Novel process for high-density buried nanopyramid array fabrication by means of dopant ion implantation and wet etching

A simple and high-throughput process to fabricate a high-density buried nanopyramid array (BNPA) on a Si surface has been developed by means of dopant ion implantation and wet etching. In this process, the combination of two interesting etching phenomena was utilized to form the BNPA. One is the enhanced etching of ion-exposed SiO₂ in HF. The other is the newly found retarded etching of ion-exposed Si in hydrazine (N₂H₄). A p-type Si(100) substrate with 27-nm-thick SiO₂ was exposed to 50-keV phosphorus ions with a dotted pattern. Then, the ion-exposed SiO₂ was selectively etched away by dipping in HF. Finally, the BNPA was formed under the patterned SiO₂ layer by dipping in hydrazine. By using this simple process, the BNPA with 250 nm pitch was successfully fabricated. The electrical property of the fabricated nanopyramid was also investigated using scanning Maxwell-stress microscopy (SMM).