Patent GB-1248564-A (GB)
Title: Improvements in or relating to copying apparatus
Inventor: HORNE DOUGLAS FAVEL
IPC: G02B21/00
Filed: 1967-10-27
Abstract: 1,248,564. Photo-copying apparatus. HILGER & WATTS Ltd. Oct.24, 1968 [Oct. 27, 1967, April 19, 1968], Nos.49009/67 and 18746/68. Heading G2A. [Also in Division G1] In a method and apparatus for reproducing a pattern from one planar element, e.g. a master mask plate, on to a second planar element, e.g. a silicon slice, using a collimated beam of light, photo-electric microscopes 24 are used to sense fiducial marks on the two elements and, if the marks are not correctly aligned, photo-cells 34 and vibratory screens 32 emit signals which correct the position of the master before an exposure is made. Sequence of operations A slice Fig.4, (not shown) is placed on a station 12 and correctly positioned against stops 54, 56 by a feeler 52. An arm 8 is then swung over the station 12, lowered to pick up the slice by suction, raised and pivoted to overlie carriers 6, (4), Fig.2 (not shown). The arm 8 is lowered to be held against pads (42) on the carrier 6 by suction, the slice being coaxially spaced from its carrier (4). The latter is now raised to contact the underside of the slice, air being supplied to the carrier (4) so that it can align itself against the bottom face of the slice. The slice is then held against its carrier by suction supplied through a line (68), the suction to the arm 8 is cut off, the carrier (4) and slice are lowered to a pre-set position and the arm 8 swung away. A master mask plate, bearing fiducial marks on its bottom surface and previously correctly positioned on a station 16a or 16b, is similarly positioned over the carrier 6 by an arm 10, which then lowers the mask plate to rest on the carrier 6 where it is held by suction. No alignment of the first mask plate is required, hence the exposure is immediately effected, the fiducial marks of the mask plate being exposed as well as its pattern. During exposure a flow of nitrogen is provided between the slice and the master. After exposure they are removed, the slice being prepared for a second exposure. Then the slice and a second master are positioned as described above, the initial correct positioning on stations 12, 16a or 16b ensuring approximate alignment when on the carriers (4), 6. Microscope Operation Before the arm 8 is swung away from over the carrier (4), the fiducial marks now present on the upper surface of the slice are illuminated with non-actinic light from sources 28 (only one shown) through projecting units (26) of the microscopes, which units have now been positioned over the carriers (4), 6. The light is reflected back from the slice fiducial marks to a beam splitter 30 where the vibrating screens 32 are provided in each of two exit paths. Any misalignment between the screen mean position and the slice fiducial marks is sensed by the photo-cells 34 and the signal emitted operates servomotors 36a, (36b) Fig.3, (now shown) to move refractor blocks 38a, 38b to centre the marks on the screens. The arm 8 is swung away and the second master mask plate positioned on the carrier 6. The refractor blocks remain in their pre-set positions, any misalignment between the fiducial marks of the master and slice causing the photo-cells 34 to operate servomotors 40a, 40b, 40c to displace the carrier 6. The projecting units (26) are then removed from the exposing light path, and an exposure is made as before. The sequence of operations may be automatically controlled.