Cologne – The specialty chemicals company LANXESS hasupgraded its Lewatit K 7333 ion exchange resin for oxygen removalfor use in the electronics industry. The improved polymer matrix inconjunction with a modified formula now enables production of thepalladium-doped, strongly alkaline anion exchanger with the veryhighest degree of purity, allowing it to be used for producing ultrapurewater (UPW) for semiconductor manufacture and waferpolishing. Only specially purified ion exchangers are used here forproducing water with an extremely high level of purity.

As one of the leading manufacturers of ion exchange resins,LANXESS aims to acquire additional customers in the electronicsindustry with this novel product and strengthen its market position.

Successful product upgraded for pioneering applications

For some years now, the ion exchanger has been successfullydeployed for the catalytic removal of oxygen from process water.“The oxygenated water flows through a filter that is filled with LewatitK 7333. In the counter flow, hydrogen is passed through the filter.The palladium-doped ion exchanger acts like a catalyst here.Hydrogen and oxygen react in a ‘cold combustion’ process to formwater,” explains Hans-Jürgen Wedemeyer, Manager TechnicalMarketing in the Liquid Purification Technologies (LPT) business unitat LANXESS.

A further application for Lewatit K 7333 is the catalytic removal of H2O2 (hydrogen peroxide) without the need for hydrogen. This technology is increasingly being used for producing ultra-pure water. The even higher-quality ultra-pure water produced in this way is needed because the residual content of ions for the ever-smaller module intervals in the semiconductor industry is specified in the ppt/ppq range. The TOC (total organic carbon) content should ideally be at the limit of detection. “Water purity requirements are becoming ever more exacting in response to the enhancement and refinement of the modules, which means that it is increasingly important that the particle count in the nanometer range are stronger decreased,” says Wedemeyer.

To achieve these very low values, a special UV lamp is used. The lamp oxidizes any residual organism in the water to produce CO2. The ion exchangers then absorb these in the form of hydrogen carbonate. One adverse side effect during treatment with ultraviolet light is the formation of hydrogen peroxide (radiolysis) which can damage the downstream ion exchangers. This leads to increased levels of TOC and the formation of particles in the downstream ion exchangers. Palladium-doped Lewatit K 7333 eliminates the hydrogen peroxide formed through radiolysis right down to the low ppt range, with the ion exchanger itself responsible for only very minimal contamination with TOC, particles, or residual ions.

“This technology is already being used in many new plants and is being retrofitted in existing plants. This is why we are expecting increased demand for our Lewatit K 7333 ion exchanger so that we can meet the ever-stricter requirements regarding water purity in the semiconductor industry,” says Wedemeyer.

Ion exchangers – indispensable for wet-chemical procedures in the electronics industry

UPW is an indispensable ingredient in the processing of wafers or the complex, wet-chemical procedures involved in photolithography in the production of microelectronics and nanoelectronics. Such processesare used to manufacture semiconductor components such ascomputer processors, memory chips, light-emitting diodes (LEDs),liquid crystal (LC) and LED displays, and photovoltaic modules. UPWis also used in microsystems technology for manufacturing andprocessing miniaturized mechanical components for micropumps,micromotors, and microvalves, for example. Ultra-pure water is animportant prerequisite for preventing or removing deposits orimpurities from delicate structures right down to the nanometer rangethat would otherwise result in production faults and indefensibly highreject rates. “As electronics become increasingly small, the qualityrequirements regarding UPW continue to increase,” saysWedemeyer.

More detailed information can be found at www.lewatit.com.