Patent ID: 6139758
Filing Date: 2000-10-31
Classification: G01F

Abstract:
A method of manufacturing a micromachined thermal flowmeter comprising the steps of:providing a lightly doped p-type silicon water;forming a lightly doped n-type region in said p-type silicon wafer;forming a heating resistor in a central region of said n-type region;forming two thermopiles in said n-type region which respectively consist of at least 10 aluminum/p-type silicon thermocouples asymmetrically located around said heating resistor;forming a metallization pattern on a surface of said p-type silicon wafer for electrically connecting said heating resistor and said thermopiles to an external circuit;forming an anodization mask on the surface of said p-type silicon wafer for preventing said n-type region and said metallization pattern from etching during an anodization process;performing said anodization process in a concentrated HF solution selectively to form a porous silicon layer in a p-type region of said p-type silicon wafer;forming a polyimide layer on the surface of said p-type silicon wafer;mounting a glass plate on a surface of said polyimide layer;thinning said p-type silicon wafer from a back side thereof to expose said porous silicon layer;removing said porous silicon layer by selective etching in a diluted base solution to form said n-type region as a thin single crystal island;coating an exposed surface of said thin single crystal silicon island with a corrosion-resistant and abrasion-resistant material; andstripping all insulating layers from metal pad surfaces of said metallization pattern.