Looking back: Artwork and mask making in Dresden for the east german megabit chip project

After the early mask making during the 1960`s in Dresden has been discussed at the 19th EMC now the view is focused to the further mask making efforts in Dresden, where the leading East German labs for research and development of microelectronics had been located. The mask making processes developed continuously, but one can recognize some different periods. First a three-stage process realized artwork originals - reticles - masks. Then a two-stage process realized reticles - masks. In the end a one-stage process realized only the reticles which were applied to the wafers by means of a waferstepper. Technology and equipment of the mask processes were developed in cooperation with other East German companies such as Carl Zeiss Jena. Some examples for microlithographic equipment are given. Finally, late in the 1980`s, in the "VEB Forschungszentrum Mikroelektronik Dresden" ZMD a high technology equipment existed which met the microlithographic challenges of a Megabit DRAM technology: chip size of about 13 mm x 5 mm, minimum features of about 1 µ. Mask making occured with the e-beam writer ZBA21, mask application was carried out with the waferstepper AÜR. The specific parameters are listed and the arrangement of the chip design (1MbitDRAM chip U61000) on the reticle is discussed with respect to the image field conditions. Some pictures show the ground plan of the reticles and the reticle masks, which were made on chromium coated glass blanks 125 mm x 125 mm.