2.4 Simulation of an AVC Scan

The simulation of an AVC scan is divided into several steps. First the parameters of the MINIMOS-NT AVC models for the injected electrons and the generated electron-hole pairs have to be determined. This has been done by Monte Carlo simulations with the program SESAME [15]. The input data for these simulations are the primary electron energy and the beam diameter. From this simulation the standard deviations for lateral and vertical direction, $\sigma_{\mathrm{l}}^{}$ and $\sigma_{\mathrm{v}}^{}$ respectively, and the vertical distance of maximum of the distribution from the surface $\mu_{\mathrm{v}}^{}$ are extracted. As explained in the previous section these parameters can be used for a range of primary energies and beam diameters without loss of accuracy.

With these parameters a series of device simulations with varying position of the electron beam is performed. From the result of these simulations the surface potential at the position of the electron beam is extracted. The extracted potential values form the AVC potential $\varphi_{\mathrm{AVC}}^{}$.

The second derivative of the extracted AVC potential $\varphi_{\mathrm{AVC}}^{}$ can then be calculated and compared to the known position of the pn-junction. From this comparison the maximum beam current can be determined which guarantees that the shift of the position where the second derivative equals zero from the junction position due to the injection of carriers is negligible.