Effects of hard masks on etching properties of metal gates
Gate stacks of metal nitrides (TaN, HfN, and TiN) or poly- wafer with (a) , (b) , and (c) PR masks; thin layer is inserted between mask and TiN to enhance adhesion under the mask in (b).
Etch rates of (a) TiN and (b) poly-Si as a function of etch time for different masks (, , and PR).
Cross-sectional scanning electron microscopy images of the etched TiN gate stacks with the various masks of (a) , (b) , and (c) PR.
XPS spectra of (a) Ti from TiN gate stacks and (b) Si from poly-Si gate stacks with various masks (solid data points represent before etching and open data points represent after etching for ). All samples were dipped into 1% diluted hydrofluoric acid for before etching to remove native-grown metal oxides. The Ti peak is composed of spin-orbit doublets, each separated by (Ref. 16). Only Ti is indicated in (a). All the XPS analyses were performed using a monochromatized source on a constant pass energy of .
XPS spectra of O peak after etching for with various masks. shows a wide range of binding energy according to the ratio of to .
Schematic illustration on the behavior of various by-products generated from the etching of TiN gate stacks for the various masks of (a) , (b) , and (c) PR. Oxygen generated from inside the chamber can be a source for the reaction because working pressure is and base pressure is in these experiments. There is a thin layer inserted between mask and TiN to enhance adhesion under mask.
Concentration of elements detected by XPS from the etched TiN gate stacks as a function of etch time for the various masks of (a) , (b) , and (c) PR.
Change of rms roughness of the etched TiN surface for various masks; negative and positive values in axis represent the decrease and increase of surface roughness after etching compared to before etching, respectively.
AFM morphology of TiN surface as a function of etch time. The etching experiments are performed at a pressure of , a source power of , and a bias voltage of : (a) , (b) , (c) , and (d) ; /lateral unit, /vertical unit.
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