SSRM and SCM observation of modified lateral diffusion of As, BF2 and Sb induced by nitride spacers.

Abstract

Initial studies (using Scanning Spreading Resistance Microscopy) on the lateral diffusion of B and As have shown an important influence of the thickness of oxy/nitride spacers. The latter phenomenon was tentatively ascribed to stress enhanced diffusion under the spacer region [1]. These studies have been complemented with Scanning Capacitance Microscopy (SCM) measurements, which confirm the SSRM-data. In fact both techniques shows a similar increase in lateral diffusion with increasing spacer thickness (∼ 0.2 nm/nm spacer thickness), whereby no effect is observed on the vertical diffusion. When using spacers with or without TEOS-liner, fairly similar enhancements could be seen. Micro-Raman and CBED stress measurements for these cases do however show a large reduction in stress when a TEOS-liner is used, suggesting that the correlation (at least to the final) stress is not really justified. A possible explanation could however be that the lateral diffusion occurs before the stress relaxation within the thermal treatment. In order to elucidate the diffusion mechanism (initial stress, interstitials, hydrogen incorporation, TED,..) we have expandedthe experimental matrix with a vacancy diffuser such as Sb and simulated the potential H-incorporation duringthe nitride deposition by a hydrogen anneal. Moreover we also have studied the impact of TED by splits with RTP-anneals before the nitride deposition.

Two-dimensional electrical characterization of ultrashallow source/drain extensions for nanoscale MOSFETs

“…In contrast, there is enhancement of the diffusion Sb [21], which is a vacancy mediated process. Stress is known to introduce anisotropy in the diffusion process [22][23][24]. Enhanced lateral diffusion of Sb compared to vertical diffusion has been observed and measured in Si substrate under nitride spacers using scanning spreading resistance microscopy (SSRM) [24].…”

“…Stress is known to introduce anisotropy in the diffusion process [22][23][24]. Enhanced lateral diffusion of Sb compared to vertical diffusion has been observed and measured in Si substrate under nitride spacers using scanning spreading resistance microscopy (SSRM) [24]. In this case the LPCVD nitride film induces anisotropic compressive stresses in Si near the film edge.…”

Mechanism behind the stress‐induced change in boron and arsenic diffusion in silicon devices and its experimental verification

“…However, there are conflicting reports on the effects of compressive stress on boron diffusion. Several research groups reported on the enhanced boron diffusion through compressive stress that is induced by the nitride spacer 5, 6, shallow trench isolation (STI) 7, Si 1− x Ge x S/D stressor 8, and TiN metal gate 9. At the same time, the retardation of boron has been observed for STI‐induced compressive stress 10, 11, and compressive stressed Si 1− x Ge x layer 12.…”