Appeal No. 96-0471
Application 07/995,582
This is a decision on appeal under 35 U.S.C. § 134 from
the final rejection of claims 1, 4-11, and 14-20. Claims 2,
3, 12, and 13 have been canceled.
We reverse.
BACKGROUND
The disclosed invention is directed to a structure for
providing junction breakdown stability for deep trench
devices. Appellant discloses that deep trench structures have
higher junction breakdown voltages than planar structures, but
have the same junction breakdown voltage instability problem
that planar junction structures possess. This instability
results when oxide-passivated junctions are subjected to
conditions which cause avalanche breakdown. Voltage
instabilities are caused by surface effects. In deep trenches
where the metallurgical junction terminates on the surface of
the sidewall, oxide passivated surfaces cause junction
breakdown instabilities because they trap charges in the
sidewall dielectric (oxide). The invention adds a lightly
doped buffer layer adjacent to the sidewalls of the deep
trench, thereby shifting the metallurgical junction away from
the sidewalls.
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