JPH05234847A - Exposure method using projection optical system - Google Patents

Abstract

PURPOSE:To prevent a leakage light to a dark part due to a beam of transmitted light from a half tone part in an exposure operation using a half-tone phase shift reticle by a method wherein a light-shielding plate which shields only a light flux passing near an optical axis is installed on a Fourier transform face with reference to a reticle pattern. CONSTITUTION:In a half-tone phase shift reticle R, a transmission part (b) exists in a substratum layer (a) in a phase shift transmission part whose transmission factor is 5 to 30%. A light-shielding plate FL is installed near a pupil face EP as a Fourier transform corresponding face with reference to a reticle pattern in a projection optical system PL; a beam of light near an optical axis is cut off. Consequently, regarding an amplitude distribution in the pupil face EP, an amplitude near the optical axis AX is removed completely. An amplitude distribution having a very small width as the inverse Fourier transform of the amplitude on the pupil face EP is generated on the face of a wafer W. since the intensity of a projection image is the square of the absolute value of an amplitude distribution, a very fine bright pattern in which an intensity distribution causing a noise has been cut off is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure and transfer technique for fine patterns required for manufacturing semiconductor integrated circuits, liquid crystal displays and the like, and more particularly to an exposure method using a projection optical system.

[0002]

2. Description of the Related Art A fine pattern such as a semiconductor circuit pattern is formed by a method called photolithography. In particular, the reduction projection method is the current mainstream, and this is to reduce an enlarged original plate (reticle) of a circuit pattern by a projection optical system and transfer it onto an object to be exposed (wafer or the like). At this time, the surface of the wafer is coated with a photosensitive film (photoresist) with a thickness of about 1 μm, and the photoresist is exposed according to the contrast (contrast) of the projected image of the reticle pattern. When this is developed, in the positive type photoresist, the resist in the light-irradiated portion (bright portion) is dissolved and removed, and the resist in the light-unirradiated portion (dark portion) is not dissolved and remains as a film. On the contrary, in the negative type photoresist, the light portion remains as a film and the dark portion dissolves. In the current technology, the positive photoresist is superior in resolution and stability to the negative photoresist,
In general wafer lithography, almost all positive photoresists are used.

The resolution (minimum pattern size that can be transferred) in the conventional projection exposure method is represented by k · λ / NA,
The resolution has been improved by shortening λ (exposure wavelength) and enlarging NA (numerical aperture of the projection optical system). Recently, the phase shift method (Japanese Patent Publication No. 62-50811, etc.) and the multiple imaging amplitude width composition method (SupperF presented at the lecture 29azc-8, 9 of the 1991 Spring Applied Physics Society)
LEX) has been proposed, and a method for improving the resolution more than before without changing the numerical aperture NA and the wavelength λ is being studied.

The phase shift method is a light transmitting portion that transmits almost all the light and a phase shifter portion that shifts the phase of the transmitted light with respect to the light passing through the transmitting portion by approximately π [rad] or an odd multiple thereof. It is an exposure method using a so-called phase shift reticle in which a desired pattern is formed by using.
At this time, the normal transmission part (phase = 0, amplitude = exp (i ×
0) = + 1) and the phase shifter (phase =
π, amplitude = exp (iπ) = − 1) is used to increase the resolution by utilizing the effect of canceling the amplitude of the light ((+1) + (− 1) = 0).

On the other hand, the multiple imaging amplitude synthesis method is a method in which a surface corresponding to a Fourier transform for a reticle pattern in a projection optical system (hereinafter abbreviated as a pupil surface) has a low transmittance near the optical axis and a peripheral transmittance. Is a method of exposing a reticle pattern by providing a light absorbing member having a high light absorption rate. This multiple imaging amplitude composition method
Particularly, it is advantageous for forming a hole pattern (fine hole pattern) or an island pattern (fine leaving pattern).

Further, the exposure for one area on the wafer is divided into a plurality of times, and the wafer is shifted by a small amount in the optical axis direction of the projection optical system for each divided exposure, and the defocused pattern image is also multiplexed. A multiple imaging method of exposing is also proposed. With this method, the focus latitude (depth of focus) can be increased particularly when a hole pattern is formed in a positive photoresist.

[0007]

An ordinary reticle pattern formed of a conventional complete light-shielding portion (chrome layer) and a complete light-transmitting portion is exposed using a projection optical system that does not absorb or shield the pupil plane. In that case, the focus latitude (depth of focus) of the projected image is determined to be approximately ± λ / 2NA ² . Therefore, in order to improve the resolution, the exposure wavelength λ is reduced to reduce the numerical aperture N.
The depth of focus inevitably becomes extremely small as A is increased. However, the actual semiconductor integrated circuit surface (the surface of one exposed region on the wafer) has irregularities of about 1 μm, and the optical thickness (actual thickness) of the photosensitive material (photoresist) for pattern transfer is further increased. / Refractive index≈0.5 μm), a depth of focus of approximately 1.5 μm or more is required for accurate pattern transfer. The exposure wavelength λ of 0.3 is 0.3
Since the depth of focus is 65 μm and the numerical aperture NA is about 0.5, the depth of focus is ± 0.365 / 2 × 0.5 ² = ± 0.73 μm. This value is 1.46 μm in width, and it can be seen that the depth of focus is already insufficient at present. Therefore, the method of further improving the resolution by shortening the exposure wavelength λ and increasing the numerical aperture NA is not practical from the viewpoint of sacrificing the depth of focus.

The phase shift method has an effect of not only improving the resolution but also increasing the depth of focus, but it is particularly applicable to a hole pattern (a pattern for partially forming fine holes in a photoresist). difficult. Assuming the use of a positive resist with good performance as described above,
This is because as a reticle structure, it is necessary to form a transparent portion (hole pattern) on the base of the chrome layer that serves as a light-shielding portion, and a phase shift portion on the transparent portion that surrounds the chrome layer. difficult. This requires two patterns of patterning: patterning for forming the light-shielding / transmissive part (patterning by etching the chrome layer) and patterning for forming the transmissive part / phase shift transmissive part (patterning by the shifter layer etching). This is because there is a need for alignment between both patternings.

Further, although these patternings are usually performed by an electron beam exposure apparatus (EB exposure apparatus), the pattern data handled by the EB exposure apparatus also includes drawing data for patterning the transparent portion / light shielding portion and the transparent portion / phase shift transmission. Both the drawing data for patterning the area are required, and an extremely large amount of data is handled. On the other hand, if a negative resist is used for the hole pattern, the phase shift reticle can be easily manufactured. The structure may be such that the hole pattern of the phase shift transmission part is formed on the glass base which becomes the transmission layer, and the patterning is performed only once. However, as described above, the negative type photoresist is inferior in performance to the positive type, and the above-mentioned multiple imaging method cannot be used together, so that the effect at the time of exposure is insufficient.

Further, in the multiple imaging amplitude composition method in which an absorbing member is provided on the pupil plane of the projection optical system, both the resolution and the focus / focus degree are improved especially for hole patterns, and a positive photoresist can be used. is there. However, the transmittance of the absorbing member on the pupil plane needs to be continuously changed concentrically from the optical axis, and it is difficult to actually manufacture this absorbing member. Further, this absorbing member generates heat or absorbs heat due to light absorption, and this is transmitted to other members of the projection optical system to induce thermal deformation and refractive index change, which leads to deterioration of the imaging performance itself. Also becomes. By the way, in order to obtain the desired effect, the amount of light absorbed by the absorbing member provided on the pupil plane reaches about 80% of the amount of light incident on the projection optical system.

A so-called halftone type phase shift has also been proposed as a phase shift reticle particularly suitable for exposing and transferring a hole pattern. This halftone type phase shift is to shift the phase by π and to provide a minute pattern of light transmission (out of phase) to the underlying layer (halftone) having a certain amount of light absorption (or reflection). It is a reticle. A minute hole pattern (bright pattern for positive resist) is formed by the interference effect of each transmitted light flux between the minute light transmitting portion and the other halftone portion. As a result, the resolution and the depth of focus at the time of exposure transfer of the hole pattern are increased. This halftone reticle has the advantage that it can be completed by one-time patterning and is easy to manufacture, but due to the transmitted light from the halftone portion, there is leakage light to the dark portion (non-pattern portion), and the projected image Reduces contrast. In addition, there is a problem that it is difficult to use it in combination with the above-mentioned multiple imaging method due to light leaked to the dark part.

Incidentally, the hole pattern formation has been described above, but this is because the hole pattern is the most difficult to form among the various patterns handled in the wafer lithography process. Therefore, if the hole pattern can be miniaturized, the entire integrated circuit can be easily miniaturized accordingly.

[0013]

In order to solve the above problems, according to the present invention, a mask (R) including a fine pattern structure is provided.
In the exposure method of illuminating the mask pattern and projecting the pattern of the mask onto the object to be exposed (W) through the projection optical system (PL), a transmissive part and a transmissive part that are substantially transparent to the light illuminating the mask. A mask that generates a minute pattern by a phase shift part having a transmittance of about 5 to 30% while generating a light beam whose phase is shifted by an odd multiple of the original light beam It is arranged on the object plane side of the system, and further, of the rays passing through this Fourier plane, at or near the Fourier plane which is in the optical Fourier transform relationship with the pattern plane of the mask in the projection optical system. Limiting member (light-shielding plate FL) that limits light rays passing near the optical axis
The object to be exposed installed on the image plane side of the projection optical system is exposed in the state where the is arranged.

[0014]

In the reticle used in the present invention, a very dark (due to the light canceling effect) dark portion is formed at the boundary between the transmitting portion and the phase shift transmitting portion (transmittance 5 to 30%), and the transmitting portion itself is bright. Transferred as an image. Further, the width of the bright image can be made narrower than in the case of the conventional completely transmissive / completely light-shielding type reticle due to the canceling effect. Further, when a reticle such as the present invention is mounted on a conventional exposure apparatus and exposed, the transmitted light (leakage light) from the phase shift transmitting portion also reaches the wafer as the exposed object. By providing a light blocking plate (spatial filter) that blocks only the light flux passing near the optical axis on the Fourier transform surface (hereinafter referred to as the pupil surface) for the reticle pattern in the projection optical system, the leak light reaches the wafer. Prevented that. This is because the spatial frequency of the pattern is high at the minute transmissive part or at the boundary part between the transmissive part and the phase shift transmissive part. This is because the light passes through without being shielded to reach the wafer and a bright image is generated. On the other hand, the underlying phase shift transmission part itself has a low spatial frequency, so that the diffracted light passes through the vicinity of the optical axis on the pupil plane of the projection optical system and is blocked by the light shielding plate and cannot reach the wafer.

[0015]

EXAMPLE An example of the pattern of the reticle R used in the example of the present invention is shown in FIG. This is the same structure as the halftone phase shift reticle used for forming the hole pattern on the premise of the positive resist. That is, there is a transparent portion b having a hole pattern in the underlayer a of the phase shift transparent portion having a transmittance of 5% to 30%.

FIG. 2B is a cross section of the reticle pattern shown in FIG. If the amplitude of the light L ₀ transmitted through the transmission part b is +1, the light L ₁ transmitted through the phase shift transmission part a
The sign of the amplitude of is negative and its magnitude is the square root of the energy transmittance. In FIG. 2, the energy transmission rate of the shifter transmission portion a is 25%. Now, if the projection optical system has a normal configuration (excluding a light-shielding member, etc.), the projection image of the transmission part b has an amplitude distribution Ab shown in FIG.
(It is slightly rounded by the optical system). On the other hand, the amplitude distribution Aa on the wafer of the projected image of the shifter transmission part a is shown in FIG.
It becomes like (D).

Since the actual image is the sum of the amplitude distributions Aa and Ab, the combined amplitude distribution is as shown by Aab in FIG. 2 (E). Since the intensity of the image light beam is the square of the absolute value of this amplitude distribution Aab, the intensity distribution Ia as shown in FIG.
It becomes b. At this time, spots of the light portion are formed on the base of the dark portion, and the hole pattern is for the positive resist. The broken line S in FIG. 2 (F) represents the threshold level of resist sensitivity, and a portion given an energy intensity higher than this is dissolved and removed during development. However, the transmitted light from the phase shift transmission part a has an intensity distribution In as a noise component in addition to the originally required transmission part b for the hole pattern. If the light amount of the intensity distribution In is large, the positive resist will undergo film verification (photosensitization), which is not preferable. However, bright spots (hole pattern)
Is the width of both transmitted light L of the transmission part b and the phase shift transmission part a.
Since it becomes thinner due to the canceling effect (interference effect) of ₀ and L _1, the transmittance of the phase shift transmitting portion a must be somewhat high (for example, 5% or more) in order to obtain a bright portion having a finer width. ..

FIG. 3 is a diagram schematically illustrating the above phenomenon based on the concept of a rediffractive optical system. In FIG. 3A, the illumination light IL is assumed to enter the reticle R vertically. The light transmitted through the reticle R is condensed on the wafer W by the telecentric projection optical system PL, and an image of the reticle pattern is formed here. Here, EP is a plane corresponding to the Fourier transform (hereinafter referred to as a pupil plane) for the reticle pattern in the projection optical system PL. The amplitude distribution of light after passing through the reticle pattern, that is, on the object of the projection optical system PL is shown in FIG.
It appears as in (B), and this distribution is Fourier transformed on the pupil plane EP to form an amplitude distribution as shown in FIG. 3 (C). Pupil E
Since P is limited in size (radius), that is, in numerical aperture NA, the optical axis AX on the pupil plane EP is equal to or larger than NA.
The amplitude distribution at a position away from is not transmitted to the wafer W. That is, the high frequency component in the Fourier spectrum is cut by the projection optical system PL, and only the low frequency component is transmitted to the wafer W (on the optical axis AX corresponds to the zero frequency). Therefore, the projected image formed on the wafer W is somewhat blunted with respect to the reticle pattern (transmission part b).

Another amplitude distribution (C) on the pupil plane EP is
The inverse Fourier transform results in the image amplitude distribution on the wafer surface (more accurately, the best focus surface). Figure 3
It shows in (D). 2 of the absolute value of the amplitude distribution of FIG.
The squared power is the intensity distribution of the projected image on the best focus plane shown in FIG. The above description is for explaining the principle of the present invention described below, and is not a function of the present invention, but a physical phenomenon that generally holds.

Next, the exposure method according to the present invention will be described with reference to FIG. Although the basic configuration of FIG. 1A is the same as that of FIG. 3A, the pupil plane EP in the projection optical system PL is used in the present invention.
A light shielding plate FL is provided in the vicinity. The light blocking plate FL cuts light distributed near the optical axis. The reticle R is the same as that shown in FIG. Therefore, the amplitude distribution of light after passing through the reticle pattern, that is, on the object plane side of the projection optical system PL is as shown in FIG. 1B, which is the same as FIG. 3B. However, the amplitude distribution on the pupil plane EP is significantly different from that shown in FIG. 3C due to the light shielding plate FL, as shown in FIG. 1C. That is, the amplitude in the vicinity of the optical axis AX is completely removed (= 0).

The amplitude distribution of the projected image on the surface of the wafer W (more precisely, the best focus surface) is again the inverse Fourier transform of the amplitude distribution chart (C) on the pupil plane EP. However, a low-frequency component, that is, a light flux that should become a large-area bright portion (that is, zero frequency to low frequency) because the low frequency component, that is, the portion near the optical axis is excluded from the amplitude distribution of the pupil plane EP, is not transmitted to the wafer W. Therefore, only the distribution of high-frequency components existing on the outer peripheral portion of the pupil plane EP is transmitted to the wafer W, and an amplitude distribution with a minute width is generated on the wafer W as shown in FIG. Since the intensity of the projected image is the square of the absolute value of the amplitude distribution shown in FIG.
As shown in (E), it becomes a minute bright pattern in which the intensity distribution In which becomes noise is cut, and it becomes possible to form a hole pattern by exposing and melting the minute area of the positive resist. Further, since the frequency components transmitted to the wafer W are those in which the high frequency components are relatively emphasized,
A finer pattern can be transferred.

Further, since the low-frequency component is shielded, the light flux from the large-area phase shift transmitting portion a is cut by the light shielding plate FL and does not reach the wafer W, so that the dark portion on the wafer W is completely dark. Becomes For this reason, there is no concern about film slippage (photosensitivity) of the positive resist. At this time, the size of the transmission part b, which is the original image of the hole pattern, is such that one side or diameter is about the resolution of the projection optical system PL. Also,
Actually, the incident angle of the light flux IL illuminating the reticle R is not only vertical but has a certain range (numerical aperture), but this value is
The numerical aperture on the reticle side of projection optical system PL is preferably 0.1 to 0.3 times (0.1 ≦ σ ≦ 0.3). That is, when the σ value, which is the ratio of the area of the light source image of the illumination optical system formed on the entrance pupil of the projection optical system PL (effectively the same as the pupil EP), is larger than 0.3, the transmission part b and the shifter transmission are transmitted. The effect of interference between the respective transmitted lights with the portion a is faint, and the effect of the present invention is reduced.

Further, the radius of the light shielding plate FL on the pupil plane EP of the projection optical system PL is set so as to shield all the direct light (0th order light component) from the illumination optical system. The radius of EP (that is, the numerical aperture) is preferably about 0.4 times. However, when the σ value determined by the size of the light source image of the illumination optical system is relatively small, for example, the σ value is 0.
When it is 1, the radius of the light shielding portion of the light shielding plate FL may be about 0.2 times the radius of the pupil EP.

Further, as the diameter of the light-shielding portion of the light-shielding plate FL is larger, the depth of focus of the pattern image is increased, but its spectral amount (illuminance on the wafer) is decreased, so that the light amount and the depth of focus are reduced. Considering the balance, it is most effective to shield 60 to 70% of the pupil radius. By the way, the intensity distribution for the hole pattern image obtained by the present invention is shown in FIG.
As shown in (E), the fineness is almost equal to the intensity distribution obtained by the conventional multiplex imaging amplitude synthesis method. However, the absorption filter in the projection optical system used in the multiplex imaging amplitude synthesis method needs to have continuously variable transmission rate according to the distance from the optical axis and have a phase inversion characteristic. Although difficult, the light-shielding plate FL in the present invention may be a complete light-shielding body, and therefore can be manufactured extremely easily by using a metal thin plate or the like. Further, as a measure against heat generation or heat storage due to light absorption, the light shielding plate FL may be provided with a cooling member or a temperature adjusting member. For example, a thin pipe through which a cooling liquid is passed is used as a light shielding plate FL.
Install along the light shield of to cool. Since the influence of this pipe is hidden by the light shielding portion of the light shielding plate FL, it does not affect the image forming characteristics at all. Such a cooling mechanism cannot be used because the light absorption filter used in the conventional multiplex imaging amplitude synthesis method needs to transmit the light flux.

Therefore, FIGS. 4 and 5 show an example of a suitable cooling mechanism for the light shielding plate FL used in the present invention. FIG. 4 is a partial cross section of the inside of the projection optical system PL provided with the light blocking plate FL, and the light blocking plate FL is attached in the lens barrel LB near the pupil plane EP. In the projection optical system PL of FIG. 4, the pupil plane EP is assumed to exist in the space (air space) between the lens elements G ₁ and G ₂ . The light blocking plate FL has a central light blocking portion FLc made of a metal substance on the upper surface (reticle side) of a transparent glass material such as quartz, and an annular light blocking portion FLr around the pupil plane EP. As shown in FIG. 5, the central light-shielding portion FLc is circular,
The annular light-shielding portion FLr is formed larger than the effective pupil diameter so that the light flux of the high frequency component cannot be blocked. Further, the light shielding plate FL is composed of an upper plate and a lower plate of quartz which form a light shielding part.
It has a layered structure, and a thin groove (both depth and width is about 2 mm) Gb for flowing a cooling fluid (gas or liquid) is formed on the bonding surface. As shown in FIG. 5, the groove Gb is laid out so that the fluid from the fluid supply hole Ki sequentially exits from the exhaust hole K ₀ along the annular light shielding portion FLr, and is further connected to the central light shielding portion FLc. It is made so that the portion directly below the central light shielding portion FLc is also cooled by passing under the four connection light shielding portions FLe that connect the annular light shielding portion FLr.

In this case, the light shielding parts FLc, Fc are formed on the quartz plate.
Although Lr and FLe are formed, a thin metal plate may be cut out in the shape of the light shielding portion shown in FIG. 5 and provided on the pupil plane EP so that it can be inserted and removed. In this case, even if a light shielding plate made of a thin metal plate is taken in and out of the projection optical system PL, the transparent part does not have the quartz transparent part as shown in FIG.

By the way, the phase shift reticle of the present invention increases the amount of diffracted light from the pattern as compared with the conventional reticle, so that the amount of light reaching the wafer W can be increased as compared with the multiple imaging amplitude combining method. Further, the phase shift reticle used in the present invention only needs to provide the minute transmissive portion b on the base of the semi-transmissive phase shift transmissive portion a, and does not need the complete light shielding portion (Cr or the like). Therefore, the patterning of the reticle only needs to be performed once, and no superposition between layers is required, and the reticle can be manufactured extremely easily. In addition, the pattern data for reticle manufacturing is completely transparent / conventional.
It also has the advantage that it can be done on the same scale as a fully shaded reticle. In another embodiment of the semi-transmissive (halftone) reticle, the transmissive part b is a bare glass surface and the phase shift transmissive part a is
May be a two-layer film including a metal thin film (darkening member) and a dielectric thin film (phase shift member).

On the other hand, the projection optical system used in the present invention may be a reflection system in addition to the refraction system, and the light source may be a bright line lamp such as a mercury lamp or a laser. Further, if broadband exposure light can be used because the projection optical system is a reflection system, broadband exposure light may be used. In this case, the phase difference in the phase shift transmission part a deviates from π [rad] for wavelength components other than the specific wavelength, but the present invention is still effective as compared with the conventional method. There is no change. Further, as described above, the exposure is divided into a plurality of times, and each of the exposed objects (wafers)
May also be used together with a multiple imaging method in which exposure is performed by slightly shifting in the optical axis direction of the projection optical system. Thereby, the effect of expanding the depth of focus can be further increased.

This state is shown in FIG. FIG. 6 (A),
(B) and (C) are hole pattern projection images obtained by the present invention. FIG. 6A shows the intensity distribution of the hole pattern image in the best focus state, and FIG.
(C) is an intensity distribution in a defocused state of a predetermined amount. At this time, multiple intensity imaging (light amount synthesis) of the respective intensity distributions of FIGS. 6A, 6B, and 6C results in FIG. 6D, and a hole pattern is formed in the positive resist.
In addition, it can be seen that there is almost no occurrence of film verification (photosensitivity) in other portions.

On the other hand, FIGS. 6E, 6F and 6G show the case where the halftone type phase shift reticle is used through the projection optical system without the light shielding plate FL, and FIG. )
Represents the intensity distribution of the hole pattern image in the best focus state, and FIGS. 6F and 6G respectively represent the intensity distribution in the defocus state. 6 (E), (F), (G)
When each intensity distribution of is image-multiplexed (combining light quantity),
As shown in (H), the amount of light (noise component In) in the other portion with respect to the hole pattern becomes a non-negligible amount, which may lead to film-verification of the positive resist. Therefore, if only the halftone type phase shift reticle is used, it is impossible to further increase the depth of focus even if the multiple imaging method is used together.

Although the focus position is discretely changed in FIGS. 6A to 6D, one exposure operation (proper exposure to one exposed region is performed without dividing the exposure into a plurality of times). Even if the wafer is continuously moved in the optical axis direction during the operation of giving the amount), the same effect of increasing the depth of focus can be obtained, and the processing time (throughput) is advantageous. The movement during exposure is not limited to the wafer, and the reticle may be moved or the projection optical system may be moved.

[0032]

As described above, according to the present invention, an exposure method for forming a fine hole pattern capable of using a positive resist can be realized by combining a phase shift reticle, which is easy to manufacture, and a projection optical system. .. Alternatively, a larger depth of focus can be obtained by moving the exposed object in the optical axis direction of the projection optical system during exposure.

Further, if a means for cooling the light shielding member provided in the projection optical system is provided, there is no fear of heat generation due to absorption of light in the projection optical system.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus configuration for carrying out an exposure method according to the present invention and an amplitude and intensity distribution of a projected image,

FIG. 2 is a diagram showing a structure of a halftone type phase shift reticle and an amplitude or intensity characteristic of a projected image;

FIG. 3 is a diagram showing an amplitude or intensity characteristic of a projected image using only a halftone type phase shift reticle;

FIG. 4 is a diagram showing a cross section of a part of the projection optical system;

FIG. 5 is a diagram showing a structure of a light shielding plate,

FIG. 6 is a diagram showing an intensity distribution of a hole pattern image when the double overlap imaging exposure method is applied.

[Explanation of symbols]

 R ... Halftone type phase shift reticle PL ... Projection optical system W ... Wafer EP ... Pupil plane (Fourier transform plane) a ... Shifter transmission part b ... Transmission part

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 7352-4M H01L 21/30 311 W

Claims (2)

[Claims] 1. An exposure method for illuminating a mask having a fine pattern structure and image-projecting the pattern of the mask onto an object to be exposed through a projection optical system. 5 to 30% while producing a transparent transmission part and a light beam whose phase is shifted by an odd multiple of π with respect to the light beam passing through the transmission part.
A mask on which the fine pattern is formed by a phase shifter having a degree of transmittance is arranged on the object plane side of the projection optical system; and further with respect to the pattern surface of the mask in the projection optical system. The object to be exposed is exposed in a state in which a limiting member for limiting a ray passing through the vicinity of the optical axis among rays passing through the Fourier plane is arranged at or near the Fourier plane optically in the Fourier transform relationship. An exposure method using a projection optical system. 2. A distance in the optical axis direction between the best imaging plane of the pattern of the mask of the projection optical system and the object to be exposed is changed during an exposure operation for one region on the object to be exposed. The method according to claim 1, wherein: