The effect of substrate materials on holding time degradation in MOS dynamic RAM

The effect of substrate materials (bulk silicon, p/p
⁺
epitaxial silicon, and intrinsic gettering silicon) on the holding time degradation of MOS dynamic RAM cells by excess minority carriers emitted from adjacent MOS devices was studied. It is shown that intrinsic gettering silicon has less susceptibility to holding time degradation than p/p
⁺
epitaxial silicon, and much less than bulk silicon. The degradation mechanism is discussed in connection with the substrate materials.