Trench MOSFET with trenched floating gates and trenched channel stop gates in termination
A trench MOSFET comprising multiple trenched floating gates in termination area is disclosed. The multiple trenched floating gates have trench depth equal to or deeper than body junction of body regions in active area. The trench MOSFET further comprises at least one trenched channel stop gate around outside of the trenched floating gates and connected to at least one sawing trenched gate extended into scribe line for prevention of leakage path formation between drain and source regions.
1. A trench MOSFET with a plurality of transistor cells in active area and multiple trenched floating gates in termination area, comprising:
an epitaxial layer of a first conductivity type onto a substrate of said first conductivity type, wherein said epitaxial layer having a lower doping concentration than said substrate;
a plurality of source regions of said first conductivity type formed near top surface of said epitaxial layer only in said active area, said source regions being connected to a source metal pad and having a higher doping concentration than said epitaxial layer;
a plurality of first type body regions of a second conductivity type formed underneath said source regions in said active area;
a plurality of second type body regions of said second conductivity type formed in said epitaxial layer around outside of said active area including said termination area, and said source regions being not disposed on top of said second type body regions;
a plurality of first type trenched gates in said active area, surrounded by said source regions and said first type body regions;
at least one second type trenched gate surrounded by said second type body regions and extending to said first type trenched gates for gate contact, wherein said at least one second type trenched gate is connected to a gate metal pad for wire bonding;
said multiple trenched floating gates formed in parallel in said termination area around outside of said active area, said multiple trenched floating gates having floating voltage and surrounded by said second type body region, having trench depth equal to or deeper than body junction of said second type body regions;
at least one trenched channel stop gate formed in said termination area and around outside of said multiple trenched floating gates, each said trenched channels top gate being connected to at least one sawing trenched gate, wherein each said sawing trenched gate is extended across a scribe line.
2. The trench MOSFET of claim 1 , wherein said second type body region adjacent said active area is connected to said source metal pad through a trenched body contact.
3. The trench MOSFET of claim 1 , wherein said second type body region adjacent said active area is not connected to said source metal pad but having floating voltage.
4. The trench MOSFET of claim 1 , wherein there is only one trenched channel stop gate formed in said termination area, wherein said only one trenched channel stop gate is connected to at least one sawing trenched gate.
5. The trench MOSFET of claim 1 , wherein there are multiple trenched channel stop gates formed in said termination area, wherein each of said trenched channel stop gates is connected to at least one sawing trenched gate.
6. The trench MOSFET of claim 1 , wherein said first conductivity type is N type and said second conductivity type is P type.
7. The trench MOSFET of claim 1 , wherein said first conductivity type is P type and said second conductivity type is N type.
8. The trench MOSFET of claim 1 , wherein said transistor cells in said active area are closed cells.
9. The trench MOSFET of claim 1 , wherein said transistor cells in said active area are stripe cells.
10. The trench MOSFET of claim 1 , wherein said at least one second type trenched gate is only disposed underneath said gate metal pad.
11. The trench MOSFET of claim 1 further comprising a gate metal runner surrounding outside of said active area and extending to said gate metal pad, wherein said at least one second type trenched gate is disposed not only underneath said gate metal pad, but also underneath said gate metal runner.
12. The trench MOSFET of claim 1 further comprising a doped region of said first conductivity type with doping concentration higher than said epitaxial layer wrapping bottoms of said first type trenched gates, said at least one second type trenched gate, said sawing trenched gate and said multiple trenched floating gates.
13. The trench MOSFET of claim 1 , wherein said multiple trenched floating gates in said termination area have same trench width and same trench depth as said first type trenched gates in said active area.
14. The trench MOSFET of claim 1 , wherein said multiple trenched floating gates in said termination area have greater trench width and greater trench depth than said first type trenched gates in said active area.
15. The trench MOSFET of claim 14 , wherein the trench width of said multiple trenched floating gates increases toward the edge of said termination area.
16. The trench MOSFET of claim 14 , wherein the trench width of said multiple trenched floating gates decreases toward the edge of said termination area.
17. The trench MOSFET of claim 1 , wherein said trenched channel stop gate and said sawing trenched gate are electrically shorted to a drain region and said second type body region around said termination area.