Process integration and performance evaluation of Ge-based quantum well channel MOSFETs for sub-22nm node digital CMOS logic technology
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Since metal-oxide-semiconductor (MOS) device was first reported around 1959 and utilized for integrated circuits in 1961, complementary MOS technology has become the mainstream of semiconductor industry. Its performance has been improved based on scaling of dimensions of MOS field-effect-transistors (MOSFET) in accordance with Moore’s law, which states that the density of MOSFETs due to scaling approximately doubles every two years. Entering into sub-100nm regime caused a lot of challenges. Traditional way of scaling no longer provided performance enhancement of individual MOSFETs. Increased channel doping which is required to prevent degradation of device electrostatics from short channel effects caused carrier mobility degradation. New inventions needed to be incorporated to sustain performance enhancement trend with scaling. Implementation of process induced strained Si technology allowed mobility enhancement, and high-K/metal gate instead of conventional poly-Si/SiO2 allowed continuing electrical gate oxide thickness scaling, hence extending the life span of Moore’s law. As we are now moving toward 22nm logic technology and below, new concerns have been rapidly aroused. Controlling power consumption and performance variability are becoming as important as developing scaled devices with enhanced performance. Expandability of strained-Si channel technology via process induced strain also faces increasing complexity from ever tighter gate pitch and difficulties in controlling defect level with the channel stress enhancement techniques. At the same time, long-lasting planar MOSFET architecture also faces serious challenges due to the limits of controlling short channel effects. New paradigms and pathways for future technology seems to be required. As a result, new material sets, new device architectures and concepts are being vigorously explored in the literature. These new trends can be categorized into three groups: MOSFET structure with (non-Si) high mobility channel materials, advanced (non-planar) MOSFET structures, and MOSFET-type structures with new device operation concepts such as tunneling FETs. This dissertation presents research on high mobility channel MOSFET structures (planar and non-planar) using group IV material (mainly SiGe) for enhanced performance and reduced operating power. This work especially focuses on improving the performance of short channel device performance of SiGe channel pMOSFETs which has long been researched yet clearly demonstrated in literature only recently. To reach the goal, novel processing technologies such as millisecond flash source/drain anneal and high pressure hydrogen post-metal anneal are explored. Finally, performance dependence on channel and substrate direction has been analyzed to find the optimal use of these SiGe channels. This work describes an exciting opportunity of weighting the possibility of using high mobility channel MOSFETs for future logic technology.