JPS63110686A - Excimer laser of multimode narrow-band oscillation - Google Patents

Abstract

PURPOSE:To obtain a laser beam having a highly stable wave length and a high output of power by measuring the wave length distribution at a laser beam section being oscillated, thereby controlling with a feedback system an alignment of etalons so that the wave length distribution does not exceed an allowable limit. CONSTITUTION:This device is composed of an output wave length detecting means 2 including a beam splitter 210 which branches and samples a part of outputs of a normal multimode narrow-band oscillation excimer laser by using etalons 1; besides it, a controlling part 3 which performs an alignment of the etalons on the basis of detected values obtained by the above output wave length detecting means 2. A part of laser beams being oscillated is branched by the beam splitter 210 and a beam of a part of a laser beam section is sampled with an optical fiber 220 and the like and then, is introduced in a wave length detector 2 made of a monitor etalon or a spectroscope 240 and others. And then, the alignment of the etalons is controlled so that a wave length detected by the wave length detector 2 may be within the prescribed limit. Thus, such a measure makes an effective diameter of the etalons larger and makes it possible to obtain an excimer laser where a spectral line width is narrow and wave lengths are highly stable and further, the output of power is high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multimode narrowband oscillation excimer laser, and particularly to an etalon control method.

[Prior art and its problems] Excimer lasers are capable of high-efficiency, high-output oscillation, so in recent years, wide-band <fff1 oscillations have been promoted, and their non-coherent properties have led to their use in photolithography, etc. is attracting attention.

For example, an injection lock type excimer laser uses an ondilator, which is a stable resonator configured to supply a laser signal with beam characteristics close to the diffraction limit, as shown in Figure 9, which shows an example of a VT manufactured by Lambda Physics. section 11 and an amplifier section 14 which is an unstable resonator configured to amplify the laser signal injected via mirrors 12 and 13.

In this excimer laser, the ondilator section 11 includes an N-discharge electrode 15, an aperture 16° 17, and an etalon 1 inside.
8, an exit mirror 19 and a rear mirror 20, the wavelength is controlled by an etalon 18, and an average t16 is provided.
, 17 to narrow down the beam to emit a laser beam having a narrow spectral linewidth and coherent beam characteristics.

The amplifier section 14 also includes a discharge electrode 21 and a mirror 22.2.
3, and is configured to force the laser light injected from the ondilator section 11 to oscillate in a cavity mode to increase its power.

This type of injection lock type excimer laser can not only emit laser light with a high output and narrow spectral linewidth, but also has an aperture, so the effective diameter of the etalon can be small, allowing for high-precision equilibrium. Although it has the advantage of not requiring any degree adjustment, it is a single mode (coherent light), so if it is used as a reduced projection light source, speckles will occur and high resolution cannot be obtained. There was a problem.

In addition, in the laser developed by AT&T, two (one!) etalons 33 are disposed between the laser chamber 31 and the output mirror 32 as shown in FIG. 10, so that the spectral line width is narrow and This enables laser oscillation with a certain number of Maki modes.

(Here, it is a 34-beam mirror.) However, even in this Hllff, when exposure is performed using a normal illumination optical system, speckles still occur because the number of transverse modes is insufficient. For this reason, it is necessary to use a scan mirror type as the illumination optical system. In this method, since the beam diameter is approximately 51111 mm, highly accurate balance adjustment is not necessary, but it complicates the structure and control of the exposure apparatus.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a multimode narrowband oscillation excimer laser suitable for reduction projection, which enables laser oscillation with high output and high wavelength stability.

[Means for solving problems]

Therefore, in the present invention, in a multimode narrow band oscillation excimer laser using an etalon, the wavelength distribution in the cross section of the oscillated laser beam is measured, and the etalon air gap, angle, Adjustment of gas pressure, etc., that is, alignment, is controlled by feedback.

[Effect]

That is, a part of the oscillated laser light is split by a beam splitter, and part of the cross-sectional light of the laser light is sampled by an optical fiber or the like and guided to a wavelength detector such as a monitor etalon or a spectrometer.

Then, the alignment of the etalon is controlled so that the wavelength detected by this wavelength detector falls within a predetermined range.

Therefore, the effective diameter of the etalon can be increased, making it possible to provide a high-output 1 ximer laser with a narrow spectral linewidth and excellent wavelength stability.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 1(a) and 1(b) are a diagram showing a multi-mode narrow band oscillation excimer laser device according to the present Sanskrit example, and a block diagram of a control section, respectively.

This 1ffff consists of an output wavelength detection means 2 including a beam spiriter 210 that splits and samples a part of the output of a normal multi-mode narrow band oscillation excimer laser using an etalon 1, and a detection of this output wavelength detection means 2. The device is characterized in that it is equipped with a control section 3 that performs alignment of the etalon 1 based on the value, and other parts have a normal structure.

Here, 4 is a laser chamber, 5 and 6 are an output mirror and a rear mirror, respectively, and laser light is output from the output mirror.

The control section 3 includes a signal processing system 301 that processes the output of the output wavelength detection means 2, a CPU 302, an etalon alignment control section 303, and a beam sample control section 304.
The CPU calculates the alignment deviation amount Pf& based on the detection value of the output wavelength detection means 2 while changing the sampling position by a beam sample control unit so that the detection value falls within a predetermined range. An actuator (not shown) is controlled to adjust the etalon air gap etc. w4 and feedback control of the etalon alignment is performed.

The output wavelength detection means 2 includes a beam spiriter 210, an optical fiber 220, and a pulse motor 230 (FIGS. 2(a) and (b) spectrometer W240) that rotates the optical fiber. It is configured to separate one portion, guide it to a spectrometer 240 via an optical fiber 220, and detect the wavelength.

Then, the optical fiber is moved by the beam sample control section 304 to control the wavelength detection position in the laser beam cross section, so that control is performed at a plurality of positions.

A flowchart of the operation in this control section is shown in FIG.

First, sample one point in the cross section of the laser beam (
action 200).

Then, the wavelength at that point is measured by the spectrometer 23 (operation 2o1).

Furthermore, the air gap of the etalon is calculated from this measured wavelength (vJ work 202).

Subsequently, the optical fiber is rotated to perform these operations 200 to 2.
Repeat step 02 three or more times to perform calculations on three or more points.

Based on these calculated values, the inclination of the etalon is calculated in CPLJ (by vJ 203).

Then, calculate the adjustment value of the etalon air gap (v
J. 204).

Send the value calculated in this way to the actuator,
Fine adjustment is performed (operation 205).

By feedback-controlling the etalon alignment in this way, it is possible to increase the effective diameter of the etalon and realize laser oscillation with narrow band oscillation and high wavelength stability.

In the above embodiment, the beam sampling method was to rotate the optical fiber by a pulse motor and sample each point on the laser beam cross section.
The present invention is not limited to this, and other sampling methods such as those shown below may be used.

Other sampling methods include changing the angle of the beam spiriter 210' using a pulse motor, as shown in FIG. There is a method that sequentially samples each point using .250. Here, the tip of the optical fiber 220' has three t! points as shown in FIGS. 6(a) and 6(b). l3Il! ! It is supported by a fiber holder 260 having a hole, and as shown in FIG. 6(C), a rotatable disk-shaped shutter 250 having one opening is further disposed on the front surface of the fiber holder. There is.

In addition, in the embodiment, as a method of etalon alignment control, a method was used in which the wavelengths at three points were detected and then the deviations of seven alignments of the etalon were calculated, but the method is not limited to this method. As shown in (a) and (b), the laser beam is sampled on a line segment between the rliFA regular part of the first gear gap 110 of the etalon where the actuator (PZT) is installed and the center of the etalon, and the laser beam is sampled to a predetermined wavelength. A method may be used in which the fine adjustment section is operated at each point.

A flowchart of this method is shown in FIG. 8 for reference.

[Effects between lights] As explained above, according to Komei, in a multi-mode narrow band oscillation excimer laser using an etalon, the wavelength distribution in the cross section of the n-oscillated laser beam is measured,
Since the etalon alignment is feedback-controlled so that the wavelength distribution is within an allowable range, it is possible to obtain a high-output laser beam with high wavelength stability.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are a diagram showing a multimode narrowband oscillation excimer laser 811F and a block diagram of a control unit, respectively, according to an embodiment of the present invention, and FIGS. 2(a) and (b) are a block diagram of the same W A side view and a plan view showing the structure of the rotating section of the optical fiber in the device, FIG. 3 is a flowchart of the operation of the control section in the device, and FIGS. 4 and 5 respectively show other sampling methods. Figure 6 (aHb
) and (C) are diagrams showing the structure of the tip of the optical fiber in the sampling method shown in FIG. 5, and FIGS. 60. Method and its Control 60 FIGS. 9 and 10, which are flowcharts of vJ production, are explanatory diagrams of a conventional excimer laser F device. 11...Ondilator section, 12.13...Mirror,
14... Amplifier section, 15... Discharge electrode, 16.17
...Aperture, 18...Etalon, 19.20.
...Mirror, 21...Discharge electrode, 22.23...Mirror, 31...Laser chamber, 32...Emission mirror, 33...Etalon, 34...Rear mirror, 1
... Etalon, 2... Output wavelength detection means, 3...
Control unit, 4... Laser chamber, 110... Air gap, 210... Beam spiriter, 220...
・Optical fiber, 230...Pulse motor, 240...
・Spectrometer, 301...Signal processing system, 302...CP
U, 303... etalon alignment control unit, 304
...Beam sample control unit. Figure 1 (Q) Figure 1 (b) Figure 2 (G) Figure 2 (b) Figure 3<IIA Figure 6 (Q) Figure 6 (b) Figure 6 (C) Figure 7 (b) Figure 8

Claims (4)

[Claims] (1) In a multimode narrowband oscillation excimer laser using an etalon, an output wavelength detection means that measures the wavelength distribution in the cross section of the laser light output, and feedback on the etalon alignment so that this wavelength distribution is within the tolerance range. 1. A multimode narrowband oscillation excimer laser, comprising: control means for controlling the multimode narrowband oscillation excimer laser. (2) The output wavelength detection means includes a beam splitter, an optical fiber, a transport means configured such that the end face of the optical fiber can be moved to a plurality of points in the cross section of the laser beam, and a wavelength detector. A multi-mode narrowband oscillation excimer laser according to claim (1). (3) A patent claim characterized in that the output wavelength detection means includes a beam splitter, a plurality of optical fibers, a shutter means for selectively and sequentially shielding the end faces of the optical fibers, and a wavelength detector. A multimode narrowband oscillation excimer laser according to item (1). (4) The output detection means includes: a beam splitter; a transport means for transporting the beam splitter; an optical fiber; and a wavelength detector. multimode narrowband oscillation excimer laser.