METHOD AND SYSTEM FOR MEASURING BUMPS BASED ON PHASE AND AMPLITUDE INFORMATION

• US 20130170712A1
• Filed: 01/02/2012
• Published: 07/04/2013
• Est. Priority Date: 01/02/2012
• Status: Active Grant

• Current Assignee: Camtek Limited (Hexagon AB)
• Original Assignee: Camtek Limited (Hexagon AB)
• Inventors: Koren, Shimon, Malinovich, Yacov, Golan, Gilad, Shur, Or
• Granted Patent: US 9,147,102 B2
• Time in Patent Office: Days
• US Class Current: 382/106
• CPC Class Codes: G01B 11/0608 Height gauges
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G01N 21/95684 Patterns showing highly reflecting parts, e.g. metallic elements
• CPC Class Codes: G02B 21/0016 Technical microscopes, e.g. for inspection or measuring in industrial production processes
• CPC Class Codes: G02B 21/0056 based on optical coherence, e.g. phase-contrast arrangements, interference arrangements
• CPC Class Codes: G06V 20/69 Microscopic objects, e.g. biological cells or cellular parts

Abstract

A device for measuring a height of a microscopic structure, the device may include: a storage circuit arranged to store information that comprises amplitude information and phase information, wherein the information is indicative of a shape and a size of the microscopic structure; a mask generation circuit arranged to threshold pixels of the amplitude information to provide a mask that comprises masked amplitude pixels; a phase information circuit arranged to apply the mask on the phase information to provide masked phase pixels; select, out of the masked phase pixels, selected phase pixels that correspond to a phase criterion, the selected phase pixels have selected phase pixels attribute values; find, out of the phase information, elected phase pixels that have the selected phase pixel attribute values; and a height calculation circuit arranged to generate a height measurement result based the elected phase pixels.

Claims

1. A device for measuring a height of a microscopic structure, the device comprises:

a storage circuit arranged to store information that comprises amplitude information and phase information, wherein the information is indicative of a shape and a size of the microscopic structure;

a mask generation circuit arranged to threshold pixels of the amplitude information to provide a mask that comprises masked amplitude pixels;

a phase information circuit arranged to apply the mask on the phase information to provide masked phase pixels;

select, out of the masked phase pixels, selected phase pixels that correspond to a phase criterion, the selected phase pixels have selected phase pixels attribute values;

find, out of the phase information, elected phase pixels that have the selected phase pixel attribute values; and

a height calculation circuit arranged to generate a height measurement result based the elected phase pixels.

2. The device according to claim 1, wherein the mask generation circuit is arranged to check whether the mask has at least a predetermined number of pixels;

wherein if the mask does not have the at least predetermined number of pixels then the mask generation circuit is arranged to lower the amplitude information to provide a modified amplitude threshold; and

wherein the phase information circuit is arranged to threshold the pixels of the amplitude information using the modified amplitude threshold.

3. The device according to claim 1, wherein the microscopic structure is a solder bump.

4. The device according to claim 1, wherein the phase criterion represent a statistical criterion selected out of an average, a standard deviation, a weight average or a median.

5. The device according to claim 1, wherein the height calculation circuit is arranged to generate a height measurement result based on a predefined approximation of the shape of the microscopic structure and on the elected phase pixels.

6. A method for measuring a height of a microscopic structure, the method comprises:

receiving or generating information that comprises amplitude information and phase information, wherein the information is indicative of a shape and a size of the microscopic structure;

thresholding pixels of the amplitude information to provide a mask that comprises masked amplitude pixels;

applying the mask on the phase information to provide masked phase pixels;

selecting, out of the masked phase pixels, selected phase pixels that correspond to a phase criterion, the selected phase pixels have selected phase pixels attribute values;

finding, out of the phase information, elected phase pixels that have the selected phase pixel attribute values; and

generating a height measurement result based the elected phase pixels.

7. The method according to claim 6, comprising:

checking whether the mask has at least a predetermined number of pixels;

wherein if the mask does not have the at least predetermined number of pixels then lowering the amplitude information to provide a modified amplitude threshold; and

thresholding the pixels of the amplitude information using the modified amplitude threshold.

8. The method according to claim 6, wherein the microscopic structure is a solder bump.

9. The method according to claim 6, wherein the phase criterion represent a statistical criterion selected out of an average, a standard deviation, a weight average, a median.

10. The method according to claim 6, comprising generating a height measurement result by generating an approximation of the shape and size of the microscopic structure based on a predefined approximation of the shape of the microscopic structure and on the elected phase pixels.

11. A device for measuring a height of a microscopic structure, the device comprises:

a storage circuit for storing a phase image and an amplitude image of the microscopic structure;

a reminder height calculation circuit arranged to calculate reminder height estimates based on the phase image pixels;

a feature extractor arranged to detect an edge of the microscopic structure on a surface of an object;

a size attribute circuit arranged to calculate a size attribute of the microscopic structure based on a size of a shape defined by the edge of the microscopic structure;

a selection circuit arranged to select a selected height range out multiple height ranges based upon the size attribute of the microscopic structure and an allowable relationship between the size attribute and height values of the microscopic structure; and

and a height calculation circuit arranged to calculate an actual height of the microscopic structure based on the selected height range and the reminder height estimate.

12. The device according to claim 11, comprising a phase offset circuit that is arranged to set a phase offset of an interferometer that is arranged to obtain the phase image and the amplitude image in response to an expected height of the microscopic structure.

13. The device according to claim 11, wherein the microscopic structure is a bump and wherein the size attribute is a diameter of the bump.

14. The device according to claim 11, comprising wherein the height calculation circuit is arranged to calculate actual height values form multiple phase image pixels of the phase image;

and process the actual height values of the multiple phase image pixels to provide the actual height of the microscopic structure.

15. The device according to claim 12, wherein the phase offset circuit is arranged to set a phase offset of the interferometer so that the expected bump height is mapped to a center of a continuous range of phase values.

16. The device according to claim 12, wherein the device further comprises:

a mask generation circuit arranged to threshold pixels of the amplitude image to provide a mask that comprises masked amplitude pixels; and

a phase information circuit arranged to apply the mask on the phase information to provide masked phase pixels;

select, out of the masked phase pixels, selected phase pixels that correspond to a phase criterion, the selected phase pixels have selected phase pixels attribute values;

find, out of the phase information, elected phase pixels that have the selected phase pixel attribute values; and

wherein the reminder height calculation circuit is arranged to calculate reminder height estimates based on the elected phase pixels of the phase image pixels.

17. A method for measuring a height of a microscopic structure, the method comprises:

generating or receiving a phase image and an amplitude image of the microscopic structure;

calculating reminder height estimates based on the phase image pixels;

detecting the edge of the microscopic structure on a surface of an object;

calculating size attribute of the microscopic structure based on a size of a shape defined by the edge of the microscopic structure;

selecting a selected height range out multiple height ranges based upon the size attribute of the microscopic structure and an allowable relationship between the size attribute and height values of the microscopic structure; and

calculating an actual height of the microscopic structure based on the selected height range and the reminder height estimate.

18. The method according to claim 17, comprising setting a phase offset of an interferometer that obtained the phase image and the amplitude image in response to an expected height of the microscopic structure.

19. The method according to claim 17, wherein the microscopic structure is a bump and wherein the size attribute is a diameter of the bump.

20. The method according to claim 17, comprising calculating actual height values form multiple phase image pixels of the phase image;

and processing the actual height values of the multiple phase image pixels to provide the actual height of the microscopic structure.

21. The method according to claim 17, wherein the generating of the phase image and the amplitude image comprises setting a phase offset of an interferometer based on an expected height of the microscopic structure so that the expected bump height is mapped to a center of a continuous range of phase values.

22. The method according to claim 17, comprising thresholding pixels of the amplitude information to provide a mask that comprises masked amplitude pixels;

applying the mask on the phase information to provide masked phase pixels;

selecting, out of the masked phase pixels, selected phase pixels that correspond to a phase criterion, the selected phase pixels have selected phase pixels attribute values;

finding, out of the phase information, elected phase pixels that have the selected phase pixel attribute values;

wherein the calculating of the reminder height estimates is based on the elected phase pixels of the phase image pixels.