Secondary electron line scans over high resolution resist images: Theoretical and experimental investigation of induced local electrical field effects

The effects of the local electric fields generated during the e‐beam inspection of high resolution resist features at low voltage are discussed. A theoretical model based on the Monte Carlo technique was developed to simulate the effect of the induced electrical fields on the primary beam and on emitted secondary electrons. It is here proved that reentering secondary electrons act as a negative feedback to the local positive retarding field when at least one of the insulating materials of the sample being inspected has a secondary electron yield bigger than one. Such a recombination mechanism is more important than primary electron absorption, as this last factor takes place far from the escape depth layer. The positive charge compensation prevents the local positive field from growing as the number of line scans increases and allows the local field to reach stability. At the top of resist features, potential values as high as 40 V were found. Although the scanning electron microscope image is highly affe...