Abstract
Thin films are a type of coating that have a very wide spectrum of applications. They may be used as single layers or composed in multilayer stacks, which significantly extend their applications. One of the most commonly used material for thin films is silicon dioxide, SiO2. Although there are other tools that can be used to measure the thickness of SiO2 films, these tools are very complex and sophisticated. In this article, we propose the use of an exponential two-layer light-material interaction model, throughout its diffuse reflectance spectra, as an alternative for the measurement of the thickness of evaporated SiO2 on Si wafers. The proposed model is evaluated experimentally by means of a 980-nm-thick SiO2 layer evaporated on a Si wafer. The results show that the proposed model has a strong correlation with the thickness measurements obtained using commercial equipment.
Highlights
Silicon dioxide, SiO2, is one kind of dielectric coating that is widely used in optical multilayer stacks, for covering the losses caused by low absorption and low scattering [1,2,3]
We propose the use of an exponential two-layer light-material interaction model as an alternative for the measurement of the thickness of evaporated SiO2 on a Si wafer, through its diffuse reflectance spectrum
It is possible to observe the congruence between both spectra in Figure 2, indicating that the model obtained a good approximation of the evaluated data
Summary
SiO2 , is one kind of dielectric coating that is widely used in optical multilayer stacks, for covering the losses caused by low absorption and low scattering [1,2,3]. One of the most important parameters for ensuring good optical quality in SiO2 layers is its density. This can be controlled by using different deposition techniques, e.g., thermal oxidation, plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD) and ion beam deposition (IBD), among others [4,5,6,7]. A number of tools can be used to measure the thickness of deposited SiO2 Among those tools, there are those based on mechanical techniques such as a stylus profiler, as well as those based on optical techniques such as ellipsometry or diffuse reflectance spectroscopy [8]. In the case of diffuse reflectance spectroscopy, a beam of white light illuminates a point on the surface of a substrate with a deposited SiO2 layer, while the diffuse reflectance spectrum is detected through a spectrometer
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