Fabrication and Characterization of Ultra-Thin PIN Silicon Detectors for Counting the Passage of MeV Ions

This paper describes the fabrication and initial characterization of an ultra-thin silicon PIN detector using a new technique in silicon nanotechnology. In collaboration with the Nuclear Physics Division and the Lund Nano Lab at Lund University, we have developed and manufactured ultra thin ΔE-detectors for spectroscopic applications. The fabrication process has been carried out using a double-polished silicon substrate n-type wafer and locally thinning by means of a 10:1 solution of 25% tetramethyl ammonium hydroxide (TMAH) with Isopropyl alcohol. More than 100 detectors of different thicknesses, down to 5 μm with active areas ranging from 0.71 to 0.172 mm², have been fabricated. The main design considerations of our thin detectors were a very low leakage current below 12 nA and a low full depletion voltage at a reverse bias less than 1.5 V. Finally, most of our thin detectors offer an energy resolution (FWHM) as low as 31 keV for 5.487 MeV alpha particles from a ²⁴¹Am source.

I. Introduction

The last few years have seen a remarkable change in semiconductor radiation detectors and radiation detection systems. Some studies have focused on silicon nano-technology developments to fabricate detectors with thicknesses less than 5 [1], [2] called ultra-thin PIN silicon detectors.