Patent GB-1227821-A (GB)
IPC: H01L21/027
Filed: 1968-05-13
Abstract: 1,227,821. Contact printing on to semi-conductors; optical apparatus, KASPER INSTRUMENTS Inc. May 13, 1968 [June 1, 1967], No. 22695/68. Heading G2A and G2J. Apparatus for aligning a mask with a workpiece, e.g. a semi-conductor chip, having a light-sensitive film to be exposed through the mask, comprises relatively movable first and second holders for the mask and workpiece, an optical unit including an ocular lens system, a rotatable turret having a plurality of positions, at least one objective lens system mounted on the turret for alignment with the ocular lens system in at least one of the turret positions to provide a magnified view of the mask and the workpiece on the first and second holders, and an illumination system including an optical element mounted on the turret for directing light on to the workpiece through the mask in another of the turret positions to expose the light-sensitive film on the workpiece. A split field microscope objective has semi-transparent mirrors 248, Fig.5, positioned on the axes at an angle of 45 degrees serving to reflect light from tungsten lamps 181 on to the mask 40 and workpiece 38, the mask and workpiece being viewed through a binocular eyepiece, the ocular lens system 152, reflective surfaces formed on right angled prism 182A and mirrors 201A. The separation of the optical axes of the split field lens system is adjustable by resiliently mounting lens retaining blocks (189), (190) Fig. 4, (not shown) on pins (192), an adjustable wedge shaped member 202 urging the blocks to move on the pins against the action of springs 196 carried on the pins. The workpiece is held in position by a vacuum chuck comprising a perforated plate 564, Fig. 11, covering a grooved chuck plate 560 which is connected to a vacuum source by a flexible pipe 576. The chuck plate is connected to a sleeve 552 which telescopically surrounds a wall 546 and is axially slidable therealong. By applying compressed air to chamber 548, the workpiece is raised to contact the mask. During the alignment process, the workpiece is lowered so as to be just out of contact with the mask, a ring 588 locked to the sleeve by applying compressed air to flexible tube 592 limiting movement of the sleeve. The holders carrying the mask and workpiece may be moved as a unitary structure for positioning in the microscope field by adjustment of a lever (394) Fig.8, (not shown) attached by a ball and socket joint (396) to a fixed plate (398) and by a further ball and socket joint 404 to a bracket (406) connected to a platform carrying the mask and workpiece holders. Relative movement between the holders is effected by the lever and socket arrangement shown in Fig.9. Vacuum lines 462, 446 are selectively connected to a vacuum line by switch 464 and secure vacuum plate 450 or vacuum plate 440 to base plate 430, in the former case fine adjustment of the holders is effected by the lever action between gimbal suspension 468 and ball and socket joint 448, arid in the latter case coarse adjustment is effected by lever action between the gimbal suspension and ball and socket joint 438. After alignment, the workpiece is raised to contact the mask, a mirror is positioned above the assembly by rotation of the turret and exposure from an ultraviolet lamp made by raising a filter positioned in the light path from the lamp for a timed interval. A loading slide (652) Fig. 12, (not shown) and an ejector slide (654) serve to transport workpieces to and from the chuck, the workpieces being angularly arranged thereon according to the crystalline structure of the semi-conductor chip by a flat portion of a generally circular chip cooperating with a V-shaped head (666) on the loading slide. Coarse and fine rotational adjustment of the chuck relative to the mask is obtained through bevelled gears 610, 612, Fig. 11, attached to control shaft 614.