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VLSI Gate Dielectric TA <sub> 2 </sub> O <sub> 5 </sub> Study On Preparation And Characteristics Of Thin Films

Posted on:2009-03-04Degree:MasterType:Thesis
Country:ChinaCandidate:D T LuoFull Text:PDF
GTID:2208360245982528Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
With the fast development of VLSI (Very Large Scale Integration), high dielectric constant (high-k) materials have been drawing much attention for replacing conventional gate dielectric material-SiO2, which is reaching its physical limit. Tantalum pentoxide (Ta2O5) is a possible candidate because of its relatively high dielectric constant, low leakage current, high breakdown strength and process compatible.In this dissertation, Ta2O5 thin film was deposited by DC reactive magnet sputtering and annealed by RTA (Rapid Thermal Annealing). AFM (Atomic Force Microscope), XRD (X-ray Diffractometer), UVS (Ultraviolet and Visible Spectrophotometer), DST (Dielectric Strength Tester) were performed to investigate the phase composition, surface property, electrical and optical properties of Ta2O5 thin film.Research showed that the relationship between ignition voltage and sputtering pressure was according Paschen's Low. Deposition rate was decreased exponentially as increasing of oxygen flow ratio, and first increased then decreased as increasing of sputtering pressure, reached max at 0.3Pa. Surface of the Ta2O5 thin films was flat, compact and without any visible defect. Rq (Root-Mean-Sq) of as-deposied Ta2O5 thin film ranged from 0.488-2.579nm, which was related with deposition rate. Surface of film was improved when the annealing temperature below crystalline temperature of Ta2O5. As-deposited Ta2O5 thin film was amorphouse, a hexagonal structure (δ-Ta2O5) was identified after annealed at 800℃, another transition fromδ-Ta2O5 to low temperature orthorhombic structure (L-Ta2O5) occurred at 9001000℃.Ta2O5 thin film with a high transmission in visible spectrum was obtained. Index of refraction n was between 2.01-2.20, the order of magnitude of extinction coefficient k was 10-4, optical band gap and break strength ranged from 3.6-4.3eV and 2-4.5 MV/cm respectively. Dielectric constant of Ta2O5 thin film was increased from 24.3-26.5 after annealed at 800℃, then decreased at higher annealing temperature. The results showed that Ta2O5 thin film prepared by DC reactive magnet sputtering had good electrical and optical properties.
Keywords/Search Tags:high-k dielectric, Ta2O5 thin film, DC reactive sputtering, RTA, electrical properties
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