Wafer processing - I Clean room environment clean room: lled temperature (20ºC), air pressure, humidity (30%) lled airbone particulates lled vibration lled lighting INESC: 250 m 2 Class 10 and 100 clean roo 250 m 2 Class 10000 (grey area) Class 100: <100 particles(>0.5m)/ft 3
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Wafer processing - I Clean room environment Semiconductor clean room: - controlled temperature (20ºC), air pressure, humidity (30%) - controlled airbone.
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Wafer processing - IClean room environment
Semiconductor clean room:- controlled temperature (20ºC), air pressure, humidity (30%)- controlled airbone particulates- controlled vibration- controlled lighting
INESC:250 m2 Class 10 and 100 clean room250 m2 Class 10000 (grey area)
Class 100:<100 particles(>0.5m)/ft3
Wafer processing - IIresist coating
1- Vapor priming for improved resist adhesion to substrate
- Resist adhesion to Si wafers is poor- Dehydration bake to remove adsorbed water from the surface- surfactant to promote adhesion : HMDS (hexamethyldisilazane)
Vapor priming is better than spin coating with a liquid solution because lower contamination
~1 monolayer
Table II.6 – Vapor prime coating steps Step description
Conditions
Wafer dehydration and purge oxygen from the chamber
Return to atmosphere (backfill) N2 inlet, 3 minutes
2- Spinning resist and soft baking
Wafer processing - IIresist coating
SVG Resist coater and developer track:
Track system for spin coating of photoresist (1.2 to 2 m thick) and for development of post-exposed wafers.
(cassettes of 25 Si wafers 6 inch)
Requirements:Good control of thickness, uniformity, viscosity, particle contaminationTypical resist thickness: 0.6-2 m
Soft baking: remove solvents and stress and promote adhesion to wafer
Wafer processing - II
6 inch metallic holder
2 mm thick
1x1 inch squares
3 inch AlTiC wafers
6 inch Si wafer
tape
x-y- table
(a)
(b)
Coating and developing Exposure
(c)
6 inchSi wafers
Wafer processing - IIIexposure
Heidelberg Instruments Direct Write Laser Lithography System:
Direct write lithography system utilizing a HeCd laser (=442 nm (g-line) / write lens NA= 0.85) capable of critical dimensions down to 0.8 m. System works with mask designs in GDS2 format.