Modeling of N₂-H₂ capacitively coupled plasma for low-k material etching

As the scale of semiconductors shrinks and the interconnect layer develops to tens level, the resistance-capacitance (RC) delay of signals through interconnection materials becomes a big obstacle for high-speed operation of integrated circuits. In order to reduce the RC delay, low-k materials will be used for intermetal dielectric (IMD) materials. As a result, new etching conditions must be developed to match the material properties. We present the modeling results of a two-frequency capacitively coupled plasma (2f-CCP) with N₂-H₂ gas mixture, which is known as a promising one for organic low-k materials etching. We have developed a self-consistent simulation tool which includes neutral-species transport model, based on the relaxation continuum (RCT) model. Not only the plasma transport and spatial distribution, but also those of neutrals are important issues for the etching process. For the etching of low-k materials by N₂-H₂ plasma, N and H atoms have a big influence on the materials. Moreover, the distributions of excited neutral species influence the plasma density and profile. Therefore, we include the neutral transport model as well as plasma one in the calculation. The plasma and neutrals are calculated self-consistently by iterating the simulation of both species until a spatiotemporal steady-state profile could be obtained. In the simulation of neutral species, the interactions of excited states and vibrational levels of both N₂ and H₂ molecules are considered too. The profiles of periodic steady-state plasma and neutrals species in the 2f-CCP system is discussed.