Vacuum Cleanliness in the Semiconductor Industry · Contamination and Cleanliness • Minimise...
Transcript of Vacuum Cleanliness in the Semiconductor Industry · Contamination and Cleanliness • Minimise...
Vacuum Cleanliness in the Semiconductor Industry
Alan Webb
Caswell
Semiconductor Processing
• Dry process techniques are fundamental in being able to produce the desired architectures required for today's and future semiconductor devices
• Economic considerations dictate large device
densities on wafers, implying smaller and smaller chips.
• As device sizes shrink, the need to work in cleaner
conditions becomes more apparent.
Completed Wafers – 2, 3 and 6”
High Yield – Low Cost
Smaller chip size - enhanced performance
Larger packing density - more chips per wafer
Contamination and cleanliness - becomes a major yield limiting factor
Protecting the wafer is the prime concern
A Bonded Chip
Layer Structures
Device Fabrication • Key Process Steps
• Lithography
• Etching
• Contact
technologies
• Annealing
• Dielectrics
• Implantation
Contamination and Cleanliness
• Minimise Contamination and Enhance Cleanliness
• Work in a controlled environment (e.g. a cleanroom )
• Tight specification of temperature, humidity and
particle control
• Temperature controlled to 1-2 °c
• Humidity within a 5% range
• Cleanroom designated “Class”
Cleanroom Specification
• Defined by “Class”, which is a particulate measurement
• US Federal Standard No. 209 (BSI BS 5295) “Environmental Cleanliness in Enclosed Spaces”
• A Cleanroom of Specification Class X has no more than X particles of size 0.5 μm present in a cubic
foot of air
• Example : Class 10 cleanroom Particle count NOT to exceed a total of 10 particles per cu. ft. of size 0.5 μm
Process Equipment in the Cleanroom
Process Equipment in the Cleanroom
Residual Gases
• The number of unwanted atoms and molecules within the environment can have a detrimental effect on dry processing.
• Both gas phase and surface effects can occur, which produce unwanted results.
• Poor quality etching could be the result or poor characteristic films could be produced.
Monitoring and Control In-situ measuring and monitoring Non obtrusive for example : Optical Emission Spectroscopy (OES) Residual Gas Analysis (RGA) A method that provides a unique “fingerprint” of the constituents within the plasma. This consists of the source gases, products of
surface interactions and contaminants.
Schematic of RGA Monitoring
Mass Spectrometry Data
Identification of Contamination
A Methane Hydrogen Etch Process
High Resolution Mass Scan
Batch Processing
Time Resolved ‘Specta’
Complex Features Realised
Chip-on-tile for Angled Waveguide Output
Summary
Lots of nothing is a vacuum A good vacuum implies good cleanliness Clean processes produces enhanced yield Greater yield gives greater profitability More profit means more money Lots of nothing making lots of money Good for Business !
All Clear ?
Questions ?