JP2001267660A - Wavelength monitor device for laser beam for semiconductor exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength monitor device equipped with an etalon suitable for both reference lights and lights to be measured. SOLUTION: This device is constituted of a single etalon (1) whose different areas are coated with reflection coating (1b) for laser (20) for semiconductor exposure and reflection coating (1a) for reference lights (10), an incidence optical system (2) for making the laser beams and the reference lights incident to the areas of the etalon (1) coated with the reflection coating (1a, 1b) corresponding to each light by alternately shifting the central axes, a converging means (3) for converging the two lights transmitted through the etalon (1), and a sensor (4) for receiving the lights from the converging means (3). Thus, the wavelength of the laser (20) for semiconductor exposure can be calculated by the sensor (4).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength monitor for laser light for semiconductor exposure, and more particularly to a wavelength monitor for laser light for semiconductor exposure for measuring the wavelength of laser light for semiconductor exposure with respect to a reference light having a known wavelength. The present invention relates to a monitor device.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor integrated circuits, the wavelength of light sources for semiconductor exposure has been shortened.
ArF excimer laser device with a wavelength of 193 nm and wavelength of 15
7 nm fluorine laser devices are promising. As for the ArF excimer laser, the laser beam has a spectral width of 4
It is as wide as about 00 pm. However, only synthetic quartz and fluorite exist as optical materials for an exposure apparatus that can be used in the vacuum ultraviolet region, and it is extremely difficult to achromatize the projection optical system of the exposure apparatus. In order to avoid the problem of chromatic aberration in the projection optical system of the exposure apparatus, the spectral width of laser light emitted from an ArF excimer laser device or a fluorine laser device, which is a light source for semiconductor lithography, is set to 0.
It is necessary to narrow the band to 6 pm or less, and the center wavelength is also required to have a wavelength stability within ± 0.1 pm.

[0003] The narrowing of the spectral line width of the laser beam for semiconductor exposure is realized by, for example, a narrowing optical system including a beam diameter expanding prism and a diffraction grating, and controlling the incident angle of light to the diffraction grating. By doing so, wavelength selection is performed.

In order to realize the above-mentioned wavelength stabilization, the wavelength and the spectral line width of the semiconductor exposure laser light which has been narrowed during the exposure are measured, and the data is measured based on the data.
A wavelength monitoring device for performing feedback control of a laser device for semiconductor exposure such as an rF excimer laser device is required.

[0005] As a conventional example of such a wavelength monitor, FIG. 2 shows the configuration of a wavelength monitor of Vale. In this apparatus, first, in a state where the shutter B is closed, reference light from a He-Ne laser having a wavelength of 632.8 nm as a standard light source is incident on a beam splitter through a reflecting mirror and a shutter A, is reflected there, and is reflected there. The light that reaches the etalon via the concave reflecting mirror reaches the etalon, and the light multiply reflected by the etalon passes through the condenser lens to form an interference fringe (fringe) formed of concentric or parallel lines on the rear focal plane. A linear array sensor (CCD) is arranged on the side focal plane, and data for correcting fluctuations in the refractive index of the etalon air and fluctuations in the mirror interval are obtained from position data of each fringe on the CCD. Next, when the shutter A is closed and the shutter B is opened, the wavelength of 193.4 n from the ArF excimer laser is emitted.
The light to be measured in the vicinity of m passes through the beam splitter from the right side of the drawing through the entrance aperture and the shutter B, is reflected by the reflecting mirror and the concave mirror, reaches the etalon, and the light multiply reflected by the etalon passes through the condenser lens. Thereafter, interference fringes (fringes) formed of concentric or parallel lines are formed on the CCD on the focal plane. From the data for correcting the fluctuation of the refractive index of the etalon air and the fluctuation of the mirror interval obtained from the position data of the fringe of the wavelength measurement light on the CCD and the position data of the reference light on the fringe, the wavelength measurement light is obtained. Is calculated.

[0006]

In such a conventional wavelength monitor, a standard light source (He-Ne laser) is used.
Measurement and laser light for semiconductor exposure (for example, ArF
Excimer laser) used the same region of the same etalon. For this reason, the reflecting mirror constituting the etalon has a wavelength of 632.8 n of He-Ne laser light.
A dielectric multi-layer coating or an aluminum coating is required for two wavelengths of m and ArF excimer laser light of 193 nm. However, it is difficult and expensive to construct a coating that can obtain sufficient reflectance and low loss characteristics for both of them.

[0007]

In order to achieve the above object, the present invention provides a wavelength monitor for a laser beam for semiconductor exposure, wherein the reflection coating for the laser beam for semiconductor exposure and the reflection coating for the reference beam are provided in separate areas. A single etalon applied to the etalon, an incident optical system for causing the laser light and the reference light to be shifted from each other with respect to the etalon so as to be incident on the regions provided with the respective reflective coatings, It is characterized by comprising a condensing means for the two transmitted lights and a sensor for receiving the light from the condensing means, wherein the sensor calculates the wavelength of the semiconductor exposure laser light.

In these wavelength monitoring devices for semiconductor exposure laser light, the semiconductor exposure laser light is ArF excimer laser light or fluorine laser light, and the reference light is He.
-Ne laser light is effective. Then, the laser light for semiconductor exposure and the reference light are shifted from each other with respect to the central axis to be incident on different regions of a single etalon, and thereafter, interference fringes and the like generated on the sensor using condensing means such as a concave reflecting mirror. The measurement is performed using. For this reason, a single etalon coating area may be divided into two parts, and one area may be provided with a reflective coating for reference light and the other area may be provided with a reflective coating for measuring a wavelength to be measured. Reflective coating is easier to apply.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wavelength monitoring apparatus for laser light for semiconductor exposure according to the present invention will be described below by exemplifying a case where ArF excimer laser light is used as laser light for semiconductor exposure.

FIG. 1 is an optical path diagram of an example of a wavelength monitor according to the present invention, and includes one etalon 1. On the incident side of the etalon 1, two concave lenses 2a and 2b are arranged side by side, and the concave lens 2a has a standard light source H
Reference light from the e-Ne laser 10 enters through the reflecting mirrors 6 and 6 and the shutter A. The wavelength measurement light from, for example, an ArF excimer laser 20 for semiconductor exposure is incident on the other concave lens 2b via the reflecting mirror 6, the entrance aperture 5, and the shutter B. The reference light converted into the divergent light by the concave lens 2a passes through the etalon 1 and is transmitted to the sensor 4 via the concave reflecting mirror 3 and the aluminum reflecting mirror 9 on the exit side.
To reach. Then, for example, the irradiation light forms a fringe on the sensor 4, and the signal processing circuit 7 calculates the wavelength by measuring the fringe. Similarly, concave lens 2
The wavelength-measuring light converted into the divergent light in b passes through different regions of the same etalon 1 and reaches the sensor 4 via the concave reflecting mirror 3 and the aluminum reflecting mirror 9 in the same manner. And similarly, a fringe of the wavelength measurement light is formed on the sensor,
The wavelength is measured and displayed by the signal processing circuit 7. Note that, as described in the related art, first, the shutter A
Is opened and the shutter B is closed to measure the He-Ne laser light, and then the shutter B is opened and the shutter A is closed to measure the excimer laser light.

Here, of the etalon, the reference light (He-N
The reflecting mirror in the area where the e-laser light is incident is provided with a dielectric multilayer coating 1a designed to reflect the reference light (He-Ne laser light) with low loss.
The reflector in the area where the wavelength measurement light (ArF excimer laser light) is incident is provided with another dielectric multilayer coating 1b designed to reflect the wavelength measurement light with low loss.

Here, the concave reflecting mirror 3 is an example of means for condensing the light passing through the etalon 1 toward the sensor.
Alternatively, a pair of achromatic lenses or the like may be used individually. Further, the aluminum reflection mirror 9 is for bending the optical path to reduce the size of the device, and is not essential. Further, as the sensor 4, for example, a single one-dimensional array optical sensor in which CCDs are arranged in one direction can be applied. A position signal from the sensor is input to a signal processing circuit 7, and a wavelength control signal 8 obtained by processing is input to an ArF excimer laser 20, and used for angle control of, for example, a diffraction grating of a narrow band optical system therein. Can be

As described above, in the present invention, using a common single etalon, first, the measured object is stopped by a shutter or the like to measure the wavelength of the reference light, and then the reference light is turned back. The light is stopped by a shutter or the like to measure the wavelength of the wavelength measurement light. In other words, the reference light and the wavelength-measuring light are made incident on separate areas of the common single etalon 1 and the wavelength of the wavelength-measuring light is measured with reference to the wavelength of the reference light. By applying such a coating, it becomes possible to perform highly accurate measurement. In this embodiment, light is incident on the sensor 4 via the aluminum reflecting mirror 9 after the etalon 1, but it may be incident directly on the sensor 4. Further, the optical system that causes the reference light and the wavelength measurement light to enter the etalon 1 is not limited to a concave lens that emits divergent light, but may be an optical system such as a convex lens that emits convergent light, or an optical system such as ground glass that emits diffused light. It doesn't matter.

Although the description of the present embodiment has been directed to an ArF excimer laser beam as the wavelength measurement light, the same applies to a fluorine laser device.

[0015]

As described above, according to the present invention, the reference light and the wavelength-measuring light are made to enter the separate regions of the common single etalon 1, and the wavelength of the wavelength-measuring light is determined with reference to the wavelength of the reference light. Therefore, it is possible to perform highly accurate measurement by applying a coating suitable for each light to the separate areas.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration diagram of a wavelength monitor device of the present invention.

FIG. 2 shows a schematic configuration diagram of a conventional wavelength monitor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Etalon 2 Concave lens 3 Concave reflecting mirror 4 Sensor 10 He-Ne laser 20 ArF excimer laser

Claims (1)

[Claims] A single etalon in which a reflective coating for laser light for semiconductor exposure and a reflective coating for reference light are applied to separate areas, and the laser light and the reference light are mutually transmitted to the etalon. An incident optical system that shifts the central axis to enter the area where each reflective coating is applied,
A semiconductor device comprising: a condensing unit for the two light beams transmitted through the etalon; and a sensor for receiving light from the condensing unit, wherein the sensor calculates a wavelength of the laser light for semiconductor exposure. Wavelength monitor for laser light for exposure.