Manufacturing process of 10 nm SiNx membranes for solid-state nanopore sensing

Abstract:
This work presents a manufacturing process of 10 nm silicon nitride (SiNx) membranes for solid-state nanopore sensing. To achieve highly homogeneous and stable thin membranes, we focus on the direct deposition of near-stoichiometric SiNx using low-pressure chemical vapor deposition (LPCVD) at a lower temperature compared to our standard processes. Before the membrane SiNx deposition, a wet silicon dioxide (SiO2) is thermally grown on the silicon (Si) wafer for ca-pacitance and stress reduction. A stack of plasma-enhanced chemical vapor deposition (PECVD) SiO2 on the front side is used in combination with LPCVD SiNx as membrane protection during a wet KOH etch through the wafer. After the KOH etch, the LPCVD SiNx is etched from the front side and the wet oxide beneath and the PECVD SiO2 over the membrane are etched to gain a free-standing membrane. 10x10 µm² membrane windows of 10 nm SiNx with excellent thickness homogeneity of 1.5% and a membrane deflection of 100 nm were obtained using this process.