Cycle time improvement in manufacturing nitrided gate oxides for ULSI CMOS applications

The nitrided gate oxides fabricated using NH₃ and/or N ₂O have been the focus of significant interest as an alternative gate dielectric to conventional silicon dioxide in submicron CMOS devices. Improved resistance to radiation exposure, suppressed interface state generation under hot carrier stress, and improved barrier properties to boron diffusion are some of the reasons for this interest. Use of NH₃ in this application (ROXNOX) might be undesirable not only due to difficulties in optimizing process conditions, but also due to the high thermal budget and long cycle limes. As a substitute to the ROXNOX process, an N₂O-oxidation process (N₂O-oxide) was investigated. The oxides were grown in a vertical reduced pressure furnace using 200 mm wafers. In this work, the process control, material analysis, device fabrication, and electrical characteristics were studied The N₂O-oxide was found to be a promising alternative gate dielectric to the conventional oxide as well as ROXNOX. Cycle time for N₂O-oxides was significantly shorter when compared with ROXNOX process cycle time