Patent ID: 6225140
Filing Date: 2001-05-01
Classification: G01L

Abstract:
A method of forming a pressure sensor, comprising the steps of:providing a silicon substrate having a sensor region and a first surface;forming a number of piezoresistor sensors in said sensor region of said silicon substrate;forming a layer of first dielectric on said first surface of said silicon substrate;patterning said layer of first dielectric thereby forming a number of openings in said layer of first dielectric wherein said openings are over said sensor region of said silicon substrate;etching a number of trenches in said sensor region of said silicon substrate using said patterned layer of first dielectric as a mask wherein each of said trenches are over said sensor region of said silicon substrate and have sidewalls, a bottom, and a depth;forming a layer of second dielectric on said silicon substrate thereby forming a conformal coating of second dielectric on said patterned layer of first dielectric, said sidewalls of each of said trenches, and said bottom of each of said trenches;etching back said layer of second dielectric thereby forming second dielectric spacers on said sidewalls of each of said trenches and removing said second dielectric from said bottom of each of said trenches;isotropically etching said bottoms of each of said trenches using said patterned layer of first dielectric and said second dielectric spacers as a mask thereby removing that part of said silicon substrate greater than a first distance from said first surface of said silicon substrate, less than a second distance from said first surface of said silicon substrate, and within said sensor region of said silicon substrate, wherein said second distance is greater than said first distance and said first distance subtracted from said second distance is between about 2 and 20 micrometers; andfilling the spaces between said sidewalls of said trenches with a third dielectric material thereby forming a flexible membrane within said sensor region of said silicon substrate.