Application example
Figure 1 shows an exemplary mapping of the resistivity of a SiC raw wafer. The edge exclusion is appr. 5 mm.
It is well known that the measured resistivity depends on the sample temperature, but also on the ambient temperature. Hence two T sensors are integrated in the measurement head. Figure 2 shows 1000 repeats of a resistivity measurement at a thick SiC boule (> 1 mm). The measurement head was driving in the home position after every measurement and the complete procedure took around 6 hours. In this time the ambient temperature changed and this test shows nicely how well the T com-pensation algorithm works. A reproducibility with s < 0.15 % is achieved with this T compensation algorithm.
Figure 1: Example of a resistivity map of a SiC wafer
Figure 2: 1000 repeats with movement to home position; with (σ < 0.15 %) and without temper-ature compensation (σ < 0.21 %)
Figure 3: average of a 5 mm map of a 6’’ boule, measured 18 times on different days and differ-ent times, σ = 0.15 %
Figure 4: dynamic temperature drift: sample was placed at a cold spot and measured during the warm up, the experiment took about 10 mins
