Very-Low-Temperature Preparation of Poly-Si Films by Plasma Chemical Vapor Deposition Using SiF₄/SiH₄/H₂ Gases

Abstract

Polycrystalline-Si (poly-Si) films have been prepared on glass substrates (Corning 7059) at a very low temperature (300°C) by conventional plasma chemical vapor deposition (plasma CVD) using SiF4/SiH4/H2 gases. The crystallinity was characterized by X-ray diffraction, reflection high-energy electron diffraction (RHEED), transmission electron microscopy (TEM) and Raman spectroscopy measurements. The effect of the SiH4 flow rate on crystallization proved to be large. The films indicated a strong <110>-preferred orientation. The crystalline fraction was estimated to be more than 80%. The average and maximum grain sizes were estimated to be 60 nm and 130 nm, respectively.

Low Temperature Growth of Polycrystalline Silicon Films by Hot-Wire Chemical Vapor Deposition Using SiCl4/H2 Gases

“…Low-temperature growth of crystalline silicon films by plasma-enhanced chemical vapor deposition (PECVD) has been demonstrated by adding fluorinated precursors such as SiH 2 F 2 and SiF 4 instead of SiH 4 /H 2 reactant only. [2][3][4] Due to the much stronger bonding energy of Si-F bonds (553 kJ·mol −1 ) than that of Si-Si bonds (327 kJ·mol −1 ), it is believed that the F radicals can etch a Si network, preferentially weak Si-Si bonds, during deposition as a result of the crystalline silicon film being deposited at low temperature. 4) However, the relatively low growth rate of the crystalline silicon films deposited using SiF 4 /H 2 by rf plasma CVD, originating either from the low decomposition efficiency of SiF 4 or from the high etching rate of the Si network by F radicals, is a serious concern with respect to further application.…”

“…A small amount of added SiH 4 is needed in general to enhance the growth rate of the crystalline silicon films using SiF 4 /H 2 . [2][3][4] To adopt the advantage of fluorinated precursors, i.e., preferentially etched weak Si-Si bonds but avoiding the low growth rate concern, the low-temperature growth of crystalline silicon films using SiCl 4 /H 2 (Si-Cl bond strength is 406 kJ·mol −1 ) by hot-wire chemical vapor deposition (HWCVD) was studied in this work. Chlorinated silanes such as SiH 2 Cl 2 , SiHCl 3 and SiCl 4 have been widely employed to deposit epitaxial silicon films at high temperature.…”

“…KEYWORDS: polycrystalline silicon films, low-temperature growth, hot-wire chemical vapor deposition, SiCl 4 …”

Particle formation in the remote plasma enhanced chemical vapor deposition of Si films from Si2H6–SiF4–H2

“…In particular, in the field of active matrix liquid crystal displays ͑AMLCDs͒, the use of polysilicon as an active layer instead of amorphous silicon has drawn much attention because the electron mobility in poly-Si is much greater than in a-Si and better performance can be achieved with a poly-Si TFT. 1,2 In AMLCD applications, low temperature processing ͑below 600°C͒ is desirable to reduce the manufacturing cost by utilizing low cost glass substrates.…”

Air Exposure Improvement of Optical Properties of Hydrogenated Nanostructured Silicon Thin Films for Optoelectronic Application

“…Thus, the role of hydrogen is to promote the nucleation and the crystallization of hydrogenated amorphous silicon at low temperature with desired grain size (Solomon et al, 1993). The use of SiF 4 has also been successfully employed to obtain more orderly materials since fluorine atoms, produced in SiF 4 plasma decomposition, are effective etchant species (Mohri et al, 1991). These facts were considered in choosing the feed gases.…”