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Definition: ultraviolet light

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).

                      Wavelength in
 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.