JP4572111B2 - Projection exposure equipment - Google Patents

Description

  The present invention relates to a projection exposure apparatus. More specifically, the present invention relates to a projection exposure apparatus that can increase the NA (numerical aperture) of a projection lens, increase the resolution, and transfer a finer pattern.

  As the design dimension is reduced and the processing pattern is miniaturized, the photolithography technique based on the reduced projection exposure method is approaching the limit of resolution. As a method for improving the resolution limit, in order to increase the NA (numerical aperture) of the projection lens, an immersion method in which the projection lens and the wafer are covered with a liquid such as pure water as a medium larger than the refractive index of air, Or what uses gas as a medium is known.

For example, Patent Document 1 describes a projection exposure apparatus that can adjust a refractive index by using a liquid or gas having an appropriate refractive index as a medium. The projection exposure apparatus of Patent Document 1 is shown in FIG. In this apparatus, the exposure light emitted from the light source 21 is irradiated to the condenser lens 26 via the first reflecting mirror 23, the integrator 24 and the second reflecting mirror 25. The condensed exposure light passes through the photomask 27 and the projection lens 28 and is irradiated onto the wafer 29 as exposure light. Here, the photomask 27 to the wafer support 30 are sealed by a sealing system 32 sealed with a single or a plurality of media 31. FIG. 2 shows an example in which the condensing lens 26 to the wafer are sealed by a sealing system 32 from the support portion 30. The closed system 32 is filled with a medium adjusted to an optimum refractive index by, for example, mixing water and chloroform.
JP-A-6-120113

  When the processing pattern is further miniaturized using the apparatus shown in FIG. 2 and the size thereof is set to about the exposure wavelength, the NA (numerical aperture) of the projection lens must be increased. In order to increase the NA (numerical aperture) of the projection lens in the apparatus of FIG. 3, a medium having a refractive index greater than air refractive index = 1 is required as a medium covering the projection lens and the wafer. An immersion method in which a liquid such as pure water is used as a medium covering the projection lens and the wafer, or a gas is used as the medium. However, in order to make the medium suitable, it is necessary to mix a plurality of media. Because it depends on the refractive index, it is difficult to control.

  In the present invention, the surface of the projection lens is coated with a material having a different refractive index, and an optimum medium is used to improve controllability, increase the NA (numerical aperture), and form a fine resist pattern by improving resolution. To do.

The projection exposure apparatus of the present invention includes an exposure light source of any one of g-line (456 nm), i-line (365 nm), KrF (248 nm), ArF (193 nm), F2 (156 nm), Ar2, and Kr2 excimer laser, and a light source A condensing system for condensing the exposure light from the photomask, a photomask for imaging the incident light from the condensing system on the wafer, and a projection optical system for projecting the transmitted light from the photomask onto the wafer, a support for supporting a wafer, at least alone from the projection optical system to the wafer support unit including a bottom surface or a medium consisting of two or more components is met the system, the surface of the projection lens of the projection lens, the projection lens And a material having a refractive index larger than that of the projection lens coated to increase the NA (numerical aperture) of the projection lens .

The material coated on the surface of the projection lens at this time preferably has a refractive index of 1.5 to 3.0. Crystal, sapphire, diamond, or tourmaline is preferable.

  The projection exposure apparatus of the present invention coats the projection lens with a NA (numerical aperture) of the projection exposure lens by coating the surface of the projection lens with a material having a different refractive index of the projection lens in order to increase the NA (numerical aperture) of the projection range. About 1.43 to 1.54, and the resolution can be improved by 7%. This effect corresponds to shortening of the exposure wavelength, and a finer resist pattern can be formed.

Next, embodiments of the present invention will be described.
The apparatus shown in FIG. 1 will be described as an example of the projection exposure apparatus of the present invention. In this apparatus, the light emitted from the light source 1 passes through the first reflecting mirror 2, the integrator 3, and the second reflecting mirror 4 and is applied to the condenser lens 5 that collects the exposure light from the light source. Exposure light that can be used as the light source 1 includes g-line (456 nm 4), i-line (365 nm), KrF (248 nm), ArF (193 nm), F2 (156 nm), Ar 2, Kr 2 excimer laser, electron beam, etc. Select or use. As a lens that can be used in the condensing system and the projection optical system, a known lens is used. For example, a lens composed of a plurality of lenses made of several types of optical glass can be used.

  The light irradiated on the condenser lens 5 is irradiated on the photomask 6 and irradiated on the wafer 7 through the projection lens 9 of the projection optical system 8 for projecting the transmitted light from the photomask 6 onto the wafer 7. Exposed. As the photomask 6, only a light shielding pattern is used, and a glass substrate is used as the mask substrate. Alternatively, a phase shift mask using a phase shifter can be used. As the phase shift mask, a shifter light-shielding type, an edge light-shielding type, or an edge-enhanced mask can be used. The material that can be used for the phase shift mask is not particularly limited, and glass, SOG, SiO2, or the like can be used, and Cr, CrO, MoSi, or the like can be used for the light shielding mask.

In the present invention, the projection lens 9 is included, and the projection lens system 8 to the wafer support 10 are sealed by a sealing system 12 in which a medium 11 is sealed. The sealing system 12 can be made small by using a structure in which the portion from the projection lens system 8 as close to the projection lens 9 as possible to the wafer support unit 10 is sealed. The closed system 12 is provided with an intake system 13 for inhaling the medium 11 and an exhaust system 14 for discharging, and the medium 11 entering from the inhalation system 13 flows toward the exhaust system 14 (in the drawing). The arrow indicates the flow of the medium). The flow of the medium 11 may be reversed, in which case the discharge system 14 is the suction side and the suction system 13 is the discharge side.
The medium 11 enclosed in the closed system 12 is not particularly defined because it depends on how far the incident angle of light from the projection lens is used, but it is desirable to use a medium having a refractive index of 1.5 or more. For example, cinnamon oil, quinoline, phenol, benzyl alcohol, tetralin, diiodomethane, or a medium having a large refractive index such as a liquid mainly composed of methylene iodide or an arsenic compound is used. In the present invention, these media are used alone, but a mixture of a plurality of media may be used as long as they can be mixed and the refractive index can be increased to 1.5 or more. For example, a medium having a refractive index greater than 1.7 can be obtained by adjusting the components of the liquid mainly composed of methylene iodide and the liquid mainly composed of arsenic compound.

In the embodiment of the present invention, CaF2 is used as the projection lens 9, and the surface of the projection lens 9 is coated with a refractive material 9a having a refractive index n larger than that of the medium 11 in the closed system and having a refractive index different from that of the projection lens 9. To do. The refractive material 9a can be formed by depositing a sputtering film of quartz on the surface of the projection lens 9, for example, in a vacuum chamber by using quartz as a target and irradiating and sputtering with argon ions. The quartz sputtering film is coated with a thickness of 0.1 to 1.0 μm. Further, the refractive material 9a may be formed by being deposited on the projection lens by vapor deposition.
As for the refractive material 9a to be coated, the preferable range of the refractive index n is 1.5 to 3.0, and it is desirable that the refractive index 9 is freely changed by the medium 11. The refractive index material 9a can be any material other than quartz, as long as the material has strong absorption in the wavelength region of the light source to be used, and sapphire, diamond, or tourmaline is used as a material having a refractive index n larger than 1.5. Sputtered films or vapor deposited films can be used. In the present invention, the NA (numerical aperture) can be controlled by changing the refractive material on the projection lens in accordance with the refractive index of the sealed medium.

In the embodiment of the present invention, CaF2 is used as the projection lens 9, the refractive index is 1.5, and the medium 11 of the closed system 12 is a medium having a refractive index of 1.5 or more, for example, cinnamon oil, Quartz (refractive index 1.54) was used as the material 9a for coating the projection lens 8.
By using these means, in this embodiment, the NA (numerical aperture) can be increased from about 1.43 to 1.54. The numerical aperture NA is expressed by NA = n · sin θ (where n is a refractive index and θ is a maximum incident angle). Theoretically, θ is less than 90 °, and sin (90 °) = 1. It is possible to estimate how many times the ratio n is, and the actual refractive index n in Patent Document 1 is 1.43, whereas in the above embodiment of the present invention, the refractive index of quartz is 1. 54, so 1.54 / 1.43 = 1.0769 times.
As a result, the resolution of the resist can be improved by 7%.

  In this embodiment, the reduction (× 0.4 or × 0.5) projection is used. However, the present invention is not limited to the production of semiconductor LSIs, and is the same size (× 1) and enlargement in an exposure apparatus for manufacturing processes such as liquid crystal. The present invention can also be applied to the case of (× 1.25) projection. Examples of the photomask include a mask having only a light shielding pattern, or a phase shift mask using a phase shifter. It is desirable that the resist material used can be the same as the conventional resist.

It is a projection exposure apparatus figure of this invention. It is a schematic sectional drawing of the conventional projection exposure apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 5 Condensing lens 6 Mask 7 Wafer 8 Projection lens system 9 Projection lens 9a Refractive material 10 Wafer support stand 11 Medium 12 Sealing system

Claims (3)

a light source for exposure of any of g-line (456 nm), i-line (365 nm), KrF (248 nm), ArF (193 nm), F2 (156 nm), Ar2, Kr2 excimer laser;
A light condensing system for condensing light for exposure from a light source;
A photomask for imaging the incident light from this condensing system on the wafer;
A projection optical system that projects the transmitted light from the photomask onto the wafer;
A support unit for supporting the wafer, a system from the projection optical system including the projection lens to the wafer support unit, or a system filled with a medium composed of two or more components ;
On the surface of the projection lens, a projection exposure apparatus, characterized in that it comprises <br/> a material with a high refractive index than coated the projection lens in order to increase the NA of the projection lens (numerical aperture). 2. The projection exposure apparatus according to claim 1, wherein the refractive index of the material coated on the surface of the projection lens is 1.5 to 3.0. The projection exposure apparatus according to claim 1, wherein the material coated on the surface of the projection lens is quartz, sapphire, diamond, or tourmaline.

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