Infrared Spectroscopy Study of a Poly-Silicon Film for Optimizing the Boron-Implanting Dose

Abstract

An experiment was carried out for recording the infrared transmission between 3 and 16 μm for a free-standing poly-silicon (Si) thin film as a function of the boron-ion implanting. The optical constants were extracted in order to optimize the postdeposition implanting of the membranes in a surface micromachined Fabry-Perot interferometer for the thermal infrared. The free-carrier concentration must not degrade the refractive index n significantly since a high and constant value over the application wavelength range is desired. Moreover, an increase in the extinction coefficient k is detrimental for the interferometer performance. On the other hand, poly-Si electrical conductivity must be doped high enough to avoid static charging and to prevent any layout-dependent distribution of the applied control voltage. We applied the variable-angle transmission spectrometry for recording the data of suspended poly-Si membranes, doped with different levels of implanting dose. The Drude model dispersion formula was exploited for extracting the optical constants n(λ) and k(λ). The optical constants are presented as a function of the dopant concentration and the electrical resistivity.[2012-0292]

MOEMS Fabry–Pérot interferometer with point-anchored Si-air mirrors for middle infrared

“…Different solutions are published [13], but our method is based on phosphosilicate glass (PSG). The phosphorus-doped PSG is sandwiched between non-doped oxides (figure 2) to prevent charge-carrier diffusion, which could deteriorate the optical properties of poly-Si [27].…”

Absorption coefficient of doped polycrystalline silicon films in infrared spectrum

“…A practical measurement setup requires millimetres size membranes for a reasonable signal level, to ensure the reflected and transmitted energy to be measured accurately [1]. However, the fabrication of the sample in which the free-standing suspended poly-Si film with a thickness of 1-2μm or less satisfies the samples size of 3.5×3.5cm 2 is more complex.…”