DB FIB for in-line process control

Cross-sectional analysis is an important tool for structural learning in the IC industry. FEI CLM-3D DualBeam (TM) system enables IC companies to rapidly collect step-to-step integration information within the FAB. Both 2- and 3-dimensional structures can be analyzed. Gate structures are a good example of a 2-D structure in which the DB FIB system can provide width, thickness, sidewall angle, as well as bottom profile. In addition, it can provide qualitative information regarding the material stack, such as the step coverage of the oxide layer over the gate silicon. Deep trench hard mask layers provide an excellent illustration of a 3-D structure in which extremely high aspect ratio elliptical trenches must be precisely cross-sectioned to reveal accurate geometric information. The DB FIB system can precisely cross-section these features to obtain the necessary precision-to-tolerance ratios. Moreover, the tool's versatility has allowed its utilization for many other 2-D and 3-D structures besides gate and deep trench. The fully automated FIB system enables to analyze whole wafer distributions without breaking the wafer, thus allowing to further process the wafer and understand how each process step impacts the next. The FIB system provides cross-sectional information typically three times faster than Failure Analysis Lab (FA Lab) thereby permitting many more learning cycles in the same time period. Wafer return is a critical capability, allowing cross-sectional analysis without sacrificing the wafer. It was, therefore, critical that the tool meet the particle and metal ion contamination requirements. Testing included full processing: load/unload, gas chemistries, gallium beam milling, and imaging. The chemical contamination data shows that all critical elements, including gallium, are within the requirements (<10(1)0 at/cm(2)). Front-side particle data also shows that the FIB method does not add more than 0.013 PWP/cm(2) (greater than 0.12 mu m particle size).