Editing Electron-beam lithography (section)

===Electron beam write time===

The minimum time to expose a given area for a given dose is given by the following formula:<ref>{{cite journal|author=Parker, N. W.|editor-first1=Elizabeth A. |editor-last1=Dobisz |doi=10.1117/12.390042|title=High-throughput NGL electron-beam direct-write lithography system|journal= Proc. SPIE |volume= 3997|page= 713 |year=2000|display-authors=etal|series=Emerging Lithographic Technologies IV|bibcode=2000SPIE.3997..713P|s2cid=109415718}}</ref>
:<math> D \cdot A = T\cdot I \,</math>

where <math>T</math> is the time to expose the object (can be divided into exposure time/step size), <math>I</math> is the beam current, <math>D</math> is the dose and <math>A</math> is the area exposed.

For example, assuming an exposure area of 1&nbsp;cm<sup>2</sup>, a dose of 10<sup>−3</sup> [[Coulomb|coulombs]]/cm<sup>2</sup>, and a beam current of 10<sup>−9</sup> [[Ampere|amperes]], the resulting minimum write time would be 10<sup>6</sup> 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 (electronics)|wafer]] during deflection), as well as time for other possible beam corrections and adjustments in the middle of writing. To cover the 700&nbsp;cm<sup>2</sup> surface area of a 300&nbsp;mm silicon wafer, the minimum write time would extend to 7*10<sup>8</sup> 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.

E-beam lithography is not suitable for high-volume manufacturing because of its limited throughput. The smaller field of electron beam writing makes for very slow pattern generation compared with photolithography (the current standard) because more exposure fields must be scanned to form the final pattern area (≤mm<sup>2</sup> for electron beam vs. ≥40&nbsp;mm<sup>2</sup> for an optical mask projection scanner). The stage moves in between field scans. The electron beam field is small enough that a rastering or serpentine stage motion is needed to pattern a 26&nbsp;mm X 33&nbsp;mm area for example, whereas in a photolithography scanner only a one-dimensional motion of a 26&nbsp;mm X 2&nbsp;mm slit field would be required.

Currently an optical [[maskless lithography]] tool<ref>[http://www.micronic.se/site_eng/product/AA65112_Sigma7500-II_product_sheet_A_001.pdf Faster and lower cost for 65&nbsp;nm and 45&nbsp;nm photomask patterning] {{dead link|date=June 2016|bot=medic}}{{cbignore|bot=medic}}</ref> is much faster than an electron beam tool used at the same resolution for photomask patterning.