Microbeams with electronically controlled high thermal impedance
In some MEMS (Micro-Electro-Mechanical Systems) applications, a tradeoff much be reached between the mechanical strength of a suspended microstructure and the thermal losses through the support beams. This is typically the case of suspended thermal MEMS, a major domain of application of CMOS-compatible bulk-micromachining technologies. This paper illustrates how suspended MEMS can be strengthened by means of additional support beams which can have a very high thermal impedance, thus having a very small impact in the thermal behavior of the microstructure. The high thermal impedance of a support beam is achieved through self-heating: an electronic control monitors the temperature drop and heats up the beam to reduce the heat flow. The control electronics of a beam is implemented using a single high-gain stage with auto-zeroing. A High Thermal Impedance Beam (HTIB) can be considered as a new MEMS design cell. We illustrate the use of this cell in the design of an Electro-Thermal Converter with long time constant, requiring several HTIB cells which can share the same control electronics. A single low-frequency high-gain stage is used, achieving 60 dB DC gain and DC offset and broadband noise below 100 muV, which is suitable for the ETC application.
thermal mems anisotropic etching cmos switched-capacitor circuits