First test measurements of a 64k pixel readout chip working in single photon counting mode

The Medipix2 chip is a pixel detector readout chip consisting of 256 x 256 identical elements, each working in single photon counting mode for positive or negative input charge signals. The chip is designed and manufactured in a six-metal 0.25 mum CMOS technology. This paper describes several electrical measurements which have been carried out on the chip prior to detector bump bonding using a dedicated readout system. Threshold linearity and variation has been measured for both electron and hole collection. The noise is similar to100e(-) RMS and the threshold can be adjusted to similar to120e(-) RMS for both polarities. The minimum operating threshold is similar to1000e(-.) (C) 2003 Elsevier B.V. All rights reserved.