Contact Etching Process Characterization by Using Angular X-Ray Photoelectron Spectroscopy Technique

The surface properties of Si02/Si structures after different steps of contact etching processes have been studied by using normal and angular x-ray photoelectron spectroscopy (XPS). Patterned samples have been successfully analyzed. After the Si02 etching treatments, the silicon of the trench bottom of patterned samples presents the same modifications as an unpatterned Si02/Si samples. These modifications are well described by a two-layer model involving a fluorocar-bon overlayer and an interface layer. The thickness and the composition of these two layers have been studied after the etching of Si02 in CHF3/CFJAr plasmas, postetching in CF4, CF4/02, oç SF6/02 plasmas, and stripping treatments. Depending on the treatment, the overlayer thickness varies from 7 to 60 A, and its relative composition of F—C bonds and C—C bonds changes. The interface layer is composed of Si—F; Si—C, and Si—U bonds. CF4/U2 postetching has been revealed to be ineffective for the removal of the SiC residues. XPS analyses performed with a monochromatized x-ra