Waferscale Processing of CdTe/CZT for Radiation Detection

The principle objective of this project is to tune existing techniques and transfer an optimised process for the wafer-scale processing of radiation detector structures on material produced by Kromek. This material is produced by a novel technique based on Physical Vapour Transport that enables the growth of high quality material on matched seed substrates of a second material. . The technology is proprietary to Kromek and places them in a unique position to exploit a potential market of 200 M$ per year (Frost & Sullivan) in the area of homeland security (and many medical applications). CZT material grown from the melt has always been difficult to grow in single crystals. 75 mm wafers normally consist of a few large crystals and material that is processed into radiation detectors is normally hand picked from pre-selected wafers. Each detector is processed on the selected wafer taking care to position the active part of the detector away from any crystal boundary and subsequently cut from the wafer. This method of detector production is very effort intensive and exceedingly expensive. There has been no possibility to date to make this process more efficient because of the artisanal nature of the fabrication required to process wafers where there is more than one crystal present. The availability of 100 mm wafers of high quality CZT will enable this to change and enable radical improvements to the process of detector fabrication and its cost. The James Watt NanoFabrication Centre at the University of Glasgow offers a uniquely equipped facility for the optimization and transfer of processes already developed at the Centre to the fabrication of high quality detector structures on the material grown by Kromek. The Centre comprises 750 m2 of clean rooms equipped with state of the art semiconductor process tools that cover the entire range of processes required to produce detector structures. The complete process equipment chain from design software through e-beam writer for mask production, photolithography, metal and dielectric deposition and reactive ion etching is available at the Centre with dedicated staff support to maintain the process tools. This proposal will adapt the techniques required for the successful processing of detectors on 100 mm wafers of CZT from Kromek and then transfer this process to the company so that they are in a position to add value to their material and more fully exploit the market for highly efficient radiation detectors, thereby maximizing the return to the company.