| AVS 54th International Symposium | |
| Electronic Materials and Processing | Friday Sessions |
| Session EM-FrM |
| Session: | Hf-based Dielectrics and Their Interfaces |
| Presenter: | S. Lee, North Carolina State University |
| Authors: | S. Lee, North Carolina State University G. Lucovsky, North Carolina State University L.B. Fleming, North Carolina State University J. Luning, Stanford Synchrotron Radiation Laboratory |
| Correspondent: | Click to Email |
There are two qualitatively different ternary alloy regimes with markedly different properties that are obtained by incorporation of nitrogen in the form of Si3N4 bonding into TM silicates. These differentiated by i) strain localization and/or strain percolation, and more importantly iii) strain reduction associated with chemical bonding self-organizations that reduce macroscopic strain by more than compensating reductions in alloy atom entropy. In order to realize strain minimization, compositional optimization by remote plasma process processing was utilized for deposition of Hf, Ti and Hf,Ti alloy Si oxynitride dielectrics. For example, the effect of Si3N4 content in (HfO2)x(Si3N4)y(SiO2)1-x-y pseudo-ternary alloys has been studied spectroscopically, and also shows systematic changes in electrical properties, including reduction of electrically-active traps, and minimization of tunneling leakage. Results from soft X-ray photoelectron spectroscopy (SXPS) valence band studies indicate no detectable hole traps for Hf Si oxynitrides with Si3N4 content ~35 - 40%, and with equal concentrations of HfO2 and SiO2, ~30-32%. These alloys show no evidence for chemical phase separation, as do Hf silicates, and other Hf Si oxynitride compositions. Optimized alloys are stable to at least 1100°C annealing. Derivative near edge x-ray absorption spectroscopy (NEXAS) comparisons for O K1 edges of HfO2 and optimized Hf Si oxynitride alloys display significantly decreases in electron trapping. The unique properties of optimized Hf Si oxynitrides are correlated with a four-fold coordination of Hf, in contrast with the 7-fold coordination of Hf in HfO2. C-V measurements indicate a dielectric constant of ~12 in optimized Hf Si oxynitrides, and a predicted value of 16-18 in Hf,Ti Si oxynitrides. Combined with low electron trapping similar to SiO2, and more than a 4 order of magnitude reduction in tunnel leakage, optimized TM Si oxynitride alloys are predicted to yield EOTs <1 nm, and possibly as low as 0.6 to 0.5 nm for aggressively scaled CMOS devices.