A microscopic Raman apparatus using an ultraviolet laser has been developed for measurement of stress in semiconductor devices. A minimum laser-spot diameter of 0.4μm is obtained at 300-nm wavelengh. This is half the size of the spot diameter obtained with a conventional Raman apparatus using a visible laser. Furthermore, coupled with the high-precision scanning system, we have succeeded to measure stress distributions with 0.05μm horizontal resolution. The penetration depth of the ultraviolet laser into silicon is about 0.07μm, which is a tenth of that of the visible laser. This enables to directly measure stress fields as thin as 0.1μm from the surface of the silicon substrates of semiconductor devices.
