Effect of Ion-Accelerated Plasma Hydrogenation and Thermal Treatments on Hydrogen Silsesquioxane (HSQ) Low-K Dielectric Films

Abstract

AbstractHydrogen silsesquioxane (HSQ), a low dielectric constant material was deposited by spin coating on Si substrates. The films were cured between 175°C and 575°C. The cured films were subjected to ion-accelerated hydrogen plasma at different DC bias voltage to reduce the dielectric constant (k) of the films. The effect of ion-accelerated hydrogen plasma on cured films was discussed and compared with (i) non-plasma, and (ii) hydrogen plasma without the accelerating DC bias. Capacitance-Voltage measurements (C-V) and Fourier Transform Infrared Spectroscopy (FTIR) studies were done on these films. The C-V measurement shows that k values increase as the curing temperature increases for all the cases. A PECVD system was used for plasma hydrogenation and ion-accelerated plasma hydrogenation. Depending on the curing temperature the dielectric constant values were found to be, (i) between ∼ 3 and 8.8 for nonplasma films, (ii) between ∼3 and 5.1 for plasma hydrogenated films, (iii) between ∼ 2.3 and 2.9 for plasma hydrogenation with ion-acceleration at 100V and between ∼2 and 2.9 for the 150V case. The ion-accelerated plasma treatment results in lower k values as compared to the nonplasma films. FTIR studies showed a reduction in intensity of Si-H peaks with increasing temperature which increases the k value. The hydrogen plasma treatment reduces the k value and the ion-accelerated hydrogen plasma further reduces the k value suggesting further hydrogen incorporation in the films.