Silicon Oxide Etching Process of NF3 and F3NO Plasmas with a Residual Gas Analyzer

The use of NF3 is significantly increasing every year. However, NF3 is a greenhouse gas with a very high global warming potential. Therefore, the development of a material to replace NF3 is required. F3NO is considered a potential replacement to NF3. In this study, the characteristics and cleaning performance of the F3NO plasma to replace the greenhouse gas NF3 were examined. Etching of SiO2 thin films was performed, the DC offset of the plasma of both gases (i.e., NF3 and F3NO) was analyzed, and a residual gas analysis was performed. Based on the analysis results, the characteristics of the F3NO plasma were studied, and the SiO2 etch rates of the NF3 and F3NO plasmas were compared. The results show that the etch rates of the two gases have a difference of 95% on average, and therefore, the cleaning performance of the F3NO plasma was demonstrated, and the potential benefit of replacing NF3 with F3NO was confirmed.

Ion-Enhanced Etching Characteristics of sp2-Rich Hydrogenated Amorphous Carbons in CF4 Plasmas and O2 Plasmas

The sp2-rich hydrogenated amorphous carbon (a-C:H) is widely adopted as hard masks in semiconductor-device fabrication processes. The ion-enhanced etch characteristics of sp2-rich a-C:H films on ion density and ion energy were investigated in CF4 plasmas and O2 plasmas in this work. The etch rate of sp2-rich a-C:H films in O2 plasmas increased linearly with ion density when no bias power was applied, while the fluorocarbon deposition was observed in CF4 plasmas instead of etching without bias power. The etch rate was found to be dependent on the half-order curve of ion energy in both CF4 plasmas and O2 plasmas when bias power was applied. An ion-enhanced etching model was suggested to fit the etch rates of a-C:H in CF4 plasmas and O2 plasmas. Then, the etch yield and the threshold energy for etching were determined based on this model from experimental etch rates in CF4 plasma and O2 plasma. The etch yield of 3.45 was observed in CF4 plasmas, while 12.3 was obtained in O2 plasmas, owing to the high reactivity of O radicals with carbon atoms. The threshold energy of 12 eV for a-C:H etching was obtained in O2 plasmas, while the high threshold energy of 156 eV was observed in CF4 plasmas. This high threshold energy is attributed to the formation of a fluorocarbon layer that protects the a-C:H films from ion-enhanced etching.

Si1-XGeX Selective Etchant for Gate-All-Around Transistors

3 formulated etchants were prepared and their etch rates were measured using blanket wafers in order to confirm that the etching reactions on Si1-XGeX and Si are controllable. Si1-XGeX selective etching with those formulations was also verified using the wafers which had Si1-XGeX and Si multi-stacked structures. Cross-sectional transmission electron microscope (TEM) images suggested that the formulations were usable for Si1-XGeX selective etching processes.

Selective Ru or Co Etch for 3nm Applications

Selective Cobalt (Co) and Ruthenium (Ru) etch chemistries are developed to provide controlled etch options with various metallization, including Al, Cu, W, Co, Ru, TiN and TaN. The pH effects on Co, Cu and W etching are reported. Diluted acids, such as 1% HF and 1% HCl, demonstrate etch rate profiles suitable for selective Co vs. W etch applications. Ru etch chemistries are alkaline oxidative based and expanded to meet 3 nm and below integration needs. Versatile applications include highly boosted Ru etch rates for thermally annealed Ru layers and TiN compatible WNx or WCN selective etching at ultra-dilutions.