Abstract: Provided is a polishing apparatus comprising a lower stool (12), a motor (18a) and a speed reducer (19a) for driving the lower stool, and a box (17) for covering at least the portion of the lower stool below the working action face. The polishing apparatus polishes a wafer by forcing the wafer to contact the lower stool and by rotating the lower stool. The box has its inside separated by partitions (31a and 31b) into a plurality of regions, and the motor for driving the lower stool is arranged in a region other than the region containing the lower stool. The polishing apparatus can manufacture a wafer of a stable shape, irrespective of the time elapsed from the running start and the presence/absence of the stop of the polishing apparatus.

Abstract: In an apparatus for lapping a wafer material, e.g., a semiconductor silicon wafer, by bonding the wafer to the lower surface of a pressing plate, mounting the pressing plate on a turn table to bring the wafer into contact with the turn table and pressing the pressing plate downwardly with a downwardly opening cup-like top ring mounted thereon, the pressing plate is pressed down not directly with the top ring alone but pressed through a rubber membrane covering the downward opening of the top ring and pressurized with compressed air under pressure regulation so that the lapping pressure on the wafer surface can be very uniform and the thus lapped wafer is excellent in respect of the flatness of each lapped surface and parallelism between lapped surfaces.

Abstract: A novel method and apparatus are provided by the invention for the precision-control of the thickness of thin work pieces under lapping in a lapping machine having an upper and lower lapping surface plates rotatable relative to each other sandwiching the work pieces with continuous supply of a lapping fluid therebetween. In the invention, the upper lapping surface place is provided with an opening in the lapping surface, in which an ultrasonic transducer means is mounted capable of projecting an ultrasonic wave to the work piece and receiving the dual echo waves reflected at the upper and the lower surface of the work piece so as that the delay time of the echo waves is transmitted as electrical signals to a control means of the lapping machine where the signals are computed in terms of the thickness of the work pieces and utilized for controlling the operation of the machine.