In the absence of the silicon nitride film on the trench sidewalls, the ambient to be used is preferably any of water vapor, oxygen, {HEAD ~ nitrogen}, hydrogen and N2O or {TAIL ~ any combination} of them 
In the absence of the silicon nitride film on the trench sidewalls , the ambient to be used is preferably any of water vapor , oxygen , { HEAD ~ nitrogen } , hydrogen and N2O or { TAIL ~ any combination } of them
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