IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Wednesday Sessions
       Session PS1-WeM

Paper PS1-WeM9
Ultra High Selective Silicon Nitride Etching with a Downstream Remote Plasma using CF@sub 4@/O@sub 2@/CH@sub 2@F@sub 2@

Wednesday, October 31, 2001, 11:00 am, Room 103

Session: Dielectric Etch II
Presenter: H. Kimura, Shibaura Technology International Corp.
Authors: S. Halle, IBM Microelectronics
K. Wilson, IBM Microelectronics
K. Settlemyer, IBM Microelectronics
H. Kimura, Shibaura Technology International Corp.
Correspondent: Click to Email
A silicon nitride etch process with ultra high selectivity to silicon oxide has been developed with CF@sub 4@/O@sub 2@/CH@sub 2@F@sub 2@/X , where X = Ar, N@sub 2@, or no buffer gas, using remote plasma chemical downstream etching. The application of an ion damage free, isotropic removal of a silicon nitride film over thin oxide has been limited to date due to the lack of a ultra high selective dry strip process with a high etch rate and good cross wafer uniformity. In contrast to previously reported work, the CF@sub 4@/O@sub 2@/CH@sub 2@F@sub 2@/X process achieves an oxide selectivity > 70:1, while maintaining a high silicon nitride etch rate >200 nm/min and a uniformity ~ 3% 1@sigma@. The addition of CH@sub 2@F@sub 2@ to the well characterized microwave discharge of CF@sub4@/O@sub 2@ and CF@sub 4@/O@sub 2@/CH@sub 2@F@sub 2@ is found to increase the silicon nitride etch by a factor of 4 and 2, while maintaining an oxide etch rate of approximately 60-70 and 30-40 Å/min, respectively. Although a small amount of N@sub 2@ addition to a CF@sub 4@/O@sub 2@ plasma has been shown to significantly enhance the silicon nitride etch rate, only in the regime of N@sub 2@/(N@sub 2@+O@sub 2@) > 0.4 does the etch rate linearly increase with N@sub 2@ addition. A film deposition, post etching, on the wafer surface is found to be water soluble. In addition, the silicon nitride etch rate decreases by a factor of 5 as the wafer temperatures increases from 50 to 70C. Experimental observations are consistent with a reactive surface layer mechanism, whereby an enhanced silicon nitride etch rate is achieved as the layer is thinned in the presence of nitric oxide (NO).