Microwave Planar Lumped Circuit Elements on Micromachined Thin Dielectric Membranes

This paper presents the technological processes developed in order to obtain high quality 1.5micrometers membranes on high resistivity (100) and (111) oriented silicon. To emphasize the outstanding characteristics of the membrane supported elements, coplanar meander-line, 'S'-line and square spiral inductors, as well as interdigitated capacitors were designed and manufactured both on dielectric membranes and on bulk SI GaAs substrates, and their equivalent circuit was developed, too. An improvement of the measured resonant frequencies by a factor of 1.7 to 1.8 was noticed. Equivalent circuits, able to simulate the behavior of the coplanar elements up to twice their resonance frequencies, were developed. The paper brings into relief, quantitatively, the superiority of the membrane supported microwave planar lumped elements.