JPH1097986A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner which can easily form interference fringes at the time of measuring the performance of an optical system and, therefore, can accurately measure the performance of the optical system. SOLUTION: An aligner uses KrF excimer laser light as laser light for exposure. The oscillation wavelength of the KrF excimer laser light emitted from a KrF excimer laser oscillator 1 is set at 248.25nm which is the wavelength of the double higher harmonic of Ar laser light having a wavelength of 496.5nm. It is also possible to use the double higher harmonic of the Ar laser light having the wavelength of 496.5nm as the laser light for measuring abberation at the time of measuring the performance (abberation) of the projection lens 6 of an aligner with an interferometer. Therefore, interference fringes can be obtained easily at the time of measuring the performance of lens 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure apparatus,
The present invention mainly relates to an exposure apparatus that uses KrF excimer laser light as an exposure light source.

[0002]

2. Description of the Related Art Conventionally, as an exposure apparatus of this type, Kr
A semiconductor exposure apparatus using a KrF excimer laser beam emitted from an F excimer laser oscillator as a light source for exposure has been proposed. The oscillation wavelength of the KrF excimer laser beam used here is 248.3, at which the highest output is obtained.
It was 85 nm.

[0003]

Generally, in a semiconductor exposure apparatus, the performance (aberration) of an optical system, particularly a projection lens, is reduced.
It must be measured using an interferometer. However, in the above conventional exposure apparatus, if the same KrF excimer laser light as the light source for exposure is used as the light source for aberration measurement, it is difficult to obtain interference fringes because the KrF excimer laser light has poor coherence, and the performance of the projection lens is poor. There is a problem that cannot be measured accurately. Further, the performance of the projection lens used at 248.385 nm was changed to the Ar of wavelength 496.5 nm.
When trying to measure with an interferometer that uses a second harmonic of laser light of 248.25 nm as a light source, aberration due to a difference in wavelength has been a problem. The present invention has been made in view of such conventional problems, and the problem is that interference fringes can be easily obtained when measuring the performance of the optical system, and therefore, the performance of the optical system can be accurately measured. It is an object of the present invention to provide an exposure apparatus which can perform measurement at a high speed.

[0004]

According to the present invention, there is provided an exposure apparatus using a laser beam having a variable oscillation wavelength as an exposure light source. It is characterized in that the wavelength is matched with the wavelength of a laser beam capable of measuring aberrations with better coherence or its harmonics with better coherence. For example, a KrF excimer laser light having an oscillation wavelength of 248.25 nm, which is a second harmonic of an Ar laser light having a wavelength of 496.5 nm, can be used as the exposure laser light, and a wavelength of 496 is used as the aberration measurement laser light. A double harmonic of a 0.5 nm Ar laser beam can be used.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an exposure apparatus according to one embodiment of the present invention. This exposure apparatus uses a KrF excimer laser oscillator 1 used as an exposure light source.
A reflecting mirror 2 for reflecting a KrF excimer laser beam emitted from the oscillator 1; an illumination optical system 4 for illuminating a pattern on a reticle 3 with the KrF excimer laser beam reflected by the mirror; And a projection lens 6 for reducing and projecting the pattern onto the wafer 5.

[0006] The KrF excimer laser oscillator 1 is a KrF excimer laser oscillator.
The oscillation wavelength of the excimer laser light can be varied by a very small amount. That is, of the laser light generated in the laser tube 1a, the laser light generated in the direction perpendicularly incident on the half mirror 1b is reflected by the half mirror 1b, travels backward, and enters the prism 1c. Also, the laser tube 1a
Of the laser light generated in the above, the laser light generated in the normal direction of the reflection surface of the half mirror 1b also enters the prism 1c. The laser beams incident on the prism 1c exit in directions slightly different from each other according to the wavelength thereof, and only the laser beams perpendicularly incident on the mirror 1d travel backward in the forward path. Thus, only the laser light having a certain wavelength oscillates, and a part of the laser light passes through the half mirror 1b and reaches the reflection mirror 2. The oscillation wavelength of the laser light can be changed by changing the installation angle of the prism 1c and the mirror 1d.

As described above, the present embodiment utilizes the fact that the oscillation wavelength of the KrF excimer laser oscillator 1 is variable by a very small amount, and makes the oscillation wavelength different from that of the KrF excimer laser light by a coherent (coherent). (Good) The wavelength of the laser light is matched. Specifically, the oscillation wavelength of the KrF excimer laser light is changed from 248.385 nm to 0.135 n.
The wavelength is changed to 248.25 nm, which is the second harmonic of Ar laser light having a wavelength of 496.5 nm, by changing the wavelength by m.
That is, the KrF excimer laser oscillator 1 has a wavelength of 24.
It is configured to emit 8.25 nm KrF excimer laser light.

Next, a wavefront aberration measuring device will be described with reference to FIG. This measuring apparatus measures the performance (aberration) of the optical system of the exposure apparatus according to the above embodiment, in particular, the projection lens 6 using an interferometer. The wavefront aberration measuring device includes an Ar laser oscillator 10 that emits Ar laser light,
A Fizeau interferometer 12 that has a Fizeau lens 11 and generates interference fringes, a reflection mirror M1 that guides Ar laser light emitted from the Ar laser oscillator 10 to the interferometer 12,
Processing for calculating wavefront aberration and the like of an imaging element 13 such as a CCD camera for imaging an interference fringe generated by the interferometer 12 and projection lens 6 as a lens to be inspected based on image information of the interference fringe captured by the imaging element 13 Device (not shown).

The Ar laser oscillator 10 is an Ar laser that emits the second harmonic (Ar laser light having a wavelength of 248.25 nm, which is a second harmonic of the Ar laser light and has a wavelength of 248.25 nm) of Ar laser light (wavelength 496.5 nm). A second harmonic oscillator of a laser is used. The second harmonic (second harmonic) of the Ar laser light emitted from the Ar laser oscillator 10 is reflected by the reflection mirror M1.
And is incident on the reflection mirror M2 of the Fizeau interferometer 12.

The Fizeau interferometer 12 includes a reflection mirror M2
The Ar laser light reflected by the light source is expanded by the beam expander 14 and reflected by the half mirror 15, and the reflected light is incident on the projection lens 6 via the Fizeau surface (reference surface) 11a which is the final surface of the Fizeau lens 11. It has become. The reference light reflected by the Fizeau surface 11a is transmitted through the half mirror 15, and then reflected by the reflection mirror M3.
An image is formed on the image sensor 13 by the imaging lens 17. On the other hand, the Fizeau surface 11a and the projection lens 6
Through the projection lens 6
The test light transmitted through the Fizeau lens 11 is transmitted through the half mirror 15, then reflected by the reflection mirror M3, and is imaged on the image sensor 13 by the imaging lens 17. Thus, interference fringes due to interference between the reference light and the test light are formed on the image sensor 13.

The exposure apparatus according to the first embodiment having the above configuration utilizes the fact that the oscillation wavelength of the KrF excimer laser oscillator 1 is variable by a very small amount, and changes the oscillation wavelength to produce a coherent Ar laser beam. 2nd harmonic wavelength 2
48.25 nm. That is, the KrF excimer laser oscillator 1 as an exposure light source has a wavelength of 24.
It is configured to emit 8.25 nm KrF excimer laser light. With such a configuration, as a light source when measuring the performance (aberration) of the optical system of the exposure apparatus, for example, the projection lens 6 by the wavefront aberration measuring apparatus shown in FIG.
An Ar laser oscillator that emits a second harmonic (wavelength: 248.25 nm) of an Ar laser beam, that is, a second harmonic oscillator 10 of an Ar laser can be used. by this,
Since the second harmonic (wavelength: 248.25 nm) of the Ar laser beam has the same wavelength as the oscillation wavelength of the KrF excimer laser oscillator 1 and has sufficiently good coherence, it is possible to easily obtain interference fringes when measuring the performance. Thus, the performance of the projection lens 6 can be accurately measured.

In the above embodiment, the oscillation wavelength of the KrF excimer laser light is changed to the Ar laser light (wavelength 496.5 nm).
) Is matched to the wavelength of 248.25 nm of the second harmonic, but the present invention is not limited to this. That is, the oscillation wavelength of the KrF excimer laser oscillator 1 is set to K
The wavelength may be the same as the coherent laser light existing separately from the rF excimer laser light or the wavelength of a higher harmonic thereof (an integer multiple of higher harmonics). In this embodiment, the prism 1c is used to change the wavelength of the exposure laser light. However, a diffraction grating can be used instead of the prism.

[0013]

As described above, according to the present invention, interference fringes can be easily obtained when the performance (aberration) of an optical system of an exposure apparatus, for example, a projection lens is measured using an interferometer. Therefore, the performance of the optical system can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a wavefront measuring apparatus for measuring the performance (aberration) of the optical system of the exposure apparatus shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... KrF excimer laser oscillator 1a ... laser tube 1b ... half mirror 1c ... prism 1d ... mirror 2 ... reflection mirror 3 ... reticle 4 ... illumination optical system 5 ... wafer 6 ... projection lens 10 ... Ar laser oscillator (the 2nd of Ar laser) 11: Fizeau lens 11a: Fizeau surface 12: Fizeau interferometer 13: Image sensor 14: Beam expander 15: Half mirror 16: Reflective spherical surface 17: Imaging lens M1, M2, M3: Reflective mirror

Claims (2)

[Claims] 1. An exposure apparatus using a laser light having a variable oscillation wavelength as an exposure light source, wherein a laser capable of measuring an oscillation wavelength of the exposure laser light with better coherence than the exposure laser light. An exposure apparatus characterized in that the wavelength is adjusted to the wavelength of light or its harmonics having good coherence. 2. The method according to claim 1, wherein a KrF excimer laser beam is used as the exposure laser beam, and an oscillation wavelength of the KrF excimer laser beam is 248.25 nm, which is a second harmonic of an Ar laser beam having a wavelength of 496.5 nm. Claim 1.
Exposure apparatus according to the above.