MOS control diode and method for manufacturing the same

• US 6,674,123 B2
• Filed: 01/28/2002
• Issued: 01/06/2004
• Est. Priority Date: 09/10/1997
• Status: Expired due to Term

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Ho-hyun
• Primary Examiner(s): ECKERT II, GEORGE C
• Application Number:
  US10/059,937
• Publication Number:
  US 20020088989A1
• Time in Patent Office: 708 Days
• Field of Search: 257/328, 257/329, 257/330, 257/332, 257/333, 257/412, 257/413, 257/109, 257/288
• US Class Current: 257/328
• CPC Class Codes: H01L 29/7391 Gated diode structures
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/861 Diodes

Abstract

A MOS control diode is provided for power switching. In the MOS control diode, a switching speed is high and a reverse leakage current characteristic is improved without additionally needing processes for improving reverse recovery time by converting a power MOSFET which is a majority carrier device to diode having two terminals. Such a MOS control diode can be achieved by forming a discontinuous area in a gate oxide film formed on the surface of a semiconductor substrate so that the conductive gate electrode is connected to the semiconductor substrate. Also, it is possible to form a trench in the semiconductor substrate, to form the gate oxide films on the sidewall of a trench, and to connect the gate electrode to the semiconductor substrate through the bottom of the trench.

Claims

1. A two-terminal MOS control trench type diode having first and second diode terminals, the diode comprising:

a semiconductor substrate having a first conductive type as a drain area;

a base well area having a second conductive type electrically coupled to the drain area, the drain area coupled to the first diode terminal;

a source well area having the first conductive type formed on the base well area, the source well area coupled to the second diode terminal;

a trench extending through the source well area, the base well area and a part of the semiconductor substrate; and

a floating conduction facilitating structure formed in the trench, insulated from the base well area, and directly coupled to the substrate, the conduction facilitating structure physically separated from both the first and second terminals.

2. The two-terminal trench type MOS control diode of claim 1, wherein the conduction facilitating structure is insulated from the base well area and the source well area by a gate oxide film formed on a sidewall of the trench.

3. The two-terminal trench type MOS control diode of claim 1, further comprising, an insulating film formed on the semiconductor substrate so as to cover the entire top side of the conduction facilitating structure and to expose some of the source well;

and

a source electrode formed on the exposed source well and the insulating film so as to cover the semiconductor substrate.

4. The two-terminal trench type MOS control diode of claim 1, wherein the conduction facilitating structure is formed of a composite layer consisting of a polysilicon layer formed on the sidewall and the bottom of the trench to a predetermined thickness and a metal layer which fills the trench.

5. The two-terminal trench type MOS control diode of claim 3, wherein the insulating film is formed of SiO2.

6. The two-terminal trench type MOS control diode of claim 1, wherein a plurality of conductive facilitating structures are respectively formed in a plurality of trenches.

7. The two-terminal trench type MOS control diode of claim 1, further comprising a drain electrode formed on a backside of the semiconductor substrate.

8. The two-terminal trench type MOS control diode of claim 1, wherein the first conductive type is N type and the second conductive type is P type.

9. A trench type control diode formed in a semiconductor substrate having a trench formed therein, the control diode comprising:

a first terminal coupled to the substrate;

a floating electrode formed in the trench and in contact with the substrate, the floating electrode free from electrode contacts;

a source well formed in the substrate; and

a second terminal coupled to the source well.

10. The control diode of claim 9 wherein the floating electrode comprises two components.

11. The control diode of claim 10 wherein one of the two components comprises polysilicon.

12. The control diode of claim 10 wherein one of the two components comprises a metal.

13. The control diode of claim 9 wherein the trench has two substantially vertical sides, and a substantially horizontal bottom.

14. The control diode of claim 13, further comprising an insulating material separating the sides of the trench from the substrate.

15. The control diode of claim 9, wherein the floating electrode substantially fills the trench.

16. The control diode of claim 9, further comprising a plurality of trenches formed in the substrate and a plurality of electrodes respectively formed in the plurality of trenches.

17. The control diode of claim 9 wherein the floating electrode completely fills the trench.

18. The control diode of claim 9 wherein the floating electrode is devoid of electrical terminations outside the diode device.

19. A two-terminal semiconductor diode structure, comprising:

a semiconductor substrate;

a doped drain area formed in the substrate;

a first diode terminal coupled to the drain area;

a trench formed in the substrate;

a conductive material substantially filling the trench and in contact with the substrate, the conductive material free from electrical terminations;

a doped source area formed in the substrate, the source area separate from the drain area;

an insulating layer covering the source well area and a top surface of the conductive material, the insulating layer having one or more contact holes formed therethrough; and

a second diode terminal disposed on the insulating layer and through the one or more contact holes to contact the source area.

20. The semiconductor diode structure of claim 19, wherein the conductive material comprises a polysilicon portion and a metal portion.

21. The semiconductor diode structure of claim 19, wherein sidewalls of the trench include an insulating material.