Arradiance is developing a high-throughput, high-resolution alternative to optical lithography that is based on its patented MCA-Equalized Source Array (MESA).  MESA is a massively parallel, solid state, ultra-compact, cold-cathode e-beam source.  The complete MESA e-beam source assembly is only 25mm high, operates reliably at low current, and delivers stable and “bright” e-beams. The core technology (patented) is the combination of an array of cold-cathode field emitters with an array of microchannel amplifiers – all made from silicon using proven CMOS and MEMS process technologies. The basic MESA architecture consists of three core components:

     ●    the cold-cathode field emitter array (FEA)

     ●    the silicon microchannel amplifier array (MCA)

     ●    the electron beam lens array (EBLA)

In the FEA, emitters are arranged in a grid on 500 micron centers so that a 50 mm x 50 mm area contains 10,000 emitter clusters (each an individual “channel”).  Each emitter cluster is ~25 microns in diameter consisting of 19 emitting tips.  The minimum distance between adjacent tips is 8 microns.

The purpose of the MCA is to amplify the output of each of the emitter clusters in the FEA by two or three orders of magnitude. The amplification provided by the MCA is fundamental to the MESA innovation and to its expected high reliability. The MCA amplification allows the emitters to be operated at low current which in turn increases emitter life by several orders of magnitude. This addresses a major problem that has plagued field emitter-based systems historically:  when run at useful currents, they degrade quickly.   In MESA, the burden of providing useful current rests on the highly robust MCA. The massively parallel nature of this system also addresses the low throughput problem that has plagued traditional e-beam systems in the past.

The MCA is operated in its saturated regime to achieve noise suppression coming from the emitters and to deliver uniform current output by each channel (that is, uniform to within the dosage parameters of the e-beam resist being exposed).   Appropriate uniformity throughout all channels of the MCA is essential.

Each FEA emitter is paired with a “channel” in the MCA.  Thus, a 50 mm x 50 mm area of the MCA also contains 10,000 “channels” on 500 micron centers.  The result is a massively parallel array of “bright” e-beam sources that can be focused directly onto a wafer surface through an array of electrostatic lenses (the EBLA). The focused beams then directly expose resist on the surface of the wafer.  With all emitters “on”, the beams can write lines across the entire active area if the wafer is moved 500 microns (the center to center spacing of each channel).

The MESA system offers high resolution, large depth of focus, and the ability to write features from 90nm down to 16nm – covering the span of the ITRS roadmap. MESA offers the following advantages and the potential to deliver all of the requirements for lithography:

     ●    High throughput rivaling production optical steppers

     ●    Extensible throughout the ITRS roadmap – from 90nm to 16nm

     ●    Scalable to any wafer size

     ●    High resolution, large depth of focus

     ●    Maskless operation

     ●    Low cost of ownership

     ●    Ultra-compact footprint – more “cluster tool”, less “stepper”

     ●    Monolithic, solid state construction

     ●    Manufacturability using standard MEMS and CMOS processes