Electrical properties of 0.1 μm and Sub-0.1 μm single-drain and LDD MOSFETs from room to liquid helium temperatures

LDD MOS transistors are very useful in order to reduce short channel and hot carrier effects in the deep submicron range. However, the driving current can be very low compared with singledrain (SD) devices due to the influence of the source-drain series resistance [1], On the other hand, low temperature operation is very attractive for the improvement of device performances in the case of single-drain transistors [2]. Nevertheless, freeze-out effects in the lightly doped regions in the case of LDD MOSFETs are supposed to alter significantly the benefits of a reduction in temperature. A recent study has shown that long channel LDD devices can operate at low temperature due to field assisted impurity ionization in the LDD's [3]. Therefore, it is very valuable to evaluate and to compare the electrical properties of very short channel devices with LDD and SD structures in a wide temperature range. We show in this paper that low temperature operation is also very promising for the optimization of the performances of sub-0.1 fxm LDD MOSFETs. A thorough investigation of the electrical characteristics between room and liquid helium temperature allow us to gain insight in the various physical mechanisms involved in the strong improvement of the performances of these MOS transistors in various temperature ranges. Moreover, the kink effect and the substrate current are also analysed as a function of temperature for SD and LDD devices in the deep submicron range.