Micromechanics

01

Introduction to MEMS

• Introduction to MEMS

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02

Anisotropic Etching of Silicon

• Crystal Orientation and Etch Rates
• The Characteristic 54.74° Angle
• (110) Silicon: Vertical Walls

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03

Sacrificial Layer Technique

• The Principle of the Sacrificial Layer
• Process Flow: Deposit, Pattern, Release
• Stiction: Sticking of Released Structures

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04

Bulk vs. Surface Micromachining

• Bulk Micromachining: Etching Into the Depth
• Surface Micromachining: Building Up on the Surface
• Which Process for Which Application?

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05

The MEMS Accelerometer

• Structure: Seismic Mass and Springs
• Capacitive Readout: The Comb Structure
• From Capacitance Change to Signal

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06

The Microphone and Pressure Sensor

• Shared Principle: Membrane Over a Cavity
• The MEMS Microphone: Membrane and Backplate
• The MEMS Pressure Sensor: Piezoresistive Readout

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07

DRIE: Deep Reactive Ion Etching

• The Limits of Wet Etching
• The Bosch Process: Alternating Etch and Passivation
• Scallops: The Characteristic Wavy Structure
• Aspect Ratio and Process Limitations

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