Investigation On Characteristics Of C₂F₆ And C₄F₈ Dual-frequency Capacitively Coupled Plasmas

The device dimension continuous shrinking in ultralarge-scale integrated chips leads to the increase of signal propagation delay, power consumption and cross-link between metal interconnects. In order to address these problems, the traditional SiO2 insulating layer must be replaced with low dielectric constant (low-k) and ultralow dielectric constant (ultralow-k, k < 2) materials. As a promising candidate for low-k and ultralow-k materials, porous SiCOH films have received closely attentions.As a low-k material used for ultralarge-scale integrated chips, the etching of porous SiCOH films is one of the most important issues. To make the precise control of etching SiCOH film, the F-rich fluorocarbon plasma must be used, and the energy of ions in the plasma could be independently controlled. So this paper investigated the characteristics of C₂F₆ and C₄F₈ plasmas in dual-frequency capacitively couple discharge using optical emission spectroscopy. As a comparison, the characteristics of CHF3 DF-CCP plasma were also presented. The effect of low-frequency power, high-frequency power and pressure on F and CF2 relative density, F/CF2 ratio and electron excitation temperature was analyzed in C₂F₆ and C₄F₈ plasmas. The characteristics of C₂F₆, C₄F₈ and CHF3 plasmas in dual-frequency capacitively couple discharge for porous SiCOH films etching were compared. The effect of low-frequency power on F, CF2 relative density, F/CF2 ratio and electron excited temperature was analyzed. The results show that the change of high-frequency power, low-frequency power and pressure in DF-CCP leads to different dissolve process of C₂F₆ and C₄F₈ plasmas, which provide a possibility for precise control of etching SiCOH film. The different F, CF2 radical concentration of plasma is related to reactive paths and energy.