Ž . Applied Surface Science 164 2000 147–155 www.elsevier.nlrlocaterapsusc Roughness and chemistry of silicon and polysilicon surfaces etched in high-density plasma: XPS, AFM and ellipsometry analysis Laetitia Rolland ) , Christophe Vallee, Marie-Claude Peignon, Christophe Cardinaud ¨ ´ ( ) Lab. des Plasmas et des Couches Mince LPCM , Institut des Materiaux Jean Rouxel, 2, Rue de la Houssiniere BP 32229 F-44322 ´ ` Nantes Cedex 03, France Abstract Surface chemistry and morphology of polysilicon thin films etched in a high-density fluorocarbon plasma under various Ž . Ž . conditions are studied by X-ray photoelectron spectroscopy XPS , atomic force microscopy AFM and spectroscopic ellipsometry. XPS reveals the presence of a fluorocarbon layer, which composition and thickness depend on the plasma conditions. Ellipsometry measurements show the need to consider the superficial roughness. Surface roughness and morphology obtained by AFM are used to define geometric models suitable to represent the top layer when processing the ellipsometry data. Results are discussed and compared to that given by the Bruggeman effective medium approximation Ž . BEMA . The BEMA model always agrees with the geometric model, which is the closest to the observed surface morphology. However, if a good agreement is obtained between surface roughness and top layer thickness for unetched or weakly damaged samples, a discrepancy is observed for the etched samples. Formation of a non-transparent fluorocarbon layer on these sample is put forward to explain this behaviour. q 2000 Elsevier Science B.V. All rights reserved. Keywords: XPS; AFM; Ellipsometry analysis 1. Introduction Characterisation and control of the surface state after etching have become one of the critical issues to master in order to meet with the requirements of today’s and tomorrow’s processes for micro-elec- tronics and micro-technology. In particular, damage to the substrate or the sub-layer, the etching process ) Corresponding author. Tel.: q 33-02-40-37-39-64; fax: q 33- 02-40-37-39-59. Ž . E-mail addresses: laetitia.rolland@cnrs-imn.fr L. Rolland , Ž . christophe.cardinaud@cnrs-imn.fr C. Cardinaud . opens onto a critical point. Such damage includes deposition of plasma species, change in the sub-layer chemical composition, modification of its structure and development or changes in surface roughness. Recently, some publications have reported on the comparison of ellipsometry and atomic force mi- Ž . wx croscopy AFM 1 , or ellipsometry, AFM and X-ray Ž . wx photo-electron spectroscopy XPS 2 for the surface characterisation of polysilicon or thermal SiO thin 2 films, respectively. Ellipsometry and AFM have been also used to investigate surface cleaning and damage wx using argon plasmas 3 on flat monocrystalline sur- faces. However, to our knowledge, similar compari- son when etching in reactive plasmas has not been 0169-4332r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-4332 00 00334-2