Device Photolithography: The Step-and-Repeat Camera

In previous papers, the equipment for converting the designer's topography into a primary pattern and the subsequent reduction in size have been described. For thin film integrated circuits, the output of the reduction camera is the master mask from which working copies can be produced for use in fabricating the device. For semiconductor devices, however, the output of the reduction camera is ten times larger than the required final image size. Thus, a further reduction in size is required. In addition, a mask for a semiconductor device consists of an array of images that are precisely placed on the master mask. Thus, the step-and-repeat camera is both a reduction camera and, through the use of a moving X-Y stage, permits the placement of images in an array covering the desired field of the mask. l.i Requirements If a final mask consisted of a single image and if only one mask level were required to produce a functioning semiconductor device, the stepand-repeat camera would be a simple tool to design and build. In 2145