Plasma deposition processes of carbon based-materials such as polycrystalline diamond and fluorocarbon films have been widely investigated and many applications have been developed, due to the diamond extreme properties and the fluorocarbon high hydrophobicity. The deposition of diamond and fluorocarbon films on silicon substrate is usually carried out via microwave and radiofrequency PECVD (Plasma Enhanced Chemical Vapor Deposition) technique, respectively. In the last two decades the square wave pulsation of the plasma in the audiofrequency range (1-2000 Hz) has been and is still considered an important and an innovative tool strongly affecting the surface kinetics and the fluid dynamics of the deposition, etching and treatment processes, as well as the film properties. Moreover, the plasma pulsation when coupled with the TROES (Time Resolved Optical Emission Spectroscopy) has revealed to give information on the mechanisms of excited species formation and their decay kinetics in the afterglow. The use of pulsed wave (PW) instead of continuous wave (CW) discharges has been explored by several groups, as it offers the possibility to add two modulation parameters: the pulse period, i.e. the time between two successive pulses, and the duty cycle indicating the percentage of the period in which the discharge is ON. The present lecture deals with the plasma deposition of polycrystalline diamond films from highly diluted (1% CH4 in H2) gas mixture and super-hydrophobic fluoracarbon (CFx) films from C2F4 gas. The PW plasmas have been studied at different audiofrequencies and duty cycles for the above two materials. Emphasis is given to the role of PW plasmas with respect to CW ones on the growth chemistry and material properties. As for polycrystalline diamond films, the deposition rates change markedly varying the duty cycle in the range 25-100% at pulse frequency of 100 Hz and remain almost constant varying the pulse frequency in the range 10-1500 Hz at duty cycle of 90 %. The power modulation affects the film morphology but does not improve the optical and structural properties: the refractive index and the quality factor of CW films are higher than PW ones. As for fluoracarbon films, the control of both the plasma phase and the film deposited is improved under PW conditions. The PW plasmas, contrary to the CW ones, allow to tune the growth precursor and correspondingly the composition, the structure and the morphology of the film exhibiting a super-water repellent surface with contact angles up to 170°.
Deposition of carbon based-materials by continuous and pulsed discharges
G Cicala
2010
Abstract
Plasma deposition processes of carbon based-materials such as polycrystalline diamond and fluorocarbon films have been widely investigated and many applications have been developed, due to the diamond extreme properties and the fluorocarbon high hydrophobicity. The deposition of diamond and fluorocarbon films on silicon substrate is usually carried out via microwave and radiofrequency PECVD (Plasma Enhanced Chemical Vapor Deposition) technique, respectively. In the last two decades the square wave pulsation of the plasma in the audiofrequency range (1-2000 Hz) has been and is still considered an important and an innovative tool strongly affecting the surface kinetics and the fluid dynamics of the deposition, etching and treatment processes, as well as the film properties. Moreover, the plasma pulsation when coupled with the TROES (Time Resolved Optical Emission Spectroscopy) has revealed to give information on the mechanisms of excited species formation and their decay kinetics in the afterglow. The use of pulsed wave (PW) instead of continuous wave (CW) discharges has been explored by several groups, as it offers the possibility to add two modulation parameters: the pulse period, i.e. the time between two successive pulses, and the duty cycle indicating the percentage of the period in which the discharge is ON. The present lecture deals with the plasma deposition of polycrystalline diamond films from highly diluted (1% CH4 in H2) gas mixture and super-hydrophobic fluoracarbon (CFx) films from C2F4 gas. The PW plasmas have been studied at different audiofrequencies and duty cycles for the above two materials. Emphasis is given to the role of PW plasmas with respect to CW ones on the growth chemistry and material properties. As for polycrystalline diamond films, the deposition rates change markedly varying the duty cycle in the range 25-100% at pulse frequency of 100 Hz and remain almost constant varying the pulse frequency in the range 10-1500 Hz at duty cycle of 90 %. The power modulation affects the film morphology but does not improve the optical and structural properties: the refractive index and the quality factor of CW films are higher than PW ones. As for fluoracarbon films, the control of both the plasma phase and the film deposited is improved under PW conditions. The PW plasmas, contrary to the CW ones, allow to tune the growth precursor and correspondingly the composition, the structure and the morphology of the film exhibiting a super-water repellent surface with contact angles up to 170°.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
