Development of a Two-Level Fabrication Process for PbTiO3 Pyroelectric Arrays

摘要

Collosal magnetoresistive (CMR) films, on lattice matched substrates, can achieve a thermal coefficient of resistance (TCR) in excess of 10%, significantly higher than the present 2% VOx. This material is not a pyroelectric but was an extension of the existing resistive bolometer approach. The resistance change which has been much studied arises from electron transport changes with temperature caused by changes in the electronic energy levels of the ferromagnetically coupled electron at different crystal sites and is a function of the composition. Lattice-matched substrates of LaAlO3 and, to a somewhat lesser degree, YSZ are excellent for growth of this material. It became apparent that an oriented film of YSZ would benefit both PbTiO3 growth and colossal magnetoresistive (CMR) film growth in the Honeywell DARPA AIM program since both detector films were similar perovskite type films where crystal growth and orientation are critical to achieving the desired properties. In 1997, this program was redirected from its initial focus on a sacrificial layer to support PbTiO3 growth to focus on the development of a YSZ buffer film for oriented growth of CMR films both in plane and out of plane. This program has resulted in the development of a process for the deposition of YSZ films with both out-of-plane and in-plane orientation on the fundamental pixel material, silicon nitride. The YSZ material technology developed in this program, has been used in the AIM program, to provide the necessary growth habitat for CMR thin films resistors. These resistors have achieved TCRs of 3.5% on silicon nitride.