This course examines the design and fabrication of MEMS structural devices. It covers AFM probes, piezoelectricity, short-range forces, resonance, thin-film deposition, and wet and plasma etching.

Syllabus

Introduction
Learning outcomes
1 Structural devices: a static role
1 Structural devices: a static role
2 Form and function, method and material
2 Form and function, method and material
2.1 Introduction
2.2 The challenge for innovation
2.3 The fabrication process for a MEMS Pirani sensor
2.4 Thermal and electrical conductance
2.5 Review
3 Building atomic force microscope probes
3 Building atomic force microscope probes
3.1 Introduction
3.2 The principles of scanning probe microscopes
3.3 The scanning tunnelling microscope
3.4 The atomic force microscope
3.5 Scanning modes of the AFM
3.5.1 Contact mode
3.5.2 Non-contact (tapping) mode
3.5.3 Lateral force (friction) mode
3.5.4 Other modes
3.6 Design considerations for AFM probes
3.6.1 Stiffness
3.6.2 Resonant frequency
3.6.3 Quality of resonance
3.6.4 Materials selection for cantilevers
3.7 Micromachining the AFM tip and cantilever
3.7.1 The machined-at-once tip and cantilever
3.7.2 The hybrid probe
3.7.3 Oxidation sharpening
3.7.4 The carbon-nanotube tip
3.8 Review
4 Piezoelectricity: motion from crystals
4 Piezoelectricity: motion from crystals
4.1 The piezoelectric effect
4.2 The piezoelectric effect at the atomic scale
4.3 PZT
5 Short range forces
5 Short range forces
5.1 Stickiness
5.1.1 London forces
5.1.2 Dipole-dipole forces
6 Vibrations and resonance
6 Vibrations and resonance
6.1 Why is resonance important?
6.2 Natural frequency of free oscillations
6.3 Damping
6.3.1 Damped harmonic oscillator
6.4 Driven oscillations and resonance
6.5 Q-value
6.6 Oscillators in general
7 Deposition
7 Deposition
7.1 Introduction
7.2 Film properties
7.2.1 Thickness control and uniformity
7.2.2 Step coverage (conformality)
7.2.3 Chemical composition
7.2.4 Microstructure
7.2.5 Stress
7.3 Depositing metals and alloys
7.3.1 Electroplating
7.3.2 Evaporation
7.3.3 Plasmas
7.3.4 Physical vapour deposition (PVD), sputtering
7.3.5 Ion beam deposition
7.3.6 Laser ablation deposition
7.4 Depositing compounds
7.4.1 Spin-on
7.4.2 Reactive PVD
7.4.3 Chemical vapour deposition (CVD)
7.4.4 Plasma-enhanced CVD (PECVD)
7.4.5 Atomic layer deposition (ALD)
7.4.6 Molecular beam epitaxy (MBE)
7.4.7 Deposition of patterned films: lift-off and damascene
8 Etching
8 Etching
8.1 Introduction
8.2 Wet etches: acids and bases
8.3 Gas-phase etching
8.3.1 Fluorine-based etching of silicon
8.3.2 Sputter etching: argon ion etching of gold
8.3.3 Reactive ion etching: chlorine/argon plasma etching of aluminium
8.3.4 Etchants and protectants: sulphur hexafluoride/oxygen plasma etching of siliconL
8.3.5 Alternative plasma chamber designs: MERIE and ICP
8.3.6 Deep silicon etching
8.4 Stopping the etch
8.4.1 Open-loop control
8.4.2 Closed-loop control
8.4.3 Self-limiting etches
8.5 Review
Conclusion
Acknowledgements