Chemistry of Materials

Area-Selective Deposition of Tantalum Nitride with Polymerizable Monolayers: From Liquid to Vapor Phase Inhibitors

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Area-selective depositions (ASDs) exploit surface reactivity differences to deposit a material on a desired growth surface. This chemically driven process produces a reflection of the prepattern, commonly, through the use of either atomic layer deposition (ALD) or chemical vapor deposition (CVD). The ASD of TaN may offer significant benefits in device fabrication. For instance, in silicon technologies, this offers the ability to lower the resistivity between metal interconnect levels and therefore to reduce stage delay (RC delay). However, the deposition of TaN thin films in an area-selective manner is challenging due to the temperature requirements for a high-quality ALD film, which may exceed the thermal stability of typical organic surface modifications. We report on the synthesis of an organic inhibitor that incorporates a thermal/photoreactive diyne moiety to enable cross-linking of the inhibitor film and subsequent use in a selective TaN process, which was maintained over a large process window, during the 300°C TaN ALD process. On patterned substrates, up to 3.8 nm of a TaN film could be deposited on SiN or mesoporous SiCOH without detectable Ta amounts on either a Cu or W surface. The same concept of cross-linking the inhibiting layer was also applied to a reactive vapor-phase inhibitor, propargylamine, found to inhibit TaN, though with a narrower process window (on blanket films). On via patterns, this selective TaN process was achieved but exhibits a distinct tapered profile. The methods described demonstrate the compatibility of several reactive inhibitors to enable the selective deposition of TaN at an ALD temperature compatible with many device fabrication schemes.