Characterization of magnetic Czochralski silicon radiation detectors

Silicon wafers grown by the Magnetic Czochralski (MCZ) method have been processed in form of pad diodes at Instituto de Microelectrònica de Barcelona (IMB-CNM) facilities. The n-type MCZ wafers were manufactured by Okmetic OYJ and they have a nominal resistivity of 1 kΩ cm. Concentrations of oxygen and carbon in MCZ wafers were measured by Secondary Ion Mass Spectroscopy (SIMS) technique to be compared to standard and oxygenated float zone (FZ) silicon material. The diodes were characterized by leakage current and capacitance measurements. The average full depletion voltage, VFD, of the pad detectors is 290±10 V, while the leakage current density at VFD+20 V is 7±3 nA/cm2. Minority carrier lifetime of MCZ, standard FZ and oxygenated FZ substrates was measured by using a quasi steady-state photoconductance technique. The uniformity of the MCZ wafers was studied before the fabrication by mapping the resistivity of the wafer and after the fabrication process by measuring the full depletion voltage and leakage current as a function of diode position on the wafer. It was found that the fabrication process did not change the resistivity of the material although no donor-killing heat treatment was performed on the wafers.