JPH06318542A - Projection aligner - Google Patents

Abstract

PURPOSE:To enable exposure of isolated pattern such as a contact hole keeping a high resolution, high focal depth and high throughput. CONSTITUTION:The light from a mercury lamp 1 is converted into almost parallel light flux with an input lens 5, a reticle 1 R1 or R2 is lit with an exposure light of the wavelength band selected from such parallel light flux through a condenser lens 9 with a narrow band interference filter plate 15A or a broad band interference filter plate 15B and a pattern image of the reticle R1 or R2 is exposed on a wafer W through a projected optical system 11. On the occasion of exposing the isolated pattern of the reticle R2, chromatic aberration on the axis is set larger than the width of the focal depth of the projected optical system 11 using the broad band interference filter plate 15B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for projecting and exposing a pattern of a reticle onto a photosensitive substrate when manufacturing a semiconductor device, a liquid crystal display device or the like by a photolithography process. Regarding

[0002]

2. Description of the Related Art Conventionally, when a semiconductor element, a liquid crystal display element, a thin film magnetic head, or the like is manufactured by a photolithography process, a pattern of a photomask or a reticle (hereinafter referred to as a "reticle") is projected by an optical projection system. There is used a projection exposure apparatus that performs projection exposure on a substrate (wafer, glass plate, etc.) to which a photosensitive material is applied via.

FIG. 7 shows a conventional projection exposure apparatus. In FIG. 7, the light emitted from a mercury lamp 1 is elliptical mirror 2.
The light thus collected is reflected by the mirror 3 and enters the input lens 5. In the vicinity of the second focus of the elliptical mirror 2, a shutter 4 for blocking the light from the mercury lamp 1 at any time is arranged. The light converted into the substantially parallel light flux by the input lens 5 enters the interference filter plate 6. Light in the wavelength band selected by the interference filter plate 6 (hereinafter, referred to as "exposure light IL1") enters a fly-eye lens 7 as an optical integrator, and a focal plane on the rear side (reticle side) of the fly-eye lens 7 is formed. A large number of secondary light sources are formed in the. The exposure light IL1 from these many secondary light sources is reflected by the mirror 8 and then condensed by the condenser lens 9 to illuminate the reticle R on the reticle stage 10 with a substantially uniform illuminance.

Under the exposure light IL1, the circuit pattern image formed on the reticle R is projected onto each shot area of the wafer W held on the wafer stage 12 via the projection optical system 11. The wafer stage 12 is an XY stage that positions the wafer W on a plane perpendicular to the optical axis of the projection optical system 11 (this plane is referred to as an XY plane), and the wafer W in the Z direction parallel to the optical axis of the projection optical system 11. It is composed of a Z stage and the like for positioning.

If this projection exposure apparatus uses the i-line of a mercury lamp as the exposure light, the axial chromatic aberration of the achromatic design of the projection optical system 11 is as shown by the curve 13 in FIG. In FIG. 8, the horizontal axis represents the wavelength of the exposure light (exposure wavelength) λ [nm], and the wavelength of the i-line (36
5 nm) is λ _i , and the numerical values on the left and right of the wavelength λ _i (+1,
-1, ... Shows the amount of deviation from the wavelength λ _i . Further, the vertical axis of FIG. 8 indicates the image forming position Z [μm] in the optical axis direction of the image plane of the projection optical system 11 with respect to the exposure light of the wavelength λ, and the image forming position Z ₀ is the result for the light of the main wavelength λ _i. The image position, and the numerical values (+1, -1, ...) At the top and bottom of the image position indicate the amount of deviation from the image forming position Z ₀ . As can be seen from the curve 13 in FIG. 8, the on-axis chromatic aberration of the conventional projection optical system 11 is on the lower side (wafer W in FIG. 7) with the main wavelength λ _i as the axis of symmetry.
It has a quadratic curve convex to the side).

FIG. 9 shows the selected wavelength range of the interference filter plate 6 when the exposure light is the i-line. In FIG.
The interference filter plate 6 has a width of 2 · Δ around the main wavelength λ _i.
Passes light in the range of λ ₁ . The width 2 · Δλ ₁ is approximately 2 nm. That is, in FIG. 7, the interference filter plate 6 passes light having a wavelength of (λ _i −Δλ ₁ ) to (λ _i + Δλ ₁ ) to the fly-eye lens 7 side as the exposure light IL1. In this case, assuming that the numerical aperture of the projection optical system 11 is NA and the process constant is K ₂ , the depth of focus F _d of the projection optical system 11 is proportional to the exposure wavelength λ _i and becomes the square of the numerical aperture NA as follows. Inversely proportional. F _d = K ₂ · λ _i / NA ² (1)

Then, FIG. 9 shows a curve 13 representing the axial chromatic aberration.
, The image forming position Z _{0 at the} dominant wavelength λ _i is shown.
Difference ΔZ between the image forming position at the wavelength (λ _i ± Δλ ₁ )
₁ was set to a value smaller than ½ of the depth of focus F _d as follows. ΔZ ₁ <F _d / 2 (2) Recently, circuit patterns of semiconductor elements and the like have become finer and finer, and projection exposure apparatuses are required to have improved resolution. Limiting resolution R of the projection optical system 11 of the projection exposure apparatus
Can be expressed as the following equation using the exposure main wavelength λ _i , the numerical aperture NA of the projection optical system, and the process constant K ₁ .
That is, the limiting resolution R is proportional to the wavelength λ _i and the numerical aperture NA
Inversely proportional to. R = K ₁ · λ _i / NA (3)

Therefore, in order to enhance the resolution, (3)
From the equation, it can be seen that it is necessary to shorten the exposure wavelength or increase the numerical aperture NA of the projection optical system. On the other hand, if the exposure wavelength is shortened or the numerical aperture NA is increased as described above, the depth of focus becomes shallower than in the equation (1). That is, conventionally, the depth of focus must be sacrificed in order to increase the resolution.

When the depth of focus is reduced as described above, a non-focused portion occurs in the exposure field of the projection optical system due to the unevenness of the substrate such as a wafer or the thickness of the photoresist, so that a manufactured semiconductor device or the like may be damaged. Yield decreases. To solve this, the substrate is moved in the optical axis direction of the projection optical system during exposure to one shot area on the substrate, and the position (focus position) of the substrate in the optical axis direction is changed variously. A method of substantially increasing the depth of focus by performing multiple exposure has been proposed (for example, JP-A-63-64).
037, JP-A-63-42122).
Also, instead of moving the substrate in the optical axis direction of the projection optical system, the same effect can be obtained by moving the reticle in the optical axis direction.

[0010]

In the prior art as described above, the substrate is moved in the optical axis direction, or the reticle is moved in the optical axis direction to perform multiple exposure, that is, a defocused image. By burning the circuit pattern with the composite image of, the effect of increasing the depth of focus can be obtained for an isolated pattern such as a contact hole. However, in the method of performing multiple exposure by moving the substrate or reticle, it takes a long time to finish the circuit pattern for one shot, and there is a disadvantage that the throughput is reduced.

In the conventional method of moving a substrate or a reticle to perform multiple exposure, when printing a periodic and dense pattern such as a line-and-space pattern, it is rather an adverse effect and the resolution is rather increased. Becomes worse.
The present invention has been made in view of the above problems, and an object thereof is to provide a projection exposure apparatus capable of exposing an isolated pattern such as a contact hole at a high depth of focus and a high throughput while maintaining a high resolution.

[0012]

A first projection exposure apparatus according to the present invention is, for example, as shown in FIGS. 1 and 2, a light source system (1, 2, 5) for supplying illumination light which has been converted into a parallel light flux. When,
A secondary light source forming means (7) for forming a plurality of secondary light sources from the illumination light and a mask (R2) on which the illumination light from the plurality of secondary light sources is condensed and a transfer pattern is formed. Condenser lens system that illuminates with almost uniform illuminance (9)
And a projection optical system (11) for projecting the pattern image of the mask (R2) onto the photosensitive substrate (W) under the illumination light, the light source system and the secondary light source formation Between the means (7) and the means (7), the wavelength selecting means (IL2) of the predetermined wavelength band of the illumination light supplied from the light source system is selected and supplied to the secondary light source forming means (7). 15
B) is arranged, and the wavelength band selected by the wavelength selection means (15B) is set to the projection optical system (1) for the illumination light (IL2).
The wavelength band is such that the axial chromatic aberration of 1) is equal to or larger than the width of the depth of focus of the projection optical system (11).

The second projection exposure apparatus according to the present invention is, for example, as shown in FIG. 1 and FIG. 4, a light source system (1, 2, 5) for supplying illumination light converted into a parallel light flux, and its illumination. A secondary light source forming means (7) for forming a plurality of secondary light sources from light and a mask (R2) on which a transfer pattern is formed by converging illumination light from the plurality of secondary light sources are substantially uniform. With a condenser lens system (9) that illuminates with a constant illuminance,
In a projection exposure apparatus having a projection optical system (11) for projecting a pattern image of a mask (R2) onto a photosensitive substrate (W) under the illumination light, the light source system and a secondary light source forming unit ( 7), the illumination light of different wavelength bands among the illumination light is selected according to the inclination angle with respect to the illumination light supplied from the light source system and is supplied to the secondary light source forming means (7). The wavelength selecting means (21) is arranged, and the wavelength selecting means (2
The driving means (22, 23, 24) for changing the inclination angle of the illumination light of 1) within a predetermined range is provided, and the inclination angle of the wavelength selecting means (21) with respect to the illumination light is changed by the driving means, and the substrate The selection width of the wavelength band of the illumination light during exposure to (W) is set to a range in which the axial chromatic aberration of the projection optical system (11) for the illumination light is equal to or larger than the width of the depth of focus of the projection optical system (11). It was done.

[0014]

According to the first projection exposure apparatus of the present invention,
For example, as shown in FIG. 3, the wavelength selection means (15B) is used.
The central wavelength of the selected wavelength band by λ_i, The selection width is 2.
Δλ₂Then the wavelength is (λ_i-Δλ₂) ~ (Λ_i+ Δλ₂)of
Illumination light is applied to the mask (R) side. Also, in FIG.
Curve 13 represents the axial chromatic aberration of the projection optical system (11)
As the center wavelength λ_iThe optical axis of the projection optical system (11)
Image formation position Z₀And the wavelength (λ_i ± Δλ₂) Image formation position
Difference from₂Is the width of the depth of focus of the projection optical system (11)
F_dIt is set above. On the other hand, in the conventional example
Is selected by the interference filter plate, as shown in FIG.
Center wavelength λ of the reflected light_iImaging position Z at ₀And both the selection range
Edge wavelength (λ_i ± Δλ₁) Difference from the image forming position ΔZ
₁Is the width F of the depth of focus of the projection optical system._dFrom 1/2
It was set to a small value.

That is, in the present invention, the mask (R) is irradiated with illumination light having a wavelength range wider than that of the conventional example, and the projection optical system (1
The value of the axial chromatic aberration in 1) is set to be twice or more that of the conventional example. By performing the exposure using the illumination light in the wide wavelength range as described above, the mask (R) or the substrate (W) is moved in the optical axis direction of the projection optical system (11) using the illumination light in the narrow wavelength range. Exposure equivalent to the case of performing multiple exposure (this is referred to as "multifocal exposure") is performed. Therefore, an isolated pattern such as a contact hole can be exposed with high resolution and high depth of focus.

Further, according to the second projection exposure apparatus of the present invention, according to the tilt angle with respect to the illumination light supplied from the light source system, the illumination light of different wavelength bands is selected from among the illumination light, and 2 Wavelength selecting means (2) supplied to the next light source forming means (7)
1) is used. Generally, it is known that the wavelength of the transmitted light shifts when the incident angle of the light beam incident on the interference filter plate is different from the designed value. Therefore, for example, a narrow band interference filter plate is used as the wavelength selection means (21). Can be used. Then, for example, as shown in FIG.
As shown in FIG. 5C, by changing the inclination angle of the wavelength selecting means 21 using the driving means during the exposure of the substrate W, as shown in FIGS. 5D to 5F, respectively. To
The wavelength range of the illumination light with which the mask (R) side is irradiated changes. Further, the changing width of the changing wavelength range is set so that the maximum value ΔZ ₂ of the difference between the image forming positions is equal to or larger than the width F _{d of the} depth of focus of the projection optical system (11). Therefore, multifocal exposure is performed as in the first projection exposure apparatus.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the projection exposure apparatus according to the present invention will be described below with reference to FIGS. These Figure 1
3, parts corresponding to those in FIGS. 7 to 9 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 1 shows a projection exposure apparatus of this example. In FIG.
A turret type rotary plate 14 is disposed between the fly eye lens 7 and the fly-eye lens 7, and a narrow band interference filter plate 15A and a wide band interference filter plate 15B are mounted on the side surface of the rotary plate 14 at 180 ° intervals. The exposure light of this example has a wavelength of λ _i (36
5 nm) i-line, narrow band interference filter plate 1
The wavelength range selected in 5A has a width of 2 · Δλ centered on the main wavelength λ _{i of} exposure, as shown in FIG. 9 of the conventional example.
_The range is narrower than ₁ (≈2 nm).

On the other hand, FIG. 3 shows a broadband interference filter plate 1.
5B shows the wavelength range to be selected, and in FIG. 3, the horizontal axis
Is the exposure wavelength λ [nm], and the vertical axis is the exposure wavelength λ
Image forming position Z [μm] in the optical axis direction of the projection optical system 11
Indicates. Then, select with the broadband interference filter plate 15B.
The wavelength range to be selected is the dominant wavelength λ_iWidth centered at 2 · Δλ ₂
The range is (≈6 nm). The curve 13 is the exposure wave.
The length is λ_i-Axis color of projection optics 11 designed by Achromatic
Shows the aberration, and in this example, the dominant wavelength λ_iImaging position Z at₀When
Wavelength (λ_i± Δλ₂) Difference from the image forming position ΔZ
₂Is about 1.4 μm. In addition, the projection optical system 11
With numerical aperture NA of 0.55, the process constant of equation (1)
Number K₂Is 1/2, the depth of focus F of the projection optical system 11 is
_dIs about 0.6 μm. Therefore, the broadband
Of the projection optical system 11 when using the cross filter plate 15B
Axial chromatic aberration (that is, the difference ΔZ₂) Is the projection light
Depth of focus F of Faculty 11_dIt is getting bigger. ΔZ₂> F_d (4)

Returning to FIG. 1, a main control system 1 for mounting the motor 16 on the rotary shaft of the rotary plate 15 and controlling the operation of the entire apparatus.
7 rotates the rotary plate 15 via the motor 16 to arrange either the narrow band interference filter plate 15A or the wide band interference filter plate 15B in front of the fly-eye lens 7. The reticle stage 10 has a first reticle R1 on which a periodical dense circuit pattern such as a line-and-space pattern is mainly formed.
The reticle loader 18 near the
A second reticle R2, on which an isolated pattern such as a contact hole is mainly formed, is placed on the top.
The main control system 17 operates the reticle loader 18 via the drive device 19 to generate the first reticle R1,
The second reticle R2 or another reticle is sequentially placed on the reticle stage 10.

Although not shown, a focus sensor for measuring the position (focus position) of the exposure surface of the wafer W in the optical axis direction of the projection optical system 11 is arranged near the projection optical system 11. ing. The main control system 17 sets the focus position of the exposure surface of the wafer W to a pre-determined best focus position by controlling the operation of the Z stage in the wafer stage 12 via the drive unit 20. Then, the main control system 17 drives the XY stage in the wafer stage 12 via the drive unit 20, so that each shot area of the wafer W is sequentially positioned in the exposure field of the projection optical system 11, and each shot area is positioned. Then, the circuit pattern image of the reticle is projected and exposed by the step-and-repeat method. Other configurations are the same as those in FIG. 7.

An example of the exposure operation of this example will be described. First, when exposing the pattern of the first reticle R1 on which a periodical dense circuit pattern such as a line-and-space pattern is formed, the rotating plate 14 is rotated as shown in FIG. Then, the narrow band interference filter plate 1 is provided between the input lens 5 and the fly-eye lens 7.
Place 5A. Thus, among the light from the mercury lamp 1, as shown in FIG. 9, the exposure light in a narrow wavelength band than the width 2 · [Delta] [lambda] ₁ about the wavelength lambda _i of the i-line is selected by the interference filter plate 15A Under the exposure light thus selected, the circuit pattern image of the first reticle R1 is projected and exposed onto the photoresist layer in each shot area of the wafer W via the projection optical system 11. It is known that multifocal exposure, in which various defocuses are performed and multiple exposure is performed, is not effective for a dense pattern. Therefore, by using a narrow band interference filter plate 15A as in this example, Such a dense pattern can be exposed on the wafer W with high resolution.

On the other hand, when exposing the pattern of the second reticle R2 in which an isolated circuit pattern such as a contact hole is mainly formed, the main control system 17 causes the drive unit 19 to operate.
The reticle loader 18 is operated via the reticle to unload the first reticle R1 from the reticle stage 10.
The second reticle R2 is placed on the reticle stage 10. Then, the main control system 17 rotates the rotary plate 14 via the motor 16, and arranges the broadband interference filter plate 15B between the input lens 5 and the fly-eye lens 7 as shown in FIG. As a result, among the light from the mercury lamp 1, as shown in FIG. 3, the exposure light IL2 in the wavelength range of width 2 · Δλ ₂ centered on the wavelength λ _{i of the} i-line is selected by the interference filter plate 15. Under this exposure light IL2, the circuit pattern image of the second reticle R2 is projected and exposed onto the photoresist layer in each shot area of the wafer W via the projection optical system 11.

At this time, in the projection optical system 11, a wide axial chromatic aberration having a width ΔZ ₂ is generated, and the circuit pattern image of the second reticle R2 is substantially defocused on the wafer W in various ways. Multiple exposure is performed. Therefore, the isolated circuit pattern of the second reticle R2 has a high resolution on the wafer W.
It is projected onto and exposed. As described above, according to this example, by using the broadband interference filter plate 15B, multifocal exposure is performed without moving the exposure surface of the wafer or the pattern surface of the reticle as in the conventional example. Further, the mechanical operation in the projection exposure apparatus is only the rotation of the rotary plate 14 in the illumination optical system, and unlike the conventional example, the reticle R2 is used.
The wafer W and the wafer W need only be aligned once for each shot. Since the setting of the broadband interference filter plate 15B only needs to be performed once when the reticle is replaced,
The exposure can be performed at high speed, and the throughput of the exposure process is extremely high.

Furthermore, since multifocal exposure is performed simply by replacing the interference filter plate 15B, the degree of multifocal exposure can be easily changed according to the reticle pattern to be exposed. Therefore, by attaching the interference filter plate having various wavelength selection characteristics to the rotary plate of FIG.
It is possible to project and expose the patterns of various reticles with a high depth of focus and a high throughput while maintaining a high resolution with one projection exposure apparatus.

Further, when moving a reticle or a wafer to perform multifocal exposure as in the conventional example, the contrast of an image is lowered by multiple exposure, and it is necessary to increase the exposure amount. As described above, the exposure time is inevitably lengthened as compared with the case where monofocal exposure is performed. On the other hand, with the method of replacing the interference filter plate as in this example, the exposure power increases almost in proportion to the transmission bandwidth of the filter, so even if the same multifocal effect is obtained, the exposure time is shorter than in the conventional example. It also has the advantage of being able to work efficiently.

Further, in the above-described embodiment, the main control system 17 is constructed with an algorithm so as to separately output the command for replacing the interference filter plates 15A and 15B and the command for replacing the reticle in parallel. Alternatively, for example, the reticle loader 18 or the like may be provided with a mechanism for identifying the type of reticle pattern, and the corresponding interference filter plate may be selected based on the identification result.

Next, a second embodiment of the present invention will be described with reference to FIGS. This example uses a drive means for changing the inclination angle of the interference filter plate instead of the turret type rotary plate 14 of FIG. 1, and the same reference numerals are given to the parts corresponding to FIG. 1 in FIG. The detailed description thereof will be omitted. FIG. 4 shows the configuration in the vicinity of the fly-eye lens 7 of this example. In FIG.
A narrow band interference filter plate 21 is arranged between the fly eye lens 7 and the fly-eye lens 7, and the end portion of the interference filter plate 21 is fixed to the support member 22.
It is attached slidably along 3. Then, the main control system 17 of FIG. 1 moves the support member 22 along the guide 23 within a predetermined range via the driving device 24, so that the interference filter plate 21 is perpendicular to the optical axis AX of the illumination optical system. The inclination angle with respect to the surface is allowed to be continuously changed within an angle range of 2 · θ. The angle range 2 · θ is set according to the pattern of the reticle to be exposed.
Other configurations are similar to those of the example of FIG. Also in this example, the dominant wavelength of the exposure wavelength is the wavelength λ _{i of the} i-line.

First, as shown in FIG. 5A, the narrow band interference filter plate 21 is set perpendicularly to the optical axis AX of the illumination optical system, and the incident angle of the light beam from the input lens 5 is almost the same. Consider the case of 0 °. In this case, the wavelength band selected by the interference filter plate 21 in the incident light flux is a region of width 2 · Δλ ₃ centered on the wavelength λ _{i of the} i-line, as shown in FIG. This width 2 · Δλ
₃ is narrower than the width 2 · Δλ ₁ of the conventional example in FIG.
In addition, in FIGS. 5D to 5F, the horizontal axis represents the exposure wavelength λ.
And the vertical axis is the image forming position Z by the projection optical system 11 for the light of the exposure wavelength λ. In addition, in this example, the incident angle of the light incident on the interference filter plate 21 is a design value (that is,
Deviate from (°) to positively utilize the phenomenon that the wavelength band of transmitted light shifts.

For example, as shown in FIG. 5B, when the interference filter plate 21 is slightly inclined from the plane perpendicular to the optical axis AX of the illumination optical system, the wavelength range of the light passing through the interference filter plate 21 is increased. Indicates that the center wavelength moves to the short wavelength side, as shown by the shaded area in FIG. The width of the wavelength range is almost the same as in the case of FIG. Furthermore, FIG.
As shown in FIG. 5C, when the interference filter plate 21 is tilted by an angle θ from a plane perpendicular to the optical axis AX of the illumination optical system, the wavelength range of the light transmitted through the interference filter plate 21 is as shown in FIG. As indicated by the area surrounded by the hatched lines in), the width is almost the same and the center wavelength shifts to the shorter wavelength side. Also, FIG.
In (d) to (f), the curve 13 indicates the projection optical system 11.
Of the image forming position Z ₀ at the wavelength λ _i and the interference filter plate 21 as shown in FIG.
Is inclined by an angle θ, the difference ΔZ ₂ from the image formation position in the light in the wavelength range selected is made larger than the depth of focus F _d of the projection optical system 11.

Next, the exposure operation of this example will be described. Destination
First, as shown in Figure 1, mainly line and space
Pattern-like periodic dense circuit pattern is formed
When exposing the pattern of the formed first reticle R1
Is a narrow band interference filter as shown in FIG.
The plate 15 is set perpendicular to the optical axis AX of the illumination optical system. this
Of the light from the mercury lamp 1 as shown in FIG.
, I-line wavelength λ _iThe width is 2 · Δλ₃
The exposure light in the narrow wavelength range of is selected by the interference filter plate 21.
Under the exposure light selected in this way and selected in this way
The circuit pattern image of the chicle R1 is projected through the projection optical system 11.
Projection exposure on the photoresist layer in each shot area of the wafer W
Be illuminated. This allows such a dense pattern
The wafer W is exposed with high resolution.

On the other hand, when exposing the pattern of the second reticle R2 in which an isolated circuit pattern such as a contact hole is mainly formed, the main control system 17 is supported via the drive unit 24 of FIG. By moving the member 22 along the guide 23, the tilt angle of the interference filter plate 21 with respect to the plane perpendicular to the optical axis AX of the illumination optical system is + θ to −θ during exposure to each shot area of the wafer W. Change continuously in the range. As a result, among the lights from the mercury lamp 1, as shown in FIGS. 5D to 5F, the light in the narrow wavelength range within the wavelength range in which the axial chromatic aberration is equal to or more than the depth of focus causes the second wavelength. An image of the circuit pattern of the reticle R2 is multiple-exposed on the photoresist layer in each shot area of the wafer W via the projection optical system 11. Therefore, the second reticle R
Two isolated circuit patterns are projected and exposed on the wafer W with high resolution.

At this time, according to the present example, since the multi-focus exposure is performed only by changing the inclination angle of the interference filter plate 21, the speed is higher than that of the conventional method of moving the reticle or the wafer. Can be exposed to light. Further, by changing the variation range of the tilt angle of the interference filter plate 21 according to the pattern of the reticle to be exposed, one projection exposure apparatus can project and expose various patterns with high resolution.

Next, a third embodiment of the present invention will be described with reference to FIG. In this example, in the projection exposure apparatus of FIG.
The characteristics of the axial chromatic aberration of the projection optical system 11 are changed. In this regard, the projection optical system 1 in the embodiment of FIG.
The axial chromatic aberration of 1 is adjusted so that the image forming positions of other wavelengths are concentrated near the image forming position Z ₀ with respect to the wavelength λ _i which is the main wavelength, as indicated by the curve 13 in FIG. That is, the curve 13 is a quadratic curve that is convex on the wafer side and has an apex at the main wavelength λ _i . On the other hand, the axial chromatic aberration of the projection optical system of the present example, as shown by the curve 25 in FIG. 6A, is centered at the image forming position Z ₀ with respect to the wavelength λ _i which is the main wavelength, and other wavelengths. The image forming positions Z of are distributed almost linearly.

Therefore, when the interference filter plate 6 of the conventional example of FIG. 7 is arranged between the input lens 5 and the fly-eye lens 7 of FIG. 1 by using such a projection optical system, FIG. As shown in, the interference filter plate 6 selects light in the wavelength range of width 2 · Δλ ₁ centered on the wavelength λ _i . The axial chromatic aberration ΔZ ₃ in this case is about four times the difference ΔZ ₁ in the conventional example of FIG. Therefore, the interference filter plate 6 of the same wavelength range as the conventional example
Even if is used, a high multifocal effect can be obtained.

Further, the broadband interference filter plate 1 of FIG.
5B is the input lens 5 and the fly-eye lens 7 in FIG.
6C, the interference filter plate 15B causes the width 2 · Δ about the wavelength λ _i as shown in FIG. 6C.
Light in the wavelength range of λ ₂ is selected. Further, the axial chromatic aberration ΔZ ₄ in this case is 3 compared with the axial chromatic aberration ΔZ ₂ in FIG.
It is about double. Therefore, even with the interference filter plate 15B having the same wavelength range as that of the embodiment of FIG. 1, a higher multifocal effect can be obtained. This means that in order to effectively obtain the multifocal effect according to the present invention, the characteristic of the axial chromatic aberration of the projection optical system should be substantially linear near the dominant wavelength as shown by the curve 25 in FIG. Means that is desirable.

Although the i-line is used as the exposure light in the above-mentioned embodiment, when the KrF excimer laser light (wavelength 248 nm) or the ArF excimer laser light (wavelength 193 nm) is used as the exposure light, The present invention can be applied only by changing the characteristics of the wavelength range of the interference filter plate. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the gist of the present invention.

[0037]

According to the first projection exposure apparatus of the present invention,
Since the wavelength band selected by the wavelength selection means is widened to make the axial chromatic aberration of the projection optical system equal to or larger than the width of the depth of focus, the mask or the substrate is not moved unlike the conventional example, and a large number of wavelengths are practically obtained at high speed. Multiple exposures at the focus are performed. Therefore,
Even with an isolated pattern such as a contact hole, exposure can be performed with a high depth of focus and a high throughput while maintaining a high resolution.

Further, since the exposure energy of the illumination light with respect to the substrate is almost proportional to the width of the wavelength range selected by the wavelength selecting means, when the broadband light is used as in the present invention, the exposure energy is large. Therefore, there is an advantage that the exposure time can be particularly shortened. Further, when the mask pattern to be exposed is a dense pattern such as a line-and-space pattern, the exposure can be performed satisfactorily by simply replacing the wavelength selection means with a narrow band one, and therefore various patterns can be obtained. One projection exposure apparatus can handle the pattern.

According to the second projection exposure apparatus of the present invention, the wavelength band to be selected is changed by changing the tilt angle of the wavelength selecting means, and the fluctuation range of the image forming position of the projection optical system is changed to the focal depth. Since the width is greater than or equal to the width, multiple exposure at multiple focal points can be performed with a mechanism that is simpler and faster than moving the mask or substrate as in the conventional example. Therefore, with an isolated pattern such as a contact hole, exposure can be performed with a high depth of focus and a high throughput while maintaining a high resolution. Furthermore, the pattern of the mask to be exposed is line
In the case of a dense pattern such as an and space pattern, the exposure is favorably performed by fixing the inclination angle of the wavelength selection means, so that one projection exposure apparatus can cope with various patterns. .

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a projection exposure apparatus according to the present invention.

FIG. 2 is an enlarged view of a main part showing a case where a broadband interference filter plate 15B is set in the front part of the fly-eye lens 7 in the embodiment of FIG.

FIG. 3 is a diagram showing a distribution of image forming positions when a broadband interference filter plate 15B is used in the first embodiment.

FIG. 4 is an enlarged view showing a main part of a second embodiment of the present invention.

5 (a) to 5 (c) are views showing a case where the inclination angle of the interference filter plate 21 is set to different states in the second embodiment, and FIGS. 5 (d) to 5 (f) are respectively FIG. 5 (a). ~
It is a figure which shows the wavelength range and imaging position of the illumination light selected corresponding to (c).

FIG. 6A is a diagram showing the characteristics of axial chromatic aberration of the projection optical system of the third embodiment of the present invention, and FIG. 6B is the result when the conventional interference filter plate is used in the third embodiment. FIG. 6C is a diagram showing the distribution of image positions, and FIG. 7C is a diagram showing the distribution of image formation positions when the broadband interference filter plate of the first embodiment is used in the third embodiment.

FIG. 7 is a configuration diagram showing a conventional projection exposure apparatus.

FIG. 8 is a diagram showing axial chromatic aberration of a projection optical system in a conventional example.

FIG. 9 is a diagram showing a distribution of image forming positions when an interference filter plate of a conventional example is used.

[Explanation of symbols]

 1 Mercury Lamp 4 Shutter 5 Input Lens 7 Fly's Eye Lens 9 Condenser Lens R1 Reticle with a dense pattern R2 Reticle with a discrete pattern 11 Projection optical system W Wafer 14 Turret type rotating plate 15A Narrow band interference Filter plate 15B Broad band interference filter plate 17 Main control system 21 Narrow band interference filter plate 23 Guide 24 Drive device

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location G11B 5/31 M 8947-5D

Claims (2)

[Claims] 1. A light source system for supplying illumination light converted into parallel light flux, a secondary light source forming means for forming a plurality of secondary light sources from the illumination light, and an illumination light from the plurality of secondary light sources. A condenser lens system that illuminates a mask on which a transfer pattern is formed by illuminating with a substantially uniform illuminance; and a projection optical system that projects a pattern image of the mask onto a photosensitive substrate under the illumination light. In the projection exposure apparatus having: the secondary light source, the illumination light of a predetermined wavelength band is selected from the illumination light supplied from the light source system between the light source system and the secondary light source forming means. A wavelength selecting unit to be provided to the forming unit is arranged, and a wavelength band selected by the wavelength selecting unit is set such that the axial chromatic aberration of the projection optical system with respect to the illumination light is equal to or larger than the width of the depth of focus of the projection optical system. Characterized by having a wavelength band Projection exposure apparatus. 2. A light source system for supplying illumination light converted into parallel light flux, a secondary light source forming means for forming a plurality of secondary light sources from the illumination light, and an illumination light from the plurality of secondary light sources. A condenser lens system that illuminates a mask on which a transfer pattern is formed by illuminating with a substantially uniform illuminance; and a projection optical system that projects a pattern image of the mask onto a photosensitive substrate under the illumination light. In a projection exposure apparatus having: a light source system and a secondary light source forming means, depending on an inclination angle with respect to the illumination light supplied from the light source system,
Arranging wavelength selecting means for selecting illumination light of different wavelength bands from the illumination light and supplying the selected light to the secondary light source forming means, and changing an inclination angle of the wavelength selecting means with respect to the illumination light within a predetermined range. Driving means for changing the inclination angle of the wavelength selecting means with respect to the illumination light by the driving means, and selecting the wavelength band of the illumination light during exposure of the substrate with the projection optical system for the illumination light. The projection exposure apparatus is characterized in that the axial chromatic aberration is set in a range that is equal to or larger than the width of the depth of focus of the projection optical system.