In order to realize enhanced performance, advanced power devices such as metal-oxide-semiconductor field effect transistors and insulated gate bipolar transistors require using ultrathin wafers down to 50 mu m. Because the wafer's back side is an active part of the majority of modem power devices, innovations in the wafer back side processing technology,enable further device improvement. In this work, the author investigated how adhesion of Ag/Ni/Ti film stack deposited by S-Gun dc magnetrons depends on sputtering conditions of the Ti underlayer. The author found that high-adhesive back side metallization can be realized when Ti is deposited with relatively low rf substrate bias power without predeposition rf plasma etch of the wafer. rf induced bias voltage in the range of -50 to -250 V ensured the best adhesion property of the film stack. A high-resolution transmission electron microscopy investigation with a quantitative x-ray energy dispersive spectroscopy compositional analysis of the interface between the Ti layer and Si substrate revealed an interfacial 1.5-2 nm thick Si-Ti mixed layer having ten times higher concentration of Ti (about 50 at. %) compared to the no-bias case. Hence, Ti deposition with rf substrate bias enhances intermixing between Ti and Si atoms by low-energy ion bombardment without accumulation of Ar atoms in the interface area as is inherent to metallization with predeposition rf plasma etch. As a result, an essentially Ti-enriched crystalline Si layer is formed on the substrate, ensuring better bonding with the Ti film, thus improving the adhesion strength of the film stack. (c) 2007 American Vacuum Society.