Semiconductor device structures and related processes
View Patent ↗Improved highly reliable power RFP structures and fabrication and operation processes. The structure includes plurality of localized dopant concentrated zones beneath the trenches of RFPs, either floating or extending and merging with the body layer of the MOSFET or connecting with the source layer through a region of vertical doped region. This local dopant zone decreases the minority carrier injection efficiency of the body diode of the device and alters the electric field distribution during the body diode reverse recovery.
1. A method for operating a semiconductor device structure, comprising:
controlling conduction between first and second source/drain electrodes through a channel location in semiconductor material using a gate electrode positioned in a first trench to provide at least ON and OFF states; and
avoiding punchthrough of said channel location, using both
one or more recessed field plates, positioned in proximity to and capacitively coupled to said semiconductor material; said recessed field plates being positioned in respective second trenches, and
one or more diffusion components of a second conductivity type lying at least partially directly beneath said respective second trenches;
whereby said diffusion components reduce depletion spreading in the OFF state.
2. A method for operating a semiconductor device structure, comprising:
controlling conduction between first and second source/drain electrodes through a channel location in semiconductor material using a gate electrode positioned in a first trench to provide at least ON and OFF states; and
avoiding punchthrough of said channel location, using both
one or more recessed field plates, positioned in proximity to and capacitively coupled to said semiconductor material; said recessed field plates being positioned in respective second trenches, and
one or more diffusion components of a second conductivity type lying at least partially directly beneath said respective second trenches;
whereby said diffusion components reduce depletion spreading in the OFF state;
wherein said device further includes a layer of dopant concentration region of second-conductivity-type that extends from a source layer to at least one location of said diffusion components.
3. The method of claim 1 , wherein the gate has a split poly configuration.
4. The method of claim 1 , wherein at least one of the recessed field plates has a split poly configuration.
5. The method of claim 1 , wherein both the gate and at least one of the recessed field plates have a split poly configuration.
6. The method of claim 1 , wherein said gate is capacitively coupled to control vertical conduction to a drain diffusion of a first conductivity type.
7. A fabrication process for making a MOSFET, comprising the actions, in any order, of:
a) providing an n-type semiconductor layer;
b) forming a p-type body in said layer;
c) forming an n-type source, which is isolated by said body, in said layer;
d) forming an insulated gate trench in said layer, and a gate electrode in said gate trench; said gate electrode being capacitively coupled to at least a portion of said body;
e) forming a second insulated trench in said layer, providing an additional dose of acceptor dopants below said trench, and forming a Recessed Field Plate electrode in said second trench; and
f) providing an additional dose of donor dopant atoms in said portion of said body, to thereby reduce the on-resistance.