Investigation of direct tunnel gate oxides fabricated by rapid thermal processing for metal oxide semiconductor field effect transistor applications

Channel lengths of the metal oxide semiconductor field effect transistor (MOSFET) are estimated to scale down to the 50 nm channel length regime by the year 2000. The gate oxide thickness is estimated to scale down to 1.5 nm for the 100 nm channel length generation and below 1.0 nm for the 50 nm generation. Conventional furnace oxidation may not be capable of controlling the oxidation process below the 2.0 nm regime. Rapid Thermal Processing (RTP) is an attractive technique that offers the advantage of shorter cycle times and higher oxidation temperatures. Two RTP oxidation processes have been investigated for direct tunnel gate oxide applications. One process was the conventional oxidation reaction via Rapid Thermal Oxidation (RTO) and the second was Rapid Thermal Chemical Vapor Deposition (RTCVD) of oxide. Both techniques were investigated as candidates for fabricating a high quality, robust, direct tunnel oxide. Process conditions capable of thermally fabricating 1.0 nm oxides were demonstrated. The quality of the oxidation recipes were evaluated with leakage currents, mobility and breakdown measurements on n-channel MOSFETs for gate oxide thicknesses down to 1.4 nm. Experimental gate leakage currents and an oxide breakdown model are used to demonstrate gate oxide scaling limitations due to power consumption and failure for advanced MOSFET integrated circuits.