JPH05182893A - Method and apparatus for exposure of pattern - Google Patents

Abstract

PURPOSE:To realize a pattern exposure method and its apparatus wherein an alignment operation can be performed in a high-accuracy line width by a method wherein the displacement amount of the relative position between a projected image and a wafer is sampled at a sampling frequency, measured and corrected. CONSTITUTION:A circuit pattern on a reticle 2 is irradiated with a beam of exposure light 11 radiated from an exposure-light optical system 1; an image which is 1/5 times the pattern on the reticle 2 is formed on the surface of a wafer 5 by using a beam of transmitted light; the image is aligned with the pattern on the wafer 5 with good accuracy. Then, the relative dislocation of the pattern on the wafer 5 from the pattern on the reticle 2 is detected; a total displacement amount (DELTAL) is found; the wafer or reticle stages 6, 3 are moved fine by DELTAL, by using a fine movement control means 10; the dislocation is corrected. Consequently, even when their relative position is changed during an exposure operation, the circuit pattern in which the line width of the pattern is 0.5mum or lower can be aligned with high accuracy in a high-accuracy line width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern exposure method and an apparatus for exposing a fine circuit pattern, and
A pattern suitable for superimposing a circuit pattern having a line width of 0.5 μm or less with a high precision line width and a high precision without being affected by low frequency vibration during exposure. −
Exposure method and apparatus therefor.

[0002]

2. Description of the Related Art Since the line width of a semiconductor circuit pattern has conventionally been 0.8 .mu.m, the variation in the line width of the pattern is. +-. 0.08 .mu.m, and the alignment accuracy is almost equal to this value. Was there. For this reason, conventionally, when the reticle pattern is reduced and exposed to ⅕ on the wafer while the wafer is moved by the step and repeat method, the exposure is started with some time after the step movement. If so, the vibration accompanying the step movement can be kept within the above accuracy, and the pattern can be exposed to a predetermined target accuracy. However, the demand for miniaturization of the pattern line width is rapidly advancing, and the line width of 0.5 to 0.3 μm is being reached.

[0003]

However, if the pattern line width is reduced to 0.5 to 0.3 .mu.m, even after a considerable amount of time has passed after the step movement, the anti-vibration mechanism of the exposure apparatus is used. Even if is activated, low-frequency vibrations of several hertz or less remain. This is the same even if the rigidity of the exposure apparatus is increased considerably,
Vibrations corresponding to the above-mentioned frequency and the resonance frequency of the structure are small but remain. Therefore, the relative positions of the mask or reticle, the projection optical system, and the wafer are:
It is changing slightly, but constantly. Therefore, even if the exposure is started after performing the alignment, there is a problem that the relative position between the reticle image and the wafer is deviated between the alignment and the start of the exposure, and the exposure time itself is 0.2 to
Since it takes about 0.4 seconds, the exposure is performed under the condition that the relative position of the reticle image and the wafer is changed during the exposure, and the pattern line width varies and the overlay accuracy decreases. There is a problem inevitable that a predetermined target accuracy cannot be obtained.

The present invention has been made in view of the above problems of the prior art.
Even if the low-frequency vibration remains and the relative position between the reticle image and the wafer changes during exposure, it is possible to prevent variations in the line width of the pattern and a decrease in overlay accuracy.
It is an object of the present invention to provide a pattern exposure method and an apparatus thereof which can superimpose a circuit pattern having a pattern line width of 0.5 μm or less with a high precision line width and a high precision.

[0005]

In order to achieve the above object, a pattern exposure method of the present invention irradiates a mask or reticle with exposure light and transmits transmitted light or reflected light of a pattern on the mask or reticle. In a pattern exposure method for performing projection exposure on a wafer via a projection optical system, a relative state change state and a displacement amount due to vibration between a wafer and a projection image of the pattern via the projection optical system. Is sampled and measured at a sampling frequency having a frequency that is several times or more the main frequency of the vibration, and the wafer or / and the mask or reticle is finely displaced during the projection exposure according to the measured value, and the projection is performed. The configuration is such that the relative position displacement between the image and the wafer is corrected.

It is effective that the sampling frequency is four times or more the main frequency of the vibration, and it is desirable that the measurement be performed during the projection exposure. Further, the fine movement displacement during the projection exposure may be controlled by using a plurality of past sampling data obtained in advance by the measurement.

Then, the displacement amount of the relative position is measured by
By at least any two or more of three in the direction perpendicular to the optical axis of the projection optical system and in the stage for holding the wafer, the projection optical system, and the stage for holding the mask or reticle. Preferably, and
The measurement of the displacement amount of the relative position is performed in a direction perpendicular to the optical axis of the projection optical system and a stage for holding the wafer,
Alternatively, and / or the stage for holding the mask or reticle and the projection optical system are used to measure the amount of positional displacement of the projection optical system, and the distance between the mask or reticle and the wafer is measured by the projection optical system. It is advisable to adopt a configuration in which the position is internally divided by the ratio of the magnification. Further, it is desirable to measure the amount of displacement of the relative position by using a pattern on the wafer and a pattern on the mask or reticle.

On the other hand, the pattern exposure apparatus of the present invention has an exposure light source, and an exposure illumination system for irradiating the light emitted from the exposure light source to a mask or reticle, and ON / OFF control of the exposure light to the mask or reticle. Exposure optical system having a shutter function, a projection optical system for projecting and exposing light transmitted or reflected by the mask or reticle onto a wafer, a reticle stage for holding the mask or reticle, and a wafer holding device. In a pattern exposure apparatus comprising a wafer stage capable of coarse and fine movements and an alignment detection system for detecting the relative position of the wafer and the mask or reticle, the mask function is used under the exposure condition in which the shutter function is ON. Alternatively, the relative position change caused by the vibration between the image projected by the projection optical system of the pattern on the reticle and the wafer. And a displacement detection system for measuring the displacement amount by sampling at a sampling frequency having a frequency four times or more the main frequency of the vibration, and a wafer or / and a mask or a reticle according to the measured change state and displacement amount. And a fine movement control means for correcting and controlling the relative position displacement between the projected image and the wafer.

The displacement detection system is one of the three stages of the wafer stage, the projection optical system, and the reticle stage.
It is preferable that at least any two or more of them can be configured to measure a displacement amount in a direction perpendicular to the optical axis of the projection optical system, and the displacement detection system can be arranged in a direction perpendicular to the optical axis of the projection optical system. Of the wafer or stage and / or the reticle stage and the projection optical system, and the displacement of the relative position by the projection optical system is measured by the mask or reticle and the wafer. It is advisable to adopt a configuration in which the distance between and is internally divided by the ratio of the magnification of the projection optical system. Further, the alignment detection system may be configured to detect a relative position between the wafer and the mask or reticle by using the pattern on the wafer and the pattern on the mask or reticle. desirable.

[0010]

With the above structure, the displacement detecting system detects the minute displacement of the relative position due to the vibration between the projected image of the pattern on the mask or reticle (hereinafter simply referred to as "reticle") and the wafer. It is possible to measure the optical system and the wafer in the direction perpendicular to the optical axis of the projection optical system even during the projection exposure. In this case, if the displacement measurement position in the projection optical system is set to a position where the distance between the reticle and the wafer is internally divided into 5: 1, both the projection optical system and the wafer are not displaced and only the reticle is displaced by ΔLr. In this case, the displacement of the reticle image on the wafer is −
⅕ΔLr, and the displacement amount of the reticle image on the wafer is 6/5 when only the projection optical system is displaced by ΔLi.
Since it is ΔLi, the total displacement amount ΔL to be measured during the projection exposure is given by the following equation: ΔL = ΔLw + 6 / 5ΔLi-1 / 5ΔLr (1) Here, ΔLw is a reference position on the wafer (for example, a chip). (Center of) and a small amount of displacement.

Since sampling at the time of the above measurement is performed at a frequency that is four times or more the main frequency of the remaining minute vibration, it is possible to grasp the outline of the amplitude and phase of the vibration, and the predetermined Measurement accuracy can be obtained.
For example, when the exposure is performed after the vibration of a relatively high frequency of tens to hundreds of tens of Hz that remains immediately after the step movement of the wafer stage is sufficiently damped, the vibration removal function of the exposure apparatus also dampens it. When exposure is performed without waiting for the complete attenuation of residual vibration after the above step movement, in order to remove the effect of vibration of several Hz that cannot be completely performed, at a sampling frequency of ten or more Hz, which is four times that frequency or more. For example, the sampling frequency is several hundred Hz, which is four times or more the above several tens to one hundred and several tens Hz.

The above sampling data is always fed back to the fine movement control means during exposure to control the residual vibration. Then, under this control condition, the deviation of the wafer with respect to the reticle image, that is, the total displacement amount ΔL measured is corrected by finely moving one or both of the wafer stage and the reticle stage by the fine movement control means. With this correction, the reticle image and the wafer are accurately superimposed even if there is a relative positional change between the reticle, the projection optical system, and the wafer, which are slight but always generated, and the pattern of the pattern is accurately overlapped. Even if the circuit pattern has a line width of 0.5 μm or less, it is possible to perform exposure with high line width and alignment accuracy.

When finely controlling the wafer stage or the like, prediction is performed by using data of a plurality of sample points which are obtained in advance in consideration of the vibration characteristics peculiar to the mechanism of the exposure apparatus, in addition to the sampling data. By performing the control, more accurate exposure can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a pattern exposure apparatus, FIG. 2 is a diagram showing a displacement state of each part of an exposure pattern, and FIG. 3 is a diagram showing a relationship between residual vibration after step movement and timing of measurement / exposure. ..

In FIG. 1, reference numeral 1 denotes an exposure optical system including an exposure light source, in which an exposure illumination system for irradiating a reticle 2 mounted on a reticle stage 3 with light emitted from the exposure light source, and a reticle 2. And a shutter function capable of controlling ON / OFF of the exposure light 11 for. 4 is reticle 2
The light transmitted through the wafer 5 placed on the wafer stage 6
A projection optical system including a reduction lens that performs projection exposure by reducing the size upward, and is configured to form an image of 1/5 times the pattern on the reticle 2 on the surface of the wafer 5 on which the pattern is already formed. Reference numeral 7 is an alignment detection system for detecting a relative position between the pattern formed on the wafer 5 and the pattern of the reticle 2, 8 is an alignment detection light, and the detection method is such that the relative position is an exposure position. Detectable methods such as Japanese Patent Publication No. 63-60525 and Japanese Patent Laid-Open No.
The method described in JP-A 1-220326 is used. A CCD one-dimensional image pickup device is used for detection, the detected data is AD-converted at high speed, and is detected at a sampling period of several ms using a digital signal processor (DSP). In addition, the alignment detection system 7 converts the alignment detection light 8 into the exposure light 1
Since the light having the same wavelength as that of No. 1 is used, the resist is exposed when the alignment detection is performed for a long time. Therefore, the alignment detection is performed in a short time, and then the alignment detection light 8 is shielded so that it does not enter the wafer 5. I have to. 9
Is the reticle 2 under the exposure condition in which the shutter function is ON.
A laser length measuring device that measures the displacement amount of the relative position due to the vibration between the projected image of the projection optical system 4 of the above pattern and the wafer 5 constitutes the displacement detection system together with the alignment detection system 7. The displacement detection system is configured to measure by sampling at a sampling frequency having a frequency four times or more the main frequency of the vibration. Laser length measuring device 9
Are laser beams 31, 3 for the respective displacements of the reticle 2, the projection optical system 4, and the wafer 5 in the direction perpendicular to the optical axis 4a of the projection optical system 4 at the moments detected by the alignment detection system 7.
Measure through 2, 33. In FIG. 1, displacements in one direction perpendicular to the optical axis 4a are measured, but a detection system in a direction perpendicular to the plane of the paper (not shown) is actually incorporated, and two directions perpendicular to the optical axis 4a are incorporated. Is measured for each. The displacement detection position of the projection optical system 4 is a position C where the space between the reticle 2 and the wafer 5 is internally divided into L ₁ : L ₂ = 5: 1 as shown in FIG. Reference numeral 10 denotes one of the wafer 5 and the reticle 2 according to the change state and the amount of displacement of the relative position between the projection image of the pattern on the reticle 2 projected by the projection optical system 4 and the wafer 5 measured by the displacement detection system. Or both of them is finely displaced, and the relative position displacement between the projected image and the wafer 5 is corrected and controlled.

With the above arrangement, the exposure optical system 1
The exposure light 11 emitted thereby illuminates the circuit pattern on the reticle 2, and the light transmitted through the reticle 2 is applied to the surface of the wafer 5 by a reduction lens in the projection optical system 4 to 1/5 of the pattern on the reticle 2. Double the image. Since it is necessary to accurately align this image formation with the already formed pattern of the wafer 5 and to expose the image of the reticle 2 on the wafer 5 in an overlapping manner, the alignment detection system 7 patterns the wafer 5.
The relative displacement between the pattern of the reticle 2 and the pattern of the reticle 2 is detected.

The above-mentioned misregistration is detected by referring to the reticle 2, the projection optical system 4 and the wafer 5, as shown in FIG.
The minute displacements ΔLr, ΔLi, and ΔLw with W are performed in the direction perpendicular to the optical axis 4a of the projection optical system 4 during the projection exposure. In this case, the displacement measurement position in the projection optical system 4 is a position C obtained by internally dividing the distance between the reticle 2 and the wafer 5 into 5: 1.
2A in which both the projection optical system 4 and the wafer 5 are not displaced, and only the reticle 2 is displaced from the reference position A of the reticle 2 by ΔLr, the reticle image on the wafer 5 is Of the reference position W of the wafer 5 is -1 /
It becomes 5ΔLr. Further, only the projection optical system 4 is the reticle 2
In the case of FIG. 2B, which is displaced from the reference position A by ΔLi, the displacement amount of the reticle image on the wafer 5 is 6/5 ΔLi from the reference position W of the wafer 5. Further, only the wafer 5 is displaced from the reference position A of the reticle 2 by ΔLw.
In the case of (c), the displacement amount of the reticle image on the wafer 5 is ΔLw even from the reference position W of the wafer 5. The positional deviation is not affected by the inclination of the projection optical system 4, and ΔL = 0 as shown in FIG. 2 (d).

From each of the minute displacements ΔLr, ΔLi, and ΔLw, the total displacement amount ΔL to be measured during the projection exposure is obtained from the equation (1), and one of the wafer stage 6 and the reticle stage 3 is controlled by the fine movement control means 10. Alternatively, both are finely moved by the obtained ΔL to correct the positional deviation. Since the respective values of ΔLr, ΔLi, and ΔLw are constantly detected during pattern exposure, even if the exposure pattern is slightly displaced on the wafer 5 due to vibration during exposure, the wafer 5 is always ΔL. It becomes possible to make fine movement corrections for the like, and it becomes possible to expose a good pattern shape to the correct alignment position. In the detection of ΔLr, ΔLi, and ΔLw, for example, when the displacement amount of the reticle 2 is so small as not to be a problem, the measurement of ΔLr is omitted, and ΔL is obtained from the detected values of ΔLi and ΔLw. -It is also possible to control the movement of the gear 6 and the like.

In the pattern exposure apparatus as shown in FIG. 1, the structure supporting each system of the apparatus has its own resonance frequencies, and residual vibrations at these frequencies occur. For example, immediately after the step movement of the wafer stage 6, a relatively high-frequency, fast-damping vibration of several tens to one hundred and several tens Hz remains, but even if the vibration is damped, the vibration is damped by the anti-vibration function of the exposure apparatus. Vibration of several Hz that cannot be completely left remains. However, since these residual vibrations have a waveform of a basic frequency as shown by a solid line in FIG. 3A or 3B, the sampling during the above measurement is the main vibration of the remaining minute vibrations. Frequency more than 4 times the frequency,
That is, when the frequency of the residual vibration is a few Hz, the sampling frequency is four times or more and ten or more Hz, or
When exposure is performed without waiting for complete attenuation of residual vibration after the step movement, in the case of several tens to one hundred and several tens Hz, by performing at a sampling frequency of several hundreds of Hz, which is four times or more, It is possible to grasp the approximate amplitude and phase of the vibration.

The above sampling data is constantly fed back to the fine movement control means 10 during exposure to control the residual vibration. FIG. 3A is an explanatory view of this state, and shows the relationship between the residual vibration and the measurement / exposure start time point during the exposure measurement control (that is, when the minute displacements of the respective parts are measured except during the step movement) Indicates. As can be seen from the figure, the uncontrolled residual vibration indicated by the solid line is measured and controlled immediately after the step movement and becomes flat as indicated by the dotted line, and the exposure is started in the stable state. This has the effect that the process can be shortened as compared with the conventional method in which the exposure is started after waiting for the stabilization of the low-frequency residual vibration with slow damping. The deviation of the wafer 5 with respect to the reticle image under the condition that the residual vibration is controlled, that is, the total displacement amount ΔL measured is controlled by the fine movement control means 10 by the wafer stage 6
Alternatively, one or both of the reticle stages 3 are finely moved for correction. With this correction, the reticle image and the wafer 5 are accurately superposed on each other even if there is a relative positional change between the reticle 2, the projection optical system 4, and the wafer 5. Even with a circuit pattern having a line width of 0.5 μm or less, it is possible to perform exposure with high line width and alignment accuracy. When finely controlling the wafer stage or the like, predictive control is performed using the sampling data and the data of a plurality of sample points obtained in advance in consideration of the vibration characteristic of the mechanism of the exposure apparatus. As a result, exposure with higher accuracy can be performed.

The fine movement control during the projection exposure of the wafer stage 6 or the like is desired to be obtained from the vibration data during the exposure, which is desirable in accordance with the current situation, but in the case where the vibration data cannot be obtained. , As shown in FIG.
The relative position between the exposure pattern and the wafer 5 when the alignment detection is performed immediately before the exposure is performed by using the data detected in the above sampling period, or the exposure is performed by the laser measuring device 9. The ΔLr, ΔLi, ΔL detected immediately before
The wafer stage 6 or the like may be driven by using the data of w. In this case, if the vibration occurring during the subsequent exposure is predicted from the detected data and the wafer stage 6 and the like are finely driven from this vibration prediction, the correct position is obtained during the exposure as shown by the dotted line in FIG. 3B. It is possible to stably control the wafer stage 6 and the like.

As a method for measuring the relative position between the reticle image and the wafer 5, other than the above method, for example, the relative position between the image on the reticle 2 and the image on the wafer 5 is directly measured. It may be done. In this case, since the measurement is performed during the exposure, it is indispensable that the measuring means does not block the exposure light 11.

Although not shown, the measurement of the change in the relative position is carried out in the vicinity of the reticle 2 through the projection optical system 4 through the pattern on the wafer 5 contrary to the method of projecting the pattern on the reticle 2. Image on the reticle 2
It is also possible to detect the relative position with respect to the upper pattern.

[0024]

As described above, according to the present invention, in the pattern exposure method and apparatus, even if the low-frequency vibration remains and the relative position between the reticle image and the wafer changes during the exposure, the pattern exposure is performed. It is possible to prevent a variation in the line width of the pattern and a decrease in the overlay accuracy. A circuit pattern with a pattern line width of 0.5 μm or less can be formed with a high precision line width.
Moreover, there is an effect that they can be superposed with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a pattern exposure apparatus of the present invention.

FIG. 2 is a diagram showing a displacement state of each part of an exposure pattern.

FIG. 3 is a diagram showing a relationship between residual vibration after step movement and timing of measurement / exposure according to the present invention.

[Explanation of symbols]

1 ... Exposure optical system, 2 ... Reticle, 3 ... Reticle stage, 4 ... Projection optical system, 5 ... Wafer, 6 ... Wafer stage, 7 ... Alignment detection system, 8 ... Alignment detection light, 9 ... Laser length measuring device, 10 ... fine movement control means 11, exposure light, 31, 32, 33 ... laser beam.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G03F 9/00 H 7818-2H

Claims (11)

[Claims] 1. A pattern exposure method in which a mask or reticle is irradiated with exposure light, and the transmitted light or reflected light of a pattern on the mask or reticle is projected and exposed on a wafer through a projection optical system. , Sampling the relative state change state and the displacement amount due to the vibration between the projection image through the projection optical system of the pattern and the wafer at a sampling frequency having a frequency of several times the main frequency of the vibration or more. Then, the wafer or
And a pattern exposure method, wherein a mask or a reticle is finely displaced during the projection exposure to correct a relative positional displacement between the projection image and the wafer. 2. The pattern exposure method according to claim 1, wherein the sampling frequency is four times or more the main frequency of the vibration. 3. The pattern exposure method according to claim 1, wherein the measurement is performed during the projection exposure. 4. A plurality of past sampling data obtained in advance by the measurement of the fine movement displacement during the projection exposure.
2. The pattern exposure method according to claim 1, wherein the pattern exposure is controlled using a pattern. 5. The measurement of the displacement amount of the relative position is performed in a direction perpendicular to the optical axis of the projection optical system, and a stage for holding the wafer, a projection optical system, a stage for holding a mask or a reticle. 2. The pattern exposure method according to claim 1, wherein the pattern exposure is performed by at least any two or more of the three. 6. The measurement of the displacement amount of the relative position is performed in a direction perpendicular to the optical axis of the projection optical system and / or a stage for holding the wafer and / or a stage for holding the mask or reticle. And the projection optical system, the position displacement amount of the projection optical system is measured at a position where the distance between the mask or reticle and the wafer is internally divided by the ratio of the magnification of the projection optical system. The pattern according to claim 1,
Exposure method. 7. The pattern exposure method according to claim 1, wherein the amount of displacement of the relative position is measured by using a pattern on the wafer and a pattern on the mask or reticle. 8. An exposure illumination system which has an exposure light source and irradiates the light emitted from the exposure light source to a mask or reticle, and ON-OFF the exposure light to the mask or reticle.
An exposure optical system having a controllable shutter function, a projection optical system for projecting and exposing light transmitted or reflected by the mask or reticle onto a wafer, a reticle stage for holding the mask or reticle, and the wafer In a pattern exposure apparatus comprising a wafer stage capable of holding and holding a wafer and capable of coarse and fine movement, and an alignment detection system for detecting a relative position between the wafer and a mask or reticle, under the exposure state in which the shutter function is ON, A sample in which the relative position change state and the displacement amount due to the vibration between the projection image of the pattern on the mask or reticle by the projection optical system and the wafer have a frequency of four times or more the main frequency of the vibration. A displacement detection system for sampling and measuring at a frequency, and a wafer or / and a mass according to the measured change state and displacement amount. Or the reticle to the fine displacement,
A pattern exposure apparatus comprising: a fine movement control means for correcting and controlling a relative position displacement between the projected image and the wafer. 9. The displacement detection system is the wafer station.
9. The pattern according to claim 8, wherein the amount of displacement in a direction perpendicular to the optical axis of the projection optical system can be measured by at least any two of the three, the projection optical system and the reticle stage. Exposure equipment. 10. The displacement detection system is configured to be capable of measuring a displacement amount in a direction perpendicular to an optical axis of the projection optical system by the wafer stage and / or the reticle stage and the projection optical system. In addition, the amount of displacement of the relative position by the projection optical system is measured at a position where the distance between the mask or reticle and the wafer is internally divided by the magnification ratio of the projection optical system. The pattern exposure apparatus described. 11. The alignment detection system can detect the relative position of the wafer and a mask or reticle by using a pattern on the wafer and a pattern on the mask or reticle. The pattern exposure apparatus according to claim 8, which is configured.