Suppression of the floating-body effect in partially-depleted SOI MOSFETs with SiGe source structure and its mechanism

• Published in: IEEE transactions on electron devices Vol. 44; no. 12; pp. 2187 - 2192
• Main Authors: Nishiyama, A., Arisumi, O., Yoshimi, M.
• Format: Journal Article
• Language: English
• Published: IEEE 01-12-1997
• Subjects: Bipolar transistors; Germanium silicon alloys; Impact ionization; Laboratories; Large scale integration; MOSFET circuits; Oxidation; Photonic band gap; Silicon germanium; Temperature dependence
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/16.644634

SiGe layers were formed in source regions of partially-depleted 0.25-/spl mu/m SOI MOSFETs by Ge implantation, and the floating-body effect was investigated for this SiGe source structure. It is found that the increase of the Ge implantation dosage suppresses kinks in I/sub d/-V/sub d/ characteristics and that the kinks disappear for devices with a Ge dose of 3/spl times/10/sup 16/ cm/sup -2/. The lowering of the drain breakdown voltage and the anomalous decrease of the subthreshold swing are also suppressed with this structure. It is confirmed that this suppression effect originates from the decrease of the current gain for source/channel/drain lateral bipolar transistors (LBJTs) with the SiGe source structure. The temperature dependence of the base current indicates that the decrease of the current gain is ascribed to the bandgap narrowing of the source region.