Papers by Keyword: Kelvin Probe

Abstract: We present a refined non-contact doping density determination in silicon carbide that incorporates 3 novel features: (1) constant surface potential method of corona charging into depletion; (2) vibrating Kelvin probe measurement of depletion surface voltage and voltage compensation maintaining constant surface potential, and (3) a unique self-consistent procedure for data analysis. The results obtained on epitaxial SiC demonstrate up to 3 times improved accuracy and enhanced repeatability giving 1σ in 10 repeats of 0.05% and 0.1% for doping in e15cm^-3 and e19cm^-3 range, respectively. An enhanced charging range enables measurement of high doping density in the e19cm^-3 range and to achieve larger depth in doping profiling. With these refinements, a non-contact doping metrology for SiC represents an industry ready alternative to Hg-CV.

Abstract: Non Visual Defects (NVD) is a category of defects that cause electrical failures but are not detected with visual wafer inspection tools. Our approach for NVD detection is based on the Kelvin probe surface voltage mapping technique. The detection of defects is enhanced using field-effect created in a non-contact manner by corona charge deposition on the surface of semiconductor. Precise defect location is accomplished with surface voltage gradient magnitude mapping that enhances delineation of defects. Detected defects are characterized locally using the corona-voltage technique or isothermal voltage transient decay analysis. Presented examples include: dielectric charge and interfacial defect mapping on 300mm Si wafers; deep level emission mapping on epitaxial SiC and mobile ion mapping in Si solar cells.

Abstract: It is very important to effectively evaluate the adhesion strength of coating. A nondestructive method to evaluate the adhesion strength of laser induction hybrid rapid cladding Cu-Fe-based coatings was investigated. The electron work function of coatings was measured by scanning Kelvin probe. It was demonstrated that the Fe-rich particles and solid solution of Fe can increase the EWF and the tensile strength. A logarithmic relationship between the ratio of EWF to dilution and the adhesion strength was established.

Abstract: Cu-BTC, also known as H-KUST 1, belongs to Metal Organic Frameworks (MOFs). Nanoporosity, relatively good thermal stability and unsaturated metal sites are some of its properties that make this MOF promising for application as a gas sensing material. In this work we chose different experimental approaches to examine trace gas sensing (5 to 50 ppm) of ethanol with Cu-BTC. Measurements with mass sensitive, as well as work function based readout, were successfully performed in dry synthetic air at room temperature. Strong, fast and concentration dependent response to ethanol was observed. In-situ measurements with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were additionally applied to visualize the adsorption of ethanol molecules on the Cu-BTC sensing layer.

Abstract: This paper is a summary of the experimental study of deep levels in a SiC crystal lattice caused by diffusion welding (DW). Investigations were carried out by DLTS and Kelvin Probe methods. Investigations revealed that DLTS method is not applicable for identification of surface states. Research conducted by the Kelvin Probe method has shown an increase in the density of surface states after the diffusion welding from 2x10¹⁵ cm^-2 to 3.5x10¹⁶ cm^-2.

Abstract: With scanning Kelvin probe and microscopy technique, the degradation process of the micro-arc oxidation (MAO) treated magnesium alloy was investigated under a 3% NaCl droplet. Because of the unique two-layer structure of the MAO specimen, the droplet penetrated in and spread through the external loose layer during the initial several minutes. Subsequently, with the increase of time, only a thin layer of electrolyte was left on the surface of the MAO specimen. During the entire corrosion process, the potential exhibited a valley type distribution, only the width of potential valley increased with time. Based on above observations, a model was proposed for describing the contamination mechanism of MAO treated magnesium alloy under droplet.

Abstract: The monitoring and optimization of wet clean and surface preparation processes is a major challenge in the microelectronics industry [1, 2]. Today, the main methods used in clean rooms are visual inspection by light scattering (principally applied to particle detection) and metallic contamination detection by Total-reflection X-Ray Fluorescence (TXRF). These methods, despite good sensitivity and recent progress [3, 4] are not sufficient, especially considering non-visual defects not measurable by light scattering, nor TXRF due to their chemical nature or to their size and location (TXRF is not applicable to light elements – with Z < 11 – and is typically a 1 cm resolution tool, with 1 to 2 cm edge exclusion). Non-vibrating Surface Potential Difference Imaging (SPDI), introduced in 2005 under the name of ChemetriQ® is an in-line, non-contact, non-destructive inspection technique based on the imaging of surface Work Function (WF) lateral non-uniformities [5]. Recent studies show very promising results for SPDI: high sensitivity to traces of metals on Si wafers with native oxide [6]; fast imaging capabilities of unpatterned or patterned wafers with sensitivity to chemical residues and charge [7, 8]. In this work, the ChemetriQ method is evaluated for in-line control of wet clean processes. The variation of SPDI data from various contaminants is compared to intra- and inter-wafer variations related to the cleaning and measurement conditions. Note that all wafer maps are presented with the notch oriented at 6:00.

Abstract: High levels of surface shear experienced during rolling, grinding or machining can cause 6000 series aluminium to develop an ultra-fine grained surface layers which dramatically increase susceptibility to filiform corrosion (FFC) under paint films. In-situ Scanning Kelvin Probe (SKP) measurements in humid air are used to compare the kinetics and mechanism of FFC on abraded and lacquer-coated samples of high copper containing AA6111 and low level copper AA6016. FFC is initiated by applying a small volume of aqueous HCl to a penetrative defect on polyvinylbutyral (PVB) coated alloy samples prior to placement in a chamber maintained at constant humidity and temperature. The SKP is then repeatedly scanned over a fixed surface area to produce a time-lapse animation showing the dynamic evolution of localized free corrosion potential patterns. The spatial distribution of potential variation provides insight into the FFC mechanism and the numerical integration of areas of dissimilar potential provides a measure of the time-dependent area of coating delamination. Various possible FFC inhibition strategies are investigated for use under circumstances where removal of the surface layer prior to application of an organic (paint) coating is not feasible. The two strategies shown in this paper are the use of an anti-corrosion pigments based on an intrinsically conducting polymer called polyaniline. An anion-exchange pigment called hydrotalcite is also used.