MULTILAYER RESIST DRY-ETCHING TECHNOLOGY FOR DEEP-SUBMICRON LITHOGRAPHY

Using an O2+HBr mixed gas plasma, multilayer resist dry etching under low substrate temperature is applied to the 0.25 mum design-rule 256Mb dynamic random access memory fabrication. Anisotropic etching profile s with a critical dimension (CD) loss less than 0.02 mum are obtained by optimizing the amount of HBr in the plasma. With exceeding amounts of HBr, the pattern width varies with the spacing of the patterned lin es due to variations of the thickness of deposited on the resist sidew all, causing a large CD loss. This phenomenon is named ''the pattern-d ependent deposition.'' An increase in the HBr flow rate enhances the p attern-dependent deposition. It is also found that the resist overetch ing can cause the pattern-dependent deposition. An electron dispersive x-ray spectroscopy analysis reveals that under etching conditions of the pattern-dependent deposition, the characteristics of deposited fil m are similar to that of an oxidized silicon film. In comparison, the deposited film is close to the silicon-rich film when there is no patt ern-dependent deposition. A mechanism, of the pattern-dependent deposi tion is discussed.