Core-level high-resolution XPS spectra of trimethylsilyl-functionalized SiO2 surfaces

Trimethylsilyl-functionalization via N-(trimethylsilyl)dimethylamine (TMSDMA) vapor exposure is used by the semiconductor industry to selectively passivate SiO2 surfaces during area selective deposition. Although the effectiveness of this molecule at inhibiting deposition has been studied, there have been very few published journal articles that include XPS analysis of this passivated SiO2 surface. In addition, none of these studies provide high-resolution deconvolution of the XPS peaks associated with the adsorbed siloxyl groups. To help rectify this, XPS was used to analyze coupons cleaved from a TMSDMA-treated, 5 nm plasma-oxidized SiO2/Si(100) wafer. High-resolution, angle-resolved XPS spectra of the Si 2p, C 1s, and O 1s core regions were collected at an emission angle of 80° with respect to the surface normal. Initial attempts to analyze the functionalized surface revealed that the molecular films degrade rapidly during analysis. In order to mitigate degradation of the organic monolayer, single-scan measurement sets (Si 2p, C 1s, and then O 1s) were performed on 78 separate analysis spots, which limits the x-ray exposure time of the functional groups at each measurement spot to 3 min. The spectra were then averaged to produce the high-resolution narrow-energy core spectra of the Si 2p, C 1s, and O 1s regions. This analysis technique, in conjunction with the high surface sensitivity of the angle-resolved XPS measurements at an emission angle of 80°, has made it possible to identify the O–Si(CH3)3 and Si–CH3 chemical shifts within the Si 2p and C 1s regions, respectively.