Photocopying – Projection printing and copying cameras – Detailed holder for photosensitive paper
Reexamination Certificate
2001-06-13
2004-05-11
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Detailed holder for photosensitive paper
C355S075000, C414S939000
Reexamination Certificate
active
06734950
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to a load-lock chamber suitably usable in an exposure apparatus which uses ultraviolet light as exposure light and which is arranged to replace the interior of the apparatus by an inactive gas and also which has a function for transferring a pattern of a mask onto a photosensitive substrate through a projection optical system, wherein the load-lock chamber is adapted to be operated continuously. In another aspect, the invention concerns an exposure apparatus having such a load-lock chamber and an exposure method that enables continuous operation.
Conventionally, the procedure of manufacturing semiconductor devices comprising very fine patterns such as LSI or VLSI uses a reduction type projection exposure apparatus which functions to project and photoprint, in a reduced scale, a circuit pattern formed on a mask onto a substrate being coated with a photosensitive material Increases in the density of the semiconductor device have forced further miniaturization, and advancement in the resist process as well as improvement of the exposure apparatus to meet the miniaturization have been pursued.
The resolving power of an exposure apparatus can be improved by, for example, shortening the exposure wavelength used or by enlarging the numerical aperture (NA) of a projection optical system.
As regards the exposure wavelength, recently, in place of i-line (365 nm), KrF excimer lasers having an emission wavelength of about 248 nm or ArF excimer lasers having an emission wavelength of about 193 nm have been developed. Further, fluorine (F
2
) lasers having an emission wavelength of about 157 nm are being developed.
In regard to deep ultraviolet light, particularly, ArF excimer lasers having a wavelength of about 193 nm or F
2
excimer lasers having an emission wavelength of about 157 nm, it is known that there is an oxygen (O
2
) absorption band in the regions about these wavelengths
For example, because of its short wavelength (157 nm), the applicability of fluorine excimer lasers to exposure apparatuses have been attempted. However, the wavelength of 157 nm is present in a range of a wavelength region generally called a vacuum ultraviolet. In such wavelength region, the absorption of light by oxygen molecules is large. As a result, the atmosphere does not transmit most of the light. Therefore, this light source can be used only in a situation that the atmospheric pressure is reduced close to vacuum and that the oxygen concentration is sufficiently lowered. According to “Photochemistry of Small Molecules”, Hideo Okabe, A Wiley-Interscience Publication, 1978, p178, the absorption coefficient of oxygen to light of a wavelength 157 nm is about 190 atm
−1
cm
−1
. This means that, when light of a wavelength 157 nm passes through a gas having an oxygen concentration of 1%, under a unit atmospheric pressure, the transmission factor T per 1 cm is only:
T=
exp(−190×1 cm×0.01 atm)=0.150.
Further, as the oxygen absorbs the light, ozones (O
3
) are produced. Various products are created by ozones, and they are deposited to surfaces of optical elements to decrease the efficiency of the optical system.
In consideration of them, in projection exposure apparatuses which use deep ultraviolet rays such as an ArF excimer laser or a F
2
excimer laser, purging means such as an inactive gas (e.g., nitrogen or an inert gas) is provided at the light path of an exposure optical system, to suppress the oxygen concentration at the light path to a low level of an order of a few ppm or less.
As described above, in exposure apparatuses using deep ultraviolet light, particularly, an ArF excimer laser having a wavelength of about 193 nm or a fluorine (F
2
) excimer laser having a wavelength of about 157 nm, because the ArF excimer laser light or F
2
excimer laser light is very easily absorbed by a substance, the light path must be purged to a level of an order of a few ppm or less. Further, this is also the case with the moisture (H
2
O). It should be reduced to a level of a ppm order.
In order to meet this, conventionally, the inside of an exposure apparatus, more particularly, the portion thereof defined for a light path of ultraviolet light, is purged by use of an inactive gas. Further, a load-lock mechanism is provided at a portion for connecting the inside of the exposure apparatus with the outside thereof. When a reticle or a wafer is to be loaded from the outside, the outside atmosphere is once isolated by the load-lock mechanism. After impurities inside the load-lock mechanism are purged by an inactive gas, the reticle or wafer is introduced into the exposure apparatus.
FIG. 1
is a schematic and sectional view of an example of a semiconductor exposure apparatus having a fluorine (F
2
) excimer laser as a light source and also a load-lock mechanism.
Denoted in
FIG. 1
at
1
is a reticle stage on which a reticle having a pattern formed thereon is placed. Denoted at
2
is a projection optical system for projecting the pattern of the reticle onto a wafer. Denoted at
3
is a wafer state for carrying a wafer thereon and being movable in the X, Y, Z, &thgr; and tilt directions. Denoted at
4
is an illumination optical system for projecting illumination light onto the reticle, and denoted at
5
is a light directing optical system for directing light from the light source to the illumination optical system
4
. Denoted at
6
is a fluorine (F
2
) excimer laser unit which is a light source, and denoted at
7
is a masking blade operable to block exposure light so as to prevent those regions on the reticle, other than a pattern region thereof, from being irradiated with the exposure light. Denoted at
8
and
9
are casings for encircling an exposure optical axis around the reticle stage
1
and the wafer stage
3
. Denoted at
10
is a He gas conditioning machine for adjusting the inside of the illumination optical system
4
and the projection optical system
2
to provide there a predetermined He ambience. Denoted at
11
and
12
are N
2
gas conditioning machines for adjusting the inside of the casings
8
and
9
to provide there a predetermined N
2
ambience. Denoted at
13
and
14
are a reticle load-lock and a wafer load-lock, respectively, to be used when a reticle and a wafer are to be loaded into the casings
8
and
9
, respectively. Denoted at
15
and
16
are a reticle hand and a wafer hand, respectively, for conveying a reticle and a wafer, respectively. Denoted at
17
is a reticle alignment mark to be used for adjusting the position of the reticle. Denoted at
18
is a reticle storage unit for storing plural reticles inside the casing
8
. Denoted at
19
is a prealignment unit for performing prealignment of a wafer.
FIG. 2
is a schematic and sectional view of another example of a semiconductor exposure apparatus having a fluorine (F
2
) excimer laser as a light source and also a load-lock mechanism.
In the exposure apparatus of
FIG. 2
, the exposure apparatus as a whole is covered by a casing
20
, and O
2
and H
2
O there are purged by a N
2
gas. Denoted at
21
is an N
2
gas conditioning machine for providing a N
2
ambience in the whole casing
20
. In this exposure apparatus, the inside spaces of a barrel
2
and an illumination optical system
4
are isolated from the inside space of the casing
20
(driving system space), and they are adjusted independently so that a He ambience is provided there. Denoted at
13
and
14
are a reticle load-lock and a wafer load-lock, respectively, to be used when a reticle and a wafer are loaded into the casings
8
and
9
, respectively.
FIG. 3
is a schematic view of an example of a semiconductor manufacturing system including an exposure apparatus such as shown in
FIG. 1
or
2
, as well as a coating and developing machine.
Denoted in
FIG. 3
at
22
is a coating and developing machine including a coater unit for coating a wafer with a resist material, and a developing unit for developing a wafer after being exposed. Denoted at
23
is an e
Adams Russell
Canon Kabushiki Kaisha
Esplin D. Ben
Fitzpatrick ,Cella, Harper & Scinto
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