Non-destructive root cause analysis on blocked contact or via

• US 6,777,676 B1
• Filed: 11/21/2002
• Issued: 08/17/2004
• Est. Priority Date: 07/05/2002
• Status: Expired due to Term

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Testoni, Anne, Wang, Ying, Tung, Yeishin
• Primary Examiner(s): Lee, John R.
• Assistant Examiner(s): SOUW, BERNARD E
• Application Number:
  US10/303,267
• Time in Patent Office: 635 Days
• Field of Search: 250/306, 250/307, 250/310, 378/44, 378/45, 378/48, 257/48, 257/750, 257/754, 438/14, 438/625, 438/672, 356/237.1, 356/241.1, 356/376
• US Class Current: 850/8
• CPC Class Codes: G01N 23/225 using electron or ion
• CPC Class Codes: H01J 2237/2561 electron

Abstract

Disclosed are apparatus and methods for characterizing a potential defect of a semiconductor structure. A charged particle beam is scanned over a structure which has a potential defect. X-rays are detected from the scanned structure. The X-rays are in response to the charged particle beam being scanned over the structure. The potential defect of the scanned structure is characterized based on the detected X-rays. For example, it may be determined whether a potentially defective via has a SiO₂ plug defect by comparing an X-ray count ratio of oxygen over silicon of the defective via with an X-ray count ratio of a known defect-free reference via. If the defective via has a relatively high ratio (more oxygen than silicon) as compared to the reference via, then it may be determined that a SiO₂ plug defect is present within the defective via. Otherwise, the via may be defmed as having a different type of defect (e.g., not a SiO₂ plug defect) or defined resulting in a “false” defect. Accordingly, specific embodiments of the present invention may be utilized to filter “false” defects from a defect sample.

Claims

1. A method of characterizing a potential defect of a semiconductor structure, comprising:

scanning a charged particle beam over a structure which has a potential defect;

detecting X-rays from the scanned structure, the X-rays being in response to the charged particle beam being scanned over the structure; and

characterizing the potential defect of the scanned structure based on the detected X-rays, wherein the characterizing operation is based on a ratio of a first X-ray intensity for a first material over a second X-ray intensity for a second material and the first and second X-ray intensities are obtained from the detected X-rays from the scanned structure, wherein the potential defect is characterized by comparing the ratio of the first X-ray intensity with one or more reference ratios.

2. A method as recited in claim 1, wherein the first X-ray intensity occurs at a first energy level that corresponds to the first material and the second X-ray intensity occurs at a second energy level that corresponds to a second material.

3. A method as recited in claim 2, wherein the scanned structure is a first via or a first contact.

4. A method as recited in claim 3, further comprising:

scanning a charged particle beam over a reference via; and

detecting X-rays from the scanned reference via, the X-rays being in response to the charged particle beam being scanned over the reference via,

wherein the potential defect is characterized by comparing the first ratio from the scanned first via or contact to a second ratio from the scanned reference via, wherein the second ratio is a third X-ray intensity for the first material over a fourth X-ray intensity for the second material, wherein the third and fourth X-ray intensities are obtained from the detected X-rays from the scanned reference via.

5. A method as recited in claim 3, further comprising locating the potential defect based on the ratio of the first X-ray intensity for the first material over the second X-ray intensity for the second material.

6. A method as recited in claim 5, further comprising:

scanning a charged particle beam over a plurality of second vias or contacts; and

detecting X-rays from the scanned second vias or contacts, the X-rays being in response to the charged particle beam being scanned over the second vias or contacts,

wherein characterizing the potential defect of the first via or contact is accomplished by determining whether the first ratio from the scanned first via or contact significantly differs from a majority of second ratios calculated for the second vias, wherein the second ratios of the plurality of vias are each calculated by dividing a third X-ray intensity for the first material by a fourth X-ray intensity for the second material, wherein the third and fourth X-ray intensities are obtained from the detected X-rays from each of the scanned second vias.

7. A method as recited in claim 3, further comprising locating the potential defect by a voltage contrast inspection of a plurality of vias.

8. A method as recited in claim 3, wherein the first and second X-ray intensity are X-ray count values.

9. A method as recited in claim 3, wherein the charged particle beam has a spot diameter substantially equal to a diameter of the via.

10. A method as recited in claim 3, wherein characterizing the potential defect includes determining whether the scanned first via or first contact contains a plug defect.

11. A method as recited in claim 10, wherein characterizing the potential defect further includes determining that the potential defect is a real defect when it is determined that the scanned first via or contact contains a plug defect and determining that the potential defect is a false defect when it is determined that the scanned first via or contact does not contain a plug defect.

12. A method as recited in claim 10, further comprising when it is determined that the first via or contact contains a plug defect, determining a size of the plug defect based on the ratio of the first X-ray intensity for the first material over the second X-ray intensity for the second material.

13. A method as recited in claim 3, wherein the first material is oxygen or silicon and the second material differs from the first material and is either oxygen or silicon.

14. A method as recited in claim 3, wherein the first material is dielectric material or a conductive material and the second material differs from the first material and is either a dielectric material or a conductive material.

15. A method as recited in claim 3, wherein characterizing the potential defect is accomplished by determining that the potential defect is a plug defect when the ratio is above a predetermined threshold.

16. A method as recited in claim 3, wherein characterizing the potential defect is accomplished by determining that the potential defect is a plug defect when the ratio is below a predetermined threshold.

17. An apparatus for characterizing a potential defect of a semiconductor structure, comprising:

a beam generator operable to direct a charged particle beam towards a structure;

a detector positioned to detect X-rays from the structure in response to the charged particle beam; and

a processor operable to;

cause the beam generator to direct a charged particle beam towards the structure; and

characterize the potential defect of the scanned structure based on the detected X-rays, wherein the characterizing operation is based on a ratio of a first X-ray intensity for a first material over a second X-ray intensity for a second material and the first and second X-ray intensities are obtained from the detected X-rays from the scanned structure, wherein the potential defect is characterized by comparing the ratio of the first X-ray intensity with one or more reference ratios.

18. An apparatus as recited in claim 17, wherein the first X-ray intensity occurs at a first energy level that corresponds to the first material and the second X-ray intensity occurs at a second energy level that corresponds to a second material.

19. An apparatus as recited in claim 18, wherein the scanned structure is a first via or a first contact.

20. An apparatus as recited in claim 19, wherein the processor is further operable to:

cause the beam generator to scan a charged particle beam over a reference via, and

wherein the potential defect is characterized by comparing the first ratio from the scanned first via or contact to a second ratio from the scanned reference via, wherein the second ratio is a third X-ray intensity for the first material over a fourth X-ray intensity for the second material, wherein the third and fourth X-ray intensities are obtained from X-rays detected from the scanned reference via.

21. An apparatus as recited in claim 19, wherein the processor is further operable to locate the potential defect based on the ratio of the first X-ray intensity for the first material over the second X-ray intensity for the second material.

22. An apparatus as recited in claim 21, wherein the processor is further operable to:

cause the beam generator to scan a charged particle beam over a plurality of second vias or contacts, and

wherein characterizing the potential defect of the first via or contact is accomplished by determining whether the first ratio from the scanned first via or contact significantly differs from a majority of second ratios calculated for the second vias, wherein the second ratios of the plurality of vias are each calculated by dividing a third X-ray intensity for the first material by a fourth X-ray intensity for the second material, wherein the third and fourth X-ray intensities are obtained from X-rays detected from each of the scanned second vias.

23. An apparatus as recited in claim 19, wherein the first and second X-ray intensity are X-ray count values.

24. An apparatus as recited in claim 19, wherein the charged particle beam has a spot diameter substantially equal to a diameter of the via.

25. An apparatus as recited in claim 19, wherein characterizing the potential defect includes determining whether the scanned first via or first contact contains a plug defect.

26. An apparatus as recited in claim 25, wherein characterizing the potential defect further includes determining that the potential defect is a real defect when it is determined that the scanned first via or contact contains a plug defect and determining that the potential defect is a false defect when it is determined that the scanned first via or contact does not contain a plug defect.

27. An apparatus as recited in claim 25, wherein the processor is further operable to determine a size of the plug defect based on the ratio of the first X-ray intensity for the first material over the second X-ray intensity for the second material when it is determined that the first via or contact contains a plug defect.

28. An apparatus as recited in claim 19, wherein characterizing the potential defect is accomplished by determining that the potential defect is a plug defect when the ratio is above a predetermined threshold.

29. An apparatus as recited in claim 19, wherein characterizing the potential defect is accomplished by determining that the potential defect is a plug defect when the ratio is below a predetermined threshold.