Analysis of failure of C-V characteristics of MIS structure with SiO 2 passivation layer deposited on InSb substrate via
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Analysis of failure of C-V characteristics of MIS structure with SiO2 passivation layer deposited on InSb substrate via Raman spectroscopy Chulkyun Seok1, Sujin Kim1, Jaeyel Lee1, Sehun Park1, Yongjo Park2,*, and Euijoon Yoon1,* 1
Department of Materials Science and Engineering, Seoul National University, Korea.
2
Advanced Institutes of Convergence Technology, Seoul National University, Korea.
ABSTRACT The effect of interfacial phases on the electrical properties of Au/Ti/SiO2/InSb metal-insulator (oxide)-semiconductor (MIS or MOS) structures was investigated by capacitance-voltage (C-V) measurements. With increasing the deposition temperature of silicon oxide from 100 to 350oC using PECVD, the change in the interfacial phases between SiO2 and InSb were analyzed by resonant Raman spectroscopy to verify the relation between the breakdown of C-V characteristics and the change of interfacial phases. The shape of C-V characteristics was dramatically changed when the deposition temperature was above 300oC. The C-V measurements and Raman spectra represented that elemental Sb accumulation resulted from the chemical reaction of Sb oxide with InSb substrate was responsible for the failure in the C-V characteristics of MIS structure. INTRODUCTION Indium antimonide (InSb) has been widely used as mid-IR detectors for the wavelength of 3~5 μm since 1950s. To fabricate a high performance device using InSb, the optimization of surface passivation layer for suppressing the dark current is one of the key issues. As a result, the change of interfacial phases between SiO2 and InSb has attracted great interest over the last several decades, with the aim of improving the performance of InSb-based devices [1, 2]. In this sense, C-V measurement is a very effective method to evaluate the bulk and interfacial trap density of the passivation layer which have a close relation with the dark current of devices. In this work, in order to find the optimized condition for the deposition of the SiO2 passivation layer, the effect of deposition temperature on the C-V characteristics of Au/Ti/SiO2/InSb was investigated.
Due to the low melting temperature of 523oC, InSb can be easily deformed and damaged by irradiated thermal energy. With increasing the deposition temperature from 100 to 350oC, the shapes of C-V curve were changed gradually and eventually the properties were failed above 300oC. In order to examine the failure of the C-V characteristics of passivation layers, the phase change of the interfacial region was studied by Raman spectroscopy.
EXPERIMENT Samples were prepared using undoped InSb(100) substrates with an electron concentration of 2 ~ 8.5 x 1014 cm-3. Before the deposition of SiO2 layer on top of InSb surface, native oxide on the surface were eliminated by a dilute HF solution (HF : Deioninzed water = 1:10). Then, the wet-etched samples were rinsed with D.I water for 2 min and blown with N2 gas. A 100 nm-thick SiO2 layer was deposited by PECVD at 100, 150, 200, 250, 300, and 350oC. The flow rates of SiH4, N2 and N2O were 160
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