Measure PI film topography by laser confocal microscope

The pursuit of thinner and lighter smartphones drives the demand for advanced packaging now. The current output of advanced packaging wafers are close to 40% of the total global wafer production. Advanced packaging technology needs to combine the circuit, cooling and other technologies to ensure that the electronic parts have the best performance and reliability. PI can meet the requirements of high heat resistance, high mechanical, high insulation, high frequency stability, low dielectric constant, dielectric loss, and low thermal expansion coefficient. PI becomes the core material for advanced packaging. However, PI uniformity, film thickness, etc. will affect the characteristics of the product, so the requirements for uniformity, thickness, etc. also tend to be strict, and various coating accuracy requirements need to be monitored with different monitoring systems. In the monitoring of uniformity, it is more difficult to monitor the surface morphology due to the transparent material. For measuring surface topography, the information on topography comes from analyzing the reflected signal, and the reflectivity of the material is affected by the ratio of the refractive indices of the two media. In this paper, when measuring the topography of a known sample, it is necessary to consider the refractive index ratio of PI and the underlying medium. Through the refractive index changes of different wavelengths, select a suitable wavelength to measure the topography.