HV-CMOS detectors in BCD8 technology

This paper presents the first pixel detector realized using the BCD8 technology of STMicroelectronics. The BCD8 is a 160 nm process with bipolar, CMOS and DMOS devices; mainly targeted for an automotive application. The silicon particle detector is realized as a pixel sensor diode with a dimension of 250 × 50 μm². To support the signal sensitivity of pixel diode, the circuit simulations have been performed with a substrate voltage of 50 V. The analog signal processing circuitry and the digital operation of the circuit is designed with the supply voltage of 1.8 V. Moreover, an analog processing part of the pixel detector circuit is confined in a unit pixel (diode sensor) to achieve 100 % fill factor. As a first phase of the design, an array of 8 pixels and 4 passive diodes have been designed and measured experimentally. The entire analog circuitry including passive diodes is implemented in a single chip. This chip has been tested experimentally with 70 V voltage capability, to evaluate its suitability. The sensor on a 125 Ωcm resistivity substrate has been characterized in the laboratory. The CMOS sensor realizes a depleted region of several tens of micrometer. The characterization shows a uniform breakdown at 70 V before irradiation and an approximate capacitance of 80 fF at 50 V of reverse bias voltage. The response to ionizing radiation is tested using radioactive sources and an X-ray tube.