Piezoelectric bimorph cantilever for actuating and sensing applications

Back side bulk micromachining has been combined with front side ferroelectric technology for making a piezo-active microsystem including a sensor and an actuator on a silicon cantilever. Stress and thickness control of the thin (10 mu) silicon beam are obtained by an original technology. The PZT piezoelectric material is deposited by the sol-gel spin coating technique. Due to the partial incompatibility of piezoelectric PZT capacitor with the methods of IC processing, a new processing route had to be found that is able to protect the sensitive area on the front side during back side micromachining. Additionally, a new method to pattern aluminum metallization in contact with platinum had to be developed to avoid electrochemical reactions in etching solutions. The beam can be sensed and actuated by the piezoelectric direct and (resp) converse effects. Sensor voltage response and actuator displacement are given up to the resonance frequency of 2.6 kHz. The device is planned to be used in a self regulated closed loop where the feedback electronics will be integrated on the chip.