Depth dependence of ultraviolet curing of organosilicate low-k thin films

Abstract

UV radiation curing has emerged as a promising postdeposition curing treatment to strengthen organosilicate interlayer dielectric thin films. We provide the evidence of film depth dependent UV curing which has important effects on through thickness mechanical and fracture properties. Force modulation atomic force microscopy measurements of the elastic modulus through the thickness of the films revealed evidence of periodic modulations of the glass stiffness which increased in magnitude with UV curing time. Furthermore, while significant increases in fracture energy were observed with UV curing time at the top of the organosilicate film, much lower increases were observed at the bottom. The increase in fracture energy with UV curing was film thickness dependent. The cohesive fracture resistance was less sensitive to UV curing. Possible explanations for the stiffness modulations through the film thickness involving UV light interference or phase separation by spinodal decomposition during the cure process are described.

Molecular Origins of the Mechanical Behavior of Hybrid Glasses

“…[ 10 ] Thus post-deposition curing to increase the network connectivity by formation of Si-O-Si bonds has been critical to achieve acceptable mechanical properties at the expense of organic component loss, fi lm shrinkage, and degradation of electro-optical performance that accompanies curing. [11][12][13] The effect of network connectivity on mechanical p Et− OC S = (1 + 3q Et− OC S )/ 4 (1) and for Et-OCS(Me) by:…”

Study of Chip–Package Interaction Parameters on Interlayer Dielectric Crack Propagation

“…With these stress-free temperature conditions for different materials and boundary conditions in the assembly, the model is simulated to cool down from reflow temperature to room temperature. Upon cooling, the assembly warps down (frowning or dome shape) because the effective coefficient of thermal expansion (CTE) of the substrate is greater than the CTE of the die [21]. Fig.…”

“…Four-point bend test technique has been used to investigate the adhesive energies of Cu and various low-k materials deposited using different processes. The fracture strength of low-k materials has been extensively researched; fracture strength of 5 J/m 2 is estimated at room temperature for chemical mechanical polishing [18], cohesive fracture strength is found to be 3.5-6 J/m 2 [19], fracture strength is found to vary between 0.5-3 J/m 2 based on loading angle [20] and between 1.8-2.4 J/m 2 [21] based on loading rates. In this work critical energy release rate of 5 J/m 2 (G 0 ) is assumed.…”

Low‐kMaterials: Recent Advances

“…This suggests a depth dependence of the UV cure. Indeed, studies using monochromatic UV radiation, where the depth dependence is significantly more severe, indicate UV light interference, which forms a standing wave during the curing process [78,79]. While underlying layers of transparent SiN can mitigate this effect and increase the adhesive fracture energy at the bottom interface, UV absorbing spacers such as SiCN negated the beneficial effects of UV irradiation at both interfaces [83].…”

“…In addition, primary consideration will be given to broadband UV radiation (λ = 200-400 nm) over monochromatic UV radiation (λ < 200 nm) due to the fact that the former is better suited for porogen removal and mechanical enhancement [76], less damaging to the dielectric material [77], less prone to standing wave effects [78,79] and the preferred spectral range of presently used manufacturing tools.…”