ULSI RELIABILITY THROUGH ULTRACLEAN PROCESSING

The simultaneous fulfillment of three principles, viz. ultraclean wafer surface, ultraclean processing environment, and perfect process-parameter control, is the key to high-performance processes for realizing advanced subhalf-micron and subquarter-micron ULSI devices. The importance of the concept has been demonstrated by the experimental results of low-temperature silicon epitaxy by the low-kinetic-energy particle process. As a result of optimizing pertinent process parameters under ultraclean conditions, high-crystallinity silicon epitaxial layers have been successfully grown at temperatures as low as 250-degrees-C Advanced copper metallization for large-current driving interconnect formation has also been established. Giant-grain copper thin films also formed by low-kinetic-energy particle process exhibit very low resistivity as well as excellent reliability against electromigration failures. Employment of native-oxide-free processing allows us to form ideal metal silicon contacts without any alloying heat cycles. Ultraclean oxidation, which is characterized by native-oxide-free and surface-microroughness-free oxidation, has been confirmed to form high-quality very thin oxide films ranging from 5 to 10 nm with complete uniformity. A low-temperature annealing ion implantation makes practical a metal gate self-aligned MOS LSI, which is crucial for high-speed CMOS having high current driving capability. All of these advanced process technologies, realized for the first time by ultraclean technology, have made it possible to establish total low-temperature processing which is most essential for high-performance subhalf-micron and subquarter-micron ULSI.