Ultra-high-aspect-ratio structures through silicon using infrared laser pulses focused with axicon-lens doublets  

作　　者：Niladri Ganguly Pol Sopena David Grojo 

机构地区：[1]Aix-Marseille University,CNRS,LP3 UMR 7341,F-13009 Marseille,France

出　　处：《Light(Advanced Manufacturing)》2024年第3期1-15,共15页光（先进制造）（英文）

基　　金：conducted using LaMP facilities at LP3.The project received funding from the French National Research Agency(ANR-22-CE92-0057-0,KiSS project)and the European Union’s Horizon 2020 research and innovation program under grant agreements No.101034324(MSCA-COFUND)and No.724480(ERC).

摘　　要：We describe how a direct combination of an axicon and a lens can represent a simple and efficient beam-shaping solution for laser material processing applications.We produce high-angle pseudo-Bessel micro-beams at 1550 nm,which would be difficult to produce by other methods.Combined with appropriate stretching of femtosecond pulses,we access optimized conditions inside semiconductors allowing us to develop high-aspect-ratio refractive-index writing methods.Using ultrafast microscopy techniques,we characterize the delivered local intensities and the triggered ionization dynamics inside silicon with 200-fs and 50-ps pulses.While similar plasma densities are produced in both cases,we show that repeated picosecond irradiation induces permanent modifications spontaneously growing shot-after-shot in the direction of the laser beam from front-surface damage to the back side of irradiated silicon wafers.The conditions for direct microexplosion and microchannel drilling similar to those today demonstrated for dielectrics still remain inaccessible.Nonetheless,this work evidences higher energy densities than those previously achieved in semiconductors and a novel percussion writing modality to create structures in silicon with aspect ratios exceeding~700 without any motion of the beam.The estimated transient change of conductivity and measured ionization fronts at near luminal speed along the observed microplasma channels support the vision of vertical electrical connections optically controllable at GHz repetition rates.The permanent silicon modifications obtained by percussion writing are light-guiding structures according to a measured positive refractive index change exceeding 10-2.These findings open the door to unique monolithic solutions for electrical and optical through-silicon-vias which are key elements for vertical interconnections in 3D chip stacks.

关 键 词：Beam-shaping Infrared ultrafast laser Silicon processing Through-silicon-via 

分 类 号：O43[机械工程—光学工程]