Electron microscope specimen and method for preparing the same

1. A method for preparing an electron microscope specimen, comprising:

providing a wafer sample having thereon an analysis region;

performing a dicing process to cut a sample piece from the wafer sample, wherein the sample piece comprises a target pillar structure and the analysis region is located on a top portion of the target pillar structure, wherein the dicing process comprises performing a first dicing process to form two first dicing trenches and a recessed ladder structure, performing a second dicing process to form two second dicing trenches on the wafer sample, wherein a height and a length of the target pillar structure are defined by the first dicing trenches; and performing a third dicing process to form a plurality of third dicing trenches between the two second dicing trenches, wherein a width of the target pillar structure is defined by the third dicing trenches, wherein a depth of each of the first dicing trenches and a depth of each of the second dicing trenches are both greater than a height of the wafer sample; and

performing a thinning process to thin the top portion of the target pillar structure.

2. The method for preparing an electron microscope specimen according to claim 1 , wherein the length is substantially equal to the width.

3. The method for preparing an electron microscope specimen according to claim 1 , wherein the third dicing process further comprises forming a plurality of dummy pillar structures.

4. The method for preparing an electron microscope specimen according to claim 3 further comprising: removing the dummy pillar structures after the third dicing process.

5. The method for preparing an electron microscope specimen according to claim 1 , wherein a depth of each of the third dicing trenches is substantially equal to the height of the target pillar structure.

6. The method for preparing an electron microscope specimen according to claim 1 further comprising: affixing the sample piece to a holder after performing the dicing process.

7. The method for preparing an electron microscope specimen according to claim 6 , wherein the holder comprises a metal half ring.

8. The method for preparing an electron microscope specimen according to claim 1 further comprising: adhering the sample piece onto an auxiliary sample before performing the dicing process.

9. The method for preparing an electron microscope specimen according to claim 8 further comprising: performing a heating process to detach the sample piece from the auxiliary sample after the dicing process.

10. The method for preparing an electron microscope specimen according to claim 1 further comprising: forming a protective layer on the target pillar structure before performing the thinning process.

11. The method for preparing an electron microscope specimen according to claim 10 , wherein the protective layer comprises metal.

12. The method for preparing an electron microscope specimen according to claim 1 , wherein the thinning process comprises using a focus ion beam.

13. The method for preparing an electron microscope specimen according to claim 1 , wherein the thinning process comprises forming a tip portion on the top portion of the target pillar structure, wherein the analysis region is located on the tip portion.

14. The method for preparing an electron microscope specimen according to claim 13 , wherein the tip portion comprises a tip height, and wherein a ratio of the length of the target pillar structure to the tip height is substantially between 2 to 0.7.

15. A method for forming a 3D image, comprising:

providing a specimen which is prepared by the method of claim 1 ;

performing an image retrieving process to capture a plurality of 2D images of the specimen from different angles by using a microscope; and

constructing the plurality of 2D images to form the 3D image.