JP2011117044A - Optical thin film, production method therefor, optical multilayer film including optical thin film, optical component having optical thin film, aligner including optical component, and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical thin film containing a fluoride, which can be produced by using a general-purpose production facility, and has a fine structure that shows a high refractive index at a wave length of 200 nm or less, and to provide a production method for the optical thin film. <P>SOLUTION: The optical thin film includes fluorides of lanthanum and gadolinium, and the ratio of the number of moles of gadolinium with respect to the total number of moles of lanthanum and gadolinium is 0.01-0.95. The method for producing the optical thin film includes: preparing a substrate; preparing a vapor deposition material in which lanthanum fluoride and gadolinium fluoride are mixed so that the ratio of the number of moles of gadolinium with respect to the total number of moles of lanthanum and gadolinium becomes 0.1-0.95; and vapor-depositing the vapor deposition material on the substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical thin film and a manufacturing method thereof, an optical multilayer film including the optical thin film, and an optical component using the optical multilayer film. Furthermore, the present invention relates to an exposure apparatus and an exposure method including the optical component.

  Recent reduction projection exposure apparatuses for manufacturing semiconductors use a high-power laser as a light source, which can oscillate light in a shorter wavelength region than a mercury lamp. Examples of the laser that is a light source include a KrF excimer laser (wavelength 248 nm) and an ArF excimer laser (wavelength 193 nm). In an optical system of an exposure apparatus using a laser as a light source, it is necessary to form an antireflection film in order to reduce light loss, flare, ghost, and the like due to surface reflection of optical components such as lenses. Further, it is necessary to form a mirror for bending the optical path of the laser beam. Such an antireflection film or mirror is composed of an alternating laminate (optical multilayer film) of a dielectric thin film (optical thin film) having a high refractive index and a dielectric thin film (optical thin film) having a low refractive index. In addition, in order to exhibit the performance of the exposure apparatus, an optical thin film is used in the exposure apparatus for various purposes.

If an optical thin film (antireflection film or mirror) is made of a material that absorbs light or has a low laser resistance, it tends to cause loss of light amount due to absorption, substrate surface change due to absorption heat generation, or film destruction. For this reason, it is desirable that the material used for the optical thin film has low absorption and high laser resistance. From such a viewpoint, substances that can be used for light with a wavelength of 200 nm or less are mainly fluorine compounds such as lanthanum fluoride (LaF ₃ ) and magnesium fluoride (MgF ₂ ), and some oxides (Aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), etc.). In particular, lanthanum fluoride (LaF ₃ ) and gadolinium fluoride (GdF ₃ ) are effective as an optical thin film of a high refractive material at a wavelength of 200 nm or less.

  For the production of these fluoride thin films, a resistance heating vacuum deposition method is generally used. There are a number of methods that are more efficient than resistance heating vacuum deposition methods, such as electron beam heating vacuum deposition and sputtering, in order to form a thin film that does not have fluorine defects. A resistance heating type vacuum deposition method which is a gentle film formation method is suitable.

  Most of the optical thin films made of fluoride formed by the conventional vacuum deposition method have a columnar structure and a low density. A typical size of one column of the columnar structure is large, about 100 nm, and is as large as the wavelength of light used in an exposure apparatus for manufacturing a semiconductor, and thus causes light scattering. Further, the columnar structure has a porous structure with a very large surface area. Therefore, the surface is oxidized and hydroxylated by moisture, oxygen, etc. in the air, and this causes the fluoride film to absorb ultraviolet rays. Furthermore, since the film contains air and water vapor in the gap and is in a mixed state with fluoride crystals, the refractive index is lower than that of dense fluoride (for example, a single crystal bulk body).

  On the other hand, there is a technique for obtaining a dense film by irradiating a vapor deposition surface with a fluorine-based gas cluster ion beam during vacuum deposition to reduce the surface roughness of the fluoride thin film (Patent Document 1). In this technology, while fluoride material is electron beam evaporated, a fluorine-based gas is introduced into a deposition tank, and this is ionized to form a beam in which gas molecules are loosely bonded to each other on the deposition surface. This is a method of irradiating the light. As a result, the surface roughness of the thin film is improved, and fluorine escape in the thin film due to electron beam evaporation is prevented.

On the other hand, it is known that aluminum fluoride (AlF ₃ ), cryolite (Na ₃ AlF ₆ ), and the like are amorphous even when deposited by a vacuum deposition method, and do not take a columnar structure. For this reason, the unevenness of the surface is small, and scattering at the crystal interface inside the film is also small.

JP 2005-232534 A

  An object of an embodiment of the present invention is an optical thin film made of a fluoride that can be manufactured using a general-purpose manufacturing facility, and exhibits a higher refractive index than a conventionally used substance and has a dense structure and an optical thin film thereof It is to provide a manufacturing method. Another object of the present invention is to provide a multilayer film using an optical thin film and an optical component having the optical thin film. Furthermore, the objective of the aspect of this invention is to provide the exposure apparatus and exposure method using the optical component.

  According to the first aspect of the present invention, the optical thin film includes a fluoride of lanthanum and gadolinium, and the ratio of the number of moles of gadolinium to the total number of moles of lanthanum and gadolinium is 0.01 to 0.00. An optical thin film that is 95 is provided.

  According to the second aspect of the present invention, there is provided a method for producing an optical thin film, wherein a substrate is prepared, and a ratio of the number of moles of gadolinium to the total number of moles of lanthanum and gadolinium is 0.01 to 0.95. Preparing a vapor deposition material in which lanthanum fluoride and gadolinium fluoride are mixed, and heating and evaporating the vapor deposition material in a vacuum to deposit the vapor deposition material on the substrate. An optical thin film manufacturing method is provided.

  According to a third aspect of the present invention, there is provided an optical multilayer film including the optical thin film of the first aspect and a low refractive index thin film having a refractive index lower than that of the optical thin film.

  According to a fourth aspect of the present invention, there is provided an optical component having the optical thin film according to the first aspect on a surface.

  According to a fifth aspect of the present invention, there is provided an exposure apparatus using the optical component of the fourth aspect.

  According to the sixth aspect of the present invention, there is provided an exposure method for performing exposure using the exposure apparatus of the fifth aspect.

  According to the aspect of the present invention, the molar ratio of gadolinium to the total number of moles of lanthanum and gadolinium in the optical thin film is set to 0.01 to 0.95, thereby comprising each single component of lanthanum fluoride and gadolinium fluoride. A refractive index higher than that of the thin film can be obtained.

  The optical thin film of the aspect of the present invention does not require special equipment, and can be manufactured using conventional equipment as it is.

It is a figure which shows the relationship between the molar ratio of gadolinium with respect to the total number of moles of lanthanum and gadolinium of the vapor deposition raw material in Example 1, and the molar ratio of gadolinium with respect to the total number of moles of lanthanum and gadolinium in an optical thin film. It is a figure which shows the relationship between the molar ratio of gadolinium with respect to the total number of moles of the lanthanum and gadolinium of the vapor deposition raw material in Example 1, and the refractive index of the optical thin film with respect to the light of wavelength 550nm and 193nm. It is a SEM photograph of a cross section and the surface of the optical thin film prepared in Sample 1 (LaF ₃ single component). 2 is a SEM photograph of a cross section and a surface of an optical thin film (x = 0.5) produced in Sample 7. (A) to (d) are Sample 3 (x = 0.05), Sample 5 (x = 0.10), Sample 6 (x = 0.30), and Sample 7 (x = 0.50), respectively. It is a SEM photograph of the section of the optical thin film produced by. It is a figure which shows the relationship between the molar ratio of the gadolinium with respect to the total number of moles of the lanthanum and gadolinium of the vapor deposition raw material in Example 1, and the surface roughness of the optical thin film surface. It is a figure which shows the relationship between the molar ratio of gadolinium with respect to the total number of moles of the lanthanum and gadolinium of the vapor deposition raw material in Example 1, and the film density of an optical thin film. FIG. 4 is a diagram showing an X-ray diffraction pattern of an optical thin film produced in Example 1. It is a figure which shows the reflectance of the anti-reflective film with respect to the light of wavelength 190-250 nm simulated in Example 2. FIG. It is a figure which shows the reflectance of the dielectric mirror with respect to the light of wavelength 190-250 nm simulated in Example 3. FIG. FIG. 10 is a schematic diagram showing a configuration of an exposure apparatus in Embodiment 4. 10 is a flowchart showing a method for manufacturing a semiconductor device, including an exposure process using an exposure apparatus in Example 4. It is a flowchart which shows the manufacturing method of a liquid crystal display element including the exposure process using the exposure apparatus in Example 4. FIG.

  Next, the optical thin film of the present invention and the production method thereof will be described in detail with reference to examples.

[Preparation of deposition materials]
For the synthesis of the vapor deposition raw material, microcrystalline particles of lanthanum fluoride (LaF ₃ ) and gadolinium fluoride (GdF ₃ ) produced by a hydrothermal synthesis method described in JP-A-2009-51966 were used. LaF ₃ and LaF ₃ so that the molar ratio of gadolinium (Gd) to the total number of moles of lanthanum (La) and gadolinium (Gd) in the vapor deposition source (Gd / (La + Gd), hereinafter referred to as x as appropriate) is a predetermined value. GdF ₃ microcrystalline particles were weighed and mixed and dispersed in water. The obtained dispersion was dried to take out the powder, molded into a cylindrical pellet, and pressurized to 50 to 100 MPa by a cold isostatic pressing method (CIP method). This molded body was heated for 1 hour in an electric furnace set at a temperature of 800 to 900 ° C. and sintered at a high temperature. The sintered body was pulverized, and the pulverized pieces were classified to about 1 to 4 mm by a sieve. This crushed piece was used as a deposition material for film formation.

[Formation of optical thin film]
The optical thin film was formed by resistance heating type vacuum evaporation using a metal boat. The substrate used was parallel plate-shaped quartz glass (Φ30 mm), and was thoroughly cleaned before film formation. During film formation, vapor deposition was performed while heating the substrate to about 300 ° C. by an infrared heater. At this time, the film was formed while monitoring the vapor deposition rate and the film thickness with a crystal resonator. The deposition rate was 5 Å / s for samples 1 to 6, 2 Å / s for samples 7 to 12, and the film thickness was about 100 nm. The degree of vacuum during the deposition was 4.0 × 10 ⁻⁴ Pa.

  Table 1 shows the molar ratios of La and Gd of the vapor deposition raw materials used for forming the optical thin film in Samples 1-12.

[Comparison of composition of deposition material and optical thin film]
The molar ratio of Gd to the total number of moles of La and Gd in the optical thin films of Samples 1 to 12 was measured by energy dispersive X-ray fluorescence (EDX) analysis. FIG. 1 shows the relationship between the Gd molar ratio (horizontal axis) in the vapor deposition material and the Gd molar ratio (vertical axis) in the optical thin film produced using the vapor deposition material. In FIG. 1, since the measurement result of each sample shows a straight line with a slope of 1, it can be seen that the molar ratio of Gd in the optical thin film substantially coincides with the molar ratio of Gd in the vapor deposition material.

  From this result, it was found that an optical thin film having the same composition ratio as that of the vapor deposition material can be obtained by using a mixture having a desired composition ratio as the vapor deposition material. As in this embodiment, when the mixture is used as an evaporation source, it is not necessary to prepare two evaporation sources and control each other's evaporation rate to perform simultaneous multi-element film formation, and an optical thin film having a desired composition by a simple method. Is obtained.

[Measurement of refractive index of thin film]
The refractive indexes at wavelengths of 550 nm and 193 nm of each optical thin film were measured. The refractive index was calculated based on the Forouhi-Bloomer model from the measured spectral transmittance and reflectance of each optical thin film sample. FIG. 2 shows the relationship between the molar ratio x of Gd to the total number of moles of La and Gd and the refractive index of the optical thin film. For further comparison, the refractive index of a thin film composed of a single component of GdF ₃ and LaF ₃ obtained by the following (formula 1) in FIG. 2 is added to the average refractive index, that is, the refractive index, averaged by their molar fractions. The predicted value when the sex is established is also shown as a straight line.

ｎ_ａｖｅ：薄膜の平均屈折率
ｎ_ＬａＦ３：ＬａＦ_３薄膜の屈折率
ｎ_ＧｄＦ３： ＧｄＦ_３薄膜の屈折率

n _ave : Average refractive index of thin film n _LaF3 : Refractive index of LaF ₃ thin film n _GdF3 : Refractive index of GdF ₃ thin film

FIG. 2 shows that the refractive index of the optical thin film at the wavelength of 550 nm and the wavelength of 193 nm increases with an increase in the molar ratio x of Gd, and becomes maximum when the molar ratio x of Gd is around 0.5. The refractive index at a wavelength of 550 nm showed a refractive index higher than the average refractive index in the range where the molar ratio x of Gd exceeded 0.1 and reached 0.8. Further, the refractive index at a wavelength of 550 nm in this range is higher than the refractive index of the LaF ₃ thin film and the refractive index of the GdF ₃ thin film. The refractive index at a wavelength of 193 nm is higher than the average refractive index when the molar ratio x of Gd is in the range of 0.01 to 0.95. Further, the refractive index of the LaF ₃ thin film and the refractive index of the GdF ₃ thin film are shown. The refractive index was equal to or higher than the refractive index. From the _above, LaF 3 GDF8 ₃ based thin film, the range of the molar ratio x of at least Gd is 0.01 to 0.95, as a high refractive index material used for the following optical thin wavelength 200 nm, than conventional high refractive index material It can be seen that it has a high refractive index.

[Observation of thin film surface and cross section]
Observation of the surface and cross section of each thin film sample was performed using a high-resolution scanning electron microscope (SEM). The SEM photographs of the surface and cross section of Sample 1 (x = 0) and Sample 7 (x = 0.5) are shown in FIGS. 3 and 4, respectively. Further, SEM photographs of cross sections of Sample 3 (x = 0.05), Sample 5 (x = 0.1), Sample 6 (x = 0.3), and Sample 7 (x = 0.5) are shown in FIG. Shown in a) to (d), respectively.

As shown in FIG. 3, in the optical thin film of LaF ₃ single component having a Gd molar ratio x of 0, that is, not containing GdF ₃ , crystalline protrusions having a size of about 60 nm are densely packed. On the other hand, in the optical thin film having a Gd molar ratio x of 0.5 shown in FIG. 4, the dense protrusions are fine (about 2 to 30 nm), the boundaries of the particles are unclear, and some columns are It was fused. Furthermore, the optical thin film having a molar ratio x of Gd of 0.5 has a smaller surface roughness of the optical thin film than the thin film of LaF ₃ single component due to the change in the structure inside the thin film. I was able to observe.

  As shown in FIG. 5, the boundary between the columnar crystals becomes unclear as the molar ratio x of Gd increases, and when the molar ratio of Gd is 0.3 or more, a clear columnar structure cannot be observed, and the fine structure inside the thin film cannot be observed. It was found that the structure changed. From the above observation results, it can be seen that the gap between the columnar crystals is reduced and the thin film is densified in at least a thin film having a gadolinium molar ratio x of 0.3 or more.

_2, why LaF 3 GDF8 ₃ system refractive index of the thin film is higher than the average refractive index, as indicated by the SEM photograph of FIG. 3-5, the films La and Gd coexist of LaF ₃ single phase This is presumably because the columnar crystals found in the thin film become finer or disappear, and the film structure changes, such as the film becoming dense and voids decreasing.

[Surface roughness measurement of thin film]
Next, the surface roughness of each thin film sample was measured with a scanning probe microscope (SPM). The measurement area was 1 μm × 1 μm. FIG. 6 shows the relationship between the molar ratio x of Gd to the total number of moles of La and Gd and the surface roughness (Ra).

As shown in FIG. 6, first, when the molar ratio x of Gd increases, the surface roughness Ra decreases, and when x further increases, the surface roughness Ra starts to increase. When the molar ratio x of Gd is 0.7, it is equivalent to a thin film of LaF ₃ single component (x = 0), and Ra increases as the molar ratio x of Gd increases.

From FIG. 6, the surface roughness x of the thin film in which the molar ratio x of Gd is at least 0.7 is equal to or less than the surface roughness of the thin film of LaF ₃ single component and the thin film of GdF ₃ single component. I understand. Furthermore, when the molar ratio x of gadolinium is in the range of 0.1 to 0.5, the surface roughness is about 1 nm, about 70% with respect to the surface roughness of the thin film of GdF ₃ single component (x = 100), The surface roughness is reduced by about 35% with respect to the surface roughness of the LaF ₃ single component thin film (x = 0).

As described above, the reason why the surface roughness of the LaF ₃ -GdF ₃ thin film is small is that the columnar crystals found in the LaF ₃ thin film are fine due to the coexistence of La and Gd, as shown in the SEM photographs of FIGS. This is thought to be due to a change in the film structure, such as the formation or disappearance of the film, the film becoming dense, and the voids are reduced. The thin film surface observation results (SEM photographs of FIGS. 3 and 4) show that the surface roughness of the thin film having a Gd molar ratio x of 0.5 is smaller than that of the LaF ₃ single component thin film. This agrees with the surface roughness measurement results shown in FIG.

[Film density]
Next, the film density of each thin film was measured using the X-ray reflectivity method (XRR). FIG. 7 shows the relationship between the molar ratio x of Gd to the total number of moles of La and Gd and the film density. For further comparison, the average film density obtained by averaging the film densities of thin films composed of a single component of GdF ₃ and LaF ₃ by their molar fraction, that is, the predicted value of the film density, which is obtained by the following (Formula 2) in FIG. Is also shown as a straight line.

ρ_ａｖｅ ：薄膜の平均膜密度
ρ_ＬａＦ３：ＬａＦ_３薄膜の膜密度
ρ_ＧｄＦ３： ＧｄＦ_３薄膜の膜密度

[rho _ave: average of the thin film density _ρ LaF3: LaF ₃ thin film density ρ _GdF3: GdF ₃ thin film density

  FIG. 7 shows that the film density increases as the molar ratio x of Gd in the vapor deposition material increases, reaches a peak, and thereafter decreases as the molar ratio x of Gd increases. In addition, in all ranges where Gd and La are mixed, the film density of each thin film is higher than the theoretical film density. The thin film having a Gd molar ratio x of 0.7 was densified by about 5% of the theoretical film density.

In FIG. 7, the reason why the film density of the LaF ₃ -GdF ₃ series thin film is higher than the average film density is that the LaF ₃ single component thin film is formed by the coexistence of La and Gd as shown in the SEM photographs of FIGS. This is presumably because the columnar crystal is made finer or disappears, the film is densified, and voids are reduced.

From the above evaluation results, the following can be understood. From Figure _2, LaF 3 GDF8 ₃ based thin film, it can be seen that a LaF ₃ single component of the thin film and GdF ₃ single component thin film and a high refractive thin films or equivalent to be used as a high refractive material. Considering the use conditions of the thin film having a high refractive index, it is preferable that the thin film has a high film density and a small surface roughness in addition to the high refractive index. From FIG. 6, in order to reduce the surface roughness, the molar ratio x of Gd in the vapor deposition raw material is preferably 0.01 to 0.7, and more preferably 0.1 to 0.5. From the cross-sectional observation of the thin film shown in FIGS. 3 to 5 and the density measurement result of the thin film shown in FIG. 7, in order to improve the film density by clearly changing the crystal structure of the thin film, at least the molar ratio x of Gd is 0.3. The above is preferable. Considering the above comprehensively, in the optical thin film used as the high refractive index material, the lower limit of the molar ratio x of Gd to the total number of moles of La and Gd is preferably 0.01 or more, more preferably 0.1 or more. More preferably, it is more preferably 0.3 or more. Further, the upper limit of the molar ratio x of Gd to the total number of moles of La and Gd is preferably 0.95 or less, more preferably 0.7 or less, and even more preferably 0.5 or less. .

  Since the optical thin film of this example has a dense structure, oxidation and hydroxylation due to moisture and oxygen in the air are suppressed, and stable optical performance can be maintained over a long period of time. In addition, although it is a high-density and high-refractive-index thin film made of fluoride, it does not require a fluorine-based gas safety measure or special ion beam irradiation device, and is easily manufactured using a conventional vacuum vapor deposition device. It has the feature that it can be.

[X-ray diffraction]
Next, in order to analyze the crystal structure of each optical thin film produced in Example 1, X-ray diffraction (XRD) of each optical thin film was measured. FIG. 8 shows the XRD measurement results with the horizontal axis as the surface interval d.

In FIG. 8, the peak marked with ● represents the peak attributed to the LaF ₃ crystal, and the peak marked with x represents the peak attributed to the GdF ₃ crystal. In a thin film having a molar ratio x of Gd of 0 to 0.7, the main peak can be attributed to the XRD pattern of the LaF ₃ crystal. Further, in the thin film having the Gd molar ratio x increased and the Gd molar ratio x 0.8, a peak of the GdF ₃ crystal is observed in addition to the peak of the LaF ₃ crystal. In a thin film having a Gd molar ratio x of 0.9 to 1.0, the main peak can be attributed to the XRD pattern of the GdF ₃ crystal. Further, in a thin film having a Gd molar ratio x of 0 to 0.7, the interplanar spacing d of the (002) plane of LaF ₃ gradually decreases as the Gd molar ratio x increases.

From the above results, it can be said that the LaF ₃ -GdF ₃ -based thin film having a Gd molar ratio x of 0.7 or less is a (La, Gd) F ₃ solid solution in which Gd is solid-solved at the La site of the LaF ₃ crystal. The thin film in this range has a LaF ₃ type crystal structure. However, since Gd is dissolved in a form of replacing La, the crystal structure is distorted, and the interplanar spacing d of the (002) plane gradually decreases. Think. This distortion of the crystal structure is considered to be the cause of changes in the film structure such as columnar crystal miniaturization and film densification shown in the SEM photographs of FIGS. An optical thin film in which the molar ratio of Gd to the total number of moles of La and Gd in the optical thin film is 0.3 to 0.7 is a (La, Gd) F ₃ solid solution, and thus has a high refractive index and film density. The surface roughness is considered small.

Assuming an antireflection film composed of a multilayer film using the thin film (x = 0.5) produced in Example 1, simulation was performed on its optical characteristics. Table 2 shows the material and film thickness of each layer of the substrate and the antireflection film. Here, λ ₀ is the design center wavelength, which is 193.4 nm. The optical film thickness (refractive index n × film thickness d) is shown as a ratio to the center wavelength λ ₀ . The thin film produced in Example 1 was used for the second layer and the fourth layer. The medium was air.

As an optical characteristic of the antireflection film, the reflectance at a wavelength of 190 to 250 nm is calculated, and the result is shown in FIG. The reflectance of the antireflection film of this example is 0.002% or less at the center wavelength λ ₀ (193.4 nm), and has antireflection performance.

  The optical thin film produced in Example 1 is dense and has a high film density. Therefore, even if the antireflection film of this embodiment is formed on the lens surface having a large curvature, the deterioration of the characteristics due to the decrease in the film density, which occurs in the periphery of the lens, is reduced.

A multilayer mirror (laser mirror) using the optical thin film (x = 0.5) produced in Example 1 was assumed, and simulation was performed on its optical characteristics. The substrate was made of quartz glass, and a structure was assumed in which high refractive index materials and low refractive index materials were alternately laminated thereon 20 times. The high refractive index material and the low refractive index material were the optical thin film (x = 0.5) and magnesium fluoride prepared in Example 2, respectively. The design center wavelength λ ₀ was 193.4 nm, and any optical film thickness (refractive index n × film thickness d) was ¼ of the center wavelength λ ₀ . The medium was air.

As the optical characteristics of the multilayer mirror, the reflectance at a wavelength of 190 to 250 nm is calculated, and the result is shown in FIG. The reflectivity of the multilayer mirror of this example shows a high reflectivity of 98% or more at the center wavelength λ ₀ (193.4 nm).

  The optical thin film produced in Example 2 is dense and has a small surface roughness. Therefore, even when a multilayer mirror composed of several tens of layers is configured as in this embodiment, surface irregularities are suppressed and scattering loss is reduced as compared with the conventional optical thin film.

  Next, a device manufacturing method including an exposure apparatus and an exposure method using the optical lens on which the antireflection film of Example 2 is formed and the multilayer mirror of Example 3 will be described.

[Exposure equipment]
As shown in FIG. 11, the exposure apparatus 100 mainly includes a light source 1, an illumination optical system IL, a reticle stage RS that holds a reticle R, a projection optical system PL, and a wafer stage WS that holds a wafer W. FIG. 11 shows the reference optical axis AX of the projection optical system PL. In FIG. 11, the Z axis is parallel to the reference optical axis AX of the projection optical system PL, the Y axis is parallel to the paper surface of FIG. 11 in the plane perpendicular to the reference optical axis AX, and the X axis is perpendicular to the paper surface of FIG. Are set respectively.

  The light source 1 includes an ArF excimer laser light source that supplies illumination light in the ultraviolet region. The light emitted from the light source 1 illuminates the reticle R on which a predetermined pattern is formed in a superimposed manner via the illumination optical system IL. The optical path between the light source 1 and the illumination optical system IL is sealed with a casing (not shown), and the space from the light source 1 to the optical member closest to the reticle in the illumination optical system IL absorbs exposure light. It is replaced with an inert gas such as helium gas or nitrogen, which is a low-rate gas, or is kept in a substantially vacuum state.

  The reticle R is held parallel to the XY plane on the reticle stage RS via the reticle holder RH. A pattern to be transferred is formed on the reticle R, and a rectangular (slit-like) pattern region having a long side along the X direction and a short side along the Y direction is illuminated in the entire pattern region. Is done. Reticle stage RS can be moved two-dimensionally along the reticle plane (ie, XY plane) by the action of a drive system (not shown), and its position coordinates are measured by interferometer RIF using reticle moving mirror RM. And the position is controlled.

  Light from the pattern formed on the reticle R forms a reticle pattern image on the wafer W, which is a photosensitive substrate, via the projection optical system PL. The wafer W is held parallel to the XY plane on the wafer stage WS via the wafer holder table WT. A rectangular exposure area having a long side along the X direction and a short side along the Y direction on the wafer W so as to optically correspond to the rectangular illumination area on the reticle R. A pattern image is formed. The wafer stage WS can be moved two-dimensionally along the wafer surface (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are measured by an interferometer WIF using a wafer moving mirror WM. In addition, the position is controlled.

  The illumination optical system IL of this embodiment includes a mirror optical system 2 composed of a plurality of mirrors that reflect the exposure light from the light source 1. For the mirror optical system 2, the multilayer mirror of Example 3 is used. Further, the projection optical system PL of the present embodiment includes a lens optical system 3 composed of a plurality of lenses. The antireflection film of Example 2 is formed on the surface of the lens of the lens optical system 3.

  Since the optical system constituting the exposure apparatus of this embodiment includes the antireflection film of Embodiment 2 and the multilayer mirror of Embodiment 3, the reflection loss and the scattering loss are reduced as compared with the conventional optical system, and durability is improved. It is excellent in nature. Therefore, the exposure apparatus of this embodiment has a feature that it has a higher throughput than the conventional exposure apparatus and can be operated stably for a long period of time.

[Device Manufacturing Method Including Exposure Method]
The above-described exposure apparatus 100 illuminates a mask (reticle R) with the light source 1 and the illumination optical system IL (illumination process), and transfers a transfer pattern formed on the mask using the projection optical system PL to a photosensitive substrate (wafer). W) can be exposed (exposure process). By developing, processing and assembling the exposed substrate, a microdevice (semiconductor element, imaging element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured.

  Hereinafter, a method of manufacturing a semiconductor device as a micro device including the step of exposing a predetermined circuit pattern onto the wafer W using the exposure apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG.

  First, in step 1 of FIG. 12, a metal film is deposited on the wafer. In the next step 2, a photoresist is applied on the metal film on the wafer. Thereafter, in step 3, the exposure apparatus 100 shown in FIG. 11 is used to sequentially expose and transfer the pattern image on the mask to each shot area on the wafer via the projection optical system. Then, after developing the photoresist on the wafer in step 4, etching is performed on the wafer using the resist pattern as a mask in step 5. Thereby, a circuit pattern corresponding to the pattern on the mask is formed in each shot area on each wafer. Thereafter, devices such as semiconductor elements are manufactured by forming a circuit pattern of an upper layer.

  In steps 1 to 3, a metal is vapor-deposited on the wafer, a resist is applied on the metal film, and exposure, development, and etching processes are performed. Prior to these processes, on the wafer. After forming a silicon oxide film, a resist may be applied on the silicon oxide film, and the steps such as exposure, development, and etching may be performed.

  Furthermore, a liquid crystal display element as a micro device can be manufactured by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate) using the exposure apparatus 100 of the present embodiment. . Hereinafter, a description will be given with reference to the flowchart of FIG. In FIG. 13, the pattern forming process (step 11) is a so-called photolithography process in which the exposure pattern 100 of the present embodiment is used to transfer and expose a mask pattern onto a photosensitive substrate (such as a glass substrate coated with a resist). Executed. By this photolithography process, a predetermined pattern including a plurality of electrodes and the like is formed on the photosensitive substrate. Thereafter, the exposed substrate is subjected to processes such as a developing process, an etching process, and a resist stripping process, whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming process (step 12).

  In the color filter forming step (step 12), a plurality of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix or three of R, G, and B A color filter is formed by arranging a plurality of stripe filter sets in the horizontal scanning line direction. Then, after the color filter forming step (step 12), a cell assembling step (step 13) is executed. In the cell assembly process (step 13), a liquid crystal panel (liquid crystal cell) is assembled using the substrate having a predetermined pattern obtained in the pattern formation process, the color filter obtained in the color filter formation process, and the like. In the cell assembly process, for example, liquid crystal is injected between the substrate having the predetermined pattern obtained in the pattern formation process and the color filter obtained in the color filter formation process to manufacture a liquid crystal panel (liquid crystal cell). To do.

  Thereafter, in the module assembling step (step 14), components such as an electric circuit and a backlight for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) are attached to complete a liquid crystal display element.

  In this embodiment, a step-and-scan type exposure apparatus that scans and exposes a mask pattern to each exposure region of the substrate while moving the mask and the substrate relative to the projection optical system is used. . However, the present invention is not limited to this, and the mask pattern is collectively transferred to the substrate while the mask and the substrate are stationary, and the mask pattern is sequentially exposed to each exposure region by sequentially moving the substrate stepwise. An AND / REPEAT type exposure apparatus can be used. Further, in this embodiment, the example using the exposure apparatus including the optical lens on which the antireflection film of Embodiment 2 is formed and the multilayer mirror of Embodiment 3 is described, but the optical thin film according to the embodiment of the present invention is provided. An exposure apparatus in which the optical component is only one of an optical lens or a multilayer mirror can also be used.

DESCRIPTION OF SYMBOLS 100 Exposure apparatus 1 Light source 2 Mirror optical system 3 Lens optical system IL Illumination optical system R Reticle RS Reticle stage PL Projection optical system W Wafer WS Wafer stage AX Reference optical axis RH Reticle holder RS Reticle stage RM Reticle moving mirror RIF Interferometer WT Wafer Holder table WM Wafer moving mirror WIF interferometer

Claims (16)

An optical thin film,
Including fluoride of lanthanum and gadolinium,
An optical thin film in which the ratio of the number of moles of gadolinium to the total number of moles of lanthanum and gadolinium is 0.01 to 0.95.   2. The optical thin film according to claim 1, wherein a ratio of the number of moles of gadolinium to the total number of moles of lanthanum and gadolinium is 0.3 to 0.7. The optical thin film according to claim 1 or 2, wherein the fluoride is a (La, Gd) F ₃ solid solution.   The optical thin film according to any one of claims 1 to 3, wherein a refractive index of the optical thin film is higher than a refractive index of a thin film made of only lanthanum fluoride and higher than a refractive index of a thin film made of only gadolinium fluoride.   The optical thin film according to any one of claims 1 to 4, wherein the surface roughness of the optical thin film is smaller than the surface roughness of the thin film made of only lanthanum fluoride and smaller than the surface roughness of the thin film made of only gadolinium fluoride. . An optical thin film manufacturing method comprising:
Preparing a substrate,
Preparing a deposition material in which lanthanum fluoride and gadolinium fluoride are mixed so that the ratio of the number of moles of gadolinium to the total number of moles of lanthanum and gadolinium is 0.1 to 0.95;
The manufacturing method of an optical thin film including vapor-depositing the said vapor deposition raw material on the said base material. The optical thin film according to any one of claims 1 to 5,
An optical multilayer film comprising a low refractive index thin film having a refractive index lower than that of the optical thin film.   8. The optical multilayer film according to claim 7, which is a multilayer film in which the optical thin film and the low refractive index thin film are alternately laminated.   The optical multilayer film according to claim 8, wherein the optical multilayer film is an antireflection film.   The optical component which has the said optical thin film as described in any one of Claims 1-5 on the surface.   The optical component which has the said optical multilayer film as described in any one of Claims 7-9 on the surface.   The optical component according to claim 11, wherein the optical component is a lens.   The optical component according to claim 11, wherein the optical component is a laser mirror.   An exposure apparatus comprising the optical component according to claim 10. The exposure apparatus includes:
A laser light source having a wavelength of 200 nm or less;
An illumination optical system having a laser mirror that reflects the laser light in a desired direction;
A mask stage for holding a mask on which a predetermined pattern is formed;
A projection optical system having a plurality of lenses, and a substrate stage for holding a substrate on which the mask pattern is projected,
The exposure apparatus according to claim 14, wherein the laser mirror and / or the lens is the optical component.   An exposure method for performing exposure using the exposure apparatus according to claim 14.

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