A new flexible scatterometer for critical dimension metrology

Abstract

At Physikalisch-Technische Bundesanstalt, the National Metrology Institute of Germany, a new type of deep ultraviolet scatterometer has been developed and set up. The concept of the system is very variable and versatile, so that many different types of measurements, e.g., classical scatterometry, ellipsometric scatterometry, polarization-dependent reflectometry, and ellipsometry can be performed. The main application is the characterization of linewidth/critical dimension (CD), grating period (pitch), and edge profile of periodically nanostructured surfaces mainly, but not only, on photomasks. Different operation wavelength between 840 and 193 nm can be used, giving also access to a variety of different at-wavelength metrology connected with state-of-the-art photolithography. It allows to adapt and to vary the measurand and measurement geometry to optimize the sensitivity and the unambiguity for the measurement problem. In this paper the concept, design, and performance of the system is described in detail. First measurement examples are shown and current and future applications are discussed.

Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry

“…Some of the most widely used configurations are single incidence angle reflectometry, 2-Θ scatterometry, spectroscopic ellipsometry, Fourier scatterometry, interferometric Fourier scatterometry,etc., [7][8][9][10][11][12][13][14][15] with a wide range of applications [16][17][18][19][20]. In an earlier paper, it has been predicted theoretically how, and under which conditions, CFS can be more sensitive than the classical IOS [21].…”

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

“…In measurement comparisons scatterometers typically show an excellent linearity to CD-SEM tools. In many cases however, systematic offsets between both systems of the order of several nm up to few 10 nm [1][2][3] are observed. These systematic deviations may be connected both to the applied measurement methods and tools, to necessary approximations in the modeling and data analysis and to imperfections and limitations of the target structures.…”

“…For this purpose we used PTB's homebuilt 'DUV' scatterometer [3] and a commercial spectroscopic ellipsometer/Mueller polarimeter (SENTECH SENresearch 850SE). These optical parameters are typically strongly correlated with potential layer compositions and heights as well as etch depth or the corresponding structure heights.…”

Joint Research on Scatterometry and AFM Wafer Metrology

“…These extensions include the application of short wavelengths down to X-rays, a stringent exploitation of the polarisation degree of freedom, using phase information of the scattered field by scanning with a focused coherent spot and new detection schemes together with the development of improved or new concepts for modelling and data analysis. a) FIGURE 1. a) Typical measurement example of nominally equal CDs on different locations (row 2 -13) on a state of the art high-end COG photomask using a commercial scatterometer (green), a commercial CD-SEM (blue) and PTBs goniometric DUV scatterometer [3]; b) the difference between measured and mean CD indicates the good CD linearity between the results obtained with PTBs scatterometer and the commercial CD-SEM For further refinement of the scatterometric algorithms, the impact of the structure form and local deviations must be taken into account. The necessary input on structure details will be provided by high resolution SEM and AFM methods, which have to be expanded to provide comparability to scatterometric measurements.…”