N.-E. Lee

The interface formation and adhesion of metals (Cu, Ta, and Ti) and low dielectric constant polymer-like organic thin films deposited by plasma-enhanced chemical vapor deposition using para-xylene precursor

Abstract The interface formation, adhesion and diffusion properties of metals (Cu, Ta, and Ti) and low dielectric constant (low k ) polymer-like organic thin films (POTFs) deposited by plasma-enhanced chemical vapor deposition (PE-CVD) using the para -xylene precursor were investigated. Cu, Ta and Ti deposited on the surfaces of POTFs treated by O 2 and N 2 plasmas generated in a magnetically-enhanced inductively coupled plasma (ME-ICP) reactor. X-ray photoelectron spectroscopy (XPS) was used to study the chemical interactions between metals and POTFs. As a result of formation of new binding states by plasma treatment, the adhesion strength of metals and POTFs was increased. Diffusion properties of metals into POTFs were investigated using Rutherford backscattering spectroscopy (RBS) for the vacuum-annealed Cu/POTFs and Ta/POTFs for 1 h at 450°C. Also, from the RBS spectra, it was observed that Cu and Ta in the post-annealed samples were not diffused into both POTFs with and without plasma surface treatments.

Chemical interaction, adhesion and diffusion properties at the interface of Cu and plasma-treated thiophene-based plasma polymer (ThioPP) films

Abstract Chemical interaction, adhesion and diffusion properties at the interface of Cu and plasma-treated thiophene-based plasma polymer (ThioPP) films deposited by plasma-enhanced chemical vapor deposition (PECVD) were studied. Surface characterization of ThioPP films treated by Ar and O 2 plasma using X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM) showed the formation of CO chemical bonds by O 2 plasma treatment and increase in surface roughness resulting in the decrease of contact angle. The chemical interaction between Cu and plasma-treated ThioPP films investigated by XPS showed the formation of CuS chemical bonding resulting in the strong adhesion of Cu on ThioPP films. Diffusion properties of Cu/ThioPP films annealed at 450°C for 1 h were surveyed by current–voltage ( I – V ) measurement. The slight reduction of Cu diffusion into ThioPP films treated by O 2 plasma compared to that of the samples untreated or treated by Ar plasma is attributed to the formation of new chemical bonding states on the surface of O 2 plasma-treated ThioPP films.

Investigation of process window during dry etching of ZnO thin films by CH4–H2–Ar inductively coupled plasma

The etching characteristics of ZnO thin films, etched with a positive photoresist mask and a process window in inductively coupled CH4–H2–Ar plasmas were investigated by varying the various process parameters. It was found that the process window for ZnO etching is closely related to the balance between the deposition and removal processes of the a-C:H (amorphous hydrogenated carbon) layer on the ZnO surface. Under certain conditions, the etch rate selectivity of ZnO to PR is infinite, because the ZnO films continue to be etched, but a net deposition of the a-C:H polymer occurs on the top of the photoresist. The measurements of the radical species in the plasma and the surface binding states by optical emission spectroscopy (OES) and x-ray photoelectron spectroscopy (XPS), respectively, revealed that the chemical reaction of the CH radicals with the Zn atoms in ZnO and the ion-enhanced removal mechanism of the a-C:H layer play an important role in determining the ZnO etch rate, as well as the etch by-prod...

Properties of amorphous tin-doped indium oxide thin films deposited by O2/Ar mixture ion beam-assisted system at room temperature

Abstract Highly transparent and conductive thin films of tin-doped indium oxide (ITO) on glass substrates were grown by the ion beam-assisted deposition (IBAD) technique without any substrate heating. X-Ray diffraction investigations indicated that all films have an amorphous structure and no other crystalline phases. The addition of Ar to O 2 flow and the increased energy of incident ions were found to reduce the resistivity of the grown films. Observed decrease in the resistivity was attributed to the increase in the carrier concentration. In the optimal growth conditions at room temperature, we obtained the electrical resistivity of 4.6×10 −4 Ω-cm, visible transmittance (at λ=550 nm) ≥90%, and optical direct band gap energy of ≅3.75 eV.

Effects of oxygen radical on the properties of indium tin oxide thin films deposited at room temperature by oxygen ion beam assisted evaporation

Abstract In this study, ITO films were deposited by an oxygen ion beam assisted evaporation technique on glass and polycarbonate substrates at room temperature and the effects of oxygen radical on the properties of ITO thin films were investigated. To generate oxygen radicals, in addition to one oxygen ion gun irradiating oxygen ions to the substrate during the ITO deposition, a separate oxygen ion gun was used without applying any voltage to acceleration grid and extraction grid while varying rf power to the ion gun. The increase of rf power to the gun increased the number of oxygen radicals. The increase of oxygen radicals to the oxygen ion beam assisted evaporation of ITO increased the optical transmittance of the ITO deposited on both glass and polycarbonate substrates. The conductivity of the deposited ITO also increased with the increase of oxygen radicals, however, too many oxygen radicals decreased the conductivity of the ITO. Hall measurement showed that the change of the carrier concentration in the film was responsible for the change of the resistivity. The increase of optical transmittance and the change of electrical conductivity with the increase of oxygen radicals were related to the oxygen incorporation to the deposited ITO thin film. ITO deposited on the polycarbonate substrate showed a little lower optical transmittance and conductivity possibly due to the higher surface roughness of the substrate. We were able to obtain room temperature ITO thin film on glass with 5.5×10 −4 Ωcm and above 85% transmittance (at 550 nm) and that on polycarbonate with 6.0×10 −4 Ωcm and approximately 85% transmittance (at 550 nm).

Effect of high-frequency variation on the etch characteristics of ArF photoresist and silicon nitride layers in dual frequency superimposed capacitively coupled plasmaa)

In this work, the deformation of ArF photoresist (PR) and etch characteristics of the ArF PR and Si3N4 layers were investigated in the dual frequency superimposed capacitively coupled plasmas under different frequency combinations by varying the process parameters such as dc self-bias voltage (Vdc), CF4∕CHF3 flow ratio, and O2 flow rate in the CF4∕CHF3∕O2∕Ar chemistry. Surface roughness measurements and morphological investigation of the line and space patterns after etching by atomic force microscopy and scanning electron microscopy, respectively, showed increased surface roughness and deformation with increasing the Vdc, the high-frequency source frequency (fHF), the CHF3 flow percentage, and the O2 flow rate. The etch rates of the ArF PR and silicon nitride layers were also increased significantly with the Vdc and fHF increased. The Si3N4∕PR etch selectivity was increased most significantly by an increase in the CHF3 flow percentage.

Field emission of nitrogen-doped diamond films

The authors investigated field emission characteristics of nitrogen-doped diamond films, which were grown using microwave plasma-enhanced chemical vapor deposition. Nitrogen-doped films showed low turn-on voltages below 2 V/μm. Secondary ion mass spectroscopy was used to compare nitrogen concentrations in the films. Morphologies, Raman spectra, the resistivities, and surface roughness of the films were changed as the nitrogen concentrations varied. The field emission properties of heavily nitrogen doped diamond films were related to the film resistivity, surface morphologies and Raman characteristics.

Global warming gas emission during plasma cleaning process of silicon nitride using c-C4F8O/O2 chemistry with additive Ar and N2

In this work, the cyclic perfluorinated ether (c-C4F8O) with very high destructive removal efficiencies (DREs) was used as an alternative process gas for cleaning of the silicon nitride chemical vapor deposition chamber. Direct plasma cleaning of silicon nitrides in a capacitively coupled plasma mode using the gas mixtures of c-C4F8O/O2, c-C4F8O/O2+Ar, and c-C4F8O/O2+N2 was investigated in order to evaluate the effects of additive gases (Ar and N2) on the global warming. Emitted net volumes of perfluorocompounds during cleaning of silicon nitride were quantitatively measured by Fourier transform-infrared spectroscopy. The effects of additive Ar and N2 on the DRE and the million metric tons of carbon equivalent (MMTCE) values were evaluated from the volumetric emission of effluents. MMTCE value for the optimized c-C4F8O/O2 cleaning was decreased by ≅64% compared to that of the C2F6/O2 chemistry as a result of decreased emission of CF4. During the cleaning process using c-C4F8O/O2 gas mixtures with additive...

Effect of N-containing additive gases on global warming gas emission during remote plasma cleaning process of silicon nitride PECVD chamber using C4F8/O2/Ar chemistry

Abstract In this study, remote plasma cleaning process was investigated in a silicon nitride plasma enhanced chemical vapor deposition chamber using C 4 F 8 /O 2 /Ar and C 4 F 8 /O 2 /Ar+additive gas. The remote plasma source used in the present experiments showed the capability of nearly complete destruction, destruction removal efficiency ≅100%, of C 4 F 8 gas with or without the additive N 2 , N 2 O and NO gases. The cleaning rate of the silicon nitride layers is increased 32–40% by adding N 2 , N 2 O and NO gases to the optimized C 4 F 8 /O 2 cleaning chemistry. This is presumably due to the effective reaction of NO radicals formed in the remote plasma with N on the silicon nitride surface, followed by the effective fluorination of Si atoms. As a result, the million metric tons of carbon equivalent values could be effectively reduced due to the decreased emission of CF 4 as well as the increased cleaning rate of the silicon nitride layers, comparable to those of NF 3 /Ar remote plasma cleaning. For the effective reduction of global warming effects, the experimental results indicate a possibility of using the alternative gas such as C 4 F 8 with the N-containing additive gases for the environmentally benign remote plasma cleaning process.

Electrical, optical, and structural characteristics of ITO thin films by krypton and oxygen dual ion-beam assisted evaporation at room temperature

Transparent conducting tin-doped indium oxide (ITO) thin films on polycarbonate and glass substrates were deposited without substrate heating and post-deposition annealing using a dual ion-beam assisted evaporation technique, where the bombardment of the growing film surfaces during electron beam evaporation was done using krypton (varied ion flux, J Kr ., and grid acceleration voltage, V a , of the krypton ion source) and oxygen (fixed ion flux and grid acceleration voltage of the oxygen ion source) ion beams. The electrical, optical, and structural effects of krypton ion-beam bombardment of the growing ITO thin films were investigated using Hall-effect measurements, X-ray photoelectron spectroscopy (XPS), UV-visible spectrometry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The total film thickness and the deposition rate were 100 nm and 0.06 nm/s, respectively. All ITO films grown with J Kr , = 1.92-3.76 × 10 14 cm -2 s -1 and V a = 100-500 V showed an amorphous structure and no other crystalline phases. As J Kr increased, the electrical conductivity and the optical transmittance of the grown films were improved compared with those of the ITO films deposited using the oxygen ion-beam only. Also, an increase of the bombardment energy by increasing V a of the krypton ion source caused the deterioration of ITO film properties. The conductivity and the optical transmittance of ITO films deposited on polycarbonate substrates were a little lower than those of films on glass substrates. At room-temperature, using optimal growth conditions, the electrical resistivity was as low as 6.4 × 10 -4 Ω cm with an electron carrier concentration n e = 4.3 × 10 20 cm -3 and a Hall mobility μ H = 26.7 cm 2 V -1 s -1 , the visible transmittance (at λ = 550 nm) was 90%, and optical direct band gap energy 3.8 eV.