e-Beam Lithographye-Beam Lithography

Antony D. HanAntony D. HanChem 750Chem 750

U of WaterlooU of Waterloo06-02-0706-02-07

What is lithography?What is lithography? Original meaning:Original meaning:

a process of printing using a non-polar ink applied to a hydrophilic a process of printing using a non-polar ink applied to a hydrophilic master plate patterned with a hydrophobic image.master plate patterned with a hydrophobic image.

Modern usageModern usage The term is more generally applied to a number of methods for The term is more generally applied to a number of methods for

replicating a predetermined master pattern on a substrate. replicating a predetermined master pattern on a substrate. Replication is effected by first coating the substrate with a radiation-Replication is effected by first coating the substrate with a radiation-

sensitive polymer film (a resist) and then exposing the film to actinic sensitive polymer film (a resist) and then exposing the film to actinic radiation in a pattern-wise manner. The radiation chemistry that results radiation in a pattern-wise manner. The radiation chemistry that results alters the physical or chemical properties of the exposed areas of the alters the physical or chemical properties of the exposed areas of the film such that they can be differentiated in a subsequent image film such that they can be differentiated in a subsequent image development step. Most commonly, the solubility of the film is modified development step. Most commonly, the solubility of the film is modified with the radiation chemistry either increasing the solubility of exposed with the radiation chemistry either increasing the solubility of exposed areas (yielding a positive image of the mask after develop) or areas (yielding a positive image of the mask after develop) or decreasing the solubility to yield a negative-tone image of the mask.decreasing the solubility to yield a negative-tone image of the mask.

Widely used in semiconductor industry and IT industry.Widely used in semiconductor industry and IT industry.

Focused eBL: ~sub 50 nm resolutionFocused eBL: ~sub 50 nm resolution

Steps involved in the EBL process.

With a beam current of 600 pA and an accelerating voltage of 100 kV, the beam diameter was approximately 3 nm.

J. Phys. Chem. B 2002, 106, 11463-11468

e-Beam Lithographye-Beam Lithography

Electron source: SEMElectron source: SEM Equipment: SEM equipped with a pattern Equipment: SEM equipped with a pattern

generator and alignment systemgenerator and alignment system e-beam control:e-beam control:

accelerating voltage (kV) operation current (pA) exposure dose (µC/cm2) exposure dwell period (µs)

eBL followed by SAeBL followed by SA

Langmuir, Vol. 20, No. 9, 2004, 3495

eBL changes the properties of coating layerseBL changes the properties of coating layers

Langmuir, Vol. 20, No. 9, 2004 3767

Applications of eBLApplications of eBL

(a) Backscattered electron (BSE) image of ZnO patternson SiOx substrates annealed in air at 700 °C for 20 min

(b) secondary electron (SE) image before annealing

(c) SE image after annealing at 700 °C for 20 min in air

(d) SE image of annealedpatterns over a large area.

Nano Lett., Vol. 5, No. 9, 2005

Applications of eBLApplications of eBL

Proceedings of SPIE Vol. 5184

LimitationLimitation

Tradeoffs for high-resolutionTradeoffs for high-resolution Time and high resolutionTime and high resolution

Improvement wrt this limitationImprovement wrt this limitation More sensitive resistsMore sensitive resists Cold developers (<10 ºC)Cold developers (<10 ºC)

Thank you!Thank you!

eBL applicationseBL applications

Langmuir, Vol. 20, No. 9, 2004 3767