Si nanopatterning by reactive ion etching through an on-chip self-assembled porous anodic alumina mask

ABSTRACT: We report on Si nanopatterning through an on-chip self-assembled porous anodic alumina (PAA) masking layer using reactive ion etching based on fluorine chemistry. Three different gases/gas mixtures were investigated: pure SF(6), SF(6)/O(2), and SF(6)/CHF(3). For the first time, a systematic investigation of the etch rate and process anisotropy was performed. It was found that in all cases, the etch rate through the PAA mask was 2 to 3 times lower than that on non-masked areas. With SF(6), the etching process is, as expected, isotropic. By the addition of O(2), the etch rate does not significantly change, while anisotropy is slightly improved. The lowest etch rate and the best anisotropy were obtained with the SF(6)/CHF(3) gas mixture. The pattern of the hexagonally arranged pores of the alumina film is, in this case, perfectly transferred to the Si surface. This is possible both on large areas and on restricted pre-defined areas on the Si wafer. PACS: 78.67.Rb, 81.07.-b, 61.46.-w