JP2010117473A - Optical filter, optical system and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical filter capable of correcting the transmittance of light greatly, an optical system and an exposure apparatus. <P>SOLUTION: The optical filter 1A, which allows incident light to be transmitted therethrough to have an illuminance distribution corrected, is provided with: a glass substrate 10; an antireflection film 20A which is arranged on a first area 12A of the glass substrate 10 and contains an MgF<SB>2</SB>layer 22; and an adjustment film 30A which is arranged on a second area 14A of the glass substrate 10 and contains an LaF<SB>3</SB>layer 32. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical filter, an optical system, and an exposure apparatus.

In an exposure apparatus, it is known to use an optical filter that obtains a desired transmittance distribution by adjusting an amount of reflection using an antireflection film made of a transparent dielectric film with low light absorption. For example, Patent Document 1 discloses that an MgF ₂ film having a refractive index lower than that of glass on a glass substrate is an even multiple at the other end so that the film thickness is an odd multiple of the light source wavelength λ / 4 at one end of the glass substrate. The glass plate (optical filter) with an antireflection film formed in the above is proposed. Patent Document 2 proposes an optical filter in which the formation density of the antireflection film is changed according to the illuminance distribution on the irradiated surface.

Other conventional techniques include Patent Documents 3 to 5.
JP-A-3-40335 Japanese Patent Laid-Open No. 3-214616 JP 11-54417 A JP 2002-305137 A JP 2003-50311 A

  However, the optical filters disclosed in Patent Documents 1 and 2 have a small correction amount of the illuminance distribution of the incident light (for example, about 4 to 5% of the maximum antireflection of the substrate), and a large correction of 20% or more. I can not cope.

  SUMMARY An advantage of some aspects of the invention is that it provides an optical filter, an optical system, and an exposure apparatus that can realize large transmittance correction.

An optical filter according to one aspect of the present invention is an optical filter that corrects an illuminance distribution of the incident light by transmitting incident light, and includes a glass substrate and an antireflection film provided on the glass substrate. And an adjustment film provided on the glass substrate and including a high refractive index fluoride layer or an aluminum oxide (Al ₂ O ₃ ) layer and having a transmittance different from that of the antireflection film. To do. An optical system having such an optical filter, an exposure apparatus, and a device manufacturing method also constitute one aspect of the present invention.

  According to the present invention, it is possible to provide an optical filter, an optical system, and an exposure apparatus that can realize large transmittance correction.

The optical filter of this embodiment transmits the light (incident light) from the light source used for the exposure and obtains the illuminance distribution (or light intensity distribution) set on the illuminated surface. It has a transmittance distribution to be corrected. In this embodiment, the wavelength of light of the light source used for exposure is 248 nm, 193 nm, or 157 nm, which is the wavelength of KrF excimer laser, ArF excimer laser, or F ₂ laser, and these are hereinafter referred to as reference wavelengths. Although the wavelengths of the lasers are strictly different, the above-described wavelengths are used in the present application for convenience.

  The transmittance distribution of the optical filter of this example is not formed by the film thickness of the antireflection film as in Patent Document 1 or the density of the antireflection film as in Patent Document 2. The transmittance distribution of the optical filter of the present embodiment is formed by an antireflection film and an adjustment film that is a separate member from the antireflection film. FIG. 1A is a plan view showing an example of the transmittance distribution of the optical filter of the present embodiment, and FIG. 1B is a graph of the transmittance portion distribution corresponding to FIG. According to the present embodiment, the difference between the maximum value and the minimum value of the transmittance shown in FIG. 1B can be set to 20% or more.

The antireflection film of this embodiment is made of a transparent dielectric material with low light absorption, and includes a layer of low refractive material (low refractive index layer). Low refractive material is a fluoride, for example, a MgF _2. The refractive index of MgF ₂ (magnesium fluoride) is 1.43 at a reference wavelength of 193 nm, for example. In the present application, “transparent” means that the absorption of the material is so small that it hardly affects the correction of the illuminance distribution, and is 1/10 or less of the target range of the transmittance distribution. Antireflection film of this embodiment is a single layer of MgF _2, or, MgF ₂ layer, composed of three layers of LaF ₃ layer and MgF ₂ layers. The optical film thickness of each layer included in the antireflection film is set to an odd multiple of 1/4 of the reference wavelength λ of the incident light in order to satisfy the light interference condition required for the antireflection film. As a result, the light amount loss of incident light can be reduced.

The adjustment film of this embodiment is made of a transparent dielectric material with low light absorption, and includes a layer of high refractive material (high refractive index layer). Unlike the transmittance of the antireflection film, the transmittance of the adjustment film may be large or small. The adjustment film is composed of a single layer (high refractive index fluoride layer or aluminum oxide layer) or a multilayer film containing fluoride or aluminum oxide (Al ₂ O ₃ ) of a high refractive material. Here, the material of high refractive index fluoride layers fluoride lanthanum _(LaF 3), fluoride gadolinium _(GdF 3), fluoride neodymium _(NdF 3), fluoride samarium _(SmF 3), fluoride ytterbium (YbF ₃ ), At least one of dysprosium fluoride (DyF ₃ ). The adjustment film may further include an MgF ₂ layer or an SiO ₂ layer. Adjustment film of the present embodiment is a single layer of LaF ₃ layer, two layers of MgF ₂ layer and LaF ₃ layer, LaF ₃ layer composed of three layers of MgF ₂ layer and LaF ₃ layer. If the reference wavelength of incident light is 193 nm or 248 nm, the adjustment film may be either fluoride or aluminum oxide (Al ₂ O ₃ ). If the reference wavelength of incident light is 157 nm, the adjustment film is fluoride.

The optical film thickness of the adjustment film is not particularly limited. However, if the adjustment film includes a fluoride or aluminum oxide (Al ₂ O ₃ ) layer of a high refractive material, only the glass substrate can be adjusted by appropriate film thickness adjustment. It is also possible to increase the amount of incident light reflected (increased reflection). Therefore, the correction amount of the transmittance can be increased.

  The antireflection film and the adjustment film of this embodiment are formed on a flat glass substrate. The glass substrate of this embodiment is made of quartz, but may be fluorite (calcium fluoride). The arrangement of the antireflection film and the adjustment film on the glass substrate will be described in the examples described later. For example, at a reference wavelength of 193 nm, quartz has a refractive index of 1.56 and fluorite has a refractive index of 1.50.

  Since the optical filter of the present embodiment uses a transparent dielectric film with little absorption, the optical filter by absorption is more in comparison with optical filters using an absorptive dielectric film or metal film as in Patent Documents 3 to 5. There is little heat generation of the element, and high laser durability can be exhibited. Further, since the transmittance distribution is accurately adjusted using the adjustment film while maintaining the film thickness and density of the antireflection film, the illuminance distribution and the effective light source distribution for illuminating the original plate in the exposure can be adjusted.

  FIG. 2 is a schematic cross-sectional view of the optical filter 1A of the first embodiment. The optical filter 1A is used for light having a reference wavelength of 193 nm or 248 nm. The optical filter 1A includes a glass substrate 10, an antireflection film 20A, and an adjustment film 30A.

  The glass substrate 10 is a transparent quartz substrate.

The antireflection film 20 </ b> A is stacked on the first region 12 </ b> A on the surface of the glass substrate 10. The antireflection film 20A is configured as a fluoride film that is a transparent dielectric material with low absorption. The fluoride film of the antireflection film 20A of Example 1 is a three-layer film (multilayer film) laminated on the glass substrate 10 in the order of the MgF ₂ layer 22, the LaF ₃ layer 24, and the MgF ₂ layer 22. The optical film thickness of each film is the reference wavelength λ / 4. As shown in FIG. 3A, the antireflection film 20A is formed (evaporated) using a mask 42 having a shielding portion 42 and an opening 44 corresponding to a region where the antireflection film 20A is to be formed. .

  The adjustment film 30 </ b> A is stacked on the second region 14 </ b> A different from the first region 12 </ b> A on the surface of the glass substrate 10. As described above, in the optical filter 1A, on the glass substrate 10, the first region 12A where the antireflection film 20A is formed and the second region 14A where the adjustment film 30A is formed are spatially separated. Yes.

The adjustment film 30 </ _b > A is configured as a fluoride film that is a transparent dielectric material with low absorption. The fluoride film of the adjustment film 30 </ _b > A of Example 1 is composed of the LaF ₃ layer 32, the MgF ₂ layer 34, and the LaF ₃ layer 32. It is a three-layer film (multilayer film) laminated on the glass substrate 10 in order. The optical film thickness of each film is the reference wavelength λ / 4.

  At this time, the transmittance of the adjustment film 30A can reduce the transmittance of the antireflection film 20A by about 15 to 20%. If necessary, the transmittance distribution may be adjusted by adding a film thickness distribution to the adjustment film 30A. Thus, the film thickness of the adjustment film 30A may change in the plane. The film thickness distribution may be one layer or multiple layers. As shown in FIG. 3B, the adjustment film 30A is formed (deposited) using a shielding part 52A and a mask 50A having an opening 54A corresponding to a region where the adjustment film 30A is to be formed. In the mask 40 and the mask 50A, the pattern of the shielding part and the opening part is reversed.

  FIG. 4 is a schematic cross-sectional view of the optical filter 1B of the second embodiment. The optical filter 1B has a configuration in which the antireflection film 20B and the adjustment film 30B are separated into layers when they cannot be spatially separated into the first region 12A and the second region 14A as shown in FIG. The optical filter 1B is used for light having a reference wavelength of 193 nm or 248 nm. The optical filter 1B includes a glass substrate 10, an antireflection film 20B, and an adjustment film 30B.

The antireflection film 20 </ b> B is laminated on the entire surface of the glass substrate 10. The antireflection film 20B is configured as a fluoride film that is a transparent dielectric material with low absorption. The fluoride film of the antireflection film 20B of Example 2 is a three-layer film (multilayer film) laminated on the glass substrate 10 in the order of the MgF ₂ layer 22, the LaF ₃ layer 24, and the MgF ₂ layer 22. The optical film thickness of each film is the reference wavelength λ / 4.

The adjustment layer 31 has a shielding part 52B and a mask 50B having an opening 54B corresponding to the area where the adjustment film 30B is to be formed on a specific area on the surface of the antireflection film 20B as shown in FIG. Laminated using. The adjustment layer 31 is configured as a fluoride film that is a transparent dielectric material with low absorption, and the fluoride film of the adjustment layer 31 of this embodiment is a single layer of the LaF ₃ layer 32.

  As described above, in the optical filter 1B, the region 12B in which the antireflection film 20B is formed and the adjustment film 30B is not formed, the antireflection film 20B, and the adjustment layer are laminated on the glass substrate 10 in this order. And the region 14B where the adjustment film 30B is formed.

FIG. 6 is a graph showing the relationship between the film thickness and transmittance of the LaF ₃ layer 32 at the reference wavelength of 193 nm in the optical filter 1B shown in FIG. The horizontal axis is the film thickness (nm) of the LaF ₃ layer 32, and the vertical axis is the transmittance (%) of the optical filter 1B.

In FIG. 6, the transmittance represents a value at normal incidence with the LaF ₃ layer 32 having a thickness of 0 nm as 100%, and the transmittance decreases with an increase in the thickness of the LaF ₃ layer 32. When the film thickness is about 25 nm, the transmittance can be reduced by about 20%. Therefore, the transmittance distribution can be provided by providing the LaF ₃ layer 32 of the adjustment layer 31 with a film thickness distribution on the order of nm. Further, by providing the adjustment layer 31 that is a high refractive index material on the outermost layer of the optical filter 1B, a larger correction can be made.

To further reduce the transmittance, the adjustment layer 31 is realized by stacking a low refractive index film and a high refractive index film in multiple layers like a two-layer structure of the MgF ₂ layer 34 and the LaF ₃ layer 32. be able to. When a single layer of LaF ₃ layer 32 is used as the adjustment layer 31, the angular characteristics are not uniform as shown in FIG. By forming a multilayer film of a low-refractive index film and a high-refractive index film, the angular characteristic can be made uniform or controlled to a positive or negative angular characteristic. Here, FIG. 7 is a graph showing an incident angle characteristic when the film thickness of the LaF ₃ layer 32 included in the adjustment layer 31 of the optical filter 1B is changed. The horizontal axis is the incident angle (°) of light, the vertical axis (left side) is the transmittance (%), and the vertical axis (right side) is the film thickness of the LaF ₃ layer 32.

FIG. 8 is a graph showing the angular characteristics of transmittance when the adjustment layer 31 is formed as a three-layer film (multilayer film) of the LaF ₃ layer 32, the MgF ₂ layer 34, and the LaF ₃ layer 32. When the transmittance in the absence of the adjustment layer 31 is 100%, and the 15% transmittance is reduced at an incidence of 0 degrees, the positive angle characteristic A and the angle of almost 0 are adjusted by adjusting the film thickness of the three-layer film. A characteristic B and a negative angle characteristic C can be realized.

  FIG. 9 is a schematic cross-sectional view of the optical filter 1C of the third embodiment. The optical filter 1C also has a configuration in which the antireflection film 20C and the adjustment film 30C are separated into layers when they cannot be spatially separated into the first region 12A and the second region 14A as shown in FIG. The optical filter 1C is used for light having a reference wavelength of 193 nm or 248 nm. The optical filter 1C includes a glass substrate 10, an antireflection film 20C, and an adjustment film 30C.

First, the adjustment film 30 </ b> C is formed (deposited) on the entire surface of the glass substrate 10. The adjustment film 30 </ _b > C is configured as a fluoride film that is a transparent dielectric material with low absorption. The fluoride film of the adjustment film 30 </ _b > C of Example 3 includes the LaF ₃ layer 32, the MgF ₂ layer 34, and the LaF ₃ layer 32. It is a three-layer film (multilayer film) laminated on the glass substrate 10 in order. The optical film thickness of each film is the reference wavelength λ / 4. If necessary, the transmittance distribution may be adjusted by adding a film thickness distribution to the adjustment film 30C. Thus, the film thickness of the adjustment film 30C may change in the plane. The film thickness distribution may be one layer or multiple layers.

  The antireflection layer 21 is laminated on a specific region on the surface of the adjustment film 30C using a mask 50B shown in FIG. In this case, the opening 54B of the mask 50B corresponds to a region where the antireflection film 20C is to be formed.

  As described above, in the optical filter 1 </ b> C, the region 12 </ b> C where the adjustment film 30 </ b> C is formed and the antireflection layer 21 is not formed exists on the glass substrate 10. In addition, there is a region 14C where an antireflection film 20C in which the adjustment film 30C and the antireflection layer 21 are laminated in this order is formed.

The antireflection layer 21 is configured as a fluoride film that is a transparent dielectric material with low absorption. Fluoride film of the antireflection layer 21 of Example 3, three layers laminated on the adjustment film 30C of a single layer or a sequence of MgF ₂ layer 22, LaF ₃ layers 24, MgF ₂ layer 22 of MgF ₂ layer 22 It is a film (multilayer film). The optical film thickness of each film is the reference wavelength λ / 4.

  In Examples 1 to 3, when it is desired to adjust the transmittance in multiple stages and have a stepwise distribution, film formation may be performed a plurality of times using a mask having a different opening for each adjustment layer. The adjustment amount may be separated on both surfaces of the lens and other plural surfaces. At that time, the film material may be changed for each adjustment layer according to the adjustment amount.

  FIG. 10 is a block diagram of the exposure apparatus 100 of the present embodiment. The exposure apparatus 100 is a step-and-scan exposure apparatus, but the present invention is also applicable to a step-and-repeat exposure apparatus. The exposure apparatus 100 includes an illumination device 110, an original plate stage 120, a projection optical system 130, and a substrate stage 140. The exposure apparatus is a projection exposure apparatus that exposes an image of the pattern of the original plate M onto the substrate W via the projection optical system 130 using a light beam from a light source.

The illumination device 110 includes a light source 112 that illuminates the original plate M and emits a light beam as exposure light, and an illumination optical system 114 that uniformly illuminates the original plate. As the light source 112, the above-described ArF excimer laser, KrF excimer laser, F ₂ laser, or the like can be used. The illumination optical system 114 includes a plurality of optical elements 114a, and any of the optical filters 1A to 1C is included therein. Any of the optical filters 1 </ b> A to 1 </ b> C is disposed, for example, on the surface of the original plate M or conjugate or Fourier transform.

  The original plate M is an original plate (mask or reticle) having a circuit pattern to be exposed. The original plate stage 120 supports and moves the original plate M. The projection optical system 130 includes a plurality of optical elements 130a, maintains the original plate M and the substrate W in an optically conjugate relationship, and projects an image of the original plate pattern onto the substrate W. The substrate stage 140 supports and drives a substrate W such as a wafer or a liquid crystal substrate.

  In the exposure, the illumination optical system 114 illuminates the original plate M with the light flux from the light source 112. The exposure light transmitted through the original plate M enters the projection optical system 130, and the projection optical system 130 projects an image of the pattern of the original plate M onto the substrate W. Since any one of the optical filters 1A to 1C is provided in the illumination optical system 114, the original plate M can be illuminated with a uniform illuminance distribution and effective light source distribution. As a result, the original plate pattern is exposed on the substrate W with high resolution (for example, in a state where line width variation is suppressed).

  A method for manufacturing a device (semiconductor integrated circuit element, liquid crystal display element, etc.) includes a step of exposing a substrate (wafer, glass plate, etc.) coated with a photosensitive agent using the exposure apparatus described above, and a step of developing the substrate. And other known processes.

It is a figure which shows an example of the transmittance | permeability distribution of the optical filter of a present Example. 3 is a cross-sectional view of the optical filter of Example 1. FIG. It is a top view of the mask which manufactures the optical filter shown in FIG. 6 is a cross-sectional view of an optical filter of Example 2. FIG. It is a top view of the mask which manufactures the optical filter shown in FIG. Is a graph showing the relationship between the film thickness and the transmittance of the optical filter of the LaF ₃ layer is an adjustment layer of the optical filter shown in FIG. Is a graph showing an incident angle characteristic in the case of changing the thickness of the LaF ₃ layer is an adjustment layer of the optical filter shown in FIG. It is a graph which shows the angle characteristic of the transmittance | permeability at the time of forming the adjustment layer of the optical filter shown in FIG. 4 as a multilayer film. 6 is a cross-sectional view of an optical filter of Example 3. FIG. It is a block diagram of the exposure apparatus of Example 4.

Explanation of symbols

M Original plate W Substrate 1A, 1B, 1C Optical filter 10 Glass substrate 12A, 12B, 12C First region 14A, 14B, 14C Second region 20A, 20B, 20C Antireflection film 30A, 30B, 30C Adjustment film 21 Antireflection layer 31 Adjustment layer 22, 34 MgF ₂ layer 24, 32 LaF ₃ layer 40, 50A, 50B Mask 42, 52A, 52B Shielding portion 44, 54A, 54B Aperture 100 Exposure device 110 Illumination device 112 Light source 114 Illumination optical system 114a, 130a Optical Element 120 Original stage 130 Projection optical system 140 Substrate stage

Claims (10)

An optical filter that corrects the illuminance distribution of the incident light by transmitting the incident light,
A glass substrate;
An antireflection film provided on the glass substrate;
An adjustment film provided on the glass substrate, including a high refractive index fluoride layer or an aluminum oxide (Al ₂ O ₃ ) layer, and having a transmittance different from that of the antireflection film;
An optical filter comprising: The material of the high refractive index fluoride layer is lanthanum fluoride (LaF ₃ ), gadolinium fluoride (GdF ₃ ), neodymium fluoride (NdF ₃ ), samarium fluoride (SmF ₃ ), ytterbium fluoride (YbF ₃ ), The optical filter according to claim 1, comprising at least one of dysprosium fluoride (DyF ₃ ).   The optical filter according to claim 1, wherein a region where the antireflection film is formed and a region where the adjustment film is formed are separated on the glass substrate.   A region where the adjustment film is formed by laminating the antireflection film and the adjustment layer in this order on the glass substrate, and a region where the antireflection film is formed and the adjustment layer is not formed And the optical filter according to claim 1 or 2.   A region where the antireflection film is formed by laminating the adjustment film and the antireflection layer in this order on the glass substrate, and the adjustment film is formed and the antireflection layer is not formed The optical filter according to claim 1, wherein a region exists. The optical filter according to claim 1, wherein the adjustment film further includes a MgF ₂ layer or a SiO ₂ layer.   The optical filter according to claim 1, wherein a thickness of the adjustment film changes in a plane.   An optical system having the optical filter according to claim 1. An illumination optical system that has the optical filter according to any one of claims 1 to 7 and illuminates an original plate;
A projection optical system that projects an image of the pattern of the original plate onto a substrate;
An exposure apparatus comprising: Exposing the substrate using the exposure apparatus according to claim 9;
Developing the exposed substrate; and
A device manufacturing method characterized by comprising: