EUV lithography is currently setting the pace for the semiconductor industry’s expectations on future progress towards the 3nm node and beyond. This technology also defines the upcoming challenges for equipment providers upstream and downstream of the production line among which wafer-level overlay and CD error requirements stand out most prominent. Registration errors on the mask, both local (mid-range) and global (long-range), contribute to overlay errors on the wafer. Here, we will present novel calibration strategies for the IMS Multi-Beam Mask Writer (MBMW) by ZEISS PROVE measurements to meet the mask registration requirements: First, we showcase how we can efficiently leverage the high precision, resolution and fast capture time of the PROVE tool to allow for extensive control and tuning of MBMW properties that affect local registration (LREG) such as systematic residual errors originating from the electron beam optics. Second, we provide insights into the MBMW Registration Improvement Correction (RIC) calibrated with PROVE technology. This feature allows removing remaining systematic local registration errors in the MBMW electron beam array field (82μm x 82μm) resulting in LREG improvement by 30% from 1.2nm to 0.8nm three-sigma. Third, we show how the PROVE technology can be applied efficiently for the calibration of the MBMW’s Thermal Expansion Correction (TEC) that allows compensating systematic global registration errors originating from thermal-mechanical deformations of the mask during the writing process.
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.
Mask Process Correction (MPC) is well established as a necessary step in mask data preparation (MDP) for electron beam mask manufacturing at advanced technology nodes from 14nm and beyond. MPC typically uses an electron scatter model to represent e-beam exposure and a process model to represent develop and etch process effects [1]. The models are used to iteratively simulate the position of layout feature edges and move edge segments to maximize the edge position accuracy of the completed mask. Selective dose assignment can be used in conjunction with edge movement to simultaneously maximize process window and edge position accuracy [2]. MPC methodology for model calibration and layout correction has been developed and optimized for the vector shaped beam (VSB) mask writers that represent the dominant mask lithography technology in use today for advanced mask manufacturing [3]. Multi-beam mask writers (MBMW) have recently been introduced and are now beginning to be used in volume photomask production [4]. These new tools are based on massively parallel raster scan architectures that significantly reduce the dependence of write time on layout complexity and are expected to augment and eventually replace VSB technology for advanced node masks as layout complexity continues to grow [5][6]. While it is expected that existing MPC methods developed for VSB lithography can be easily adapted to MBMW, a rigorous examination of mask error correction for MBMW is necessary to fully confirm applicability of current tools and methods, and to identify any modifications that may be required to achieve the desired CD performance of MBMW. In this paper we will present the results of such a study and confirm the readiness of MPC for multi-beam mask lithography.
As optical lithography is extended into 10nm and below nodes, advanced designs are becoming a key challenge for mask manufacturers. Techniques including advanced Optical Proximity Correction (OPC) and Inverse Lithography Technology (ILT) result in structures that pose a range of issues across the mask manufacturing process. Among the new challenges are continued shrinking Sub-Resolution Assist Features (SRAFs), curvilinear SRAFs, and other complex mask geometries that are counter-intuitive relative to the desired wafer pattern. Considerable capability improvements over current mask making methods are necessary to meet the new requirements particularly regarding minimum feature resolution and pattern fidelity. Advanced processes using the IMS Multi-beam Mask Writer (MBMW) are feasible solutions to these coming challenges. In this paper, we study one such process, characterizing mask manufacturing capability of 10nm and below structures with particular focus on minimum resolution and pattern fidelity.
As optical lithography is extended into 10nm and below nodes, advanced designs are becoming a key challenge for mask
manufacturers. Techniques including advanced optical proximity correction (OPC) and Inverse Lithography
Technology (ILT) result in structures that pose a range of issues across the mask manufacturing process. Among the
new challenges are continued shrinking sub-resolution assist features (SRAFs), curvilinear SRAFs, and other complex
mask geometries that are counter-intuitive relative to the desired wafer pattern. Considerable capability improvements
over current mask making methods are necessary to meet the new requirements particularly regarding minimum feature
resolution and pattern fidelity. Advanced processes using the IMS Multi-beam Mask Writer (MBMW) are feasible
solutions to these coming challenges. In this paper, Part 2 of our study, we further characterize an MBMW process for
10nm and below logic node mask manufacturing including advanced pattern analysis and write time demonstration.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.