Double Beam Photoconductivity Modulation System and its Application to the Characterization of a Process of Photoresist Removal

Abstract

ABSTRACTA laser/microwave method using two lasers of different wavelengths for carrier injection is proposed to evaluate near surface regions. These lasers are a He-Ne (wavelength=633nm, penetration depth=∼3μm) and a YAG lasers (wavelength=1060nm, penetration depth=∼500μm). Using a microwave probe, the amount of injected excess carriers can be detected. The carrier concentration is mainly dependent on the condition of the surface when carriers are excited by the He-Ne laser. It is mainly dependent on the condition of the bulk region when carriers are excited by YAG laser. We refer to microwave intensities detected by the He-Ne and the YAG lasers as the surface-recombination-velocity-related microwave intensity (SRMI) and bulkrelated microwave intensity (BRMI), respectively. We refer to the difference between SRMI and BRMI as relative SRMI (R-SRNI), which is closely related to the condition of surface and surface active region. We evaluate the near surface regions of the samples after plasma and wet etching for removing the photoresist layer. And we evaluate the near surface regions of the samples after a heat treatment which is done to recover the damage introduced by plasma etching. It is found that the R-SRMI method is better suited to near surface region evaluation than conventional lifetime measurements.