Hamburg 2001 – wissenschaftliches Programm
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DS: Dünne Schichten
DS 3: Schichteigenschaften I
DS 3.3: Vortrag
Montag, 26. März 2001, 11:30–11:45, S 5.1
Porosity and stiffness of aerogel films characterised by wideband ultrasonic surface waves — •C. Flannery1, C. Murray2, I. Streiter2, and S.E. Schulz2 — 1Paul-Drude-Institut fuer Festkoerperelektronik, Berlin — 2Zentrum fuer Mikrotechnologien, T.U. Chemnitz
This work reports characterization of density/porosity and Young’s modulus values of a range of nanoporous silica aerogel films via dispersion of laser-generated wideband surface acoustic waves. The technique shows clear relations between dielectric constant, porosity and Young’s modulus. The films had porosities of 60–70% and Young’s moduli of 1-2 GPa. Both density/porosity and Young’s modulus show a strong correlation with film dielectric constant. Young’s modulus is shown to reduce drastically with porosity, providing valuable information about material stiffness which is of vital importance with respect to ability to withstand chemical-mechanical polishing. Porosity can be measured to better than 1%. The technique is rapid, relatively cheap and nondestructive, and has the potential to provide density measurements quicker and more accurately than other techniques. The additional ability to assess stiffness is a further advantage. Use of the method can provide valuable process control to develop and standardise nanoporous silica film properties.