Paper TF-ThP13
Transmission of Plasma-Generated Free Radicals through Silicon Nitride Dielectric Films
Thursday, November 10, 2016, 6:00 pm, Room Hall D
| Session: |
Thin Films Poster Session |
| Presenter: |
G. Sabat, University of Wisconsin-Madison |
| Authors: |
F.A. Choudhury, University of Wisconsin-Madison
G. Sabat, University of Wisconsin-Madison
M. Sussman, University of Wisconsin-Madison
Y. Nishi, Stanford University
J.L. Shohet, University of Wisconsin-Madison
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| Correspondent: |
Click to Email |
A high concentration of free-radicals is present in many processing plasmas, which affects the processing conditions and the properties of materials exposed to the plasma. Determining the types and concentrations of these free radicals is critical in order to determine their effects on the materials being processed. Previous work utilized simulations[1] to determine the free-radical density and doses from the processing plasma. Several techniques have been developed and tested over the years for radical measurements[2], but the methods do not provide a direct measurement of the free radical concentrations at the location of the sample during processing. A new technique, using fluorophore dyes, that can detect free radicals in a processing plasma and determine the their fluence at the surface of a sample during processing is investigated. The fluorophores used in this work is Alexa Fluor® 488. After reaction with reactive oxygen species (ROS), the bright green fluorescence (excitation/emission maxima ~490/515 nm) of the dye is significantly degraded. This degradation is measured using a fluorometer. The change in intensity of the fluorescence is used to measure the free radical fluence incident on the sample holder under various plasma conditions. This technique is also used to determine the number of free radicals that can penetrate through a layer of Silicon Nitride (SiN) film as follows. Alexa 488 is placed under free-standing SiN films of various thicknesses and exposed to oxygen plasma to determine the absorption coefficient and penetration depth of the free radicals. Using this method, the absorption length was found to be about 30 nm. Using X-ray Reflection (XRR) spectroscopy, it was found that the top 25 nm of the plasma-exposed film is modified which corresponds to the depth of free radical induced damage. This work has been supported by the Semiconductor Research Corporation under Contract No. 2008-KJ-1871 and the National Science Foundation under Grant No. CBET-1066231.
1 Shi, H. and Huang, H., Bao, J., Liu, J., Ho, P. S., Zhou, Y., Pender, J.T., Armacost, M. D. and Kyser, D., Journal of Vacuum Science & Technology B, 30, 011206 (2012)
2 Moon, C.S., Takeda, K., Takashima, S., Sekine, M., Setsuhara, Y., Shiratani, M., and Hori, M., Journal of Applied Physics, 107, 103310 (2010)