Improving the dielectric breakdown field of silicon light-emitting-diode sub-mount by a hybrid nanosecond laser drilling strategy

Abstract

This study investigated the feasibility of conventional nanosecond (ns) laser drilling strategy and a new hybrid ns laser drilling strategy for the formation of through-silicon via (TSV), adopted in light-emitting-diode (LED) sub-mount application. In this research work, the most widely known technique, namely, the voltage ramp, was applied to measure the dielectric breakdown voltage of LED sub-mount with 1-μm-thick silicon dioxide deposited on TSV surface and sidewall. The greater value of dielectric breakdown field indicates the performance of better dielectric step coverage on TSV and better reliability of LED sub-mount. Experimental results show that the hybrid TSV drilling strategy represents an improvement of 623% dielectric breakdown field over conventional ns laser drilling method with the same oxidation process condition. The improved breakdown voltage relies on the obtained of smooth TSV sidewall and without wafer surface debris fabricated with the new drilling strategy. The mechanism of how the hybrid drilling strategy achieves smooth TSV sidewalls is also explained. Through this study, it has been demonstrated that with the new hybrid ns laser drilling strategy, it is feasible to achieve a spike-free TSV sidewall to ensure good dielectric step coverage by subsequent oxidation process.