Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
2002-08-13
2004-12-21
Kim, Peter B. (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S052000
Reexamination Certificate
active
06833905
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to light emitting apparatuses, and more particularly to a light emitting apparatus for forming light for exposing an object such as a single crystal substrate for a semiconductor wafer and a glass plate for a liquid crystal display (LCD), an illumination apparatus using the same, an exposure apparatus, and a device fabricating method. The present invention is applicable to an exposure apparatus that uses, as exposure light, light in an extreme ultraviolet (“EUV”) range with, for example, a wavelength of 20 nm to 10 nm and light in a range with a wavelength shorter than EUV.
Recent years have sought for fine semiconductor devices drastically, and demanded resolution of 50 nm or less more recently. The conventional, most effective mass production method for realizing device miniaturization has been the photolithography that uses laser with an oscillating wavelength of 200 nm or less, to be more concrete, an ArF excimer laser with a wavelength of 193 nm and F
2
laser with a wavelength of 157 nm.
However, the principles of optics apparently indicates that resolution obtained by using an interference of light has a limit that it is equivalent to, or at most so much as 40% of an exposure wavelength. For example, the resolution R becomes about 70 nm from the following equation when a numerical aperture (NA) of a projection lens for demagnified transfer is raised as high as 0.7 with a pattern on an original (such as a mask or reticle) as an object plane and a wafer plane as an image plane, F
2
laser is used, and a proportional constant k
1
is 0.3:
R
=
k
1
λ
N
A
Therefore, an excimer waveband cannot necessarily satisfy the recent miniaturization requirement down to a resolution of 50 nm or less.
Accordingly, an exposure method has recently been proposed which uses EUV light with a wavelength shorter than an excimer beam (soft-X-ray with, e.g., a wavelength of about 13~14 nm). Given the EUV light, a resolution of 30 nm or less can be obtained from the above equation even when the NA is, for example, 0.3, and the proportional constant k
1
is, for example, 0.64. It would thus possible to establish the NA of a projection lens to be small, and ensure a permissible range of a device manufacturing process represented by the proportional constant k
1
.
The EUV light occurs when an excitation beam from a light source (i.e., excitation beam light source) is condensed onto a target to excite the target.
Here, a fluctuating light exit direction of a beam from the excitation beam light source accordingly fluctuates a position at which the beam is irradiated onto the target, and consequently a EUV-generating light emission point. In addition, the fluctuations in the EUV-generating light emission point negatively influence the performance of an illumination apparatus and exposure apparatus that use the generated EUV light.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a light producing apparatus whose EUV-generating light emission point is not so affected even when a light exit direction of a beam from an excitation beam light source fluctuates, an illumination apparatus using the same, an exposure apparatus, and a device fabricating method.
A light producing apparatus of one aspect of the present invention for irradiating a beam from a light source to a target to produce light having a wavelength different from the beam includes a first condensing optical system for condensing the beam from the light source, and an imaging optical system for imaging onto the target under a demagnification a condensing point of the beam by said first condensing optical system.
An illumination apparatus of another aspect of the present invention for illuminating an illuminated plane using light produced by the above light producing apparatus. The light produced by the light producing apparatus has, but is not limited to, a wavelength of 20 nm or less.
The illumination apparatus may include a second condensing optical system for condensing the light from the light producing apparatus, an optical integrator for receiving light from said second condensing optical system, and a first condenser system for superimposing a plurality of beams emitted from said optical integrator onto the illuminated plane. A configuration of the optical integrator that uniformly illuminates the illuminated plane would prevent uneven illuminance at the illuminated plane.
In one embodiment, the second condensing optical system includes a condensing mirror for condensing light from said light producing apparatus, and a second condenser system for condensing light from the condensing mirror into said optical integrator, wherein an aperture of the condensing mirror and an incident surface of said optical integrator are arranged optically conjugate with each other. Since the condensing mirror has the fixed aperture conjugate with the incident surface of the optical integrator, a positional offset of the light emission point under this configuration would not affect a light amount distribution of the optical integrator.
In another embodiment, the second condensing optical system may include a condensing mirror for condensing light from said light producing apparatus, and a second condenser system for condensing light from the condensing mirror into the optical integrator, and wherein the target of said light producing apparatus and an incident surface of the optical integrator are arranged optically conjugate with each other.
The illumination apparatus may further include a second condensing optical system for condensing light from said light producing apparatus onto the illuminated plane, the second condensing optical system comprising a plurality of condensing mirrors, wherein respective beams from the plurality of condensing mirrors illuminate a common illumination region on the illuminated plane. The beam from the light source may be a laser beam or an electron beam. A laser beam would be excitation laser (e.g., excimer laser, YAG laser, semiconductor laser, and solid state laser).
An exposure apparatus as still another aspect of the present invention uses the above illumination apparatus to illuminate a pattern of an original to project the pattern onto an exposed object by using a projection optical system. Such an exposure apparatus also exhibits operations similar to those of the above illumination apparatus.
A device fabricating method as still another aspect of the present invention includes the steps of projecting and exposing an object with a device pattern of an original by using the above exposure apparatus and performing a predetermined process for the object exposed. Claims for a device fabricating method for performing operations similar to that of the above exposure apparatus cover devices as intermediate and final products. Such devices include semiconductor chips like an LSI and VLSI, CCDs, LCDs, magnetic sensors, thin film magnetic heads, and the like.
Other objects and further features of the present invention will become readily apparent from the following description of the preferred embodiments with reference to accompanying drawings.
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patent: 5896438 (1999-04-01), Miyake et al.
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patent: 6504896 (2003-01-01), Miyake et al.
patent: 2001/0055103 (2001-12-01), Nishi
patent: 2002/0044629 (2002-04-01), Hertz et al.
patent: 2002/0191170 (2002-12-01), Komatsuda
patent: LO 09-115803 (1997-05-01), None
patent: LO 09-115813 (1997-05-01), None
patent: LO 09-298140 (1997-11-01), None
patent: LO 10-70058 (1998-03-01), None
English Abstract for JPLO 09-115803.
English Abstract for JPLO 09-115813.
English Abstract for JPLO 09-298140.
English Abstract for JPLO 10-70058.
Kim Peter B.
Morgan & Finnegan L.L.P.
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