Method for manufacturing silicon carbide semiconductor device and silicon carbide semiconductor device
A method for manufacturing a silicon carbide semiconductor device includes the steps of preparing a silicon carbide substrate having a first main surface and a second main surface located on a side opposite to the first main surface, forming an epitaxial layer on the first main surface, the epitaxial layer having a first conductivity type and having a third main surface located on a side opposite to a side on which the silicon carbide substrate is located, forming a trench, which includes side walls intersecting with the third main surface and a bottom portion connected to the side walls, in the epitaxial layer, widening an opening of the trench, and forming an embedded region, which has a second conductivity type different from the first conductivity type, in the trench. The epitaxial layer adjacent to the embedded region and the embedded region constitute a superjunction structure.
1. A method for manufacturing a silicon carbide semiconductor device, comprising the steps of:
preparing a silicon carbide substrate having a first main surface and a second main surface located on a side opposite to said first main surface;
forming an epitaxial layer on said first main surface, said epitaxial layer having a first conductivity type and having a third main surface located on a side opposite to a side on which said silicon carbide substrate is located;
forming a trench, which includes side walls intersecting with said third main surface and a bottom portion connected to said side walls, in said epitaxial layer;
widening an opening of said trench so that said side walls are inclined by greater than or equal to 45° and less than or equal to 80° with respect to said third main surface; and
forming an embedded region, which has a second conductivity type different from said first conductivity type, so as to fill said trench,
said epitaxial layer adjacent to said embedded region and said embedded region constituting a superjunction structure, the method further comprising the steps of:
forming an impurity region having said second conductivity type on said embedded region;
forming a first electrode on said impurity region; and
forming a second electrode in contact with said second main surface.
2. The method for manufacturing a silicon carbide semiconductor device according to claim 1 , wherein
said embedded region is formed such that a concentration of an impurity having said second conductivity type is reduced from said bottom portion toward said opening, and
said epitaxial layer is formed such that a concentration of an impurity having said first conductivity type increases from said first main surface toward said third main surface.
3. The method for manufacturing a silicon carbide semiconductor device according to claim 1 , wherein said step of forming a trench and said step of widening an opening are performed simultaneously.
4. A method for manufacturing a silicon carbide semiconductor device, comprising the steps of:
preparing a silicon carbide substrate having a first main surface and a second main surface located on a side opposite to said first main surface;
forming an epitaxial layer on said first main surface, said epitaxial layer having a first conductivity type and having a third main surface located on a side opposite to a side on which said silicon carbide substrate is located;
forming a trench, which includes side walls intersecting with said third main surface and a bottom portion connected to said side walls, in said epitaxial layer, said trench being formed to extend along a <11-20> direction when viewed in a plan view;
widening an opening of said trench; and
forming an embedded region, which has a second conductivity type different from said first conductivity type, so as to fill said trench,
said epitaxial layer adjacent to said embedded region and said embedded region constituting a superjunction structure, the method further comprising the steps of:
forming an impurity region having said second conductivity type on said embedded region;
forming a first electrode on said impurity region; and
forming a second electrode in contact with said second main surface.
5. The method for manufacturing a silicon carbide semiconductor device according to claim 4 , wherein a plurality of trenches are formed in stripe.