High-Q micromachined three-dimensional integrated inductors for high-frequency applications

Abstract

Three-dimensional micromachined inductors are fabricated on high-resistivity ͑10 k⍀ cm͒ and low-resistivity ͑10 ⍀ cm͒ Si substrates using a stressed metal technology. On high-resistivity Si substrate with low-k dielectric material ͑SU-8™͒, this technology achieves a quality factor Q of 75 for a 1 nH inductor at frequencies around 4 GHz and a self-resonant frequency f sr above 20 GHz. Using Si bulk micromachining to etch away the low-resistivity Si substrate with a combination of deep reactive ion etching and tetramethyl ammonium hydroxide etching methods, a 1.2 nH inductor achieves a peak quality factor Q of 140 at a frequency of 12 GHz with a self-resonant frequency f sr above 40 GHz. The dependence of high-frequency performance on the inductor's variables, such as the number of turns, turn-to-turn gap, and substrate type, has been investigated. Excellent performance is achieved by removing the substrate due to the complete elimination of substrate losses and the reduction of the parasitic capacitance. This technology is simple and provides high performance integrated inductors on Si or compound-semiconductor platforms.

A novel vertical comb-drive electrostatic actuator using a one layer process

“…The residual stress has been widely used in micro devices [31][32][33][34][35][36][37][38][39]. The actuator presented in this paper uses the residual stress gradient to construct the moving comb layer.…”

“…The difference between the present actuator and other reported micro devices [31][32][33][34][35][36][37][38][39] using residual stress lies in: (1) The present actuator uses a mature and commercial microfabrication process, i.e. MetalMUMPs and the residual stress gradient is in the nickel layer fabricated using this process.…”

Design and simulation of digitally tunable high-Q on-chip inductor

“…Fully integrated VCOs with on-chip fixed inductor and microelectromechanical-systems (MEMS) variable capacitor have been reported [1], [2]. Recently, high-Q integrated inductors have acquired considerable research attention [2]- [5]. Moreover, several tunable inductor architectures have been designed and synthesized [6]- [15].…”