APPLICATION NOTE Mx™ Software Films Analysis Coherence Scanning Interferometers (CSI) are a rapid, non-contact method of measuring both transparent films and the substrate underlying them. Instruments like the Zygo Nexview™ profiler system can provide film thickness and thickness variation, as well as top surface and substrate roughness, all in a single measurement. While originally useful mainly in the semiconductor industry, this technique has more recently found applications in microfluidics, consumer electronics, food packaging and more. Film Analysis for Mx™ Software The original generation of signal processing methods for CSI instruments was appropriate only for measuring a single, opaque surface. When a surface with a transparent film was measured, the reflection from the secondary surface would cause the algorithm to fail. Modern specialized techniques can decode this more complex signal and produce results for both the transparent film and the underlying substrate. This method allows for excellent interpretation of film structures as thin as 1.5µm optical thickness. As the majority of transparent films have indices of refraction between 1.4 and 1.6, a 1.5 µm optical thickness converts to approximately 1 µm physical limit thickness lower limit. Below this limit, the signals begin to overlap, and film thickness measurements become more difficult. However, down to about 0.5 µm (optical thickness), the top surface of a film can be isolated and surface texture analyzed. Illumination Considerations Figure 1: Typical CSI Signal Figure 2: CSI signal of a film showing 2 distinct interference signals In order to separate the multiple modulation signals, the Films Analysis software uses Zygo’s patented signal analysis techniques, which compare the complex, whitelight interferometry signal created by a thin film sample to the simpler signal created by a smooth surface without a film. High quality measurements through a transparent film require that particular attention be paid to the numerical aperture (NA) of the illumination used for the test. Typically, the secondary signal of a film weakens at the NA and magnification increase. This limits the thickness of a film that can be measured by higher magnification objectives. NewView™ and Nexview™ instruments are equipped with an adjustable aperture stop, allowing the user to effectively decrease the NA of the system and increase fringe contrast for thick film metrology. Typical Performance Several transparent films ranging from 1 µm to 50 µm of physical thickness were measured using various objectives. The following table shows the excellent repeatability that

Repeatability Over 20 Measurements Film 1.027 µm Si02 1.939 µm Si02 4.885 µm Si02 50.411 µm resist Typical Data Conclusion The Films Analysis package for Mx™ software combined with Zygo’s flagship profiler, the Nexview™, is the fastest and most versatile tool available for quantification and visualization of film surface and thickness characteristics. Zygo’s patented analysis algorithms allow for unparalleled repeatability for total confidence in your film metrology. Mx™ Films Analysis software simultaneously provides data for the top surface, second surface (usually the substrate surface), and...