Effects of Plasma and Wet Processes on Si-Rich Anti-Reflective Coating to Address Selective Trilayer Rework for Sub-20nm Technology Nodes

When performing trilayer rework in advanced technology nodes, removing only the top photoresist selectively to the underlying Si-containing anti-reflective coating raises advantages in terms of cost, cycle time and defectivity. However Si-BARC materials exhibit a high sensitivity to usual lithography rework processes, in that their physical or optical properties, thickness or chemical composition are readily affected. These modifications can induce a shift in lithography process window, making the process impossible in the most extreme cases. Therefore, the preferred trilayer rework process so far remains the removal of the entire stack. This article reports the extensive study of Si-BARC modifications versus rework process, including both plasmas and chemical treatments. The most innocuous processes were then tested regarding their capability to remove 193nm photoresists on top of the SOC + Si-BARC stack.