The important position of lithography technology in the semiconductor industry (4)

The important position of lithography technology in the semiconductor industry (4)

    ●Characteristics and etching of light waves

   Before understanding several currently active lithography technologies, let's first understand the characteristics of light waves. Light waves have multiple frequencies. Frequency refers to the number of waves passing through a point in space in any time interval (usually one second). Its unit of measurement is cycle (wave)/second, or hertz (Hz). The frequency of visible light is called color, ranging from 430 trillion Hz (red) to 750 trillion Hz (violet). Of course, the total range of frequencies is beyond the visible spectrum, from radio waves of less than one billion Hz to gamma rays of more than 3 billion Hz.

Frequency and energy of light waves

   As mentioned above, light waves are energy waves. The energy of light waves is proportional to its frequency: high-frequency light has higher energy, and low-frequency light has lower energy. Therefore, gamma rays have the highest energy and radio waves have the lowest energy. Among visible light, violet light has the largest energy, while red light has the smallest energy.

The location of EUV extreme ultraviolet light

   In the above figure, we can clearly see the position of EUV extreme ultraviolet light in the spectrum. This is a very short-wavelength lithography technology, and its exposure wavelength is about 13.5nm. According to the current theoretically believed relationship between wavelength and etching accuracy, EUV technology can etch transistors with processes below 5nm.

   With the increasing demand for integrated circuit product technology, photolithography technology has continuously improved the resolution to produce finer device sizes. The progress of global lithography technology. Traditionally, improving the resolution of photolithography is nothing more than shortening the exposure wavelength and increasing the numerical aperture NA of the lens . Generally, shortening the wavelength is one of the most effective methods.

   But at present, in terms of shortening the wavelength, various lithography equipment vendors are encountering difficulties, or shortening the wavelength has become the biggest challenge for the entire industry. Among the various active lithography technologies, EUV technology has the shortest exposure wavelength, but it is currently very difficult to advance. Although the 193nm traditional optical lithography technology is old, but with the addition of immersive technology, it has been able to extend to about 22nm process in.