Effects of ultraviolet (UV) irradiation in air and under vacuum on low-k dielectrics

Abstract

This work addresses the effect of ultraviolet radiation of wavelengths longer than 250 nm on Si-CH3 bonds in porous low-k dielectrics. Porous low-k films (k = 2.3) were exposed to 4.9 eV (254 nm) ultraviolet (UV) radiation in both air and vacuum for one hour. Using Fourier Transform Infrared (FTIR) spectroscopy, the chemical structures of the dielectric films were analyzed before and after the UV exposure. UV irradiation in air led to Si-CH3 bond depletion in the low-k material and made the films hydrophilic. However, no change in Si-CH3 bond concentration was observed when the same samples were exposed to UV under vacuum with a similar fluence. These results indicate that UV exposures in vacuum with wavelengths longer than ∼250 nm do not result in Si-CH3 depletion in low-k films. However, if the irradiation takes place in air, the UV irradiation removes Si-CH3 although direct photolysis of air species does not occur above ∼242nm. We propose that photons along with molecular oxygen and, water, synergistically demethylate the low-k films.

Impact of VUV photons on SiO2 and organosilicate low-k dielectrics: General behavior, practical applications, and atomic models

“…Besides, a chemical reaction with O2 results in Si-Ox based bond formation. Behera et al200 and Choudhury et al201 reported similar synergetic effect of VUV radiation with NH3 and air, respectively. These results show that photo-induced effects with molecular species can play an important role in SiCOH films damage and should be discussed separately.In further study147 , the authors report the measured films damage induced by VUV photons, by O radicals, and by O2 plasma in the conditions of the study146 .…”

Graphene oxide modifications induced by excimer laser irradiations

“…GO laser irradiation is drastically modified by the laser irradiation and its changes depend on the laser parameters 23–25 (pulse energy and duration, wavelength, and fluence) and irradiation conditions (vacuum, air, gas, and focalization). For instance, significant difference occurs if the irradiation is performed in air or in vacuum, generally producing high oxygen reduction effects in vacuum and oxidation effects in air, as reported in the literature 26–28 . In this work, we focus on the study on defect generation in graphene, induced by exposure to an ultraviolet (UV) excimer laser, emitting 23‐ns pulses at 248‐nm wavelength.…”

“…For instance, significant difference occurs if the irradiation is performed in air or in vacuum, generally producing high oxygen reduction effects in vacuum and oxidation effects in air, as reported in the literature. [26][27][28] In this work, we focus on the study on defect generation in graphene, induced by exposure to an ultraviolet (UV) excimer laser, emitting 23-ns pulses at 248-nm wavelength. We compare the irradiation of GO substrates in air and under vacuum, showing through Raman spectroscopy, that, defects are introduced in both cases, at different rates.…”

Broadband Dielectric Spectroscopic Characterization of Thermal Stability of Low-k Dielectric Thin Films for Micro- and Nanoelectronic Applications

“…It has been demonstrated that optical photons (~4.9 eV (254 nm)) synergistically act with molecular oxygen and water to cleave Si-CH 3 bonds in porous polyhydral oligomeric silsesquioxane (POSS) low-k (p-SiCOH) films. 16 In the case of plasma enhanced chemical vapor deposited (PECVD) fluorocarbon films, the thermal decomposition occurs over a broad range of temperatures. However, there is a critical temperature (depending on the stereochemistry of the polymer backbone), beyond which, the slowest step in the thermal decomposition reaction is dependent on the diffusion of decomposition by-product materials out of the film.…”