Phenomena of n-type metal-oxide-semiconductor-field-effect-transistors with contact etch stop layer stressor for different channel lengths

In this paper, n-type metal-oxide-semiconductor-field-effect-transistors (nMOSFETs) combining contact etch stop layer (CESL), SiGe channel, and Si-cap have been fabricated. The simulation results and electrical properties have also been investigated and indicated that the CESL type (tensile or compressive) or channel length (short or long) has a significant effect on the stress distribution of the channel. This is important because the stress in the channel region affects the carrier mobility and therefore the device performance. In order to verify the simulation results, the electrical properties such as mobility and output characteristics have been measured. According to the output characteristics, as channel length is 0.11 μm, the tensile CESL can enhance the performance of nMOSFETs. However, the improved trend is inverted when the channel length increases. On the other hand, we have also compared the threshold voltage (Vt) roll-off and subthreshold swing (SS) for different structures. The results show that the devices exhibit a worse Vt roll-off when CESL is adopted and SS degrades more when compressive stress is induced in the channel.