An on-chip ECC circuit for correcting soft errors in DRAMs with trench capacitors

摘要

A modified error-correcting code that can correct up to two soft errors on each row (word line) in a dynamic random-access memory (DRAM) chip is proposed. Double-bit soft errors frequently occur in DRAM cells with trench capacitors, when charged alpha particles impinge on the intervening space between two vertical capacitors causing plasma shorts between them. The conventional on-chip error-correcting codes (ECCs) cannot correct such double-bit word-line soft errors, which significantly increase the uncorrectable error rate (UER). An ECC circuit that uses an augmented rectangular product code to detect and correct double-bit soft errors is presented. The proposed circuit automatically corrects the addressed bit if it is faulty, and then quickly locates the other faulty bit. A comprehensive study is made to estimate improvements in soft error rate (SER) and mean time to failure (MTTF). The ability of the circuit to correct soft errors in the presence of multiple-bit errors has also been analyzed by combinatorial enumeration.