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Surface Contaminant Detection in Semiconductors Using Noncontacting Techniques
Journal of The Electrochemical Society
Abstract
It is well known that, as device geometries continue to shrink, contaminants such as micro particles as well as metallic and
organic contaminants have an ever-increasing impact on device yields. Therefore their detection and identification are of
great importance for the microelectronics industry. In this work, the possibility to detect surface contamination on silicon
wafers with fast, simple, nondestructive and noncontacting methods is presented, and the capability of using scanning Kelvin
probe technique to map surface contaminants on Si wafers is shown. The method proved to be useful for the analyses of surface
contaminants because the results obtained were comparable with the ones obtained by well-established spectroscopic methods
like space-resolved Fourier transform infrared spectroscopy. © 2003 The Electrochemical Society. All rights reserved.
... With other techniques, it is possible to detect nonvolatile contamination or even both volatile and nonvolatile contamination. These techniques include, e.g., laser-scanning wafer inspection, scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and microfluorescence spectroscopy [3], light scattering measurement [light point defect (LPD)] [4], pyrolysis-GC, pyrolysis-MS, pyrolysis-GC/MS, secondary ion MS with time-of-flight mass analyzer (SIMS-TOF) [5]- [7], Fourier-transform infrared spectroscopy (FTIR) with different sampling and measurement systems such as attenuated total reflection (ATR) and multiple internal reflection IR spectroscopy (MIRIS) [8], atomic force microscopy (AFM) [2], scanning Kelvin probe technique [9], capillary electrophoresis (CE) [10], and total reflection X-ray fluorescence (TXRF) with nearedge X-ray absorption fine structure (NEXAFS) [11]. Many of these analytical techniques have been compared in the analysis of organic contamination from silicon wafers [2], [12]. ...
This paper presents a new analytical setup that aims for a qualitative analysis of both volatile and nonvolatile organic contamination simultaneously from one whole silicon wafer. The aim was to develop a screening method that can be used for the identification of the source(s) of organic contamination for quality control in the manufacturing process. The model compounds used in the analysis were a solvent (toluene), a photoresist, and a resist stripper solution. The instrumental setup consisted of a heatable chamber for sample handling and an online mass spectrometer for detection. The organic contamination could be directly desorbed from the surface of the silicon wafer (volatile organic components) or pyrolyzed/desorbed from the surface in air atmosphere at elevated temperature (nonvolatile components), and consequently detected by the mass spectrometer. The mass spectra and the ion chromatograms obtained by the mass spectrometer during the heating of the silicon wafer can be used for the identification of all organic compounds on the silicon wafer and thus, for the identification of a possible source of contamination.
Scanning Kelvin probe and surface photovoltage methods have been implemented in a single tool to obtain information on surface,
as well as on bulk, electronic properties of mono- and multicrystalline Si wafers. The two combined methods allow for the
measurement, in a noncontacting and nondestructive way, of three parameters: minority carrier diffusion length, majority carrier
distribution in the near-surface region, and work function difference over the whole wafer area. Examples of the application
of these methods to the characterization of crystalline wafers are presented. © 2004 The Electrochemical Society. All rights
reserved.
The aim of this work was to study the effect of solar cell processing steps on the electrical quality of the material, using photoluminescence spectroscopy as a non-contact technique. It was confirmed that consecutive steps in solar cell processing not only lead to electronic quality upgrading in Ribbon and multicrystalline silicon wafers, but also to the introduction of recombining defects. Furthermore, the importance and usefulness of photoluminescence technique on the overall improvement of the substrate material is discussed. r 2004 Elsevier B.V. All rights reserved.
Various polycrystalline silicon ribbons, grown with the edge‐defined film‐fed growth (EFG) technique, are annealed at the temperatures from 450 to 1250 °C. The EFG ribbon growth technique introduces high C and O concentration which results in specific annealing behavior due to defect interactions. It is shown that oxygen in‐diffusion during the crystal growth produces an oxygen‐rich layer close to the surface of the ribbon, containing mostly SiO x agglomerates unstable at higher temperatures. Carbon concentration that exceeds the oxygen concentration causes a formation of high‐temperature [C,O] complexes which could not be found in Si material with an inverted carbon‐to‐oxygen concentration ratio.
A novel wafer scale detection system for defects and chemical contamination in semiconductors based upon the Scanning Kelvin Probe (SKP) is presented. It incorporates traditional work function (φ) topography with high resolution (<0.1 meV), surface photovoltage (SPV) measurement and surface photovoltage–deep level transient spectroscopy (SPV–DLTS). This permits quasi-simultaneous determination of surface charge, surface potential and carrier lifetime, as well as the characterisation of deep level defects.
Using a peak-to-peak ratio method, and a computer assisted Nicolet 7199 Fourier transform IR spectrometer to obtain absorbance spectra in the 8-18 microns wavelength range, oxygen and carbon concentrations as impurity in silicon ribbons were determined. Results indicate negligible oxygen impurities, a higher carbon content in silicon ribbons than in more conventionally grown materials, and a constant carbon distribution along the growth direction, with redistribution occurring for edge-defined film-grown ribbons perpendicular to the growth direction, where a hyperbolic profile is assumed.
A novel wafer scale detection system for defects and chemical contamination in semiconductors based upon the Scanning Kelvin Probe (SKP) is presented. It incorporates traditional work function (wf) topography with high resolution (<0.1 meV), Surface Photovoltage (SPV) measurement and the acquisition of SPV transients with time constants down to I ts. This permits quasi-simultaneous determination of surface charge, surface barrier height and bulk minority carrier lifetime. Monitoring variations of these parameters after chemical treatments give an accurate indication of the location and amount of contamination.
The SKP system is introduced and the SPV and SPV transient measurement modes are discussed. Measurements on Fe-contaminated and Au-implanted Si wafers demonstrate the feasibility of the system for defect and impurity characterisation in semiconductors. The system is both non-contact and non-destructive, requires no wafer preparation and can be applied in both ambient and vacuum environments.