Integrating area-selective catalytic PMMA etching with PMMA-inhibited area-selective deposition of HfO2

A fully self-aligned process integrating catalytic area-selective etching (ASE) of poly(methyl methacrylate) (PMMA) with PMMA-inhibited atomic layer deposition (ALD) of HfO2 was developed and demonstrated at 300 °C. CoOx was employed as a catalytic surface to promote the O2-driven etching of PMMA, while SiO2 does not show such behavior under identical conditions. In an oxygen atmosphere, PMMA on CoOx exhibited temperature-dependent thinning consistent with catalytic activation, enabling selective polymer removal without photolithography. The inhibition of HfO2 nucleation on PMMA increased strongly with temperature, extending the nucleation delay from fewer than 60 cycles at 200 °C to more than 190 cycles at 300 °C. Combining these two effects enabled a continuous, single-chamber sequence in which PMMA removal on CoOx was followed by selective HfO2 deposition. Ellipsometry and x-ray photoelectron spectroscopy confirmed 21 nm of HfO2 growth on CoOx and no measurable deposition on PMMA-covered SiO2. The process represents an all-oxide, high-temperature area-selective deposition route compatible with backend-of-line materials and demonstrates the use of catalytic polymer etching to achieve lithography-free self-alignment.