Low GWP and low emission gas for BEOL ILD trench patterning

Over the past few years, numerous countries and semiconductor manufacturing entities have unveiled their commitments to achieving net-zero carbon emissions by 2050 or even sooner. When it comes to manufacturing chips, plasma etch processes contribute significantly to emissions, especially in dielectric etching. Back End of Line (BEOL) trench etching is a process repeated for each metal layer that ultimately makes up a high volume of gas over the total production process. Trench structures in Interlayer Dielectric (ILD) are traditionally etched using fluorocarbon and hydrofluorocarbon gases such as CF₄ or CHF₃. Unfortunately, these gases have very high Global Warming Potentials (GWP). While abatement reduces final emissions of these high GWP molecules by a significant percentage, some level of emission is currently unavoidable. Despite strides in developing these alternative chemistries, high quality data packages on relevant patterns, confirming strong performance across a variety of CDs and structures, are still lacking. Accurately forecasting the gases emitted post-plasma remains elusive. As trench CDs, profiles, and pattern fidelity can directly impact device performance, there may be significant concerns about changing a well-known process at this step. In this work, we will present an innovative low GWP etching gas developed by Air Liquide to serve as a replacement for traditional etchants in BEOL ILD trench etch (AL#1). AL#1 has low GWP₁₀₀ (⪅1) and unlike many other low GWP fluorocarbons, this gas is also not classified as a per- and Polyfluoroalkyl Substance (PFAS) (not present in OECD database (as of Oct 2024)). Matching/better etch performance is demonstrated by comparison to CHF₃ on relevant trench patterns provided through the Intel Test Vehicle Program. Reduced CO₂eq emissions are demonstrated by FTIR measurements of the exhaust stream of a 300mm CCP plasma etch chamber.