Reticle processes for 256-Mbit DRAM

In manufacturing 256-Mbit DRAM reticles, it is said that 4x reticles will be required. In this case, we must control 1.0 micrometers patterns on the reticle. Therefore, to achieve this accuracy, we need to solve some problems at various stages in manufacturing including exposure, process, and inspection. We studied the process and tried to solve some problems. As a result of our experiments, some effective methods were found. They are: (1) use of thinner resist; and (2) improvement of etchant and the wet etching method. This has the advantage of only needing minor changes of existing techniques. This paper describes the effects of these techniques and the critical dimension (CD) uniformity of reticles.