Semiconductor Devices and Methods for Making the Same

• US 20110127601A1
• Filed: 12/02/2009
• Published: 06/02/2011
• Est. Priority Date: 12/02/2009
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Kim, Suku, Dolny, Gary, Murphy, James J.
• Granted Patent: US 8,129,778 B2
• Time in Patent Office: Days
• US Class Current: 257/330
• CPC Class Codes: H01L 29/0634 Multiple reduced surface field (multi-RESURF) structures, e.g. double RESURF, charge compensation, cool, superjunction (SJ), 3D-RESURF, composite buffer (CB) structures
• CPC Class Codes: H01L 29/1066 Gate region of field-effect devices with PN junction gate
• CPC Class Codes: H01L 29/7722 using static field induced regions, e.g. SIT, PBT
• CPC Class Codes: H01L 29/8083 Vertical transistors SIT H01L29/7722

Abstract

Semiconductor devices and methods for making such devices that are especially suited for high-frequency applications are described. The semiconductor devices combine a SIT (or a junction field-effect transistor [JFET]) architecture with a PN super-junction structure. The SIT architecture can be made using a trench formation containing a gate that is sandwiched between thick dielectric layers. While the gate is vertically sandwiched between the two isolating regions in the trench, it is also connected to a region of one conductivity type of the super-junction structure, thereby allowing control of the current path of the semiconductor device. Such semiconductor devices have a lower specific resistance and capacitance relative to conventional planar gate and recessed gate SIT semiconductor devices. Other embodiments are described.

Claims

1. A semiconductor device, comprising:

a semiconductor substrate heavily doped with a dopant of a first conductivity type;

an epitaxial layer on the substrate, the epitaxial layer being lightly doped with a dopant of a first conductivity type with a concentration gradient;

a trench formed in the epitaxial layer, the trench containing a sidewall that is lightly doped with a dopant of a second conductivity type, a first insulating region in a lower portion of the trench and a second insulating region in an upper portion of the trench, the first and second insulating regions sandwiching a conductive or semiconductive layer;

a source layer contacting the upper surface of the epitaxial layer and the upper surface of the second insulating region; and

a drain contacting a bottom portion of the substrate.

2. The device of claim 1, wherein the first conductivity type dopant is an n-type dopant and the second conductivity type dopant is a p-type dopant.

3. The device of claim 1, wherein the first conductivity type dopant is a p-type dopant and the second conductivity type dopant is a n-type dopant.

4. The device of claim 1, wherein the concentration gradient of the epitaxial layer has a higher concentration at an upper surface and a lower concentration near the substrate;

5. The device of claim 4, wherein the concentration gradient decreases from the upper surface to the substrate in a substantially uniform or substantially step-wise manner.

6. The device of claim 1, wherein the first and second insulating regions comprise a deposited oxide or nitride material.

7. The device of claim 1, wherein the trench comprises a sidewall with an angle range from about 90 to about 70 degrees.

8. The device of claim 1, wherein the trench sidewall dopant has been implanted at an angle ranging from more than 0 to about 40 degrees.

9. The device of claim 1, wherein the trench extends into the substrate.

17. The device of claim 1, wherein the trench sidewall dopant has been implanted at an angle ranging from more than 0 to about 40 degrees.

10. A semiconductor device, comprising:

a semiconductor substrate heavily doped with a dopant of a first conductivity type;

an epitaxial layer on the substrate, the epitaxial layer being lightly doped with a dopant of a first conductivity type with a concentration gradient;

a contact region on the upper surface of the epitaxial layer, the contact region being heavily doped with a dopant of a first conductivity type;

a trench formed in the epitaxial layer, the trench containing a sidewall that is lightly doped with a dopant of a second conductivity type to form a super-junction with the epitaxial layer, and the trench containing a gate electrically connected to the sidewall and insulated by upper and lower insulating regions in the trench;

a source layer contacting the upper surface of the epitaxial layer and the upper surface of the upper insulating region; and

a drain contacting a bottom portion of the substrate.

11. The device of claim 10, wherein the first conductivity type dopant is a p-type dopant and the second conductivity type dopant is a n-type dopant.

12. The device of claim 10, wherein the first conductivity type dopant is a n-type dopant and the second conductivity type dopant is a p-type dopant.

13. The device of claim 10, wherein the concentration gradient of the epitaxial layer has a higher concentration at an upper surface and a lower concentration near the substrate;

14. The device of claim 13, wherein the concentration gradient decreases from the upper surface to the substrate in a substantially uniform or substantially step-wise manner.

15. The device of claim 10, wherein the first and second insulating regions comprise a deposited oxide material.

16. The device of claim 10, wherein the trench comprises a sidewall with an angle range from about 90 to about 70 degrees.

18. An electronic apparatus containing a semiconductor device, comprising:

a semiconductor substrate heavily doped with a dopant of a first conductivity type;

an epitaxial layer on the substrate, the epitaxial layer being lightly doped with a dopant of a first conductivity type with a concentration gradient;

a trench formed in the epitaxial layer, the trench containing a sidewall that is lightly doped with a dopant of a second conductivity type, a first insulating region in a lower portion of the trench and a second insulating region in an upper portion of the trench, the first and second insulating regions sandwiching a conductive layer;

a source layer contacting the upper surface of the epitaxial layer and the upper surface of the second insulating region; and

a drain contacting a bottom portion of the substrate.

19. The apparatus of claim 18, wherein the concentration gradient of the epitaxial layer has a higher concentration at an upper surface and a lower concentration near the substrate;

20. The apparatus of claim 19, wherein the concentration gradient decreases from the upper surface to the substrate in a substantially uniform or substantially step-wise manner.

21. An electronic apparatus containing a semiconductor device, comprising:

a semiconductor substrate heavily doped with a dopant of a first conductivity type;

an epitaxial layer on the substrate, the epitaxial layer being lightly doped with a dopant of a first conductivity type with a concentration gradient;

a contact region on the upper surface of the epitaxial layer, the contact region being heavily doped with a dopant of a first conductivity type;

a trench formed in the epitaxial layer, the trench containing a sidewall that is lightly doped with a dopant of a second conductivity type to form a super-junction with the epitaxial layer, and the trench containing a gate electrically connected to the sidewall and insulated by upper and lower insulating regions in the trench;

a source layer contacting the upper* surface of the epitaxial layer and the upper surface of the upper insulating region; and

a drain contacting a bottom portion of the substrate.

22. The apparatus of claim 21, wherein the concentration gradient of the epitaxial layer has a higher concentration at an upper surface and a lower concentration near the substrate;

23. The apparatus of claim 22, wherein the concentration gradient decreases from the upper surface to the substrate in a substantially uniform or substantially step-wise manner.