Single-step deep reactive ion etch of silicon for through-via applications with alternative gas mixtures

Bosch processes involving C4F8 and SF6 have been conventionally used for through-silicon via etch. Given the high global warming potential (GWP) of C4F8 and the increasing importance of deep-Si etch processes for packaging applications in future technology nodes, it is of great interest to investigate alternative plasma chemistries to focus on sustainability in future process development. Given their lower GWPs, C4F6 and CH4 admixtures have been investigated as an alternative to C4F8 and BCl3 has been utilized as an etchant additive along with SF6 in a single-step non-Bosch process. Parametric experiments including precursor combination, pressure, and substrate temperatures have been presented. With the single-step admixture gas etching, “transition” discontinuities are observed for which a formation mechanism is proposed. Geometric and depth dependencies are analyzed in the context of this and previous work. Optical emission spectra of the gas phase are discussed; sample surface analyses are done using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry and results are presented.