The application provides a monolithic integrated multifunctional composite sensor and a preparation method thereof, and adopts single-
silicon single-surface
silicon microfabrication technology to predefine and cover a first micro groove of a gas flow sensing unit, to form a pressure
reference cavity and a
pressure sensitive diaphragm first, to predefine a single-
crystal silicon thermocouple arm and a heating
resistor pattern through the first micro groove and a side wall protection, to protect the
pressure sensing unit through a heat insulation medium layer, to form a heat insulation cavity and a
temperature sensing unit, to finally realize integration of the gas flow sensing unit, the
pressure sensing unit and the
temperature sensing unit on the same monolithic
wafer, and to realize the structure of the heat insulation cavity and the pressure
reference cavity in the same single-
crystal silicon substrate. The method replaces traditional double-sided
processing technology, solves the problem that a traditional composite
chip is difficult to realize small size, avoids a complex process caused by a traditional silicon-silicon or silicon-glass bonding structure, greatly reduces process difficulty and cost, improves the yield of the composite
chip, and improves the reliability of the sensor.