EXCIMER-LASER ABLATION OF PZT THIN-FILMS ON SILICON CANTILEVER BEAMS

Laser ablation was used to realise piezoelectric films for use in a low-voltage cantilever bimorph actuator structure. Neodymium-doped lead zirconium titanate (PZT) targets were ablated by a pulsed XeCl excimer laser (wavelength 308 nm). The deposited films showed a better morphology than those ablated using a Nd:YAG laser. Since the deposited films had high density and small particulate size it was possible to produce a capacitor structure without causing short circuits during the second electrode deposition. The depositions were made onto the inner electrode layer on the silicon substrates (thickness 50 mu m) at a distance of 20 mm between substrate and target using a laser beam fluence of 1 J/cm(2). Growth rates were typically 3 Angstrom/s. Films were analysed by EDS, XRD and Raman measurements. Both the target density and the beam intensity were important in determining the film composition. The as-deposited PZT films were amorphous. Optimising the annealing conditions resulted in trigonal perovskite being achieved as the main phase. Direct current bending characteristics of the low-voltage bimorph cantilever element structure were measured as a function of voltage using a Michelson interferometer.