A wet‐etch method with improved yield for realizing polysilicon resistors in batch fabrication of MEMS pressure sensor

Abstract

PurposeThe purpose of this paper is to present a selective wet‐etching method of boron doped low‐pressure chemical vapour deposition (LPCVD) polysilicon film for the realization of piezoresistors over the bulk micromachined diaphragm of (100) silicon with improved yield and uniformity.Design/methodology/approachThe method introduces discretization of the LPCVD polysilicon film using prior etching for the grid thus dividing each chip on the entire wafer. The selective etching of polysilicon for realizing of piezoresistors is limited to each chip area with individual boundaries.FindingsThe method provides a uniform etching on the entire silicon wafer irrespective of its size and leads to economize the fabrication process in a batch production environment with improved yield.Research limitations/implicationsThe method introduces one extra process step of photolithography and subsequent etching for discretizing the polysilicon film.Practical implicationsThe method is useful to enhance yield while defining metal lines for contact purposes on fabricated electronic structures using microelectronics. Stress developed in LPCVD polysilicon can be removed using proposed approach of discretization of polysilicon film.Originality/valueThe work is an outcome of regular fabrication work using conventional approaches in an R&D environment. The proposed method replaces the costly reactive ion etching techniques with stable reproducibility and ease in its implementation.