Multibeam mask writers (MBMW) from IMS Nanofabrication developed in the last decade are currently being used for leading edge mask patterning. The ability to utilize low sensitivity resists required to pattern complex mask patterns with good edge placement control made MBMW the tool of choice for leading edge extreme ultraviolet (EUV) mask patterning. The next generation of High-NA EUV masks will require smaller features, more complex figures and reduction of edge placement errors. These requirements may exceed the capability of the current MBMW tools. Recently IMS announced the next generation MBMW tools to address this challenge. This paper will explore the effectiveness of the proposed improvements on addressing High-NA EUV mask patterning challenges.
Background: EUV lithography is making substantial progress in optimizing (i) tool, (ii) mask blanks, and (iii) resist materials to support the next generation EUV imaging performance. EUV masks use a variety of absorbers and capping layers fabricated on mirroring multi-layer (ML) stacks.
Aim: The highly conformal e-beam resist-patterning process needs to understand the absorbed intensity distribution spread from the electron scattering in the resist/substrate stack, as well as the consecutive radiation-chemical effects induced by the electron energy spread together with the dissolution behavior of the resist.
Approach: We present the results of resist response to 50-keV electron multi-beam exposure based on statistical numerical simulation on different EUV absorbers and reflecting ML stacks directly compared with the numerical lithographic parameters extracted from the experimental resist screening. The experiments were performed with the IMS Nanofabrication Multi-Beam Mask Writer (MBMW) ALPHA tool in a positive Chemically Amplified Resist provided by FUJIFILM, coated on experimental EUV masks with different stack compositions prepared by HOYA.
Results: All input parameters for MBMW corrections were precisely specified to the corresponding absorbed energy distribution signature of the specific EUV stack. Experiments confirmed the necessity to match the model calibration values to each small change in the mask stack composition.
Conclusions: The method was successfully implemented into leading-edge mask writing and resist/substrate/tool testing for achieving the sub-7-nm node at different EUV-mask stacks.
EUV Lithography makes substantial progress in optimizing (i) tool, (ii) mask blanks, and (iii) resist materials to support the next generation EUV imaging performance. Novel EUV masks use a variety of absorbers and capping layers fabricated on mirroring multilayer stacks coated on ULE substrate. 50 keV electron multi-beams are used to write high-resolution patterns in an appropriate resist coated over the absorber layer stack. The main goal of multi-beam mask writing (MBMW) has been the precise geometry control and faithful reproduction of the intended pattern on the substrate.
The highly conform MBMW resist-patterning process needs to understand the absorbed intensity distribution from the electron scattering in the resist/substrate stack, as well as the consecutive radiation-chemical effects induced by the electron energy spread together with the nonlinear dissolution behavior of the resist. It is difficult to exactly calculate the relative contribution of these factors separately, but their overall effect can be modeled by the analytic 'point spread' response function (PSF) for the resist.
The ultimate resolution is determined by the amount of laterally- and back-scattered electrons from specific target compositions. These interaction events cause proximity, fogging, local heating, and surface charging effects, defining the accurate pattern.
Simulations have shown alterations in the absorbed energy distributions of EUV masks with different stacks, and the experiments approved the results from the calculations. We present results of resist response to the electron multi-beam exposure based on statistical numerical simulation on different EUV-stacks directly compared with the corresponding numerical lithographic parameters extracted from the experimental resist screening. Consequently, all input parameters for MBMW writing corrections were precisely specified to the corresponding absorbed energy distribution signature of the concrete EUV mask.
The experiments were performed with the IMS MBMW-101 ALPHA tool in a high dose positive-tone chemically amplified resist (pCAR), provided by FUJIFILM, and coated on experimental EUV masks containing different novel stack compositions as prepared at HOYA Corporation.
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