An invisible band of radiation at the upper end of the visible light spectrum. With wavelengths from 10 to 400 nm, ultraviolet (UV) starts at the end of visible light and ends at the beginning of X-rays. The primary source of ultraviolet light is the sun, and most of the UV that reaches earth is in the lower-frequency, longer-wavelength Ultraviolet "A" region (see below).
Although ultraviolet (UV) light is widely known as a disinfectant, it was also used to erase EPROM chips. After several minutes of exposure to UV light, the chip could be programmed again (see EPROM
Ultraviolet for Chip Making
For a long time, chip lithography, which exposes the silicon to a pattern of light, has been using 193 nm far ultraviolet (FUV) as the source. However, because light cannot create a pattern smaller than its own wavelength, several photomasks are used, and complex chips require dozens of lithography steps.
After 10 nm process technology came into production, extreme ultraviolet (EUV) in the 13.5 nm range is considered the next-generation light source because its wavelength is closer to the feature size (see process technology
Ultraviolet Region Nanometers (nm)
Long Wave "A" UVA 315-400
Medium Wave "B" UVB 280-315
Short Wave "C" UVC 100-280
Near NUV 300-400
Middle MUV 200-300
Far FUV 122-200
Vacuum VUV 10-200
Extreme EUV 10-121
Deep DUV Below 300
Ultraviolet in the Spectrum
The ultraviolet band comes after visible light and ends at the beginning of X-rays.