A Comparison of Retrograde and Conventional N-Wells for Sub-Micron CMOS Circuits

A general and direct comparison of retrograde and conventional n-well CMOS technologies is reported. The advantages of the retrograde structures in terms of packing density, isolation and short channel PMOS characteristics are demonstrated. The conventional wells offer slightly better circuit performance due to lower p + to n-well junction capacitance. However, the major difference between the well types lies in their latchup susceptibility: here the retrograde wells have a significant advantage due to their lower sheet resistance and greater tolerance to very thin p-on-p + epitaxial layers.