Kazumichi Mitsusada

Design for alpha immunity of MOS dynamic RAM's

Soft error rate(SER) analysis model named HSERAM has been developed to provide a design tool for alpha immunity of MOS dynamic RAMs. The model is verified through the good agreement between the simulated and the measured SER of 64K bit dynamic RAMs. The SER of the metal folded-bit-line structure is compared around 10 times favorably with that of the diffused open-bit-line one in case of the same signal charge. Accelerated testing with increased alpha flux is risky for bit line mode soft error with large signal charge because of few alpha particles of low angle incidence which are most harmful in package mounted devices. Also shown briefly are the effectiveness of a protective coating to reduce SER and the measurement techniques easily equipped to detect 10-5ppm level of U and Th in semiconductor component materials.