抄録
Recently, the semiconductor substrates for integrated circuits (ICs) have been required to become as thin as 50 mm, because the many electronic devices are strongly demanded to be miniaturized and light-weighted. Machining of such thin substrates with conventional dicing techniques is very difficult. Therefore, we have proposed to process them using femtosecond laser ablation. In this work, we have investigated the influence of conditions of doubled pulse laser such as delay time and fluence on the depth and diameter in order to develop a new dicing technique for very thin ICs. Double pulse laser ( λ = 780 nm, τ = 150 fs, ƒ = 10 Hz, Δt = 0 ∼ 100 ps, E1+E2 = 100 μJ ) was focused on the Si substrate with a plano-convex lens with a nominal focal length of 100 mm. In the case of the delay time of 10 ps, the singularly shallow and flat-bottomed holes was obtained. When the substrates have been diced on this condition, the bottom of the processing groove was flat and very smooth, whereas many microcracks started from the bottom of the groove formed by conventional method have been observed. From these results, we were able to find out the some processing conditions using femtosecond laser applicable dicing of thin Si substrate.
