Company Background and Mission
The rapid growth of the telecommunications market has dramatically increased the demand for high-speed analog and digital microelectronic devices. Such circuits are preferentially fabricated on substrates with high electrical resistivity. Therefore, sales of semi-insulating GaAs, InP and SiC wafers are growing rapidly. Concurrently, steady improvements of the crystal growth and wafer fabrication technologies yield better material quality and increased wafer diameters.
Due to the high basic cost of the starting materials and the demanding crystal growth procedures, compound semiconductor wafers, including GaAs, InP and SiC, are very expensive, as compared to silicon. Therefore, improvements must be achieved while maintaining or even reducing the cost per substrate area. High performance production compatible characterization equipment, offering inexpensive, nondestructive and rapid material quality assessment, is an essential contribution to meet the combined challenges of quality improvement and cost reduction.
Strict wafer quality control demands routine assessment of the absolute value and the lateral variation of resistivity across the wafer area. A topogram reproducing the fluctuations of state-of-the-art material with adequate lateral resolution requires several thousand individual measurements. The data must be generated with excellent repeatability and fast enough to yield timely results as required by mass production control.
The COntactless REsistivity MApping measurement system is designed to meet these demanding goals. It is based on an innovative capacitance technique originally developed at the Fraunhofer Institute IAF in Germany and now exclusively licensed to SemiMap Scientific Instruments GmbH. The quantitative, absolute evaluation is based on first principles and does not require calibration standards. Commercial wafers are evaluated without contacts and without any preceding sample preparation, hence remain available for further characterization or for sale. It is, therefore, possible to sell characterized wafers.
COREMA - WT is used worldwide by substrate vendors for routine production control and quality assessment of high resistivity wafers. The fabrication steps determining the lateral homogeneity, in particular crystal growth and post-growth thermal annealing, are most effectively controlled and further optimization is supported. Because the electrical resistivity reacts to virtually each and every deviation of process parameters, COREMA - WT offers a quality assessment and failure analysis capability going far beyond the control of resistivity alone.
The various measurement, evaluation and documentation procedures are supported by dedicated software. A choice of topographic displays including gray scale or color coding as well as pseudo-3D representation is supplied for survey at a glance and convincing presentation to substrate customers. Powerful statistical analysis tools are provided and easy interfacing with data management systems is possible.
In summary, COREMA - WT provides substrate resistivity evaluation extending far beyond the performance of conventional techniques with respect to speed, precision, repeatability, lateral resolution, cost saving and scrutiny of characterization.
Further upgrading of the evaluation capabilities, to be offered as add-on or stand-alone systems, are available:
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