Fabrication of a coupler waveguide cavity based on large-scale sacrificial layer technology

Abstract

To solve the difficult problem for the removal of large size sacrificial layers when preparing a terahertz coupler, a new approach is proposed using poly two methyl silicone as a sacrificial layer. Due to its hydrophobicity and high elasticity, cross-linked polydimethylsiloxane (PDMS) can be gently withdrawn from the cavity just after the upper suspension structure is completed. To achieve a robust super structure, we spirt silicon dioxide on the surface of the PDMS to increase its hydrophilicity resulting in large scale preparation of the sacrificial layer. This process greatly reduces the steps and equipments needed for traditional processing technologies. To obtain a good suspended structure, we sputtered silica on its surface to increase the hydrophilicity of PDMS. Experiments show that PDMS may fill the entire cavity, and that the surface has a certain adhesion after treatment, satisfying the preparation requirements of the upper structure. This approach solves the problems involving the fabrication process such as difficulty in removing the large-scale sacrificial layer, reducing the number of complex microfabrication steps and the equipment required resulting in a more cost and time-effective solution. The duration for removal of PDMS from SU-8 structures is also much lower (saving approximately 95% of time) compared to conventional photoresistance technology.