Development of Si/SiGe technology for microwave integrated circuits

Ternent, Gary (2000) Development of Si/SiGe technology for microwave integrated circuits. PhD thesis, University of Glasgow.

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Abstract

A complete fabrication process has been developed for the realisation of Si/SiGe microwave integrated circuits (SIMICs). Using the process, a number of active and passive elements for microwave circuits have been demonstrated including 1. Metal gate p-SiGe MOSFETs . 2. Low loss transmission lines on CMOS grade silicon. 3. High quality spiral inductors on CMOS grade silicon. 4. High performance metal gate strained silicon n-MOSFETs. Single stage amplifiers have been designed based on the technology developed in this work. The MOSFETs have good DC performance. Strained SiGe p-channel MOSFETs with 1 mum gate length have an extrinsic transconductance of 36 mS/mm. Strained silicon n-channel MOSFETs with 0.3 mum gate length have extrinsic transconductance of 230 mS/mm. The RF performance of a metal gate 0.3 mum gate length strained silicon MOSFET is measured, with cut off frequency and maximum frequency of oscillation of 20 GHz and 21 GHz respectively. Coplanar waveguide transmission lines of 50 Ohm characteristic impedance, fabricated using spin on dielectrics on a CMOS grade silicon subsfrate, have losses less than 0.5 dB/mm up to 60 GHz. Spiral inductors fabricated on the low loss dielectric have Q > 15. Using the passive and active element library developed, single stage amplifiers were designed with gain of 12 dB at 3 GHz or 7.5 dB at 6 GHz. The device layer structures were designed using a simple ID Poisson solver. The p-channel device used a concentration graded SiGe channel to obtain high mobility and carrier concentration. The n-channel RF device with a strained silicon channel incorporates a metal gate technology that is'directly responsible for the high values of f achieved. The spiral inductors and coplanar waveguides are fabricated using a spin on dielectric process to separate them from the lossy silicon substrate. The same technology is used to reduce the parasitic capacitance of device contact pads. The engineering conclusion of this work is that SIMICs, for applications in the frequency range 1 to 10 GHz, can be made with the current passive and active element library at the University of Glasgow. Further improvement in both passive and active element performance to increase the frequency is set out in future work. From a practical viewpoint a process is now in place that will underpin the University of Glasgow's Si / SiGe SIMIC projects in the future.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Chris Wilkinson
Keywords: Electrical engineering
Date of Award: 2000
Depositing User: Enlighten Team
Unique ID: glathesis:2000-71990
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:11
Last Modified: 24 May 2019 15:11
URI: http://theses.gla.ac.uk/id/eprint/71990

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