JP2004140390A - Illumination optical system, exposure device and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination optical system and an exposure device, illuminating a region to be illuminated at a uniform illuminance, in which centroid of intensity of a light ray made incident on the region to be illuminated is accorded with a center of the light ray, and to provide a method for manufacturing a device using them. <P>SOLUTION: The illumination optical system illuminating a surface to be illuminated with a light whose wavelength from a light source is 200 nm or less comprises: a field stop provided with an opening for defining a illuminating region of the surface to be illuminated; a reflective optical system which images the opening on the surface to be illuminated by using a light flux which has passed through the opening of the field stop; and an adjusting mechanism which adjusts an angle of a main light ray of the light flux, made incident on the surface to be illuminated, to the surface to be illuminated. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an illumination optical system, and particularly to a single crystal substrate for a semiconductor wafer and a liquid crystal display (LCD) using a light source in an extreme ultraviolet region (EUV: extreme ultraviolet) having a wavelength of 200 nm to 10 nm or an X-ray region as a light source. The present invention relates to an illumination optical system for exposing an object to be processed, such as a glass substrate, an exposure apparatus, and a device manufacturing method.

縮小 As a method of manufacturing a semiconductor circuit element having a fine pattern, there is, for example, a reduction projection exposure method using EUV light having a wavelength of 13.4 nm. In this method, a mask or a reticle on which a circuit pattern is formed (in the present application, these are used interchangeably) is illuminated with EUV light, an image of the pattern on the mask is reduced and projected on a wafer surface, and the surface of the mask is resized. The pattern is transferred by exposing the resist.

Resolution R of the projection exposure apparatus, the wavelength of the exposure light source lambda, given by the following equation using the numerical aperture (NA) and the proportionality constant k ₁ of the exposure apparatus.

Further, means a focal range that can maintain a constant imaging performance and depth of focus, depth of focus DOF is given by the following equation using the proportional constant k _2.

FIG. 18 shows an outline of a main part of a conventional EUV reduction projection exposure apparatus 1000. In FIG. 18, reference numeral 1001 denotes an emission point of EUV light, 1002 denotes an EUV light flux, 1003 denotes a filter, 1004 denotes a first paraboloid of revolution, 1005 denotes a reflection type integrator, 1006 denotes a second paraboloid of revolution, 1007 Denotes a reflection type mask, 1008 denotes a plurality of mirror systems constituting a projection optical system, 1009 denotes a wafer, 1010 denotes a mask stage, 1011 denotes a wafer stage, 1012 denotes an arc-shaped aperture, 1013 denotes a laser light source, and 1014 denotes a laser focusing optical system. Reference numeral 1017 denotes a vacuum container. FIG. 19 is a plan view showing a relationship between an illumination area 1015 on the mask 1007 and an arc-shaped area 1016 on which exposure is performed.

As described above, the exposure apparatus 1000 includes the light source units 1013 and 1014 that generate EUV light, the illumination optical system (that is, the first rotating parabolic mirror 1004, the reflective integrator 1005, and the second rotating parabolic mirror 1006). ), A reflective mask 1007, a projection optical system 1008, a wafer 1009, a stage 1010 on which a mask is mounted, a stage 1011 on which a wafer is mounted, an alignment mechanism (not shown) for precisely adjusting the positions of the mask and the wafer, and a method for preventing EUV light attenuation. It comprises a vacuum vessel 1017 for keeping the entire optical system in a vacuum and an exhaust device (not shown).

The illumination optical system converges EUV light 1002 from the light emitting point 1001 with a first rotating parabolic mirror 1004 and irradiates it with a reflective integrator 1005 to form a secondary light source. The EUV light is condensed by the second paraboloid of revolution mirror 1006 so as to be superimposed, and the mask 1007 is uniformly illuminated.

The reflective mask 1007 is formed by forming a transfer pattern in which a non-reflective portion made of an EUV absorber or the like is provided on a multilayer film reflective mirror. The EUV light having the information of the circuit pattern reflected by the reflective mask 1007 forms an image on the surface of the wafer 1009 by the projection optical system 1008.

(4) The projection optical system 1008 is designed such that a thin arc-shaped region off axis with respect to the center of the optical axis has good imaging performance. Therefore, an aperture 1012 having an arc-shaped opening is provided immediately before the wafer 1009 so that only the thin arc-shaped region is used for exposure. Then, in order to transfer the pattern on the entire surface of the mask having the rectangular shape, the reflection type mask 1007 and the wafer 1009 are simultaneously scanned and exposed.

Here, the projection optical system 1008 is configured by a plurality of multilayer film reflecting mirrors and configured to reduce and project the pattern on the mask 1007 onto the surface of the wafer 1009, and usually uses an image-side telecentric system. It should be noted that the object side (reflective mask side) is usually of a non-telecentric configuration in order to avoid physical interference with the illumination light beam incident on the reflective mask 1007.

The laser light from the laser light source 1013 is condensed by a laser condensing optical system 1014 on a target (not shown) at the position of the light emitting point 1001 to generate a high temperature plasma light source. EUV light 1002 emitted from the plasma light source by thermal radiation is reflected by the first rotating parabolic mirror 1004 to become a parallel EUV light flux. This light beam is reflected by the reflection type integrator 1005 to form a number of secondary light sources.

(4) The EUV light from the secondary light source is reflected by the second paraboloid of revolution mirror 1006 to illuminate the reflective mask 1007. Here, the distance from the secondary light source to the second rotating parabolic mirror 1006 and the distance from the second rotating parabolic mirror 1006 to the reflective mask 1007 are equal to the focal length of the second rotating parabolic mirror 1006. Is set.

(4) Since the focal point of the second rotating parabolic mirror 1006 is located at the position of the secondary light source, EUV light emitted from one of the secondary light sources irradiates the reflective mask 1007 with a parallel light beam. This fills the Koehler illumination. That is, the EUV light that illuminates one point on the reflective mask 1007 is an overlap of the EUV light emitted from all the secondary light sources.

As shown in FIG. 19, the illumination region 1015 on the mask surface is similar to the planar shape of the reflection surface of the convex or concave mirror which is a component of the reflection type integrator 1005, and the arc region 1016 where exposure is actually performed is formed. It is a substantially rectangular area that includes. The projection optical system 1008 is designed such that an image of the secondary light source is projected on the entrance pupil plane of the projection optical system 1008.

In addition, various proposals have been made regarding exposure apparatuses that use EUV light as exposure light (for example, see Patent Documents 1 to 3).

JP 07-235472 A JP-A-10-70058 JP-A-11-312638

(4) The circular arc region of the mask 1007 needs to be illuminated without illuminance unevenness. In addition, it is necessary to match the center of the light intensity of the light beam incident on the circular arc region with the center of the light beam. However, in the conventional EUV reduction projection exposure apparatus 1000, these conditions are not always satisfied. Therefore, if the center of gravity of the light beam does not coincide with the center at a certain point in the circular arc region, the effect is substantially the same as that of the principal ray of the illumination light having been shifted from the desired direction, and the mask pattern can be exposed normally. Had the problem of disappearing.

Further, as shown in FIG. 19, the mask 1007 is irradiated with EUV light on a substantially rectangular area 1015 including an arc area 1016 on which exposure is actually performed. The light was shielded by the arcuate aperture 1012 and wasted. That is, the conventional EUV reduction projection exposure apparatus 1000 has a problem that the exposure time is long because the loss of the exposure light amount is extremely large, and the throughput cannot be increased.

Further, the conventional EUV reduction projection exposure apparatus 1000 has a problem that the optical axis of the reflected light from the mask 1007 does not coincide with the optical axis of the projection optical system 1008, and the reflected light is vignetted by the projection optical system 1008. I was

Therefore, an object of the present invention is to provide an illumination optical system, an exposure apparatus, and an exposure apparatus that illuminate an illuminated area with uniform illuminance and match the center of light intensity of a light ray incident on the illuminated area with the center of the light ray. An object of the present invention is to provide a device manufacturing method.

Another object of the present invention is to provide an illumination optical system, an exposure apparatus, and a device manufacturing method using the same, which reduce the loss of light amount, shorten the exposure time, and improve the throughput.

Still another object of the present invention is to provide an illumination optical system, an exposure apparatus, and a device manufacturing method using the same, in which the optical axis of light reflected from a mask coincides with the optical axis of a projection optical system.

In order to achieve the above object, an illumination optical system according to one aspect of the present invention defines an illumination area of the illumination surface in an illumination optical system that illuminates the illumination surface with light having a wavelength of 200 nm or less from a light source. A field stop provided with an opening for light, a reflection optical system that forms an image of the opening on the surface to be illuminated with a light beam passing through the opening of the field stop, and a principal ray of a light beam incident on the surface to be illuminated. And an adjusting mechanism for adjusting an angle with respect to the illuminated surface.

According to another aspect of the present invention, there is provided an illumination optical system for illuminating a surface to be illuminated with light having a wavelength of 200 nm or less from a light source, wherein a reflection type integrator and a plurality of light beams from the reflection type integrator are received by the illumination optical system. A condenser mirror superimposed on the illumination surface, a reflection optical system for guiding light from the condenser mirror to the surface to be illuminated, and an adjustment for adjusting an angle of a principal ray of a light beam incident on the surface to be illuminated with respect to the surface to be illuminated. And a mechanism.

An exposure apparatus as still another aspect of the present invention illuminates a pattern formed on a reticle or a mask with light from a light source by the above-described illumination optical system, and projects the pattern onto a target object by a projection optical system. It is characterized by the following.

A device manufacturing method as still another aspect of the present invention includes a step of exposing a substrate with a device pattern using the above-described exposure apparatus, and a step of performing a predetermined process on the exposed substrate. I do.

Other objects and further features of the present invention will become apparent by preferred embodiments described below with reference to the accompanying drawings.

According to the illumination device and the exposure device of the present invention, uniform circular illumination can be performed with high efficiency, and illuminance unevenness can be eliminated. Further, even if the light source fluctuates, the influence on the exposure can be removed by stabilizing the incident angle of the light beam on the irradiated surface.

Hereinafter, the exposure apparatus 10 according to the first embodiment of the present invention will be described in detail with reference to the accompanying drawings. The exposure apparatus 10 of the present invention is a projection exposure apparatus that performs step-and-scan exposure using EUV light (for example, a wavelength of 13.4 nm) as illumination light for exposure. The exposure apparatus 10 includes a light source unit 100, an illumination optical system 200, a mask 300, a projection optical system 400, and an object 500, as shown in FIG. The exposure apparatus 10 further includes a mask stage 350 on which the mask 300 is mounted, and a wafer stage 550 on which the object 500 is mounted. The mask stage 350 and the wafer stage 550 are connected to a control unit (not shown). Drive control. The light source unit 100 and the illumination optical system 200 constitute an illumination device. Here, FIG. 1 is a schematic diagram of the exposure apparatus 10.

Since the transmittance of EUV light to the atmosphere is low, the exposure apparatus 10 stores the light source unit 100 in the vacuum container 12 and stores the remaining components 200 to 550 in the vacuum container 14. However, the present invention includes a case where at least an optical path through which EUV light passes is maintained in a vacuum atmosphere.

The light source unit 100 generates EUV light from the plasma light emitting point 120. The light source unit 100 includes a nozzle 130 for ejecting a droplet serving as a target for plasma generation, a droplet collecting unit 140 for collecting and reusing a droplet that has not been irradiated with the excitation laser light, and a spheroid mirror 150. And a filter 170.

(4) The high-output excitation pulse laser beam 110 emitted from an excitation laser section including an excitation laser light source and a condensing optical system (not shown) is configured to be condensed at a position of a light emitting point 120. In addition, a droplet (for example, Xe) serving as a target of the laser plasma light source is continuously ejected from the nozzle 130 at fixed time intervals, and passes through the focal point 120. When the droplet ejected as described above comes to the position of exactly 120, the excitation pulse laser beam 110 irradiates the droplet to generate a high-temperature plasma emission point 120, and the thermal radiation from the plasma is generated. Generates EUV light radially.

In this embodiment, a droplet of Xe is used as a target. However, as a target, a cluster generated by adiabatic expansion by injecting Xe gas from a nozzle into a vacuum or a solid formed by cooling Xe gas on a metal surface is used. Alternatively, a tape using a metal such as Cu may be selected. In the present embodiment, the EUV light is generated using the laser plasma method, but an undulator may be used as the EUV light source. Further, as a method for producing EUV light, a discharge method such as a Z-pinch method, plasma focus, capillary discharge, and hollow cathode triggered Z-pinch may be used.

Ｅ The EUV light emitted from the plasma emission point 120 is condensed by the spheroidal mirror 150 and extracted as an EUV light beam 160. The spheroidal mirror 150 is formed with a reflective multilayer film for efficiently reflecting EUV light. The spheroidal mirror 150 becomes high in temperature during exposure to partially absorb radiant energy from the high-temperature plasma 120. For this purpose, a material such as a metal having a high thermal conductivity is used as a material, and a cooling means (not shown) is provided so that the material is constantly cooled. The filter 170 cuts plasma and particles scattered from the periphery (debris), and cuts a wavelength unnecessary for EUV exposure. The EUV light beam 160 is introduced into the illumination optical system 200 of the vacuum container 14 from a window 210 provided at the boundary between the vacuum containers 12 and 14. The window 210 has a function of passing the EUV light beam 160 while maintaining a vacuum.

The illumination optical system 200 uniformly illuminates the mask 300 with arc-shaped EUV light corresponding to the arc-shaped field of view of the reflection-type reduction projection optical system 400, and rotates the paraboloid mirrors 220 and 260 and the paraboloid mirror 240. , Reflection type integrators 230 and 250, a masking blade 270, relay optical systems 282 to 286 (hereinafter collectively referred to as “280” unless otherwise specified), and a correction mechanism 290.

The paraboloid-of-rotation mirror 220 reflects the EUV light beam 160 introduced from the window 210 to form a parallel light beam 222. Next, the EUV light 222 that has become a parallel light beam is incident on a reflective convex cylindrical surface integrator 230 having a plurality of convex cylindrical surfaces 232. EUV light radiated from the secondary light source formed by each cylindrical surface 232 of the integrator 230 is condensed and superimposed by the parabolic mirror 240, so that the reflective integrator 250 having the plurality of convex cylindrical surfaces 252 is formed. It is possible to illuminate the cylinder alignment direction with a substantially uniform intensity distribution.

The reflective integrator 230 has a plurality of cylindrical surfaces, and illuminates the reflective integrator 250 uniformly (that is, substantially Koehler illumination as described later) together with the paraboloid of revolution 240. Accordingly, the light intensity distribution in the radial direction of the arc illumination region described later can be made uniform, and the effective light source distribution from the reflective integrator 250 can be made uniform. The reflection type integrators 230 and 250 may be replaced by a fly-eye mirror 230A in which a large number of minute convex or concave spherical surfaces having a repetition period are two-dimensionally arranged as shown in FIG.

The reflection type integrator 250 has a plurality of cylindrical surfaces and illuminates the mask surface uniformly. Here, the principle of uniformly illuminating the arc region by the integrator 250 will be described in detail with reference to FIGS. Here, FIG. 2A is a schematic perspective view when parallel light is incident on an integrator 250 having a plurality of reflective convex cylindrical surfaces 252. The incident direction of the light beam represents the case of the integrator 250. FIG. 2B is a schematic perspective view of an integrator 250A having a plurality of reflective concave cylindrical surfaces 252A having the same effect as that of FIG. 2A. The integrator 230 has the same structure as the integrator 250 having the reflective convex cylindrical surface 252 shown in FIG. Both the integrators 230 and 250 may be replaced by an integrator 250A having a reflective concave cylindrical surface 252A shown in FIG. 2B, or may be configured by a combination of these irregularities.

As shown in FIG. 2A, when a substantially parallel EUV light beam is incident on a reflective integrator 250 having a plurality of cylindrical surfaces 252, a secondary light source is formed by the integrator 250 and emitted from the secondary light source. The angular distribution of the EUV light becomes conical. Next, by illuminating the mask 300 or a surface conjugate with the mask 300 by reflecting the EUV light with a reflecting mirror having a focal point at the position of the secondary light source, arc-shaped illumination becomes possible.

FIG. 3 is a partially enlarged view of the integrator 250 having the reflective convex cylindrical surface 252, and FIGS. 4A and 4B are EUV light on the cylindrical surface 252 of the integrator 250 having the reflective convex cylindrical surface 252. FIG. 5 is a perspective view and a vector diagram for explaining reflection, and FIG. 5 is a diagram for explaining the angular distribution of EUV light reflected on the cylindrical surface 252 of the integrator 250 having the reflective convex cylindrical surface 252.

In order to explain the operation of the reflective integrator 250 having a plurality of cylindrical surfaces 252, first, the behavior of reflected light when parallel light enters one cylindrical reflecting mirror will be described with reference to FIG. Now, as shown in FIG. 4A, consider a case where parallel light is incident on one cylindrical surface at an angle of θ with respect to a plane (xy plane) perpendicular to the Z axis which is the central axis. The light vector parallel incident light is P _1, the normal vector of the reflecting surface of the cylindrical surface shape with n, P ₁ and n are defined by the following vector equation. For convenience, except that are designated in particular, the arrows are omitted representing the vector to be added to the head of such P ₁ and n.

Referring to FIG. 4 (b), the orthogonal projection vector of the n of -P ₁ When a, a is represented by the following equation.

Further, ray vector of the reflected light P ₂ is given by the following equation.

From Equation 5 and 6, _{P 2} is given by the following equation.

In this case the vector obtained by projecting the ray vector of the reflected light P ₂ in the xy plane to is Q,
Q is given by the following equation.

Thus, when plotted in the phase space shown in FIG. 5, Q exists in a range of -2φ ≦ 2α ≦ 2φ on the circumference of the radius R = cos θ. That is, the reflected light P ₂ becomes a conical shape of the divergent light, so that the secondary light source is present at the position of the apex of the conical surface. This secondary light source exists as a real image outside the reflecting surface if the cylindrical surface is concave, and exists as a virtual image inside the reflecting surface when the cylindrical surface is convex.

Also, though the reflecting surface, as shown in FIG. 3 is limited to a part of a cylindrical surface, when the central angle of 2φ is light base vector of the reflected light P _2, as shown in FIG. 5 xy plane Above is a circular arc having a central angle of 4φ.

Next, parallel light is incident on a reflecting mirror consisting of a part of a cylindrical surface. The rotating parabolic reflecting mirror having a focal length f and having a focal point at the position of the secondary light source, Let us consider a case where the irradiated surface is arranged at a position separated by f. The light emitted from the secondary light source becomes divergent light having a conical surface, is reflected by a reflecting mirror having a focal length f, and becomes parallel light. The reflected light at this time is a sheet beam having an arc-shaped cross section with a radius f × cos θ and a central angle of 4φ. Therefore, only an arc-shaped region having a radius f × cos θ and a central angle 4φ on the irradiated surface is illuminated.

So far, one cylindrical surface reflecting mirror has been described. Next, as shown in FIG. 2A, a large-area integrator 250 in which a large number of cylindrical surfaces 252 are arranged in parallel is provided. Consider the case where light is incident in the illustrated direction. As in the previous example, if the rotating parabolic reflector and the mask 300 are arranged, the angular distribution of light reflected by the mirror having a large number of cylindrical surfaces arranged in parallel is the same as in the previous example. On the mask 300, an arc-shaped region having a radius of f × cos θ and a central angle of 4φ is illuminated. In addition, since light incident on one point on the mask 300 reaches from the entire irradiation area of the reflecting mirror in which a large number of cylindrical surfaces are arranged in parallel, the angular spread is D / f. The numerical aperture NA is given by sin θ, and the numerical aperture of the illumination optical system 200 is D / (2f). Assuming that the numerical aperture on the mask 300 side of the projection optical system 400 is NAp1, the coherence factor σ is σ = D / (2fNAp1). Therefore, the optimum coherence factor σ can be set according to the thickness of the parallel light incident on the integrator 250.

The principle of illuminating the arc region by the integrator 250 described above and the main configuration of the present embodiment that can more effectively and uniformly illuminate the arc region using the integrator 230 are described in FIG. This will be described in detail below with reference to FIG.

In FIG. 6, the linear directions 235 of the plurality of convex cylindrical reflecting surfaces 232 of the integrator 230 are arranged in a direction perpendicular to the paper surface. In the drawing, reference numeral 233 denotes a lower surface of the integrator 230. The linear directions 255 of the plurality of convex cylindrical reflecting surfaces 252 of the integrator 250 are arranged in a direction parallel to the paper surface. In the figure, reference numeral 253 denotes an upper surface of the integrator 250.

As described above, it is an important point of this embodiment that the spatial arrangement of the two integrators 230 and 250 is such that the alignment directions 235 and 255 of the convex cylindrical reflecting surfaces 232 and 252 are orthogonal to each other. As shown, more uniform arc illumination is possible.

When the substantially parallel EUV light flux 222 is incident on the reflection surface 231 of the integrator 230 as shown in FIG. 6, that is, perpendicular to the direction 235, a virtual image of the secondary light source is generated inside the integrator 230, and EUV light is reflected by the target small predetermined divergence angle theta ₁ from each secondary light source. The diverging EUV light is incident on the reflection surface 251 of the integrator 250 via the parabolic mirror 240 as a substantially parallel light beam.

The parabolic mirror 240 is arranged so that its focal position substantially coincides with the reflection surface 231 of the integrator 230, and the reflected light from each cylindrical surface 232 on the reflection surface 231 is reflected on the reflection surface 251 of the integrator 250. Each is set to overlap. The parabolic mirror 240 needs to have a parabolic cross-section because the light intensity distribution in the longitudinal direction of the cylindrical reflecting surface 251 of the integrator 250 only needs to be uniform, but does not necessarily need to be a rotating parabolic mirror. . In this way, the parabolic mirror 240 is arranged on the reflection surface 251 of the integrator 250 so as to be almost Koehler illumination. With such an arrangement, a more uniform intensity distribution is formed on the reflection surface 251 of the integrator 250, particularly in the direction of 255.

The EUV light beam reflected by the integrator 250 having the plurality of convex cylindrical reflection surfaces 252 is condensed by the paraboloid of revolution 260 as described in detail with reference to FIGS. A uniform circular illumination area is formed on the masking blade 270 disposed at the position of the focal length f.

The masking blade 270 has a light-shielding portion 272 made of a material that absorbs EUV light, and a desired arc-shaped opening 274 optimal for exposure as shown in a front view partially shown in FIG. The masking blade 270 shields unnecessary stray light that does not contribute to arc illumination and satisfactorily reduces illuminance unevenness by setting a desired slit width or partially changing the slit width by a slit width variable mechanism (not shown). It has a function to correct.

With the above-described configuration, in the circular arc illumination region, in the angular direction (that is, the θ direction) along the circular arc, a plurality of light beams from the plurality of cylindrical surfaces 252 of the integrator 250 are superimposed so that the uniformity is obtained. Is achieved, and in the radial direction perpendicular to the arc (that is, the r direction), the uniformity is achieved by superimposing a plurality of light beams from the integrator 230. As a result, it is possible to perform a uniform arc illumination that is significantly more efficient and more uniform than before.

The EUV light flux that has passed through the arc-shaped opening of the masking blade 270 is converted into a desired magnification by the relay optical system 280, and then forms an arc illumination area on the reflective mask 300 held on the mask stage 350. Perform arc lighting. The relay optical system 280 formed by a plurality of mirror surfaces has a function of enlarging or reducing the arc shape at a predetermined magnification.

The correction mechanism 290 is a chief ray (optical axis) adjustment mechanism. By slightly eccentrically moving and rotating the mirror position of the relay optical system 280, the reflected light from the reflective mask 300 is reflected on the incident side of the projection optical system 400. It has the function of correcting the optical axis so that it matches well.

8, the masking blade 270 may be arranged near the mask 300 to reduce the number of relay optical systems 280. Here, FIG. 8 is a schematic view of a main part of a modification of the exposure apparatus 10 shown in FIG. The same members as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In order to obtain a high reflectance for EUV light almost directly incident on the surface of each mirror including the mask 300, two types of material layers having a large difference in refractive index and a small absorption are formed at a period of about half the exposure wavelength. A multilayer film that is repeatedly laminated is formed. In order to obtain the highest possible reflectance, it is usual to use Mo and Si as the material, but even in that case, the obtained reflectance is about 60% to 70%.

Therefore, in the illumination optical system 200, it is necessary to minimize the number of mirrors used in order to suppress the loss of the reflection intensity. The feature of this embodiment is that a masking blade 270 having an arc-shaped opening is arranged near the reflection surface of the reflection type mask 300, so that the relay optical systems 282 and 284 in FIG. The point is that the efficiency of the 200 is improved.

Next, another embodiment of the present invention capable of setting a desired illumination condition will be described with reference to FIG. Here, FIG. 9 is a schematic view showing an exposure apparatus 10B according to the third embodiment of the present invention.

In comparison with the exposure apparatus 10 shown in FIG. 1, the exposure apparatus 10B includes two reflective integrators 230 and 230B that can be switched according to desired illumination conditions, diaphragms 236 and 256, and diaphragm driving systems 238 and 258. Have.

The reflective integrators 230 and 230B are reflective integrators having a plurality of convex cylindrical surfaces, but have different radii of curvature (and therefore power) from the cylindrical surfaces. Hereinafter, a method of setting the coherence factor σ, that is, the numerical aperture of the illumination system to a desired value by switching between the integrators 230 and 230B will be described.

FIG. 10 is a schematic diagram of a surface of an integrator 230 having a plurality of convex cylindrical reflecting surfaces 232, and FIG. 11 is a schematic diagram of a surface of an integrator 230B. Here integrator 230 and the cylindrical surface 232 and the curvature of the 232B of 230B radius _{r 1} and _{r 2} are set to _r 1 _{<r 2.}

Now, in FIG. 10, it is assumed that a parallel light beam is incident on the convex cylindrical reflection surface 231 of the integrator 230 from above the plane of the paper. In this case, the luminous flux is diverged by the convex cylindrical reflecting surface 231, but the converging point exists as a virtual image at a distance r _1/2 from the center of curvature O inside the convex surface. Therefore, the reflected light diverges at a divergence angle theta ₁ which is given by the following equation.

Similarly, in the integrator 230B, the focal point is present as a virtual image from the center of curvature O of the convex cylindrical surface 232B at a distance _r 2/2. Therefore, the reflected light diverges at a divergence angle theta ₂ which is given by the following equation.

Here, the relationship of θ ₁ > θ ₂ is established from r ₁ <r ₂ . In other words, towards the divergence angle theta ₁ of the light flux reflected by the integrator 230 is larger than the divergence angle theta ₂ of the light flux reflected by the integrator 230B.

12 and 13 are schematic diagrams illustrating a method of switching the numerical aperture of the illumination optical system 200 by switching between the integrators 230 and 230B. In FIG. 12, when a substantially parallel EUV light beam 222 enters the cylindrical reflection surface 231 of the integrator 230 via the stop 236 as shown in the figure, a virtual image of the secondary light source is generated inside the integrator 230, and a predetermined divergence angle is obtained. EUV light is reflected from the respective secondary light sources at theta _1. The diverging EUV light is condensed by a parabolic mirror 240 having a focal length f ₁ , and is incident on the reflection surface 251 of the integrator 250 via the stop 256 as a substantially parallel light beam.

EUV light flux reflected by the integrator 250 having a plurality of convex cylindrical reflecting surface 251 is condensed by the rotational parabolic mirror 260, on which the focal length masking blade 270 which is disposed at the position of f _2, uniform A circular arc illumination area. Here, NA ₁ the numerical aperture of the illumination optical system 200 in the masking blade 270 is given by the following equation.

The numerical aperture NA ₁ is an amount proportional to the numerical aperture of the illumination optical system 200 on the reflective mask 300 and is proportional to the divergence angle θ ₁ .

As shown in FIG. 13, when switched by the switching mechanism (not shown) the integrator 230 to 230B, similarly, the numerical aperture NA ₂ of the illumination optical system 200 in the masking blade 270 is given by the following equation.

from θ _1> θ _2, large numerical aperture of the illumination optical system 200 is obtained than when using the integrator 230 with an integrator 230B, the coherence factor σ is larger.

In the above description, an example in which the two integrators 230 and 230B are switched has been described. However, in order to change the coherence factor σ stepwise, two or more integrators 230 having different divergence angles are switched using a turret or the like. May be configured. By controlling the aperture 256 in accordance with the switching of the integrator 230 and controlling the diameter of the light beam incident on the integrator 250 to a desired size, the control of σ with higher accuracy may be performed.

The stop 236 is provided on the front surface of the reflection type integrator 230 or 230B, and has a light blocking part 237a and an opening 237b. The aperture 236 is driven by an aperture drive system 238 to continuously vary the opening diameter of the opening 237b. The opening diameter of the opening 237b is adjusted by a signal from a control system (not shown) input to the aperture driving system 238. Any configuration known in the art, such as an iris diaphragm device using a cam, can be applied to the diaphragm drive system 238.

広 が り By changing the aperture diameter of the stop 236, it is possible to adjust the spread of the light beam incident on the integrator 250 in the direction parallel to the paper surface (as indicated by the dotted line in the figure). That is, if the aperture diameter of the stop 236 in FIG. 9 is increased, it is possible to adjust the radial width of the arc slit that becomes the illumination area in the masking blade 270. In addition, not only switching of the integrators 230 and 230B, but also adjusting the aperture 256 to change the thickness D of the light beam incident on the integrator 250, change the coherence factor σ to a desired one, and correct uneven illuminance. You can also.

The stop 256 is provided on the front surface of the reflection type integrator 250 and can be driven by the stop drive system 258 to form a desired effective light source distribution. The stop 256 has a light blocking portion 257a and an opening 257b.

The EUV luminous flux reflected by the integrator 250 having a plurality of convex cylindrical reflecting surfaces via the stop 256 is condensed by the paraboloid of revolution 260, and is uniformly spread on the masking blade 270 arranged at the focal position. A circular arc illumination area.

Hereinafter, a method of performing deformed illumination such as annular illumination by switching the stop 256 will be described with reference to FIGS. 14 and 15. FIGS. 14A to 14C are plan views showing apertures applicable to the aperture 256. FIG. FIG. 14A shows an aperture 256A for normal illumination, FIG. 14B shows an aperture 256B for so-called annular illumination, and FIG. 14C shows an aperture 256C for so-called quadrupole illumination. Is shown. For example, as shown in the stop 256 in FIG. 9, several such opening patterns are prepared as a turret, and the turret is rotated by receiving a signal from a control system (not shown) by the stop drive system 258. Can be switched to a desired opening shape. Alternatively, another mechanical method may be used without using the turret, for example, a plurality of apertures may be arranged and sequentially switched.

The stop 256 is arranged near the reflection surface 251 of the integrator 250 as shown in FIG. Therefore, assuming that the incident angle of the light beam incident on the integrator 250 is θ, the light beam diameter on the reflection surface 251 of the integrator 250 extends in a direction parallel to the paper surface at a magnification of 1 / cos θ. Accordingly, the shape of the opening 257b of the stop 256 must also be extended in the same direction at a magnification of 1 / cos θ. In FIG. 14, for example, an aperture 256A is used to reduce the diameter of the incident light beam to a circle, and the aspect ratio of the ellipse is 1 / cos θ. The same applies to the stops 256B and 256C.

Next, the principle of performing modified illumination by the stop 256 will be described by taking the stop 256B in the annular illumination mode as an example. Modified illumination method, the super-resolution technology to miniaturize by reducing the value of the proportionality constant _{k 1} in Equation 1: a (RET Resolution Enhanced Technology). If the resolution is improved by shortening the wavelength in Expression 1, the depth of focus is reduced in Expression 2, but the modified illumination method is preferable because Expression 2 does not involve reduction in the depth of focus.

FIG. 15 is a diagram in which the integrator 250, the paraboloid of revolution 260, and the masking blade 270 shown in FIG. 9 are extracted. FIG. 15A is a side view, and FIG. It is the top view seen. The stop 256B in the annular illumination mode is arranged as shown in FIG. 15A, but is not shown in FIG. 15B for ease of explanation.

The luminous flux incident on the reflection type integrator 250 is shielded by the stop 256 at the central part of the optical axis and a part of the outer diameter part, and is reflected by the elliptical ring-shaped distribution 259. The shape of the distribution 259 matches the shape of the aperture of the stop 256B. The light beam is condensed by a parabolic reflector 260 rotates to form a uniform illumination region of arcuate shape at the position of the masking blade 270 which is disposed at the position of the focal length f _2. At this time, since the center of the light beam is shielded, the condensed light beam becomes a light beam indicated by a hatched portion 262 in FIG. This is the same in FIG. 15B, and the light flux is indicated by the hatched portion 264. As described above, the reflective integrator 250 superimposes the secondary light source in the angular direction of the circular arc region, and sets the mask 300 (by critical illumination) so as to collect all the light beams in one point in the radial direction of the circular arc region. Light up. This indicates that the distribution like 278 at the position of the intersection of the principal ray and the optical axis, that is, the pupil plane position 295, that is, the annular illumination is being performed.

{Returning to FIG. 1 again, the exposure method of this embodiment will be described continuously. 8 and 9 after the mask 300.

The reflection type mask 300 has a transfer pattern in which a non-reflection portion made of an EUV absorber or the like is provided on a multilayer film reflection mirror. The EUV reflected light having the circuit pattern information from the reflective mask 300 illuminated in an arc shape is projected and imaged by the projection optical system 400 onto the object 500 coated with a photosensitive material at a magnification optimal for exposure. Then, the circuit pattern is exposed. The projection optical system 400 according to the present embodiment is a reflection type projection optical system including six mirrors, but the number of mirrors is not limited to six, but may be a desired number such as four, five, or eight. Can be used.

The object 500 is fixed to the wafer stage 550 and has a function of moving up, down, front, back, left and right on the paper surface, and its movement is controlled by a length measuring device such as a laser interferometer (not shown). Assuming that the magnification of the projection optical system 400 is M, for example, the reflective mask 300 is scanned at a speed v in a direction parallel to the plane of the paper, and at the same time, the object 500 is synchronized at a speed v / M in a direction parallel to the plane of the paper. By scanning, the entire surface is exposed.

In the present embodiment, the exposure is performed on the wafer. However, the processing target band 500 as an exposure target is not limited to the wafer, and includes a liquid crystal substrate and other processing targets. A photoresist is applied to the object to be processed 500. The photoresist application step includes a pretreatment, an adhesion improver application process, a photoresist application process, and a pre-bake process. Pretreatment includes washing, drying and the like. The adhesion improver application treatment is a surface modification treatment (that is, a hydrophobic treatment by applying a surfactant) for increasing the adhesion between the photoresist and the base, and the organic film such as HMDS (Hexamethyl-disilazane) is treated. Coat or steam. Prebaking is a baking (firing) step, but is softer than that after development, and removes the solvent.

The wafer stage 550 supports the object 500 to be processed. As the stage 550, any structure known in the art can be applied, and for example, the target object 500 is moved in the XYZ directions using a linear motor. The mask 300 and the object to be processed 500 are controlled by a control unit (not shown) and scanned synchronously. The positions of the mask stage 350 and the wafer stage 550 are monitored by, for example, a laser interferometer or the like, and both are driven at a constant speed ratio.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus 10 will be described with reference to FIGS. FIG. 16 is a flowchart for explaining the manufacture of devices (semiconductor chips such as ICs and LSIs, LCDs, CCDs, etc.). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), the circuit of the device is designed. Step 2 (mask fabrication) forms a mask on which the designed circuit pattern is formed. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a preprocess, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). . In step 6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 17 is a detailed flowchart of the wafer process in Step 4. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the surface of the wafer. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 1 to expose a circuit pattern on the mask onto the wafer. Step 17 (development) develops the exposed wafer. Step 18 (etching) removes portions other than the developed resist image. Step 19 (resist stripping) removes unnecessary resist after etching. By repeating these steps, multiple circuit patterns are formed on the wafer. According to the manufacturing method of this embodiment, it is possible to manufacture a device having higher quality than the conventional device. As described above, the device manufacturing method using the exposure apparatus 10 and the resulting device also function as one aspect of the present invention.

Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the invention. For example, although the present embodiment has been described using EUV light, the present invention can be applied to a light source in the X-ray region.

FIG. 1 is a schematic diagram illustrating an exposure apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic perspective view showing two types of integrators applicable to the reflection type integrator of the exposure apparatus shown in FIG. FIG. 3 is a schematic diagram for explaining the operation of a reflective integrator having a convex cylindrical surface shown in FIG. FIG. 4 is a schematic perspective view for explaining light beam reflection on a cylindrical surface of the reflection type integrator shown in FIG. 3. FIG. 5 is a diagram for describing an angular distribution of a light beam reflected on the cylindrical surface illustrated in FIG. 4. FIG. 2 is an enlarged view of forming an arc illumination by two integrators of the exposure apparatus shown in FIG. 1. FIG. 7 is a schematic perspective view showing a modification of the reflection type integrator on the light source side shown in FIG. 1. FIG. 6 is a schematic diagram illustrating an exposure apparatus according to a second embodiment of the present invention. FIG. 9 is a schematic diagram illustrating an exposure apparatus according to a third embodiment of the present invention. FIG. 10 is a schematic diagram of one light source-side integrator provided in the exposure apparatus shown in FIG. 9. FIG. 10 is a schematic diagram of the other light source side integrator provided in the exposure apparatus shown in FIG. 9. FIG. 10 is a schematic diagram illustrating a method of switching a numerical aperture of an illumination optical system by switching a light source side integrator of the exposure apparatus shown in FIG. 9. FIG. 10 is a schematic diagram illustrating a method of switching a numerical aperture of an illumination optical system by switching a light source side integrator of the exposure apparatus shown in FIG. 9. FIG. 10 is a plan view illustrating an example of an aperture used for a mask-side integrator of the exposure apparatus shown in FIG. 9. FIG. 10 is a diagram in which a mask-side integrator, a rotating parabolic mirror, and a masking blade of the exposure apparatus shown in FIG. 9 are extracted. 6 is a flowchart for explaining the manufacture of a device (a semiconductor chip such as an IC or LSI, an LCD, a CCD, or the like). 17 is a detailed flowchart of a wafer process in Step 4 shown in FIG. It is a schematic diagram of a conventional exposure apparatus. FIG. 19 is a plan view for explaining a relationship between an illumination area of a mask of the exposure apparatus shown in FIG. 18 and an area used for exposure.

Explanation of reference numerals

10, 10A, 10B Exposure apparatus 100 Light source unit 200 Illumination optical system 230, 230A, 230B Reflective integrator 231 Reflective surface 232 Cylindrical surface 236 Aperture 240 Parabolic mirror 250, 250A Reflective integrator 251 Reflective surface 252 Cylindrical surface 256, 256A -C Aperture 270 Masking blade 280 (282-288) Relay optical system 300 Reflective mask 400 Projection optical system 500 Workpiece

Claims (6)

In an illumination optical system that illuminates an illuminated surface with light having a wavelength of 200 nm or less from a light source,
A field stop provided with an opening for defining an illumination area of the illuminated surface,
A reflection optical system that forms an image of the opening on the surface to be illuminated with a light beam passing through the opening of the field stop;
An illumination mechanism for adjusting an angle of a principal ray of a light beam incident on the illumination surface with respect to the illumination surface. In an illumination optical system that illuminates an illuminated surface with light having a wavelength of 200 nm or less from a light source,
A reflective integrator,
A condenser mirror for superimposing a plurality of light beams from the reflection type integrator on the illuminated surface;
A reflection optical system for guiding light from the condenser mirror to the surface to be irradiated,
An illumination mechanism for adjusting an angle of a principal ray of a light beam incident on the surface to be illuminated with respect to the surface to be illuminated. The illumination optical system according to claim 1, wherein the adjusting mechanism moves at least one mirror of the reflection optical system in an eccentric manner and / or a rotational manner. 3. The illumination optical system according to claim 2, wherein the reflection optical system includes one mirror. An illumination optical system according to claim 1 illuminates a pattern formed on a reticle or a mask with light from a light source, and projects the pattern onto an object to be processed by a projection optical system. An exposure apparatus characterized by the following. Exposing a substrate with a device pattern using the exposure apparatus according to claim 5;
Performing a predetermined process on the exposed substrate.