Impact of Wet Bevel Etching on WDC Films and Advanced Interconnect Structures
As BEOL scaling continues, the introduction of new interconnect materials such as tungsten-doped carbon (WDC) creates a strong need for robust bevel control and compatible cleaning schemes. Conventional metal hardmask materials, such as titanium nitride (TiN), commonly used in BEOL patterning, exhibit high compressive stress that can induce line wiggling, leading to electrical shorts in the interconnect. To address this challenge, novel materials such as WDC have been proposed. However, integrating WDC into BEOL process flows is nontrivial. Because film depositions can wrap around the bevel, undesired films in this region can significantly impact downstream tool performance through issues such as arcing or metal contamination, posing a major challenge for defectivity control. Therefore, alongside new material innovations, developing robust bevel etch strategies has become an essential part of process development. In this case, WDC residues at the wafer bevel must be effectively removed without damaging surrounding dielectric films or degrading device yield. While bevel RIE provides fast material removal, insufficient selectivity can cause over-etch into the silicon substrate at the wafer edge. This edge silicon damage can reduce mechanical robustness at the bevel and increase wafer breakage risk. A wet-clean-based bevel etch with higher selectivity and milder removal than the bevel RIE process may offer a solution to mitigate these concerns.
In this work, we systematically evaluated wet bevel etch processes for WDC and assessed their impact on BEOL interconnect yield. Two different wet-clean chemistries were investigated to achieve complete WDC removal at the bevel. The etching performance on WDC and its selectivity to TEOS materials was compared. Complete WDC removal was achieved using the optimized process, and surface analysis confirmed that carbon residues were eliminated. Electrical tests on patterned wafers showed performance comparable to RIE bevel etching, demonstrating that optimized wet bevel processes can enable reliable BEOL integration of WDC while maintaining interconnect integrity.
BIOGRAPHY
Dr. Wei‑Shang Lo is a Process Engineer in WET Chemical Process at IBM Research in Albany, New York, where he develops wet chemical solutions for advanced semiconductor technologies, including 2 nm gate‑all‑around (GAA) devices and beyond. His work focuses on defining process windows, designing experiments, stabilizing high‑risk manufacturing steps, and enabling new chemistries aligned with IBM’s technology roadmap. Dr. Lo’s research expertise lies at the intersection of materials chemistry, molecular spectroscopy, and semiconductor process development, with particular emphasis on molecular‑level interactions at solid–liquid interfaces. He has led innovations in wet cleaning by elucidating the physicochemical mechanisms governing defectivity, material compatibility, and process robustness in advanced device integration. Prior to joining IBM, Dr. Lo was a Postdoctoral Fellow in Chemistry at the University of Wisconsin–Madison and received his Ph.D. in Chemistry from Boston College. He has received multiple honors, including IBM Tech Awards and Joint Development Alliance technical development awards, recognizing his contributions to advanced semiconductor manufacturing.