AVS 53rd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS1+MS+NM-TuM

Paper PS1+MS+NM-TuM2
Plasma Impact on ArF Resist Line Edge Roughness

Tuesday, November 14, 2006, 8:20 am, Room 2009

Session: Plasma Patterning
Presenter: J. Thiault, LTM / CNRS France
Authors: J. Thiault, LTM / CNRS France
E. Pargon, LTM / CNRS France
J. Foucher, CEA LETI France
O. Joubert, LTM / CNRS France
G. Cunge, LTM / CNRS France
Correspondent: Click to Email
As Critical Dimensions for semiconductor devices shrink too few tens of nanometers, the Line Edge Roughness (LER) or Line Width Roughness (LWR) becomes a critical issue because it can degrade resolution and linewidth accuracy that causes fluctuations of transistors performances. ArF resist patterns present a LWR of about 8 nm after lithography that is possibly transferred into the underlayers during plasma processing steps, resulting in a final LWR above the requirements of the International Technology Roadmap for Semiconductors (ITRS, which tolerates a LWR of around 3 nm for the 65nm technology node). In this study, isolated ArF resist patterns have been exposed to different plasma chemistries under identical processing conditions to investigate the impact of the plasma chemistry on the resist LWR. The sidewall roughness characterization has been performed using 3D Atomic Force Microscope (AFM3D) and top view Scanning Electron Microscope (CD-SEM). Experimental results tend to show that when the plasma/resist interaction is strongly chemically driven, such as in O@sub 2@ or SF@sub 6@ plasmas, with no bias applied to the wafer, the resist sidewalls are not smoothen. However, using plasma conditions where the ion bombardment component of the plasma is increased (by applying a bias power to the wafer), a LWR reduction is measured. This trend has been confirmed by exposing resist patterns to chemically inert plasmas such as Ar plasmas. Moreover, we have investigated plasma curing treatment on resist patterns, currently used in semiconductor manufacturing to reinforce the etching resistance of the resist. In this type of plasma (HBr based) where the ion current density is high and ion energy low, we also observe a decrease in LWR. All these trends suggest that the anisotropic ion flux is responsible for the smoothing of the resist sidewall roughness by eroding the bumps present on the resist sidewall.