| AVS 59th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM-ThP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | J.L. Shohet, University of Wisconsin-Madison |
| Authors: | H. Sinha, University of Wisconsin-Madison J.L. Shohet, University of Wisconsin-Madison |
| Correspondent: | Click to Email |
VUV irradiation causes electron photoemission from dielectrics. Photoemission occurs from defect states in the dielectric band gap and results in trapped positive charges. We propose an equivalent-circuit model using which, once the circuit parameters are determined, charging of dielectric materials under VUV irradiation can be predicted. The circuit includes a dielectric capacitor, the intrinsic and photo conductivities of the dielectric and substrate, and the processes of photoemission and photoinjection. The model has the back of the substrate grounded through an ammeter to the vacuum chamber. The ammeter reads the substrate current. To simulate the circuit between the dielectric sample and the vacuum chamber that collects photoemitted electrons, a photodiode is used. The sample itself, i.e. the dielectric deposited on a Si substrate, is represented by a combination of capacitors, resistors and dependent voltage sources. An ideal dielectric can be expressed as a parallel-plate capacitor. However in a real dielectric leakage currents are present due to defect states. Thus, we include a resistor in parallel to the capacitor that represents the intrinsic conductivity. In addition, photoconductivity is introduced in the dielectric during VUV radiation, which is shown by another resistor in parallel to the capacitance. A dependent voltage source models the electron depopulation from the defect states. We represent the substrate, which is a semiconductor, by a resistor. This resistor signifies the intrinsic resistance. As VUV photons also cause electron-hole pair generation in substrate, a resistor as a photoconductivity component is added in parallel to the intrinsic resistor. The circuit components were determined using experimental photoemission/substrate current data for SiCOH. The prediction of photoemission/substrate current using the model was found to match experimental results over different thickness of SiCOH. To conclude, an equivalent circuit can model the effect of VUV radiation on charging and currents in dielectrics.
This work has been supported by Semiconductor Research Corporation under Contact No. 2008-KJ-1871 and the National Science Foundation under Grant CBET-1066231. The UW-Madison Synchrotron is funded by NSF under Grant DMR- 0537588.