Confocal fluorescence microscopy for geometry parameter measurements of submerged micro-structures

Due to the challenging environment of micro-manufacturing techniques where the workpiece is submerged in a fluid, a contactless in situ capable measurement is required for quality control. However, the in situ conditions and the small specimen dimensions hinder the use of conventional metrology. Confocal fluorescence microscopy is shown to enable step height measurements of a specimen submerged in a 2.6 mm thick fluid layer with an uncertainty of 8.8 μm by fitting a model of the fluorescence intensity to the measured signal. To ascertain the potential of the proposed measurement approach, the minimal achievable uncertainty of 0.07 μm for a shot-noise-limited signal is derived.