4. Immersion lithography technology supports leading-edge semiconductor production

Explanatory diagram of Immersion Lithography method. Using the refractive index of purified water by filling the space between the projection lens and the silicon wafer with purified water, this method achieves a higher resolving power.

Since their advent, semiconductors have rapidly become smaller and an increasing number of functions can be achieved with them. As this evolution has progressed, Nikon has continued to develop lithography technologies with higher resolution capabilities to keep up with the ongoing miniaturization of semiconductors. With the progress of miniaturization, however, a theoretical barrier was reached that prevented existing lithography technology from handling the smaller sizes. The solution to this problem was Immersion Lithography Technology, which Nikon incorporated into its semiconductor lithography systems.

When a straw put in a glass of water is viewed from above, it appears to be bent underwater because the refractive index of water is higher than that of air. Immersion lithography uses this principle and achieves a higher resolving power by filling the space between the projection lens and the wafer with purified water—the refractive index of purified water is higher at 1.44 than that of air (1.00). In immersion lithography, purified water itself is used like a lens. This technology makes it possible to overcome the aforementioned barrier and enables exposure at 38 nanometers or less.

For today's leading-edge semiconductors, these semiconductor lithography systems use multiple patterning technology* to mass produce node processes less than 10 nanometers.
Semiconductors that have become highly integrated with immersion lithography technology are used for a wide variety of applications, making our lives increasingly comfortable and convenient.

  • *Multiple patterning refers to a circuit pattern that has been divided into two or more patterns with a feature density low enough to be printed with an existing semiconductor lithography system, and these patterns are then combined to ultimately render a high feature density.