Quality improvement of plasma-beam-deposited amorphous hydrogenated carbon with higher growth rate

Abstract

An improved plasma beam deposition set-up, based on an expanding thermal plasma, is presented. Amorphous hydrogenated carbon films have been deposited on glass and crystalline silicon, under variation of the arc current and admixed acetylene flow. The films have been analysed ex situ with infrared absorption spectroscopy, broadband visible light transmission and nano-indentation measurements. These techniques reveal the growth rate, refractive index, bonded C-H density, optical bandgap and hardness. The growth rate and refractive index are found to increase with decreasing arc current and increasing acetylene flow admixture. The quality of the films in terms of refractive index and hardness increases with increasing growth rate and inverse energy coefficient, whereas the bonded hydrogen concentration and optical bandgap then decrease. From comparison of the growth rate dependency with the inverse energy coefficient dependency, we conclude that the growth rate is the preferred parameter in terms of which to describe the film properties because it is directly related to the plasma composition.

Optical and mechanical properties of plasma-beam-deposited amorphous hydrogenated carbon

“…[7][8][9] A major advantage of this technique compared to most commonly used plasmaenhanced chemical-vapor-deposition ͑PECVD͒ techniques 6 is the more efficient dissociation of the admixed precursors. This results in much higher growth rates, currently up to 75 nm/s for a-C:H material.…”

“…9 These films have been deposited under variation of the plasma ionization degree and the admixed hydrocarbon flux. No additional substrate biasing has been applied and the energy of the ions therefore is determined by the self-bias which is only a few volts; thus, an energetic ion bombardment of the surface is not present.…”

Synergistic etch rates during low-energetic plasma etching of hydrogenated amorphous carbon

“…59,60 The variety in sp 2 to sp 3 ratio and hydrogen content leads to several different types of a-C:H, many of which can be deposited by PE-CVD. [20][21][22]59 PE-CVD is a well known technique in our group and is used in this work as well to prepare a-C:H samples for etching. The deposited carbon material should furthermore be seen as a generic material model for carbon rather than the study of a very specific type of a-C:H. Even so, the (initial) properties of these samples together with the deposition process are described in Sec.…”

“…IV. [20][21][22] To deposit these samples, acetylene (15 sccs) is added via an injection ring to an Ar plasma (100 sccs, 75 A, 4.5 kW) at a background (BG) pressure of 30 Pa. The substrate temperature is 250 C, with a backflow of helium (1 sccs) for improved thermal contact.…”

“…a-C:H thin films deposited with plasma-enhanced chemical vapour deposition (PE-CVD) are used as a model material. [20][21][22] The incident ion flux is thereby determined via electrical probe measurements, while radical fluxes are estimated from previous work in our group. Variations in the particle flux between the different plasma systems can then be accounted for when comparing the etch rates of each system.…”