A Highly Reliable Low Temperature Al-Cu Line/Via Metallization for Sub-Half Micrometer CMOS

Abstract

In this paper we present significant advances over the current art in terms of enhanced electromigration lifetime, low temperature deposition, and improved damascene capability of Al-Cu via/line structure. The electromigration data shows that Al-Cu via/interconnect structure deposited by a new low pressure sputtering process (LPS) results in at least “9X” better electromigration life time (t50) to that of conventionally used CVD W stud/Al-Cu interconnect structure. This significant improvement in the reliability may be attributed to the “breakthrough” in void-free filling of high aspect ratio (3 to 4) sub-half micrometer vias with low resistivity metal such as Al-Cu at as low temperature as room temperature. The LPS process eliminates the need of a collimator normally used to fill or coat the vias and improves throughput by factor of 5X at least compared to collimation. The extendibility of this technique beyond 0.25 µm contact geometries is demonstrated. The integration of the LPS process, Al-Cu via/interconnects using damascene process demonstrates a working 512 K SRAM chip with 0.5 µm minimum groundrules. © 1995 IEEE