Metallized and oxidized silicon macropore arrays filled with a scintillator for CCD-based X-ray imaging detectors

Abstract

Silicon charge-coupled devices (CCDs) covered with a scintillating film are now available on the market for use in digital medical imaging. However, these devices could still be improved in terms of sensitivity and especially spatial resolution by coating the CCD with an array of scintillating waveguides. In this paper, such waveguides were fabricated by first etching pores in silicon, then performing metallization or oxidation of the pore walls and finally filling the pores with CsI(Tl). The resulting structures were observed using scanning electron microscopy and tested under X-ray exposure. Theoretical efficiencies of macropore arrays filled with CsI(Tl) were also calculated, indicating that the optimal pore depth for metallized macropore arrays is about 80 /spl mu/m while it is around 350 /spl mu/m for oxidized ones. This result, together with the roughness of the metal coating, explains why lower SNR values were measured with the metallized macropores. Indeed, the macropore arrays had depths in the range of 210-390 /spl mu/m, which is favorable to oxidized structures.