Fluorine-doped SiO 2 and fluorocarbon low- k dielectrics investigated by SIMS

Abstract

In this work, we present secondary ion mass spectrometry (SIMS) investigations of the incorporation of fluorine into thin SiO 2 films adapted as low- k dielectrics in the metal-oxide-semiconductor (MOS) devices. The insulating SiOF oxides with the thickness ranging from 1 up to 15 nm have been prepared by plasma-enhanced chemical vapor deposition (PECVD) and/or by reactive ion etching (RIE) methods on 〈1 0 0〉 oriented p-Si substrates with the use of either CF 4 or CHF 3 source of the plasma. SIMS experiments were performed using ultra-low energy (1 keV) argon ion beam and quadrupole mass analyzer. Depth profiles of the resulting dielectric films illustrate: (i) the incorporation of F into the SiO 2 matrix is accomplished by either the CHF 3 or CF 4 plasmas; (ii) no etching of SiO 2 matrix is observed by using of CHF 3; (iii) CHF 3 is a source of fluorocarbon film deposition on top of the SiO 2 that prevents the SiO 2 etching; and (iv) fluorine quantifications done based on implantation criteria give the maximum concentrations within the films from 6.0 × 10 18 to 2.4 × 10 20 atoms/cm 3 depending on the different fluoridation conditions. The F concentration in SiO 2 increases with the r.f. power of CF 4 or with decreasing a gas pressure of CHF 3 plasma.