Structure of low dielectric constant to extreme low dielectric constant SiCOH films: Fourier transform infrared spectroscopy characterization

Abstract

Carbon doped oxide dielectrics comprised of Si, C, O, and H (SiCOH) have been prepared by plasma enhanced chemical vapor deposition (PECVD) from mixtures of tetramethylcyclotetrasiloxane (TMCTS) and an organic precursor. The films have been analyzed by determining their elemental composition and by Fourier transform infrared spectroscopy with deconvolution of the absorption peaks. The analysis has shown that PECVD of TMCTS produces a highly crosslinked networked SiCOH film. Dissociation of TMCTS appears to dominate the deposition chemistry as evidenced by the multitude of bonding environments and formation of linear chains and branches. Extensive crosslinking of TMCTS rings occurs through Si–Si, Si–CH2–Si, Si–O–Si, and Si–CH2–O–Si moieties. The films deposited from mixtures of TMCTS and organic precursor incorporate hydrocarbon fragments into the films. This incorporation occurs most probably through the reaction of the organic precursor and the Si–H bonds of TMCTS. Annealing the SiCOH films deposited from TMCTS and organic precursor results in a large loss of carbon and hydrogen from the films resulting from the fragmentation and loss of the incorporated organic component. The deconvolution of the Si–O–Si asymmetric stretching band of the annealed films shows the existence of a larger fraction of a cage structure and a correspondingly smaller fraction of a networked (highly crosslinked) structure in the SiCOH films deposited from mixtures of TMCTS with organic precursor relative to the films deposited from TMCTS only. The evolution of the volatile hydrocarbon fragments during annealing results in the formation of nanopores and subsequent reduction of the dielectric constants of the films to extreme low-k values.

Low and Ultralow Dielectric Constant Films Prepared by Plasma‐enhanced Chemical Vapor Deposition

“…Typical FTIR spectra of such fi lms are presented in . A weak absorption at 1358 cm −1 can also be sometimes observed and assigned to bending of C-H in Si-CH 2 -Si cross-links (references for specifi c peak identifi cations can be found elsewhere [15]). …”

“…Structural characterization of amorphous fi lms is extremely diffi cult, but we have shown that it is possible to use FTIR to characterize the different bonding arrangements in the fi lms and to obtain insights in the structure of SiCOH [15]. Typical FTIR spectra of such fi lms are presented in .…”

“…FTIR absorption peaks enable the identifi cation of the different bond structures in the fi lms. In some cases, peaks were deconvoluted into individual components to get a better understanding of the fi lm structure [15]. FTIR analysis can also be used to follow modifi cations in the fi lms as a result of processing of the dielectric or its exposure to the environment, but only if such changes are larger than a few percent.…”

Electroluminescent properties of Tb-doped carbon-enriched silicon oxide

“…Two main absorption bands are at 780 and 1000 cm -1 . The first one is due to C Si  stretching vibration with possible minor contribution from CH 3 rocking in ) [10][11][12][13]. The absorption band at 1000 cm -1 in a -SiO 1-x : C x : H films is commonly ascribed to rocking/waging vibration modes in CH 2 radicals attached to silicon atoms [12].…”

Characterization of SiC:H films deposited using HMDS precursor with C2H2 dilution gas by remote PECVD system

“…6), 7) The most commonly used low-k material, fluorosilicate, has a k-value of 3.5, which is slightly lower than SiO2. In order to reduce the RC delay time, more low-k materials with k-values less than 2 must be introduced.…”