Study of Transmission Performance of Optical Through Silicon via: From a Fabrication Imperfection Perspective

Optical through silicon vias (OTSVs) have been regarded as a promising alternative to conventional (electrical) through silicon vias (TSVs) for the next-generation electro-optic heterogeneous integration. This study systematically examines the influence of fabrication imperfections on the transmission performance in terms of incident light misalignment, via geometry variation, and sidewall roughness. The results demonstrate that over a finite range of beam widths, the insertion loss can be maintained at a relatively low level of less than −0.16 dBm, and this low-loss window broadens with increasing via diameter. Moreover, an increased diameter exhibits greater tolerance to the lateral offset, as for 10 μm, 20 μm, and 30 μm vias, the insertion loss rises to 3 dB at axis misalignments of 5 μm, 10 μm, and 15 μm, respectively. Additionally, smaller-diameter OTSVs are considerably more sensitive to sidewall slope angles than their larger-diameter counterparts. Additionally, minimizing the sidewall roughness is critical for maximizing the coupling efficiency, which suggests that the etch-passivation shift needs to be as quick as possible during the deep reactive ion etch (DRIE) process. With the proposed fabrication approach and comprehensive analysis of fabrication imperfection factors, this study provides essential insights for the development of high-performance OTSVs in advanced 3D optoelectronic integration.