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Chemicals
We are minimizing our use of hazardous substances through, for example, substitution, process optimization, hardware modifications, on-site generation, recycling or reuse, and the installation of Total Chemical Management (TCM) in partnership with key suppliers.
Engineers working on wet processes (wafer cleaning processes using chemicals) are at the forefront of our efforts to reduce the use of chemicals, in order to bring environmental improvements, better safety and cost savings. The chemicals we target are photoresists, developers, sulphuric acid, fluorhydric acid, hydrogen peroxide and solvents.
In 1999, ST formalized a corporate chemical-saving road-map based on best practices.
Total chemicals consumption per manufacturing units has improved from 1.36kg per wafer in 2000 to 1.24kg in 2001 for front-end sites and from 0.38kg per thousand units in 2000 to 0.21kg in 2001 for assembly sites.
Overall, after two years of reduced chemical consumption, the rate increased by 0.2 tonnes per $ million of added value in 2001. This result is mainly affected by a lower added value because of the market downturn in 2001.
CHEMICAL CONSUMPTION
Our goal remains to reduce overall consumption by 5%.
EXAMPLES
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Use of diluted chemicals in spray processors through hardware modifications. The cost of the diluted formula can be reduced by 46% as it uses less chemicals. This recipe is being rolled out to our manufacturing sites where the same equipment is available. |
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Total sulfuric acid substitution with de-ionized water and ozone in a particular process. Our site in Agrate, Italy has already processed four million wafers saving more than 90,000 liters of sulphuric acid, 20,000 liters of hydrogen peroxide and 6,000 liters of ammonia compared with 2000. This has led to savings of more than k$175. |
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Replacement of old wet benches with new equipment, which consumes less chemicals and gives better process performance. |
Our manufacturing site in Tours (France) has drastically reduced its sulfuric acid consumption from 2.1kg per wafer in December 1999 to 0.7kg in December 2001. The net saving on chemicals over one year is evaluated at 400 tonnes of sulfuric acid and 133 tonnes of hydrogen peroxide. Return of investment was below two years.
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