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COREMA - WT (Wafer Topography)    [Data Sheet]

The COntactless REsistivity MApping measurement system COREMA-WT provides nondestructive full wafer resistivity characterization with utmost precision, resolution and measurement speed. It is based on a contactless capacitance technique developed at the Fraunhofer Institute for Applied Solid State Physics in Freiburg/Germany. It is most valuable for detailed, yet rapid, production compatible control of the fabrication process steps that determine the lateral homogeneity of the wafer. Exploratory process optimization is supported most effectively. 

The capacitive metal electrodes above and below the wafer are positioned by fast and precise xy translation. They are defining local sample and air capacitors at the desired measurement spot. A charging voltage step is applied to the RC circuit and the dynamic charge redistribution is recorded. The resistivity is obtained from the initial and final charge values and the relaxation time. Since the evaluation, based on first principles, is using relative units only and because all geometric parameters cancel, the resistivity values are obtained in absolute units without any instrumental calibration factors involved. A standard test method documentation (DIN 50447) is available.

The individual measurement takes only a fraction of a second. Hence, full wafer topography is obtained within very acceptable time. For instance, recording and evaluating 100 mm diameter wafer topogram with a 1.4 mm step size between data points takes approximately 20 minutes.

The system is typically used by vendors and customers for routine production control and quality assessment of semi-insulating wafers. The standard system with a resistivity measurement range 1E6 to 1E9 Ωcm range is preferentially used for GaAs and InP. For SiC and GaN a system with extended range 1E5 to 1E12 Ωcm is available.

The complete measurement process, including data evaluation and professional presentation is supported and controlled by user-friendly software based on Microsoft Windows. The software interface includes setup of the desired measurement routine, on-line supervision of the measurement process, display of the topographic data and detailed statistical evaluation. Various topographic displays including grey-scale, color coded as well as pseudo-3D representations are available, providing a convincing, customer oriented product quality and assessment and specification verification.  

   COREMA - WT system for resistivity measurements


   Resistivity Topogram of a 100 mm GaAs wafer


IF you have questions or comments, please send your E-mail to: info@semimap.de 
Last modification: 24/06/19