Low temperature, cost-effective process for manufacturing silicon radiation detectors

Researchers at the SLAC National Accelerator Laboratory have developed a cost-effective method for using low temperature microwave annealing to create diode termination contacts on silicon sensors. By eliminating the need for high temperatures, this process enables fabrication of important structures that could not otherwise be built. This includes shallow entrance windows for radiation detectors, thinned sensors for high energy particle physics (HEP), and post -processed backside for high resistivity CMOS sensors and CCD's. For example: in entrance windows, low temperature annealing avoids driving dopants deeper; for HEP sensors, diode arrays can be built on standard-thickness wafers which are thinned after the frontside is complete; and for CMOS image sensors, the backside can be annealed without damaging the frontside that is already fabricated. This technology could be used to manufacture sensors for detecting soft x-rays, optical light, UV light, low energy electrons or ions.

Stage of Research
The inventors have used this microwave annealing technique to build a prototype for the backside contact on planar sensor wafers. Bench measurement of the reverse bias diode currents show reasonable dark current and no junction breakdown up to 200V, comparable to junctions annealed by conventional techniques. The inventors have also validated the prototype sensor device by successfully measuring an Fe-55 x-ray spectrum.