The new high-throughput maskless tool developed at DARPA, achieves high throughput through the simultaneous deployment of 1 million parallel electron beamlets. Illustration: DARPA
DARPA said its Maskless Nanowriter program is developing a massively parallel, direct-write, electron-beam lithography tool with a write speed more than 100 times faster than current single-column eBeam tools. If successful, the program will eliminate the need for expensive mask sets and will increase economic viability of small-lot production for custom, ASICs and micro-electromechanical systems. The new Nanowriter tool is targeted at the 45-nm lithography node with technology scalable to 32 nm and beyond
DARPA said the program recently achieved two important milestones when it demonstrated a micro-lens array to pattern a beam into 1 million electron beamlets and showed a second-generation eBeam column designed to significantly reduce pattern blur.
In this new high-throughput maskless tool, high throughput is achieved through the simultaneous deployment of 1 million parallel electron beamlets.
The goal of the Maskless Nanowriter program is to produce a maskless electron-beam-direct-write (EBDW) lithography tool using a novel Reflection Electron Beam Lithography (REBL) concept invented by KLA-Tencor. A critical component of the Maskless Nanowriter program is the use of a reflective electron beam pattern generator that converts design data for an integrated circuit into a column of 1 million electron beams, controlled and modulated individually, to write the circuit pattern directly onto the wafer at very high throughput. This tool will be designed for nanolithography at the 45 nm node with a technology that can be scaled to the 32 nm node and beyond. Success in the development of the REBL technology will eliminate costly mask sets and increased economic viability for small lot production (1 – 20 wafers) of state-of-the-art custom ASICs (Application-Specific Integrated Circuits), NEMS/MEMS devices, and nanophotonic devices for DoD applications. The EBDW technology developed during this program will also result in maskless lithography tools that can be installed in the Trusted Foundry to enable affordable production of small lots of state-of-the-art DoD nanosystems for a broad spectrum of DoD applications. Additionally, the technology will find wide application in the commercial sector for nanopatterning masks for DUV lithography and templates for imprint lithography, thus defraying tool infrastructure costs to the DoD.
The spatially uniform, low energy spread electron beam is created on a thermionic cathode, accelerated to high energy (50 kilovolt), and rotated 90o via a magnetic prism toward a metal plate known as the dynamic pattern generator (DPG). The DPG features a 256 x 4000 array of micron-scale metal pixels, each pixel capable of individual biasing, that modulate the electron beams by biasing particular pixels of the array at either a low negative voltage (-2.1 volts) or at ground potential. When pixels are biased at -2.1 volts, the local electron beam is reflected; when pixels are biased at ground potential, the local electron beam is absorbed at very near zero energy. The patterned, reflected electron beam is then reaccelerated to 50 keV, rotated 90o by the magnetic prism, demagnified by a factor-of-50 in a magnetic optical system, and used to pattern the resist on the surface of the wafer.
The REBL tool to be developed in the Maskless Nanowriter program allows high throughput, greatly simplifies the electron optics required, and utilizes existing IC technology for easy addressing of the individual pixels. With a total beam current of 20 mA at the DPG (11 mA at the wafer), 5-to-7 300 mm-wafer-levels can be patterned in 1 hour, representing a write speed more than 100 times faster than available from existing single electron beam, direct-write technology. By delivering patterning performance compatible with the 45 nm node and beyond at several wafers per hour without the requirement for masks, Nanowriter will enable affordable and timely production of state-of-the art ICs in small lots entirely within secure facilities. In addition, it provides a commercially viable EBDW tool to ensure continued availability of custom ASICs for DoD applications.
Journal of Vacuum Science Technology – Reflective electron beam lithography: A maskless ebeam direct write lithography approach using the reflective electron beam lithography concept (8 pages, Nov 15, 2010)
Reflective electron beam litography (REBL) utilizes several novel technologies to generate and expose lithographic patterns at throughputs that could make ebeam maskless lithography feasible for high volume manufacturing. The REBL program was described in a previous article [ P. Petric et al., J. Vac. Sci. Technol. B 27, 161 (2009) ] 2 years ago. This article will review the system architecture and the progress of REBL in the past 2 years. The main technologies making REBL unique are the reflective electron optics, the rotary stage, and the dynamic pattern generator (DPG). Changes in how these concepts have been implemented in a new design will be discussed. The main disadvantage of today’s electron beam direct write is low throughput; it takes many tens of hours to expose a 300 mm wafer today using ebeam lithography. The projected system throughput performance with the integrated technology of the reflective optics, DPG, and a multiple wafer rotary stage will be shown incorporating the performance data for the new column design