用于半导体和光伏行业的离子交换树脂
在对于加工晶片，或微纳电子生产中光刻所涉及的复杂湿化学程序步骤来说，超纯水（UPW）在不可或缺的。这些工艺用于制造半导体元件，如计算机处理器、存储芯片、发光二极管（LED）、液晶（LC）和LED显示器、以及光伏模块。
超纯水还用于微系统技术中，用来制造和加工如微型泵、微型电机和微型阀等的微型化机械部件。精细结构中精确到纳米级的沉积或杂质会导致生产故障和难以辨识的高废品率，而超纯水则是防止或去除这些沉积或杂质的重要先决条件。随着电子产品向越来越小的尺寸发展，对超纯水的质量要求也越来越严格。
Lewatit® UltraPure (UP) 系列离子交换树脂在可靠高效的生产超纯水方面发挥着重要作用，这其中包括单独工作的树脂，以及混床和终端抛光树脂。它们的特点都是有机物的释放量特别低，因此对工艺序列中TOC浓度的增加几乎没有作用（低ΔTOC，总有机碳）。更重要的是，纳米级的金属和颗粒的排放被降到最低。
为了生产超纯水，首先需对补充水或循环工艺水进行脱盐。然后对其进行最终抛光，以达到所需的极低电导率水平。在用特殊离子交换树脂进行最终抛光后，所获得的水将具有最高的纯度。如有必要，可通过一系列过滤步骤进一步降低水的颗粒含量。
除了过滤步骤外，特殊的离子交换树脂还可以从一开始就防止在超纯水生产过程中由于树脂侵蚀而形成颗粒。为此，侵蚀性过氧化氢被从水中去除。
我们的LewaPlus®设计软件可以在量身定制的基础上对离子交换树脂和交换阶段的各种组合进行建模分析。这为用户提供了最大的信心，即他们将获得相关补给水的最佳处理解决方案，和给定情况下所需的工艺水质。
A special ion exchanger doped with palladium is suitable for eliminating the hydrogen peroxide that forms in photochemically induced radical processes during TOC removal in the process of UPW production due to UV irradiation of the water. Lewatit® K7333 is able to break down hydrogen peroxide catalytically, thus forming water and oxygen.
This can guard against erosion of the polymer structure in the ion exchanger for final polishing that is used in the last purification step. A possible source of tiny particles is thereby reliably eliminated.
In the production of UPW, the working mixed bed absorbs those ions that remain in the water following demineralization during pre-purification. In particular, these include complex anions with a relatively weak binding tendency such as silicate, borate, and hydrogen carbonate. Since these working mixed beds still absorb significant amounts of salts, regeneration of the resin components makes economic sense.
Final polishing is the last purification step for UPW that must meet the highest purity requirements as imposed for the production of highly integrated microprocessors, for example. Here, traces of ions in the ppb and even ppt ranges that the working mixed bed left in the ultra-pure water are removed in an ultra-pure final polishing mixed bed.
This is a reliable means of adhering to the specifications for electrical resistivity; residual content of metal ions, silicate, and borate in particular; and particle limits that are necessary for smooth, efficient production of high-quality semiconductor components.
In line with the variety of impurities that enter the water during the production process for semiconductor components or photovoltaic modules, waste water treatment is tailored for the impurities found in each application. Where etching processes are used, this involves treating the acidic waste water and removing fluoride in particular. Abrasives that contain copper are used in the chemical/mechanical polishing of wafers, with the result that copper that is hazardous for aquatic organisms also enters the waste water.
Waste water from photovoltaic cell production may contain environmentally harmful compounds of antimony, lead, cadmium, selenium, or tellurium, for example. Ion exchange using selective exchange resins is a proven and efficient method for even removing traces of impurities like these from the water reliably, thus preventing a risk to humans and the environment.
