James Smith, Nigel Crosland, Samuel Doran, Robert Dowling, John Hartley, Philip Hoyle, David M. King, Lawrence Kutcher, Andrew McClelland, Martin Turnidge
The Vistec VB3001 Gaussian electron-beam lithography system at the College of Nanoscale Science and Engineering (CNSE) in Albany routinely exposes 300 mm wafers to meet the requirements of nano-patterning for metrology and process tool qualification. CNSE and Vistec are partners in a continuous throughput improvement program. The second set of upgrades from this program has recently been implemented on CNSE’s VB300 and includes an increase in the maximum exposure clock frequency to 100 MHz and corresponding improvements to the sub-field deflection and beam blanker. To quantify the improvements, we have used an established suite of benchmark patterns2 to compare throughput “before and after”. These benchmark patterns show an average throughput improvement factor of 4 times over the timings at the start of the continuous improvement program.
The Vistec VB300 Gaussian electron-beam lithography system at the College of Nanoscale Science and Engineering
(CNSE) in Albany routinely exposes 300 mm wafers to meet the requirements of nano-patterning for metrology and
process tool qualification. CNSE and Vistec are partners in a continuous throughput improvement program. The first
stage of this program has recently been implemented on CNSE’s VB300. To quantify the improvements, we have
defined a suite of benchmark patterns to compare throughput “before and after”, which we plan to use throughout the
entire program. These benchmark patterns show throughput improvements of up to a factor of 2.5 on the VB300. We
believe this method of measuring throughput could be applied to other lithography systems that exhibit a throughput
dependency on pattern type.
At the end of 2008, the College of Nanoscale Science and Engineering (CNSE) formally accepted a Vistec VB300
Gaussian electron beam lithography system. The system is a key component of the overall lithography strategy of the
College and complements existing state of the art tooling for 193nm immersion, Extreme Ultra Violet and nanoimprint.
The demonstrated resolving power of the system easily exceeds that of the facility's optical scanners. Together with
300mm wafer compatibility, and a class 1 mini environment, the system is well poised to execute its primary mission of
supporting a variety of programs in post CMOS device integration. For a 300mm tool to be able to exchange wafers
with other tooling in a full flow line it is necessary to pass stringent backside metal contamination testing. TXRF (total
reflection x-ray fluorescence) testing performed with 300mm wafers on the VB300 satisfied the permitted metal
contamination levels and cleared the way for introduction of ebeam patterned wafers into the process flow. Most of the
tooling in the 300mm line handles wafers in front opening universal pods (FOUPS). With the relatively low throughput
of the system (hours per wafer, not wafers per hour), this type of interface is not required. In order to maintain a low
level of defects, 300mm wafers are removed from the FOUPS in the class 1 mini environment and loaded into the
system.
In addition to the 300mm capability, the system supports a wide range of wafer sizes, photomasks and piece parts. This
enables the platform to support the 200mm activities at the College as well as the small samples frequently encountered
with novel materials that have no support tooling available for 200mm and 300mm wafer sizes.
The VB300 platform readily met the Vistec standard acceptance test specifications. The paper presents details of the acceptance test together with examples of additional work in progress that includes implementation of rigorous tool monitor standards, imprint template fabrication and mix and match overlay between the VB300 and optical patterning tools.
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