Suspended Diamond-Shaped Nanowire With Four Facets for High-Performance Ge Gate-All-Around FETs

• Published in: IEEE transactions on electron devices 2016-10, Vol.63 (10), p.3837-3843
• Main Authors: Fu-Ju Hou, Po-Jung Sung, Fu-Kuo Hsueh, Chien-Ting Wu, Yao-Jen Lee, Yiming Li, Samukawa, Seiji, Tuo-Hung Hou
• Format: Article
• Language: English
• Subjects: Dry etching; gate-all-around (GAA); germanium (Ge); isotropic/anisotropic etching; Logic gates; Nanoscale devices; nanowire (NW); Scanning electron microscopy; Silicon
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2016.2597317

A feasible pathway to scale germanium (Ge) FETs in future technology nodes has been proposed using the tunable diamond-shaped Ge nanowire (NW). The Ge NW was obtained through a simple top-down dry etching and blanket Ge epitaxy techniques readily available in mass production. The different etching selectivity of surface orientations for Cl 2 and HBr was employed for the three-step isotropic/anisotropic/isotropic dry etching. The ratio of Cl 2 and HBr, mask width, and Ge recess depth were crucial for forming the nearly defect-free suspended Ge channel through effective removal of dislocations near the Si/Ge interface. This technique could also be applied for forming diamond-shaped Si NWs. The suspended diamond-shaped NW gate-all-around NWFETs feature excellent electrostatics, the favorable {111} surfaces along the (110) direction with high carrier mobility, and the nearly defect-free Ge channel. The pFET with a high I ON /I OFF ratio of 6 × 107 and promising nFET performance have been demonstrated successfully.