NEW DRY SURFACE-IMAGING PROCESS FOR X-RAY-LITHOGRAPHY

Ultra-LSIs (ULSIs) now require innovative microfabrication processes to achieve gigabit-scale integration. In order to meet this requirement, a new surface-imaging process involving the dry development of polysilane resist is investigated for use in X-ray lithography from the viewpoints of achieving a dry development process and of improving resolution. Poly(cyclohexylmethylsilane) (PCHMS) is used for the dry-developing surface-imaging layer. We confirm that PCHMS has positive-tone characteristics by ultraviolet (UV) absorption spectroscopy and photon-stimulated ion desorption (PSD) measurements. PSD analyses also clarify that chain side groups of polysilane are desorbed prior to Si-Si backbone desorption, and that heating drastically improves dry-development sensitivity. PCHMS patterns replicated by dry-development can be transferred to the bottom layer resist by O2 reactive-ion etching and, as a result, high-aspect-ratio resist patterns can be replicated. The possibility of applying this process to X-ray projection lithography is also discussed.