Micromachined mass flow sensor and methods of making the same,申请号US20080985879-传众专利搜索

Micromachined mass flow sensor and methods of making the same

申请公布号：US2008271525(A1)

申请号：US20080985879

申请日期：2008.04.03

申请公布日期：2008.11.06

发明人：WANG GAOFENG;CHEN CHIH-CHANG;YAO YAHONG;HUANG LIJI

分类号：G01F1/69;G03H1/26;G02F1/00;G03H1/08

主分类号：G01F1/69

摘要：A mass flow sensor is manufactured by a process of carrying out a micro-machining process on an N or lightly doped P-type silicon substrate with orientation <100>. This mass flow sensor comprises a central thin-film heater and a pair of thin-film heat sensing elements, and a thermally isolated membrane for supporting the heater and the sensors out of contact with the substrate base. The mass flow sensor is arranged for integration on a same silicon substrate to form a one-dimensional or two-dimensional array in order to expand the dynamic measurement range. For each sensor, the thermally isolated membrane is formed by a process that includes a step of first depositing dielectric thin-film layers over the substrate and then performing a backside etching process on a bulk silicon with TMAH or KOH or carrying out a dry plasma etch until the bottom dielectric thin-film layer is exposed. Before backside etching the bulk silicon, rectangular openings are formed on the dielectric thin-film layers by applying a plasma etching to separate the area of heater and sensing elements from the rest of the membrane.