Release of Chemicals

Case Study: Reducing methanol emissions through process improvements / Toshiba Consumer Products (Thailand) Co., Ltd.

In the manufacturing process for refrigerators, methanol is used for cleaning and other purposes. Since much of it was being discharged into the atmosphere, however, Toshiba Consumer Products continued to take measures to reduce methanol emissions. In FY2009, the company started to use neutral detergents as an alternative, reducing methanol emissions by six tons annually. However, no alternative cleaning agent could be used to clean the insulating material which leaks during the process in which such material is injected into refrigerators due to the nature of the material. Thus in FY2010, in order to prevent the fundamental cause of the problem, methanol leaks, environmental management officers worked with the design and manufacturing departments to analyze the location where the substance was escaping. Through these efforts, the company improved the metal molds, sealed the leak, and dramatically cut back the amount of methanol used, thereby reducing methanol emissions from 16.0 tons to 3.7 tons annually.

Case Study: Reducing VOC emissions in the fluorescent lamp manufacturing process / Toshiba Lighting and Technology Corporation

Fluorescent lamp manufacturing process

In the manufacturing process for fluorescent lamps, butyl acetate is used as a solvent when fluorescent substances are applied. Butyl acetate, a VOC targeted for reduction, has been emitted into the atmosphere after fluorescent substances were applied and dried. Toshiba Lighting and Technology Corp. recently reduced its emissions into the atmosphere substantially by installing a butyl acetate removal system at the overflows. This system, which uses the regenerative catalytic incineration method, employs catalysts to burn and decompose butyl acetate. In addition, butyl acetate can be burned using early heat sources alone by storing heat obtained from incineration, enabling the efficient processing of the substance. Furthermore, since practically no fuel is used, CO₂ and NOx emissions from fuel can be reduced. Thus the company takes care to avoid secondary environmental pollution.

Case Study: Reducing IPA emissions in the semiconductor wafer cleaning process / Semiconductor Company, Toshiba Corporation

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.

Case Study 1: Management of Chemical Substances and Communications in the Semiconductor Factory Won the Special Commendation, 4th PRTR Award 2007 / Yokkaichi Operations, Toshiba Corp.

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.

Case Study 2: Reduction in the Amount of Cleaning Agents used at a Production Site in China / Toshiba Dalian Television Corporation

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.

Case Study: Resist Stripping Technology Enabling Reuse of Chemicals / Corporate Manufacturing Engineering Center, Toshiba Corp.

Industry's First Electrolyzed Sulfuric Acid Method

[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%.

Outline of Development

The new technology was developed as a substitute for the conventional sulfuric acid hydrogen peroxide mixture (SPM) technology applied in the resist stripping process.

1. Comparison with the conventional method

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)

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Peroxymonosulfuric acid is activated sulfuric acid, a strong oxidizer that facilitates resist stripping.

[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)

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In terms of production of peroxymonosulfuric acid and resist stripping performance, the new method is comparable to SPM.

2. Impact (estimate)

Impact on resist-stripping process (pattern rework process): Sulfuric acid use reduced by approximately 70% and hydrogen peroxide use reduced to zero

Press Release

• Toshiba, Shibaura Mechatronics and Chlorine Engineers Together Establish New Chemical-reuse Environment-conscious Semiconductor Resist Stripping Technology (A separate window will open.)