The core of the desktop automatic film thickness gauge is to detect the differences in characteristics between the film layer and the substrate through physical or optical methods, automatically calculate and output the film thickness value. Different principle models are adapted to different film layer scenarios. The following are a brief introduction to the three most common working principles:
1. Contact type (mechanical probe method)
This is the most fundamental principle. The high-precision probe of the instrument slowly contacts the surface of the sample, moves from the substrate to above the film layer, and directly measures the actual thickness of the film layer through the height difference sensed by the probe. The advantage is high precision, suitable for thick films (such as metal films and coatings), but it may cause slight damage to the sample surface.
2. Optical method (reflection/refraction method)
Working by utilizing the reflection or interference characteristics of light is also a very common type of desktop design. After the light is irradiated onto the surface of the film layer, it will simultaneously undergo reflection on the surface of the film layer and reflection at the interface between the film layer and the substrate, and the two reflected beams will produce interference fringes. The instrument automatically calculates the film thickness by analyzing parameters such as the spacing and intensity of interference fringes, combined with the optical refractive index of the film layer. Suitable for thin films (such as optical films, semiconductor films), non-contact without damaging the sample.
3. Vortex flu response method
Mainly targeting conductive film layers (such as metal films). The probe of the instrument generates an alternating magnetic field. When the magnetic field approaches the conductive film layer, eddy currents are generated inside the film layer, which in turn affect the magnetic field strength of the probe. The eddy current intensity varies with different film thicknesses, and the instrument automatically calculates the film thickness by detecting the change in magnetic field. Suitable for rapid detection of metal films and conductive coatings, non-contact and highly efficient.