| AVS 57th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuA |
| Session: | Defects in Semiconductors and Oxides |
| Presenter: | M. Nichols, University of Wisconsin-Madison |
| Authors: | H. Sinha, University of Wisconsin-Madison J. Lauer, University of Wisconsin-Madison M. Nichols, University of Wisconsin-Madison A. Sehgal, University of Wisconsin-Madison N.M. Russell, Tokyo Electron Limited M. Tomoyasu, Tokyo Electron Limited G.A. Antonelli, Novellus Systems, Inc. Y. Nishi, Stanford University J.L. Shohet, University of Wisconsin-Madison |
| Correspondent: | Click to Email |
High frequency capacitance-voltage (C-V) measurements are used to determine the effects of vacuum ultraviolet (VUV) and ultraviolet (UV) irradiation on defect states in porous low-k organosilicate (SiCOH) dielectrics. The dielectric was deposited by plasma enhanced chemical vapor deposition (PECVD) on silicon with 15-nm layer of thermally grown oxide. We determined from VUV spectroscopy that defect states are present in the band gap of the dielectrics.[i] [#_edn1] A non-zero flat-band voltage obtained from C-V characteristics also confirmed the presence of defect states in the dielectric. In addition, the defect states are a source of electrons that can move in the dielectric under influence of electric fields. This causes hysteresis loops observed in the C-V characteristics. VUV photon irradiation depopulates trapped electrons from defect states within the dielectric. Depopulation results in photoemission of the electrons creating trapped positive charge.[ii] [#_edn2] This is evidenced by a negative shift in the flat-band voltage of the C-V characteristic. Some of the depopulated electrons are not able to overcome electron affinity and reside in conduction band. Thus, more charge is available in the dielectric to move under the influence of electric field. Hence, after VUV irradiation the hysteresis loop of C-V characteristic widens. UV irradiation reverses both the shift in the flat-band voltage and the widening of the hysteresis loop, by repopulating the defect states with electrons photoinjected from the silicon substrate.1,2 Thus, UV reduces the number of trapped positive charges in the dielectric and can effectively repair processing-induced damage.
This work was supported by the Semiconductor Research Corporation under Contract Number 2008-KJ-1781. We thank Tokyo Electron Limited and Novellus Systems for providing samples. The UW Synchrotron is supported by NSF Grant DMR-0084402.
[1] J.L. Lauer, H. Sinha, M.T. Nichols, G. A. Antonelli, Y.Nishi and J.L. Shohet, "Charge Trapping within UV and VUV Irradiated low-k porous organosilicate dielectrics," Journal of the Electrochemical Society (submitted for publication)
[2] H. Sinha, J.L. Lauer, M.T. Nichols, G.A. Antonelli, Y. Nishi and J.L. Shohet, Applied Physics Letters 96 052901 (2010)