Ulrich Scheler

Application aspects of the Si-CARL bilayer process

The basic chemistry and lithographic characteristics of anhydride- containing, diazo-based NUV and DUV resists as well as silylation of top resist patterns with aqueous solutions of silicon-containing diamines in the Si-CARL bilayer process (CARL: Chemical Amplification of Resist Lines) were reported recently. This paper describes technical control of the Si-CARL process for g-line and DUV in a 6 inch pilot line using automatic equipment. Linewidth uniformity of top resist patterns is not affected by silylation and is found to be 0.045 micrometers (3(sigma) ) for nominal 0.4 micrometers lines/spaces, the resolution limit of the 0.55 NA g- line stepper used. Both overexposure and linewidth increase due to silylation conditions can be used in the Si-CARL process for optimization of defocus latitudes. With the use of a 0.55 NA g-line stepper total defocus latitudes are 2.8 micrometers for 0.6 micrometers equal lines and spaces and > 3.2 micrometers for isolated 0.6 micrometers spaces. In order to meet the requirement for sufficient throughput on KrF-excimerlaser steppers the sensitivity of DUV top resists is improved by chemical variations of resist polymers. The use of maleimide-containing resist polymers with improved alkaline solubility in diazo-inhibited top resists allows resolution of 0.25 micrometers lines and spaces at 161 mJ/cm2 on a 0.37 NA KrF-excimerlaser stepper. Further considerable improvement of DUV sensitivity to 11 mJ/cm2 was achieved using an acid-catalyzed top resist based on onium-salt and a terpolymer containing N-t-BOC-maleimide-units.