JP3358090B2 - Illumination apparatus, exposure apparatus having the illumination apparatus, and device manufacturing method using the exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for producing, for example, ULSI circuit patterns.

[0002]

2. Description of the Related Art In order to promote the miniaturization of LSIs, it is essential to improve the resolution performance of a projection exposure apparatus for transferring a circuit pattern. Excimer steppers of the type in which the oscillation spectrum of the KrF excimer laser is narrowed and chromatic aberration of the projection lens system is not generated have been put into practical use since the announcement of ATT in 1986. This type of apparatus uses a shorter wavelength compared to a conventional mercury lamp using g-line or i-line, and therefore has a higher resolution and a higher fidelity of reticle pattern transfer. LS
It is considered to be the most suitable exposure apparatus for I.

In order to narrow the oscillation spectrum of an excimer laser, a light source device having a configuration as shown in FIG. 8 is used. This laser light source is Kr, F
A gain section 31 and an output-side beam splitter 34 for enclosing a gas mixture such as 2, Ne or the like and amplifying light generated by discharge.
And a prism 32 for narrowing the spectrum and a grating 33.

A part of the narrowed output light is branched by a beam splitter 35 and is incident on a wavelength monitor 36.
Information on the center wavelength and the spectrum width of the spectrum is sent from the wavelength monitor 36 to the wavelength control unit 37.
Controls the rotation angle of the grating 33 based on this information to stabilize the center wavelength of the output beam at a substantially constant value. The prism 32, the grating 33
In some cases, an etalon may be used instead of, or an appropriate combination of them may be used. However, the control range of the wavelength control unit 37 was only the management of the center wavelength.

[0005]

In the above-mentioned excimer laser light source, the oscillation spectrum of the laser is narrowed as shown by a solid line A in FIG. In the figure, a broken line B shows the case where there is no band-narrowing element such as the prism 32 and the grating 33 and there is only a mere total reflection mirror, that is, the spectrum of the laser beam which is not band-narrowed. At this time, the spectrum width △ λ _G (FWHM) is 300 to 400 pm, and the half width of the spectrum A when the band is narrowed △ λ ₀
Is about 100 times larger than the value of about 3 pm.

By narrowing the spectrum, the chromatic aberration of the projection lens of the exposure optical system can be almost ignored. However, in practice, in addition to the originally required spectrum which is narrowed, the ASE (Amplified Spontaneous Emissi
on) It is generally known that light is slightly output from the laser light source as background light of intensity I _BG .

[0007] Most of the intensity of the background light appears as a flare on the image plane of the beam, and is affected by the chromatic aberration of the image forming optical system to lower the contrast of the image formed. This decrease in contrast not only increases the minimum resolution line width, but also increases the minimum resolution line width.
At a line width of 35 μm, there is a problem that the depth of focus, which should originally be deep, becomes shallow.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem, to obtain a lighting device which removes background light of a narrow band spectrum and emits laser light having a narrower spectrum width.

[0009]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 includes band narrowing means (32, 33) for narrowing the spectrum width of laser light ,
A laser light source (1) for emitting a laser beam narrowed is made by fasciated means, narrowing the name of the its narrowed section
After being emitted and after being emitted from the laser light source
Acting on the laser light, the narrowed laser light and
Separately , the illuminating device is provided with extraction means (24, 25, 27, 29) for limiting the background light appearing as a flare. According to the second aspect of the present invention, the band narrowing means (32, 33) for narrowing the spectrum width of the laser beam is provided.
A laser light source (1) for emitting a laser beam narrowed by the band narrowing means;
Emitted from the laser light source after banding
And extracting means (24, 25, 27, 29) for operating on the laser light after being subjected to the light and limiting the background light emitted without being narrowed by the laser light source. .

[0010]

[0011]

[0012]

According to the present invention, there is provided an exposure apparatus provided with an extracting means for restricting a light beam from a laser light source in a predetermined area of a cross section of the light beam and extracting only a fundamentally necessary fundamental light beam narrowed. Background light emitted without being narrowed by the light source can be removed. Further, the presence or absence of background light is determined based on the result of the detection means for detecting the relationship (spectral characteristic) between the wavelength and the intensity of the laser light, and the determination result is fed back to operate the adjustment means via the control means. To adjust the extraction means.

Here, the operation of the present invention will be described by taking as an example the case where a slit is used as the extracting means. In the detection of the spectral characteristics of the laser light, it is difficult to determine the presence or absence of the background light at normal output, as shown in FIG. 9, because the intensity of the background light is much smaller than that of the narrowed spectrum. .

However, since the shape of the spectral characteristic of the excimer laser light is generally expressed by Gaussian or Lorentzian, it can be expressed by a quadratic function by making it logarithmic. Therefore, in the present invention, as shown in FIG. 7, a logarithmic value of the energy intensity value of the detected spectral characteristic data is obtained. As a result, the background light appears at the bottom of the peak in FIG. 7 as shown by a curve BG, so that the presence or absence of the background light can be easily determined.

That is, if the data of the spectral characteristic without the background light as shown by the broken line in FIG. 7 is used as a reference, it is compared with the detection data as shown by the solid line in FIG. The presence or absence of BG can be easily determined. By feeding back the result and operating the adjusting means to adjust the slit width, laser light from which background light has been removed can be obtained.

As described above, in the present invention,
The presence or absence of the background light can be easily detected by converting the spectral characteristics of the detected laser light into a logarithmic value, and the background light can be removed by adjusting the extraction means according to the detection result.

[0017]

Embodiments of the present invention will be described below. In FIG.
FIG. 1 is a schematic configuration diagram of a projection exposure apparatus suitable for using an illumination device according to an embodiment of the present invention. The configuration of this embodiment is
A KrF excimer laser light source 1 having a narrowed spectrum and wavelength stabilization, an extraction member 2 having a driving device, a spectral characteristic detector 3, a variable attenuator 4 for changing the intensity of laser light, and an intensity distribution in a cross-sectional direction of a beam. Beam uniformizing element 5, beam splitter 6, variable blind 7 for defining beam illumination area, mirror 8, condenser lens 9, reticle R, projection lens PL, wafer W, light amount detector 11, exposure amount control And 10.

The extraction member 2 removes the flare of the output of the laser light source 1, that is, the background light. The detection result by the detector 3 is fed back to the driving device,
The extraction member 2 is controlled. Hereinafter, the extraction member will be described.

FIG. 2 shows an embodiment in which a light-shielding member having a slit-shaped opening (hereinafter, simply referred to as a slit) is used as an extracting member. In the figure, excimer laser 1
, The narrowed laser light is emitted together with the non-narrowed background light. The slit 24 limits the background light that appears as a flare, and only the narrowed spectrum that is originally required for exposure
Through the opening. The opening has a structure in which the width can be freely changed both vertically and horizontally by the driving unit 23.

A part of the laser light passing through the slit 24 is reflected by the beam splitter 22 and enters a detector 3 for detecting spectral characteristics, for example, a spectroscope.
The detection result by the detector 3 is represented by logarithmic conversion of the energy intensity on the vertical axis as shown in FIG. The arithmetic comparison unit in the computer 21 is given a spectral characteristic without background light as shown by a broken line in FIG. 7 as a reference, and constantly compares this with a detection result to determine whether there is background light BG. Make a decision.

When the background light is confirmed, the control unit in the computer 21 controls the drive unit 23 to reduce the width of the slit 24 based on the result. By repeating this operation, a narrow band spectrum having a high purity (narrow in the spectrum width) without the background light can be obtained.

FIG. 3 is a flowchart showing the above-described sequence. That is, the spectral characteristics of the laser beam are detected (step 101), and the logarithm of the intensity value at each wavelength is obtained (step 102). From this result, the presence or absence of background light is determined (step 10).
3, 104), when there is background light,
Stop receiving the oscillation from the stepper (step 10
5).

In an ordinary exposure apparatus, cooperative control is performed between the laser side and the stepper side by an interface signal. If the background light is detected by the detection of the spectral characteristics, the stepper is notified that oscillation cannot be accepted, and the laser light is transmitted to the stepper (particularly on the wafer) by means such as closing a shutter in the illumination optical system.
Out of reach. Then, the drive unit is controlled to adjust the shape of the opening of the slit.

While the background light is detected, this routine is repeated to adjust the slit. If the result of the spectral characteristic detection indicates that the background light has been removed, the suspension of the reception of oscillation is released. Then, if an oscillation command is issued from the stepper side (step 107), the laser beam is oscillated according to the command (steps 108, 10).
9).

FIG. 4 shows a case where a lens system and a slit are used in combination as an extracting member. A lens system 25 having a driving unit 23 is arranged between the excimer laser unit 1 and the slit 24, and the optical element of the lens system 25 is moved to change the cross-sectional shape of the laser beam applied to the slit 24. Eliminate background light that appears as flares.

In the case where only the slit is used as in the case of FIG. 2, the cross-sectional shape of the light beam after passing through the slit may be smaller than desired by changing the shape of the slit opening. Therefore, if the lens system 25 is used as described above and the shape of the opening of the slit 24 is not changed, the cross-sectional shape of the laser beam incident on the attenuator 4 shown in FIG. 1 can be made desired. .
Therefore, there is no need to change or adjust the configuration of the device after the attenuator 4.

FIG. 5 shows a configuration in which a laser beam applied to a slit is focused. For example, the laser beam is condensed on a slit 24a disposed near the focal position by a lens system 27a including a cylindrical lens or the like, and flare in a direction perpendicular to the longitudinal direction of the slit is removed.

The laser light having passed through the slit 24a is condensed by the lens system 27b in a direction substantially orthogonal to the above-mentioned direction, and the flare in that direction is removed by the slit 24b disposed near the focal position of the lens system 27b. You. Since the laser beam that has passed through the slit 24b is divergent, the configuration may be such that the optical beam is arranged in the optical path after the slit 24b to make the cross-sectional shape of the light beam a desired one.

The slits 24a and 24b are moved along the optical axis of the laser beam by the driving units 23a and 23b, respectively, and change the area where flare is restricted (shielded). Alternatively, the positions of the slits 24a and 24b may be fixed, and the lens systems 27a and 27b may be moved. In the drawing, the light condensing state is shown in two planes substantially orthogonal to each other on one plane for convenience.

It is not particularly necessary to remove the flare twice by using two slits 24a and 24b, and it is also possible to adopt a configuration in which laser light is focused on the slit by using one focusing optical system. There is a similar effect. In each of the embodiments shown in FIG. 2, FIG. 4, and FIG. 5, flare is removed by slits. However, similar effects can be obtained by replacing the slits with pinholes.

FIG. 6 uses an etalon as an extraction member. By irradiating the etalon 29 with the narrowed laser light oscillated from the laser light source 1 and controlling the inclination of the etalon 29, that is, by controlling the incident angle of the laser light to the etalon 29, the background light is reduced. Remove. This uses etalon 29 as a filter.

By limiting the laser beam transmitted through the etalon 29 by the slit 24, background light can be further removed. However, the slit 24 does not need to be provided. It is needless to say that the etalon can be applied to the embodiments shown in FIGS. 1, 4 and 5 described above.

In the above embodiment, the spectroscope is used as an example of the means for detecting the relationship between the wavelength and the intensity of the laser light after the background light is removed. However, the fringe of the laser light is obtained by using an etalon. May be detected. Also in this case, the presence or absence of the background light can be determined by calculating the logarithm of the intensity value as in the above-described embodiment.

As a laser light source, an ArF excimer laser, an F ₂ laser or the like may be used in addition to the KrF excimer laser. Furthermore, when the present invention is applied to a case where a harmonic of a solid-state laser such as a YAG laser or a free electron laser is used, the purity of the spectrum is improved.

[0035]

As described above, according to the present invention, since unnecessary background light other than the originally required spectrum of the band-narrowed laser light can be removed, the contrast of the image formed on the wafer surface can be reduced. There is an effect of improving. Further, the spectral width can be controlled, and a narrower spectral width can be obtained, which can also contribute to an improvement in image contrast.

Further, by improving the contrast of the image,
Not only can a finer pattern be transferred, so that it is possible to cope with an increase in the density of the LSI, but also the depth of focus is increased and the line width control accuracy of the LSI is improved, so that the yield is improved.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a background light removal system when a slit is used as a limiting means of the present invention.

FIG. 3 is a flowchart showing a sequence of a background light removing mechanism of the present invention.

FIG. 4 is an explanatory diagram of a background light removal system when a lens and a slit are used as extraction means of the present invention.

FIG. 5 is an explanatory diagram of another example of the background light removing system when a lens and a slit are used as the extracting means of the present invention.

FIG. 6 is an explanatory diagram of a background light removal system when an etalon is used as an extraction unit of the present invention.

FIG. 7 is a diagram showing a spectrum intensity for explaining the operation of the present invention.

FIG. 8 is a schematic configuration diagram of a laser light source unit of a conventional projection exposure apparatus.

FIG. 9 is an explanatory diagram of spectral narrowing.

[Explanation of symbols]

 1: excimer laser light source 2: extraction member 3: detector 4: variable attenuator R: reticle PL: projection lens W: wafer 11: excimer laser 32: prism 33: grating 22: beam splitter 23: driving unit 24, 24a, 24b: slit 25: lens system 27a, 27b: lens system 29: etalon 21: computer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-250776 (JP, A) JP-A-3-54816 (JP, A) JP-A-1-287427 (JP, A) JP-A-2- 260412 (JP, A) JP-A-2-244708 (JP, A) JP-A-63-269518 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7 / 20 H01S 3/00

Claims (15)

(57) [Claims] 1. A narrow for narrowing the spectral width of the laser beam
Banding means, and the band was narrowed by the band narrowing means.
A laser light source that emits laser light, and after the band has been narrowed by the band narrowing means; and
Working on the laser light emitted from the laser light source
An illumination unit for limiting background light that appears as a flare separately from the narrowed laser light . 2. A narrow-to narrowing the spectral width of the laser beam
Banding means, and the band was narrowed by the band narrowing means.
A laser light source that emits laser light, and after the band has been narrowed by the band narrowing means; and
Working on the laser light emitted from the laser light source
And use, lighting apparatus characterized by having an extraction means for limiting the background light emitted without being narrow band of from the laser light source. 3. The apparatus according to claim 1, further comprising detecting means for detecting a relationship between a wavelength and an intensity of the laser light.
Or the lighting device according to 2. 4. The lighting device according to claim 3, further comprising a determination unit configured to determine the presence or absence of the noise component based on a detection result of the detection unit. 5. An arithmetic unit for obtaining a logarithmic value of the intensity based on the relationship between the wavelength and the intensity of the laser light and using the calculated value as detection data, wherein the determination unit comprises: The lighting device according to claim 4, further comprising: a memory that stores reference data indicating a relationship between wavelength and intensity; and a comparing unit that compares the detection data with the reference data. 6. The laser light source according to claim 3, wherein the laser light source controls reception of an oscillation command from outside the laser light source based on a detection result of the detection unit. Lighting equipment. 7. The apparatus according to claim 3, further comprising a driving unit that drives the extraction unit in accordance with a detection result of the detection unit to change a spectrum extraction range by the extraction unit. The lighting device according to claim 1. 8. The lighting device according to claim 1, wherein the extraction unit includes a light-shielding member having an opening that allows only the narrowed spectrum to pass therethrough. . 9. The lighting device according to claim 8, wherein the size of the opening can be changed according to the relationship between the wavelength and the intensity of the laser light. 10. An optical member disposed on a laser light path between the laser light source and the light blocking member, and changing the cross-sectional shape of the laser light irradiated on the light blocking member by moving on the light path. The lighting device according to claim 8, further comprising: 11. An optical member disposed on a laser light path between the laser light source and the light shielding member, and further comprising an optical member for condensing the laser light irradiated on the light shielding member. The lighting device according to claim 1. 12. The apparatus according to claim 1, wherein the extraction unit includes an etalon that can be tilted with respect to the laser beam.
The lighting device according to any one of claims 7 to 7. 13. The lighting device according to claim 12, wherein the extraction unit further includes a light-blocking member having an opening that allows only a spectrum narrowed by the etalon to pass therethrough. 14. An exposure apparatus comprising: the illumination device according to claim 1; and exposing a predetermined pattern on a substrate by using the laser light generated by the illumination device. apparatus. 15. An exposure apparatus according to claim 14,
Exposing a predetermined pattern on the mask onto the substrate
A device manufacturing method, comprising: