AVS 49th International Symposium
    Plasma Science Friday Sessions
       Session PS-FrM

Paper PS-FrM3
Etch Mechanisms of SiOC and Selectivity to SiO@sub2@ and SiC in Fluorocarbon Based Plasmas

Friday, November 8, 2002, 9:00 am, Room C-103

Session: Plasma Surface Interactions II
Presenter: N. Posseme, CNRS/LTM, France
Authors: N. Posseme, CNRS/LTM, France
T. Chevolleau, CNRS/LTM, France
L. Vallier, CNRS/LTM, France
O. Joubert, CNRS/LTM, France
P. Mangiagalli, Applied Materials, France
Correspondent: Click to Email
In CMOS technology, the traditional SiO@sub2@ is being replaced by the so called low k materials in order to reduce the total resistance capacitance (RC) delay in the interconnect levels. Many inorganic materials such as doped oxide and organic materials are being investigated as potential candidates. In this work, the study is focused on the etching of two carbon doped oxide materials: SiOC (k = 2.9) and porous SiOC (k=2.2 with a porosity of 40%). With these new inorganic materials, fluorocarbon-based etch processes have to be revisited to obtain adequate profile control in high aspect ratio structures, high etch rate and good selectivities to etch stop or hard mask such as SiO@sub2@ (k = 3.9) and SiC (k = 4). This study is dedicated to an analysis of the etch mechanisms of SiOC, SiO@sub2@ and SiC in fluorocarbon plasmas. The etching of these materials is carried out on blanket wafers in a MERIE reactor (Magnetically Enhanced Reactive Ion Etcher) using different fluorocarbon gas (CF@sub4@, C@sub4@F@sub6@, CH@sub2@F@sub2@) mixed with Ar, O@sub2@ and N@sub2@. X-ray Photoelectron Spectroscopy (XPS) analysis of the surface after partial etching shows that the fluorocarbon layer thickness formed at the surface plays a key role in controlling the etch rate and selectivity of SiOC, SiO@sub2@ and SiC. The XPS results indicate that the fluorocarbon layer thickness depends on the plasma chemistry and also on the oxygen and carbon concentration in the etched materials The polymerising gas addition such as CH@sub2@F@sub2@ to CF@sub4@/N@sub2@/Ar gas mixture induces an increase in thickness of the fluorocarbon layer which generates a decrease in etch rate. Similar XPS analysis are also conducted on the SiOC sidewalls using the chemical topography analysis technique.