AVS 53rd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA6
Profile Control and Sidewall Modifications of Narrow Porous ULK Trenches after Plasma Etching and Pore Sealing Treatments

Tuesday, November 14, 2006, 3:40 pm, Room 2011

Session: Etch for Advanced Interconnect II
Presenter: M. Darnon, CNRS-LTM-France
Authors: M. Darnon, CNRS-LTM-France
T. Chevolleau, CNRS-LTM-France
D. Eon, CNRS-LTM-France
F. Bailly, CNRS-IMN-France
L. Vallier, CNRS-LTM-France
J. Torres, STM-France
O. Joubert, CNRS-LTM-France
Correspondent: Click to Email
In CMOS technology, for most of the interlayer dielectric materials, low k values are obtained by introducing porosity in order to reduce the total resistance capacitance delay in the interconnect levels. Trench or via patterns are currently transferred into porous SiOCH (p-SiOCH) using a dual hard mask strategy. In this work, we have investigated the profile control in narrow trenches etched using a metallic hard mask, and the characterization of the dielectric material degradation induced by the etching and pore sealing processes. The stack investigated is composed of 600 nm p-SiOCH, 40 nm SiO@sub 2@, 45 nm TiN and 100 nm photoresist (PR). The 200 mm wafers are patterned using direct ebeam lithography to achieve aggressive trenches dimensions down to 50 nm. The etching of p-SiOCH trenches is performed in a Magnetically Enhanced Reactive Ion Etcher (MERIE) using fluorocarbon gas mixtures. Pore sealing treatments on the patterned structures are achieved in a CH@sub 4@ or NH@sub 3@ plasma. Trenches profiles are observed by Scanning Electron Microscopy (SEM). Sidewalls and bottom surface composition are determined using chemical topography analysis by X-ray Photoelectron Spectroscopy (XPS). A parametric study reveals that profile distortions are attributed to by-products redeposition and hard mask faceting. The by-products redeposition is minimized by increasing the wafer temperature and/or using low polymerizing chemistries. The faceting is strongly reduced by lowering the ion bombardment. Whatever the etching conditions, the porous materials are modified on the trenches sidewalls. After narrow trenches etching with the optimized etch conditions, the impact of the pore sealing plasma treatments on the sidewalls and bottom modification is investigated. XPS analyses reveal that the pore sealing is attributed to the formation of a carbon rich layer with CH@sub 4@ plasma or a SiO@sub x@ layer with NH@sub 3@ plasma.