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Structural and bonding properties of carbon nitride modifications synthesized by RF plasmas
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Type
Thesis
Author
Jiang, Ning
Supervisor
Xu, Shuyan
Abstract
This thesis addresses the problem concerned with the structure, bonding states and application of novel materials: carbon nitride and carbon nitride based modification synthesized by means of rf plasmas.
The rf reactive diode magnetron sputtering system is used to synthesize carbon nitride film with N2 as a reactive and sputtering gas and graphite as a target. The formation of amorphous sub-stoichiometric carbon nitride (CNx) has been identified by XPS, FTIR and XRD. As an example, a potential application of carbon nitride as optical coating material is investigated. The results show that high transmittance can be achieved by a combination of a low rf power and inclusion of H2 in the precursors. Another application is the use of carbon nitride as a diffusion barrier against Cu diffusion. A study of the depth profile of Cu concentration after high temperature annealing indicates that CNx thin film can indeed resist Cu diffusion up to 400oC, a typical metallization temperature in semiconductor processing.
A great emphasis of this work has been laid on the modification of carbon nitride by introducing aluminum (A1), silicon (Si) or titanium (Ti) into the binary compound, forming a ternary compound or CNx containing composite. Three different modification models are established. For Al-modified carbon nitride, A1-N, A1-N and C-N bonds are predominant and the material has an atomic configuration like cubic structure that is induced by tetrahedral carbon. The structure of the A1-modified CN consists of a cubic AIN and tetrahedral carbon. For Si-modified carbon nitride, however, both C-N and Si-N bonds are more energetically preferred than C-Si bond. As such, the C-N units are bridged by Si atom forming a C-N-Si-N-C network. Modification is thus realized via substitution of Si atom by C atom in Si3N4 structure, resulting in a SiCN ternary material. Finally, for Ti-modified carbon nitride, the film is a composite material consisting of both TiN and TiC. No C-N bond is detected in this case.
The initial research work on carbon nitride modification has been undertaken using an rf reactive diode sputtering combined with a plasma enhanced chemical vapor deposition system. A large amount of oxygen is observed in the film. A mechanism concerning the O incorporation is proposed. The O contamination is actually originated from the incomplete dissociation of N2 at low plasma power. In order to overcome this drawback, a low frequency inductively coupled plasma (LFICP) assisted magnetron sputtering system utilizing a high rf power supply has been set up. The results show that the O contamination is greatly reduced. The independent control of plasma production, target sputtering and deposition processes in the ICP assisted magnetron sputtering make this system very suitable for modified carbon nitride film deposition.
During the entire experimentation, an in-situ optical emission spectroscopy (OES) has been employed for identifying the reactive species in the plasma. A discharge mechanism has been proposed and the CN radical formed in plasma is essentially responsible for the formation of C-N bond in the film, and both CH and N I radicals are respectively responsible for the A1-C and A1-N bonds.
The rf reactive diode magnetron sputtering system is used to synthesize carbon nitride film with N2 as a reactive and sputtering gas and graphite as a target. The formation of amorphous sub-stoichiometric carbon nitride (CNx) has been identified by XPS, FTIR and XRD. As an example, a potential application of carbon nitride as optical coating material is investigated. The results show that high transmittance can be achieved by a combination of a low rf power and inclusion of H2 in the precursors. Another application is the use of carbon nitride as a diffusion barrier against Cu diffusion. A study of the depth profile of Cu concentration after high temperature annealing indicates that CNx thin film can indeed resist Cu diffusion up to 400oC, a typical metallization temperature in semiconductor processing.
A great emphasis of this work has been laid on the modification of carbon nitride by introducing aluminum (A1), silicon (Si) or titanium (Ti) into the binary compound, forming a ternary compound or CNx containing composite. Three different modification models are established. For Al-modified carbon nitride, A1-N, A1-N and C-N bonds are predominant and the material has an atomic configuration like cubic structure that is induced by tetrahedral carbon. The structure of the A1-modified CN consists of a cubic AIN and tetrahedral carbon. For Si-modified carbon nitride, however, both C-N and Si-N bonds are more energetically preferred than C-Si bond. As such, the C-N units are bridged by Si atom forming a C-N-Si-N-C network. Modification is thus realized via substitution of Si atom by C atom in Si3N4 structure, resulting in a SiCN ternary material. Finally, for Ti-modified carbon nitride, the film is a composite material consisting of both TiN and TiC. No C-N bond is detected in this case.
The initial research work on carbon nitride modification has been undertaken using an rf reactive diode sputtering combined with a plasma enhanced chemical vapor deposition system. A large amount of oxygen is observed in the film. A mechanism concerning the O incorporation is proposed. The O contamination is actually originated from the incomplete dissociation of N2 at low plasma power. In order to overcome this drawback, a low frequency inductively coupled plasma (LFICP) assisted magnetron sputtering system utilizing a high rf power supply has been set up. The results show that the O contamination is greatly reduced. The independent control of plasma production, target sputtering and deposition processes in the ICP assisted magnetron sputtering make this system very suitable for modified carbon nitride film deposition.
During the entire experimentation, an in-situ optical emission spectroscopy (OES) has been employed for identifying the reactive species in the plasma. A discharge mechanism has been proposed and the CN radical formed in plasma is essentially responsible for the formation of C-N bond in the film, and both CH and N I radicals are respectively responsible for the A1-C and A1-N bonds.
Date Issued
2002
Call Number
TK7871.15.F5 Jia
Date Submitted
2002