A new technique for the fabrication of thin silicon radiation detectors

The,fabrication of silicon radiation detectors with thicknesses lower than 30 mu m requires non-standard processing equipment and procedures. Such detectors are commonly manufactured by vias in thick silicon wafers of typically 300 mu m in order to locally create on small areas thin detectors. Since the etching step controls the thickness and uniformity of the detector, it must provide a constant and controllable etch rate and should not modify the surface micro-roughness, rendering this manufacturing technique critical.-As an alternative, we have developed a new technique for the fabrication of thin detectors based on the use of substrates Presenting a buried etch-stop layer. The detector thickness, its uniformity and the surface roughness are fixed and controlled by the substrate specifications. 5 to 30 mu m thick pin silicon diodes with surfaces ranging from 1 to 100 mm(2) have been fabricated. Using this technique, thickness uniformity as low as +/- 0.05 mu m can be obtained on 5 mu m thick defectors over 100 mm(2) area. 30 mu m thick pin detectors (S = 64 mm(2)) are fully depleted at zero bias and exhibit an energy resolution of less than 120 keV (similar to 2 %) for 5.5 MeV alpha particles. This constitutes a breakthrough towards the low cost fabrication of thin silicon radiation detectors using planar technology.