Patent Number: 
Section: description

In accordance with the present invention, a system is provided for collimating and optionally focusing light, such as preferably light in the x-ray spectrum or light with wavelengths less than about 13 nanometers. Other wavelengths of light also can be collimated or optionally focussed in accordance with the present invention, as well, so long as the light is within the reflective or collimating range of the reflector or guide channel. In this description, the term xe2x80x9clightxe2x80x9d will be used synonymously with the term xe2x80x9cradiationxe2x80x9d to refer to the wavelengths that are collimated and/or focused in the present invention, for example, in the x-ray spectrum or in wavelengths less than about 13 nanometers. As illustrated in FIGS. 1-5, a source 10, such as an x-ray or other light source is provided. The figures illustrate an x-ray source, such as would be used in an x-ray lithography system in which a plasma target, located approximately at the point indicated by source 10 is excited by a beam source, such as a high energy laser, electron beam, proton beam or photon beam. The source 10 emits light in the desired wavelengths. In the figures, the emitted light is depicted diagrammatically with arrows 20. Light, such as x-rays, emitted from the source 10 is collected by the collimator 30. The collimator includes a reflector apparatus 40 and a guide channel apparatus 50. The reflector serves to gather and reflect in a desired fashion the light 20 from the source 10 that is outside the guide channel 50, but still within the reflector 40, such in the region between the guide channel 50 and the reflector 40, as illustrated in FIGS. 1-3. Any suitable reflector can be used that can reflect the light 20 from the source 10. In the preferred embodiment, the reflector 40 is adapted to reflect x-rays. In one embodiment, a conical, parabolic resonance reflector or grazing incidence reflector with a shape similar to the guide channel 50 is used to increase the solid angle collected and produce a circular, square, etc. annular x-ray beam whose inside dimensions are approximately equal to the exit dimensions of the polycapillary collimator. It should be understood that any shaped reflector 40 (for example parabolic resonance reflector or grazing incidence reflector) can be used that can achieve collimating and/or focusing the portions of the incoming light that are received and reflected by it. The shape of the exit beam generated can be any shape and does not necessarily need to match the shape of the guide channel 50, although in the preferred embodiment, the exit beam from the reflector 40 does generally match that of the guide channel 50. In the preferred embodiment, a grazing incidence reflector or resonance reflective optic can be used as the reflector 40. The reflector 40 is shaped to reflect light into a collimated orientation. In operation, a portion of the incident light 20 hits the reflective inner surface 45 of the reflector 40 and is reflected in a more linear fashion, i.e. it is collimated. The collimated light exiting collimator 30 is illustrated with arrows 60 in FIG. 1. As illustrated, the exiting light 60 preferably has a substantially collimated profile. The output beam shape, intensity profile and/or collimation angle can be adjusted, if desired, using an absorber 65. For example, an absorber 65 positioned towards the exit end 140 of the collimator 30 can adjust the intensity profile. In one embodiment, the intensity of the light exiting the collimator 30 close to the reflector 40 at the exit 140 is less intense than that slightly further away from the reflector 40 at the exit 140, but still outside the guide channel 50. Accordingly, in this embodiment, the light intensity gradually increases with distance from the reflector 40. In order to generate a flat intensity profile a graduated absorber may be used. In other words, the absorber 65 absorbs less light close to the reflector. The use of such an absorber 65 is particularly beneficial where it is desired to have a uniform intensity profile in the exiting light 60. The guide channel apparatus 50 serves to gather and transmit in a collimated fashion light 20 from the light source 10 that reaches the beginning 70 of the guide channel 50. Any suitable guide channel 50 can be used that gather the incoming light 20 and transmit it in a collimated fashion. In the preferred embodiment, the guide channel 50 is adapted to gather and transmit x-rays. In the preferred embodiment, plural guide channel elements 80 are in the guide channel 50. The guide channel elements 80 preferably include polycapillary tubes, or microchannel plates, or a combination of polycapillary tubes and microchannel plates are used in the guide channel apparatus 50. The guide channel collimates or focuses the central portion of the x-ray beam in a desired shape, such as circular, elliptic, square, or rectangular shape. The individual guide channel elements (i.e. polycapillary tubes and/or microchannel plates) are referenced with number 80 in the figures. The polycapillary tubes or microchannel plates 80 are arranged in any pattern to collect incoming light 80 and transmit it to a desired location. The individual polycapillary tubes 80 within the guide channel 50 can optionally be tapered, such as having a changing width over the length of the tube. In addition, the polycapillary tubes 80 can be monolithic such as by being bonded or melted together, or formed within a matrix. As illustrated in FIG. 1, the light 60 exiting the collimator 30 is collimated by the guide channel apparatus 50. In one embodiment, as illustrated in FIG. 1, there is a gap 85 between the guide channel elements 80 (such as polycapillary tubes or microchannel plates 80) and the reflector 40. In this embodiment, a portion of the exit beam 60 comes from the reflector and a portion from the guide channel 50. In another embodiment, as illustrated in FIG. 2, the elements 80 of the guide channel 50 extend to the reflector 40. In this embodiment, the exit beam 60 comes from the guide channel 50. In operation, a portion of the incoming light 20 is reflected off the reflector 40 and is received in one or more of the guide channel elements 80, i.e. those which are closer to the reflector 40 and oriented to receive light reflected by the reflector 40. Any geometry of the polycapillary tubes or microchannel plates 80 can be used. In the embodiment illustrated in FIG. 4, a half of a generally square cross-sectional arrangement of polycapillary tubes 80 is provided. Alternatively, a circular arrangement can be used as indicated by arc 90 in FIG. 4. One exemplary application of the collimator 30 of the present invention is in x-ray lithography or microlithography. In such lithography operations, the collimated light 60 exiting from the collimator 30 is received by a mask/photoresist on a wafer or other substrate to be processed. In a typical embodiment, the collimated light 60 is directed using directing optics and/or focusing optics to a desired location. In an alternative embodiment, it is desired to focus the emitted light. This embodiment is illustrated in FIG. 3. In this embodiment, the reflector is shaped as a focusing optic and will be referred to as a xe2x80x9cfocusing optic 42xe2x80x9d. Any shape can be selected for the focusing optic 42, which will receive the incoming light and reflect it to a focus location 120. In one embodiment, a generally elliptical cross-sectional shape is used for the focusing optic 42. In a preferred embodiment, the focusing optic 42 includes two generally parabolic reflectors 40 linearly arranged. In the embodiment where two reflectors 40 are used, the reflectors optionally may have the same profile, or alternatively may have different profiles. The upstream reflector portion 46 preferably has the same profile as the downstream reflector portion 48, resulting in a reflection of the light towards a focus point 120. Using a focusing optic 42 is of particular use in non-lithography applications, such as tomography, x-ray photoelectron spectroscopy, x-ray diffraction, x-ray microscopy and x-ray flourescence. It should be noted that, for ease of illustration and discussion, FIGS. 1-4 illustrate a cross-section of a top portion of collimators in accordance with the present invention. A full cross-section of the embodiment illustrated in FIG. 1 is shown in FIG. 5. In operation, incident light 20, such as x-rays, is received by the collimator, such as through an aperture 130. A portion of the incident light 20 is reflected off reflector 40 and exits via exit aperture 140. Another portion of the incident light 20 is received within and guided through the guide channel and exits via exit aperture 140. The intensity of the exiting light 60 can be adjusted such as by absorber 65, which preferably is positioned at or near the exit aperture 140. In the x-ray embodiment, the exit light can be used for x-ray lithography, such as in the manufacture of integrated circuits and other electronic components. Thus, it is seen that an apparatus and method for collimating light, such as x-rays or other wavelengths is provided. One skilled in the art will appreciate that the present invention can be practiced by other than the preferred embodiments, which are presented in this description for purposes of illustration and not limitation. It is noted that various equivalents for the particular embodiments discussed in this description may practice the invention as well.