Novel Mechanism of Neutron-Induced Multi-Cell Error in CMOS Devices Tracked Down from 3D Device Simulation

In recent CMOS devices, multi-cell error induced by cosmic neutron, in which memory state change extends over multiple memory cells, is becoming serious. However, its mechanism has not been clarified yet because conventional analysis by device simulation has not included multiple memory cells domain. Our novel method is to create the device model including multiple memory cells and perform 3D simulation. Analyzing current transients and current distribution, we identified multi-cell error as a chain reaction as follows: (1) parasitic bipolar in "target" CMOSFET is turned on by secondary ions produced by ion strike, (2) this parasitic bipolar action causes well voltage shift, (3) lastly parasitic bipolar in adjacent CMOSFETs are turned on and thus error propagates