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Info 2: MEMS-related Words

The following contains words you might encounter when talking to MEMS people, but might have hesitated to ask what they mean.

Actuator: Device converting energy (electric, chemical, etc.) into mechanical work.

Material characterization using an AFM probe

AFM: Atomic Force Microscopy. Visualizes features on an atomic scale.

Anisotropic etching: Direction-dependent etching. Often based on the periodic order of crystalline materials (anisotropy).

Anisotropy: Different material or processing properties in different directions.

Anodic (field-assisted) bonding: Bonding conductive to non-conductive materials (e.g. silicon to glass) using heat and high-voltage-generated electrostatic forces.

ASIC: Application-Specific Integrated Circuit. En electronic chip specially designed for a certain customer and application.

Batch: Production of many components at the same time.

Bonding: Joining of parts in a permanent way.

Bulk micromachining: Tailoring structures by machining a wafer's interior.

Cleanroom: Ultra-clean area with a controlled environment.

CMOS: Complementary Metal Oxide Semiconductor. Type of integrated electronics often used in one-chip solutions.

CVD: Chemical Vapor Deposition. Deposition of thin layers on the surface through chemical reactions.

Dielectric material: A non-conducting material.

Direct wafer bonding: Bonding wafers without using an intermediate adhesive material.

Dry etching: Processes based on chemically aggressive gases (e.g. RIE), plasma, and particle-bombardment.

EDM: Electro Discharge Machining. Milling using electric sparks.

EDP: Ethylene Diamine Pyrocatechol. An alternative to KOH for wet etching of silicon.

Electroplate: Deposition of metals using an electric current and an electrolyte solution.

Electrostatic force: Mechanical force caused by a voltage difference between two electrodes.

Epitaxy: Atom by atom growth of layers that adjust to the crystallographic orientation of the substrate (a single crystal).

Etch stop: Technique of stopping the etching at well-defined locations, e.g. at silicon-insulator interfaces or P-N junctions in semiconductors.

Etching: Removal of material, often with chemical processes.

Evaporation: Deposition using a heated source that sublimate or boil. Low pressure ensures high directionality of the vapor condensing at the substrate.

Simulation of material characterization via an AFM probe

Fab: Factory for microstructures (nickname similar to lab).

FEA/FEM: Finite Element Analysis and Method. Simulation procedure for analyzing multiphysics behavior.

FIB: Focused Ion Beam. Finely focused ion beam (often Ga+) used for imaging, milling and deposition.

Fused silica: Non-crystalline (amorphous) quartz.

GaAs: Gallium Arsenide. Semiconductor with optical and piezoelectric properties.

HF: Hydrofluoric acid. Ingredient in etchants that attack SiO2 (incl. quartz).

Hydrophilic: A drop of water will wet a hydrophilic surface.

Hydrophobic: The opposite to hydrophilic.

Isotropic etching: Direction-independent etch speed.

KOH: Potassium Hydroxide. A common etchant for wet etching of silicon.

LCVD: Laser-assisted CVD.

LIGA: Lithographie, Galvanoformung, Abformung. Synchrotron radiation is used to form high-aspect ratio polymeric structures suitable for metal filling by electrodeposition and as masters for replication.

Lithography: Copying a mask-pattern onto a surface, e.g. using light or X-ray.

Lorentz force: Mechanical force caused by an electric current in a magnetic field.

LPCVD: Low Pressure CVD.

Mask: Pattern to be copied with etching or deposition.

MCM: Multi Chip Module.

MEMS: MicroElectroMechanical System. See 'Microsystem' and 'MST'. Acronym originally used primarily in the USA. Used today in most parts of the world.

Micromachine: See MST. Word primarily used in Asia.

Micromachining: Processes for microstructure fabrication. Originating from the semiconductor industry's processes.

Microstructure: Structure featuring small geometries (sub-µm to mm). Often fabricated using micromachining.

Microsystem: System including one or more microstructures or assembled using microtechnology.

Micro Structure Bulletin

µ-TAS: Miniaturized Total Analysis System. Integrated chemical sensor system.

MOEMS: MicroOptoElectroMechanical System.

MPW: Multi Project Wafer. Several projects share the space and cost of a wafer.

MSB: Micro Structure Bulletin. Nordic MEMS newsletter published in 1993-1999.

MSK: MikroStrukturKurs. Swedish MEMS course first held in 1994.

MST: MicroSystem Technology (regionally also MicroStructure Technology). See 'Microsystem'. Acronym originally used in Europe but is now often replaced with 'MEMS'.

Micro Structure Workshop

MSW: Micro Structure Workshop. Nordic biennial MEMS workshop first held in 1994.

OEM: Original Equipment Manufacturers sell to system manufacturers instead of directly to customers.

One-chip solution: Sensor element and its electronics integrated on one chip.

Photoresist: Substance used to protect areas not to be etched. Patterned via lithography followed by removal (etching) of exposed (or unexposed) areas.

Piezoelectricity: Mechanical stress generated by electric field/charge, and vice versa. Present in strongly anisotropic dielectrics, e.g. quartz.

Piezoresistance: The dependence of resistivity on mechanical stress. Involves mainly semiconductors, e.g. silicon.

Plasma: Cloud of ionized gas and electrons.

Polysilicon: Silicon consisting of crystalline grains. Often deposited via CVD or PVD.

PVD: Physical Vapor Deposition. Deposition processes such as sputtering and evaporation.

PZT: Lead Zirconate Titanate. Large-strain piezoelectric ceramic.

Quartz wafer with tuning forks

Quartz glass: See fused silica.

Quartz: Crystalline SiO2. An inert, highly stable, and piezoelectric material. Used, for example, for tuning fork watch crystals.

Resonator: Mechanical structure that vibrates, sometimes at a resonance frequency.

RIE: Reactive Ion Etching. Dry etching based on plasma with chemically active gas ions.

Sacrificial layer etching: Removal of a buried fast-etching layer used, for example, to create freely movable structures.

SEM: Scanning Electron Microscopy. Features too small for optical microscopy made visible by scanning the sample with an electron beam.

Sensor: Device providing useful output to a specified stimulus. May react also to other stimuli, e.g. temperature.

Detail of silicon accelerometer

Silicon fusion bonding: High-temperature hermetic bonding. Its atomic nature means high-quality bond interfaces.

Silicon: The most popular material in micromachining.

SME: Small to Medium-sized Enterprise (company).

SOI: Silicon On Insulator. An oxide layer sandwiched between two silicon layers, used in etching as an etch stop barrier and sacrificial layer.

Sputtering: Deposition based on bombarding a source by ions from a gas plasma. Knocked out atoms lose their directionality when passing through the plasma on their way to the substrate.

Stiction: Undesired adhesion of movable solids in very close proximity, caused by forces such as Van der Waals, capillary and hydrogen bridging.

Surface micromachining: Forming structures via deposition and etching of thin layers on the waferÂ’s surface.

TEM: Transmission Electron Microscopy. Visualizes details in thin slices via the transmission of an electron beam.

Transducer: Device, e.g. sensor or actuator, converting energy from one domain to another, calibrated to minimize conversion errors.

Wafer: Thin slice of material suitable for batch processing. Normally circular with diameters in the 50-300 mm range.

Wet etching: Etching using chemically aggressive liquids.

Wire bonding: Making electrical connection by attaching thin gold or aluminum wires.

Yield: Fraction of functioning components after processing.

(Excerpt from Micro Structure Bulletin − MSB 99:4 ©)