Miniature MEMS Switches for RF Applications

This paper presents a new way to design MEMS (microelectromechanical system) metal contact switches for RF applications using miniature MEMS cantilevers. A single 25 × 25 μm switch is first demonstrated with a Au-to-Ru contact, C
_u
= 5 fF and R
_on
= 7 Ω at an actuation voltage of 55 V. The measured switching time is 2.2 μs and the release time is <;1 μs. The switch is robust to stress effects (residual and stress gradients) which increases its yield on large wafers. To reduce the effective switch resistance, 10-20 miniature RF MEMS switches have been placed in parallel and result in equal current division between the switches, an up-state capacitance of 30-65 fF and a down-state resistance of 1.4-1.5 Ω. Furthermore, 10-20 element back-to-back switch arrays are developed and result in a marked improvement in the reliability of the overall switching device. A series-shunt design is also demonstrated with greatly improved isolation. The device has a figure-of-merit of f
_c
= 1/(2πR
_on
C
_u
) = 3.8 THz (R
_on
C
_u
= 42 fs).