3.1.2 Source and Drain Doping

The source and drain doping profiles are modeled using Gaussian functions which will be described in Section 3.1.5. They are shown in Fig. 3.3 for Device Generation A and Device Generation B. The maximum impurity concentration at the surface is 10$^{20}$ cm$^{-3}$. The exact values of the junction depths depend on the substrate background doping. Rough values are 50-120 nm for the 0.25 $\mu$m device and 20-48 nm for the 0.1 $\mu$m device.

Figure 3.3: The source and drain doping profiles in units (cm$^{-3}$) for Device Generation A (top) and Device Generation B (bottom).

The shallow source/drain implants of Fig. 3.3 are usually called ``source/drain extensions'' or just ``tips''. Additional deep source/drain implants normally used to reduce the series resistance and to provide a good interface to the contacts are not taken into consideration in this work since a proper design of deep source/drain implants implies that they do not significantly affect what happens in the channel region of a MOS transistor.