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Density multiplication of nanostructures fabricated by ultralow voltage electron beam lithography using PMMA as positive- and negative-tone resist
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10.1116/1.3657512
/content/avs/journal/jvstb/29/6/10.1116/1.3657512
http://aip.metastore.ingenta.com/content/avs/journal/jvstb/29/6/10.1116/1.3657512
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Examples of initial exposure patterns created with Raith GDS II software: (a) array of single-pixel dots; (b) single pixel periodic grating pattern; (c) array of single pixel lines in a cross configuration; and (d) array of single pixel lines forming a T-junction. For the dot array design in (a), initial pitches of 80 nm and 100 nm were used, whereas the designs in (b)–(d) employed an initial line pitch of 100 nm.

Image of FIG. 2.
FIG. 2.

SEM images of an initially 100 nm × 100 nm pitch array of single pixel dots exposed with 1 keV electrons in a 30 nm thick PMMA layer on Si substrate and developed at −15 °C for 5 s. The panels correspond to point doses of (a) 9.99 fC/dot, (b) 19.98 fC/dot, (c) 33.30 fC/dot, and (d) 36.63 fC/dot. Panels (a) and (b) show both regions where PMMA is cross-linked, responding as a negative-tone resist, and regions of undeveloped PMMA. Panels (c) and (d) illustrate the density multiplication with a capacity of control over the feature size via dose variation.

Image of FIG. 3.
FIG. 3.

Two-dimensional cross-sections of the predicted 3D distributions of the yield of main chain scissions per monomer in PMMA in a periodic array of single pixel dots employing 1 keV exposure of a 30 nm thick layer of PMMA on Si substrate with a point dose of ∼33.3 fC/dot; (a) the lateral {X,Y} distribution of the yield of scissions per monomer at the bottom of the resist layer; (b) a distribution of the yield of scission in the {X,Z} plane. The plots illustrate relative (normalized) distributions of the scission yield. In the legend, 1.00 corresponds to the maximum scission yield in the image. The dimensions are in angstroms.

Image of FIG. 4.
FIG. 4.

High magnification SEM images of density multiplication in an array of dots with a premultiplication pitch of 80 nm. The PMMA layer with an initial thickness of 43 nm on Si substrate was exposed with 1 keV voltage at a dose of 12.5 fC/dot and developed for 5 s at −15 °C. (a) Plan view; (b) view at a 45° angle; (c) inset of structures and sidewall from Fig. 4(b), viewed at a 45° angle.

Image of FIG. 5.
FIG. 5.

SEM images of density multiplication in an array of lines with a premultiplication pitch of 100 nm. The PMMA layer with an initial thickness of 43 nm on Si substrate was exposed with a 1 keV voltage at a dose of 2000 pC/cm and developed for 5 s at −20 °C. (a) Plan view; (b) 70° angled view.

Image of FIG. 6.
FIG. 6.

Plots of the predicted nominal yield of scissions per monomer of PMMA for a periodic array of 100 nm pitch dots in an initially 30 nm thick layer of PMMA on Si substrate, exposed with 1 keV voltage and a point dose of 33.3 fC/dot. (a) The dependence on the lateral position at the top of the resist; (b) the dependence at the bottom of the resist; (c) the dependence on depth in an exposed spot. In (a) and (b), X is the lateral coordinate, and in (c), Z = 0 corresponds to the bottom of the resist. The dimensions are in angstroms. In (b), the arrows indicate the level of scission corresponding to a width of 37.9 nm, corresponding to the observed diameter of the cross-linked spot at similar conditions.

Image of FIG. 7.
FIG. 7.

Plots of the predicted nominal yield of scissions per monomer for the case of 100 nm pitch single pixel lines (periodic grating) in an initially 43 nm thick layer of PMMA on Si substrate, exposed with 1 keV voltage and a line dose of 2000 pC/cm: (a) the dependence on the lateral position at the top of the resist; (b) the dependence at the bottom of the resist; (c) the dependence on depth for an exposed line. The dimensions are in angstroms. In (b), the arrows indicate the level of scission corresponding to a width of 21.5 nm, corresponding to the observed diameter of the cross-linked spot at similar conditions.

Image of FIG. 8.
FIG. 8.

SEM images of density multiplication in cross and T-junction nanostructures formed by single pixel lines with an initial pitch of 100 nm. The nanostructures were fabricated in an initially 43 nm thick PMMA layer on Si substrate, exposed with 1 keV and developed in an MIBK:IPA 3:1 mixture for 5 s at −20 °C. (a) Plan view of cross structure with some underexposure; (b) higher resolution 70° angle view of cross structure; (c) plan view of T-junction structure showing density multiplication at the junction area; (d) 70° angle view of T-junction structures showing density multiplication at the junction area.

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/content/avs/journal/jvstb/29/6/10.1116/1.3657512
2011-11-02
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Density multiplication of nanostructures fabricated by ultralow voltage electron beam lithography using PMMA as positive- and negative-tone resist
http://aip.metastore.ingenta.com/content/avs/journal/jvstb/29/6/10.1116/1.3657512
10.1116/1.3657512
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