A Non-Aging Screen to Prevent Wearout of Ultra-Thin Dielectrics

As MOS gate dielectrics are scaled to thinner dimensions, lognormal statistics determine the limit at which aging screens are no longer effective in reducing the time-dependent failure rate of dielectric breakdown. This paper presents an alternative non-aging reliability screen as applied to ultra-thin DRAM storage gate dielectrics. Early breakdown is correlated with increased dielectric leakage current, which can be detected using the DRAM charge retention characteristics at elevated voltage across the storage dielectric. Accelerated lifetest of screened production 64K DRAMs has confirmed the effectiveness of using non-aging screens to enhance product reliability.