Space efficient high-voltage termination and process for fabricating same
A high-voltage termination for a semiconductor device includes a substrate of a first conductivity type, an implanted device region of a second conductivity type of the semiconductor device, a shallow trench disposed in the substrate adjacent to the implanted device region, a doped extension region of the second conductivity type extending between the implanted device region and a first edge of the shallow trench adjacent to the implanted device region, a junction termination extension region of the second conductivity type formed in the shallow trench contacting the extension region and extending past a second edge of the shallow trench opposite the implanted device region, an insulating layer formed over at least a portion of the extension region and over the junction termination extension region, and a metal layer formed over the insulating layer extending into at least a portion of the shallow trench and electrically connected to the extension region.
1. A high-voltage termination for a semiconductor device comprising:
a substrate of a first conductivity type;
a well of a second conductivity type opposite the first conductivity type formed at a top surface of, and extending into the substrate of the first conductivity type
an implanted device region of the first conductivity type formed at the top surface of, and extending into the well of the second conductivity type, the implanted device region forming a part of the semiconductor device;
a shallow trench disposed in the substrate, the shallow trench having sloped sidewalls, a first edge that is adjacent to the well and a second edge on the opposite side of the shallow trench;
a doped extension region of the second conductivity type formed in the substrate, the doped extension region having a doping concentration greater than a doping concentration of the well and extending between the well and the first edge of the shallow trench;
a junction termination extension region of the second conductivity type formed beneath the shallow trench and contacting the doped extension region, the junction termination region having a doping concentration less than the doping concentration of the doped extension region and extending past the second edge of the shallow trench;
an insulating layer formed directly over at least a portion of the doped extension region and directly over the junction termination extension region; and
a metal layer formed over the insulating layer, the metal layer extending into at least a portion of the shallow trench, the metal layer electrically connected through a via in the insulating layer to the doped extension region.
2. The high-voltage termination of claim 1 wherein a distance from the first edge of the shallow trench to the second edge of the shallow trench, and a length of a portion of the junction termination extension region that extends past the second edge of the shallow trench together form a termination length of the high-voltage termination.
3. The high-voltage termination of claim 1 further comprising a second insulating layer formed over the metal layer and the insulating layer.
4. The high-voltage termination of claim 1 wherein the substrate of the first conductivity type is an epitaxial layer disposed over an underlying substrate.
5. The high-voltage termination of claim 4 wherein:
the epitaxial layer is an epitaxial SiC layer; and
the underlying substrate is a SiC substrate.
6. The high-voltage termination of claim 5 wherein:
the epitaxial SiC layer is doped with nitrogen; and
the underlying SiC substrate is doped with nitrogen.
7. The high-voltage termination of claim 6 wherein:
the epitaxial SiC layer is doped with nitrogen to a concentration of from about 1e14/cm 3 to about 2e16/cm 3 ; and
the underlying SiC substrate is doped with nitrogen to a resistivity of about 0.02 ohm-cm.
8. The high-voltage termination of claim 1 wherein:
the doped extension region is implanted with one of aluminum and boron; and
the junction termination extension region is implanted with one of aluminum and boron.
9. The high-voltage termination of claim 8 wherein:
the doped extension region is implanted with one of aluminum and boron with a dose of between about 1e13/cm 2 to about 1e15/cm 2 ; and
the junction termination extension region is implanted with one of aluminum and boron with a dose of between about 1e11/cm 2 to about 1e13/cm 2 .
10. The high-voltage termination of claim 1 ,
wherein the shallow trench has a depth of between about 2 μm to about 5 μm; and
wherein a length of the shallow trench is a distance from the first edge of the shallow trench to the second edge of the shallow trench,
wherein the high-voltage termination has a termination length defined by the length of the shallow trench and an extension of the junction termination extension region beyond the second edge of the trench, and
wherein the termination length is selected to withstand a preselected blocking voltage.
11. The high-voltage termination of claim 2 wherein the termination length is between about 20 μm to about 55 μm.
12. A transistor with high-voltage termination, comprising:
a substrate of a first conductivity type;
a drain region formed in a back side of the substrate;
a well of a second conductivity type opposite the first conductivity type formed at a top surface of, and extending into, the substrate;
a source region formed within the well;
a gate disposed over the source and drain regions;
a shallow trench disposed in the substrate, the shallow trench having sloped sidewalls, a first edge that is adjacent to the well and a second edge on the opposite side of the shallow trench;
a doped extension region of the second conductivity type, opposite the first conductivity type, formed in the substrate and extending from the first edge of the shallow trench and contacting the well;
a junction termination extension region of the second conductivity type formed beneath the shallow trench and contacting the doped extension region, the junction termination extension region extending past the second edge of the shallow trench;
an insulating layer formed directly over at least a portion of the extension region and directly over the junction termination extension region; and
a metal layer formed over the insulating layer, the metal layer extending into at least a portion of the shallow trench, the metal layer electrically connected through a via in the insulating layer to the doped extension region.
13. The transistor of claim 12 ,
wherein the well is a p-well,
wherein the junction termination extension region has a doping concentration less than a doping concentration of the doped extension region, and
wherein the doping concentration of the doped extension region is greater than a doping concentration of the well.
14. The transistor of claim 12 wherein a distance from the first edge of the shallow trench to the second edge of the shallow trench, and a length of a portion of the junction termination extension region that extends past the second edge of the shallow trench together form a termination length of the high-voltage termination for the transistor.