Multicellular FET having a Schottky diode merged therewith

• US 5,111,253 A
• Filed: 08/28/1990
• Issued: 05/05/1992
• Est. Priority Date: 05/09/1989
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: General Electric Company
• Inventors: Chang, Hsueh-Rong, Korman, Charles S., Baliga, Bantval J.
• Primary Examiner(s): James, Andrew J.
• Assistant Examiner(s): Nguyen, Viet Q.
• Application Number:
  US07/576,125
• Time in Patent Office: 616 Days
• Field of Search: 357/15, 357/23.4, 357/38
• US Class Current: 257/341
• CPC Class Codes: H01L 27/0727 in combination with diodes, or capacitors or resistors
• CPC Class Codes: H01L 29/0619 with a supplementary region doped oppositely to or in rectifying contact with the semiconductor containing or contacting region, e.g. guard rings with PN or Schottky junction
• CPC Class Codes: H01L 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• CPC Class Codes: H01L 29/7806 the other device being a Schottky barrier diode
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A semiconductor power switching device comprises a multicellular FET structure with a Schottky barrier diode structure interspersed therewith with at least some of the FET cells being free of Schottky barrier portions. The ratio of Schottky barrier contact area to FET cell area in the overall device may be adjusted to tailor the device for operation at specific current densities.

Claims

1. A semiconductor device comprising:

first and second main electrodes;

a body of semiconductor material including;

a multicellular FET including a plurality of FET cells each connected between said first and second main electrodes; and

a Schottky diode connected between said first and second main electrodes;

said Schottky diode including a plurality of Schottky contacts interspersed with said FET cells;

a plurality of said FET cells not having Schottky contacts within the cells of said plurality; and

at least one of said FET cells being spaced from the plurality of Schottky contacts by an intervening FET cell.

2. The semiconductor device recited in claim 1 wherein:

none of said FET cells has a Schottky contact within the particular cell.

3. The semiconductor device recited in claim 1 wherein:

said Schottky diode occupies between 5% and 50% of the combined area occupied area occupied by said Schottky diode and said FET cells.

4. The semiconductor device recited in claim 1 wherein:

said Schottky diode comprises a plurality of cells.

5. A semiconductor device comprising:

first and second main electrodes;

a body of semiconductor material including;

a multicellular FET including a plurality of FET cells each connected between said first and second main electrodes;

a Schottky diode connected between said first and second main electrodes;

said Schottky diode spacing apart first and second ones of said FET cells within said body of semiconductor material; and

at least one of said FET cells being spaced from said Schottky diode by an intervening FET cell.

6. The semiconductor device recited in claim 5 wherein:

said Schottkey diode comprises a plurality of spaced-apart Schottky contacts; and

some of said FET cells space apart adjacent ones of said Schottky contacts.

7. The semiconductor device recited in claim 6 wherein:

said Schottky diode comprises a plurality of Schottky diode cells.

8. The semiconductor device recited in claim 7 wherein:

said Schottky diode cells are interspersed with said FET cells.

9. A semiconductor device comprising:

first and second main electrodes; and

a body of semiconductor material including;

a multicellular FET including a plurality of FET cells each connected between said first and second main electrodes,

a multicellular Schottky diode including a plurality of Schottky diode cells each connected between said first and second main electrodes,

said FET cells being interspersed with said Schottky diode cells, and

at least one of said FET cells being spaced from the plurality of Schottky diode cells by an intervening FET cell.

10. The semiconductor device recited in claim 9 wherein:

said Schottky diode cells occupy between 5% and 50% of the combined area occupied by Schottky diode cells and FET cells.

11. The semiconductor device recited in claim 10 wherein:

said FET cells are stripe cells;

said Schottky diode cells are stripe cells; and

adjacent ones of said Schottky diode cells are spaced apart by a plurality of said FET cells.

12. The semiconductor device recited in claim 9 wherein:

said FET cells are stripe cells;

said Schottky diode cells are stripe cells; and

adjacent ones of said Schottky diode cells are spaced apart by a plurality of said FET cells.

13. A semiconductor device comprising a body of semiconductor material having first and second major opposed surfaces and including:

a first main region of one type conductivity extending to both said first and second major surfaces;

a plurality of base regions of opposite type conductivity each disposed in said first main region and extending to said second major surface; and

a plurality of second main regions each disposed in one of said base regions and extending to said second major surface of said body;

a first main electrode disposed on said first major surface of said body in ohmic contact with said first main region;

a second main electrode disposed on said second major surface of said body in ohmic contact with each of said second main regions;

an insulated gate electrode disposed on said second major surface of said body and extending from (1) over each of said second main regions across a portion of the base region in which said each of said second main regions is disposed to (2) over said first main region to control the conductivity of a channel extending through said base region between said each of said second main regions and said first main region;

said base regions, second main regions and said gate electrode together with said first main region comprising a multicellular field effect transistor structure in which each of said base regions is part of a different FET cell;

said second main electrode also being disposed in Schottky contact with said first main region at said second major surface of said body to form a Schottky diode connected between said first and second main electrodes;

said Schottky diode including a plurality of Schottky contacts interspersed with said field effect transistor cells;

a plurality of said FET cells not having Schottky contacts within the cells of said plurality; and

at least one of said FET cells being spaced from the plurality of Schottky contacts by an intervening FET cell.

14. The semiconductor device recited in claim 13 wherein said first main region includes a first, relatively lightly doped drift portion and a second, more heavily doped contact portion disposed adjacent said first main electrode.

15. The semiconductor device recited in claim 13 wherein:

none of said FET cells has a Schottky contact within the particular cell.

16. The semiconductor device recited in claim 13 wherein:

said Schottky diode comprises a plurality of spaced apart cells.

17. The semiconductor device recited in claim 16 wherein:

said Schottky diode cells are stripe cells having a length and a width wherein said length is substantially greater than said width.

18. The semiconductor device recited in claim 17 wherein:

said FET cells are stripe cells having a width and a length with their length being substantially greater than their width; and

the lengths of said FET cells are disposed substantially parallel to the lengths of said Schottky diode cells.

19. The semiconductor device recited in claim 16 wherein:

said FET cells are stripe cells having a length and a width wherein said length is substantially greater than said width.

20. The semiconductor device recited in claim 19 wherein said Schottky diode cells are stripe cells having a width and a length with their length being substantially greater than their width;

and

the lengths of said Schottky diode cells are disposed substantially parallel to the lengths of said FET cells.

21. The semiconductor device recited in claim 13 wherein:

said body includes a trench structure adjacent said second major surface, whereby said second major surface has a planar portion and a trench wall portion;

said base regions and said second main regions both extend to said trench wall portion of said second major surface;

said gate electrode is disposed within said trench structure; and

said channels are disposed at least in part adjacent said trench wall portions of said second major surface.

22. A semiconductor device comprising a body of semiconductor material having first and second major opposed surfaces and including:

a first main region of one type conductivity extending to both said first and second major surfaces;

a plurality of base regions of opposite type coductivity each disposed in said first main region and extending to said second major surface; and

a plurality of second main regions each disposed in one of said base regions and extending to said second major surface of said body;

a first main electrode disposed on said first major surface of said body in ohmic contact with said first main region,

23. a second main electrode disposed on said second major surface of said body in ohmic contact with each of said second main regions;

an insulated gate electrode disposed on said second major surface of said body and extending from (1) over each of said second main regions across a portion of the base region in which said each of said second main regions is disposed to (2) over said first main region to control the conductivity of a channel extending through said base region between said each of said second main regions and first main region;

said base regions, second main regions and said gate electrode together with said first main region comprising a multicellular field effect transistor structure in which each of said base regions is part of a different FET cell;

said second main electrode also being disposed in Schottky contact with said first main region at said second major surface of said body, in the central portion of the active area of said second major surface, to form a Schottky diode connected between said first and second main electrodes and substantially centered within the area occupied by said multicellular field effect transistor; and

a plurality of said FET cells not having a Schottky contact within the cells of said plurality.

25. The semiconductor device recited in claim 23 wherein said first main region includes a first, relatively lightly doped drift portion and a second, more heavily doped contact portion disposed adjacent said first main electrode.

26. The semiconductor device recited in claim 23 wherein:

none of said FET cells has a Schottky contact within the particular cell.

27. The semiconductor device recited in claim 23 wherein:

said Schottky diode comprises a plurality of spaced apart cells.

28. The semiconductor device recited in claim 26 wherein:

said Schottky diode cells are stripe cells having a length and a width wherein said length is substantially greater than said width.

29. The semiconductor device recited in claim 27 wherein said FET cells are stripe cells having a width and a length with their length being substantially greater than their width;

and

the lengths of said FET cells are disposed substantially parallel to the lengths of said Schottky diode cells.

30. The semiconductor device recited in claim 26 wherein:

said FET cells are stripe cells having a length and a width wherein said length is substantially greater than said width.

31. The semiconductor device recited in claim 29 wherein said Schottky diode cells are stripe cells having a width and a length with their length being substantially greater than their width;

and

the lengths of said Schottky diode cells are disposed substantially parallel to the lengths of said FET cells.

32. The semiconductor device recited in claim 23 wherein:

said body includes a trench structure adjacent said second major surface, whereby said second major surface has a planar portion and a trench portion;

said base regions and said second main regions both extend to said second major surface within said trench structure;

said gate electrode is disposed within said trench structure; and

said channels are disposed at least in part adjacent said trench portion of said second major surface.

24. A semiconductor device comprising a body of semiconductor material having first and second major opposed surfaces and including:

a first main region of one type conductivity extending to both said first and second major surfaces;

a plurality of base regions of opposite type conductivity each disposed in said first main region and extending to said second major surface; and

a plurality of second main regions each disposed in one of said base regions and extending to said second major surface of said body;

a first main electrode disposed on said first major surface of said body in ohmic contact with said first main region;

a second main electrode disposed on said second major surface of said body in ohmic contact with each of said base and second main regions;

an insulated gate electrode disposed on said second major surface of said body and extending from (1) over each of said second main regions across a portion of the base region in which said each of said second main regions is disposed to (2) over said first main region to control the conductivity of a channel extending through said base region between said each of said second main regions and first main region;

said base regions, second main regions and said gate electrode together with said first main region comprising a multicellular field effect transistor structure in which each of said base regions is part of a different FET cell;

said second main electrode also being disposed in Schottky contact with said first main region at said second major surface of said body to form a Schottky diode connected between said first and second main electrodes;

said Schottky diode being interspersed with said field effect transistor cells;

a plurality of said FET cells not having a Schottky contact within the cells of said plurality; and

at least one of said base regions having channel region portions at opposed sides thereof and including a heavily doped portion disposed between said opposed channel region portions and extending into ohmic contact with said second main electrode.