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Please ask a more specific question - what you are interested in - the purpose/meaning of STI, or its technology/manufacturing process, or how it looks like on the layout, or what isolation is, in general, etc.?
Successor to LOCOS, STI uses a dry trench etch and is
able to dig higher aspect ratios and finer spacings.
I've never understood why LOCOS or STI are considered
"isolation" when really it's all about the junctions. There
remains a silicon path between devices, below LOCOS
or STI; conduction and carrier diffusion are only slightly
inconvenienced by a longer path.
LOCOS and STI both serve as "hard masks" for the S/D
and extension / halo implants. The implants in these areas
stop in the oxide.
I think it's called "isolation" because STI trench goes below n+ and p+ source/drain implant regions, hence neighboring n+ and p+ diffusion areas are electrically isolated form each other.
Of course, this isolation can be achieved without LOCOS or STI, using junctions (junction isolation), but the problem with it is that it requires a large area, as compared to LOCOS or STI.
Of course, there is a path below STI, but it is a resistive path for the wells (for the same doping type), while n+ and p+ diffusions can "talk" to each other only via minority carrier transport...
In that they only mentioned How sti will protects from latch up and leakage current.
They didn't mention how to avoid the LOD effect which is caused by the STI.
You should have a layer called active, or diff, or od, or moat - meaning "active silicon".
STI is present everywhere where "active" is absent, i.e. STI = NOT ACTIVE (speaking SVRF language).
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