The Characteristics of Hafnium-Based Thin Film by Sol-Gel Spinning Techniques with Different Post Annealing Temperatures Treatment

• Main Authors: Liu, Yi-Jung, 劉伊容
• Other Authors: Lei, Tan-Fu
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/28010987800274279215

碩士 === 國立交通大學 === 理學院IC製程化學產業專班 === 97 === The scaling of silicon-based microelectronics devices has led to large leakage current of the silicon dioxide layer as a gate dielectric. It is necessary to replace the SiO2 with high dielectric constant (high-κ) oxides. The sol-gel method has attracted attention as a low temperature route to oxide materials. Facile film fabrication is possible with low operation costs and simple facilities. Using hafnium chloride (HfCl4) source by the surface sol-gel method, a gel is a solid material network containing a liquid component. Hafnium(IV) tetrachloride (98% Aldrich) and ethanol (≥99.8%Fluka) were used without further purification. The precursor solution was prepared by dissolving HfCl4 in ethanol stirred for 10min, then 1-hexanol was added slowly and the mixture was stirred for 10min at room temperature. The molar ratios of the components were: HfCl4: EtOH: CH3(CH2)5OH = 1: 80: 10. The molar ratio of the sample has the better performance. The surface and structural and electric properties of sol-gel derived HfO2 films have been investigated. The water droplet contact angles reached constant values between 80 and 100° after the films were left for 1-4 days in air at ambient temperature, indicating that the film surface exhibited hydrophobicity. Hydrophobicity was maintained even after the films were treated with organic solvents. Scanning electron microscopy observation showed that the film surface was smooth and uniform. The HfO2 in the films crystallized to the monoclinic phase at post deposition annealing temperatures between 500 and 550°C and no other phases were observed to 800°C. The refractive index and optical gap of the films were 1.88-1.93 and 5.1 eV, respectively. It is established from the preceding results that the surface sol-gel process enables solution-based fabrication of high quality HfO2 films. The surface sol-gel process, as based on chemical sorption of precursor materials, is particularly suitable for maintaining nano-film uniformity over a wide surface area. In contrast, formation of amorphous nano-films by spin-coating leads to nano-grains and less-homogeneous metal oxide network and inferior electrical properties. In this thesis, the improved characteristics of hafnium dielectrics with rapid thermal annealing are investigated. Based on the experimental results, the rapid thermal annealing can effectively improve the reliability and quality of hafnium dioxide owing to the elimination of traps in the dielectrics and interfacial layer between HfO2 and SiO2. Besides, we report the temperature dependence of gate leakage current by way of the data result analysis is F-P tunneling. The electric field dependence of gate leakage current by way of the data result analysis is F-N tunneling. We have fabricated a Al/HfO2/SiO2(IL)/Si/Al gate stack capacitor during the different annealing temperature for OFET application.