Cyber-Physical System of laser micro processing for semiconductor package fabrication

Abstract

The process rule of a semiconductor is getting smaller and smaller. Accordingly, the size of a via hole or line and space in a package is also becoming smaller. In addition, yearly evolving materials are being tested as substrate materials for the next-generation higher-frequency circuit boards or buildup substrates. The laser micro-hole drilling is a key technology for realizing these demands, and development of lasers with higher output power and shorter wavelengths is being vigorously conducted in order to drill smaller holes at higher speeds. On the other hand, significant challenges exist for drilling small holes in newly emerging materials. Depending on the parameters, drilling can damage the copper film behind the hole or chip the material due to its own brittleness. Therefore, it is necessary to optimize various processing parameters such as laser pulse width, pulse energy, repetition frequency, irradiation time, wavelength, and beam trajectory according to the required design, including hole diameter, aspect ratio, and pitch. Currently, parameter optimization is being done manually in a trial- and-error manner, which could take several months or even years for new materials or designs. The time required for feasibility testing can slow down the design process, and also forces material manufacturers to spend a great deal of time examining what kind of material composition will actually be used.