JP2000058628A - Pre-alignment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pre-alignment device which can realize high-accuracy pre-alignment without applying load to a stage. SOLUTION: A pre-alignment device is provided with a light emitting section 32, which radiates detecting light upon the edge 36 of an object and a light receiving section 39 which detects the detecting light 31 which passes through the edge 36. The light emitting section 32 and light receiving section 29 are respectively incorporated in structures above and below a wafer stage 50. In addition, a hole 51 is formed through the stage 50 for passing the detecting light 31. Therefore, this pre-alignment device can detect the edge 36 with high accuracy even through the pre-alignment device has nearly the same configuration as that of the conventional pre-alignment device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-alignment apparatus for relatively coarsely positioning an object such as a wafer on a moving stage of a reduction projection exposure apparatus or an inspection apparatus for a semiconductor or the like. In particular, the present invention relates to a pre-alignment apparatus improved so as to be as light as possible for high-speed driving.

[0002]

2. Description of the Related Art The prior art will be described by taking a reduction projection exposure apparatus as an example. 2. Description of the Related Art A reduction projection exposure apparatus is an apparatus that projects a device pattern on a reticle in a reduced size onto a sensitive substrate such as a semiconductor wafer and transfers the reduced pattern onto a resist film applied on the wafer surface. In this exposure apparatus, it is necessary to accurately position the wafer with respect to the optical system of the exposure apparatus so that a pattern can be transferred to a desired position on the wafer. The positioning operation for that purpose is called alignment.

[0003] The alignment is divided into two stages: a pre-alignment that is performed first and a precise alignment that is performed thereafter. In pre-alignment, a wafer sent from a wafer cassette to a wafer loader is placed on a wafer stage with relatively coarse accuracy (for example, 20 to 50 μm). In this pre-alignment, a non-contact optical pre-alignment sensor is usually used to measure the position of the edge of the wafer.

FIG. 2 is a side view schematically showing a configuration example of a typical pre-alignment apparatus in a conventional exposure apparatus. The projection optical system barrel 1 of the exposure apparatus is shown in the upper part of the figure. A projection lens (not shown) and the like are housed in the lens barrel.

A wafer stage 3 and a wafer holder 2 are shown below the projection optical system lens barrel 1. The wafer stage 3 generally has an individual slide mechanism that moves in three stages (X direction, Y direction, Z direction (optical axis direction)) or four stages (further, in the θ direction). Each mechanism includes a linear or rotating guide rail and a drive mechanism (neither shown).

The wafer holder 2 is mounted on a stage 3 and has a disk shape having a wafer holding mechanism such as a vacuum chuck or an electrostatic chuck. A center pin 4 is provided at the center of the wafer holder 2 so as to be able to move up and down and rotate. A wafer transfer device (not shown) places the wafer on the center pin 4 and lowers after rotating by a necessary angle during pre-alignment, which will be described later, and places the wafer 15 on the wafer holder 2. Thereafter, the wafer holder is operated, and the wafer 15 is firmly fixed on the holder 2.
On the other hand, after the end of the exposure, the fixing of the holder 2 is released, and the center pins 4 are raised to lift the wafer 15. Then, the wafer transfer device unloads the wafer 15 out of the exposure device.

A pre-alignment sensor in this conventional exposure apparatus will be described. In the wafer stage 3, a light emitting unit 12 including an LED or the like is provided. Light emitted from the light emitting section 12 toward the center of the wafer stage is condensed by the lens 13 and is emitted upward upon hitting the mirror 14 (detection light 11). The detection light 11 forms an image on the edge 16 of the wafer 15. Detection light 1 that has passed through the edge 16
Numeral 1 faces upward and hits a mirror 17 installed in the projection optical system lens barrel 1. The detection light reflected outward in the horizontal direction by the mirror 17 is collected by the lens 18 and
Image.

The light receiving section 19 is composed of a CCD line sensor or the like. An image of the wafer edge 16 is formed on the light receiving section 19, and a signal about the position of the edge is sent to the controller 20. At least three such pre-alignment sensors are provided around the wafer holder 2, and the controller 20 uses the signals from the sensors to determine whether the wafer 15
And the rotation angle are calculated. Then, pre-alignment of the wafer is performed by adding an offset to the stage position or rotating the center pin 4.

FIG. 3 is a plan view showing a typical arrangement of the pre-alignment sensors on the circumference of the wafer. A notch 1 for azimuth angle detection is provided on the outer periphery of the wafer 15.
5a is in one place. Pre-alignment sensor 1
0 is substantially 1 on the circumference including the position of the notch 15a.
It is arranged at three locations with a 20 ° distribution.

[0010]

In the prior art as described above, since a part of the pre-alignment sensor is installed on the wafer stage, the wafer stage becomes heavier and the speed of the stage is increased. There was a problem that it became an obstacle. In addition, the light emitting unit, the lens, and the mirror weigh, for example, several hundred g per one sensor.

The present invention has been made in view of such a problem, and an object of the present invention is to realize a pre-alignment method using a conventional high-precision pre-alignment method without applying a load to the stage.

[0012]

In order to solve the above-mentioned problems, a pre-alignment apparatus of the present invention is an apparatus for pre-aligning an object on a moving stage; and irradiating a detection light to an edge of the object. A light-emitting unit; and a light-receiving unit that detects detection light passing through the edge of the object, wherein both the light-emitting unit and the light-receiving unit are installed outside the moving stage. Therefore, the weight of the light emitting part, light receiving part, etc. of the pre-alignment sensor is
Since both are applied to structures other than the wafer stage, no load is applied to the wafer stage. This can reduce the weight of the wafer stage.

[0013]

In the present invention, both the light receiving portion and the light emitting portion of the sensor are fixed to the upper and lower structures of the wafer stage, and the moving stage is provided with holes through which the detection light passes. Is preferred. In this case, a passage hole is provided in the wafer stage, and high-precision wafer edge detection is possible in almost the same manner as in the related art.

Hereinafter, description will be made with reference to the drawings. FIG.
FIG. 1 is a schematic cross-sectional view showing the periphery of a stage of an exposure apparatus having a pre-alignment apparatus according to one embodiment of the present invention. In this figure, the wafer holder 40 and the wafer stage 5 are shown.
0 is shown. The wafer holder 40 is, for example, a vacuum chuck or an electrostatic chuck as in the related art. The wafer stage 50 is driven in a horizontal plane by a guide rail and a linear motor (not shown). A hole 49 is opened at the center of the wafer holder 40 and the wafer stage 50. The center pin 47 passes through the hole 49. The center pin 47 is connected to the drive mechanism 4 connected to the lower end thereof.
8 for driving up and down and rotation. The wafer 35 is placed on the center pins 47. The center pin 47 is housed below the stage except when the wafer is loaded or unloaded, so that it does not hinder the movement of the stage.

Wafer stage 50 and wafer holder 40
A through hole 51 is formed at a position outside the center pin 47 and extends vertically. The detection light 31 of the pre-alignment sensor passes through this passage hole 51. In a lower frame 53 outside the lower part of the wafer stage 50, a light emitting unit 32 composed of an LED or the like is provided. The light emitted from the light emitting section 32 toward the center of the wafer stage is condensed by the lens 33 and strikes the mirror 34 and is emitted upward (detection light 31). The detection light 31 forms an image on the edge 36 of the wafer 35. The detection light 31 having passed through the edge 36 is directed upward, and a mirror 37 provided in an upper frame 54 which is a separate member from the projection optical system lens barrel 1.
Hit. The detection light reflected horizontally outward by the mirror 37 is condensed by the lens 38 and forms an image on the light receiving unit 39. That is, the light emitting section 32 of the alignment sensor, the lens 3
3. The mirror 34 is all disposed in the lower structure, and the mirror 37, the lens 38, and the light receiving unit 39 are all disposed in the upper structure.

The light receiving section 39 is composed of a CCD line sensor or the like. An image of the wafer edge 36 is formed on the light receiving section 39, and a signal about the position of the edge is sent to the controller 20. At least three such pre-alignment sensors are provided around the wafer holder 40, and the controller 20 uses the signals from those sensors to determine whether the wafer 35
And the rotation angle are calculated. Then, the wafer is pre-aligned by adding an offset to the stage position, rotating the center pin 47, or the like.

As described above, in the pre-alignment apparatus of this embodiment, both the light-emitting portion and the light-receiving portion are fixed to the structures above and below the wafer stage 50. Therefore, no load is applied to the wafer stage 50, and the weight of the wafer stage can be reduced. Further, a hole 51 through which the detection light 31 passes is formed in the stage 50, and it is possible to detect a wafer edge with high accuracy by using an alignment sensor having almost the same form as that of the related art.

[0018]

As is apparent from the above description, according to the present invention, in a reduction projection exposure apparatus for a semiconductor or the like, the stage for positioning an object such as a wafer can be made as light as possible and suitable for high-speed driving. Device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing the periphery of a stage of an exposure apparatus having a pre-alignment apparatus according to one embodiment of the present invention.

FIG. 2 is a side view schematically showing a configuration example of a typical pre-alignment apparatus in a conventional exposure apparatus.

FIG. 3 is a plan view showing a typical arrangement of pre-alignment sensors on the circumference of a wafer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Projection optical system barrel 2 Wafer holder 3 Wafer stage 4 Center pin 10 Pre-alignment sensor 11 Detection light 12 Light emitting unit 13 Lens 14 Mirror 15 Wafer 15a Notch 16 Wafer edge 17 Mirror 18 Lens 19 Light receiving unit 20 Controller 31 Detection light 32 Light emitting unit 33 Lens 34 Mirror 35 Wafer 36 Wafer edge 37 Mirror 38 Lens 39 Light receiving unit 40 Wafer holder 47 Center pin 48 Drive mechanism 49 Hole 50 Wafer stage 51 Passing hole

Claims (2)

[Claims] An apparatus for pre-aligning an object on a moving stage, comprising: a light-emitting unit for irradiating the object edge with detection light; a light-receiving unit for detecting detection light passing through the object edge; A pre-alignment device, wherein both the light emitting unit and the light receiving unit are installed outside the moving stage. 2. A light-receiving unit and a light-emitting unit of the sensor are fixed to structures above and below the moving stage, and a hole through which the detection light passes is formed in the stage. Item 2. The pre-alignment apparatus according to Item 1.