Atomic fluorine beam etching of silicon and related materials

Abstract

A 1 eV neutral atomic fluorine beam has been shown to produce etch rates in silicon as high as 1 μm/min. Using a CaF2 resist layer we fabricated 120 μm deep by 1 μm wide trenches (aspect ratio 120:1) in silicon with little sidewall taper (slopes of about 1000:1) or aspect-ratio dependent etching effects. Achieving such anisotropic etching suggests that the scattered species do not contribute significantly to sidewall etching under the conditions of this experiment. We estimate that the ultimate depth attainable for a 1 μm wide trench is about 250 μm and that the critical parameter for attaining a trench of a certain depth is the aspect ratio. Our observations and analysis suggest that this etching technique can be used to fabricate trenches on a nanoscale level while maintaining high aspect ratios of 100 or greater.

Etching silicon by SF6 in a continuous and pulsed power helicon reactor

“…There have been a number of studies using ''hyperthermal'' beams of neutral fluorine ͑and other species͒. 15,16 which show high etch rates and efficient use of the available fluorine. These experiments have no ions involved and the results of Giapis 15 for etching of silicon by atomic fluorine are very close to those presented here for the high flow rates.…”

Optical Diagnostics of SF6 Low Pressure Plasma Jet Applied to Silicon Etching

“…The density n F is given by the following relationship , (1) where I F and I Ar denote the emission intensities at 703.7 and 750.4 nm, n Ar represents the ground state Ar density and K F is the ratio of the excitation efficiencies of F and Ar and depends on several parameters such as cross sections for excitation of F and Ar by electron impact, the electron density and the EEDF. Several studies indicate that the value of K F for fluorinated gases such as SF 6 and CF 4 lies between 0.56-4.0 (11,12). In this work, the used value of K F is based on the lowest value published, i.e., 0.56.…”

“…(a) Atomic fluorine density and (b) % F in gas estimated as a function of SF 6 gas pressure for three different rf power.The influence of oxygen concentration within the SF 6 +O 2 plasma From numerous published works, it is known that the addition of O 2 to the SF6 gas accelerates the etch rates of Si-based materials. This occurs because the addition of O 2 creates a new path to creation of F atoms through the oxidation reaction of SF x (…”

High-aspect-ratio patterning by ClF3-Ar neutral cluster etching

“…If a neutral reactive gas cluster beam can effectively etch materials, it is expected that the reactive gas cluster should have high speed, high selectivity, and high precision, and should cause minimal damage. It has been demonstrated that fluorine atom beam etching has an advantage over plasma etching in fabricating deep high-aspect-ratio structures in silicon [11]. Silicon is rapidly etched by gas-phase halogen fluorides such as ClF 3 , BrF 3 , BrF 5 , and IF 5 , in analogy to XeF 2 etching silicon.…”