Post-chemical mechanical polishing cleaning of silicon wafers with laser-induced plasma

Abstract

During chemical-mechanical polishing (CMP), wafers are subjected to various particle sources such as slurry, polishing pads and polishing machines. Consequently, wafer post-CMP cleaning is crucial in micro- and nano-manufacturing to improve yield. In conventional cleaning process, the wafer is subjected to forces whose magnitudes are large enough to potentially cause substrate damage. This damage concern is becoming more severe as the characteristic feature size shrinks to sub-100-nm region. The development of dry, rapid, non-contact and non-destructive particle removal methods has been emerging as a critical requirement for post-CMP cleaning. In recent years a novel technique for particle removal using the pressure field generated by pulsed laser-induced plasma (LIP) has been introduced for cleaning surfaces and trenches. In the current study, it is demonstrated that the LIP removal technique is capable of removing ceria CMP particles with size of 100 nm and above without any substrate damage. The results reported in this study prove that LIP can also be applied over extended areas for post-CMP cleaning. It is possible to remove smaller particles at lower gap distances but the minimum particle size that can be removed is limited by the risk of substrate damage. Results reported in this study indicate that the LIP particle removal technique has significant potential for post-CMP cleaning in the near future.