MEMS micro-flow sensor chips are widely used in the following fields. MEMS gas micro-flow sensor chips are widely used in the following medical, industrial, communications, automotive and smart home fields. 

  ·Sleep dyspnea

  ·Treatment machine 

  ·Ventilator/respirator 

  ·Anesthesia machine·Oxygen generator 

  ·Oxygen concentrator 

  ·Hydrometer 

  ·Gas stratification separation instrument

  ·Variable air volume controller (HVAC)

The basic principle of the MEMS-based hot film gas flow sensor is shown in the figure below. It is a micro-bridge structure using MEMS technology, and its base is basic silicon material. The microstructured chip consists of a thin-film thermally isolated bridge containing a heater and temperature sensor device, all suspended above an etched microcavity. The heating temperature is more than 100 degrees above the ambient temperature. The operation of the MEMS microflow sensor is based on the principle of heat transfer where the measured gas flow flows through the MEMS sensor chip to generate heat exchange. The air flows through the bridge and transfers heat to the sensing element, causing a change in resistance. The output voltage changes proportionally with the flow of media through the package. The specially designed housing guides airflow precisely, helping to detect flow speed and direction.

 The research content of this project is 

  A. Based on the relationship between gas flow, the temperature compensation principle of the sensor, and the characteristics of the two working modes of the sensor, a design plan for the sensor chip is proposed. 

  B. Use heat transfer knowledge and computer simulation software to design a hot film gas flow sensor, and use the simulation results to determine the heating resistance, ambient temperature resistance and temperature measuring resistance of the hot film gas mass sensor and their resistance on the sensor chip surface. The position distribution of the sensor was analyzed, and the influence of the thickness of the silicon nitride film masking layer on the sensor's platinum resistor surface on the sensor was analyzed to provide a basis for the sensor design. A thermally distributed MEMS hot film gas flow sensor was designed.

  C. Analyze the processing technology of the hot film gas flow sensor, determine the processing technology plan according to the designed structure of the hot film gas flow sensor, and select the appropriate MEMS processing technology according to the technology plan to complete the production of the flow sensor chip.