Stress-enhancement in free-standing Si pillars through nonequilibrium dehydrogenation in SiN:H stress-liners by ultraviolet light irradiation

Tensile-strained Si pillars are desired to achieve three-dimensional (3D) transistors with high speed. Effects of ultraviolet (UV) light irradiation on tensile strains in Si pillars covered with SiN:H stress-liners are investigated as a function of the wavelength (172-436 nm). Tensile-stress enhancement is found at specific wavelengths (200-330 nm) under low-temperature heating (400 deg. C), where dehydrogenation in SiN:H is clearly detected by infrared absorption measurements. On the other hand, equilibrium dehydrogenation by high-temperature heating (>700 deg. C) without UV-irradiation does not cause tensile-stress enhancement. This nonequilibrium dehydrogenation at low temperatures opens up possibility of 3D transistors with high carrier mobility.