of  FIG. 36  along cut line  37 - 37 ′. 
         FIG. 38  is an enlarged view of area  38  of  FIG. 3 , for an embodiment corresponding to  FIGS. 28-37 . 
         FIG. 39  is a flow diagram illustrating a method of manufacturing the stacked structure, in accordance with one embodiment of the invention. 
         FIG. 40  is a flow diagram illustrating a method of manufacturing the stacked structure, in accordance with another embodiment of the invention. 
         FIG. 41  is a cut view of a microelectronic device including a plurality of die and a heat spreader sandwiched between the plurality of die, in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In some known microelectronic devices, electrical power and signals are transferred between dies on opposite sides of a heat spreader by using conductors that go around the heat spreader. Unlike some known microelectronic devices, a heat spreader in accordance with embodiments of the invention allows electrical power and signals to be transferred between dies on opposite sides of the heat spreader by allowing such signals to go through one or more openings in the heat spreader. 
     A heat spreader in accordance with embodiments of the invention has an electrically insulated through hole within at least one opening in the heat spreader. In one embodiment, the electrically insulated through hole is in a shape of a cylinder extending from one major surface of the heat spreader to an opposite major surface of the heat spreader. Electrically conductive material in the electrically insulated through hole allows for passage of a signal between dies on opposite sides of the heat spreader while advantageously preventing such signal from shorting to the heat spreader. 
       FIG. 1  is a perspective view of a microelectronic assembly  100  in accordance with one embodiment of the invention, and a simplified portion of a microelectronic package  103 . The microelectronic assembly  100  includes a stacked structure  101  that may, in one embodiment, be surrounded by an encapsulant. The microelectronic assembly  100  may be implemented with an encapsulant or may be implemented without an encapsulant. In  FIG. 1 , the dashed lines  102  represent an outline of a microelectronic package  103  that may be included in one embodiment. Several elements and structures of a typical microelectronic package  103  have been omitted from  FIG. 1  for simplicity of illustration and because such elements and structures are not needed to understand the claimed invention. Some examples of such omitted elements and structures are external connections, pads, bumps, solder balls and wires. In one embodiment (see  FIG. 1 ), the stacked structure  101  includes a heat spreader  104  sandwiched between a first die  106  and a second die  108 . In another embodiment (see  FIG. 41 ), the stacked structure  101  includes a heat spreader  104  sandwiched between a stack of two or more die. The first die  106  is thermally coupled to a first major surface  501  (see  FIG. 5 ) of the heat spreader  104 . The second die  108  is thermally coupled to a second major surface  502  (see  FIG. 5 ) of the heat spreader  104 . There may also be an adhesive (not shown) between the heat spreader  104  and each die  106 ,  108 . The phrase “thermally coupled” includes, but is not limited to, being in direct contact. In the embodiment shown in  FIG. 1 , a portion  110  of the heat spreader  104  is not sandwiched between the two die  106 ,  108 . Such portion  110  may extend outside of the microelectronic package  100  and may be thermally connected to a heat sink (not shown). The first die  106  is shown with five (5) through vias, or, if the die is silicon, through silicon vias (TSVs)  121 - 125 . An actual die may have more than one hundred TSVs. For simplicity of illustration, the five (5) TSVs  121 - 125  are shown in arranged along a line. In an actual die, the TSVs may not be arranged along a line. The discussion that follows assumes an embodiment of the stacked structure  101  in which the second die  108  has a TSV that is approximately aligned with each of the five (5) TSVs  121 - 125  of the first die  106 , as shown in the drawings. In another embodiment (not shown), only a portion of each such TSV of the second die  108  is aligned with only a portion of each of the five (5) TSVs  121 - 125  of the first die  106 . 
       FIG. 2  is a bottom plan view of the one embodiment of the stacked structure  101  showing the second die  108  and the portion  110  of the heat spreader  104 , and showing a cut line  3 - 3 ′. The second die includes TSVs  221 - 225 . In one embodiment, as illustrated, when assembled into the stacked structure  101 , TSVs  121 - 125  of the first die  106  are collinear with TSVs  221 - 225  of the second die  108 . In another embodiment (not shown), when assembled into the stacked structure  101 , TSVs  121 - 125  of the first die  106  are at least partially aligned with TSVs  221 - 225  of the second die  108 . Areas  4 ,  15  encompass a portion of the heat spreader  104  near the TSV  223  and a portion of the second die  108  near the TSV  223 , respectively. A more detailed view of area  4  of the heat spreader  104  is shown in  FIG. 4 . A more detailed view of area  15  of the second die  108  is shown in  FIG. 15 . 
       FIG. 3  is a cut view of the one embodiment of the stacked structure  101  along cut line  3 - 3 ′. Typically, the die  106 ,  108  has a thickness of about 100 μm after polishing. In one embodiment, the TSV has an aspect ratio of 10:1 or less. Therefore, a 100 μm long TSV typically has a diameter of at least 10 μm. Areas  27 ,  38  encompass a portion of the stacked structure  101 . Different embodiments of this portion of the stacked structure  101  are shown in more detail in  FIGS. 27 and 38 . 
     The heat spreader includes a thermally conductive material. In one embodiment, the heat spreader is aluminum nitride. In one embodiment, the heat spreader  104  is metallic because metal has a very high thermal conductivity. Examples of such metal include gold, silver, copper and aluminum. Although metal has very high thermal conductivity, it also has high electrical conductivity. Thus, the electrical power and signals that are passed through the heat spreader  104  are electrically isolated from the heat spreader. Failure to electrically isolate the heat spreader  104  from such electrical power and signals may result in shorted circuits or other device failures. 
     Method of Making at Least One Insulated Hole in a Heat Spreader when the Heat Spreader is in a Form of a Piece Part 
     In one embodiment, the heat spreader  104  may be formed from a self-supporting sheet, foil or plate of metal or another heat conductive material. In such an embodiment, the heat spreader  104  may be considered a “piece part”.  FIG. 4  is a top plan view of area  4  (see  FIG. 2 ) of the heat spreader  104 , and showing a cut line  5 - 5 ′. In one embodiment, the heat spreader  104 , and the portion thereof, illustrated in  FIGS. 1-14  is in a form of a piece part.  FIG. 4  illustrates the heat spreader  104  after formation of an opening  401  in the heat spreader. The opening  401  in the heat spreader  104  will be at least approximately aligned with TSV  223  of the second die  108  after assembly of the stacked structure  101 . When the heat spreader  104  is in a form of a piece part, the opening  401  may be made by one of lithographic patterning and dry etching, wet etching, drilling, punching, milling, laser or by other conventional methods. The opening  401  in the heat spreader  104  can be of any shape. The opening  401  appears circular in the top view of  FIG. 4 . 
       FIG. 5  is a view of the heat spreader  104  along cut line  5 - 5 ′ of  FIG. 4 . As illustrated in  FIG. 5 , in one embodiment, the opening  401  can be considered to have a cylindrical shape with a circular cross-section. Typically, heat spreader  104  has a thickness  503  in the range of about 50 μm to 200 μm, when it is in the form of a piece part. 
     An electrically insulating material (hereinafter “insulator”)  603  is disposed in the opening  401  of the heat spreader  104 .  FIG. 6  is a cut view of the heat spreader  104  along cut line  5 - 5 ′ of  FIG. 4 , subsequent to deposition of the insulator  603  in the opening  401  of the heat spreader. 
     In accordance with various embodiments of the invention, there is an electrically insulated through hole (hereinafter “insulated hole”)  705  in the insulator  603 .  FIG. 7  is a top plan view of the heat spreader  104  subsequent to formation of the insulated hole  705  in the insulator  603  in the opening  401  of the heat spreader. When the heat spreader  104  is a piece part, the insulated hole  705  in the insulator  603  is created by performing one or more of the following actions: lithographic patterning and dry etching, wet etching, stamping, drilling, punching, or by other conventional methods. The insulated hole  705  in the insulator  603  can be of any shape. In one embodiment, the insulated hole  705  has a circular shape, and, to the extent that the insulator has a significant thickness, the insulated hole can be considered to have a cylindrical shape with a circular cross-section. Typically, a diameter of the insulated hole  705  is approximately equal to a diameter of a TSV. The insulator  603  electrically isolates the heat spreader  104  from any electrical conductive material that may be in the insulated hole  705 . In one embodiment, the insulator  603  is a dielectric. The insulator  603  can be silicon dioxide, silicon nitride, tetraethyl orthosilicate (TEOS) or a non-electrically conductive polymer. Any portion of the insulator  603  that extends beyond the major surfaces  501 ,  502  of the heat spreader  104  is removed by polishing or etch back or by other conventional means, thus allowing better thermal conductivity between the two die  106 ,  108  and the heat spreader. 
       FIG. 8  is a cut view of the heat spreader  104  along cut line  8 - 8 ′ of  FIG. 7 , for a first embodiment. In  FIG. 8 , surfaces of the insulator  603  are flush with each of the major surfaces  501 ,  502  of the heat spreader  104 . 
       FIG. 9  is a cut view of the heat spreader  104  along cut line  8 - 8 ′ of  FIG. 7 , for a second embodiment. In the second embodiment, the insulator  603  in the opening  401  of the heat spreader  104  is recessed from one or both of the major surfaces  501 ,  502  of the heat spreader. In  FIG. 9 , the insulator  603  is recessed from only the first major surface  501  of the heat spreader  104 . 
     In one embodiment of making the insulated hole  705  in the opening  401 , the insulated hole  705  is formed prior to placement of the heat spreader  104  onto either of the die  106 ,  108 . 
     In another embodiment of making the insulated hole  705  in the opening  401 , the second major surface  502  of the heat spreader  104  is placed and bonded or adhered onto die  108 , wherein each approximately cylindrically-shaped opening  401  of the heat spreader approximately aligns with, i.e., is nearly collinear with, with an approximately cylindrically-shaped TSV  221 - 225  of die  108 . Then, the insulator  603  is disposed in the opening  401  of the heat spreader  104 . Then, the insulated hole  705  is formed in the insulator  603 . Then, die  106  is placed and bonded or adhered onto the first major surface  501  of the heat spreader  104 , wherein each TSV  121 - 125  of die  106  aligns with each opening  401  of the heat spreader. 
     When the heat spreader  104  is in the form of a piece part, oxide or nitride films could be used to form the insulator  603 , which would likely require that the heat spreader be attached to a temporary backing (tape) or substrate for deposition. Excess material on the surface of the heat spreader  104  outside the opening  401  would then be removed through wet etching, dry etching, or polishing. In another embodiment, the insulator  603  is a non-electrically conductive polymer that is sprayed, deposited, evaporated, or coated onto the heat spreader  104 . Again, excess material would then be removed. Adhesion between the insulator  603  and the heat spreader  104  keeps the insulator inside the opening  401 . Alternatively, a stack of different dielectric materials, e.g., oxide with caps of polymer, could be used as the insulator  603  to achieve good electrical insulation while also maintaining the dielectric stack inside the opening  401  of the heat spreader  104 . 
     Methods of Assembling a Stacked Microelectronic Structure when the Heat Spreader is in the Form of a Piece Part that Already has at Least One Insulated Hole 
       FIG. 10  is a cut view of the first die  106  including TSV  123 , the heat spreader  104  including the insulated hole  705 , and the second die  108  including TSV  223 . Die  106  has an active, or front, side  1001  and an inactive, or back, side  1002 . Die  108  has a front side  1003  and a back side  1004 . In one embodiment, a front side  1001  of die  106  and a front side  1003  of die  108  are thermally coupled to the heat spreader  104 . The front side of a die is the heat-generating side of the die because the integrated circuitry is on the front side of the die. An insulating film (not shown) is disposed on a front side of a die when the front side of the die is to be thermally coupled to a heat spreader. However, when a heat spreader made of aluminum nitride, no insulating film is needed. In another embodiment (not shown), the back side  1002 ,  1004  of one or both of the die  106 ,  108  are thermally coupled to the heat spreader  104 . The back side  1002 ,  1004  does not require an insulating film between the die  106 ,  108  and the electrically conductive heat spreader  104 . The TSV  123 ,  223  includes an electrically insulating lining  1009  (hereinafter “lining”). In one embodiment, the lining  1009  is a dielectric such as silicon dioxide or silicon nitride. In one embodiment, the lining  1009  is an oxide. In one embodiment, prior to assembly into the stacked structure  101 , the TSV  123 ,  223  of the respective die  106 ,  108  are pre-filled with an electrically conductive substance  1305  (see  FIG. 13 ) within the lining  1009 . The lining  1009  of the TSV  123 ,  223  electrically isolates the electrically conductive substance  1305  in the TSV from the die  106 ,  108 , except where connections to circuitry on the die are selectively made. In one embodiment, such electrically conductive substance  1305  in the TSV  123 ,  223  is one of copper and tungsten. In another embodiment, such electrically conductive substance  1305  in the TSV  123 ,  223  is a conductive epoxy. 
     Referring now to  FIGS. 10-12 . In one method (continuous fill) of manufacturing a microelectronic assembly, the heat spreader  104  is in the form of a piece part. In a first step of such method, at least two die  106 ,  108  each having a TSV  123 ,  223  that is not filled with any conductive material are provided, and a heat spreader  104  that has an insulated hole  705  that is not filled with any electrically conductive material is provided. 
       FIG. 11  is a cut view of the first die  106 , the heat spreader  104  and the second die  108 , subsequent to being brought together to form the stacked structure  101 . In a second step, the heat spreader  104  is sandwiched between the two die  106 ,  108 , with a die abutting the two major surfaces  501 ,  502  of the heat spreader and with the insulated hole  705  of the heat spreader aligned with the TSVs  123 ,  223  of the dies. In one embodiment, the front side  1001 ,  1003  of each die abuts one of the major surfaces  501 ,  502  of the heat spreader  104 . As part of the second step, an adhesive may be used to keep the three pieces together. 
       FIG. 12  is a cut view of the stacked structure  101 , subsequent to the TSVs  123 ,  223  and the insulated hole  705  being filled with a continuous fill material  1207 . In a third step, the TSVs  123 ,  223  and the insulated hole  705  in the heat spreader  104  are filled, during a single action, or continuous process, with the fill material  1207 . In other words, in the continuous fill method of manufacturing the microelectronic assembly  100 , a same fill material is disposed in the TSVs  123 ,  223  and in the insulated hole  705  of the heat spreader  104 . The fill material  1207  is electrically conductive. In one embodiment, the fill material  1207  is tungsten. In another embodiment, the fill material  1207  is copper. 
     Referring now to  FIG. 13 . Another method of manufacturing the microelectronic assembly  100  when the heat spreader  104  is in the form of a piece part includes a solder ball. In a first step of such other method, at least two die  106 ,  108  each having a respective TSV  123 ,  223  that is pre-filled with an electrically conductive material are provided, and a heat spreader  104  that has an insulated hole  705  that is not filled with any electrically conductive material is provided. In a second step, the heat spreader  104  and one die  108  of the at least two die  106 ,  108  are brought together with the one die  106  abutting major surface  502  of the heat spreader and with the insulated hole  705  of the heat spreader aligned with the TSV  223  of the one die  108 . In a third step, a solder ball  1308  is placed at the insulated hole  705  of the heat spreader  104 . The solder ball  1308  has a volume of approximately equal to a volume of the insulated hole  705 . A diameter of the solder ball  1308  is such that the solder ball can make contact (during step four) with electrically conductive substance  1305  in the TSVs  123 ,  223  with which the solder ball is intended to form an electrical connection. A diameter of the opening  401  in the heat spreader  104  is larger than a diameter of TSVs  123 ,  223  so that the solder ball  1308  does not create a “stand-off” that would hinder heat transfer between the die  106 ,  108  and the heat spreader  104 . In a fourth step, another die  106  of the at least two die  106 ,  108  is brought together with the heat spreader  104  and the one die  108 , with the other die  106  abutting the other major surface  501  of the heat spreader, and with the TSV  123  of the other die  106  aligned with the insulated hole  705  of the heat spreader. An adhesive may be used to keep the three pieces together. In a fifth step, the solder ball  1308  is reflowed, thereby forming an electrically conductive path between the die  106 ,  108 . More specifically, after reflow of the solder ball  1308 , an electrically conductive path is formed between the electrically conductive substance  1305  in TSV  123  of die  106  and the electrically conductive substance  1305  in TSV  223  of die  108 . Because of the presence of the insulator  603  surrounding the solder in the heat spreader  104 , the electrically conductive path between the two die  106 ,  108  is advantageously electrically isolated from the heat spreader. 
     In another embodiment, a B-staged, i.e., partially cured, conductive polymer ball (not shown) is used to connect the TSVs  123 ,  223  of the two die  106 ,  108 . The B-staged conductive polymer ball is used instead of the solder ball  1308 . The B-staged conductive polymer ball may have a lower attach temperature than the solder ball  1308  and may have longer fatigue life than solder. 
     Referring now to  FIG. 14 . Yet another method of manufacturing the microelectronic assembly  100  when the heat spreader  104  is in the form of a piece part, includes an interconnect element  1406  and a relatively thin solder cap (not shown). The interconnect element  1406  has a top surface  1407  and a bottom surface  1408 . The relatively thin solder cap is added to the top surface  1407  and a bottom surface  1408  of the interconnect element  1406 . In a first step in such yet another method, at least two die  106 ,  108  each having a respective TSV  123 ,  223  that is pre-filled with an electrically conductive material are provided, and a heat spreader  104  that has an insulated hole  705  that is not filled with any electrically conductive material is provided. In a second step, the insulated hole  705  of the heat spreader  104  is filled with an interconnect element  1406 . The interconnect element  1406  is an electrical conductor. In one embodiment, the interconnect element  1406  is made of the same material as the heat spreader  104 , e.g., copper. In a first variation, the top surface  1407  and the bottom surface  1408  of the interconnect element  1406  are planar with the major surfaces  501 ,  502 , respectively, of the heat spreader  104 . In a second variation, one or both of the top surface  1407  and the bottom surface  1408  of the interconnect element  1406  undergoes counter boring. As a result, in such second variation, one or both of the top surface  1407  and the bottom surface  1408  of the interconnect element  1406  is recessed from the respective major surface  501 ,  502  of the heat spreader  104 . In the second variation, as shown in  FIG. 9 , the insulator  603  in the opening  401  of the heat spreader  104  may also be recessed from the major surfaces  501 ,  502  of the heat spreader, to provide an insulated region into which the solder of a solder cap can flow during step five. In a third step, a solder cap is placed on the top surface  1407  and on the bottom surface  1408  of the interconnect element  1406 . In a fourth step, the heat spreader  104  is sandwiched between the two die  106 ,  108 , with the insulated hole  705  of the heat spreader aligned with the TSVs  123 ,  223  of the respective dies  106 ,  108 . An adhesive may be used to keep the three pieces together. In a fifth step, the solder cap is reflowed, thereby forming, in conjunction with the interconnection element  1406 , an electrically conductive path between the first die  106  and the second die  108 . 
     Methods of Forming a Heat Spreader by Depositing a Layer of Metal onto a Die; 
     Forming Openings in the Heat Spreader; Placing an Insulator in the Opening; and Forming Insulated Holes in the Insulator 
     In other embodiments, the heat spreader  104  is formed by depositing a layer, e.g., a film, of a metal onto a die which, at the time of depositing, may be part of a wafer or may be a singulated die. In one embodiment, the film of metal is deposited onto the die. In such embodiment, the film of metal becomes the heat spreader  104 . In one embodiment, the depositing of the layer of metal is accomplished by plating in a bath or by sputtering. Typically, the film of the metal so deposited has a thickness in the range of about 5 μm to 10 μm. 
     Metal Polish 
     In one of such other embodiments in which the heat spreader  104  is formed by depositing a layer of metal onto a die, a metal that is difficult to etch but easy to polish is deposited onto the die. One example of such a metal is copper. 
       FIG. 15  is a top plan view of area  15  of die  108  after the TSV  223 , including lining  1009 , is filled with the electrically conductive substance  1305 .  FIG. 15  shows area  15  of die  108  prior to formation of the heat spreader  104  on the front side  1003 . In another embodiment, the heat spreader  104  is formed on the back side  1004  of the die  108 . Prior to formation of the heat spreader  104  on the front side  1003  of the die  108 , one or more passivation layers (not shown) are added to the front side. No passivation layer is required when a heat spreader is formed on a back side of a die. 
       FIG. 16  is a cut view of  FIG. 15  along cut line  16 - 16 ′. TSV  223  extends between the front side  1003  and the back side  1004  of die  108 , and the electrically conductive substance  1305  is shown surrounded by the lining  1009  in the TSV  223 . The die  108  may part of a wafer or singulated die. The die may be silicon or another semiconductor material. The die  108  contains electrical circuits on the front side  1003  of the die. The TSV  223  electrically connects circuitry on the front side  1003  of die  108  to the back side  1004  of the die. The lining  1009  prevents electrical power or electrical signals carried by the TSV  223  from electrically connecting to the die  108 , except where an electrical connection is intended. 
     Referring now to  FIG. 17 . In a next step in a method of forming the heat spreader  104 , a dielectric  1701  is deposited onto an entire front side  1003  of die  108 . In one embodiment, the dielectric  1701  may be silicon dioxide, silicon nitride or a non-electrically conductive polymer.  FIG. 17  is a top plan view of area  15  of die  108  subsequent to deposition of the dielectric  1701  on the front side  1003  of the die, showing a cut line  18 - 18 ′.  FIG. 18  is a cut view of  FIG. 17  along cut line  18 - 18 ′. 
     Referring now to  FIG. 19 . Most of the dielectric  1701  is selectively removed by photolithography or dry etching. The portion of the dielectric  1701  above the TSV  223  and above a small region around the TSV is not removed.  FIG. 19  is a top plan view of area  15  of die  108  subsequent to selective removal of the dielectric  1701  on the front side  1003  of die  108 , showing a cut line  20 - 20 ′.  FIG. 20  is a cut view of  FIG. 19  along cut line  20 - 20 ′.  FIGS. 19 and 20  show the result of patterning of the dielectric  1701  to form caps over the TSV  223  on the front side  1003  of die  108 . 
     Referring now to  FIG. 21 . In next step, copper  2101  or another metal in another embodiment, is deposited onto an entire front side of die  108 , such as by plating.  FIG. 21  is a top plan view of area  15  of die  108  subsequent to deposition of the copper  2101  on the front side  1003  of die  108 , showing a cut line  22 - 22 ′.  FIG. 22  is a cut view of  FIG. 21  along cut line  22 - 22 ′.  FIGS. 21 and 22  show the result of forming the heat spreader  104  by depositing a film, or layer, of copper  2101  onto the front side  1003  of die  108 . During the formation of a copper film, a barrier layer (not shown) such as Ti, TiN, Ta and TaN may be used to aid the formation of the copper film. 
     Referring now to  FIG. 23 .  FIG. 23  is a top plan view of area  15  of die  108  subsequent to polish or etchback of the copper  2101  on the front side  1003  of the die, showing a cut line  24 - 24 ′. In this step, chemical mechanical planarization (CMP) of the copper may be performed.  FIG. 24  is a cut view of  FIG. 23  along cut line  24 - 24 ′.  FIGS. 23 and 24  show the results of copper polish or etchback to expose the dielectric  1701  above the TSV  223  on the die  108 . The remaining film of copper  2101  may be approximately coplanar with the tops of the dielectric  1701 , which allows a film copper on die  108  to act as the heat spreader  104  for both the die  106  and the die  108  after the two die and the heat spreader are assembled. In another embodiment, the copper film may be lower or higher than the tops of the dielectric  1701  as required to make contact between the heat spreader  104  and the die  106  during assembly of the stacked structure  101 . 
     Referring now to  FIG. 25 .  FIG. 25  is a top plan view of area  15  of die  108  subsequent to selective removal of the dielectric  1701  on the front side  1003  of the die, showing a cut line  26 - 26 ′.  FIG. 26  is a cut view of  FIG. 25  along cut line  26 - 26 ′.  FIGS. 25 and 26  show a patterned dielectric cap  2501  above the TSV of die  108 . Patterning may be accomplished through lithographic patterning and dry etching or other conventional methods. At this step, the insulated hole  705  in the patterned dielectric cap  2501  is formed which exposes the underlying electrically conductive substance  1305  of the TSV  223 . The patterned dielectric cap  2501  advantageously prevents electrical contact between the electrically conductive substance  1305  in the TSV  223  and the rest of the die  108  and/or the heat spreader  104  (in this embodiment, the film of copper  2101 ). In one embodiment, the insulated hole  705  in the dielectric cap  2501  may be counter bored, counter sunk, tapered or recessed to provide additional space for the solder bond  1308  to expand laterally during assembling without allowing an electrical connection between the solder bond and the die  108  and/or the heat spreader  104 . 
     Referring now to  FIG. 27 , a solder ball  1308  is placed at the insulated hole of the dielectric cap  2501  of die  108 . Alternative, copper studs or similar bonding techniques may be used. The ball bond creates an electrical connection between the electrically conductive substance  1305  of TSV  223  of die  108  and the electrically conductive substance  1305  of TSV  123  of die  106 , while the dielectric cap  2501  advantageously prevents a short between the ball bond and other portions of the die  108  and/or the heat spreader  104  from occurring.  FIG. 27  shows die  108 , the heat spreader  104  and the die  106  just prior to assembly into the stacked structure  101 . Next, die  106  is placed such that it is thermally coupled to a surface of the heat spreader  104  that is opposite of die  108  such that the TSV of die  106  is aligned with the solder ball  1308 . Then, the solder ball  1308 , and possibly also the electrically conductive substance  1305 , is reflowed. 
     Metallic Subtractive Etch 
     In another of such other embodiments in which a layer of metal is deposited onto a die, a metal that is easy to etch, but may or may not be easy to polish, is deposited onto the die. An example of such a metal is aluminum. 
     Referring again to  FIGS. 15 and 16 , a top plan view of area  15  of die  108  prior to formation of the heat spreader  104  on the front side  1003  of die  108 , and a cut view thereof are illustrated, which shows the starting point of the metallic subtractive etch method. 
     Referring now to  FIG. 28 . In a next step of the metallic subtractive etch method, aluminum  2801  or another metal in another embodiment, is deposited, such as by sputtering, onto the entire front side  1003  of die  108 , thereby producing an aluminum film, or layer.  FIG. 28  is a top plan view of area  15  of die  108  subsequent to deposition of the aluminum  2801  on the front side  1003  of die  108 , showing a cut line  29 - 29 ′.  FIG. 29  is a cut view of  FIG. 28  along cut line  29 - 29 ′. During the formation of an aluminum film, a barrier layer (not shown) such as Ti, TiN, Ta and TaN may be used to aid the formation of the aluminum film. 
     Referring now to  FIG. 30 . In a next step, the film of aluminum  2801  is patterned through subtractive etch. Subtractive etch of the aluminum film removes the aluminum  2801  near the TSV  223  thereby creating the opening  401 , which is a region free of aluminum. The aluminum  2801  is selectively removed by photolithography or etching.  FIG. 30  is a top plan view of area  15  of die  108  subsequent to selective removal of some of the aluminum  2801 , showing a cut line  31 - 31 ′.  FIG. 31  is a cut view of  FIG. 30  along cut line  31 - 31 ′. 
     Referring now to  FIG. 32 . In a next step, a dielectric  3201  is placed over the aluminum film including in the opening  401  above the TSV  223  of the die  108 . Oxide deposition followed by oxide polish or etchback may be used to fill the aluminum-free region above the TSV  223 .  FIG. 32  is a top plan view of area  15  of die  108  subsequent to deposition of the dielectric  3201  onto the front side  1003  of the die, showing a cut line  33 - 33 ′.  FIG. 33  is a cut view of  FIG. 32  along cut line  33 - 33 ′. 
     Referring now to  FIG. 34 . In a next step, CMP or etchback is performed on only the dielectric  3201 , and not on the aluminum  2801 .  FIG. 34  is a top plan view of area  15  of die  108  subsequent to selective removal of some of the dielectric  3201 , showing a cut line  35 - 35 .  FIG. 35 ′ is a cut view of  FIG. 34  along cut line  35 - 35 ′. 
     Referring now to  FIG. 36 . In a next step, the dielectric  3201  is then patterned to expose the electrically conductive substance  1305  of the TSV  223  while electrically separating the heat spreader  104  (in this embodiment, the film of aluminum  2801 ) from the electrically conductive substance  1305  of the TSV.  FIG. 36  is a top plan view of area  15  of die  108  subsequent to further selective removal of some of the dielectric  3201 , showing a cut line  37 - 37 ′.  FIG. 37  is a cut view of  FIG. 36  along cut line  37 - 37 ′. 
       FIG. 38  is an enlarged view of area  38  of  FIG. 3 , for an embodiment corresponding to  FIGS. 28-37 .  FIG. 38  shows die  108 , the heat spreader  104  and the die  106  just prior to assembly into the stacked structure  101 . Next, die  106  is placed such that it is thermally coupled to a surface of the heat spreader  104  that is opposite of die  108  such that the TSV of die  106  is aligned with the solder ball  1308 . Then, the solder ball  1308 , and possibly also the electrically conductive substance  1305 , is reflowed. 
       FIG. 39  is a flow diagram  3900  illustrating a method of manufacturing the stacked structure  101 , in accordance with one embodiment of the invention. At step  3902 , the heat spreader  104  is provided. At step  3904 , the opening  401  is made in the heat spreader  104 . At step  3906 , the insulator  603  is disposed in the opening  401 . At step  3908 , the insulated hole  705  is made in the insulator  603 . At step  3910 , the die  108  that has the TSV  223  is provided. At step  3912 , the die  108  is placed such that it is thermally coupled to a major surface  502  of the heat spreader  104 . At step  3914 , the TSV  223  of the die  108  is aligned with the insulated hole  705  of the heat spreader  104 . At step  3916 , the die  106  that has the TSV  123  is provided. In one variation, in a next step, a solder ball  1308  is placed at the insulated hole  705 . At step  3918 , the die  106  is placed such that it is thermally coupled to a major surface  501  of the heat spreader  104 . At step  3920 , the TSV  1223  of the die  106  is aligned with the insulated hole  705  of the heat spreader  104 . In another variation, in a subsequent step, the TSV  223  of die  108 , the insulated hole  705  of the heat spreader  104  and the TSV  123  of die  106  are filled with an electrically conductive continuous fill material  1207  in a single action. 
       FIG. 40  is a flow diagram  4000  illustrating a method of manufacturing the stacked structure  101 , in accordance with another embodiment of the invention. At step  4002 , die  106  and  108  are provided, each die having a TSV  123 ,  223  that has an insulating lining  1009  and an electrically conductive substance  1305  within the electrically insulating lining. At step  4004 , a dielectric  1701  is deposited onto an entire front side  1003  (or back side  1005 ) of the die  108 . At step  4006 , the dielectric is removed except for the dielectric  1701  on, and slightly beyond, the TSV  223  of die  108 . At step  4008 , a film or layer of metal  2101 , which forms the heat spreader  104 , is deposited onto the front side  1003  of the die  108 . At step  4010 , the metal  2101  is removed until the dielectric  1701  becomes exposed. At step  4012 , a center portion of the dielectric  1701  is removed until the electrically conductive substance  1305  becomes exposed. At step  4014 , a solder ball  1308  is placed on the electrically conductive substance  1305  at the center portion of the dielectric  1701 . At step  4016 , the die  106  is placed such that it is thermally coupled to a side of the heat spreader  104  opposite the die  108 . At step  4018 , the TSV  123  of die  106  is aligned with the solder ball  1308 . At step  4020 , the solder ball  1308  is reflowed, thereby creating an electrical connection between the electrically conductive substance  1305  in the TSV  123  of die  106  and the electrically conductive substance  1305  in the TSV  223  of die  108 . 
       FIG. 41  is a cut view of a microelectronic device  4100  that includes the stacked structure  101 , in accordance with one embodiment of the invention. The microelectronic device  4100  includes die  106 ,  108  and heat spreader  104  sandwiched between the die. The microelectronic device  4100  includes a first stack  4101  of die comprising die  106  and  4111 - 4114 , and a second stack  4102  of die comprising die  108  and die  4115 - 4118 . In one embodiment, die  106  and  108  are microprocessors and die  4111 - 4118  are memory. The microelectronic device  4100  includes a plurality of flip chip bumps  4120 . The microelectronic device  4100  includes a plurality of TSVs  4121  on one side of the heat spreader  104  and a plurality of TSVs  4122  on an opposite side of the heat spreader. Each TSV  4121  is electrically coupled to one of the TSVs  4122  via an insulated hole  705 . Each flip chip bump  4120  is electrically coupled to one of the TSVs  4121 . Each flip chip bump  4120  can be electrically coupled to a conductive pathway in a package substrate (not shown) within a microelectronic package. In some embodiments, the heat spreader  104  of the microelectronic device  4100  is thermally coupled to a heat sink. 
     In another embodiment (not shown), one of more TSVs  123 - 125  and  221 - 225  may be intentionally electrically connected to the heat spreader  104 . This electrical connection may advantageously create a ground connection for circuitry in the die  106 ,  108 . 
     In some embodiments, an adhesive may be added between the heat spreader  104  and the die  106 ,  108 . In one embodiment, the adhesive is added prior to making the at least one opening  401  in the heat spreader  104 . In another embodiment, the adhesive is added after making the at least one opening  401  in the heat spreader  104  using a stencil that prevents adhesive being applied near the at least one opening. In one embodiment, the adhesive may be selected from the group of epoxies including thermoset, thermoplastic and B-staged or the like. 
     In one embodiment of the stacked structure  101 , the at least one die comprises a stack of dies. In such embodiment, dies are arranged into stacks prior to placing the stack such that it is thermally coupled to the heat spreader  104 . When such stack is formed, the dies can be already singulated, or the dies can be in wafer form and a stack of wafers is then singulated. The at least one insulated hole  705  in the heat spreader  104  can be used in conjunction with a TSV that extends through such stack of dies. 
     In one embodiment of the stacked structure  101 , a plurality of stacks is placed such that it is thermally coupled to the heat spreader  104 . In such embodiment, the insulated holes  705  in the heat spreader  104  can be used in conjunction with a plurality of TSVs, the TSV extending through a different stack of such plurality of stacks. 
     The insulated holes  705  in the heat spreader  104  can be used in conjunction with various types of stacks and various types of die. For example, a stack could be interleaved or not interleaved, a stack could be staggered or not staggered, each die could be of a same type or each die could be of a different type (e.g., processor, memory, etc.), and each die could have the same dimensions (i.e., area and/or thickness) or could have different dimensions. 
     In one embodiment, one or both die  106  and die  108  comprise one or more microprocessors. A die that comprises a microprocessor is typically much larger in area than a die of memory. When one or both die  106  and die  108  comprise a microprocessor, each die  106 ,  108  may have four memory die, one memory die in each quadrant of the die  106 ,  108 . Each such memory die may include a stack of a plurality of memory die. When dies of microprocessors and dies of memory are in a stack, the dies of the microprocessors are placed directly adjacent to each side of the heat spreader because a typical die of a microprocessor may generate 10 W or more of heat, whereas die of memory may generate only 0.5 W of heat. The insulated holes  705  allow memory that is stacked on one microprocessor to be accessed by the other microprocessor in spite of each microprocessor being on an opposite side of the heat spreader  104 . 
     By now it should be appreciated that a heat spreader  104  located between two die  106 ,  108  has been disclosed, wherein a region of the heat spreader between the two die includes at least one insulated hole  705  for isolated electrically coupled vias to extend through the heat spreader from one of the two die to the other of the two die. 
     In one embodiment, a method of manufacturing the microelectronic device  4100  comprises providing the heat spreader  104  which has the first major surface  501  and the second major surface  502  opposite the first major surface. The heat spreader has the opening  401 , the insulator  603  in the opening, the electrically insulated through hole  705  in the insulator, and the electrically conductive material  1308 ,  1406  in the electrically insulated through hole. The method further comprises providing the first die  106  and the second die  108 , each die having the through via  123 ,  223  and the electrically conductive substance  1305  therein; thermally coupling the first die  106  to at least a portion of the first major surface  501  of the heat spreader  104 , the portion including the opening  401 , wherein the first die is located with respect to the first major surface of the heat spreader; and thermally coupling the second die  108  to at least a portion of the second major surface  502  of the heat spreader, the portion including the opening, wherein the second die is located with respect to the second major surface of the heat spreader. The electrically conductive material  1308 ,  1406  in the electrically insulated through hole  705  of the heat spreader  104  is coupled to the electrically conductive substance  1305  in the through via  123  of the first die  106  and to the electrically conductive substance  1305  in the through via  223  of the second die  108 . 
     In another embodiment, a method of manufacturing the microelectronic assembly  100  comprises providing the first die  106  that has at least one through via  223 . The at least one through via has the electrically insulating lining  1009  and the electrically conductive substance  1305  therein. The thermally conductive material  2101 ,  2801  is located on the surface  1003  of the first die and is thermally coupled to the first die. The thermally conductive material defines the opening  401  in the thermally conductive material. The dielectric material  1701 ,  3201  is located in the opening. The dielectric material defines the hole  705  in the dielectric material. The hole includes the electrically conductive material  1308 ,  1406 . The method further includes thermally coupling the second die  108  to the thermally conductive material  2101 ,  2801  located on the surface  1003  of the first die  106 . The second die has at least one through via  123  having the electrically insulating lining  1009 . The at least one through via has the electrically conductive substance  1305  within a volume defined by the electrically insulating lining. The electrically conductive material  1308  in the hole  705  is electrically coupled to the electrically conductive substance  1305  in the through via  223  of the first die  106  and to the electrically conductive substance  1305  in the through via  123  of the second die  108 . 
     In still another embodiment, a method of manufacturing the microelectronic assembly  100  comprises the steps of providing the heat spreader  104  which has the first major surface  501  and the second major surface  502  opposite the first major surface; thermally coupling at least one die  106  to at least a portion of the first major surface of the heat spreader; thermally coupling at least one other die  108  to at least a portion of the second major surface of the heat spreader; forming the opening  401  in the heat spreader, the opening located in a region of the heat spreader between the at least one die and the at least one other die; disposing the insulator  603  in the opening to produce an electrically insulated through hole  705  in the insulator; and disposing electrically conductive material  1308 ,  1406  in the electrically insulated through hole in the insulator. 
     The term “align” includes approximately or nearly align such that the electrically conductive material, e.g., the solder ball  1308 , in the insulated hole  705  is electrically coupled to the electrically conductive substance  1305  in the TSV  223  of the first die  106  and to the electrically conductive substance  1305  in the TSV  123  of the second die  108 . 
     The terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. 
     Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. 
     Note that the term “couple” has been used to denote that one or more additional elements may be interposed between two elements that are coupled. 
     The specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. Any benefits, advantages or solutions to problems described herein with regard to specific embodiments are not intended to be construed as a critical, required or essential feature or element of any or all the claims. 
     The Detailed Description section, and not the Abstract section, is intended to be used to interpret the claims. The Abstract section may set forth one or more but not all embodiments of the invention, and the Abstract section is not intended to limit the invention or the claims in any way. 
     Although the invention is described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below.