MICROSCOPY AND IMAGING
The advancement of semiconductors is among the most vital endeavours in technology
Compound Semi-
Doping and Topographic Variation Visualised by Tomas Meyer, Judith Beer and Damon Strom - Oxford Instruments WITec
emiconductors are the materials from which the engines of the information age are built, and their
Conductor Analysis WITH CORRELATIVE RAMAN IMAGING Based on inelastic light scattering
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advancement is among the most vital endeavors in technology. The first step in their production generally involves crystal growth and sectioning into thin wafers. The wafers are then altered using methods such as doping to give them specific electronic properties. Access to the subtlest details of these chemical and structural modifications on the sub-micrometer scale is crucial in new device development and final product quality control.
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by molecules that produces unique energy shifts, Raman spectroscopy can quickly identify material components. In Raman imaging, a spectrum is acquired at each pixel by scanning the sample, which provides local chemical information. Confocal Raman imaging features a beam path that strongly rejects light from outside the focal plane for generating depth scans and 3D measurements. Raman microscopy is a powerful
tool for semiconductor research that can nondestructively acquire high- resolution, spatially-resolved information to determine the chemical composition of a sample, visualize component distribution, and characterize properties such as crystallinity, strain, stress or doping. This is particularly valuable for compound semiconductors, which often consist of multiple elements and complex structures.
The measurements below demonstrate the insight that correlative Raman imaging can provide to researchers investigating stress, doping and topographic variation in a large-area wafer measurement, and evaluating a Frank-Read source in a 3D correlative Raman and photoluminescence imaging experiment.
TOPOGRAPHIC RAMAN IMAGING OF A SiC WAFER To meet the challenge of maintaining nanoscale precision across the surface of a 150 mm (6 inch) diameter Silicon Carbide (SiC) wafer, a WITec alpha300 Raman system was used. This example was outfitted with a large-area scanning stage and a TrueSurface profilometry module to compensate for topographic variations. Raman imaging revealed alterations
in the doping-sensitive A1(LO)- mode at 960 rel. cm-1 of the Raman spectrum (Fig. 1A) for a region within the wafer (Fig. 1B). Compared to the bulk wafer area (red), this region contained a higher doping concentration (blue). The sensitivity of the system enabled the detection of minimal shifts of the E2(high) mode at 776 rel. cm-1 which is sensitive
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