TERS applications to silicon strain characterization

Arianna LUCIA, CNIS Sapienza Università di Roma and Giuseppe MOCCIA, LFoundry

Ever since the Tip-Enhanced Raman Spectroscopy technique was developed in early 2000s, the research about nanotechnology world has demanded more and more often the capability to study and analyze nanometrical objects in a rapid way. Some instruments have nanometrical sensitivity, but they don’t entirely fulfill the metrology and analysis requested specifications. Through Raman spectroscopy it’s possible to learn much information about an element, but the diffraction’s limit on spatial resolution prevents the studies on nanometrical scale. Connecting this technique with the scanning microscopy allows to overtake this limit; the result is the Tip-Enhanced Raman Spectroscopy (TERS). In this technique we have the simultaneous use of an atomic force microscope and a Raman spectrometer.

The TERS spectrum is different from a Raman spectrum because the enhanced signal from the sample area next the tip apex gives unique and different information and only from the surface sample. With TERS we can have overlapping data from the sample: chemical, physical and topographycal information. We can detect different features of the sample, about its quantity, its crystallinity and its lattice strain, with nanometrical resolution. All this data are connected with a topographycal sample map. The technique is non-destructive and has short time period measurements.  In manufacturing world, especially in semiconductor and electronical industries, the miniaturization trend leads to produce ever smaller devices. This technique can present an advantageous approach to characterize device surfaces. The technique has the capability to observe and detect the localizated strained silicon on a real device, with a nanometric spatial resolution comparable with the tip radius and a resolution power greater than the conventional micro-Raman.

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