High-Performance Silicone Glue Etchant Enabled by Linear Alkane Swelling Solvents for Wafer Support System Debonding

In this study, a high-performance silicone glue etchant incorporating a linear alkane swelling solvent (LASS) is proposed for the wafer supporting system (WSS) debonding process in wafer-level packaging (WLP). Conventional etchants consisting of tetrabutylammonium fluoride (TBAF) dissolved in N-ethyl-2-pyrrolidone (NEP) exhibit limited removal efficiency because naked F- ions cannot easily penetrate the densely crosslinked siloxane network, and their activity is reduced by moisture uptake. To overcome these limitations, a LASS-assisted etching system is designed by combining TBAF-containing polar solvents with linear alkanes selected based on Hildebrand solubility parameters. Among the tested solvents, pentane induces the largest swelling of the silicone adhesive, increasing the free volume of the polymer matrix and facilitating efficient F- diffusion. As a result, the optimized etchant containing 3.0 wt% TBAF in N-octyl-2-pyrrolidone (NOP) and 70.0 wt% pentane exhibits superior removal performance compared with the conventional TBAF/NEP etchant. It completely removes silicone adhesive residues from patterned wafers within 60 s without observable damage to the photosensitive polyimide passivation layer, as confirmed by optical microscopy and FT-IR spectroscopy. The LASS-containing etchant also maintains its removal performance at water contents of up to 2.0 wt%, whereas the performance of the LASS-free etchant degraded at 0.1 wt% water. Based on this moisture-dependent behavior, The FT-IR OH/CH₃ peak-intensity ratio is proposed as a certificate-of-analysis (CoA) parameter for quality control of both colored and non-colored etchants. These results demonstrate that PENT70-F/NOP provides a practical strategy for efficient silicone adhesive removal and etchant quality control during WSS debonding.
- This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. RS-2025-25396489)