Guard ring having electrically isolated lightening bars

• US 6,927,345 B2
• Filed: 05/16/2002
• Issued: 08/09/2005
• Est. Priority Date: 05/16/2002
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Wu, Tien-Chi, Huang, George, Chen, Kou-Chou, Hsu, Huai-Jen
• Primary Examiner(s): Cuneo, Kamand
• Assistant Examiner(s): Norris, Jeremy
• Application Number:
  US10/150,321
• Publication Number:
  US 20030213612A1
• Time in Patent Office: 1,181 Days
• Field of Search: 174/250, 174/255, 174/260, 174/261, 361816-818, 430/5
• US Class Current: 174/255
• CPC Class Codes: G03F 1/40 Electrostatic discharge [ESD] related features, e.g. antistatic coatings or a conductive metal layer around the periphery of the mask substrate
• CPC Class Codes: G03F 7/70941 Stray fields and charges, e.g. stray light, scattered light, flare, transmission loss
• CPC Class Codes: H01L 21/68714 the wafers being placed on a susceptor, stage or support
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A guard ring for protecting against electrostatic discharge (ESD) that has electrically isolated lightning bars has a substrate, a first ring, and a second ring. The first ring is on the substrate and has a number of electrically connected lightning bars. The second ring is also on the substrate and concentric to the first ring, but has a number of lightning bars that are electrically isolated from one another. The first ring may be the outer ring and the second ring may be the inner ring, or vice-versa. The guard ring has an ESD breakdown voltage that does not change, even after the first ring or the second ring has protected against ESD. The guard ring may protect a semiconductor component like a semiconductor photomask or a semiconductor device.

Claims

1. A guard ring for electrostatic discharge (ESD) protection comprising:

a substrate;

a first ring on the substrate having a plurality of electrically connected lightning bars, each bar being substantially rectangular in shape, the electrically connected lightning bars defining a plurality of gaps, each gap between two immediately adjacent electrically connected lightning bars; and

,

a second ring on the substrate, concentric to the first ring, and having a plurality of lightning bars electrically isolated from one another, all of the lightning bars of the second ring each at least substantially situated within one of the gaps defined by the electrically connected lightning bars of the first ring.

2. The guard ring of claim 1, wherein the guard ring has an ESD breakdown voltage that, even after one of the first ring and the second ring has protected against ESD, remains the same.

3. The guard ring of claim 1, wherein the first ring is an outer ring, and the second ring is an inner ring.

4. The guard ring of claim 1, wherein the first ring is an inner ring, and the second ring is an outer ring.

5. The guard ring of claim 1, wherein the plurality of lightning bars of the second ring are completely electrically isolated from one another.

6. The guard ring of claim 1, wherein the substrate is at least substantially transparent, and each of the first ring and the second ring is at least substantially opaque.

7. The guard ring of claim 1, wherein the substrate is one of glass and quartz.

8. The guard ring of claim 1, wherein each of the first ring and the second ring is chrome.

9. The guard ring of claim 1, wherein the substrate is a substrate of a photomask, such that the guard ring provides for ESD protection of the photomask.

10. A photomask comprising:

a substantially transparent substrate;

a circuit area formed on the substantially transparent substrate that is substantially opaque;

an inner ring on the substrate that is substantially opaque and that surrounds the circuit area, the inner ring providing electrostatic discharge (ESD) protection of the circuit area;

an outer ring on the substrate concentric to the inner ring that is substantially opaque, the outer ring also providing ESD protection of the circuit area;

a plurality of electrically connected lightning bars that are part of one of the inner ring and the outer ring, the electrically connected lightning bars defining a plurality of gaps, each gap between two immediately adjacent electrically connected lightning bars; and

,

a plurality of lightning bars that are electrically isolated from one another and that are part of another of the inner ring and the outer ring, all of the lightning bars that are electrically isolated from one another each at least substantially situated within one of the gaps defined by the electrically connected lightning bars.

11. The photomask of claim 10, wherein the guard ring has an ESD breakdown voltage that, even after one of the inner ring and the outer ring has protected against ESD, remains the same.

12. The photomask of claim 10, wherein the plurality of electrically connected lightning bars are part of the inner ring, and the plurality of lightning bars that are electrically isolated from one another are part of the outer ring.

13. The photomask of claim 10, wherein the plurality of electrically connected lightning bars are part of the outer ring, and the plurality of lightning bars that are electrically isolated from one another are part of the inner ring.

14. The photomask of claim 10, wherein the plurality of lightning bars that are electrically isolated from one another are completely electrically isolated from one another.

15. The photomask of claim 10, wherein the substrate is one of glass and quartz.

16. The photomask of claim 10, wherein the circuit area, the inner ring, and the outer ring are chrome.