Soft-X-Ray Projection Lithography - Experiments And Practical Printers

The feasibility of using X-ray projection cameras as a practical lithography tool for making integrated circuits with tenth-micron features was investigated in experiments performed with a 20-fold reduction Schwarzschild camera operating at 36 nm and 14 nm, and with a 1:1 magnification Offner ring field system at 40 nm. The paper examines the requirements on the resist, the source, the camera design and the fabrication of its mirrors, the mask, and the alignment system. The experiments proved that high-reflectance multilayer mirrors are capable of diffraction limited imaging. Some problems exposed by the experiments, such as the deposition of carbon on surfaces exposed to X-rays, are discussed.