Evaluation of the elastic scattering effect in electron spectroscopies, i.e. XPS, AES, EPES etc., is important for the quantitative surface analysis. We classify the elastic scattering effects and emphasize the importance of a choice of the elastic-scattering differential-cross-sections based on Rutherford scattering, Thomas-Fermi-Dirac potential, and Dirac-Hartree-Fock potential for the detailed estimation of the elastic scattering effects. We also mention of the simple way to deal with the average practical effective attenuation length (average PEAL) including elastic scattering effects and demonstrate this average PEAL is useful for the analysis of angle-resolved high-energy XPS.
The design rule of semiconductor devices in 1984s, when optical microscope was used for critical dimension measurement of device patterns, was around 1.3 µm. Instead of the optical microscope which did not provide enough resolution for the further device shrinkage, CD-SEM (Critical-Dimension Scanning Electron Microscope) was used for 1 µm or smaller design rule. This report introduces recent CD-SEM technologies and future prospect for such smaller design rule. Furthermore, evaluation of CD-measurement accuracy is introduced. It consists of short-term and long-term repeatabilities and tool-to-tool matching. A new linewidth-measurement algorithm is implemented for better short-term repeatability. A method of contrast-gradient is used for tool-to-tool matching. A traceable standard-sample for magnification calibration is also used.
X-ray reflectivity (XRR) is a powerful technique for evaluating nanometer scale film structures. In principle, it is rested on interference of X-rays reflected on surface and interface of the film stacks. If we have a proper structural model for film stacks, calculation of XRR pattern is a physically well-defined procedure based on the Fresnel formula that only needs well known physical constants, wavelength of X-ray and refractive indices of film materials for X-ray. Therefore, XRR is capable of providing standard nano-film thickness ensuring SI unit traceability. We discuss roots of errors for the evaluated film structures, for example, miss-alignment of sample positions andso on. We also present several trials to diminish uncertainties of measured film structures.
We have developed an electron spectroscopy which will be SI traceable. Recent achievements for this spectroscopy are presented; the transmission and energy calibrations for our novel cylindrical Auger electron analyzer. The transmission was observed by using a well defined mini-electron gun as a virtual electron source at the sample position and two Faraday cups just before the input mesh and the final Auger electron detector measured the electron currents. The ratio of the two currents gave the transmission. Meshes used in the CMA showed a lens effect of both plus and minus features, and also played as an electron scattering object. In the energy calibration, the primary electron has been used as a reference energy in which the acceleration voltage is SI traceable, thus the peak positions of the thermal electrons emitted from the electron source were simulated by PC. The simulation revealed the shift of the peak position of the thermal electrons. Electronics for the current and voltage measurements were also developed, particularly a metrological high voltage divider was valuable.
This article describes the inelastic scattering effect in surface electron spectroscopies such as XPS and AES. In order to improve the accuracy of quantitative surface analysis, it is very important to describe the attenuation rate of the electron signal due to inelastic scattering events in a solid. For this, “attenuation length (AL)” has been used for a long time to describe the attenuation rate. AL is, however, replaced by the “effective attenuation length (EAL)”, which includes the elastic scattering effect, because the signal electrons may not vary exponentially with the thickness of an overlayer film due to the elastic scattering. Then, the calculations and measurements of physical quantities such as electron inelastic mean free path (IMFP) and EAL are described.
Ametrology atomic force microscope (AFM) equipped with high-resolution laser interferometers is presented. Key technologies and an uncertainty estimation of the AFM system to realize the accuracy of dimensional measurements in the order of several subnanometers are described. In the international preliminary comparison for 1-dimensional gratings, where national metrology institutes in foreign countries joined, the calibrated pitch values of the measurands by the NMIJ's metrology AFM well matched with the reference value calculated from all attendee's values within estimated uncertainties in the range from 0.15 to 0.50 nm. This shows that AFM would be one of the most promising metrological tools for dimensional measurements of fine structures with the size of a few hundreds of nanometers, and with a uncertainty with the order of 1 nm, in nanodevice fabrication and ultraprecision machining processes, if their major uncertainty components are reduced.
Anti-fouling paints for ship bottoms, that are no harm to the environment, are desired in the situations, such as prohibition of global use of a tributyltin compound (TBT), the sudden rise in crude oil price, and the reduction of the amount of carbon dioxide discharge. TBT not only causes usual environmental pollution, but also includes the danger of causing endocrine disrupters. Therefore, an anti-fouling paint, must not contain an elution element. Under these circumstances, new anti-fouling systems, i) a patient that does not contain an elution element into the seawater at all, and ii) a biofilm. Moreover, from a viewpoint of energy saving, we aim at developing (iii) paints of energy saving further from the self-polish type paint that has the high energy-saving effect. By making paint film realize the function of the living thing gained in process of evolution, we are developing paint films of unprecedented low frictional resistance. Here, I introduce about the new anti-fouling system by which we are advancing the stare examination of anti-fouling paint for the future.