| 摘要 |
1319882 Polishing MONSANTO CO 20 Oct 1971 [21 Oct 1970] 48805/71 Heading B3D A process for polishing a wafer 44, such as a semi-conductor, comprises pressing the wafer between a mounting pad 40 and a polishing surface 17, the coefficient of static friction between the wafer and mounting pad being greater than the coefficient of static and dynamic friction between the wafer and the polishing surface, and producing relative motion between the polishing surface and the wafer, the wafer remaining fixed with respect to the mounting pad as a result of the different coefficients of friction. In apparatus for carrying out the method, the polishing surface is of poromeric material such as fibre reinforced polyurethane foam mounted with its substrate surface exposed on a turn-table 14 spaced from an outer wall 12 whereby a space 16 therebetween permits a polishing agent, such as silica sol supplied in droplets 50 to flow freely away from the table. The mounting pad 42 is also of poromeric material and is secured to a disc 40 with its front surface, i.e. its high friction surface which is a coating of unreinforced microporous polyurethane exposed. The disc is mounted by a spherical bearing 36 on a pin 32 extending from an arm 22 carried by a shaft 24 controlled for vertical and horizontal movement. The wafer 44 is initially held by surface tension on the pad 42 and is then pressed against the polishing surface 17, the higher friction retaining the wafer on the pad as it is rotated by the rotation of the turn-table. In another embodiment, the polishing surface has an outer annular area 18, Fig. 3, of low friction poromeric substrate material and an inner area of higher friction material such as polyester reinforced polyurethane with its front surface exposed. In the first embodiment, after polishing, the wafer is removed from the pad by a suction tool, whereas, in the second embodiment, at the end of polishing by the surface 20, a rotational impulse of the turn-table releases the wafer from the pad. More than one wafer may be polished at the same time by having a plurality of mounting pads carried by pins on arms extending from the arm 22. The wafer may be a refractory oxide or magnetic bubble material. |
