JPH0781824B2 - Alignment device - Google Patents

Description

The present invention relates to an alignment apparatus used in, for example, a reduction projection exposure apparatus, and in particular, an improvement of an alignment apparatus having at least two sets of alignment optical systems. It is about.

[Prior Art] A reduction projection type exposure apparatus requires highly accurate alignment or alignment with respect to a mask and a wafer, for example, alignment with respect to each of X, Y, and θ axes. It

However, a single alignment light source is used in the entire alignment apparatus, and the illumination light output from this light source is divided and used for the above-described three-direction alignment.

[Problems to be Solved by the Invention] However, in the conventional alignment apparatus as described above, since the illumination light of a single light source is divided and guided to a plurality of alignment optical systems, the light amount of the illumination light is greatly attenuated. However, in some cases, there is an inconvenience that a sufficient amount of light necessary for alignment cannot be obtained.

The present invention has been made in view of the above points, and it is possible to improve the alignment accuracy in a plurality of alignment optical systems by effectively utilizing the illumination light for alignment output from a single light source. It is an object of the present invention to provide an alignment device that can be used.

[Means for Solving the Problems] The present invention provides a polarization direction rotating means for rotating the polarization direction of the polarized illumination light for alignment output from a single light source, and an illumination light transmitted through the polarization rotating means. The above problem is solved by providing an optical path switching means for sending to any alignment optical system depending on the polarization direction.

[Operation] In the present invention, the polarization direction of the illumination light output from the single light source is rotated by the polarization rotating means.

Then, this illumination light is sent to the alignment optical system corresponding to the polarization direction by the optical path switching means.

That is, the illumination light is incident on one of the alignment optical systems without being divided according to the polarization direction.

EXAMPLES Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention. In this figure, a laser oscillator 10 as a light source outputs linearly polarized alignment light LA, and the output alignment light LA is a first quarter-wave plate (hereinafter, referred to as “λ / 4
It is designed to be input to 12). The alignment light LA is changed from linearly polarized light to circularly polarized light LB by the λ / 4 plate 12.

Next, this circularly polarized alignment light LB is generated by the second λ / 4 plate.
It is supposed to be incident on 14. The alignment light LB is
Due to the inclination of the optical axis of the second λ / 4 plate 14, the linearly polarized alignment light LC having a polarization plane of an arbitrary angle is obtained.

The optical axis of the second λ / 4 plate 14 is rotatable by the motor 16, and the rotation of the motor 16 is controlled by the control circuit 18
Is controlled by.

Therefore, when the motor 16 is constantly rotated based on a command from the control circuit 18, the polarization direction of the incident alignment light LB changes at a constant cycle, and the S-polarized and P-polarized alignment lights LCS and LCP are changed at regular intervals. Obtainable.

Next, the alignment light LC enters the polarization beam splitter 20. This polarization beam splitter
20 has a function of, for example, almost transmitting the P-polarized incident alignment light LCP and almost reflecting the S-polarized incident alignment light LCS.

Next, in the alignment light output direction of the polarization beam splitter 20, the prism 2 is passed through the beam shaping means 22 and 24, respectively.
6 and 28 are arranged respectively, and these prisms 26 and 28
On the light output side of the mirror 3 through the lens systems 30 and 32, respectively.
4 and 36 are arranged respectively. These mirrors 34, 36
Is for guiding the alignment lights LCP and LCS in the direction of the projection optical system 38.

Below the projection optical system 38, a wafer W to be aligned is arranged. The wafer W is placed on the stage 40.

Of the above parts, the beam shaping means 22, the prism 26, the lens system 30, and the mirror 34 form a first alignment optical system A. Further, the beam shaping means 24, the prism 28, the lens system 32, and the mirror 36 constitute a second alignment optical system B.

Next, the overall operation of the above embodiment will be described.

The linearly polarized alignment light LA output from the laser oscillator 10 passes through the first λ / 4 plate 12, becomes circularly polarized alignment light LB, and enters the second λ / 4 plate 14.

The rotation of the optical axis of the second λ / 4 plate 14 by the motor 16 is controlled by a command from the control circuit 18 in synchronization with the measurement timing of the alignment optical systems A and B described above. That is, S-polarized or P-polarized alignment light is output from the second λ / 4 plate 14 in accordance with the alignment optical system in which the alignment measurement is performed.

For example, when measurement is performed by the alignment optical system A, the motor 16 is driven by the control of the control circuit 18, and the P-polarized alignment light LCP is output from the λ / 4 plate 14.

This alignment light LCP passes through the polarization beam splitter 20 as shown in FIG.
And is aligned.

On the other hand, when measurement is performed by the alignment optical system B, the motor 16 is driven by the control of the control circuit 18, and the S-polarized alignment light LCS is output from the λ / 4 plate 14.

As shown in FIG. 3, the alignment light LCS is reflected by the polarization beam splitter 20, enters the alignment optical system B, and is aligned.

As described above, by the optical axis rotation control of the λ / 4 plate 14, the alignment light LA output from the laser oscillator 20 enters one of the alignment optical systems A and B and is divided into each alignment optical system. It does not enter. Therefore, the alignment light can be effectively used, and the detection light from a large object to be measured can be obtained by the alignment light having a large light amount, and the detection sensitivity can be improved.

On the contrary, if the detected light from the DUT is too strong, rotate the λ / 4 plate 14 to adjust the alignment light.
It is convenient to control the polarization plane of the LC and adjust the light quantity of the output alignment light LCP or LCS of the polarization beam splitter 20.

It should be noted that the present invention is not limited to the above-described embodiments at all, and for example, in the above-mentioned embodiments, a biaxial or bidirectional alignment optical system has been shown. Is what applies.

Further, the rotating means for the polarization direction of the alignment light is not limited to the above embodiment, and for example, a Faraday rotating element may be used.

Further, as the light source, in addition to a laser oscillator that outputs a linearly polarized laser beam, a polarizing plate, a wavelength plate or other optical elements may be used to appropriately polarize the light of the light source.

[Effects of the Invention] As described above, according to the present invention, the polarization direction of polarized light for alignment output from a single light source is rotated, and the path is switched in accordance with this polarization direction.
Since the alignment light is guided to one of the alignment optics without being split (equal division), the alignment illumination light output from a single light source can be effectively used. Therefore, it is possible to improve the alignment accuracy in the plurality of alignment optical systems.

[Brief description of drawings]

FIG. 1 is a perspective view showing the construction of an embodiment of the present invention, and FIGS. 2 and 3 are explanatory views showing the operation of the apparatus of FIG. 10 …… Laser oscillator, 12,14 …… λ / 4 plate, 16 …… Motor, 18 …… Control circuit, 20 …… Polarization beam splitter, 38
…… Projection optics, A, B …… Alignment optics, LA, LB, L
C, LCP, LCS …… Alignment light.

Claims (2)

[Claims] 1. An alignment apparatus which has at least two sets of alignment optical systems, and sends out polarized illumination light for alignment output from a single light source to each of these alignment optical systems. An alignment apparatus comprising: a polarization rotating means for rotating the polarization direction; and an optical path switching means for sending the illumination light transmitted through the polarization rotating means to either of the alignment optical systems according to the polarization direction. . 2. The alignment apparatus according to claim 1, wherein the polarization rotating means is constituted by either one of two quarter-wave plates or a Faraday rotating element.