Effect of Water Addition to Choline Chloride–Urea Deep Eutectic Solvent (DES) on the Removal of Post-Etch Resid ues Formed on Copper

Feasibility of dissolution of post-etch residues (PERs) formed on copper in formulations containing a mixture of urea (U)-choline chloride (CC) deep eutectic solvent (DES) and water (W) has been investigated. PER films were formed on copper surface by spin coating deep ultraviolet photoresist film, followed by CF
₄
/O
₂
plasma etching. The residue removal process was characterized using X-ray photoelectron spectroscopy and scanning electron microscopy techniques. Effective removal of PER was obtained in water-DES solutions containing as high as 90% water in the temperature range of 20-40
^°
C. Additionally, the etch rates of copper and siloxane-based low-k dielectric material in water-DES solutions were found to be lower than that in deaerated 250:1 [H
₂
O: hydrofluoric acid (HF) (49%) volume ratio] dilute HF solutions.