Cleaning with Supercritical

Ken Laintz and Dale Spall

Los Alamos NATIONAL LABORATORY Chemical Science and Technology Organic Analytical Chemistry CST-12, MS E537 Los Alamos, New Mexico 87545 (505) 665-3545, FAX (505) 667-6561 Outline

Supercritical Fluids

Cleaning Operations using Supercritial Fluid

Experimental Cleaning Results

Other Cleaning Applications

Significant Properties of Supercritical Fluids

0 High diffusivity results in high mass transfer

0 Low and surface tension results in small pore penetration

0 High density results in properties similar to liquids

0 Density is a selective function of temperature and pressure

Solute Extraction and Removal Kinetics

Extraction Time Operational Economics of Cleaning Prospects

Direct Labor Indirect Labor Factory Costs Labor Expenses Benefits Factory Overhead Depreciation Cycle Time Costs Maintenance New Technology Changeover Costs Facility Space Costs

Consumables Consumables Disposal Costs Liability Costs Utilities Energy and Utilities Aqueous Supercritical CO2 Taxes and Fees Administration Semi-aqueous Finance Capital Costs Finance Charges Quality Cost of Quality JAAST Joint Association for the Advancement of 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 Applied Separations DOE U. Mass. Lowell Allied Signal Autoclave Engineers EPA U. South Carolina Ciba Vision CF Technologies SNL Boeing ISCO LANL IBM National Forge PNL Honeywell Liquid Carbonic NASA-LARC Draper Labs Pressure Products Ind., Inc. NSWC/IH Litton Thar Design Inland Technologies

Comparison of Removal Efficiencies for Different Contamination Levels of TRIM® SOL Comparison of Drawing Oil Removal from Stainless Steel using CO2 and Freon-113

Freon- 113 CO2

CO2 Density (g/mL) Overall Small Scale Contaminant Removal Results

n Substrates 18 metals, ,quartz, sapphire, and 24 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 Wax Negative n Problem: Organic solvent resist stripping methods use chlorinated solvents and sulfonic acids. n Issues Toxicity Flammability Disposal n Solution: Investigate the use of supercritical CO2 for resist removal. Silicon Wafer Photoresist Removal using Supercritical CO2

n Binary, two-step solvent cleaning system necessary for resist removal using supercritical CO2 processing. Positive Resist: Supercritical CO2 treatment followed by secondary solvent wash Wax Resist: Hydrocarbon solvent treatment followed by supercritical CO2 wash Negative Resist: Solvent combinations under investigation n Supercritical CO2 processing cleans as well as and better than current solvent stripping methods for positive and wax resists. Dry-Cleaning with Carbon Dioxide

Ken Laintz and Dale Spall

Los Alamos NATIONAL LABORATORY Chemical Science and Technology Organic Analytical Chemistry CST-12, MS E537 Los Alamos, New Mexico 87545 (505) 665-3545, FAX (505) 667-6561 Summary

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

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

n Cleaning with supercritical carbon dioxide tends to be substrate independent

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

Cleaning with supercritical carbon dioxide is an economically viable solution to many cleaning problems Acknowledgments

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

This work was performed under funding from the Industrial Waste Reduction Program Office, Office of Industrial Technology, Department of Energy.