CSPAD αlpha

An important milestone was reached in the development of intelligent CMOS photodetectors. With the now new generation of CSPADs, Fraunhofer IMS shows new forms of integration of single-photon avalanche diodes (SPAD) in CMOS.

The CSPAD αlpha combines for the first time the highly sensitive photodetectors (SPAD wafer) with their electronics (ROIC wafer) in the form of a three-dimensional chip stack. The in-house developed wafer-to-wafer interconnection technology allows the integration of high-resolution pixel matrices with fast readout electronics in a very small space. CSPAD αlpha demonstrates with its LiDAR capabilities the quality of this new connection method and forms the basis for further chip designs.

With 32 x 24 pixels, distance measurements can be carried out using only one illumination (Flash-LiDAR) at a readout rate of 26 kHz. The TDCs (Time to Digital Converter) are integrated on chip in the readout electronics and enable a time resolution of 312.5 ps and a distance resolution of about 4.6 cm, respectively.

Apart from the typical application area of LiDAR, the CSPAD αlpha can also be used in the fields of spectroscopy, quantum technology and data encryption, among others.