Overcoming Contact Resistance in Next-Generation Devices

As I explained in my previous post titled, Contact Resistance and its Role in Limiting Transistor Performance, tungsten (W) has been widely used in logic contact and local interconnect fill applications for its low resistivity and conformal bulk fill characteristics. But with interconnect dimensions now so small, contact resistivity is slowing transistor performance.

To relieve the contact resistance bottleneck, we developed the new Endura® Volta™ CVD W system to produce the industry’s first metal-organic, plasma-enhanced CVD W. This unique film performs the dual functions of the conventional TiN barrier and W nucleation layers, and can lower contact resistance by up to 90% depending upon critical dimensions and process flow (Fig. 1).

Fig. 1. By 10nm CD, the Volta W process lowers plug resistance almost 90% compared to standard flows.

The Volta CVD W film bonds strongly to dielectrics and prevents fluorine diffusion from the subsequent bulk deposition process. Its resistivity is more than 70% lower than that of TiN. Further, as the film is primarily W, it is an effective nucleation substrate for bulk W. By using this new single film to fulfill both barrier and nucleation functions, the total thickness of interface films is thinner and contact resistance is reduced (Fig. 2). 

Fig. 2. Replacing barrier and nucleation layers with the new CVD W film significantly lowers contact resistance.

By improving device power delivery, performance and efficiency, the Volta CVD W film extends W contact metallization for next-generation devices. Lower resistance also allows for more aggressive scaling at a given node, which will enable higher density devices.

In my next post, I’ll address the challenge of yield loss that accompanies contact scaling.

Visit our web site learn more about the Endura® Volta™ CVD W system.

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