Developing High Aspect Ratio Optical Drill by Integrating Sub-wavelength Annular Aperture and Excimer Laser: se 3D-IC TSV as Application Platforms

The main thrust of this thesis is to develop a high aspect ratio optical drill by integrating sub-wavelength annular aperture (SAA) and KrF excimer laser. The proposed new structure of SAA is made from metal, covered with metallic oxide by high temperature oxidation. This thesis discusses the effect of Ti/TiO2 and Al/Al2O3 composite layer and finds the optimal film thickness to be 110 nm and 200 nm when a 16μm diameter of SAA at wavelength of 248 nm is studied. Silicon thin film as the material of SAA is also discussed and the optimal film thickness is identified to be 100 nm. The SAA structure can render a quasi-Bessel beam and small focal spot with long depth of focus such that the designed structure can drill a high aspect ratio hole on silicon wafer by adjusting the energy of excimer laser. The drilled diameter of SAA is less than 1μm, which is about 30% of the smallest drilled diameter of present far-field laser driller. Moreover, the diameter is in close proximity to SNOM near-field driller, but the depth of the hole from SAA is more than 13 times to that from SNOM driller.This Silicon wafer optical drill can be applied to 3D IC through-silicon via (TSV) , and hopefully can reduce the size, power consumption, and time delay of an IC chip. Through this technique, performance of 3D IC may be improved.