Subnanometer-resolution depth profiling of boron atoms and lattice defects in silicon ultrashallow junctions by ion beam techniques

Abstract

The continued research and development effort on silicon ultrashallow junctions has posed a great challenge to materials characterization, due to the need for depth profiling of dopants and silicon lattice defects with a subnanometer resolution. In this work, we report on a method combining ion beam analysis (Rutherford backscattering, ion channeling, and nuclear reaction analysis) with room-temperature UV-assisted oxidation and chemical wet etching for obtaining high-resolution (∼0.5 nm) depth distributions of total boron atoms, electrically activated boron atoms and silicon lattice defects in silicon ultrashallow junctions. The application of this method was demonstrated by profiling silicon junctions as shallow as 8 nm, created by 200-eV boron ion implantation followed annealing by various techniques. The capability to profile boron at such high resolution has resulted in observation of boron segregation. Additionally, the ability for depth profiling Si lattice defects offered by this method has aided in the understanding of thermal and laser annealing effects on defect formation in Si junctions. Our experimental results are compared with those obtained using other techniques such as secondary ion mass spectroscopy and four-point probe, and differences are discussed in detail.

Simultaneous depth-profiling of electrical and elemental properties of ion-implanted arsenic in silicon by combining secondary-ion mass spectrometry with resistivity measurements

“…The resolution can therefore be improved by either (i) increasing the frequency at which measurements are made, by (ii) reducing the sputter rate, or by a combination of both factors. For a very low beam energy (<1 keV) a depth resolution better than 1 nm was found to be possible [15]. Two other issues are apparent when one inspects the raw SIMSAR plot with respect to DHM or RDP profiles.…”

Systematic compositional analysis of sputter-deposited boron-containing thin films

“…20,21 The performance of such small devices is determined by the distribution of implanted B dopant atoms, their electrical activation and nanostructure. 22,23 In addition, B has recently attracted attention for power device fabrication in the silicon carbide technology as it improves the channel mobility of metal-oxide-semiconductor field-effect transistors by incorporating into interfacial regions. 24,25 Moreover, there is a class of boron-containing materials formed by mixing B and transition metals, referred to as transition-metal diborides (TMB2), which have high melting points, excellent hardness, good tribological and corrosion properties, relatively low electrical resistivity, and high thermal and chemical stability.…”

“…IBA can be also combined with ion channeling to provide information about the lattice location and electrical activation of dopants, which are not possible with SIMS. 23 The motivation for this study is to critically evaluate the analysis conditions of the techniques in Table I, except SIMS, and to seek the best practice for elemental-composition determination in TMBx. In this context, we first determine the elemental compositions of TMBx thin films (TM = Ti, Zr, and Hf) grown by dc magnetron sputtering (DCMS) with EDX and XPS as two widely used analytical methods.…”