Influence of Cu electroplating solutions on boron carbon nitride (BCN) film

Cu electroplating is required for the fabrication of Cu/low-k interconnections. The permeation of a plating solution into low-k films during Cu electroplating is a serious challenge for 45-nm nodes and more complex devices. We investigated the influence of Cu electroplating solutions on boron carbon nitride (BCN) as a low-k film. After dipping it into a Cu electroplating solution that contained additives, the BCN film's hydrophilic surface changed to a hydrophobic surface, and the incorporation of water into the BCN film was suppressed by surfactant adsorption. Sulfuric residue was detected on the BCN sample by thermal desorption spectroscopy after treatment in the Cu electroplating solution with additives; however, it was found through electrical measurements that this solution did not affect the leakage current or the dielectric constant of the BCN film. We successfully fabricated an electroplating Cu layer on a BCN film with good adhesion, and we believe that this BCN film is a sufficiently useful material for Cu/BCN integration in LSI.     

Fourier transform infrared spectroscopy investigation of chemical bonding in low-k a-SiC:H thin films

Fourier Transform Infrared (FTIR) Spectroscopy has long been utilized as an analytical technique for qualitatively determining the presence of various different chemical bonds in gasses, liquids, solids, and on surfaces. Most recently, FTIR has been proven to be extremely useful for understanding the different types of bonding present in low dielectric constant “low-k” organosilicate materials. These low-k materials are predominantly utilized in the nanoelectronics industry as the interlayer dielectric material in advanced Cu interconnect structures. In this article, we utilize FTIR to perform a detailed analysis of the changes in chemical bonding that occur in Plasma Enhanced Chemically Vapor Deposited (PECVD) low-k a-SiC:H thin films. PECVD low-k a-SiC:H materials are equally important in advanced Cu interconnects and are utilized as both etch stop and Cu diffusion barrier layers. We specifically investigate the changes that occur in low-k a-SiC:H films as the dielectric constant and mass density of these films are decreased from > 7 to < 3 and from 2.5 to 1 g/cm³ respectively. We show that decreases in mass density and dielectric constant are accompanied by both an increase in terminal SiH_x and CH_x bonding and a decrease in SiC network bonding. At densities of 1.85 g/cm³, the concentration of terminal SiH_x bonding peaks and subsequent hydrogen incorporation are achieved predominantly via terminal CH₃ groups. Low-k a-SiC:H films with k < 3.5 and density < 1.3 g/cm³ can be achieved via incorporating larger organic phenyl groups but result in non-stoichiometric carbon rich films. Electron beam curing of these lower density a-SiC:H films results in volatilization of the phenyl groups leaving behind nanoporous regions and production of some CCC chain linkages in the network.     

Mass and bond density measurements for PECVD a-SiCx:H thin films using Fourier transform-infrared spectroscopy

The absolute concentration of chemical bonds in Plasma Enhanced Chemically Vapor Deposited (PECVD) a-SiC_x:H thin films have been determined via combining transmission Fourier-Transform Infra-red (FTIR) spectroscopy with X-ray Reflectivity (XRR) and Rutherford Backscattering (RBS) mass density and composition measurements. Specifically, we demonstrate in this paper that the integrated absorbance for the Si-C stretch in FTIR is linearly proportional to the mass density of PECVD a-SiC_x:H films as determined by XRR and RBS. This linear relationship allows us to accurately determine the IR absorption cross section for the Si-C stretch. Using these cross sections in combination with IR proportionality constants/cross sections published by other researchers, we demonstrate that mass densities in agreement with XRR and RBS can be calculated from the integrated absorbances of the Si-C, Si-H, and C-H stretches in FTIR spectra. From additional mass balance relationships, we further demonstrate that the full elemental and bond concentrations can be determined. This analysis reveals the presence of significant Si-Si and C-C bonding in the a-SiC_x:H films that was not clearly identified in previous FTIR investigations due to the low IR activity for these homopolar bonds. The bond and mass density calculations are demonstrated for both 3C-SiC and a-SiC_x:H thin films with mass density values ranging from 1 to 3.2 g/cm³.     

A Facile Strategy for Non-fluorinated Intrinsic Low-k and Low-loss Dielectric Polymers: Valid Exploitation of Secondary Relaxation Behaviors

High-performance low-k and low-loss circuit materials are urgently needed in the field of microelectronics due to the upcoming FifthGeneration Mobile Communications Technology(5 G Technology).Herein,a facile design strategy for non-fluorinated intrinsic low-k and low-loss polyimides is reported by fully considering the secondary relaxation behaviors of the polymer chains.A new amorphous non-fluorinated polymer(TmBPPA)with a k value of 2.23 and a loss tangent lower than 3.94×10^-3 at 104 Hz has been designed and synthesized,which to the best of our knowledge is the lowest value amongst the non-fluorinated and non-porous polymers reported in literature.Meanwhile,TmBPPA exhibits excellent overall properties,such as excellent thermostability,good mechanical properties,low moisture absorption,and high bonding strength.As high-performance flexible circuit materials,all these characteristics are highly expected to meet the present and future demands for high density,high speed,and high frequency electronic circuit used in 5 G wireless networks.     

Influence of oxygen plasma treatment on boron carbon nitride film composition

Variations in the composition and bonds of boron carbon nitride (BCN) film caused due to an oxygen (O₂) plasma ashing process are investigated for a low dielectric constant (low-k) insulating film for next generation LSI devices. The O₂ plasma treatment is preformed for BCN samples with various C compositions. The etching rate of BCN films with an O₂ plasma decreases with increasing C composition. The reaction of O atoms is suppressed in the BCN film with a high C composition. B-N and B-C bonds with lower bond energies are easily broken by the O₂ plasma and replaced by the generation of B-O, N-O, and C-O bonds. The B-atom concentration for all samples is decreased significantly by the O₂ plasma treatment. Ion bombardment may play a more dominant role than the O-atom reaction in the etching of the BCN film. The existence of C-N bonds with a high bonding energy may suppress etching and incorporation of O atoms.     

Polyimide/hollow silica sphere hybrid films with low dielectric constant

Abstract

Polyimide (PI)/hollow silica (HS) sphere hybrid films with low dielectric constant values (low-k) were synthesized via thermal imidization process using pyromellitic dianhydride (PMDA)/4,4′-oxydianiline (ODA) as the polymer matrix and HS spheres as inorganic particles with the closed air voids. The monodispersed HS spheres were synthesized via a one-step process, which means that the formation of silica shells and dissolution of the core particles (polystyrene particles) occurs in the same medium. The HS particles have uniform size of ca. 1.5 μm in diameter and ca. 100 nm in shell thickness. PI/HS sphere hybrid films synthesized using mixture of polyamic acid (PAA) and HS spheres prepared via one-pot process, which means that the production of PAA and HS spheres mixture occurs with the polymerization of PMDA and ODA in the same bottle. HS spheres of two different kinds (pristine HS spheres (PHS spheres) and amine-modified HS spheres (AHS spheres)) were used for the preparation of the hybrid films. With the varying contents of AHS spheres in the range of 1–10 wt%, the dielectric constants of the PI/AHS sphere hybrid films were reduced from 3.1 of pure PI to 1.81 by incorporating 5 wt% AHS. The dielectric constants of the PI/PHS sphere hybrid films were reduced to 1.86 by incorporating 5 wt% PHS. Organic–inorganic hybrid porous polyimides may be expected as prime candidates for polymeric insulators due to their high thermal stability, good mechanical properties, solvent resistance, and low-k.