Plasma Halogenated a-C:H as Growth Inhibiting Layer for ASD of Titanium Oxide

Authored by: M. Krishtab, J. Hung, R. Koret, I. Turovets, K. Shah, S. Rangarajan, L. Warad, V. Zhang, R. Ameloot, S. Armini | SPIE 2020, February 1, 2020

The native self-alignment of area-selective deposition (ASD) processes makes this technology a promising solution for
precise pattern positioning in the EUV era. The key challenge for any ASD process is its defectivity associated with the
deposition on the growth-inhibiting surface. Therefore, the ability to qualify an ASD process using the appropriate set of
in-line metrology tools is crucial for up-scaling of the technology. In this work, we present a new concept of area-selective
ALD TiO2 growth and use it as an example to show the potential of in-line OCD and XPS tools for evaluation of ASD
processes. The proposed novel process is based on selective growth of TiO2 on top of SiO2/SiN in the presence of plasma
halogenated amorphous carbon (a-C:H) acting as a growth-inhibiting layer. The exposure of a-C:H to CF4 or Cl2 plasma
results in formation of a thin halogen-rich film suppressing nucleation of TiO2, while the latter is minimally affected on
the plasma treated SiNx or SiO2 layers. The selectivity was assessed on both blanket films and 45 nm half-pitch a-C:H line
patterns. The analysis of blanket a-C:H substrates showed that the plasma chlorination provides a substantially more
efficient growth inhibition as compared to the fluorination. However, the ability of the CF4-plasma to etch the topmost
surface of the a-C:H makes it more favorable for application on a-C:H patterns, surface of which is typically contaminated
with residues from hard-mask or from the patterning plasma. Therefore, the pre-cleaning of the a-C:H line pattern surface
with CF4-plasma is required to restore the growth blocking efficiency of the chlorinated a-C:H.
Keywords: area-selective deposition, ALD, amorphous carbon, defectivity, OCD, XPS, in-line metrology