M. N. Filippov

First Russian standards in nanotechnology

The problem of ensuring uniformity of measurements in nanotechnology is discussed. A functional block diagram is developed for length unit size transfer from the primary length standard (meter) to the nanometric range. The first six Russian national standards are presented, which ensure this transfer using scanning electron and atomic force microscopes.

Russian standards for dimensional measurements for nanotechnologies

In order to provide the uniformity of measurements at the nanoscale, seven national standards have been developed in the Russian Federation. Of these seven standards, three standards specify the procedures of fabrication and certification of linear measures with the linewidth lying in the nanometer range. The other four standards specify the procedures of verification and calibration of customers atomic force microscopes and scanning electron microscopes, intended to perform measurements of linear dimensions of relief nanostructures. For an atomic force microscope, the following four parameters can be deduced: scale factor for the video signal, effective radius of the cantilever tip, scale factor for the vertical axis of the microscope, relative deflection of the microscopes Z-scanner from the orthogonality to the plane of a sample surface. For a scanning electron microscope, the following two parameters can be deduced: scale factor for the video signal and the effective diameter of the electron beam. The standards came into force in 2008.

Measurements of linear sizes of relief elements in the nanometer range using a scanning electron microscope

We present results of the study of forming the image in a scanning electron microscope (SEM). The effects of the electron beam energy and of the beam diameter on the signal profile are demonstrated. Methods of SEM calibration including the measurement of the electron beam diameter are presented. The formulas relating the size of the trapezoidal structures to the length of the reference portions of the SEM signals are presented. Examples of measurements of linear sizes of relief structures are given.

SEM probe defocusing method of measurement of linear sizes of nanorelief elements

The new method of measurement of linear sizes of nanorelief elements is presented. The applicability of this method to linear measurements of nanorelief elements with trapezoid profile and wide and small inclination angles of side walls is demonstrated. The results of developed method and direct measurements are compared. Examples of measurements of linear sizes of relief pitch structures are given.

Nanorelief elements in reference measures for scanning electron microscopy

The single elements of relief (protrusions and steps) fabricated by anisotropic etching of the surface of the silicon wafer congruent the crystallographic plane (100) in the scanning electron microscope have been studied. The image registration in the low energy secondary electron collection mode was carried out, and the influence of the probe electron energy and its diameter on the microscope signal formation by relief elements scanning was studied. The electron beam energy varied at the range of 0.3 - 20 keV, the probe diameter changed in the limits of 14 - 500 nm. The widths of upper bases of protrusions varied within 14 - 500 nm. The correlation analysis of experimental results, carried out by the authors, demonstrate high quality of the structures studied.

Beam Current Dependence of SEM Electron Probe Diameter

A method has been developed for measuring the dependence of the electron probe diameter d in a scanning electron microscope SEM on the beam current J. The relationship for the CAMSCAN CS-44 SEM is d(J) ~ J1/4, whereas electron probe formation theory gives d(J) ~ J3/8; the reasons for these differences are considered.

Measurements of linear sizes of relief elements in the nanometer range using an atomic force microscope

The results of the study of image formation in atomic force microscope (AFM) are presented. Effects of the radius and the angular characteristics of the cantilever tip, as well as of the relief of the surface being studied, on the signal shape are discussed. Methods of AFM calibration, including the calibration of all three scales with the use of only one certified size of a test object and the measurement of the cantilever tip radius, are presented. Formulas are obtained that relate the sizes of trapezoidal structures to the sizes of the control intervals chosen in the AFM signals.

One possibility of mathematically modeling the thermal effect of a finely focused electron beam on a homogeneous semiconductor

The problem of heat distribution in materials irradiated with finely focused medium-energy electron beams is considered by means of mathematical simulation. A model is developed by solving a multidimensional heat-transfer steady equation using the Green function. A model that can be applied to a broad class of solid bodies and the range of energies of primary electrons is used as the source function. Some results are illustrated using the example of semiconductor materials used in electronics.

Test objects for automated dimensional measurements at the nanoscale level using a scanning electron microscope

Two types of test objects for automated measurements of critical dimensions with scanning electron microscopes (SEMs) are described. The first type can be used for SEM calibration along two coordinates in a wide range of magnifications (to perform dimensional measurements in the range from 10 nm to 100 μm without making recalibration), including determination of the electron beam diameter. The second type is recommended for embedding into the integrated circuits (ICs) to monitor the focusing of the SEM electron beam in the course of dimensional measurements of IC elements. Measurement and monitoring of the SEM magnification and electron beam diameter is necessary to measure the linewidth (the sizes of the upper and lower bases of the IC trapezoidal relief elements) in the nanometer range.

Direct measurement of the linewidth of relief element on AFM in nanometer range

The article includes the results of the study of image formation in atomic force microscope (AFM). The influence of radius and angle characteristics of cantilever tip as well as the relief of the surface studied on the signal waveform is shown. The authors demonstrate the techniques of AFM calibration and direct measurement of linear sizes of trapezoid structures including the line width with the use of AFM signal and its first derivative. There were obtained the equations establishing relations the sizes of trapezoid structures with the sizes of test segments chosen on AFM signals.