Overlay metrology using X-rays

• US 20070224518A1
• Filed: 03/27/2006
• Published: 09/27/2007
• Est. Priority Date: 03/27/2006
• Status: Active Grant

• Current Assignee: Bruker Technologies Ltd. (Bruker Corporation)
• Original Assignee: Jordan Valley Applied Radiation Ltd.
• Inventors: Yokhin, Boris, Mazor, Isaac, Dikopoltsev, Alex, Jameson, Sean
• Granted Patent: US 7,481,579 B2
• Time in Patent Office: Days
• US Class Current: 430/5
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching

Abstract

A method for inspection includes directing a beam of X-rays to impinge upon an area of a sample containing first and second features formed respectively in first and second thin film layers, which are overlaid on a surface of the sample. A pattern of the X-rays diffracted from the first and second features is detected and analyzed in order to assess an alignment of the first and second features.

Claims

1. A method for inspection, comprising:

directing a beam of X-rays to impinge upon an area of a sample containing first and second features formed respectively in first and second thin film layers, which are overlaid on a surface of the sample;

detecting a pattern of the X-rays diffracted from the first and second features; and

analyzing the pattern in order to assess an alignment of the first and second features.

2. The method according to claim 1, wherein detecting the pattern of the X-rays comprises detecting the diffracted X-rays following transmission of the beam through the sample.

3. The method according to claim 2, wherein the sample has first and second opposing sides, and wherein directing the beam comprises directing the beam to pass through the sample from the first side to the second side, and wherein the first and second thin film layers are formed on the second side of the sample.

4. The method according to claim 1, wherein directing the beam of X-rays comprises collimating and monochromatizing the beam.

5. The method according to claim 1, wherein detecting the pattern comprises using an array of X-ray detectors to detect the diffracted X-rays as a function of angle relative to the beam.

6. The method according to claim 1, wherein the pattern comprises diffraction lobes having respective amplitudes, and wherein analyzing the pattern comprises determining that the first and second features are misaligned responsively to a variation in the respective amplitudes of the diffraction lobes in the detected pattern.

7. The method according to claim 1, wherein detecting the pattern comprises detecting a two-dimensional diffraction pattern, and wherein analyzing the pattern comprises assessing the alignment with respect to two axes.

8. The method according to claim 1, wherein the sample comprises a semiconductor wafer, and wherein the first and second features comprise alignment targets formed by a photolithographic process on the surface of the wafer.

16. The apparatus according to claim 1, wherein the sample comprises a semiconductor wafer, and wherein the first and second features comprise alignment targets formed by a photolithographic process on the surface of the wafer.

9. Apparatus for inspection, comprising:

an X-ray source, which is configured to direct a beam of X-rays to impinge upon an area of a sample containing first and second features formed respectively in first and second thin film layers, which are overlaid on a surface of the sample;

a detector, which is arranged to detect a pattern of the X-rays diffracted from the first and second features; and

a signal processor, which is coupled to analyze the pattern in order to assess an alignment of the first and second features.

10. The apparatus according to claim 9, wherein the X-ray source and detector are arranged so that the detector detects the diffracted X-rays following transmission of the beam through the sample.

11. The apparatus according to claim 10, wherein the sample has first and second opposing sides, and wherein the X-ray source is configured to direct the beam to pass through the sample from the first side to the second side, and wherein the first and second thin film layers are formed on the second side of the sample.

12. The apparatus according to claim 9, wherein the X-ray source comprises an X-ray tube and X-ray optics for collimating and monochromatizing the beam.

13. The apparatus according to claim 9, wherein the detector comprises an array of X-ray detectors, which are arranged so as to detect the diffracted X-rays as a function of angle relative to the beam.

14. The apparatus according to claim 9, wherein the pattern comprises diffraction lobes having respective amplitudes, and wherein the signal processor is adapted to determine that the first and second features are misaligned responsively to a variation in the respective amplitudes of the diffraction lobes in the detected pattern.

15. The apparatus according to claim 9, wherein the pattern comprises a two-dimensional diffraction pattern, and wherein the signal processor is adapted to analyze the pattern so as to assess the alignment with respect to two axes.