Carbon-doped Silicon Oxide Films Research Articles

Carbon-Doped Silicon Oxide Films with Hydrocarbon Network Bonds for Low-k Dielectrics: Theoretical Investigations

We have computationally explored the chemical structures of carbon-doped silicon oxide (SiOCH) films that give the smallest dielectric constant (k) under the required mechanical strength for low-k dielectrics. The focus of this study is on the SiOCH structures that have hydrocarbon components in the polymer network as cross-links. It has been found that SiOCH films of small dielectric constants can have improved mechanical strengths if the hydrocarbon components form cross-links, instead of the terminal methyl groups in the conventional structure. The calculated results suggest that SiOCH films of ideal structures can have substantially smaller dielectric constants than films of current interconnect technology with the same mechanical strengths.

Investigation of low dielectric carbon-doped silicon oxide films prepared by PECVD using methyltrimethoxysilane precursor

Carbon-doped silicon oxide (SiOC(-H)) films with low dielectric constant were deposited on a p-type Si(100) substrate using inductively coupled plasma chemical vapor deposition with methyltrimethoxysilane (MTMS:CH 3Si(OCH 3) 3) precursor and oxygen gases. Fourier transform infrared spectroscopy was used to investigate the bonding configurations and atomic concentrations within the films. The dielectric constant of SiOC(-H) composite film depends on the relative carbon concentration and the content of the ring link mode in SiOC(-H) bonding structure. The lowest dielectric constant of an annealed film at 400 °C was 2.25, which was deposited with [MTMS / (MTMS + O 2)] flow rate ratio of 100%.

The characteristics of carbon-doped silicon oxide films with nano-pore structure deposited using UV-assisted PECVD

SiOC(–H) films with low dielectric constant were deposited on p-type Si(100) substrate using ultraviolet (UV)-source assisted plasma-enhanced chemical vapor deposition with a mixture of bis-trimethylsilylmethane (BTMSM: H 9C 3–Si–CH 2–Si–C 3H 9) and oxygen gases. Fourier transform infrared spectroscopy was used to investigate the bonding configuration and relative carbon content of the SiOC(–H) films. UV illumination of the BTMSM/O 2 plasma was used to control the plasma parameters and deposition properties. The addition of He gas to the mixture of BTMSM and O 2 raised the electron density from 2.5 × 10 9 to 9.8 × 10 9 cm − 3. The lowest dielectric constant was 2.4, and was deposited using a mixture of BTMSM + O 2 + He gases with UV illumination. The bonding structure of the SiOC(–H) composite film consists of distinct Si–O–Si and Si–O–C bonds, indicating the existence of caged Si–C bonds, and this enhances the porosity of the film. UV illumination increased the relative content of the ring link mode of the SiOC(–H) films.

Impact of reductive N2∕H2 plasma on porous low-dielectric constant SiCOH thin films

Porous low-dielectric constant (low-κ) SiCOH thin films deposited using a plasma-enhanced chemical-vapor deposition have been comprehensively characterized before and after exposure to a reactive-ion-etch-type plasma of N2 and H2 chemistry. The low-κ film studied in this work is a carbon-doped silicon oxide film with a dielectric constant (κ) of 2.5. Studies show that a top dense layer is formed as a result of significant surface film densification after exposure to N2∕H2 plasma while the underlying bulk layer remains largely unchanged. The top dense layer is found to seal the porous bulk SiCOH film. SiCOH films experienced significant thickness reduction, κ increase, and leakage current degradation after plasma exposure, accompanied by density increase, pore collapse, carbon depletion, and moisture content increase in the top dense layer. Both film densification and removal processes during N2∕H2 plasma treatment were found to play important roles in the thickness reduction and κ increase of this porous low-κ SiCOH film. A model based upon mutually limiting film densification and removal processes is proposed for the continuous thickness reduction during plasma exposure. A combination of surface film densification, thickness ratio increase of top dense layer to bulk layer, and moisture content increase results in the increase in κ value of this SiCOH film.

Effect of oxygen plasma treatment on low dielectric constant carbon-doped silicon oxide thin films

Low dielectric constant (low k) carbon-doped silicon oxide (CDO) films are obtained by plasma-enhanced chemical vapor deposition. The k value of the as-deposited CDO film is less than 2.9. However, the k value may be changed during the integration process. In integration process, photoresist removal is commonly implemented with oxygen plasma ashing or by wet chemical stripping. In this work, the impact of oxygen plasma treatment has been investigated on the quality of the low-k CDO films. Different plasma treatment conditions, including variable pressure, r.f. power, and treatment time were employed. A variety of techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), atomic force microscopy (AFM), and scanning electron microscope (SEM) were used to analyze the effect of the oxygen plasma post-treatment on the low-k CDO films. The result indicates that oxygen plasma will damage the CDO film by removing the entire carbon content in the upper part of the film with increasing treatment time, which results in an increase in the k value and film thickness loss. Our result also confirms that with low r.f. power and low pressure, the damage will be less.

Low dielectric constant films prepared by plasma-enhanced chemical vapor deposition from trimethylsilane

Dielectric materials with lower permittivity (low k) are required for isolation to reduce the interconnect RC delay in deep submicron integrated circuit. In this work, carbon-doped silicon oxide films are investigated as a potential low k material. The films were prepared by the radio frequency plasma-enhanced chemical vapor deposition (PECVD) technique from trimethylsilane (3MS) in an oxygen (O 2) environment. The O 2/3MS flow ratio (in sccm) was varied from 50:600 to 900:600 to investigate its effects on the properties of the films. The films were also annealed at 400 °C in an N 2 atmosphere for 30 min to determine the thermal stability of their properties. Thickness and refractive index were measured by opti-probe. Chemical structures were characterized by Fourier transform infrared spectroscopy (FTIR). Dielectric constants were measured using a Si/insulator/mercury probe structure. It was found that the deposition rate increased almost three times while the refractive index decreased from 1.46 to 1.39 with increasing oxygen concentration in the gas feed. Dielectric constants as low as 2.9 have been obtained for the as-prepared film with a O 2/3MS flow ratio of 100:600. FTIR spectra revealed that more Si–CH and Si–CH 3 groups were introduced into the silicon dioxide backbone of the films at this flow ratio, and the low dielectric constant obtained is attributed to the increased incorporation of carbon in the form Si–CH 3 bond, which has lower polarizability compared to the Si–O bonds that were replaced. The annealing has been found to lower the dielectric constant of the films, but has no effect on their composition and chemical structure.

Stability of Carbon-Doped Silicon Oxide Low-k Thin Films

The impact of and plasma treatments on the properties of low-dielectric-constant (low-k) carbon-doped silicon oxide (CDO) film, deposited by plasma-enhanced chemical vapor deposition, has been investigated. The thermal stability and the effect of moisture penetration on low-k films have also been evaluated. It is found that and plasma treatments of low-k films result in some loss of C content and increase in moisture uptake. This increases the k value and leakage current of the film. The and plasma treatments do not add any N content in the films. Therefore, it does not cause the resist contamination of chemically amplified-type photoresists. High thermal stability of the low-k CDO material is confirmed by isothermal thermogravimetric analysis of the low-k CDO powder and there is no weight loss or change of composition of the low-k CDO film after seven thermal cycles at 425°C for 1 h in ambient. A pressure cooker test of the film carried out at ∼2 atm, 120°C, and 100% relative humidity for 24 h has been found to increase the k value by 7% and leakage current by two orders of magnitude. © 2004 The Electrochemical Society. All rights reserved.

The influence of carbon content in carbon-doped silicon oxide film by thermal treatment

Carbon-doped silicon oxide (SiOC) low- k dielectric film was deposited on a p-type Si(100) substrate with mixture of bis-trimethylsilylmethane (BTMSM) and oxygen by inductively coupled plasma chemical vapor deposition (ICPCVD). Electron density and electron temperature of ∼10 12 cm −3 and 1.6 eV, respectively, were obtained at low pressure (<300 mTorr) and radio frequency (RF) power of approximately 300 W. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the bonding configurations, porosity and atomic concentrations within the films. The carbon content increased and the film density decreased in films annealed at 400 °C in vacuum. SiOSi and SiOC bonds were separately identified in the bonding structure of SiOC composite films. We can deduce the existence of caged SiO bonds and enhanced porosity of the film from these results. The dielectric constant of the SiOC composite film depends on the relative carbon content and the pore density. The porosity calculated is 68% when the dielectric constant is approximately 2.1.

Reduction of Oxygen Plasma Damage by Postdeposition Helium Plasma Treatment for Carbon-Doped Silicon Oxide Low Dielectric Constant Films

The low dielectric constant (low k) carbon doped silicon oxide (CDO) films are obtained by plasma-enhanced chemical vapor deposition. The impact of oxygen plasma treatment on the properties of low k films has been investigated and it is found that O 2 plasma treatment damages the CDO film by removing C and part of Si contents in the film. This results in the loss of film thickness and increase in k value of the film. Postdeposition He plasma treatment has been confirmed to be effective in reducing the O 2 plasma damage on the CDO films significantly. With He plasma pretreatment, the thickness loss after O 2 plasma is reduced, and k value remains the same as the as-deposited CDO film compared to the film without the He plasma pretreatment. Also analysis of film properties by Fourier transform infrared spectroscopy. secondary ion mass spectrometry, atomic force microscopy, and scanning electron microscopy indicates that there is no obvious change of the properties of low k CDO films after O 2 plasma for postdeposition He plasma pretreated films.