AVS 47th International Symposium
    Thin Films Thursday Sessions
       Session TF-ThM

Paper TF-ThM5
Characterizing Bi-Layer ARC for Advanced Lithography

Thursday, October 5, 2000, 9:40 am, Room 203

Session: Optical Films
Presenter: I. Bloomer, n&k Technology
Authors: I. Bloomer, n&k Technology
D.V. Likhachev, n&k Technology
J. Lam, n&k Technology
D. Harrison, n&k Technology
Correspondent: Click to Email
Bi-layer ARCs consisting of Si@sub3@N@sub4@/Si-rich SiN@subx@/Si-substrate are gaining attention for advanced lithography applications. Such bi-layer ARCs are more effective than single-layer ARCs in reducing standing waves, and furthermore provide wider processing latitude for overall ARC thickness. The processing conditions for a stoichiometric film such as Si@sub3@N@sub4@ are well controlled, and therefore its index of refraction, n, and the extinction coefficient, k, are well established. By contrast, the n and k values of a silicon-rich SiN@subx@ film are variable and strongly dependent on the gas distribution of the processing chamber. Typically the output is a film with non-uniform composition along the z-axis. For such bi-layer ARCs, rapid and accurate characterization is imperative to produce a consistent, uniform product. We will present a metrology technique, based on the 'n&k Method', that accurately and rapidly characterizes bi-layer ARCs despite variations and non-uniformities. With this method, the thicknesses of both the Si@sub3@N@sub4@ and the non-uniform silicon-rich SiN@subx@ layers are determined simultaneously, along with the n and k spectra (190 to 1000nm) of the non-uniform silicon-rich SiN@subx@ layer, which is determined as a function of z. The “n&k Method” is based on broad-band reflectance that incorporates all-reflective optics to provide a signal-to-noise ratio of better than 0.2% over the entire measured wavelength range of 190 to 1000nm. The Forouhi-Bloomer model for n and k is used to analyze the raw data. Results for a series of samples with silicon-rich SiN@subx@ thicknesses ranging from 180 to 300 Šand the Si@sub3@N@sub4@ thicknesses ranging from 1000 to 1300 Šwill be presented, along with the results of the z-direction compositional non-uniformity of the silicon-rich SiN@subx@ layer. We will also discuss how these results can be used to optimize the manufacturing process for bi-layer ARCs.