Revealing Copper Contamination in Silicon after Low Temperature Treatments

Abstract

In this paper we address the problem of revealing copper contamination induced in the device region by the final part of the process. A method to reveal the effects of copper contamination is identified based on the recovery of MOS capacitors from deep depletion. In the presence of copper contamination carrier generation is dominated by surface generation, which is not surprising because copper is known to be prone to surface segregation. Copper segregation at the wafer surface was also confirmed by TOF-SIMS measurements. The measurements of surface generation velocity are non-destructive and the required structures can be easily integrated in device wafers. However, a recovery of the copper-related surface generation velocity with the time spent after the thermal treatment was observed. For this reason, it is important that the measurements are carried out in a short time after the thermal treatment responsible for copper segregation at the wafer surface.