Cranfield University

Dr Paul Kirby

Reader in Microsystems
Location: Building 70, Cranfield campus
E: p.b.kirby@cranfield.ac.uk
T: +44 (0)1234 754067
Manufacturing and Materials

Current activities

A functional materials Microsystems device processing capability has been established with a balance of industrial, research council and EU funding.

 Current capabilities of process include:

• high resolution (~1µm) photolithography including front and back side wafer alignment
• patterning of metal, semiconductor and insulator thin films using wet and dry etching processes
• high aspect ratio processing of silicon structures using sophisticated Deep Reactive Ion Etching capability
• metrology for measuring device topography, layer stresses and optical inspection
• magnetron and dc sputtering techniques for metal and dielectric thin films for device applications.

Established activities in the following  research areas of Microsystems Technology:

• electronic materials for passive component devices - on-going research into developing deposition techniques and methods for thin film materials that have high dielectric constant and low-loss
• piezoelectric MEMS devices - development of fabrication processes for the incorporation of ferroelectric and piezoelectric materials into silicon MEMS devices

Cranfield is currently amongst the world leaders in this field as many novel fabrication processes have been developed in order to make multi-layer, multi-material MEMS devices. These include plasma techniques for etching thin film inorganic and ceramic materials. Silicon etching techniques include inductively coupled deep reactive ion etching to produce high-aspect ration structures.

• device modelling
• RF-MEMS - Wireless communication is showing explosive growth of emerging consumer and military applications of radio frequency (RF), microwave and millimetre wave circuits and systems. However, many circuits in order to take advantage of their desirable functions use, discrete off-wafer components that cannot at present be incorporated on-chip. RF-MEMS devices such as Thin Film Bulk Acoustic resonators, piezoelectric and electrostatically actuated RF switches, and a novel piezoelectric coupled cantilever filter structure are under development. Physical, inertial  and Biological sensors based on sensing and actuation in multi-material, microsystem devices
• Bio-Microsystems development -The feasibility of using microsystem technology to make a Patch Clamp system for measuring ion-current transport across cell membranes is being investigated. The 3-axis piezoelectric accelerometer that was developed at Cranfield is being studied for use application in a human body movement system that can monitor walking recovery of people that have had traumas such as strokes.

Clients

Background

Dr Paul B Kirby joined Cranfield in October 1998 as Senior Lecturer in Microsystems after spending 15 years in the electronics industry. He undertook his PhD at the Cavendish Laboratory, Cambridge University, performing original research into the defects states in semiconductor materials. After completing his PhD he took up a one-year World Trade Fellowship award to undertake research at IBM’s Thomas J Watson Research Centre, where he studied the application of amorphous silicon to solar cells and thin film transistors. After IBM he spent four years as a Research Fellow at Harvard University performing fundamental material studies for device applications.

In 1985 he returned to the UK working for GEC-Marconi, first at the Hirst Research Centre in Wembley and then at the GEC-Marconi Research Centre at Caswell. He was involved in a wide range of applied material and device studies on III-V semiconductors including: low temperature photoluminescence studies of MBE grown GaAs/AlGaAs quantum well and superlattice structures. In 1989 he initiated studies of the psuedomorphic GaAs/InGaAs system which eventually replaced GaAs/AlGaAs as the material used for high frequency High Electron Mobility Transistors. This transistor was used in the input amplifier of satellite direct broadcast receivers and has subsequently become the basis of HEMT based Monolithic Microwave Circuits at GEC-Marconi. 

In 1991 he was responsible for developing flip-chip bonding techniques for WLAN circuits and successfully developed techniques for processing high dielectric ferroelectric materials onto microwave circuits. From 1993 as Microsystems Manager, he led a group at Caswell developing device applications of ferroelectric thin films. Many original device processes were developed during this period. Particular successes include the incorporation of high dielectric constant thin films as D.C. blocking capacitors into an MCM circuit, development of Thin Film Bulk Acoustic Resonators and a state-of-the-art, high performance, three-axis micromachined accelerometer incorporating piezoelectric thin films as the sensing layers. The accelerometer was designed for modal analysis and noise monitoring in the work place.

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