Strategies for Defect-Free and Deep Wet Etching of Pyrex 7740

In this paper, two aspects in the wet glass etching, the pre-annealing of the glass and the mask process, are taken into consideration to achieve the deep and defect-free wet etching of Pyrex glass. Compared with the conventional strategies, i.e., HF solution component and mask kinds, our experiment results prove the pre-annealing is another key role to obtain theoretical isotropy character in wet etching. Besides, the high temperature pre-annealing dramatically improves the structure profiles and reduces the notching defects. Additionally, a novel multilayer mask process is proposed. With 1.5μm PR/ 100nm Au/ 100 nm Au/ 20 nm Cr mask and > 450 °C pre-annealing, > 150 μm deep and non-pin-holes Pyrex glass structures are achieved and the roughness of etched surface is lower than 1 nm.