The energy distribution of ballistic electrons in a dc/rf hybrid parallel-plate capacitively coupled plasma reactor was measured. Ballistic electrons originated as secondaries produced by ion and electron bombardment of the electrodes. The energy distribution of ballistic electrons peaked at the value of the negative bias applied to the dc electrode. As that bias became more negative, the ballistic electron current on the rf substrate electrode increased dramatically. The ion current on the dc electrode also increased.

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One of the most challenging and recurring problems when modeling plasmas is the lack of data on the key atomic and molecular reactions that drive plasma processes. Even when there are data for

Atomic layer etching (ALE) is a promising technique that can solve the challenges associated with continuous or pulsed plasma processes—trade-offs between selectivity, profile, and aspect ratio dependent etching. Compared to silicon, oxide, and other materials, atomic layer etching of silicon nitride has not been extensively reported. In this paper, the authors demonstrate the self-limited etching of silicon nitride in a commercial plasma etch chamber. The process discussed in this paper consists of two sequential steps—surface modification in hydrogen plasma followed by the removal of modified layers in fluorinated plasma. In addition to the ALE characteristics, the authors also demonstrate that the process is anisotropic and the selectivity to oxide is >100. Although the saturated etch rate of one monolayer per cycle could not be attained, self-limited etching of silicon nitride still enables us to incorporate the benefits of atomic layer etching such as an absence of isodense bias and an extremely high selectivity to oxide into practical etch applications.

We undertake a dielectric breakdown failure analysis of thin hexagonal boron nitride (h-BN) by conduction atomic force microscopy. The breakdown field is 21 MV cm–1 for 3 nm-thick h-BN, and the breakdown voltage statistics follows a tight monomodal Weibull distribution, indicating the material suitability as a gate dielectric. Breakdown effects extend over an area of ∼100 nm diameter and evolve by defect generation in the h-BN, with increasing conductance under repeated stressing; but the breakdown current–voltage (I–V) curves differ from conventional ultrathin SiO2 and HfO2 films. Specifically, there are indications that 2D layering is influencing the breakdown as follows: (i) Fowler–Nordheim fitting of successive I–V curves after stressing often proceeds in discrete monolayer thickness values of ∼0.3 nm, an effect that we propose arises from electrical “shorting” between adjacent layers, and (ii) the Weibull slope decreases as film thickness increases, indicating that the defect generation is not random but occurs preferentially at specific locations.