Paper PS-MoM2
Enhancing Fin Retention in Low-K Spacer Etch Processes Using a Highly Selective Etch Chemistry

Monday, November 7, 2016, 8:40 am, Room 104B

Low-k spacer materials such as SiBCN have garnered attention recently for advanced technology nodes due to their controllable electrical conductivity, low thermal expansion coefficient and potential for reducing loading capacitance. [1] Of particular concern in a spacer etch process is reducing the damage caused to materials such as the bottom oxide (BOX) and the underlying fins in FinFET systems. This is often a difficult challenge owing to the tight pitches and widely disparate critical dimensions (CDs) between the fin and gate geometries.

We present a spacer etch process using a novel high-selectivity gas chemistry that shows minimal damage in a FinFET system with SiBCN spacer deposited over SiGe fins. In addition to reduced damage compared to a conventional CH₃F/O₂ plasma chemistry, we also demonstrate greatly improved throughput even at low duty cycles by taking advantage of the unique chemical properties of the gas. We show <5nm SiGe fin loss for long overetch values, with minimal box loss as measured by high-resolution transmission electron microscopy (TEM).

The effect of pulsed plasma parameters are analyzed via optical emission spectroscopy (OES) in an attempt to define the etching mechanisms, as well as explain the difference between blanket etch conditions and patterned features. We focus on the effect of He dilution within the plasma as well as the effect of phase difference between source and bias for synchronous pulsing cases.

References:

[1] R.G. Southwick et al., IEEE International Reliability Physics Symposium pp. BD.2.1-2.4, 2014