Etching
Removing material through the resist openings.
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At a glance
Inputs
- Patterned (resist-masked) wafer
- Etchant gases or liquids
- Plasma power (dry etch)
Outputs
- Wafer with the pattern etched into the target layer
What is it?
Selectively removing material where the resist pattern leaves it exposed, transferring the resist pattern into the underlying device layer.
Why is it needed?
Etching turns the temporary resist stencil into permanent structure in the real materials — trenches, gates, contacts, and vias. Its directionality and selectivity determine feature fidelity.
How does it work?
Wet etching uses chemical baths and is often isotropic (etches in all directions). Dry/plasma etching uses reactive ions and can be highly anisotropic, cutting straight down to make vertical features.
A good etch is selective — it attacks the target far faster than the mask or the layer beneath — and is precisely timed or endpoint-detected to stop at the right depth.
Critical parameters
- Anisotropy
- Selectivity
- Etch rate
- Critical-dimension control
- Endpoint detection
Typical defects
- Undercut
- Over/under-etch
- Sidewall roughness
- Etch residue / polymer
Equipment involved
- Reactive-ion etch (RIE) tools
- Deep-RIE / plasma etchers
- Wet benches
Materials involved
- Etchant gases (e.g. fluorine/chlorine chemistries)
- Wet etchants
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