Thermally Conductive Bonding of Silicon Chip Employing Metal Multilayer
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
A metal multilayer from a silicon chip to a cooling device achieves a mechanically strong, chemically stable bond with excellent thermal resistivity. The metal multilayer consists of three components. A silicon-adhesion layer (e.g., Al), a remelt layer (e.g., Sn or SnAu), and a protective layer (e.g., Au) are deposited on silicon. Typical layer thicknesses are 100 nm, 5000 nm, and 50 nm, respectively. Bonding occurs when two similarly metallized silicon surfaces are contacted and heated to approximately 240ŒC. An important aspect of this metallurgy is the reaction of the thin Al film with the native silicon oxide. The aluminum bonds strongly by reducing the SiO2 to form a thin Al/Al2O3/Si/SiO2 interface  The remelt layer provides adhesion between silicon wafers and compensates for slightly non-planar surfaces.