A new technique for the fabrication of thin silicon radiation detectors

Abstract

The fabrication of silicon radiation detectors with thicknesses lower than 30 /spl mu/m requires non-standard processing equipment and procedures. Such detectors are commonly manufactured by vias in thick silicon wafers of typically 300 /spl 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 microroughness, 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 /spl mu/m thick pin silicon diodes with surfaces ranging from 1 to 100 mm/sup 2/ have been fabricated. Using this technique, thickness uniformity as low as /spl plusmn/0.05 /spl mu/m can be obtained on 5 /spl mu/m thick detectors over 100 mm/sup 2/ area. 30 /spl mu/m thick pin detectors (S=64 mm/sup 2/) are fully depleted at zero bias and exhibit an energy resolution of less than 120 keV (/spl sim/2 %) for 5.5 MeV alpha particles. This constitutes a breakthrough towards the low cost fabrication of thin silicon radiation detectors using planar technology.