The Due2lab team took part in an ambitious project for the development of a new class of CdZnTe detectors called 3D drift strip detector, or striped detector. Strip detectors are mostly used in astrophysics applications, such as sensors for the focal plane of powerful radiation telescopes in the energy range between 10 keV and 10 MeV.
The manufacture of this type of double segmentation detector (both anode and cathode require a delicate electrode patterning process) is a real technological challenge. Besides the criticality of the double segmentation, the operation of the 3D drift strip detector requires the application of relatively high potential differences between adjacent metal electrodes (at least 50 V between adjacent strips, a few hundred microns apart). For this reason Due2lab had to develop a new technology to minimize the surface dark currents between the strips, in order to guarantee the correct polarization of the detector.
This technology consists in depositing a thin layer of high resistivity oxide on the surface of the CZT between one stripe and another. The deposition of a thin film (<100 nm) of Al2O3 is able to reduce the surface dark currents by a factor of 10 or more. Thanks to this development, Due2lab has therefore also acquired skills in depositing thin insulating films using plasma techniques such as sputtering and Pulsed Electron Deposition (PED). The technology developed by Due2lab is compatible with standard photolithographic processes and can potentially be used for any type of detector.
The electrical connection of the strip detector (bonding) is an equally critical process step. In addition to the minimization of surface currents, Due2lab has also developed the technology to perform electrical bonding of the strips to specially designed boards at low temperature.
Thanks to the skills acquired in the last few years regarding the manufacture and bonding of 3D drift strip detector, Due2lab is now able to offer these unique detection modules in the world.