JPH04268715A - Method of exposure - Google Patents

Abstract

PURPOSE:To improve the contrast of the projected image of pattern by using the patterned reticle of pattern composed of a semi-transmission part having the prescribed phase difference and a transmittance against the transmitted light from a transmission part. CONSTITUTION:An almost (2n+1-1)pi (n is an integral number) phase difference is given to the light flux passing through a transmitting part 12a. A mask 11 is composed of a transmitting part 12a and a semi-transmitting part 12b having the transmission factor against the light flux of about 1/4 or lower than the transmitting part 12a. A light flux, which is limited to pass through a local region having the center point at the position which is made eccentric from the optical axis AX of an illuminating optical system on the plane in the illuminating optical system, which becomes the Fourie surface, where the microscopic pattern group 12 of a mask 11 is present, or the plane in the vicinity of the above-mentioned surface, is used. As a result, the light flux can be made incident by tilting it at an angle, corresponding to the degree of minuteness of a microscopic pattern group 12, in the prescribed direction against the mask 11.

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 of semiconductor devices and the like.

0002

[Prior Art] In conventional exposure methods, 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. Furthermore, a circuit pattern was drawn on the reticle used in this device, which consisted of a transmitting part with a transmittance of almost 100% for the illumination light flux and a light-blocking part with a transmittance of almost 0%. .

Furthermore, in a predetermined region of the transmitting section, the phase of the transmitted light is set by π(r
It has also been proposed to use a phase shift reticle provided with a so-called phase shifter (dielectric thin film) that shifts the phase by an amount of ad). With this phase shift reticle,
It is possible to transfer a finer pattern than when using a reticle (hereinafter generally referred to as a reticle) consisting only of a transmitting part and a light blocking part. That is, it has the effect of improving resolution.

In addition, by moving or vibrating the object to be exposed (wafer, etc.) in the optical axis direction of the projection optical system during exposure,
A method for increasing the apparent depth of focus of an exposure device (hereinafter referred to as
A progressive focus exposure method (referred to as a progressive focus exposure method) has also been proposed.

[0005]

However, in conventional exposure methods, when the above-mentioned normal reticle is used, the fineness (width, pitch) of the circuit pattern on the reticle that can be resolved on the wafer depends on the exposure method used. The wavelength of the exposure light of the device is λ (μm), and the numerical aperture on the reticle side of the projection optical system is NA.
The limit was approximately λ/NA (μm). This is because images are formed by diffraction and interference phenomena that occur because light is a wave, and the passing position of diffracted light from a pattern with a size below this limit on the pupil plane of the projection optical system is , as shown in FIG. That is, the only light beam that can pass through the pupil plane 18 of the projection optical system is the 0th-order diffracted light Dov, and the +1st-order diffracted light Dpv and -1st-order diffracted light Dmv cannot pass through the pupil plane 18 of the projection optical system. Therefore, the light flux that reaches the wafer is only the 0th-order diffracted light Dov, and no interference fringes (that is, pattern images) are generated.

On the other hand, when a phase shift reticle is used, it is possible to transfer a finer pattern than when a normal reticle is used, but the phase shift reticle is difficult to manufacture. For example, for a normal reticle, it is sufficient to simply form a light shielding part, but for a phase shift reticle, after forming a light shielding part, it is necessary to further form a phase shifter. Therefore, it is necessary to perform patterning at least twice in total and to align each pattern. Moreover, a method for inspecting a phase shift reticle has not yet been established, and it is currently difficult to put it into practical use.

Furthermore, in the above-mentioned progressive focus exposure method, a pattern that exists alone (a pattern in which the ratio of the width of a line part of a pattern such as a light shielding part to the width of a space part is about 1:3 or more, in other words, For example, for patterns in which the pitch of the pattern is about four times or more the width of the line portion of the pattern (hereinafter referred to as an isolated pattern), an apparently larger depth of focus can be obtained compared to the normal exposure method. , it is less effective for patterns other than isolated patterns. Furthermore, it is theoretically impossible to improve the resolution using this method alone.

The present invention has been made in view of the above problems, and is an exposure method that enables transfer of finer patterns (that is, higher resolution) using a regular reticle that is easy to manufacture. The purpose is to realize the method.

[0009]

[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), each fine pattern in the fine pattern group (12) has a transparent part (12a) whose transmittance to the light beam is approximately 1, and a transparent part (12a).
The semi-transparent part (12
b), and the fine pattern group (
12) passes through a local area centered at a position eccentric from the optical axis (AX) of the illumination optical system within the plane (15) in the illumination optical system, which is the Fourier plane of the plane where 12) exists, or a plane in the vicinity thereof. By using a luminous flux that is so limited, the luminous flux is incident on the mask (11) in a predetermined direction at an angle corresponding to the degree of fineness of the fine pattern group (12).

0010

[Function] In the present invention, a transmitting portion having a high transmittance for the illumination light beam, a phase difference of approximately (2n+1)π (n is an integer) for the light beam passing through this transmitting portion, and the illumination The transmittance for the luminous flux is 1/4 of the above transmission part.
A reticle is used that has a circuit pattern consisting of semi-transparent parts that are less than 100% translucent. By controlling the transmittance of the semi-transparent part, the intensity of the diffracted light generated from the reticle pattern (for example, the intensity of the 0th-order diffracted light and the 1st-order diffracted light generated from the periodic pattern) and the ratio thereof can be controlled. Therefore, by providing the optimum transmittance according to the line width, periodicity (pitch), directionality, etc. of each pattern, the optimum imaging state can be provided to each pattern.

Furthermore, since the center position of the local region through which the illumination light flux passes within the pupil plane of the illumination optical system is made variable, it is possible to perform optimal illumination according to the line width, directionality, etc. of the pattern. Thereby, the resolution of the pattern and the depth of focus can be improved. Furthermore, since the wafer is moved or vibrated in the direction of the optical axis of the projection optical system during wafer exposure, it is possible to set the optimum focus position from the top to the bottom of the step on the wafer surface. becomes.

0012

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 units 7a and 7b are arranged in a pattern 12 on the reticle 11.
The lens systems 8, 10 and the reflecting mirror 9
A plane that becomes a Fourier plane (pupil plane of the illumination optical system) 15
, or 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. 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. 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. 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 exit surface of the fly-eye lens 5 (pupil surface 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 conventional apparatus 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 pattern is transmitted to the projection optical system 13.
Even if the pattern cannot be resolved, if the reticle is illuminated using the above device, the illumination light flux emitted from the emission parts 7a and 7b of the light splitter 7 will be Since the light is incident on the reticle 11 at a predetermined angle, a total of two light fluxes, including one of the ±1st-order diffracted lights generated from the reticle pattern and the 0th-order diffracted light, can pass through the projection optical system. It becomes possible to resolve even small pitch (fine) patterns.

Next, the pattern of the reticle used in the embodiment of the present invention will be explained with reference to FIG. FIG. 4 is a diagram showing the pattern of a reticle used in the exposure method according to the embodiment of the present invention. On one surface of the reticle 11, which is a light-transmitting glass substrate, a semi-transparent part 12b having a predetermined transmittance and a transmitting part 12a having a high transmittance are formed as a circuit pattern 12. Semi-transparent part 12b
The transmitted light that passes through the transmitting portion 12a has a phase difference of approximately (2n+1)π (n is an integer) with respect to the transmitted light that passes through the transmitting portion 12a, and the transmitted energy is approximately 1/4 or less. There is. This transparent portion 12a may be any bare surface of the reticle 11. Further, the semi-transparent part 12b is formed of a metal thin film, a dielectric thin film (particularly an absorptive dielectric thin film), or a multilayer film of these materials. In FIG. 4, portion A represents a so-called line and space pattern, portion B represents an isolated space pattern, and portion C represents an isolated line pattern.

These patterns can be formed by forming a film of the above material on one surface of the reticle 11 and then patterning it once. Therefore, the phase shift reticle
It is much easier to manufacture than the case where the light shielding member and the phase shifter are patterned twice and the alignment between these patterns is required. As described above, the pattern is composed of a transmitting part and a semi-transmitting part in which the phase of transmitted light is different from the transmitted light from the transmitting part by (2n+1)π and the transmitted energy is about 1/4 or less. A reticle having a reticle is illuminated with a light beam that passes through a local region centered at a position offset from the optical axis in the pupil plane of the illumination optical system, and is projected onto the wafer through the projection optical system for exposure. This exposure method will be explained with reference to FIG.

FIG. 5 is a diagram showing the generation of diffracted light from a circuit pattern and image formation when a reticle is illuminated using the exposure method according to the embodiment of the present invention. A one-dimensional so-called 1:1 line-and-space pattern is drawn on the projection optical system 13 side of the reticle 11, consisting of a transparent portion 12a and a semi-transparent portion 12b. In the projection exposure apparatus used in the present invention, as described above, the local region through which the illumination light flux passes is centered at a position eccentric from the optical axis within the pupil plane of the illumination optical system. Therefore, the illumination light flux L0 that illuminates the reticle 11 is
The light enters the reticle 11 at a predetermined angle of incidence from a direction (X direction) substantially perpendicular to the direction in which one pattern is drawn. Note that this angle of incidence and direction of incidence are uniquely determined by the position of the diffracted light generated by the pattern on the reticle within the pupil plane of the projection optical system. The fineness of the pattern (width, pitch) from the pattern on the reticle
0th order light Dov, +1st order light Dpv in the direction of the diffraction angle according to
, −1st order light Dmv is generated. In FIG. 5, the projection optical system 1
Of the three light beams, two light beams, the 0th-order light Dov and the +1st-order light Dpv, pass through the light beam 3 and reach the wafer 14.
These two beams form interference fringes on the wafer 14, that is, pattern 1.
2 images are formed. In this case, the pupil plane 1 of the projection optical system 13
FIG. 7 shows the positions of the 0th-order diffracted light Dov and the +1st-order diffracted light Dpv in 8. The pitch of the pattern used is the same as the reticle pattern used in the conventional exposure method shown in FIG. 6, and therefore the interval between the 0th-order diffracted light Dov and the +1st-order diffracted light Dpv is equal to that shown in FIG.

The resolution limit of a pattern according to the conventional exposure method is determined by whether or not the ±1st-order diffracted light can pass through the projection optical system. That is, conventionally, when the pitch of the pattern is P, the pattern size given by P>λ/NA has been the resolution limit. In contrast, in the exposure method according to the embodiment of the present invention, the resolution limit is approximately P>λ/2NA. This is true not only for the reticle pattern used in the exposure method according to the embodiment of the present invention, but also for the conventional reticle pattern.

When the reticle is illuminated using the exposure method according to the present invention as described above, the 0th order diffracted light Dov and +
The intensity ratio with the first-order diffracted light Dpv changes depending on the amplitude transmittance of the semi-transparent section 12b. For example, when the amplitude transmittance of the transmissive part 12a is 1, if the amplitude transmittance of the semi-transmissive part is 0 (light-shielding part with a transmittance of 0%), the above intensity ratio is approximately 1:0.
It becomes 4. In general, the contrast of the image of the pattern 12 generated on the wafer 14, that is, the contrast of two light beams (0th-order diffracted light Dov and +
The contrast of the interference fringes of the first-order diffracted light Dpv) is maximum (
100%), and as the intensity ratio deviates from 1:1, the contrast decreases. Therefore, if the intensity ratio of the 0th-order light and the 1st-order light is 1:0.4, as in the conventional 1:1 line-and-space pattern consisting of a transmitting part and a light-blocking part, the contrast of the image will decrease. .

[0020] Reticle pattern used in the present invention (1
For example, when the amplitude transmittance of the transmissive part 12a is set to 1, the amplitude transmittance of the semi-transmissive part 12b is -0.222 (phase difference π for the light beam passing through the transmissive part 12a). , transmittance of 4.93%), the intensity ratio of the 0th-order diffracted light Dov and the +1st-order diffracted light Dpv can be set to 1:1, and therefore the contrast of the image can be set to 100%. Further, the transmittance of the semi-transparent part is 4.93%, which is sufficient to replace a conventional light shielding member, considering the photosensitive characteristics of the photoresist.

As mentioned above, the pattern of the reticle used in the cases shown in FIGS. 5 and 7 is a one-dimensional line and space pattern, but the actual reticle pattern is, for example, the line and space pattern described above. It also includes a line and space pattern in the orthogonal direction (X direction). An example of a line and space pattern in this direction is shown in FIG. This pattern has the same configuration as the pattern shown in FIG. 5, and the directions in which the pattern is drawn are perpendicular to each other. A projection optical system for diffracted light generated in the pattern 12 when this pattern is irradiated with an illumination light beam from the same direction as the illumination in the example shown in FIG. 7, that is, the same direction (X direction) as the direction in which the pattern is drawn. FIG. 9 shows the passing position on the pupil plane 18. in this case,
Only the 0th order diffracted light Doh can pass through the projection optical system 13, but both the ±1st order diffracted lights Dph and Dmh pass through the pupil plane 18.
cannot pass through the projection optical system. Therefore, only the 0th-order diffracted light Doh reaches the wafer, and no interference fringes, that is, no images are formed. The direction shown in Figure 8 (
For line-and-space patterns that have a direction (
The illumination light beam may be irradiated from the Y direction). FIG. 10 shows the passing position of the diffracted light generated from the pattern on the pupil plane 18 of the projection optical system in this case. At this time, the 0th order diffracted light Doh,
Since the −1st-order diffracted light Dmh passes through the projection optical system, interference fringes of two light beams, that is, a pattern image is formed on the wafer. From the above, the illumination light flux that illuminates a reticle pattern having a line and space pattern in two orthogonal directions (two-dimensional) may be such that it produces two 0th-order diffracted lights, Dov and Doh, as shown in Figure 11. It's a good thing. Incidentally, the diffracted light Dov in FIG. 11 is in the direction as shown in FIG. 8, and similarly to the pattern shown in FIG. For patterns where , it does not have any effect on imaging, but rather has the opposite effect. In other words, 0
Since only the second-order diffracted light reaches the wafer, a constant positional offset (a constant amount of light over the entire exposed area) is given. This offset reduces the contrast of the pattern image produced on the wafer.

FIG. 13 shows a conventional one-dimensional 1:1 line-and-space pattern consisting of only a transmitting part and a light shielding part (the amplitude transmittance of the light shielding part is 0 for the transmitting part having an amplitude transmittance of 1). 2 according to the present invention as shown in FIG.
FIG. 6 is a diagram illustrating an example of a calculation result of image intensity when illumination is performed from a certain direction. At this time, the image intensity is indicated by E13,
The contrast of the image is approximately 53%. This is because the contrast is lowered due to the offset of the 0th order diffracted light as described above. In current photoresists, the image contrast required to form a line-and-space pattern is about 60%, so it is not possible to form an image on the resist with a pattern of conventional configuration. In order to avoid a decrease in contrast due to this offset, it is considered that the intensity ratio between the 0th-order diffracted light and the 1st-order diffracted light should be set such that the 0th-order diffracted light is relatively smaller than the 1st-order diffracted light. Therefore, the present invention is applied to a photomask in which the amplitude transmittance of the semi-transmissive part is -0.3 (phase difference π for the light flux passing through the transmitting part, transmittance 9%) with respect to the transmitting part having an amplitude transmittance of 1. FIG. 12 shows an example of the calculation results of the image intensity when illumination is performed using the method. At this time, the image intensity is indicated by E12. This image also has a contrast of about 70%, which is sufficient to pattern existing photoresists. This is because the amplitude transmittance of the semi-transparent part of the reticle is set to about -0.3, so that the 0th order diffracted light generated from the line-and-space pattern is reduced compared to the conventional one, that is, the offset is reduced. On the other hand, the intensity of the first-order diffracted light increases compared to the conventional method. Note that it is clear that a one-dimensional 1:1 line-and-space pattern in a direction perpendicular to the direction of the pattern shown here as an example of the calculation result is also imaged with a similar contrast. In other words, when illuminating a reticle with a two-dimensional 1:1 line-and-space pattern with light beams from two directions suitable for the directionality of each pattern, the amplitude transmittance of the semi-transparent part of the reticle pattern should be -0. If it is set to about 3 (assuming the amplitude transmittance of the transmitting part to be 1), it becomes possible to suppress the decrease in contrast due to the offset of the 0th order diffracted light as much as possible.

By the way, since the line width and directionality of the reticle pattern used are not specific to one type,
The center position of the local area through which the illumination light flux passes in the pupil plane 15 of the illumination optical system of the projection exposure apparatus used in the embodiment of the present invention, that is, the exit part 7a of the light splitter (optical fiber) 7 shown in FIG. The position of the illumination optical system 7b on the pupil plane 15 is
It is desirable that it is variable depending on the type of pattern. In other words, this is because the direction and angle of incidence of the illumination light beam onto the reticle are determined by the direction, width, and pitch in which the pattern is drawn, respectively. For example, in the case of a one-dimensional line-and-space pattern extending in a direction perpendicular to the X direction as shown in FIG. . That is, the illumination light beam L0 is incident on the reticle 11 parallel to the plane of the paper. Furthermore, if the incident angle of the illumination light beam L0 is determined so that the 0th-order diffracted light Dov and the 1st-order diffracted light Dpv generated from the pattern 12 pass through positions that are approximately equidistant from the optical axis AX on the pupil plane 18, The depth of focus of the image can be increased.

In accordance with the incident direction determined in this manner, the eccentric direction from the optical axis AX of the center position of the local area through which the illumination light flux passes within the pupil of the illumination optical system is determined, and the line width of the pattern is determined. Optical axis A depending on the angle of incidence determined by
The amount of eccentricity from X will be determined. The center position of the local area through which the illumination light beam passes within the pupil plane of the illumination optical system is determined as described above.

When illuminating patterns drawn in two-dimensional directions, it is preferable to illuminate from two directions in accordance with the direction of each pattern, as described above. The semi-transparent part of the reticle pattern used at this time preferably has an amplitude transmittance of about -0.3. In addition, since the illumination light beams are in two directions, that is, two, for each of the two light beams,
It is preferable to use a total of four light beams, including two light beams that are symmetrical about the optical axis of the projection optical system. In this case, since the direction of the center of gravity of the light quantity of these light beams coincides with the optical axis of the projection optical system, it is possible to prevent a lateral positional shift (telecentering shift) of the image that occurs when the wafer is slightly defocused. Furthermore, when illuminating a reticle having a one-dimensional line-and-space pattern as shown in FIG. 5, it is preferable to similarly illuminate with two light beams that are symmetrical about the optical axis of the projection optical system. Note that when illuminating a one-dimensional pattern, the intensity ratio of the 0th-order diffracted light and the 1st-order diffracted light generated from the pattern is exactly 1:
1, there is no need to illuminate with two light beams from directions symmetrical to the optical axis. However, this is limited to the case where the pattern has only one pitch.

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. . Further, the drive members 16a, 16b, 16c, and 16d are movably supported on the support member 16e, and are movable on the circumference around the optical axis AX (in a plane perpendicular to the paper in FIG. 2). ing. These mechanisms allow the point through which the chief ray passes to move to any position on the Fourier plane 15. 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 is progressively moved or vibrated in the direction of the optical axis AX of the projection optical system 13 during one exposure. Use the focus exposure method. First, the wafer movement range or vibration range, which is set in consideration of the depth of focus of the projection optical system 13 and the level difference on the wafer surface, is divided into a plurality of steps, such as a lower part, a middle part, and an upper part. Then, one exposure is divided into the number of steps for each step, and one exposure is completed when the exposure of all steps is completed. It is widely known that by using this method, it is possible to increase the apparent depth of focus of the projection optical system, especially for isolated patterns. This progressive focus exposure method is not limited to moving the wafer; for example, at least one of the optical members constituting the projection optical system
It is also possible to adopt a configuration in which the imaging plane of the projection optical system is moved by moving the two.

Generally, for dense continuous patterns such as line and space patterns, as already mentioned,
If the 0th-order diffracted light and the 1st-order diffracted light are illuminated so that they pass through positions equidistant from the optical axis on the pupil plane of the projection optical system, the depth of focus increases. However, actual reticle patterns include both dense continuous patterns such as line-and-space patterns and so-called isolated patterns. Therefore, for such reticles, if a progressive focus exposure method in which the wafer is moved or vibrated during exposure is used in conjunction with the above illumination method, it is possible to increase the apparent depth of focus for any pattern. It is. For example, the wafer 14 is held in the exposure apparatus shown in FIG. 1, and the projection optical system 1 is
This can be realized by providing a movable stage WS that moves or vibrates the wafer 14 in the direction of the optical axis 3, and a control circuit 20 that controls both the movable stage WS and the shutter 19 provided in the illumination optical system. This control circuit 20
is used to give an operation command to the movable stage WS in conjunction with the command to open and close the shutter 19.

In the projection exposure apparatus used in the present invention, the numerical aperture of the light beam illuminating the reticle or each of the plurality of light beams satisfies the coherence factor (σ value) of the exposure apparatus such that 0.1<σ< It is desirable that it be about 0.3. If the σ value is too small, the fidelity of the image will decrease due to the proximity effect, and on the other hand, if it is too large, the coherence between the light flux that passes through the transmissive part and the light flux that passes through the semi-transmissive part will decrease. The effectiveness of the invention is reduced. For this reason, for example, Figure 1
In the case of the apparatus shown in , the diameters of the optical fiber emitting portions 7a and 7b may be set 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 to
may be adjustable.

[0030]

As described above, according to the present invention, a pattern consisting of a transmitting part and a semi-transmitting part having a predetermined phase difference and transmittance for light transmitted from the transmitting part is drawn. By using a reticle, the intensity ratio between the 0th-order diffracted light and the 1st-order diffracted light can be arbitrarily controlled, so that the contrast of the projected image of the pattern can be improved. Furthermore, it is possible to obtain a resolution equivalent to that of a phase shift reticle by using a reticle that is easy to manufacture and has a pattern with a structure similar to that of a conventional reticle.

Furthermore, especially when illuminating a reticle having a two-dimensional pattern with light beams from two directions suitable for the direction of each pattern, the amplitude transmittance of the semi-transmissive part relative to the transmissive part should be set to an appropriate value. If the intensity ratio of the 0th-order diffracted light and the 1st-order diffracted light is set such that the 0th-order diffracted light is relatively smaller than the 1st-order diffracted light, the 0th-order diffracted light that becomes an offset can be reduced, and the image Decrease in contrast can be prevented.

Furthermore, the direction of incidence of the illumination light beam can be changed depending on the pattern of the reticle used, and therefore an optimal exposure method can be realized depending on the type of reticle. Additionally, by moving or vibrating the substrate in the optical axis direction of the projection optical system during exposure, it is possible to increase the depth of focus, especially for isolated patterns.

[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 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 the generation of diffracted light from a circuit pattern and image formation when a reticle is illuminated using the exposure method according to the embodiment of the present invention.

FIG. 6 is a diagram showing the passing position of diffracted light generated from a pattern on the pupil plane of the projection optical system when performing an exposure method according to the conventional technology.

FIG. 7 is a diagram showing the passing position of the diffracted light generated from the pattern on the pupil plane of the projection optical system when the reticle shown in FIG. 5 is illuminated;

[Fig. 8] A diagram showing an example of a line and space pattern with a different directionality from the pattern shown in Fig. 5.

9 is a diagram showing the passage position of the diffracted light generated from the pattern on the pupil plane of the projection optical system when the pattern shown in FIG. 8 is illuminated by the exposure method shown in FIG. 5;

10 is a diagram showing the passage position of the diffracted light generated from the pattern on the pupil plane of the projection optical system when the pattern shown in FIG. 8 is illuminated with the illumination light beam from a direction perpendicular to the direction of the illumination light beam shown in FIG. 5;

[Figure 11] Two dimensional line and space patterns
Diagram showing the passing position of the diffracted light generated from the pattern on the pupil plane of the projection optical system when illuminated with the illumination light beam from the direction

FIG. 12 is a diagram showing the image intensity distribution of a pattern on a wafer when the exposure method according to the embodiment of the present invention is performed.

FIG. 13 is a diagram showing the image intensity distribution of a pattern on a wafer when a conventional exposure method is used.

[Explanation of symbols]

7 Light splitter (optical fiber) 11 Reticle 12 Pattern 12a Transmissive section 12b Semi-transmissive section 15 Fourier plane for the pattern surface of the 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 18 Pupil plane 19 of projection optical system Shutter 20 Control circuit L0 Illumination light flux Dov 0th order diffraction light Dpv +1st order diffraction light Dmv -1st order diffraction light Doh 0th order Dfracted light Dph + 1st-order diffracted light Dmh - 1st-order diffracted light E12 Intensity distribution of pattern image E13 Intensity distribution of pattern image WS Movable stage

Claims (3)

[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:
Each fine pattern in the fine pattern group has a transmitting part whose transmittance for the light beam is approximately 1, and a phase difference of approximately (2n+1)π (n is an integer) to the light beam passing through the transmitting part. and a semi-transparent part whose transmittance for the luminous flux is about 1/4 or less of that of the transparent part,
a surface in the illumination optical system that becomes a Fourier surface of the mask;
Alternatively, by defining the light flux passing within a plane in the vicinity thereof to a local area having a center at a position eccentric from the optical axis of the illumination optical system, the light flux that irradiates the mask is directed to the fine pattern group in a predetermined direction. An exposure method characterized by tilting the light by an angle corresponding to the fineness of the image. 2. The angle is determined by the line width and periodicity of each fine pattern in the fine pattern group, and the direction is determined by the directionality of the pattern, and the direction 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 in accordance with the determined incident direction of the light beam. 3. When projecting and exposing the fine pattern group onto the photosensitive substrate, the photosensitive substrate and the imaging surface of the projection optical system are moved or vibrated relative to each other in the optical axis direction. The exposure method according to claim 1 or 2, characterized in that: