A new failure mechanism related to grain growth in DRAMs

A cell plate leakage phenomenon which degrades retention time was investigated in a dynamic RAM (DRAM) with planar cells. The authors describe a failure mechanism of the leakage. They have derived such a mechanism through analytical techniques such as photo-emission microscopy, high-resolution scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM), and high-resolution Auger electron microscopy. It was found that the leakage phenomenon is a new failure mode related to grain growth of polycrystalline silicon under oxidation-induced compressive stress. Localized stress causes irregular grain growth and the development of protuberances of silicon. The protuberance causes build-up of the phosphorus-rich SiO/sub 2/ at the open grain boundary and phosphorus diffuses into the capacitor gate SiO/sub 2/, resulting in the capacitor gate SiO/sub 2/ leakage through the trapping centers of phosphorus.<>