Etsuji Ohmura

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"Stealth Dicing (SD) " was developed to solve such inherent problems of dicing process as debris contaminants and unnecessary thermal damage on work wafer. In SD, laser beam power of transmissible wavelength is absorbed only around focal point in the wafer by utilizing temperature dependence of absorption coefficient of the wafer. And these absorbed power(More)
Stealth dicing has outstanding advantages over conventional dicing methods such as blade dicing and laser ablation method. Therefore, stealth dicing is being already used for the wafer manufacturing, and the process started to be spread in the market. In this paper, the relationship between absorption coefficient and resistivity which is the most important(More)
ldquoStealth dicing (SD)rdquo was developed to solve inherent problems of a dicing process such as debris contaminants and unnecessary thermal damages on a work wafer. A completely dry process is another big advantage over other dicing methods. In SD, the laser beam power of transmissible wavelength is absorbed only around focal point in the wafer by(More)
Ultrashort-pulse lasers are highly useful tools in the field of microfabrication. In microfabrication, the laser pulse is usually very short, in the picosecond or subpicosecond range; therefore, it is very difficult to observe the transient material processing phenomena experimentally. Over the years, the authors have conducted molecular dynamics (MD)(More)
In the frequency conversion, phase matching is essential to obtain the most effective efficiency. However the crystal temperature deviation causes undesirable conversion because the phase matching condition depends on the temperature. Frequency conversion efficiency is higher as the input intensity is higher. Thus the focused beam is usually used as input(More)
In this paper, we present laser-induced structural modifications inside BK7 glass (OHARA, S-BSL7) using a femtosecond laser and a CO2 laser system. A femtosecond laser has extremely short pulse duration (less than 10 sec) and high peak power. When an intense femtosecond laser pulse irradiates inside transparent material, the nonlinear absorption phenomenon(More)
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