Sebastian Koch, Development Engineer, Infineon Technologies AG
Sebastian Koch was born in Merseburg, Germany in 1988. He received his B.Sc. degree in engineering physics in 2010 and his M.Sc. degree in applied and engineering physics in 2012, both from Technische Universität München, Munich, Germany. From 2013 to 2016 he worked as a Ph.D. student with Intel Deutschland GmbH, Neubiberg, Germany. Sebastian Koch joined Infineon Technologies AG, Neubiberg, Germany in 2017 and is currently working as a modeling engineer and laboratory head.
Measurement Uncertainties Due to Hitherto Unspecified Offsets Between Source Measurement Units
Measurement system analysis of setups involving more than one DC source reveals that although each source measurement unit (SMU) is calibrated according to specifications, measurement uncertainties can be significantly larger than expected due to unspecified potential offsets between multiple SMUs. The results of a transfer characteristic measurement of a MOSFET device before and after adjustment of the potential equalization will be shown. Four SMUs are used to bias gate, source, drain and bulk terminals. Each individual measurement is highly repeatable and shows good agreement between measured drain current and the current measured by another SMU at the source terminal (< 150 ppm difference). However, when the SMU at the drain terminal is switched out for another one of the same model, we observe a 3.9 percent (39,000 ppm) variance of measured currents. This inaccuracy is mainly due to potential offsets between the SMUs. A simple improvement of the potential equalization of the SMUs can bring the uncertainty down by one order of magnitude (3,600 ppm). With increasing requirements regarding quality management (ISO 9001 / IATF 16949:2016), we would like to raise awareness of this issue which is so far neither subjected to specifications nor dealt with by regular calibration efforts. Our aim is to convince both users and vendors of SMUs that specifications, calibration possibilities or at least best-practice solutions should be provided for the common use case of employing multiple SMUs in one measurement.