An Assessment of the Location of As-Grown Electron Traps in /HfSiO Stacks

Replacing SiON by high-kappa layers is a pressing issue for CMOS technologies. The presence of as-grown electron traps in HfO₂ is a major obstacle, since they can induce threshold-voltage instability, reduce electron mobility, and result in early breakdown. Their location has not been clarified and is addressed in this letter. By selecting test conditions carefully and using samples with a progressive reduction of HfO₂ thickness, the authors are able to rule out that traps are piled up near the HfO₂/HfSiO interface. A uniform distribution throughout HfO₂ does not agree with the test data, either. Results support that trapping is negligible near to one or both ends of the HfO₂ layer when compared with trapping in the central region