Electron Spin Resonance Studies of Silicon Dioxide Films on Silicon in Integrated Circuits Using Spin Dependent Recombin
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ELECTRON SPIN RESONANCE STUDIES OF SILICON DIOXIDE FILMS ON SILICON IN INTEGRATED CIRCUITS USING SPIN DEPENDENT RECOMBINATION M. A. JUPINA and P. M. LENAHAN Pennsylvania State University, University Park, PA 16802 ABSTRACT The technique of spin dependent recombination (SDR) allows the electron spin resonance (ESR) observation of electrically-active point defects in a single metal-oxidesemiconductor field-effect transistor (MOSFET) with surface areas of only 104 cm2 and Si/Si0 2 interface point defect densities of _101 t /cm 2. With SDR's enhanced sensitivity, devices with different processing details are explored. Differences in the E' spectra for variations in the oxidation processing are discussed. INTRODUCTION Over the last two decades, electron spin resonance (ESR) techniques have been quite successful in exploring the atomic scale structure of defects in large area metal-oxidesemiconductor (MOS) structures. However, ordinary ESR detection techniques are many orders of magnitude too insensitive to permit studies of individual metal-oxidesemiconductor field-effect transistors (MOSFETs). A technique known as spin dependent recombination (SDR) allows rapid (a few minutes) detection of low densities (_101 l/cm 2 ) of point defects in single MOSFETs in integrated circuits. Using SDR, we observe radiation-induced Pb and E' centers in individual MOSFETs (10- 4/cm 2 ). Earlier ESR studies of extremely large (-1cm 2 ) capacitor structures have identified the Pb and E' centers as the dominant radiation-induced defects in MOS structures [1-31. The Pb center is a trivalent silicon defect located at the Si/Si02 interface; the E' center is an oxygen deficient silicon defect in the oxide. Our SDR observations reconfirm and extend earlier ESR work on MOS structures. This present study on integrated circuits answers objections to the relevance of earlier ESR work on large area MOS structures in their relation to MOSFETs in integrated circuits. It has been established for several years that SDR detection techniques have quite high sensitivity to Pb-like interface defects in several systems [4,5]. Chen and Lang [6] as well as Henderson [7] have shown that SDR may be applied to the Si/Si0 2 system. Recently, Vranch et al. [8] demonstrated that Pb centers could be detected via SDR in a gate-control diode with a large gate area and a high interface state density. Unlike our study, the Vranch study was unable to detect the presence of E' centers in their SDR measurements. Our measurements involve MOSFETs with different oxidation processing histories. Differences in the SDR spectra of the E' centers are discussed.
Mat. Res. Soc. Symp. Proc. Vol. 159. @1990 Materials Research Society
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OUR EXPERIMENT Just as in standard ESR, SDR detects the presence of paramagnetic point defects, that is, defects with an unpaired electron. The technique exploits that the capture cross-section of a paramagnetic trapping center is affected by its spin state. Several somewhat contradictory models [9-11] have been proposed to explain the spin depende
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