Exposure method, illuminating device, and exposure system

Details Exposure method, illuminating device, and exposure system Exposure method, illuminating device, and exposure system

2001-12-31

2003-07-22

Fuller, Rodney (Department: 2851)

Photocopying

Projection printing and copying cameras

Step and repeat

C355S067000

Reexamination Certificate

active

06597430

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an exposure method to be used when a mask pattern is transferred onto a substrate such as a wafer in a lithography step for producing a device which includes, for example, a semiconductor element, a liquid crystal display element, a plasma display, and a thin film magnetic head. In particular, the present invention is suitable for an exposure apparatus based on the use of an illuminating apparatus which is provided with an optical system for realizing a uniform illuminance distribution on an illumination objective.
BACKGROUND ART
A variety of exposure apparatuses are known, including, for example, projection exposure apparatuses of the full-field exposure type or the scanning exposure type (for example, based on the step-and-scan system), and exposure apparatuses based on the proximity system to be used, for example, when semiconductor elements are produced. Such an exposure apparatus is provided with an illumination optical system for illuminating a pattern on a reticle with a uniform illuminance distribution by using an illumination light beam (exposure light beam) for exposure in order that the minute pattern on the reticle as a mask is highly accurately transferred onto a wafer (or a glass plate or the like) applied with resist, as a substrate.
An optical integrator such as a fly's eye lens has been hitherto used as an optical member for uniformizing the illuminance distribution. An illumination optical system, which is provided with two-stage fly's eye lenses (double fly's eyes) in order to enhance the uniformity of the illuminance distribution, is disclosed, for example, in Japanese Patent Application Laid-Open No. 6-196389 and U.S. Pat. No. 5,636,003 corresponding thereto.
FIG.
17
(
a
) shows main components of a conventional illumination optical system provided with two-stage fly's eye lenses. With reference to FIG.
17
(
a
), an illumination light beam IL having a width BW
1
, which is radiated from an unillustrated exposure light source, comes into a first fly's eye lens
65
. Illumination light beams, which come from a plurality of light source images formed on a light-outgoing plane of the first fly's eye lens
65
, come into a second fly's eye lens
67
via a light-collecting lens system
66
. An illumination light beam, which comes from the second fly's eye lens
67
, illuminates a reticle R via a condenser lens system
68
.
On the other hand, FIG.
17
(
b
) shows main components of a conventional illumination optical system which has a one-stage fly's eye lens (single fly's eye). With reference to FIG.
17
(
b
), an illumination light beam IL, which has a width BW
2
, comes into a fly's eye lens
69
. Illumination light beams, which come from respective light source images formed on light-outgoing planes of respective lens elements of the fly's eye lens
69
, illuminate a reticle R in a superimposed manner via a condenser lens system
70
.
In the case of the double fly's eye system of the former, the number of the light source images formed in a predetermined direction on the light-outgoing plane of the fly's eye lens
67
is represented by N
1
·N
2
provided that N
1
and N
2
represent the numbers of arrangement of lens elements of the fly's eye lenses
65
,
67
in the predetermined direction. On the other hand, in the case of the single fly's eye system of the latter, it is necessary that the fly's eye lens
69
is subdivided so that the number of arrangement of the fly's eye lens
69
is about N
1
·N
2
in a predetermined direction in order to obtain the same degree of the uniformity of the illuminance distribution as that of the double fly's eye system in the predetermined direction.
The exposure light beam has a narrow wavelength width, and it has relatively high coherence (coherency). Therefore, if the exposure light beam is used as it is, then interference fringes which are called speckles are generated on the illumination area of the reticle, and it is feared that any unevenness of the exposure amount is caused thereby. In view of this fact, in order to reduce the temporal coherence of the exposure light beam (or shorten the coherence time) and reduce the interference fringes, Japanese Patent Publication No. 7-104500 (Japanese Patent No. 2071956) discloses a delay optical system in which the exposure light beam is divided into two by using a beam splitter, and two-divided light fluxes are superimposed again after giving a predetermined difference in optical path to them. On the other hand, Japanese Patent No. 2590510 discloses an exposure apparatus in which the temporal coherence is reduced by radiating an exposure light beam onto a beam splitter surface of a delay optical system having a polygonal cross section in which one surface is the beam splitter surface and the remaining surfaces are reflecting surfaces (or total reflection surfaces).
As described above, the conventional exposure apparatus uses the illumination optical system which is provided with the one-stage optical integrator or the two-stage optical integrators. Further, the technique to avoid the occurrence of speckles has been developed. In such circumstances, the exposure wavelength is shortened in an advanced manner in recent years in order to obtain a higher resolution. At present, the KrF excimer laser light beam (wavelength: 248 nm) is dominantly used. In future, investigation will be made to use the vacuum ultraviolet light beam such as the ArF excimer laser light beam (wavelength: 193 nm) and the F
2
laser light beam (wavelength: 157 nm). Such a laser beam has high coherence as compared with the conventional bright line. When the laser beam having the short wavelength as described above is allowed to pass through a projection optical system composed of a refractive system, then the usable saltpeter material is limited, for example, to quartz glass and fluorite, and it is difficult to extinguish the color. Therefore, the wavelength of the laser beam is usually narrow-banded, for example, to have an order of the half value width of about 0.1 to 1 pm. The coherence of the laser beam narrow-banded as described above is further enhanced, resulting in high contrast of the interference fringes (speckles). Therefore, it is necessary to use a more highly-advanced technique in order to avoid the occurrence of interference fringes.
Recently, the areal size per one chip of the semiconductor element is increased. Further, it is also effective to increase the numerical aperture of the projection optical system in order to obtain a higher resolution. However, it gradually becomes difficult to design and produce a projection optical system with which high image formation performance is successfully obtained over an entire exposure area that is large and wide. In view of the above, the attention is attracted to a scanning exposure type projection exposure apparatus in which exposure is performed by synchronously moving a reticle and a wafer with respect to a projection optical system in a state in which an exposure light beam is radiated into a slender slit-shaped illumination area on the reticle. In this case, the narrower the width of the illumination area in the scanning direction (hereinafter referred to as “slit width”) is, the wider the width of the exposure field is, when a projection optical system having an identical size is used. As a result, it is possible to perform the exposure for a chip pattern having a large areal size. However, when the pulse light beam such as the excimer laser light beam is used, it is necessary that the number of exposure pulses for each point on the wafer is not less than a predetermined minimum number of pulses, taking the dispersion or irregularity of the pulse energy into consideration. When the movement velocity of the stage is increased in order to enhance the throughput in a state in which the slit width is made narrow, the number of exposure pulses is consequently decreased. However, it is possible to increa

Affiliated with

Also associated with

Rating

Exposure method, illuminating device, and exposure system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Exposure method, illuminating device, and exposure system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Exposure method, illuminating device, and exposure system will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3028312