Planarized Aluminum Deposition by High Temperature Evaporation

Improving step coverage and preferably providing a planarized top surface during the deposition process, is expected to improve the yield and reliability associated with metallization of vertical wall, large aspect ratio windows. In this paper, the evaporation of aluminum onto a heated substrate is used to fill and planarize topography. The final substrate temperature required to provide enough aluminum surface mobility for planarization is 450C. A final substrate temperature of about 400C provides a sufficient mobility enhancement to improve step coverage without planarization. In both cases, the initial deposition up to a thickness corresponding to the oxide depth is below 300C in order to reduce shadowing and to provide via filling while minimizing void formation. Typically, an additional 50% aluminum thickness is deposited while ramping the substrate temperature to 400-450C. Details of the evaporation system and process will be discussed.