Ultralow-<i>k</i> Amorphous Boron Nitride Film for Copper Interconnect Capping Layer
Kiryong Kim, Hyeongjoon Kim, Sun-Woo Lee, Min Yung Lee, Gyusoup Lee, Youngkeun Park, Heetae Kim, Yun‐Hee Lee, Minsu Kim, Kyung Yeol, Min Ju Kim, Taek-Soo Kim, Hyeon Suk Shin, Byung Jin Cho
Abstract
We report the feasibility of ultralow- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> amorphous boron nitride ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN) film as a new capping layer for copper (Cu) interconnects. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN thin films were successfully deposited using a plasma-enhanced chemical vapor deposition (PECVD) process. The CVD-grown <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN showed a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> -value as low as 2.0 at 3 nm thickness, low leakage current density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 7\times 10^{-{8}}$ </tex-math></inline-formula> A/cm2), and high breakdown field ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 8.8 MV/cm) comparable to a conventional SiN blocking layer. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN has excellent thermal stability up to 1000 °C, implying that the film can be used not only for the back-end-of-line (BEOL) but also for the front-end-of-line (FEOL) processes. A 7-nm-thick <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN film successfully blocked Cu diffusion at temperatures up to 500 °C. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN film also showed excellent adhesion to Cu, with an adhesion energy of 2.90 ±0.51 J/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{{2}}$ </tex-math></inline-formula> between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN and Cu. The COMSOL multiphysics simulation predicted that, compared to a conventional SiN capping layer, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN capping layer would reduce interconnect RC delay by up to 17%. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -BN was proven to be a promising new candidate for a capping layer to reduce RC delay in Cu interconnect systems.