Design and Simulation of Membrane Supported Transmission Lines for Interconnects in a Mm-Wave Multichip Module

Abstract

Abstract-Investigations are conducted into low-loss, low-dispersion fully shielded membrane-supported striplines designed for use in a millimeter-wave multi-chip-module. Two types of transmission line are studied: a membrane-supported shielded stripline and a novel variation of this where the membrane material is removed in areas of little mechanical importance to reduce attenuation and dispersion. The latter is possible through the exploitation of a versatile micromachining technique using SU-8 for both the membrane and the shielding. The micromachining techniques used for the fabrication of the microshielding allows for the conformal packaging of lines and devices, with the ultimate aim of the realization of novel components for 3D system-in-a-package type modules. Extensive simulated results obtained from rigorous electromagnetic modeling are presented that fully characterize both types of line and, where possible, are compared to measured results. Loss mechanisms are investigated for both line types and simulations suggest that losses as low as 0.39 dB/cm and effective relative permittivities of less than 1.05 are possible at a frequency of 100 GHz, comparing well with other demonstrated membrane supported transmission lines. The methods used for investigation of line characteristics and analysis of single-mode, nonleaky frequency range are applicable to any variety of membrane supported transmission line. The basics of line fabrication are given along with measurement results and de-embedding techniques used at V-band.

Design of a Non-Contact Vertical Transition for a 3d Mm-Wave Multi-Chip Module Based on Shielded Membrane Supported Interconnects

“…This paper describes the design, modeling and characterization of a non-contact vertical transition suitable for use in a 3D MCM employing the membrane supported transmission line interconnects developed in [1]. The results show that for an optimized 60 GHz transition, insertion losses of less than 1 dB over a 28 GHz bandwidth should be possible.…”

“…The results show that for an optimized 60 GHz transition, insertion losses of less than 1 dB over a 28 GHz bandwidth should be possible. Further analysis has also shown that through the use of the membrane material removal technique described in [1,2] this bandwidth could be increased to around 44 GHz.…”

“…This would be extremely challenging on a silicon membrane due to the forces involved during the processing and assembly stages, and their inflexible processing sequence. This potentially makes the approach to line fabrication and assembly described in [1] a realizing technology for 3D MCMs using membrane-supported interconnects.…”

“…The origins for this type of transmission line lie in a combination of the work conducted using a membrane-supported CPW (coplanar-waveguide) geometry on a SiO 2 /Si 3 N 4 /SiO 2 membrane [3][4][5][6][7][8] (also demonstrated using a polymer or epoxy membrane [9][10][11]), and also that involving a self-packaged, grounded CPW (GCPW) configuration using micromachined silicon [12][13][14][15][16][17]. The work described in [1,2] is an extension of these earlier types of miniature membranesupported transmission lines with the addition of full shielding and conversion to a stripline-type geometry. This involved the use of a versatile photo-epoxy, SU-8 [18][19][20][21][22] for the fabrication of both the shielding and the membrane, which has already been proven in micromachining applications.…”

“…The advantages of membrane-supported lines and passive components for millimeter-wave frequencies include extremely low-loss and dispersion [1,2] along with the potential for high-performance passives such as inductors, capacitors [3], directional couplers [4] and antenna arrays [5]. The origins for this type of transmission line lie in a combination of the work conducted using a membrane-supported CPW (coplanar-waveguide) geometry on a SiO 2 /Si 3 N 4 /SiO 2 membrane [3][4][5][6][7][8] (also demonstrated using a polymer or epoxy membrane [9][10][11]), and also that involving a self-packaged, grounded CPW (GCPW) configuration using micromachined silicon [12][13][14][15][16][17].…”