Plasma halogenated a-C:H as growth inhibiting layer for ASD of titanium oxide

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.