Quartz lens life extended.
The Osaka National Research Institute said it has developed a way to prolong the usable lifetime of the quartz glass lenses used for LSI photolithographic equipment.
By controlling the organization of the quartz glass at the molecular level, the material can be protected from the deteriorative effects of ultraviolet light, enabling the lens to be used twice as long as normal.
This, in turn, will help lower manufacturing costs for future generations of semiconductor devices, which will require the use of more powerful light sources to define their finer-scale circuit patterns. The basic technology has been confirmed and it can be quickly put to practical use, the institute said.
To make the new lens material, quartz glass is subjected to a high pressure of 2,000 atmospheres and a high temperature of 1,200 C.
When this is done, the composition becomes exacter and the atoms arrange in a less disorderly way, protecting against the decline in light transitivity that normally happens to quartz glass when it is repeatedly exposed to UV light.
Tests demonstrated that the material shows relatively little decline in light transmittivity even when exposed to X-rays, which have a far greater deteriorative effect on conventional lenses than UV light.
The more orderly the glass structure, the less tendency it has to deteriorate due to exposure to light from the krypton-fluoride lasers now used in semiconductor manufacture.
A similar effect is expected with light from the argon-fluoride lasers that will be used for next-generation chips, the institute noted. At room temperature, the composition of the glass remains in this more ordered state semi-permanently, it added. |
