METALLIZATION SCHEMES FOR DIELECTRIC THIN-FILM CAPACITORS

A detailed analysis of Pt/Ti, Pt/TiO2, and Pt/ZrO2 electrodes was carr ied out to develop a bottom electrode stack for sol-gel derived thin h im capacitors. For the Pt/Ti stack, the choice of layer thickness and deposition temperature is found to affect adhesion to the SiO2/Si subs trate as well as the extent of hillock formation and Pt-Ti interaction . By using elevated temperature deposition, Pt films close to 1 mu m i n thickness can be produced with relatively good adhesion and morpholo gical stability using Ti adhesion layers. In addition, Pt films grown on ZrO2 and TiO2 adhesion layers exhibit little morphological change a nd no degradation in sheet resistance after annealing at 650 degrees C . However, neither ZrO2 nor TiO2 are as effective as Ti metal in promo ting Pt adhesion. Experiments aimed at establishing a correlation betw een hillock formation and capacitor yield revealed two important resul ts. First, the behavior of Pt/Ti stacks during annealing in air is mar kedly different from their behavior during PZT him crystallization. Se cond, preannealing of the Pt/Ti in air prior to PZT film growth actual ly improves capacitor yield, even though hillock formation occurs duri ng the preannealing treatment. Implications of these results regarding the role of hillocks in controlling capacitor yield are discussed.