Microstructure of a-C:H films prepared on a microtrench and analysis of ions and radicals behavior

Journal Article · Fri Aug 28 04:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4929427· OSTI ID:22494805

Hirata, Yuki; Choi, Junho ^[1]

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1. Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

Amorphous carbon films (a-C:H) were prepared on a microtrench (4-μm pitch and 4-μm depth), and the uniformity of film thickness and microstructure of the films on the top, sidewall, and bottom surfaces of the microtrench were evaluated by scanning electron microscopy and Raman spectroscopy. The a-C:H films were prepared by bipolar-type plasma based ion implantation and deposition (bipolar PBII&D), and the negative pulse voltage, which is the main parameter dominating the film structure, was changed from −1.0 to −15 kV. Moreover, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision (PIC-MCC) and Direct Simulation Monte Carlo (DSMC) to investigate the coating mechanism for the microtrench. The results reveal that the thickness uniformity of a-C:H films improves with decreasing negative pulse voltage due to the decreasing inertia of incoming ions from the trench mouth, although the film thickness on the sidewall tends to be much smaller than that on the top and bottom surfaces of the trench. The normalized flux and the film thickness show similar behavior, i.e., the normalized flux or thickness at the bottom surface increases at low negative pulse voltages and then saturates at a certain value, whereas at the sidewall it monotonically decreases with increasing negative voltage. The microstructure of a-C:H films on the sidewall surface is very different from that on the top and bottom surfaces. The film structure at a low negative pulse voltage shifts to more of a polymer-like carbon (PLC) structure due to the lower incident energy of ions. Although the radical flux on the sidewall increases slightly, the overall film structure is not significantly changed because this film formation at a low negative voltage is originally dominated by radicals. On the other hand, the flux of radicals is dominant on the sidewall in the case of high negative pulse voltage, resulting in a deviation from the Raman behavior of a-C:H films deposited by bipolar PBII&D. This tendency intensifies as the negative voltage becomes greater. Also, the energy of incident ions on the sidewall of the trench increases with increasing negative voltage, which causes a shift in the Raman data of the sidewall to the bottom right corner on the figure depicting the relationship of the FWHM(G) and the G-peak position, indicating increased graphitization of a-C:H film.

• OSTI ID: 22494805
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 118; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CARBON
COMPUTERIZED SIMULATION
DEPOSITION
ELECTRIC POTENTIAL
GRAPHITIZATION
ION IMPLANTATION
IONS
MICROSTRUCTURE
MONTE CARLO METHOD
PLASMA
POLYMERS
PULSES
RADICALS
RAMAN SPECTROSCOPY
SCANNING ELECTRON MICROSCOPY
SURFACES
THICKNESS
THIN FILMS