Design of Thermal Conductivity Gas Sensor with Silicon Cap

This paper presents the design of a suspended micro hotplate-based thermal conductivity gas sensor. A rectangular silicon cap is packaged above the micro hotplate, creating a 20μm air gap. This design increases the proportion of heat dissipation through gaseous thermal conduction in the total heat dissipation of the chip, significantly improving the sensitivity of gas detection. By comparing the differences in total thermal conductivity between the chip with the cap and without it, it can be observed that gas conduction, directly related to gas concentration, constitutes more than 91% of the total thermal conductivity. Through evaluations conducted on a mixture of nitrogen gas with
$\text{SF}_6$
and H2, the chip with the silicon cap demonstrated effective detection of changes in
$\text{SF}_{6}$
at 200ppm and H2 at 50ppm.