Effect of substrate composition on the piezoelectric response of reactively sputtered AlN thin films

Deposition parameters were found to have a marked effect on piezoelectric r esponse of reactive radio frequency (RF) sputtered AlN thin films. We obser ved piezoelectric response values ranging from -3.5 to +4.2 pm/V for 1 mu m thick AlN films deposited onto Ti//Ru electrode stacks. This substantial v ariation in piezoelectric response occurred despite the fact that all of th e AIN thin films exhibited the correct crystallographic orientation for pie zoelectric activity ((0002) crystallographic planes parallel to the substra te). An investigation of the effects of deposition parameters, in particula r the nature of the Ru//AlN interface, was conducted. The lag time between deposition of adjacent thin film layers appeared to have the greatest affec t on the value of the piezoelectric response. This result suggests that a c hemical reaction occurring on the Ru thin film surface is responsible for c hanging an important thin film property such as dipole orientation within t he overlying AlN thin film. (C) 1999 Elsevier Science S.A. All rights reser ved.