Photo-Response of Metal-Oxide-Semiconductor Capacitance with Atomic Layer Deposited High-K Dielectric as Gate Insulator

• Main Authors: Chu-Jen Chang, 張居仁
• Other Authors: You-Lin Wu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/04069515428761367866

碩士 === 國立暨南國際大學 === 電機工程學系 === 99 === In this thesis, metal-oxide-semiconductor capacitors (MOSC) with high-k dielectric HfO2 deposited by atomic layer deposition (ALD) were fabricated, and indium tin oxide (ITO) prepared by sputtering was used as the gate metal material. By taking advantage of the transparent and conductive characteristics of the indium tin oxide, the MOSC was shined with visible light and its capacitance-voltage (C-V) characteristic was measured before and after illumination. Photo-response of the MOSC subjected to high-energy -ray irradiation was also carried out in this work such that the charge trapping mechanism of the HfO2 high-k dielectric under visible light illumination can be realized. During the C-V measurements swept from inversion to accumulation, we found large flat-band voltage shift to the left in the C-V curves due to holes injection into the oxide as long as the sweep voltage reaches the accumulation region. This indicates that hole-trapping near the HfO2/Si interface in accumulation is the dominant effect before the MOSC being subjected to irradiation. Large amount of electron trapping is observed when the MOSC is subjected to visible light illumination. Compared with the pre-illuminated C-V characteristics, there is a small difference in the flat-band voltage shift in the C-V curves obtained after the light is turned off due to some electron-trapping occurred in the oxide during previous light illumination. This electron-trapping was caused by electrons injection near the HfO2/Si interface when the sweep voltage was in inversion region during light illumination. For the post-illuminated C-V measurements swept from accumulation to inversion, only negligible flat-band voltage shift was found when comparing with the pre-illuminated C-V curves. In this case, it is believed that holes were already trapped by the trapping center in the oxide when the sweep voltage starting at the accumulation region. For the MOSC subjected to -ray irradiation, the increase of electron-trapping inside the HfO2 layer caused by irradiation cancels the hole-trapping due to the sweep voltage at accumulation, which makes the post-illuminated C-V curves shift only slightly to the left or even no shift at all when compared with the pre-illuminated C-V curves.