Low-temperature technique of thin silicon ion implanted epitaxial detectors

A new technique of large-area thin ion implanted silicon detectors has been developed within the R&D performed by the FAZIA Collaboration. The essence of the technique is the application of a low-temperature baking process instead of high-temperature annealing. This thermal treatment is performed after B + ion implantation and Al evaporation of detector contacts, made by using a single adjusted Al mask. Extremely thin silicon pads can be therefore obtained. The thickness distribution along the X and Y directions was measured for a prototype chip by the energy loss of α -particles from 241 Am (〈 E α 〉 = 5.5 MeV). Preliminary tests on the first thin detector (area ≈ 20 × 20 mm 2 ) were performed at the INFN-LNS cyclotron in Catania (Italy) using products emitted in the heavy-ion reaction 84 Kr ( E = 35 A MeV) + 112 Sn. The ΔE − E ion identification plot was obtained using a telescope consisting of our thin ΔE detector (21 μ m thick) followed by a typical FAZIA 510 μ m E detector of the same active area. The charge distribution of measured ions is presented together with a quantitative evaluation of the quality of the Z resolution. The threshold is lower than 2 A MeV depending on the ion charge.