Merged-PiN schottky (MPS) diode having a doped region surrounding a plurality of wells, and a method for manufacturing the same
An MPS diode and a manufacturing method is provided. The diode includes a semiconductor body including an active area and an adjacent termination area, the active area includes a drift region of a first conductivity type, and a plurality of wells of a second type different from the first conductivity type, the wells being mutually spaced apart, each well forming a respective PN-junction with the drift region. The diode further includes a metal layer assembly arranged on a surface of the semiconductor body and at least one metal layer, the metal layer assembly forming a plurality of Schottky contacts together with the drift region and a plurality of respective Ohmic contacts with the wells. The drift region includes a doped region surrounding each of the wells and having a higher dopant concentration than a remainder of the drift region, and the doped region is spaced apart from the termination area.
1 . A merged PiN Schottky (MPS) diode, comprising:
a semiconductor body including an active area and a termination area adjacent to the active area, wherein the active area comprises:
a drift region of a first conductivity type; and
a plurality of wells of a second conductivity type different from the first conductivity type, wherein the plurality of wells being mutually spaced apart, each well forming a respective PN-junction with the drift region;
a metal layer assembly arranged on a surface of the semiconductor body and comprising at least one metal layer, wherein the metal layer assembly form a plurality of Schottky contacts together with the drift region and a plurality of respective Ohmic contacts with the plurality of wells;
wherein the drift region comprises a doped region surrounding each of the plurality of wells and has a higher dopant concentration than a remainder of the drift region, and wherein the doped region is spaced apart from the termination area; and
wherein from the surface in a direction perpendicular to the surface, the dopant concentration of the doped region increases, and wherein the doped region includes a substantially uniformly doped upper region and a substantially uniformly doped lower region below the upper region; and/or
wherein the doped region comprises an inner region and an outer region laterally adjacent to the inner region, and wherein the outer region has a lower dopant concentration than the inner region.
2 . The MPS diode according to claim 1 , wherein the doped region includes the upper region and the lower region, and wherein the lower region extends from between 70% and 90% of a depth of the plurality of wells to a depth of the doped region.
3 . The MPS diode according to claim 1 , wherein the doped region includes the upper region and the lower region, and wherein the lower region has a dopant concentration that is at least two times higher than a dopant concentration of the upper region.
4 . The MPS diode according to claim 1 , wherein the doped region includes the upper region and the lower region, and wherein the doped region further includes one or more substantially uniformly doped middle regions arranged between the upper region and the lower region and has a dopant concentration between that of the upper region and the lower region.
5 . The MPS diode according to claim 1 , wherein the doped region extends laterally in at most 98% of the active area.
6 . The MPS diode according to claim 1 , wherein the doped region comprises the inner region and the outer region, and wherein the outer region has a sloped dopant profile in an outward direction from a center of the doped region.
7 . The MPS diode according to claim 1 , wherein the doped region comprises the inner region and the outer region, and wherein the inner region has a dopant concentration that is at least two times higher than a dopant concentration of the outer region.
8 . The MPS diode according to claim 1 , wherein the dopant concentration of the doped region is at least two times greater than the dopant concentration of the remainder of the drift region.
9 . The MPS diode according to claim 1 , wherein each pair of adjacently arranged wells among the plurality of wells has a spacing therebetween and the dopant concentration of the doped region is selected so that, at breakdown, an electrical field strength at an interface between the metal layer assembly and the drift region is below 70% of an electrical field strength at the PN junctions between the plurality of wells and the drift region.
10 . The MPS diode according to claim 1 , wherein the semiconductor body comprises a substrate and an epitaxial layer arranged on the substrate, wherein the active area and the termination area are arranged in the epitaxial layer, wherein the metal layer assembly forms a first terminal of the MPS diode, wherein the MPS diode further comprises a contact arranged on the substrate, and wherein the contact forms a second terminal of the MPS diode.
11 . The MPS diode according to claim 1 , wherein the plurality of wells are formed as parallel strips or as concentric shapes; and/or wherein each of the plurality of wells further comprises a subregion at the surface of the semiconductor body, wherein the subregion has a higher dopant concentration than a remainder of the well for enabling an Ohmic contact with the metal layer assembly and/or the subregion.
12 . The MPS diode according to claim 1 , wherein the termination area comprises a termination region of the second conductivity type extending from the surface to a third depth in the semiconductor body, and wherein the second depth is equal to or greater than the third depth.
13 . The MPS diode according to claim 12 , wherein the plurality of wells has a dopant concentration that is at least 10 times greater than a dopant concentration of the termination region.
14 . The MPS diode according to claim 1 , wherein the plurality of wells extend from the surface to a first depth into the semiconductor body, wherein the doped region extends from the surface to a second depth into the semiconductor body, and wherein the second depth is at least 20% greater than the first depth.
15 . The MPS diode according to claim 14 , wherein the termination area comprises a termination region of the second conductivity type extending from the surface to a third depth in the semiconductor body, and wherein the second depth is equal to or greater than the third depth.
16 . The MPS diode according to claim 14 , wherein the doped region includes the upper region and the lower region, and wherein the lower region extends from between 70% and 90% of a depth of the plurality of wells to a depth of the doped region.
17 . The MPS diode according to claim 14 , wherein the doped region includes the upper region and the lower region, and wherein the lower region has a dopant concentration that is at least two times higher than a dopant concentration of the upper region.
18 . The MPS diode according to claim 14 , wherein the doped region includes the upper region and the lower region, and wherein the doped region further includes one or more substantially uniformly doped middle regions arranged between the upper region and the lower region and has a dopant concentration between that of the upper region and the lower region.
19 . The MPS diode according to claim 14 , wherein the doped region extends laterally in at most 98% of the active area.
20 . A method for manufacturing a merged-PiN Schottky (MPS) diode, comprising:
providing a semiconductor body including an active area and a termination area adjacent to the active area, wherein the active area comprises a drift region of a first conductivity type;
forming a doped region in the drift region, the doped region having a higher dopant concentration than a remainder of the drift region, wherein the doped region is spaced apart from the termination area;
forming a plurality of wells of a second conductivity type different from the first conductivity type in the doped region, wherein the plurality of wells being mutually spaced apart, with each well forming a respective PN-junction with the drift region;
arranging a metal layer assembly on the surface, wherein the metal layer assembly comprising at least one metal layer, wherein the metal layer assembly forms a plurality of Schottky contacts together with the drift region and a plurality of respective Ohmic contacts with the plurality of wells; and
wherein from the surface in the direction perpendicular to the surface, the dopant concentration of the doped region increases, wherein the doped region includes a substantially uniformly doped upper region and a substantially uniformly doped lower region below the upper region; and/or
wherein the doped region comprises an inner region and an outer region laterally adjacent to the inner region, and wherein the outer region has a lower dopant concentration than the inner region.