Neil M. Mackie

SURFACE INTERACTIONS OF CF2 RADICALS DURING DEPOSITION OF AMORPHOUS FLUOROCARBON FILMS FROM CHF3 PLASMAS

Surface reactivities for CF2 radicals formed in a CHF3 plasma molecular beam are measured during film deposition on a variety of substrates. The imaging of radicals interacting with surfaces (IRIS) technique was used to collect spatially resolved laser-induced fluorescence (LIF) images of CF2 radicals interacting with SiO2, Si3N4, Si, 304 stainless steel, and system 8 photoresist substrates. Films deposited during IRIS experiments were characterized using x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy and were found to be nearly identical in composition on all substrates. Simulation of LIF cross-sectional data shows high scattering coefficients for CF2 radicals on all substrates. These extremely large scattering coefficients (>1.0) indicate that CF2 molecules are generated through plasma interactions with the substrate. Possible CF2 surface generation mechanisms are discussed, with consideration of CF and ion bombardment contributions to the generation of CF2.

Ion and substrate effects on surface reactions of CF2 using C2F6,C2F6/H2, and hexafluoropropylene oxide plasmas

The surface reactivity of CF2 radicals has been characterized during plasma processing of a variety of substrates using the imaging of radicals interacting with surfaces technique. The plasma molecular beam sources are 100% C2F6, 50/50 C2F6/H2, and 100% hexafluoropropylene oxide (HFPO) gas mixtures. Simulation of spatially resolved laser-induced fluorescence images in the 100% C2F6 system shows that CF2 has a scatter value, S, >1.0 with SiO2, polyimide and photoresist substrates. A scatter of >1.0 indicates that CF2 molecules are generated at the surface during plasma processing. With the 50/50 C2F6/H2 plasma, CF2 exhibits a lower scatter value (∼0.85) on Si, SiO2, and polyimide substrates. With the HFPO plasma source, S⩾1 for all continuous wave powers and substrates processed. Values of S∼0.8 are obtained for ion-free and pulsed plasmas, however, revealing ion collisions with the substrate play an important role in the surface generation of CF2. The radical-surface interaction data are correlated with d...

Comparison of films deposited from pulsed and continuous wave acetonitrile and acrylonitrile plasmas

Continuous wave (CW) and pulsed acetonitrile and acrylonitrile plasmas have been used to deposit thin nitrogen-containing films. Changes in film composition with applied CW power and pulse duty cycle have been monitored using Fourier transform infrared spectroscopy (FTIR) and deposition rates have been measured for both systems. A detailed description of FTIR peak assignments is presented and shows that the composition of films deposited from acetonitrile are insensitive to CW input power and duty cycle. In contrast, acrylonitrile films exhibit a strong compositional dependence on CW input power and duty cycle with the growth of highly conjugated imine and nitrile species. These monomer dependent compositional changes are discussed in terms of their structure, pulse off time durations, and equivalent pulsed and CW applied rf powers. Optical emission spectroscopy (OES) and deposition rate data afford further insight into film formation processes with the two monomers.

Surface Interactions of Radicals During Plasma Processing of Polymers

Surface interactions of radical species were investigated using the imaging of radicals interacting with surfaces (IRIS) technique during plasma surface modification of polymers. Three plasma systems were investigated by spatially probing the laser induced fluorescence of individual radical species and determining their surface scattering coefficients, S. The behavior of CF2 moieties on polymer surfaces was studied using the fluorocarbon plasmas C2F6 and hexafluoropropylene oxide (HFPO). Three types of surface interactions were observed, surface generation of CF2 (S > 1), surface loss of CF2 (S < 1), and unit scattering (S = 1). Surface loss of CF2 was seen in HFPO plasmas, while CF2 was generated in C2F6 systems. The differences between these systems is believed to be the result of different overall surface interactions, specifically film deposition in the HFPO system and etching in the C2F6 system. Using NH3 plasmas, the surface interactions of NH2 radicals with polymers was also investigated. Here, NH2 is generated at the surface of polyethylene and polytetrafluoroethylene substrates, but is consumed on polyimide substrates. Ion effects were also investigated by placing a grounded mesh in the path of the molecular beam to remove charged species.

SURFACE INTERACTIONS OF CF2 RADICALS IN FLUOROCARBON PLASMAS WITH A VARIETY OF SUBSTRATE MATERIALS

The surface reactivity of CF2 radicals during plasma processing of Si and 304 stainless steel substrates measured using the imaging of radicals interacting with surfaces (IRIS) technique are reported. The molecular beam source is a 100% CHF3 plasma. Under IRIS conditions, an amorphous fluorocarbon film is deposited on each substrate. Simulation of crosssectional data shows CF2 surface reactivities of -0.65 ± 0.03 on silicon and -0.63 ± 0.03 on stainless steel. The effect of reduced ion bombardment during plasma processing on the surface generation of CF2 radicals is also examined.