Number
309-EN
Section
General Section
Use
Sector
Manufacture of computer, electronic and optical products, electrical equipment
Function
Semiconductor and photovoltaic agent
Process
Other
Product category
Semiconductors
washing ad cleaning products
Application
Semiconductors industry
Abstract
The unreacted photoresist on semi-conductor surface can be cleaned using a mixture of supercritical carbon dioxide and propylene carbonate. This alternative can replace the mixture of corrosive sulphuric acid and hydrogen peroxide which is often used for the operation. Substitution reduces the quantities of materials and wastes and gives very good quality results.
Substituted substances
Sulphuric acid
CAS No. 7664-93-9 EC No. 231-639-5 Index No. 016-020-00-8
Chemical group
Inorganic acid
Classification: hazard statements
H314 Causes severe skin burns and eye damage
Other adverse effects
Strong inorganic acid mists: 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Hydrogen peroxide
CAS No. 7722-84-1 EC No. 231-765-0 Index No. 008-003-00-9
Chemical group
Peroxides
Classification: hazard statements
H271 May cause fire or explosion; strong oxidiser
H332 Harmful if inhaled
H302 Harmful if swallowed
H314 Causes severe skin burns and eye damage
Alternative Substances
Propylene carbonate
CAS No. 108-32-7 EC No. 203-572-1 Index No. 607-194-00-1
Chemical group
Carbonic acid esters
Classification: hazard statements
H319 Causes serious eye irritation
Carbon dioxide
CAS No. 124-38-9 EC No. 204-696-9 Index No.
Chemical group
Carbonyl compounds
Reliability of information
Internet information: data are from an internet document and only a basic and partial evaluation could be performed
Reason substitution
CMR
Hazard Assessment
Substance to be substance: Sulphuric acid causes severe skin burns and eye damage. It has strong inorganic acid mists which are category 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Hydrogen peroxide is not listed in the SUBSPORTplus Database. Alternative substances: Carbon dioxide is not toxic but emissions or leakages in confined, unventilated spaces may be hazardous due to oxygen replacement. carbon dioxide is a greenhouse gas and unless it is generated as by- product or from atmosphere, or recovered from a natural source, the technology may contribute to increasing the company's carbon footprint. Propylene carbonate (PC) is not listed in the SUBSPORTplus Database and has no harmonised classification according to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation).
Description of Substitution
About 20% of the operations in the semiconductor industry are surface cleaning and stripping. The unreacted photoresist, for example, has to be removed. A common procedure for removing it uses a mixture of hydrogen peroxide and sulphuric acid in aqueous solution. Problem is that, as the pieces get smaller the high water surface tension negatively affects the cleaning. The alternative substance, supercritical carbon dioxide, does not have this problem because of its very low surface tension. However, because it does not have a good enough stripping efficiency it is better when mixed with propylene carbonate (PC). Using the mixture of carbon dioxide and CP provides better results and it is reported to cut costs and reduce the quantity of wastes. The alternatives also prevents using sulphuric acid and hydrogen peroxide that may cause severe burns. Precautions need however to be taken for handling pressurised carbon dioxide The substitution case is extracted from a report (point 4.4.2) about the properties, hazards and use of propylene carbonate as possible alternative to various solvents (see Information supplier).
Case/substitution evaluation
Implementing the substitution needs significant changes but it reduces the overall costs. The advantage of the alternative is that it generates very little wastes since supercritical carbon dioxide totally evaporates while acid or alkali cleaning needs water rinsing. The mixture of carbon dioxide and PC avoids handling and storing sulphuric acid, which is highly corrosive and hydrogen peroxide which is a highly reactive and if concentrated enough may explode if heated or generate fires in contact with combustible substances. If carbon dioxide is not obtained as by product, from atmosphere or recycled, it increases the carbon footprint of the company.
State of implementation
In use
Date and place of implementation
USA
Availability ofAlternative
The alternative is available on the market
Type of information supplier
Research
Contact
BÉGIN, Denis, Charles BEAUDRY, Michel GÉRIN. La substitution des solvants par le carbone de propylène, Rapport B-070 http://www.irsst.qc.ca/media/documents/PubIRSST/B-070.pdf
Further information
J.B. Rubin, L.B. Davenhall, C.M.V. Taylor, L.D. Sivils, T. Pierce, Karl Tiefert, 'CO2-Based Supercritical Fluids as Replacements for Photoresist- Stripping Solvents 'https://www.researchgate.net/publication/255666671_CO_2Based_Supercritical_Fluids_as_Replacements_for_Photoresist_Stripping_Solvents
Type of publication and availability
Document available freely on internet (in French)
Publication source: author, company, institute, year
The presentation is based on the report written by BÉGIN, Denis, Charles BEAUDRY, Michel GÉRIN. La substitution des solvants par le carbone de propylène, Rapport B-070, published on the website of the Institut de recherche Robert-Sauvé en santé et en sécurité du travail- IRSST in 2005.
Publication source
Type of publication and availability
http://www.irsst.qc.ca/media/documents/PubIRSST/B-070.pdf
Date, reviewed
November 26, 2021