Phase-shifting lithographic masks with improved resolution

Details Phase-shifting lithographic masks with improved resolution Phase-shifting lithographic masks with improved resolution

1993-02-19

1994-10-25

McCamish, Marion E.

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

430311, 430323, 430396, G03F 700

Patent

active

053588274

ABSTRACT:
In order to print an isolated feature having a width W in a photoresist layer using an optical radiation imaging system whose lateral magnification is equal to m, a phase-shifting mask is used having a corresponding isolated feature. In one embodiment this corresponding isolated feature has a central square portion having a refractive index n.sub.1 and a thickness t.sub.1, and a peripheral (rim) square-ring phase-shifting portion having a width B, as well as a refractive index n.sub.2 and a thickness t.sub.2, such that the phase-shift .phi.=2.pi.(n.sub.2 t.sub.2 -n.sub.1 t.sub.1)/.lambda. of the central portion relative to the peripheral portion is equal to .pi. radian or odd multiple integral thereof. The width C of the central portion advantageously is selected such that mC/W is equal to at least 1.2, and preferably greater than 1.5, rather than unity. In another embodiment, the isolated feature has an opaque central portion, also of width C, and a peripheral square-ring phase-shifting portion having a width B and having a phase-shift of .pi. radian relative to a surrounding transparent wide area ("bright field")--in which case, advantageously the value of m(C+2B)/W is equal to less than 1/(1.2), and preferably less than 1/(1.5).

REFERENCES:
patent: 4895779 (1990-01-01), Yoshioka et al.
patent: 5045417 (1991-09-01), Okamoto
Nitayama, A. et al., "New Phase Shifting Mask with Self-Aligned Phase Shifters for a Quarter Micron Photolithography," International Electron Device Meeting (IEDM) Technical Digest, pp. 57-60 (3.3.1-3.3.4) Dec. 1989.
Brunner, T., "Self-Aligned Phase Shift Masks for Contacts," SEMATECH Innovation for America's Future, Nov. 12, 1990.
Nakagawa et al., "Fabrication of 64M Dram with i-Line Phase-Shift Lithography," IEDM Technical Digest, (1990).
Todokoro et al., "Self-Aligned Phase Shifting Mask for Contact Hole Fabrication," Microelectronic Engineering, 13 (1991) pp. 131-134.
Garofalo, J. G. et al., "Phase-Shifting Structures for Isolated Features," SPIE vol. 1463 Optical/Laser Microlithography IV (1991) pp. 151-166.

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