Sputtering of pure boron using a magnetron without a radio-frequency supply

Abstract

Boron at room temperature is insulating and therefore conventionally sputtered using radiofrequency (RF) power supplies including their power-matching networks. In this contribution we show that through a suitable ignition assistance, via temporary application of a high voltage (~ 600 V) to the substrate holder or auxiliary electrode, the magnetron discharge can be ignited using a conventional mid-frequency power supply without matching network.Once the discharge is ignited, the assisting voltage can be reduced to less than 50 V, and after the boron target surface is at elevated temperature, thereby exhibiting sufficient conductivity, the assisting voltage can be turned off. The deposition of boron and boron nitride films has been demonstrated with a deposition rate of approximately 400 nm/h for a power of 250 W.

Magnetron sputtering and electron beam evaporation systems for pure boron thin film coatings

“…The considered methods for obtaining pure boron coatings using magnetron discharge [20] and forevacuum electron source [21] are original and first implemented by the authors of the article. The analog of the first method can be considered a highfrequency magnetron discharge with a dielectric target [19]. In this case, the surface positive charge of the sputtering ions on the boron target is neutralized by the electron flux from the plasma with a pulse of reverse polarity.…”

“…The disadvantages of this approach are the presence of impurities in the coatings and the need to use special filters to purify the plasma from the macroparticle fraction generated of the vacuum arc [18]. To deposit boron coatings, a radio-frequency magnetron sputter with pure crystalline boron target can be used, but deposition rate for such devices is relatively low and amounts to a few nanometers per minute [19]. The implementation of the processes of evaporation and ionization of boron by electron beams is hampered by low electrical conductivity of the target material made of pure boron, which, in turn, makes it difficult to focus the beam on it, due to the electrical charging of its surface by the beam.…”

Low temperature pure boron layer deposition for Si diode and micromachining applications

“…In the semiconductor field, ultrapure amorphous boron (a-B) is mostly prepared either by CVD [25,85], where it is common to decompose the molecule vapor of boron hydrides (BxHy) on the wafer surface and in the vacuum, or by PVD [86,87], where the solid phase elemental boron target is vaporized by plasma or electron beam, and boron atoms will subsequently land on the surface. In the chemical approach, the decomposition of boranes is usually realized by plasma or pyrolysis, such as direct current (DC)/radio frequency (RF)/electron cyclotron resonance (ECR) PECVD or LPCVD.…”

Electron-Beam Synthesis of Dielectric Coatings Using Forevacuum Plasma Electron Sources (Review)

“…In this way, it is possible to produce boron-based coatings, but the main problem posed here is cracking and destruction of the pure boron target due to the mechanical stress caused by heating. Let us consider the possibility of the self-sputtering regime in the pulsed magnetron discharge system with a pure boron cathode described in papers [31,32]. The use of a bipolar voltage pulse, in combination with negative potential applied to the collector, ensured stable burning of the magnetron discharge with a frequency of 300-350 kHz, which is much lower than the «standard» magnetron frequency (13.5 MHz).…”

“…discharge system with a pure boron cathode described in papers [31,32]. The use of a bipolar voltage pulse, in combination with negative potential applied to the collector, ensured stable burning of the magnetron discharge with a frequency of 300-350 kHz, which is much lower than the «standard» magnetron frequency (13.5 MHz).…”