Embodiments of the invention use silicon on porous silicon wafers to produce a reduced-thickness IC device wafers. After device manufacturing, a temporary support is bonded to the device layer. The uppermost silicon layer is then separated from the silicon substrate by splitting the porous silicon layer. The porous silicon layer and temporary support are then removed and packaging is completed. Embodiments of the invention provide reliable, low cost methods and apparatuses for producing reduced-thickness IC device wafers to substantially increase thermal conductivity between the device layer of an IC device and a heat sink. In alternative embodiments, the layered silicon substrate includes an insulator layer on a layer of porous silicon and a silicon layer on the insulator layer.
A method and article to provide a three-dimensional (3-D) IC wafer process flow. In some embodiments, the method and article include bonding a device layer of a multilayer wafer to a device layer of another multilayer wafer to form a bonded pair of device layers, each of the multilayer wafers including a layer of silicon on a layer of porous silicon (SiOPSi) on a silicon substrate where the device layer is formed in the silicon layer, separating the bonded pair of device layers from one of the silicon substrates by splitting one of the porous silicon layers, and separating the bonded pair of device layers from the remaining silicon substrate by splitting the other one of the porous silicon layers to provide a vertically stacked wafer.
A pumping medium for an electro-osmotic pump made of porous silicon. The porous silicon may result in a lower required pumping voltage and a smaller form factor for an equivalent flow rate and pressure generation as compared to conventional glass frits. The porous silicon may also provide a better thermodynamic efficiency over conventional glass frits for use in electro-osmotic pumps. The increased efficiency of the porous silicon may provide an low-power, high flow rate, high pressure, small form factor, vibration-free pump for cooling microelectronic devices, such as integrated circuit chips.
A method for preparing porous silicon in which an oxidized single crystal silicon wafer is first bonded to a polycrystalline wafer. The oxidized high quality wafer is then thinned to the desired thickness by grinding and polishing. An oxide may then be deposited on the wafer and patterned to expose regions were the porous silicon will be formed. The single crystal silicon wafer may then etched in the unmasked areas of the pattern to thin the single crystal silicon wafer to the desired thickness in the range of 0.1 microns to 1.0 microns. Next, the porous silicon may be formed using standard techniques. Once the porous silicon is formed the polycrystalline silicon wafer may be ground away and the oxide layer may be undercut to expose the porous silicon. Finally, an appropriate liner material may be applied to the porous silicon.
