Lianjun Liu

Piezoelectric PZT Thin Films in the 100nm Range: A Solution for Actuators Embedded in Low Voltage Devices

This paper reports the piezoelectric properties of sputtered and sol gel PZT thin films investigated in a low thickness range (100-250nm). Piezoelectric-elastic bimorphs including very thin PZT films were realized and the maximum reachable deflection at 5V was characterized. The depoling effect experienced by the PZT versus the maximum post process temperature is also discussed which leads to the motivation of developing low thickness range PZT thin films. Elastic-piezoelectric bimorphs were realized and exhibited deflection higher than 5¿m at 5V. Moreover, these bimorphs showed only a 10% decrease of the deflection after 5 billions cycles.

Dynamic analytical modelling and piezoelectric characterization of a Pb(Zr, Ti)O3/SiN cantilever with losses

In this paper a method to determine the piezoelectric constant of thin films is described. The characterization method is based on the dynamic behaviour of a heterogeneous cantilever. The electric behaviour of the bimorph is simplified in order to reach the lumped-element model which is common in the literature. Expressions of the motional elements have quite simple values. The characterization method has the advantage of being based on the resonance and anti-resonance frequencies and is therefore purely electrical. This characterization method includes the dielectric, fluidic and mechanical losses. An experimental protocol was written in order to measure each of these parameters (dielectric losses, quality factor and resonance–anti-resonance frequencies) used to evaluate the piezoelectric constant through an analytical formula which includes the losses. The dynamic characterization developed was compared to a classic static measurement of the piezoelectric constant. The two methods show similar results which validate the technique. The PZT piezoelectric constant has been evaluated on a thin film cantilever and shows a maximum absolute value of 5 C m-2 for a 120 nm thin film.

A static capacitance probe structure for resolving the sidewall skew angle of Silicon Deep Reactive-Ion Etching

This work presents a static capacitive probe structure that enables quantitative characterization of the effective sidewall skew angle of the Silicon Deep-Reactive-Ion-Etching (DRIE) using static LCR prober at ambient environment. The design is capable of resolving sidewall skew angles around both in-plane axes independently and simultaneously with the same sensitivity. The measured distributions of the sidewall skew angle across 8-inch wafers conform to empirical expectation and correlate tightly with quadrature error distributions measured gyroscopes from the same wafers. This work provides an easy, accurate and batch solution to the long existing challenge of resolving such process features in an industrial manufacturing environment.