A new damascene structure for submicrometer interconnect wiring

A damascene structure for forming high-density interconnect wiring is presented. The structure results in improved open and short yields, lower sheet resistances, and comparable contact/via resistances, and it shows excellent filling of high-aspect-ratio long lines with high copper content. The key aspect of this technique is the ability to combine soft, low-resistance metal (Al alloy, Cu alloy, etc.) deposited by physical vapor deposition (PVD) with a hard metal (W) deposited by chemical vapor deposition (CVD) with high wear resistance. As a result a structure with a good polish stop, better alloying capability, and high yields can be fabricated while maintaining planarity at all levels. This structure is applied to a dense 512 K SRAM design with 0.5 mu m minimum ground rules, resulting in improved yield of partially functional chips at second-level metal compared to the conventional reactive ion etching (RIE) structure.<
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