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

Abstract

Purpose-The 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/approach-The 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. Findings-The 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/implications-The method introduces one extra process step of photolithography and subsequent etching for discretizing the polysilicon film. Practical implications-The 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/value-The 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.

A High Pressure Sensor with Circular Diaphragm Based on MEMS Technology

“…The four piezoresistors are connected in the form of Wheatstone bridge to output electric signal caused by pressure in Fig. 4 [7]. The power supply is constant current.…”

Fabrication of a membrane type double cavity vacuum‐sealed micro sensor for absolute pressure based on front‐side lateral etching technology

“…This technique utilizes advantages of surface as well as bulk micromachining in order to form a cavity under the defined membrane type diaphragm. The present work also utilizes the wet etching of polysilicon layer (Singh et al , 2009) for the realization of resistors. The double cavity vacuum‐sealed sensor having two diaphragms has an advantage of being used as a pressure sensor as well as a flow sensor.…”