Charge Sheet Superjunction (CSSJ) - A new superjunction concept

A new superjunction concept called Charge Sheet Superjunction (CSSJ) is proposed based on simulation studies; a fabrication procedure for practical realization of this concept is also suggested. The CSSJ structure is obtained by replacing the p-pillar of a conventional Superjunction (SJ) by a negative charge sheet. This structural modification minimizes the loss of conduction area to yield a lower specific on-resistance RONSP, and tailors the 2-D field distribution so as to provide a slightly higher breakdown voltage, V BR. Simulations show that, as compared to a SJ, the CSSJ has - 30 % lower RONSP for VBR = 300 V, and - 20 % lower V BR sensitivity to 20 % charge imbalance for VBR = 500 V and AONSP ∼5 mΩ-cm2. One way a negative charge sheet could be realized is by the replacement of the p-pillar of the SJ with a thin Al 2O3 layer; the interface between Al2O 3 and silicon has a negative fixed charge. Thus, fabrication of a CSSJ avoids the complex process involved in the realization of alternate n- and p-pillars. © 2007 IEEE.