Abstract
A cleaning process using anhydrous HF (AHF)/methanol and ozone is carried out in a STEAG-AST Vapor Phase Cleaning module (VPC). This module is integrated in a state-of-the-art cluster tool also consisting of a STEAG-AST Rapid Thermal Oxidation module (RTO). The dependence of AHF vapor phase etch rate of thermally grown silicon dioxide on different process parameters, such as etch time, AHF-flow, and temperature is evaluated. The optimized etch process is found to be at a temperature of 40°C and at a pressure of 50 mbar for this VPC module. Using the above etch parameters various combinations of vapor phase surface preparation chemistries combining AHF etching and ozone/UV cleaning are evaluated.
To demonstrate the feasibility of this cluster tool for advanced gate dielectric formation, 4.0 nm thin oxide is grown directly after the cleaning in the RTO module without breaking the vacuum. Time dependent dielectric breakdown results for oxides pre-oxidation-cleaned in AHF, and in AHF followed by ozone are compared to a reference sample without any dry pre-oxidation cleaning. It can be shown, that the cleaning in AHF with a subsequent ozone step at 200°C under UV light leads to improved breakdown characteristics compared to AHF/methanol cleanings without such subsequent ozone/UV step or conventional wet cleaning using HF-Dip.
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Acknowledgement
The authors would like to thank Silke Paul and Matthias Beichele for assistance in preparing the samples, and Igor Kasko and Richard Oechsner for helpful discussions.
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Froeschle, B., Deutschmann, L., Bauer, A.J. et al. Characterization of Oxide Etching and Wafer Cleaning using Vapor-Phase Anhydrous HF and Ozone. MRS Online Proceedings Library 470, 237–242 (1997). https://doi.org/10.1557/PROC-470-237
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DOI: https://doi.org/10.1557/PROC-470-237