Robust silicon deep etching without thermal isolation in large mass and long spring structures

This paper suggests a complete solution for thermal isolation which hinders a stable fabrication of silicon micro-structures with a large proof mass and long springs when the device is released using silicon deep etching process. Comprehensive analysis on a thermal equivalent circuit and the implementation of thin metal layers have successfully reduced a temperature rise down to 6.16 °C whereas conventional fabrication method shows 217 °C temperature rise in simulation. The reduction of the temperature rise leads to an improved spring width of 34.2 μm (20 μm without the metal layer) in case of the designed width of 40 μm. As a result, the resonant frequency of a proposed model is improved to 678 Hz while a reference model shows 439 Hz, where the simulated frequency of design is 754 Hz.