Investigation Of Etching SiCOH Films By Dual-Frequency Capacitively Coupled Plasma

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. Compared with that of SiO2, the etching rate of SiCOH films increases with reduced film density due to the existing of pores in the film, resulting in roughness, the formation of micro-trenches, and variations in the etched depth, which make the precise profile control of etched patterns uncontrollable in the etching process.To make the precise control of etching SiCOH film, the etching fluorocarbon plasma must be F-rich, and the energy of plasma could be independently controlled. We investigate the characteristic of 13.56MHz/2MHz,27.12MHz/2MHz,60MHz/2MHz dual-frequency capacitively couple plasma (DF-CCP) of CHF3 and the etching of SiCOH film. The results show that power increase of low-frequency (LF) source can make the controllable etching of SiCOH film, and frequency increase of high-frequency (HF) source can reduce the power for the etching. Combined with the plasma analysis, the controllable etching of SiCOH film is related to the increase of F in plasma and the inhibiting of CF2 which caused by the increase of LF power and HF frequency.