Low temperature formation of C54–TiSi2 using titanium alloys

Abstract

We demonstrate that the temperature at which the C49 TiSi2 phase transforms to the C54 TiSi2 phase can be lowered more than 100 °C by alloying Ti with small amounts of Mo, Ta, or Nb. Titanium alloy blanket films, containing from 1 to 20 at. % Mo, Ta, or Nb were deposited onto undoped polycrystalline Si substrates. The temperature at which the C49–C54 transformation occurs during annealing at constant ramp rate was determined by in situ sheet resistance and x-ray diffraction measurements. Tantalum and niobium additions reduce the transformation temperature without causing a large increase in resistivity of the resulting C54 TiSi2 phase, while Mo additions lead to a large increase in resistivity. Titanium tantalum alloys were also used to form C54 TiSi2 on isolated regions of arsenic doped Si(100) and polycrystalline Si having linewidths ranging from 0.13 to 0.56 μm. The C54 phase transformation temperature was lowered by over 100 °C for both the blanket and fine line samples. As the concentration of Mo, Ta, or Nb in the Ti alloys increase, or as the linewidth decreases, an additional diffraction peak appears in in situ x-ray diffraction which is consistent with increasing amounts of the higher resistivity C40 silicide phase.

Integrations and challenges of novel high-k gate stacks in advanced CMOS technology

“…Titanium Silicides suffered from difficulties in forming the low resistivity phase on narrow poly lines, as well as its silicon diffusion dominated formation of Silicides leading to bridging problems [302][303][304][305]. There are several methods to solve this problem, such as, refractory metal Nb, Ta or Mo alloyed with Ti or implanted into silicon, or introducing a thin refractory metal layer between titanium and silicon before thermal annealing [306,307]. The refractory metal Silicide will promote the low-resistivity phase formation by a template effect [308].…”

Morphological and phase stability of nickel–germanosilicide on Si1−xGex under thermal stress

“…1,2 The vexatious problem with the formation of the desired low-resistivity C54 phase of TiSi 2 ͑15-20 ⍀ cm͒ has resulted in the use of other low-resistivity silicides such as CoSi 2 and NiSi in electronic devices, 2-4 although significant improvements in enhancing the C54 phase formation at lower temperatures have been shown by incorporation of refractory metals in the Ti-Si system [5][6][7][8][9] or by amorphization of the Si prior to silicidation. 10 The low formation temperature ͑below 500°C͒, low Si consumption during silicidation, low resistivity ͑14 -20 ⍀ cm͒, low contact resistivity to both types of Si and no reported dependence of phase formation on geometrical dimensions have made NiSi an attractive alternative for electrical contacts in sub-100 nm CMOS technology.…”

Enhanced growth of CoSi2 thin films on (001)Si with Co/Au/Co sandwich structures

“…In previous studies, it has been demonstrated that the nucleation of metal silicides is significantly influenced by the presence of an interposing metal layer [6][7][8][9], a capping layer [10,11], and alloying elements [12][13][14][15]. For the formation of CoSi 2 thin films, recent studies have shown that the nucleation temperature of CoSi 2 was found to be dramatically lowered in the presence of small amounts of Au [8,16,17].…”