Cost-effective pattern generation for 64 Mb and 256 Mb photomasks

The specifications of reticles for 64 Mb and 256 Mb DRAMs (0.35 mu m and 0.25 mu m design rules) show that the use of leading edge pattern generators is not required for all levels. By using writers optimized for the requirements of each level a lower total cost can be achieved. A laser reticle writer will be described that can be used together with a leading edge system in a mix and match mode. The writer has the capability to expose the new 230 x 230 x 9 mm reticle standard. In addition to larger die size the increased reticle size gives a throughput advantage since more die fit on each reticle. Introducing the 230 mm reticles at levels with less stringent specifications, lowers the technical risk compared to introduction at the critical levels. The higher productivity of the 230 mm also makes it feasible to use advanced DUV step and scan tools for a larger number of levels. The innovative data path design of the pattern generator allows the pattern data to be processed sufficiently fast not to limit the writing speed. This makes write times independent of pattern complexity. The pattern registration is addressed by a very rigid stage design and an innovative stage surface. Mix and match capability is enhanced by using an adjustment method for the coordinate system to fit a measuring tool or a different pattern generator.