EPITAXIAL FIELD STOP REGION FOR SEMICONDUCTOR DEVICES
A semiconductor device includes a backside contact and a substrate. An epitaxial field stop region may be formed on the substrate with a graded doping profile that decreases with distance away from the substrate, and an epitaxial drift region may be formed adjacent to the epitaxial field stop region. A frontside device may be formed on the epitaxial drift region.
1 . A semiconductor device, comprising:
a backside contact;
a substrate adjacent to the backside contact;
an epitaxial field stop region formed on the substrate and having a graded doping profile that decreases with distance away from the substrate;
an epitaxial drift region adjacent to the epitaxial field stop region; and
a frontside device formed on the epitaxial drift region.
2 . The semiconductor device of claim 1 , wherein the epitaxial drift region has a substantially uniform doping profile.
3 . The semiconductor device of claim 1 , wherein the epitaxial drift region and the epitaxial field stop region have a doping of a first conductivity type, and the substrate has a doping of a second conductivity type.
4 . The semiconductor device of claim 1 , wherein the epitaxial field stop region includes a proton implant proximal to the substrate.
5 . The semiconductor device of claim 1 , wherein the frontside device includes an insulated gate bipolar transistor (IGBT).
6 . The semiconductor device of claim 1 , wherein the frontside device includes fast recovery diode (FRD).
7 . The semiconductor device of claim 1 , wherein the graded doping profile linearly decreases with distance away from the substrate.
8 . The semiconductor device of claim 1 , wherein the graded doping profile has a stepped decrease with distance away from the substrate.
9 . A semiconductor device, comprising:
a backside contact;
a substrate adjacent to the backside contact and having a doping of a first conductivity type;
an epitaxial field stop region formed on the substrate and having a graded doping profile of a second conductivity type that decreases with distance away from the substrate;
an epitaxial drift region adjacent to the epitaxial field stop region and having a substantially uniform doping profile of the second conductivity type; and
a frontside device formed on the epitaxial drift region.
10 . The semiconductor device of claim 9 , wherein the epitaxial field stop region includes a proton implant proximal to the substrate.
11 . The semiconductor device of claim 9 , wherein the graded doping profile linearly decreases with distance away from the substrate.
12 . The semiconductor device of claim 9 , wherein the graded doping profile has a stepped decrease with distance away from the substrate.
13 . A method of making a semiconductor device, comprising:
performing at least one epitaxial growth process on a substrate to obtain an epitaxial field stop region on the substrate and an epitaxial drift region on the epitaxial field stop region; and
performing frontside processing to form at least one frontside device on the epitaxial drift region.
14 . The method of claim 13 , wherein performing the at least one epitaxial growth process includes forming a graded doping profile within the epitaxial field stop region that linearly decreases with distance away from the substrate.
15 . The method of claim 14 , wherein forming the graded doping profile comprises:
performing the at least one epitaxial growth process as a single epitaxial growth process in which process parameters are adjusted to obtain the graded doping profile.
16 . The method of claim 14 , wherein forming the graded doping profile comprises:
performing the at least one epitaxial growth process as a multi-step epitaxial growth process to obtain doping peaks within the epitaxial field stop region; and
performing an annealing process during the frontside processing that diffuses the doping peaks and thereby provides the graded doping profile.
17 . The method of claim 13 , wherein the epitaxial field stop region and the epitaxial drift region have a doping of a first conductivity type, the method further comprising:
performing a backside implant process to provide the substrate with a doping of a second conductivity type.
18 . The method of claim 13 , wherein the epitaxial field stop region and the epitaxial drift region have a doping of a first conductivity type, the method further comprising:
performing a backside implant process to implant dopants of the first conductivity type in a region of the epitaxial field stop region proximal to the substrate.
19 . The method of claim 18 , wherein the backside implant process includes a proton implant performed at approximately 400 keV or less.
20 . The method of claim 13 , further comprising:
performing a backside grinding process to thin the substrate, after the frontside processing.