High-Performance SiGe MODFET Technology

Abstract

An overview of SiGe modulation-doped field-effect transistor (MODFET) technology is provided. The layer structures and mobility enhancements for both p-and n-channel modulation-doped quantum wells are described and compared to mobilities in Si/SiO 2 inversion layers. Next, previous results on high-performance n-and p-MODFETs fabricated at IBM and elsewhere are reviewed, followed by recent results on laterally-scaled Si/SiGe n-MODFETs with gate lengths as small as 70 nm. We conclude with a discussion of the materials issues for the future vertical and lateral scaling of SiGe MODFETs.

Laterally scaled Si-Si/sub 0.7/Ge/sub 0.3/ n-MODFETs with f/sub max/>200 GHz and low operating bias

“…The observed improvement compared to Si MOSFETs at low drain bias is attributed to the higher mobility, which is about higher than standard Si-SiO inversion layers at similar densities [11]. The results agree qualitatively with the simulation results of [12], which predicted % higher velocity in strained-Si at an electric field equal to one-tenth of the saturation electric field for unstrained-Si.…”

“…A shallower quantum well will reduce the effect of fringing capacitance that can degrade , and also reduce the influence of the drain on the channel potential which leads to high output conductance. In addition, the utilization of p-well doping, or a buried insulating layer [11] will also be useful to control output conductance and off-state leakage, and allow further scaling of .…”

“…The relatively high output conductance of these devices is due to the fact that no p-well doping was utilized. Significant improvement in is expected by using a buried p-well layer, which can suppress the deep source-to-drain leakage current without degrading the channel mobility [11]. Despite the proximity of the gate to the source and drain implants, the gate leakage in these devices was very low.…”

Low-frequency noise in buried-channel SiGe n-MODFETs

“…The compatibility of SiGe MODFET processes with traditional silicon-based wafer manufacturing can provide high performance devices at low cost. Up to 5Â mobility enhancement has been obtained in SiGe MODFETs when compared to unstrained silicon surface channel MOSFETs [2]. Unlike III-V MODFETs, SiGe MODFETs have the ability to achieve complementary device topologies on the same wafer.…”

DC Performance and Low Frequency Noise in n-MOSFETs using Self-Aligned Poly-Si/SiGe Gate

“…Recently, local technique to overcome the problem of growing Poly-Si undoped layer and Si/SiGe undoped layer structures (9) were reported. The literature shows a technique by growing Si/SiGe modulation-doped layer structures on implanted p-type buffer layers (10). This technique for MODFET device structure is a Si/SiGe channel design and it is more complex than a technique for MOSFET structure with a poly-Si/SiGe gate design.…”