Process for manufacturing micro-mechanical sensors

Claim 1

A method of making an air mass sensor, comprising the steps of: forming a first (25) and a second (20) monocrystalline silicon wafer, each having an upper and a lower major surface, parallel to each other; doping a plurality of regions (7) of said first wafer (25), adjacent its upper major surface (6), to define etch stops; anisotropically etching the lower major surface of said first wafer (25) to thereby form an almost continous trough (26) surrounding each doped region (7) and to define respective individual sensor elements (10) interconnected by bridges (27), and further etching a central cavity (11) under each doped region (7) to define a relatively thin, thermally responsive portion; forming a plurality of resistor elements (14, 15, 16) on said thermally responsive portion of each individual sensor element (10); anisotropically etching the upper major surface of said second wafer (20) to define a plurality of recesses (21), each having lateral dimensions matching dimensions of each sensor element (10), and sidewalls (12) whose inclination matches an inclination of sidewalls (13) of each sensor element (10); mounting said second wafer (20) on a substrate (8); and inserting each sensor element (10) into one of said recesses (21) until said upper major surface (6) of said sensor element is co-planar with the upper major surface of said second wafer.

Claim 2

A method of making an air mass sensor, comprising the steps of: forming a first (25) and a second (20) monocrystalline silicon wafer, each having an upper and a lower major surface, parallel to each other; doping a plurality of regions (7) of said first wafer (25), adjacent its upper major surface (6), to define etch stops; anisotropically etching the lower major surface of said first wafer (25) to thereby form an almost continous trough (26) surrounding each doped region (7) and to define respective individual sensor elements (10) interconnected by bridges (27), and further etching a central cavity (11) under each doped region (7) to define a relatively thin, thermally responsive portion; forming a plurality of resistor elements (14, 15, 16) on said thermally responsive portion of each individual sensor element (10); anisotropically etching the upper major surface of said second wafer (20) to define a plurality of recesses (21), each having lateral dimensions matching dimensions of each sensor element (10), and sidewalls (12) whose inclination matches an inclination of sidewalls (13) of each sensor element (10); mounting said second wafer (20) on a substrate (8); and inserting each sensor element (10) into one of said recesses (21) until said upper major surface (6) of said sensor element is co-planar with the upper major surface of said second wafer.