Diffractive lenses for high resolution laser based failure analysis

In this paper, we demonstrate a practical alternative to the conventional SIL, which overcomes the above limitations. We show that it is possible to fabricate a lens directly on the back side of the silicon of the device under test. This lens works on principles of diffractive optics and is around 250 nm thick. The lens may be fabricated in about 1 hour, using a combination of FIB ion implantation lithography, followed by plasma etching. In combination with a commercial IR microscope objective, the lens shows diffraction-limited resolution as expected from its numerical aperture. It should be noted that the lens works only for monochromatic light, but this is not a drawback when applied to laser based techniques