AVS 47th International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoA

Paper PS2-MoA8
Transfer Etch Profile Control for 248 nm Bilayer Thin Film Imaging

Monday, October 2, 2000, 4:20 pm, Room 311

Session: Plasma Etching of Conductors
Presenter: S. Halle, IBM Microelectronics
Authors: S. Halle, IBM Microelectronics
R. Wise, IBM Microelectronics
J. Brown, IBM Microelectronics
O. Genz, Infineon Technologies Corporation
A. Thomas, IBM Microelectronics
T. Dyer, IBM Microelectronics
A.P. Mahorowala, IBM T.J. Watson Research Center
M. Angelopoulos, IBM T.J. Watson Research Center
S. Johnston, Lam Research Corporation
Correspondent: Click to Email
The technique of bilayer thin film imaging and transfer etch is expected to play an important role for extending 248 nm lithographic patterning to 135 nm and below feature sizes. Previous studies have demonstrated the utility of an O@sub 2@/SO@sub 2@ process in a poly TCP reactor to anisotropically etch the patterned resist through a novolak-like underlayer selective to a Si-containing imaging layer. In this study, both the width and profile control over a range of aspect ratios of a bilayer transfer etch for a 135 nm contact-like deep trench (DT) mask level and a equal line-space (LS) mask printed over severe topography, are examined. Transfer etch studies show that both the profile and the width of the etched feature can be controlled by both the ratio of O@sub 2@/SO@sub 2@ and the bias voltage in the TCP reactor to produce a zero bias vertical profile. The linewidth of the etched feature can be tailored with a positive or negative slope by either decreasing or increasing the ratio of O@sub 2@/SO@sub 2@, respectively, or decreasing or increasing the bias voltage, respectively. As the aspect ratio of the underlayer etch is varied from 5 to 8 in the DT level or as the feature is over-etched by 30%, the linewidth of the etched feature is unchanged. As the lithographic alignment of the LS mask level is incrementally varied with respect to a recessed trench from a previously patterned DT level, the transfer etch can be examined to aspect ratios >10, resulting in a minimum effective width of approximately 25 nm However, at the highest aspect ratios, the trajectory of the transfer etch is observed to be shifted from normal incidence by as much as 45 degrees. Semi-empirical models are used to examine the origin of the altered trajectory of the ions, by determining the relative contribution of ion shadowing from the geometric asymmetry of the transfer into the recess and of the charging effect from thin dielectric films along the sidewall.