Enhanced Thermo–Mechanical Reliability of Ultralow-K Dielectrics with Self-Organized Molecular Pores

Abstract

This paper reported the enhancement in thermo-mechanical properties and chemical stability of porous SiCOH dielectric thin films fabricated with molecularly scaled pores of uniform size and distribution. The resulting porous dielectric thin films were found to exhibit far stronger resistance to thermo-mechanical instability mechanisms common to conventional SiCOH dielectric thin films without forgoing an ultralow dielectric constant (i.e., ultralow-k). Specifically, the elastic modulus measured by nano-indentation was 13 GPa, which was substantially higher than the value of 6 GPa for a porous low-k film deposited by a conventional method, while dielectric constant exhibited an identical value of 2.1. They also showed excellent resistance against viscoplastic deformation, as measured by the ball indentation method, which represented the degree of chemical degradation of the internal bonds. Indentation depth was measured at 5 nm after a 4-h indentation test at 400 °C, which indicated an ~89% decrease compared with conventional SiCOH film. Evolution of film shrinkage and dielectric constant after annealing and plasma exposure were reduced in the low-k film with a self-organized molecular film. Analysis of the film structure via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated an increase in symmetric linear Si–O–Si molecular chains with terminal –CH3 bonds that were believed to be responsible for both the decrease in dipole moment/dielectric constant and the formation of molecular scaled pores. The observed enhanced mechanical and chemical properties were also attributed to this unique nano-porous structure.

A promising low‐dielectric‐constant material with good comprehensive performance upon heating

“…3D woven spacer Kevlar/ polyimide composites prepared by combining 3D weaving technology and thermal imidization process exhibited more than 96% of the retention rate of their compressive strength and a low dielectric constant of 1.36 when the temperature was rose to 300 C. 17 Moreover, the thermomechanical stability and reliability of an ultralow-k dielectric film can be significantly enhanced through fabricating a porous SiCOH dielectric thin film. 18 Although these methods are feasible, complex steps, and expensive materials were usually involved.…”

Millisecond flash lamp curing for porosity generation in thin films

“…A class of porous materials that requires a proper porous design is the low-k dielectric thin films used as interlayer insulators in microelectronic applications 12 , 13 . For instance, during the fabrication of low-k thin films, large and interconnected pores result in observable plasma-induced damages that cause charges to build up and ultimately increase the leakage current 14 . Furthermore, porous low-k dielectrics with interconnected pores have poor mechanical properties, which complicates their incorporation into microchips 15 .…”