One of the ways to use a focused ion beam in lithographic processes to create nanostructures is through the exposure of special sensitive materials, i.e., resists. As a result of exposure, the solubility of such a material increases (“positive” resist) or, conversely, decreases (“negative” resist). Subsequent selective irradiation and development of the resist make it possible to create a predetermined pattern on the substrate. This work is aimed at developing the theoretical foundations for this ion lithography method. A practically important case of stopping heavy ions in an organic resist, the average atomic mass of which is much less than the mass of the incident ion, is considered. Expressions for the “energy” and transport lengths of ions are obtained. The calculations are carried out assuming a power-law interaction potential. The “energy” length characterizes the depth of penetration of ions into the material, and the transport length is related to beam expansion due to scattering. Therefore, these lengths are the main characteristics of the zone in which the ion-beam energy is absorbed.

The energy deposited in resist during its exposure by ion beam was simulated for ions from a set of rare gases and for gallium. It was shown that the distribution of energy density can be approximated by the product of two Gaussian functions. One of them describes the lateral distribution of energy, the second the dependence on depth. The widths and centres of these Gaussian functions are determined by the energy length (also mentioned in the literature as "Range" or "mean length of trajectories"), the mass of ions and the average atomic number of resist. The obtained description would make it possible to estimate the size of the resist modified volume for any type of ion with energy of tens keV. So it can be used for a priori estimates of resolution and performance, as well as for the choice of beam energy and ion type based on this. Keywords: lithography, nanostructuring, ion beam, resist, modeling, deposited energy.

In this study, the key lithographic performance of PMMA 950K resist was evaluated by exposure to a 30 keV focused gallium (Ga⁺) ion beam. The sensitivity and contrast of PMMA 950K were directly compared with those of electron exposure under identical development conditions. It was found that the sensitivity of PMMA 950K to Ga⁺ ions for 50 nm films reaches a value of about 0.4 μC/cm², which is more than 250 times higher than its sensitivity to electron exposure. A method for evaluating the resist contrast during ion exposure is proposed in this work, taking into account the highly non-uniform dose distribution across the resist depth; it yielded a contrast value of γ = 2.6, which is consistent with the result obtained with electron exposure (γ = 2.8). In addition, a pronounced dependence of the resist sensitivity on the resist thickness was found: with an increase in thickness from 10 nm to 60 nm the sensitivity decreases by an order of magnitude. The obtained results form a reliable methodological basis for characterizing the behavior of polymer resists under ion irradiation and provide valuable recommendations for optimizing lithography with a focused beam of Ga⁺ ions when creating nanostructures for microelectronics, photonics, and quantum technologies.

The use of a special device that limits the field of view of a detector, i.e., a confocal collimator, is one of the approaches to obtaining information about the spatial distribution of the detected material in the methods for radionuclide diagnostics (in medicine) and X-ray fluorescence analysis (in material science). This device is a monolithic construction with a large number of straight channels whose axes are directed towards a single point that is the focus of the confocal collimator. The possibility of fabricating confocal collimators using 3D printing technology is demonstrated. The advantages of 3D printing are simplicity, reliability, and wide availability. It is shown that the use of a confocal collimator in radionuclide diagnostics instead of a single-channel collimator is advantageous, since it substantially increases the sensitivity (by 2−7 times) with the simultaneous improvement of the resolution (approximately by 9 times). The applicability of the confocal collimator for determining the depth of occurrence of a radiation source, i.e., for measuring the three-dimensional distribution of the emitting (fluorescent) substance, is also demonstrated.

The feature of the promising tool of lithographic nanostructuring based on selective exposure of polymer resist by ion beam is very compact (of about tens of nanometers) beam interaction volume. Herewith the main part of beam energy is deposited in the resist and is spent to its modification. It causes the set of advantages specific for this method: sub-10 nanometer resolution achievable, very high energy efficiency and almost complete absence of proximity effect. But also due to this feature absorbed doze essentially inhomogeneous in resist and the dissolution rate is strongly dependent on depth. So the common procedure of resist contrast determination cannot be applied anymore. In the present work a new method for resist contrast determination considering the relation between dissolution rate and deposited energy density is suggested and realized. By using it for PMMA resist irradiated by 30 keV Ga⁺ ion beam the value of contrast was determined to be 3.1 and ions energy length was estimated to be 42 nm.

A solar cell on a wafer of multicrystalline silicon containing grain boundaries was studied by the induced-current method. The sample was scanned by an electron beam and by a laser beam at two...