KR20130011835A - Immersion lithography equipment - Google Patents

Abstract

PURPOSE: Immersion lithography equipment is provided to prevent an impurity or a by-product from being absorbed to a lens unit by periodically vibrating immersion medium. CONSTITUTION: A wafer is mounted on a stage. A lens unit(100) provides the light source for exposure on the wafer. A hood(400) is arranged between the lens unit and the wafer to contact immersion medium with a part of the wafer. A vibration generator(430) is mounted to the hood and applies vibration to the immersion medium.

Description

Immersion lithography equipment

FIELD OF THE INVENTION The present invention relates to semiconductor lithography techniques, and more particularly to immersion lithography equipment.

As semiconductor devices become highly integrated and circuit patterns become increasingly finer, the difficulty in pattern transfer of fine circuit patterns onto wafers increases. In order to transfer an image of a finer circuit pattern onto a wafer, a light source having a shorter wavelength band is required for an exposure light source used in a lithography process. The resolution in the lithography process is evaluated as a function of the inverse of the numerical aperture NA (number of aperture) of the lens projecting the image and the wavelength of the light source, but a shorter wavelength band is required to obtain higher resolution. In order to induce the effect of using the light source of shorter wavelength range while maintaining the wavelength range of the exposure light source, immersion lithography equipment using the difference in refractive index between two different media is employed.

The immersion lithography apparatus is configured to provide an immersion medium between the lens portion and the wafer as a solution such as water so that the ArF light, which is an exposure light source, is reduced and projected onto the lens portion, and then enters the wafer through the immersion medium. Since the resolution is improved by the difference in refractive index between the immersion medium and the lens portion, it is possible to reduce and project an image of a circuit pattern having a smaller size onto the wafer. In other words, ArF excimer laser light incident to the immersion medium passes through a refractive angle greater than the angle of incidence according to Snell's law, and the circuit pattern transferred onto the wafer by the refraction of the exposure light in the immersion medium can be imaged to a finer size. It becomes possible. Accordingly, the immersion lithography apparatus can transfer the pattern image of the smaller line width onto the wafer as compared with the case where no immersion medium is introduced.

The immersion lithography apparatus must supply the immersion medium to flow between the lens unit and the wafer. If an irregular flow occurs when the immersion medium is introduced, it becomes difficult to maintain a homogeneous medium. If the immersion medium is in a heterogeneous state, it may cause a defect that distorts the shape of the transferred image like a haze. Thus, the immersion medium should remain flowing in a homogeneous state, but in order to perform a continuous exposure process, when the stage on which the wafer is mounted is scanned or moved, the stage moves up and down and is separated. As the stage is moved, an irregular force is transmitted to the flow flow of the immersion medium, resulting in an uneven flow flow. That is, the vertical movement of the stage and the plane movement hinder the flow of the immersion medium, thereby causing an irregular vibration in the immersion medium, thereby reducing the exposure accuracy due to the irregular refraction of the light due to the inhomogeneous medium state. . Immersion media in an inhomogeneous state cause undesired distorted image transfer on the wafer, and there is a need for development of a method capable of overcoming this.

An object of the present invention is to provide an immersion lithography apparatus capable of uniformly inducing a flow flow of an immersion medium flowing between a lens portion and a wafer, thereby suppressing exposure inaccuracy caused by an irregular flow flow of the immersion medium.

One aspect of the invention, the stage (stage) on which the wafer is mounted; A lens unit providing an exposure light source on the wafer; A hood introduced between the lens portion and the wafer such that an immersion medium supplied and flowing between the lens portion and the wafer contacts some restricted area of the wafer; And a vibration generator mounted on the hood to apply vibration to the immersion medium.

The vibration generator may include an ultrasonic generator for periodically applying ultrasonic vibration to the immersion medium.

According to an embodiment of the present invention, it is possible to uniformly induce the flow flow of the immersion medium flowing between the lens portion and the wafer, thereby providing an immersion lithography apparatus that suppresses exposure inaccuracy defects caused by the irregular flow flow of the immersion medium. have.

1 is a diagram illustrating immersion lithography equipment according to an embodiment of the present invention.

Embodiments of the present invention present immersion lithography equipment configured to periodically apply vibration to the flow of immersion medium so that the flow of immersion medium, such as water, remains homogeneous. In order to offset the irregular flow or irregular vibration generated in the immersion medium, the vibration generator is mounted in a hood introduced for supplying the immersion medium. The vibration generator may include an ultrasonic generator for generating ultrasonic vibrations. Ultrasonic vibrations generated at the vibration generating unit are applied to the water supplied to the immersion medium to maintain the flowability of the water periodically, and are periodically applied to the flow of water. Ultrasonic vibration can cancel out irregular flow, irregular flow or irregular vibration generated in the flow of water, which is an immersion medium, so that the flow of water is kept constant at all times. Accordingly, the flow flow of the immersion medium can be kept constant, so that the state of the immersion medium remains homogeneous and the exposure process can be performed. Therefore, it is possible to effectively suppress the pattern transfer defect in the exposure process and to transfer the pattern image onto the wafer more precisely.

Referring to FIG. 1, an immersion lithography apparatus according to an embodiment of the present invention may include a lens unit 100 through which an exposure light source such as ArF light is transmitted. The lens unit 100 is composed of a plurality of lenses as the reduction projection optics to transfer the pattern image provided by the reticle onto the wafer 200. In the lower portion of the lens unit 100, a wafer 200 is mounted on a stage 300 and introduced. Although not shown, the wafer layer 200 is provided with a resist layer to be exposed.

An immersion medium 410 such as water is supplied between the wafer 200 and the lens unit 100, and a hood 400 for supplying and recovering the immersion medium 410 is introduced. The hood 400 is introduced to locally expose a portion of the wafer 200 to restrict the immersion medium 410 into contact with a portion of the wafer 200. The immersion medium 410 is supplied through the inlet 401 of the hood 400, is recovered to the outlet 403, and flows between the wafer 200 and the lens unit 100. In this case, in order to apply vibration, for example, ultrasonic vibration, to the flow of the immersion medium 410 that is in contact with the wafer 200, the vibration generator 430 is mounted on the hood 400. The vibration generator 430 includes an ultrasonic generator for generating ultrasonic vibration and is attached to the hood 400 body adjacent to the immersion medium 410 in contact with the wafer 200.

When the stage 300 is moved relative to the lens unit 100 for the scan exposure of the wafer 200, the stage 300 descends to be spaced apart from the hood 400 and then moved. Since the wafer 200 is spaced apart from the lens unit 100 when the stage 300 moves, the gap is generated. Thus, in order to recover the immersion medium 410 flowing out of the hood 400 by the gap, that is, water flow The hood 400 is provided with an absorbing portion 405 that sucks out the water flowing out. When the stage 300 rises again after the stage 300 moves and the clearance between the wafer 200 and the lens unit 100 returns to a normal state, abnormal and irregular vortex or vibration flows in the immersion medium 410. May be induced. This irregular flow causes local refractive index variations in the immersion medium 410, which can cause image transfer defects or image formation defects during the exposure process.

In the exemplary embodiment of the present invention, vibration is periodically applied to the immersion medium 410 by using the vibration generator 430, and the applied vibration is an irregular and local vortex or vibration flow generated in the immersion medium 410. To offset. In spite of the occurrence of irregular vortex, it can be offset to a homogeneous medium state, so that the immersion medium 410 can be maintained more effectively in a homogeneous state, thereby more effectively suppressing the occurrence of defects during the exposure process. have. In addition, by applying vibration to the immersion medium 410 periodically, impurities or by-products caused by the resist layer of the wafer 200 may be effectively prevented from being adsorbed to the lens unit 100. Therefore, by-products or impurities may be adsorbed or fixed to the lens unit 100 to effectively prevent the phenomenon that the transmittance of the lens is lowered. In addition, since the vibration generating unit 430 is mounted on the hood 400, it is possible to suppress the vibration from being applied directly to the lens unit 100, and an error occurs in the alignment of the lens unit 100 due to the vibration. Alternatively, damage to the lens unit 100 may be suppressed.

As described above, the immersion lithography apparatus according to the embodiment of the present invention can maintain the immersion medium 410 in a homogeneous state, and can suppress the occurrence of non-uniform local vortex or flow in the immersion medium 410. Accordingly, it is possible to effectively prevent the refractive index from being changed by the non-irregular state of the immersed medium 410, thereby reducing the accuracy of exposure, thereby improving the reproducibility and productivity of the exposure process. In addition, by inducing an effect of continuously cleaning the contamination on the lens unit 100, it is possible to reduce the cost and time consumed in the maintenance of the equipment.

100: lens portion, 200: wafer,
300: stage, 400: hood,
410: immersion medium, 430: vibration generating unit.

Claims (2)

A stage on which the wafer is mounted;
A lens unit providing an exposure light source on the wafer;
A hood introduced between the lens portion and the wafer such that an immersion medium supplied and flowing between the lens portion and the wafer contacts some restricted area of the wafer; And
Immersion lithography apparatus comprising a vibration generating unit mounted to the hood for applying vibration to the immersion medium.
The method of claim 1,
The vibration generating unit
Immersion lithography apparatus comprising an ultrasonic generator for periodically applying ultrasonic vibration to the immersion medium.

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