Utilizing surface modification in plasma‐enhanced cyclic etching of tantalum nitride to surpass lithographic limits

Abstract

Pitch subdivision of tantalum nitride (TaN) lines is demonstrated across a 200 mm wafer using a cyclic quasi‐atomic layer etch process in an inductively coupled plasma reactor. Chlorine (Cl2) and hydrogen (H 2) chemistries are introduced sequentially to an argon plasma in discrete steps to etch the TaN film. The starting lithographic pattern with critical dimension (CD) of approximately 82 nm and pitch of 200 nm thus yields lines of approximately 40 nm CD and 100 nm pitch with minimal line edge roughness increase. We identify a synergistic effect between H 2‐exposed TaN and Cl 2 plasma as contributing to this result, as well as a potential link to surface oxidation. Optical emission spectroscopy analysis of the plasma discharge is used to characterize reactive species densities and explain the observed changes in profile.

Foundations of atomic-level plasma processing in nanoelectronics

“…PE-ALE has been also used to etch metals, metal oxides, and metal nitrides [147][148][149][150][151][152]. Some metals and metal oxides are known to be 'difficult to etch' in dry processing because byproducts of these materials formed in halogen-based plasma processes are typically non-volatile.…”

“…Some metals and metal oxides are known to be 'difficult to etch' in dry processing because byproducts of these materials formed in halogen-based plasma processes are typically non-volatile. However, chlorine exposure has been used to modify the surfaces in the first halfcycle of anisotropic PE-ALE of Cr [153], HfO 2 [147], GaN, AlGaN [149], and TaN [151,152]. Ar + plasma irradiation took place in the second half-cycle.…”

“…For some metal oxides, the presence of hydrogen (H) atoms enhances the etch rate by Ar + ion bombardment [58,64,65,[154][155][156][157]. For example, in anisotropic PE-ALE of LaAlSiO x [148], Sn-doped In 2 O 3 (ITO) [150], and TaN [151,152], the surface was modified by hydrogen plasma irradiation in the first half-cycle.…”

Rethinking surface reactions in nanoscale dry processes toward atomic precision and beyond: a physics and chemistry perspective

“…By utilizing the high selectivity of the cyclic etching process, a pitch splitting effect was demonstrated using the oxidized Ta-containing redeposition as a self-aligned mask with half the pitch of the original lithography. 34) Further investigation into controlling the etching profile through variation of the cyclic process parameters is ongoing. This approach has unique potential to extend the limits of plasma etching.…”