Extended drain metal-oxide-semiconductor transistor
Devices and methods for forming a device are disclosed. A transistor is formed on the substrate. The transistor includes a gate, a source and a drain. An insulation layer is formed on the substrate. The insulation layer is partially disposed on the gate and a sidewall of the gate. The drain is offset from the gate by the insulation layer. An overlayer is formed on the substrate covering the transistor and insulation layer. A field plate in the form of a field plate contact is formed in the overlayer. The field plate contact is disposed on and coupled to the insulation layer for mitigating the formation of electric field adjacent to drain side of the gate.
1. A method for forming a device comprising:
providing a substrate, wherein the substrate comprises a medium voltage (MV) device region, wherein the MV device region comprises
first, second, and third wells,
wherein the second and third wells are disposed in the first well, the second and third wells are distinct wells,
wherein the first well is lightly doped with first polarity type dopants, the second well is intermediately doped with second polarity type dopants and the third well is intermediately doped with first polarity type dopants, and
wherein the first well is a deep well, the second doped well is a body well, and the third doped well is a drift well;
forming a first polarity type transistor on the substrate in the MV device region, wherein the transistor comprises a gate, a source and a drain;
forming an insulation layer on the substrate, wherein the insulation layer is partially disposed on the gate and a sidewall of the gate, and wherein the drain is offset from the gate by the insulation layer;
forming an overlayer on the substrate covering the transistor and insulation layer; and
forming a field plate in the form of a field plate contact in the overlayer, wherein the field plate contact is disposed on and coupled to the insulation layer for mitigating the formation of electric field adjacent to drain side of the gate.
2. The method of claim 1 wherein the overlayer comprises an etch stop layer and a dielectric layer, and wherein the etch stop layer is disposed between the insulation layer and the dielectric layer.
3. The method of claim 1 wherein forming the overlayer on the substrate comprises forming a first opening in the dielectric layer.
4. The method of claim 3 wherein the first opening comprises a first elongated trench, and wherein forming the field plate in the form of a field plate contact comprises filling the first elongated trench with a conductive material.
5. The method of claim 1 wherein the field plate contact is a long strip which traverses the transistor in a direction perpendicular to a channel length of the transistor.
6. The method of claim 1 wherein the field plate contact comprises a series of field plate contact plugs arranged in a column in a direction perpendicular to a channel length of the transistor.
7. The method of claim 1 wherein forming the overlayer on the substrate comprises forming a plurality of second openings in the overlayer, wherein each of the second openings correspond to contact terminals of the transistor.
8. The method of claim 7 further comprising filling the plurality of second openings with a conductive material to form a plurality of contact plugs.
9. The method of claim 8 wherein the contact plugs are formed as a series of contact plugs arranged in a column in a direction perpendicular to a channel length of the transistor.
10. The method of claim 1 wherein the source is formed in the second doped well and the drain is formed in the drift well.
11. A method for forming a device comprising:
providing a substrate, wherein the substrate comprises a medium voltage (MV) device region, wherein the MV device region comprises
first, second, and third wells,
wherein the second and third wells are disposed in the first well, the second and third wells are distinct wells,
wherein the first well is lightly doped with first polarity type dopants, the second well is intermediately doped with second polarity type dopants and the third well is intermediately doped with first polarity type dopants, and
wherein the first well is a deep well, the second doped well is a body well, and the third doped well is a drift well;
forming a transistor on the substrate in the MV device region, wherein the transistor comprises a gate;
forming an insulation layer on the substrate, wherein the insulation layer is partially disposed on the gate and a sidewall of the gate;
forming an etch stop layer on the substrate, wherein the etch stop layer covers the transistor;
forming a dielectric layer over the etch stop layer; and
forming a field plate in the form of a field plate contact in the etch stop layer and dielectric layer, wherein the field plate contact is disposed on and coupled to the insulation layer.
12. The method of claim 11 further comprising forming a first opening in the etch stop layer and dielectric layer.
13. The method of claim 12 wherein forming the first opening in the etch stop layer and dielectric layer comprises:
etching the dielectric layer to form an elongated opening; and
etching the etch stop layer to form the first opening which corresponds to the elongated opening, wherein the etched dielectric layer serves as an etch mask.
14. The method of claim 13 further comprising filling the first opening with a conductive material to form the field plate contact.
15. The method of claim 11 further comprising forming a plurality of second openings in the etch stop layer and dielectric layer.
16. The method of claim 15 wherein forming the plurality of second openings in the etch stop layer and dielectric layer comprises:
etching the dielectric layer to form a plurality of via holes; and
etching the etch stop layer to form the plurality of second openings which correspond to the via holes, wherein the etched dielectric layer serves as an etch mask.
17. The method of claim 11 wherein the transistor comprises a drain and wherein the drain is offset from the gate by the insulation layer.
18. The method of claim 11 wherein the field plate contact is a long strip which traverses the transistor in a direction perpendicular to a channel length of the transistor.
19. A device comprising:
a substrate, wherein the substrate comprises a medium voltage (MV) device region, wherein the MV device region comprises
first, second, and third wells,
wherein the second and third wells are disposed in the first well, the second and third wells are distinct wells;
wherein the first well is lightly doped with first polarity type dopants, the second well is intermediately doped with second polarity type dopants and the third well is intermediately doped with first polarity type dopants, and
wherein the first well is a deep well, the second doped well is a body well, and the third doped well is a drift well; and
a transistor disposed on the substrate in the MV device region, wherein the transistor comprises a gate, a source and a drain;
an insulation layer disposed on the substrate, wherein the insulation layer is partially disposed on the gate and a sidewall of the gate, and wherein the drain is offset from the gate by the insulation layer;
an overlayer disposed on the substrate covering the transistor and insulation layer; and
a field plate in the form of a field plate contact disposed in the overlayer, wherein the field plate contact is disposed on and coupled to the insulation layer for mitigating the formation of electric field adjacent to drain side of the gate.