Wai Lo

Deposition and Characterization of Polycrystalline Si1 − x Ge x Films for CMOS Transistors Gate Electrode Applications

Polycrystalline Si 1 - x Ge x (poly-SiGe) is a known gate electrode material that can mitigate poly-depletion effects, which exist in deep submicrometer complementary metal-oxide-semiconductor (CMOS) transistors, due to its lower dopant activation temperatures and smaller bandgaps. As an important step toward the manufacturing of poly-SiGe electrode-based CMOS transistors with enhanced performances, this study focuses on the deposition of poly-SiGe films with different structural features and the characterization of the physical properties of these films. The electrical performance and the reduction in poly-depletion effects of the poly-SiGe electrodes in capacitors fabricated using these films were verified using capacitance-voltage measurements.

Process Characterization and Control of Polycrystalline SiGe as the Gate Electrode in CMOS Fabrication

Polycrystalline Si 1 - x Ge x (poly-SiGe) films have been proposed as a promising alternative to the currently employed polycrystalline silicon (poly-Si) gate electrode for complementary metal-oxide-semiconductor (CMOS) field effect transistor technology due to lower resistivity, less boron penetration, and less gate depletion than that of poly-Si gate. The use of Poly-SiGe as the gate electrode, however, has serious implications on transistor fabrication processes such as plasma dry etching, resist ashing, wafer cleaning, and oxidation. In this work, we investigate the impact of these processes on the polycrystalline Si 1 - x Ge x profile and the critical dimension (CD) of the gate electrode. The process improvements and an integration scheme using an oxide liner are presented to minimize the profile and CD variations introduced by the fabrication processes.