Fine Pattern Etching of W-Ti Absorber for X-Ray Mask with Electron Cyclotron Resonance Discharge Plasmas

The process of etching an amorphous W-Ti absorber using a Cr mask and electron cycrotron resonance discharge plasmas was investigated to fabricate an X-ray mask with a resolution below 0.1 µm. Highly selective and anisotropic etching has been achieved using a mixture of SF6, CHF3 and He gases, by cooling the stage to about -50°C and with the control of the plasma conditions to increase ion assist reactions. It was also found that high selectivity (50-150) of W-Ti to Cr or ITO and a small microloading effect were advantageous to uniformly etch patterns of various sizes. Moreover, the microfabrication of a smooth W-Ti absorber has been demonstrated for lines and spaces patterns below 0.1 µm and 1-Gbit-class dynamic random access memory patterns.