Multi-VT of Stacked GeSn Nanosheets by ALD WNxCy Work Function Metal

• Published in: IEEE transactions on electron devices 2022-07, Vol.69 (7), p.3611-3616
• Main Authors: Chen, Yu-Rui, Huang, Bo-Wei, Cheng, Chun-Yi, Hsieh, Wan-Hsuan, Tsai, Chung-En, Tu, Chien-Te, Liu, Yi-Chun, Liu, C. W.
• Format: Article
• Language: English
• Subjects: Annealing; Atomic layer deposition; Atomic layer epitaxy; dipole; Dipoles; Germanium; Intermetallic compounds; Logic gates; Metals; Modulation; Nanosheets; Nitrogen; Oxidation; Oxygen atoms; Silicon; Silicon dioxide; stacked GeSn nanosheets (NSs); Thickness; threshold voltage (<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">VT ); tungsten nitride carbon; work function metal (WFM); Work functions
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2022.3177386

The effective work function (EWF) of WN x C y on SiO 2 /Si stacks can be modulated from 4.3 to 4.8 eV by plasma-enhanced atomic layer deposition. At higher annealing temperature, more oxidation of WN x C y near SiO 2 can yield larger dipole with the direction from thin interfacial WN x C y :O to bulk WN x C y , and thus EWF increases. WN 0.12 C 0.23 with lower nitrogen content captures more oxygen atoms in the interfacial WN x C y from SiO 2 than WN 0.39 C 0.1 and yields larger work function. Using different thicknesses of top WN 0.12 C 0.23 and bottom WN 0.39 C 0.1 with constant total thickness, the EWF can be tuned by dipole strength at WN 0.39 C 0.1 /WN x C y :O interface. The dipole-controlled WN x C y work function metal is integrated on the stacked GeSn nanosheets (NSs) to achieve multi- {V}_{T} modulation. {V}_{T} for stacked Ge 0.87 Sn 0.13 NSs is increasingly negative with increasing WN 0.39 C 0.1 thickness with a wide {V}_{T} tunability of 510 mV.