Electrical and structural properties of poly-SiGe film formed by pulsed-laser annealing

Abstract

Electrical and structural properties of polycrystalline silicon germanium (poly-SiGe) films fabricated by pulsed-laser annealing were investigated. Observation of laser-induced melt-regrowth of SiGe films using transient conductance measurement revealed that the melt depth and the crystallization velocity increased as Ge concentration increased. The increase of the crystallization velocity resulted in increase of the average size of crystalline grains from 66 to 120 nm at the laser energy density of 360 mJ/cm2 with increasing Ge concentration from 0 to 60%. The crystalline volume ratio obtained by reflectivity spectra in the ultraviolet region also increased from 0.83 to 1.0. Numerical analysis revealed that the density of electrically active defects decreased from 3.5×1018 to 1.1×1018 cm−3 as Ge concentration increased from 0 to 80%. The density of defect states of Si0.8Ge0.2 films were reduced from 3.5×1018 to 1.9×1018 cm−3 by 13.56-MHz hydrogen plasma treatment at 250 °C, 30 W, and 130 Pa for 30 s. However, the plasma treatment did not reduce the defect density for Si0.4Ge0.6 and Si0.2Ge0.8 films.

Electrical properties for poly-Ge films fabricated by pulsed laser annealing

“…The defect states were localized at grain boundaries, which distributed uniformly in the bandgap. The crystalline grain size was assumed as 126 nm for poly-Ge films and 50 nm for poly-Si films on the base of our previous investigation [10,11]. Analysis of experimental conductivity with different temperatures by the numerical calculation program gave the density of defect states in the bandgap.…”

Pulsed laser crystallization of silicon–germanium films

“…Amorphous Ge (a-Ge), a-Ge/a-Si, SiGe alloy and a-Si films were formed on quartz substrate at room temperature by methods of plasma sputtering and molecular-beam deposition in a high vacuum [13]. The aluminum-gap electrodes with a width and length of 0.14 and 0.2 cm were then formed by thermal evaporation.…”

“…Pulsed laser crystallization SiGe is therefore interesting in application to fabrication of TFT with a high carrier mobility. However, few researches have been reported on pulsed laser crystallization of Ge or SiGe films [12,13].…”

Electrical properties of phosphorus-doped polycrystalline germanium formed by solid-phase and metal-induced crystallization

“…For the successful integration of monolithic 3D-ICs, germanium (Ge) is considered as the channel material of transistors above conventional aluminum (Al) or copper (Cu) based interconnect layers because of its low melting point and high carrier mobility, enabling integration of high performance devices at low temperature which prevents the thermal degradation of bottom interconnect layers. In order to fabricate germanium on insulator (GeOI) structure at low temperatures for monolithic 3D-IC, various crystallization processes, such as solid phase crystallization (SPC), metal induced crystallization (MIC), and laser anneal, have been reported [1][2][3]. Up to present, the electrical properties including carrier type, concentration, and mobility were not clearly investigated in polycrystalline Ge (poly-Ge) films.…”