Yasunari Soda

The Effects of Secondary Electrons from a Silion Substrate on SR X-Ray Lithography

The effects of secondary electrons from an Si substrate have been investigated quantitatively in SR lithography. It is confirmed that secondary electrons from an Si substrate produce undercuts of 0.1 µm in depth in the replicated resist patterns. The Si KLL Auger electron proves to be the main cause of this problem. This is ascertained through analysis of many kinds of secondary electrons. Moreover, eliminating the wavelength which excites the Si 1s electron from the exposing SR is one promising way to lessen this problem. The resolution of SR lithography is also confirmed to improve to less than 0.1 µm in the practical wavelength, if secondary electrons from the substrate are effectively minimized.

Oxidation effect on an x‐ray induced reaction of a polyolefinsulfone‐type resist

The effect of ambient atmospheric conditions during x‐ray exposure on the sensitivity of a new type positive resist, which contains poly(2‐methylpentene‐1‐sulfone) as the radiation‐sensitive compound, is studied. Resist sensitivity to x rays is seen to depend strongly on oxygen pressure during exposure. Sensitivity in air is only one‐sixth of that in a vacuum. Using Fourier transform infrared spectral analysis of the resist film following x‐ray irradiation, it is found that the alkyl radical of poly(2‐methylpentene‐1‐sulfone) generated by x‐ray irradiation is easily scavenged by the oxygen molecule in air, thus retarding its further unzipping decomposition.