Al planarization technology for application in quarter micrometer devices was explored. High temperature flow process as well as two-step cold/hot sputtering processes were investigated. Quarter micrometer contacts of dept 1.2 mu m were successfully filled by two-step cold/hot sputtering. Multilayer structures were planarized, yielding via resistance (<0.6 Omega) lower than those of metallization based on tungsten-plugs. The key factors for reliable filing of contacts are a low base pressure, adequate coverage of the wetting layer (titanium) and continuous coverage of the first nucleation layer in the contacts. A low temperature (450 degrees C) process was demonstrated. Aluminum deposited onto titanium results in a high surface reflectivity (210%. normalized to bare Si at 436 nm). In comparison with the flow process, the two-step cold/hot sputtering process showed a unique advantage in that it was able to fill high aspect ratio contacts at low temperature.