Resolution limits in x-ray lithography calculated by means of x-ray lithography simulator XMAS

Resolution in x-ray lithography is influenced mainly by the exposure geometry, the resist's behavior, and by the Fresnel diffraction as well. The range of photoelectrons created by the soft x-rays, which can also effect the resolution, has been investigated theoretically and experimentally. The effective range remains below 20 nm depending on the resist material and on the exposure wavelength. As the photoelectrons do not limit the resolution in synchroton lithography under practical conditions (proximity gap greater than 20 micrometers), this effect is not considered explicitly in the x-ray lithography simulator XMAS which enables the three-dimensional simulation of resist profiles. The application of XMAS to synchrotron lithography and the related one-layer resist systems reveals a Fresnel-limited resolution somewhere between 0.1 and 0.2 micrometers, depending on the actual resist parameters.