Wafer thermal desorption spectrometry in a rapid thermal processor using atmospheric pressure ionization mass spectrometry

This paper demonstrates the possibility of performing thermal desorption spectrometry (TDS) on wafers in an atmospheric pressure rapid thermal processor (RTP). A special gas sampling system is described, which allows the analysis of gas composition inside the RTP chamber with atmospheric pressure ionization mass spectrometry (APIMS). Sampling is controlled with no valve operation and high dilution of the sample gas flow can be achieved while maintaining a short sample transfer time. It is shown how gas flows can be optimized to improve the sensitivity and resolution of TDS spectra. The RTP-APIMS setup was used in a study of H ₂O absorption by low dielectric constant fluorinated silica glass (FSG) films, helping to develop a cap that reduced H₂O absorption upon storage by a factor of 60. NH₃ is shown to desorb from FSG and SiO₂ films deposited by plasma-enhanced chemical vapor deposition (PECVD), which may be of concern for the reliability of integrated circuits