Plasma deposition of low dielectric constant (k=2.2∼2.4) Boron Nitride on methylsilsesquioxane-based nanoporous films

Abstract

The growth of low dielectric constant (k) Boron Nitride (BN) film on silicon as wel1 as methylsilsesquioxane-based nanoporous films (LKD-5109) using plasma-discharged borazine was investigated. BN films were grown using microwave plasma (2.45GHz) or radio-frequency (rf) atom beam deposition (13.56MHz) on LKD-5109 in order to evaluate the compatibility of the two plasma processes with the physical integrity of the nanoporous films. Capacitance–voltage measurements were used to characterize the dielectric constants of the films on silicon and BN-integrated LKD (keff≈2.4). The composition and phases of the films were studied using cross-section transmission electron microscopy and electron-energy-loss spectroscopy. Although the microwave plasma process could produce BCxN films with a k value of 2.2, the process was not compatible with the nanoporous LKD substrate due to the ion-induced damage of the films. We found that only the rf atom beam deposition process, which was characterized by low-energy neutral fluxes, maintained the dielectric property of the BN-integrated LKD stack at an overall value of 2.4. In addition, the deposited BN films can act as an effective copper diffusion barrier on the LKD and can be lithographically processed to form trench patterns.