Resolution enhancement technologies are methods used to modify the photomasks in the lithographic processes used to make integrated circuits (ICs or "chips") to compensate for limitations in the optical resolution of the projection systems. These processes allow the creation of features well beyond the limit that would normally apply due to the Rayleigh criterion. Modern technologies allow the creation of features on the order of 5 nanometers (nm), far below the normal resolution possible using deep ultraviolet (DUV) light. Background Integrated circuits are created in a multi-step process known as photolithography. This process starts with the design of the IC circuitry as a series of layers than will be patterned onto the surface of a sheet of silicon or other semiconductor material known as a wafer. Each layer of the ultimate design is patterned onto a photomask, which in modern systems is made of fine lines of chromium deposited on highly purified quartz glass. Chromium is used because it is highly opaque to UV light, and quartz because it has limited thermal expansion under the intense heat of the light sources as well as being highly transparent to ultraviolet light. The mask is positioned over the wafer and then exposed to an intense UV light source. The UV light drives chemical reactions in a thin layer of photoresist on the surface of the wafer, causing the photographic pattern to be physically recreated on the wafer. When light shines on a pattern like that on a mask, diffraction effects occur. This causes the sharply focussed light from the UV lamp to spread out on the far side of the mask and becoming increasingly unfocussed over distance. In early systems in the 1970s, avoiding these effects required the mask to be placed in direct contact with the wafer in order to reduce the distance from the mask to the surface. When the mask was lifted it would often pull off the resist coating and ruin that wafer. Producing a diffraction-free image was ultimately solved through the projection aligner systems, which dominated chip making through the 1970s and early 1980s. The relentless drive of Moore's law ultimately reached the limit of what the projection aligners could handle. Efforts were made to extend their lifetimes by moving to ever-higher UV wavelengths, first to DUV and then to EUV, but the small amounts of light given off at these wavelengths made the machines impractical, requiring