Electrically Scaled Hafnium Oxide Based Ge Devices

Abstract

As device feature sizes have continued to scale, new device engineering and dielectric materials with engineered properties are becoming essential in overcoming the issues in scaled CMOS devices such as short channel effects. Some of the recent innovations in reducing short channel effects and improved performance are through the introduction of FinFETs, nanowires, and high mobility channel materials. High mobility channel materials, such as Ge and III-V (InGaAs, GaAs), are attracting increasing interest due to the possibility of realizing increased performance even without scaling the gate length of the device (1-3). Ge is particularly attractive for use as a channel material for P-type MOSFETs due to its high hole mobility and Si VLSI high volume manufacturing compatibility. In this paper we report progress in high-k phase engineering through HfO2:ZrO2 doping combined with intermittent annealing and post deposition microwave plasma oxidation in order to achieve sub nm EOT with reasonable leakage. In this regard, 300mm epi Ge/Al2O3/ZrO2/TiN MOSCAP devices were fabricated using epitaxially grown Ge. We have utilized a TEL CertasTM Chemical Oxide Removal (COR) process (4), which uses anhydrous HF and ammonia, rather than traditional wet cleaning, to remove Ge native oxides without damaging or roughening the fragile Ge surface. The high-k stack Al2O3/HfxZr1-xO2 were deposited by atomic layer deposition on a TEL Triase +TM tool. The ALD HfxZr1-xO2 films were deposited using a cyclical deposition and annealing scheme (termed DADA) (5-6). Prior to the ALD HfxZr1-xO2 a thin ALD Al2O3 was deposited. An additional post microwave plasma oxidation was also carried out in situ. A post plasma Al2O3/ZrO2control sample with no DADA process was also fabricated. Figure 1 shows electrical leakage Jg vs equivalent oxide thickness (EOT). The electrical analysis show a scaled EOT of ~0.6nm with the combination of DADA and post plasma oxidation compared to the control sample with only post plasma oxidation processed, see Fig.1. In addition, DADA processed samples without additional post plasma oxidation (6) resulted in very high leakage. The impact of post plasma oxidation and DADA on the electrical and physical characteristics of the Hf based dielectrics will be discussed in detail.