Temperature modeling and reliability of metal-to-metal amorphous-silicon antifuses in the on-state.

摘要

Antifuses are used as interconnects in field-programmable gate arrays (FPGA) for high-speed applications because of their low interconnect delays. An antifuse is a thin layer of material between two electrodes. In this project, we are concerned with the Al/{dollar}alpha{dollar}-Si/Al system. An antifuse is initially in its OFF state having a resistance on the order of a few G{dollar}Omega .{dollar} It is programmed by applying a voltage pulse across its electrodes. This programming pulse forms a permanent low-resistance conducting link. The resistance is now on the order 20 to 200 {dollar}Omega .{dollar} Metal-to-metal amorphous-silicon antifuses are an ideal candidate for high-density, high-speed applications because of their low capacitance and low ON-resistance.; In this project, we investigate the reliability of the ON-state and determine the operating conditions for 10-year lifetime. The ON-state properties are strongly dependent on the programming conditions. A new model for the growth of the conducting filament is presented, that explains the observed experimental results. This model is a thermal model, based on melting of the amorphous-silicon layer. Numerical methods investigating the above model are also presented. The antifuse in its ON-state suffers from two reliability considerations which can seriously affect device performance. If a high current or voltage pulse is applied across the antifuse, it reverts to a high-resistance state. This phenomenon is called "switch-off". Switch-off is believed to be due to the melting of the conductive link. Stressing the antifuse for a period of time leads to a high-resistance state, thus resulting in a second mode of failure associated with an electromigration-like phenomenon, depending strongly on the stress current or voltage. Both these failure modes depend on the programming conditions. Models and experimental results for the above two modes of failure are presented and discussed. From experimental results of ON-state antifuse lifetimes, programming and operating conditions for the antifuse are presented.; A reliable estimate of the temperature of the conductive link is an important tool in understanding failure processes because the failure modes are strongly dependent on the temperature of the antifuse. Experimental and numerical methods that will determine the temperature of the conducting link are proposed and will be used to verify the failure models.