Effect of the transient enhanced diffusion of boron on the characteristics of sub-0.1 μm n-MOSFETS

This paper reports the evaluation results of the channel boron (B) distribution in the sub-0.1 μm n-MOSFETs. Two types of n-MOSFETs (the post-source/drain (S/D) channel ion implantation (I/I) device and the pre-S/D channel I/I device) were fabricated and their channel B distributions were evaluated by using an advanced process simulator as a common measure. In the post-S/D channel I/I devices, the reverse short channel effect (RSCE) is not observed because the transient enhanced diffusion (TED) of B due to the high-energy channel I/I occurs uniformly in the channel. On the other hand, it has been found that the B depletion due to the transient enhanced drift pulled by the built-in electric field between the S/D-extension and the channel regions becomes significant in the sub-0.1 μm region. In the post-S/D channel I/I devices, it has been found that the sheet charge distribution responsible for the RSCE is localized within a distance of 100 nm from the S/D-extension junction. This localization contradicts the large interstitial diffusivity experimentally confirmed by the diffusion of the buried B marker layers. Another interesting feature in the post-S/D channel I/I devices is that the sheet charge distribution suddenly decreases where the distance from the S/D-extension junction is smaller than 30 nm. From this result, it is expected that the RSCE becomes less significant in the sub-0.1 μm n-MOSFETs.