| dc.description.abstract | With the development of semiconductor technology, more materials are used in semiconductor manufacturing processes. Quartz has many special properties, such as piezoelectricity, insulation, and light transmission. It has been widely used in biomedical and MEMS components. In these components, in order to avoid the dust, particles and liquid effects on the operation or performance, the surface hydrophobicity, hysteresis, and self-cleaning properties may play important roles. In this study, we use chromium thin film as an etching mask on the Z-cut quartz wafers. Then, we use the wet etching process to make nanostructures on the quartz surface. Finally, we will discuss how the nanostructures affect surface contact angle and wettability.
In this paper, a nanometer thick non-continuous chromium layer is deposited on the quartz wafer as an etching mask. Ammonium bifluoride solution is used as the etchant to etch quartz to form nanoneedles on the quartz surface. The etched structures for different etching time are observed by scanning electron microscopy and compared with the models from literatures.
In the results, the distribution of structures is not uniform and there are many defects between structures due to the uneven growth of the thin film. The surface wettability switches from hydrophilic to hydrophobic. In the static contact angle measurement, we found that for high structure-density samples, the measured contact angles are close to the values predicted by the Cassie-Baxter model. However, with the reduction in the structure density, the contact angles are lower than that of the Cassie-Baxter model. The reason causes the phenomenon is the droplets penetration into the structures. In addition, the dynamic contact angle measurements show that the advancing contact angles of wafers are close to the static contact angle values, because there are lots of defects on the surface. However, due to the defects, the samples have lower receding angle, and thus the hysteresis on the surface is worse, causing that the droplet is hard to slide or roll on the surface. The quartz wafer prepared by the method of this study will have a high hydrophobicity, but serious surface hysteresis. | en_US |