Lifetime Study For A Poly Fuse In A 0.35µm Polycide CMOS Process

Poly Fuses are used as the base element for One Time Programmable Cells in a standard CMOS process. The element is built in principle by a small Poly Silicon line, which is optimized by layout for the usage within a standard CMOS process specification. No special process modules like high voltage devices are needed to implement such an element. Using a defined programming current, the resistor of the Poly Fuse will increase irreversibly over several orders of magnitude. By building an adequate electronic circuit the different level of resistances are detected. The digital information can be stored into a digital cell. Since the resistance of the programmed Poly Fuse is not stable over lifetime, the drift of the resistance is subject to investigation in this paper. An electronic circuit, detecting resistance levels of a Poly Fuse, has to handle this resistance drift.

The goal of this study is to show that a Poly Fuse has a sufficient life time stability to be used as a storage element even in high reliability circuits. This paper will show the drift of the resistance of a Poly Fuse over the whole range of programming currents for a standard polycide 0.35µm CMOS process. The Poly Fuse for the selected process is build by two different layers, which gives some special performance in terms of programming current.