Solid phase crystallization of amorphous Si1−xGex films deposited on SiO2 by molecular beam epitaxy

Abstract

We have investigated solid phase crystallization behavior of the molecular beam epitaxy grown amorphous Si1−xGex (x=0 to 0.53) alloy layers using x-ray diffractometry and transmission electron microscopy (TEM). Our results show that the thermal budget for the full crystallization of the film is significantly reduced as the Ge concentration in the film is increased. In addition, we find that a pure amorphous Si film crystallizes with a strong (111) texture while that of the Si1−xGex alloy film crystallizes with a (311) texture suggesting that the solid phase crystallization mechanism is changed by the incorporation of Ge. TEM analysis of the crystallized film shows that the grain morphology of the pure Si is an elliptical and/or a dendrite shape with a high density of microtwins in the grains while that of the Si0.47Ge0.53 alloy is more or less equiaxed shape with a much lower density of defects. From these results, we conclude that the crystallization mechanism changes from a twin-assisted growth mode to a random growth mode as the Ge concentration in the film is increased.

Microscopic studies of metal-induced lateral crystallization in SiGe

“…Such a morphology is quite similar to that of Si 0.47 Ge 0.53 crystallites obtained by the solid phase crystallization ͑SPC͒ process. 16 It should be noted that, the growth rate of SiGe crystals obtained by the present MILC process are almost comparable with that by the SPC. Consequently, we can conclude that needlelike crystal growth initiates, then the nucleation of SiGe crystals take place around them, and finally they grow by SPC process forming long rod-shaped poly-SiGe.…”

Nanostructured SiGe thin Films Obtained Through MIC Processing

“…All observed peaks can be allocated to crystalline Si 80 Ge 20 . The crystallization temperature of SiGe is reported to be around 650 °C varying with composition and annealing conditions [23]. But as crystalline SiGe was already detected at an annealing temperature of 400 °C, the occurrence of MIC is clearly demonstrated.…”

Effect of Sn on crystallinity and electronic property of low temperature grown polycrystalline-Si1−−Ge Sn layers on SiO2

“…The energy band gap of poly-Si 1Àx Ge x with an Si content as high as 20% is as large as 1 eV which is comparable to bulk Si, hence sufficient low off-leakage current can be expected in poly-Si 1Àx Ge x metaloxide-semiconductor field effect transistors. The formation of poly-Si 1Àx Ge x layer by using solid phase crystallization (SPC) from amorphous phase has been reported [2][3][4]. However, the crystallization temperature of poly-Si 1Àx Ge x is generally as high as 550-700°C [2], and such a high crystallization temperature is not suitable for the fabrication process of 3D ULSI devices.…”