DEPFET Macropixel Detectors for MIXS: First Electrical Qualification Measurements

The Mercury Imaging X-ray Spectrometer (MIXS) is one of the instruments on board the Mercury Planetary Orbiter of the fifth European Space Agency (ESA) cornerstone mission BepiColombo. This spectrometer comprises two instruments and allows imaging X-ray spectroscopy of the Mercurian surface. The focal plane arrays for the energy and spatial resolved detection of X-rays are based on depleted P-channel FET (DEPFET) macropixel detectors. We report on the first electrical qualification measurements of DEPFET macropixel flight hardware, which are done at room temperature. The measurement of the transistor properties of all DEPFET pixels allows the selection of 100% electrically defect-free devices at an early stage directly after completion of the production process. Additionally, these measurements allow to investigate topics such as the homogeneity of transistor parameters across the detector matrix, to monitor die-to-die variations for matrices from the same wafer, and to investigate the differences between dies from different wafers in order to learn about the stability and reproducibility of the production process. The test results demonstrate good homogeneity and yield for the investigated detector matrices from the first production batch.