The semiconductor industry started to conquer the nm-scale in process technology to create the next generation of microsized integrated circuits. With the down-scaling of semiconductor structures, surfaces and interfaces need precise control to achieve high yielding integrated circuits. For roughness determination of high quality surfaces and thickness control of ultra-thin layers, X-ray scattering proves to be an innovative tool. We demonstrate that specular and diffuse X-ray scattering from a silicon surface with a thin thermal oxide allows the precise determination of real structure parameters such as roughness, bulk density, oxide thickness, lateral correlation length and fractal dimension.

Atomic force microscopy and x-ray scattering are applied to describe changes in the morphology of Si( 100) surfaces due to wet chemical processing. With atomic force microscopy, the rms roughness o in dependence on the lateral scan length XO is measured. Additionally, two lateral order parameters are determined, the lateral correlation length L and Hurst parameter h. With x-ray scattering, the corresponding parameters are determined. X-ray reflectometry provides the rms roughness o of the silicon surface as well as the silicon density p. X-ray diffuse or off-specular scattering gives information on the lateral order of surfaces and interfaces and allows to recalculate the fractal parameters L and h of the silicon surfaces investigated. For the results of o, L and h, atomic force microscopy and x-ray scattering give different quantities. This is attributed to the differing vertical and lateral resolution of the methods applied. Whereas x-ray scattering provides only one set of values for o, L and h, atomic force microscopy can yield different sets of values dependent on the lateral scan length X0 chosen in the atomic force microscopy measurements.

The effect of different metallic contaminants on MOS structures is reviewed. Cleaning processes tend to consist of long sequences of individual steps. Each step is often performed in its own tank resulting in large equipment. It is the purpose of this work to introduce reduced cleaning with improved cleanliness performance. Also a lot of attention is devoted to final rinsing, particularly with respect to the risk of metal recontamination.

The paper presents a new strategy for cleaning of silicon wafers. A novel class of chelating agents added to alkaline cleaning mixtures provides promising performance without negative effects such as metal redeposition due to residual metal contamination of the cleaning solution. The superior capability of the new cleaning process is confirmed by the results obtained from wafer surface metal analysis as well as from minority carrier lifetime and diffusion length measurements and gate oxide integrity tests. Particle densities and surface roughness are not influenced by the presence of the chelating agents in the cleaning solution. TOF–SIMS measurements do not indicate any deposition of chelating agent on the wafer surface. With this type of modified SC-1 cleaning procedure the acid SC-2 step used in conventional RCA cleans to remove the metals deposited in the preceding SC-1 step is unnecessary resulting in substantial cost savings with respect to chemicals, waste, equipment and space.

This paper presents a new class of complexing agents (CA) for application in SC-1 cleaning solution. The prevention of metal precipitation to the silicon surface by using this type of chelating agent is demonstrated in intentionally contaminated dilute SC-1 solutions by metal surface analyses (VPD-DSE-TXRF, VPD-DSE-AA, SPV, ELYMAT) and GOI tests of 6 " epi and non-epi wafers. Precipitation of CA related organic matter on the wafer surface could be excluded by TOF-SIMS measurements. Particle analyses and wafer surface roughness are not influenced by the addition of the complexing agents. With this type of advanced SC-I solution the need for the SC-2 step as in conventional RCA clean to remove the metal precipitants from the preceeding SC-1 step seems to be obsolete.

Atomic force microscopy and x-ray scattering are applied to describe changes in the morphology of Si( 100) surfaces due to wet chemical processing. With atomic force microscopy, the rms roughness o in dependence on the lateral scan length XO is measured. Additionally, two lateral order parameters are determined, the lateral correlation length L and Hurst parameter h. With x-ray scattering, the corresponding parameters are determined. X-ray reflectometry provides the rms roughness o of the silicon surface as well as the silicon density p. X-ray diffuse or off-specular scattering gives information on the lateral order of surfaces and interfaces and allows to recalculate the fractal parameters L and h of the silicon surfaces investigated. For the results of o, L and h, atomic force microscopy and x-ray scattering give different quantities. This is attributed to the differing vertical and lateral resolution of the methods applied. Whereas x-ray scattering provides only one set of values for o, L and h, atomic force microscopy can yield different sets of values dependent on the lateral scan length X0 chosen in the atomic force microscopy measurements.

The H2O2 in NH4OH/H2O2/H2O cleaning mixture is known to be subject to decomposition [1]. This decomposition not only results in a gradual change of the composition of the cleaning mixture but has also been correlated with degradation of the silicon wafer surface integrity, particularly if made hydrophobic by an HF treatment [1-5]. Several experimental studies on the kinetics of the decomposition of H2O2 in SCl-like cleaning solutions have been performed [3-6].

Submicron semiconductor manufacturing requires ultra-clean processes and materials to achieve high product yields. It is demonstrated that electrothermal evaporation (ETV) in a graphite furnace coupled with ICPMS offers a new possibility for a fast simultaneous analysis of eight elements with detection limits below 0.2 ng/g in conc. hydrofluoric acid and buffered oxide etch (ammonium fluoride/hydrogen fluoride mixture). ETV-ICPMS also comprises significant improvements in the analysis of metal contamination on silicon wafer surfaces with respect to currently used methods. The contaminants on the surface are usually analyzed by total reflexion X-ray fluorescence spectrometry (TXRF) or dissolved by HF vapour (vapour phase decomposition; VPD) or a mixture of hydrofluoric acid and hydrogen peroxide (droplet surface etching, DSE) and analyzed by GFAA or TXRF. ETV-ICPMS combines the advantages of both analytical methods: the multielemental advantage of TXRF and the possibility to analyze light elements like Al, Mg, Na which may not be analyzed by TXRF. With VPD/DSE-ETV-ICPMS detection limits between 0.2 and 2×109 atoms cm−2 on a 6″ wafer have been achieved in a simultaneous analysis of eight elements. The main advantage of ETV-ICPMS versus conventional ICPMS in both applications — chemical and surface analysis — is its capability to analyze Fe in the sub-ng/g range. As Fe is one of the most important impurities in semiconductor manufacturing ETV-ICPMS is much more useful for semiconductor applications than low-resolution ICPMS. For the present application potassium iodide was used as a modifier. It enhances the sensitivity by a factor of 3–4 and improves the reproducibility significantly.

The physical principles and analytical capabilities of TXRF are discussed and compared to other surface sensitive techniques. Metallic trace impurities on silicon surfaces are readily identified with detection limits down to 1011 atoms/cm2 (10−4 monolayers). Other advantages are simple sample preparation and the possibility of analyzing insulating layers without charging problems. The method has been applied to quantify coverages of Fe, Ni, Cu and Au on Si(100) surfaces, deposited from intentionally doped solutions (NH3/H2O2 and HF/NH4F). It turns out that certain metal/solution combinations cause large surface coverages on the silicon wafer, even if the metal concentration in the solution is very low (μg/kg range).