Optimisation of doped microcrystalline silicon films deposited at very low temperatures by hot-wire CVD

Abstract

In this paper we present new results on doped c-Si:H thin films deposited by Hot-Wire Chemical Vapour Deposition (HWCVD) in the very low temperature range (125-275 ºC). The doped layers were obtained by the addition of diborane or phosphine in the gas phase during deposition. The incorporation of boron and phosphorus in the films and their influence on the crystalline fraction are studied by Secondary Ion Mass Spectrometry and Raman Spectroscopy respectively. Good electrical transport properties were obtained in this deposition regime, with best dark conductivities of 2.6 S/cm and 9.8 S/cm for the p-and n-doped films respectively. The effect of the hydrogen dilution and the layer thickness on the electrical properties are also studied. Some technological conclusions referred to cross contamination could be deduced from the nominally undoped samples obtained in the same chamber after p-and n-type heavily doped layers.

Top-gate microcrystalline silicon TFTs processed at low temperature (<200 °C)

“…Then, N type as well as P type top gate TFTs have been processed using 200 nm-thick microcrystalline silicon (µc-Si:H) film as active layer. The deposition is performed by HWCVD in a multichamber reactor described elsewhere [1]. 2x2 square inch glass covered with 200 nm Atmospheric Pressure CVD (APCVD) deposited SiO 2 are used as substrate.…”

Low temperature amorphous and nanocrystalline silicon thin film transistors deposited by Hot-Wire CVD on glass substrate

“…Top gate TFTs have been processed using 200 nm-thick a-Si:H or nc-Si:H silicon films deposited by HWCVD in a multichamber deposition set-up described elsewhere [5] were the same as those of undoped nc-Si:H). In amorphous TFTs, undoped a-Si:H and n-type nc-Si:H layers were deposited in different chambers, whereas in the case of nc-Si:H ones, deposition of all HWCVD layers took place in the same chamber, just closing the shutter a few seconds to avoid the pressure peak upon the inclusion of PH 3 in the gas mixture.…”

Silicon-Based Third Generation Photovoltaics

“…The ohmic contacts were obtained by thermal evaporation of Al, followed by sintering at a temperature (500-530°C) lower than the Al-Si eutectic temperature to allow the Al to spike down into the film (Voz et al, 2000). The schematic view of the final structure for the lateral resistivity measurements is presented on the Fig.…”