Implications of Rarefied Gas Damping for RF MEMS Reliability

Abstract

Abstract.Capacitive and ohmic RF MEMS switches are based on micron-sized structures moving under electrostatic force in a gaseous environment. Recent experimental measurements [4,5] point to a critical role of gas-phase effects on the lifetime of RF MEMS switches. In this paper, we analyze rarefied flow effects on the gas-damping behavior of typical capacitive switches. Several damping models based on Reynolds equation [7,8] and on Boltzmann kinetic equation [9,6] are applied to quantify the effects of uncertainties in fabrication and operating conditions on the impact velocity of switch contact surfaces for various switch configurations. Implications of rarefied flow effects in the gas damping for design and analysis of RF MEMS devices are discussed. It has been demonstrated that although all damping models considered predict a similar damping quality factor and agree well for predictions of closing time, the models differ by a factor of two and more in predicting the impact velocity and acceleration at contact. Implications of parameter uncertainties on the key reliability-related parameters such as the pull-in voltage, closing time and impact velocity are also discussed.

Kinetic and thermodynamic treatment for the exact solution of the unsteady Rayleigh flow problem of a rarefied homogeneous charged gas

“…(7), using the dimensionless variable defined in Eq. (12). After dropping the bars, we get the following equations (neglecting the displacement current) [46]:…”

“…The low-speed flows can often be described by the Reynolds equation, a simplified form of the Navier-Stokes equations, with negligible convective terms [12]. The Reynolds equation is often used to describe fluidic effects in micro-systems with gas confined in long gaps.…”

“…Relevant applications within a rarefied gas include upper atmospheric simulations [2], such as the Space Shuttle Orbiter [3], the Magellan Spacecraft [4], the Stardust Sample Return Capsule [5], and the Mars Pathfinder [6]. Additional relevance outside that of upper-atmospheric studies includes chemical vapor deposition [7], the micro filter [8], and micro-electro mechanical systems (MEMS) [9][10][11][12]. Traditionally, the Boltzmann equation, based on kinetic theory, remained the only appropriate option for the solution of these rarefied gases.…”

Kinetic and thermodynamic treatment for the exact solution of the unsteady Rayleigh flow problem of a rarefied homogeneous charged gas

“…Relevant applications within a rarefied gas include upper atmospheric simulations [2], such as the Space Shuttle Orbiter [3], the Magellan Spacecraft [4], the Stardust Sample Return Capsule [5], and the Mars Pathfinder [6]. Additional relevance outside that of upper-atmospheric studies includes chemical vapor deposition [7], the micro filter [8], and micro-electro mechanical systems (MEMS) [9][10][11][12]. Traditionally, the Boltzmann equation, based on kinetic theory, remained the only appropriate option for the solution of these rarefied gases.…”

Kinetic treatment for the exact solution of the unsteady Rayleigh flow problem of a rarefied homogeneous charged gas bounded by an oscillating plate

“…Relevant applications within a rarefied gas include upper atmospheric simulations [3], including the Space Shuttle Orbiter, the Magellan Spacecraft, the Stardust Sample Return Capsule, and the Mars Pathfinder. Additional relevance outside that of upper-atmospheric studies includes chemical vapor deposition [4], the micro filter [5], and MEMS [6][7][8][9]. Traditionally, the Boltzmann equation, based on kinetic theory, remained the only appropriate option for the solution of these rarefied gases.…”