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

Abstract

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.

Indirect geometry measurement method based on confocal microscopy and fluorescent microparticles

“…Mikulewitsch et al [11,12] in 2020 goes one step further and does not measure the surface boundary layer wetted with fluorescent dye, but instead pursues the concept of Indirect Geometry Measurement (InOGeM) for the first time by not measuring the object itself, but its imprint in the surrounding medium. Mikulewitsch et al measures the fluorescence response of the process liquid enriched with a fluorescent dye in the wet-chemical laser ablation process, and thus the volume of liquid surrounding the measurement geometry.…”

“…In their problem -of the measured object within a liquid -Mikulewitsch et al set a rectangular function (1 for z0< z< z1 and 0 otherwise) for the response function of the medium  and solves the convolution integral (2) analytically [11]:…”

Indirect fluorescence-based in situ geometry measurement for laser chemical machining

“…The principle of the indirect geometry measurement is based on the detection of light emitted by a fluid, in which the specimen is submerged, instead of light scattered or reflected on the specimen surface [8]. By employing a technique capable of axial light sectioning, the detected fluorescence signal S(z) can be limited to a small volume around the focal plane of the objective.…”

Evaluating the resolution of conventional optical microscopes through point spread function measurement

“…Various types of microscopes, including fluorescence, 1 , 2 , 3 electron, 4 , 5 and scanning microscopes, 6 , 7 , 8 , 9 are currently available for micro/nanoscale observations. However, conventional optical microscopes are nondestructive, fast, and dynamic; therefore, they remain important observation tools in biomedicine, microelectronics, chemistry, and precision instrument manufacturing.…”