Performance improvement in electron-beam reticle writing system

Several experiments in order to improve throughput and accuracy have been carried out on electron beam reticle writing system which adopts variably shaped beam, vector scanning, and continuously moving stage. Stage speed optimization process by the stripe is introduced to reduce the writing time loss which arises from constant stage speed through writing a reticle. As a result, writing time decreases to 2/3 on average and the throughput of 2 reticles of 64 Mbit DRAM class per hour can be realized. Substrate clamping configuration for writing and measuring machine affects the substrate flexure and deteriorates the global positioning accuracy. The change of clamping point number form 4 to 3 for each machine improves the reproducibility of global distortion to 47% or more. The multipass writing method is effective to reduce stripe stitching error and fluctuation of the main-field position. In the case of multiplicity of 4, stripe stitching error and fluctuation of the main-field are 20 nm and 13 nm, respectively. The writing time ratio compared with single-pass writing is 1.6 even in 4-pass writing. Therefore, throughput should also be emphasized in view of accuracy improvements.