| AVS 58th Annual International Symposium and Exhibition | |
| Plasma Science and Technology Division | Wednesday Sessions |
| Session PS+EM-WeA |
| Session: | Low-K Materials & Integration |
| Presenter: | Romain Hurand, STMicroelectronics, France |
| Authors: | R. Hurand, STMicroelectronics, France M. Darnon, CNRS-LTM, France T. Chevolleau, CNRS-LTM, France D. Fuard, CNRS-LTM, France F. Bailly, STMicroelectronics, France R. Bouyssou, STMicroelectronics, France T. David, CEA Leti, France O. Joubert, CNRS-LTM, France F. Leverd, STMicroelectronics, France |
| Correspondent: | Click to Email |
With the continuous downscaling of devices, interconnects get narrower and narrower, and necessitate using porous low-k as insulator. Plasma processes required for the integration of low-k may cause damage at the sidewalls of the patterns, which degrades the dielectric properties of the material. The impact of the modified layer on the low-k sidewalls is becoming more critical when interconnects dimensions are scaled down. Developing low-damage plasma processes for porous low-k materials integration is compulsory, but requires a trustworthy characterization technique. Electron microscopy which leads to material shrinkage and does not precisely reveal the damaged layers is reaching its limitations. A new characterization technique, so-called Scatterometric Porosimetry has been recently proposed (Bouyssou et al. JVSTB, 2010). In this paper, we explain the principles of the method and demonstrate it can be used on complex industrial-relevant dielectric patterns (more than 9 dielectric layers, 140nm pitch). This technique can also be used to determine fundamental mechanisms of plasma induced modification to porous low-k dielectrics.
Scatterometric Porosimetry (SP) is a combination of scatterometry and porosimetric ellipsometry. Scatterometric measurements under vacuum give access to the pattern dimensions while measurements under controlled partial pressure of solvent give access to the material porosity or permeation (with low-polar solvent) or to the thickness of the hydrophilic damaged layer when water is used as a solvent.
Using this technique on an industrial stack, we determined the pattern profile and damaged layer thickness at the pattern sidewalls after each step of the etch process in a non destructive and high accuracy way. We identified that low-k main etch step is more damaging than barrier open or post etch plasma treatments: the damaged layer thickness representing 28% of the low-k width. On the contrary, the pattern profile is mostly controlled by the barrier opening step. A similar trend is measurable by SEM using decoration technique (measure before and after HF dip) but with less accuracy. We also investigated by SP the kinetic of sidewall modification during standard plasma processes including fluorocarbon-based processes or oxidizing or reducing plasma treatments.