Photolithographic system including light filter that compensates for lens error

Abstract

A photolithographic system including a light filter that varies light intensity according to measured dimensional data that characterizes a lens error is disclosed. The light filter compensates for the lens error by reducing the light intensity of the image pattern as the lens error increases. In this manner, when the lens error causes focusing variations that result in enlarged portions of the image pattern, the light filter reduces the light intensity transmitted to the enlarged portions of the image pattern. This, in turn, reduces the rate in which regions of the photoresist layer beneath the enlarged portions of the image pattern are rendered soluble to a subsequent developer. As a result, after the photoresist layer is developed, linewidth variations that otherwise result from the lens error are reduced due to the light filter. Preferably, the light filter includes a light-absorbing film such as a semi-transparent layer such as calcium fluoride on a light-transmitting base such as a quartz plate, and the thickness of the light-absorbing film varies in accordance with the measured dimensional data to provide the desired variations in light intensity. The invention is particularly well-suited for patterning a photoresist layer that defines polysilicon gates of an integrated circuit device.

Dependencies are inferred from the claim text.