Imad F. Husein

The effect of high-dose nitrogen plasma immersion ion implantation on silicone surfaces

The effect of plasma immersion ion implantation (PIII) treatment on silicone surfaces was investigated by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR-ATR), and scanning electron microscopy (SEM). Low-energy (at voltages of 4 and 8 kV) and high-fluence (8 × 10 17 cm −2 ) implantation of nitrogen was performed using an inductively coupled plasma source (ICP) at low pressure (∼0.03 Pa). The IR absorption spectra showed a significant decomposition in the CH3, Si-CH3, and C-F groups of the silicone surface after PIII treatment. The percentage of decomposition was dependent on the implantation energy. The XPS C 1s spectra of the PIII modified surfaces showed an increase in the polar carboxyl (O-C=O) groups and a decrease in the CF3 groups. PIII treatment shifted the XPS Si 2p peak of silicone to a higher binding energy (around 103.2 eV) and the N 1s peak to lower binding energy (around 398.5 eV). The modified Si 2p, N 1s, and O 1s spectra suggest the formation of SiOx phases, silicon oxynitrides, and silicon nitrides on the silicone surface after PIII treatment.

Synthesis of carbon nitride thin films by vacuum arcs

Abstract Carbon nitride (CN) thin films were synthesized by combining vacuum arcs and plasma ion implantation techniques. Three methods were investigated: plasma ion implantation into carbon films deposited by anodic vacuum arcs (AAPII), continuous cathodic vacuum arc with plasma ion implantation (CAPII) and pulsed cathodic vacuum arc (PCA). The films were found to be amorphous by X-ray diffraction (XRD). X-Ray photoelectron spectroscopy (XPS) and Raman spectroscopy analysis indicated the formation of C N, C N and C≡N bonds. Calculations of the surface tension components (dispersion and polar) of the films using the contact angle measurement technique suggested the formation of covalent carbon-nitrogen bonds. The CN films exhibited improved adhesion relative to the pure carbon films as indicated by adhesion calculations and the reduction in interfacial tension between the films and the substrate. A hardness of 18.9 GPa was obtained by nanoindentation measurements for CN films with an N/C ratio of 0.135.

Surface energy and chemistry of ethylene-propylene-diene elastomer (EPDM) treated by plasma immersion ion implantation

This letter reports on the changes in surface energy and its correlation to the induced chemical changes in EPDM surfaces after Ar+ ion treatment by the plasma immersion ion implantation (PIII) technique [1]. PIII combines the characteristics of the ion beam implantation technique and the low-pressure plasma treatment technique. Recently, a number of studies showed the viability of the PIII technique in enhancing the wettability, surface hardness, and wear resistance of a variety of polymer surfaces [2–6]. Dong et al. showed that nitrogen treatment of ultrahigh molecular weight polyethylene (UHMWPE) by PIII improved significantly the surface hardness, elastic modulus, and wear resistance of UHMWPE in comparison with conventional plasma treatment [4]. Tonosaki et al. showed that carbon ion implantation into polyolefin (APO) plastics by PIII produced surfaces with hardness superior to those surfaces implanted by the conventional ion implantation method [5]. Lacoste et al. reported on the effects of oxygen ion implantation by PIII on the wettability of polystyrene [6]. Our group reported on the structural transformation of silicone polymer surfaces to a ceramic-like surface by argon and nitrogen ion implantation at high doses using the PIII technique [2, 3]. In the PIII treatment method, the sample to be treated is immersed in a plasma that is usually maintained at low pressure (between 0.03–1 Pa) and plasma densities between 108–1011 ions cm−3. Then a series of negative high voltage pulses (typically few volts to 300 kV) are applied to the sample. The plasma ions are accelerated across the surrounding sheath and are implanted into the sample surface. The PIII technique offers many attractive features over the conventional beam implantation method [1]. Large areas and three-dimensional objects can be processed by PIII at rate orders of magnitude faster than by the conventional implantation and without the need for sample manipulation. And in applications requiring low energy implantation (less than 10 keV) and high doses, the conventional ion beam technique is limited by the focusing optics [1]. The surface modification of ethylene-propylenediene rubbers (EPDM) has been investigated by chemical treatment [7] and various plasma treatments [8–10].

Chemical structure modification of silicone surfaces by plasma immersion ion implantation

Polymer materials with surface chemical structures that exhibit properties different than the bulk properties are of great interest in many applications such as adhesion, friction, and biocompatible materials [1, 2]. In this paper, we report on the modification of the chemical structure of silicone surfaces by Ar plasma immersion ion implantation (PIII). Surface modification of silicon based polymers has been investigated using ion beams [3, 4] and plasma treatment [5–7]. Suzuki et al. reported on the effects of ions beam implantation on the wettability of silicone rubber [3, 4]. Morra et al. investigated the hydrophobic recovery of oxygen plasma treated polydimethylsiloxane (PDMS) surfaces [5]. The mechanisms of hydrophobic recovery of plasma treated PDMS were addressed by Owen and Smith [6]. Everaertet al. showed that the aging of plasma treated silicone rubber can be slowed down by repeating the plasma treatment [7]. Plasma immersion ion implantation (PIII) is a relatively new technique for the surface modification of materials. In recent years, the PIII technique has been used in semiconductor processing applications with promising results in shallow junction formation, polycrystalline silicon thin film transistor hydrogenation, and the formation of silicon on insulator materials [8]. Recently, we showed that PIII treatment of silicone and EPDM at high doses reduced the surface coefficient of friction considerably [9]. In the PIII treatment, the sample to be treated is immersed in a plasma that is usually maintained at low pressure (between 0.03–1 Pa) and plasma densities between 10 8–1011 ions cm−3. Then a series of negative high voltage pulses (typically few volts to 300 kV) are applied to the sample. The plasma ions are accelerated across the surrounding sheath and are implanted into the sample surface. This implantation technique offers many attractive features over the conventional ion beam implantation method [8]. Large areas and three-dimensional objects can be processed by PIII at a rate orders of magnitude faster than by the conventional implantation and without the need for sample manipulation. And in applications requiring low energy implantation (less than 10 keV) and high doses, the conventional ion beam technique is limited by the

Plasma ion implantation hydrogenation of poly-Si CMOS thin-film transistors at low energy and high dose rate using an inductively-coupled plasma source

Defect passivation in polycrystalline silicon (poly-Si) CMOS thin-film transistors (TFTs) has been performed by plasma ion implantation (PII) hydrogenation process. Implantation at low energy (2 keV) and high dose rate(/spl sim/10/sup 16//cm/sup 2/ S) was achieved by an inductively-coupled plasma source. The device parameter improvements are saturated in 3-4 min, which is much shorter than other hydrogenation methods reported in the literature. The stress measurements indicate that the devices hydrogenated by this new technique have much better long-term reliability than that hydrogenated by other techniques.

Plasma Immersion Ion Implantation Modification of Surface Properties of Polymer Material

The use of plasma immersion ion implantation (PIII) as a novel method for the treatment of polymer surfaces is investigated. The effect of PIII treatment on the coefficient of friction, contact angle modification, and surface energy of silicone and EPDM (ethylene-propylene-diene monomer) rubber are investigated as a function of pulse voltage, treatment time, and gas species. Low energy (0--8 keV) and high dose ({approximately}10{sup 17}--10{sup 18} ions/cm{sup 2}) implantation of N{sub 2}, Ar, and CF{sub 4} is performed using an inductively coupled plasma source (ICP) at low pressure (0.2 mTorr). PIII treatment reduces the coefficient of friction ({micro}) of silicone rubber from {mu} = 0.464 to the range {mu} = 0.176--0.274, and {mu} of EPDM rubber decreases from 0.9 to the range {mu} = 0.27--0.416 depending on processing conditions. The contact angle of water and diiodomethylene decreases after implantation and increases at higher doses for both silicone and EPDM rubber.

PLASMA IMMERSION ION IMPLANTATION FOR MATERIALS MODIFICATION AND SEMICONDUCTOR PROCESSING : CARBON NITRIDE FILMS AND POLY-SI TFTS HYDROGENATION

Abstract This paper provides a review of the recent research on plasma immersion ion implantation (PIII) for materials modification and semiconductor processing performed by the Plasma Science group at Northeastern University. The results from two PIII experiments: thin carbon films modification by nitrogen implantation and the hydrogenation of polycrystalline silicon (poly-Si) thin film transistors (TFTs) for defect passivation are presented. For the nitrogen implanted carbon films (CNx), low energy PIII (∼ 2 keV) formed covalent carbon-nitrogen bonds in the carbon films and reduced the interfacial tension between the films and the substrate which suggest an improvement in adhesion. Conventional ion beam (IB) nitrogen implantation produced CNx films with less nitrogen to carbon ratio [N] [C] and significant surface damage. In the hydrogenation of poly-Si TFTs experiment, a high hydrogenation efficiency was achieved by low energy (1 keV) and high dose rate (∼ 1016/cm2 s) implantation using an inductively coupled plasma (ICP) source. Significant improvement in the device parameters (e.g., leakage current, effective mobility, threshold voltage, and subthreshold slope) was achieved in a fraction of the time needed by other hydrogenation methods.

Anodic vacuum arc deposition of carbon and nitrogen containing carbon films

Summary form only given, as follows. The anodic vacuum are was used to deposit thin carbon films (a-C) on Si substrates. The arc produces a partially ionized carbon vapor plasma (less than 20% ionized) and is sustained by a consumable anode. Films with thickness around 0.8-1.7 /spl mu/m were deposited with a deposition rate of 0.5 /spl mu/m/min. The a-C films were modified by nitrogen plasma immersion ion implantation (PIII). The effects of nitrogen implantation on the structure and characteristics of the a-C films were investigated by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and surface energy calculations from the contact angle measurements. XPS C 1s and N 1s spectra suggest a possible formation of covalent carbon-nitrogen bonds. The a-C films Raman spectra have a G band at 1577 cm/sup -1/ and a D band at 1350 cm/sup -l/, while the implanted films show a broad asymmetric peak around 1500 cm/sup -1/. Surface energy analysis indicates that the nitrogen implanted films have lower interfacial tension with the silicon substrate.