Metrology and registration system and method for laminography and tomography
A metrology system that uses an imaging system to monitor alignment features on the sample or sample holder of an X-ray laminography or tomography system. the metrology system has the capability to provide both sample shift and sample rotation movement data to a data acquisition system. These shift and rotation data can be used in alignment routines to produce 3D reconstructions from the X-ray images/projections. The metrology system is based on an imaging and focusing measurement of intrinsic feature of the sample or artificial features fabricated on the sample or sample holder.
1. A metrology system integrated into an X-ray laminography or tomography system, comprising:
an illumination source for illuminating an alignment target;
an objective lens;
a spatially resolved detector for detecting images of the alignment target formed by the objective lens; and
a stage system that rotates a sample of the laminography or tomography system and the alignment target.
2. A metrology system as in claimed 1 , wherein the illumination source produces infra-red light.
3. A metrology system as in claimed 1 , wherein the illumination source produces visible light.
4. A metrology system as in claimed 1 , wherein the illumination source produces ultra-violet light.
5. A metrology system as in claimed 1 , wherein the objective lens has a numerical aperture of 0.1 to 0.9.
6. A metrology system as in claimed 1 , wherein the objective lens is an immersion lens with an numerical aperture of 0.5 to 1.4.
7. A metrology system as in claimed 1 , wherein detector has at least 1,024×1,024 pixels.
8. A metrology system as in claimed 1 , further comprising a controller for shifting images from the laminography or tomography system in response to the images of the alignment target.
9. A metrology system as in claimed 1 , further comprising a controller for processing image from the laminography or tomography system to generate a 3D image in response to the images of the alignment target.
10. A metrology system as in claimed 1 , further comprising an objective lens stage for adjusting a focus position of the objective lens.
11. A metrology system as in claimed 10 , wherein the objective lens stage is a mechanical bearing stage.
12. A metrology system as in claimed 10 , wherein the objective lens stage is a flexure stage.
13. A metrology system as in claimed 10 , wherein the objective lens stage is driven by a DC motor.
14. A metrology system as in claimed 10 , wherein the objective lens stage is driven by a stepper motor.
15. A metrology system as in claimed 10 , wherein the objective lens stage is driven by a piezo-electric motor.
16. A metrology system as in claimed 1 , wherein the alignment target is a pattern fabricated a sample holder of the stage system.
17. A metrology system as in claimed 16 , where the pattern comprises a grid pattern.
18. A metrology system as in claimed 17 , where a grid pattern has variable spacing.
19. A metrology system as in claimed 18 , where the grid pattern has a random spacing.
20. A metrology system as in claimed 18 , where the grid pattern has a spacing based on prime number.
21. A metrology system as in claimed 18 , where the grid pattern has a spacing based on the chirp function.
22. A metrology method for a an X-ray laminography or tomography system, comprising:
capturing X-ray images of a sample and rotating the sample between images;
detecting optical images of the sample or a sample mounting system for each of the X-ray images;
determining shifts in the sample between the X-ray images with reference to the optical images;
shifting the X-ray images with respect to each other in response to the determined shifts in the optical images; and
performing a reconstruction process on the shifted X-ray images to produce a three dimensional image of the sample.
23. A method as claimed in claim 22 , wherein the step of detecting the optical images comprises detecting a pattern formed on a sample mounting plate.
24. A method as claimed in claim 22 , further comprising determining vertical shifts in the sample by reference to focus changes in the optical images.