Superjunction semiconductor device with oppositely doped semiconductor regions formed in trenches
A trench etch mask is formed on a process surface of a semiconductor layer. By using the trench etch mask, both first trenches and second trenches are formed that extend from the process surface into the semiconductor layer. The first and second trenches alternate along at least one horizontal direction parallel to the process surface. First semiconductor regions of a first conductivity type are formed in the first trenches. Second semiconductor regions of a second, opposite conductivity type are formed in the second trenches.
1. A super junction semiconductor device, comprising:
a semiconductor portion that comprises a drift layer comprising first semiconductor regions of a first conductivity and second semiconductor regions of an opposite second conductivity type,
wherein the first semiconductor regions are disposed in first trenches formed in the semiconductor portion,
wherein the second semiconductor regions are disposed in second trenches formed in the semiconductor portion,
wherein the first and second semiconductor regions alternate along at least one horizontal direction parallel to a first surface of the semiconductor portion,
wherein surfaces that connect points of equal dopant concentration in the first and second semiconductor regions are not undulated, and
wherein at half a distance between vertical center axes of neighboring first and second semiconductor regions a concentration of dopants of the first conductivity type is at most 30% of a maximum dopant concentration in the first semiconductor regions.
2. The superjunction semiconductor device of claim 1 , wherein at half the distance between vertical center axes of directly adjoining first and second semiconductor regions the dopant concentration of dopants of the first conductivity type is at most 15% of the maximum dopant concentration in the first semiconductor regions.
3. The superjunction semiconductor device of claim 1 , further comprising:
a second superjunction structure stacked with a first superjunction structure comprising the first and second semiconductor regions.
4. The superjunction semiconductor device of claim 1 , wherein the drift layer has the first conductivity type and a vertical extension of the first semiconductor regions is greater than a vertical extension of the second semiconductor regions.
5. The superjunction semiconductor device of claim 1 , wherein a dopant concentration per unit area in both the first and second semiconductor regions locally changes with decreasing distance to a lateral surface of the semiconductor portion.
6. The superjunction semiconductor device of claim 1 , wherein a dopant concentration per unit area in the first or the second semiconductor regions locally changes with respect to a dopant concentration per unit area in the other of the second and first semiconductor regions with decreasing distance to a lateral surface of the semiconductor portion.
7. The superjunction semiconductor device of claim 1 , wherein portions of the drift layer separate neighboring first and second semiconductor regions.
8. The superjunction semiconductor device of claim 1 , wherein the first and second semiconductor regions alternate along two orthogonal horizontal directions.
9. A super junction semiconductor device, comprising:
a semiconductor portion that comprises a drift layer comprising first semiconductor regions of a first conductivity and second semiconductor regions of an opposite second conductivity type,
wherein the first and second semiconductor regions alternate along at least one horizontal direction parallel to a first surface of the semiconductor portion,
wherein surfaces that connect points of equal dopant concentration in the first and second semiconductor regions are not undulated, and
wherein at a pn junction between directly adjoining first and second semiconductor regions a concentration of dopants of the first conductivity type is at most 30% of a maximum dopant concentration in the first semiconductor regions.