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Title: Work function and process integration issues of metal gate materials in CMOS technology
Authors: REN CHI
Keywords: CMOS, Metal Gate Electrode, Work Function, Integration, Thermal Stability, Lanthanide-incorporated Metal Nitride
Issue Date: 30-Apr-2007
Citation: REN CHI (2007-04-30). Work function and process integration issues of metal gate materials in CMOS technology. ScholarBank@NUS Repository.
Abstract: Metal gate electrode has been considered as a promising replacement of the conventional poly-Si gate electrode for continuous scaling of CMOS. In this thesis, the work function and process integration issues of the metal gate technology have been discussed. Firstly, the influence of the metal-dielectric interface on the effective work function was investigated systematically. A model considering the impact of extrinsic states created at the gate-dielectric interface was proposed to qualitatively explain the dependence of metal effective work function on the interface chemistry and thermal annealing process. Secondly, for the first time, a novel approach to tune the effective work function of refractory metal nitrides was demonstrated by incorporating lanthanide elements. A work function value of 4.2~4.3 eV had been obtained even after a 1000C RTA treatment, attractive for NMOS applications. In addition, the material and electrical properties of lanthanide-incorporated metal nitrides were explored systematically and the relationship between the nitrogen concentration and the thermal stability of these materials was investigated. Thirdly, two different dual metal gate integration approaches had been described and demonstrated: one is a gate-first dual metal gate integration scheme by metal inter-diffusion and another is a gate-last integration process by using HfN as a dummy gate electrode. The advantage and potential issues of these integration approaches in CMOS process had been discussed in detail.
Appears in Collections:Ph.D Theses (Open)

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