A silicon/solder bilayer thermal actuator for compensating thermal drift of silicon suspensions

We introduce a novel thermal compensation scheme to passively compensate the temperature coefficient of Young´s modulus with a thermal actuator using solder encapsulated by silicon cavities. Our approach produces a silicon/solder bilayer within the base of a suspension to effect an angular strain deflecting the proof mass supported by the suspension. A proof-of-principal thermal actuator has been fabricated. Temperature cycling experiments give a good agreement with both closed form and FEA models. We apply this technique to produce a thermally compensated low-frequency vertical microseismometer, without affecting the mechanical and electrical properties of the suspension. Using this approach we demonstrate the thermal coefficient of a vertical suspension is reduced from -60ppm to less than 1ppm/C.