Thermally robust dual-work function ALD-MN/sub x/ MOSFETs using conventional CMOS process flow

Abstract

A b s t r a c t Thermally stable dual work function metal gates are demonstrated using a conventional CMOS process flow. The gate structure consists of poly-Siimetal nitrides (MNJ SiON (or highk)iSi slack with atomic layer deposition (ALD)-TaN, for thc NFET and ALD-WN, for the PFET. Much enhanced dnve current (Id) and transconductance (G,) values, and reduced off current (Ion) characteristics were attained with ALD-MN, gated devices over control poly-Si and PVD-MN, devices within controllable V, shifts. Excellent scalability of dual work function MN,ihigh-k gate stack was demonstrated the EOT was down to 6.68, with low leakage in a low thermal budget device scheme. IntroductionWith aggressive scaling of CMOS devices, it is imperative to replace poly-Si gates by metal gates to eliminate poly-depletion. The most desired metal gates should possess work functions close to Si band edges for CMOSFETs. More importantly, these metal gates should be thermally stable to employ a conventional process flow for fabrication; however, it is extremely challenging to identify two thermally stable metal gates with the correct work functions [1,2]. Furthermore, lhe method of preparing the metal gates is critical due

Effectiveness of low power dual-Vt designs in nano-scale technologies under process parameter variations

“…This becomes more evident in future nano-scale technologies where a higher baseline halo concentration is needed to suppress the worsening of V t roll-off and DIBL with device scaling. In technologies where one cannot afford a higher halo doping, high-V t devices can be realized by using metal gates -materials with higher work functions --without impacting the junction BTBT leakage and process variation [10]. Metal gates are being explored not only to have proper control on realizing devices having high-V t , but also to achieve high performance while maintaining short channel effect.…”

The Work Function Behavior of Aluminum-Doped Titanium Carbide Grown by Atomic Layer Deposition

“…These requirements render the conventional metal sputtering process unsuitable [3], [4], and they demand the use of a metal atomic layer deposition (ALD) process as it provides atomic scale controllability and conformability. However, the properties of ALD metal electrodes have not been extensively studied, especially for ALD metal carbide [5], [6]. Several metal carbides [7]- [9] are emerging as attractive metal electrodes for future logic devices due to their low work function and excellent thermal stability.…”

Effects of boron diffusion in pMOSFETs with TiN-HfSiO gate stack

“…Li et al reported a dependence of TiN thickness on stress [6], resulting in stressed-induced damage to the gate dielectric. To enhance thermal stability of the metal nitride gate, a polysilicon/TiN stack was suggested and was shown to produce more stable capacitance-voltage (C-V) curves and two orders of magnitude lower gate leakage current compared to TiN gate only [7]. Since polysilicon receives source/drain (S/D) implantation in the self-aligned CMOS process, it is important to evaluate dopant diffusion in polysilicon/metal gate structure.…”