Coaxial imaging for indentation instruments

Abstract

Modifications to the indenter probe tips and transducer, and proper selection of optics in an indentation system allow straight down optical viewing of the sample surface under the indentation tip by a microscope, by providing an optical path through the transducer from the sample surface under the tip to a microscope objective, thereby simplifying alignment of the tip to features on the sample.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a top view of a prior art transducer used for nanoindentation. FIG. 1B is a cross sectional view of the transducer as viewed straight from the side, and FIG. 1C is a cross sectional view, as seen from an angle slightly higher than in FIG. 1B.

FIG. 2A is a cross sectional view of a transducer modified to provide a light path through the transducer. The viewing angle is similar to that in FIG. 1C. FIG. 2B is a cross sectional view of the modified transducer, as viewed straight from the side, and also including a diagrammatic view of a sample, a lens, and the path taken by optical rays through the lens and transducer to the sample surface.

FIG. 3A is a diagrammatic view of the relationship between the optical path rays of a lens of NA 0.6 and an indenter probe tip with a total included angle of 70°. FIG. 3B shows that slightly raising the indenter probe tip increases the number of optical rays that clear the tip and reach the sample surface, thereby improving the imaging ability.

FIG. 4 is a diagrammatic view of the relationship between the optical path rays of a lens of NA 0.6 and an indenter probe tip raised 0.025 mm above a sample surface, where the majority of the probe tip has a total included angle of 45°, but the region closest to the sample has an angle of 130.7° and a width of 0.025 mm. Even more of the optical path rays clear the probe tip than in FIG. 3B, thereby further improving the imaging ability.

FIG. 5 is a diagrammatic view showing the relationship between the outermost optical path rays for four lenses from Table 1 and an indentation tip modified to improve the optical imaging capability.

Claims

1: In a mechanical probe based measurement instrument including a transducer, a tip attached to the transducer, a sample, and an optical system including at least one lens, the improvement comprising an unobstructed optical path between the sample and the lens; whereby the lens forms an image of the sample surface directly under the tip, allowing the tip to be aligned to a particular portion or feature on the sample without the use of a large lateral travel stage.

2: The instrument of claim 1, wherein the transducer is located between the lens and the sample, and the unobstructed optical path is provided by at least one hole in the structure of the transducer, the at least one hole being located proximate said tip.

3: The instrument of claim 2, wherein said unobstructed optical path is further provided by selecting said lens to have a cone of accepted light wider than the included angle of said tip.

4: The instrument of claim 2, wherein said unobstructed optical path is further provided by modifying the shape of said tip such that the portion of said tip proximate said sample includes a main portion located farther from said sample and a faceted portion located closer to said sample, wherein the angle between a face of said faceted portion and the central axis of said tip is larger than the angle between said main portion and said central axis.

5: The instrument of claim 3, wherein said unobstructed optical path is improved by raising said tip above the surface of said sample.

6: The instrument of claim 4, wherein said unobstructed optical path is improved by raising said tip above the surface of said sample.

7: The instrument of claim 4, wherein the included angle of the main portion of said tip is less than 60 degrees and the angle between said faceted portion and said central axis is greater than 30 degrees.

8: The instrument of claim 4, wherein the included angle of the main portion of said tip is less than 45 degrees and the angle between said faceted portion and said central axis is greater than 35 degrees.

9: The instrument of claim 4, wherein the included angle of the main portion of said tip is approximately 30 degrees and the angle between said faceted portion and said central axis is approximately 65 degrees.

10: The instrument of claim 4, wherein the included angle of the main portion of said tip is approximately 30 degrees and the angle between said faceted portion and said central axis is approximately 35 degrees.

11: The instrument of claim 1, wherein the transducer is located between the lens and the sample, and the unobstructed optical path is provided by fabricating said transducer at least partially from optically transparent material.

12: The instrument of claim 11, wherein said unobstructed optical path is further provided by selecting said lens to have a cone of accepted light wider than the included angle of said tip.

13: The instrument of claim 12, wherein said unobstructed optical path is further provided by modifying the shape of said tip such that the portion of said tip proximate said sample includes a main portion located farther from said sample and a faceted portion located closer to said sample, wherein the angle between a face of said faceted portion and the central axis of said tip is larger than the angle between said main portion and said central axis.

14: The instrument of claim 13, wherein said unobstructed optical path is improved by raising said tip above the surface of said sample.

15: The instrument of claim 14, wherein said unobstructed optical path is improved by raising said tip above the surface of said sample.

16: The instrument of claim 14, wherein the included angle of the main portion of said tip is less than 60 degrees and the angle between said faceted portion and said central axis is greater than 30 degrees.

17: The instrument of claim 14, wherein the included angle of the main portion of said tip is less than 45 degrees and the angle between said faceted portion and said central axis is greater than 35 degrees.

18: The instrument of claim 14, wherein the included angle of the main portion of said tip is approximately 30 degrees and the angle between said faceted portion and said central axis is approximately 65 degrees.

19: The instrument of claim 14, wherein the included angle of the main portion of said tip is approximately 30 degrees and the angle between said faceted portion and said central axis is approximately 35 degrees.