Low-Temperature Polycrystalline Silicon Thin-Film Flash Memory With Hafnium Silicate

• Published in: IEEE transactions on electron devices 2007-03, Vol.54 (3), p.531-536
• Main Authors: LIN, Yu-Hsien, CHIEN, Chao-Hsin, CHOU, Tung-Huan, CHAO, Tien-Sheng, LEI, Tan-Fu
• Format: Article
• Language: English
• Subjects: Applied sciences; Channels; Crystal defects; Design. Technologies. Operation analysis. Testing; Disturbances; Electronics; Exact sciences and technology; Flash memory; Flash memory (computers); Grain boundaries; Hafnium; hafnium silicate; Integrated circuits; Integrated circuits by function (including memories and processors); nonvolatile memories; polycrystalline silicon thin-film transistor (poly-Si-TFT); Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicates; Thin films; Transistors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2006.890379

In this paper, we have successfully fabricated poly-Si-oxide-nitride-oxide-silicon (SONOS)-type poly-Si-thin-film transistor (TFT) memories employing hafnium silicate as the trapping layer with low-thermal budget processing (les600degC). It was demonstrated that the fabricated memories exhibited good performance in terms of relatively large memory window, high program/erase speed (1 ms/10 ms), long retention time (>10 6 s for 20% charge loss), and 2-bit operation. Interestingly, we found that these memories depicted very unique disturbance behaviors, which are obviously distinct from those observed in the conventional SONOS-type Flash memories. We thought these specific characteristics are closely related to the presence of the inherent defects along the grain boundaries. Therefore, the elimination of the traps along the grain boundaries in the channel is an important factor for achieving high performance of the SONOS-type poly-Si-TFT Flash memory