DevelopingPositive Negative

Etching andStripping

Polymer Resist

Thin Film

Substrate

Resist Resist

ExposingRadiation

Figure 1.1. Schematic of positive and negative resists.

Log Exposure Dose

Resist Film ThicknessRemaining after Development

0

1

D0 –ThresholdDose

DC –ClearingDose

CD

DLog 0

10

Figure 1.2.a. Characteristic curve of a hypothetical positive tone resist. b) optical projection lithography schematic.

Figure 1.2.b. Optical projection lithography schematic.

source

condenser

Cr on glassmask

reductionoptics

image inresist onwafer

Figure 1.3.a. Dual-mask PSM technique. The original pattern for the gate is modified to create a phase shift mask and a “trim” mask. The phase shift mask creates a thin line exposure and the trim mask defines the remaining features.

PSM regular mask image

Original gate pattern

Figure 1.3.b. SEM micrograph of DSP chip with 120 nm gates printed with 248nm DUV lithography and dual-mask PSM technique. The original gate size was 250 nm.

Figure 1.4. Gaussian beam, shaped beam, and cell projection DWEB schematics.

1974 1978 1990

Gaussian Shaped Beam Cell/Character

Increasing Throughput

SEM

Figure 1.5. Schematic of Electron Projection Lithography employing scattering contrast.

IMAGE IN RESIST

Figure 1.6. Schematic of a focused ion beam system.

Figure 1.7. Atomic force microscope image of topography in PMMA following FIB exposure at 1pA beam current and a total irradiation time of 20 s per feature. (From Ref. 24 by permission of American Institute of Physics.)

Figure 1.8.a. Variation of feature size with distance of sample from focus position in FIB. (From Ref. 23 by permission of American Institute of Physics.)

0.00

0.05

0.10

0.15

0.20

0.25

0 100 200 300 400

Depth of Focus (m)

Fea

ture

Bro

aden

ing

(m

)

1.00 micronfeatures

0.25 micronfeatures

Figure 1.8.b. FIB-induced Pt deposition onto the periphery of a 5 cm radius of curvature gold-coated glass lens, corresponding to height differences of order 30 m. All images and patterns are recorded without refocusing of the ion beam. Sub 100 nm resolution is maintained over the entire field.

Figure 1.9. Schematic illustration of the microcontact printing process. (From Ref. 31 by permission of Elsevier.)

a

d

b

c

e

Figure 1.10. Schematic of nanoimprinting lithography process. (From Ref. 37 by permission of American Institute of Physics.)