Electron cyclotron resonance plasma enhanced chemical vapour deposition and optical properties of SiOx thin films

The composition, bonding configuration, hydrogen content, and paramagnetic defects of SiO x H y thin films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH 4 and O 2 as precursor gases. The film composition was measured by heavy ion elastic recoil detection analysis and energy dispersive x-ray spectroscopy. Suboxide films with compositions ranging from SiO 2 to SiH 0.38 were obtained. Infrared spectroscopy showed the presence of different Si-O and Si-H vibration modes. The usual estimation of the oxygen to silicon ratio by the wave number of the Si-O-Si stretching band was not accurate for films far from stoichiometry. These off-stoichiometric films also showed a broader Si-O-Si stretching peak than the stoichiometric ones, indicating a higher bonding disorder. The position of the Si-O-Si bending and rocking modes did not depend on the film composition. On the other hand, the peak position of the Si-H modes were found strongly dependent on the Si environment. By single-wavelength ellipsometry at ϭ632.8 nm the refractive index n was found to range between 1.45 (SiO 2 ) and 2.04 (SiO 0.06 H 0.36 ). Electron spin resonance measurements showed that stoichiometric films presented the well known EЈ center ("SiϵO 3 ) with concentrations in the 10 16 -10 17 cm Ϫ3 range, while for Si-rich films (xӶ1) the Si dangling bond center (Si DB , "SiϵSi 3 ) was the only detectable defect, with concentrations in the 10 18 -10 19 cm Ϫ3 range. In near-stoichiometric films both EЈ and Si DB centers were found.

Section: Methodsmentioning

confidence: 99%

Bonding configuration and density of defects of SiOxHy thin films deposited by the electron cyclotron resonance plasma method

Andrés

Prado

Mártil

et al. 2003

“…Further details of the deposition system are given elsewhere. 16 The precursor gases used were high-purity SiH 4 and O 2 , and films of different compositions were obtained depending on gases flow ratio, that we define in this article in the same way that Bulkin et al, 17 i.e., R b ϭ͓SiH 4 ͔/(͓SiH 4 ͔ϩ͓O 2 ͔). R b values comprised between 0.2 and 0.9 were used in this study.…”

Section: Methodsmentioning

confidence: 99%

Thermally induced modifications on bonding configuration and density of defects of plasma deposited SiOx:H films

Andrés

Prado

Mártil

et al. 2002

The bonding configuration, hydrogen evolution, and defect content of rapid thermally annealed ͑RTA͒ SiO x :H films of different compositions were studied. Infrared absorption measurements showed that all the hydrogen present in the films is lost at annealing temperatures below 600°C without any change in the oxygen to silicon ratio of the films. The activation energy of the hydrogen release is in the 0.21-0.41 eV range independently of film composition, suggesting that the process occurs via network bond reactions. For annealing temperatures higher than 700°C, a change in the Si-O-Si stretching wave number from the initial unannealed value to the 1070-1080 cm Ϫ1 range was promoted, independently of the initial film composition. Electron spin resonance measurements showed that all the films contain two type of bulk paramagnetic defects: the EЈ center (•SiwO 3 ) and the silicon dangling bond center (•SiwSi 3 ). The RTA process promotes a general decrease of defect concentration for annealing temperatures below 400°C. At higher temperatures, EЈ center disappears, and the •SiwSi 3 center increases its concentration up to the 10 17 -10 18 cm Ϫ3 range. This suggests that the RTA at higher temperatures promotes the formation of a high-quality, almost defect-free, SiO 2 matrix in which highly defective Si nanocrystals are also formed, where the •SiwSi 3 centers are located.

“…16,44 The broad peak at a maximum wavenumber of around 670 cm À1 consists of O-Al-O bending modes (650 cm À1 À 700 cm À1 ), Al-O stretching modes for Al-O in octahedral matrices (400 cm À1 À530 cm À1 ), and Al-O stretching modes in tetrahedral and octahedral matrices (750 cm À1 À 850 cm À1 ). [45][46][47][48][49][50] The peak around 900 cm À1 À 1300 cm À1 is assigned to Si-O and O-Si-O stretching modes and optical phonon modes. [50][51][52][53] At around 1300 cm À1 À 1750 cm À1 , the two peaks can be related to asymmetric vibration modes of H-O-H; O-C-O, and C ¼ O.…”

Section: Resultsmentioning

confidence: 99%

“…[45][46][47][48][49][50] The peak around 900 cm À1 À 1300 cm À1 is assigned to Si-O and O-Si-O stretching modes and optical phonon modes. [50][51][52][53] At around 1300 cm À1 À 1750 cm À1 , the two peaks can be related to asymmetric vibration modes of H-O-H; O-C-O, and C ¼ O. [54][55][56][57][58] The feature at 3000 cm À1 À 3800 cm À1 can be assigned to Si-OH and O-H stretching modes.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A study on Si/Al2O3 paramagnetic point defects

Kühnhold-Pospischil

Saint‐Cast

Hofmann

et al. 2016

In this contribution, negative charges and electronic traps related to the Si=Al 2 O 3 interface were measured and related to paramagnetic point defects and molecular vibrations. To this end, contactless capacitance voltage measurements, X-band electron paramagnetic resonance (EPR), and infrared spectroscopy were carried out, and their results were compared. A change in the negative charge density and electron trap density at the Si=Al 2 O 3 interface was achieved by adding a thermally grown SiO 2 layer with varying thicknesses and conducting an additional temperature treatment. Using EPR, five paramagnetic moments were detected in Si=ðSiO 2 Þ=Al 2 O 3 samples with g values of g 1 ¼ 2:008160:0002; g 2 ¼ 2:005460:0002; g 3 ¼ 2:000360:0002; g 4 ¼ 2:002660:0002, and g 5 ¼ 2:002960:0002. Variation of the Al 2 O 3 layer thickness shows that paramagnetic species associated with g 1 , g 2 , and g 3 are located at the Si=Al 2 O 3 interface, and those with g 4 and g 5 are located within the bulk Al 2 O 3 . Furthermore, g 1 , g 2 , and g 3 were shown to originate from oxygen plasma exposure during Al 2 O 3 deposition. Comparing the g values and their location within the Si=Al 2 O 3 system, g 1 and g 3 can be attributed to P b0 centers, g 3 to Si dangling bonds (Si-dbs), and g 4 and g 5 to rotating methyl radicals. All paramagnetic moments observed in this contribution disappear after a 5-min temperature treatment at 450 C. The deposition of an additional thermal SiO 2 layer between the Si and the Al 2 O 3 decreases the negative fixed charge density and defect density by about one order of magnitude. In this contribution, these changes can be correlated with a decrease in amplitude of the Si-db signal. P b0 and the methyl radical signals were less affected by this additional SiO 2 layer. Based on these observations, microscopic models for the negative fixed charge density (Q tot ) and the interface trap density (D it ) and the connection between these values are proposed. Published by AIP Publishing. [http://dx