Field-effect transistor, and methods for production
A field-effect transistor. The field-effect transistor includes: a source layer doped according to a first type, a drain layer doped according to a first type, a channel layer located vertically between the source layer doped according to the first type and the drain layer doped according to the first type, and a gate trench which extends vertically from the source layer doped according to the first type to the drift layer doped according to the first type and adjoins the channel layer. The channel layer has, at least on average, a lower doping of the second type and a higher doping of the first type in a region that is more than a specified distance from the gate trench than in a region that is less than the specified distance from the gate trench. Methods for production are also described.
1 . A field-effect transistor, comprising:
a source layer doped according to a first type;
a drain layer doped according to the first type;
a channel layer located vertically between the source layer doped according to the first type and the drain layer doped according to the first type; and
a gate trench which extends vertically from the source layer doped according to the first type to the drain layer doped according to the first type and adjoins the channel layer;
wherein the channel layer has, at least on average, a lower doping of a second type or a higher doping of the first type in a region that is more than a specified distance from the gate trench than in a region that is less than the specified distance away from the gate trench.
2 . The field-effect transistor according to claim 1 , further comprising a gate electrode which is arranged in the gate trench and is divided into at least two parts in such a way that a region of a bottom of the gate trench remains free.
3 . The field-effect transistor according to claim 1 , wherein the channel layer is doped according to the second type.
4 . The field-effect transistor according to claim 1 , further comprising a shielding region doped according to the second type and located vertically below the gate trench in the drain layer doped according to the first type.
5 . The field-effect transistor according to claim 1 , wherein the field-effect transistor is a SiC or GaN field-effect transistor.
6 . A method for producing a field-effect transistor, comprising the following steps:
providing a starting material including: a source layer doped according to a first type, a drain layer doped according to the first type, and a channel layer located vertically between the source layer doped according to the first type and the drain layer doped according to the first type;
increasing a doping of the first type or reducing a doping of the second type in the channel layer in a doping region that is more than a specified distance from a gate region in which a gate trench is to be formed; and
at least partially forming the gate trench in the gate region so that the gate trench extends vertically from the source layer doped according to the first type to the drain layer doped according to the first type and adjoins the channel layer.
7 . The method according to claim 6 , further comprising, prior to increasing the doping of the first type or reducing the doping of the second type:
applying, onto the source layer doped according to the first type, a mask in the gate region, wherein a spacer layer has been or is applied to side walls of the mask and extends to the doping region.
8 . The method according to claim 7 , further comprising, prior to at least partially forming the gate trench: inverting the mask, wherein the spacer layer is retained to form an inverted mask, and wherein at least partially forming the gate trench takes place using the inverted mask with the spacer layer.
9 . The method according to claim 8 , further comprising, prior to at least partially forming the gate trench: forming or increasing a doping of the second type in the gate region, using the inverted mask with the spacer layer.
10 . The method according to claim 6 , further comprising, prior to increasing the doping of the first type or reducing the doping of the second type: forming or increasing a doping of the second type in the channel layer, as a planar doping of the second type.
11 . The method according to claim 6 , further comprising, after at least partially forming the gate trench: forming a shielding region doped according to the second type in the drain layer doped according to the first type at a bottom of the gate trench, after previously forming a spacer layer on side walls of the gate trench.
12 . The method according to claim 6 , wherein the drain layer doped according to the first type includes a drift layer doped according to the first type and a spread layer doped according to the first type.
13 . The method according to claim 6 , further comprising, after at least partially forming the gate trench: introducing a gate electrode, which is at least partially surrounded by a dielectric, into the gate trench, after previously forming a spacer layer on side walls of the gate trench.
14 . The method according to claim 13 , wherein the gate electrode is divided into at least two parts in such a way that, upon introduction, a region of a bottom of the gate trench remains free.
15 . The method according to claim 14 , further comprising, after introduction of the gate electrode: metallizing, including contacting a shielding structure at an end of a cell field or between the gate electrode divided into two parts.
16 . A method for producing a field-effect transistor, comprising the following steps:
providing a starting material including: a source layer doped according to a first type, a drain layer doped according to the first type and including a drift layer doped according to the first type and a spread layer doped according to the first type, a channel layer located vertically between the source layer doped according to the first type and the drain layer doped according to the first type, wherein the spread layer doped according to the first type is located vertically between the channel layer and the drift layer doped according to the first type, and has a higher doping of the first type than the drift layer doped according to the first type;
at least partially forming a gate trench in a gate region so that the gate trench extends vertically from the source layer doped according to the first type to the drain layer doped according to the first type and adjoins the channel layer; and
increasing a doping of a second type or reducing a doping of the first type in the channel layer in an intermediate region extending from the gate region to a specified distance, through implantation, into the gate trench.