Substrate effects on the properties of the pyroelectric thin film IR detectors

Abstract

Pyroelectric Pb(Zr 0.3Ti 0.7)O 3 thin film IR detectors were successfully fabricated and systematically characterised. The Pb(Zr 0.3Ti 0.7)O 3 thin film was deposited onto Pt/Ti/Si 3N 4/SiO 2/Si substrate by the sol–gel process. Four different substrate processing alternatives were studied for their effects on the pyroelectric responses of the IR detectors. The substrate processing alternatives were the combinations of the Si etching and the Pt/Ti patterning. In the Si etched substrate, the Si 3N 4/SiO 2 composite layer was used as silicon etch-stop, and was used as the membrane to support the PZT pyroelectric film element as well. The measured pyroelectric current and voltage responses of detectors fabricated on the micro-machined thin Si 3N 4/SiO 2 membrane were two orders of magnitude higher than those of the detectors on bulk-silicon. For detectors on the membrane substrate, the Pt/Ti patterned-detectors showed a two-times higher pyroelectric response than that of not-patterned-detectors. On the other hand, the pyroelectric response of the detectors on the not-etched Si substrate was almost the same, regardless of the Pt/Ti patterning. It was also found that the rise-time strongly depended on the substrate thickness, the thicker the substrate was, the longer the rise-time.