화학공학소재연구정보센터
Thin Solid Films, Vol.520, No.14, 4808-4811, 2012
Metal-induced negative oxide charge detected by an alternating current surface photovoltage in thermally oxidized Fe-contaminated n-type Si (001) wafers
The atomic-bridging type negative oxide charge in SiO2 is investigated using the Fe-contaminated (001) surface of n-type Si wafers. The investigation is done on the basis of a chemical analysis and a method in which the frequency-dependent alternating current (AC) surface photovoltage (SPV) is measured. At room temperature, an AC SPV appears and gradually increases, saturating after approximately one day (with an Fe concentration on the Si surface of 4.0 x 10(13) atoms/cm(2)). The AC SPV eventually becomes inversely proportional to frequency except at very low frequencies (<10 Hz) corresponding to weak or strong inversion, indicating that the negative Fe induced oxide charge appears in the form of a (FeOSi)(-) network. Also, in Fe-contaminated n-type Si(001) surfaces thermally oxidized at between 550 and 650 degrees C for 60 min, strong inversion is unquestionably observed, proving that the (FeOSi) network survives and that most of the added Fe has segregated into the region closest to the surface of the thin SiO2 film. At 850 degrees C and/or for long oxidation times, the AC SPV decreases and ultimately disappears, implying that the (FeOSi)(-) network has collapsed and may have changed into Fe2O3. A model for the metal-induced negative oxide charge in the conventional oxide charge diagram is proposed. (C) 2011 Elsevier B.V. All rights reserved.