Tetsu Sekine

Comparison of AES chemical shifts with XPS chemical shifts

Abstract Scanning Auger microprobe equipped with a concentric hemispherical analyzer allows us to measure AES spectra with high-energy resolution. The question is the extent of chemical state information obtainable by AES. XPS chemical shifts and AES chemical shifts, derived from transition energies available from literature, have been compared for many compounds. The mean values were found to be for peak shift 1.71 eV in the case of XPS and −3.86 eV for AES, and the standard deviations were 2.38 eV for XPS and 3.62 eV for AES. We found that the chemical shifts in AES were generally 1.5 times larger than in XPS. For some elements such as Fe, Co, Ni, and Cu, the AES chemical shifts are exceptionally small, but the peak shapes differ depending on the chemical states.

Theoretical and experimental studies of N(E) spectra in auger electron spectroscopy

Abstract A new Monte Carlo simulation approach has been developed to describe the full energy spectrum, N(E), from the elastic peak in the high energy region to the slow secondary electrons in the low energy region, for kV electrons. The Monte Carlo calculations were performed for 3 kV electrons impinging on Cu, Au and Si at normal incidence and at an angle of 45°, respectively. To compare the simulation results, the EN(E) measurements were done on these elements under the same conditions using a commercial Auger microprobe, JAMP-30. It has been confirmed through the comparison that the present Monte Carlo approach describes the experiment very well. As another application of practical interest, we have simulated how the energy loss peaks of 1 kV electrons change as Cu deposition onto a Si substrate proceeds. The result clearly indicates that the plasmon loss peaks of Si substrates become unobservable with a CMA of common use when the surface coverage of Cu film becomes 5 A thick.

POLYMER ANALYSIS BY AUGER ELECTRON SPECTROSCOPY USING SECTIONING AND CRYOGENIC COOLING

Abstract Efficient polymer analyses have been performed by Auger electron spectroscopy in combination with sectioning and cryogenic cooling, to prevent surface charging and polymer damage during electron beam exposure. Polymer samples of sub-micron thickness have been found to be free of surface-charge effects, and cryogenic cooling (which was applied to the polymer AES analysis for the first time) has made it possible to measure volatile components (components other than carbon). A high resolution Cl Auger image has been obtained for acrylonitrile/vinylidene chloride copolymer. The distribution of oxygen and nitrogen in the cross-section of oxidized polyacrylonitrile (PAN) fibers has been measured by this method, with results which show it to be effective for the microanalysis of polymer samples.

Focused ion beam optical column design and consideration on minimum attainable beam size

We discussed a two lens optical system focused ion beam (FIB) employing a Ga-emitter (LMIS), whose acceleration voltage Vacc is ranged 30–100 kV, which will be used for milling and secondary ion microscope observation purposes. On such an optical system, we investigated the relation between minimum obtainable beam diameter and chromatic aberration coefficient against Vacc, and studied the possibility of improving FIB resolution by increasing the Vacc. The beam diameter is mainly determined by the size of a Gaussian image and the chromatic aberration, especially that of objective lens, if the beam current is very low. From this fact, we showed that the magnification optimization method which is one of the optical optimization methods can be greatly simplified at a lower beam current region. Using this simplified method, we summarized a guide line for evaluating an Vacc value from the standpoint of realizing a finer beam. Also given is information useful for designing a FIB column in consideration of optimi...

Development of high spatial resolution Auger microscope as applied to semiconductor analysis

Abstract An Auger microscope equipped with aZrO/WSchottky field emitter was developed. For Auger analysis, spatial resolution under a probe current of more than 1 nA is important. Under such conditions, the aberration by the condenser lens is not negligible. To reduce it, the distance from the emitter to the principal plane of the first condenser lens is reduced by forming its magnetic field overlapping with the accelerating field of the electron. As a result, a spherical aberration coefficient of 10 mm (accelerating voltage 30 kV) was achieved and the spatial resolution was about 10 nm with a probe current of 10 nA and an accelerating voltage of 25 kV. The newly developed Auger microscope combined with the probe tracking system has enabled an Auger image to be obtained, in which a 40 nm gate oxide layer in a cross-sectioned integrated circuit device is clearly observed.

Influence of first lens on magnification optimization method in two-lens FIB optical system

Focused ion beam (FIB) tools are widely used for scanning ion microscope (SIM) image observation and for ion milling in semiconductor and other industries. The demands for a higher resolution in SIM and for a more intensive beam in ion milling are increasing. Limiting in 2 lenses FIB optical system, we studied the influence of the first lenss properties, particularly magnification M1 and extraction voltage Vext, on the attainable beam diameter through an optimizing calculation. From this point of view, we investigated the attainable smallest beam size in the low current region by varying the parameters of the first lens, and found out that the lower extraction voltage has an advantage for getting a smaller beam. It is of big concern, as far as emission is possible, how much the extraction voltage can be minimized. It is related to M1, and the change of Vext between 5 and 12 kV produces the beam size variation of about 1 to approximately 1.5 nm. It is not negligible compared with the beam size of approximately 5 nm, which is attainable today. Therefore, we have a possibility to reduce the beam size by reviewing the first lens properties including Vext. Finally, a guide line is shown for the FIB column design from this point of view.

An automated specimen stage drive system for scanning auger microanalysis

Abstract An automated specimen stage drive system is described. It can be used to move specimens 20mm in the x direction, 20mm in the y direction and 3mm in the z direction. The system may be added to existing manual stages. One set of coordinates (x, y, z) uniquely defines a point on the specimen for any degree of specimen tilt. The system includes an automation package which enables wide area Auger mapping, wide area ion sputtering, extended length Auger linescans and features of interest relocation. Auger map data can be presented in a number of formats including a gray scale image, pseudo-color image and a multi-element overlay. Auger map data may also be processed using a variety of 3 × 3 and 5 × 5 matrices. The statistical nature of the data may be examined using histogram and correlation diagrams. The configuration of the automated specimen stage system is described. Examples of the data produced using this system are presented.