Simulation is essential to successful design of modern semiconductors

Lithographic processes belong to the most critical steps in the fabrication of m icroelectronic circuits. Optical projection lithography which transfers the layo ut of a mask into a photoresist at the top surface of a silicon wafer is still t he workhorse of semiconductor industry. Nowadays, optical lithography is pushed to its ultimate limits. The minimum feature size Dx, which can be printed on mic roelectronic circuits by optical projection methods, is given by the famous Rayl eigh equation Dx=k1´l/NA. Here l specifies the wavelength of the used monochroma tic light and NA stands for the numerical aperture of the system. The so called technology factor k1 depends on the illumination geometry, on the mask type, and on the contrast of the photoresist.