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About Toshiba > Social and Environmental Activities > Environmental Management > Eco Processes > Management of Chemicals:
Toshiba Group strives to reduce the consumption of substances targeted for usage reduction if they have large direct impacts on the environment. By business segment, home appliances and semiconductors account for nearly 80% of the total emissions of such substances, and by region, 70% of such emissions originate from Japan. In FY2008, Toshiba Group gave priority to taking measures for substances contained in paints and cleaning solvents, which ranked high in such emissions, and promoted such initiatives as introducing systems for removing volatile organic compounds (VOCs) into the paint process, using alternative substances for the cleaning process, and replacing cleaning agents with alternative agents in the semiconductor production process. However, since the number of production bases subject to control rose and production volumes grew during the first half of the year, increasing the amount of substances whose use was to be reduced, Toshiba Group was unable to attain the goal of reducing such substances by 35% compared to the FY2000 level by FY2008. In FY2009 and thereafter, it plans to use alternative substances and rethink processes as an upstream countermeasure and introduce emission removal systems as a downstream countermeasure.
A look at the substances handled, however, shows that semiconductors and social infrastructure systems account for more than 80% of the total, with substances used for chemical reactions and wastewater treatment ranked high. The material balance for PRTR-covered chemicals indicates that 28% of them are consumed together with the products that contain them and 52% are removed through neutralization and adsorption, which taken together represent the majority of the chemicals handled. It also indicates that only about 5% of the chemicals used are discharged into the air or public water systems. Going forward, Toshiba Group will continue to ascertain how chemicals are being used and manage their use properly.
Shown below is the balance of the total material volume based on the PRTR Law in Toshiba Group.
The Semiconductor Company uses isopropyl alcohol (IPA) when it produces semiconductors. It substantially reduced the amount of IPA released into the atmosphere by using a simple water shower to adsorb and remove the substance. IPA can be removed efficiently by installing this system inside the equipment that uses IPA and treating IPA at locations close to where IPA is generated in high concentrations.
In addition, low-cost measures can be taken by installing this system in equipment immediately after the equipment is installed. IPA contained in exhaust gas is reduced by 75%, helping to significantly improve the removal rate compared to the previous system. IPA adsorbed by a water shower is reused as a nutrient for activated sludge in the biological treatment process for wastewater.
The Yokkaichi Operations manufactures flash memory chips for SD memory cards, etc., wherein control of the increase in emissions resulting from the increased production volume increase was a critical issue. As specific emission reduction measures, the Operations has steadily “decreased the amount handled for manufacturing processes and products”, “reduced emissions through the introduction of waste water recovery equipment” and so on, resulting in a 36% reduction in the amount handled and a 24% reduction in emissions in FY2007 (equivalent to the rate of net production output, as compared with FY2001). It also has carried out impact investigations of the surrounding environment, regularly attended liaison conferences with local residents since its foundation and proactive efforts have been made to disclose activity on environmental data, etc.
While 2.4 tons a year of isopropyl alcohol was previously consumed to clean components in the television manufacturing processes, the corporation has succeeded in decreasing this to 1.2 tons a year, thanks to improvements in the cleaning processes and the substitution of cleaning agents. This has translated into an emission reduction to 0.6 tons from 2.2 tons, namely a decrease of 1.6 tons.
[Conventional method]:In the semiconductor manufacturing process, resist must be removed once etching is completed. With the conventional technology, a resist removal agent (peroxymonosulfuric acid) is produced by mixing sulfuric acid with hydrogen peroxide, and because sulfuric acid is diluted by hydrogen peroxide, it is difficult to recycle the sulfuric acid.
The new technology produces the resist removal agent by electrolysis, eliminates the use of hydrogen peroxide for dilution of sulfuric acid, and allows recycling of sulfuric acid. It also reduces the volume of sulfuric acid used in resist stripping by 70%, contributing to reduction of environmental impacts and enhancement of the efficiency of wastewater treatment. Moreover, it improves productivity by shortening resist stripping time by 20%.
The new technology was developed as a substitute for the conventional sulfuric acid hydrogen peroxide mixture (SPM) technology applied in the resist stripping process.
Conventional method: In the conventional SPM resist-stripping method, sulfuric acid is activated by mixing it with hydrogen peroxide, accelerating the reaction with the resist.
H2SO4(sulfuric acid) + H2O2(hydrogen peroxide) → H2SOs(peroxymonosulfuric acid) + H2O(water)
[New method]: The new technology achieves the same reaction and result as SPM but uses electrolyzed sulfuric acid. This is achieved by exciting the acid.
H2SO4(sulfuric acid) + H2O(water) → H2SOs(peroxymonosulfuric acid) + 2H+(hydrogen ion) + 2e-(electron)
Impact on resist-stripping process (pattern rework process): Sulfuric acid use reduced by approximately 70% and hydrogen peroxide use reduced to zero
Substances covered by PRTR (Amount Handled, Amount Released) FY2008 PRTR Data (PDF:36KB)Substances covered by PRTR (Amount Handled, Amount Released) FY2007 PRTR Data (PDF:64KB)Substances covered by PRTR (Amount Handled, Amount Released) FY2006 PRTR Data (PDF:36KB)Substances covered by PRTR (Amount Handled, Amount Released) FY2005 PRTR Data (PDF:11KB)Toshiba Group's PRTR data for individual business sites (results for FY2008) (PDF:74KB)Toshiba Group's PRTR data for individual business sites (results for FY2007) (PDF:108KB)Toshiba Group's PRTR data for individual business sites (results for FY2006) (PDF:76KB)Toshiba Group's PRTR data for individual business sites (results for FY2005) (PDF:28KB)indicates a link that opens in a new window.
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