3D Microscope And Methods Of Measuring Patterned Substrates

• US 20120019626A1
• Filed: 06/29/2011
• Published: 01/26/2012
• Est. Priority Date: 07/23/2010
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation
• Original Assignee: Zeta Instruments, Inc. (KLA Corporation)
• Inventors: Hou, Zhen, Xu, James Jianguo, Lee, Ken Kinsun, Nguyen, Hung Phi, Kudinar, Rusmin, Soetarman, Ronny, Stainton, James Nelson
• Granted Patent: US 9,389,408 B2
• Time in Patent Office: Days
• US Class Current: 348/50
• CPC Class Codes: G01N 2021/0168 for the measurement cycle
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G02B 21/0016 Technical microscopes, e.g. for inspection or measuring in industrial production processes
• CPC Class Codes: G02B 21/0028 specially adapted for specific applications, e.g. for endoscopes, ophthalmoscopes, attachments to conventional microscopes
• CPC Class Codes: G02B 21/0032 Optical details of illumination, e.g. light-sources, pinholes, beam splitters, slits, fibers G02B21/0036 - G02B21/008; means for illumination of specimens in general G02B21/06
• CPC Class Codes: G02B 21/006 focusing arrangements; selection of the plane to be imaged
• CPC Class Codes: G02B 21/367 providing an output produced by processing a plurality of individual source images, e.g. image tiling, montage, composite images, depth sectioning, image comparison
• CPC Class Codes: G06T 2207/10056 Microscopic image
• CPC Class Codes: G06T 2207/10152 Varying illumination
• CPC Class Codes: G06T 2207/20068 Projection on vertical or horizontal image axis
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes

Abstract

A three-dimensional (3D) microscope for patterned substrate measurement can include an objective lens, a reflected illuminator, a transmitted illuminator, a focusing adjustment device, an optical sensor, and a processor. The focusing adjustment device can automatically adjust the objective lens focus at a plurality of Z steps. The optical sensor can be capable of acquiring images at each of these Z steps. The processor can control the reflected illuminator, the transmitted illuminator, the focusing adjustment device, and the optical sensor. The processor can be configured to capture first and second images at multiple Z steps, the first image with the pattern using the reflected illuminator and the second image without the pattern using one of the reflected illuminator and the transmitted illuminator.

Claims

1. A 3D microscope for patterned substrate measurement, the 3D microscope comprising:

an objective lens;

a reflected illuminator configured to provide reflected light for a sample including a patterned substrate and to project an image of a patterned article onto and remove the image of the patterned article from a focal plane of the objective lens;

a transmitted illuminator configured to provide transmitted illumination for the sample;

a focusing adjustment device for automating objective lens focus adjustment at a plurality of Z steps;

an optical sensor capable of acquiring images at each Z step; and

a processor for controlling the reflected illuminator, the transmitted illuminator, the focusing adjustment device, and the optical sensor, the processor configured to capture first and second images at multiple Z steps, the first image with the pattern using the reflected illuminator and the second image without the pattern using one of the reflected illuminator and the transmitted illuminator.

2. The 3D microscope of claim 1, wherein the patterned article is a piece of glass with a pre-determined pattern thereon.

3. The 3D microscope of claim 1, wherein the optical sensor includes one of a charge-coupled device (CCD) camera and a complementary metal-oxide semiconductor (CMOS) camera.

4. The 3D microscope of claim 1, wherein the transmitted illuminator is a light emitting diode (LED) and one of a lens and a lens group.

5. The 3D microscope of claim 1, wherein the focusing adjustment device is one of a motorized mechanical Z stage and a piezo Z stage.

6. The 3D microscope of claim 5, wherein the motorized Z stage includes one of a lead screw and a ball screw coupled to a linear bearing.

7. The 3D microscope of claim 5, wherein the piezo Z stage is mounted on one of a sample chuck and a microscope turret.

8. A method of designing a 3D microscope for measurement, the method comprising:

providing an objective lens;

providing a reflected illuminator configured to provide reflected light for a sample and project an image of a patterned article onto and remove the image of the patterned article from a focal plane of the objective lens;

providing a transmitted illuminator configured to provide transmitted illumination for the sample;

providing a focusing adjustment device for automating objective lens focus adjustment at a plurality of Z steps;

providing an optical sensor capable of acquiring images at each Z step; and

providing a processor for controlling the reflected illuminator, the transmitted illuminator, the focusing adjustment device, and the optical sensor, the processor configured to capture first and second images at multiple Z steps, the first image with the pattern using the reflected illuminator and the second image without the pattern using one of the reflected illuminator and the transmitted illuminator.

9. The method of claim 8, wherein the patterned article is a piece of glass with a pre-determined pattern.

10. The method of claim 8, wherein the optical sensor includes one of a charge-coupled device (CCD) camera and a complementary metal-oxide semiconductor (CMOS) camera.

11. The method of claim 8, wherein the transmitted illuminator is a light emitting diode (LED) and one of a lens and a lens group.

12. The method of claim 8, wherein the focusing adjustment device is one of a motorized mechanical Z stage and a piezo Z stage.

13. The method of claim 12, wherein the motorized Z stage includes one of a lead screw and a ball screw coupled to a linear bearing.

14. The method of claim 12, wherein the piezo Z stage is mounted on one of a sample chuck and a microscope turret.

15. A method of measuring a patterned substrate sample, the patterned substrate sample including a plurality of patterned substrate features, the method comprising:

varying a relative distance between the patterned substrate sample and an objective lens at predetermined steps;

at one or more of the predetermined steps;

projecting an image of a patterned article onto a focal plane of the objective lens;

capturing a first image with a pattern associated with the patterned article and the sample, and storing the first image in a first image array;

capturing a second image of the sample without the pattern associated with the patterned article, and storing the second image in a second image array;

generating a first mask to roughly distinguish the patterned substrate features from a background area of the patterned substrate sample based on the second image array;

generating a second mask to accurately distinguish the patterned substrate features from the background area based on the first image array and the first mask;

determining a top of each patterned substrate feature using the second mask and one of the first image array and the second image array; and

calculating geometric parameters of patterned substrate features using the second mask and the top of each patterned substrate feature.

16. The method of claim 15, wherein capturing the second image includes using one of a reflected illuminator and a transmitted illuminator.

17. The method of claim 16, wherein the transmitted illuminator is a light emitting diode (LED) and one of a lens and a lens group.

18. The method of claim 15, wherein generating the first mask includes using one of color, intensity, or a combination of both color and intensity.

19. The method of claim 15, wherein generating the second mask includes using a thresholding method.

20. The method of claim 15, wherein the geometric parameters include size, pitch, height, space, and top size of the patterned substrate features.

21. The method of claim 15, wherein varying the relative distance between the patterned substrate sample and the objective lens includes using one of a motorized mechanical Z stage and a piezo Z stage.

22. The method of claim 21, wherein the motorized Z stage includes one of a lead screw and a ball screw coupled to a linear bearing.

23. The method of claim 21, wherein the piezo Z stage is mounted on one of a sample chuck and a microscope turret.

24. A method of measuring a patterned substrate sample, the patterned substrate sample including a plurality of patterned substrate features, the method comprising:

automatically varying a relative distance between the patterned substrate sample and an objective lens at pre-determined steps, the automatically varying including an auto-focus;

at one or more of the pre-determined steps;

projecting an image of a patterned article onto a focal plane of the objective lens;

capturing a first image with a pattern associated with the patterned article and the sample, and storing the first image in a first image array;

capturing a second image of the sample without the pattern associated with the patterned article, and storing the second image in a second image array;

generating a first mask to roughly distinguish the patterned substrate features from a background area of the patterned substrate sample based on the second image array;

generating a second mask to accurately distinguish the patterned substrate features from the background area based on the first image array and the first mask;

determining a top of each patterned substrate feature using the second mask and one of the first image array and the second image array; and

calculating geometric parameters of patterned substrate features using the second mask and the top of each patterned substrate feature.

25. The method of claim 24, wherein capturing the second image includes using one of a reflected illuminator and a transmitted illuminator.

26. The method of claim 25, wherein the transmitted illuminator is a light emitting diode (LED) and one of a lens and a lens group.

27. The method of claim 24, wherein generating the first mask includes using one of color, intensity, and a combination of both color and intensity.

28. The method of claim 24, wherein generating the second mask includes using a threshold method.

29. The method of claim 24, wherein the geometric parameters include size, pitch, height, space, and top size of the patterned substrate features.

30. The method of claim 24, wherein varying the relative distance between the patterned substrate sample and the objective lens includes using one of a motorized mechanical Z stage and a piezo Z stage.

31. The method of claim 30, wherein the motorized Z stage includes one of a lead screw and a ball screw coupled to a linear bearing.

32. The method of claim 30, wherein the piezo Z stage is mounted on one of a sample chuck and a microscope turret.

33. The method of claim 24, wherein the auto-focus includes a first auto-focus technique and a second auto-focus technique.

34. The method of claim 33, wherein the first auto-focus technique includes a conditional early exit.

35. The method of claim 34, wherein the conditional early exit includes determining whether more than a threshold scan range is done.

36. The method of claim 35, wherein when more than the threshold scan range is done, then calculating a standard deviation from accumulated contrast values, otherwise continue scanning.

37. The method of claim 36, wherein the conditional early exit further includes determining whether the maximum contrast value is more than a specified minimum early exit threshold and a current step contrast is less than a maximum contrast by at least the standard deviation.

38. The method of claim 34, wherein the first auto-focus technique includes capturing images while the Z stage is moving between scan steps, thereby allowing a speed of the first auto-focus to be as fast as a camera frame rate.

39. The method of claim 34, wherein the second auto-focus technique has a step size smaller than that of the first auto-focus technique.

40. The method of claim 39, wherein the second auto-focus technique includes detecting a falling contrast pattern.

41. The method of claim 40, wherein the falling contrast pattern is a scan step with peak contrast, followed at least a plurality of scan steps of lower contrast values.

42. The method of claim 41, wherein the plurality of scan steps is four scan steps.