Multilayer silicon rich oxide films (SRO) or silicon rich oxy-nitride (SRON) films are attractive for their application in opto-electronic devices. The electro-optical characterization of the devices has to be correlated to the compositional structure of the films, in order to improve the fabrication process and as ultimate goal to enhance the device efficiency.
In this work secondary ion mass spectrometry (SIMS), variable angle spectroscopy ellipsometry (VASE) and atomic force microscopy (AFM) are used to investigate the structure, composition and morphology of multilayer SRON films. Three/four SRON sequential layers were deposited on silicon wafers by PECVD and silicon, nitrogen and oxygen content was varied by changing the N2O/SiH4 ratio. The total thickness of the resulting SRON stack is about 50nm.
SIMS analyses of Cs+, NCs+, OCs+, SiCs+, in MCs+ methodology are performed by a Cameca SC-ultra instrument. Depth profiles obtained at 3keV of primary beam impact energy and at 500eV with and without sample rotation are discussed. SIMS analyses are affected by sputtering rate variations and ion yield changes throughout the various layers. Here a quantification method to obtain silicon concentration is proposed [1].
Fitting SIMS results with VASE measurements is pointed out as a proper method to establish layers composition and thickness.
Moreover a detailed analysis of films morphology is obtained by AFM. The SRON stack is sputtered by SIMS until a certain layer is exposed, which is then analyzed by AFM. Alternatively an AFM analysis of the multilayer cross section is carried out. The two methods are compared.
[1] M. Barozzi, E. Iacob, L. Vanzetti, M. Bersani, M. Anderle, G. Pucker, C. Kompocholis, Analytical methodology development for Silicon–rich-oxide chemical physical characterization, accepted for publication in Reviews on Advanced Materials Science, Symp. A, E-MRS Fall Meeting, Warsaw, Poland, Sept. 2-8 2006.
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