Thickness measurement of photoresist layer and ITO layer in touch screen:
Touch screen sample: cover the glass substrate with ITO conductive layer and photoresist (square pattern), use MProbeMSP Vis Film Thickness Gauge for measurement, the measurement range of this Film Thickness Gauge is 10nm-20um, equipped with a microscope, including a CCD , for imaging and navigating to the measurement location.
The photoresist is about 15umX15um (Figure 1), using a 40x objective lens, the diameter of the measured spot is about 10um.
Figure 1 Photoresist spots (15umX15um), imaged with a 40x objective lens
Figure 1 Photoresist spots (15umX15um), imaged with a 40x objective lens
The refractive index of the photoresist is fitted by the Cauchy model (1.65). Figure 2 is the measured reflectance curve, and the thick film model is used to calculate the thickness. Because the thickness of the photoresist is between 3um-4um, and the ITO layer is very thin in this example, the influence of the ITO layer is not considered. The thickness of the ITO layer is measured separately (see Figure 4)
Figure 2. Reflectance Spectrum of Photoresist
Figure 3 Film thickness analysis results, the thickness of the photoresist is 3.561um
Figure 4 The thickness of the ITO conductive layer is 12.8nm
