Buckled beam mechanical memory using an asymmetric piezoresistor for readout

Abstract

This paper presents a non-volatile mechanical memory bit that uses a bistable beam that buckles into one of two stable positions. The beam buckles because of compressive stress that is applied by oxidizing the silicon beam. In order to process a wafer with a released, buckled beam, it was necessary to use a stencil mask for the last steps to minimize damage to the device. The stencil mask is used to the etch contact openings in the thermal oxide and to deposit metal for electrical connection. Parallel electrodes located close to the bistable beam are used to electrostatically write the bit value, and asymmetric piezoresistors located at each anchor point of the bistable beam are used to read the bit value. The design was optimized using simulations, and the relationship between the readout signal, beam length, and piezoresistor length were found. The measurements demonstrate that the memory bit is promising for non-volatile memory applications where its inherent radiation hardness is required.