The present invention provides methods for depositing a tungsten nitride layer on a substrate, where the methods provide good tungsten nitride adhesion to the substrate, fine control over deposition thickness, and good step coverage over high aspect ratio regions of the substrate. To accomplish this, the invention provides a pulsed nucleation layer method for depositing tungsten nitride. Generally, the invention employs at least the following operations (performed in various orders): (i) providing a layer of reducing agent on a substrate surface, (ii) contacting the substrate surface with a tungsten containing precursor to form a tungsten layer on the substrate, and (iii) nitriding the tungsten layer to form tungsten nitride.

 

In many cases, the substrate is a semiconductor wafer or a partially fabricated semiconductor wafer. Applications of the invention include using tungsten nitride as (or as part of) a copper diffusion barrier, a gate electrode, a capacitor electrode, and a diffusion barrier and/or adhesion layer in tungsten plugs, a sacrificial hard mask for use in dual damascene copper interconnect formation, and a light shield for CCD devices. Of course, the invention can be used in other applications requiring high-quality tungsten nitride layers. In many of these applications, the tungsten nitride is deposited at least partially over a dielectric material.

 

In some preferred embodiments, the reducing agent is a boron-containing agent, preferably a borane such as diborane (B2H6). The borane reducing agent may be introduced as a gas phase reactant that decomposes on the substrate surface, creating a boron containing “sacrificial layer.” Preferably, this sacrificial layer is between about 3 and 20 angstroms thick and deposited at a temperature between about 200 and 400 degrees C.

 

 

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