A set of multiple electron-beam ͑e-beam͒ aperture/blanker chips have been fabricated using silicon microelectro-mechanical systems ͑MEMS͒ techniques. The aperture sizes range from 8 to 4 m ͑nominal͒ squares, and the chip configurations feature either eight individually controlled monopolar blanker electrodes or four bipolar electrode pairs. The chips replace the shapers of a 20 kV AEBLE™ shaped e-beam lithography column. The apertures in the chips convert an incident 150 m diameter e-beam into multiple beamlets. Each beamlet can be independently blanked off of a 100 m aperture placed at the following beam crossover. Data are presented that demonstrates the ability to independently blank each beamlet by applying 10 V. Magnified images of the beamlets show square or rectangular shapes with sharp corners, indicating that the apertures were properly fabricated. The degree of electrostatic blanker crosstalk was measured and found to be up to 15% at the crossover plane for different pairs of beamlets, but no observable beam displacement occurred at the image plane. We compared the experimental results to a rough model that estimates the effect of the electrostatic field distribution of one excited blanker electrode on the unblanked beams. The results matched to within 20%.
Articles you may be interested inRecent tests of negative electron affinity photocathodes as source for electron lithography and microscopy Lifetime and reliability results for a negative electron affinity photocathode in a demountable vacuum system This work focuses on two issues crucial to achieving high throughput with a negative electron affinity semiconductor photocathode source. Monte Carlo simulations indicate that for a 50 kV system, as much as 8 A of current may be delivered to the wafer to achieve a raw throughput of 20 8 in. wafers per hour with 0.1 m minimum feature size ͑assuming a resist sensitivity of 10 C/cm 2 ͒. In order to achieve the throughput potential of this approach, suboptical emission areas are required; this suggests the use of cathode patterning. Two patterning alternatives have been investigated experimentally, and both approaches have been used to generate arrays of more than 100 electron beams with source sizes as small as 150 nm. However, each type of patterned cathode presents unique challenges to fabrication and performance in a practical multibeam system. Different source configurations ͑number of beams, beam current, beam spacing, etc.͒ create a system-level tradeoff between resolution and throughput. Results from patterned cathode experiments and system modeling are presented.
Scaled measurements of global space-charge induced image blur in electron beam projection systemThe effect of Coulomb interactions in electron-beam lithography systems are usually described in terms of the blur induced by stochastic electron-electron interactions. Here, we show both by an efficient Monte Carlo simulation and by a global space-charge model, that the aberrations induced by the lensing action of global space charge can be equally significant. For a 4:1 telecentric reduction projection optics operating at 100 kV beam energy and 25 A total current, we obtain about 150 nm blur independent of any stochastic effects. The global space-charge model requires less than 5 min computation on a 450 MHz workstation. The aberration coefficients of the global space-charge-induced lens can be evaluated, and because they scale directly with the perveance of the beam, can be used to evaluate the global space-charge effect over a wide variety of conditions. When the Monte Carlo and global space-charge models are used together, the stochastic-only portion of the beam blur can be extracted.
Alternative electron beam technologies to conventional single beam systems have the potential to increase beam current by an order of magnitude, into the 1–10 μA range. The technique we are investigating is to insert an aperture array at an object plane in a lithography system, thus creating an array of beamlets which are imaged as a dot matrix. Each aperture is surrounded by an independently controlled electrostatic microblanker which can modulate the beamlet passing through the aperture in conjuction with a blanking aperture placed at a crossover further down the column. An existing 20 kV shaped beam column with a LaB6 source providing 5 μA of illumination current over a 150 μm×150 μm square area is used as a test stand. The column is used to test prototype microblanker chips. Power dissipation calculations show less than a 10 K temperature rise over the prototype chips. Work has begun on a second generation prototype blanker array which will overcome many of the processing difficulties encountered with the first prototype. Specifically, the new all-silicon process will allow fabrication of smaller apertures which require less demagnification and a shorter electron-optical column.
Partial blanking of an electron beam using a quadrupole lensElectron optical image correction subsystem in electron beam projection lithography
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