Comparative study of NBTI as a function of Si film orientation and thickness in SOI pMOSFETs Sung Jun Jang a , Dae Hyun Ka a , Chong Gun Yu a , Kwan-Su Kim b , Won-Ju Cho b , Jong Tae Park a, * a Department of Electronics Engineering, University of Incheon #177 Dohwa-Dong Nam-Gu, Incheon 402-749, Republic of Korea b Department of Electronic Materials Engineering, Kwangwoon University #447-1 Wolgye-Dong Nowon-Gu, Seoul, Republic of Korea Received 28 June 2007 Available online 4 September 2007 Abstract Negative bias temperature instability of SOI pMOSFET is investigated as a function of Si film orientation and film thickness. It is observed that NBTI induced threshold voltage shift is bigger for (1 1 0) MOSFETs in comparison to (1 0 0) MOSFETs and it decreases with the decrease of Si film thickness. The possible reason for less degradation of thinner Si film devices is explained by the small gate current due to low oxide field. The activation energy is independent on Si film orientation. The dependence of recovery behavior on the Si film orientation is studied by comparing of a conventional stress-measurement-stress technique with un-interrupted stress technique. It is also observed that the NBTI effect is underestimated and the recovery phenomenon is more profound in (1 1 0) MOSFETs. Ó 2007 Elsevier Ltd. All rights reserved. 1. Introduction Since NBTI in pMOSFETs degrades the threshold volt- age (V TH ) and drive current, it becomes a serious reliability issues for both analog and digital CMOS circuits [1]. So far it is believed that the NBTI induced threshold voltage shift is linked to the creation of donor-like interface states and possible positive fixed charge into oxide. The NBTI reli- ability in SOI devices is more important than bulk CMOS devices due to the SOI structure itself such as floating body, channel coupling, BOX quality and self heating effects [2]. Recently it is shown that ultra-thin body (1 1 0) pMOS- FETs have an excellent mobility and can be one of the most promising structures for future VLSI because of its higher short channel effects immunity [3,4]. On the other hand, NBTI induced device degradation is more significant for (1 1 0) MOSFETs due to higher bonded hydrogen den- sity at the interface [5]. Recently the methodologies for the NBTI characteriza- tion have pointed out to have serious effects in measure- ment [6,7]. In general, the bias-temperature stress is removed when the NBTI characterization is performed. The recovery of threshold voltage shift after the removal of the bias-temperature stress has been observed. And thus it is reported that the NBTI effects is underestimated in stress-measurement-stress (SMS) technique in comparison with un-interrupted stress technique (UIS) [6]. Although many studies on NBTI characterization for thin gate dielectric devices have been published [8,9], we have not found any previous studies on NBTI characterization with Si film thickness (T Si ). In this work, the NBTI effect is investigated as a function of Si film orientation and T Si . The dependence of the recovery behavior on Si film orien- tation is also studied by comparing SMS technique with UIS technique. 2. Device fabrication and measurement Fig. 1 shows the schematic view of the ultra-thin body SOI pMOSFET fabricated on (1 0 0) and (1 1 0) SIMOX 0026-2714/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.microrel.2007.07.015 * Corresponding author. Tel.: +82 32 770 8445; fax: +82 32 770 2371. E-mail address: jtpark@incheon.ac.kr (J.T. Park). www.elsevier.com/locate/microrel Microelectronics Reliability 47 (2007) 1411–1415