Radiant energy – Supported for nonsignalling objects of irradiation – With source support
Reexamination Certificate
2002-03-22
2003-12-30
Lee, John R. (Department: 2881)
Radiant energy
Supported for nonsignalling objects of irradiation
With source support
C250S494100, C250S50400H, C313S114000, C313S011000, C313S012000
Reexamination Certificate
active
06670616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to ultraviolet-light irradiation apparatuses and, more particularly, to an ultraviolet-light irradiation apparatus for eliminating an electric charge after various plasma processes in a semiconductor manufacturing process.
In a manufacturing process of a flash memory, irradiation of an ultraviolet-light by a low-pressure mercury lamp is widely used in a process of eliminating an electric charge after carrying out a plasma process such as an etching process. That is, an electric charge of a semiconductor wafer is eliminated by irradiating an ultraviolet light onto the semiconductor wafer. The low-pressure mercury lamp used for such a process is a consumable component part, and it is required to replace the low-pressure mercury lamp with new one since an illumination intensity will become below a specified value when certain hours of use has passed. Therefore, there is a demand for reducing a cost for replacing a low-pressure mercury lamp. Moreover, the is a demand for improving productivity by improving an irradiation efficiency of a low-pressure mercury lamp so as to reduce an irradiation time.
2. Description of the Related Art
FIG. 1
is an illustrative cross-sectional view of a conventional ultraviolet-light irradiation apparatus
1
used for eliminating an electric charge of semiconductor wafers.
FIG. 2
is a side view of the ultraviolet-light irradiation apparatus
1
shown in FIG.
1
. The ultraviolet-light irradiation apparatus
1
comprises a wafer support plate
2
as a placement stage provided in a housing and a plurality of low-pressure mercury lamps
4
provided above the wafer support plate
2
. The low-pressure mercury lamp
4
emits an ultraviolet light having a wave length of 254 nm, and irradiates the ultraviolet light onto a wafer W placed on the wafer support plate
2
.
An electric charge of the wafer W is eliminated by the irradiation of the ultraviolet light. A reflective mirror
3
is provided above the low-pressure mercury lamps
4
. The reflective mirror
3
reflects the ultraviolet light, which is emitted upward by the low-pressure mercury lamps
4
, so that the ultraviolet light is irradiated onto the wafer W as much as possible. Moreover, a reflective mirror
5
is also provided on each side of the low-pressure mercury lamps
4
.
FIG. 3
is a plan view of the reflective mirror
3
viewed from the reflective surface side. The reflective mirror
3
is formed as a bottom surface of an exhaust passage
7
, and is provided with may exhaust holes
3
a
, which are small holes or openings, as shown in FIG.
3
. An end (right-hand side of
FIG. 2
) of the exhaust passage
7
, which has the reflective mirror
3
as a bottom surface, is closed, and air is suctioned through the other end (left-hand side of
FIG. 2
) of the exhaust passage
7
. Therefore, air heated by a temperature rise of the tube walls of the low-pressure mercury lamps
4
is suctioned into the exhaust passage
7
through the exhaust holes
3
a,
and is exhausted to an exterior of the ultraviolet-light irradiation apparatus
1
.
Accordingly, the hot air around the low-pressure mercury lamps
4
is exhausted so that the temperature of the tube walls of the low-pressure mercury lamps
4
is prevented from rising excessively. Moreover, a water-cooling mechanism
9
is provided above the exhaust passage
7
so as to cool the ultraviolet-light irradiation apparatus
1
including the low-pressure mercury lamps
4
, which also prevents an excessive temperature rise.
The exhaust holes
3
a
shown in
FIG. 3
are circular pores having a diameter of 10 mm, and are arranged along a longitudinal direction of the low-pressure mercury lamps
4
. As mentioned above, since air is suctioned through one end of the exhaust passage
7
and exhausted from the other end, a pressure difference is generated between the opposite ends of the exhaust passage
7
, which causes deviation in an amount of air suctioned through the exhaust holes
3
a.
That is, an amount of air suctioned through the exhaust holes
3
a
near the suction side (left-hand side of
FIG. 2
) is larger than an amount of air suctioned through the exhaust holes
3
a
near the opposite side (right-hand side of FIG.
2
). If an amount of exhaust air passing through the exhaust passage
7
is adjusted so as to set a temperature of the low-pressure mercury lamps
4
at the side opposite to the suction side to an appropriate temperature, the low-pressure mercury lamps
4
near the suction side are excessively cooled, which prevents the whole low-pressure mercury lamps
4
from being uniformly cooled.
Thus, there is a problem in that an excessively cooled potion is formed in the tube walls of the low-pressure mercury lamp
4
, which reduces the irradiation efficiency. Moreover, the reflective surface of the reflective mirror
3
shown in
FIG. 3
has mere a flat surface configuration, and the reflective efficiency is not taken into consideration. That is, as indicated by an arrow in
FIG. 1
, an ultraviolet light projected from an upper part of the low-pressure ultraviolet light
4
is reflected in a direction other than a direction toward the wafer W or irradiated onto a side of the apparatus without reflection. Thus, the consideration for turning an ultraviolet light in the direction of wafer W efficiently is not made with respect to the reflective mirror
3
which has the reflective surface of a mere flat-surface configuration, and there is a problem in that efficient ultraviolet-light irradiation is not performed.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful ultraviolet-light irradiation apparatus in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide an ultraviolet-light irradiation apparatus in which irradiation lamps are uniformly cooled to achieve an appropriate temperature of the walls of the lamps and the ultraviolet light emitted from the lamps is efficiently reflected toward an object to be irradiated so that the ultraviolet light is efficiently irradiated onto the object to be irradiated.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention an ultraviolet-light irradiation apparatus comprising: a plurality of low-pressure mercury lamps arranged in parallel; a placement stage provided under the low-pressure mercury lamps so that an object onto which an ultraviolet light emitted by the low-pressure mercury lamps is irradiated is placed on the placement stage; a reflective mirror arranged above the low-pressure mercury lamps so as to reflect the ultraviolet light emitted by the low-pressure mercury lamps; and an exhaust passage defined by the reflective mirror, the exhaust passage suctioning air around the low-pressure mercury lamps and exhausting the suctioned air to outside, wherein the reflective mirror has a plurality of openings arranged along a longitudinal direction of the low-pressure mercury lamps, and a part of the openings has a size different from a size of other parts of the openings.
According to the above-mentioned invention, an amount of air suctioned through the reflective mirror can be locally changed along the longitudinal direction of the low-pressure mercury lamps so as to adjust a degree of cooling partially. Therefore, when variation arises in a cooling effect along the longitudinal direction of the low-pressure mercury lamps, a uniform cooling effect can be acquired by locally changing a size of a part of the openings. Thus, a bulb temperature of the low-pressure mercury lamps can be uniformized, which extends the service life of the low-pressure mercury lamps.
In the ultraviolet-light irradiation apparatus according to the present invention, the exhaust passage may have a closed end and a suction end opposite to the closed end along a longitudinal direction thereof so as to suction air through the opening by exhausting the air from the suction en
Fujitsu AMD Semiconductor Limited
Hughes James P.
Lee John R.
Westerman Hattori Daniels & Adrian LLP
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