Yuanzhong Zhou

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.

Fabrication of low dielectric constant materials for ULSI multilevel interconnection by plasma ion implantation

High dose-rate plasma ion implantation (PII) has been utilized to produce low dielectric constant (k) SiO/sub 2/ films for high quality interlayer dielectrics. The SiO/sub 2/ films are fluorine-doped/carbon-doped by PII with CF/sub 4/ plasma in an inductively-coupled plasma (ICP) reactor. It is found that the use of CF/sub 4/ doping results in exceptional dielectric properties which differ significantly from fluorinated SiO/sub 2/. The dielectric constant of the SiO/sub 2/ film is reduced from 4.1 to 3.5 after 5 minute PII, other electrical parameters such as bulk resistivity and dielectric breakdown strength are also improved.

Optimizing high efficient plasma immersion ion implantation hydrogenation for poly-Si thin film transistors

An Inductively-Coupled Plasma (ICP) source was used for defect passivation in polycrystalline silicon (poly-Si) Thin Film Transistors (TFTs) using Plasma Immersion Ion Implantation (PIII) hydrogenation. Because ICP source has higher ion density and lower working pressure, an optimal PIII hydrogenation process with low voltage (−2 kV) and high frequency (16.7 kHz) pulse has been performed. Process simulation indicates that a very high dose rate (∼ 1016/cm2 s) can be delivered to the substrate. The improvement of device parameters saturates in 4 min with damage free and better device reliability.

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.

Short-Time Hydrogen Passivation of Poly-Si CMOS Thin film Transistors by High Dose Rate Plasma Ion Implantation

Plasma ion implantation (PII) hydrogenation has been developed for defect passivation in polycrystalline silicon (poly-Si) thin film transistors (TFTs). A high dose rate PII process using a microwave multipolar bucket (MMB) plasma source and a 12.5 kHz pulse generator achieves saturation of device parameter improvement in 5 minutes, which is much shorter than other hydrogenation methods investigated thus far. These results have been achieved in one sixth the implant time of our previous PII experiments and are in good agreement with our process simulation.

N-Type Doping by Plasma Ion Implantation Using a PH 3 SDS System

PH 3 SDS (safe delivery system) gas was used for the first time in P11 doping experiments to fabricate n + p junctions and NMOS devices. Two gas recipes (PH 3 diluted in H 2 and He) were investigated. Under lower pressure, a minimum etching effect was observed. A 4x10 15 /cm 2 phosphorus dose and a 22 Ω/□ sheet resistance were achieved in 4 seconds. Very low contamination level was involved. An anomalous tail of P profile in Si substrate was observed using SIMS measurements.

Plasma Ion Implantation for Flat Panel Displays

Development of ion doping and hydrogenation equipment using plasma ion implantation (PII) is being studied. It is shown that low energy, high throughput operation could eliminate problems associated with etching, charging, cooling, and contamination. The applications of a new plasma source and neural network implementation optimization are also reported.

Two-dimensional simulation and modeling for dynamic sheath expansion during plasma immersion ion implantation

Summary form only given. Plasma immersion ion implantation (PIII) has been utilized as a low cost, low energy doping method for large area targets with applications to semiconductor manufacturing. They include doping, shallow junction formation, hydrogenation for poly-Si thin film transistors, and SIMOX (Separated by IMplant of OXygen) structure formation. The characteristics of the dynamic sheath expansion during PIII process is very important for the optimum PIII configuration design and process control in order to obtain more accurate doping results such as the implant dose and impurity profile. For example, the sheath thickness is critical to chamber design and monoenergic ion implant for a more accurate control of as-implanted impurity profile of shallow junction and SIMOX structures. A PDP2 simulation code has been used to simulate PIII processes which aid in the understanding of the physics of PIII processes and obtain the optimum process parameters. PDP2 code is a two-dimensional planar bounded plasma simulator. The Particle-in-Cell method is implemented to solve for the particles and field parameters self-consistently. The code also uses a Monte Carlo scheme to model charged and neutral particle collisions. In order to minimize the simulation time, a pseudo two-dimensional analytical dynamic sheath model has also been developed. It is simple and has an acceptable accuracy but in a very small fraction of the computing time by PDP2 simulations. This model was verified by comparing with the PDP2 computer simulations and the experimental results of the PIII doping processes.

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.

Low-Dielectric Constant SiO(F,C) Films for ULSI Interconnections Prepared by CF 4 Plasma Ion Implantation

Plasma ion implantation (PII) doping technique has been utilized to prepare a new lowdielectric constant (low k) material SiO(F,C). Fluorine and carbon were implanted into SiO 2 films by CF 4 PII using an ICP plasma reactor. The effective dielectric constant of the films was significantly reduced after PH doping. An analysis of a double layer model indicated that a high quality dielectric layer with a dielectric constant down to 2.8 can be achieved by an optimized PII process. Contrasting to other conventional low-k material techniques, PII process also improved bulk resistivity and electrical field breakdown strength. The improvement possibly resulted from adding carbon into the films. The etching effect of CF 4 PII could be beneficial to planarization and gap filling of dielectric interlayer.