Effect of OFF-state stress on reliability of nMOSFET in SWD circuits of DRAM. (September 2018)

• Record Type: Journal Article
• Authors: Kim, Jongkyun; Lee, Namhyun; Kim, Gang-Jun; Lee, Young-Yun; Seok, Jungeun; Lee, Yunsung
• Is Part Of: Microelectronics and reliability. Volume 88/90(2018)
• Page Start: 183
• Page End: 185
• Publication Date: 2018-09
• Subjects: DRAM -- OFF-state stress -- Word line -- SWD -- Reliability; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2018.06.101
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: In this paper, we investigate the effect of OFF-State stress occurring at nMOSFET in a sub word-line driver (SWD) circuit under the DRAM operating conditions. Through the experimental study, we found that the increase in the number of OFF-carriers by the OFF-State stress caused the significant decrease of ON-current ( I on ). During the initial period, the OFF-State stress generated the positive oxide charges ( Q ox ) and the interface traps ( N it ), which caused the increase of OFF-current ( I off ) and the decrease of I on . After the degradations were saturated, both the Ion and I off decreased due to the increase in the number of OFF-carriers. Also the OFF-State degradation increased with decreasing source voltage, channel doping concentration, and channel length. Furthermore, the sensitivity of the OFF-State degradation to body bias ( V b ) increased with scaling the oxide thickness ( T ox ). These new observations suggest that the OFF-State degradation for core transistors can impose the significant limitation on the SWD circuit design in DRAM such as scaling of dimension and determination of word-line voltage. Highlights: The OFF-State stress mechanism in nMOSFET of SWD circuit during DRAM operation was investigated. The OFF-State stress increased the I off, caused the increase in the number of OFF-carriers, and eventually decreased in I on . As Vs and V b become deeper, the degradation of OFF-State stress increases. The sensitivity of the OFF-State degradation to V b increased with the T ox .