Magnetic field effects on cylindrical magnetron reactive ion etching of Si/SiO2 in CF4 and CF4/H2 plasmas J. Vac. Sci. Technol. A 7, 987 (1989); 10.1116/1.575788Xray photoemission spectroscopy characterization of silicon surfaces after CF4/H2 magnetron ion etching: Comparisons to reactive ion etching

Damagelcontamination effects of dry etching in two different modes, plasma etching (PE) and reactive ion etching (RIE), on silicon surfaces just after oxide etching were studied. The electrical measurements on aluminum Schottky diodes were used to evaluate the effect of dry processing and various post-etch treatments on a Si substrate. The presence of heavy metal contamination on the Si surface as a result of dry etching is confirmed by secondary ion mass spectroscopy (SIMS) and SECCO etch defect decoration. C-r (minority-carrier lifetime) measurements on special guard ring devices were used as indirect evidence of heavy metal contaminants. The quality of a gate oxide grown on Si surfaces after dry-etching conditions is examined through breakdown voltage. Improved device electron mobility is observed for the RIE-exposed Si surface compared to PE, due to the smoother surface after the RIE process.

A comprehensive characterization of the damage and contamination produced in silicon by CC1F3/H2 reactive ion etching is presented. This highly selective SiO2-to-Si reactive ion etching process unfortunately produces all three of the deleterious damage-contamination layers that can result from dry etching exposure; viz., CC1F3/H2 reactive ion etching produces a residue layer on the Si surface, a permeated layer at the Si near-surface, and a layer of damaged Si. Various post-RIE-exposure, surface-recovery approaches are evaluated in this report. The results indicate that in order to restore the surface to a device-quality state, it is not sufficient to simply eliminate surface contamination. Damage incurred in the silicon bonding must be restored or removed. The latter can be accomplished by suitable treatments such as wet chemical silicon etch or silicide formation.

Passivated Cu lines deposited by CVD, electroplating, and sputter-reflow were investigated using x-ray diffraction. Blanket films of the three types were measured for strain and texture post-deposition and after an anneal step to mimic the passivation temperature step. Texture in the CVD films was random, while the electroplated and sputtered films showed a strong {111} texture. Lines were then measured of each type. The measured strain was modeled using finite element calculations. While the strain in Cu was high compared to Al lines of similar geometry, no stress voiding was observed using high voltage scanning electron microscopy.

It is demonstrated, using two very different techniques (viz., CF4 reactive ion etching and Ar ion beam etching), that dry etching exposure causes extensive boron acceptor neutralization in silicon. This boron neutralization is observed to occur as far as microns below the etched surface with etching exposures of only ≂1 min. Neutralization occurs if the temperature does not exceed about 180 °C during etching; it may be annealed out by subsequent exposure to such temperatures. Adsorbed water vapor or, alternatively, hydrogen inherent in the silicon is proposed to provide hydrogen-related species which cause this neutralization. Protons created in the plasma from these sources, or hydrogen-related species directly liberated from their sources on or in the solid, may be injected into the silicon during the energetic ion impact constantly present in dry etching. This observation of boron neutralization deep below the etched surface demonstrates that dry etching exposure causes extensive permeation of foreign species into the etched material.