Raman spectroscopy of strain in subwavelength microelectronic devices

The use of Raman spectroscopy to determine strain in microelectronic devices is intrinsically limited by optical diffraction. The critical issue is not the limited spatial resolution itself, but rather the averaging of inhomogeneously strained regions reducing the sensitivity significantly. To eliminate this effect, we took advantage of the near-field properties of an illuminated subwavelength periodic structure. As it is possible to restrict the investigated volume to the transistor channel only, the sensitivity increases significantly. The technique is advantaged by a very small pitch of the devices, and therefore can be also used in the future technological nodes.