JPH02276234A - Laser exposure device - Google Patents

Abstract

PURPOSE:To avoid any out of focus during the exposure process of a pattern in small line width while augmenting the throughput during the exposure process of another pattern in relatively large line width by a method wherein the width dimension of a slit controlling the expansion angle of laser beams is changed corresponding to the line width of the pattern to be exposed. CONSTITUTION:The expansion angle of laser beams L outputted from a laser oscillator 1 is controlled by a slit 28 provided by a pair of slit sheets 25, 26 and simultaneously the laser beams L in the central wavelength corresponding to an oblique angle of a diffracttion grating 8 are oscillated by an output mirror 6 so as to be entered into an exposure part 9. Thus, the laser beams L expose a pattern formed on a reticle 12 to a wafer 14 provided in the exposure part 9. For example, when the minimum line width of the pattern exposed to the wafer 14 exceeds 1mum, the width dimension W of the slit 28 provided by the pair of slit sheets 25, 26 is set up to be 10mm by a driving motor 18 while when the minimum line width is 1-0.7mum, the width dimension of the slit is set up to be 7mm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a laser exposure apparatus for exposing a workpiece to a predetermined pattern using narrow band laser light.

(Prior Art) For example, in a semiconductor manufacturing process, a pattern exposure process is one of the very important processes. In recent years, I.C.
With the increase in capacity, the patterns are also becoming finer, and in response to this, exposure light sources are also becoming shorter in wavelength to improve resolution.

However, if a wavelength of 300nA or less is required, it is difficult to use a conventional high-pressure mercury lamp as a light source, and a new KrP excimer laser (wavelength of 248nm) is required.
m) has come to be used. At the wavelength of 248rv, there are few materials that can be used as glass materials for lenses.
It is difficult to achromatize exposure lenses.

On the other hand, when an excimer laser oscillates normally, its spectral width is 0.4 to 0. [ins, and if this is passed through a non-achromatic lens (monochromatic lens), defocus will occur due to chromatic aberration. Therefore, in order to prevent such defocusing, laser light is used with a narrow band. Usually, the line width of the exposed pattern is 0.5 μm
In this case, the spectral width of the laser beam is narrowed to a spectral width of about 5 nm for Q and OQ.

By the way, when narrowing the band of laser light to a spectral width below a certain level, the band cannot be reliably narrowed unless the beam divergence angle of the laser light is restricted by a regulating member in which a slit is formed. For example, in order to set the spectral width to 0.005n11, it is necessary to suppress the beam width to about 5u using a slit. however,
The average laser output was significantly reduced when the beam cross-sectional area was regulated by slits, and was about 2 watts when a slit regulating member with a width of 5 slits was used.

On the other hand, the number of exposures per hour (throughput) is approximately proportional to the laser output, so if exposure is performed using a laser beam whose divergence angle is sufficiently regulated by a slit as a light source, the throughput will be significantly limited. become. Therefore, when exposing patterns with various line widths, even when exposing patterns with relatively large line widths,
It was not possible to increase throughput, leading to a decline in productivity.

(Problem to be Solved by the Invention) In this way, when narrowing the band of laser light in order to prevent defocusing of a pattern to be exposed, a slit with a width dimension that can obtain the minimum line width without causing defocusing is used. Since the spread angle of the laser beam is regulated using a regulating member formed with Ta.

This invention was made based on the above-mentioned circumstances, and its purpose is to control the spread angle of laser light so that defocus does not occur when exposing patterns with small line widths, and to An object of the present invention is to provide a laser exposure apparatus that can increase throughput when exposing a relatively large pattern.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to solve the above problems, the present invention provides a pair of discharge electrodes disposed facing each other and spaced apart in an airtight container in which a gas laser medium is sealed. A laser oscillation unit having an optical resonator disposed with these discharge electrodes in between, and a substantially rectangular laser whose length is the direction of the discharge that is output from the laser oscillation unit and generated between the pair of discharge electrodes. A regulating means for regulating the spread angle of light; a wavelength selection means for narrowing the band of the laser light whose spread angle is regulated by the regulating means; and an exposure section that exposes a predetermined pattern on the workpiece,
The regulating means has a slit that regulates the spread angle of the laser beam output from the laser oscillation section, and the slit is arranged in a direction perpendicular to the discharge direction between the pair of discharge electrodes and the optical axis of the optical resonator. The width dimension of Mwi is freely configured.

With this configuration, when exposing a pattern with a small line width, the width of the slit in the regulating member is made smaller to reduce the spectral width of the laser beam, thereby preventing defocusing. When the line width of the pattern is relatively large, the width of the slit is increased to increase the average output of the laser beam, thereby increasing the throughput.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. The laser exposure apparatus shown in FIG. 1 includes a laser oscillation section 1 such as an excimer laser. This laser oscillation section 1 has an excitation section 2. As shown in FIG. 4, the excitation section 2 is composed of a closed container 3 containing a laser medium, and a pair of discharge electrodes 4 disposed in the closed container 3 at a distance from each other and facing each other. Therefore, when a high voltage is applied between the pair of discharge electrodes 4, laser light having an elongated rectangular cross section is emitted along the direction in which the discharge electrodes 4 are separated.

1. At both ends of the excitation section 2, regulating means 5 for regulating the spread angle of the laser beam are disposed, respectively, with a configuration to be described later. An output mirror 6 is disposed on one of the regulating means 5 and facing away from the other regulating means 5, and a resonator is formed with the output mirror 6 on the other regulating means 5 via a magnifying optical system 7 consisting of a plurality of prisms 7a. A diffraction grating 8 is arranged as a wavelength selection means for selecting laser light of a predetermined wavelength.

The laser light output from the output mirror 6 enters the exposure section 9. The exposure section 9 has a folding mirror 11 that changes the traveling direction of the laser light incident thereon. The laser beam whose course has been changed by the folding mirror 11 passes through the reticle 12 and enters the exposure lens 13, after which the pattern formed on the reticle 12 is exposed onto the wafer 14.

The regulating means 5 has a main body 15 in the shape of a hollow box, as shown in FIGS. 2 and 3. A drive shaft 16 having one end pivotally connected to one end of the main body 15 is rotatably provided within the main body 15 . A coupling 1 is attached to the other end of this drive shaft 16.
A drive motor 18 is connected via 7. A first worm gear section 19 is formed at one end of the drive shaft 16, and a second worm gear section 21 facing opposite to the first worm gear section 19 is formed at the other end.

The first worm gear section 19 has a first guide rod 22.
One end portion is engaged with the second worm gear portion 21, and the second worm gear portion 21 is engaged with the second worm gear portion 21.
One end of the guide rod 23 is engaged with the guide rod 23 . The other end of each guide rod 22, 23 is slidably inserted into a through hole 24 that is elongated along the longitudinal direction of one side of the main body 15. One end of a first slit plate 25 and a second slit plate 26 are connected to the other end of each guide rod 22, 23 protruding from the through hole 24, respectively. One end of each slit plate 25, 26 is slidably held by a pair of guide bodies 27 provided parallel to one side of the main body 15 and spaced apart from each other. Therefore, when the drive shaft 16 is rotationally driven by the drive motor 18, the -pair of slit plates 25 and 26 are driven in the directions of approaching and separating as shown by the arrows. Thereby, the width dimension W of the slit 28 formed by the opposing one end surfaces 25a and 26a of the pair of slit plates 25 and 26 can be arbitrarily set.

Note that one end of the slit 28 is closed by an arm 28a extending from the other end of the first slit plate 25, and the other end is closed by a guide body 2 provided on the upper surface of the main body 15.
7, the slit 28 maintains its elongated rectangular shape even if its width changes! j.

The regulating means 5 configured in this manner is arranged such that the elongated direction of the slit 28 is aligned with the direction of separation between the pair of discharge electrodes 4 disposed in the excitation section 2, so that discharge from the excitation section 2 is caused. Laser beam axes are now regulated.

In FIG. 1, 29 is a first control section for controlling the drive motor 18 of the regulating means 5, and 31 is a second control section for controlling the exposure section 9.

In the laser exposure apparatus configured in this way, when the laser oscillation section 1 is operated, the laser light output from the laser oscillation section 1 is transmitted to the pair of slit plates 2 of the regulating means 5.
The spread angle is regulated by the slits 28 formed by the diffraction gratings 8, and laser light having a center wavelength corresponding to the inclination angle of the diffraction grating 8 is oscillated from the output mirror 6 and enters the exposure section 9. Thereby, the laser beam exposes the pattern formed on the reticle 12 onto the wafer 14 provided in the exposure section 9.

The width dimension W of the slit 28 formed by the pair of slit plates 25 and 26 is set according to the line width of the pattern to be exposed on the wafer 14. For example, if the minimum line width of the pattern to be exposed on the wafer 14 is 11 or more, the pair of slit plates 25.
The width dimension W of the slit 28 formed by the slit 26 is set to lh+*, and if the minimum line width is 1 to 0.7-, the slit 2
The width dimension W of 8 is set to 7 dragons, and the minimum line width is set to 0.
If the amount is 5 to 0.7 μl, it is set to 5 stages.

Under such setting conditions, the following was confirmed through experiments. That is, the width dimension W of the slit 28 is 5
When set to u+, the spread angle of the laser beam is greatly regulated compared to the case of lh+s, and the spectral width is also reduced to 0.005n, so the linewidth is 0.5 to G,
A seven-line pattern can be exposed without defocusing. However, since the output of laser light is reduced to about 2 watts, the throughput cannot be increased.

When the width dimension of the slit 28 is set to 7■■, the spectral width of the laser beam becomes 0.008n, and the slit 28
Although the width dimension of 8 is larger than that of 5, the minimum line width is 0.7 to 1. Although some defocus occurs when exposing an Otrm pattern, the effect is negligible.

On the other hand, since the output of the laser light increases to 4 watts, the throughput can be doubled compared to the case of 5 stages.

When the width of the slit 28 is set to lh, the spectral width increases to 0.015 nm, but the output also increases to 8 watts. As the spectral width increases, chromatic aberration occurs in the exposure lens 13 of the exposure section 9, causing some defocusing, but this effect can be ignored if the line width is 1.0 μm. On the other hand, the output of the laser beam is 8 watts, which is four times greater than when the number of slits 28 is 5-1, so the throughput can be quadrupled.

In this way, by changing the width of the slit 28 according to the line width of the pattern to be exposed, when the line width increases, the throughput can be increased while maintaining the exposure accuracy corresponding to the line width.

FIG. 5 shows another embodiment of the present invention, and this embodiment differs from the above embodiment in the means for selecting the wavelength of the laser beam output from the laser oscillation section 1.

That is, instead of the enlarging optical system 7 and the diffraction grating 8, a pair of etalons 35 and a high reflection mirror 36 are sequentially arranged on one end side of the laser oscillation section 1. Even if there is a laser beam, the etalon 35 can select a laser beam having a predetermined center wavelength.

Further, in each of the above embodiments, the regulating means 5 is provided at both ends of the laser oscillation section 1, but even if it is provided only at either end, the spread angle of the laser beam can be limited. Furthermore, an alexandrite slab laser may be used instead of the excimer laser, and the type of laser is not limited at all.

[Effects and Effects of the Invention] As described above, in the present invention, the width dimension of the slit that regulates the spread angle of the laser beam is changed depending on the line width of the pattern to be exposed. Therefore, when exposing a pattern with a large line width, the output of the laser beam can be increased by increasing the width of the slit.
This increases throughput and improves productivity.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a laser exposure apparatus showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of the regulating means, FIG. 3 is a perspective view of the regulating means, and FIG. 4 is the same as that shown in FIG. 1. IV-I
FIG. 5, which is a sectional view of the laser discharge section taken along the V line, is a configuration diagram of a laser exposure apparatus showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Laser oscillation part, 3... Sealed container, 4... Discharge electrode, 5... Regulation means, 8... Diffraction grating (wavelength selection means) 9... Exposure part, 14...・Wafer (work) 28...Slit. Applicant's agent Patent attorney Takehiko Suzue Figure 4 Figure 4

Claims (1)

[Claims] A laser oscillation unit including a pair of discharge electrodes arranged to be spaced apart from each other in an airtight container in which a gas laser medium is sealed, and an optical resonator arranged between these discharge electrodes, and from this laser oscillation unit. A regulating means for regulating the divergence angle of a substantially rectangular laser beam whose length is the discharge direction that is output and generated between the pair of discharge electrodes, and a narrow band of the laser light whose divergence angle is regulated by the regulating means. and an exposure unit that exposes a predetermined pattern on the workpiece by the laser beam narrowed by the wavelength selection unit, and the regulating unit includes a wavelength selection unit for controlling the output from the laser oscillation unit. The slit has a slit that regulates the spread angle of the laser beam, and the slit is configured to have a width adjustable in a direction perpendicular to the discharge direction between the pair of discharge electrodes and the optical axis of the optical resonator. A laser exposure device characterized by: