Acoustics – Sound-modifying means – Housing or enclosure
Reexamination Certificate
2000-07-28
2002-09-17
Dang, Khanh (Department: 2837)
Acoustics
Sound-modifying means
Housing or enclosure
C181S292000, C355S053000
Reexamination Certificate
active
06450288
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an air-conditioning apparatus useful for temperature controlling of a machine tool, a measuring apparatus or an exposure apparatus for use in fabricating a semiconductor device, and also relates to a partition for use in the air-conditioning apparatus and an exposure apparatus equipped with the air-conditioning apparatus and the partition.
BACKGROUND OF THE INVENTION
In the currently used ultra-high-precision machine tools and measuring apparatuses (e.g., an interferometer), very high working accuracy and measurement accuracy are often required. To meet the requirement of such very high accuracy, careful consideration must be taken to the entire arrangement and constitution of the apparatus, as well as the environment where the apparatus is placed. In particular, the change in temperature of the environment apparently affects the accuracy of the apparatus to a great extent. Accordingly, it is required to prevent the temperature variation in the environment to a minimum to achieve ultra-high-precision working accuracy and measurement accuracy. In general, a high accuracy of the apparatus can be achieved by placing and operating the apparatus in a constant temperature room where the room temperature is controlled. However, for an apparatus in which a still higher accuracy is required and therefore a precise temperature control in the environment when the apparatus is placed is needed, the accuracy can be achieved by providing a chamber for the apparatus and precisely controlling the temperature of the interior of the chamber by means of an air-conditioner installed outside of the chamber.
The schematic illustration of a conventional air-conditioning apparatus used for the temperature control of an ultra-high-precision machine tool or measuring apparatus is shown in FIG.
4
.
FIG. 4
illustrates an example of a reduction projection exposure apparatus for use in the manufacture of an integrated circuit (IC), which comprises the main body of the reduction projection exposure apparatus, a chamber and an air-conditioning apparatus. A light or laser beam
4
emitted from a light source
3
which is placed in a case different from the chamber, is irradiated onto a reticle
6
on which a circuit pattern for the integrated circuit is formed. The light or laser beam
4
passed through the reticle
6
is incident to a projection lens
5
, where the light or laser beam is converged (e.g., converged to ⅕) and then irradiated onto a silicon wafer
7
mounted on a wafer stage
8
. The silicon wafer
7
is mounted on the wafer stage
8
and is configured to be movable on a plane perpendicular to the light axis of the projection lens
5
by means of a movement mechanism for the wafer stage
8
in accordance with a command output from an external device. Upon the alignment of the wafer stage
8
being completed, the light or laser beam
4
emitted from the light source
3
is irradiated onto the reticle
6
and then converged through the projection lens
5
to project the circuit pattern formed on the reticle
6
onto a chip or shot region on the silicon wafer
7
, whereby a photosensitive agent applied on the chip or shot region on the silicon wafer
7
is exposed to the light or laser beam
4
.
Upon the reduction projection exposure process being completed, the wafer stage
8
is driven again to be aligned. Then, the subsequent reduction projection exposure process is performed. In this manner, with the repeated alignment and exposure process, the circuit pattern for the IC is projected in reduced form onto the silicon wafer
7
.
The reduction projection exposure apparatus is subjected to the change in temperature of the environment and the vibrations transmitted to the apparatus, resulting in the formation of uneven line widths. For the purpose of eliminating these causative factors as much as possible, the main body of the reduction projection exposure apparatus is mounted on a vibration isolation table
2
and the entire apparatus is housed in a chamber
9
. The chamber
9
receives air
12
brown from an air-conditioner
10
which comprises an air-blower
13
(which serves both as an air-blower and an air exhauster) and a heat exchanger
11
. The temperature-controlled air is fed into the chamber
9
via a duct
15
and a filter
14
. The temperature in the chamber
9
is continuously monitored by a sensor. The signal output from the sensor is fed back into the air-conditioner
10
to control the air-conditioner
10
so that there is no difference between the actual temperature in the chamber
9
and the set temperature. The chamber
9
has a partition having high thermal insulating properties so that the temperature variation occurring outside of the chamber
9
gives no influence on the temperature inside of the chamber
9
. A conventionally used partition is one having a cross-sectional structure as shown in FIG.
5
. The partition consists of a rigid urethane foam
17
sandwiched by a pair of steel or aluminum plates
16
. The partition is used for imparting a strength to the chamber, and also used primarily in expectation of its thermal insulating effect.
The main body of the reduction exposure apparatus in the chamber
9
is mounted on the vibration isolation table
2
which is mounted on an independent base
21
on the ground
20
. The chamber
9
and the air-conditioner
10
are mounted on a floor member
23
which is supported by struts
22
on the ground
20
. A cushioning material
24
is filled between the floor member
23
and the independent base
21
.
The recent demand for ultra-high-precision in an apparatus has been increased to a level that cannot be achieved merely by the temperature control of the environment around the apparatus.
For example, the line width of an IC pattern required in such a reduction projection exposure apparatus as mentioned above is less than 0.35 &mgr;m. In the future, the reduction projection exposure apparatus would be expected to cover line widths around 0.25 &mgr;m and even around 0.15 &mgr;m. In this connection, even negligible disturbance factors that have been hitherto insignificant are increasingly becoming the topic, and the countermeasures against such disturbance factors should be taken.
What is consider as one of the disturbance factors is a noise transmitted to a chamber from the environment where the chamber is installed through a partition. In the case of a reduction projection exposure apparatus, a chamber typically is installed in a clean room. Noises generated in the clean room are transmitted to the partition of the chamber via air (as a medium), and transmitted in turn from the partition to the main body of the reduction projection exposure apparatus or the individual constituent parts (e.g., a projection lens, a stage and a wafer) to cause vibration thereof. As a result, there will be came up some problems, such as relative displacement among the individual constituent parts of the reduction projection exposure apparatus and difficulty in constantly maintaining a fine line width on the exposed plane.
The data of the noise levels measured both inside and outside of the chamber installed in a clean room is shown in FIG.
6
. During the measurement, the air-conditioner which blows air into the chamber is stopped to detect only the noises intruding from the outside of the chamber. The partition of the chamber used is a conventional one having a cross-sectional constitution as shown in FIG.
5
. As shown in the graphs of
FIG. 6
, even inside of the chamber, extremely low-frequency noises out of the audio range (i.e., low-frequency vibrations transmitted as compressional waves in air) are detected, which have sound pressure levels of about 69 dB at the maximum. It may suppose that the low-frequency noises are generated by a large air-blower for temperature-controlling the clean room and a duct which guides the temperature-controlled air into the chamber, and that the noises intruding into the clean room are transmitted to the chamber through the partition of the chambe
Akiyama Kyoichi
Hachisuka Masaru
Kou Gentoku
Ogawa Makoto
Ogawa Yoshinori
Dang Khanh
Nikon Corporation
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