Paper EM-WeM3
Characterization of High-k Dielectric and Metal Gate Film Stack by AR-XPS

Wednesday, October 22, 2008, 8:40 am, Room 210

The implementation of a higher-k hafnium-based dielectric coupled with an atomically engineered oxynitride interface addresses gate leakage while maintaining high mobility. In conjunction with the new dielectric stack, metal gates are replacing polysilicon gate electrodes for material compatibility and performance. Devices made with high-k/metal gates can achieve >100x improvement in gate leakage, with significantly greater switching speed. The desirable properties of the dielectric High-K layer are : high dielectric constant; low leakage current; and thermal stability against reaction or diffusion to ensure sharp interfaces with both the substrate Si and the gate metal . Extensive characterization of such materials in thin-film form is crucial not only for the selection of alternative gate dielectrics and processes, but also for the development of an appropriate metrology of the high-k films on Si. This paper will report recent results on structural and compositional properties of Al2O3 deposited on 20A ALD HfO2 / 8A SiO2 . This stack was capped with 20A TiN . Angle-resolved XPS showed that after the high temperature anneal Al diffused into the dielectric stack with its concentration peaking at the HfO2/SiO2 interface and some remaining at the HfO2 surface. No Al was detected near the Si substrate interface suggesting that the insertion of Al2O3 cap layer at the high-k/metal gate interface and subsequent high temperature process should not degrade the device channel mobility. The AR-XPS and the TEM results are compared to the electrical data.