Structural properties of a-Si:H related to ion energy distributions in VHF silane deposition plasmas

Hamers, E. A. G.; Sark, W.G.J.H.M. van; Bezemer, Jeff; Meiling, H.; Weg, W. F. van der

doi:10.1016/s0022-3093(98)00453-0

Cited by 46 publications

(60 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fig. 4b (in agreement with results observed by Hamers,33,34 Smets,23 and Wank 35 indicates that increasing ion momentum results in an initially rapid decrease in film porosity in the tensile region, followed by a nearly invariant low porosity in the compressive region.…”

Section: Void Collapse Effects On Stresssupporting

confidence: 89%

Structural origins of intrinsic stress in amorphous silicon thin films

et al. 2012

View full text Add to dashboard Cite

Hydrogenated amorphous silicon (a-Si:H) refers to a broad class of atomic configurations, sharing a lack of long-range order, but varying significantly in material properties including optical constants, porosity, hydrogen content, and intrinsic stress. It has long been known that deposition conditions affect microstructure, but much work remains to uncover the correlation between these parameters and their influence on electrical, mechanical, and optical properties critical for high-performance a-Si:H photovoltaic devices. We synthesize and augment several previous models of deposition phenomena and ion bombardment, developing a refined model correlating plasma enhanced chemical vapor deposition (PECVD) conditions (pressure and discharge power and frequency) to the development of intrinsic stress in thin films. As predicted by the model presented herein, we observe that film compressive stress varies nearly linearly with bombarding ion momentum and with a (-1/4) power dependence on deposition pressure, that tensile stress is proportional to a reduction in film porosity, and the net film intrinsic stress results from a balance between these two forces. We observe the hydrogen bonding configuration to evolve with increasing ion momentum, shifting from a voiddominated configuration to a silicon monohydride configuration. Through this enhanced understanding of the structure-property-process relation of a-Si:H films, improved tunability of optical, mechanical, structural, and electronic properties should be achievable.

show abstract

Section: Void Collapse Effects On Stresssupporting

confidence: 89%

Structural origins of intrinsic stress in amorphous silicon thin films

et al. 2012

View full text Add to dashboard Cite

show abstract

“…33,34 That it is possible to deposit high quality a-Si:H at lower substrate temperatures when sufficient ion bombardment takes place is also suggested by Abelson. 61 Moreover, a relation between the ion energy and both the film density and R* is indicated by the data of Hamers et al 62 Using rf and VHF PECVD, it was shown that dense films with R*Ͻ0.1 were obtained when 5 eV ion energy was available per Si atom deposited. This observation is consistent with the fact that films with reasonable properties can be obtained at 3 nm/s by rf PECVD when depositing at the cathode and using somewhat higher substrate temperatures ͑350°C͒ than usually.…”

Section: B Comparison With A-si:h Deposited By Other Techniquesmentioning

confidence: 98%

Hydrogenated amorphous silicon deposited at very high growth rates by an expanding Ar–H2–SiH4 plasma

Kessels

Severens

Smets

et al. 2001

Journal of Applied Physics

View full text Add to dashboard Cite

The properties of hydrogenated amorphous silicon (a-Si:H) deposited at very high growth rates (6–80 nm/s) by means of a remote Ar–H2–SiH4 plasma have been investigated as a function of the H2 flow in the Ar–H2 operated plasma source. Both the structural and optoelectronic properties of the films improve with increasing H2 flow, and a-Si:H suitable for the application in solar cells has been obtained at deposition rates of 10 nm/s for high H2 flows and a substrate temperature of 400 °C. The “optimized” material has a hole drift mobility which is about a factor of 10 higher than for standard a-Si:H. The electron drift mobility, however, is slightly lower than for standard a-Si:H. Furthermore, preliminary results on solar cells with intrinsic a-Si:H deposited at 7 nm/s are presented. Relating the film properties to the SiH4 dissociation reactions reveals that optimum film quality is obtained for conditions where H from the plasma source governs SiH4 dissociation and where SiH3 contributes dominantly to film growth. Conditions where ion-induced dissociation reactions of SiH4 prevail and where the contribution of SiH3 to film growth is much smaller lead to inferior film properties. A large contribution of very reactive (poly)silane radicals is suggested as the reason for this inferior film quality. Furthermore, a comparison with film properties and process conditions of other a-Si:H deposition techniques is presented.

show abstract

“…The technique is based on a cascaded arc as developed by Maecker [35] in 1956. Initial research on a-Si:H deposition with the cascaded arc was performed by Meeusen [36,37] who obtained optimum deposition conditions while optimising on the refractive index. Further optimisation has been carried out by Severens [38], Kessels [39], and Smets [40] to get a better understanding on growth conditions and plasma conditions that would result in solar grade a-Si:H. In 1997 a project was initiated that resulted in CASCADE, a project to integrate a-Si:H deposited at large growth rates with a cascaded arc expanding thermal plasma into solar cell structures.…”

Section: Statement Of the Problemmentioning

confidence: 99%

“…Concerning the energetic ions it seems that ions with energy up to 25 eV have an important contribution to the material quality obtained with RF-PECVD [e.g. [79][80][81]. Finger et al also observed that an increased ion flux resulted in less hydrogen contributing to the stretching mode peak between 2060 and 2100 cm -1 [82].…”

Section: Measurementsmentioning

confidence: 99%

“…Furthermore, the ETP plasma does not have a large amount of atomic hydrogen and energetic ions (up to 25 eV) at the growing surface under conditions that result in good quality a-Si:H. The ions have low energy and the only hydrogen is the hydrogen that is released from the radicals that contribute to growth [33]. Both hydrogen and ions can help to rearrange the growing silicon atoms [34][35][36][37]. Therefore, it is possible that besides the larger growth rate [26], the lower hydrogen content and/or the lack of energetic ions at the growing surface can result in a somewhat rougher surface of the ETP layers.…”

Section: 12: Relative Quantum Efficiency Showing the Degradation Permentioning

confidence: 99%

See 1 more Smart Citation

Integration of Expanding Thermal Plasma deposited Hydrogenated Amorphous Silicon in Solar Cells

et al. 2002

View full text Add to dashboard Cite

A cascaded arc expanding thermal plasma is used to deposit intrinsic hydrogenated amorphous silicon at growth rates between 0.2 and 3 nm/s. Incorporation into a single junction p-i-n solar cell resulted in an initial efficiency of 6.7%, whereas all the optical and initial electrical properties of the individual layers are comparable with RF-PECVD deposited films. In this cell the intrinsic layer was deposited at 0.85 nm/s and at a deposition temperature of 250°C, which is the temperature limit for growing the p-i-n sequence. The cell efficiency is limited by the fill factor and using a buffer layer at the p-i interface deposited with RF-PECVD at low growth rate can increase this. The increase in fill factor is a result of a lower initial defect density near the p-i interface then obtained with the expanding thermal plasma, resulting in better charge carrier collection. To use larger growth rates, while maintaining the material properties, higher deposition temperatures are required. Higher deposition temperatures result in a smaller optical bandgap for the intrinsic layer and deterioration of the p-type layer, resulting in a lower opencircuit voltage. First results on applying a buffer layer will also be presented.

show abstract

Structural properties of a-Si:H related to ion energy distributions in VHF silane deposition plasmas

Cited by 46 publications

References 29 publications

Structural origins of intrinsic stress in amorphous silicon thin films

Structural origins of intrinsic stress in amorphous silicon thin films

Hydrogenated amorphous silicon deposited at very high growth rates by an expanding Ar–H2–SiH4 plasma

Integration of Expanding Thermal Plasma deposited Hydrogenated Amorphous Silicon in Solar Cells

Contact Info

Product

Resources

About