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The effect of Young's modulus of contact-etch-stop layer (CESL) stressor on the strained-Si MOSFET

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Abstract

In the analytic solution of residual stresses and bending in multi-layer/substrate systems, Young's modulus of contact-etch-stop layer (CESL) stressor is a potential factor affecting the channel stress of complementary metal–oxide–semiconductor (CMOS) devices. To increase the level of Young's modulus of CESL stressor, the stress level of silicon channels could be boosted at a constant stress level and thickness of CESL as the result of stress simulation. Young's moduli of two widely adopted CESL stressors measured by a nanoindenter instrument, low-pressure chemical vapor deposition silicon nitride (LP-SiN) and plasma-enhanced chemical vapor deposition silicon nitride (PE-SiN), were 375.7 and 224.7 GPa, respectively. As a result of stress stimulation, the channel stress induced by LPSiN CESL could increase 30% higher than that of PE-SiN CESL. Through the use of a tensile 1 GPa CESL stressor for the 90 nm n-FETs, an extra 4% enhancement in drive current ID,sat was obtained in the device with an LP-SiN CESL as compared to that with PE-SiN. The electrical data is in good agreement with the prediction of the stress simulation.

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