AL PLANARIZATION PROCESSES FOR MULTILAYER METALLIZATION OF QUARTER MICROMETER DEVICES

Al planarization technology for application in quarter micrometer devi ces was explored. High temperature flow process as well as two-step co ld/hot sputtering processes were investigated. Quarter micrometer cont acts of dept 1.2 mu m were successfully filled by two-step cold/hot sp uttering. Multilayer structures were planarized, yielding via resistan ce (<0.6 Omega) lower than those of metallization based on tungsten-pl ugs. The key factors for reliable filing of contacts are a low base pr essure, adequate coverage of the wetting layer (titanium) and continuo us coverage of the first nucleation layer in the contacts. A low tempe rature (450 degrees C) process was demonstrated. Aluminum deposited on to titanium results in a high surface reflectivity (210%. normalized t o bare Si at 436 nm). In comparison with the flow process, the two-ste p cold/hot sputtering process showed a unique advantage in that it was able to fill high aspect ratio contacts at low temperature.