Sheet resistance as a function of a Co-silicided polysilicon linewidth, where polysilicon is As doped. Sheet resistance is measured after RTP1 ( for ; diamond symbols) and after RTP2 ( for ; open symbols).
Top view secondary electron images of Co-silicided, As-doped polysilicon lines having a width of (a) 85, (b) 45, and (c) . Alongside the polysilicon lines spacers are visible. Co silicide is formed with RTP2 at for . One can see no signs of degradation for the line, the onset of grain separation for the line, and complete separation in the case of a linewidth.
Schematic representation of the FIB cross section along the length of the polysilicon structure.
Bright-field image of an -wide Co-silicided (RTP2 at ; ) polysilicon (As-doped) line cross sectioned along the length. Pt on top of the was used as a contrast layer.
(a) HAADF image of a line (B doped; RTP2 at for ) demonstrating the silicide agglomeration in terms of Si/silicide inversion; (b) Si, Co, O, and Pt energy dispersive x-ray mapping of the corresponding sample. Pt is used as a contrast layer.
Sheet resistance as a function of Co-silicided polysilicon linewidth, where polysilicon is As doped. The Co silicide is formed using two-step RTP scheme: RTP1 at for and RTP2 at after: (a) 30; (b) 60; (c) 90; (d) 270, and (e) . All measurements correspond to the same wafer. Note the reduced transformation rate at the narrow linewidths.
Average sheet resistance as a function of annealing time for the different linewidth groups (the average linewidths are indicated). The anneals are performed at . Note that the sheet resistance value in case of the line stays nearly constant, indicating that the transformation of CoSi into has virtually stopped.
Representative top view secondary electron image of a Co-silicided polysilicon (As-doped) line having a width of approximately using RTP2 conditions of for . Alongside the polysilicon lines, spacers are visible. No signs of degradation were found.
Bright-field image of a Co-silicided (RTP2 at ), As-doped polysilicon line (width ) cross sectioned along the length, showing the presence of CoSi grains. TiN was used as a capping layer. The subsurface voids might be attributed to sample preparation or the etching away of unconverted Co.
Cumulative probability plots of sheet resistance of lines with and without nitrogen implantation through CoSi using different RTP2 conditions. TiN was used as a capping layer.
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