As the semiconductor industry continues to fulfill Moore’s law, thin film thickness is one of the most rapidly scaled dimensions. Consequently, chip manufacturers must implement metrology systems that will be effective for statistical process control of ultra-thin dielectrics.
Ellipsometry is a non-destructive technique, capable of being used for any transparent and semitransparent medium. It can measure a wide range of layer thickness from a fraction of mono-atomic layer to several micrometers.
Ellipsometry allows the determination of the thickness of single layers and multi-layer stacks. In addition, it allows the absolute characterisation of optical properties of materials by extraction of the N and K data.
Using Spectroscopic Ellipsometry, up to 7 layers can be analysed simultaneously in one measurement in order to extract the thickness of every individual layer. Material optical properties also, can be obtained over a wide spectral range, from Deep UV to near InfraRed.
Unlike other optical techniques, this method requires neither reference sample nor reference beam like reflectometry. Moreover, ellipsometry has the advantage of high sensitivity due to the additional measurement of the phase of light at different wavelengths. As a consequence, it allows analysis of complex structures like multi-layers with rough interfaces and unknown material composition.