Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-03-04
2001-06-12
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S702000, C361S706000, C361S710000, C361S767000, C257S706000, C257S707000, C174S016300, C165S080300
Reexamination Certificate
active
06246583
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to semiconductor devices and more particularly to a method and apparatus for removing heat from a semiconductor device.
BACKGROUND OF THE INVENTION
A semiconductor device mounted within a carrier package has a maximum operating temperature dictated by the heat removal methods of the carrier package. If heat generated by a packaged semiconductor device is not effectively dissipated via the device's carrier package, the temperature of the device will increase until the device's maximum operating temperature is exceeded (i.e., until the device overheats), and the device will be damaged or destroyed.
Most semiconductor devices are formed from bulk silicon (e.g., from bulk silicon wafers), a material that has excellent thermal conduction properties. A bulk silicon device primarily dissipates heat through the backside of the silicon wafer die from which the silicon device is formed. For example, a conventional “packaged” semiconductor device may comprise a silicon wafer die having circuit elements formed on a first side or “frontside” thereof, an alumina substrate coupled to the frontside of the wafer die via a plurality of solder balls, a module cover coupled to a second or “backside” of the wafer die and to the substrate, and a heat sink coupled to the module cover. Heat primarily is dissipated from the semiconductor device via a “backside” thermal path from the frontside to the backside of the wafer die, from the backside of the wafer die to the module cover, from the module cover to the heat sink, and from the heat sink to the ambient environment.
Backside thermal paths are fairly effective at removing heat from semiconductor devices formed from bulk silicon wafers. However, the drive for higher speed and higher density circuits has lead to the use of non-conventional device materials such as silicon-on-insulator (SOI) wafers. An SOI wafer possesses an electrically insulating region between the frontside of the wafer (e.g., where the circuit elements are formed) and the backside of the wafer (e.g., where a module cover and a heat sink typically are coupled). This electrically insulating region has poor thermal conduction properties and significantly decreases the efficiency with which heat is conducted from the frontside to the backside of an SOI wafer (e.g., increases the “thermal resistance” of the wafer's backside thermal path). Therefore, conventional backside thermal paths are ineffective at removing heat from semiconductor devices formed on SOI wafers (i.e., SOI devices).
Accordingly, a need exists for a method and apparatus for removing heat from semiconductor devices formed on semiconductor wafers having backside thermal paths of high thermal resistance.
SUMMARY OF THE INVENTION
To address the needs of the prior art, an inventive apparatus and method are provided that remove sufficient heat from both SOI and non-SOI semiconductor devices to prevent the devices from overheating during operation. A plurality of thermally conductive pads (e.g., electrically conductive studs) are coupled to a first side of a semiconductor device having circuit elements formed thereon. As used herein, “coupled” means coupled directly or indirectly (e.g., via a non-electrically conductive, but thermally conductive material) so as to operate.
The thermally conductive pads are coupled to a substrate, and the substrate is provided with means for extracting heat from the thermally conductive pads. The means for extracting heat preferably comprises one or more metallic planes such as a ground plane, a voltage plane or the like. A module cover having a thermally conductive path formed therein also may be coupled between the substrate's means for extracting heat and a heat sink to further aid in heat removal from the thermally conductive pads, and thus from the semiconductor device. Thermally conductive pads additionally may be coupled between the semiconductor device and I/O pins of the substrate to improve heat dissipation via the I/O pins.
The combination of the thermally conductive pads, of the means for extracting heat from the substrate and of the module cover having a thermally conductive path, greatly enhances heat dissipation from a semiconductor device and therefore significantly reduces the risk of device overheating. The heat dissipation properties of the semiconductor device module formed from the semiconductor device, the substrate, the module cover and the heat sink may be further improved by tailoring other module material properties (e.g., by using epoxies having high thermal conductivities, by increasing the size of the heat sink, etc.).
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings. dr
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit of a reference number identifies the drawing in which the reference number first appears.
FIG. 1
is a cross-sectional view of an inventive SOI device configured in accordance with the present invention; and
FIG. 2
is a cross-sectional view of an inventive semiconductor device module configured in accordance with the present invention.
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Cronin John E.
Patel Janak G.
Schmidt Dennis A.
Datskovsky Michael
Dugan & Dugan
International Business Machines - Corporation
Peterson Peter W.
Picard Leo P.
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