Dopant penetration studies through Hf silicate

Abstract

We present a study of the penetration of B, P, and As through Hf silicate (HfSixOy) and the effect of N incorporation in Hf silicate (HfSixOyNz) on dopant penetration from doped polycrystalline silicon capping layers. The extent of penetration through Hf silicate was found to be dependent upon the thermal annealing budget for each dopant investigated as follows: B(T⩾950°C∕60s), P(T⩾1000°C∕20s), and As (T⩾1050°C∕60s). We propose that the enhanced diffusion observed for these dopants in HfSixOy, compared with that of SiO2 films, is related to grain boundary formation resulting from HfSixOy film crystallization. We also find that, as in the case of SiO2, N incorporation inhibits dopant (B, P, and As) diffusion through the Hf silicate and thus penetration into the underlying Si substrate. Only B penetration is clearly observed through HfSiON films for anneals at 1050 °C for durations of 10 s or longer. The calculated B diffusivity through the HfSixOyNz layer is D0=5.2×10−15cm2∕s.

Thermal decomposition mechanisms of hafnium and zirconium silicates at the atomic scale

“…One consequence of phase separation is that the deleterious diffusion of dopants ͑B, P, and As͒ through HSOs is higher than that through SiO 2 . 16 These findings demonstrate that MSOs do not possess the requisite thermal stability for use as a single-phase MOS gate dielectric. Some studies have provided a deeper understanding of the decomposition process.…”

“…A similar strategy is followed in Ref. 21 16 . We thus obtain 14 symmetry-distinct compositions for each of HSO and ZSO.…”

Surface-directed spinodal decomposition in the pseudobinary alloy (HfO2)x(SiO2)1−x

“…14 Amorphous thin films are suitable for CMOS transistors since grain boundaries in polycrystalline structures can introduce conducting paths. 15 However, phase separation has been reported in ͑ZrO 2 ͒ x ͑SiO 2 ͒ 1−x and ͑HfO 2 ͒ x ͑SiO 2 ͒ 1−x systems with x = 0.15-0.80 at a typical dopant activation temperature with the attendant crystallization of ZrO 2 or HfO 2 . 16,17 Kim and McIntyre 10 calculated the metastable extensions of the miscibility gap and spinodal for the ZrO 2 -SiO 2 system based on available phase diagrams and predicted that, upon rapid thermal annealing at conventional device processing temperatures, the ͑ZrO 2 ͒ x ͑SiO 2 ͒ 1−x system with a composition in the spinodal ͑x = 0.1− 0.6͒ will separate into two phases having compositions given by such metastable extensions of the miscibility gap.…”

Surface-directed spinodal decomposition in hafnium silicate thin films

“…11 Amorphous thin films are suitable for CMOS transistors since grain boundaries in polycrystalline structures can become conducting paths. 12 However, phase separation has been reported in ͑ZrO 2 ͒ x ͑SiO 2 ͒ 1−x and ͑HfO 2 ͒ x ͑SiO 2 ͒ 1−x systems with x = 0.15-0.80 at a typical dopant activation temperature with the attendant crystallization of ZrO 2 or HfO 2 .…”