Interferometric patterning for lithography

Details Interferometric patterning for lithography Interferometric patterning for lithography

2002-02-07

2003-12-30

Font, Frank G. (Department: 2877)

Optics: measuring and testing

By light interference

C356S521000

Reexamination Certificate

active

06671054

ABSTRACT:

TECHNICAL FIELD
This invention relates to interferometric patterning.
BACKGROUND
Interference patterns of alternating bright and dark lines are used to expose photo-resists to test their quality and to determine the resolution that can be achieved. Optical schemes for generating interference patterns are illustrated in
FIG. 1
a
and
FIG. 1
b
. In
FIG. 1
a
, an arrangement known as Young's configuration, two overlapping beams
106
and
108
of plane waves generate interference patterns on a substrate
102
. In
FIG. 1
b
, an arrangement known as a Lloyd's mirror, a plane mirror
104
is used to divert a portion of a beam
110
such that it interferes with another portion to produce interference patterns on substrate
102
.
The exposed photo-resist has line structures with a pitch, p, given by p=&lgr;/(2×sin [&thgr;]), where &lgr; is the wavelength of the plane waves and &thgr; is the half-angle of convergence. This pitch increases with wavelength. The line size is set by selection of the amount of time and intensity of exposure. A higher amount of exposure results in a smaller line width when using a positive tone photo-resist (i.e., a resist having the portions exposed to light removed after development).
Typically, coherent light sources are used to generate the interference patterns since interfering waves must be spatially and temporally coherent.


REFERENCES:
patent: 3633037 (1972-01-01), Langenbeck
patent: 3698814 (1972-10-01), Clark
Claude Montcalm et al., “Extreme Ultraviolet Coatings for the Next Generation Lithography,” Optical Interference Coatings, OSA Technical Digest (Optical society iof America, Washington, DC 32001, pp. ThA1-1 to ThA1-3.

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