Systematic Characterization of Plasma-Etched Trenches on 4H-SiC Wafers

Effect of Discharge Gas Composition on SiC Etching in an HFE-347mmy/O2/Ar Plasma

This study explores the impact of varying discharge gas compositions on the etching performance of silicon carbide (SiC) in a heptafluoroisopropyl methyl ether (HFE-347mmy)/O2/Ar plasma. SiC is increasingly favored for high-temperature and high-power applications due to its wide bandgap and high dielectric strength, but its chemical stability makes it challenging to etch. This research explores the use of HFE-347mmy as a low-global-warming-potential (GWP) alternative to the conventional high-GWP fluorinated gasses that are typically used in plasma etching. By examining the behavior of SiC etch rates and analyzing the formation of fluorocarbon films and Si-O bonds, this study provides insights into optimizing plasma conditions for effective SiC etching, while addressing environmental concerns associated with high-GWP gasses.

Chemical and Morphological Modifications Induced by Argon Plasma Treatments on Fluorinated Polybenzoxazole Films

Fluorinated photodefinable polymers are widely employed as re-distribution layers in wafer-level packaging to produce microelectronic devices because of their suitable low dielectric constant and moisture absorption, high mechanical toughness, thermal conductivity and stability, and chemical inertness. Typically, fluorinated photodefinable polybenzoxazoles (F-PBOs) are the most used in this field. In the present work, we investigated by atomic force microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy the morphological and chemical modifications induced by Ar plasma treatments on F-PBO films. This process, used to remove surface contaminant species, as well as increase the polymeric surface roughness, to improve the adhesion to the other components during electronic packaging, is a crucial step during the manufacturing of some microelectronic devices. We found that argon plasma treatments determine the wanted drastic increase of the polymer surface roughness but, in the presence of a patterned silver layer on F-PBO, needed for the fabrication of electric contacts in microelectronic devices, also induce some unwanted formation of silver fluoride species.

Effects of MWCNTs on Char Layer Structure and Physicochemical Reaction in Ethylene Propylene Diene Monomer Insulators

As one of the most promising ablative fillers, multi-walled carbon nanotubes (MWCNTs) have been used to improve the ablative resistance of Ethylene–Propylene–Diene Monomer (EPDM) insulators by facilitating the carbothermal reduction reaction of silica. However, the contribution of MWCNTs to char layer structure of the insulators was unclear. In this work, the effects of MWCNTs on char layer structure and ablative resistance were investigated in different EPDM-based insulators with and without silica. The results showed that adding only 3 phr MWCNTs can reduce the linear ablation rate of EPDM-based insulators without silica by 31.7%, while 6 phr MWCNTs are required to obtain similar results in EPDM-based insulators with silica. The char layer morphology of the two insulators gradually evolved into a dense porous structure as MWCNTs content increased, but their formation mechanisms were different. The XRD and Raman spectrum showed that different physicochemical reactions occurred around MWCNTs under different charring components. The proposed ablation mechanism was further verified by designing alternating multilayer distribution of MWCNTs and silica. This work can guide the construction of desirable char layer structure for increasing the ablative resistance of EPDM-based insulators.