High silicon etch rates by hot filament generated atomic hydrogen

Abstract

The etching of hydrogenated amorphous silicon (a-Si:H) and microcrystalline silicon by hot tungsten filament generated atomic hydrogen has been investigated. Room-temperature etch rates of 27 Å s −1 for amorphous and 20 Å s −1 for microcrystalline silicon have been achieved. Boron doping decreases the etch rate, whereas phosphorus doping does not affect it. No surface roughening occurs, even for the highest a-Si:H etch rates. In the initial phase of the etch process, however, a bond structure modification arises close to the surface. An increase of microcrystalline silicon etch rates towards the substrate/film interface reflects the coalescence of the microcrystalline nuclei. Hot filament atomic hydrogen etching provides high etch rates of amorphous and polycrystalline silicon with a high selectivity against metals and thermal oxide. Due to its simple setup and control, this kind of hydrogen etching is very interesting for applications in semiconductor technology where F-or Cl-etchants are to be avoided.

In-SituMeasurements of Charged Nanoparticles Generated During Hot Wire Chemical Vapor Deposition of Silicon Using Particle Beam Mass Spectrometer

“…• C. It is widely known that an appreciable amount of atomic hydrogen is generated by HWCVD and the atomic hydrogen etches silicon (Wanka and Schubert 1997). Moreover, they reported that the etching rate of Si increased with increasing wire temperature in HWCVD.…”

Etching of a-Si:H thin films by hydrogen plasma: A view from in situ spectroscopic ellipsometry

“…18 This particular behaviour agrees with the high diffusivity of hydrogen in boron-doped silicon 43 and the greater etch resistance of this material against H atoms. 47 Indeed, the very same catalytic effect of BH 3 that boosts the growth rate of p-type a-Si:H 48, 49 reduces the etch rate of boron-doped Si during atomic-hydrogen etching. Indeed, etching of boron-doped material promotes the formation of hydroboron radicals, which rarely escape from the surface.…”

Chemical sputtering by H2+ and H3+ ions during silicon deposition

“…This temperature maximum in the yield has not been reported for atomic H produced with a tungsten filament. 13 Since the Si etch yield of the 20 eV D 3 þ beam is much lower than one should expect from chemical sputtering, Balden and Roth suggested that E dam is about 30 eV for c-Si. Then, the results confirm that etching of D 3 þ with ion energies below E dam is similar to atomic H etching: the etch yield of atomic H etching 6,7 at 130 C is about 0.015.…”

“…Si-Si bond breaking reactions involved in atomic H etching have an activation energy of about 0.4 eV. 12 However, Wanka and Schubert 13 observed that the aSi:H etch rate by atomic H, formed with a hot-tungsten filament, reduces for temperatures above room temperature. Two mechanisms can explain this observation: reduced atomic H surface coverage at elevated temperatures due to either enhanced atomic H recombination and desorption 14 or enhanced atomic H diffusion into the bulk.…”