Anti-reflection-coating thickness measurements on textured silicon surfaces: Evaluation and accuracy of different measurement techniques

The accuracy and reliability of different techniques for inline quality control of antireflection coatings (ARC) on industrial relevant surfaces are analyzed and rules to improve the accuracy of the systems are derived. For this, four systems are compared with respect to the setup and the way of ARC thickness calculation. Raw data and measured thicknesses are evaluated with respect to a reference system, to identify for each surface texture the system which is suited best and to identify the physical reasons for deviations. Angle-dependent simulations and measurements of the spectral reflectance on monocrystalline wafers with a pyramidally-etched surface reveal that different angle corrections for mc-Si and Cz-Si are required. Besides evaluating the spectral position of the reflectance minimum, a least-squares fit of the spectral reflectance of partially textured Cz-Si is presented and evaluated.