Semiconductor device with field electrode and field dielectric

• US 9,530,847 B2
• Filed: 07/14/2015
• Issued: 12/27/2016
• Est. Priority Date: 07/15/2014
• Status: Active Grant

• Current Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Original Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Inventors: Hirler, Franz, Poelzl, Martin
• Primary Examiner(s): Wilson, Allan R
• Application Number:
  US14/799,095
• Publication Number:
  US 20160020287A1
• Time in Patent Office: 532 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/28008 Making conductor-insulator-semiconductor electrodes
• CPC Class Codes: H01L 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/423 not carrying the current to be rectified, amplified or switched
• CPC Class Codes: H01L 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• CPC Class Codes: H01L 29/513 the variation being perpendicular to the channel plane
• CPC Class Codes: H01L 29/739 controlled by field-effect, e.g. bipolar static induction transistors [BSIT] unijunction transistors H01L29/705
• CPC Class Codes: H01L 29/7397 and a gate structure lying on a slanted or vertical surface or formed in a groove, e.g. trench gate IGBT
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/7827 Vertical transistors H01L29/7802, H01L29/78642 take precedence

Abstract

A semiconductor device includes a field electrode structure that includes a field electrode and a field dielectric surrounding the field electrode. The field dielectric includes a first dielectric layer and a second dielectric layer having a smaller band gap and/or a lower conduction band edge than the first dielectric layer. A semiconductor body includes a transistor section that surrounds the field electrode structure and directly adjoins the first dielectric layer. The transistor section includes a source zone, a first drift zone section and a body zone separating the source zone and the first drift zone section. The body zone forms a first pn junction with the source zone and a second pn junction with the first drift zone section.

Claims

1. A semiconductor device, comprising:

a field electrode structure comprising a field electrode and a field dielectric, wherein the field dielectric is positioned between the field electrode and a drift zone section, and wherein the field dielectric comprises a first dielectric layer and a second dielectric layer having at least one of a smaller band gap and a lower conduction band edge than the first dielectric layer; and

a semiconductor body comprising a transistor section surrounding the field electrode structure, directly adjoining the first dielectric layer, and comprising a source zone, the drift zone section and a body zone separating the source zone and the drift zone section, the body zone forming a first pn junction with the source zone and a second pn junction with the drift zone section;

wherein the field dielectric further comprises a third dielectric layer, and wherein the second dielectric layer is sandwiched between the first dielectric layer and the third dielectric layer;

a gate structure comprising a gate electrode and a gate dielectric separating the gate electrode and the body zone, wherein the gate structure surrounds the field electrode structure;

wherein the transistor section is sandwiched between the field electrode structure and the gate structure in a horizontal plane parallel to a first surface of the semiconductor body.

2. The semiconductor device of claim 1, wherein

the first dielectric layer is an oxide layer.

3. The semiconductor device of claim 1, wherein

the second dielectric layer is a silicon nitride layer.

4. The semiconductor device of claim 1, wherein

the gate electrodes of a plurality of transistor cells form a grid embedding the transistor sections of the transistor cells.

5. The semiconductor device of claim 1, wherein

the gate electrode is formed between the field electrode and the transistor section in a horizontal plane parallel to a first surface of the semiconductor body.

6. The semiconductor device of claim 5, wherein

the transistor sections of a plurality of transistor cells form a grid embedding the gate structures and field electrode structures of the transistor cells.

7. The semiconductor device of claim 1, wherein

the field electrode extends in a vertical direction perpendicular to a horizontal plane parallel to a first surface of the semiconductor body .

8. The semiconductor device of claim 1, wherein

the field electrode comprises a first horizontal extension and a second horizontal extension orthogonal to the first horizontal extension.

9. The semiconductor device of claim 1, wherein

a horizontal cross-sectional area of the field electrode is a circle or a square with rounded corners or a regular hexagon with rounded corners.

10. The semiconductor device of claim 1, wherein

the first dielectric layer separates the second dielectric layer from the transistor section.

11. The semiconductor device of claim 1, wherein

the third dielectric layer is an oxygen-containing layer.

12. The semiconductor device of claim 1, wherein

the third dielectric layer is a deposited silicon oxide layer with a thickness in a range from 10 nm to 30 nm.

13. The semiconductor device of claim 1, wherein

a thickness of the second dielectric layer is in a range from 10 nm to 30 nm.

14. The semiconductor device of claim 1, wherein

the first dielectric layer is a thermally grown silicon oxide layer.

15. A semiconductor device, comprising:

a field electrode structure comprising a field electrode and a field dielectric, wherein the field dielectric is positioned between the field electrode and a drift zone section, and wherein the field dielectric comprises a first dielectric layer and a second dielectric layer having at least one of a smaller band gap and a lower conduction band edge than the first dielectric layer; and

a semiconductor body comprising a transistor section surrounding the field electrode structure, directly adjoining the first dielectric layer, and comprising a source zone, the drift zone section and a body zone separating the source zone and the drift zone section, the body zone forming a first pn junction with the source zone and a second pn junction with the drift zone section;

wherein the field dielectric further comprises a third dielectric layer, and wherein the second dielectric layer is sandwiched between the first dielectric layer and the third dielectric layer;

wherein the second dielectric layer is formed at most in the lower third of the vertical extension of the field electrode structure.

16. A semiconductor device, comprising:

a field electrode structure comprising a field electrode and a field dielectric surrounding the field electrode, wherein the field dielectric comprises a first dielectric layer and a second dielectric layer having at least one of a smaller band gap and a lower conduction band edge than the first dielectric layer;

a semiconductor body comprising a transistor section surrounding the field electrode structure, directly adjoining the first dielectric layer, and comprising a source zone, a drift zone section and a body zone separating the source zone and the drift zone section, the body zone forming a first pn junction with the source zone and a second pn junction with the drift zone section; and

a gate electrode formed between the field electrode and the transistor section, wherein a top edge of the gate electrode and a top edge of the field electrode are in a horizontal plane parallel to a first surface of the semiconductor body.