Revolutionizing reactive ion etching: ion-enhanced surface autocatalytic reactions enabling ultra-high throughput using cryogenic hydrogen-fluoride plasma
Shih‐Nan Hsiao, Yusuke Imai, Makoto Sekine, Ryutaro Suda, Yuki Iijima, Yoshihide Kihara, Kenji Ishikawa, Masaru Hori
Abstract
Reactive ion etching (RIE) has been a foundation of semiconductor industry for the past 50 years, enabling the production of countless wafer everyday through its principle of synergistic reaction between chemical gases and ions. However, as device architectures advance, conventional RIE struggles with processing complex 3-dimensional structures with small features and high aspect ratios, leading to significantly reduced throughput due to the diminishing effectiveness of these synergistic reactions. This study demonstrates the transformative potential of plasma etching with hydrogen fluoride at cryogenic temperature, leveraging synergistic reactions between ions, physisorbed species and materials surface to dramatically enhance etching throughput. The co-adsorption of HF/H 2 O, confirmed by in situ Fourier transform infrared spectroscopy, on a cooled substrate results in a wet-like HF etching mechanism for SiO 2 , reducing the etching activation barrier to nearly zero. Unlike the linear dependence observed in conventional RIE, the etch rate under this approach exhibits an exponential increase with bias voltage, driven by the observed ion-enhanced surface autocatalytic reactions. This concerted mechanism demonstrates the promise of cryogenic plasma etching for enabling ultra-high throughput. Additionally, it supports sustainable development goals by eliminating the use of conventional fluorocarbon etching gases with high global warming potentials and addressing the need for energy conservation in semiconductor manufacturing.