Multi-step aluminum planarization process

Summary form only given. A major prerequisite for voidless planarization is the initial formation of a smooth continuous aluminum film on the walls of the vias. Thermal control diffusion length can then be used to transport metal from the top surface into the features. This has been achieved using a high throughput, multistep process on an ECLIPSE sputtering system. The initial substrate temperature determines the film thickness requirements for complete film coalescence. A smooth continuous film can be produced within the first step 250 Å if deposited below 200°C. At higher temperatures a continuous film may not be formed until a much larger amount of aluminum is deposited, and shadowing of the opening may occur before via filling can be done. Once the continuous coating is formed, wafer temperature is elevated to a level where surface mobility is greatly enhanced: typically between 400°C and 500°C