Abstract

A vacuum spinner chuck having improved holding power for thin wafers is obtained by providing a retention means for moveably holding an O-ring on the peripheral edge of the chuck. There is a first part-circular portion adjacent the upper surface of the chuck, arranged so that in the absence of vacuum the O-ring protrudes above the chuck surface and contacts the wafer. Below this first part-circular portion is a second sloped portion which tilts away from the surface of the spinner chuck by an angle preferably in the range 30-60 degrees. There is a smooth transition between these two portions. When vacuum is applied to the space between the wafer and the chuck, the wafer presses on the O-ring causing it to stretch and move down from the part-circular portion onto the sloped portion until the wafer rests on the surface of the chuck. The stretch creates an opposing force which holds the O-ring in contact with the wafer and the spinner chuck to prevent loss of vacuum. The stretch automatically returns the O-ring to its initial position when the vacuum is removed. The holding power of the chuck is doubled.