Development of a MEMS Cell Library for Integrated Microsystems, ACtuators and Sensors (CLIMACS) in Silicon

Introduction

This £1.1M project is a collaborative venture between the Universities of Edinburgh and Strathclyde and will create a fully sustainable infrastructure for the design, fabrication, and characterisation of a prototype silicon based micro-system cell library that can be directly integrated with the latest mainstream IC technology. The project will concentrate on developing the MEMS building block technology that can be directly integrated with foundry silicon. The strategy of concentrating resources on only the value added portion of the system has two distinct advantages. First it gives any MEMS technology we develop access to the latest IC technology without the partners having to devote any resources to supporting a small geometry IC process. Secondly, it also simplifies the commercialisation of any system on a chip as only access needs to be arranged to equipment used for post processing.

Equipment and Resources

Strathclyde will lead work on advanced MEMS design, modelling and characterisation. This project will provide them with modelling software for the design of advanced sensors and actuators together with a microscope-coupled high-speed camera and an illumination system to help characterise the in-plane motion of micro-mechanical structures. The high speed camera is needed to obtain detailed motion analysis of microsystems, in order to: verify the correct operation of the actuators and sensors; ensure co-ordinated operation of moving parts within complex systems (e.g. pump/valve membranes; gear trains in microtransmissions); maximise electrical to mechanical conversion efficiency (particularly applicable to microactuators); provide kinetic data for calibration of numerical models (e.g. material properties); study fluid flow in microchannels; study response of components and systems in harsh conditions (e.g. shock loads, vibration, temperature); investigate reasons for premature failure (e.g. due to fracture, fatigue, imbalance, friction, wear) and therefore improve lifetime of components and systems.

Edinburgh will concentrate on developing processes compatible with post-processing foundry wafers and on electrical characterisation. The facilities already in place at Edinburgh form an excellent basis for the proposed MEMS technology developments. This project provides two extra items of equipment which helps to complete the MEMS equipment portfolio. These are a deep etcher and a lithography system that enables the alignment of structures on both sides of the wafer. The etcher provides the ability to produce high aspect ratio structures in silicon while maintaining near vertical sidewalls. This has numerous applications in MEMS but perhaps the most exciting is that it will enable the proposers to pioneer truly 3D structures using a damascene process that takes advantage of Institute of Integrated Micro and nano Systems' extensive Chemical Mechanical Polishing (CMP) expertise. The double sided alignment system is essential for producing micro-system devices e.g. when holes need to be etched right through the wafer to produce membrane structures or when fluid input is required. Both the above items will be capable of processing 150 and 200mm wafers as the latest generations of IC technology are only available on wafers of this diameter. Initial project goals include the development of two MEMS demonstrator systems; a mechanically based fibre optic switching system for optical communications and a miniature drug dispensing system.

Associated Departments

Within Edinburgh the following departments have applications which the consortium will be addressing. Department of Physics and Astronomy (liquid crystal over silicon devices, deformable mirrors), Mech Eng (fluid control), Genetics (drug delivery), Observatory (bolometers), Physiology (neuron irrigation), Medicine (drug dispensing systems). Departments in Strathclyde include Pharmaceutical Sci (micro-dialysis), Chemistry (analytical systems), and Bio Eng (medical implants).

Summary

This collaborative project will involve the development of a cell library microsystems components and the development of the technology to integrate them in to demonstrator systems. Most of the design and characterisation will take place at Strathclyde with the technology developments will take place in the microfabrication facilities at Edinburgh. These are by far the most advanced in Scotland's Universities, routinely post-processing 150mm commercially produced foundry wafers. The relocation of this equipment into the new 250 m2 in the Scottish Microelectronics Centre's (SMC) class 10 cleanrooms places the project in an environment that matches University facilities worldwide. The significant post-processing experience that Edinburgh has on large foundry wafer with complex circuitry is not normally undertaken by academic research groups. This ability to integrate silicon MEMS devices directly with commercially produced control circuitry, provides the project with opportunities that can be matched by few organisations in the world.