Ferroelectric thin and thick films for sensing and decoupling functions

This study investigates two distinct and promising applications of ferroelectric films: thin films as integral decoupling capacitors in high-speed multichip modules (MCMs), and integral bypass capacitors in GaAs monolithic microwave integrated circuits (MMICs); and thick films as the active layer in micromachined monomorph sonar transducers for underwater acoustic imaging.; The demands of integral decoupling/bypass capacitors require high dielectric permittivity, low losses, and, most importantly, limited relaxation of dielectric dispersion at frequencies above 1 GHz. A method utilizing a vector network analyzer, a coplanar waveguide (CPW) test fixture, and the LRM (Line-Reflect-Match) calibration technique was used to characterize sol-gel-derived ferroelectric thin films. Results show no significant dielectric dispersion of ferroelectric PLZT films up to at least 20 GHz. Activity of domain wall motion, which causes dielectric relaxation at GHz frequencies, appears very limited on thin-film ferroelectrics due to finer grain sizes and fewer domains. These findings suggest promise in the use of ferroelectric thin films as integral capacitors for switching-noise decoupling and bias bypass at microwave frequencies.; The achievement of ferroelectric thick film fabrication through the sol-gel route described in this work provides a significant breakthrough in the development of high-resolution acoustic imaging sensor arrays. One-{dollar}murm m{dollar}-thick PZT films of MPB composition, {dollar}rm Pb(Zrsb{lcub}0.52{rcub}Tisb{lcub}0.48{rcub})Osb3,{dollar} show a maximum {dollar}dsb{lcub}33{rcub}=194rm pC/N,{dollar} and {dollar}varepsilonsb{lcub}r{rcub}=1310,{dollar} which compare favorably with values reported for PZT bulk ceramics. Thicker films up to 12 {dollar}murm m{dollar} thickness show highly textured (100) orientation. The films were marked by saturation values of {dollar}dsb{lcub}33{rcub}=340{lcub}rm pC/N{rcub}; gsb{lcub}33{rcub}=27times 10sp{lcub}-3{rcub}rm V{dollar}-m/N; {dollar}varepsilonsb{lcub}r{rcub}=1450;{dollar} and {dollar}Psb{lcub}R{rcub}=27murm C/cmsp2{dollar} as film thicknesses increase above a certain value. Dielectric breakdown strengths of PZT(52/48) thick films are superior to the predicted values derived from the bulk ceramic model; e.g., 2.7 MV/cm for 1 {dollar}murm m{dollar} films (1 MV/cm in bulk), and 1 MV/cm for 4 {dollar}murm m{dollar} films (0.6 MV/cm in bulk). Results obtained by applying the lanthanum-doping concept, used in PZT bulk ceramics, to thin/thick films disagree with expectations.; Micromachined monomorph sonar transducers using PZT(52/48) thick films (5 {dollar}murm m){dollar} as an active layer provide a favorable acoustic sensitivity of {dollar}-{dollar}225 dB // {dollar}rm 1V/mu Pa{dollar} at 1 MHz, which is within a few dB of FEA calculations.