Strong Read and Write Interference Induced by Breakdown Failure in Crossbar Arrays

Cell-to-cell interference due to the sneak current is a known and important issue in high-density 4F2 crossbar arrays. However, the interference between normal cells and high-leakage breakdown (BD) cells is rarely discussed. We show that such interference degrades the array read and write yields dramatically based on experiments and simulation. A rule-based analytical model for BD interference is developed by leveraging the quantitative understanding of the different interference modes and their equivalent circuits. This model achieves equivalent accuracy but is at least 100 times faster than the SPICE circuit simulator. It is used in the Monte Carlo simulation for providing sensible statistics on the spatial dependence of interference. The results show that merely 3% of BD cells result in zero array yield for a crossbar array size larger than $128\times128$. The minimal requirement of device yield (non-BD percentage) increases with the array size in order to maintain a reasonable array yield. Thus, BD interference should be recognized as one of the most critical concerns for developing future crossbar arrays.