Characterization of Atom Diffusion in Polycrystalline Si/SiGe/Si Stacked Gate

Yoshikazu MORIWAKI
Daisuke AZUMA
Seiichiro HIGASHI

IEICE TRANSACTIONS on Electronics   Vol.E88-C    No.4    pp.646-650
Publication Date: 2005/04/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.4.646
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Fundamental and Application of Advanced Semiconductor Devices)
Category: Si Devices and Processes
SiGe gate,  gate depletion,  

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We have fabricated poly-Si/Si0.7Ge0.3/Si stacked gate on 4 nm-thick SiO2/Si(100), and examined the diffusion of Ge and impurities as a function of annealing temperature in the range of 800-1000 by energy dispersive X-ray spectroscopy (EDX) and secondary ion mass spectrometry (SIMS). It is reviealed that germanium atoms diffuse into 100 nm-thick silicon cap layer uniformly after 1000 annealing for 30 min and the crystallinity of As+ doped poly-SiGe is better than that of doped poly-SiGe. Also, in comparison with poly-Si gate MOS capacitors, we have confirmed that MOS capcitors with p+ and n+ SiGe gates show a 0.2 V reduction in the flat-band voltage for p+ gate and no change for n+ gate, with no increase in gate leakage current with respect to the oxide voltage. This result is attributable to the difference in the energy band structure between Si and Si0.7Ge0.3.