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To establish fast, nondestructive, and inexpensive methods for resistivity measurements of SiC wafers, different resistivity-measurement techniques were tested for characterization of semi-insulating SiC wafers, namely, the four-point probe method with removable graphite contacts, the van der Pauw method with annealed metal and diffused contacts, the current-voltage (I-V) technique, and the contactless resistivity-measurement method. Comparison of different techniques is presented. The resistivity values of the semi-insulating SiC wafer measured using different techniques agree fairly well. As a result, application of removable graphite contacts is proposed for fast and nondestructive resistivity measurement of SiC wafers using the four-point probe method. High-temperature van der Pauw and room-temperature Hall characterization for the tested semi-insulating SiC wafer was also obtained and reported in this work.
Key words: Resistivity, silicon carbide, four-point probe method, van der Pauw method, contactless-resistivity measurement
INTRODUCTION
Fast and nondestructive methods for the specification of the main SiC-wafer parameters are very important for providing fast feedback to the growth effort and SiC-wafer users. In Si technology, the resistivity is measured using four-point probe stations with pin contacts or different contactless methods. The very high resistance introduced by the contacts into the measurement circuit is the principle problem that makes the commercially available four-point probe systems with pin contacts extremely difficult to implement for SiC-wafer characterization. Reported resistivity measurements on SiC wafers using the van der Pauw method1,2 is typically done on samples with annealed metal contacts, which is time consuming, and therefore, fast characterization response cannot be provided. Moreover, it was recently reported that annealing of SiC wafers decreases substrate bulk resistivity.3,4 This aspect is crucial because the substrate is subjected to high temperatures during epitaxial growth of GaN or SiC films for the fabrication of microwave devices. Hence, for such applications, it is essential to determine the resistivity of the substrate after high-temperature annealing. Commercially available contactless resistivity gauges allow resistivity measurement in the range 0.001-100 [Omega]-cm on wafers with a minimum diameter of about 2 in. Although commercial systems for contactless resistivity measurements in a range 10^sup 5^-10^sup 11^ [Omega]-cm do exist, these systems are expensive and, therefore, not widely used. Accounting for the preceding difficulties, the objective of this work was to establish a relatively inexpensive, fast, and nondestructive resistivity measurement method...