A nondestructive analysis technique for residual thin films in deep-submicron contact holes

A new type of scanning electron microscope has been developed to check for residual materials in deep-submicron contact holes without cracking the wafer. To detect the characteristic X-rays emitted from resudues, the microscope has an energy-dispersive X-ray detector located near the electron beam axis between the condenser and objective lenses. When the residual materials are irradiated with a focused low energy (2 keV) electron beam, we can easily identify materials and determine their amount from the observed X-ray energy and intensity. The analysis technique can detect a 20 nm thick SiO2 film remaining at the bottom of a 0.2 μm diameter contact hole (2 μm deep) patterned on a SiO2 layer. This technique is a key tool to speed up the development of semiconductor devices and improve production yield in its fabrication process.