Short-ranged structural rearrangement and enhancement of mechanical properties of organosilicate glasses induced by ultraviolet radiation

Abstract

The short-ranged bonding structure of organosilicate glasses can vary to a great extent and is directly linked to the mechanical properties of the thin film material. The combined action of ultraviolet (UV) radiation and thermal activation is shown to generate a pronounced rearrangement in the bonding structure of thin organosilicate glass films involving no significant compositional change or film densification. Nuclear magnetic resonance spectroscopy indicates loss of –OH groups and an increase of the degree of cross-linking of the organosilicate matrix for UV-treated films. Fourier transform infrared spectroscopy shows a pronounced enhancement of the Si–O–Si network bond structure, indicating the formation of more energetically stable silica bonds. Investigation with x-ray reflectivity and ellipsometric porosimetry indicated only minor film densification. As a consequence, the mechanical properties of microporous organosilicate dielectric films are substantially enhanced while preserving the organosilicate nature and pristine porosity of the films. UV-treated films show an increase in elastic modulus and hardness of more than 40%, and a similar improvement in fracture energy compared to untreated films. A minor increase in material dielectric constant from 3.0 to 3.15 was observed after UV treatment. This mechanism is of high relevance for the application of organosilicate glasses as dielectric materials for microelectronics interconnects, for which a high mechanical stability and a low dielectric constant are both essential film requirements.

Toward Successful Integration of Porous Low-k Materials: Strategies Addressing Plasma Damage

“…14 This is currently solved by chip design, post-deposition treatments of existing low-k materials with a thermal ultraviolet (UV) source 15,16 or laser spike annealing (LSA) 17 and through the development of carbon-bridged materials with superior mechanical properties at a given k. [18][19][20][21][22][23] While the decrease in mechanical properties has been successfully addressed, integration problems related to the increased porosity with decreasing k are still pending. In case of the latter, the huge increase in accessible surface area leads to integration related damage, such as material modification occurring during exposure to plasma and wet chemical processes.…”

Dielectric Recovery of Plasma Damaged Organosilicate Low-k Films

“…UV radiation and thermal activation are commonly used to remove porogen to improve the mechanical properties of asdeposited low-k dielectrics [18]. But in this study, they were used for bulk recovery of plasma damaged OSG low-k dielectrics.…”

Molecular simulation strategy for mechanical modeling of amorphous/porous low-dielectric constant materials

“…The simulated Young's moduli for molecular models before and after UV treatment is 14.3 and 19.0 GPa, which resemble the experimental results of 11.0 and 16.0 GPa, where the porosities are 7.0% and 8.0%. 6 The average pore size in the model is approximately 0.8 nm in diameter, while the experiment shows 1.5-2.0 nm. 15 When the model size is large enough, the effect of the local randomization of the basic building blocks is averaged out.…”

“…A T-rich SiOC:H molecule before UV treatment, with concentrations of Q, T, D, and pore as 16.3%, 46.3%, 31.3%, and 6.0% ͑porosity͒ measured by NMR, 6 is modeled. Note that the molecular model illustrated in Fig.…”