notes

Make my brief discourse

MSN 551 Class Notes

LITHOGRAPHY

Why perform we need lithography?

Why do we necessity lithography?

LITHOGRAPHY
It is a catholic name given to processes used to
abalienation patterns on to a substrate to circumscribe
structures that make up devices

Optical lithography: Uses s~

Electron Beam lithography: Uses electrons

Ion beam lithography: Uses energetic ions to
attack with bombs and pattern surfaces
Soft lithography: Uses automatic contact
indentation to transfer patterns

Optical Lithography: Summary

A photoresist is exposed by light

Photoresist undergoes chemical modification

A developer is used to engrave away modified (or
unmodified) parts of the photoresist
Pattern make over is achieved.

coat

expose

develop

Main performance paremeters for
lithography

Resolution: How inconsiderable features can you
Registration: How tight be possible to you align different
layers (about 1/3 explication for optical
lithography)
Throughput: How immovable (cm^2/minutes) can you
disclose?

Coating resists: Spin coating

Easiest method of coat a flat substrate
The wafer (substrate) is placed attached a rotating
table (chuck).
The tap is rotated at a fixed rotational urge
(rpm, rotations per minute) for a fixed substance of
time.
Depending on viscosity of the withstand, a certain
thickness of film fragments on the substrate.
We want uniform (constant thickness) films that
conform the external part (coat sharp edges and
deep groves)

Coating resists: Spin covering

Coating: Alternatives

Spray coating

Dip coating

Substrate is dipped and then the resists is allow to
flow with gravity

Meniscus covering

Resist is sprayed onto the substrate

Substrate is inverted and pulled from beginning to end a resist bath

Plasma coating

Thin photoresist films be able to be deposited by certain
plasmas

Success of reaped ground method depends on wettability and glutinousness

Spin coating...

Essay for cheap