JPS61166128A - Aligner - Google Patents

Abstract

PURPOSE:To improve the precision of manual alignment, by a method wherein a photoirradiating part projects linear polarized light with a plurality of different wavelengths while an imagery optical system is constituted so that the linear polarizing direction may be rectangularly changed to the light with respective different wavelengths. CONSTITUTION:When a lamp 18 of a photo irradiating part 14 lights in case of manual alignment, linear polarized light with two different wavelengths is projected through a filter 19 and a polarized light filter 20 to irradiate a photomask 1 through a halfmirror 21 partly reflected while the remaining light transmitting the photomask 1 reaches wafer 2 through an imagery optical system 5 to be reflected on the wafer 2 reversing to the system 5 again to join with the reflected light on the photomask 1. At this time, the polarizing direction of the reflected light on the wafer 2 is rectangularly changed. Resultantly the polarized light with rectangularly changeable polarizing direction may be rectangularly changed through an objective lens 31 and lambda/2 plate 32 to reach an observation part 7 being reflected on another halfmirror 30, a roof prism 13 making visual alignment observation feasible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an aligner, and particularly to an aligner that improves alignment accuracy by preventing alignment defects caused by light interference.

[Background technology]

The photolithography technology required for the manufacture of semiconductor devices requires an aligner to transfer the patterns of a reticle, photomask, etc. onto a semiconductor wafer, etc. Position (
After alignment), the photomask pattern is transferred onto the wafer.

In order to perform this alignment with high precision, the most effective method is to match the alignment mark on the photomask with the Ueno mark using an optical system.
It is difficult to clearly distinguish between the light reflected by the photomask and the light reflected by the wafer, and the alignment work is complicated and difficult.

For this reason, aligners that use polarized light for alignment have been proposed. In other words, this aligner is! M-line polarized light is projected onto a photomask, part of the polarized light is reflected from the photomask, and the other part of the polarized light is projected onto the wafer through the photomask and an imaging optical system that transfers this photomask pattern onto the wafer. The reflected light is then retraced through the imaging optical system and photomask.
The light is combined with the light reflected from the photomask and sent to the detection system. Then, by utilizing the fact that the phase of the directly spun polarized light that has traveled back and forth within the aforementioned imaging optical system is changed by λ/2, that is, the ′ direction of the linearly polarized light is changed to the right angle direction, the reflection of the photomask is The light and the reflected light from the wafer are separated by a polarizing beam splitter. Then, only the alignment mark on the photomask is detected from the light reflected from the photomask, and each alignment mark on the photomask and wafer is simultaneously detected from the light reflected from the wafer and passed through the photomask. The photomask and wafer can be easily aligned from the signal.

By the way, in order to perform manual alignment in this type of aligner, a light irradiation section is provided that irradiates the wafer through a photomask or an imaging optical system, but the light from the light irradiation section that is reflected from the photomask or wafer is used to illuminate the photomask. An observation section is provided to visually observe each alignment mark on the wafer. Also in this case, linearly polarized light is used for the light from the light irradiation section.

However, in conventional aligners, this light irradiation part uses linearly polarized light (monochromatic light) with the same wavelength as that for alignment described above (for example, aligners such as Canon's MPA-500FA). . Therefore, the light reflected on the wafer surface is interfered with by the thin film (for example, Sin, film) on the wafer surface, causing interference fringes, making visual observation in the observation section difficult, and reducing the accuracy of manual alignment. The inventors have discovered that a problem arises in that the efficiency of manual alignment work is lowered.

[Purpose of the invention]

An object of the present invention is to provide an aligner that suppresses light interference and facilitates visual observation, thereby improving the accuracy of alignment, particularly manual alignment, and improving the efficiency of alignment work. It is in.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the light irradiation section is configured to emit linearly polarized light of a plurality of different wavelengths, and the imaging optical system changes the direction of the linearly polarized light to a direction perpendicular to each of these wavelengths. By configuring it so that it can be obtained, visual observation in the observation section can be easily performed by suppressing interference caused by light emitted from the light irradiation section while matching with a system that performs alignment using a polarizing beam splitter (auto alignment). This makes it possible to improve alignment precision especially during manual alignment and to improve alignment work efficiency.

〔Example〕

FIG. 1 is an overall configuration diagram illustrating an aligner according to an embodiment of the present invention. The aligner 4 includes a photomask 1 as a transfer pattern member, and a wafer mask 1 as a transfer target member placed on an XY table 3. 2 are set respectively.

The aligner 4 has an imaging optical system 5 disposed between the photomask 1 and the wafer 2 for transferring the pattern of the photomask 1 onto the wafer 2 (projection exposure), and a laser scanning section above the photomask 1. 6. Observation section 7. It has left and right pattern (alignment mark) detection sections 8A and 8B.

The laser scanning unit 6 scans a specific wavelength, for example, λ-63.
A laser light source 9 that emits a linearly polarized laser beam of 28A, and a polygon mirror 10 that scans this laser beam.
．． It is equipped with an F-θ lens 11 for scanning speed correction. The observation unit 7 also includes a prism group 1 consisting of a plurality of prisms.
2 and an eyepiece 13, and a roof prism 13 is provided at the most extreme position of the prism group 12 for optically connecting to the left and right pattern detection sections 8A and 8B.

The left and right pattern detecting sections 8A and 8B serve as a source for manual alignment, as will be explained below with respect to the left pattern detecting section 8A (the right pattern detecting section 8B is given the same reference numeral). A light irradiation unit 14, an MD (mask direct) detection unit 15 that detects only the alignment marks on the photomask 1, and a photomask 1 and a sea urchin.
MW that integrally detects each alignment mark in C2
(Mask/wafer) It is composed of a detection section 16, an objective lens 31, and a λ/2 plate 32. The light irradiation section 14
is a lamp 18 that emits white light, and 2 from this white light.
Light of two different wavelengths (one of which has the same wavelength as the laser beam, in this example, λ-6328A).

λ-5145A), a polarizing filter 20 that linearly polarizes these lights, and a no-f mirror 21 provided on the main optical path. MD
The detection unit 15 includes a photodetector 22. as a photoelectric element.
Focusing lens 23. It includes a polarizing beam splitter 24, a half mirror 25, and a mirror 26, and in particular, the polarizing beam splitter 24 is installed so that it can reflect only the polarized light reflected by the photomask 1, as will be described later.

The MW detection section 16 also includes a photodetector 27. Focusing lens 28. Polarizing beam splitter 29 and half mirror
30, and this polarizing beam splitter 29 is installed so as to be able to reflect only the polarized light reflected by Ueno 1, as will be described later.

On the other hand, the λ/2 plate 32 is configured to be able to change the polarization direction of the linearly polarized light of the two different wavelengths in the respective orthogonal directions, and is located on the optical path of the reflected light at least at the MD detection section 15.
It is installed on the front side (lower side in the figure).

Further, the imaging optical system 5 similarly allows the polarization directions of the two linearly polarized lights of different wavelengths to be changed in the perpendicular direction by transmitting them back and forth.

Note that the technique in which the imaging optical system 5 and the λ/2 plate 32 change the respective polarization directions of two different wavelengths of linearly polarized light to a perpendicular direction is already known, so a detailed explanation will be omitted. .

According to the above configuration, the linearly polarized laser beam emitted from the laser light source 9 is transmitted to the polygon mirror 10 and the F-θ
It is scanned by a lens 11 and divided by a roof prism 13 into left and right pattern detection sections 8A and 8B.

If the laser beam guided to the left pattern detection section 8A is, for example, P polarized light, as schematically shown in FIG. It becomes S1 polarized light. After passing through the objective lens 31, the light is projected onto the photomask 1, and a portion of it is reflected as S-polarized light in the same polarization direction as the S-polarized light.

The light that has passed through the photomask 1 passes through the imaging optical system 5 and is projected onto the wafer 2, where it is reflected, and then travels backward through the imaging optical system 5 again. together with the reflected light. At this time, by passing through the imaging optical system 5 back and forth, the polarization direction of the 81-polarized light is changed to a right angle, and it becomes P-polarized light. Then, the S and P polarizations, whose polarization directions are perpendicular to each other, pass through the objective lens 31, and then pass through the λ/2 plate 32 again, where the polarization directions are changed to perpendicular directions, respectively, and P2→S3, S, → Changed to P3 polarized light respectively.

A part of these originals is reflected by the half mirror 25 and the mirror 26, and is sent to the polarizing beam splitter 24 of the MD detection unit 15 as polarized light in the S direction, here P3.
Only the polarized light is reflected and detected by the photodetector 22. That is, only the light reflected by the photomask 1 is detected, and only the alignment mark on the photomask 1 can be detected from this.

On the other hand, the light that has passed through the half mirror 5 passes through the half mirror 30 and then reaches the polarizing beam splitter 29 of the MW detection unit 16, where the polarizing beam splitter 29 is directed in a direction 90° different from the polarizing beam splitter 24. Since the beam splitter is installed in the beam splitter, only the polarized light in the S direction, in this case 83 polarized light, is reflected and detected by the photodetector 27. That is, only the light reflected by the wafer 2 is detected, and each alignment mark on the wafer 2 and the photomask 1 is detected simultaneously. Therefore, automatic alignment can be realized by the interaction of these rain detection units 15 and 16.

On the other hand, during manual alignment, when the lamp 18 of the light irradiation section 14 is turned on, linearly polarized light of two different wavelengths is emitted by the filter 19 and the polarizing filter 20, and the half mirror 21 irradiates the odomask 1. A part of this original is reflected as is (without changing the polarization direction) by the photomask 1, and the other part passes through the photomask 1, passes through the imaging element system 5, reaches the wafer 2, and is reflected here. After that, the imaging optical system 5 is moved backwards again, and the photomask 1 is
After passing through the photomask 10, the light is combined with the reflected light from the photomask 10. At this time, it goes without saying that the polarization direction of the light reflected from the wafer 2 is changed at right angles as described above.

Therefore, the polarized lights whose polarization directions are perpendicular to each other pass through the objective lens 3], further pass through the λ/2 plate 32, have their polarization directions changed to the perpendicular direction, and are reflected by the half mirror 30 and the roof prism 13 for observation. At step 7, the alignment mark can be visually observed and manual alignment can be achieved.

At this time, since the light from the light irradiation unit 14 uses light of two different wavelengths, even if there is a thin film such as a 5in2 film on the surface of the wafer 2, there is no interference like when using one monochromatic light. The generation of fringes can be suppressed, and therefore, observation problems caused by interference can be prevented. In addition, the light of two different wavelengths is linearly polarized, and the imaging optical system 5 and λ/2
Since the plate 32 is configured to change the polarization direction perpendicularly to each of these wavelengths, the light of each wavelength can maintain its linearly polarized state until it reaches the observation section 7, thereby reducing visual observation. It does not occur.

Therefore, observation during manual alignment can be made better, alignment precision can be improved, and alignment work can be made easier.

Further, the present aligner can be constructed by changing the configuration of the light irradiation section, the imaging optical system, and the λ/2 plate of the conventionally configured aligner, and the configuration and manufacturing can be simplified.

〔effect〕

(1) While the photomask is irradiated with linearly polarized light of two different wavelengths from the light irradiation unit for manual alignment, the imaging optical system through which a part of the light is reflected by Ueno The structure is configured to change the polarization direction perpendicular to each of the three different wavelengths of light, making it possible to observe the light reflected by a photomask or wafer in its linearly polarized state. It is possible to prevent problems and improve alignment accuracy by improving observation using linearly polarized light, and to improve alignment work efficiency.

(2) The aligner of the present invention can be configured by changing part of the configuration of the conventional aligner (light irradiation unit, imaging optical system, λ/2 plate, etc.), and the aligner can be easily configured and manufactured.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, linearly polarized light having three or more different wavelengths may be used, and the imaging optical system may be configured to accommodate this. Furthermore, by using laser beams with two or more different wavelengths, it is possible to suppress problems caused by interference during auto-alignment. Note that the λ/2 plate can be omitted by changing the configurations of the MD detection section and the PMW detection section.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to photomasks and aligners for alignment between wafers, which are the background fields of application of the invention, but the invention is not limited thereto. It can be applied as an aligner for original plates and other pattern transfers.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the misexploded aligner, and FIG. 2 is a schematic configuration diagram of the main parts for explaining its operation. DESCRIPTION OF SYMBOLS 1... Photomask, 2... Wafer, 4... Aligner, 5... Imaging optical system, 6... Laser scanning part, 7... Observation part, 8A, 8B... Pattern Detection unit, 9... Laser light source, 10... Polygon mirror, 1
3... Roof prism, 14... Original irradiation part, 15...
・MD detection unit, 18...Lamp, 19...Filter, 20...Polarizing filter, 22...Photodetector, 26...Buddha splitter, 27...Photodetector, 31...Objective lens , 32...λ/2 provisional. X (-1)

Claims (1)

[Claims] 1. Linearly polarized light is projected onto a transfer target member through a transfer pattern member or an imaging optical system, and the reflected light from each member is separated by a polarizing beam splitter and individually detected. The aligner aligns a transferred pattern member and a transferred member, and includes a light irradiation unit that irradiates light onto the transferred member through the transferred pattern member or an imaging optical system, and a light irradiation unit that irradiates light reflected from each of the members. an observation section that visually observes the alignment marks provided on each member using light from the light source, and the light irradiation section is configured to be able to emit linearly polarized light of a plurality of different wavelengths;
An aligner characterized in that the imaging optical system is configured to be able to change the direction of linearly polarized light of the plurality of lights of different wavelengths to a direction perpendicular to each other. 2. The aligner according to claim 1, wherein a λ/2 plate is installed on the reflected optical path of each member to change the direction of linearly polarized light of each different wavelength to a right angle direction.