Nano-mechanical cantilever arrays for low-power and low-voltage embedded nonvolatile memory applications

摘要

A new non-volatile memory technology for embedded memory applications is described. The technology uses one cantilever per cell with two stable states to store information. The two stable states are either stuck down to a landing electrode or not. Because the cantilever and landing electrodes are conducting, each cantilever can be read easily by measuring the contact resistance between the two. The cantilever stays in the 'on' state due to short range attractive forces at the contact including metal-to-metal bonding and Van der Waals forces. Using standard CMOS processing equipment and materials the cantilevers are designed to switch at the native voltages found in micro-controllers, making this technology an attractive alternative to other forms of embedded non-volatile memory as it reduces the memory block area by eliminating the requirement for charge pumps. With scaling of the cantilever geometries, the switching speed drops to below 100ns making it much faster to program and erase than FLASH and SONOS devices. The high activation energies associated with adhesion ensure that the technology is reliable over a wide temperature range. In this paper we discuss how the cantilevers are encapsulated in a wafer scale CMOS process and how the resulting micro-cavities are qualified. We will discuss how the contact adhesion forces are modeled to give controllable erasure of the cantilever into the 'off state.