X-ray imaging: applications to patterning and lithography

X-ray lithography (XRL) is a patterning technique for the fabrication of semiconductor devices with very small dimensions (less than or equal to 100 nm). In this process the device and circuit layout images are formed by exposing a thin layer of organic material, the photoresist. XRL is based on the idea that the short wavelength (approximate to 1 nm) of the radiation allows a faithful reproduction of the desired pattern to very small dimensions. The physics of the interaction of the x-rays with matter dictates many aspects of the technique: the imaging process is controlled by Fresnel diffraction, and the recording process by the interaction of low-energy photoelectrons with the resist material. Phase shift effects play a key role in the image formation process, and are used to improve the sharpness of the image. To achieve high-resolution patterning it is necessary to carefully design the pattern itself, and optimize several exposure parameters. This paper presents a detailed discussion of the image formation process, and a brief review of other technical aspects of the technology.