Lattice scale inspection of semiconductor interfaces via non-destructive camera-less 3D T-ray imaging

摘要

Interfaces play critical roles in all semiconductor fabrication processes and on the electronic properties of semiconductors. Especially, devices involving plurality of interfaces is now of paramount importance. As such the interfaces have been a subject of intensive studies. However, effective characterization of interfaces is complicated because of inherent unknowns involved. For example, consider the case outlined in Fig. 1 where two layers of materials have been deposited on a silicon substrate (Si). The silicon wafer is known to be well characterized. The material properties of Layer-1 (L1) and Llayer-2 (L2) may also be known by themselves; but deposition involves transforming a solid material in to vapor or liquid phase and then back into solid by the deposition process. As a result, the deposited materials' lattice will/may suffer from imperfections and defects such as stacking fault and dislocations. Based on such imperfections, different types of interfaces may be defined. The system outlined in Fig. 1 , may/will produce unknowns such as the lattice structure of Layer-1 and Layer-2, the interface between Layer-1/Layer-2, and the interface between Layer-1/silicon substrate. Only known entity in Fig. 1 is the silicon lattice; however, the deposition process still may influence the top surface of the substrate and thus the silicon lattice may suffer from defect formation and/or some rearrangement of the surface atoms. Quantification of such interfaces at the lattice scale is a huge challenge by the current state of the art; especially, a non-destructive inspection of the deposited layers and interfaces that requires interrogation across the depth.