Spectrum of Defect States in Porous Organic Low-k Dielectric Films, Annealed in Argon and Nitrogen

Abstract

AbstractDefect spectrum N(E) of porous organic dielectric (POD) films is studied with capacitance deep-level-transient-spectroscopy (C-DLTS) in the energy range up to 0.7 eV below conduction band bottom Ec. The POD films were prepared by spin coating onto 200mm p-type (1 – 10 Δcm) single-side polished silicon substrates followed by baking at 325°C on a hot plate and curing at 425°C in furnace. The film thickness is in the 5000 – 6000 Å range. The ‘sandwich’ -type NiCr/POD/p-Si/NiCr test structures showed both rectifying DC current-voltage characteristics and linear 1/C2 vs. DC reverse bias voltage. These confirm the applicability of the C-DLTS technique for defect spectrum deconvolution and the n-type conductivity of the studied films. Isochronal annealing (30 min in argon or 60 min in nitrogen) has been performed over the temperature range 300°C - 650°C. The N(E) distribution is only slightly affected by annealing in argon. However, the distribution depends strongly on the annealing temperature in nitrogen ambient. A strong N(E) peak at Ec – E = 0.55 – 0.60 eV is detected in all samples annealed in argon but this peak is practically absent in samples annealed in nitrogen at Ta < 480°C. On the other hand, two new peaks at Ec – E = 0.12 and 0.20 eV appear in the N(E) spectrum of the samples annealed in nitrogen at Ta = 650°C. The different features of the defect spectrum are attributed to different interactions of argon and nitrogen with dangling carbon bonds on the intra-pore surfaces.