Neutralization of Acceptors and Formation of Agglomerates in Silicon Wafers Due to Intrinsic Point Defects Created by Chemomechanical Polishing and by Quenching

Abstract

Due to polishing swirl‐free silicon wafers chemomechanically structural defects are created. Moreover, in case of boron‐doped wafers the resistance is increased. Structural defects as well as an increase of resistance are also observed after quenching from 750°C in air. At increased resistance boron is neutralized by a defect diffusing fast at room temperature. The defect behaviour differs markedly from that of atomic hydrogen and of iron. This defect is looked upon as an intrinsic point defect. Intrinsic point defects are also assumed to be the origin of the structural defects observed. Their formation energy is the same as for new oxygen donors and as the activation energy on annihilation of thermal donors.

Physics of Copper in Silicon

“…It is interesting that contamination of Si wafers with Cu during chemomechanical polishing, a phenomenon discovered over ten years ago, 8,32,33,[111][112][113] is essentially a reversed out-diffusion, with initially little or no Cu in the wafer and a plentiful supply of Cu by the contaminated slurry to the surface. A principle difference, however, is that the near-surface band bending, which slows the outdiffusion of Cu by repelling Cu i ϩ from the surface into the bulk of p-type wafers, now drives Cu into the wafer during chemomechanical polishing.…”

Acceptor Compensation in Silicon Induced by Chemomechanical Polishing

“…Another group related the resistivity increase to the creation of intrinsic point defects during the polishing process (13). The structural defects and their kinetics were compared to those in quenched samples, and analogy considerations led to the assumption that vacancies or selfinterstitials would be the most probable cause of the boron neutralization.…”