Patent Number: 
Section: description

Referring to FIG. 1, there is shown a partially cutaway perspective view of an electron beam device 10 with a deflection lens for use in electron beam lithography in accordance with the principles of the present invention. The electron beam device 10 includes a tapered envelope 12 having a circular cross-section. Disposed on an end of the envelope 12 is a mounting socket 14 (partially shown in the figure) for electrically connecting the electron beam device 10 to a source of electrical power as well as to a source of control signals for operation of the electron beam device. Electron beam device 10 includes an electron gun 16 which is attached to and electrically coupled to the mounting socket 14. Electron gun 16 generates energetic electrons and forms the electrons into a beam 40 as shown in the partial sectional view of the electron beam device of FIG. 2. For simplicity, the electron beam device""s envelope has been omitted from the sectional view of FIG. 2. Energetic electrons in the electron beam 40 travel in the direction of the arrow heads superimposed on the electron beam as shown in FIG. 2. The energetic electrons in the electron beam 40 are directed by the electron gun 16 along a longitudinal axis 38 (shown in the figures in dotted line form) of the electron beam device 10. Electron beam 40 initially transits an electron beam limiter 18 comprised of first, second and third apertured plates 20, 24, and 28. An exploded perspective view of the electron beam limiter 18 is shown in FIG. 1a. Each of the first, second and third plates 20, 24 and 28 is in the general form of a flat, round disk with each of the disks aligned along the axis 38 of the electron beam device 10. First plate 20 includes a center circular aperture 20a. Second plate 24 also includes a center circular aperture 24a. Finally, third plate 28 includes a center circular aperture 28a. The electron beam is directed through the three aligned apertures 20a, 24a and 28a in the first, second and third plates 20, 24 and 28. As shown in FIG. 1a, the three apertures 20a, 24a and 28a are of different sizes, with aperture 20a being the largest and aperture 28a being the smallest. Thus, the three beam passing apertures 20a, 20b and 20c are of decreasing size in proceeding in the direction of travel of the electron beam. Each of the three apertures 20a, 24a and 28a is sized so as to intercept a peripheral portion of the electron beam directed through the aligned apertures. Thus, aperture 20a intercepts a peripheral portion of the original electron beam, resulting in a reduction in the cross-section of the beam. Similarly, aperture 24a intercepts the peripheral portion of the reduced electron beam to further reduce the cross-section of the beam, with the beam then directed through aperture 28a in the third plate 28. Aperture 28a further reduces the cross-section of the beam to provide the beam with a very small cross-sectional area to produce a well defined electron beam spot size of very small dimensions on a target 36 which is aligned with the electron beam device 10 so as to intercept the electron beam. In the present example, target 36 is a substrate on which is formed an integrated circuit pattern by the electron beam 40 as it is displaced over the substrate in a manner described below. Disposed between adjacent apertured plates and aligned along the electron beam device""s longitudinal axis 38 are respective beam centering electrodes. Thus, a first beam centering electrode 22 is disposed intermediate the first and second apertured plates 20, 24. Similarly, a second beam electrode 26 is disposed intermediate the second and third apertured plates 24, 28. Each of the first and second beam positioning electrodes 22, 26 is coaxially disposed about the electron beam device""s longitudinal axis 38 and is comprised of plural electrode elements disposed in a spaced manner about the axis. Thus, the first beam positioning electrode 22 includes first, second, third and fourth electrode elements 22a, 22b, 22c and 22d. The four electrode elements are symmetrically disposed about the electron beam device""s longitudinal axis 38 in a spaced manner with the electron beam transiting the space between the four electrode elements. The second beam positioning electrode 26 similarly includes first, second, third and fourth electrode elements 26a, 26b, 26c and 26d which are symmetrical disposed about axis 38 in a spaced manner. Each of the electrode elements in each of the first and second beam positioning electrodes 22, 26 is connected to a set of voltage sources for electrostatically charging the electrode elements. This can be seen for the case of electrode elements 22a and 26a which are shown in FIG. 2 connected to voltage sources V4 and V5, respectively. The second and fourth electrode elements of each of the first and second beam centering electrodes 22 and 26 are similarly connected to respective voltage sources for electrostatically charging the electrode elements. Pairs of electrode elements in each of the first and second beam centering electrodes 22, 26 diametrically disposed on opposed sides of the axis 38 electrostatically center the electron beam 40 within the three aligned apertures 20a, 24a and 28a respectively in the first, second and third plates 20, 24 and 28. The relative polarity and voltage difference between diametrically opposed electrode elements is used to precisely position the electron beam. This ensures that the most intense, or densest, portion of the electron beam 40 is used for forming the reduced cross-section electron beam incident on the target 36. Referring to FIG. 1b, there is shown another embodiment of an electronic beam limiting arrangement for use in the present invention. FIG. 1b is a sectional view, where even the electron beam 62 is shown in section. Electron beam 62 first transits a beam centering device 64 having an aperture 64a through which the beam is directed. Beam centering device 64 electrostatically centers the electron beam 62 as described above in terms of the previously described embodiment. After transiting the beam centering device 64, the electron beam 62 is then directed through a tapered aperture 66a in a beam limiting plate 66 as the beam travels in the direction of arrow 65. Tapered aperture 66a reduces the cross-section of the electron beam 62 as the beam transits the beam limiting plate 66 as shown in the figure. The beam limiting plate 66 is preferably comprised of a heat resistant metal such as platinum having a thickness sufficient to dissipate the heat generated by electron beam 62 incident upon the plate. Electron beam 40 is focused on the target 36 by means of the combination of a first focusing electrode 30 and electrostatic electron lenses 32 and 34. As shown in the figures, the first focusing electrode 30 is preferably in the form of a hollow cylinder aligned along the electron beam device""s longitudinal axis 38. Electrostatic electron lens 34 may also be in the form of a hollow cylinder aligned coaxially with the electron beam device""s longitudinal axis 38 as shown in FIG. 2. Electrostatic electron lens 34 may also be in the form of first, second, third and fourth lens elements 34a, 34b, 34c and 34d as shown in FIG. 1. Each of the lens elements is in the form of a rectangular, flat plate, with the plates arranged concentrically about the electron beam device""s longitudinal axis 38 in a spaced manner. The plane of each of the first, second, third and fourth flat lens elements 34a, 34b, 34c and 34d is aligned parallel with the electron beam device""s longitudinal axis 38 or they may be tapered. A first focus voltage VF1 is provided to the first cylindrical focusing electrode 30, while a second focus voltage VF2 is provided to the electrostatic electron lens 34. Where the electrostatic electron lens 34 is comprised of the four lens elements 34a, 34b, 34c and 34d shown in FIG. 1, the second focus voltage VF2 is provided to each of the four lens elements. First and second electrostatic lenses are formed between the first focusing electrode 30 and an electron beam deflector 32 and between the electron beam deflector 32 and the electrostatic electron lens 34. In combination, the first focusing lens formed by electrodes 30 and 32 and the second focusing lens formed by electrodes 32 and 34 focus the electron beam 40 to a small spot on target 36. Disposed intermediate the first cylindrical focusing electrode 30 and the electrostatic electron lens 34 and also aligned along the electron beam device""s longitudinal axis 38 is the aforementioned electron beam deflector 32. In the described embodiment, electron beam deflector 32 is comprised of first, second, third and fourth generally flat deflector plates 32a, 32b, 32c and 32d. By applying an appropriate polarity and dynamic voltage value to each of the four deflector plates, the electron beam 40 is displaced over the target 36 in tracing out an electronic integrated circuit pattern on the target. The first and third lens elements 32a, 32c displace the electron beam 40 in a first direction while the second and fourth lens elements 32b, 32d displace the electron beam in a second direction. The first and second directions are transverse to one another, allowing the electron beam 40 to trace out a two-dimensional raster figure representing an electronic integrated circuit pattern on the target 36. A first dynamic sweep voltage VS1(t)+VF is applied to the first lens element 32a, while a second dynamic sweep voltage VS2(t)+VF is applied to the third lens element 32c as shown in FIG. 2. This permits the first and second lens elements 32a, 32c to displace the electron beam 40 in a direction generally in the plane of the figure. A similar sweep voltage arrangement is applied to the second and fourth lens elements 32b, 32d to displace the electron beam 40 in a direction generally perpendicular to the plane of the figure. A combination of the four electrostatically charged deflector plates deflects the electron beam 40 in two dimensions as the beam traces an electronic circuit pattern on target 36. Various voltages are provided to the components of the electron beam device 10 as shown in FIG. 2. Thus, Vanode is an anode voltage provided to the device""s electron gun 16 as well as to the first, second and third apertured plates 20, 24 and 28. Fixed focus voltages V1 and V2 are respectively provided to the first cylindrical focusing electrode 30 and the electrostatic electron lens 34. Time variable deflection voltages VS1(t)+VF and VS2(t)+VF change with time and respectively provided to the first and third deflector plates 32a and 32c. Similar variable voltages are provided to the second and fourth deflective plates 32b and 32d although this is not shown in the figures for simplicity. A focus VF is added to the aforementioned time variable deflection voltages to provide a composite voltage to each of the four deflector plates. The V3 is provided to the target 36. FIG. 2 also includes additional elements not shown in FIG. 1 which form another embodiment of the present invention. Shown in FIG. 2 are auxiliary deflector plates 32axe2x80x2 and 32cxe2x80x2. Another pair of opposed auxiliary deflector plates disposed to the adjacent deflector plates 32axe2x80x2 and 32cxe2x80x2 are included in this embodiment of the invention, but are not shown in the figure for simplicity. The second set of auxiliary deflector plates are disposed between the first set of deflector plates 32a-32d and the electrostatic electron lens 34. As shown in FIG. 2, the second set of auxiliary deflector plates are much shorter than the first set of deflector plates and thus provide a much shorter deflection region for electron beam 40. A voltage VS3(t)+VF is provided to deflector plate 32axe2x80x2, while voltage VS4(t)+VF is provided to deflector plate 32cxe2x80x2. Similar voltages are provided to the other two auxiliary deflector plates disposed adjacent deflector plates 32axe2x80x2 and 32cxe2x80x2. Thus, different deflection voltages are provided to the first and second sets of deflector plates as shown in FIG. 2. The first set of deflector plates including deflector plates 32a-32d are used for deflecting the electron beam 40 over the entire raster area of coverage as defined by target 36. The second deflection region defined by the supplemental deflector plates including plates 32axe2x80x2 and 32cxe2x80x2 are used for more precise positioning of the electron beam 40 on target 36. Thus, the auxiliary deflector plates including plates 32axe2x80x2 and 32cxe2x80x2 provide a region of reduced deflection sensitivity for more precise positioning of the electron beam 40 on target 36. In the preferred embodiment, the dynamic voltages provided to both the primary and supplemental deflector plates are digitized voltage for more accurate positioning of the electron beam 40 on target 36. Referring to FIG. 3, there is shown a graphic representation of electron beam density as a function of the size of a circular electron beam passing aperture for three different size apertures aligned along a common axis in accordance with one aspect of the present invention. As previously described, the first aperture plate 20 has a beam passing aperture of diameter d1, while the second aperture plate 24 has a beam passing aperture of diameter d2. The third aperture plate 28 has a beam passing aperture of diameter d3, where d1 greater than d2 greater than d3. As shown in FIG. 3, a cross-sectional diameter of the electron beam is reduced to the diameter d1 of the aperture in the first plate 20 as the beam transits this plate. The cross-sectional diameter of the electron beam is further reduced to d2 as the beam transits the second plate 24. The cross-sectional diameter of the beam is further reduced to d3 when the electron beam transits the aperture in the third plate 28. It is in this manner that the cross-section of the beam is reduced to a small spot on the illuminated target 36 by using plural, spaced plates each having a smaller beam passing aperture. The cross-section of the electron beam may be reduced to a very small size without damaging the beam limiting plates such as by melting the portion of plate upon which the high energy electron beam is incident. The multi-stage beam intercepting arrangement of the present invention avoids damage by the high energy electron beam by isolating and dividing the high energy absorption among plural beam limiting plates. The tapered beam limiting aperture described above is made possible by use of the proper heat-resistant materials and by providing the beam limiting plate with sufficient thickness to be able to dissipate the absorbed energy in the form of heat. FIG. 4 is a graphic representation of electron beam density profile as a function of the size of the electron beam passing aperture for the case of the largest beam. passing aperture in the first apertured plate 20. A comparison of FIGS. 3 and 4 shows that the second and third apertured plates 24, 28 further reduce the electron beam""s profile, or cross-section, after the beam transits the aperture in the first plate 20. Referring to FIG. 5, there is shown a multipie electron beam device array 50 in accordance with another aspect of the present invention. As shown in the figure, plural electron beam devices 52a-52f are positioned above a substrate 54 and are arranged in an Mxc3x97N matrix array for directing plural electron beams onto the substrate for simultaneously forming plural electronic circuit patterns on the substrate. In this manner, a large number of electronic circuit patterns may be simultaneously formed on the substrate 54 which may then be divided into smaller sections, each forming a separate individual semiconductor integrated circuit wafer. Alternatively, each electron beam may be incident on a separate semiconductor integrated circuit wafer for forming an integrated circuit pattern simultaneously on plural substrates. Also as shown in the figure in simplified schematic diagram form, each of the plural electron beam devices 52a-52f is attached to and supported by a support/displacement mechanism 56 (shown in the figure in dotted line form). The support/displacement mechanism 56 is connected to each of the electron beam devices 52a-52f for supporting and displacing the electron beam devices in simultaneously forming plural electronic circuit patterns on the substrate 54. The support/displacement mechanism 56 is shown simply as a planar element engaging and supporting each of the electron beam devices 52a-52f, but may take other forms such as separate mechanisms for supporting and displacing each of the electron beam devices. The support/displacement mechanism 56 may include convention displacement means as such as a stepping motor. In the alternative, each of the electron beam devices 52a-52f may be attached to a fixed support/displacement mechanism 56 and the substrate 54 may be displaced so that each of the respective electron beams trace out a separate electronic integrated circuit pattern on the substrate. Also as shown in the figure, each individual electron beam device may be connected to a common shared electronics drive circuit 42 which provides electric power and control inputs to each device. The shared electronic drive 42 provides such inputs as high voltage, focus voltages, dynamic deflection voltages, video drive signals, etc., to reduce the cost of the matrix array of electron beam devices. Referring to FIG. 6, there is shown another embodiment of a stacked electron beam device array 70 in accordance with another aspect of the present invention. In the stacked electron beam device array 70 of FIG. 6, an upper array of electron beam devices 72 (where only one of the electron beam devices is numbered for simplicity) is positioned above a first substrate 74 for directing plural electron beams onto the substrate for simultaneously forming plural electron beam circuit patterns on the substrate. Similarly, plural lower electron beam devices 76 direct electron beams onto a second lower substrate 78 for simultaneously forming plural electron circuit patterns on the substrate. The electron beam device matrix array of FIG. 5 and the stacked matrix array of electron beam devices of FIG. 6 allows for the simultaneous manufacture of large numbers of electronic integrated circuit patterns simultaneously to increase the throughput and reduce the cost of electronic circuit manufacture. These three dimensional matrix arrays also reduce the clean room space requirements for the integrated circuit pattern forming elements which also reduces manufacturing costs involved in building and maintaining an expensive xe2x80x9csuper clean room.xe2x80x9d The matrix array and stacked matrix array of multiple electron beam devices shown in FIGS. 5 and 6 is made possible by the small size of the electron beam device of the present invention which incorporates the inventive deflection lens arrangement. While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the relevant arts that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.