Investigation of fabricating ultra deep and high aspect ratio electrical isolation trench without void

This paper reports an improved method of fabricating ultra deep (40-120 mu m) and high aspect ratio (more than 25: 1) electrical isolation trench without void to increase the mechanical strength and reliability of the isolation trench in monolithic integration of bulk micromachining MEMS sensors. Before etching and refilling the trench, 0.1 mu m oxide and 3-4 mu m poly-silicon are LPCVD deposited on the wafer surface as sacrificial films. After etching trench by DRIE, such sacrificial films are removed to enlarge the trench opening. Then this trench is refilled well without voids using, LPCVD oxide and poly-silicon. Such electrical isolation trench has been used in the monolithic Integration of bulk micromachining WEMS gyroscope, which has shown high performance. Such isolation trench has sufficient mechanical strength to sustain the bulk MEMS structure. Electrical test shows that such isolation trench can electrically isolate the MEMS structure effectively from one another and from the on-chip detection electronics. The average resistance in the range of 0-100V is more than 10(11) Omega and no breakdown under 100V.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000227342202073&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, Electrical & ElectronicMaterials Science, MultidisciplinaryPhysics, Condensed MatterCPCI-S(ISTP)