A. Physical Properties
The poly agglomeration fuse (PAF) is made from a polysilicon line shunted on top by a layer of Ti-silicide which is used as the gate in CMOS processes. It is programmed via current stress which results in temperatures high enough to cause agglomeration of the Ti-silicide [2]. The damage due to programming of the element has been found to be very subtle and confined to the Ti-silicide and its interface with the underlying poly layer and the overlying dielectric. The integrity of the entire overlying stack from the passivation to the overlying ILD is found to be intact and no collateral damage has been observed (see Fig. 1,2). This is in contrast with traditional poly or metal fuses which require openings in the overlying layers to facilitate removal of fuse material, and therefore, a post program passivation step. Typically, a fuse link is drawn at minimum allowable width with a few microns of length (see Fig. 2). The effect of fuse doping and geometry on its performance has been investigated extensively and will follow.

B. Electrical Properties
Prior to programming, electrical properties of the fuse are determined by the salicide layer on top which has a sheet resistance of about 4 ohms per square in our study, resulting in a typical resistance of about 50-100 ohms depending on the dimensions of the fuse. Injection of current beyond a certain level results in a sudden increase in resistance indicating formation of discontinuities in the silicide layer. The value of this resistance varies greatly from device to device. In our structures, post program resistance varied from several hundred Ohms to several hundred kOhms. Post program I-V characteristics are found to be nonlinear and therefore, the value of resistance varies with applied bias.
 

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