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A model is proposed to describe the wetting and dewetting dynamics on a spinning wafer with a non-wetting surface. The model is based on the dynamic balance between the wetting and dewetting velocities. The proposed model predicts a theoretical lower limit for the media flow rate to completely wet a wafer surface as a function of the contact angle and wafer rotational speed. The model predictions are found to agree reasonably well with experimental results. The model is also used to develop a low flow process for the removal of titanium nitride. A 66% flow rate reduction is achieved in comparison with the baseline process.

In this work the damage added on gate stack features after batch megasonic cleaning is identified and classified by SEM review. To understand if damaging is a random or a clustered process, damage clustering distributions are compared with a theoretical random distribution of damage sites. In the damaged areas, defect clusters are observed that we explain by the presence of so-called weak spots in the neighborhood of a damaging event. Only a limited influence of the megasonic cleaning settings was found on the damage-size distributions. This suggests that, for the cleaning conditions investigated in this work, the number of added defects varied with the amount of the damage events but the event strength remains the same.

Cleaning technologies employing physical forces (such as megasonic and high-velocity-aerosol cleaning) are usually evaluated by comparing the particle removal efficiency on blanket wafers with damage formation on fragile structures, typically gate stack type structures. However patterned wafers provide a much more realistic cleaning challenge. Particle removal efficiencies from trenches in micrometer dimension have been evaluated using high-velocity-aerosol cleaning. When using short cleaning times, a large decrease in cleaning efficiency is found for even modest pattern dimension. By extending the cleaning time, cleaning efficiencies comparable to blanket-wafer tests can be reached. Moreover, batch megasonic cleaning shows a similar decrease in performance as high-velocity-aerosol cleaning.