Effect of C:F Deposition on Etching of SiCOH Low-k Films in CHF3 60 MHz/2 MHz Dual-Frequency Capacitively Coupled Plasma

Abstract

Effect of C:F deposition on SiCOH etching in a CHF3 dual-frequency capacitively couple plasma, driven by a high-frequency source of 60 MHz (HF) and a low-frequency source of 2 MHz (LF) simultaneously, is investigated. With the increase in LF power, the change of C:F layer from dense C:F layer to porous C:F layer and further to C:F filling gaps was observed, which led to the transition from films deposition to films etching. The change of C:F layer is related to the bombardment by energetic ions and CF2 concentration in the plasma. As the LF power increased to 35∼40 W, the energetic ions and the low CF2 concentration led to a suppression of C:F deposition. Therefore, the SiCOH films can be etched at higher LF power.