Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2002-04-10
2004-11-16
Guerrero, Maria F. (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S401000, C257S409000, C257S494000
Reexamination Certificate
active
06818958
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to semiconductor devices and more specifically relates to a structure and process to improve the threshold voltage stability of a MOSgated device under high temperature reverse bias.
BACKGROUND OF THE INVENTION
The threshold voltage (V
th
) of MOSgated devices has been found to shift under high temperature reverse bias (HTRB).
More specifically, a V
th
shift of about (−) 1 volt has been found after about 500 to 1000 hours HTRB.
It is believed that this is caused by sodium ions in the field oxide which drift laterally and accumulate at the edge of the channel in the first active cell or stripe.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention, a cut is made in the P
+
oxide layer to eliminate an Na
+
diffusion path. This cut has been found to substantially stabilize V
th
in HTRB up to 1000 hours.
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Guerrero Maria F.
International Rectifier Corporation
Ostrolenk Faber Gerb & Soffen, LLP
Soward Ida M.
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