Trench transistor and method for fabricating a trench transistor

• US 7,790,550 B2
• Filed: 08/05/2008
• Issued: 09/07/2010
• Est. Priority Date: 08/31/2005
• Status: Expired due to Fees

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Hirler, Franz, Zundel, Markus, Zelsacher, Rudolf, Poelzl, Martin
• Primary Examiner(s): Menz; Douglas M
• Application Number:
  US12/186,242
• Publication Number:
  US 20090206401A1
• Time in Patent Office: 763 Days
• Field of Search: 257/328, 257/330, 438/270
• US Class Current: 438/270
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/404 Multiple field plate structures
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/41 characterised by their shape, relative sizes or dispositions
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/66734 with a step of recessing the gate electrode, e.g. to form a trench gate electrode
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A trench transistor having a semiconductor body, in which a trench structure and an electrode structure embedded in the trench structure is disclosed. The electrode structure is electrically insulated from the semiconductor body by an insulation structure. The electrode structure has a gate electrode structure and a field electrode structure arranged below the gate electrode structure and electrically insulated from the latter. There is provided between the gate electrode structure and the field electrode structure a shielding structure for reducing the capacitive coupling between the gate electrode structure and the field electrode structure.

Claims

1. A method for producing a trench transistor from a preprocessed semiconductor body, comprising:

providing a trench structure;

providing a field electrode structure embedded in the trench structure;

wherein the field electrode structure is electrically insulated from the semiconductor body by a field electrode insulation structure by;

depositing insulating material on the field electrode structure;

forming a gate electrode insulation structure;

forming a gate electrode structure; and

providing a shielding electrode at a fixed potential and electrically insulated from the gate electrode structure, the field electrode structure and the semiconductor body.

2. The method of claim 1, wherein the deposition of insulating material comprises:

forming a protective oxide layer on the semiconductor body;

forming a silicon nitride or polysilicon layer on the protective oxide layer;

filling the remaining free spaces in the trench structure with insulating material; and

etching back the resulting layer composite comprising protective oxide layer, silicon nitride or polysilicon layer and the insulating material into the trench structure as far as a specific depth, so that the insulating material has a desired thickness.

3. The trench method of claim 1, wherein the shielding electrode is at source potential.

4. The method of claim 1 further comprising configuring the internal resistances of the shielding electrode and the current/voltage supply of the shielding electrode such that their sum is less than a corresponding internal resistance sums for the gate electrode structure and the field electrode structure.

5. The method of claim 1 further comprising forming a shielding structure with a shielding insulation layer, the thickness of which is greater than the thickness of the insulation structure region which insulates the field electrode structure from the semiconductor body.

6. A trench transistor, having a semiconductor body, comprising:

a trench structure;

an electrode structure embedded in the trench structure;

the electrode structure being electrically insulated from the semiconductor body by an insulation structure and having a gate electrode structure and a field electrode structure arranged below the gate electrode structure and electrically insulated from the latter; and

there being provided between the gate electrode structure and the field electrode structure a shielding structure for reducing the capacitive coupling between the gate electrode structure and the field electrode structure, wherein the shielding structure has a shielding insulation layer, the k value of which is less than the k value of the insulation structure; and

a shielding electrode at a fixed potential and electrically insulated from the gate electrode structure, the field electrode structure and the semiconductor body.

7. The trench transistor of claim 6, wherein the shielding electrode is at source potential.

8. The trench transistor of claim 6, wherein the sum of the internal resistances of the shielding electrode and the current/voltage supply of the shielding electrode is less than corresponding internal resistance sums for the gate electrode structure and the field electrode structure.

9. The trench transistor of claim 6, wherein the thickness of the shielding insulation layer is greater than double the thickness of the insulation structure region which insulates the gate electrode structure from the semiconductor body, or greater than double the thickness of the insulation structure region which insulates the field electrode structure from the semiconductor body.

10. The trench transistor as claimed in claim 9, wherein the shielding insulation layer is a layer sequence comprising a first oxide layer, a nitride layer and a second oxide layer.

11. The trench transistor as claimed in claim 6, wherein the shielding structure is a cavity.

12. The trench transistor as claimed in claim 6, wherein the horizontal distances between the shielding structure and the semiconductor body are less than the horizontal distances between the gate electrode structure and the semiconductor body.

13. A method for producing a trench transistor comprising:

providing a trench structure;

forming a field electrode structure embedded in the trench structure;

depositing insulating material on the field electrode structure;

forming a gate electrode insulation structure;

forming a gate electrode structure;

wherein the field electrode structure is electrically insulated from a semiconductor body by a field electrode insulation; and

forming a shielding electrode at a fixed potential and electrically insulated from the gate electrode structure, the field electrode structure and the semiconductor body.