Characteristics of the line width variation due to lens flare and its dependency on optical parameters

In this paper, we have investigated the line width variation depending on the amount of flare in DUV (248 nm) exposure tools and the optical parameters affecting line width variation due to flare. The field to be exposed was divided into two regions. One half has the open ratio of about 0% and the other about 100%. Since the open ratio means the ratio between the diffracted light by line and space patterns and the scattered light by flare, the change in open ratio corresponds to the change in the amount of flare. Also, since flare affects the line width variation to a limited range, we can decide the flare affected range (FAR) by measuring the line width from the boundary between 0 and 100% open ratio toward each direction.