AVS 59th Annual International Symposium and Exhibition
    MEMS and NEMS Tuesday Sessions
       Session MN-TuP

Paper MN-TuP3
Development of Deposition and Etching Processes of Thick ZnS Films for Pixel Level Packaging of Infrared Focal Plane Arrays

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Session: MEMS and NEMS Poster Session
Presenter: B. Glück, ST Microelectronics, France
Authors: B. Glück, ST Microelectronics, France
G. Rodriguez, CEA, LETI, MINATEC Campus, France
G. Dumont, CEA, LETI, MINATEC Campus, France
S. Barnola, CEA, LETI, MINATEC Campus, France
Correspondent: Click to Email
Because of its transparency in the medium and long wave infrared light (MWIR and LWIR) zinc sulphide (ZnS) is an attractive material to make optical windows for infrared devices. Moreover, its relatively low optical index can be used advantageously in association with high index material such as Germanium (Ge) to create an anti-reflecting coating.In our application a thick ZnS film of about 1.2µm is deposited on top of the Ge to create the infrared window of a micro packaging structure for micro-bolometer devices in 200mm. This window has to be opened at the end of the process flow to realise the contacts. This study focuses on the deposition of ZnS by electron beam evaporation and its reactive ion etching to form the first layer of the IR-window. The integration of these processes in the fabrication of infrared focal plane arrays is presented in this work.In particular structure and morphology of the deposited ZnS films were investigated by X-ray diffraction, X-ray reflection, atomic force microscopy and scanning electron microscopy. Spectroscopic ellipsometry measurements were done to determine the optical properties. Concerning ZnS etching we developed a HBr based etch process that is also applicable to etch the Ge layer underneath using the same mask. The main process trends were investigated to maximise the etch rate and the selectivity to photoresist.