Impact of STI mechanical stress in highly scaled MOSFETs

Intensive experiment on highly scaled MOSFETs with mask gate lengths down to 90 nm shows significant sensitivities (up to 10 %) of drive current per unit width to the shrinking of active area size down to 0.6 μm as well as to the gate placement distance from STI (shallow trench isolation) edge. This suggests the impact of STI induced mechanical stress along the direction of the channel current flow. Even n-and p-channel FETs are observed to behave in opposite trends with respect to the lateral active area size. Mechanical stress simulation of underlying entire front-end process line is conducted also intensively. Systematic analysis turns out strikingly that the experimental drive current sensitivity tracks well the compressive-type strain along the channel, leading to a correlation established between the two. This work promises exploration of mechanical stress issues in future nanoscale devices and circuits.