Highly selective etching of silicon nitride over silicon and silicon dioxide

Abstract

Subsurface reactions of silicon nitride in a highly selective etching process of silicon oxide over silicon nitride High aspect ratio SiO 2 etching with high resist selectivity improved by addition of organosilane to tetrafluoroethyl trifluoromethyl ether Selective etching of SiO 2 over polycrystalline silicon using CHF 3 in an inductively coupled plasma reactor Use of 2H-heptafluoropropane, 1-iodoheptafluoropropane, and 2-iodoheptafluoropropane for a high aspect ratio via etch in a high density plasma etch tool A highly selective dry etching process for the removal of silicon nitride ͑Si 3 N 4 ) layers from silicon and silicon dioxide (SiO 2 ) is described and its mechanism examined. This new process employs a remote O 2 /N 2 discharge with much smaller flows of CF 4 or NF 3 as a fluorine source as compared to conventional Si 3 N 4 removal processes. Etch rates of Si 3 N 4 of more than 30 nm/min were achieved for CF 4 as a source of fluorine, while simultaneously the etch rate ratio of Si 3 N 4 to polycrystalline silicon was as high as 40, and SiO 2 was not etched at all. For NF 3 as a fluorine source, Si 3 N 4 etch rates of 50 nm/min were achieved, while the etch rate ratios to polycrystalline silicon and SiO 2 were approximately 100 and 70, respectively. In situ ellipsometry shows the formation of an approximately 10-nm-thick reactive layer on top of the polycrystalline silicon. This oxidized reactive layer suppresses etching reactions of the reactive gas phase species with the silicon.

A three-mask process for fabricating vacuum-sealed capacitive micromachined ultrasonic transducers using anodic bonding

“…although highly selective, i.e., 100:1, dry etching of silicon nitride over silicon can be achieved with high flows of o 2 and n 2 , and relatively small additions of cF 4 and nF 3 as a source of fluorine [33], an etch-stop layer on top of the silicon plate would allow use of standard etch recipes and would prevent pitting on the silicon plate due to overetching. The addition of an etchstop on top of the silicon plate could be a significant addition to the presented process flow; slight overetching at this step is desired to ensure that there is no silicon nitride left on the exposed metal bottom electrode before the final metal deposition on the bond pad.…”

Extreme Water Confinement Amidst Superhydrophilic Su8 Micropatterned Walls.

“…The peak-fitting analysis of the C1s spectrum scans of the untreated surfaces, showed two components positioned at BE = 285.0 eV and 286.8 eV, which were assigned to the presence of aliphatic and aromatic carbon (C-C, C=C, C-H) and ether carbon (C=O), respectively. The presence of aromatic compounds was confirmed by the presence of -* shake-up satellite positioned at BE = 291.3 eV and carbonates (Fig 2 and Table S1-S2), (Kastenmeier et al, 1999;Jeong et al, 2003;Seemann et al, 2005). Exposure to the inert Ar plasma causes structural and chemical changes to the surface with an enrichment of C=O and COO groups on SU-8 and breakage of the O-H and C-H bonds (Zhang et al, 2005).…”

Inductively coupled plasma etching of ultra-shallow Si3N4 nanostructures using SF6/C4F8 chemistry

“…For Si 3 N 4 plasma etching, fluorine gases such as CH 3 F [8], CF 4 [9], SF 6 [10] and NF 3 [11] are mixed with O 2 , N 2 , H 2 or NO in order to get a high anisotropy and a high selectivity over SiO 2 and Si. Fluorine species can react with Si 3 N 4 to form volatile SiF 4 compounds whereas fluorocarbon polymer deposition on surface inhibits the etching of silicon nitride [12].…”