Acceptor Compensation in Silicon Induced by Chemomechanical Polishing

Abstract

The acceptor compensation in polishing of p-type silicon with ammonia or amine-containing silica sol slurries has formerly been explained by the well-known inactivation of boron with atomic hydrogen or by the action of lattice selfinterstitials. We give evidence by neutron activation analysis, energy-dispersive x-ray analysis, secondary ion mass spectroscopy and photoluminescence spectroscopy that traces of copper in the slurry are responsible for this effect. A mechanism for the chemomechanical polishing of silicon and the incorporation of copper into the wafer is suggested.

Impact of Research on Defects in Silicon on the Microelectronic Industry

“…Collaboration between industry and universities was at work, too in uncovering the puzzle of Cu contamination during chemomechanical polishing [42,43]. It was discovered in polishing experiments on highly boron-doped Si that a transient passivation behavior by in-diffusion of Cu can occur even near room-temperature with an estimated diffusion rate of about 10 ± ±7 cm 2 /s which was several orders of magnitude larger than extrapolated from high temperature data.…”

Quantitative Evaluation of Gettering Efficiencies Below 1×10[sup 12] Atoms∕cm[sup 3] in p-Type Silicon Using a [sup 65]Cu Tracer

“…Then silicon hydrides reduce Cu 2+ to Cu + , leaving hydrogen molecules, and the diamine molecules released to the slurry solution form a Si-Cu bond on silicon surfaces. The Cu + ions thus produced diffuse into bulk silicon even at room temperature due to its small ionic radius of 60 pm, 9 and atomic radius of 128 pm. In other words, the diamine additives help copper ions to diffuse into bulk silicon after complexing with copper ions; unfortunately, the identities of diamines used and their concentrations in the slurry were proprietary.…”

“…9 The copper ions are then precipitated as copper-rich silicide at the Si/SiO 2 interface in bulk silicon. 9,10 At times, however, the copper diffuses out to the wafer surface and forms agglomerated particles or pits. 11,12 Figure 1 shows a typical example of particle agglomerates containing copper atoms on a silicon wafer surface and their magnified image obtained by scanning electron microscopy ͑SEM͒.…”

Impact of the Unique Physical Properties of Copper in Silicon on Characterization of Copper Diffusion Barriers

“…The knowledge of the true diffusion coefficient of Cu i enabled us to explain the phenomenon of room temperature in-diffusion of copper during chemical-mechanical polishing [39], and its fast out-diffusion from the bulk to the surface during subsequent storage of the wafer [40,41]. Equation (4) predicts that the time which it takes copper to diffuse from one wafer surface to another or to completely diffuse out to the wafer surface will increase with the increasing boron concentration, and will decrease with the increasing temperature.…”