X-ray or gamma ray systems or devices – Specific application – Lithography
Reexamination Certificate
2000-05-11
2001-09-11
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Lithography
C378S161000
Reexamination Certificate
active
06289077
ABSTRACT:
This application is based on Japanese Patent Applications No. HEI-9-115871 and No. HEI-9-115872 both filed on May 6, 1997 and No. HEI-10-45506 filed on Feb. 26, 1998, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a transmission system for synchrotron radiation light (SR light), and more particularly to an SR light transmission system capable of giving an intensity distribution to SR light in a cross sectional plane perpendicular to its optical axis and to an SR light transmission system irradiating a certain area by swinging up and down the transporting direction of the SR light using a swinging mirror.
b) Description of the Related Art
With reference to
FIG. 1
, the structure of a conventional X-ray exposure system will be described. Reference to
FIG. 1
is also made when embodiments of the invention are described later.
The X-ray exposure system is constituted of an SR light generator unit
1
, an SR light transmission unit
10
and an X-ray stepper
50
.
The SR light generator unit
1
is constituted of a vacuum room
2
and an electron beam circular orbit
3
formed therein. SR light is radiated from electrons moving along the circular orbit
3
. This SR light is output from a beam output port of the vacuum room
2
.
The SR light transmission unit
10
has an incoming vacuum duct
11
, a mirror box
12
and an outgoing vacuum duct
30
. Incoming opening
13
and outgoing opening
14
are formed in the wall of the mirror box
12
. The incoming vacuum duct
11
hermetically communicates the beam output port of the SR light generator unit
1
with the incoming opening
13
. In the vacuum duct
11
, a vacuum shielding valve (not shown), an SR light shielding shutter (not shown) and the like are mounted. The input port of the outgoing vacuum duct
30
is hermetically coupled to the outgoing opening
14
.
A reflection mirror
15
is disposed in the mirror box
12
and supported by a mirror swinging mechanism
16
. SR light entered the mirror box
12
via the incoming opening
13
is reflected by the mirror
15
and enters the outgoing vacuum duct
130
via the outgoing opening
14
. The mirror
15
is disposed such that its incidence plane containing an optical center axis of incidence SR light and a normal to a reflection plane at the reflection point and such that an angle between the optical center axis and the reflection plane is about 1 to 2°, i.e., the incidence angle is about 89 to 88°.
The swinging mechanism
16
swings the mirror
15
by using an axis, vertical to the incidence plane and passing the reflection point of SR light, i.e., a horizontal rotary shaft as a swing axis. As the mirror
15
swings, reflected SR light is swung up and down. The swing axis may be set to a position different from the reflection point of SR light.
An output window made of a beryllium thin film is formed in a window flange
37
which is hermetically mounted on an output end of the outgoing vacuum duct
30
. SR light entered the outgoing vacuum duct
30
transmits through the output window formed in the window flange
37
and is radiated to the outside of the vacuum duct
30
. An X-ray stepper
50
is disposed facing the window flange
37
. The X-ray stepper
50
holds a semiconductor substrate
51
at the position where SR light radiated from the window flange
37
is applied. An exposure mask
52
is supported in front of the semiconductor substrate
51
.
Although SR light is irradiated omnidirectionally in the horizontal plane, it has only a spread of about +/−1 mrad (mili-radian) in the vertical plane. By swinging the mirror
15
, SR light is swung in the vertical direction so that SR light can be applied to a broad surface area of the semiconductor substrate
51
.
SR light diverges in the horizontal direction. This SR light is therefore converged in the horizontal direction to make it parallel light fluxes, so that a use efficiency of SR light radiated from the light source can be improved. If the intensity of X-ray is increased, the X-ray exposure time can be shortened.
In order to converge SR light in the horizontal direction, as the mirror
15
shown in
FIG. 1
, a cylindrical mirror or a troidal mirror is used. A substantial focal length of a cylindrical mirror or troidal mirror changes with an incidence angle of SR light. As the mirror
15
is swung, the incident angle changes and the focal length with respect to the horizontal plane changes with the incidence angle correspondingly.
As the focal length changes, an energy density of SR light on the surface of the semiconductor substrate
51
changes. It is therefore difficult to uniformly apply X-rays to the surface of the semiconductor substrate
51
.
SR light reflected by a cylindrical mirror or a troidal mirror has a shape extending along generally a circular line in the cross sectional plane (beam cross section) perpendicular to the optical axis. Therefore, an SR light radiation area on the exposure surface of the semiconductor substrate
51
has also a shape extending along generally a circular line. SR light can be applied to a broad area by moving this radiation area in the radial direction passing through a center point of the circular line.
A length of the circular radiation area cut along a straight line parallel to the motion direction of the area becomes longer at the position remoter from the center of the radiation area in the horizontal direction. The exposure amount on the exposure plane obtained by swinging the mirror and moving such an exposure area in the vertical direction on the exposure plane, becomes larger at the position remoter from the center of the exposed area. It is therefore difficult to uniformly expose the exposure plane by using SR light having the circular radiation area.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an SR light transmission system capable of improving an exposure performance of an exposure apparatus using SR light.
It is another object of the present invention to provide a synchrotron radiation light transmission system capable of making a distribution of exposure amounts in an exposure area nearly uniform.
According to one aspect of the present invention, there is provided a synchrotron radiation light transmission system, comprising: a mirror box formed with an incoming opening and an outgoing opening through which synchrotron radiation light having a horizontally elongated cross section passes; a mirror disposed in the mirror box for reflecting the synchrotron radiation light; and a swinging mechanism for supporting the mirror so as to allow the synchrotron radiation light entered the mirror box via the incoming opening to be reflected by the mirror and to change a travelling direction in a vertical plane and for swinging the mirror to change a change angle of the travelling direction, wherein a swing axis is on a cross line, or on its extension, between an incidence plane of the synchrotron radiation light and a tangential plane of the mirror at a reflection point and also on an incidence side of the synchrotron radiation light from the reflection point, the reflection point of the synchrotron radiation light moves on a reflection plane of the mirror as the mirror swings, and the mirror is swung so that an incidence angle becomes larger as a distance between a light source of the synchrotron radiation light and the reflection point becomes longer.
If the mirror is a cylindrical surface mirror, a troidal mirror, a conical surface mirror or the like, a focal length in the horizontal plane changes with an incidence angle of synchrotron radiation light. A change in the focal length is compensated by changing the position of the reflection point to thereby form suitable reflected SR light.
According to another aspect of the present invention, there is provided a synchrotron radiation light transmission system, comprising: a mirror box formed with an incoming opening and an outgoing opening through which synchrotron radiation lig
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Porta David P.
Sumitomo Heavy Industrie's, Ltd.
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