With more and more photonic data presence in e-beam lithography, the need for efficient and accurate data fracturing is
required to meet acceptable manufacturing cycle time. Large photonic based layouts now create high shot count patterns
for VSB based tools. Multiple angles, sweeping curves, and non-orthogonal data create a challenge for today’s e-beam
tools that are more efficient on Manhattan style data. This paper describes techniques developed and used for creating
fractured data for VSB based pattern generators.
Proximity Effect Correction is also applied during the fracture process, taking into account variable shot sizes to apply
for accuracy and design style. Choosing different fracture routines for pattern data on-the-fly allows for fast and efficient
processing. Data interpretation is essential for processing curvilinear data as to its size, angle, and complexity. Fracturing
complex angled data into "efficient" shot counts is no longer practical as shot creation now requires knowledge of the
actual data content as seen in photonic based pattern data.
Simulation and physical printing results prove the implementations for accuracy and write times compared to traditional
VSB writing strategies on photonic data. Geometry tolerance is used as part of the fracturing algorithm for controlling
edge placement accuracy and tuning to different e-beam processing parameters.
The development of multiple e-beam lithography equipment is seen as an alternative for next generation lithography.
However, similarly to EUV lithography, this technology faces important challenges in controlling the contamination of
the optics due to deposition of carbon layer induced by the outgassed chemical species from resist under electron
bombardment. An experimental setup was designed and built at LETI to study the outgassed species and observe the
carbon layer. In this setup, resist coated wafers 100 mm size are exposed under a 5 kV e-beam gun. During exposure, byproducts
from outgassed species are monitored with a Residual Gas Analyzer (RGA). The identification of outgassed
chemical species is done with an ex-situ TD-GC-MS analysis (ThermoDesorption-Gaz Chromatography-Mass
Spectrometry). In a second part of this investigation, we observed the contamination carbon layer growth induced by the
outgassing. Thereby, we fabricated a device which consists of a silicon membrane with micro-machined apertures.
During e-beam exposure, this device simulates the multiple parallel beams of the optic system of a maskless lithography
tool. The deposited contamination layer on device is then observed and thickness measured under SEM. In this paper, we
present the results of outgassing and contamination on 3 chemically amplified resists showing that contamination is not
directly dependent of the overall outgassing rate but on first order of the outgassing from Photo Acid Generator (PAG). It
also reports on the performance in reducing outgassing and contamination of applying a top-coat layer on top of the resist
and shows that reduction is more important for contamination than for outgassing.
In emerging high-vacuum multi e-beams exposure tools, the release of hydrocarbonaceous species (precursor) by resists outgassing is unavoidable and leads to premature contamination of optics projection systems. In this work, we present an experimental methodology aiming at resist outgassing qualification. A specific experimental setup was designed to monitor the induced outgassing phenomena by irradiating resist coated on 100mm silicon wafer. The wafer can be exposed through specific silicon micromachined membranes (called mimics) that are representative of the optics projection system usually embedded in real multi e-beam exposure tools. A Quadrupole Mass Spectrometer (QMS) is plugged into the vacuum chamber and enables in-situ analysis of the by-products outgassing. Combining this tool with the Thermo Desorption - Gas Chromatography coupled to Mass Spectroscopy (TD-GC-MS) analysis, we could not only determine the outgassing amount of different resists but also identify all the outgassed by-products and their origin. Finally, the Focus Ion Beam combined to Scanning Electron Microscopy (FIB-SEM) and X-ray Photoelectron Spectroscopy (XPS) characterization techniques were used to determine the contamination layer thickness and elementary composition, respectively. A first process oriented conclusion from this work shows that the use of a thin topcoat layer can considerably reduce the resist outgassing amount and, consequently, the hydrocarbonaceous contamination layer induced on the mimics. The outgassing amount as well as the top-coat efficiency was shown to be mainly dependent on the resist chemical properties. The contamination layer growth was shown to be dependent on e-beam current density and hydrocarbon pressure in the vicinity of the mimics.