JP2002353098A - Method and aligner for exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an aligner for exposure which can transfer an image of a fine isolated pattern formed on a mask to a wafer with high resolution. SOLUTION: The method for exposing comprises a step of projecting the isolated pattern of the mask on a surface to be exposed, with a light having a certain wavelength by a projection optical system, a step of irradiating the mask with the light from a predetermined direction, so that the phase of luminous flux incident to the surface to be exposed from both ends of the pattern via the optical system is deviated by substantially a half-wavelength of the flux.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an exposure method, and more particularly, to an exposure method used for manufacturing devices such as a single crystal substrate for a semiconductor wafer and a glass substrate for a liquid crystal display (LCD). And an apparatus, a device manufacturing method, and a device manufactured from the object to be processed. The present invention is suitable for, for example, an exposure method for projecting and exposing a fine isolated pattern on an object to be processed in a photolithography process.

[0002]

2. Description of the Related Art When a device is manufactured using photolithography technology, a pattern drawn on a mask or a reticle (the terms are used interchangeably in this application) is projected onto a wafer by a projection optical system. 2. Related Art A projection exposure apparatus for transferring a pattern has been conventionally used. The projection optical system interferes and forms an image of the diffracted light from the pattern on the wafer, and interferes the 0th-order and ± 1st-order diffracted lights (that is, three light beams) from the pattern in normal exposure.

The mask pattern includes an adjacent periodic line and space (L & S) pattern, an array of adjacent and periodic contact holes, an isolated line pattern and an isolated contact hole which are not adjacent to each other. In order to transfer a pattern, it is necessary to select optimal exposure conditions (illumination conditions, exposure dose, etc.) according to the type of pattern.

The resolution R of the projection exposure apparatus is determined by the wavelength λ of the light source.
And the numerical aperture (NA) of the projection optical system, and is given by the following Rayleigh equation.

[0005]

(Equation 1)

[0006] Here, _{k 1} is a process constant determined by such developing process, in the case of normal exposure is _{k 1} is about 0.5 to 0.7.

In response to the recent increase in the degree of integration of devices, finer patterns to be transferred, that is, higher resolution have been increasingly required. To obtain a high resolution, the numerical aperture N
It is effective to increase A and decrease the wavelength λ, but these improvements have reached the limit at this stage. Therefore, a modified illumination method and a phase shift mask technique of interfering and forming an image of two light beams in diffracted light having passed through a pattern have been conventionally proposed. The modified illumination method is sometimes called an oblique incidence illumination method or the like, but illuminates the mask pattern at an angle inclined from the optical axis, and forms an image by causing the 0th-order diffracted light and the + or -1st-order diffracted light to interfere with each other. . Further, the phase shift mask sets the phase of an adjacent light transmitting portion of the mask to 18.
By inverting by 0 °, the 0th-order diffracted light is canceled out and two ± 1st-order diffracted lights interfere to form an image. According to these techniques, it is possible to a k ₁ of the above equation substantially 0.25, contributes to high resolution.

[0008]

However, the above technique is effective for simple patterns such as periodic L & S patterns, but is difficult to apply to isolated line patterns. Since it is difficult to apply to complicated patterns in which L & S patterns are mixed, sufficient resolution cannot be obtained for these patterns. In particular, regarding the latter pattern, the semiconductor industry in recent years is shifting production to a system chip having higher added value and a mixture of various patterns, and it is necessary to mix a plurality of types of patterns in a mask. ing.
In addition, there is a demand for simultaneously exposing the latter pattern without exchanging masks in order to prevent a decrease in the number of sheets processed per unit time (throughput).

Accordingly, it is an exemplary object of the present invention to provide an exposure method and apparatus capable of exposing a mask pattern including a fine isolated line pattern or a complicated pattern obtained by combining an isolated line pattern and an L & S pattern with high resolution. I do.

[0010]

According to one aspect of the present invention, there is provided an exposure method including the step of projecting an isolated pattern of a mask onto a surface to be exposed by a projection optical system using light of a certain wavelength. The mask is illuminated from a predetermined direction by the light so that a phase between light beams coming out of both ends of the isolated pattern of the pattern and entering the surface to be exposed via the projection optical system is substantially shifted by a half wavelength of the light beam. It is characterized by doing. The phase shift between the light beams satisfies (λ / 2) + mλ, where λ is the wavelength and m is an integer. Further, in an exposure method as another aspect of the present invention, a phase of an illumination light beam incident on both ends of the isolated pattern with respect to a lateral direction of the isolated line pattern on the mask The illumination is performed so as to be shifted by an amount corresponding to a sum of a half wavelength and an integral multiple of the wavelength, and the illumination light beam having passed through the mask is projected onto a surface to be exposed via a projection optical system. An exposure method as still another aspect of the present invention is a method of illuminating a pattern on an object surface with an illumination light beam having a wavelength λ, and projecting and exposing an image of the pattern on an image surface via a projection optical system. In the above, an isolated line pattern provided on the object plane and having a width L in the short direction is represented by Lsin θ =
By illuminating so as to satisfy (λ / 2) + mλ, a dark line corresponding to the isolated line pattern is formed on the image plane. In these exposure methods, the phases of the scattered light generated from both ends are inverted, so that they cancel each other out on the surface to be exposed to form a sharp optical image and improve the resolution.

The isolated line pattern is formed by a halftone type phase shift member that transmits a part of incident light and inverts the phase of the transmitted light by 180 ° with respect to the light transmitted through a part where the pattern is not provided. It may be formed and its transmittance may be set such that the light intensity at the center of the dark line formed on the image plane becomes zero. Since the halftone type phase shift member is relatively effective for an isolated pattern, it can be combined with the above-described exposure method to enhance its operation. The mask has a line width and an interval of L
Further, the illumination may be a modified illumination for causing two diffracted lights generated from the illumination light beam to interfere with each other. Thus, the isolated line pattern and the L & S pattern can be simultaneously exposed.

In a mask according to another aspect of the present invention, when illuminated by the above-described exposure method, the light intensity distribution on the surface to be exposed becomes zero at the center of the isolated line pattern in the short direction. The isolated line pattern is formed by a halftone phase shifter set to such transmittance. Such a mask can form a high-contrast image because the light intensity on the surface to be exposed becomes zero.

An exposure apparatus as still another aspect of the present invention includes an illumination device for performing the above-described illumination and a projection optical system for performing the above-described projection. Such an exposure apparatus has the same operation as the above-described exposure method. Further, a device manufacturing method as still another aspect of the present invention includes a step of projecting and exposing an object to be processed using the above-described exposure apparatus, and a step of performing a predetermined process on the object to be exposed and projected. Having. The claims of the device manufacturing method having the same operation as that of the above-described exposure method extend to the device itself as an intermediate and final product. Such devices are, for example, semiconductor chips such as LSI and VSLI, C
Includes CDs, LCDs, magnetic sensors, thin-film magnetic heads, etc.

A further object or other feature of the present invention is that
The present invention will be clarified by preferred embodiments described below with reference to the accompanying drawings.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exemplary exposure apparatus 1 according to the present invention will be described below with reference to the accompanying drawings. Here, FIG.
1 is a schematic block diagram of an exposure apparatus 1. Exposure device 1
As shown in FIG. 6, an illumination device 100 for illuminating a mask 10 on which a circuit pattern is formed, a stage 45 for supporting a plate, and projection optics for projecting diffracted light generated from the illuminated mask pattern onto a plate 30 System 300.

The exposure apparatus 1 uses, for example, a mask 10 by a step-and-repeat method or a step-and-scan method.
Is a projection exposure apparatus for exposing the circuit pattern formed on the plate 30 to the substrate 30. Such an exposure apparatus is suitable for a submicron or quarter-micron lithography process. Hereinafter, in this embodiment, a step-and-scan type exposure apparatus (also referred to as a “scanner”) will be described as an example. Here, in the “step and repeat method”, the wafer is continuously scanned with respect to the mask to expose the mask pattern to the wafer, and after the exposure of one shot is completed, the wafer is stepped to expose the next shot. This is an exposure method that moves to an area. The “step-and-repeat method” is an exposure method in which the wafer is step-moved for each batch exposure of a shot of the wafer, and the next shot is moved to an exposure area.

The mask 10 is formed with a circuit pattern (in this embodiment, an isolated line pattern 11) to be transferred to a transparent substrate 12 made of, for example, quartz, and may be called a stage (not shown) (“reticle stage”). )
Supported by Diffracted light generated from the illumination light passing through the mask 10 passes through the projection optical system 300 and is projected on the plate 30.

FIG. 1 is a schematic sectional view of a mask 10.
Referring to FIG. 1, a mask 10 includes a transparent substrate 12, and an isolated line pattern 11 is formed by a light-shielding portion 14 having a line width L in a short direction A thereof. The light shielding unit 14
For example, it is formed of chromium or the like. Note that, as described later, the light shielding unit 14 may be replaced with a light transmitting unit that converts the phase of transmitted light. The mask 10 according to the present embodiment
Is an one-dimensional object elongated in the direction perpendicular to the plane of the drawing for the sake of simplicity and explanation. The line width L is, for example, about 0.15 μm,
The size is such that the lighting device 100 can perform exposure collectively. In the description here, the imaging magnification of the projection optical system 300 is set to 1 for convenience. However, in an actual apparatus, the pattern on the mask is reduced and projected to 1/4 or 1/5 on the plate 30. In many cases, a configuration is adopted. In that case, the line width of the light-shielding portion on the mask has a size enlarged to 4L or 5L.

The plate 30 is an object to be processed such as a wafer or a liquid crystal substrate. The plate 30 is coated with a photoresist. The photoresist coating process includes pretreatment,
An adhesion improver application process, a photoresist application process,
And a pre-bake process. Pretreatment includes washing, drying and the like. The adhesion improver application treatment is a surface modification (that is, hydrophobicity treatment by applying a surfactant) treatment for improving the adhesion between the photoresist and the base, and the HMDS (Hexam
An organic film such as ethyl-disilazane is coated or steamed. Prebaking is a baking (firing) step, but is softer than that after development, and removes the solvent.

The plate 30 is supported on a stage (sometimes called a “wafer stage”) 45. The stage 45 may employ any configuration known in the art, and a detailed description of its structure and operation will be omitted. For example, the stage 45 can move the plate 30 in the XY directions using a linear motor. The mask 10 and the plate 30 are scanned, for example, synchronously, and the positions of the reticle stage and the stage 45 are
For example, they are monitored by a laser interferometer or the like, and both are driven at a constant speed ratio. The stage 45 is, for example,
The reticle stage and the projection optical system 300 are provided on a stage base supported on a floor or the like via a damper.
For example, the lens barrel base is provided on a lens barrel base (not shown) supported via a damper or the like on a base frame mounted on a floor or the like.

The illumination device 100 illuminates the mask 10 on which the isolated pattern for transfer is formed, and has a light source section 110 and an illumination optical system 120.

The light source section 110 uses, for example, a laser as a light source. The laser is a 193 nm wavelength Ar
F excimer laser, KrF excimer laser with a wavelength of about 248 nm, may be used, such as _{F 2} excimer laser with a wavelength of approximately 157 nm, the kind of laser is not limited to an excimer laser, for example, may be used YAG laser However, the number of lasers is not limited. For example, if two solid-state lasers operating independently are used, there is no coherence between the solid-state lasers, and speckle due to coherence is considerably reduced. In order to further reduce speckle, the optical system may be swung linearly or rotationally. When a laser is used for the light source unit 12, a light beam shaping optical system for shaping a parallel light beam from a laser light source into a desired beam shape, and an incoherent optical system for making a coherent laser beam incoherent are used. Is preferred. Light source unit 1
The light source that can be used for the light source 10 is not limited to a laser, and one or more lamps such as a mercury lamp and a xenon lamp can be used. In the present embodiment, the light source unit 110
Generates exposure light of wavelength λ.

The illumination optical system 120 is an optical system for illuminating the mask 10. In this embodiment, the illumination optical system 120 irradiates the mask 10 with the illumination light 400 having the wavelength λ at an angle θ from the optical axis H of the projection optical system 300. Illuminates the mask 10. However, illumination by the illumination optical system 120 of the present embodiment is different from conventional oblique illumination. The feature of the conventional oblique illumination method is that the illumination light is inclined by an angle θ in a plane including the repetition direction of the periodic pattern, whereas the illumination optical system 120 of the present embodiment has an isolated line pattern. This is because a periodic pattern such as 11 is not used.

In determining the angle θ, the present inventor:
First, the deterioration of the optical image due to the change in the line width L when θ = 0 was studied. First, image formation when the isolated line pattern 501 is vertically illuminated as shown in FIG. 10 will be described. In FIG. 10, a mask 500 has a transparent substrate 502 and a light shielding portion 504 having a line width L. The light-shielding portion 504 forms an isolated line pattern 501 as a mask pattern. For convenience of explanation, it is assumed that the mask pattern is a one-dimensional object elongated in the direction perpendicular to the plane of the drawing. When the mask 500 is illuminated with the illumination light 550 having the wavelength λ, the light beams 552 and 5
And scattered light 556 scattered at both ends of the light shielding portion 502 along with
And 558 enter the projection optical system 520 and
An optical image 530 is formed on the substrate. As will be understood, the scattered lights 556 and 558 interfere at a central position O corresponding to the center of the light-shielding portion 504 on the wafer 540, and increase the light intensity that should be zero. As a result, the contrast decreases and the optical image 530 deteriorates.

On the wafer 540, a photosensitive resist 54 is provided.
5, the resist 501 is exposed to the optical image 530, and the pattern 501 of the mask 500 is transferred onto the wafer 540. Wafer 5 obtained after transfer
Reference numeral 40 has a resist shape as shown in FIG. FIG.
1A shows a resist shape on the wafer 540 when the resist 545a is of a negative type, and FIG.
Reference numeral 45b denotes a resist shape on the wafer 540 in the case of a positive type. However, when the line width L of the light-shielding portion 504 shown in FIG. 10 is reduced, the optical image 530 becomes unclear. Therefore, there is a lower limit on the width Y of the resist image that can be formed.

FIG. 12 shows the deterioration of the optical image 530 due to the change in the line width L of the light-shielding portion 504. The vertical axis of the graph represents the light intensity, and the intensity at a position not affected by the light-shielding portion 504 is 1
It is standardized so that The horizontal axis is a value obtained by standardizing the size of the line width L by λ / NA (numerical aperture of the projection optical system 30). For example, λ = 193 nm, NA = 0.7
In the case of (1), the value shown in the figure × 276 nm is the actual value. In the graph, the line width L of the light shielding portion 504 is set to 1
, The light intensity distribution on the wafer 540 when the line width L of the light shielding unit 504 is 0.5 and the line width L of the light shielding unit 504 is 0.25.

In order to form a fine pattern image on the wafer 540, it is necessary to reduce the width of a portion (dark portion) where the light intensity is weakened. At the same time, it is necessary to suppress the light intensity of the dark portion to be almost zero. is necessary. Referring to FIG. 12, as the line width L of the light-shielding portion 504 decreases, the width of the dark portion w decreases. However, from the condition that the light intensity at the center of the dark part is suppressed to zero, the line width L of the light-shielding part 504 is equal to 0.1.
It is understood that about 5 is the lower limit. Here, if the width w of the dark portion at the position where the light intensity becomes 0.5 (that is, the width Y of the resist image on which the optical image can be formed) is defined, w is given by the following equation. It becomes the minimum value.

[0028]

(Equation 2)

Therefore, if the line width L of the light shielding portion 504 is reduced (for example, to about 0.15 μm as in this embodiment), a good optical image 530 cannot be obtained. The isolated mask pattern cannot be formed.

Next, the present inventor has proposed a light shielding unit 5 shown in FIG.
04 was replaced with a transparent phase shift member, and the deterioration of the optical image was examined in the same manner. FIG. 13 shows a mask 500A in this case. The mask 500A has a transparent substrate 502 and a transparent phase shifter 506. When illuminated by the illumination light 550, the light flux 562 transmitted through the phase shifter 506 and the light flux 564 transmitted through a portion where the phase shifter 506 does not exist,
A relative phase difference of 180 degrees occurs between 566. Therefore, assuming that the refractive index of the phase shifter 506 is n, the thickness d is determined by the following equation.

[0031]

(Equation 3)

The isolated line pattern 5 on the mask 500A
FIG. 14 shows the deterioration of an optical image formed on a wafer (not shown) when such a phase shifter 506 is used as 01A. Decreasing the width L of the phase shifter 506 to decrease the width of the dark portion of the image is similar to the case where the mask 500 is used as described with reference to FIG. Here, as in the case of FIG. 12, if the light intensity at the center of the dark part becomes substantially zero as a condition for obtaining a good image, the width of the phase shifter 506 is L = 0.25.
The degree is the lower limit. If the width w of the dark part is defined at a position where the light intensity becomes 0.5 as before, w is given by the following equation, and this is the minimum value of the line width of the dark part.

[0033]

(Equation 4)

W in Equation 4 is w = 0.7 in Equation 2.
The light shielding portion 504 is slightly smaller than 77.
The effect of using the phase shifter 506 in place of the above is shown. However, the improved value has not been able to provide a resolution that satisfies the demand for higher integration of LSIs and the like for exposure for forming a fine isolated line pattern.
This includes scattered light 568 and 5 that are in phase with each other.
69.

Returning to FIG. 1, the illumination optical system 120 of the present embodiment illuminates the plate 30 so as to satisfy the following condition in order to eliminate the adverse effects on the plate 30 due to the scattered lights 402 and 404. The incident angle θ of the light 400 is set.

[0036]

(Equation 5)

The condition of Equation 5 corresponds to the phase of the light beam illuminating the right end and the left end of the light-shielding portion 14 being relatively shifted by 180 degrees (that is, the length λ / 2). Because the illumination light 40
Among 0, the optical path difference between the light reaching the left end 15 and the light reaching the right end 16 of the light shielding unit 14 shown in FIG. 1 corresponds to Lsin θ, and if this is a half wavelength (λ / 2), Because it becomes. Equation 5 is expressed by the following equation 5 using an integer m.
It can be appreciated that the general formula shown in FIG.

[0038]

(Equation 6)

According to Equation 5, the phase of the scattered light 402 emitted from the left end 15 of the light shielding unit 14 and the phase of the scattered light 404 emitted from the right end 16 of the light shielding unit 14 are relatively inverted. The luminous fluxes 406 and 408 transmitted through the mask 10 as they are together with the scattered light 402 and 404
Incident on. Therefore, the scattered lights 402 and 404 passing through the projection optical system 300 are incident on the plate 30 with a phase difference of substantially a half wavelength occurring, and partially overlap. However, the directions of the arrows of the light beams 406 and 408 and the scattered lights 402 and 404 that have passed through the mask 10 as they are are not shown in the actual directions but are shown for convenience.

The illumination optical system 120 includes a lens, a mirror, a light integrator, a stop, and the like. For example, a condenser lens, a fly-eye lens, an aperture stop, a condenser lens, a slit, and an imaging optical system are arranged in this order. The illumination optical system 120 can be used regardless of on-axis light or off-axis light. The light integrator includes a fly-eye lens, an integrator formed by stacking two sets of cylindrical lens array (or lenticular lenses) plates, and the like, but may be replaced with an optical rod or a diffraction element. Illumination optical system 12 of the present embodiment
0 indicates the optical axis (not shown) of the optical axis H of the projection optical system 300.
The oblique incident illumination light to the mask 10 may be generated by inclining the mask 10 by an angle θ from. Alternatively, the illumination optical system 120 generates the obliquely incident illumination light to the mask 10 by controlling the shape of an aperture stop disposed immediately after the exit surface of a fly-eye lens (not shown), for example. In any case, in the present embodiment, the angle θ defined in Expression 5 is calculated in advance and fixed. However, the fixing of the illumination angle θ is not essential to the present invention, and in another embodiment described later, the angle θ is variably adjusted according to the isolated line pattern 11 used. The shape of the aperture stop will be described together with the other embodiments.

The projection optical system 300 projects the light passing through the mask 10 onto the plate 30 to form an optical image 410. The projection optical system 300 includes an optical system including only a plurality of lens elements, an optical system including a plurality of lens elements and at least one concave mirror (catadioptric optical system), a plurality of lens elements and at least one kinoform. For example, an optical system having a diffractive optical element such as an optical system, an all-mirror optical system, or the like can be used. When chromatic aberration needs to be corrected, a plurality of lens elements made of glass materials having mutually different dispersion values (Abbe values) may be used, or a diffractive optical element may be configured to cause dispersion in a direction opposite to that of the lens element. I do.

In the projection optical system 300, the positions of the light beams 406 and 408 are reversed before and after the projection optical system 300, as shown in FIG. However, the present invention can be applied to a case where the projection optical system 300 forms an erect image. Since the phases of the scattered lights 402 and 404 are inverted, they cancel each other out on the plate 30 projected by the projection optical system 300, so that a high-quality optical image 410 can be formed.

In the exposure, a light beam emitted from the light source unit 110 is introduced into the illumination optical system 120 as exposure light having a wavelength λ after passing through a beam shaping system and the like. The mask 10 is illuminated at the illumination angle θ represented by Expression 5.

Step-and-scan exposure apparatus 1
If so, the light source unit 110 and the projection optical system 300 are fixed, and the mask 10 and the plate 30 are synchronously scanned to expose the entire shot. Further, the stage of the plate 30 is stepped to move to the next shot, and a number of shots are exposed and transferred onto the plate 30. Thus, the isolated pattern is transferred onto the plate 30. If the exposure apparatus 1 is a step-and-repeat method, the exposure is performed with the mask 10 and the plate 30 stationary.

The scattered light 402 and 40 passing through the mask 10
The light beam 4 and the light beams 406 and 408 are reduced and projected on the plate 30 at a predetermined magnification by the image forming action of the projection optical system 300 to form an optical image 410. The optical image 410 contains the scattered light 4
02 and 404 and the luminous flux 4 transmitted through the mask 10 as it is
06 and 408 interfere with each other on the plate 30. Since the center position O on the plate 30 is geometrically optically a shadow of the light shielding portion 14 of the mask 10 and there is no light beam transmitted through the mask 10 as it is, only the scattered light 402 and 404 from both ends of the light shielding portion 14 interfere. Forms an optical image.

The mask 1 at the illumination angle θ expressed by Expression 5
By illuminating 0, the phases of the scattered lights 402 and 404 are inverted, so that the amplitudes of the scattered lights 402 and 404 cancel each other out at the central position O on the plate 30, and as a result, a very sharp dark line is formed. It becomes possible. In other words, the present invention can suppress the deterioration of the optical image 410 due to the scattered lights 402 and 404. As a result, the exposure apparatus 1 transfers the pattern to the resist with high precision, thereby achieving high-quality devices (semiconductor elements, LCD elements,
An image sensor (such as a CCD) and a thin-film magnetic head can be provided.

Here, the illumination angle θ represented by Expression 5 is
It is different from the illumination angle by the conventional oblique illumination method,
This will be described with reference to FIG. Here, FIG. 15 is a schematic cross-sectional view for explaining the principle of the conventional oblique illumination method. In the mask 500B, a light-shielding portion 505 having a width L is periodically formed on a transparent substrate 502, and a pattern 5 having a period 2L is formed.
01B is formed. The feature of the conventional oblique incidence illumination method is that the illumination light 570 is inclined by an angle θ in a plane (paper surface) including the direction B in which the periodic pattern repeats, and the 0th-order diffracted light 572 generated in the direction of the angle θ and the angle β 1 that occurs in the direction
That is, an image is formed on a wafer (not shown) by the next diffraction light 576. Here, by selecting the condition of β = θ, two beams of diffracted light are generated.
The range of the resolvable pattern line width shown in FIG. To make β = θ, the incident angle θ of the illumination light 570
Must be set so as to satisfy Equation 7 below.

[0048]

(Equation 7)

[0049]

(Equation 8)

As described above, when illuminating the mask 10 composed of the light-shielding portions 14 having the line width L according to the present embodiment, the illumination angle θ by the conventional oblique incidence illumination method for illuminating a periodic pattern is compared. It is understood from Equations 5 and 8 that the illumination angle θ of the present invention for illuminating the isolated line pattern is doubled by sin.

[0051]

Embodiment 1 FIG. 2 shows simulation results for demonstrating the effect of the present invention. Here, FIG. 2 is a graph showing a comparison of optical images when the isolated line pattern 11 having the line width L = 0.6 is vertically illuminated and when oblique incidence illumination is performed so as to satisfy Expression 5. It is. As described above, the value of L and the horizontal axis in the figure are values normalized by λ / NA. As can be understood from the figure, the line width of the dark part is significantly reduced by applying the oblique illumination of the present invention,
Correspondingly, it becomes possible to form an isolated pattern having a finer line width on the plate 30 than in the related art.

[0052]

Embodiment 2 In the results of FIG. 2, the line width of the dark portion is narrowed by the oblique incidence illumination method of the present invention, but the light intensity at the center position O on the plate 30 is not zero. this is,
The light intensity at the center position O is the scattered light 402 and 40 shown in FIG.
4, the scattered lights 402 and 404 have inverted phases at the center position O, but cannot be completely canceled out because the amplitudes of the scattered lights 402 and 404 are different. Will be interpreted.

Therefore, a mask 10 (not shown) replaced with a halftone type phase shifter that transmits a part of the light beam incident on the light shielding unit 14 and inverts the phase of the transmitted light from the surroundings.
A was used. The halftone phase shifter is, for example,
It can be composed of a MoSi-based semipermeable membrane, and the transmittance and the phase can be set, for example, by setting the thickness and the concentration of the MoSi-based semipermeable membrane.

In the present embodiment, the amplitude transmittance of the halftone phase shifter is set to 46% (the intensity transmittance is 21%), the phase is set to 180 degrees, and the line width L of the isolated line pattern 11 is set to 0.6. Set. FIG. 3 shows a light intensity distribution appearing on the plate 30 when the mask 10A is illuminated at the illumination angle θ represented by Expression 5. As in FIG. 2, the vertical axis represents the light intensity, and is standardized so that the intensity at a position where the light-shielding portion 14 does not affect becomes 1. The horizontal axis represents the line width L normalized by λ / NA (numerical aperture of the projection optical system 300). It is understood from the results of FIG. 3 that an ideal light intensity distribution with a light line width of zero and a light intensity of zero at the center position O on the plate 30 is realized.

If the width w of the dark portion at the position where the light intensity is 0.5 is defined, w is given by the following equation.

[0056]

(Equation 9)

The value of w is the minimum value of the dark line width due to the oblique incidence illumination according to the present invention. Compared with the dark line width w represented by Expressions 2 and 4, a very large improvement in resolution is realized. You can see that there is.

It is preferable that the illumination device 100 irradiates the mask 10 with the illumination light 400 symmetrically from two directions. FIG. 4 shows an example in which the illumination light 400 is provided from the left direction 400a and the right direction 400b. The optical image 410 is affected by the aberration and / or the depth of focus inherent in the projection optical system 300.
When there is a shift in the horizontal direction, the illumination lights 400a and 400b symmetrically provided from the two left and right directions have an effect of preventing the optical image 410 from becoming asymmetric.

[0059]

Third Embodiment An exposure method for simultaneously improving the resolution of a periodic pattern and an isolated line pattern formed on a mask 10B as an example of the mask 10 will be described with reference to FIG. Here, FIG. 5 is a schematic sectional view of the mask 10B. Referring to FIG. 1, a mask 10B includes a transparent substrate 12, and a light-shielding portion 14 having a line width L forms an isolated line pattern 11 shown in FIG. Illumination light 400
(The illumination light 400a incident from the left direction and the illumination light 400b incident from the right direction) are expressed by the relationship of Expression 5 in order to apply the oblique incidence illumination method of the present invention to the line width L and the illumination angle θ of the light shielding unit 14. Have maintained.

The mask 10B further has a light shielding portion 14B for forming the periodic pattern 11A. The light-shielding part 14B is set so that the line width is L / 2 and the pitch of the periodic pattern including the light-shielding part 14B and the light transmitting part 17 is L. This configuration is a condition for improving the resolution of the periodic pattern of the mask 10A by the conventional oblique illumination method. This can be understood from the fact that if L in Equation 7 representing the optimum illumination angle θ for the conventional oblique illumination method is replaced with L / 2, it becomes equivalent to Equation 5.

In the pattern configuration of the mask 10B, the resolution of the periodic pattern 11A is improved by the effect of the conventional oblique incidence illumination method, and the resolution of the isolated line pattern 11 is improved by the effect of the oblique incidence illumination method of the present invention as described above. Is improved. Therefore, the resolution of the isolated line pattern 11 and the periodic pattern 11A formed on the mask 10B can be simultaneously improved.

[0062]

Embodiment 4 The illumination device 100 may variably control the illumination angle θ with respect to an arbitrary mask 10. Such an embodiment will be described with reference to FIGS. Here, FIG.
Is a schematic sectional view of an exposure apparatus 1A as a modified example of the exposure apparatus 1. Exposure apparatus 1A differs from exposure apparatus 1 in having illumination control section 170.

The illumination control section 170 has a detection section 172, a calculation section 174, and a drive section 176. Detector 172
Is connected to the mask 10 and the operation unit 174, and the mask 1
The line width L of the isolated line pattern 11 formed by the 0 light shielding portion 14 is read. For example, the detection unit 172 uses the mask 1
0, the line width L of the isolated line pattern 11
Read an identifier or a bar code or the like for identifying. The isolated line pattern 11 formed on the read mask 10
Is transmitted to the arithmetic unit 174. Arithmetic unit 174
Is connected to the detecting unit 172 and the driving unit 176, recognizes the position of the isolated line pattern 11 of the mask 10 based on the data from the detecting unit 172, calculates the illumination angle θ expressed by Expression 5, and drives the driving unit 176. Drive unit 176
Is connected to the arithmetic unit 174 and the illumination device 100, and drives the illumination device 100 to illuminate the mask 10 at the illumination angle θ calculated by the arithmetic unit 174.

For example, the arithmetic unit 174 forms the illumination angle θ by rotating a turret provided with a plurality of aperture stops 150 shown in FIG. 8 and selecting an optimal aperture stop. It should be noted that reference numeral 150 is the same as reference numeral 15 described below.
0A, 150B, etc. shall be summarized.

Hereinafter, referring to FIG.
An exemplary shape applicable to is described. Here, FIG.
4 is a schematic plan view of an exemplary shape of the aperture stop 150. FIG. FIG. 16A is a schematic plan view of an aperture stop 150A having a light-shielding portion 151A and a light-transmitting portion having a transmittance of 1 formed by a quadrupole circle 152. The circular aperture 152 provides illumination light having a central position σ of 1 or less, and is ± 45 degrees and ± 1 respectively.
It is arranged at 35 degrees. Preferably, the σ of the illumination light provided by each circle 152 is equal. The shape of the opening 153 can be variously changed such as a quadrangle, other polygons, and a part of a sector. Further, σ may exceed 1. FIG. 16 (B)
FIG. 9 is a schematic plan view of an aperture stop 150B having a light-shielding portion 151B and a light-transmitting portion having a transmittance of 1 formed by an annular zone opening 153.

The turret (not shown) is provided with a plurality of aperture stops 150 having different σ (ie, different positions and dimensions of the circle 152 and the annular zone 153), and the arithmetic unit 174 operates the aperture stop to provide the optimum illumination angle θ. Select 150.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus 1 will be described with reference to FIGS. FIG. 8 is a flowchart for explaining the manufacture of devices (semiconductor chips such as ICs and LSIs, LCDs, CCDs, etc.). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), the circuit of the device is designed. Step 2 (mask fabrication) forms a mask on which the designed circuit pattern is formed. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is referred to as a preprocess, and an actual circuit is formed on the wafer by the lithography technique of the present invention using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). . In step 6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 9 is a detailed flowchart of the wafer process in Step 4. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the surface of the wafer. Step 13
In (electrode formation), electrodes are formed on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. Step 15 (resist processing)
Then, a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 1 to expose a circuit pattern on the mask onto the wafer. Step 17 (development) develops the exposed wafer. Step 18 (etching) removes portions other than the developed resist image. Step 19 (resist stripping) removes unnecessary resist after etching. By repeating these steps, multiple circuit patterns are formed on the wafer.

According to the exposure method and apparatus of the present invention, a fine isolated line pattern image can be transferred onto a wafer without using a special mask structure which is difficult to manufacture.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the invention.

[0071]

According to the exposure method and apparatus of the present invention, a fine isolated line pattern, an isolated line pattern and L &
A mask pattern including a complicated pattern obtained by combining S patterns can be exposed with high resolution. Further, the device manufacturing method using such an exposure method and apparatus can manufacture a high-quality device.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an exposure apparatus according to the present invention.

FIG. 2 is a light intensity distribution appearing on a plate by oblique incidence illumination according to the present invention and conventional vertical illumination.

FIG. 3 is a light intensity distribution appearing on a plate when a halftone phase shift mask is exposed by an oblique incidence illumination method according to the present invention.

FIG. 4 is a diagram showing an example in which illumination according to the present invention is provided symmetrically from two directions, left and right.

FIG. 5 is a schematic sectional view of a modified example of the mask shown in FIG.

FIG. 6 is a schematic sectional view of an exposure apparatus as one aspect of the present invention.

FIG. 7 is a schematic sectional view of a modification of the exposure apparatus shown in FIG.

FIG. 8 is a flowchart illustrating a device manufacturing method having an exposure step according to the present invention.

9 is a detailed flowchart of step 4 shown in FIG.

FIG. 10 is a schematic cross-sectional view illustrating a conventional method of exposing an isolated line pattern formed by a light-shielding portion with vertical illumination light.

FIG. 11 is a schematic cross-sectional view showing a pattern shape formed according to the type of resist formed on a wafer.

12 is a light intensity distribution appearing on a wafer by the exposure shown in FIG.

FIG. 13 is a schematic cross-sectional view illustrating a conventional method for exposing an isolated line pattern formed by a halftone phase shifter with vertical illumination light.

14 is a light intensity distribution appearing on a wafer by the exposure shown in FIG.

FIG. 15 is a schematic cross-sectional view for explaining the principle of a conventional oblique incidence illumination method.

16 is a schematic plan view of an aperture stop applicable to the exposure apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exposure apparatus 10 and 10a Mask 14, 14B Shielding part 400 Illumination light 402, 404 Scattered light 410 Optical image

Claims (12)

[Claims] 1. An exposure method comprising projecting an isolated pattern of a mask onto a surface to be exposed by a projection optical system using light of a certain wavelength, wherein the projection optical system exits from both ends of the isolated pattern of the isolated pattern. Irradiating the mask from a predetermined direction with the light such that the phase between the light beams incident on the surface to be exposed via the light beam is substantially shifted by a half wavelength of the light beam. 2. The exposure method according to claim 1, wherein the phase shift between the light beams satisfies (λ / 2) + mλ, where λ is the wavelength and m is an integer. 3. An isolated line pattern formed on a mask, wherein a phase of an illuminating light beam incident on both ends of the isolated pattern in a lateral direction of the isolated line pattern is a sum of a half wavelength of the illuminating light beam and an integral multiple of the wavelength. An exposure method comprising: illuminating the object so as to be shifted by an amount corresponding to the above; 4. A method of illuminating a pattern on an object plane with an illumination light beam having a wavelength λ and projecting and exposing an image of the pattern on an image plane via a projection optical system, wherein the pattern is provided on the object plane; An isolated line pattern having a width L in the short side direction is defined by m as an integer, and obliquely with respect to the short side direction at an angle θ with the optical axis of the projection optical system, L sin θ = (λ /
2) An exposure method, wherein a dark line corresponding to the isolated line pattern is formed on the image plane by illuminating so as to satisfy + mλ. 5. The halftone phase shifter according to claim 1, wherein the isolated line pattern transmits a part of the incident light and inverts the phase of the transmitted light by 180 ° with respect to the light transmitted through a part where the pattern is not provided. 5. The exposure method according to claim 3, wherein the exposure method is formed from a member and the transmittance thereof is set such that the light intensity at the center of the dark line formed on the image plane becomes zero. 6. The mask has a line width and an interval both of L / 2.
The exposure method according to claim 3, further comprising a line and space pattern, wherein the illumination is modified illumination for causing two diffracted lights generated from the illumination light beam to interfere with each other. 7. An isolated line pattern formed on a mask is displaced by a sum of a half wavelength and an integral multiple of a wavelength of an illumination light beam incident on both ends of the isolated pattern in a lateral direction of the isolated line pattern. And a projection optical system for projecting the illumination light beam having passed through the mask onto a surface to be exposed via a projection optical system. 8. The mask has a line width and an interval both of L / 2.
8. The exposure according to claim 7, further comprising a line and space pattern, wherein the illuminating device simultaneously illuminates the isolated line pattern and the line and space pattern by modified illumination for causing two diffracted lights generated from the illumination light beam to interfere with each other. apparatus. 9. The exposure apparatus according to claim 7, further comprising: a control unit that determines an illumination angle of the illumination light beam with respect to the mask according to the isolated line pattern and controls the illumination device. 10. A step of projecting and exposing an object to be processed by using the exposure apparatus according to any one of claims 7 to 9, and a step of performing a predetermined process on the object to be exposed and projected. A device manufacturing method comprising: 11. A device manufactured from an object to be projected and exposed by using the exposure apparatus according to claim 7. Description: 12. The transmittance is set such that the light intensity distribution on the surface to be exposed becomes 0 at the center of the isolated line pattern in the lateral direction when illuminated by the exposure method according to claim 3. A mask, wherein the isolated line pattern is formed by a halftone phase shifter.