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Among several potential materials, HfO2 is a promising candidate as an alternative gate dielectric for future CMOS devices in terms of its thermodynamic stability on Si and high dielectric constant (~25) [1]. Since the required equivalent oxide thickness after the 65 nm node era will be less than 1 nm, it is important to establish a reliable technique to fabricate and control such ultrathin films with atomic-scale precision. Pulsed-source metal-organic chemical vapor deposition (PS-MOCVD) is a potential technique to deposit the ultrathin films with good surface coverage and with large area uniformity. Furthermore, in situ optical growth monitoring technique was chosen for good reproducibility and good throughput [2]. In this paper, the preparation of HfO2 thin films by PS-MOCVD, combined with in situ ellipsometry monitoring of film growth, is discussed. 2. Experimental P-type Si (100) wafers were used as substrates. Hf[N(CH3)2]4 was used as the source for hafnium and was introduced to the chamber by Ar carrier gas. O2 gas was used as the oxidizing agent. The hafnium compound and oxygen were supplied alternatively. Ar purge gas was supplied between Hf source and O2. The supply durations of source-carrying Ar (ts), O2 (to), and Ar purge gas (tp) were important parameters, which were varied in these experiments. Total pressure in the reaction chamber during deposition was held at 1.5 Torr. The substrate temperature was maintained at 300 o C. In situ ellipsometry measurements were performed using a commercial ellipsometer which was attached to the reaction chamber. The time evolution of two different ellipsometry angles, ∆ and Ψ, was recorded simultaneously during deposition. We focused on ∆ only because the change of Ψ during a deposition was negligible. MIS diode structure using Al electrodes was fabricated for measurements of C-V and J-V characteristics.

Pulsed-source MOCVD HfO2 ultrathin film growth optimized by in situ ellipsometry monitoring