X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2000-02-02
2002-07-16
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S901000
Reexamination Certificate
active
06421409
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the field of computed tomography imaging and in particular, to computed tomography imaging of packaged integrated circuits utilizing a very small x-ray or gamma-ray source, a rotating sample carrier or stage, a large-area detector array, a deconvolution algorithm, and optics including a Fresnel zone plate.
2. Description of the Related Art
As integrated circuits become larger and more complex, the integrated package necessarily becomes larger and more complex. An important source of integrated circuit failure stems from flaws in the packaging process. Virtually all methods for inspecting the bonds in a packaged integrated circuit require destruction of the package and the use of a high-magnification microscope or a scanning electron microscope. The integrated circuit industry is very interested in the development of a non-destructive inspection system. Computed tomography techniques can produce image “slices” of an object without destroying the object. To date, however, computed tomography approaches have been unable to achieve the required spatial resolution to inspect packaged devices for small cracks in the bonds and in the interconnections. There is a long-felt need for novel x-ray or gamma ray focusing techniques and image enhancement techniques to obtain the required resolution in a computed tomographic imaging system.
SUMMARY OF THE INVENTION
The concept proposed here employs novel x-ray or gamma ray focusing techniques and image enhancement techniques to obtain the required resolution in a tomographic imaging system. While each individual element of a presently preferred embodiment has been applied elsewhere, the combination and interaction of these elements is unique and provides the enhanced resolution not available in the prior art.
An ultra-high resolution computed X-ray or gamma-ray computed tomography system in accordance with the inventive arrangements can be used for inspecting packaged integrated circuits with the required spatial resolution needed to inspect packaged devices for small cracks in the bonds and in the interconnections. In the presently preferred embodiment, the method utilizes, and the system comprises, a sub-micron x-ray or gamma ray source, a large-area detector array and a rotating sample stage. The source is positioned very near the object under test and the large-area detector is positioned some distance from the object under test. The detector array can comprise either an array of charge-coupled device (CCD) detectors coupled to a phosphor screen or an image intensifier screen. In either case, the object under test is illuminated by a cone beam of x-rays or gamma rays which serves to magnify the image projected onto the large area detector array. The magnification permits the use of relatively large detector elements, on the order of approximately 10 microns×10 microns, to image micron-scale features. The system resolution is then limited by the size of the radiation source. Several approaches can be employed in accordance with the inventive arrangements to minimize the radiation source size. A first approach is using a micro-focal x-ray tube to obtain a source size of 10 microns or less. Focusing optics such as a Fresnel zone plate can then be used to further reduce the effective source size to 1 micron or less. Alternately, a second approach is using a small high activity gamma ray source, on the order of several microns, can be used in conjunction with focusing optics. With either approach, the acquired image is convolved with the ideal image in the detected image. The effective source size can be further reduced using algorithms to separate the contribution of the source geometry from the acquired image.
A method for ultra-high resolution computed tomography imaging, in accordance with the inventive arrangements, comprises the steps of: focusing a high energy particle beam onto a target object; acquiring a 2-dimensional projection data set representative of the target object; generating a corrected projection data set by applying a deconvolution algorithm to the 2-dimensional data set; storing the corrected projection data set; incrementally rotating the target object through an angle of approximately 180°, and after each the incremental rotation, repeating the radiating, acquiring, generating and storing steps; and, after the rotating step, applying a cone-beam algorithm to the corrected projection data sets to generate a 3-dimensional image.
The method can comprise the step of radiating the target object with x-rays or gamma rays.
The method can comprise the step of focusing the beam with an optical member, for example a Fresnel zone plate.
The spot focus of the beam can be reduced to a size not greater than approximately 1 micron, or even to a size not greater than approximately 0.5 microns.
The method can comprise the step of applying a modified tomographic reconstruction algorithm to the corrected projection data sets.
The method can further comprise the step of experimentally determining a transfer function for the deconvolution algorithm.
The method can comprise the step of incrementally rotating the target object through a total of 180° plus the angle of the fan beam.
REFERENCES:
patent: 5566341 (1996-10-01), Roberson et al.
patent: 5740224 (1998-04-01), Müller et al.
Devoti, R. et al., “A Synchrotron Radiation Microprobe for X-ray Fluorescence and Microtomography at ELETTRA. Focusing with Bent Cyrstals, ” Nuclear Instruments & Methods in Physics Research, B54, pp. 424-428, Amsterdam, NL (Mar. 2, 1991).
Machin, K. et al., “Cone-beam X-ray Microtomography of Small Specimens, ” 2362 Physics in Medicine & Biology 39, No. 10, pp. 1639-1667, Bristol, G.B. (1994).
Weitkamp, T. et al., “An Imaging and Microtomography Facility at the ESRF Beamline ID 22, ” Proceedings of the 1999 SPIE Conference on Developments in X-ray Tomography II, Denver, CO pp. 311-317 (Jul. 1999).
McNulty, J., et al., “Design and Performance of the 2-ID-B Scanning X-ray Microscope, ” Proceedings of the 1999 SPIE Conference on X-ray Microfocusing: Applications and Techniques, San Diego, CA, pp. 67-74 (Jul. 1998).
Gleason Shaun S.
Paulus Michael J.
Sari-Sarraf Hamed
Thomas, Jr. Clarence E.
Tobin, Jr. Kenneth William
Bruce David V.
Senterfitt Akerman
UT-Battelle LLC
LandOfFree
Ultra-high resolution computed tomography imaging does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ultra-high resolution computed tomography imaging, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultra-high resolution computed tomography imaging will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2900537