The effect of bias-temperature stress on Na+ incorporation into thin insulating films

作者：Krivec Stefan; Buchmayr Michael; Detzel Thomas; Froemling Till; Fleig Juergen; Hutter Herbert^*

来源：Analytical and Bioanalytical Chemistry, 2011, 400(3): 649-657.

DOI：10.1007/s00216-011-4686-z

• Mobile ions
• Bias-temperature stress ToF-SIMS
• Barrier layers

The action of Na+ incorporation into thin insulating films and transport therein under influence of a bias voltage and temperature (BT stress) is the subject of this work. Deposited onto highly n-doped Si wafers, the insulators get BT stressed and subsequently investigated by means of time-of-flight-secondary ion mass spectrometry (ToF-SIMS). A thin PMMA film, spin-coated onto the insulator, serves as host matrix for a defined amount of Na+, provided via sodium triflate. Combining BT stress and ToF-SIMS depth profiling enables the unambiguous detection of Na+, incorporated into the insulating material. The insulators of interest vary in their nitride content: SiO2, SiOxNy, and Si3N4. For SiO2, it is shown that once a threshold BT stress is exceeded, Na+ gets quantitatively incorporated from PMMA into the underlying insulator, finally accumulating at the SiO2/Si interface. A quantitative assessment by combination of Butler-Volmer kinetics with hopping dynamics reveals activation energies of E (a) = 1.55-2.04 eV for Na+ transport in SiO2 with varying thickness. On the other hand, SiOxNy and Si3N4 films show a different Na+ incorporation characteristic in this type of experiment, which can be explained by the higher coordination of nitrogen and hence the reduced Na+ permeability within these insulators.

• 出版日期2011-5