Patent ID: 7765679
Filing Date: 2010-08-03
Classification: G01F,Y10T

Abstract:
1. A method for manufacturing a flow rate sensor comprising: providing a silicon substrate and forming a silicon oxide layer on a bottom surface as a back surface of said silicon substrate followed by applying a low pressure chemical vapor deposition (LPCVD) process to deposit a silicon nitride layer on top of said silicon substrate as a front surface opposite the back surface; forming temperature sensing elements and a heater on top of said silicon nitride layer; covering said front surface with a passivation layer and depositing wet etch protection layers on top of said passivation layer on said front surface of said substrate and bulk-etching said silicon substrate from said back surface opposite said sensing elements with a wet anisotropic etch for exposing said silicon nitride layer as a thermally isolated membrane supporting said temperature sensing elements and said heater on top of said silicon nitride layer; and removing said wet etch protection layers from said front surface and said silicon oxide layer from said back surface whereby said flow rate sensor is supported on a bare silicon substrate.