| 摘要 |
<p>An electrostatic clamp (20) or chuck and method uses soft square wave, slew rate limited, A.C. clamping voltages and a balanced, differential drive for clamping flat articles such as semiconductor wafers (14) to pedestals (5), wafer transfer blades (19), and the like, with a large ratio of clamping force to clamping voltage, reduced decay of the clamping force and associated nearly constant maximum clamping force, instantaneous elimination of remnant clamping force when the clamping voltage is removed (instant off operation), isolation of the clamped article from the clamping voltage, and substantial elimination of vibration. Preferably, the A.C. frequency is 0.1 to 60 Hz. The instant off operation is enhanced by increasing the frequency as the clamping voltage is decreased. <IMAGE></p> |
