Development of highly accurate X-ray mask with high-density patterns

Highly accurate X-ray masks with high-density patterns have been newly deve loped. SiC film is used as a membrane and Ta film deposited by electron cyc lotron resonance (ECR) sputtering method is used as an absorber. Ru film is deposited as an intermediate layer between the membrane and the absorber t o prevent the distortion caused by the fabrication of high-density patterns . A membrane process in which the absorber is patterned after back-etching and a distortion compensation method by electron beam (EB) writing are adop ted to reduce pattern displacement By combining these techniques, highly ac curate X-ray masks with high-density patterns, which correspond to 4-Gbit-c lass dynamic random access memory (DRAM) pattern density, can be fabricated with distortions less than 40 nm.