Fast simulation method for parameter reconstruction in optical metrology

A method for automatic computation of parameter derivatives of numerically computed light scattering signals is demonstrated. The finite-element based method is validated in a numerical convergence study, and it is applied to investigate the sensitivity of a scatterometric setup with respect to geometrical parameters of the scattering target. The method can significantly improve numerical performance of design optimization, parameter reconstruction, sensitivity analysis, and other applications

Comparison of far field characterisation of DOEs with a goniometric DUV-scatterometer and a CCD-based system

We have measured far field diffraction patterns of different diffractive optical elements at an illumination wavelength of 193 nm using a new type of goniometric DUV (deep ultraviolet) scatterometer, which has been developed and set up recently at the PTB, the national metrology institute of Germany. This system offers both a high dynamic range and angular resolution. The scatterometer is especially suitable to analyse weak background light like stray light and local variations of the diffraction patterns over the DOEs (diffractive optical element). The measurement results are compared with measurements using a CCD (charge-coupled device)-based imaging DOE measurement system from Carl Zeiss SMT. An excellent agreement is demonstrated

Scatterometry reference standards to improve tool matching and traceability in lithographical nanomanufacturing

High quality scatterometry standard samples have been developed to improve the tool matching between different scatterometry methods and tools as well as with high resolution microscopic methods such as scanning electron microscopy or atomic force microscopy and to support traceable and absolute scatterometric critical dimension metrology in lithographic nanomanufacturing. First samples based on one dimensional Si or on Si 3 N 4 grating targets have been manufactured and characterized for this purpose. The etched gratings have periods down to 50 nm and contain areas of reduced density to enable AFM measurements for comparison. Each sample contains additionally at least one large area scatterometry target suitable for grazing incidence small angle X ray scattering. We present the current design and the characterization of structure details and the grating quality based on AFM, optical, EUV and X Ray scatterometry as well as spectroscopic ellipsometry measurements. The final traceable calibration of these standards is currently performed by applying and combining different scatterometric as well as imaging calibration methods. We present first calibration results and discuss the final design and the aimed specifications of the standard samples to face the tough requirements for future technology nodes in lithography

Widely usable interpolation formulae for hyperfine splittings in the

Based on new systematic high precision measurements of hyperfine splittings in different rovibrational bands of 127I2 in the near infrared spectral range between 778 nm and 816 nm, and the data in the range from 660 nm to 514 nm available from literature, the quantum number dependence of the different hyperfine interaction parameters was reinvestigated. As detailed as possible parameters were re-fitted from the reported hyperfine splittings in literature, considering that the interaction parameters should vary smoothly with the vibrational and rotational quantum numbers, and follow appropriate physical models. This type of consistency has not been sufficiently taken into account by other authors. To our knowledge it is now possible for the first time to separate the hfs contributions of the two electronic states $B ^{3}\Pi_{0^{+}_{u}}$ and $X ^{1}\Sigma^{+}_{g}$ for optical transitions in a very large wavelength range. New interpolation formulae could be derived for both states, describing the quantum number dependences of the nuclear electric quadrupole, of the nuclear spin-rotation and also of the nuclear spin-spin interactions. Using these new interpolation formulae the hyperfine splittings for the components with the quantum number condition $F-J=0$ can be calculated with an uncertainty of ≤30 kHz for transitions in the wavelength range between 514 nm and 820 nm

High precision description of the rovibronic structure of the I

A precise description of the B-X spectrum of the I2 molecule has been developed. All presently available high precision measurements on the B-X spectrum of the I2 molecule in the visible were introduced into a model based on molecular potentials for the two electronic states involved, the transition frequencies being the differences of the energy eigenvalues for the rovibrational levels in those potentials. This approach allows, depending on the quality of the input data, a prediction of iodine lines with a 2σ uncertainty of less than 30 MHz from 514 nm to 815 nm of most bands in that range. In the range between 526 nm to 667 nm, where highly precise systematic measurements exist, a smaller 2σ uncertainty of 3 MHz is achieved. Moreover, a precise local model description of selected bands of the B-X spectrum has been derived from high precision measurements of iodine lines in the near infrared between 778 nm and 815 nm. This approach by using a Dunham parameter description allows to predict lines of these bands with a 1σ uncertainty of less than 200 kHz. All this information including the systematically studied hyperfine structure can be combined in a computer program for predicting the details of the iodine B-X spectrum with high reliability, serving as a convenient tool in spectroscopic calibration tasks.