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

Dong-Yurl Yu,Y. K. Sa,Junhyuk Son,Junghwan Bang,Yun-Chan Kim

doi:10.3390/ma14092284

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.

Highlights

Introduction iationsDielectric thin films with ultralow values of dielectric constant (k), close to or lower than two, have been one of the most intensively investigated materials in recent years for use in on-chip interconnects in high performance ultra-large-scale integrated (ULSI)devices [1,2]
In order to evaluate the change in elastic modulus and hardness of the p-SiCOH films, a series of nano-indentation tests were conducted first on the specimens prepared by the different deposition methods
The measured elastic modulus value of 13 GPa for the p-SiOCH film deposited by the structural method is substantially higher than the value of 6 GPa determined for the pSiOCH film formed by subtractive methods and is high relative to those previously reported for p-SiCOH thin films deposited by other methods but with similar dielectric constant values [49,50]

Summary

Introduction

Dielectric thin films with ultralow values of dielectric constant (k), close to or lower than two, have been one of the most intensively investigated materials in recent years for use in on-chip interconnects in high performance ultra-large-scale integrated (ULSI). Devices [1,2]. In order to reduce signal interference in ULSI interconnects caused by what is known as the resistance–capacitance (RC) delay, both the resistance of the metal line and the associated capacitance of the interlayer dielectric (ILD) layer should be decreased [3,4]. Insulating dielectrics with ultralow values of dielectric constant relative to the traditional ILD material (silicon dioxide—SiO2 ) are needed to enable current ULSI devices and continued miniaturization to support future integrated products [5,6].

Methods

Results

Conclusion