JPH0653114A - Reduction projection aligner - Google Patents

Abstract

PURPOSE:To make focusing possible even if a wafer, a semiconductor substrate, has an unevenness larger than a focus depth and to form an image of a pattern of a reticle accurately and to transfer the image onto the wafer. CONSTITUTION:This is a reduction projection aligner which transfers a reduced pattern of a reticle 3 onto a wafer 5. On an X-Y stage 6 on which the wafer 5 is mounted, at least three electrostriction elements 9 are located with balance. Then, voltage is applied to these electrostriction elements 9 in stages from a driving power supply 7 and the X-Y stage 6 is vibrated up and down larger than a difference in level of an uneven surface of the wafer 5 and a projecting section of the uneven surface is focused on a recessed section accurately for forming an image of the reticle 3 and then for transferring the image onto the wafer 5 accurately. This equipment is especially effective for a projection lens with a large aperture diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction projection exposure apparatus for transferring an electric circuit pattern onto a semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 2 is a diagram showing a configuration of an example of a conventional reduction projection exposure apparatus. Conventionally, a reduction projection exposure apparatus of this type includes, for example, an illumination system 1 for converting light emitted from a light source into a single wavelength as shown in FIG. 2, and a reticle 3 formed by enlarging an electric circuit pattern at a certain magnification. And an optical system 2 for irradiating single-wavelength light through the reticle 3.
And an XY stage 6 for placing the wafer 5 which is a semiconductor substrate, and a reduction lens for reducing and projecting the electric circuit pattern of the reticle 3 onto the wafer 5 on the XY stage 6.

In this reduction projection exposure apparatus, the light from the illumination system 1 is passed through the optical system 2 to irradiate the reticle 3 to project an electric circuit pattern enlarged to a certain magnification (10 times or 5 times). The projected electric circuit pattern is reduced to the original size through the reduction lens 4 (1/10 or 1).
/ 5), an image is formed on an area surface of the wafer 5 placed on the XY stage 6, and the electric circuit pattern is transferred.

Then, the XY stage 6 is moved in the XY directions to be positioned in each region of the wafer, each region is irradiated with pattern light, and the above-described operation is repeated until the pattern is transferred onto the entire surface of the wafer.

The resolution R obtained by the projection optical system of such a reduction projection exposure apparatus and the depth of focus DOF at that time
Is conveniently given by R = kaλ / NA DOF = ± kbλ / NA ² from the NA (numerical aperture) of the optical system and the exposure wavelength λ. Here, kakb is a constant determined by the resolution of the resist material itself and the controllability of the process.

[0006]

In this conventional reduction projection exposure apparatus, the depth of focus DOF becomes smaller as the lesbian numerical aperture NA is increased in order to increase the resolution (reduce R) as described above. In recent years, electric circuit patterns formed on a semiconductor substrate have become finer, and many manufacturing processes have been performed, so that surface irregularities are formed and the cross-sectional structure becomes complicated. When the lens numerical aperture NA is increased in order to increase the resolution in response to miniaturization, the depth of focus becomes smaller, and there is a problem that the focus cannot be adjusted depending on the location and correct exposure cannot be performed.

An object of the present invention is to provide a reduction projection exposure apparatus which can form a focused pattern even if the surface has irregularities and can perform correct exposure.

[0008]

A reduction projection exposure apparatus according to the present invention is an illumination source for converting light emitted from a light source into a single wavelength.
A reticle formed by an electric circuit pattern with a certain magnification, a condenser lens for irradiating the reticle with the light that is converted into a single wavelength, an XY stage on which a semiconductor substrate is mounted, and a pattern of the reticle are reduced to reduce the reticle. It is provided with a lens for projecting onto a wafer, an electrostrictive element sandwiched between the divided parts of the XY stage, and a drive power source for periodically applying a voltage to the electrostrictive element.

[0009]

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

FIG. 1 is a view showing the arrangement of a reduction projection exposure apparatus according to an embodiment of the present invention. In this reduction projection exposure apparatus, as shown in FIG. 1, an electrostrictive element 9 is sandwiched between an XY stage 6 on which a wafer 5 onto which a pattern of a reticle 3 is transferred is placed, and a voltage is periodically applied to the electrostrictive element 9. That is, the drive power supply 7 for applying the voltage is provided.

Other than this, the reduction projection exposure apparatus is similar to the conventional one, and the reduction projection exposure apparatus has a condenser lens 2 for converging the illumination light generated from the illumination source 1 and a reticle for transmitting the condensed light and forming a pattern. 3, a projection lens for reducing an optical image transmitted through the reticle 3 to form an image on the wafer 5, and an XY stage 6 on which the wafer 5 is mounted.

Further, the electrostrictive elements 9 sandwiched between the XY stage 6 are evenly arranged in three places, and the XY stage surface is kept so as to be straight with respect to the optical axis. Of course, these electrostrictive elements 9 have the same characteristics. Then, the range of dimensional change in the thickness direction due to the voltage, which is a characteristic thereof, is to be equal to or larger than the required depth of focus. For example, in the case of the exposure apparatus at the present time, at least 1.5 μm or more is sufficient. With such a dimensional change, an ordinary ceramic piezoelectric material can be sufficiently obtained. On the other hand, the drive power supply 7 for driving the electrostrictive element 9 is a low-frequency Palace voltage generator that generates voltage stepwise. This is
This is to periodically change the height of the wafer 5 placed on the XY stage 6. For example, X per exposure shot
That is, the Y stage 6 is vibrated about tens of times. Such a low frequency pulse voltage generator can be easily obtained by a known technique.

Next, the operation of this reduction projection exposure apparatus will be described, for example, in the case where the wafer has irregularities of 0.35 μm. First, an alignment mechanism (not shown) is used to set the optical axis alignment and the average focal length of the projection lens 4 and the concave and convex portions of the wafer. Next, the dimensional change amount in the thickness direction is set to 0.35 μm and the frequency 100 is set to the driving power supply 7.
Next, the XY stage 6 is moved to position the wafer 5. Next, the illumination source 1 is operated and the drive power supply 7 is operated in accordance with the command signal from the control unit 8, and the wafer 5 is exposed and transferred. As a result, when the vibration direction changes, the concave and convex portions are focused during the stop time of the stage 6, so that the pattern is accurately imaged. Also, since the resist is exposed only during the stop time, the irradiation time is extended as necessary to expose the resist.

[0014]

As described above, according to the present invention, the electrostrictive element is sandwiched between the XY stage, the power source for driving the electrostrictive element is provided, and the XY stage is vibrated vertically.
Even if there is unevenness on the surface, there is an effect that it is possible to transfer the imaged pattern accurately by focusing.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a reduction projection exposure apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 1 Illumination Source 2 Condenser Lens 3 Reticle 4 Projection Lens 5 Wafer 6 XY Stage 7 Drive Power Supply 8 Controller 9 Electrostrictive Element

Claims (1)

[Claims] 1. An illumination source for converting light emitted from a light source into a single wavelength, a reticle formed by an electric circuit pattern at a certain magnification, and a condenser lens for irradiating the reticle with the single wavelength converted light. , X for mounting semiconductor substrate
A Y stage, a lens for reducing the pattern of the reticle and projecting it onto the wafer, an electrostrictive element sandwiched between the divided parts of the XY stage, and a voltage is periodically applied to the electrostrictive element. A reduction projection exposure apparatus, comprising: