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Definition: ultraviolet light

An invisible band of radiation with wavelengths from 400 to 10 nm, ultraviolet (UV) light 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 light that reaches earth is in the lower-frequency UVA 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 can be programmed again (see EPROM).

Ultraviolet for Chip Making
Chips are made by using lithography to create the layers of a transistor. Each layer is exposed to light through a pattern (mask), and for a long time, far ultraviolet (FUV) was the light source for state-of-the-art chips. However, because light cannot create a pattern smaller than its own wavelength, to make the transistor elements even smaller, extreme ultraviolet (EUV) has become the latest light source for chips 5 nm and below. Netherlands-based ASML Holding makes the EUV stepper machines, which are extremely expensive. See reticle, photolithography and EUV machine.

Before and After EUV
EUV is state-of-the-art, but larger-wavelength DUV and FUV are more than adequate for the billions of microcontrollers made every year. There are myriad applications for chips that do not require the fastest and most advanced processing. Of course, microcontroller chips costing as little as 50 cents today are much more powerful than the first commercial computers that in today's dollars cost more than a million (see microcontroller and UNIVAC I).

Instead of the photolithographic techniques used today, X-rays and electron beams are envisioned to create the patterns on future chips in order to shrink transistors below one nanometer (see angstrom era and process technology).

  Ultraviolet Region         (nm)

  UVA  Long-wave "A"       315-400
  UVB  Medium-wave "B"     280-315
  UVC  Short-wave "C"      100-280

  NUV  Near ultraviolet    300-400
  MUV  Middle ultraviolet  200-300
  DUV  Deep Ultraviolet     < 300
  FUV  Far ultraviolet     122-200
  Ly-a Lyman-alpha         121.6
  VUV  Vacuum ultraviolet   < 200
  EUV  Extreme ultraviolet  10-121

Ultraviolet in the Spectrum
The ultraviolet band is between visible light and X-rays.