|AVS 55th International Symposium & Exhibition|
|Plasma Science and Technology||Friday Sessions|
|Session:||Plasma-Surface Interactions in Materials Processing II|
|Presenter:||J.L. Shohet, University of Wisconsin-Madison|
|Authors:||J.L. Shohet, University of Wisconsin-Madison
J.L. Lauer, University of Wisconsin-Madison
G.S. Upadhyaya, University of Wisconsin-Madison
Y. Nishi, Stanford University
|Correspondent:||Click to Email|
The integration of high-k/metal gate stacks into CMOS technology poses several integration problems for the microelectronic industry. The metal gate electrode is often deposited on the high-k dielectric using plasma-sputter deposition; as a result, the high-k dielectric will be directly exposed to the plasma during metal-gate deposition. Plasma-induced charging damage from energetic electrons, ions, and photons has been found to degrade the electrical characteristics and reliability of the gate dielectric. In this work we use synchrotron radiation to determine the role that VUV radiation has in the production of electron-hole pairs created in HFO2 dielectrics on Si wafers with conductivities of 1000 and 4000 Ohm-cm. We determined the general valance band structure of the HfO2 dielectrics in the photon energy range of 5 and 30 eV. Since Argon is the feed gas most often used in plasma sputter deposition we determined the response of HfO2 films with thicknesses between 4 and 20 nm to the Ar-I emission line at 106.6 nm (11.6 eV), which is often the most intense emission line from an Ar plasma. After the dielectrics are irradiated with VUV, we measured the surface potential as a function of position across the irradiated region with a Kelvin probe. By measuring the surface potential for various thicknesses we are able to separately determine the density of surface and interface trapped charge. From the trapped charge densities we estimate the voltage across the dielectric during irradiation with the use of a mathematical model. By combining the current measurements with the estimated voltage across the dielectric we can determine the conductivity of the dielectric layers as a function of photon flux density. In addition, we determine the effect of annealing temperature of HfO2 dielectrics as a function of total photon dose and compare the results to that of SiO2 films of similar thickness. There appears to be a correlation between the VUV-induced current density and annealing temperature with the total-induced charge measured after VUV irradiation.
Supported by the National Science Foundation under Grant Number DMR-0306582 and the Semiconductor Research Corporation under Contract Number 2008-KJ-1781. The Synchrotron Radiation Center is funded by the National Science Foundation under Grant Number DMR-0537588. *G.S. Upadhyaya present address: Lam Research Corporation, Fremont, CA.