| AVS 55th International Symposium & Exhibition | |
| Plasma Science and Technology | Friday Sessions |
| Session PS1-FrM |
| Session: | Plasma-Surface Interactions in Materials Processing II |
| Presenter: | J.L. Lauer, University of Wisconsin-Madison |
| Authors: | J.L. Lauer, University of Wisconsin-Madison J.L. Shohet, University of Wisconsin-Madison Y. Nishi, Stanford University |
| Correspondent: | Click to Email |
Several integration challenges arise during plasma processing of back-end-of-line (BEOL) dielectrics with the scaling of interconnects from the 65 nm to the 45 nm technology node. This work focuses on the role that vacuum ultraviolet (VUV) radiation has in producing and/or mitigating damage to BEOL dielectrics during plasma processing. Vacuum ultraviolet (VUV) radiation with photons in the energy range of 5 to 30 eV produced by high-density plasmas in plasma-processing systems can cause degradation of electronic devices by producing changes in the optical, mechanical, chemical and electrical properties of dielectrics. In particular, VUV radiation is capable of creating electron-hole pairs within dielectrics. As a consequence of the increased conductivity, the dielectric layer acts as an antenna, being able to collect charges from the plasma which can cause charging damage. To determine how VUV can affect the electrical properties of dielectrics, we utilize synchrotron radiation incident on silicon wafers coated with dielectric layers which, in contrast to plasma exposure, has only photon flux incident on the dielectric surface. Measurements of the charging currents during VUV exposure appearing on dielectrics of various thickness and composition were made. In addition, the total induced charge that remains within the dielectric after VUV exposure was measured with a Kelvin probe. We show the effect VUV has on the induced trapped charge and conductivity of porous SiCOH films with dielectric constants between 2.55 and 3.00 for various film thicknesses. In addition, we compare the valence-band structure between 5 and 30 eV for different etch-stop dielectrics (SiN, SiC, oxygen-doped SiC, and nitrogen-doped SiC) and determine how the accumulation of space charge controls the conductivity of these films. These effects are compared with results obtained with SiO2 to determine the potential integration challenges that these new dielectrics will pose in the future.
Work supported by the Semiconductor Research Corporation under Contract 2008-KJ-1781 and in part by NSF under grant DMR-0306582. The Synchrotron Radiation Center is funded by NSF under Grant Number DMR-0537588.