Characterization of conductive filament rupture in Al:HfO2 high-k dielectrics.

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Metal–insulator–metal (MIM) capacitors are key components of advanced integrated circuits (IC). They are widely used to perform decoupling, filtering, or RF functions. They also play a central role in memory applications. These devices are generally built around high-k dielectrics such as HfO₂.

When high-k dielectrics are subjected to a constant stress voltage, conductive paths composed of oxygen vacancies are formed between the electrodes, leading to a low resistive state. Ultimately, this can lead to dielectric breakdown, i.e. the loss of the insulating properties.

The study aims to characterize the rupture of these conductive paths under the influence of the temperature to extract the diffusion constant and activation energy characterizing the diffusion of oxygen vacancies in Al-doped HfO₂. These learnings will strengthen the current understanding of high-k dielectrics degradation mechanisms.

The following activities are foreseen:

• Al:HfOx films will be degraded to a low resistive state by ramping the voltage until a given compliance current. The rupture of the filament will then be monitored at various temperatures.
• The kinetics of rupture for fresh and pre-stress structures will be compared.
• Several thicknesses & Al doping concentration will be studied.

• Data preparation and data analyses will be performed by the student.
• Finally, lifetime models will be developed to estimate the maximum use voltage and temperature for various mission profiles.