A PROM Element Based on Salicide Agglomeration of Poly Fuses in a CMOS Logic Process (Continued)

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Modeling and Simulation

In order to look for an optimum fuse design, numerical simulation of temperature in the element under current stress has been performed. The simulation is based on a two dimensional model with an added loss term to the overlying and underlying layers. Thermal conductivity of the silicide layer and the heat loss coefficient were fitting parameters. Assuming that fusing occurs when the temperature of the fuse reaches 800C (silicide agglomeration temperature [2]), the simulation is able to predict fusing current using a single set of fitting parameters for various fuse geometry with good accuracy (see Fig. 5,9) and provides insight into the distribution of temperature and its gradient in the element.
Figure 6: various fuse shapes. All elements are p-type, about 2um long. (a) width=0.22um, (b) width=0.27um, (c,d) width=0.22um/0.27um.
Figure 7: Pre-programmed fuse resistance of structures in figure 6.
Figure 8: Post program resistance of fuses in Figure 6.
 

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