Higher Anisotropy And Improved Surface Conditions For 90nm Node Mosionicp Dry Etch

Embedded-attenuated phase shift masks (EAPSMs) have been an indispensable enabling technology for < 130 nm node device fabrication. The precise etching of MoSiON is a key process in high quality phase shift mask manufacturing. Fluorine-based plasma chemistry has been used widely to date, but it is difficult to control CD (Critical Dimension) and phase uniformity. This stems mainly from the large Cr undercut and surface roughness due to the reaction of fluorine radicals with the phase shifting layer. In this paper, etch characteristics of the MoSiON layer using CF4, O-2, and He in an inductively coupled plasma (ICP) were examined for the manufacturing of phase shift masks for 90-nm node design rules. The dependency of etch parameters such as ICP power, bias power (DC bias voltage), pressure, CF4 concentration, and O-2 concentration on the etch properties of MoSiON were tested. We have investigated vertical slope, surface morphology, and minimum CD bias. This optimized process condition showed that intra-mask phase uniformity was below 1% (3-sigma) over a 135 mm x 135 mm mask area and transmittance uniformity was 8.68% +/- 0.09%. CD uniformity was 5.5nm (3-sigma), CD linearity was 5.0nm over 300nm to 1300nm, and Cr-to-MoSiON CD bias was 2.0nm. The MoSiON profile was nearly vertical and the surface morphology was very clean.