Patent Number: 052590135
Section: summary

FIELD OF INVENTION This invention relates to apparatus and a method for using hard x-rays to obtain high resolution alteration of observed image dimensions (magnification or reduction) and, more particularly, to an apparatus and method for providing alteration of image dimensions in up to three dimensions employing asymmetric x-ray diffraction from flat, optically polished surfaces of two mutually orthogonal nearly perfect crystals and direct generation of, for example, magnified images by an x-ray sensitive CCD detector or direct generation of precisely reduced undistorted image patterns onto materials such as photo-resists on substrates. BACKGROUND OF THE PRIOR ART There are many scientific and engineering activities which require highly detailed and precise information concerning specific materials. These include: fabrication of novel microelectronic and photonic device materials designed on the atomic scale; rapid solidification of metals to obtain unusual strength, ductility and corrosion resistance; and production of improved ceramics and composite materials which typically are highly vulnerable to thermal and mechanical problems during processing. In these and other comparable activities, it is often essential to examine a specimen of a selected material at very high resolution, e.g. to detect lines of less than 1 micrometer width and/or to resolve lines as little as 1.2 micrometer apart. Such high resolution requires advances in the state of the art of x-ray imaging, as practiced in the techniques of radiography, tomography, and diffraction topography. Also, in many applications, including microcardiography and high resolution tomography, it is highly desirable to obtain three-dimensional imaging of the specimens. In fact, x-ray microtomography is a rapidly developing field for the detection of flaws and defects inside materials produced for industrial applications. For example, the structure of all materials as they are formed is often locally non-uniform over regions of the order of 1 micrometer. Inhomogeneities occurring in diffusion layers and grain boundaries, local compositional variations, regionally homogeneous strains (residual stresses) and inhomogeneous strains, etc., often alter the behavior of materials from their originally designed characteristics. Successful fabrication of tailored materials having structures not found in nature depends entirely on minute structural details and their influence on the properties and performance of the object fabricated therefrom. Similarly, in microelectronic devices, where different atoms are doped in mutually coherent layers, the thickness and shape of doped layers may change and may cause degradation of functional properties intended to be obtained by the designer. What is needed in such instances is a measurement technique to "see" what happens locally, and to pinpoint local events of significance with high spatial resolution. It is to such needs that the present invention is directed. The invention magnifies, in one or two dimensions, parallel projection monochromatic x-ray images. Such images are obtained, for example, by the techniques of radiography, tomography, and diffraction topography, when the specimen is irradiated with well collimated monochromatic x-rays. It should be understood that other materials, such as tissue samples from living beings and plants, also may be studied advantageously by high resolution viewing and adequate magnification to clarify significant details, e.g., the presence of abnormal cells or the like. What is needed, therefore, are apparatus and methods for significantly magnifying a view that is originally generated by the passage of short wave-length hard x-rays through a thin specimen of a selected material. For certain applications, using the same apparatus and method with obvious changes, the x-rays are reflected off a selected surface of a specimen to study its local topography with very high resolution. It is to such needs that the present invention is directed. The invention magnifies, in one or two dimensions, parallel projection monochromatic x-ray images. Such images are obtained, for example, by the techniques of radiography, tomography, and diffraction topography, when the specimen is irradiated with well collimated monochromatic x-rays. A paper titled "Improvement of Spatial Resolution of Monochromatic X-ray CT Using Synchrotron Radiation" by Sakamoto et al., Japanese Journal of Applied Physics, Volume 27, No. 1, January 1988, pp. 127-132, discloses an x-ray computer tomography technique using synchrotron radiation (SR) as an x-ray source to generate CT images of improved quality. A method is disclosed for improving the spatial resolution, involving the one-dimensional magnification of projection images using asymmetric diffraction. The disclosed method employs a scintillator covering the detector surface. The best spatial resolution obtained was about 15 to 20 micrometers, using a magnification factor of 9.0. The dispersal of visible light, generated by x-rays, in the scintillator appeared to degrade significantly the spatial resolution, as stated on page 130 of the same paper. There are numerous devices and systems known and commercially available for generating magnified images of very fine details in material samples. U.S. Pat. No. 4,672,651, to Horiba et al., discloses apparatus and a method in which respective cone-like beams of x-rays are projected from two different directions through a person's body, and the transmitted x-rays are analyzed to generate a projection image. A contrast medium is initially injected into the body to reach a part of the body which is of interest. A direct x-ray detector is used which can also convert a received signal into an optical image which can be directed into a TV camera. U.S. Pat. No. 4,635,197, to Vinegar et al., discloses a high-resolution tomographic imaging method, wherein a sample is scanned at many points in corresponding cross-sections which are separated by a distance less than the width of an x-ray beam of a CAT scanner. The measured density function thus obtained is deconvolved, with the beam width function for the CAT for each of the plurality of points, to thereby obtain the actual density function for the plurality of points. This information is directly used to generate an image of a sample which has a spatial resolution in the axial direction that is smaller than the width of the x-ray beam of the CAT. U.S. Pat. No. 5,012,498, to Cuzin et al., discloses an x-ray tomography device which enables the generation of an image at a plane identified transversely through an object. It comprises an x-ray source which supplies high energy pulses which traverse the object. Both the source of the x-rays and the detector are stationary, and the object is rotated. U.S. Pat. No. Re. 32,779, to Kruger, discloses a radiographic system employing multi-linear arrays of electronic radiation detectors of the CCD type. An x-ray source provides a diverging x-ray beam which passes through portions of a human body to be received first through an image intensifier and then passed through a lens or other focusing device. The transmitted-radiation is focused upon a multi-linear array which comprises a two-dimensional CCD detector. There clearly exists a need for a high resolution, one-, two- or three-dimensional magnification system and corresponding methods which permit magnifications of up to 200 times the original at resolutions enabling study of features less than 1 micrometer in size and for separation of adjacent features at close to the 1 micrometer level of precision. The present invention, as described more fully hereinafter, is believed to answer this need. Persons of ordinary skill in the art, upon understanding the present disclosure, are expected to consider obvious modifications of both the apparatus and the method disclosed herein. Such modifications and variations are intended to be comprehended within the scope of the invention described below in detail SUMMARY OF THE INVENTION Accordingly, it is a principal object of this invention to provide an apparatus for generating a highly magnified or demagnified image of fine structural details, at the micrometer or submicrometer level of resolution, within or on the surface of a specimen, by asymmetric dynamical x-ray diffraction. Because of the reciprocity theorem applicable to x-ray optics, the term "magnification" also implies the shrinkage of an image, that is "demagnification". This is so well known that this implication will not, hereafter, be mentioned explicitly. It is a further object of this invention to provide an apparatus and a method for generating highly magnified images of structural details at the micrometer level within or at the surface of a specimen, by asymmetric dynamical x-ray diffraction, preferably from a flat optically polished surface of a nearly-perfect crystal, using a monochromatic hard x-ray beam. It is an even further object of this invention to provide two-dimensional highly-magnified images of structural details at the micronmeter level in or at the surface of a specimen, by employing a parallel, hard, monochromatic x-ray beam, asymmetrically diffracting the same from optically flat polished surfaces of two nearly perfect crystals placed orthogonally to each other and directly converting the x-ray photons to electrical charges, without prior conversion to optical photons, to generate a high resolution two-dimensional and recordable magnified image. It is another related further object of this invention to provide apparatus and a method for x-ray phase contrast microscopy, in which the two-dimensionally magnified high resolution images of strain fields around flaws and defects in materials are generated in addition to the normal shape images of these flaws and defects, particularly when the initial x-ray beam containing the image of structural details is obtained from specimen materials under Bragg diffraction conditions. It is also a related further object of this invention to provide apparatus and a method for generating a three-dimensional, highly-magnified, high-resolution image of structural details of a specimen, using a parallel beam of hard, monochromatic, x-rays and direct conversion of information-bearing x-ray photons to visible photons. These and other related objects are realized by providing an apparatus comprising: means for applying a parallel first x-ray beam of predetermined energy and brilliance to a portion of the specimen, to thereby generate a parallel second x-ray beam which contains an initial image relating to the specimen; PA1 a first nearly perfect crystal formed to provide a first diffraction surface oriented to receive said second x-ray beam at a first angle of incidence to dynamically diffract the same and to thereby generate a parallel third x-ray beam containing a first one-dimensional magnification of said initial image, said third x-ray beam being reflected with respect to said first diffraction surface at a first angle of reflectance relative thereto; and PA1 x-ray sensitive detector means for receiving said third x-ray beam and directly generating therefrom an output corresponding to a first magnified image; PA1 monochromator means for monochromatizing said first x-ray beam prior to application thereof to said specimen; PA1 means for applying a parallel first x-ray beam of predetermined energy and brilliance to a portion of the specimen, to thereby generate a parallel second x-ray beam which contains an initial image relating to the specimen; PA1 a first nearly perfect crystal formed to provide a first diffraction surface oriented to receive said second x-ray beam at a first angle of incidence to dynamically diffract the same and to thereby generate a parallel third x-ray beam containing a first one-dimensional alteration of said initial image; said third x-ray beam being reflected with respect to said first diffraction surface at a first angle of reflectance relative thereto; PA1 a second nearly perfect crystal, similar to the first nearly perfect crystal, formed to provide a second diffraction surface oriented orthogonally with respect to said first diffraction surface and disposed to receive said third x-ray beam at a second angle of incidence to dynamically diffract the same and to reflect a parallel fourth x-ray beam containing a second one-dimensional alteration of said first dimensional alteration to the same degree, but orthogonally directed to said first dimensional alteration, the combined effect of both one-dimensional alterations being an undistorted two-dimensional alteration of said initial image, said fourth x-ray beam being reflected with respect to said second diffraction surface at a second angle of reflectance relative thereto; and PA1 x-ray sensitive detector means for receiving said fourth x-ray beam and directly generating therefrom an output corresponding to a two-dimensional second magnified image. PA1 means for applying a parallel first x-ray beam of predetermined energy and brilliance to a portion of the specimen, to thereby generate a parallel second x-ray beam which contains an initial image relating to the specimen; PA1 a first highly perfect crystal formed to provide a first diffraction surface oriented to receive said second x-ray beam at a first angle of incidence to dynamically diffract the same and to thereby generate a parallel third x-ray beam containing a first magnification of said initial image, said third x-ray beam being reflected with respect to said first diffraction surface at a first angle of reflectance relative thereto; PA1 a second nearly perfect crystal, similar to the first nearly perfect crystal, formed to provide a second diffraction surface oriented orthogonally with respect to said first diffraction surface and disposed to receive said third x-ray beam at a second angle of incidence to dynamically diffract the same and to reflect a parallel fourth x-ray beam containing a second one-dimensional alteration of said first one-dimensional alteration to the same degree, but orthogonally directed to said first one-dimensional alteration, the combined effect of both one-dimensional alterations being an undistorted two-dimensional alteration of said initial image, said fourth x-ray beam being reflected with respect to said second diffraction surface at a second angle of reflectance relative thereto; PA1 x-ray sensitive detector means for receiving said fourth x-ray beam and directly generating therefrom an output corresponding to a two-dimensional second magnified image; PA1 monochromator means for monochromatizing said first x-ray beam prior to application thereof to said specimen; PA1 disposition adjustment means for providing fine adjustments to the dispositions of said specimen relative to said first nearly perfect crystal, of said first nearly perfect crystal with respect to said second highly perfect crystal, and of said second highly perfect crystal relative to said detector means; PA1 computer means for controlling said adjustment means; PA1 means for rotating said specimen through a predetermined angle; and PA1 means for digitizing and processing data generated by said detector means in relation to a rotation of said specimen to develop a three-dimensionally magnified image of said specimen. PA1 applying a parallel first x-ray beam of predetermined energy and brilliance to a portion of the specimen to generate a parallel second x-ray beam which contains an initial image relating to the specimen; PA1 positioning a first highly-perfect crystal to orient a first diffraction surface thereof to receive said second x-ray beam at a first angle of incidence to dynamically diffract the same to generate a parallel third x-ray beam containing a first magnification of said initial image and reflecting said third x-ray beam with respect to said first diffraction surface and a first angle of reflectance relative thereto; PA1 disposing a second highly-perfect crystal to orient a second diffraction surface thereof orthogonally with respect to said first diffraction surface, said second diffraction surface being disposed to receive said third x-ray beam at a second angle of incidence to dynamically diffract the same and to reflect a parallel fourth x-ray beam containing a second magnification of said first magnification in a direction orthogonal to a direction of said first magnification, said fourth x-ray beam being reflected with respect to said second diffraction surface at a second angle of reflectance relative thereto; and PA1 receiving said fourth x-ray beam at an x-ray sensitive direct detecting means for generating therefrom an output corresponding to a two-dimensional second magnified image. In another aspect of the invention, there is provided a system for obtaining a two-dimensionally altered high-resolution image of a specimen, comprising: In yet another aspect of this invention, there is provided a system for generating a three-dimensionally magnified high-resolution image of a specimen, comprising: In another related aspect of this invention, there is provided a method for directly generating a two- or three-dimensionally magnified high-resolution image of a specimen, comprising the steps of: