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We describe a method of detecting nanometer-level gap and tip/tilt alignment between a focusing zone plate mask and a silicon substrate using interferometric-spatial-phase-imaging (ISPI). The zone plate mask is used to generate submicrometer focused light spot to induce silicon nanowire growth in a CVD process. ISPI makes use of diffracting fringes from gratings and checkerboards fabricated on the mask to determine the correct gapping distance for the focusing zone plates. The method is capable of detecting alignment inside a gas-flow chamber with variable pressure.

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Arsenic is a ubiquitous carcinogen and mutagen that has created serious human health problems around the world. It is released into the environment from both anthropogenic and natural sources [1]. Many studies have demonstrated anthropogenic sources such as the combustion of fuels, and the use of pesticides contributes As at three times higher levels than natural ones [2]. As toxicity and migration are significantly correlated with its speciation and oxidation state in the environment. In general, inorganic As species are more toxic than organic As species, As 2 O 3 (As(III)) is more toxic than As 2 O 5 (As(V)). As exposure has been reported to be related to several types of cancer, including skin, lung, and urinary bladder [3][4]. Therefore, it has aroused a global concern and substantial investigation in various environments in past decades.Humans are exposed to As through oral ingestion, such as food and water, but inhaled exposure is thought to be another important As source in industrial areas. It was reported that As concentration in air from urban and industrial districts was significantly higher than those in rural areas [4]. Previous studies indicated that more than 90% of atmospheric As exists mainly in fine airborne Pol. J. Environ. Stud. Vol. 26, No. 2 (2017) , respectively.

On-product overlay (OPO) is an important indicator of device yield. In this work, we show that stressed thin films used in semiconductor manufacturing can be an important contributor to OPO at multiple length scales. Depending on the stress level, film thickness, and the mask design, the overlay impact can be a few nanometers for the exposure of the next lithography layer. A predictive compact model based on pattern density is developed to accurately predict this overlay impact. The model is then verified using short-loop dual damascene wafers with stress split. The predictive model opens a new opportunity for model-based mask correction during optical proximity correction to increase the overlay margin for subsequent lithography exposures.