| AVS 65th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Wednesday Sessions |
| Session PS+EM-WeA |
| Session: | Advanced BEOL/Interconnect Etching |
| Presenter: | Qing Su, University of Nebraska-Lincoln |
| Authors: | Q. Su, University of Nebraska-Lincoln T. Wang, Texas A&M University J. Gigax, Texas A&M University L. Shao, Texas A&M University W. Lanford, University at Albany M. Nastasi, University of Nebraska-Lincoln L. Li, Intel Corporation G. Bhattarai, University of Missouri-Kansas City M.M. Paquette, University of Missouri-Kansas City S.W. King, Intel Corporation |
| Correspondent: | Click to Email |
Low-k dielectric materials are well known to be sensitive to process induced damage during back-end-of-line (BEOL) patterning and metallization. This sensitivity has been largely attributed to the incorporation of terminal organic groups into the structure of low-k dielectric materials to lower dielectric permitivity and the subsequent loss of the terminal organic groups during BEOL processing. However, the correlations between the actual atomic structure of low-k dielectrics and their susceptibility to BEOL damage have been largely qualitative. A more quantitative metric for relating both the atomic structure and network topology of low-k dielectrics to downstream processing would allow for more efficient design and selection of materials for BEOL as well as pitch division multi-pattern applications.
Toward this end, we have investigated the ion radiation damage resistance for a series of low-k and high-k dielectric amorphous hydrogenated silicon carbide (a-SiC:H) thin films, wherein atomic structure and topological constraints have been previously shown to play a remarkably fundamental role in determining the full spectrum of electrical, optical, thermal, and mechanical properties. We specifically show the response of a-SiC:H films with > 37% hydrogen content and mean atomic coordination (<r> ) ≤ 2.7 subjected to 120 keV He+ irradiation with damage level to 1 displacment per atom (dpa). Significant hydrogen loss, bond rearrangement, and mechanical stiffening were induced in these films. In contrast, comparatively minor changes were observed for a-SiCH films with <35% hydrogen content and <r> > 2.7 also exposed to the same He+ irradiation. The observed radiation hardness threshold at <r>rad > 2.7 is above the theoretically predicted rigidity percolation threshold of <r>c = 2.4. As we will show, the higher observed radiation hardness threshold can be interpreted as evidence that terminal hydrogen bonds and bond bending forces associated with two-fold coordinated motifs are too weak to function as constraints in collisions with high energy ions. Eliminating these constraints from consideration would increase <r>c to > 2.7 in agreement with the observed <r>rad = 2.7. These results demonstrate the key role of network coordination and topological constraints in ion damage resistance and perhaps provides new criteria for the design of new ion damage resistant / tolerant materials.