In-situ Monitoring System Equipped with FT-IR and QMS and Thermal Decomposition of Zr(NCH3C2H5)4 Precursor
Authors: Park In-Sung , Seong Sejong , Jung Yongchan , Lee Taehoon , Ahn Jin-Ho , An Jong-Ki , Yun Juyoung 
Published: February 2020

ZrO2 have been widely used as dielectric layers in metal–insulator–metal and metal-oxide-semiconductor capacitors, charge trapping layers in non-volatile flash memory devices, and insulating layers in resistive switching memory devices owing to their high dielectric constant and good insulating property. For application in the aforementioned semiconductor devices, the ZrO2 films have been prepared on semiconductor or metal substrate by an atomic layer deposition (ALD) method. In the ALD process, the film grows through a unique surface reaction between the vaporized precursor and reactant, since both reagents are alternately supplied onto each substrate surface. The choice of proper metal precursor is very crucial for a successful ALD process. The main requirements of metal precursors are high vapor pressure at its supplying temperature, no self-decomposition at the process temperature, and an aggressive reaction with the ligands on the surface. Generally, the chemical qualities of metal precursor kept at high temperature should not be degraded with time elapse to maintain the constant qualities of the grown films. However, studies on time dependent quality variation or quality monitoring of precursor have been little reported.

In this work, the time-dependent thermal stability and chemical properties of Zr precursor, (CpZr(N(CH3)2)3, have been monitored and investigated using FT-IR, TGA, DSC and NMR analysis with time variation. The influence of metal precursor on material and chemical properties of grown ZrO2 films with time elapse also analyzed with growth rate, XPS, AES. Finally, electrical properties of metal-oxide-semiconductor capacitors with ALD-ZrO2 film have been also analyzed using C-V and J-V measurements.

Liquid CpZr(N(CH3)2)3 shows a high vapor pressure and is evaporated smoothly less than 1% residue between 150℃ and 200℃. After precursor boiling at high temperatures of 80-120℃ for 4 weeks, TG, NMR, and FT-IR analyses were performed. It is observed that there is little variation and peak transition, meaning the stable thermal properties of precursor with time elapse. For example, in FT-IR measurement, the peaks are detected such as CH3 symmetric stretch, N-CH3 symmetric stretch, CH3 deformation, CH3 vibration, and NC2 symmetric stretch. Each relative amount ratio of each peaks is constant with time elapse.

The precursor of CpZr(N(CH3)2)3 was supplied into ALD chamber at 40°C and ZrO2 films were atomic-layer-deposited at 300°C with H2O. The compositional analyses of ALD-ZrO2 were performed with elapsed time. ALD-ZrO2 thin films show no transition of peaks of Zr 3d and O 1s and no variation of area ratio each peak with time-elapsed precursor.

To measure electrical properties of ZrO2 film, metal-ZrO2-Si capacitors were fabricated and C-V and J-V analyses were performed. The electrical properties were traced for 8 weeks without serious change of their characteristics of CET and leakage current density.