JPH0743883A - Exposing method and photomask to be used in this exposing method - Google Patents

Abstract

PURPOSE:To provide a photomask introduced with coherence on a pattern forming surface of the photomask as a parameter in design. CONSTITUTION:A halfwave plate 24 is deposited in the opening pattern between light shielding films 21B an 21C among the opening patterns formed between the light shielding films 21A, 21B,... deposited on a glass substrate 20 of the photomask R. The intensity of the combined light beams of the light beams transmitted through the halfwave plate 24 and the light beams past the opening patterns on both sides if illuminating light beams ILB are random polarized is the incoherent sum of the light beams past the opening patterns on both sides and the light beams past the halfwave plate 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo-sensitive substrate through a projection optical system or by a proximity method when a semiconductor device such as ULSI or a liquid crystal display device is manufactured by a photolithography process. The present invention relates to an exposure method of an exposure apparatus used to expose the top and a photomask used in this exposure method.

[0002]

2. Description of the Related Art When manufacturing a semiconductor element, a liquid crystal display element, a thin film magnetic head, etc. by a photolithography process,
An exposure apparatus that exposes a pattern of a photomask or reticle (hereinafter collectively referred to as “photomask”) onto a substrate (wafer, glass plate, etc.) coated with a photoresist through a projection optical system or by a proximity method. Is used.

A conventional ordinary photomask used as an original plate in such an exposure apparatus has a pattern formed on a glass substrate 20 by a light shielding film 21 such as chromium as shown in FIG. 5 (a). is there. With the increase in the density of integrated circuit patterns and the like, higher resolution is also required for patterns to be transferred onto a photosensitive substrate. As a method for increasing the resolution, there have been proposed techniques for making various improvements on a photomask.

The first conventional technique is Japanese Patent Publication No. 62-5081.
This is a so-called phase shift mask method typified by Japanese Patent Publication No.
Although various modifications have been proposed for the phase shift mask, the essence of the phase shift mask method is to control the phase of light passing through the photomask. That is, FIG.
FIG. 5B shows an example of a photomask used in the phase shift mask method. In FIG. 5B, the glass substrate 20 is used.
A periodic opening pattern is formed by a light-shielding film 21 made of chrome or the like on the lower surface of, and the phase shifters 22A and 22B are arranged in a part of the opening pattern. Here, the light having the amplitude ψ ₁ that has passed through the portion where the phase shifter 22A is present and the light having the amplitude ψ ₂ that has passed through the opening pattern in which the phase shifter is not arranged have the opposite phases, and thus, It enhances the resolution of matching patterns.

The second conventional technique is disclosed in, for example, Japanese Patent Laid-Open No. 5-88.
As disclosed in Japanese Patent No. 356, the polarization characteristics of light are utilized. FIG. 5C shows a photomask (so-called polarization mask) used in the second conventional technique. In FIG. 5C, an opening pattern is formed on the lower surface of the glass substrate 20 by a light shielding film 21 such as chromium. The polarizing plate 23 is formed and arranged on these opening patterns. Polarizing plate 2
3 is arranged so that only the polarized component vibrating in the direction perpendicular to the paper surface of FIG. 5C is transmitted. Therefore, at the time of image formation, an image is formed on the image plane with a polarization component (S-polarized light) that vibrates perpendicularly to the incident surface of the image formation light.
As a result, the mutual interference effect of the image forming lights is enhanced and the resolution can be expected to be improved.

[0006]

The above-mentioned conventional techniques also have their own limitations from the viewpoint of improving the resolution. That is, as in the phase shift mask of FIG. 5B and the polarization mask of FIG. 5C, there is a disadvantage that the pattern on the photomask cannot be faithfully transferred onto the photosensitive substrate due to the pseudo peak. What is a pseudo peak?
This is a phenomenon in which a sub-peak of the light intensity distribution is generated in a portion of the photomask that does not correspond to the original opening, which is caused by the light interference effect.

That is, the pseudo peak means that the light having the amplitude ψ _{1 and} the light having the amplitude ψ ₂ in FIG. 5B and the light having the amplitude ψ _{3 and} the light having the amplitude ψ ₄ in FIG. Each is due to their coherence with each other.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an exposure method capable of suppressing the occurrence of a pseudo peak by adjusting the mutual coherency (coherence) of lights passing through an opening pattern of a photomask. It is another object of the present invention to provide a photomask that can be used in such an exposure method, that is, a photomask in which coherency (coherence) on the pattern formation surface of the photomask is introduced as a design parameter. And

[0008]

In the exposure method according to the present invention, for example, as shown in FIG. 1, a photomask (R) having one or a plurality of aperture patterns formed thereon is illuminated with illumination light, and the aperture patterns are formed. In the method of projecting and exposing the image of (1) on a photosensitive substrate via a projection optical system, the polarization component of the illumination light in the direction of the main axis and the A phase shift plate (24) that gives a predetermined phase difference to the polarization component of the illumination light parallel to the axis perpendicular to the main axis is arranged, and the coherency of light passing through each aperture pattern is adjusted to adjust each of them. The image of the aperture pattern is projected and exposed on the substrate.

The first photomask of the present invention is, for example, as shown in FIG. 1, in a light-shielding film (21A to 21D) deposited on a substrate (20) transparent to predetermined illumination light. In a photomask in which a plurality of aperture patterns are formed on a part of the aperture patterns, the polarization pattern of the illumination light in the direction of the main axis and the illumination light parallel to the axis perpendicular to the main axis It is covered with a phase shift plate (24) that gives a predetermined phase difference to the polarized component.

Further, the second photomask of the present invention is, for example, as shown in FIG. 3, one or a plurality of photomasks are provided in a light-shielding film (21E) deposited on a substrate transparent to predetermined illumination light. In the photomask in which the opening patterns of the above are formed, at least one opening pattern (2
In a part of the region (27) of 5), a phase shift plate that gives a predetermined phase difference to the polarization component of the illumination light in the direction of the main axis and the polarization component of the illumination light parallel to the axis perpendicular to the main axis is provided. It is arranged.

Further, in the first photomask,
For example, as shown in FIG. 2, the adjacent opening patterns of the plurality of opening patterns are respectively phase shift plates (24A,
When covered with 24B), it is desirable to make the directions of the main axes of the phase shift plates (24A, 24B) adjacent to each other non-parallel. Further, in the first photomask, an example of the phase shift plate (24, 24A, 24B) is a ½ wavelength plate or a ¼ wavelength plate.

[0012]

The principle of the present invention will be described with reference to FIG.
In the photomask (R) used in this case, an opening pattern is formed between the light shielding films (21A to 21D) deposited on the transparent substrate (20), and a part of the opening pattern serves as a phase shift plate. It is assumed that the half-wave plate (24) is arranged. The amplitude of light passing through the _{aperture 1} the amplitude of the light [psi, 1/2-wavelength plate (24) is arranged to pass through the opening of the portion having no half-wave plate as [psi _2, and the amplitude [psi ₁ Light Amplitude ψ ₂
Think about interference with light. Since the illumination light is usually unpolarized, it can be considered as an incoherent sum of two orthogonal polarization components.

A straight line parallel to the main axis of the half-wave plate (24)
For the polarization component, the amplitude ψ ₁And amplitude ψ₂Same as
If it is in phase, it is formed by the interference of these two lights.
Light intensity is | ψ₁+ ψ₂|² Is. On the other hand, 1/2 wavelength
1 for the linearly polarized light component perpendicular to the principal axis of the plate (24)
Amplitude ψ₂Is half a wavelength
Amplitude ψ₂The light's phase is reversed
And the amplitude ψ₁Light and amplitude ψ₂Formed by the light of
The light intensity is | ψ₁-ψ₂|² Is.

This state is shown in FIGS. 1 (b) and 1 (c). That is, FIG. 1B shows a half-wave plate (2
4) Amplitude transmittance distribution of the photomask observed with a linearly polarized light component parallel to the principal axis of 4). FIG. 1C shows the amplitude transmittance distribution of the photomask observed in the linearly polarized light component orthogonal to the main axis of the half-wave plate (24). Now, the light intensity I formed as a result of the interference between the light of the amplitude ψ _{1 and} the light of the amplitude ψ ₂ is given by the intensity sum of FIG. 1 (b) and FIG. 1 (c). That is, the light intensity I is as follows.

[0015]

## EQU1 ## I = (1/2) {| ψ ₁ + ψ ₂ | ² + | ψ ₁ -ψ ₂ | ² } = | ψ ₁ | ² + | ψ ₂ | ² where the coefficient 1/2 is Since two polarization directions are considered, they are coefficients for the normalization. The above formula gives the amplitude ψ
It is the sum of the intensities of the light of _{1 and} the light of amplitude ψ ₂ . This indicates that the light with the amplitude ψ _{1 and} the light with the amplitude ψ ₂ are incoherent. In other words, Figure 1
The three opening patterns shown in FIG.
This is equivalent to the division into the two opening patterns of (d) and the one opening pattern of FIG.

Further, in the state of FIG. 1B, it is assumed that the light with the amplitude ψ _{1 and} the light with the amplitude ψ ₂ have the same phase, but in general, when there is a phase difference φ, instead of (Equation 1), , The following (Equation 2)
The light intensity I is calculated as follows. As a result, the phase difference φ
It turns out that the result is the same regardless of.

[0017]

## EQU2 ## I = (1/2) {| ψ ₁ + exp (iφ) ψ ₂ | ² + ｜ ψ ₁ -exp
(iφ) ψ ₂ | ² } = | ψ ₁ | ² + | ψ ₂ | ^{2 In} order to simplify the explanation, the light with the amplitude ψ ₁ that has passed through the opening of the raw glass and the half-wave plate are described above. Although the light having the amplitude ψ ₂ that has passed through the portion (24) has been described, the present invention has a wider range of application.

Now, the two amplitudes ψ_ALight and amplitude ψ_BWith the light of
, The amplitude ψ_ALight passes through the phase shift plate with the phase difference Δ,
Amplitude ψ_BLight passes through the phase shift plate with the phase difference Δ ′,
If the angle between the main axes of the phase shift plates is θ,
Width ψ_ALight and amplitude ψ_BLight intensity I formed by
Is as follows. Where ψ_A ^*And ψ_B ^*Are respectively ψ _A
And ψ_BIs the conjugate conjugate of.

[0019]

## EQU3 ## I = | ψ _A | ² + | ψ _B | ² + C (θ, Δ, Δ ′) (ψ _A ^* ψ
_B + ψ _A ψ _B ^* ) However, the parameter C (θ, Δ, Δ ′) is expressed as follows.

[0020]

[Equation 4] C (θ, Δ, Δ ′) = cos ² θ · cos {(Δ−Δ ′) /
2} + sin ² θ · cos {(Δ + Δ ′) / 2} (Equation 3) indicates that various interference states can be realized depending on the value of the parameter C. To give a few examples
The following image formation can be realized by the value of the parameter C. When C (θ, Δ, Δ ′) = 1, I = | ψ _A + ψ _B | ² , and coherent imaging is performed. When C (θ, Δ, Δ ′) = 0, I = | ψ _A | ² + | ψ _B | ²
Then, incoherent imaging is performed. When C (θ, Δ, Δ ′) = − 1, I = | ψ _A −ψ _B | ² , and phase inversion and coherent imaging is performed.

For example, in the example of FIG. 1 described above, the phase difference Δ of the light having the amplitude ψ ₁ that has passed through the opening is 0, the half-wave plate (2
Since the phase difference Δ ′ of the light of amplitude ψ ₂ that has passed through 4) is π,
From (Equation 4), the value of the parameter C (θ, Δ, Δ ′) becomes 0, and it can be confirmed again in FIG. _{1 that} the light with the amplitude ψ _{1 and} the light with the amplitude ψ ₂ are incoherent.
(Equation 3) and (Equation 4) indicate that various interference states can be realized depending on the phase difference amount of the phase shift plate to be used and, when using a plurality of phase shift plates, depending on the angle formed between the main axes. . Here are some simple examples. Example 1) Phase difference Δ is 0
When the element glass of No. 1 and the quarter wave plate having the phase difference Δ ′ of π / 2 are used, the parameter C (θ, Δ,
Δ ') is as follows.

C (θ, Δ, Δ ') = 1/2 ^1/2 Therefore, the light intensity distribution I is as follows.

[0023]

[Equation 5]

That is, the coherent state and the incoherent state are intermediate states in which the following ratios are mixed.

[0025]

[Equation 6]

Example 2) When two quarter-wave plates are used,
That is, when both the phase difference Δ and the phase difference Δ ′ are π / 2,
From the equation (4), the parameter C (θ, Δ, Δ ′) is as follows. C (θ, Δ, Δ ′) = cos ² θ Therefore, the value of the parameter C can take values from 0 to 1 depending on the angle θ formed by the main axes of the two quarter-wave plates. An arbitrary state between coherent and incoherent can be obtained as the interference state between the light of amplitude ψ _{A and} the light of amplitude ψ _B.

Example 3) When two half-wave plates are used,
That is, when both the phase difference Δ and the phase difference Δ ′ are π, the parameter C (θ, Δ, Δ ′) is as follows from (Equation 4). C (θ, Δ, Δ ′) = cos ² θ−sin ² θ = cos 2θ Therefore, depending on the angle θ formed by the main axes of the two half-wave plates, the value of C ranges from -1 to 1. As the interference state between the light of amplitude ψ _{A and} the light of amplitude ψ _B ,
Coherent, incoherent, phase-inverted and coherent, and any intermediate states in between are obtained. The above is an example given to facilitate understanding of the principle of the present invention.

Further, the above description mainly relates to the case of controlling the coherency of light beams passing through different aperture patterns, but the coherency of light beams passing through different regions in one aperture pattern is also the same method. Can be controlled. That is, as shown in FIG. 3, the phase shift plate is arranged in a partial area (27) in one opening pattern (25), or a partial area (27) and other areas (26, By arranging different phase shift plates in 28) and coherency, it is possible to control the coherency between the light passing through the region (27) and the light passing through the other regions (26, 28) to an arbitrary state. . Thereby, for example, even with an isolated pattern, it is possible to perform exposure with a deep depth of focus and suppressing a pseudo peak.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. Prior to the description of the photomask of the embodiment, an example of a projection exposure apparatus used for exposing the pattern of the photomask of the embodiment onto a photosensitive substrate will be described with reference to FIG. FIG. 6 shows a schematic configuration of the projection exposure apparatus of the present embodiment. In FIG. 6, the illumination light emitted from the mercury lamp 1 is reflected by the elliptical mirror 2, and then the input lens 4 and a predetermined wavelength band. Of the light is selectively incident on the fly-eye lens 7 through the first and second filter plates 5 and 6. A shutter 3 for switching irradiation and blocking of illumination light is arranged near the second focal point of the elliptic mirror 2, and a main control system 16 for controlling the operation of the entire device opens and closes the shutter 3 via a driving device 17. .

Rear side of the fly-eye lens 7 (reticle side)
An aperture stop for illumination light (hereinafter referred to as “σ stop”) 8 is arranged on the focal plane, and illumination light from a large number of secondary light sources in the σ stop 8 is reflected by a mirror 9, The pattern area of the photomask R is illuminated with a uniform illuminance via the relay lens 10, variable field diaphragm (reticle blind) 11, second relay lens 12, mirror 13 and condenser lens 14. In this case, the arrangement surface of the variable field stop 11 is conjugate with the pattern formation surface of the photomask R,
The arrangement surface of the σ stop 8 is conjugate with the pupil surface of the projection optical system PL (Fourier transform surface of the pattern area of the photomask R). The main control system 16 sets the shapes of the openings of the σ diaphragm 8 and the variable field diaphragm 11 to predetermined shapes via the drive device 18.

Further, the photomask R is used as a mask stage R.
The reticle reader 15 is held on ST and arranged in the vicinity of reticle stage RST. When the photomask R is loaded onto the mask stage RST by a reticle loader system (not shown), the reticle information (bar code, etc.) formed on the photomask R is read by the reticle reader 15, and the read reticle information is mainly read. It is supplied to the control system 16. As a result, the main control system 16 can recognize the contents of the photomask R currently held on the mask stage RST (type of pattern, minimum line width of pattern, etc.).

Under the illumination light ILB emitted from the condenser lens 14, the pattern image of the photomask R is projected and exposed through the projection optical system PL onto the wafer W coated with the photoresist. Wafer W is wafer stage WS
The wafer stage WST, which is placed on T, positions the wafer W in the XY plane perpendicular to the optical axis AX of the projection optical system PL, and positions the wafer W in the Z direction parallel to the optical axis AX. It is composed of a Z stage and the like. The main control system 16 controls the operation of the wafer stage WST via the drive unit 19 so that a desired shot area of the wafer W is positioned within the exposure field of the projection optical system PL and the shot area is projected. The position (focus position) of the optical system PL in the optical axis direction is set to the position of the image plane of the projection optical system PL.

The photomasks of the following embodiments are not limited to the projection exposure apparatus as shown in FIG. 6 but also a proxy for transferring the pattern of the photomask onto a wafer arranged close to or in close contact with the photomask. Exposure can also be performed with a Miti type exposure apparatus. Next, a first embodiment of the photomask R used in this example will be described with reference to FIG.

FIG. 1A shows a photomask R of this embodiment.
FIG. 1 (a) shows a part of the glass substrate 2
0 is coated with light-shielding films 21A, 21B, ... Of chromium or the like, and a half-wave plate 24 is coated on the opening pattern between the light-shielding films 21B and 21C. Illumination light IL
Since B is normally non-polarized light, as described in the explanation of the principle of the present invention, the light intensities obtained on the wafer are orthogonal to each other.
It can be thought of as the sum of the incoherences of the two polarization components.

Here, considering the linearly polarized light component parallel to the main axis of the half-wave plate 24 and the linearly polarized light component perpendicular to the main axis, the amplitude of the photomask R seen from each polarized light component. The transmittance distributions are as shown in FIG. 1 (b) and FIG. 1 (c), and the sum of these intensities is shown in FIG. 1 (d) and FIG.
It is the same as the intensity sum with (e). That is, the exposure by the photomask R shown in FIG. 1A is multiple exposure by the photomask having the amplitude transmittance distribution of FIG. 1D and the photomask having the amplitude transmittance distribution of FIG. 1E. You get the same result as you did. That is, by using the ½ wavelength plate 24, it is possible to achieve the same effect as that of performing double exposure with two photomasks that have been divided into patterns with one photomask. As a result, the pattern density can be substantially reduced and the resolution can be improved. Also,
Since the lights passing through the adjacent aperture patterns become incoherent to each other, it is possible to reduce the pseudo peak generated by the light interference effect, the shape distortion of the pattern, and the like.

As a second embodiment of the present invention, an example in which a plurality of phase shift plates are used or a phase shifter and a phase shift plate are used together will be described with reference to FIG. FIG. 2B shows a part of the photomask R of the second embodiment.
In (b), an opening pattern is formed between the light-shielding films 21A, 21B, ... Of chromium or the like deposited on the glass substrate 20. Then, the light shielding film 21D and the light shielding film 21E
The phase shifter 22A is applied to the opening pattern between the light shielding film 21A and the light shielding film 21B, and the opening pattern between the light shielding film 21B and the light shielding film 21C has a half wavelength. Plates 24A and 24B are applied. However, FIG. 2 which is a plan view of FIG.
As shown in (a), the direction of the main axis R1 of the half-wave plate 24A and the direction of the main axis R2 of the half-wave plate 24B are orthogonal to each other.

The photomask of this embodiment is subjected to linear polarization in two directions parallel and perpendicular to the main axis of the half-wave plate 24A (that is, perpendicular and parallel to the main axis of the half-wave plate 24B). When observed by the component, it is observed as an amplitude transmittance distribution as shown in FIG. 2 (c) and FIG. 2 (d), respectively.
2 (c) and FIG. 2 (d) do not interfere with each other.
If the intensity sum of (c) and FIG. 2 (d) is taken, it becomes the same as the intensity sum of FIG. 2 (e) and FIG. 2 (f). Therefore, by arranging the half-wave plates 24A and 24B with their principal axes orthogonal to each other, the interference relationship between the lights passing through these two aperture patterns is the same as in the case where the phase shifter 22A is arranged. In addition, a coherent state can be realized. Moreover, it is possible to make incoherent with light that has passed through other portions (light that has passed through an aperture in which nothing is arranged and the phase shifter 22A) while maintaining this relationship.

In this way, 1 /
By arranging the phase shift plates such as the two-wavelength plates 24A and 24B, mutual coherency of light passing through the aperture pattern can be changed. As a result, the design parameters of the photomask are increased, and it is possible to approach the realization of ideal image formation. As for the arrangement of the phase shift plate on the photomask, it is not always necessary to cover one opening pattern with one phase shift plate. An example of such a photomask will be described as a third embodiment of the present invention with reference to FIG. This embodiment is an application of the present invention when exposing an isolated pattern such as a contact hole pattern.

FIG. 3 shows an enlarged view of a part of the photomask R of this example. In FIG. 3, a rectangular opening pattern 25 is formed in the light shielding film 21E attached to the lower surface of the glass substrate. Central rectangular area 2 in this opening pattern 25
6 and the surrounding frame-shaped region 28 are out of phase with each other. That is, the phase shifter is arranged in one of the central region 26 and the peripheral region 28. Further, a half-wave plate is attached to the middle frame-shaped region 27 in the opening pattern 25. In this case, the light passing through the intermediate region 27 is made incoherent with respect to the light passing through the regions 26 and 28.

The edge-enhanced phase shift mask of the prior art corresponds to the state where there is no intermediate region 27 in FIG. In addition to the peak of the light intensity corresponding to the pattern, a pseudo peak was apt to occur. On the other hand, in the case of using the photomask of the present embodiment shown in FIG. 3, by providing the intermediate region 27, the intermediate region 27 is provided, and the intermediate region 27 and the peripheral region 28 are provided with an intermediate region. The light passing through the area 27 can be made incoherent to adjust the interference effect and realize an appropriate light intensity distribution.

Next, a photomask according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a main part of the photomask R of this example. In FIG. 4, two sets of opening pattern rows 29 and 30 are periodically formed in a predetermined direction in a light-shielding film deposited on a glass substrate. A single opening pattern 31 extending in the predetermined direction is formed between the opening pattern rows 29 and 30. In this example, the half-wave plate 32 covers the intermediate opening pattern 31.
To wear. If the half-wave plate 32 is not provided, the projected image of the intermediate aperture pattern 31 is affected by the projected images of the adjacent periodic aperture pattern rows 29 and 30, and the image fidelity is improved. There is a risk of deterioration and pattern distortion. On the other hand, when the half-wave plate 32 is provided as in the present embodiment, the light passing through the aperture pattern 31 and the light passing through the adjacent aperture pattern rows 29 and 30 are made incoherent to each other. Thus, each aperture pattern is projected with high image fidelity.

Although the half-wave plate is used as the phase shift plate in the above embodiment, the gist of the present invention is to arrange the phase shift plate on the photomask to open the aperture on the photomask. It is to freely control the coherency (coherency) between the light passing through the pattern and to arbitrarily create coherent, incoherent, phase-inverted coherent, and intermediate states thereof. In this sense, as the phase shift plate, it is apparent that a quarter wavelength plate or any optical element that produces various phase differences between the principal axis and the direction perpendicular to the principal axis can be used.

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.

[0044]

According to the exposure method of the present invention, since the phase shift plate is arranged on a part or the whole of the predetermined opening pattern on the photomask, mutual coherency of light passing through the opening pattern (possible). The degree of interference) can be adjusted. Therefore, there is an advantage that it is possible to suppress the occurrence of the pseudo peak and perform the exposure in a favorable image formation state.

By thus providing the phase shift plate on the photomask, the coherency between the light passing through the aperture pattern can be freely changed. In other words, it is possible to freely set which of the coherent light, the incoherent light, the coherent light of phase inversion, and an intermediate state between them, which sets the light passing through the aperture pattern, depending on the state of the photomask. This is the most essential effect of the present invention.

Further, according to the first and second photomasks of the present invention, by disposing the phase shift plate on a part or all of the predetermined opening pattern, the mutual opening patterns are set as parameters for designing the photomask. Coherency can be introduced. As a result, when the phase shift plate is provided in a part of the plurality of opening patterns as in the first photomask, the light passing through the opening patterns is incoherent, for example, so that one sheet of With the photomask, it is possible to perform the same exposure as in the case of performing double exposure with two photomasks. This substantially means a reduction in pattern density, in other words, an improvement in resolution. Further, making them mutually incoherent also means that pseudo peaks that are sometimes observed due to pattern shapes and the like are reduced.

When the phase shift plate is arranged in a partial area of one opening pattern like the second photomask,
It is possible to expose an isolated pattern with high resolution while suppressing the pseudo peaks that are seen in the edge enhancement type phase shift mask. Further, by making the directions of the principal axes of two adjacent phase shift plates (1/2 wavelength plate, etc.) orthogonal to each other, it is possible to obtain an effect equivalent to that of a phase shifter, and further, these phase shift plates are attached. It is possible to make light that has passed through one portion incoherent with respect to light that has passed through another portion.

[Brief description of drawings]

FIG. 1A is an enlarged cross-sectional view showing a main part of a photomask according to a first embodiment of the present invention, and FIGS.
It is explanatory drawing of the amplitude transmittance distribution by the photomask of an Example.

2A is an enlarged plan view showing a main part of a photomask according to a second embodiment of the present invention, FIG. 2B is an enlarged sectional view from the front direction of FIG. 2A, and FIGS. 5F is an explanatory diagram of the amplitude transmittance distribution by the photomask of the second embodiment.

FIG. 3 is an enlarged plan view showing a main part of a photomask according to a third embodiment of the present invention.

FIG. 4 is an enlarged plan view showing a main part of a photomask according to a fourth embodiment of the present invention.

5A is an enlarged sectional view showing an essential part of a conventional ordinary photomask, FIG. 5B is an enlarged sectional view showing an essential part of a conventional phase shift mask, and FIG. 5C is a so-called polarization mask essential part. It is an enlarged plan view showing a portion.

FIG. 6 is a configuration diagram showing an example of a projection exposure apparatus for performing exposure using the photomask of the embodiment.

[Explanation of symbols]

 R Photomask W Wafer 20 Glass substrate 21A to 21E Light-shielding film 22A Phase shifter 24, 24A, 24B 1/2 wavelength plate

Claims (5)

[Claims] 1. A method of illuminating a photomask having one or a plurality of aperture patterns with illumination light and projecting an image of the aperture pattern onto a photosensitive substrate through a projection optical system, A part or all of each opening pattern on the photomask is provided with a predetermined phase difference between the polarization component of the illumination light in the direction of the principal axis and the polarization component of the illumination light parallel to the axis perpendicular to the principal axis. An exposure method comprising arranging a phase plate, adjusting the mutual coherency of light passing through the aperture patterns, and projecting and exposing the images of the aperture patterns on the substrate. 2. A photomask having a plurality of opening patterns formed in a light-shielding film deposited on a substrate transparent to predetermined illumination light, wherein a part of the opening patterns is A photomask covered with a phase shift plate that gives a predetermined phase difference to the polarization component of the illumination light in the direction of the principal axis and the polarization component of the illumination light parallel to the axis perpendicular to the principal axis. 3. A photomask having one or a plurality of opening patterns formed in a light-shielding film deposited on a substrate transparent to predetermined illumination light, wherein at least one of the opening patterns is provided. In a part of the area of the opening pattern, a phase shift plate that gives a predetermined phase difference to the polarization component of the illumination light in the direction of the main axis and the polarization component of the illumination light parallel to the axis perpendicular to the main axis is arranged. A photomask characterized by. 4. When the adjacent opening patterns of the plurality of opening patterns are respectively covered with the phase shift plate, the directions of the main axes of the adjacent phase shift plates are made non-parallel. The photomask according to claim 2. 5. The phase shift plate is a half wave plate or a quarter wave plate.
The photomask according to claim 2, wherein the photomask is a wave plate.