Adjustable shadow mask for improving uniformity of film deposition using multiple monitoring points along radius of substrate

Abstract

A vacuum chamber deposits thin films on a substrate by sputtering a target. The beam of atoms or ions from the target is partially blocked by a shadow or adjustable uniformity mask, reducing the deposition rate onto the substrate. The adjustable uniformity mask has several adjustable fingers. The fingers extend or retract to enlarge or reduce the size of the mask. Each finger covers a different annular region or radius of the substrate. The deposition rate at different substrate radii is thus adjustable by the fingers. Several optical beams monitor the film transmittance at different substrate radii. A transmittance profile is continually generated during deposition. As deposition proceeds, radii with a thicker film have their fingers extended to reduce their deposition rate, producing a more uniform film thickness across all radii. Motors extend or retract the individual fingers.