JPH04268714A - Method of exposure - Google Patents

Abstract

PURPOSE:To obtain an exposing method with which high degree of resolution can be obtained by increasing efficiency using the reticle formed by a light- shielding part and a light-transmitting part only and by providing an auxiliary pattern. CONSTITUTION:When a reticle 11, having auxiliary patterns 12b and 12c of the size smaller than the limit of resolution in the vicinity of a circuit pattern 12a, is going to be illuminated, the light flux L2 which illuminates the reticle is inclined in the prescribed direction at the angle in accordance with the degree of minuteness of the pattern by regulating the light flux passing through the plane of the optical system of illumination, which becomes the Fourier surface of the reticle, in the region having the center point at the position which is made eccentric from the optical axis of the optical system of illumination. An equiwave-surfaced light flux, which is inverted in respective phase, can be made to irradiate on a circuit pattern and an auxiliary pattern, the amplitude distribution of the light flux passing through both patterns are cancelled each other, and a pattern image of the intensity distribution having a sharp peak can be obtained.

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 this method, the reticle is illuminated 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 is 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.

[0005]

However, in conventional exposure methods, the fineness (width, pitch) of the circuit pattern on the reticle that can be transferred onto the wafer is determined by the exposure wavelength of the exposure equipment used in 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 using diffraction and interference phenomena that occur because light is a wave, so it is possible to shorten the exposure wavelength or increase the numerical aperture of the projection optical system. In principle, the resolution can be improved. 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. Also, the numerical aperture NA of the projection optical system is currently
It is already at its technical limit, and it is extremely difficult to increase the NA any 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 resolved circularly by the projection optical system, closer to a square, which essentially improves the resolution (resolution of finer patterns). (statue) 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 this phase shift method has an auxiliary pattern that is provided with a so-called phase shifter that makes the phase of transmitted light different by π (rad) from the transmitted light from the original circuit pattern. It is located near the pattern. 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.

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, which is the same as the conventional one, and increases the effect of providing an auxiliary pattern. The purpose of the present invention is to provide an exposure method that provides high resolution.

[0009]

[Means for Solving the Problems] To achieve the above object, the present invention uses a mask (11
) on the photosensitive substrate (
14), an auxiliary pattern (12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 12b, 14b, 14b, 2b, and 14) having a size approximately equal to or less than the resolution limit of the projection optical system (13) are provided in the vicinity of each fine pattern (12a, 12d) in the fine pattern group (12). 12c, 12e, 12f) are provided, and the light flux passing through the plane (15) in the illumination optical system, which is the Fourier plane of the mask (11), or a plane in the vicinity thereof, is directed to the optical axis of the illumination optical system (1 to 10). By defining a local area with its center at a position eccentric from (AX), the light beam illuminating the mask (11) is tilted in a predetermined direction by an angle corresponding to the degree of fineness of the fine pattern group (12). .

0010

[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.

[0011]

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 diffracted light generated by the pattern 12 on the reticle 11 forms an image on the wafer 14 via the projection optical system 13, and the image of the pattern 12 is transferred. The wafer 14 is placed in a plane perpendicular to the optical axis AX.
It is placed on a wafer stage WS that is movable in the dimensional direction, and the transfer area of the pattern 12 can be sequentially moved. It is assumed that this exposure apparatus has a shutter for controlling the amount of light irradiated onto the reticle 11, a irradiance meter, etc. in the illumination optical system. Also, as 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 exit surfaces of the light source 1 and the fly-eye lens 5 (pupil plane 15 of the illumination optical system), 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 transfer surface of the wafer 14 are conjugate with each other. In addition, another fly's eye lens may be added closer to the reticle 11 than the light splitter 7, that is, 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. In addition, the projection optical system 13
, and depending on the state of correction of chromatic aberration of 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 reticle is illuminated using a conventional device, only the 0th-order light of the diffracted light generated by a fine periodic pattern can pass through the projection optical system 13, making it difficult to resolve the pattern. Even if you are unable to
When the reticle is illuminated using the above-mentioned device, the illumination light flux emitted from the emission parts 7a and 7b of the light splitter 7 is incident on the reticle 11 at a predetermined angle, so that the ±1st-order diffracted light generated from the reticle pattern Either 1 luminous flux and 0
Together with the next diffracted light, two light beams can pass through the pupil plane of the projection optical system, and the pitch is smaller (fine).
It becomes possible to resolve 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.

In the projection exposure apparatus used in the embodiment of the present invention, the central 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 in 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. Become.

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 on the reticle is the illumination light beam L2 tilted as shown in FIG. )
It is preferable that the light be illuminated by two luminous fluxes. In other words, it is preferable that the center positions of the local regions through which the illumination light flux passes through on the pupil plane 15 of the illumination optical system be set at two locations that are approximately 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 a grid pattern as shown in FIG. 6 and a hole pattern as 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 flux is illuminated from a direction perpendicular to the direction in which each pattern is drawn, but as mentioned earlier, the incident angle and direction of incidence of the illumination light flux 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. For more information on this, see Figure 1.
1 will be used for explanation. 11(a) and 11(c) are diagrams each showing an example of a portion of a pattern formed on the reticle 11. FIG. FIG. 11(b) shows the center position of the local area through which the illumination light flux passes through in the pupil plane 15 of the illumination optical system that is optimal for the pattern of FIG. 11(a) (the position of the secondary light source by the light splitter), 11 (representing the center of the illumination luminous flux), and similarly Fig. 11 (
d) is a diagram showing the optimal position of the secondary light source 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 12r (transparent pattern) and auxiliary patterns 12s and 12t on both sides thereof. There is. As mentioned above,
The widths of the auxiliary patterns 12s and 12t are approximately equal to or less than the resolution limit. Further, it is assumed that the auxiliary patterns 12s and 12t are spaced apart by d.

FIG. 11(b) shows the secondary light source (
It is a figure showing the position of injection parts 7a-7d). At this time,
The optimal position of each secondary light source 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). Furthermore, Figure 1
1(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 is the same as that of FIG. 11(a) when the pattern is viewed from the same direction. There is. Line segments Lα and Lβ are α and Lβ, respectively, from the center C through which the optical axis passes.
When the distance is β and the exposure wavelength is λ, α=β=
Equal to f・λ/d. (F is the focal length of the optical system (lens or lens group) that has a Fourier transform relationship between the pattern surface of the reticle and the pupil surface 15.) These line segments Lα
, Lβ are incident on the reticle surface at an angle (from a direction that is not perpendicular) to the pattern. Then, when considering the cross section A-B in the direction perpendicular to the direction in which the isolated space pattern shown in FIG. 11(a) is drawn,
The amplitudes of the light irradiated onto the auxiliary patterns 12s and 12t and the circuit pattern 12r have inverted signs (inverted phases). 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.
δy0 /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 12r and each auxiliary pattern 12s, 12
Since the distance from t is d/2, the circuit pattern 12
The amplitude on r is expressed as ψ0r=const. ×exp(-2πix0/d)
Then, on the auxiliary patterns 12s and 12t, ψ
0s=const. ×exp{−2πi(x0 −d/
2)/d} = ψ0r x exp {2πi x 1/2} = -ψ0r ψ0r = const. ×exp{−2πi(x0 +d
/2)/d}=ψ0r×exp{2πi×(-1/2)}=-ψ0r. Therefore, as mentioned earlier, the circuit pattern 12r
The amplitude of the illumination light on the top and the amplitude of the illumination light on the auxiliary patterns 12s and 12t can be made to have opposite signs, that is, the phase of the wavefront of the illumination light beam can be inverted.

FIG. 11(c) is a diagram showing an isolated hole pattern, in which a plurality of auxiliary patterns 12v1 to 12v4 are provided near each side of the hole pattern 12u. At this time, the intervals between each auxiliary pattern are as shown in the figure, X, Y
Assume that the directions are dx and dy, 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 as shown in FIG.
In addition to the same line segments Lα and Lβ as shown in FIG. In this case, line segment Lα
, the position on Lβ is the auxiliary pattern 12 provided in the X direction.
v1, 12v3, and the line segment L
The position on γ and Lε is the auxiliary pattern 1 provided in the Y direction.
This corresponds to 2v2 and 12v4. Furthermore, Figure 1
The position and rotational relationship between 1(c) and 11(d) are shown in FIG.
The relationship is the same as that between (a) and FIG. 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 12v provided in the X direction
1 , 12v3 , and the auxiliary patterns 12v2 , 12v4 provided in the Y direction, this is the optimal light source position, 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 may also be possible to 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.

In the above embodiments, a case has been described in which a reticle having a circuit pattern consisting of a transparent portion and an auxiliary pattern (isolated space pattern) is used. Similar effects can be obtained even when using a reticle that has This corresponds to the so-called "Babinet's theorem."

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, image fidelity will be reduced due to the proximity effect, and on the other hand, if it is too large, the light interference 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 type exposure apparatus used has a light intensity distribution of the illumination light beam concentrated in a local area having its center at a position 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 embodiment, the light shielding portion (hatched portion) is made of a light shielding material such as chrome, but this light shielding portion 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.

[0036]

[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, the effect of improving resolution by providing an auxiliary pattern increases, so instead of using a phase shift reticle etc., a reticle consisting only of a normal light-shielding part and a transmitting part is used to achieve finer and phase-resolving power than before. It is possible to transfer the same pattern as when using a 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.

[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 side view 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 plan view showing a schematic configuration of a light splitter and a driving member of a projection exposure apparatus that is 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.

[Figure 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; (b) is a schematic diagram showing the state when illumination is performed using the exposure method according to the conventional technology. Diagram showing the amplitude distribution of light transmitted through the pattern part (
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).

[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 L2 Illumination light flux L2a Positive uniform wave surface L2b of illumination light flux Negative uniform wave surface Aa of illumination light flux 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 Intensity distribution of the image of the auxiliary pattern w2 Width of transferred image

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 approximately equal to or less than the resolution limit of the projection optical system is provided near each fine pattern in the fine pattern group, and the auxiliary pattern is provided on the surface in the illumination optical system that becomes the Fourier surface of the mask, or in the vicinity thereof. By defining the light flux passing through the plane in a local region having a center at a position eccentric from the optical axis of the illumination optical system, the light flux illuminating the mask is directed in a predetermined direction to the fineness of the fine pattern group. An exposure method characterized by tilting at a corresponding angle. 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.