Paper PS2+MS-MoM10
Feature Profile Simulation for Organic Low-k Etching in 2f-CCP in H₂/N₂

Monday, October 15, 2007, 11:00 am, Room 607

As the size of ULSI continuously shrinks up to 45 nm in 2010 and multi-layer interconnect with more than 12 layers is applied, RC (resistance-capacitance) signal delay should be made smaller to meet the demand for higher performance of signal transmission. The dielectric constant of interlayer dielectric (ILD) can be reduced by lowering electric polarizability of the material. Alternatively introducing nano-holes within the material to reduce its density, decreases the k value. Increasing porosity is considered as a promising candidate for obtaining low-k ILD, though it may bring up new serious problems in its processing. Materials with low dielectric constant tend to possess poor mechanical strength and adhesiveness to the wire. In addition, low-k dielectric has low heat conductance and low resistance against heat, which makes it difficult to go through the post annealing in back-end processes. Currently, H₂/N₂ plasma is developed as the most suitable tool for the etching of organic low-k material. The etching profile is determined under the balance among isotropic etching by reactive H radical, physical sputtering by energetic ions and surface protection by the deposition of N radical. In order to attain the optimal profile, detailed understanding of these elements throughout the whole plasma etcher is strongly required. We have developed an integrated simulation consisting of the flux-velocity distribution of reactive species and the feature profile evolution of organic low-k etching in two frequency capacitively coupled plasma (2f-CCP) in the admixture of H₂/N₂.¹ In the present study, we will first estimate the density of reactive species, such as H, N and NH_x radicals, generated mainly via direct dissociation from parent gas molecules. Further, the effect of dissociation degree on the etching profile will be discussed as a function of the mixture ratio of feed gases.

¹K. Ishihara et. al., Plasma Physics and Controlled Fusion, 48, B99 (2006).