Development of a new type of highly effective etchant solution for glue residue in wafer-level packaging process

Abstract

We synthesize an etchant solution designed to remove polydimethylsiloxane (PDMS) residues from semiconductor wafers during wafer-to-wafer processing in advanced semiconductor packaging (AVP). The etchant solution is produced by combining hexane, a nonpolar swelling solvent, with tetrabutylammonium fluoride (TBAF), a fluorine-based compound, to enhance PDMS etching. We evaluate the etching rate of PDMS using various solvent mixtures, including 1-vinyl-2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, and 1-octyl-2-pyrrolidone (NOP), with different concentrations of TBAF (1.0–5.0 wt%). Notably, NOP, which contains octyl groups, demonstrates the highest PDMS etching rate, particularly when combined with 70.0 wt% hexane. The optimized solution, F3-NOP/H70, achieves an etching rate of 85.7 μm/min. Further testing confirms that the F3-NOP/H70 solution effectively removes PDMS residues from wafer surfaces without damaging dielectric layers, such as the photosolder resist and photosensitive polyimide. These results indicate that the F3-NOP/H70 solution efficiently dissolves and removes PDMS residues and preserves the integrity of adjacent wafer components, making it a promising candidate for AVP applications. This study emphasizes the importance of selecting appropriate solvent systems for residue removal in semiconductor manufacturing and offers a practical solution to enhance device quality and reliability. This approach can potentially be applied at various stages of semiconductor processing, where residue management is essential.