APPARATUSES AND METHODS FOR SEMICONDUCTOR DIE HEAT DISSIPATION
1. An apparatus, comprising:
- a substrate;
a thermal interface layer disposed on a surface of the substrate; and
a heat spreader with a plurality of substrate-facing protrusions in proximity to the thermal interface layer, wherein the heat spreader covers an entire surface of a top die of a stack of semiconductor die.
Apparatuses and methods for semiconductor die heat dissipation are described. For example, an apparatus for semiconductor die heat dissipation may include a substrate and a heat spreader. The substrate may include a thermal interface layer disposed on a surface of the substrate, such as disposed between the substrate and the heat spreader. The heat spreader may include a plurality of substrate-facing protrusions in contact with the thermal interface layer, wherein the plurality of substrate-facing protrusions are disposed at least partially through the thermal interface layer.
- 1. An apparatus, comprising:
a substrate; a thermal interface layer disposed on a surface of the substrate; and a heat spreader with a plurality of substrate-facing protrusions in proximity to the thermal interface layer, wherein the heat spreader covers an entire surface of a top die of a stack of semiconductor die.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- 10. An apparatus, comprising:
a stack of semiconductor die, the stack of semiconductor die including a top die and a bottom die; and a heat spreader including a first portion with a plurality of first protrusions and a second portion with a plurality of second protrusions, the first portion of the heater spreader covering a surface of the top die, the second portion of the heat spreader covering at least one surface of the bottom die.
- View Dependent Claims (11, 12)
- 13. An apparatus, comprising:
a stack of semiconductor die, the stack of semiconductor die including a first die and a second die; and a heat spreader including at least one first downward facing pillar in close proximity to a thermal interface layer disposed on the first die, the heat spreader further including at least one second downward facing pillar in close proximity to another thermal interface layer disposed on the second die.
- View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
This application is a continuation of U.S. application Ser. No. 16/272,190 filed Feb. 11, 2019, which is a divisional of U.S. patent application Ser. No. 14/626,575 filed Feb. 19, 2015. The aforementioned applications are incorporated herein by reference, in their entirety, for any purpose.
The evolution of electronics is forcing component manufacturers to develop smaller devices while providing greater functionality and speed. The combination of these size and operational goals may lead to increases in internal heat generation. The increase in heat generation may be due to obstructed or inefficient thermal paths in combination with higher operating power consumption. For the components to continue to provide the performance desired, the extra heat may need to be dissipated. At a time when components (and the systems including the components) were larger, dissipation of any extra heat may have been more easily accomplished due to heat dissipating bulk materials and/or the air flow around the components. Currently, however, small, high powered devices and components containing multiple co-packaged die may benefit from packaging that provides higher thermal conductivity paths for dissipating the heat generated within such devices.
Apparatuses and methods for heat extraction from packaged semiconductor devices are disclosed herein. Certain details are set forth below to provide a sufficient understanding of embodiments of the disclosure. However, it will be clear to one having skill in the art that embodiments of the disclosure may be practiced without these particular details. Moreover, the particular embodiments of the present disclosure described herein are provided by way of example and should not be used to limit the scope of the disclosure to these particular embodiments. In other instances, well-known circuits, control signals, timing protocols, and software operations have not been shown in detail in order to avoid unnecessarily obscuring the disclosure.
As noted, thermal management of semiconductor devices is an ever increasing concern and due in part to combinations of device size and power consumption. Other factors may also contribute to thermal concerns, such as multiple die packaged together for example. Heat extraction barriers such as multiple interfaces may contribute to the problems of multiple co-packaged die. At elevated operating levels, the overall heat generated by multiple co-packaged die may increase. Such an increase in heat generation may be due to the proximity of several co-packaged die exacerbating heat conduction and adding to an operating environment at an elevated temperature. For example, a co-package stack of die may present a difficult heat extraction configuration due to the multiple interfaces the heat may need to travel before reaching an external surface of the package for dissipation. Additionally, lateral heat extraction may also be limited due to die packaging configurations. The additional heat, if not efficiently removed from the stack of die, may cause one or more die in the stack to experience temperatures above their specified limits. Such thermal problems may lead to malfunctioning or inoperable devices.
Packaging may play a role in enhancing heat extraction. Heat sinks may be added to packaging in an effort to dissipate heat more efficiently. Packaging materials may be designed to have increased thermal conductivity characteristics aimed at improving heat dissipation. These packaging materials may include metal fillers to improve thermal conductivity, for example. Most of these approaches, however, may be more focused external to the package or minimally related to the package itself. More package-centric approaches may focus on supplying heat conduction paths from die to package, but these approaches may be limited by the material used for the die and package or space limited.
In the case of a multi-die package, for example, the extraction of heat may be inhibited due to the many interfaces through which the heat may need to travel. The interfaces may impede the flow of heat in directions perpendicular to the die surface, but may also impede planar heat flow within a die. The interfaces may be due to die fabrication, e.g., many layers of metal and passivation layers built up on an active surface of the die, and/or to the die being stacked, multiple die stacked on top of one another. The interfaces may cause the heat flow to be reduced due to reflection and the materials of the die may reduce heat flow due to variations in thermal conductivity. Further, the distance from a heat generating source, e.g., an active area of a die, to a heat-dissipating packaging surface may also reduce heat dissipation. Moreover, low thermal conductivity of the various package materials may also adversely affect heat dissipation.
One solution to increase the heat extraction from a co-packaged die stack may be to package the die stack with a conformal heat spreader that includes internally-facing protrusions. The internally-facing protrusions may be in close proximity to and/or touching one or more die in the die stack. The internally-facing protrusions may be die stack facing and may provide for increased heat spreader surface area to provide an improved thermal path. The internally-facing protrusions may contact or be in close proximity to the top die of the stack and to one or more other die of the stack, such as the bottom die. The reduced distance from the die surface to a bottom surface of each of the protrusions may provide improved thermal pathways from the die to the package/heat spreader. A bottom surface of the protrusions along with sides of the protrusions may reduce the distance through which heat may travel from the die surface to the heat spreader. The reduced distance between the die surface and heat spreader may include a small volume (e.g., a thin layer) of a thermal interface material that is formed between the heat spreader and the die. An alternative solution may involve the protrusions of the heat spreader contacting or coming into close proximity to thermal dissipation pads formed on the backside of one or more die of the die stack. The “backside” of the die may be a face of the die opposite a face of the die that includes the active elements, e.g., transistors and logic gates, which may be referred to as the “front side” of the die. The thermal dissipation pads may further enhance heat dissipation of the die stack.
In a non-limiting example, each of the plurality of die 106 A-D may be a memory die, such as non-volatile or volatile memory die. The die 108 may be an interface die or a logic die. The stack of die, including the plurality of die 106 A-D and the die 108, may be interconnected with through-via interconnects (not shown), which may be a common bus for command and data signals to propagate within the stack of die. The command and data signals may be externally provided to the stack of die by the host and data may be provided to the host in response. Additionally, the die 108 may receive data and command signals from one or more external components, and in response provide the data/command signals to a target die 106 of the plurality of die 106 A-D.
In the example shown in
The combination 100 may further include a thermal interface layer 104 disposed between the die 106 A, exposed edges of the die 108 and the heat spreader 102. The thermal interface layer 104 may be included to assist with heat transfer from the die stack to the heat spreader 102, and may also assist in mounting, e.g., attaching, the heat spreader 102 to the die stack. The thermal interface layer 104 may be an epoxy material that may or may not include metal fillers, such as indium or gallium. The metal fillers may be included to enhance thermal conduction, and may be indium or gold. The thickness of the thermal interface layer 104 may be from 20 to 50 microns, which may be dependent upon fabrication process and/or due to normal variations in the fabrication process. The thermal interface layer 104 may have a thermal conductivity rating of 2 W/mK to 10 W/mK, and the variation in thermal conductivity may be due to the presence, or lack thereof, of the filler materials present.
As discussed above, one solution to the problem of dissipating heat from a stack of semiconductor die may include decreasing a distance from a heat sink to a surface of a die. An example embodiment of the solution may involve adding a plurality of protrusions 114 to the heat spreader 102. The plurality of protrusions may be internally-facing, e.g., die-facing, such as depicted by the protrusions 114 shown in
As heat moves from the stack of die 106 A-D and the die 108 to the heat spreader 102, the areas of the die 106 A and the exposed portions of the die 108 under one or more of the protrusions 114 may be characterized as having increased thermal conductivity due to the reduction of the thermal interface layer 104 under the protrusions 114/heat spreader 102. Increased thermal conductivity may also be obtained when one or more of the protrusions 114 are in contact with the die 106A or the die 108. Thus, either or both situations—protrusions in close proximity to or in contact with a die surface—may provide enhanced heat dissipation for the combination 100.
Thermal dissipation provided by the heat spreader 102 may further be enhanced due to increased surface area of the underside of the heat spreader 102 facing the stack of die 106, 108. The protrusions 114, for example, may be pillars protruding from the underside of the heat spreader 102, with each pillar having a bottom surface and one or more side surfaces, e.g., rectangular pillars or round pillars. The bottom surface of each pillar, as discussed above, may either be in contact with a die surface or in close proximity to the die surface such that a volume of the thermal interface layer is reduced between the die and pillar surface. The sides of each pillar may further improve the heat dissipation due to the increased surface area they provide for heat extraction by the heat spreader 102.
The interface between the protrusions 114 and the die 106 A depicted in
Similar to the heat spreader 102 of
The protrusions 216 may be in close proximity to one or more thermal dissipation pads 206 so that a reduced volume of the thermal interface layer 204 is disposed between one or more of the protrusions 216 and one or more of the thermal dissipation pads 206. Alternatively or additionally, one or more of the protrusions 216 may make direct, physical contact with one or more thermal dissipation pads 206.
The connection between one or more protrusions 216 and one or more thermal dissipation pads 206 may be either direct physical contact due to proximity or a metallic bond may be formed between the two. The thermal dissipation pads 206 may be coated with or formed from one or more metals. The one or more metals may be a metal stack that includes copper, nickel, and gold or palladium, for example. The protrusion-side of the heat spreader 202 may be similarly coated. A eutectic bond may then be formed between one or more of the thermal dissipation pads 206 and one or more of the protrusions 216 by subjecting the combination 200 to one or more heat treatments and or re-flow processes. The eutectic bond may further improve heat dissipation of the combination 200.
Thermal dissipation may improve whether or not one or more of the thermal dissipation pads 206 and one more of the protrusions 216 are in direct physical contact. For example, a reduction in volume of the thermal interface layer 204 between a protrusion 216 and a thermal dissipation pad 206 may provide improved thermal dissipation. The improved thermal dissipation may be due, at least in part, to an improved heat dissipation path between the die 208 A, and/or the die 210 and the heat spreader 202. Additionally, there may be embodiments where a subset of the plurality of protrusions 216 are in contact with one or more thermal dissipation pads 206 while other protrusions are in close proximity to one or more thermal dissipation pads 206.
The thermal dissipation pads 304 may be formed from one or more metals, such as a stack of copper, nickel, and gold. In some examples, palladium is used instead of gold. The one or more metals used to form the thermal dissipation pads 304 may be similar to the one or more metals used to form the through-via bonding pads 302. The array pattern the bonding pads shown for the die 300 in
The layout of the thermal dissipation pads 304 and the through-via bonding pads 302 may determine a layout and design configuration for heat spreader protrusions. Because it may be desirable to avoid contact between heat spreader protrusions and through-via bonding pads 302, heat spreader protrusions may be designed so that one or more spaces between the protrusions align with the through-via bonding pads 302 when the heat spreader is mounted onto a stack of die, as depicted in
The number and shape of the protrusions may vary based on the design of the die that the heat spreader may be mounted upon, e.g., die with and without thermal dissipation pads. Further, the spacing between the die may also vary based on heat spreader size, die size/design, protrusion size, or combinations thereof. The size, shape, number, and layout of the protrusions, any of which fall within the scope of the present disclosure, may at least be driven by thermal dissipation improvement.
A thermal interface layer deposed between a die and a heat spreader, such as the thermal interface layers 104 and 204 of
Since the heat spreader 400 may also be a conformal lid for a stack of die, the heat spreader 400 may take the U-type shape as depicted in
The heat spreader 400 may be fabricated by various methods and the size of the protrusions may determine the method used for their fabrication. The U-type shape of the heat spreader 400 may be formed through a stamping process and the protrusions may be formed during the stamping process or by additional fabrication steps. For example, if the bottom surface of each of the protrusions are 0.5 mm on a side, then the heat spreader including the protrusions may be fabricated using a conventional metal stamping process. If, however, the protrusions 404 are smaller, around 50 microns on a side for example, then the heat spreader body 402 may be stamped and the protrusions 404 formed through masking and etching. Additionally, if eutectic bonds are to be formed with thermal dissipation pads, for example, then the heat spreader, or at least bottom face of the protrusions 404, may be coated with a metal, such as gold or tin. Tolerances and variations in the heat spreader 400 fabrication process may influence whether or not the protrusions 404 make contact with a die and/or a thermal dissipation pad of a die. The height of the protrusions may be designed to target contact, but protrusions that are shorter due to fabrication process variation may still be substantially close to the die and/or thermal dissipation pads to improve heat dissipation characteristics of the heat spreader 400.
The heat spreader 400 die mounting process may include dispensing a thermal interface layer material onto the top of the die stack, such as the top of the die 208A and the exposed edges of the die 210 of
The die stacks depicted in
From the foregoing it will be appreciated that, although specific embodiments of the disclosure have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the disclosure. Accordingly, the disclosure is not limited except as by the appended claims.