Cleaning with SupercriticalCarbon Dioxide

Ken Laintz and Dale Spall

Los AlamosNATIONAL LABORATORY

Chemical Science and TechnologyOrganic Analytical Chemistry

CST-12, MS E537Los Alamos, New Mexico 87545

(505) 665-3545, FAX (505) 667-6561

Outline

Supercritical Fluids

Cleaning Operations using

Supercritial Fluid Solvents

Experimental Cleaning Results

Other Cleaning Applications

Significant Properties of Supercritical Fluids

0 High diffusivity results in high mass transfer

0 Low viscosity and surface tension results in small porepenetration

0 High density results in solvent properties similar to liquids

0 Density is a selective function of temperature andpressure

Solute Extraction and Removal Kinetics

Extraction Time

Operational Economics of Cleaning Prospects

Factory Costs

Consumables

Utilities

Finance

Quality

Direct LaborIndirect LaborLabor ExpensesBenefitsFactory OverheadDepreciationCycle Time CostsMaintenanceNew Technology Changeover CostsFacility Space Costs

ConsumablesDisposal CostsLiability Costs

Energy and Utilities

Taxes and FeesAdministration

Capital CostsFinance Charges

Cost of Quality

Aqueous Supercritical CO2Semi-aqueous

J A A S TJoint Association for the Advancement of

Supercritical Fluid Technology

Mission: To develop and disseminate SCF cleaning applications in support of environmentally

conscious manufacturing to meet the needs of the government and industry

Members

Hughes Aerospace

Allied Signal

Ciba Vision

Boeing

IBM

Honeywell

Draper Labs

Litton

Inland Technologies

Applied Separations DOE

Autoclave Engineers EPA

CF Technologies SNL

ISCO

National Forge

Liquid Carbonic

Pressure Products Ind., Inc.

Thar Design

LANL

PNL

NASA-LARC

NSWC/IH

U. Mass. Lowell

U. South Carolina

Comparison of Removal Efficiencies for DifferentContamination Levels of TRIM® SOL

Comparison of Drawing Oil Removal fromStainless Steel using CO2 and Freon-113

Freon- 113CO2

CO2 Density (g/mL)

Overall Small Scale ContaminantRemoval Results

n Substrates 18 metals, glass,quartz, sapphire, and 24 polymers

n Contaminants 14 cutting oils, 17 machining oils, silicone fluids, 5 water

soluble cutting fluids, and 182 individual chemicals

n Observations Removals on the order of 85-100% for most compounds

Substrate independent

Silicon Wafer Photoresist Removal using Supercritical CO2

n Resist Types Positive W a xN e g a t i v e

n Problem: Organic solvent resist stripping methods usechlorinated solvents and sulfonic acids.

n Issues Toxicity Flammability

D i s p o s a l

n Solution: Investigate the use of supercritical CO2 for resistremoval.

Silicon Wafer Photoresist Removalusing Supercritical CO2

n Binary, two-step solvent cleaning system necessaryfor resist removal using supercritical CO2 processing.

Positive Resist: Supercritical CO2 treatmentfollowed by secondary solvent wash

Wax Resist: Hydrocarbon solvent treatmentfollowed by supercritical CO2 wash

Negative Resist: Solvent combinations underinvestigation

n Supercritical CO2 processing cleans as well as andbetter than current solvent stripping methods forpositive and wax resists.

Dry-Cleaning withCarbon Dioxide

Ken Laintz and Dale Spall

Los AlamosNATIONAL LABORATORY

Chemical Science and TechnologyOrganic Analytical Chemistry

CST-12, MS E537Los Alamos, New Mexico 87545

(505) 665-3545, FAX (505) 667-6561

Summary

n Super-critical carbon dioxide is capable of removing common contaminantsfrom a variety of surfaces to precision cleaning levels

n Supercritical carbon dioxide can remove oils down to and below levelsobtained using a Freon wash

n Cleaning with supercritical carbon dioxide tends to be substrateindependent

n Supercritical carbon dioxide cleaning efficiency translates from small scaleto large scale

Cleaning with supercritical carbon dioxide is an economically viablesolution to many cleaning problems

Acknowledgments

Collaborators:Jerry Barton, Leah Bustos, Dale Sivils, and Sarah B. Williams

This work was performed under funding from the IndustrialWaste Reduction Program Office, Office of IndustrialTechnology, Department of Energy.