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June 02, 2009

Electron Beam Lithography


Vistec’s Gaussian Beam systems which are characterized by a 3nm spot size at 100keV acceleration voltage are the system of choice for nanotechnology and most advanced research applications. Vistec’s Variable Shaped Beam systems are most advanced systems for electron-beam direct write in terms of throughput, accuracy and automation.

Vistec has a range of systems.

The Vistec EBPG5200 is a high performance nanolithography system with full 200mm writing capability. This Electron Beam Lithography system presents a further evolutionary stage of the highly successful and field-proven EBPG series and offers a wide range of leading edge solutions for both direct write nano-lithography and R&D mask making in Universities and Commercial Centres of excellence.

Key Features
* High current density Thermal Field Emission gun for operation at 20, 50 and 100 kV
* Routine production of line with structures to less than 8 nm level
* max. stage travel range 210 mm x 210 mm
* Rapid exposure with 50 MHz pattern generator
* Includes automatic 10-holder airlock as standard
* GUI for ease of use for diverse "multi user environments"

Electron Beam lithography at wikipedia

The minimum time to expose a given area for a given dose is given by the following formula:

Dose * exposed area = beam current * exposure time/ step size **2 = total charge of incident electrons

For example, assuming an exposure area of 1 cm^2, a dose of 10-3 Coulombs/cm^2, and a beam current of 10-9 Amperes, the resulting minimum write time would be 10^6 seconds (about 12 days). This minimum write time does not include time for the stage to move back and forth, as well as time for the beam to be blanked (blocked from the wafer during deflection), as well as time for other possible beam corrections and adjustments in the middle of writing. To cover the 700 cm^2 surface area of a 300 mm silicon wafer, the minimum write time would extend to 7*10^8 seconds, about 22 years. This is a factor of about 10 million times slower than current optical lithography tools. It is clear that throughput is a serious limitation for electron beam lithography, especially when writing dense patterns over a large area.

Parallel E-Beam Lithography
There has been significant interest in the development of multiple electron beam approaches to lithography in order to increase throughput. This work has been supported by SEMATECH and start-up companies such as Multibeam Systems and Mapper. However, the degree of parallelism required to be competitive would need to be very high (at least 10 million, as estimated above); this is far in excess of most scheduled demonstrations





MAPPER is working on a new, patented technology for making chips without a mask and using electron beams.
This approach enables improved performance and reduces costs. The company´s major innovation is the use of one system through which more than 10,000 parallel electron beams can pass. MAPPER uses fibre-optics, which is capable of transporting a large quantity of information.

In October 2008, Mapper and Taiwan Semiconductor Manufacturing Co. have signed an agreement, according to which Mapper will ship its first 300mm multiple-electron-beam maskless lithography platform for process development and device prototyping to TSMC. This platform gives TSMC the opportunity to take the next step forward in exploring multiple e-beam technology as a lithography option at 22nm and more advanced process nodes.

Jack Sun, vice president of R&D of TSMC said: "Mapper's technology holds great promise for cost-effective manufacturing at 22nm and beyond. We are therefore going to test Mapper's solution to see whether it will live up to its promise. Using this first tool we will be able to explore its viability for manufacturing. Mapper's solution is a serious candidate to become the future lithography standard"





Multibeam has developed a family of MBXÔ Engines. Each MBXÔ Engine consists of either a 10-column linear array for patterning or inspecting 300mm wafers (MBX-10), a 7-column array for 200mm wafers (MBX-7), or a 5-column array for 150mm wafers or masks (MBX-5). For higher throughput, Multibeam MBXÔ Engines may incorporate multiple linear arrays into a two-dimensional array spanning the entire wafer.

To boost throughput, each e-beam column includes a thermal field emitter (TFE) electron source and incorporates unique IP that shapes beams while retaining high current density. High current density reduces flash time, the time it takes for resist to be exposed, enabling each Multibeam column to print a feature in tens of nanoseconds.


FURTHER READING
Next generation lithography at wikipedia.

Candidates for next-generation lithography include: extreme ultraviolet lithography (EUV-lithography), X-ray lithography, electron beam lithography, focused ion beam lithography, and nanoimprint lithography.Eeach NGL candidate faced more competition from the extension of photolithography than from any other NGL candidate, as more and more methods of improving photolithography continued to be developed, including optical proximity correction, off-axis illumination, phase-shift masks, liquid immersion lithography, and double patterning. Even within the area of photolithography, there is a list of "next-generation" techniques, including two-photon lithography, 157 nm wavelength, and high-index immersion.



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