Formation of High-Aspect-Ratio through Silicon Vias (TSVs) with a Broad Range of Diameter by Uniform Metal-Assisted Chemical Etching (MaCE)

Abstract

Through silicon vias are key components in 2.5D and 3D microelectronic packaging. Deep silicon etching is the critical step in fabrications of TSVs. Uniform metal-assisted chemical etching (MaCE) has been considered as a promising method to the conventional deep reaction ion etching for deep silicon etching. In this paper, we demonstrated that the uniform MaCE method is capable of fabricating vertical holes with a wide range of diameter of 5-100 µm for various TSVs applications. The Au catalysts in MaCE of large diameter features show slight deformation, possible due to a hindered transport of HF. We have further demonstrated that uniform vertical holes can be fabricated by MaCE using Au catalysts deposited from either e-beam evaporation or DC sputtering. The sputtered Au catalysts, reported for the first time, may carry separated Au particles etching laterally and produce pores on the sidewall of the etched holes. By optimizing the Au thickness, the sidewall etching could be minimized and uniform vertical etching profiles could be achieved. The DC sputtering method provides a fast and more accessible way for prototype tests in MaCE research and other researches where deep silicon etching is required.