JPH01181520A - Aligner - Google Patents

Abstract

PURPOSE:To obtain a resolution exceeding a specified level and to reduce an error in the dimension of resolution line width by detecting the wave length of light from light source and by controlling the projection magnification rate of projection optical system and the position relationship of water for the mask pattern image-forming position of mask pattern. CONSTITUTION:A wave length detection means 5 measures oscillation wave length of light flux from an eczema laser 1 which incided being reflected by a half mirror 2 for example with one pulse or a plurality of pulses. A control means 13 allows the projection magnification rate of a projection optic system 9 to be within a certain allowable range and focusing position to be within an allowable range of focus depth at a measured wave length being based on the measured result from the wave length detection means 5 and a predetermined sequence. Then, control signal is transmitted to a field lens drive part 8 for projection magnification rate and to a Z-stage drive part 11 for focus position, respectively. It allows a fixed amount of resolution to be constantly retained and a projection pattern image with less error of image dimensions to be obtained.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an exposure apparatus, and in particular, in the production of integrated circuits such as ICs and LSIs, a pattern on a mask or reticle surface is projected onto a wafer surface by a projection optical system. The present invention relates to an exposure apparatus suitable for exposure.

(Prior Art) Generally, in an exposure apparatus for manufacturing integrated circuits such as ICs and LSIs, a mask pattern depicting an electronic circuit pattern is illuminated by an illumination system, and the mask pattern is projected onto a wafer surface by a projection optical system. Projected and exposed. In such photolithography technology, from the viewpoint of resolution on the wafer surface, it is advantageous to use wavelengths in the deep ultraviolet region, where the diffraction effect is small.

However, the optical glass constituting the projection optical system generally has low transmittance in the deep ultraviolet region, and there are currently very few optical glasses that can be used.

For example, there are only two types of optical glass, quartz and fluorite, that transmit relatively well the far-ultraviolet wavelength region of about 230 to 330 nm.

Among these, fluorite has problems with workability and homogeneity, so quartz is currently the main material used as optical glass in the far ultraviolet region.

If the projection optical system is configured with a single glass made of quartz, it is not possible to correct chromatic aberration well, so if the emission spectrum width of the light source is widened, the resolution will be poor even though light in the far ultraviolet region is used. It won't improve that much. For this reason, the exposure apparatus requires a light source that emits a light beam with a narrow emission spectrum width in the far ultraviolet region.

An excimer laser is a light source that has high output and emits a light beam in the far ultraviolet region with a narrow emission spectrum width.

The emission spectrum width of this excimer laser is usually 0.5
Since it is on the order of nm, if it is used as it is as a light source for an exposure device, it will be affected by chromatic aberration. For this reason, when using an excimer laser as a light source for an exposure device, it is necessary to narrow the spectral width.

Narrowing the band of an excimer laser is usually achieved by combining a wavelength selection element within a laser resonator and forcibly oscillating only a specific wavelength within the natural emission spectrum width of the excimer laser.

When such an excimer laser with a narrow wavelength band is used as a light source for exposure, if mechanical vibrations, thermal expansion and contraction, etc. are applied to the wavelength selection element during exposure, the oscillation wavelength shifts and the focus position and projection The magnification shifts, the resolution decreases, and resolution dimensional errors may occur.

(Problems to be Solved by the Invention) The present invention provides that when an excimer laser with a narrow wavelength band is used as a light source for an exposure device, even if the oscillation wavelength of the excimer laser changes during exposure, the mask pattern remains unchanged. The purpose of the present invention is to provide an exposure apparatus that can satisfactorily correct changes in the focus state and projection magnification in each shot on eight surfaces, and can always obtain a projection pattern image that has a resolution above a certain level and has little resolution line width dimensional error. shall be.

(Means for solving the problem) In an exposure apparatus that projects and exposes a mask pattern illuminated by an illumination system onto eight sea urchin faces using a projection optical system, wavelength detection detects the wavelength of light from a light source of the illumination system. and control means for controlling at least one of the projection magnification of the projection optical system and the relative positional relationship of the wafer with respect to the imaging position of the mask pattern using the output signal from the wavelength detection means. The control means performs the control every time the mask pattern is projected onto the eight faces of the sea urchin.

(Embodiment) FIG. 1 is a schematic diagram of an embodiment of the present invention. In this embodiment, the wavelength detection means detects the oscillation wavelength of the light beam from the light source, and the control means controls the relative positional relationship between the mask pattern in the exposure device and the surface of the sea urchin according to the value of the oscillation wavelength at that time. Indicates when to do so.

In the figure, 1 is a light source such as a narrow-band excimer laser, 2
A half mirror divides the light beam from the excimer laser 1 into two directions: the shutter 3 and the wavelength detection means 5. 4
is a total reflection mirror that causes the light beam that has passed through the shutter 3 to be incident on the illumination optical system 7. The illumination optical system 7 magnifies the incident light beam and uniformly illuminates the mask (circuit) pattern on the 15 reticles. 14 is a field lens,
8 is a field lens driving section, and 9 is a projection optical system. The projection optical system 9 projects the mask pattern onto 16 eight sea urchin faces arranged on a stage 14 at a predetermined reduction magnification. Reference numeral 10 is a Z stage, and 12 is an XY stage.These stages drive and control the wafer in a predetermined direction. 11 is a two-stage drive section.

In this embodiment, the shutter 3, total reflection mirror 4, and illumination optical system 7 constitute one element of the illumination system.

The wavelength detection means 5 measures the oscillation wavelength of the light beam from the excimer laser 1 reflected by the half mirror 2 and incident thereon, for example, with one pulse or a plurality of pulses, and transmits the measurement results from a CPU (sequence controller) or the like. The data is transferred to the control means 13 consisting of: The control means 13 is the wavelength detection means 5
The projection magnification is adjusted so that the projection magnification of the projection optical system 9 falls within a certain tolerance range and the focus position falls within the tolerance range of the depth of focus at the measurement wavelength based on the measurement results from and a predetermined sequence. Control signals are transferred to the field lens drive unit 8 regarding the focus position, and to the two-stage drive unit 11 regarding the focus position. The field lens driving section 8 and the Z stage driving section 11 drive the field lens 14 and the Z stage, respectively, based on control signals from the control means 13.

As a result, in this embodiment, even if the oscillation wavelength of the light beam from the excimer laser 1 changes, the relative positional relationship between the mask pattern and the wafer is always kept within a preset tolerance range.

Furthermore, in this type of exposure apparatus, it is known that environmental changes such as the temperature, air pressure, and humidity around the projection optical system 9 are factors that cause the projection magnification and focus position to fluctuate as described above. Therefore, at least one of these parameters is monitored simultaneously with the wavelength detection, and in addition to the wavelength information, the field lens drive unit 8 and the Z stage are Controls the drive unit 11.

In addition, in this embodiment, the field lens 14 and the Z stage 1
0 is used to adjust the magnification and position the wafer 16 to the focus position of the projection optical system 9. In addition, the ports SP4, 687, 322.4, 690, 528, and
, 699, 505, etc. are applicable. No matter what method is used, by using the output signal from the wavelength detection device of the present invention and controlling each exposure position (shot), the mask pattern can be accurately detected at each exposure position at all times. It can be transferred to

In this embodiment, the position of the wafer 16 in the optical axis direction of the projection optical system 9 is monitored by an air microsensor or an optical sensor (not shown). These wafers 1
The position sensor 6 is described in the above USP, and detailed explanation is omitted here. This is performed based on the wafer position signal from the position sensor and the output signal from the wavelength detection means 5 described above.

FIG. 2 shows an exposure sequence using this means.

First, the XY stage is driven to the exposure position (first shot on the wafer 16) at S-t.

Then, in S-2, the oscillation wavelength of the excimer laser immediately before exposure is measured, and in S-3, it is checked whether this measured wavelength is within a preset tolerance range, and if it is within the tolerance range, S-4 Perform exposure with .

In addition, if it is not within the allowable range, the projection magnification and focus during exposure are corrected by the control means 13 described above according to the amount of variation in the wavelength measured in S-6, and from S-2 to S-3
Repeat the action. When the exposure is completed in S-4, the XY stage is driven to the next exposure position (second shot on the wafer 16) in S-5, and the steps S-1 to S-
Returns the actions up to 6 in green. Therefore, just before re-exposure, the control means 1
3, the projection magnification and focus position are always adjusted with high precision.

FIGS. 3 and 4 are schematic diagrams of a portion of a wavelength detection device that detects the oscillation wavelength from a laser.

FIG. 3 shows that by projecting the fringes formed by the etalon 33 of the laser beam 23 that has passed through the concave lens 31 and the aperture 32 onto the surface of the CCD 34 serving as a detector, and measuring the interval between the fringes by the signal detection unit 36, The amount of deviation from a certain oscillation wavelength is detected.

FIG. 4 shows that the light flux that has passed through the aperture 41 and the magnifying optical system 42 is incident on the grating 43, and the grating 43
A normal spectroscopic system is constructed, and the convex lens 44 focuses the light onto the surface of the CCD 45 serving as a detector.The wavelength of the laser beam 23 is detected by determining the position of the bright spot at that time using the signal detection section 47.

Further, wavelength detection devices are required to have very strict accuracy. For this reason, for example, the holding precision of the optical elements and detection elements constituting the wavelength detection device is also severe. For example, in the wavelength detection device shown in Fig. 3, the parallelism distance between the two elements 33 is important, and in the wavelength detection device shown in Fig. 4, which uses a grating, the holding angle accuracy of the grating is important. It's coming.

Furthermore, the oscillation wavelength from a laser is directly influenced by the medium in the optical path. Therefore, if the wavelength detection unit is placed in a normal environment, environmental changes such as changes in temperature or atmospheric pressure may cause the optical element, detection element, and their holder to expand or contract, or the density of the medium in the optical path may change. This change causes errors in measurements for wavelength stabilization and changes the laser oscillation wavelength. Therefore, the wavelength detection device can detect temperature, atmospheric pressure,
It is preferable to use the device under conditions where the surrounding environment such as humidity is maintained constant.

In this embodiment, the wavelength detection means 5 may be placed anywhere, such as inside the illumination optical system 7 or a part of the shutter 3, as long as the detected wavelength of the light beam from the excimer laser 1 can be measured. .

Further, in this embodiment, any light source other than the excimer laser can be used as long as it emits a narrow band oscillation wavelength.

(Effects of the Invention) According to the present invention, even if the oscillation wavelength of a light source such as an excimer laser used for exposure equipment changes during exposure, the projection magnification, focus state, etc. on the eight faces of the mask pattern can be set in advance. Because it can be kept within the allowable range,
It is possible to achieve an exposure apparatus that always has a constant resolution and can obtain a projected pattern image with little resolution dimensional error.

In particular, if the relative positional relationship between the mask pattern and the wafer is adjusted for each exposure, an exposure apparatus that can always obtain a stable projected pattern image can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a flowchart of an exposure sequence using this embodiment, and FIGS. 3 and 4 are schematic diagrams of a wavelength detection device. In the figure, 1 is a light source, 2 is a half mirror, 13 is a shutter,
4 is a total reflection mirror, 5 is a wavelength detection means, 6 is a shutter drive section, 7 is an illumination optical system, 8 is a field lens drive section, 9 is a projection optical system, 14 is a stage, 13 is a control means,
15 is a reticle, and 16 is a wafer. Patent applicant Canon Co., Ltd. Figure 2 Figure 3

Claims (1)

[Claims] (1) In an exposure apparatus that projects and exposes a mask pattern illuminated by an illumination system onto a wafer surface using a projection optical system, a wavelength detection means for detecting the wavelength of light from a light source of the illumination system; control means for controlling at least one of the projection magnification of the projection optical system and the relative positional relationship of the wafer with respect to the imaging position of the mask pattern using the output signal of the control means; An exposure apparatus characterized in that the above-mentioned mask pattern is projected onto a wafer surface for each projection exposure.