Skip to content
MecAgentMecAgent
Chapter 13Micro & nano

Micro- and nanofabrication

Micro- and nanofabrication makes structures far smaller than a hair: the transistors in a chip, the gears of a watch, the fibers in a filter. Instead of cutting or squeezing bulk material, these processes grow, draw, deposit or remove matter in steps measured in microns (thousandths of a millimeter) or even single atoms.

The big idea

At this scale, ordinary tools are useless: no drill bit is thin enough and no hand is steady enough. So the work is done by light, ions, electric fields and chemistry, which can be focused or controlled far below what the eye can see. Think of it as writing with a beam instead of carving with a knife: the finer the beam, the finer the writing.

This chapter works between the width of a hair and the size of an atomLog scale: each tick is ten times the one to its left0.1 nm1 nm10 nm100 nm1 µm10 µm100 µm1 mm0.1 to 0.3 nmtens of nmabout 10 µmabout 70 µmAtomTransistor featuresTypical cellHuman hair1 to 100 nm1 µm to 1 mmNanoscaleMicroscale
size ladder · from atoms to a hair, on a log scaleEach tick is ten times larger than the one to its left, so a hair is several hundred thousand times wider than an atom.

Many of these processes run in cleanrooms: rooms whose air is filtered until it holds thousands of times fewer dust particles than ordinary air, with workers in full-body suits. A single speck of dust is far larger than a transistor, so one particle landing on a wafer can ruin a chip.

The 9 processes in this chapter

13.1Czochralski crystal growth (silicon wafers)Pulls a giant single crystal of silicon slowly out of a meltOpen the lesson13.2PhotolithographyProjects a pattern with light onto a light-sensitive coating, then etches itOpen the lesson13.3Molecular beam epitaxy (MBE)Grows a crystal one atomic layer at a time from beams in ultra-high vacuumOpen the lesson13.4Atomic layer deposition (ALD)Coats a surface one atomic layer per cycle with alternating gasesOpen the lesson13.5Focused ion beam (FIB)Mills or adds material with a beam of ions under a microscopeOpen the lesson13.6Femtosecond laser machiningRemoves material with ultrashort laser pulses, without meltingOpen the lesson13.7LIGADraws deep slots with X-rays or UV, fills them with nickel, then molds copiesOpen the lesson13.8Two-photon polymerizationHardens resin only at a laser focus to print 3D micro-partsOpen the lesson13.9ElectrospinningPulls a polymer jet into nanofibers with high voltageOpen the lesson

Side by side

ProcessIn one lineBest forBatch sizePrecision
13.1Czochralski crystal growth (silicon wafers)Pulls a giant single crystal of silicon slowly out of a meltSilicon wafers for chips and solar cellsContinuous production of ingotsA near-perfect crystal, sliced into wafers up to 300 mm across
13.2PhotolithographyProjects a pattern with light onto a light-sensitive coating, then etches itComputer chips, sensors, MEMSMass production, millions of chipsFeatures down to tens of nanometers
13.3Molecular beam epitaxy (MBE)Grows a crystal one atomic layer at a time from beams in ultra-high vacuumLasers, LEDs, fast transistors, researchSmall batches of wafersSingle atomic layers
13.4Atomic layer deposition (ALD)Coats a surface one atomic layer per cycle with alternating gasesUltra-thin films in chips, coatings inside deep holesHigh-volume chip productionAbout a tenth of a nanometer per cycle
13.5Focused ion beam (FIB)Mills or adds material with a beam of ions under a microscopeRepairing chips, preparing samples, prototypesOne-offsDown to about 10 nanometers
13.6Femtosecond laser machiningRemoves material with ultrashort laser pulses, without meltingStents, glass cutting, micro-holesPrototypes to large seriesA few microns
13.7LIGADraws deep slots with X-rays or UV, fills them with nickel, then molds copiesWatch parts, micro-gears, micro-moldsSmall to medium; plastic copies in large seriesSub-micron, very tall straight walls
13.8Two-photon polymerizationHardens resin only at a laser focus to print 3D micro-partsMicro-optics, cell scaffolds, prototypesOne-offs and small seriesSub-micron detail
13.9ElectrospinningPulls a polymer jet into nanofibers with high voltageFilters, wound dressings, tissue scaffoldsLab samples to roll-to-roll linesFibers tens of nanometers to a few microns thick

How to choose within this family

  • Making the base material for chips? Silicon crystals come from Czochralski growth, and the finest crystal layers from MBE.
  • Patterning millions of identical flat devices: photolithography; adding films a few atoms thick: ALD.
  • Fixing, cutting or inspecting one tiny spot: focused ion beam; machining micro-features in metal or glass: femtosecond laser.
  • Tall metal micro-parts with straight walls: LIGA; true 3D micro-shapes: two-photon polymerization.
  • Large areas of fine fiber web, cheaply: electrospinning.

Key words

Micron (µm)
a thousandth of a millimeter; a hair is about 70 µm wide.
Nanometer (nm)
a thousandth of a micron; a few atoms side by side.
Wafer
a thin, polished disc of crystal, usually silicon, on which chips are built.
Resist
a coating that light, X-rays or electrons change chemically, used as a stencil.
Cleanroom
a room with heavily filtered air, kept almost free of dust.
Vacuum chamber
a sealed box pumped empty of air, so atoms and beams travel freely.
MEMS
micro-electro-mechanical systems, tiny machines and sensors built on chips.
Voxel
a 3D pixel, the smallest volume a process can form at once.

Try it

Put AI to work in your CAD.

Model parts, generate drawings and automate the repetitive work inside your CAD software.

Download (Free)Book a demo