PEC Reliability in 3D E-beam DOE Nanopatterning

0451587 - ÚPT 2016 RIV US eng J - Journal Article
Krátký, Stanislav - Urbánek, Michal - Kolařík, Vladimír
PEC Reliability in 3D E-beam DOE Nanopatterning.
Microscopy and Microanalysis. Roč. 21, S4 (2015), s. 230-235. ISSN 1431-9276. E-ISSN 1435-8115
R&D Projects: GA MŠMT(CZ) LO1212
Institutional support: RVO:68081731
Keywords : proximity effect correction * diffractive optical elements
Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering
Impact factor: 1.730, year: 2015

Diffractive optical elements (DOE) such as computer generated holograms (CGH) and blazed gratings are commonly used in coherent optics (beam splitters, beam shapers, diffusers)and security features. High quality preparation of these structures is necessary to obtain designed properties. Electron beam lithography (EBL) is one of method which allows creating fine structures in high resolution. The most undesired influence during the preparation of structures by EBL is proximity effect causing the adjacent regions to exposed one will receive non-zero dose. This effect is described by point spread function (PSF) which represents the absorbed energy distribution in radial distance from the point of incidence after point exposure. These PSF are usually obtained by Monte Carlo simulation in different programs (using various MC models). If the PSF function is known it can be used for proximity effect correction (PEC). Approximation of PSF can be done and then the key parameters (α, β, η) can be used for PEC also. There are several models for 3D PEC calculating and their authors claims their reliability is quite high. However, our contribution shows that the situation about 3D PEC for relief DOE is not so clear. This contribution deals with various correction approaches on multilevel structures (8 levels CGH, 8-levels blazed gratings with period of 2,5 and 10 um) prepared by Gaussian e-beam writer with accelerating voltage of 100 kV. The correction of backscattered electrons energy contribution plays crucial role in this case. All structures were prepared in PMMA resist with thickness of 2 um. Various software (Sceleton and Tracer) is used to obtain PSF and two PSF representations are applied (numerical PSF and Gaussian approximation – α, β, η parameters). It gives us four possibilities to calculate PEC. The Simulation of designed DOE shape with using of corrected doses and resist contrast curve shows different results for each approach.
Permanent Link: http://hdl.handle.net/11104/0252722