Impact of Nitrogen Profile in Gate Nitrided-Oxide on Deep-Submicron CMOS Performance and Reliability

Silicon dioxide has been used for the gate insulator in CMOS with gate lengths down to 0.25 µm. However, when we enter the sub-0.18 µm era, nitrogen atoms must be incorporated into the silicon dioxide to prevent an undesirable penetration of boron atoms from the gate electrode to the Si substrate. In this paper, we describe the effects of the nitrogen atom profile on CMOS performance and reliability and clarify the mechanisms underlying these effects. We show that high-performance, high-reliability CMOSFETs can be achieved by using a newly developed nitrided-oxide process that features a 900°C gate nitrided-oxide and establishes different nitrogen concentrations between the gate and extension area. When we enter the sub-100 nm-gate-length era of CMOS, we will need to replace thermal nitridation for the gate oxide with an alternative nitridation process, for example, plasma nitridation.

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