Patent Number: 
Section: description

Having reference now to the drawings, in FIG. 1A, there is shown a precision focusing x-ray collimator fabricating system in accordance with the present invention generally designated by the reference character 100. It should be understood that precision focusing x-ray collimator fabricating system 100 can also be used for fabricating non-focusing x-ray collimators. Precision focusing x-ray collimator fabricating system 100 includes a highly collimated synchrotron radiation source 102, such as an Advanced Photon Source (APS) at Argonne National Laboratory. Referring also to FIGS. 1B and 1C, synchrotron radiation source 102 is used with a scanner 104 for moving a substrate 106. For a non-focusing collimator, scanner 104 includes a first stage 108 mounted vertically or perpendicular to the beam to move the substrate 106 in the Z-direction while the substrate 106 is scanned vertically in the Z-direction. For a focusing collimator, scanner 104 includes a second stage 110 mounted on the first stage 108 that can rotate in the Y-Z plane about the X-axis, at a varying angle W of inclination of the substrate 106 as a function of the position of the Z-direction during the scan. A scanner controller 112 operatively controls the scanner 104 and stages 108, 110 with precise computer control, such as a multiaxis servo motor controller or with an arrangement of appropriate mechanical linkages. Precision focusing x-ray collimator fabricating system 100 includes a plurality of substrate processing stages including substrate coating stages 114, an exposure stage 116, a substrate x-ray resist development stage 118, a substrate electroplating stage 120, an optional substrate refinishing stage 122, an optional substrate resist removal stage 124, and an optional substrate removal stage 126. Referring to FIG. 1D, there is shown the substrate 106 together with a mask 130 that can be used for exposure to define a pattern of x-ray. The mask 130 is clamped to the substrate as indicated by lines 132 to provide the mask 130 in proximity and fixed to the substrate 106 between the substrate 106 and the highly collimated x-ray radiation source 102. Referring now the FIGS. 2 and 3, there are shown exemplary sequential steps for fabricating precision focusing x-ray collimators in accordance with the present invention. First a substrate 106 that is electrically conductive is used or the substrate 106 is coated with a thin layer of electrically conductive material 302, such as a metal suitable for use as a plating base for subsequent electroforming as indicated in a block 202. The substrate 106 may be x-ray transparent or not. Next, the substrate is coated with a layer of positive or negative x-ray resist, such as positive x-ray resist polymethylmethacrylate (PMMA), or a negative x-ray resist SU-8 epoxy described by U.S. Pat. No. 4,882,245 owned by IBM Corporation, of sufficient thickness such as 100 xcexcm to many mm, with appropriate adhesion promoters as necessary as indicated in a block 204. The x-ray resist is exposed to a pattern of x-ray by way of the synchrotron radiation source 102; the pattern delineating the grid or array of apertures to collimate the x-rays as indicated in a block 206. The exposed parts of the PMMA are removed by development in an appropriate solvent as indicated in a block 208. Metal capable of absorbing x-rays, such as gold, nickel, copper, platinum, zinc, lead, tin and alloys thereof, or another galvanic metal, is electroplated into the regions where the x-ray resist has been removed, starting from the previously deposited plating base as indicated in a block 210. Optionally, the surface is refinished to planarize as indicated in a block 212. Next remaining resist is optionally removed as indicated in a block 214. Finally, an optional substrate removal to release the grid may be provided as indicated in a block 216. During the exposure of the x-ray resist 304 carried by the substrate 106 to a pattern of x-ray by way of the synchrotron radiation source 102 at block 206 in FIGS. 2 and 3 can be varied to fabricate non-focusing or precision focusing x-ray collimators in accordance with the present invention. During exposure for non-focusing x-ray collimators, the substrate 106 is normally kept perpendicular to the impinging x-rays. For example, assume that the x-rays are propagated horizontally in the Y-direction as shown in FIG. 1B. With the synchrotron radiation source 102, the x-rays from the electron storage ring bend magnet, while highly collimated, are confined to a horizontal plane, such as a plane in the X-direction. As a result, to expose a two-dimensional area on the substrate 106, the substrate is scanned vertically in the Z-direction. If the substrate 106 is aligned to the X-Z plane, the x-rays will impinge normal to the substrate surface and the final collimator will provide collimation in the same direction, without focusing. During exposure for precision focusing x-ray collimators, the substrate is scanned in the Z-direction while the angle of inclination of the substrate is varied as a function of the position in the Z-direction during the scan to produce the precision focusing x-ray collimators. In accordance with a feature of the invention, when the substrate 106 is inclined with respect to the Z-direction, while still aligned in the X-direction, the exposure has the same relative angle to the substrate, and the final collimator provides collimation in the inclined direction. A collimator can be formed that focuses in one direction by changing the angle the substrate forms with respect to the exposing x-rays while the substrate 106 is being scanned through the beam in the Z-direction. This is done by placing the substrate 106 on the scanner stage 110 that can rotate in the Y-Z plane about the X-axis, and changing the angle as the substrate 106 is being scanned vertically in the Z-direction. The angle of inclination can be controlled mechanically by fixing an arm to the scanner stage 110 and to the position of the desired focus located in the plane of the exposing x-rays. Alternatively, the angle of inclination can be precisely controlled with the scanner controller 112. It should be understood that the production of a collimator that focuses in two directions can be achieved by first exposing through a grating mask in one direction, then rotating the substrate by 90 degrees in the X-Z plane while keeping the grating mask fixed. Then exposing again so that the sum of the exposures is a two-dimensional grid with a variable angle of inclination with respect to the substrate surface as a function of distance from the center of both the X and Z directions. Also, by selectively varying the relationship of the angle of inclination to the Z-position, a resulting collimator is produced that focuses at different distances for X versus Z, or may provide different focus distance as a function of the distance from the center of the collimator. While the present invention has been described with reference to the details of the embodiments of the invention shown in the drawing, these details are not intended to limit the scope of the invention as claimed in the appended claims.