Device Photolithography: Reduction Cameras: Optical Design and Adjustment

This paper and the paper immediately following describe the two reduction cameras which have been developed to serve as part of the photolithographic mask-making facility described in this issue. The primary pattern generator 1 generates artwork masks which are nominally 17.5 cm square. This size was determined by various optical and mechanical considerations. The two reduction cameras reproduce these masks at the two specific, reduced sizes required for use as masters for tantalum thin film circuits and interconnection substrates; the reduced masks from one of these cameras (the 3.5X camera, shown in Fig. 1) can also serve as the reticle in the step-and-repeat camera. 2 The two reduction ratios, together with the corresponding mask size and minimum linewidths, are summarized in Table I. In each size the minimum linewidth is 1/5000 of the width of the mask. This reduction in mask size carried out by the reduction cameras must be accomplished without significant loss of resolution in the 2117