Soft-error study of DRAMs using nuclear microprobe

A method for evaluation of soft errors in DRAMs using a nuclear microprobe developed in order to investigate the local sensitive structure is discussed. The susceptibility in the mapping image of a soft error caused by an ion incident onto or near a storage cell in a DRAM can be directly monitored by this method. Soft errors are induced within 4 mu m of the monitored memory cell. The retrograde well formed by MeV ion implantation has experimentally shown a reduction in soft errors. The charge collection into n/sup +/ layers with a retrograde well and a conventional well was estimated through the device simulation. These simulations agreed with the experimental results.<
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