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Two ways to pyroelectric P(VDF/TrFE) thin film sensors and arrays

: Köhler, R.; Neumann, N.; Gottfried Gottfried, R.


Microelectronic engineering 29 (1995), S.79-84
ISSN: 0167-9317
Fraunhofer IMS, Außenstelle Dresden ( IPMS) ()
Dünnschichttechnik; Infrarotsensor; Pyroelektrischer Sensor; Wärmeisolation

A central problem of the sensor design is the thermal insulation of the P(VDF/TrFE) thin film from the read-out circuit. Two variations have been examined - thin carrier membranes of SiO2/Si3N4 produced by back etching and thick thermal insulating layers out of spin-coated polymers with via holes. Membrane sensors consisting of 1 mu m P(VDF/TrFE) thin film deposited on a 0.65 mu m thick membrane show within the frequency range of 10 Hz to 1 kHz comparatively higher values for responsivity and specific detectivity than insulating layer sensors. The insulating layer sensors have in the most favourable case a themal cut-off frequency of about 100 Hz. The optimal layer thickness for the compound of BCB (benzocyclobutene) and P(VDF/TrFE) for a chopper frequency of about 100 Hz is at approximately 18...25 mu m. The advantages of the design with insulating layer are a filling factor of almost 100 per cent independently of the pixel size and very small pixels of about (50x50) mu m2.