A Study on the Role of Pre-Cleaning and a New Method to Strengthen Gate Oxide Quality.

Abstract

Isopropyl alcohol (IPA) has been conventionally used for pre-cleaning processes. As the device size decreased, the gate oxide layer became thinner. As a result, the quality of the gate oxide was degraded by a pre-cleaning process, and oxide reliabilities and product yield were affected. In this study, we investigate whether the carbon generated on the silicon interface after the IPA drying process might have induced gate oxide breakdown. Time-dependent dielectric breakdown (TDDB) failure increased in frequency since carbon contaminations were increased in the oxide according to the amount of IPA. Organic contaminations resulted in a lower energy level, and electron tunneling occurred through the gate oxide. When an external electric field was applied, organic materials in the gate oxide layer were aligned, and a percolation path formed to cause breakdown. Finally, we suggest a new cleaning method using carbon-free O3 deionized (DI) water as a dry-cleaning method to improve oxide dielectric breakdown. An O3 DI dry cleaning process could reduce carbon particles in the oxide layer and decrease gate oxide failure by 7%.