Chun-Li Liu

Two-dimensional ultrashallow junction characterization of metal-oxide-semiconductor field effect transistors with strained silicon

Strained Si has been realized as one of the most promising candidates of next generation complementary metal-oxide-semiconductor technology. Since the carrier mobility can be significantly increased with strained Si lattice, the device speed can be further increased without reducing the critical dimensions. However, ultrashallow junction engineering becomes more challenging due to much complicated dopant diffusion behavior. We have used scanning capacitance microscopy and dopant selective etching to characterize such differences by comparing the devices fabricated with strained Si channel and with conventional unstrained Si. The devices we used are p-type channel complementary metal-oxide-semiconductor field effect transistors fabricated with 130 nm technology, with strained Si channel built on SiGe pseudosubstrate. Significant differences were observed in the formation of source/drain (S/D) extensions. The junction profile shows abrupt transition from S/D extension to S/D comparing with unstrained Si. Me...

Secondary ion mass spectrometry characterization of source/drain junctions for strained silicon channel metal–oxide–semiconductor field-effect transistors

As complementary metal–oxide–semiconductor (CMOS) devices approach the sub-100-nm dimensions in accordance with Moore’s Law, several major technical barriers exist with the formation of ultrashallow junctions. Strained silicon CMOS devices have the advantages of higher carrier mobility and high current drive. The use of silicon germanium substrates for strain in the silicon channel presents many challenges for CMOS integration including maintaining the channel strain and effect on shallow source/drain (SD) junctions. Low energy secondary ion mass spectrometry (SIMS) has been used to study boron and arsenic diffusion behavior in strained silicon and in SiGe. In addition, diffusion of germanium from the relaxed SiGe into the strained silicon layer will be discussed in relationship with SD implant and annealing. SIMS experimental results will also be compared to theoretical simulation results.