Scatterometry from crossed grating structures in different configurations

Abstract

Scatterometry proved to be a powerful technique for CD and profile metrology. In contrast to alternative methods like scanning electron microscopy (SEM) it is an integral method that reconstructs structure parameters from a comparison between measured and simulated spectra. It is well established in the field of line / space gratings and gaining importance for crossed grating structures. The simulation tool MicroSim, which was developed at the Institute for Technical Optics (ITO) in Stuttgart, has recently been extended to arbitrarily shaped crossed grating structures. Besides the shape also the pitches and mode numbers in the two directions of periodic continuation can be selected freely. In this article, different measurement configurations are discussed regarding as an example an asymmetric crossed grating structure. The depth of an asymmetric etch ought to be measured as well as its width. For the depth a conventional spectroscopic ellipsometric setup can be applied, whereas for the width an angle scan is proposed. In this configuration the wavelength remains constant while the sample is rotated around its normal.

Influence of line edge roughness (LER) on angular resolved and on spectroscopic scatterometry

“…It includes state of the art RCWA algorithms [34,35,36]. In the recent time it has been extended to diffraction from arbitrary 3D structures [23,24] with even improved convergence behavior [37] compared to known approaches. The RCWA algorithm yields complex electric fields in the respective ps coordinate system of each diffraction order.…”

“…[19,20,21,22] In this field the technique is still facing serious problems such as enormous computation times and insufficient modeling facilities. The authors of this work presented investigations on 3D scatterometry [23,24] as well as first investigations on rough sidewalls [25] in the recent time.…”

Solving the inverse grating problem by white light interference Fourier scatterometry

“…19 It is based on the RCWA [20][21][22] for diffraction from arbitrary three-dimensional structures 23 and includes some improved convergence methods. 24 To simulate white light, it is necessary to calculate the diffraction spectrum for every wavelength.…”

Interpretation of azimuthal angle dependence of periodic gratings in Mueller matrix spectroscopic ellipsometry

“…Lie et al and Novikova et al investigated asymmetric gratings with different side wall angles with this technique [13,14]. Furthermore, holographic one-dimensional gratings with a structured nickel layer on a chrome on glass sample were characterized by MM SE [15], as well as two-dimensional photoresist hole gratings on silicon wafers [16,17]. MM SE was also applied to line gratings on photomasks [18,19].…”