Method for determining a radiation power and an exposure apparatus
View Patent ↗Method for determining a mean radiation power P rad 0 _ of electromagnetic radiation of a radiation source, the radiation being intensity-modulated with modulation frequency ω 0 , in a predetermined time interval. The method provides a reflector designed to reflect electromagnetic radiation of the radiation source and electromagnetic radiation of a test radiation source, irradiates a predetermined area of the reflector with the source electromagnetic radiation, at least partially irradiates the predetermined area of the reflector with electromagnetic radiation of the test radiation source, measures a ω 0 -modulated power component P test,ω 0 (t) of a reflected test radiation power P test (t) of an electromagnetic radiation of the test radiation source, the radiation being reflected from the area, in the predetermined time interval, determines a mean value P test , ω 0 0 _ of the measured ω 0 -modulated power component P test,ω 0 (t) of the reflected test radiation power P test (t) in the predetermined time interval, and determines the mean radiation power P rad 0 _ from the relationship P rad 0 _ = a · P test , ω 0 0 _ , where a is a predetermined constant.
1. A method for determining a mean radiation power
P
rad
0
_
of an electromagnetic radiation of a radiation source, the radiation being intensity-modulated with modulation frequency ω 0 , in a predetermined time interval t 0 to t 0 +Δt, comprising:
providing a reflector, which is designed to reflect electromagnetic radiation of the radiation source and electromagnetic radiation of a test radiation source;
irradiating a predetermined area of the reflector with the electromagnetic radiation of the radiation source;
at least partially irradiating the predetermined area of the reflector with electromagnetic radiation of the test radiation source;
measuring a ω 0 -modulated power component P test,ω 0 (t) of a reflected test radiation power P test (t) of an electromagnetic radiation of the test radiation source, the radiation being reflected from the area, in the predetermined time interval;
determining a mean value
P
test
,
ω
0
0
_
of the measured ω 0 -modulated power component P test,ω 0 (t) of the reflected test radiation power P test (t) in the predetermined time interval; and
determining the mean radiation power
P
rad
0
_
from the relationship
P
rad
0
_
=
a
·
P
test
,
ω
0
0
_
,
where a is a predetermined or predeterminable constant.
2. The method as claimed in claim 1 , further comprising regulating an output power of the radiation source such that a difference between a mean radiation power
P
rad
1
_
of electromagnetic radiation of the radiation source in a time interval t 1 to t 1 +Δt and a desired radiation power P rad desired is essentially minimized, where t 1 >t 0 +Δt holds true.
3. The method as claimed in claim 1 , wherein the method steps are carried out repeatedly in the order specified.
4. The method as claimed in claim 1 , wherein the predetermined time interval has a magnitude of 0.1 ms to 10 ms.
5. The method as claimed in claim 1 , wherein the predetermined time interval has a magnitude of 1 ms.
6. The method as claimed in claim 1 , wherein the radiation source is an EUV radiation source.
7. The method as claimed in claim 1 , wherein the test radiation source is an He—Ne laser or a semiconductor laser having an essentially constant test radiation power.
8. The method as claimed in claim 1 , wherein a beam direction of the radiation source and a beam direction of the test radiation source are arranged at an angle with respect to one another.
9. The method as claimed in claim 8 , wherein the angle is essentially 0°.
10. The method as claimed in claim 9 , wherein the angle is between essentially 0° and essentially 90°.
11. The method as claimed in claim 9 , wherein the angle is between 30° and 70°.
12. An exposure apparatus for exposing a material with electromagnetic radiation, comprising:
a radiation source, which is designed to generate an electromagnetic radiation intensity-modulated with modulation frequency ω 0 ;
a test radiation source, which is designed to generate electromagnetic radiation;
a reflector, which is designed to reflect both the electromagnetic radiation of the radiation source and the electromagnetic radiation of the test radiation source;
a measuring device, which is designed to measure a ω 0 -modulated power component P test,ω 0 (t) of a reflected test radiation power P test (t) of an electromagnetic radiation of the test radiation source, the radiation being reflected from the reflector; and
a determining device, which is designed to determine a mean value
P
test
,
ω
0
0
_
of the measured ω 0 -modulated power component P test,ω 0 (t) of the reflected test radiation power P test (t) in a predetermined time interval and to determine the mean radiation power
P
rad
0
_
from the relationship
P
rad
0
_
=
a
·
P
test
,
ω
0
0
_
,
where a is a predetermined or predeterminable constant.
13. The exposure apparatus as claimed in claim 12 , further comprising a regulating device, which is designed to regulate an output power of the electromagnetic radiation of the radiation source, such that a difference between a mean radiation power
P
rad
1
_
of electromagnetic radiation of the radiation source in a time interval t 1 to t 1 +Δt and a desired radiation power P rad desired is essentially minimized, where t 1 >t 0 +Δt holds true.
14. The exposure apparatus as claimed in claim 12 , wherein an EUV lithography exposure apparatus is involved.
15. The exposure apparatus as claimed in claim 12 , wherein the predetermined time interval has a magnitude of 0.1 ms to 10 ms.
16. The exposure apparatus as claimed in claim 12 , wherein the predetermined time interval has a magnitude of 1 ms.
17. The exposure apparatus as claimed in claim 12 , wherein the test radiation source is an He—Ne laser or a semiconductor laser designed to emit radiation having an essentially constant test radiation power.
18. The exposure apparatus as claimed in claim 12 , wherein a beam direction of the radiation source and a beam direction of the test radiation source are arranged at an angle with respect to one another.
19. The exposure apparatus as claimed in claim 18 , wherein the angle is essentially 0°.
20. The exposure apparatus as claimed in claim 18 , wherein the angle is between essentially 0° and essentially 90°.
21. The exposure apparatus as claimed in claim 18 , wherein the angle is between 30° and 70°.
22. An exposure apparatus for exposing a material with electromagnetic radiation, comprising:
a radiation generating means for generating an electromagnetic radiation intensity-modulated with modulation frequency ω 0 ;
a test radiation generating means for generating electromagnetic radiation;
a reflecting means for reflecting both the electromagnetic radiation of the radiation generating means and the electromagnetic radiation of the test radiation generating means;
a measuring means for measuring a ω 0 -modulated power component P test,ω 0 (t) of a reflected test radiation power P test (t) of an electromagnetic radiation of the test radiation generating means, the radiation being reflected from the reflecting means; and
a determining means for determining a mean value
P
test
,
ω
0
0
_
or the measured ω 0 -modulated power component P test,ω 0 (t) of the reflected test radiation power P test (t) in a predetermined time interval and for determining the mean radiation power
P
rad
0
_
from the relationship
P
rad
0
_
=
a
·
P
test
,
ω
0
0
_
,
where a is a predetermined or predeterminable constant.