Semiconductor device having super junction structure and method for manufacturing the same

Abstract

A semiconductor device having a super junction structure includes: multiple first columns extending in a current flowing direction; and multiple second columns extending in the current flowing direction. The first and second columns are alternately arranged in an alternating direction. Each first column provides a drift layer. The first and second columns have a boundary therebetween, from which a depletion layer expands in case of an off-state. At least one of the first columns and the second columns have an impurity dose, which is inhomogeneous by location with respect to the alternating direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a cross sectional view showing a semiconductor device according to a first embodiment mode;

FIG. 2 is a partially enlarged cross sectional view showing a super junction structure in the device shown in FIG. 1;

FIG. 3 is a graph showing a voltage waveform and a current waveform in the device shown in FIG. 1 in case of switching;

FIG. 4 is a cross sectional view showing a semiconductor device according to a second embodiment mode;

FIG. 5 is a partially enlarged cross sectional view showing a super junction structure in the device shown in FIG. 4;

FIG. 6 is a cross sectional view showing a semiconductor device according to a third embodiment mode;

FIG. 7 is a partially enlarged cross sectional view showing a super junction structure in the device shown in FIG. 6;

FIGS. 8-11 are cross sectional views explaining a method for manufacturing the semiconductor device shown in FIG. 6;

FIG. 12 is a cross sectional view explaining another method for manufacturing the semiconductor device shown in FIG. 6;

FIG. 13 is a partially enlarged cross sectional view showing a super junction structure in a semiconductor device according to a fourth embodiment mode;

FIG. 14 is a partially enlarged cross sectional view showing a depletion layer in the super junction structure in FIG. 13;

FIG. 15 is a partially enlarged cross sectional view showing a super junction structure in a semiconductor device according to a modification of the fourth embodiment mode;

FIG. 16 is a cross sectional view showing another semiconductor device according to a first modification of the third embodiment mode;

FIG. 17 is a perspective view showing further another semiconductor device according to a second modification of the third embodiment mode;

FIG. 18 is a graph showing a relationship between a deviation of impurity surface concentration and a breakdown voltage;

FIG. 19 is a cross sectional view showing a semiconductor device as a comparison of the first embodiment mode;

FIGS. 20-22 are partially enlarged cross sectional views showing a depletion layer in the device shown in FIG. 19;

FIG. 23 is a graph showing a voltage waveform and a current waveform of the device shown in FIG. 19 in case of switching;

FIG. 24 is a cross sectional view showing a semiconductor device according to a fifth embodiment mode;

FIG. 25 is a cross sectional view showing the device taken along line XXV-XXV in FIG. 24;

FIGS. 26A and 26B are cross sectional views showing a depletion layer in the device shown in FIG. 25;

FIGS. 27A and 27B are cross sectional views showing a depletion layer in a semiconductor device having no bridge portion as a comparison of the fifth embodiment mode;

FIGS. 28-29 and 31-32 are cross sectional views explaining a method for manufacturing the device shown in FIG. 25;

FIG. 30 is a perspective view explaining the method for manufacturing the device shown in FIG. 25;

FIG. 33 is a cross sectional view showing a semiconductor device according to a sixth embodiment mode; and

FIG. 34 is a perspective view showing the semiconductor device having no bridge portion as a comparison of the fifth embodiment mode.

Claims

1. A semiconductor device having a super junction structure comprising: a plurality of first columns having a first conductive type and extending in a current flowing direction; anda plurality of second columns having a second conductive type and extending in the current flowing direction, whereinthe first columns and the second columns are alternately arranged in an alternating direction perpendicular to the current flowing direction so that the super junction structure is provided,each first column provides a drift layer in case of an on-state for flowing a current therethrough,the first columns and the second columns have a boundary between the first column and the second column, from which a depletion layer expands in case of an off-state, andat least one of the first columns and the second columns have an impurity dose, which is inhomogeneous by location with respect to the alternating direction.

2. The device according to claim 1, wherein each first column has a first impurity concentration,each second column has a second impurity concentration, andat least one of the first impurity concentration and the second impurity concentration varies by location with respect to the alternating direction.

3. The device according to claim 1, wherein each first column has a first width in the alternating direction,each second column has a second width in the alternative direction, andat least one of the first width and the second width varies by location with respect to the alternating direction.

4. The device according to claim 1, wherein each first column has a first width in the alternating direction,the first width is constant by location with respect to the alternating direction,each second column has a second width in the alternative direction,the second width is constant by location with respect to the alternating direction,each first column has a first impurity concentration,each second column has a second impurity concentration, andthe first impurity concentration and the second impurity concentration vary by location with respect to the alternating direction.

5. The device according to claim 1, wherein each first column has a first width in the alternating direction,the first width is constant by location with respect to the alternating direction,each second column has a second width in the alternative direction,the second width is constant by location with respect to the alternating direction,each first column has a first impurity concentration,each second column has a second impurity concentration,the first impurity concentration varies by location with respect to the alternating direction, andthe second impurity concentration is constant by location with respect to the alternating direction.

6. The device according to claim 1, wherein each first column has a first impurity concentration,the first impurity concentration is constant by location with respect to the alternating direction,each second column has a second impurity concentration,the second impurity concentration is constant by location with respect to the alternating direction,each first column has a first width in the alternating direction,each second column has a second width in the alternative direction,the first width varies by location with respect to the alternating direction, andthe second width is constant by location with respect to the alternating direction.

7. The device according to claim 1, wherein at least one of the impurity doses of the first columns and the second columns includes a first dose and a second dose,the device has a maximum breakdown voltage when the one of the impurity doses is a predetermined optimum impurity dose,the first dose is higher than the optimum impurity dose by a predetermined value, andthe surface second density is lower than the optimum impurity dose by the predetermined value.

8. The device according to claim 1, wherein at least one of the impurity doses of the first columns and the second columns includes a first dose, at least one middle dose and a second dose,the device has a maximum breakdown voltage when the one of the impurity doses is a predetermined optimum impurity dose,the first dose is higher than the optimum impurity dose by a predetermined value,the surface second density is lower than the optimum impurity dose by the predetermined value, andthe middle dose is disposed in a region between the first dose and the second dose.

9. The device according to claim 1, wherein the device is a vertical type MOSFET or a lateral type MOSFET.

10. A semiconductor device having a super junction structure comprising: a plurality of first columns having a first conductive type and extending in a current flowing direction; anda plurality of second columns having a second conductive type and extending in the current flowing direction, whereinthe first columns and the second columns are alternately arranged in an alternating direction perpendicular to the current flowing direction so that the super junction structure is provided,each first column provides a drift layer in case of an on-state for flowing a current therein,the first columns and the second columns have a boundary between the first column and the second column, from which a depletion layer expands in case of an off-state, andat least one of the first columns and the second columns have an impurity dose, which is inhomogeneous by location with respect to the current flowing direction.

11. The device according to claim 10, wherein each first column has a first impurity concentration,the first impurity concentration is constant by location with respect to the alternating direction,each second column has a second impurity concentration,the second impurity concentration is constant by location with respect to the alternating direction,each first column has a first width in the alternating direction,each second column has a second width in the alternative direction, andthe first width and the second width vary by location with respect to the current flowing direction.

12. The device according to claim 10, wherein at least one of the impurity doses of the first columns and the second columns includes a first dose and a second dose,the device has a maximum breakdown voltage when the one of the impurity doses is a predetermined optimum impurity dose,the first dose is higher than the optimum impurity dose by a predetermined value, andthe surface second density is lower than the optimum impurity dose by the predetermined value.

13. The device according to claim 10, wherein at least one of the impurity doses of the first columns and the second columns includes a first dose, at least one middle dose and a second dose,the device has a maximum breakdown voltage when the one of the impurity doses is a predetermined optimum impurity dose,the first dose is higher than the optimum impurity dose by a predetermined value,the surface second density is lower than the optimum impurity dose by the predetermined value, andthe middle dose is disposed in a region between the first dose and the second dose.

14. The device according to claim 10, wherein the device is a vertical type MOSFET or a lateral type MOSFET.

15. A method for manufacturing a semiconductor device having a super junction structure, the method comprising: preparing a semiconductor substrate having a first conductive type;forming a plurality of trenches in the substrate, wherein each trench has a constant width along with a first direction, and wherein a distance between neighboring two trenches along with the first direction includes at least a first distance and a second distance;forming an epitaxial film having a second conductive type on the substrate so that the trenches are filled with the epitaxial film; andflattening one side of the substrate, on which the epitaxial film is formed.

16. A semiconductor device having a super junction structure comprising: a plurality of first columns having a first conductive type and extending in a current flowing direction; anda plurality of second columns having a second conductive type and extending in the current flowing direction, whereinthe first columns and the second columns are alternately arranged in an alternating direction perpendicular to the current flowing direction so that the super junction structure is provided,each first column provides a drift layer in case of an on-state for flowing a current therethrough,the first columns and the second columns have a boundary between the first column and the second column, from which a depletion layer expands in case of an off-state,each of the first columns and the second columns have a stripe planar pattern on a plane perpendicular to the current flowing direction, andat least one of the first columns and the second columns have a bridge portion, which connects one first or second column and a neighboring first or second column.

17. The device according to claim 16, wherein the other one of the first columns and the second columns have a width along with the alternating direction,the bridge portion has a width along with an extending direction of the stripe planar pattern, which is perpendicular to the alternating direction, andthe width of the bridge portion is smaller than the width of the other one of the first columns and the second columns.

18. The device according to claim 16, wherein the bridge portion includes a plurality of bridge elements,the bridge elements have a distance between one bridge element and a neighboring bridge element along with an extending direction of the stripe planar pattern, which is perpendicular to the alternating direction, andthe distance of the bridge elements varies by location.

19. The device according to claim 16, wherein the bridge portion includes a plurality of bridge elements,each bridge element has a width along with an extending direction of the stripe planar pattern, which is perpendicular to the alternating direction, andthe width of the bridge elements varies by location.

20. The device according to claim 16, wherein the device is a vertical type MOSFET or a lateral type MOSFET.

21. A method for manufacturing a semiconductor device having a super junction structure, the method comprising: preparing a semiconductor substrate having a first conductive type;forming a plurality of trenches in the substrate, wherein each trench has a constant width along with a first direction, wherein the trenches have a constant distance between neighboring two trenches along with the first direction, and wherein each trench extends intermittently in a second direction, which is perpendicular to the first direction; andforming an epitaxial film having a second conductive type on the substrate so that the trenches are filled with the epitaxial film.

22. The method according to claim 21, wherein the trenches have a break portion, at which extending of the trenches stops,the break portion has a width along with the second direction, andthe width of the break portion is smaller than the constant width of the trenches.

23. The method according to claim 21, wherein the trenches have a plurality of break portions, at which extending of the trenches stops,the break portions have a distance between one break portion and a neighboring break portion along with the second direction, andthe distance of the break portions varies by location.

24. The method according to claim 21, wherein the trenches have a plurality of break portions, at which extending of the trenches stops,each break portion has a width along with the second direction, andthe width of the break portions varies by location.