フェムト秒レーザーによる材料加工に関する研究 : 高時間分解能イメージングなどによる加工過程の計測

概要

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Recently, femtosecond lasers have become to used for the microfabrication such as drilling and cutting of various kind of materials which can be used in the MEMS (Micro Electro Mechanical Systems) technology. However it is generally said that thermal effects can be decrease by using short pulsed lasers, the burr and the molten walls are often observed around the drilled holes in certain kinds of material such as Si even if the femtosecond laser is used. Then, we have tried to estimate the degree of the thermal effects during the drilling process with the femtosecond lasers. In this work, we observed the diameter of the hole formation with double pulsed laser changing delay time between the two pulses. Double pulsed laser (λ=780 nm, τ=100fs, f=10 Hz, Δt= 0-40ps, E1, E2= 100μJ ) was focused on the Si substrate and glass using a lens with a focal length of 100mm. An image-intensified CCD camera with a high-speed gate of 5 ns was utilized to take images of a drilled hole during the drilling process. As a result, the double pulsed laser can be expected to suppress the heat influence from the single pulse laser. Especially, at delay time of about 5-7 ps, heat influence became the minimum. We think that these phenomena caused by the fact that the second pulse was irradiated some metalized surface which was made by the liquefaction by the first pulse irradiation.
宮崎大学の論文
2007-08-30