Growth kinetics of amorphous interlayers in Ti thin films on epitaxial Si–Ge layers on silicon and germanium

Abstract

The growth kinetics of amorphous interlayers (a interlayers) formed by solid-state diffusion in ultrahigh vacuum deposited polycrystalline Ti thin films on germanium and epitaxial Si1−xGex (x=0.3, 0.4 and 0.7) alloys grown on (001) Si and (111) Ge has been investigated by transmission electron microscopy and Auger electron spectroscopy. The growth of a interlayers in all systems was found to follow a linear growth behavior initially. The activation energies for the linear growth of a interlayers were found to decrease with the Ge content and are 1.0±0.2, 0.95±0.2, 0.85±0.2, and 0.7±0.2 eV for Ti/Si0.7Ge0.3, Ti/Si0.6Ge0.4, Ti/Si0.3Ge0.7, and Ti/Ge systems, respectively. The maximum thickness of a interlayer was found to increase with the Ge content with x⩽0.4. On the other hand, the formation temperature of crystalline phase was observed to decrease with the Ge content. Essential factors for the formation and growth of a interlayer are discussed. The results are compared with the Ti/Si system.

Titanium-based ohmic contacts in advanced CMOS technology

“…As-formed TiSi x Ge y with Ge PAI3 exhibits much higher Si and lower Ge percentage contents compared to the reference, which can be explained in terms of the enhanced diffusion of both Si and Ge atoms, as well as the reaction competition between Ti/Si and Ti/Ge. It is well known that Si atoms diffuse faster than Ge and also more readily to react with Ti [73][74][75][76]. As a result, as-formed TiSi x Ge y with Ge PAI showing much higher Si and lower Ge percentage contents can be understood.…”

Role of an interlayer at a TiN/Ge contact to alleviate the intrinsic Fermi-level pinning position toward the conduction band edge

“…11 They observed an a-IL with a thickness of 2 nm for the asdeposited samples and an increase in the thickness as the annealing temperature was increased to 400 C for 30 min, followed by the appearance of a crystalline phase after annealing at 450 C for 30 min. These results were similar to the present HAADF-STEM results.…”

Role of Post-Deposition Annealing of Sputtered Ti on Fermi Level Depinning in Ti/TiOx/n-Ge

“…There are many reports on sputtering of Ti on n-Si resulted in an amorphous interlayer and even a modulation of SBH. 20,25,26 Yet on the Ge substrate, it has been reported that by sputtering Ti on Ge, only the SBH values of 0.548 6 and 0.58 eV 18 were obtained, indicating no depinning effect though amorphous IL was also formed. 18,27 In our system, the reaction between Ti and Ge is caused by energetic particle bombardment during sputter deposition under 0.45 Pa pressure and 150 W power.…”

“…We chose 200°C because this temperature is lower than the formation temperature of germinates. 20 The growth rate of ALD TiO 2 was about 0.5 Å/ cycle and the growth cycles ranged from six to sixty. Then MS or MIS structures were fabricated for the electrical measurements.…”