Abstract
SiO2 thin films are deposited by radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) technique using SiH4 and N2O as precursor gases. The stoichiometry of SiO2 thin films is determined by the X-ray photoelectron spectroscopy (XPS), and the optical constant n and k are obtained by using variable angle spectroscopic ellipsometer (VASE) in the spectral range 380–1600 nm. The refractive index and extinction coefficient of the deposited SiO2 thin films at 500 nm are 1.464 and 0.0069, respectively. The deposition rate of SiO2 thin films is controlled by changing the reaction pressure. The effects of deposition rate, film thickness, and microstructure size on the conformality of SiO2 thin films are studied. The conformality of SiO2 thin films increases from 0.68 to 0.91, with the increase of deposition rate of the SiO2 thin film from 20.84 to 41.92 nm/min. The conformality of SiO2 thin films decreases with the increase of film thickness, and the higher the step height, the smaller the conformality of SiO2 thin films.
Highlights
Coatings 2021, 11, 510. https://SiO2 is a commonly used optical thin film material with low refractive index
When the thin film is deposited on a patterned substrate with chemical vapor deposition (CVD) technology, it is easy to obtain good conformality, while it is difficult with physical vapor deposition (PVD) [18,19]
The step coverage is generally defined as the ratio of the film thickness at the trenc In this work, the new method to quantitatively measure the conformality of thin films bottom to the thickness on the flat at the trench mouth opening, as shown in Figure 1a on patterned substrate is proposed
Summary
SiO2 is a commonly used optical thin film material with low refractive index. Several new applications for SiO2 thin films will require conformal coverage (good conformality) of micro- and nano-scale features in the substrate. Conformality, conformal coverage, or step coverage are important for many applications such as array optical filters, microelectronics [7,8,9], integrated circuit technologies [10,11], and nano-imprint lithography [12,13]. When the thin film is deposited on a patterned substrate with CVD technology, it is easy to obtain good conformality, while it is difficult with PVD [18,19]
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