A 100-nm patterned x-ray mask technology based on amorphous SiC membranes

A mask technology based on amorphous SiC membranes and stress minimized W and Au absorbers has been developed to reach 100-nm critical linewidth pattern. Using low temperature techniques, plasma-enhanced chemical vapor deposition and rf triode sputtering, very smooth large membranes (45×45 mm2 with a surface roughness <5 nm) have been produced. Two absorber technologies have been developed: gold electroplating in a cyanide bath and tungsten rf sputtering with subsequent dry etching. Induced film stresses were investigated as a function of the absorber microstructure and minimized by a fine adjustment of the deposition parameters. With a new process, based on a single patterned resist layer, we succeeded in transfering patterns with linewidth down to 100 nm. To demonstrate the dimensional quality of the x-ray masks, x-ray exposures have been performed under synchrotron radiation at Super-ACO:150-nm-wide line and 450-nm-wide space gratings have been obtained in 1.7-μm-thick PMMA resist by contact printing. This faithfully replicates the mask patterns.