Electron multi-beam mask writers address the challenge of long mask write times for increasingly complex masks. The writing speed of the IMS multi-beam mask writer under consideration here depends on the data path and blanking device speed provided for exposing the patterns. It was initially believed that the maximum dose required for exposing the patterns could also be a limiting factor. We present a proximity effect correction scheme that improves image quality (compared to a dose-only correction) and allows for a maximum dose limit. We test this scheme with and without maximum dose limit, and compare the achieved image quality against that for a dose-only correction. The results of this simulation study are verified by comparing top down SEM images of resist structures from exposures using the different corrections.
Proc. SPIE. 7748, Photomask and Next-Generation Lithography Mask Technology XVII
KEYWORDS: Electron beam lithography, Data modeling, Scattering, Calibration, Computer simulations, Scanning electron microscopy, Monte Carlo methods, Photoresist processing, Process modeling, Chemically amplified resists
With the constantly improving maturity of e-beam direct write exposure tools and processes for applications in high volume
manufacturing, new challenges with regard to speed, throughput, correction and verification have to be faced. One objective
of the MAGIC high-throughput maskless lithography project  is the application of the physics-based simulation in a
virtual e-beam direct write environment to investigate proximity effects and develop comprehensive correction
methodologies . To support this, a rigorous e-beam lithography simulator for the feature scale has been developed . The
patterning behavior is determined by modeling electron scattering, exposure, and resist processing inside the film stack, in
analogy with corresponding simulation capabilities for the optical and EUV case. Some model parameters, in particular for
the resist modeling cannot be derived from first principles or direct measurements but need to be determined through a
To gain experience with the calibration of chemically amplified resists (CAR) for e-beam lithography, test pattern exposures
have been performed for a negative tone CAR using a variable-shaped beam writer operating at 50kV. A recently
implemented model calibration methodology has been applied to determine the optimum set of resist model parameters.
While the calibration is based on 1D (lines & spaces) patterns only, the model results are compared to 2D test structures for
KEYWORDS: Point spread functions, Cadmium, Data modeling, Error analysis, 3D modeling, Critical dimension metrology, Geometrical optics, Virtual reality, Electron beam direct write lithography, Model-based design
We demonstrate a flow for e-beam proximity correction (EBPC) to e-beam direct write (EBDW) wafer manufacturing
processes, demonstrating a solution that covers all steps from the generation of a test pattern for (experimental or virtual)
measurement data creation, over e-beam model fitting, proximity effect correction (PEC), and verification of the results.
We base our approach on a predictive, physical e-beam simulation tool, with the possibility to complement this with
experimental data, and the goal of preparing the EBPC methods for the advent of high-volume EBDW tools.
As an example, we apply and compare dose correction and geometric correction for low and high electron energies on
1D and 2D test patterns. In particular, we show some results of model-based geometric correction as it is typical for the
optical case, but enhanced for the particularities of e-beam technology.
The results are used to discuss PEC strategies, with respect to short and long range effects.
An e-beam exposure module has been developed for an existing lithography simulator, covering aspects of e-beam inter-action with the stack, exposure of the resist by the e-beam as well as development of the resist. The goal of the simulation is to complement experimental data with insights that are difficult or impossible to obtain experimentally and to provide advanced capabilities for process optimization. Simulations are performed for an iso-dense pattern to show that in the case of 5kV acceleration voltage, a standard dose correction works well for tight beams with 5nm blur but is very challenging for 30nm beam blur. Geometric corrections will most likely be needed for a wide beam blur.