Characterization of interface quality between various low-temperature oxides and Si using room-temperature-photoluminesc
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Woo Sik Yooa) WaferMasters, Inc., San Jose, California 95112 (Received 29 November 2012; accepted 18 March 2013)
The quality of interface between ultrathin silicon dioxide films and their silicon (Si) wafers was characterized using room-temperature photoluminescence (RTPL) and Raman spectroscopy. Three types of low-temperature (350 °C or room temperature) oxide films on Si grown by different techniques were measured and compared with Si wafers having native oxide and high-temperature thermally grown oxide films. Significant RTPL spectra and intensity variations were measured among low-temperature oxide films. Very strong excitation wave length dependence of RTPL spectra and intensity was observed from the low-temperature oxide films on Si whereas the RTPL spectra and intensity from Si with native oxide and thermally grown oxide films were consistent. Stress in the Si lattice, with different low-temperature oxide layers, showed noticeable differences depending on the oxidation technique used. Key device performance parameters of image sensor devices fabricated using three different low-temperature oxide films showed good correlation with the RTPL and Raman measurement results. The RTPL spectra and Raman shifts are very sensitive to the quality of the oxide/Si interface and can be used as an interface quality monitoring technique.
I. INTRODUCTION
Most circuits utilize complementary metal–oxide– semiconductor (CMOS) devices which include both p- and n-channel types. Despite the simple structure and fabrication process steps of CMOS devices, the lack of availability of a good oxide/semiconductor system without excessive leakage, oxide charges, and interface traps has delayed significant progress for a long time. The oxide quality improvement over the years has enabled improvements in respect of CMOS device manufacturing.1 The importance of surface and oxide/semiconductor interface quality is increasing as thinner oxide layers are being used in advanced devices. With scaling of devices, lateral and vertical dimensions of devices have been shrinking steadily over the years. Ultrathin, high-quality gate oxide films, without excessive thermal exposure, are essential for fabricating advanced CMOS devices.2 Low-temperature, high-quality oxidation techniques have been actively investigated in the industry for several decades.3,4 Establishing proper oxide/silicon (Si) interface characterization techniques has been very important for the development of effective ultrathin oxide a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.78 J. Mater. Res., Vol. 28, No. 9, May 14, 2013
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layers on Si. Until now, the quality of the gate oxide has been primarily characterized by electrical characteristics of the CMOS devices. Subtle and unexpected oxide integrity and/or oxide/Si interface quality variations in CMOS device production lines can be detrimental to device yields, reliability and performance. As the oxide film thicknesses get thin
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