Thickness Measurement Of Transparent Films Research Articles

Large-Area Thickness Measurement of Transparent Films Based on a Multichannel Spectral Interference Sensor

Thickness measurement of thin films is essential for quality control in the manufacturing process of the semiconductor and display industries. Real-time monitoring of film thickness during production is an urgent technical problem to be solved. In this study, a method for large-area thickness measurement of transparent films based on a multichannel spectral interference sensor is proposed. The sensor simultaneously acquires multichannel spectral interference signals through a combination of fan-out fiber optic bundles, detection probes, and an imaging spectrometer. The spectral data are calibrated and transformed into the wavenumber dimension, and then the power spectral density estimation method is used to demodulate the data frequency to swiftly derive the film thickness. The thickness measurement capacity of the proposed system is successfully validated on two standard film samples with a relative deviation of less than 0.38% and a relative standard deviation of less than 0.044%. The total spectral acquisition and calculation time for a single multichannel measurement was approximately 7.5 ms. The experimental results on polyimide films show that the measurement efficiency of the system is at least 4 times higher than that of the traditional system, indicating the potential of the multichannel spectral interference sensor for online monitoring in film production.

A micro-fabricated optical scanner for rapid non-contact thickness measurement of transparent films

In this work a fiber optic scanner for non-contact thickness measurement of transparent and semi-transparent films is presented. Thickness measurement is performed by scanning the focal point of a microlens across the thickness of a film and logging the intensity signal of the single scattering light reflected back from the sample. When the focal point of the scanning microlens passes the surface boundaries of the sample, intensity peaks are detected in the reflecting signal. Thickness is calculated using the index of refraction of the sample and the displacement of the lens between intensity peaks. The measurement is performed in a fraction of a second to eliminate signal artifacts that are due to the external vibrations. A magnetically driven micro-fabricated actuator is developed for actuating the microlens. Scanning range of 204 μm at resonant frequency of 544 Hz is achieved when an AC magnetic field of 14 mT is applied. To evaluate the scanner, thickness of SU-8 negative photoresist layers deposited on silicon wafers was measured.

A fast operating laser device for measuring the thicknesses of transparent solid and liquid films

A fast operating device for thickness measurement of transparent films has been designed and tested. Its principle of operation is based on the film reflection dependence on the laser beam incidence angle. The alteration of the incidence angle is produced by means of nonspherical optics. The single measurement time is less than 0.001 s, so this device allows the measurement of film thickness irregularities and investigation of the spreading liquid film thickness kinetics. The measurement frequency is 50 per second.