Abstract

The demand driven by applications of MEMS (Micro-Electro-Mechanical Systems), calls for smaller devices, which are produced in various shapes and geometries. This imposes significant strain on the fabrication procedure, often resulting in elevated costs. As one of the main fabrication techniques, wet etching is an attractive alternative to dry etching because of its low cost. However, in this method, for etching and/or cleaning of wafers, we use liquid chemicals, which may result in stiction of suspended structures. Thus, the drying process is being an essential step in wet processing. If we do not have a proper technique to evaporate liquid inside structures, stiction would be unavoidable and may cause failure in fabricated devices. Low Consumption IPA (IsoPropyl Alcohol) dryer (LuCID) is an innovative and fully automated drying tool. LuCID is a Marangoni style dryer that uses IPA to vaporize water on wafer surface and in cavities of the fabricated microdevices, followed by drying with heated . With the assistance of Centre de Collaboration MiQro Innovation (C2MI) and Teledyne DALSA partnership, a set of test structures was fabricated in view of optimization of the drying procedure. These test wafers include ribbons and cantilevers with different sizes to test stiction under various conditions. Both surface and bulk micromachining methods were tested with most common structural materials, such as Low Stress Nitride (LSN) and In-Situ Doped Polysilicon (ISDP) layer. With changing LuCID parameters controlling amount and type of IPA injections drying cycle was optimized and the results of this study will be presented in this work. The influence of the liquid and solid surface tension on stiction has been investigated in this study. Moreover, by using LuCID after wet etching, we show that by adjusting the concentration of IPA injected during the drying process, it is possible to reduce stiction.