JPH05205998A - Light exposure device - Google Patents

Abstract

PURPOSE:To prevent a wafer stage of a light exposure device from deteriorating in alignment accuracy due to the heat released with the movement of the wafer stage. CONSTITUTION:A light exposure device is equipped with a stage 1 where a support pad which supports a wafer is placed, a bar mirror 4 is provided onto the stage 1 to detect the position of the stage 1, and a cooling part 2 is interposed between the stage 1 and the bar mirror 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly to an apparatus for detecting the position of a wafer stage with high accuracy.

[0002]

2. Description of the Related Art The minimum processing size of a semiconductor device has been miniaturized year by year, and has reached the level of 0.35 .mu.m in the latest field. Therefore, even in the photolithography process, high alignment accuracy of the wafer is required, and in particular, the alignment accuracy of the stage on which the holding table holding the wafer is mounted is an important factor.

FIG. 5 is a plan view of an apparatus for explaining the alignment of the wafer stage. As shown in FIG. 5, the stage 1 is composed of an X stage 1a, which is a top table, a Y stage 1b, and a θ-Z stage 1c, and a bar mirror 4a for aligning in the X direction on the X stage 1a.
And a bar mirror 4b for positioning in the Y direction are placed, and laser interferometers 7a and 7b are installed so as to face the bar mirrors 4a and 4b, respectively.
And a motor 6 for aligning the Y stage 1b.
The ball screws 8a and 8b are driven by a and 6b.

The alignment is performed by laser interferometers 7a and 7b.
Laser beam from the bar mirror 4 on the X stage 1a
Laser interferometers 7a and 7a are reflected by a and b, respectively.
It is performed by re-incident on b.

At this time, the positioning accuracy is determined by the resolution of the laser interferometer and the deformation of the bar mirrors 4a and 4b within a short time.

FIG. 6 is a perspective view of an essential part of a conventional wafer stage for an exposure apparatus.

As shown in FIG. 6, the bar mirror 4 is placed directly on the stage 1, and the laser interferometer 7 shown in FIG.
The alignment of the stage in each direction of XY- [theta] -Z is performed using a and 7b.

[0008]

However, in the above method, the stage 1 associated with the alignment and exposure operations is used.
The movement of heat causes heat to be generated from the movable part, and the heat may be transmitted to the bar mirror 4 directly mounted on the stage 1 through the material of the stage 1, and the bar mirror 4 may be deformed by the heat. As a result, the stage 1 is displaced, causing a misalignment of about 0.1 μm at maximum, which is a level that cannot be ignored in a 0.35 μm class device.

It will be shown using the data shown in FIGS. 3 and 4 that the cause of this positional deviation is due to the heat generated from the stage 1.

FIG. 3 is a diagram showing the temperature change in the chamber due to the movement of the stage (stage running). The horizontal axis shows the time (minutes) and the vertical axis shows the temperature (° C.) in the chamber. As shown in Figure 3, there was stage movement 5
It can be seen that the temperature rise in the chamber is severe between 0 to 150 minutes and 290 to 400 minutes. From this, it can be seen that the movement of the stage 1 generates heat.

Next, FIG. 4 is a diagram showing the alignment accuracy of the stage of the wafer. The horizontal axis shows the number of processed wafers, and the vertical axis shows the standard deviation (μm) of the stage accuracy of alignment in the X and Y directions. .. As shown in FIG. 4, as the number of processed wafers increases, the accuracy of stage alignment deteriorates. The reason for this is that in order to print a pattern on one wafer, the stage 1 moves a number of times corresponding to the number of shots, and as a result, heat is generated from the stage 1 as shown in FIG. 4 and the bar mirror 4 is deformed by the heat, resulting in stage 1
It is probable that the registration accuracy of was deteriorated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an exposure apparatus having a stage with high alignment accuracy while avoiding conduction of heat generated by movement of the stage to the bar mirror.

[0013]

According to the present invention, there is provided an exposure apparatus comprising a stage on which a holding table for holding a wafer is mounted, and the stage position detection is performed on the stage. Equipped with a bar mirror for
The exposure apparatus is characterized in that a cooling unit is provided between the stage and the bar mirror.

According to the present invention, it is preferable that the cooling section is provided with a pipe for circulating a cooling liquid.

[0015]

According to the present invention, as shown in FIG. 1, the cooling unit 2 is provided between the stage 1 and the bar mirror 4, and the cooling unit 2 is maintained at a temperature substantially equal to the temperature of the chamber so that The heat generated by the movement is absorbed by the cooling unit 2 so that the heat is not transmitted to the bar mirror 4, and the bar mirror 4 is kept in a constant temperature state even if the temperature inside the chamber increases due to the movement of the stage 1. Since it is placed on the cooling unit 2, the temperature rise of the bar mirror 4 can be avoided, and as a result, the deformation of the bar mirror 4 due to heat is eliminated, so that highly accurate position detection of the stage 1 can be performed.

Further, according to the present invention, as shown in FIG. 1, the liquid in the constant temperature bath 5 which is maintained at the same temperature as the set temperature in the chamber is circulated in the pipe 3 of the cooling unit 2 to cool the cooling unit. 2 can be kept at a constant temperature. As a result, the temperature of the bar mirror 4 can be preferably kept constant.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of an essential part of an exposure apparatus showing an embodiment according to the present invention.

As shown in FIG. 1, a cooling unit 2 for cooling the lower surface of the bar mirror 4 is placed on the stage 1. The bar mirror 4 is mounted in close contact with the flat upper surface of the cooling unit 2 in order to improve thermal conductivity with the cooling unit 2.

The cooling unit 2 is connected to the constant temperature bath 5 through an inlet pipe 3a and an outlet pipe 3b provided on the side surface of the constant temperature bath 5.
A pipe 3 is provided inside the cooling unit 2 as will be described later, and a liquid can be circulated.

In the constant temperature bath 5, a CFC-based constant temperature liquid 5a is held and stored at a temperature substantially equal to the temperature in the chamber.

Since the constant temperature liquid 5a circulates through the inlet pipe 3a, the pipe 3 and the outlet pipe 3b sequentially, the cooling unit 2 can be maintained at the same temperature as the constant temperature liquid 5c.

FIG. 2 is a horizontal sectional view of the cooling section shown in FIG.

As shown in FIG. 2, a pipe 3 is provided inside the cooling unit 2.
The cooling liquid 3c is supplied from the thermostatic bath 5 through the inlet pipe 3a inside the pipe 3, and is output to the outlet pipe 3b to circulate.

The inlet pipe 3a and the outlet pipe 3b connected to the cooling unit 2 are provided in the central upper part of the side surface of the cooling unit 2 so that the cooling liquid 3c is brought close to the bar mirror 4 and the thermal conductivity to the bar mirror 4 is improved. Has been. Further, the tube 3 has a helical shape so as to have a large surface area and good thermal conductivity to the bar mirror 4.

The heat generated from the stage 1 is absorbed by the cooling unit 2 by the exposure apparatus shown in FIGS. 1 and 2, and the bar mirror 4 is cooled by the constant cooling liquid 3c circulating in the tube 3.
Since it can be kept at a constant temperature, the accuracy of alignment of the stage 1 can be improved.

As for the material of the cooling section 2, the upper part of the tube 3 in contact with the bar mirror 4 is made of a material having good thermal conductivity, and the lower part of the tube 3 in contact with the stage 1 is made of a material having low thermal conductivity. The conduction of heat from 1 to the bar mirror 4 can be avoided more effectively.

[0028]

As described above, according to the present invention, the cooling unit is provided on the wafer stage, and the bar mirror for detecting the position of the stage is provided on the cooling unit. Therefore, the deformation of the bar mirror due to heat can be avoided and the wafer stage can be aligned with high accuracy.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part of an exposure apparatus showing one embodiment according to the present invention.

FIG. 2 is a sectional view of a cooling unit of the exposure apparatus shown in FIG.

FIG. 3 is a diagram showing a temperature change in a chamber due to movement of a wafer stage.

FIG. 4 is a diagram showing alignment accuracy of a wafer stage.

FIG. 5 is a plan view of an exposure alignment device.

FIG. 6 is a perspective view of a main part of a conventional exposure apparatus.

[Explanation of symbols]

 1 stage 1a X stage 1b Y stage 1c θ-Z stage 2 Cooling section 3 Tube 3a Inlet tube 3b Outlet tube 3c Cooling liquid 4, 4a, 4b Bar mirror 5 Constant temperature bath 5a Constant temperature liquid 6 Motor 7 Laser interferometer 8 Ball screw

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01L 21/68 F 8418-4M 7352-4M H01L 21/30 311 M

Claims (2)

[Claims] 1. An exposure apparatus comprising a stage on which a holding table for holding a wafer is mounted, wherein a bar mirror for detecting the position of the stage is provided on an upper portion of the stage, An exposure apparatus comprising a cooling unit between the bar mirror and the bar mirror. 2. The exposure apparatus according to claim 1, wherein the cooling unit is provided with a pipe for circulating a cooling liquid.