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 VBR. Simulations show that, as compared to a SJ, the CSSJ has ~30% lower RONSP for VBR = 300 V, and ~20 % lower VBR sensitivity to 20% charge imbalance for VBR = 500 V and RONSP ~5 mOmega- cm2. One way a negative charge sheet could be realized is by the replacement of the p-pillar of the SJ with a thin Al₂O₃ layer; the interface between Al₂O₃ 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.