Characteristics of HfO/sub 2/ pMOSFET prepared by B/sub 2/H/sub 6/ plasma doping and KrF excimer laser annealing

The electrical characteristics of HfO/sub 2/ pMOSFETs prepared by B/sub 2/H/sub 6/ plasma doping and excimer laser annealing were investigated. Various metal gate electrodes were evaluated to protect the high-/spl kappa/ oxide during laser irradiation. Although the aluminum gate electrode showed superior reflectivity to the laser, the equivalent oxide thickness was increased due to the interaction between aluminum and HfO/sub 2/, which resulted in reduced capacitance. In contrast, the Al-TaN stacked gate showed good reflectivity up to laser energy of 500 mJ/cm/sup 2/ and improved capacitance was obtained compared with the Al gate. For the first time, the electrical characteristics of a HfO/sub 2/ pMOSFET with an Al-TaN gate fabricated by plasma doping and excimer laser annealing were demonstrated. It was also demonstrated that plasma doping and excimer laser annealing combined with a metal gate could be applied for high-/spl kappa/ oxide MOSFET fabrication.

I. Introduction

Various high- gate dielectrics have been studied to replace in the sub-1.5-nm thickness regime. There are many requirements for the high- oxide such as equivalent oxide thickness of less than 1.5 nm, low interface trap density , negligible hysteresis, and good thermal stability. Among the various high- oxides, has been highlighted to replace because of its high dielectric constant, large bandgap, and compatibility with conventional CMOS processes [1], [2]. However, since the crystallization temperature of is less than 700, the structural and electrical properties of high- oxide are degraded after standard high temperature source/drain (S/D) activation annealing [3], [4]. In addition, during the high-temperature process, interfacial oxide with low dielectric constant can be grown between and the Si substrate [3], [5]. Although a replacement gate process was reported to avoid high temperature treatment of high- materials, the fabrication process was complex due to the addition of a mask process and chemical mechanical polishing [6] [7] [8]. Therefore, for the application of high- oxide to MOSFET device fabrication, reduction of the thermal budget for S/D activation and the improvement of high- oxide thermal stability are required simultaneously. Previously, we reported that excimer laser annealing was an effective method for S/D activation and for ultra-shallow junction formation [9]. By laser annealing, complete activation above the solid solubility limit and a box-shaped dopant profile without enhanced diffusion are possible. In addition, the process time is less than 100 ns, which is very short compared with that of rapid thermal annealing (RTA). If a metal gate with high reflectance such as aluminum (Al) is used, it will be possible to fabricate a high- oxide MOSFET without high- oxide degradation in the stage of S/D annealing. In this paper, for the first time, we fabricated a pMOSFET with an Al–TaN stacked gate using plasma doping and KrF excimer laser annealing and investigated the electrical characteristics. In addition, the capacitance and leakage current of capacitors with various metal gates were evaluated under laser anneal condition.