Apparatus and methods for semiconductor IC failure detection

• US 7,067,335 B2
• Filed: 10/02/2002
• Issued: 06/27/2006
• Est. Priority Date: 08/25/2000
• Status: Expired due to Term

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Verma, Gaurav, Weiner, Kurt H.
• Primary Examiner(s): Pham, Hoai
• Assistant Examiner(s): Farahani, Dana
• Application Number:
  US10/264,625
• Publication Number:
  US 20030071261A1
• Time in Patent Office: 1,364 Days
• Field of Search: 438/10, 438/11, 438/16, 438/17, 438/18, 438/12, 438/13, 324/765, 324/751, 324/537, 257/48
• US Class Current: 438/16
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01R 31/2644 Adaptations of individual semiconductor devices to facilitate the testing thereof
• CPC Class Codes: G01R 31/307 of integrated circuits
• CPC Class Codes: H01L 22/34 Circuits for electrically characterising or monitoring manufacturing processes, e. g. whole test die, wafers filled with test structures, on-board-devices incorporated on each die, process control monitors or pad structures thereof, devices in scribe line switching, multiplexing, gating devices G01R19/25; process control with lithography, e.g. dose control, G03F7/20; structures for alignment control by optical means G03F7/70633

Abstract

An improved voltage contrast test structure is disclosed. In general terms, the test structure can be fabricated in a single photolithography step or with a single reticle or mask. The test structure includes substructures which are designed to have a particular voltage potential pattern during a voltage contrast inspection. For example, when an electron beam is scanned across the test structure, an expected pattern of intensities are produced and imaged as a result of the expected voltage potentials of the test structure. However, when there is an unexpected pattern of voltage potentials present during the voltage contrast inspection, this indicates that a defect is present within the test structure. To produce different voltage potentials, a first set of substructures are coupled to a relatively large conductive structure, such as a large conductive pad, so that the first set of substructures charges more slowly than a second set of substructures that are not coupled to the relatively large conductive structure. Mechanisms for fabricating such a test structure are also disclosed. Additionally, searching mechanisms for quickly locating defects within such a test structure, as well as other types of voltage contrast structures, during a voltage contrast inspection are also provided.

Claims

1. A method of inspecting a test structure, comprising:

initially scanning two or more initial portions of the test structure with a charged particle beam to image the initial portions and determine whether there is a defect present within a plurality of potential defect portions that have different locations than the initial portions based on whether there is an unexpected pattern of one or more intensity levels within the imaged initial portions, wherein the potential defect portions are not scanned by the particle beam during the initial scanning; and

when the initial scanning results in a determination that a defect is present in one or more of the potential defect portions, sequentially stepping to one or more of the potential defect portions of the test structure and scanning the one or more potential defect portions of the test structure with a charged particle beam to thereby image the one or more potential defect portions and locate the defect, wherein the defect is located when an unexpected pattern of one or more intensity levels are present within a one of the imaged potential defect portions.

2. A method as recited in claim 1, wherein the stepping is in the form of a binary search pattern for locating the defect.

3. A method as recited in claim 1, wherein initially scanning two or more initial portions of the test structure with a charged particle beam to determine whether there is a defect present is accomplished by:

scanning a first end of the test structure to obtain a first intensity level for the first end;

scanning a second end of the test structure to obtain a second intensity level for the second end; and

when the first end intensity level differs from the second end intensity level, determining that the test structure has an open defect.

4. A method as recited in claim 1, wherein the stepping to one or more potential defect portions of the test structure and scanning the one or more potential defect portions of the test structure with a charged particle beam to thereby locate the defect comprises:

a) stepping to a first current portion of the test structure and scanning the first current portion of the test structure for a defect;

b) when the defect is not found and a transition in intensity occurs between the previous scan and current scan, stepping to a next portion of the test structure that is between the previous scan and the current scan; and

c) when the defect is not found and a transition in intensity does not occur between the previous scan and current scan, stepping to a next portion of the test structure that is not between the previous scan and the current scan.

5. A method as recited in claim 4, wherein the next portion is halfway between the previous and current scan when the defect is not found and a transition in intensity occurs between the previous scan and current scan, and the next position is halfway between the current scan and an end of the test structure that is not between the previous and current scan when defect is not found and a transition in intensity does not occur between the previous scan and current scan.

6. A method as recited in claim 5, the method further comprising determining whether the current scan includes a transition in intensity point for the current scan that is not the defect, wherein the stepping to the next portion operation is performed in a new direction when the current scan includes the transition in intensity point that is not the defect.

7. A method as recited in claim 6, wherein the new direction of the next scan is perpendicular to a direction of the previous scan.

8. A method as recited in claim 4, repeating operation (b) and (c) until the defect is found.

9. A method as recited in claim 4, wherein the defect can be an open defect and the defect is found when a transition in intensity occurs within the test structure itself.

10. A method as recited in claim 9, wherein the open defect can be a partially open defect.

11. A method as recited in claim 4, wherein the defect can be a short defect and the defect is found when a physical short is found within the test structure.