Uniformity & focusing

Uniformity is crucial to the lithography process. Several factors influence uniformity. When a lamp is initially installed it is adjusted within the range of the optical mirror system, which usually entails searching for the maximum intensity and best uniformity. However, maximum intensity and the best uniformity usually do not coincide. The user must adjust the lamp to meet their requirements. As the lamp ages, a slow change in uniformity occurs. This is caused by the burn back of the cathode and the resulting change in the electrode shape.