Carmen I. Butoi

Comparison of pulsed and downstream deposition of fluorocarbon materials from C3F8 and c-C4F8 plasmas

Materials deposited in continuous wave (cw) and pulsed low-pressure octafluoropropane (C3F8) and octafluorocyclobutane (c-C4F8) plasmas were characterized using Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy, static contact angle measurements, spectroscopic ellipsometry, and scanning electron microscopy (SEM). Fluorocarbon (FC) materials deposited in pulsed plasmas were less crosslinked than those deposited in cw plasmas with equivalent input powers. Within each system, higher F/C ratio materials were deposited by lowering the plasma input power/duty cycle. Using downstream depositions had a similar effect on film composition, but also resulted in decreased deposition rates. SEM analysis showed that decreases in the flexibility of the fluorocarbon films were correlated with increases in the percent of crosslinking. Additionally, the smoothness of the film surfaces suggests that polymerization processes occur on the substrate surface. Overall, films deposited in C4F8 plasm...

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...

Mechanisms for deposition and etching in fluorosilane plasma processing of silicon

A variety of analytical tools have been used to examine the gas-phase and surface chemistry of SiF4 and SiF4/H2 plasmas interacting with Si substrates. The effect of rf power (P) and source gas ratios on film composition, gas-phase species densities, and plasma–surface interactions of SiF and SiF2 have been studied. Film characterization was performed using Fourier transfer infrared, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry. Using the imaging of radicals interacting with surfaces technique, spatially resolved laser-induced fluorescence images of SiFx radicals were collected and used to characterize both the plasma-surface interface and the gas phase. Additional gas-phase characterization was achieved using optical emission spectroscopy and mass spectrometry. From all of these data, three plasma types have been defined. In etching systems (type 1) (e.g., 100% SiF4 plasmas at P>20 W), no net deposition occurs, and SiF2 radicals are produced at the surface. When only F atom incorporat...

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.