CONTACT ETCHING PROCESS CHARACTERIZATION BY USING ANGULAR X-RAY PHOTOELECTRON-SPECTROSCOPY TECHNIQUE

The surface properties of SiO2/Si structures after different steps of contact etching processes have been studied by using normal and angula r x-ray photoelectron spectroscopy (XPS). Patterned samples have been successfully analyzed. After the SiO2 etching treatments, the silicon of the trench bottom of patterned samples presents the same modificati ons as an unpatterned SiO2/Si samples. These modifications are well de scribed by a two-layer model involving a fluorocarbon overlayer and an interface layer. The thickness and the composition of these two layer s have been studied after the etching of SiO2 in CHF3/CF4/Ar plasmas, postetching in CF4, CF4/O-2 or SF6/O-2 plasmas, and stripping treatmen ts. Depending on the treatment, the overlayer thickness varies from 7 to 60 Angstrom, and its relative composition of F-C bonds and C-C bond s changes. The interface layer is composed of Si-F, Si-C, and Si-O bon ds. CF4/O-2 postetching has been revealed to be ineffective for the re moval of the SiC residues. XPS analyses performed with a monochromatiz ed x-ray source have permitted the estimation of structural damage: th e damaged silicon resulting from the etching step is removed by each o f the three postetching treatments studied in this work. Finally, the sidewall surfaces of the structure have been characterized by using an angular analysis technique with a shadowing effect.