JP2006049563A - Method of suppressing degradation of optical element used for extreme ultraviolet ray exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of requiring strict storage environment control or a protective film for suppressing degradation of an optical element. <P>SOLUTION: The optical element is suppressed from degrading by arranging a shielding body, in tight-contact manner, on the surface of optical element used for an extreme ultraviolet ray exposure device. The shielding body is made from such material as has oxygen transmissivity of 300 mL/(m<SP>2</SP>24h MPa) or less and water vapor transmissivity of 100 ml/(m<SP>2</SP>24h) or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for suppressing deterioration of an optical element for an extreme ultraviolet exposure apparatus due to oxygen, moisture, or the like. In the present specification and claims, extreme ultraviolet light is also called EUV (Extreme Ultraviolet) light, which means light having a wavelength of 100 nm or less.

  As the degree of integration of semiconductor integrated circuits increases, the circuit pattern becomes finer, and the exposure apparatus using visible light or ultraviolet light that has been used conventionally has become insufficient in resolution. As is well known, the resolution of the exposure apparatus is inversely proportional to the numerical aperture (NA) of the transfer optical system and proportional to the wavelength of light used for exposure. Therefore, as one attempt to increase the resolution, an attempt has been made to use an EUV (sometimes referred to as soft X-ray) light source having a short wavelength for exposure transfer instead of visible light or ultraviolet light.

As an optical element for extreme ultraviolet exposure equipment, metals such as Si, Mo, C, Sr, Y, Ru, and Rh, carbides such as B ₄ C, and other compounds are alternately formed on an optical material substrate such as glass. A mirror that is laminated and whose spectral characteristics are arbitrarily changed is used. When these optical elements are stored for a long period of time, moisture, oxygen, organic (phthalate ester, etc.) and inorganic (NO _x , SO _x gas, etc.) gases contained in the storage environment are adsorbed on the surface of the optical element or enter the film. Or cause a chemical reaction to deteriorate the performance (spectral characteristics, durability, etc.) of the optical element. In order to suppress such deterioration, it is necessary to strictly manage the storage environment. Removing harmful impurities such as moisture, oxygen, organic and inorganic gases contained in gases and liquids in the room and storage of optical elements requires large exclusion devices and equipment, increasing costs and reducing production efficiency Is the cause of Further, although a method of forming a protective film as the uppermost layer of the optical element is common, it is often impossible to obtain desired optical performance by attaching the extra protective film. This is because the protective film also functions as a part of the optical element.

  Therefore, an object of the present invention is to solve the above-described problems and provide a method for suppressing deterioration of an optical element that does not require strict storage environment management and does not require a protective film.

In order to achieve the above-mentioned object, the present invention is a method for suppressing deterioration of an optical element by placing a shield in close contact with the surface of an optical element used in an extreme ultraviolet exposure apparatus, wherein the shielding The body provides a method characterized by comprising an oxygen permeability of 300 mL / m ² · 24 h · MPa and a water vapor permeability of 100 ml / m ² · 24 h or less.

  In this case, it is preferable that the surface of the shield that contacts the optical element has the same surface shape as the optical element. Since it is the same surface shape, a shield can be stuck more closely and it can prevent more effectively that harmful gas contacts an optical element surface.

  Moreover, it is preferable that the shield is made of a material softer than the optical element. By using a soft material for the shield, it is possible to prevent the surface of the optical element that comes into contact from being damaged.

In this case, it is preferable that the shield is one of glass, metal, and resin.
In addition, optical elements for extreme ultraviolet exposure equipment are alternately composed of metals such as Si, Mo, C, Sr, Y, Ru, and Rh, carbides such as B ₄ C, and other compounds on a substrate such as glass. So-called multilayer mirrors, multilayer masks, total reflection mirrors, and the like are shown.

According to the present invention, an oxygen permeability is 300 mL / m ² · 24 h · MPa, and a water vapor permeability of 100 ml / m ² · 24 h or less is adhered to the optical element so that the substance constituting the surface of the optical element Contact with gas can be suppressed. If the contact is reduced, the probability of harmful gas adsorbing, intruding into a substance constituting the optical element, and causing a chemical reaction is greatly suppressed, so that deterioration can be suppressed. Accordingly, strict storage environment management and a protective film are not required, and it is possible to easily suppress deterioration of the optical element.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a storage example of an optical element which is an example of an embodiment of the present invention. In this example, a mirror will be described as an example of the optical element.

  Reference numeral 1 denotes a mirror substrate, 2 denotes a multilayer film formed on the mirror (in this example, an alternating multilayer film of Mo and Si), 3 denotes a shielding body, and 4 denotes a shielding body holding jig. A mirror 5 is constituted by the mirror substrate 1 and the multilayer film 2. In this example, the mirror 5 is described as a plane mirror for convenience of explanation. However, a mirror having a spherical shape, an aspherical surface, or the like can be treated in the same manner. The shape is preferably the same as the aspherical shape. In this example, the outer diameter of the mirror 5 is a circle, but other shapes may be used. The shielding member holding jig 4 includes an annular lower holding plate 41 that is in contact with the shielding member 3 and sandwiched from the lower side of the drawing, and a circular upper third holding plate 46 and a holding plate 46 that are in contact with the back surface of the mirror 5. Further, the second restraining plate 42 to be restrained, the annular first restraining plate 43 for restraining the second restraining plate 42 from above, the bar screw 45 and the nut 44 for fixing the first restraining plate 43 and the lower restraining plate 41. It consists of. The first holding plate 43 and the lower holding plate 41 are fixed at three places by a bar screw 45 and a nut 44. In addition, the 3rd suppression board 46 which contacts the back surface of the mirror 5 is comprised by the soft material so that the back surface of the mirror 5 may not be damaged. After the mirror 5 is brought into close contact with the shield 3, the mirror 5 is fixed by the shield holding jig 4. Note that the shielding member holding jig 4 is not limited to the example of the present embodiment, and any member can be used as long as the shielding member 3 can be kept in close contact with the mirror 5.

The shield 3 to be in close contact with the optical element is a material having a low gas permeability such as glass, metal, or resin. The lower the gas permeability, the better. There are several ways to express gas permeability. For example, the gas permeability and water vapor permeability test methods based on JIS-Z-0208 and JIS-K-7126 are measured, and each is 300 mL / m ² · 24 h.・ MPa (oxygen gas), 100ml / m ² · 24h or less. If the above value is satisfied, the gas can be sufficiently shielded. However, it is necessary to select a material that does not emit a gas that reacts with or has an adverse effect on the surface of the optical element according to the optical element.

  By being in close contact with the optical element, contact between a substance constituting the surface of the optical element and a harmful gas can be suppressed. If the contact is reduced, the probability of harmful gas adsorbing to a substance constituting the surface of the optical element, entering the film, or causing a chemical reaction is greatly suppressed, so that deterioration can be suppressed. When adhering to the optical element, if the optical element is previously washed with a solution or light irradiation, the adhesion is enhanced. When the optical element is stored and used, the shield may be removed by hand. However, care should be taken because there is a possibility of damaging the surface of the optical element during attachment / removal. For this reason, it is desirable to select a shield that is softer than the surface of the optical element and to accurately match the surface shape. In that respect, a resin is advantageous because it is soft. There are also resins that can be applied to be cured later, and by using them, the optical element and the resin can be brought into close contact with each other.

It is the form schematic of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mirror board | substrate 2 Multilayer film 3 Shielding body 4 Shielding body holding jig 5 Mirror

Claims (6)

A method of suppressing deterioration of an optical element by closely placing a shield on the surface of an optical element used in an extreme ultraviolet exposure apparatus,
The shield is made of a material having an oxygen permeability of 300 mL / m ² · 24 h · MPa and a water vapor permeability of 100 ml / m ² · 24 h or less. The method according to claim 1, wherein a surface of the shield that contacts the optical element has the same surface shape as the optical element. The method according to claim 1, wherein the shield is made of a material softer than the optical element. The method of claim 1, wherein the shield is glass. The method of claim 1, wherein the shield is a metal. The method of claim 1, wherein the shield is a resin.