Developing TSV wet cleaning chemistry for quantum computing application

Abstract

New 3D-integration routes for superconducting Josephson junction qubits include the development of an interposer die with through‑silicon vias (TSV) for vertical and compact interconnections. Since fluoropolymer dielectric residues remaining in the vias may be detrimental for subsequent processes or qubit functionality, they must be removed without damaging the structure or other materials. Therefore, we developed a new O2 plasma-free, selective and non-toxic wet cleaning solution that can remove both the fluoropolymer from the vias and the photoresist used for TSV patterning from the surface. Key formulation physico-chemical properties are discussed based on cleaning results obtained by scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). Also discussed is evidence of the dissolution and removal of fluoropolymer formed during Bosch etching. Finally, SEM and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses confirm complete removal of fluoropolymer residue from the vias. These encouraging results confirm a viable, manufacturable one-step wet cleaning process for TSVs designed for 3D packaging of qubits and other applications.