Effects of Methyl Terminal and Carbon Bridging Groups Ratio on Critical Properties of Porous Organosilicate-Glass Films.

Alexey S Vishnevskiy,Jing Zhang,Sergej Naumov,Wei-Tsung Chuang,Yu-Hsuan Wu,Mikhail R Baklanov,Jihperng Leu,Konstantin A Vorotilov,Dmitry S Seregin,Md Rasadujjaman

doi:10.3390/ma13204484

Abstract

Organosilicate glass-based porous low dielectic constant films with different ratios of terminal methyl to bridging organic (methylene, ethylene and 1,4-phenylene) groups are spin-on deposited by using a mixture of alkylenesiloxane with organic bridges and methyltrimethoxysilane, followed by soft baking at 120–200 °C and curing at 430 °C. The films’ porosity was controlled by using sacrificial template Brij® L4. Changes of the films’ refractive indices, mechanical properties, k-values, porosity and pore structure versus chemical composition of the film’s matrix are evaluated and compared with methyl-terminated low-k materials. The chemical resistance of the films to annealing in oxygen-containing atmosphere is evaluated by using density functional theory (DFT). It is found that the introduction of bridging groups changes their porosity and pore structure, increases Young’s modulus, but the improvement of mechanical properties happens simultaneously with the increase in the refractive index and k-value. The 1,4-phenylene bridging groups have the strongest impact on the films’ properties. Mechanisms of oxidative degradation of carbon bridges are studied and it is shown that 1,4-phenylene-bridged films have the highest stability. Methylene- and ethylene-bridged films are less stable but methylene-bridged films show slightly higher stability than ethylene-bridged films.

Highlights

Low dielectric constant materials and low resistivity metals (Cu, Co, Ru etc.) have been introduced into microelectronics technology to replace traditional SiO2 and Al since the late 1990s.The implementation of Cu and low-k dielectrics was required to reduce the signal propagation delay in interconnection structures of ultra large-scale integration (ULSI) devices, and to reduce power dissipation and cross-talk noise between the metal lines [1,2].Materials 2020, 13, 4484; doi:10.3390/ma13204484 www.mdpi.com/journal/materialsAfter extensive evaluation of different low-k candidates from organic polymers to metal–organic frameworks [3], organosilicate glass (OSG)-based films have been recognized as the most suitable low-k materials for the present ULSI technology
The second part of the work reports results of ab initio density functional theory (DFT) calculations to understand the nature of chemical reactions during the interaction of carbon bridges with residual oxygen
Additional information related to resistance of the deposited films to thermal annealing, and the mechanisms of their possible destruction by residual oxygen, was obtained by density functional theory (DFT)

Summary

Introduction

Low dielectric constant (low-k) materials and low resistivity metals (Cu, Co, Ru etc.) have been introduced into microelectronics technology to replace traditional SiO2 and Al since the late 1990s. The second part of the work reports results of ab initio density functional theory (DFT) calculations to understand the nature of chemical reactions during the interaction of carbon bridges with residual oxygen (for instance, during thermal curing or integration processes) These results are important for the selection of the materials most suitable for integration into ULSI devices. The dielectric constant was estimated in the frequency range of 1 to 100 kHz. Additional information related to resistance of the deposited films to thermal annealing, and the mechanisms of their possible destruction by residual oxygen, was obtained by density functional theory (DFT). The difference of the calculated H and G between the reactants and products are presented as the reaction enthalpies (∆H) and Gibbs free energies (∆G)

Results and Discussion

Pore Geometries Characterized by GISAXS

Conclusions