JPH04273428A - Exposure method - Google Patents

Abstract

PURPOSE:To provide an exposure method which can obtain a high resolution by a method wherein a reticle which is formed of only a light-shielding part and a light-transmitting part is used and an effect obtained by installing an auxiliary pattern is increased. CONSTITUTION:When a reticle 11 provided with auxiliary patterns 12b, 12c whose size is nearly equal to or smaller than that of a circuit pattern 12a near the circuit pattern is irradiated, a light flux which is passed through the plane of an illumination optical system to be used as the Fourier plane of the recticle is prescribed in a region whose center is situated at the position which is eccentric from the optical axis of the illumination optical system. Thereby, the reticle is irradiated with the light flux which is tilted to the prescribed direction by an angle corresponding to the fineness degree of the pattern; a wafer and the reticle are moved relatively to the optical-axis direction of a projection optical system. Especially when the auxiliary patterns whose size is nearly equal to that of the circuit pattern are formed, it is possible to transcribed only the circuit pattern at high resolution by moving them to the optical-axis direction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method for forming circuit patterns for semiconductor devices and the like.

0002

[Prior Art] In the conventional exposure method, the surface of the illumination optical system (hereinafter referred to as the pupil surface of the illumination optical system), which is the Fourier plane of the surface on which the pattern on the mask (reticle) exists, or a surface near the surface In the above, a method was used to illuminate a reticle using a projection type exposure apparatus configured to illuminate the reticle with a light beam having a circular cross section such that the light intensity distribution was centered on the optical axis of the illumination optical system. The magnitude of the incident angle of the illumination light beam onto the reticle (that is, the numerical aperture of the illumination light beam) is determined by the ratio of the numerical aperture of the illumination light beam to the reticle-side numerical aperture of the projection optical system, the so-called coherence factor (σ value) of 0. .3<σ<0.6 was common. FIG. 10 shows how the reticle is irradiated with the illumination light beam in this exposure apparatus.

FIG. 10A is a diagram showing a state in which a pattern on a reticle is irradiated with an illumination light beam in a conventional exposure method. A circuit pattern 12p to be transferred is drawn on the reticle 11 used in this exposure method, and the remaining portions are shaded portions (hatched portions). The illumination light L1 is irradiated almost perpendicularly to this pattern. Moreover, FIG. 10(b)
10A is a diagram showing the amplitude distribution of light transmitted through a pattern portion when the conventional exposure method shown in FIG. 10(a) is performed. FIG. At this time, the complex amplitude of the light transmitted through the circuit pattern 12p has approximately the same value within the circuit pattern 12p. It is assumed that this value is +1 and a positive amplitude distribution Ap is generated on the wafer. This is a superposition integral of the shape of the circuit pattern 12p and the point image amplitude distribution of the projection optical system used. Further, FIG. 10(c) is a diagram showing the intensity distribution of light reaching the wafer when the conventional exposure method shown in FIG. 10(a) is performed. This intensity distribution is the square of the absolute value of the amplitude distribution Ap, and is expressed as Ep. Further, the width having a light intensity that exposes the resist on the wafer is indicated by a range W1 indicated by a broken line. Therefore, a pattern with a width W1 is transferred onto the wafer.

When performing pattern exposure using the above-mentioned apparatus, technical improvements such as shortening the exposure wavelength and increasing the numerical aperture of the projection optical system have been made in order to improve the resolution of the image of the circuit pattern. It had been. In addition, in the current semiconductor device manufacturing process, film formation, photolithography (
Normally, the cycles of circuit pattern transfer) and etching are repeated about 20 times. The thickness of each film formed is about 0.05 μm to 1 μm, and therefore, as the process progresses, a step difference of about several μm occurs on the wafer. If a pattern is further projected and exposed onto a wafer with a step, the focus will be different between the top and bottom of the step, making it impossible to obtain good resolution. In order to simultaneously obtain good resolution from the top to the bottom of this step, a projection exposure apparatus with a large depth of focus is required. For this reason, recently, a method (hereinafter referred to as
A progressive focus exposure method (referred to as a progressive focus exposure method) has been proposed. In other words, this means that the wafer is moved in the optical axis direction of the projection optical system during exposure.
Alternatively, by vibrating, at least the upper and lower parts of the step are respectively focused.

[0005]

However, in conventional exposure methods, the fineness (width, pitch) of a circuit pattern on a reticle that can be transferred onto a wafer depends on the exposure wavelength of the exposure equipment used (λ (μm)). The limit was about λ/NA (μm), where NA is the numerical aperture on the reticle side of the projection optical system. This is because images are formed by diffraction and interference phenomena that occur because light is a wave.Therefore, it is possible in principle to shorten the exposure wavelength or increase the numerical aperture of the projection optical system. The resolution will improve. However, when the wavelength is shorter than 200 nm, there are many problems such as the lack of suitable optical materials that transmit this wavelength and the occurrence of absorption by air. Furthermore, the numerical aperture NA of the projection optical system is already at its technical limit, and it is extremely difficult to increase the NA further.

Under these circumstances, in order to improve the image quality of the pattern, a proposal has been made to provide an auxiliary pattern in the vicinity of the original circuit pattern, the size of which is too large to be resolved. However, the improvement in image quality in this case is to make the image of a minute square pattern, which is projected circularly by the projection optical system, more similar to a square, and the essential improvement in resolution (resolution of finer patterns) is to improve the image quality. ) cannot be expected.

[0007] Recently, a method called a phase shift method has been proposed, and improvements in resolution have been reported. The reticle used in the phase shift method is placed near the original circuit pattern on the reticle so that the phase of the transmitted light is π compared to the original circuit pattern.
An auxiliary pattern is provided with a so-called phase shifter that differs by (rad). The aim is to improve the contrast of the pattern image through interference between the light transmitted from the auxiliary pattern and the light transmitted from the original circuit pattern, thereby reducing the line width of the original circuit pattern that can be resolved. be. However, the manufacturing process of the reticle with a phase shifter used in the phase shift method is complicated, and therefore the incidence of defects is high, and the manufacturing cost is also extremely high. Furthermore, there are many problems such as the fact that defect inspection methods and defect correction methods have not yet been established, and it is currently difficult to put it into practical use.

Furthermore, in the progressive focus exposure method described above, a single pattern (with a duty ratio of 1)
: For patterns whose pitch is about 3 or more, in other words, patterns whose pitch is about 4 times or more the width of the line part of the pattern (hereinafter referred to as isolated patterns), the apparent Although a large depth of focus can be obtained, it is theoretically impossible to improve resolution using this method alone.

The present invention has been made in view of the above-mentioned problems, and uses a reticle formed only of a light-shielding part and a transmitting part, as in the past, and increases the effect of providing an auxiliary pattern. The purpose of this invention is to provide an exposure method that provides high resolution.

0010

[Means for Solving the Problems] To achieve the above object, the present invention uses a mask (14) using the light flux from the illumination optical system (1 to 10).
) on the photosensitive substrate (
14), in the exposure method of projection exposure, auxiliary patterns (12b, 12c) of the same size or smaller as the fine patterns (12a, 12d) are placed near each fine pattern (12a, 12d) in the fine pattern group (12). , 12e, 12f
) is provided, and a surface (15
), or the illumination optical system (1 to 10
) by using a light beam that is restricted to pass through a local region centered at a position eccentric from the optical axis (AX) of the mask (11), the fine pattern group (12) The fine pattern (12a, 12a,
12d), and auxiliary patterns (12b, 12c, 12e
, 12f), the projection contrast of the fine patterns (12a, 12d) is increased, and the fine pattern group (12
) on the photosensitive substrate (14), the photosensitive substrate (14) and the imaging plane of the projection optical system (13) are moved or vibrated relative to each other in the optical axis (AX) direction. And so.

[0011]

[Operation] In the present invention, a reticle is used that has an auxiliary pattern with a width that is less than the resolution limit of the projection optical system near the circuit pattern to be transferred, and the (hereinafter represented by the pupil plane of the illumination optical system), the reticle is irradiated with a limited light beam that passes through a local region whose center is eccentric from the optical axis of the illumination optical system. Therefore, if the center of the local area through which the light flux passes is set at a predetermined position determined by the pattern's line width and directionality (the direction in which the pattern is drawn), etc., the circuit pattern to be transferred and its vicinity can be It becomes possible to irradiate a light beam whose wavefront phase is mutually inverted with respect to the auxiliary pattern provided in the auxiliary pattern.

Furthermore, since the wafer is moved or vibrated in the optical axis direction of the projection optical system during exposure of the wafer,
It becomes possible to set the optimum focus position from the top to the bottom of the step on the wafer surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a schematic configuration of a projection type exposure apparatus most suitable for applying an exposure method according to an embodiment of the present invention. The light flux generated by light source 1 is sent to elliptical mirror 2 and reflecting mirror 3.
and enters the fly-eye lens 5 via the lens system 4. The light beam exiting the fly's eye lens 5 passes through a lens system 6 and enters a light splitter 7 such as an optical fiber. The light splitter 7 divides the light flux incident from the input section 7i into a plurality of parts, and outputs the divided light beams from the plurality of emission parts 7a and 7b. The exit surfaces of the exit sections 7a and 7b are formed into a Fourier plane (pupil plane of the illumination optical system) 15 via lens systems 8 and 10 and a reflecting mirror 9 with respect to the surface where the pattern 12 on the reticle 11 exists.
or is provided within a plane in the vicinity thereof. The distances of the positions of these emission parts 7a and 7b from the optical axis AX are determined according to the angle of incidence of the illumination light beam onto the reticle 11. The plurality of light beams emitted from the emission sections 7a and 7b illuminate the reticle 11 through a lens system 8, a reflecting mirror 9, and a lens system 10 at respective predetermined incident angles. This reticle 11
is placed on the reticle stage RS. The members from the light source 1 to the lens system 10 described above constitute the illumination optical system of the exposure apparatus.
is provided so as to be movable forward and backward with respect to the light beam, and controls the irradiation of the illumination light beam onto the reticle 11, that is, the exposure of the circuit pattern 12 onto the wafer 14. Pattern 1 on reticle 11
The diffracted light generated in step 2 forms an image on the wafer 14 via the projection optical system 13, and an image of the pattern 12 is transferred thereto. The wafer 14 is placed on a movable stage WS, and the projection optical system 13
It is possible to move or vibrate in the direction of the optical axis AX. The movable stage WS is electrically connected to the control device 20, and the shutter 19 is also electrically connected to the control device 20. The control device 20 issues commands to open and close the shutter 19, and also moves the movable stage WS.
and issues vibration commands. The control device 20 may determine the movement conditions (the relationship between the movement position and movement speed, and the movement speed and movement time) of the movable stage WS, and
The control device 20 has a movement condition input means, and the conditions may be input by an operator. In any case,
It is desirable that the movement range or vibration amplitude of the movable stage WS takes into account the depth of focus of the projection optical system 13 and the condition of the surface of the wafer 14 (steps, etc.). It is assumed that this exposure apparatus has a irradiance meter or the like for measuring the amount of light irradiated onto the reticle 11 in the illumination optical system. Further, as the light source 1, a bright line lamp such as a mercury lamp or a laser light source is used. Further, in this embodiment, an optical fiber is used as the light splitter 7 that splits the illumination light beam, but other members such as a diffraction grating or a polygonal prism may also be used.

In the above configuration, the light source 1 and the shutter 1
9. Exit surface of fly-eye lens 5 (pupil surface 1 of illumination optical system)
5) The exit surface of the optical fiber 7 and the pupil surface 18 of the projection optical system 13 are conjugate with each other, and the entrance surface of the fly's eye lens 5, the entrance surface of the optical fiber 7, the pattern surface of the reticle 11, and the pupil surface of the wafer 14 are conjugate with each other. The transfer planes are conjugate to each other.

In addition, on the reticle 11 side from the light splitter 7,
That is, another fly's eye lens may be added near the exit surfaces of the exit sections 7a and 7b for uniform illumination. At this time, the fly's eye lens may be a single lens or may be composed of a plurality of fly's eye lens groups. Further, depending on the correction state of chromatic aberration of the projection optical system 13 and the illumination optical systems 1 to 10, a wavelength selection element (such as an interference filter) may be added to the illumination optical system.

When a conventional device is used to illuminate a reticle having a pattern with a pitch below the resolution limit, only the 0th-order light of the diffracted light generated by the fine periodic pattern passes through the projection optical system 13. Even if the pattern cannot be resolved, if the reticle is illuminated using the above device, the exit section 7 of the light splitter 7 can be
Since the illumination light beams emitted from a and 7b enter the reticle 11 at a predetermined angle, a total of two light beams, one of the ±1st-order diffracted lights generated from the reticle pattern and the 0th-order diffracted light, enter the projection optical system. This makes it possible to resolve even smaller pitch (fine) patterns.

Next, the reticle pattern used in the embodiment of the present invention will be explained with reference to FIGS. 4, 5, 6, 7, and 8. FIG. 4(a) is a diagram showing a pattern of a reticle used in an embodiment of the present invention. A light shielding member (shaded area) made of chrome or the like is patterned as a circuit pattern on one surface of the reticle 11, which is a light-transmitting glass substrate. Transmissive portions 12a, 12b, and 12c are provided in the light shielding member as so-called isolated space patterns. Further, FIG. 4(b) is a diagram showing another example of the reticle pattern used in the embodiment of the present invention. In this case, light shielding portions 12d, 12e, and 12f are patterned on the reticle 11 as so-called isolated line patterns. Among the above patterns, the transmitting portion 12a and the light shielding portion 12d are the circuit patterns to be transferred, and the transmitting portions 12b, 12c and the light shielding portions 12e, 12f are auxiliary patterns whose width is less than the resolution limit of the projection optical system. .

FIGS. 5, 6, 7, and 8 are diagrams showing examples of reticle patterns used in embodiments of the present invention. FIG. 5 is a plan view showing an example of the same isolated space pattern as shown in FIG. 4(a) above, and shows circuit pattern 1.
Auxiliary patterns 12h and 12i (transparent part) are on both sides of 2g.
is drawn. Although the auxiliary pattern for this space pattern is added only to the width (horizontal) direction of the pattern 12g, the auxiliary pattern may be similarly added to the tip of the pattern 12g in the length (longitudinal) direction. In this case, it is possible to reduce changes in the length of the pattern 12g due to defocus.

FIG. 6 shows an example in which an auxiliary pattern 12k formed of frame-shaped transparent parts is provided in a light-shielding area 12l surrounded by a circuit pattern 12j formed of grid-shaped transparent parts. FIG. 7 shows an example in which a plurality of auxiliary patterns 12n are provided near each side of a so-called hole pattern 12m. Regarding the hole pattern, as shown in Figure 8, hole pattern 1
An auxiliary pattern 12q may be provided to surround 2o. This hole pattern 12o is not limited to a rectangular shape, and may be, for example, a circular or regular octagonal pattern.

In either example, the width (short side) of the auxiliary pattern is approximately equal to or less than the resolution limit of the projection optical system of the projection exposure apparatus used, and the distance from the circuit pattern is also within the range of the projection exposure apparatus used. The resolution should be about the resolution limit of the projection optical system. As described above, the reticle on which the circuit pattern with the auxiliary pattern is drawn is restricted to pass through a local region whose center is eccentric from the optical axis of the illumination optical system in the pupil plane of the illumination optical system. The wafer is illuminated with a light beam and projected onto the wafer via a projection optical system. This exposure method will be explained with reference to FIG.

FIG. 9(a) is a schematic diagram showing a state in which the reticle is irradiated with the illumination light beam when illumination is performed using the exposure method according to the embodiment of the present invention. On the pattern surface of the reticle 11, in the vicinity of the circuit pattern 12a to be transferred, there is an auxiliary pattern 12b, which is approximately below the resolution limit of the projection optical system.
12c is provided. The width of the circuit pattern 12a is shown in FIG.
It is the same as the circuit pattern 12p shown in (a), and the auxiliary patterns 12b and 12c are approximately below the resolution limit of the projection optical system. At this time, if the reticle is illuminated with a luminous flux that is restricted to pass through a local area whose center is eccentric from the optical axis of the illumination optical system on the pupil plane of the illumination optical system, the illumination luminous flux L2 will be The light is incident from a direction tilted at a predetermined angle (not perpendicular). This angle and direction correspond to the circuit pattern 12a and the auxiliary pattern 12.
In order to be optimal for the line width and directionality of b and 12c,
If the center position of the local area through which the above-described light flux passes is determined, the circuit pattern 12a is illuminated with a positive amplitude, and both the auxiliary patterns 12b and 12c are illuminated with a negative amplitude. Among the equal wavefronts of this illumination light flux L2, those with positive amplitude are shown by a solid line L2a, and those with negative amplitude are shown by a broken line L2b. Incidentally, the angle of incidence θ of the illumination light flux with respect to the pattern is based on the auxiliary pattern 1.
It is an angle given by sin θ=λ/d, where d is the distance between 2b and 12c. Further, the incident direction includes a direction vector in the direction in which the pattern is drawn (the longitudinal direction of the pattern), and is a direction within a plane defined by the incident angle θ. This will be discussed later.

FIG. 9(b) is a diagram showing the amplitude distribution of light transmitted through the pattern portion when the exposure method shown in FIG. 9(a) is used. At this time, the complex amplitudes of the light transmitted through the circuit pattern 12a and the auxiliary patterns 12b and 12c are +, -, and -, respectively, as described above. As a result, a positive amplitude distribution Aa and negative amplitude distributions Ab and Ac occur on the wafer. Since the widths of the circuit patterns 12a and 12p are almost the same, the amplitude distribution Aa of the image of the pattern 12a is the same as the amplitude distribution Ap obtained by the conventional exposure method shown in FIG. 10(b).
It is almost the same as However, in the case of the present invention, the amplitude distributions Ab and Ac from the auxiliary patterns 12b and 12c are added to this. Therefore, the amplitude distribution Aa (>0) from the circuit pattern and the amplitude distribution Ab from the auxiliary pattern
, Ac (<0) cancel each other out, and therefore the intensity distribution of the image appears as a sharp peak like Ea shown in FIG. 9(c). Of this intensity distribution Ea, the width with the intensity that exposes the resist on the wafer (the amount of exposure that is completely removed or preserved by development) is the width W2, which is narrower than the width W1 shown in FIG. 10(c). shown. Therefore, it is possible to transfer a pattern having a width W2 finer than the width W1 obtained by the conventional method.

Next, a case will be described in which the auxiliary patterns 12b and 12c have the same size as the circuit pattern 12a. The circuit pattern 12a is the same as that shown in FIG. 9(a), and the illumination method is also the same. In this case, in the amplitude distribution of the light transmitted through the pattern, Ab and Ac, which are the components of the light transmitted through the auxiliary patterns 12b and 12c, become larger on the negative side in the amplitude distribution shown in FIG. 9(b). Therefore, the intensity distribution of the image of the circuit pattern 12a has a sharper (narrower) peak than Ea in FIG. 9(c), as shown in FIG. 9(d).
a', and the width W2' of the image of the circuit pattern 12a can be made finer than the width W2 shown in FIG. 9(c). However, the intensities Eb' and Ec' of the images of the auxiliary patterns 12b and 12c naturally increase, and there is a possibility that even unnecessary patterns may be transferred onto the wafer. Figure 9(d)
The exposure amount Eth indicated by a broken line inside indicates the exposure amount at which the positive resist is completely removed, and the exposure amount Es indicates the exposure amount at which the positive resist begins to thin. In other words, Et
At an exposure dose of h or more, the resist is completely removed, and at an exposure dose of Es or less, the resist remains completely without film thinning. Therefore, Eb′ of the intensity distribution shown in FIG. 9(d)
, Ec' indicate that the positive resist remains while causing so-called film thinning. From this, the widths of the auxiliary patterns 12b and 12c may be set to optimal values depending on the characteristics of the resist and the amount of exposure. Alternatively, the exposure amount may be selected such that only Ea' in the intensity distribution exceeds Eth, and Eb' and Ec' are equal to or less than Es. Although the intensity distribution and the exposure amount are shown in the same drawing in FIG. 9(d), for convenience, they will be considered as equivalent. The same applies below.

In the projection exposure apparatus used in the embodiment of the present invention, the center position of the local area through which the illumination light flux passes in the pupil plane of the illumination optical system, that is, the exit of the light splitter (optical fiber) 7 shown in FIG. Pupil plane 15 of the illumination optical system of parts 7a and 7b
It is desirable that the position of the reticle is variable depending on the direction, width, pitch, etc. of the pattern of the reticle used. In other words, this is because the angle and direction of incidence of the illumination light beam onto the reticle are determined by the direction, width, and pitch (in this case, especially the spacing between the auxiliary patterns) of the pattern, respectively. More specifically, the reticle may be illuminated with such a light beam that equal wavefronts with opposite phases reach the circuit pattern to be transferred and the auxiliary pattern in the vicinity thereof. The direction of eccentricity from the optical axis AX on the pupil plane of the illumination optical system is determined according to the incident direction determined in this way, and the amount of eccentricity from the optical axis AX is determined according to the angle of incidence.

In the case of a one-dimensional space pattern as shown in FIG. 5 described above (the same applies to the case of a line pattern), the illumination light flux is applied to the pattern on the reticle, for example, as shown in FIG. 9(a).
It is sufficient that the light is incident from the direction shown in . That is, FIG. 9(a
) is the circuit pattern 12a and the auxiliary patterns 12b, 1
2c is shown, and the illumination light beam L2 is incident on the reticle 11 parallel to the plane of the paper. In the case of a one-dimensional space pattern and a line pattern, the direction of incidence of the illumination light beam onto the reticle is, for example, as shown in FIG. It is preferable that the light be illuminated by two luminous fluxes (as shown in the figure). In other words, it is preferable that the center positions of the local areas through which the illumination light beam passes through the pupil plane 15 of the illumination optical system be set at two locations that are substantially symmetrical with respect to the optical axis AX. This is to reduce image positional deviation (so-called telecentering deviation) due to the influence of wavefront aberration when the wafer is defocused. Therefore, when the wafer is accurately at the best focus position, a light beam from one direction as shown in the figure may be sufficient. However, this is limited to the case where the auxiliary patterns on the reticle 11 have only one spacing and directionality. The center position of the local area through which the illumination light flux passes in the pupil plane of the illumination optical system of the projection exposure apparatus is determined as described above.

Furthermore, in the case of the grid pattern shown in FIG. 6 and the hole pattern shown in FIGS. 7 and 8, each pattern has an auxiliary pattern in two-dimensional directions. In this case, the illumination light beam may be incident from a direction perpendicular to the direction in which each auxiliary pattern is drawn, for example. Therefore, the center position of the local area through which the illumination light flux passes on the pupil plane of the illumination optical system is
The two locations determined as described above or the four locations may be used. In other words, when illuminating a pattern drawn in a two-dimensional direction, the center position of the local area through which the illumination light flux passes is the optical axis A.
When using two locations eccentric from X, the two locations are optimal for the auxiliary pattern in the two-dimensional direction, and when using four locations, each location is symmetrical to the previous two locations with respect to the optical axis AX. Just add two places. In this case, if the center positions are set at four locations, the light intensity center of the total illumination light flux can be aligned with the optical axis AX, so the horizontal position of the image that occurs when the wafer is slightly defocused Misalignment (telecenter misalignment) can be prevented.

In the above embodiments, the light beam is illuminated from a direction perpendicular to the direction in which each pattern is drawn, but as mentioned earlier, the angle of incidence and the direction of incidence of the illumination light beam with respect to the pattern are as follows: This is determined by the distance between the pattern on the reticle and the auxiliary pattern, and the direction in which each pattern is drawn. This will be further explained using FIG. 11. 11(a) and 11(c) are diagrams each showing an example of a part of a pattern formed on the reticle 11, and FIG. 11(b) shows an optimal illumination optical system for the pattern of FIG. 11(a). 1 shows the center position of the local area through which the illumination light flux passes in the pupil plane 15 (this is the position of the secondary light source image by the light splitter and represents the center of the illumination light flux), and similarly, FIG.
1(d) is a diagram showing the optimal position of the secondary light source image in the case of the pattern of FIG. 11(c).

FIG. 11(a) is a diagram showing a one-dimensional isolated space pattern, and this pattern consists of an original circuit pattern 12g' (transparent pattern) and auxiliary patterns 12h' and 12i' on both sides thereof. It consists of As described above, the widths of the auxiliary patterns 12h' and 12i' are approximately equal to or less than the resolution limit. In addition, auxiliary patterns 12h', 12i
' are separated by d.

FIG. 11(b) is a diagram showing the optimal position of the secondary light source image (the exit portions 7a to 7d) in the pupil plane 15 of the illumination optical system for the pattern of FIG. 11(a). . At this time, the optimal position of each secondary light source image formed on the Fourier transform plane is an arbitrary position on the line segment Lα and the line segment Lβ in the Y direction assumed in the pupil plane, as shown in FIG. 11(b). becomes. Note that FIG. 11(b) is a diagram of the pupil plane 15 for the pattern viewed from the optical axis direction, and the coordinate system X, Y within the pupil plane 15.
are the same as in FIG. 11(a) when the pattern is viewed from the same direction. Line segments Lα and Lβ are spaced apart by α and β, respectively, from the center C through which the optical axis passes, and when the exposure wavelength is λ,
It is equal to α=β=f·λ/d. (F is the focal length of the optical system (lens or lens group) that has a Fourier transform relationship between the reticle pattern surface and the pupil surface 15.) The illumination light flux emitted from these line segments Lα and Lβ is Incident at an angle (not perpendicular) to the pattern. When considering the cross section A-B in the direction perpendicular to the direction in which the isolated space pattern shown in FIG.
The amplitude of the light irradiated to 2g' has an inverted sign (inverted phase). For example, the illumination light flux generated from point D shown in FIG. 11(b) has an amplitude distribution on the pattern surface of the reticle 11 as follows: ψ=exp{−2πi(βx/fλ+δy/fλ)}.

Here, since β=f・λ/d, ψ=
exp{−2πi(x/d+δy/fλ)}. Now, if the y-coordinate of the cross section A-B in FIG.
πiδy0 /fλ).

Here, exp(-2πiδy0 /fλ
) is constant (=const.) with respect to x. Therefore, the amplitude of light at cross section A-B is ψ0 = const. ×exp(−2πix/d). circuit pattern 12g' and each auxiliary pattern 12h',
12i' is d/2, so the amplitude on the circuit pattern 12g' is expressed as ψ0g'=const. ×exp(−2πix0 /d
), then on the auxiliary patterns 12h' and 12i',
ψ0h′=const. ×exp{−2πi(x0
-d/2)/d} =ψ0r×exp
{2πi×1/2} =−ψ0g′ ψ0i′=const. ×exp{−2πi(x0
+d/2)/d} =ψ0r×exp
{2πi×(-1/2)} =-ψ0g
′ becomes. Therefore, as mentioned earlier, the circuit pattern 12g
The amplitude of the illumination light on ' and the auxiliary patterns 12h' and 12i
It is possible to reverse the sign of the amplitude of the illumination light above , that is, to invert the phase of the wavefront of the illumination light flux.

FIG. 11(c) is a diagram showing an isolated hole pattern, in which a plurality of auxiliary patterns 12n1 to 12n4 are provided near each side of the hole pattern 12m'. At this time, the intervals between each auxiliary pattern are as shown in the figure.
Assume that the directions are dx and dy in the X and Y directions, respectively. Such a pattern can be considered as a two-dimensional extension of the pattern shown in FIG. 11(a). Therefore,
The position of the secondary light source image on the illumination optical system pupil plane 15 is shown in FIG.
In addition to the same line segments Lα and Lβ as in (b),
) may be on the line segments Lγ and Lε shown in FIG. In this case, the positions on the line segments Lα, Lβ correspond to the auxiliary patterns 12n1, 12n3 provided in the X direction, and the positions on the line segments Lγ, Lε correspond to the auxiliary patterns 12v2, 12v2, provided in the Y direction. 12v4. In addition, the position and rotational relationship between FIG. 11(c) and FIG. 11(d) are as follows.
This is the same as the relationship between FIGS. 11(a) and 11(b).

Here, α=β=f・λ/dxγ=ε=f
・λ/dy. Also, the position of the secondary light source image is on the pupil plane 15 on the line segment L.
Intersections Pζ, Pη, Pκ, P of α, Lβ, and Lγ, Lε
If it is on μ, the auxiliary pattern 12n provided in the X direction
1, 12n3, and the auxiliary patterns 12n2, 12n4 provided in the Y direction, the light source position is optimal, which is preferable. In addition, FIGS. 11(b) and 11(d)
), the actual position of the secondary light source image (light intensity distribution) is not limited to only on the line segments Lα, Lβ, Lγ, Lε, but may vary to some extent centered on Lα, Lβ, Lγ, Lε. (that is, the coherence factor σ has a certain value, which will be described later).

In the above, we have assumed that the two-dimensional pattern is a pattern that has two-dimensional directionality at the same location on the reticle, but it can also be used when there are multiple patterns that have different directionality at different locations within the same pattern. The above method can be applied. For example, the pattern shown in FIG. 6 is an example. If the pattern on the reticle has multiple directions, or if the auxiliary patterns have multiple spacings, the optimal position of the secondary light source image is determined according to each directionality and spacing of the pattern, as described above. It becomes a thing, but
Alternatively, the secondary light source image may be placed at the average position of each optimum position. Further, this average position may be a weighted average that is weighted according to the degree of fineness and importance of the pattern.

From the above, it is desirable that the exposure apparatus to which the exposure method according to the embodiment of the present invention is applied has a light amount distribution adjustment function as shown in FIGS. 2 and 3. Here, an example of the configuration of the injection section and the driving member will be explained based on FIGS. 2 and 3. FIGS. 2 and 3 are diagrams showing a schematic configuration of a light splitter and a driving member of a projection type exposure apparatus most suitable for applying the exposure method according to the embodiment of the present invention. FIG. 2 shows the configuration of the exposure apparatus as seen from a direction perpendicular to the optical axis, and FIG. 3 shows the configuration as seen from the optical axis direction. These diagrams show a configuration in which the number of passing points of the chief ray of the illumination light beam on the pupil plane of the illumination optical system is four. The injection parts 7a, 7b, 7c, and 7d are connected to drive members 16a, 16b, 16c, and 16d via variable length support rods 17a, 17b, 17c, and 17d, respectively, and are movable in the direction of arrow A. . Also, the driving member 16
a, 16b, 16c, and 16d are movably supported on the support member 16e, and are movable on a circumference centered on the optical axis AX (in a plane perpendicular to the plane of paper in FIG. 2). These mechanisms allow the position of the secondary light source image to be moved to any position within the pupil plane 15 of the illumination optical system. It should be noted that the number of emitting portions 7a, 7b, 7c, and 7d is not limited to four, but may be an optimal number depending on the type of reticle pattern used.

When using the above illumination method and simultaneously exposing the circuit pattern 12 onto the wafer 14, the wafer 14 and the imaging plane of the projection optical system 13 are aligned relative to the optical axis AX during one exposure. A progressive focus exposure method that moves or vibrates in the direction is used. This means, for example, that the wafer movement range or vibration range is set in consideration of the depth of focus of the projection optical system 13 and the level difference on the wafer surface, such as the lower part, middle part, etc.
Split into multiple steps such as the top. Then, one exposure may be divided for each step, and one exposure may be completed when the exposure of all steps is completed.

Next, using FIG. 12, we will explain why the apparent depth of focus on the wafer increases due to movement or vibration of the wafer in the optical axis direction during exposure in the exposure method according to the embodiment of the present invention. I will explain. FIG. 12A is a diagram showing the intensity distribution of each exposure applied to the lower part of the step when stepwise exposure is performed using the exposure method according to the embodiment of the present invention. Further, FIG. 12(b) is a diagram showing the intensity distribution of each exposure similarly applied to the middle part of the step. Furthermore, Fig. 12(c)
2 is a diagram showing the intensity distribution of each exposure applied to the upper part of the step. In this case, the lower position is represented by -Z1, the middle position by Z0, and the upper position by +Z1. The pattern to be exposed is, for example, a hole pattern (micro rectangle) 12m as shown in FIG. This hole pattern 12
The intensity distribution of the projected image of m on the wafer 14 is shown as Fmn, and the subscript m=1 indicates the focus position -Z1, m
=2 represents the focus position Z0, m=3 represents the focus position +Z1, and n=1, 2, and 3 represent the number of exposures (order), respectively. That is, F11 is when the first exposure is performed at focus position -Z1, F22 is when the second exposure is performed at focus position Z0, and F3 is
3 represents the respective intensity distributions when the third exposure is performed at the focus position +Z1.

First, when the first exposure is performed by focusing the best imaging plane of the projection lens on the lower part (position -Z1) of the pattern step on the wafer, the step is as shown in FIG. 12(a). 12(b), (
As shown in c), the intensity distribution F11' deteriorates rapidly (the peak value decreases and the width increases). Next, when the best imaging plane is focused on the middle part of the pattern step (position Z0) and a second exposure is performed, a sharp intensity distribution F22 is imaged in the middle part, but in the lower part and upper part, respectively. Deteriorated intensity distribution F22'
appears. Similarly, in the third exposure, the focus is set on the upper part of the pattern step (position +Z1), so a sharp intensity distribution F33 is obtained at the upper part, and an intensity distribution F33' which deteriorates towards the middle and lower part is obtained. .

When three exposures are completed in this manner, sharp image distributions F11, F22, and F33 are obtained at least once in the lower, middle, and upper portions of the pattern steps. As shown in FIG. 12(a), the integrated light amount of the intensity distributions F11, F22', and F33' is applied to the lower resist, and the integrated light amount distribution becomes as shown in FIG. 12(d). In the figure, the level Eth indicated by a broken line is the amount of exposure necessary to expose the positive resist. Similarly, for the resist in the middle of the pattern step, the intensity distribution is F22, F11'
, F33' is given as shown in FIG. 12(e), and for the resist above the pattern step, the integrated light amount of intensity distributions F33, F11', and F22' is given as shown in FIG. 12(f). It is given as follows. In any of these three steps, a good image intensity distribution of the hole pattern is given to the resist, and as a result, the apparent depth of focus is reduced over a width of 2Z1 from the top to the bottom of the step. Expansion will take place.

In this embodiment, the wafer is placed at three discrete positions during exposure, but the same effect can be obtained even if the position is changed continuously. Further, the shutter 19 may be repeatedly opened and closed for each stage exposure, or it may be kept open until all stage exposures are completed and closed when one exposure is completed. Further, in the above embodiment, the wafer 14 is moved, but the image forming surface of the projection optical system may be moved by moving at least one of the optical members constituting the projection optical system. I do not care.

In this embodiment, the case where a reticle having a circuit pattern consisting of a transparent part and an auxiliary pattern (isolated space pattern) is used has been described above. Similar effects can be obtained even when using a reticle having a pattern (isolated line pattern) consisting of . This corresponds to the so-called "Babinet's theorem." By the way, if a pattern is used in which both the circuit pattern and the auxiliary pattern are made up of a light-shielding part and the other part is made up of a light-transmitting part, a new effect is produced by using the progressive focus exposure method in combination, which is particularly effective. Regarding this, Figures 13, 14 and 1
This will be explained with reference to 5.

FIG. 13 is a diagram showing another example of a reticle pattern used in the exposure method according to the embodiment of the present invention. This is an example of a pattern (isolated line pattern) in which both the circuit pattern and the auxiliary pattern are composed of light-shielding parts, and a circuit pattern 12r is provided on the reticle, and auxiliary patterns 12s and 12t are provided in the vicinity thereof. In this case, the width of the auxiliary patterns 12s and 12t is the same as that of the circuit pattern 12.
It was set to be the same as r. Further, the spacing between the auxiliary patterns 12s and 12t and the circuit pattern 12r was made the same as the width of the circuit pattern 12r. FIG. 14 shows the intensity distribution of a projected image obtained when a pattern as shown in FIG. 13 is illuminated using the exposure method according to the embodiment of the present invention. FIG. 14(a) is a diagram showing the intensity distribution Ia of the projected image at the best focus position, and FIG. 14(b) is a diagram showing the intensity distribution Ib of the projected image at the defocus position. In addition, FIG. 14(c) shows the intensity distribution Ic that shows the sum of the intensity distribution Ia at the best focus position and the intensity distribution Ib at the defocus position, and this is the intensity distribution Ic that shows the sum of the intensity distribution Ia at the best focus position and the intensity distribution Ib at the defocus position. When moving or vibrating (when using progressive focus exposure method)
It corresponds to the statue of In the image at the best focus position, as shown in FIG. 14A, the image intensities of the circuit pattern 12r and the auxiliary patterns 12s and 12t both appear as dark lines with extremely high contrast. However, in the image at the defocus position, as shown in FIG. 14(b), the image of the circuit pattern 12r appears as a dark line with high contrast, but the images of the auxiliary patterns 12s and 12t appear as blurred dark lines with low contrast. Therefore, when the wafer is moved or vibrated in the optical axis direction of the projection optical system during exposure, the image intensity distribution Ic becomes the sum of the intensity distributions Ia and Ib, and the image of the circuit pattern 12r is extremely dark, but the auxiliary The images of the patterns 12s and 12t can be made not so dark. At this time, for example, when using a positive resist, the exposure amount Es at which the resist begins to thin and the exposure amount Eth at which the resist is completely removed are shown in FIG.
If the settings are as shown in c), (actually, the exposure amount Es
, and Eth, the intensity distribution Ic is such as shown in FIG. If the exposure amount is set so that the exposure amount is greater than or equal to the exposure amount Eth, an extremely fine line pattern (pattern remaining in the resist) can be formed on the wafer. Note that the auxiliary patterns 12s and 12t are the circuit pattern 12r.
Although it may be a thinner pattern, in order to improve the resolution (reduce the line width), it is necessary to use a pattern with the same size as the circuit pattern 12r as explained in the example shown in FIG. 9(d) above. It is desirable that the pattern be In addition to the above-mentioned pattern example, there is also a pattern having a shape as shown in FIG. 6, in which the light-shielding part and the light-transmitting part are opposite, that is, surrounded by a circuit pattern formed of grid-like light-shielding parts. The same can be said of a pattern in which an auxiliary pattern formed of a frame-shaped light-shielding portion is provided in a light-transmitting region.

Furthermore, FIG. 15 shows a circuit pattern 12u formed in the vicinity of a circuit pattern 12u formed of a light-shielding portion such as a square.
This is an example in which an auxiliary pattern 12v formed of a light-shielding portion having the same size and shape as shown in FIG. Light shielding part 1 shown in FIG.
It is assumed that 2u and 12v are lined up at a predetermined pitch in the vertical and horizontal directions, respectively. The pattern shown in FIG. 15 is considered to be a two-dimensional extension of the pattern shown in FIG. 13, and its image is almost the same as that shown in FIG. 14. Therefore, by using the pattern shown in FIG. 15 and using a positive resist, extremely fine isolated islands (local,
In other words, it is possible to form a pattern in which resist remains in the form of islands. Furthermore, the size of the auxiliary pattern 12v is the same as that of the circuit pattern 12u.
Although it may be smaller, it is preferable to have the same size in order to improve the resolution of the circuit pattern 12u. Further, the shape of the auxiliary pattern 12v does not have to be the same as that of the circuit pattern 12u. In this case, for example, a pattern with a shape as shown in FIG. 8 in which the light-shielding part and the light-transmitting part are reversed, that is, a frame-shaped light-shielding part with a light-transmitting part in a predetermined area sandwiched around a rectangular light-shielding part is used. The same can be said for patterns provided with sections. Although the case where both the patterns shown in FIGS. 13 and 15 are exposed to light on a positive resist has been described, the same effect can be obtained when a negative resist is exposed to light. In this case, the pattern in Figure 13 is an isolated space pattern (
The result is a pattern in which the resist is removed in a line, as shown in Figure 15.
The pattern becomes an isolated hole pattern (a pattern in which the resist is locally removed). Further, the exposure amount Eth shown by a broken line in FIG. 14(c) represents the exposure amount at which the negative resist completely remains, and Es represents the exposure amount at which the negative resist is completely removed. In other words, at an exposure dose of Eth or more, the resist remains completely without film thinning, and at an exposure dose of Es or less, the resist is completely removed. Regarding the current photoresist, both negative type and positive type are Eth.
= about 2.Es.

As described above, when both the circuit pattern and the auxiliary pattern are patterns formed by light-shielding parts, the intensity distribution of the image on the wafer according to the present invention is as shown in FIG.
As shown in Ic shown in c), even if the auxiliary pattern is about the same size as the circuit pattern, the auxiliary pattern will not be transferred, but rather an extremely fine pattern will be transferred even if the auxiliary pattern is about the same size. It can be said that it can be done. In other words, if the width of the auxiliary pattern is made to be approximately the same size as the circuit pattern in order to improve resolution, there is a risk that the image of this auxiliary pattern may also be transferred. Therefore, in order to prevent this transfer, a progressive focus exposure method may be used in combination. On the other hand, even when both the circuit pattern and the auxiliary pattern are patterns formed of transparent parts (space patterns), the auxiliary pattern is made to have the same level as the circuit pattern, as explained in the example of FIG. 9(d). It is possible. However, for space patterns,
Compared to a pattern (line pattern) formed in a light-shielding area, resist film loss is slightly more likely to occur. This is because, with respect to the above-mentioned exposure amounts Eth and Es, the curves representing the image intensity distribution of the pattern are completely opposite between the space pattern and the line pattern. In short, it is easier to control the image intensity with respect to the exposure amounts Eth and Es by using a line pattern. In other words, when a space pattern is used, the intensity distribution of the image is necessarily the exposure amount Et
This means that control is difficult because it falls within the range affected by h and Es.

In addition, in the projection exposure apparatus used in the present invention, the numerical aperture of each of the light flux illuminating the reticle or a plurality of light fluxes satisfies the σ value of 0.1<σ<
It is desirable that it be about 0.3. If the σ value is too small, the resolution of the image will decrease due to the proximity effect, and on the other hand, if the σ value is too large, the interference of light between the circuit pattern and the auxiliary pattern will be weakened, reducing the effects of the present invention. For this reason, for example, in the case of the apparatus shown in FIG.
It is preferable to set the diameter to a size that satisfies the condition of 0.1<σ<0.3. Alternatively, a variable aperture may be provided in the illumination optical system so that the σ value can be adjusted. Furthermore, it is preferable that the numerical aperture of the projection optical system itself is variable depending on the line width, directionality, etc. of the pattern.

In the above embodiments, as described above, the projection exposure apparatus used has a light intensity distribution of the illumination light beam concentrated in a local area whose center is eccentric from the optical axis on the pupil plane of the illumination optical system. However, as a modification, it is also possible to use an exposure device having an annular light amount distribution on the pupil plane (or the Fourier transform surface in the illumination optical system). In this case, the outer diameter of the annular light intensity distribution is approximately 0.6 to 0.8, equivalent to the σ value, and the inner diameter is approximately 0.3 to 0.8, equivalent to the σ value.
It is good to set it to about 0.6.

In the example of the pattern used in this example, the light shielding part (shaded part) is made of a light shielding material such as chrome, but this light shielding part may be made of a single layer phase shifter. . For example, this method uses a phase shifter that changes the phase of transmitted light by π, and the size of the attached part of this phase shifter is smaller than the resolution limit of the projection optical system, and the diffraction generated at the edge of the phase shifter is The light beams are arranged in a matrix with pitches such that diffracted light of orders other than the 0th order of light does not pass through the projection optical system. In the light-shielding portion having such a configuration, the light that passes through each of the adhered portion and non-deposited portion of the phase shifter has a phase difference of π and cancels each other out, resulting in a dark portion on the wafer. In other words,
It is possible to obtain a light-shielding effect on the wafer without providing a light-shielding property on the reticle.

[0048]

[Effects of the Invention] As described above, according to the present invention, it is possible to illuminate the circuit pattern to be transferred and the auxiliary pattern in the vicinity thereof with a light beam such that equal wavefronts with opposite phases reach each other, and therefore, The amplitude distributions of the light beams that pass through both patterns cancel each other out, making it possible to obtain a pattern image with an intensity distribution having a sharp peak. In other words, by performing the illumination method according to the present invention, it is possible to enhance the effect of the auxiliary pattern, and instead of using a phase shift reticle etc., a reticle consisting only of a normal light shielding part and a transmitting part can be used. It is possible to transfer a pattern that is finer than the conventional method and is equivalent to that when using a phase shift reticle.

Furthermore, by making the center position of the local area through which the illumination light beam passes in the pupil plane of the illumination optical system variable, it is possible to achieve optimal exposure for various reticles with different pattern line widths, directionality, etc. It can be realized. moreover,
When exposing a pattern, by relatively moving or vibrating the substrate and the image plane of the projection optical system in the optical axis direction,
It is also possible to expand the apparent depth of focus. In particular, when using an auxiliary pattern with a width comparable to that of the circuit pattern, this movement or vibration in the optical axis direction may cause
It becomes possible to prevent the transfer of the auxiliary pattern and transfer only the circuit pattern with high resolution.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus most suitable for applying an exposure method according to an embodiment of the present invention.

[Figure 2]
A diagram showing a schematic configuration of a light splitter and a driving member of a projection exposure apparatus suitable for applying an exposure method according to an embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a light splitter and a driving member of a projection exposure apparatus most suitable for applying the exposure method according to the embodiment of the present invention.

FIG. 4 is a diagram showing the pattern of a reticle used in an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a reticle pattern used in an embodiment of the present invention.

FIG. 6 is a diagram showing an example of a reticle pattern used in an embodiment of the present invention.

FIG. 7 is a diagram showing an example of a reticle pattern used in an embodiment of the present invention.

FIG. 8 is a diagram showing an example of a reticle pattern used in an embodiment of the present invention.

FIG. 9(a) is a schematic diagram showing the irradiation state of the illumination light beam onto the reticle when illumination is performed using the exposure method according to the embodiment of the present invention; FIG. Diagram (c) showing the amplitude distribution of light passing through the pattern portion when illumination is performed using the method is a diagram showing the image intensity distribution of the pattern when illumination is performed using the exposure method according to the embodiment of the present invention. (d) is a diagram showing the image intensity distribution of a pattern when illumination is performed using the exposure method according to the embodiment of the present invention.

FIG. 10(a) is a schematic diagram showing the irradiation state of the illumination light beam onto the reticle when illumination is performed using the exposure method according to the conventional technology; FIG. A diagram showing the amplitude distribution of light passing through the pattern section when performing
c) is a diagram showing the image intensity distribution of a pattern when illumination is performed using a conventional exposure method.

[Figure 11] (a)
, (c) both show examples of a part of the pattern formed on the reticle. (b) shows the passage of the illumination light flux within the pupil plane of the optimal illumination optical system in the case of the pattern of FIG. 11 (a). Diagram (d) showing the center position of the local area is a diagram showing the center position of the local area through which the illumination light flux passes in the pupil plane of the optimal illumination optical system in the case of the pattern of FIG. 11(c).

FIG. 12(a) shows the intensity distribution of each exposure given to the lower part of the step when stepwise exposure is performed using the exposure method according to the embodiment of the present invention; FIG. 12(b) shows the exposure method according to the embodiment of the present invention; Figure (c) shows the intensity distribution of each exposure applied to the middle part of the step when stepwise exposure is performed using the exposure method according to the embodiment of the present invention. Figure (d) showing the intensity distribution of the exposure method according to the embodiment of the present invention is a figure (e) showing the integrated light quantity distribution given to the lower part of the step when performing stepwise exposure using the exposure method according to the embodiment of the present invention. Figure (f) shows the cumulative light amount distribution given to the middle part of the step when stepwise exposure is performed using the exposure method according to the embodiment of the present invention. Diagram shown

FIG. 13 is a diagram showing another example of a reticle pattern used in the exposure method according to the embodiment of the present invention.

FIG. 14 (a) shows the intensity distribution of the projected image at the best focus position. (b) shows the intensity distribution of the projected image at the defocus position. (c) shows the intensity distribution of the projected image at the best focus position. Diagram showing the sum of the intensity distribution and the intensity distribution of the projected image at the defocused position

FIG. 15 is a diagram showing another example of a reticle pattern used in the exposure method according to the embodiment of the present invention.

[Explanation of symbols]

7 Light splitter (optical fiber) 11 Reticle 12 Pattern 12a Circuit pattern 12b Auxiliary pattern 12c Auxiliary pattern 12d Circuit pattern 12e Auxiliary pattern 12f Auxiliary pattern 15 Fourier plane of pattern surface of reticle (pupil plane of illumination optical system) 16a Drive member 16b Drive Member 16c Drive member 16d Drive member 16e Support member 17a Variable length support rod 17b Variable length support rod 17c Variable length support rod 17d Variable length support rod 19 Shutter 20 Control device L2 Illumination light flux L2a Positive uniform wavefront L2b of illumination light flux Negative equal wavefront Aa Amplitude distribution of transmitted light of the circuit pattern Ab Amplitude distribution of transmitted light of the auxiliary pattern Ac Amplitude distribution of transmitted light of the auxiliary pattern Ea Intensity distribution of the image of the circuit pattern Eb Intensity distribution of the image of the auxiliary pattern Ec Auxiliary pattern Intensity distribution of image Ea' Intensity distribution of image of circuit pattern Eb' Intensity distribution of image of auxiliary pattern Ec' Intensity distribution of image of auxiliary pattern Ia Intensity distribution of image Ib Intensity distribution of image Ic Intensity distribution of image W2 Transferred image Width W2 'Width WS of transferred image Movable stage

Claims (2)

[Claims] 1. An exposure method in which a group of fine patterns on a mask is illuminated with a light beam from an illumination optical system, and the group of fine patterns is projected onto a photosensitive substrate via a projection optical system, comprising:
An auxiliary pattern having a size equal to or smaller than the fine pattern is provided near each fine pattern in the fine pattern group,
a surface in the illumination optical system that becomes a Fourier surface of the mask;
Alternatively, the light flux passing through a plane in the vicinity thereof is defined in a local region having a center at a position eccentric from the optical axis of the illumination optical system, so that the mask is directed in a predetermined direction to the fineness of the fine pattern group. irradiating with a light beam tilted at a corresponding angle to increase the projection contrast of the fine pattern between the fine pattern and the auxiliary pattern;
An exposure method characterized by moving or vibrating the photosensitive substrate and an imaging plane of the projection optical system relative to each other in the optical axis direction when projecting and exposing the fine pattern group onto the photosensitive substrate. . 2. The angle is determined by the line width of each fine pattern in the fine pattern group, and the direction is determined by the directionality of the pattern, and is determined by the angle and the direction. 2. The exposure method according to claim 1, wherein the center position of a local region through which the light beam passes in the Fourier plane or a plane in the vicinity thereof is adjusted depending on the direction of incidence of the light beam.