SiCOH低k介质中低表面粗糙度沟道的刻蚀研究

Low Roughness Trench Etched in SiCOH Low-k Films with C_2F_6/O_2/Ar Dual-Frequency Capacitively-Coupled Plasmas

采用60 MHz/2 MHz双频率驱动的容性耦合放电等离子体技术,以C2F6/O2/Ar为刻蚀气体,开展了SiCOH低k介质中刻蚀低表面粗糙度沟道的研究。主要研究了O2/C2F6流量比对与SiCOH低k薄膜之间的刻蚀选择性的影响,以及O2/C2F6流量比、下电极功率对沟道刻蚀特性的影响。发现在O2/C2F6流量比为0.1以下时,光致抗蚀剂掩膜层与SiCOH低k薄膜之间具有较好的刻蚀选择性。对于沟道刻蚀,在O2/C2F6流量比为0.1时,下电极功率对沟道的表面粗糙度和剖面结构具有明显的影响。在下电极功率为30 W时,刻蚀的沟道底部平坦、沟道壁陡直,槽形完好,沟道底面的平均表面粗糙度降低至3.32 nm,因此,可以在SiCOH低k薄膜中刻蚀剖面结构完整的低表面粗糙度沟道。

Here, we addressed the etching of low roughness trench in the low-k SiCOH films with the C2F6/O2/Ar, dual-frequency （60 MHz/2 MHz） capacitively-coupled plasma. The impacts of the etching conditions on plasma etching of trench were evaluated. The results show that the ratio of O2 and C2F6 flow-rate and low frequency （LF） power have a ma- jor impact on the profile and average roughness of the trench. For example, at a ratio of 0.1 and a LF power of 30 W, a well-defined trench, with deep, vertical walls and a flat bottom,3.32 nm in average roughness, was etched, possibly be- cause of a good selectivity between the photo-resist and low-k SiCOH films, and because of a moderate ions bombard- ment.Besides,O-rich Si-O2 bonding was observed on the etched surfaces. However, a higher ratio of O2 and C2F6 flow- rate, say 0.20 to 0.50, or a higher LF power over-etched the photo-resist, resulting in a wider and rougher trench because of an increased transversal-etching of the low-k SiCOH films.