Selective dry etching of TiAlC over TiN using nonhalogen N2/H2 plasma

• Selective etch (TiAlC/TiN) used N 2 /H 2 plasma at low pressure and low temperature. • Higher selectivity was at higher substrate temperatures and lower bias powers. • Chemical etching of TiAlC and TiN predominated at lower bias powers. • A process window for selective etching of TiAlC/TiN was built. • Modified layer with C-N and N–H bonds/TiAlC is more volatile than Ti-(N)-H bonds/TiN. Metal compounds such as TiAlC and TiN are used as work function metals in 3D multilayer logic semiconductor devices. Selective dry etching of these Ti compounds is highly desirable but challenging due to similar volatile products generated during the etching process. This study introduces the first instance of etch selectivity of TiAlC over TiN using low-pressure and low-temperature N 2 /H 2 plasma. A capacitively coupled plasma etcher generated N 2 /H 2 plasmas containing active species such as N, NH, and H to selectively modify TiAlC over TiN. The etching behavior and plasma-surface reaction were analyzed using in situ spectroscopic ellipsometry, optical emission spectroscopy, and X-ray photoelectron spectroscopy. Higher selectivity was achieved at higher substrate temperatures (up to 50 °C) or lower bias powers. The reaction between N 2 /H 2 plasma and TiAlC is more thermodynamically favorable than with TiN (ion-enhanced etching activation energy E a(TiAlC) = 0.044 eV/atom and E a(TiN) = 0.006 eV/atom). A process window for selective etching (TiAlC/TiN) was identified at lower bias powers, where chemical etching predominated. This study proposes a mechanism focusing on differences in chemical reactions between metal carbides and metal nitrides with N 2 /H 2 plasma to form different volatile products, highlighting the potential to develop nonhalogen chemistries for selective etching metal compounds.